mm/mmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * mm/mmap.c
   4  *
   5  * Written by obz.
   6  *
   7  * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/kernel.h>
  13 #include <linux/slab.h>
  14 #include <linux/backing-dev.h>
  15 #include <linux/mm.h>
  16 #include <linux/vmacache.h>
  17 #include <linux/shm.h>
  18 #include <linux/mman.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/swap.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/capability.h>
  23 #include <linux/init.h>
  24 #include <linux/file.h>
  25 #include <linux/fs.h>
  26 #include <linux/personality.h>
  27 #include <linux/security.h>
  28 #include <linux/hugetlb.h>
  29 #include <linux/shmem_fs.h>
  30 #include <linux/profile.h>
  31 #include <linux/export.h>
  32 #include <linux/mount.h>
  33 #include <linux/mempolicy.h>
  34 #include <linux/rmap.h>
  35 #include <linux/mmu_notifier.h>
  36 #include <linux/mmdebug.h>
  37 #include <linux/perf_event.h>
  38 #include <linux/audit.h>
  39 #include <linux/khugepaged.h>
  40 #include <linux/uprobes.h>
  41 #include <linux/rbtree_augmented.h>
  42 #include <linux/notifier.h>
  43 #include <linux/memory.h>
  44 #include <linux/printk.h>
  45 #include <linux/userfaultfd_k.h>
  46 #include <linux/moduleparam.h>
  47 #include <linux/pkeys.h>
  48 #include <linux/oom.h>
  49 #include <linux/sched/mm.h>
  50
  51 #include <linux/uaccess.h>
  52 #include <asm/cacheflush.h>
  53 #include <asm/tlb.h>
  54 #include <asm/mmu_context.h>
  55
  56 #include "internal.h"
  57
  58 #ifndef arch_mmap_check
  59 #define arch_mmap_check(addr, len, flags)       (0)
  60 #endif
  61
  62 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
  63 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
  64 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
  65 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
  66 #endif
  67 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
  68 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
  69 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
  70 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
  71 #endif
  72
  73 static bool ignore_rlimit_data;
  74 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
  75
  76 static void unmap_region(struct mm_struct *mm,
  77                 struct vm_area_struct *vma, struct vm_area_struct *prev,
  78                 unsigned long start, unsigned long end);
  79
  80 /* description of effects of mapping type and prot in current implementation.
  81  * this is due to the limited x86 page protection hardware.  The expected
  82  * behavior is in parens:
  83  *
  84  * map_type     prot
  85  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
  86  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  87  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
  88  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  89  *
  90  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  91  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
  92  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  93  *
  94  * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
  95  * MAP_PRIVATE:
  96  *                                                              r: (no) no
  97  *                                                              w: (no) no
  98  *                                                              x: (yes) yes
  99  */
 100 pgprot_t protection_map[16] __ro_after_init = {
 101         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
 102         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
 103 };
 104
 105 #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
 106 static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
 107 {
 108         return prot;
 109 }
 110 #endif
 111
 112 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 113 {
 114         pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
 115                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
 116                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
 117
 118         return arch_filter_pgprot(ret);
 119 }
 120 EXPORT_SYMBOL(vm_get_page_prot);
 121
 122 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 123 {
 124         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
 125 }
 126
 127 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
 128 void vma_set_page_prot(struct vm_area_struct *vma)
 129 {
 130         unsigned long vm_flags = vma->vm_flags;
 131         pgprot_t vm_page_prot;
 132
 133         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
 134         if (vma_wants_writenotify(vma, vm_page_prot)) {
 135                 vm_flags &= ~VM_SHARED;
 136                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
 137         }
 138         /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
 139         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
 140 }
 141
 142 /*
 143  * Requires inode->i_mapping->i_mmap_rwsem
 144  */
 145 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
 146                 struct file *file, struct address_space *mapping)
 147 {
 148         if (vma->vm_flags & VM_DENYWRITE)
 149                 atomic_inc(&file_inode(file)->i_writecount);
 150         if (vma->vm_flags & VM_SHARED)
 151                 mapping_unmap_writable(mapping);
 152
 153         flush_dcache_mmap_lock(mapping);
 154         vma_interval_tree_remove(vma, &mapping->i_mmap);
 155         flush_dcache_mmap_unlock(mapping);
 156 }
 157
 158 /*
 159  * Unlink a file-based vm structure from its interval tree, to hide
 160  * vma from rmap and vmtruncate before freeing its page tables.
 161  */
 162 void unlink_file_vma(struct vm_area_struct *vma)
 163 {
 164         struct file *file = vma->vm_file;
 165
 166         if (file) {
 167                 struct address_space *mapping = file->f_mapping;
 168                 i_mmap_lock_write(mapping);
 169                 __remove_shared_vm_struct(vma, file, mapping);
 170                 i_mmap_unlock_write(mapping);
 171         }
 172 }
 173
 174 /*
 175  * Close a vm structure and free it, returning the next.
 176  */
 177 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
 178 {
 179         struct vm_area_struct *next = vma->vm_next;
 180
 181         might_sleep();
 182         if (vma->vm_ops && vma->vm_ops->close)
 183                 vma->vm_ops->close(vma);
 184         if (vma->vm_file)
 185                 fput(vma->vm_file);
 186         mpol_put(vma_policy(vma));
 187         vm_area_free(vma);
 188         return next;
 189 }
 190
 191 static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
 192                 struct list_head *uf);
 193 SYSCALL_DEFINE1(brk, unsigned long, brk)
 194 {
 195         unsigned long retval;
 196         unsigned long newbrk, oldbrk, origbrk;
 197         struct mm_struct *mm = current->mm;
 198         struct vm_area_struct *next;
 199         unsigned long min_brk;
 200         bool populate;
 201         bool downgraded = false;
 202         LIST_HEAD(uf);
 203
 204         brk = untagged_addr(brk);
 205
 206         if (down_write_killable(&mm->mmap_sem))
 207                 return -EINTR;
 208
 209         origbrk = mm->brk;
 210
 211 #ifdef CONFIG_COMPAT_BRK
 212         /*
 213          * CONFIG_COMPAT_BRK can still be overridden by setting
 214          * randomize_va_space to 2, which will still cause mm->start_brk
 215          * to be arbitrarily shifted
 216          */
 217         if (current->brk_randomized)
 218                 min_brk = mm->start_brk;
 219         else
 220                 min_brk = mm->end_data;
 221 #else
 222         min_brk = mm->start_brk;
 223 #endif
 224         if (brk < min_brk)
 225                 goto out;
 226
 227         /*
 228          * Check against rlimit here. If this check is done later after the test
 229          * of oldbrk with newbrk then it can escape the test and let the data
 230          * segment grow beyond its set limit the in case where the limit is
 231          * not page aligned -Ram Gupta
 232          */
 233         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
 234                               mm->end_data, mm->start_data))
 235                 goto out;
 236
 237         newbrk = PAGE_ALIGN(brk);
 238         oldbrk = PAGE_ALIGN(mm->brk);
 239         if (oldbrk == newbrk) {
 240                 mm->brk = brk;
 241                 goto success;
 242         }
 243
 244         /*
 245          * Always allow shrinking brk.
 246          * __do_munmap() may downgrade mmap_sem to read.
 247          */
 248         if (brk <= mm->brk) {
 249                 int ret;
 250
 251                 /*
 252                  * mm->brk must to be protected by write mmap_sem so update it
 253                  * before downgrading mmap_sem. When __do_munmap() fails,
 254                  * mm->brk will be restored from origbrk.
 255                  */
 256                 mm->brk = brk;
 257                 ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
 258                 if (ret < 0) {
 259                         mm->brk = origbrk;
 260                         goto out;
 261                 } else if (ret == 1) {
 262                         downgraded = true;
 263                 }
 264                 goto success;
 265         }
 266
 267         /* Check against existing mmap mappings. */
 268         next = find_vma(mm, oldbrk);
 269         if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
 270                 goto out;
 271
 272         /* Ok, looks good - let it rip. */
 273         if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
 274                 goto out;
 275         mm->brk = brk;
 276
 277 success:
 278         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
 279         if (downgraded)
 280                 up_read(&mm->mmap_sem);
 281         else
 282                 up_write(&mm->mmap_sem);
 283         userfaultfd_unmap_complete(mm, &uf);
 284         if (populate)
 285                 mm_populate(oldbrk, newbrk - oldbrk);
 286         return brk;
 287
 288 out:
 289         retval = origbrk;
 290         up_write(&mm->mmap_sem);
 291         return retval;
 292 }
 293
 294 static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
 295 {
 296         unsigned long gap, prev_end;
 297
 298         /*
 299          * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
 300          * allow two stack_guard_gaps between them here, and when choosing
 301          * an unmapped area; whereas when expanding we only require one.
 302          * That's a little inconsistent, but keeps the code here simpler.
 303          */
 304         gap = vm_start_gap(vma);
 305         if (vma->vm_prev) {
 306                 prev_end = vm_end_gap(vma->vm_prev);
 307                 if (gap > prev_end)
 308                         gap -= prev_end;
 309                 else
 310                         gap = 0;
 311         }
 312         return gap;
 313 }
 314
 315 #ifdef CONFIG_DEBUG_VM_RB
 316 static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
 317 {
 318         unsigned long max = vma_compute_gap(vma), subtree_gap;
 319         if (vma->vm_rb.rb_left) {
 320                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
 321                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
 322                 if (subtree_gap > max)
 323                         max = subtree_gap;
 324         }
 325         if (vma->vm_rb.rb_right) {
 326                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
 327                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
 328                 if (subtree_gap > max)
 329                         max = subtree_gap;
 330         }
 331         return max;
 332 }
 333
 334 static int browse_rb(struct mm_struct *mm)
 335 {
 336         struct rb_root *root = &mm->mm_rb;
 337         int i = 0, j, bug = 0;
 338         struct rb_node *nd, *pn = NULL;
 339         unsigned long prev = 0, pend = 0;
 340
 341         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 342                 struct vm_area_struct *vma;
 343                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 344                 if (vma->vm_start < prev) {
 345                         pr_emerg("vm_start %lx < prev %lx\n",
 346                                   vma->vm_start, prev);
 347                         bug = 1;
 348                 }
 349                 if (vma->vm_start < pend) {
 350                         pr_emerg("vm_start %lx < pend %lx\n",
 351                                   vma->vm_start, pend);
 352                         bug = 1;
 353                 }
 354                 if (vma->vm_start > vma->vm_end) {
 355                         pr_emerg("vm_start %lx > vm_end %lx\n",
 356                                   vma->vm_start, vma->vm_end);
 357                         bug = 1;
 358                 }
 359                 spin_lock(&mm->page_table_lock);
 360                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
 361                         pr_emerg("free gap %lx, correct %lx\n",
 362                                vma->rb_subtree_gap,
 363                                vma_compute_subtree_gap(vma));
 364                         bug = 1;
 365                 }
 366                 spin_unlock(&mm->page_table_lock);
 367                 i++;
 368                 pn = nd;
 369                 prev = vma->vm_start;
 370                 pend = vma->vm_end;
 371         }
 372         j = 0;
 373         for (nd = pn; nd; nd = rb_prev(nd))
 374                 j++;
 375         if (i != j) {
 376                 pr_emerg("backwards %d, forwards %d\n", j, i);
 377                 bug = 1;
 378         }
 379         return bug ? -1 : i;
 380 }
 381
 382 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
 383 {
 384         struct rb_node *nd;
 385
 386         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 387                 struct vm_area_struct *vma;
 388                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 389                 VM_BUG_ON_VMA(vma != ignore &&
 390                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
 391                         vma);
 392         }
 393 }
 394
 395 static void validate_mm(struct mm_struct *mm)
 396 {
 397         int bug = 0;
 398         int i = 0;
 399         unsigned long highest_address = 0;
 400         struct vm_area_struct *vma = mm->mmap;
 401
 402         while (vma) {
 403                 struct anon_vma *anon_vma = vma->anon_vma;
 404                 struct anon_vma_chain *avc;
 405
 406                 if (anon_vma) {
 407                         anon_vma_lock_read(anon_vma);
 408                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 409                                 anon_vma_interval_tree_verify(avc);
 410                         anon_vma_unlock_read(anon_vma);
 411                 }
 412
 413                 highest_address = vm_end_gap(vma);
 414                 vma = vma->vm_next;
 415                 i++;
 416         }
 417         if (i != mm->map_count) {
 418                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
 419                 bug = 1;
 420         }
 421         if (highest_address != mm->highest_vm_end) {
 422                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
 423                           mm->highest_vm_end, highest_address);
 424                 bug = 1;
 425         }
 426         i = browse_rb(mm);
 427         if (i != mm->map_count) {
 428                 if (i != -1)
 429                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
 430                 bug = 1;
 431         }
 432         VM_BUG_ON_MM(bug, mm);
 433 }
 434 #else
 435 #define validate_mm_rb(root, ignore) do { } while (0)
 436 #define validate_mm(mm) do { } while (0)
 437 #endif
 438
 439 RB_DECLARE_CALLBACKS_MAX(static, vma_gap_callbacks,
 440                          struct vm_area_struct, vm_rb,
 441                          unsigned long, rb_subtree_gap, vma_compute_gap)
 442
 443 /*
 444  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
 445  * vma->vm_prev->vm_end values changed, without modifying the vma's position
 446  * in the rbtree.
 447  */
 448 static void vma_gap_update(struct vm_area_struct *vma)
 449 {
 450         /*
 451          * As it turns out, RB_DECLARE_CALLBACKS_MAX() already created
 452          * a callback function that does exactly what we want.
 453          */
 454         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
 455 }
 456
 457 static inline void vma_rb_insert(struct vm_area_struct *vma,
 458                                  struct rb_root *root)
 459 {
 460         /* All rb_subtree_gap values must be consistent prior to insertion */
 461         validate_mm_rb(root, NULL);
 462
 463         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
 464 }
 465
 466 static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
 467 {
 468         /*
 469          * Note rb_erase_augmented is a fairly large inline function,
 470          * so make sure we instantiate it only once with our desired
 471          * augmented rbtree callbacks.
 472          */
 473         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
 474 }
 475
 476 static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
 477                                                 struct rb_root *root,
 478                                                 struct vm_area_struct *ignore)
 479 {
 480         /*
 481          * All rb_subtree_gap values must be consistent prior to erase,
 482          * with the possible exception of the "next" vma being erased if
 483          * next->vm_start was reduced.
 484          */
 485         validate_mm_rb(root, ignore);
 486
 487         __vma_rb_erase(vma, root);
 488 }
 489
 490 static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
 491                                          struct rb_root *root)
 492 {
 493         /*
 494          * All rb_subtree_gap values must be consistent prior to erase,
 495          * with the possible exception of the vma being erased.
 496          */
 497         validate_mm_rb(root, vma);
 498
 499         __vma_rb_erase(vma, root);
 500 }
 501
 502 /*
 503  * vma has some anon_vma assigned, and is already inserted on that
 504  * anon_vma's interval trees.
 505  *
 506  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
 507  * vma must be removed from the anon_vma's interval trees using
 508  * anon_vma_interval_tree_pre_update_vma().
 509  *
 510  * After the update, the vma will be reinserted using
 511  * anon_vma_interval_tree_post_update_vma().
 512  *
 513  * The entire update must be protected by exclusive mmap_sem and by
 514  * the root anon_vma's mutex.
 515  */
 516 static inline void
 517 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
 518 {
 519         struct anon_vma_chain *avc;
 520
 521         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 522                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
 523 }
 524
 525 static inline void
 526 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
 527 {
 528         struct anon_vma_chain *avc;
 529
 530         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 531                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
 532 }
 533
 534 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 535                 unsigned long end, struct vm_area_struct **pprev,
 536                 struct rb_node ***rb_link, struct rb_node **rb_parent)
 537 {
 538         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
 539
 540         __rb_link = &mm->mm_rb.rb_node;
 541         rb_prev = __rb_parent = NULL;
 542
 543         while (*__rb_link) {
 544                 struct vm_area_struct *vma_tmp;
 545
 546                 __rb_parent = *__rb_link;
 547                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
 548
 549                 if (vma_tmp->vm_end > addr) {
 550                         /* Fail if an existing vma overlaps the area */
 551                         if (vma_tmp->vm_start < end)
 552                                 return -ENOMEM;
 553                         __rb_link = &__rb_parent->rb_left;
 554                 } else {
 555                         rb_prev = __rb_parent;
 556                         __rb_link = &__rb_parent->rb_right;
 557                 }
 558         }
 559
 560         *pprev = NULL;
 561         if (rb_prev)
 562                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
 563         *rb_link = __rb_link;
 564         *rb_parent = __rb_parent;
 565         return 0;
 566 }
 567
 568 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 569                 unsigned long addr, unsigned long end)
 570 {
 571         unsigned long nr_pages = 0;
 572         struct vm_area_struct *vma;
 573
 574         /* Find first overlaping mapping */
 575         vma = find_vma_intersection(mm, addr, end);
 576         if (!vma)
 577                 return 0;
 578
 579         nr_pages = (min(end, vma->vm_end) -
 580                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
 581
 582         /* Iterate over the rest of the overlaps */
 583         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
 584                 unsigned long overlap_len;
 585
 586                 if (vma->vm_start > end)
 587                         break;
 588
 589                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
 590                 nr_pages += overlap_len >> PAGE_SHIFT;
 591         }
 592
 593         return nr_pages;
 594 }
 595
 596 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
 597                 struct rb_node **rb_link, struct rb_node *rb_parent)
 598 {
 599         /* Update tracking information for the gap following the new vma. */
 600         if (vma->vm_next)
 601                 vma_gap_update(vma->vm_next);
 602         else
 603                 mm->highest_vm_end = vm_end_gap(vma);
 604
 605         /*
 606          * vma->vm_prev wasn't known when we followed the rbtree to find the
 607          * correct insertion point for that vma. As a result, we could not
 608          * update the vma vm_rb parents rb_subtree_gap values on the way down.
 609          * So, we first insert the vma with a zero rb_subtree_gap value
 610          * (to be consistent with what we did on the way down), and then
 611          * immediately update the gap to the correct value. Finally we
 612          * rebalance the rbtree after all augmented values have been set.
 613          */
 614         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
 615         vma->rb_subtree_gap = 0;
 616         vma_gap_update(vma);
 617         vma_rb_insert(vma, &mm->mm_rb);
 618 }
 619
 620 static void __vma_link_file(struct vm_area_struct *vma)
 621 {
 622         struct file *file;
 623
 624         file = vma->vm_file;
 625         if (file) {
 626                 struct address_space *mapping = file->f_mapping;
 627
 628                 if (vma->vm_flags & VM_DENYWRITE)
 629                         atomic_dec(&file_inode(file)->i_writecount);
 630                 if (vma->vm_flags & VM_SHARED)
 631                         atomic_inc(&mapping->i_mmap_writable);
 632
 633                 flush_dcache_mmap_lock(mapping);
 634                 vma_interval_tree_insert(vma, &mapping->i_mmap);
 635                 flush_dcache_mmap_unlock(mapping);
 636         }
 637 }
 638
 639 static void
 640 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 641         struct vm_area_struct *prev, struct rb_node **rb_link,
 642         struct rb_node *rb_parent)
 643 {
 644         __vma_link_list(mm, vma, prev);
 645         __vma_link_rb(mm, vma, rb_link, rb_parent);
 646 }
 647
 648 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 649                         struct vm_area_struct *prev, struct rb_node **rb_link,
 650                         struct rb_node *rb_parent)
 651 {
 652         struct address_space *mapping = NULL;
 653
 654         if (vma->vm_file) {
 655                 mapping = vma->vm_file->f_mapping;
 656                 i_mmap_lock_write(mapping);
 657         }
 658
 659         __vma_link(mm, vma, prev, rb_link, rb_parent);
 660         __vma_link_file(vma);
 661
 662         if (mapping)
 663                 i_mmap_unlock_write(mapping);
 664
 665         mm->map_count++;
 666         validate_mm(mm);
 667 }
 668
 669 /*
 670  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
 671  * mm's list and rbtree.  It has already been inserted into the interval tree.
 672  */
 673 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 674 {
 675         struct vm_area_struct *prev;
 676         struct rb_node **rb_link, *rb_parent;
 677
 678         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
 679                            &prev, &rb_link, &rb_parent))
 680                 BUG();
 681         __vma_link(mm, vma, prev, rb_link, rb_parent);
 682         mm->map_count++;
 683 }
 684
 685 static __always_inline void __vma_unlink_common(struct mm_struct *mm,
 686                                                 struct vm_area_struct *vma,
 687                                                 struct vm_area_struct *ignore)
 688 {
 689         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
 690         __vma_unlink_list(mm, vma);
 691         /* Kill the cache */
 692         vmacache_invalidate(mm);
 693 }
 694
 695 /*
 696  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
 697  * is already present in an i_mmap tree without adjusting the tree.
 698  * The following helper function should be used when such adjustments
 699  * are necessary.  The "insert" vma (if any) is to be inserted
 700  * before we drop the necessary locks.
 701  */
 702 int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 703         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
 704         struct vm_area_struct *expand)
 705 {
 706         struct mm_struct *mm = vma->vm_mm;
 707         struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
 708         struct address_space *mapping = NULL;
 709         struct rb_root_cached *root = NULL;
 710         struct anon_vma *anon_vma = NULL;
 711         struct file *file = vma->vm_file;
 712         bool start_changed = false, end_changed = false;
 713         long adjust_next = 0;
 714         int remove_next = 0;
 715
 716         if (next && !insert) {
 717                 struct vm_area_struct *exporter = NULL, *importer = NULL;
 718
 719                 if (end >= next->vm_end) {
 720                         /*
 721                          * vma expands, overlapping all the next, and
 722                          * perhaps the one after too (mprotect case 6).
 723                          * The only other cases that gets here are
 724                          * case 1, case 7 and case 8.
 725                          */
 726                         if (next == expand) {
 727                                 /*
 728                                  * The only case where we don't expand "vma"
 729                                  * and we expand "next" instead is case 8.
 730                                  */
 731                                 VM_WARN_ON(end != next->vm_end);
 732                                 /*
 733                                  * remove_next == 3 means we're
 734                                  * removing "vma" and that to do so we
 735                                  * swapped "vma" and "next".
 736                                  */
 737                                 remove_next = 3;
 738                                 VM_WARN_ON(file != next->vm_file);
 739                                 swap(vma, next);
 740                         } else {
 741                                 VM_WARN_ON(expand != vma);
 742                                 /*
 743                                  * case 1, 6, 7, remove_next == 2 is case 6,
 744                                  * remove_next == 1 is case 1 or 7.
 745                                  */
 746                                 remove_next = 1 + (end > next->vm_end);
 747                                 VM_WARN_ON(remove_next == 2 &&
 748                                            end != next->vm_next->vm_end);
 749                                 /* trim end to next, for case 6 first pass */
 750                                 end = next->vm_end;
 751                         }
 752
 753                         exporter = next;
 754                         importer = vma;
 755
 756                         /*
 757                          * If next doesn't have anon_vma, import from vma after
 758                          * next, if the vma overlaps with it.
 759                          */
 760                         if (remove_next == 2 && !next->anon_vma)
 761                                 exporter = next->vm_next;
 762
 763                 } else if (end > next->vm_start) {
 764                         /*
 765                          * vma expands, overlapping part of the next:
 766                          * mprotect case 5 shifting the boundary up.
 767                          */
 768                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
 769                         exporter = next;
 770                         importer = vma;
 771                         VM_WARN_ON(expand != importer);
 772                 } else if (end < vma->vm_end) {
 773                         /*
 774                          * vma shrinks, and !insert tells it's not
 775                          * split_vma inserting another: so it must be
 776                          * mprotect case 4 shifting the boundary down.
 777                          */
 778                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
 779                         exporter = vma;
 780                         importer = next;
 781                         VM_WARN_ON(expand != importer);
 782                 }
 783
 784                 /*
 785                  * Easily overlooked: when mprotect shifts the boundary,
 786                  * make sure the expanding vma has anon_vma set if the
 787                  * shrinking vma had, to cover any anon pages imported.
 788                  */
 789                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
 790                         int error;
 791
 792                         importer->anon_vma = exporter->anon_vma;
 793                         error = anon_vma_clone(importer, exporter);
 794                         if (error)
 795                                 return error;
 796                 }
 797         }
 798 again:
 799         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
 800
 801         if (file) {
 802                 mapping = file->f_mapping;
 803                 root = &mapping->i_mmap;
 804                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
 805
 806                 if (adjust_next)
 807                         uprobe_munmap(next, next->vm_start, next->vm_end);
 808
 809                 i_mmap_lock_write(mapping);
 810                 if (insert) {
 811                         /*
 812                          * Put into interval tree now, so instantiated pages
 813                          * are visible to arm/parisc __flush_dcache_page
 814                          * throughout; but we cannot insert into address
 815                          * space until vma start or end is updated.
 816                          */
 817                         __vma_link_file(insert);
 818                 }
 819         }
 820
 821         anon_vma = vma->anon_vma;
 822         if (!anon_vma && adjust_next)
 823                 anon_vma = next->anon_vma;
 824         if (anon_vma) {
 825                 VM_WARN_ON(adjust_next && next->anon_vma &&
 826                            anon_vma != next->anon_vma);
 827                 anon_vma_lock_write(anon_vma);
 828                 anon_vma_interval_tree_pre_update_vma(vma);
 829                 if (adjust_next)
 830                         anon_vma_interval_tree_pre_update_vma(next);
 831         }
 832
 833         if (root) {
 834                 flush_dcache_mmap_lock(mapping);
 835                 vma_interval_tree_remove(vma, root);
 836                 if (adjust_next)
 837                         vma_interval_tree_remove(next, root);
 838         }
 839
 840         if (start != vma->vm_start) {
 841                 vma->vm_start = start;
 842                 start_changed = true;
 843         }
 844         if (end != vma->vm_end) {
 845                 vma->vm_end = end;
 846                 end_changed = true;
 847         }
 848         vma->vm_pgoff = pgoff;
 849         if (adjust_next) {
 850                 next->vm_start += adjust_next << PAGE_SHIFT;
 851                 next->vm_pgoff += adjust_next;
 852         }
 853
 854         if (root) {
 855                 if (adjust_next)
 856                         vma_interval_tree_insert(next, root);
 857                 vma_interval_tree_insert(vma, root);
 858                 flush_dcache_mmap_unlock(mapping);
 859         }
 860
 861         if (remove_next) {
 862                 /*
 863                  * vma_merge has merged next into vma, and needs
 864                  * us to remove next before dropping the locks.
 865                  */
 866                 if (remove_next != 3)
 867                         __vma_unlink_common(mm, next, next);
 868                 else
 869                         /*
 870                          * vma is not before next if they've been
 871                          * swapped.
 872                          *
 873                          * pre-swap() next->vm_start was reduced so
 874                          * tell validate_mm_rb to ignore pre-swap()
 875                          * "next" (which is stored in post-swap()
 876                          * "vma").
 877                          */
 878                         __vma_unlink_common(mm, next, vma);
 879                 if (file)
 880                         __remove_shared_vm_struct(next, file, mapping);
 881         } else if (insert) {
 882                 /*
 883                  * split_vma has split insert from vma, and needs
 884                  * us to insert it before dropping the locks
 885                  * (it may either follow vma or precede it).
 886                  */
 887                 __insert_vm_struct(mm, insert);
 888         } else {
 889                 if (start_changed)
 890                         vma_gap_update(vma);
 891                 if (end_changed) {
 892                         if (!next)
 893                                 mm->highest_vm_end = vm_end_gap(vma);
 894                         else if (!adjust_next)
 895                                 vma_gap_update(next);
 896                 }
 897         }
 898
 899         if (anon_vma) {
 900                 anon_vma_interval_tree_post_update_vma(vma);
 901                 if (adjust_next)
 902                         anon_vma_interval_tree_post_update_vma(next);
 903                 anon_vma_unlock_write(anon_vma);
 904         }
 905         if (mapping)
 906                 i_mmap_unlock_write(mapping);
 907
 908         if (root) {
 909                 uprobe_mmap(vma);
 910
 911                 if (adjust_next)
 912                         uprobe_mmap(next);
 913         }
 914
 915         if (remove_next) {
 916                 if (file) {
 917                         uprobe_munmap(next, next->vm_start, next->vm_end);
 918                         fput(file);
 919                 }
 920                 if (next->anon_vma)
 921                         anon_vma_merge(vma, next);
 922                 mm->map_count--;
 923                 mpol_put(vma_policy(next));
 924                 vm_area_free(next);
 925                 /*
 926                  * In mprotect's case 6 (see comments on vma_merge),
 927                  * we must remove another next too. It would clutter
 928                  * up the code too much to do both in one go.
 929                  */
 930                 if (remove_next != 3) {
 931                         /*
 932                          * If "next" was removed and vma->vm_end was
 933                          * expanded (up) over it, in turn
 934                          * "next->vm_prev->vm_end" changed and the
 935                          * "vma->vm_next" gap must be updated.
 936                          */
 937                         next = vma->vm_next;
 938                 } else {
 939                         /*
 940                          * For the scope of the comment "next" and
 941                          * "vma" considered pre-swap(): if "vma" was
 942                          * removed, next->vm_start was expanded (down)
 943                          * over it and the "next" gap must be updated.
 944                          * Because of the swap() the post-swap() "vma"
 945                          * actually points to pre-swap() "next"
 946                          * (post-swap() "next" as opposed is now a
 947                          * dangling pointer).
 948                          */
 949                         next = vma;
 950                 }
 951                 if (remove_next == 2) {
 952                         remove_next = 1;
 953                         end = next->vm_end;
 954                         goto again;
 955                 }
 956                 else if (next)
 957                         vma_gap_update(next);
 958                 else {
 959                         /*
 960                          * If remove_next == 2 we obviously can't
 961                          * reach this path.
 962                          *
 963                          * If remove_next == 3 we can't reach this
 964                          * path because pre-swap() next is always not
 965                          * NULL. pre-swap() "next" is not being
 966                          * removed and its next->vm_end is not altered
 967                          * (and furthermore "end" already matches
 968                          * next->vm_end in remove_next == 3).
 969                          *
 970                          * We reach this only in the remove_next == 1
 971                          * case if the "next" vma that was removed was
 972                          * the highest vma of the mm. However in such
 973                          * case next->vm_end == "end" and the extended
 974                          * "vma" has vma->vm_end == next->vm_end so
 975                          * mm->highest_vm_end doesn't need any update
 976                          * in remove_next == 1 case.
 977                          */
 978                         VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
 979                 }
 980         }
 981         if (insert && file)
 982                 uprobe_mmap(insert);
 983
 984         validate_mm(mm);
 985
 986         return 0;
 987 }
 988
 989 /*
 990  * If the vma has a ->close operation then the driver probably needs to release
 991  * per-vma resources, so we don't attempt to merge those.
 992  */
 993 static inline int is_mergeable_vma(struct vm_area_struct *vma,
 994                                 struct file *file, unsigned long vm_flags,
 995                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
 996 {
 997         /*
 998          * VM_SOFTDIRTY should not prevent from VMA merging, if we
 999          * match the flags but dirty bit -- the caller should mark
1000          * merged VMA as dirty. If dirty bit won't be excluded from
1001          * comparison, we increase pressure on the memory system forcing
1002          * the kernel to generate new VMAs when old one could be
1003          * extended instead.
1004          */
1005         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
1006                 return 0;
1007         if (vma->vm_file != file)
1008                 return 0;
1009         if (vma->vm_ops && vma->vm_ops->close)
1010                 return 0;
1011         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
1012                 return 0;
1013         return 1;
1014 }
1015
1016 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
1017                                         struct anon_vma *anon_vma2,
1018                                         struct vm_area_struct *vma)
1019 {
1020         /*
1021          * The list_is_singular() test is to avoid merging VMA cloned from
1022          * parents. This can improve scalability caused by anon_vma lock.
1023          */
1024         if ((!anon_vma1 || !anon_vma2) && (!vma ||
1025                 list_is_singular(&vma->anon_vma_chain)))
1026                 return 1;
1027         return anon_vma1 == anon_vma2;
1028 }
1029
1030 /*
1031  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1032  * in front of (at a lower virtual address and file offset than) the vma.
1033  *
1034  * We cannot merge two vmas if they have differently assigned (non-NULL)
1035  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1036  *
1037  * We don't check here for the merged mmap wrapping around the end of pagecache
1038  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
1039  * wrap, nor mmaps which cover the final page at index -1UL.
1040  */
1041 static int
1042 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1043                      struct anon_vma *anon_vma, struct file *file,
1044                      pgoff_t vm_pgoff,
1045                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1046 {
1047         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1048             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1049                 if (vma->vm_pgoff == vm_pgoff)
1050                         return 1;
1051         }
1052         return 0;
1053 }
1054
1055 /*
1056  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1057  * beyond (at a higher virtual address and file offset than) the vma.
1058  *
1059  * We cannot merge two vmas if they have differently assigned (non-NULL)
1060  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1061  */
1062 static int
1063 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1064                     struct anon_vma *anon_vma, struct file *file,
1065                     pgoff_t vm_pgoff,
1066                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1067 {
1068         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1069             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1070                 pgoff_t vm_pglen;
1071                 vm_pglen = vma_pages(vma);
1072                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1073                         return 1;
1074         }
1075         return 0;
1076 }
1077
1078 /*
1079  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1080  * whether that can be merged with its predecessor or its successor.
1081  * Or both (it neatly fills a hole).
1082  *
1083  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1084  * certain not to be mapped by the time vma_merge is called; but when
1085  * called for mprotect, it is certain to be already mapped (either at
1086  * an offset within prev, or at the start of next), and the flags of
1087  * this area are about to be changed to vm_flags - and the no-change
1088  * case has already been eliminated.
1089  *
1090  * The following mprotect cases have to be considered, where AAAA is
1091  * the area passed down from mprotect_fixup, never extending beyond one
1092  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1093  *
1094  *     AAAA             AAAA                   AAAA
1095  *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
1096  *    cannot merge    might become       might become
1097  *                    PPNNNNNNNNNN       PPPPPPPPPPNN
1098  *    mmap, brk or    case 4 below       case 5 below
1099  *    mremap move:
1100  *                        AAAA               AAAA
1101  *                    PPPP    NNNN       PPPPNNNNXXXX
1102  *                    might become       might become
1103  *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
1104  *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
1105  *                    PPPPNNNNNNNN 3     PPPPXXXXXXXX 8
1106  *
1107  * It is important for case 8 that the vma NNNN overlapping the
1108  * region AAAA is never going to extended over XXXX. Instead XXXX must
1109  * be extended in region AAAA and NNNN must be removed. This way in
1110  * all cases where vma_merge succeeds, the moment vma_adjust drops the
1111  * rmap_locks, the properties of the merged vma will be already
1112  * correct for the whole merged range. Some of those properties like
1113  * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1114  * be correct for the whole merged range immediately after the
1115  * rmap_locks are released. Otherwise if XXXX would be removed and
1116  * NNNN would be extended over the XXXX range, remove_migration_ptes
1117  * or other rmap walkers (if working on addresses beyond the "end"
1118  * parameter) may establish ptes with the wrong permissions of NNNN
1119  * instead of the right permissions of XXXX.
1120  */
1121 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1122                         struct vm_area_struct *prev, unsigned long addr,
1123                         unsigned long end, unsigned long vm_flags,
1124                         struct anon_vma *anon_vma, struct file *file,
1125                         pgoff_t pgoff, struct mempolicy *policy,
1126                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1127 {
1128         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1129         struct vm_area_struct *area, *next;
1130         int err;
1131
1132         /*
1133          * We later require that vma->vm_flags == vm_flags,
1134          * so this tests vma->vm_flags & VM_SPECIAL, too.
1135          */
1136         if (vm_flags & VM_SPECIAL)
1137                 return NULL;
1138
1139         if (prev)
1140                 next = prev->vm_next;
1141         else
1142                 next = mm->mmap;
1143         area = next;
1144         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
1145                 next = next->vm_next;
1146
1147         /* verify some invariant that must be enforced by the caller */
1148         VM_WARN_ON(prev && addr <= prev->vm_start);
1149         VM_WARN_ON(area && end > area->vm_end);
1150         VM_WARN_ON(addr >= end);
1151
1152         /*
1153          * Can it merge with the predecessor?
1154          */
1155         if (prev && prev->vm_end == addr &&
1156                         mpol_equal(vma_policy(prev), policy) &&
1157                         can_vma_merge_after(prev, vm_flags,
1158                                             anon_vma, file, pgoff,
1159                                             vm_userfaultfd_ctx)) {
1160                 /*
1161                  * OK, it can.  Can we now merge in the successor as well?
1162                  */
1163                 if (next && end == next->vm_start &&
1164                                 mpol_equal(policy, vma_policy(next)) &&
1165                                 can_vma_merge_before(next, vm_flags,
1166                                                      anon_vma, file,
1167                                                      pgoff+pglen,
1168                                                      vm_userfaultfd_ctx) &&
1169                                 is_mergeable_anon_vma(prev->anon_vma,
1170                                                       next->anon_vma, NULL)) {
1171                                                         /* cases 1, 6 */
1172                         err = __vma_adjust(prev, prev->vm_start,
1173                                          next->vm_end, prev->vm_pgoff, NULL,
1174                                          prev);
1175                 } else                                  /* cases 2, 5, 7 */
1176                         err = __vma_adjust(prev, prev->vm_start,
1177                                          end, prev->vm_pgoff, NULL, prev);
1178                 if (err)
1179                         return NULL;
1180                 khugepaged_enter_vma_merge(prev, vm_flags);
1181                 return prev;
1182         }
1183
1184         /*
1185          * Can this new request be merged in front of next?
1186          */
1187         if (next && end == next->vm_start &&
1188                         mpol_equal(policy, vma_policy(next)) &&
1189                         can_vma_merge_before(next, vm_flags,
1190                                              anon_vma, file, pgoff+pglen,
1191                                              vm_userfaultfd_ctx)) {
1192                 if (prev && addr < prev->vm_end)        /* case 4 */
1193                         err = __vma_adjust(prev, prev->vm_start,
1194                                          addr, prev->vm_pgoff, NULL, next);
1195                 else {                                  /* cases 3, 8 */
1196                         err = __vma_adjust(area, addr, next->vm_end,
1197                                          next->vm_pgoff - pglen, NULL, next);
1198                         /*
1199                          * In case 3 area is already equal to next and
1200                          * this is a noop, but in case 8 "area" has
1201                          * been removed and next was expanded over it.
1202                          */
1203                         area = next;
1204                 }
1205                 if (err)
1206                         return NULL;
1207                 khugepaged_enter_vma_merge(area, vm_flags);
1208                 return area;
1209         }
1210
1211         return NULL;
1212 }
1213
1214 /*
1215  * Rough compatbility check to quickly see if it's even worth looking
1216  * at sharing an anon_vma.
1217  *
1218  * They need to have the same vm_file, and the flags can only differ
1219  * in things that mprotect may change.
1220  *
1221  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1222  * we can merge the two vma's. For example, we refuse to merge a vma if
1223  * there is a vm_ops->close() function, because that indicates that the
1224  * driver is doing some kind of reference counting. But that doesn't
1225  * really matter for the anon_vma sharing case.
1226  */
1227 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1228 {
1229         return a->vm_end == b->vm_start &&
1230                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1231                 a->vm_file == b->vm_file &&
1232                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1233                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1234 }
1235
1236 /*
1237  * Do some basic sanity checking to see if we can re-use the anon_vma
1238  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1239  * the same as 'old', the other will be the new one that is trying
1240  * to share the anon_vma.
1241  *
1242  * NOTE! This runs with mm_sem held for reading, so it is possible that
1243  * the anon_vma of 'old' is concurrently in the process of being set up
1244  * by another page fault trying to merge _that_. But that's ok: if it
1245  * is being set up, that automatically means that it will be a singleton
1246  * acceptable for merging, so we can do all of this optimistically. But
1247  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1248  *
1249  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1250  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1251  * is to return an anon_vma that is "complex" due to having gone through
1252  * a fork).
1253  *
1254  * We also make sure that the two vma's are compatible (adjacent,
1255  * and with the same memory policies). That's all stable, even with just
1256  * a read lock on the mm_sem.
1257  */
1258 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1259 {
1260         if (anon_vma_compatible(a, b)) {
1261                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1262
1263                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1264                         return anon_vma;
1265         }
1266         return NULL;
1267 }
1268
1269 /*
1270  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1271  * neighbouring vmas for a suitable anon_vma, before it goes off
1272  * to allocate a new anon_vma.  It checks because a repetitive
1273  * sequence of mprotects and faults may otherwise lead to distinct
1274  * anon_vmas being allocated, preventing vma merge in subsequent
1275  * mprotect.
1276  */
1277 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1278 {
1279         struct anon_vma *anon_vma;
1280         struct vm_area_struct *near;
1281
1282         near = vma->vm_next;
1283         if (!near)
1284                 goto try_prev;
1285
1286         anon_vma = reusable_anon_vma(near, vma, near);
1287         if (anon_vma)
1288                 return anon_vma;
1289 try_prev:
1290         near = vma->vm_prev;
1291         if (!near)
1292                 goto none;
1293
1294         anon_vma = reusable_anon_vma(near, near, vma);
1295         if (anon_vma)
1296                 return anon_vma;
1297 none:
1298         /*
1299          * There's no absolute need to look only at touching neighbours:
1300          * we could search further afield for "compatible" anon_vmas.
1301          * But it would probably just be a waste of time searching,
1302          * or lead to too many vmas hanging off the same anon_vma.
1303          * We're trying to allow mprotect remerging later on,
1304          * not trying to minimize memory used for anon_vmas.
1305          */
1306         return NULL;
1307 }
1308
1309 /*
1310  * If a hint addr is less than mmap_min_addr change hint to be as
1311  * low as possible but still greater than mmap_min_addr
1312  */
1313 static inline unsigned long round_hint_to_min(unsigned long hint)
1314 {
1315         hint &= PAGE_MASK;
1316         if (((void *)hint != NULL) &&
1317             (hint < mmap_min_addr))
1318                 return PAGE_ALIGN(mmap_min_addr);
1319         return hint;
1320 }
1321
1322 static inline int mlock_future_check(struct mm_struct *mm,
1323                                      unsigned long flags,
1324                                      unsigned long len)
1325 {
1326         unsigned long locked, lock_limit;
1327
1328         /*  mlock MCL_FUTURE? */
1329         if (flags & VM_LOCKED) {
1330                 locked = len >> PAGE_SHIFT;
1331                 locked += mm->locked_vm;
1332                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1333                 lock_limit >>= PAGE_SHIFT;
1334                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1335                         return -EAGAIN;
1336         }
1337         return 0;
1338 }
1339
1340 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
1341 {
1342         if (S_ISREG(inode->i_mode))
1343                 return MAX_LFS_FILESIZE;
1344
1345         if (S_ISBLK(inode->i_mode))
1346                 return MAX_LFS_FILESIZE;
1347
1348         if (S_ISSOCK(inode->i_mode))
1349                 return MAX_LFS_FILESIZE;
1350
1351         /* Special "we do even unsigned file positions" case */
1352         if (file->f_mode & FMODE_UNSIGNED_OFFSET)
1353                 return 0;
1354
1355         /* Yes, random drivers might want more. But I'm tired of buggy drivers */
1356         return ULONG_MAX;
1357 }
1358
1359 static inline bool file_mmap_ok(struct file *file, struct inode *inode,
1360                                 unsigned long pgoff, unsigned long len)
1361 {
1362         u64 maxsize = file_mmap_size_max(file, inode);
1363
1364         if (maxsize && len > maxsize)
1365                 return false;
1366         maxsize -= len;
1367         if (pgoff > maxsize >> PAGE_SHIFT)
1368                 return false;
1369         return true;
1370 }
1371
1372 /*
1373  * The caller must hold down_write(&current->mm->mmap_sem).
1374  */
1375 unsigned long do_mmap(struct file *file, unsigned long addr,
1376                         unsigned long len, unsigned long prot,
1377                         unsigned long flags, vm_flags_t vm_flags,
1378                         unsigned long pgoff, unsigned long *populate,
1379                         struct list_head *uf)
1380 {
1381         struct mm_struct *mm = current->mm;
1382         int pkey = 0;
1383
1384         *populate = 0;
1385
1386         if (!len)
1387                 return -EINVAL;
1388
1389         /*
1390          * Does the application expect PROT_READ to imply PROT_EXEC?
1391          *
1392          * (the exception is when the underlying filesystem is noexec
1393          *  mounted, in which case we dont add PROT_EXEC.)
1394          */
1395         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1396                 if (!(file && path_noexec(&file->f_path)))
1397                         prot |= PROT_EXEC;
1398
1399         /* force arch specific MAP_FIXED handling in get_unmapped_area */
1400         if (flags & MAP_FIXED_NOREPLACE)
1401                 flags |= MAP_FIXED;
1402
1403         if (!(flags & MAP_FIXED))
1404                 addr = round_hint_to_min(addr);
1405
1406         /* Careful about overflows.. */
1407         len = PAGE_ALIGN(len);
1408         if (!len)
1409                 return -ENOMEM;
1410
1411         /* offset overflow? */
1412         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1413                 return -EOVERFLOW;
1414
1415         /* Too many mappings? */
1416         if (mm->map_count > sysctl_max_map_count)
1417                 return -ENOMEM;
1418
1419         /* Obtain the address to map to. we verify (or select) it and ensure
1420          * that it represents a valid section of the address space.
1421          */
1422         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1423         if (IS_ERR_VALUE(addr))
1424                 return addr;
1425
1426         if (flags & MAP_FIXED_NOREPLACE) {
1427                 struct vm_area_struct *vma = find_vma(mm, addr);
1428
1429                 if (vma && vma->vm_start < addr + len)
1430                         return -EEXIST;
1431         }
1432
1433         if (prot == PROT_EXEC) {
1434                 pkey = execute_only_pkey(mm);
1435                 if (pkey < 0)
1436                         pkey = 0;
1437         }
1438
1439         /* Do simple checking here so the lower-level routines won't have
1440          * to. we assume access permissions have been handled by the open
1441          * of the memory object, so we don't do any here.
1442          */
1443         vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1444                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1445
1446         if (flags & MAP_LOCKED)
1447                 if (!can_do_mlock())
1448                         return -EPERM;
1449
1450         if (mlock_future_check(mm, vm_flags, len))
1451                 return -EAGAIN;
1452
1453         if (file) {
1454                 struct inode *inode = file_inode(file);
1455                 unsigned long flags_mask;
1456
1457                 if (!file_mmap_ok(file, inode, pgoff, len))
1458                         return -EOVERFLOW;
1459
1460                 flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
1461
1462                 switch (flags & MAP_TYPE) {
1463                 case MAP_SHARED:
1464                         /*
1465                          * Force use of MAP_SHARED_VALIDATE with non-legacy
1466                          * flags. E.g. MAP_SYNC is dangerous to use with
1467                          * MAP_SHARED as you don't know which consistency model
1468                          * you will get. We silently ignore unsupported flags
1469                          * with MAP_SHARED to preserve backward compatibility.
1470                          */
1471                         flags &= LEGACY_MAP_MASK;
1472                         /* fall through */
1473                 case MAP_SHARED_VALIDATE:
1474                         if (flags & ~flags_mask)
1475                                 return -EOPNOTSUPP;
1476                         if (prot & PROT_WRITE) {
1477                                 if (!(file->f_mode & FMODE_WRITE))
1478                                         return -EACCES;
1479                                 if (IS_SWAPFILE(file->f_mapping->host))
1480                                         return -ETXTBSY;
1481                         }
1482
1483                         /*
1484                          * Make sure we don't allow writing to an append-only
1485                          * file..
1486                          */
1487                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1488                                 return -EACCES;
1489
1490                         /*
1491                          * Make sure there are no mandatory locks on the file.
1492                          */
1493                         if (locks_verify_locked(file))
1494                                 return -EAGAIN;
1495
1496                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1497                         if (!(file->f_mode & FMODE_WRITE))
1498                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1499
1500                         /* fall through */
1501                 case MAP_PRIVATE:
1502                         if (!(file->f_mode & FMODE_READ))
1503                                 return -EACCES;
1504                         if (path_noexec(&file->f_path)) {
1505                                 if (vm_flags & VM_EXEC)
1506                                         return -EPERM;
1507                                 vm_flags &= ~VM_MAYEXEC;
1508                         }
1509
1510                         if (!file->f_op->mmap)
1511                                 return -ENODEV;
1512                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1513                                 return -EINVAL;
1514                         break;
1515
1516                 default:
1517                         return -EINVAL;
1518                 }
1519         } else {
1520                 switch (flags & MAP_TYPE) {
1521                 case MAP_SHARED:
1522                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1523                                 return -EINVAL;
1524                         /*
1525                          * Ignore pgoff.
1526                          */
1527                         pgoff = 0;
1528                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1529                         break;
1530                 case MAP_PRIVATE:
1531                         /*
1532                          * Set pgoff according to addr for anon_vma.
1533                          */
1534                         pgoff = addr >> PAGE_SHIFT;
1535                         break;
1536                 default:
1537                         return -EINVAL;
1538                 }
1539         }
1540
1541         /*
1542          * Set 'VM_NORESERVE' if we should not account for the
1543          * memory use of this mapping.
1544          */
1545         if (flags & MAP_NORESERVE) {
1546                 /* We honor MAP_NORESERVE if allowed to overcommit */
1547                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1548                         vm_flags |= VM_NORESERVE;
1549
1550                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1551                 if (file && is_file_hugepages(file))
1552                         vm_flags |= VM_NORESERVE;
1553         }
1554
1555         addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1556         if (!IS_ERR_VALUE(addr) &&
1557             ((vm_flags & VM_LOCKED) ||
1558              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1559                 *populate = len;
1560         return addr;
1561 }
1562
1563 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1564                               unsigned long prot, unsigned long flags,
1565                               unsigned long fd, unsigned long pgoff)
1566 {
1567         struct file *file = NULL;
1568         unsigned long retval;
1569
1570         addr = untagged_addr(addr);
1571
1572         if (!(flags & MAP_ANONYMOUS)) {
1573                 audit_mmap_fd(fd, flags);
1574                 file = fget(fd);
1575                 if (!file)
1576                         return -EBADF;
1577                 if (is_file_hugepages(file))
1578                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1579                 retval = -EINVAL;
1580                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1581                         goto out_fput;
1582         } else if (flags & MAP_HUGETLB) {
1583                 struct user_struct *user = NULL;
1584                 struct hstate *hs;
1585
1586                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1587                 if (!hs)
1588                         return -EINVAL;
1589
1590                 len = ALIGN(len, huge_page_size(hs));
1591                 /*
1592                  * VM_NORESERVE is used because the reservations will be
1593                  * taken when vm_ops->mmap() is called
1594                  * A dummy user value is used because we are not locking
1595                  * memory so no accounting is necessary
1596                  */
1597                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1598                                 VM_NORESERVE,
1599                                 &user, HUGETLB_ANONHUGE_INODE,
1600                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1601                 if (IS_ERR(file))
1602                         return PTR_ERR(file);
1603         }
1604
1605         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1606
1607         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1608 out_fput:
1609         if (file)
1610                 fput(file);
1611         return retval;
1612 }
1613
1614 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1615                 unsigned long, prot, unsigned long, flags,
1616                 unsigned long, fd, unsigned long, pgoff)
1617 {
1618         return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1619 }
1620
1621 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1622 struct mmap_arg_struct {
1623         unsigned long addr;
1624         unsigned long len;
1625         unsigned long prot;
1626         unsigned long flags;
1627         unsigned long fd;
1628         unsigned long offset;
1629 };
1630
1631 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1632 {
1633         struct mmap_arg_struct a;
1634
1635         if (copy_from_user(&a, arg, sizeof(a)))
1636                 return -EFAULT;
1637         if (offset_in_page(a.offset))
1638                 return -EINVAL;
1639
1640         return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1641                                a.offset >> PAGE_SHIFT);
1642 }
1643 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1644
1645 /*
1646  * Some shared mappings will want the pages marked read-only
1647  * to track write events. If so, we'll downgrade vm_page_prot
1648  * to the private version (using protection_map[] without the
1649  * VM_SHARED bit).
1650  */
1651 int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1652 {
1653         vm_flags_t vm_flags = vma->vm_flags;
1654         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1655
1656         /* If it was private or non-writable, the write bit is already clear */
1657         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1658                 return 0;
1659
1660         /* The backer wishes to know when pages are first written to? */
1661         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1662                 return 1;
1663
1664         /* The open routine did something to the protections that pgprot_modify
1665          * won't preserve? */
1666         if (pgprot_val(vm_page_prot) !=
1667             pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1668                 return 0;
1669
1670         /* Do we need to track softdirty? */
1671         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1672                 return 1;
1673
1674         /* Specialty mapping? */
1675         if (vm_flags & VM_PFNMAP)
1676                 return 0;
1677
1678         /* Can the mapping track the dirty pages? */
1679         return vma->vm_file && vma->vm_file->f_mapping &&
1680                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1681 }
1682
1683 /*
1684  * We account for memory if it's a private writeable mapping,
1685  * not hugepages and VM_NORESERVE wasn't set.
1686  */
1687 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1688 {
1689         /*
1690          * hugetlb has its own accounting separate from the core VM
1691          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1692          */
1693         if (file && is_file_hugepages(file))
1694                 return 0;
1695
1696         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1697 }
1698
1699 unsigned long mmap_region(struct file *file, unsigned long addr,
1700                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1701                 struct list_head *uf)
1702 {
1703         struct mm_struct *mm = current->mm;
1704         struct vm_area_struct *vma, *prev;
1705         int error;
1706         struct rb_node **rb_link, *rb_parent;
1707         unsigned long charged = 0;
1708
1709         /* Check against address space limit. */
1710         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1711                 unsigned long nr_pages;
1712
1713                 /*
1714                  * MAP_FIXED may remove pages of mappings that intersects with
1715                  * requested mapping. Account for the pages it would unmap.
1716                  */
1717                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1718
1719                 if (!may_expand_vm(mm, vm_flags,
1720                                         (len >> PAGE_SHIFT) - nr_pages))
1721                         return -ENOMEM;
1722         }
1723
1724         /* Clear old maps */
1725         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1726                               &rb_parent)) {
1727                 if (do_munmap(mm, addr, len, uf))
1728                         return -ENOMEM;
1729         }
1730
1731         /*
1732          * Private writable mapping: check memory availability
1733          */
1734         if (accountable_mapping(file, vm_flags)) {
1735                 charged = len >> PAGE_SHIFT;
1736                 if (security_vm_enough_memory_mm(mm, charged))
1737                         return -ENOMEM;
1738                 vm_flags |= VM_ACCOUNT;
1739         }
1740
1741         /*
1742          * Can we just expand an old mapping?
1743          */
1744         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1745                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1746         if (vma)
1747                 goto out;
1748
1749         /*
1750          * Determine the object being mapped and call the appropriate
1751          * specific mapper. the address has already been validated, but
1752          * not unmapped, but the maps are removed from the list.
1753          */
1754         vma = vm_area_alloc(mm);
1755         if (!vma) {
1756                 error = -ENOMEM;
1757                 goto unacct_error;
1758         }
1759
1760         vma->vm_start = addr;
1761         vma->vm_end = addr + len;
1762         vma->vm_flags = vm_flags;
1763         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1764         vma->vm_pgoff = pgoff;
1765
1766         if (file) {
1767                 if (vm_flags & VM_DENYWRITE) {
1768                         error = deny_write_access(file);
1769                         if (error)
1770                                 goto free_vma;
1771                 }
1772                 if (vm_flags & VM_SHARED) {
1773                         error = mapping_map_writable(file->f_mapping);
1774                         if (error)
1775                                 goto allow_write_and_free_vma;
1776                 }
1777
1778                 /* ->mmap() can change vma->vm_file, but must guarantee that
1779                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1780                  * and map writably if VM_SHARED is set. This usually means the
1781                  * new file must not have been exposed to user-space, yet.
1782                  */
1783                 vma->vm_file = get_file(file);
1784                 error = call_mmap(file, vma);
1785                 if (error)
1786                         goto unmap_and_free_vma;
1787
1788                 /* Can addr have changed??
1789                  *
1790                  * Answer: Yes, several device drivers can do it in their
1791                  *         f_op->mmap method. -DaveM
1792                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1793                  *      be updated for vma_link()
1794                  */
1795                 WARN_ON_ONCE(addr != vma->vm_start);
1796
1797                 addr = vma->vm_start;
1798                 vm_flags = vma->vm_flags;
1799         } else if (vm_flags & VM_SHARED) {
1800                 error = shmem_zero_setup(vma);
1801                 if (error)
1802                         goto free_vma;
1803         } else {
1804                 vma_set_anonymous(vma);
1805         }
1806
1807         vma_link(mm, vma, prev, rb_link, rb_parent);
1808         /* Once vma denies write, undo our temporary denial count */
1809         if (file) {
1810                 if (vm_flags & VM_SHARED)
1811                         mapping_unmap_writable(file->f_mapping);
1812                 if (vm_flags & VM_DENYWRITE)
1813                         allow_write_access(file);
1814         }
1815         file = vma->vm_file;
1816 out:
1817         perf_event_mmap(vma);
1818
1819         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1820         if (vm_flags & VM_LOCKED) {
1821                 if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
1822                                         is_vm_hugetlb_page(vma) ||
1823                                         vma == get_gate_vma(current->mm))
1824                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1825                 else
1826                         mm->locked_vm += (len >> PAGE_SHIFT);
1827         }
1828
1829         if (file)
1830                 uprobe_mmap(vma);
1831
1832         /*
1833          * New (or expanded) vma always get soft dirty status.
1834          * Otherwise user-space soft-dirty page tracker won't
1835          * be able to distinguish situation when vma area unmapped,
1836          * then new mapped in-place (which must be aimed as
1837          * a completely new data area).
1838          */
1839         vma->vm_flags |= VM_SOFTDIRTY;
1840
1841         vma_set_page_prot(vma);
1842
1843         return addr;
1844
1845 unmap_and_free_vma:
1846         vma->vm_file = NULL;
1847         fput(file);
1848
1849         /* Undo any partial mapping done by a device driver. */
1850         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1851         charged = 0;
1852         if (vm_flags & VM_SHARED)
1853                 mapping_unmap_writable(file->f_mapping);
1854 allow_write_and_free_vma:
1855         if (vm_flags & VM_DENYWRITE)
1856                 allow_write_access(file);
1857 free_vma:
1858         vm_area_free(vma);
1859 unacct_error:
1860         if (charged)
1861                 vm_unacct_memory(charged);
1862         return error;
1863 }
1864
1865 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1866 {
1867         /*
1868          * We implement the search by looking for an rbtree node that
1869          * immediately follows a suitable gap. That is,
1870          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1871          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1872          * - gap_end - gap_start >= length
1873          */
1874
1875         struct mm_struct *mm = current->mm;
1876         struct vm_area_struct *vma;
1877         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1878
1879         /* Adjust search length to account for worst case alignment overhead */
1880         length = info->length + info->align_mask;
1881         if (length < info->length)
1882                 return -ENOMEM;
1883
1884         /* Adjust search limits by the desired length */
1885         if (info->high_limit < length)
1886                 return -ENOMEM;
1887         high_limit = info->high_limit - length;
1888
1889         if (info->low_limit > high_limit)
1890                 return -ENOMEM;
1891         low_limit = info->low_limit + length;
1892
1893         /* Check if rbtree root looks promising */
1894         if (RB_EMPTY_ROOT(&mm->mm_rb))
1895                 goto check_highest;
1896         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1897         if (vma->rb_subtree_gap < length)
1898                 goto check_highest;
1899
1900         while (true) {
1901                 /* Visit left subtree if it looks promising */
1902                 gap_end = vm_start_gap(vma);
1903                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1904                         struct vm_area_struct *left =
1905                                 rb_entry(vma->vm_rb.rb_left,
1906                                          struct vm_area_struct, vm_rb);
1907                         if (left->rb_subtree_gap >= length) {
1908                                 vma = left;
1909                                 continue;
1910                         }
1911                 }
1912
1913                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1914 check_current:
1915                 /* Check if current node has a suitable gap */
1916                 if (gap_start > high_limit)
1917                         return -ENOMEM;
1918                 if (gap_end >= low_limit &&
1919                     gap_end > gap_start && gap_end - gap_start >= length)
1920                         goto found;
1921
1922                 /* Visit right subtree if it looks promising */
1923                 if (vma->vm_rb.rb_right) {
1924                         struct vm_area_struct *right =
1925                                 rb_entry(vma->vm_rb.rb_right,
1926                                          struct vm_area_struct, vm_rb);
1927                         if (right->rb_subtree_gap >= length) {
1928                                 vma = right;
1929                                 continue;
1930                         }
1931                 }
1932
1933                 /* Go back up the rbtree to find next candidate node */
1934                 while (true) {
1935                         struct rb_node *prev = &vma->vm_rb;
1936                         if (!rb_parent(prev))
1937                                 goto check_highest;
1938                         vma = rb_entry(rb_parent(prev),
1939                                        struct vm_area_struct, vm_rb);
1940                         if (prev == vma->vm_rb.rb_left) {
1941                                 gap_start = vm_end_gap(vma->vm_prev);
1942                                 gap_end = vm_start_gap(vma);
1943                                 goto check_current;
1944                         }
1945                 }
1946         }
1947
1948 check_highest:
1949         /* Check highest gap, which does not precede any rbtree node */
1950         gap_start = mm->highest_vm_end;
1951         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1952         if (gap_start > high_limit)
1953                 return -ENOMEM;
1954
1955 found:
1956         /* We found a suitable gap. Clip it with the original low_limit. */
1957         if (gap_start < info->low_limit)
1958                 gap_start = info->low_limit;
1959
1960         /* Adjust gap address to the desired alignment */
1961         gap_start += (info->align_offset - gap_start) & info->align_mask;
1962
1963         VM_BUG_ON(gap_start + info->length > info->high_limit);
1964         VM_BUG_ON(gap_start + info->length > gap_end);
1965         return gap_start;
1966 }
1967
1968 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1969 {
1970         struct mm_struct *mm = current->mm;
1971         struct vm_area_struct *vma;
1972         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1973
1974         /* Adjust search length to account for worst case alignment overhead */
1975         length = info->length + info->align_mask;
1976         if (length < info->length)
1977                 return -ENOMEM;
1978
1979         /*
1980          * Adjust search limits by the desired length.
1981          * See implementation comment at top of unmapped_area().
1982          */
1983         gap_end = info->high_limit;
1984         if (gap_end < length)
1985                 return -ENOMEM;
1986         high_limit = gap_end - length;
1987
1988         if (info->low_limit > high_limit)
1989                 return -ENOMEM;
1990         low_limit = info->low_limit + length;
1991
1992         /* Check highest gap, which does not precede any rbtree node */
1993         gap_start = mm->highest_vm_end;
1994         if (gap_start <= high_limit)
1995                 goto found_highest;
1996
1997         /* Check if rbtree root looks promising */
1998         if (RB_EMPTY_ROOT(&mm->mm_rb))
1999                 return -ENOMEM;
2000         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
2001         if (vma->rb_subtree_gap < length)
2002                 return -ENOMEM;
2003
2004         while (true) {
2005                 /* Visit right subtree if it looks promising */
2006                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
2007                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
2008                         struct vm_area_struct *right =
2009                                 rb_entry(vma->vm_rb.rb_right,
2010                                          struct vm_area_struct, vm_rb);
2011                         if (right->rb_subtree_gap >= length) {
2012                                 vma = right;
2013                                 continue;
2014                         }
2015                 }
2016
2017 check_current:
2018                 /* Check if current node has a suitable gap */
2019                 gap_end = vm_start_gap(vma);
2020                 if (gap_end < low_limit)
2021                         return -ENOMEM;
2022                 if (gap_start <= high_limit &&
2023                     gap_end > gap_start && gap_end - gap_start >= length)
2024                         goto found;
2025
2026                 /* Visit left subtree if it looks promising */
2027                 if (vma->vm_rb.rb_left) {
2028                         struct vm_area_struct *left =
2029                                 rb_entry(vma->vm_rb.rb_left,
2030                                          struct vm_area_struct, vm_rb);
2031                         if (left->rb_subtree_gap >= length) {
2032                                 vma = left;
2033                                 continue;
2034                         }
2035                 }
2036
2037                 /* Go back up the rbtree to find next candidate node */
2038                 while (true) {
2039                         struct rb_node *prev = &vma->vm_rb;
2040                         if (!rb_parent(prev))
2041                                 return -ENOMEM;
2042                         vma = rb_entry(rb_parent(prev),
2043                                        struct vm_area_struct, vm_rb);
2044                         if (prev == vma->vm_rb.rb_right) {
2045                                 gap_start = vma->vm_prev ?
2046                                         vm_end_gap(vma->vm_prev) : 0;
2047                                 goto check_current;
2048                         }
2049                 }
2050         }
2051
2052 found:
2053         /* We found a suitable gap. Clip it with the original high_limit. */
2054         if (gap_end > info->high_limit)
2055                 gap_end = info->high_limit;
2056
2057 found_highest:
2058         /* Compute highest gap address at the desired alignment */
2059         gap_end -= info->length;
2060         gap_end -= (gap_end - info->align_offset) & info->align_mask;
2061
2062         VM_BUG_ON(gap_end < info->low_limit);
2063         VM_BUG_ON(gap_end < gap_start);
2064         return gap_end;
2065 }
2066
2067
2068 #ifndef arch_get_mmap_end
2069 #define arch_get_mmap_end(addr) (TASK_SIZE)
2070 #endif
2071
2072 #ifndef arch_get_mmap_base
2073 #define arch_get_mmap_base(addr, base) (base)
2074 #endif
2075
2076 /* Get an address range which is currently unmapped.
2077  * For shmat() with addr=0.
2078  *
2079  * Ugly calling convention alert:
2080  * Return value with the low bits set means error value,
2081  * ie
2082  *      if (ret & ~PAGE_MASK)
2083  *              error = ret;
2084  *
2085  * This function "knows" that -ENOMEM has the bits set.
2086  */
2087 #ifndef HAVE_ARCH_UNMAPPED_AREA
2088 unsigned long
2089 arch_get_unmapped_area(struct file *filp, unsigned long addr,
2090                 unsigned long len, unsigned long pgoff, unsigned long flags)
2091 {
2092         struct mm_struct *mm = current->mm;
2093         struct vm_area_struct *vma, *prev;
2094         struct vm_unmapped_area_info info;
2095         const unsigned long mmap_end = arch_get_mmap_end(addr);
2096
2097         if (len > mmap_end - mmap_min_addr)
2098                 return -ENOMEM;
2099
2100         if (flags & MAP_FIXED)
2101                 return addr;
2102
2103         if (addr) {
2104                 addr = PAGE_ALIGN(addr);
2105                 vma = find_vma_prev(mm, addr, &prev);
2106                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2107                     (!vma || addr + len <= vm_start_gap(vma)) &&
2108                     (!prev || addr >= vm_end_gap(prev)))
2109                         return addr;
2110         }
2111
2112         info.flags = 0;
2113         info.length = len;
2114         info.low_limit = mm->mmap_base;
2115         info.high_limit = mmap_end;
2116         info.align_mask = 0;
2117         return vm_unmapped_area(&info);
2118 }
2119 #endif
2120
2121 /*
2122  * This mmap-allocator allocates new areas top-down from below the
2123  * stack's low limit (the base):
2124  */
2125 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2126 unsigned long
2127 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
2128                           unsigned long len, unsigned long pgoff,
2129                           unsigned long flags)
2130 {
2131         struct vm_area_struct *vma, *prev;
2132         struct mm_struct *mm = current->mm;
2133         struct vm_unmapped_area_info info;
2134         const unsigned long mmap_end = arch_get_mmap_end(addr);
2135
2136         /* requested length too big for entire address space */
2137         if (len > mmap_end - mmap_min_addr)
2138                 return -ENOMEM;
2139
2140         if (flags & MAP_FIXED)
2141                 return addr;
2142
2143         /* requesting a specific address */
2144         if (addr) {
2145                 addr = PAGE_ALIGN(addr);
2146                 vma = find_vma_prev(mm, addr, &prev);
2147                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2148                                 (!vma || addr + len <= vm_start_gap(vma)) &&
2149                                 (!prev || addr >= vm_end_gap(prev)))
2150                         return addr;
2151         }
2152
2153         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2154         info.length = len;
2155         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2156         info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
2157         info.align_mask = 0;
2158         addr = vm_unmapped_area(&info);
2159
2160         /*
2161          * A failed mmap() very likely causes application failure,
2162          * so fall back to the bottom-up function here. This scenario
2163          * can happen with large stack limits and large mmap()
2164          * allocations.
2165          */
2166         if (offset_in_page(addr)) {
2167                 VM_BUG_ON(addr != -ENOMEM);
2168                 info.flags = 0;
2169                 info.low_limit = TASK_UNMAPPED_BASE;
2170                 info.high_limit = mmap_end;
2171                 addr = vm_unmapped_area(&info);
2172         }
2173
2174         return addr;
2175 }
2176 #endif
2177
2178 unsigned long
2179 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2180                 unsigned long pgoff, unsigned long flags)
2181 {
2182         unsigned long (*get_area)(struct file *, unsigned long,
2183                                   unsigned long, unsigned long, unsigned long);
2184
2185         unsigned long error = arch_mmap_check(addr, len, flags);
2186         if (error)
2187                 return error;
2188
2189         /* Careful about overflows.. */
2190         if (len > TASK_SIZE)
2191                 return -ENOMEM;
2192
2193         get_area = current->mm->get_unmapped_area;
2194         if (file) {
2195                 if (file->f_op->get_unmapped_area)
2196                         get_area = file->f_op->get_unmapped_area;
2197         } else if (flags & MAP_SHARED) {
2198                 /*
2199                  * mmap_region() will call shmem_zero_setup() to create a file,
2200                  * so use shmem's get_unmapped_area in case it can be huge.
2201                  * do_mmap_pgoff() will clear pgoff, so match alignment.
2202                  */
2203                 pgoff = 0;
2204                 get_area = shmem_get_unmapped_area;
2205         }
2206
2207         addr = get_area(file, addr, len, pgoff, flags);
2208         if (IS_ERR_VALUE(addr))
2209                 return addr;
2210
2211         if (addr > TASK_SIZE - len)
2212                 return -ENOMEM;
2213         if (offset_in_page(addr))
2214                 return -EINVAL;
2215
2216         error = security_mmap_addr(addr);
2217         return error ? error : addr;
2218 }
2219
2220 EXPORT_SYMBOL(get_unmapped_area);
2221
2222 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2223 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2224 {
2225         struct rb_node *rb_node;
2226         struct vm_area_struct *vma;
2227
2228         /* Check the cache first. */
2229         vma = vmacache_find(mm, addr);
2230         if (likely(vma))
2231                 return vma;
2232
2233         rb_node = mm->mm_rb.rb_node;
2234
2235         while (rb_node) {
2236                 struct vm_area_struct *tmp;
2237
2238                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2239
2240                 if (tmp->vm_end > addr) {
2241                         vma = tmp;
2242                         if (tmp->vm_start <= addr)
2243                                 break;
2244                         rb_node = rb_node->rb_left;
2245                 } else
2246                         rb_node = rb_node->rb_right;
2247         }
2248
2249         if (vma)
2250                 vmacache_update(addr, vma);
2251         return vma;
2252 }
2253
2254 EXPORT_SYMBOL(find_vma);
2255
2256 /*
2257  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2258  */
2259 struct vm_area_struct *
2260 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2261                         struct vm_area_struct **pprev)
2262 {
2263         struct vm_area_struct *vma;
2264
2265         vma = find_vma(mm, addr);
2266         if (vma) {
2267                 *pprev = vma->vm_prev;
2268         } else {
2269                 struct rb_node *rb_node = rb_last(&mm->mm_rb);
2270
2271                 *pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
2272         }
2273         return vma;
2274 }
2275
2276 /*
2277  * Verify that the stack growth is acceptable and
2278  * update accounting. This is shared with both the
2279  * grow-up and grow-down cases.
2280  */
2281 static int acct_stack_growth(struct vm_area_struct *vma,
2282                              unsigned long size, unsigned long grow)
2283 {
2284         struct mm_struct *mm = vma->vm_mm;
2285         unsigned long new_start;
2286
2287         /* address space limit tests */
2288         if (!may_expand_vm(mm, vma->vm_flags, grow))
2289                 return -ENOMEM;
2290
2291         /* Stack limit test */
2292         if (size > rlimit(RLIMIT_STACK))
2293                 return -ENOMEM;
2294
2295         /* mlock limit tests */
2296         if (vma->vm_flags & VM_LOCKED) {
2297                 unsigned long locked;
2298                 unsigned long limit;
2299                 locked = mm->locked_vm + grow;
2300                 limit = rlimit(RLIMIT_MEMLOCK);
2301                 limit >>= PAGE_SHIFT;
2302                 if (locked > limit && !capable(CAP_IPC_LOCK))
2303                         return -ENOMEM;
2304         }
2305
2306         /* Check to ensure the stack will not grow into a hugetlb-only region */
2307         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2308                         vma->vm_end - size;
2309         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2310                 return -EFAULT;
2311
2312         /*
2313          * Overcommit..  This must be the final test, as it will
2314          * update security statistics.
2315          */
2316         if (security_vm_enough_memory_mm(mm, grow))
2317                 return -ENOMEM;
2318
2319         return 0;
2320 }
2321
2322 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2323 /*
2324  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2325  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2326  */
2327 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2328 {
2329         struct mm_struct *mm = vma->vm_mm;
2330         struct vm_area_struct *next;
2331         unsigned long gap_addr;
2332         int error = 0;
2333
2334         if (!(vma->vm_flags & VM_GROWSUP))
2335                 return -EFAULT;
2336
2337         /* Guard against exceeding limits of the address space. */
2338         address &= PAGE_MASK;
2339         if (address >= (TASK_SIZE & PAGE_MASK))
2340                 return -ENOMEM;
2341         address += PAGE_SIZE;
2342
2343         /* Enforce stack_guard_gap */
2344         gap_addr = address + stack_guard_gap;
2345
2346         /* Guard against overflow */
2347         if (gap_addr < address || gap_addr > TASK_SIZE)
2348                 gap_addr = TASK_SIZE;
2349
2350         next = vma->vm_next;
2351         if (next && next->vm_start < gap_addr &&
2352                         (next->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2353                 if (!(next->vm_flags & VM_GROWSUP))
2354                         return -ENOMEM;
2355                 /* Check that both stack segments have the same anon_vma? */
2356         }
2357
2358         /* We must make sure the anon_vma is allocated. */
2359         if (unlikely(anon_vma_prepare(vma)))
2360                 return -ENOMEM;
2361
2362         /*
2363          * vma->vm_start/vm_end cannot change under us because the caller
2364          * is required to hold the mmap_sem in read mode.  We need the
2365          * anon_vma lock to serialize against concurrent expand_stacks.
2366          */
2367         anon_vma_lock_write(vma->anon_vma);
2368
2369         /* Somebody else might have raced and expanded it already */
2370         if (address > vma->vm_end) {
2371                 unsigned long size, grow;
2372
2373                 size = address - vma->vm_start;
2374                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2375
2376                 error = -ENOMEM;
2377                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2378                         error = acct_stack_growth(vma, size, grow);
2379                         if (!error) {
2380                                 /*
2381                                  * vma_gap_update() doesn't support concurrent
2382                                  * updates, but we only hold a shared mmap_sem
2383                                  * lock here, so we need to protect against
2384                                  * concurrent vma expansions.
2385                                  * anon_vma_lock_write() doesn't help here, as
2386                                  * we don't guarantee that all growable vmas
2387                                  * in a mm share the same root anon vma.
2388                                  * So, we reuse mm->page_table_lock to guard
2389                                  * against concurrent vma expansions.
2390                                  */
2391                                 spin_lock(&mm->page_table_lock);
2392                                 if (vma->vm_flags & VM_LOCKED)
2393                                         mm->locked_vm += grow;
2394                                 vm_stat_account(mm, vma->vm_flags, grow);
2395                                 anon_vma_interval_tree_pre_update_vma(vma);
2396                                 vma->vm_end = address;
2397                                 anon_vma_interval_tree_post_update_vma(vma);
2398                                 if (vma->vm_next)
2399                                         vma_gap_update(vma->vm_next);
2400                                 else
2401                                         mm->highest_vm_end = vm_end_gap(vma);
2402                                 spin_unlock(&mm->page_table_lock);
2403
2404                                 perf_event_mmap(vma);
2405                         }
2406                 }
2407         }
2408         anon_vma_unlock_write(vma->anon_vma);
2409         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2410         validate_mm(mm);
2411         return error;
2412 }
2413 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2414
2415 /*
2416  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2417  */
2418 int expand_downwards(struct vm_area_struct *vma,
2419                                    unsigned long address)
2420 {
2421         struct mm_struct *mm = vma->vm_mm;
2422         struct vm_area_struct *prev;
2423         int error = 0;
2424
2425         address &= PAGE_MASK;
2426         if (address < mmap_min_addr)
2427                 return -EPERM;
2428
2429         /* Enforce stack_guard_gap */
2430         prev = vma->vm_prev;
2431         /* Check that both stack segments have the same anon_vma? */
2432         if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2433                         (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2434                 if (address - prev->vm_end < stack_guard_gap)
2435                         return -ENOMEM;
2436         }
2437
2438         /* We must make sure the anon_vma is allocated. */
2439         if (unlikely(anon_vma_prepare(vma)))
2440                 return -ENOMEM;
2441
2442         /*
2443          * vma->vm_start/vm_end cannot change under us because the caller
2444          * is required to hold the mmap_sem in read mode.  We need the
2445          * anon_vma lock to serialize against concurrent expand_stacks.
2446          */
2447         anon_vma_lock_write(vma->anon_vma);
2448
2449         /* Somebody else might have raced and expanded it already */
2450         if (address < vma->vm_start) {
2451                 unsigned long size, grow;
2452
2453                 size = vma->vm_end - address;
2454                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2455
2456                 error = -ENOMEM;
2457                 if (grow <= vma->vm_pgoff) {
2458                         error = acct_stack_growth(vma, size, grow);
2459                         if (!error) {
2460                                 /*
2461                                  * vma_gap_update() doesn't support concurrent
2462                                  * updates, but we only hold a shared mmap_sem
2463                                  * lock here, so we need to protect against
2464                                  * concurrent vma expansions.
2465                                  * anon_vma_lock_write() doesn't help here, as
2466                                  * we don't guarantee that all growable vmas
2467                                  * in a mm share the same root anon vma.
2468                                  * So, we reuse mm->page_table_lock to guard
2469                                  * against concurrent vma expansions.
2470                                  */
2471                                 spin_lock(&mm->page_table_lock);
2472                                 if (vma->vm_flags & VM_LOCKED)
2473                                         mm->locked_vm += grow;
2474                                 vm_stat_account(mm, vma->vm_flags, grow);
2475                                 anon_vma_interval_tree_pre_update_vma(vma);
2476                                 vma->vm_start = address;
2477                                 vma->vm_pgoff -= grow;
2478                                 anon_vma_interval_tree_post_update_vma(vma);
2479                                 vma_gap_update(vma);
2480                                 spin_unlock(&mm->page_table_lock);
2481
2482                                 perf_event_mmap(vma);
2483                         }
2484                 }
2485         }
2486         anon_vma_unlock_write(vma->anon_vma);
2487         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2488         validate_mm(mm);
2489         return error;
2490 }
2491
2492 /* enforced gap between the expanding stack and other mappings. */
2493 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2494
2495 static int __init cmdline_parse_stack_guard_gap(char *p)
2496 {
2497         unsigned long val;
2498         char *endptr;
2499
2500         val = simple_strtoul(p, &endptr, 10);
2501         if (!*endptr)
2502                 stack_guard_gap = val << PAGE_SHIFT;
2503
2504         return 0;
2505 }
2506 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2507
2508 #ifdef CONFIG_STACK_GROWSUP
2509 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2510 {
2511         return expand_upwards(vma, address);
2512 }
2513
2514 struct vm_area_struct *
2515 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2516 {
2517         struct vm_area_struct *vma, *prev;
2518
2519         addr &= PAGE_MASK;
2520         vma = find_vma_prev(mm, addr, &prev);
2521         if (vma && (vma->vm_start <= addr))
2522                 return vma;
2523         /* don't alter vm_end if the coredump is running */
2524         if (!prev || !mmget_still_valid(mm) || expand_stack(prev, addr))
2525                 return NULL;
2526         if (prev->vm_flags & VM_LOCKED)
2527                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2528         return prev;
2529 }
2530 #else
2531 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2532 {
2533         return expand_downwards(vma, address);
2534 }
2535
2536 struct vm_area_struct *
2537 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2538 {
2539         struct vm_area_struct *vma;
2540         unsigned long start;
2541
2542         addr &= PAGE_MASK;
2543         vma = find_vma(mm, addr);
2544         if (!vma)
2545                 return NULL;
2546         if (vma->vm_start <= addr)
2547                 return vma;
2548         if (!(vma->vm_flags & VM_GROWSDOWN))
2549                 return NULL;
2550         /* don't alter vm_start if the coredump is running */
2551         if (!mmget_still_valid(mm))
2552                 return NULL;
2553         start = vma->vm_start;
2554         if (expand_stack(vma, addr))
2555                 return NULL;
2556         if (vma->vm_flags & VM_LOCKED)
2557                 populate_vma_page_range(vma, addr, start, NULL);
2558         return vma;
2559 }
2560 #endif
2561
2562 EXPORT_SYMBOL_GPL(find_extend_vma);
2563
2564 /*
2565  * Ok - we have the memory areas we should free on the vma list,
2566  * so release them, and do the vma updates.
2567  *
2568  * Called with the mm semaphore held.
2569  */
2570 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2571 {
2572         unsigned long nr_accounted = 0;
2573
2574         /* Update high watermark before we lower total_vm */
2575         update_hiwater_vm(mm);
2576         do {
2577                 long nrpages = vma_pages(vma);
2578
2579                 if (vma->vm_flags & VM_ACCOUNT)
2580                         nr_accounted += nrpages;
2581                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2582                 vma = remove_vma(vma);
2583         } while (vma);
2584         vm_unacct_memory(nr_accounted);
2585         validate_mm(mm);
2586 }
2587
2588 /*
2589  * Get rid of page table information in the indicated region.
2590  *
2591  * Called with the mm semaphore held.
2592  */
2593 static void unmap_region(struct mm_struct *mm,
2594                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2595                 unsigned long start, unsigned long end)
2596 {
2597         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2598         struct mmu_gather tlb;
2599
2600         lru_add_drain();
2601         tlb_gather_mmu(&tlb, mm, start, end);
2602         update_hiwater_rss(mm);
2603         unmap_vmas(&tlb, vma, start, end);
2604         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2605                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2606         tlb_finish_mmu(&tlb, start, end);
2607 }
2608
2609 /*
2610  * Create a list of vma's touched by the unmap, removing them from the mm's
2611  * vma list as we go..
2612  */
2613 static void
2614 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2615         struct vm_area_struct *prev, unsigned long end)
2616 {
2617         struct vm_area_struct **insertion_point;
2618         struct vm_area_struct *tail_vma = NULL;
2619
2620         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2621         vma->vm_prev = NULL;
2622         do {
2623                 vma_rb_erase(vma, &mm->mm_rb);
2624                 mm->map_count--;
2625                 tail_vma = vma;
2626                 vma = vma->vm_next;
2627         } while (vma && vma->vm_start < end);
2628         *insertion_point = vma;
2629         if (vma) {
2630                 vma->vm_prev = prev;
2631                 vma_gap_update(vma);
2632         } else
2633                 mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2634         tail_vma->vm_next = NULL;
2635
2636         /* Kill the cache */
2637         vmacache_invalidate(mm);
2638 }
2639
2640 /*
2641  * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2642  * has already been checked or doesn't make sense to fail.
2643  */
2644 int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2645                 unsigned long addr, int new_below)
2646 {
2647         struct vm_area_struct *new;
2648         int err;
2649
2650         if (vma->vm_ops && vma->vm_ops->split) {
2651                 err = vma->vm_ops->split(vma, addr);
2652                 if (err)
2653                         return err;
2654         }
2655
2656         new = vm_area_dup(vma);
2657         if (!new)
2658                 return -ENOMEM;
2659
2660         if (new_below)
2661                 new->vm_end = addr;
2662         else {
2663                 new->vm_start = addr;
2664                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2665         }
2666
2667         err = vma_dup_policy(vma, new);
2668         if (err)
2669                 goto out_free_vma;
2670
2671         err = anon_vma_clone(new, vma);
2672         if (err)
2673                 goto out_free_mpol;
2674
2675         if (new->vm_file)
2676                 get_file(new->vm_file);
2677
2678         if (new->vm_ops && new->vm_ops->open)
2679                 new->vm_ops->open(new);
2680
2681         if (new_below)
2682                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2683                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2684         else
2685                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2686
2687         /* Success. */
2688         if (!err)
2689                 return 0;
2690
2691         /* Clean everything up if vma_adjust failed. */
2692         if (new->vm_ops && new->vm_ops->close)
2693                 new->vm_ops->close(new);
2694         if (new->vm_file)
2695                 fput(new->vm_file);
2696         unlink_anon_vmas(new);
2697  out_free_mpol:
2698         mpol_put(vma_policy(new));
2699  out_free_vma:
2700         vm_area_free(new);
2701         return err;
2702 }
2703
2704 /*
2705  * Split a vma into two pieces at address 'addr', a new vma is allocated
2706  * either for the first part or the tail.
2707  */
2708 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2709               unsigned long addr, int new_below)
2710 {
2711         if (mm->map_count >= sysctl_max_map_count)
2712                 return -ENOMEM;
2713
2714         return __split_vma(mm, vma, addr, new_below);
2715 }
2716
2717 /* Munmap is split into 2 main parts -- this part which finds
2718  * what needs doing, and the areas themselves, which do the
2719  * work.  This now handles partial unmappings.
2720  * Jeremy Fitzhardinge <jeremy@goop.org>
2721  */
2722 int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2723                 struct list_head *uf, bool downgrade)
2724 {
2725         unsigned long end;
2726         struct vm_area_struct *vma, *prev, *last;
2727
2728         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2729                 return -EINVAL;
2730
2731         len = PAGE_ALIGN(len);
2732         end = start + len;
2733         if (len == 0)
2734                 return -EINVAL;
2735
2736         /*
2737          * arch_unmap() might do unmaps itself.  It must be called
2738          * and finish any rbtree manipulation before this code
2739          * runs and also starts to manipulate the rbtree.
2740          */
2741         arch_unmap(mm, start, end);
2742
2743         /* Find the first overlapping VMA */
2744         vma = find_vma(mm, start);
2745         if (!vma)
2746                 return 0;
2747         prev = vma->vm_prev;
2748         /* we have  start < vma->vm_end  */
2749
2750         /* if it doesn't overlap, we have nothing.. */
2751         if (vma->vm_start >= end)
2752                 return 0;
2753
2754         /*
2755          * If we need to split any vma, do it now to save pain later.
2756          *
2757          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2758          * unmapped vm_area_struct will remain in use: so lower split_vma
2759          * places tmp vma above, and higher split_vma places tmp vma below.
2760          */
2761         if (start > vma->vm_start) {
2762                 int error;
2763
2764                 /*
2765                  * Make sure that map_count on return from munmap() will
2766                  * not exceed its limit; but let map_count go just above
2767                  * its limit temporarily, to help free resources as expected.
2768                  */
2769                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2770                         return -ENOMEM;
2771
2772                 error = __split_vma(mm, vma, start, 0);
2773                 if (error)
2774                         return error;
2775                 prev = vma;
2776         }
2777
2778         /* Does it split the last one? */
2779         last = find_vma(mm, end);
2780         if (last && end > last->vm_start) {
2781                 int error = __split_vma(mm, last, end, 1);
2782                 if (error)
2783                         return error;
2784         }
2785         vma = prev ? prev->vm_next : mm->mmap;
2786
2787         if (unlikely(uf)) {
2788                 /*
2789                  * If userfaultfd_unmap_prep returns an error the vmas
2790                  * will remain splitted, but userland will get a
2791                  * highly unexpected error anyway. This is no
2792                  * different than the case where the first of the two
2793                  * __split_vma fails, but we don't undo the first
2794                  * split, despite we could. This is unlikely enough
2795                  * failure that it's not worth optimizing it for.
2796                  */
2797                 int error = userfaultfd_unmap_prep(vma, start, end, uf);
2798                 if (error)
2799                         return error;
2800         }
2801
2802         /*
2803          * unlock any mlock()ed ranges before detaching vmas
2804          */
2805         if (mm->locked_vm) {
2806                 struct vm_area_struct *tmp = vma;
2807                 while (tmp && tmp->vm_start < end) {
2808                         if (tmp->vm_flags & VM_LOCKED) {
2809                                 mm->locked_vm -= vma_pages(tmp);
2810                                 munlock_vma_pages_all(tmp);
2811                         }
2812
2813                         tmp = tmp->vm_next;
2814                 }
2815         }
2816
2817         /* Detach vmas from rbtree */
2818         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2819
2820         if (downgrade)
2821                 downgrade_write(&mm->mmap_sem);
2822
2823         unmap_region(mm, vma, prev, start, end);
2824
2825         /* Fix up all other VM information */
2826         remove_vma_list(mm, vma);
2827
2828         return downgrade ? 1 : 0;
2829 }
2830
2831 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2832               struct list_head *uf)
2833 {
2834         return __do_munmap(mm, start, len, uf, false);
2835 }
2836
2837 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
2838 {
2839         int ret;
2840         struct mm_struct *mm = current->mm;
2841         LIST_HEAD(uf);
2842
2843         if (down_write_killable(&mm->mmap_sem))
2844                 return -EINTR;
2845
2846         ret = __do_munmap(mm, start, len, &uf, downgrade);
2847         /*
2848          * Returning 1 indicates mmap_sem is downgraded.
2849          * But 1 is not legal return value of vm_munmap() and munmap(), reset
2850          * it to 0 before return.
2851          */
2852         if (ret == 1) {
2853                 up_read(&mm->mmap_sem);
2854                 ret = 0;
2855         } else
2856                 up_write(&mm->mmap_sem);
2857
2858         userfaultfd_unmap_complete(mm, &uf);
2859         return ret;
2860 }
2861
2862 int vm_munmap(unsigned long start, size_t len)
2863 {
2864         return __vm_munmap(start, len, false);
2865 }
2866 EXPORT_SYMBOL(vm_munmap);
2867
2868 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2869 {
2870         addr = untagged_addr(addr);
2871         profile_munmap(addr);
2872         return __vm_munmap(addr, len, true);
2873 }
2874
2875
2876 /*
2877  * Emulation of deprecated remap_file_pages() syscall.
2878  */
2879 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2880                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2881 {
2882
2883         struct mm_struct *mm = current->mm;
2884         struct vm_area_struct *vma;
2885         unsigned long populate = 0;
2886         unsigned long ret = -EINVAL;
2887         struct file *file;
2888
2889         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
2890                      current->comm, current->pid);
2891
2892         if (prot)
2893                 return ret;
2894         start = start & PAGE_MASK;
2895         size = size & PAGE_MASK;
2896
2897         if (start + size <= start)
2898                 return ret;
2899
2900         /* Does pgoff wrap? */
2901         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2902                 return ret;
2903
2904         if (down_write_killable(&mm->mmap_sem))
2905                 return -EINTR;
2906
2907         vma = find_vma(mm, start);
2908
2909         if (!vma || !(vma->vm_flags & VM_SHARED))
2910                 goto out;
2911
2912         if (start < vma->vm_start)
2913                 goto out;
2914
2915         if (start + size > vma->vm_end) {
2916                 struct vm_area_struct *next;
2917
2918                 for (next = vma->vm_next; next; next = next->vm_next) {
2919                         /* hole between vmas ? */
2920                         if (next->vm_start != next->vm_prev->vm_end)
2921                                 goto out;
2922
2923                         if (next->vm_file != vma->vm_file)
2924                                 goto out;
2925
2926                         if (next->vm_flags != vma->vm_flags)
2927                                 goto out;
2928
2929                         if (start + size <= next->vm_end)
2930                                 break;
2931                 }
2932
2933                 if (!next)
2934                         goto out;
2935         }
2936
2937         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2938         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2939         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2940
2941         flags &= MAP_NONBLOCK;
2942         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2943         if (vma->vm_flags & VM_LOCKED) {
2944                 struct vm_area_struct *tmp;
2945                 flags |= MAP_LOCKED;
2946
2947                 /* drop PG_Mlocked flag for over-mapped range */
2948                 for (tmp = vma; tmp->vm_start >= start + size;
2949                                 tmp = tmp->vm_next) {
2950                         /*
2951                          * Split pmd and munlock page on the border
2952                          * of the range.
2953                          */
2954                         vma_adjust_trans_huge(tmp, start, start + size, 0);
2955
2956                         munlock_vma_pages_range(tmp,
2957                                         max(tmp->vm_start, start),
2958                                         min(tmp->vm_end, start + size));
2959                 }
2960         }
2961
2962         file = get_file(vma->vm_file);
2963         ret = do_mmap_pgoff(vma->vm_file, start, size,
2964                         prot, flags, pgoff, &populate, NULL);
2965         fput(file);
2966 out:
2967         up_write(&mm->mmap_sem);
2968         if (populate)
2969                 mm_populate(ret, populate);
2970         if (!IS_ERR_VALUE(ret))
2971                 ret = 0;
2972         return ret;
2973 }
2974
2975 /*
2976  *  this is really a simplified "do_mmap".  it only handles
2977  *  anonymous maps.  eventually we may be able to do some
2978  *  brk-specific accounting here.
2979  */
2980 static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags, struct list_head *uf)
2981 {
2982         struct mm_struct *mm = current->mm;
2983         struct vm_area_struct *vma, *prev;
2984         struct rb_node **rb_link, *rb_parent;
2985         pgoff_t pgoff = addr >> PAGE_SHIFT;
2986         int error;
2987         unsigned long mapped_addr;
2988
2989         /* Until we need other flags, refuse anything except VM_EXEC. */
2990         if ((flags & (~VM_EXEC)) != 0)
2991                 return -EINVAL;
2992         flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2993
2994         mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2995         if (IS_ERR_VALUE(mapped_addr))
2996                 return mapped_addr;
2997
2998         error = mlock_future_check(mm, mm->def_flags, len);
2999         if (error)
3000                 return error;
3001
3002         /*
3003          * Clear old maps.  this also does some error checking for us
3004          */
3005         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
3006                               &rb_parent)) {
3007                 if (do_munmap(mm, addr, len, uf))
3008                         return -ENOMEM;
3009         }
3010
3011         /* Check against address space limits *after* clearing old maps... */
3012         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
3013                 return -ENOMEM;
3014
3015         if (mm->map_count > sysctl_max_map_count)
3016                 return -ENOMEM;
3017
3018         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
3019                 return -ENOMEM;
3020
3021         /* Can we just expand an old private anonymous mapping? */
3022         vma = vma_merge(mm, prev, addr, addr + len, flags,
3023                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
3024         if (vma)
3025                 goto out;
3026
3027         /*
3028          * create a vma struct for an anonymous mapping
3029          */
3030         vma = vm_area_alloc(mm);
3031         if (!vma) {
3032                 vm_unacct_memory(len >> PAGE_SHIFT);
3033                 return -ENOMEM;
3034         }
3035
3036         vma_set_anonymous(vma);
3037         vma->vm_start = addr;
3038         vma->vm_end = addr + len;
3039         vma->vm_pgoff = pgoff;
3040         vma->vm_flags = flags;
3041         vma->vm_page_prot = vm_get_page_prot(flags);
3042         vma_link(mm, vma, prev, rb_link, rb_parent);
3043 out:
3044         perf_event_mmap(vma);
3045         mm->total_vm += len >> PAGE_SHIFT;
3046         mm->data_vm += len >> PAGE_SHIFT;
3047         if (flags & VM_LOCKED)
3048                 mm->locked_vm += (len >> PAGE_SHIFT);
3049         vma->vm_flags |= VM_SOFTDIRTY;
3050         return 0;
3051 }
3052
3053 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
3054 {
3055         struct mm_struct *mm = current->mm;
3056         unsigned long len;
3057         int ret;
3058         bool populate;
3059         LIST_HEAD(uf);
3060
3061         len = PAGE_ALIGN(request);
3062         if (len < request)
3063                 return -ENOMEM;
3064         if (!len)
3065                 return 0;
3066
3067         if (down_write_killable(&mm->mmap_sem))
3068                 return -EINTR;
3069
3070         ret = do_brk_flags(addr, len, flags, &uf);
3071         populate = ((mm->def_flags & VM_LOCKED) != 0);
3072         up_write(&mm->mmap_sem);
3073         userfaultfd_unmap_complete(mm, &uf);
3074         if (populate && !ret)
3075                 mm_populate(addr, len);
3076         return ret;
3077 }
3078 EXPORT_SYMBOL(vm_brk_flags);
3079
3080 int vm_brk(unsigned long addr, unsigned long len)
3081 {
3082         return vm_brk_flags(addr, len, 0);
3083 }
3084 EXPORT_SYMBOL(vm_brk);
3085
3086 /* Release all mmaps. */
3087 void exit_mmap(struct mm_struct *mm)
3088 {
3089         struct mmu_gather tlb;
3090         struct vm_area_struct *vma;
3091         unsigned long nr_accounted = 0;
3092
3093         /* mm's last user has gone, and its about to be pulled down */
3094         mmu_notifier_release(mm);
3095
3096         if (unlikely(mm_is_oom_victim(mm))) {
3097                 /*
3098                  * Manually reap the mm to free as much memory as possible.
3099                  * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
3100                  * this mm from further consideration.  Taking mm->mmap_sem for
3101                  * write after setting MMF_OOM_SKIP will guarantee that the oom
3102                  * reaper will not run on this mm again after mmap_sem is
3103                  * dropped.
3104                  *
3105                  * Nothing can be holding mm->mmap_sem here and the above call
3106                  * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
3107                  * __oom_reap_task_mm() will not block.
3108                  *
3109                  * This needs to be done before calling munlock_vma_pages_all(),
3110                  * which clears VM_LOCKED, otherwise the oom reaper cannot
3111                  * reliably test it.
3112                  */
3113                 (void)__oom_reap_task_mm(mm);
3114
3115                 set_bit(MMF_OOM_SKIP, &mm->flags);
3116                 down_write(&mm->mmap_sem);
3117                 up_write(&mm->mmap_sem);
3118         }
3119
3120         if (mm->locked_vm) {
3121                 vma = mm->mmap;
3122                 while (vma) {
3123                         if (vma->vm_flags & VM_LOCKED)
3124                                 munlock_vma_pages_all(vma);
3125                         vma = vma->vm_next;
3126                 }
3127         }
3128
3129         arch_exit_mmap(mm);
3130
3131         vma = mm->mmap;
3132         if (!vma)       /* Can happen if dup_mmap() received an OOM */
3133                 return;
3134
3135         lru_add_drain();
3136         flush_cache_mm(mm);
3137         tlb_gather_mmu(&tlb, mm, 0, -1);
3138         /* update_hiwater_rss(mm) here? but nobody should be looking */
3139         /* Use -1 here to ensure all VMAs in the mm are unmapped */
3140         unmap_vmas(&tlb, vma, 0, -1);
3141         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
3142         tlb_finish_mmu(&tlb, 0, -1);
3143
3144         /*
3145          * Walk the list again, actually closing and freeing it,
3146          * with preemption enabled, without holding any MM locks.
3147          */
3148         while (vma) {
3149                 if (vma->vm_flags & VM_ACCOUNT)
3150                         nr_accounted += vma_pages(vma);
3151                 vma = remove_vma(vma);
3152         }
3153         vm_unacct_memory(nr_accounted);
3154 }
3155
3156 /* Insert vm structure into process list sorted by address
3157  * and into the inode's i_mmap tree.  If vm_file is non-NULL
3158  * then i_mmap_rwsem is taken here.
3159  */
3160 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3161 {
3162         struct vm_area_struct *prev;
3163         struct rb_node **rb_link, *rb_parent;
3164
3165         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3166                            &prev, &rb_link, &rb_parent))
3167                 return -ENOMEM;
3168         if ((vma->vm_flags & VM_ACCOUNT) &&
3169              security_vm_enough_memory_mm(mm, vma_pages(vma)))
3170                 return -ENOMEM;
3171
3172         /*
3173          * The vm_pgoff of a purely anonymous vma should be irrelevant
3174          * until its first write fault, when page's anon_vma and index
3175          * are set.  But now set the vm_pgoff it will almost certainly
3176          * end up with (unless mremap moves it elsewhere before that
3177          * first wfault), so /proc/pid/maps tells a consistent story.
3178          *
3179          * By setting it to reflect the virtual start address of the
3180          * vma, merges and splits can happen in a seamless way, just
3181          * using the existing file pgoff checks and manipulations.
3182          * Similarly in do_mmap_pgoff and in do_brk.
3183          */
3184         if (vma_is_anonymous(vma)) {
3185                 BUG_ON(vma->anon_vma);
3186                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3187         }
3188
3189         vma_link(mm, vma, prev, rb_link, rb_parent);
3190         return 0;
3191 }
3192
3193 /*
3194  * Copy the vma structure to a new location in the same mm,
3195  * prior to moving page table entries, to effect an mremap move.
3196  */
3197 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3198         unsigned long addr, unsigned long len, pgoff_t pgoff,
3199         bool *need_rmap_locks)
3200 {
3201         struct vm_area_struct *vma = *vmap;
3202         unsigned long vma_start = vma->vm_start;
3203         struct mm_struct *mm = vma->vm_mm;
3204         struct vm_area_struct *new_vma, *prev;
3205         struct rb_node **rb_link, *rb_parent;
3206         bool faulted_in_anon_vma = true;
3207
3208         /*
3209          * If anonymous vma has not yet been faulted, update new pgoff
3210          * to match new location, to increase its chance of merging.
3211          */
3212         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3213                 pgoff = addr >> PAGE_SHIFT;
3214                 faulted_in_anon_vma = false;
3215         }
3216
3217         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3218                 return NULL;    /* should never get here */
3219         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3220                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3221                             vma->vm_userfaultfd_ctx);
3222         if (new_vma) {
3223                 /*
3224                  * Source vma may have been merged into new_vma
3225                  */
3226                 if (unlikely(vma_start >= new_vma->vm_start &&
3227                              vma_start < new_vma->vm_end)) {
3228                         /*
3229                          * The only way we can get a vma_merge with
3230                          * self during an mremap is if the vma hasn't
3231                          * been faulted in yet and we were allowed to
3232                          * reset the dst vma->vm_pgoff to the
3233                          * destination address of the mremap to allow
3234                          * the merge to happen. mremap must change the
3235                          * vm_pgoff linearity between src and dst vmas
3236                          * (in turn preventing a vma_merge) to be
3237                          * safe. It is only safe to keep the vm_pgoff
3238                          * linear if there are no pages mapped yet.
3239                          */
3240                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3241                         *vmap = vma = new_vma;
3242                 }
3243                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3244         } else {
3245                 new_vma = vm_area_dup(vma);
3246                 if (!new_vma)
3247                         goto out;
3248                 new_vma->vm_start = addr;
3249                 new_vma->vm_end = addr + len;
3250                 new_vma->vm_pgoff = pgoff;
3251                 if (vma_dup_policy(vma, new_vma))
3252                         goto out_free_vma;
3253                 if (anon_vma_clone(new_vma, vma))
3254                         goto out_free_mempol;
3255                 if (new_vma->vm_file)
3256                         get_file(new_vma->vm_file);
3257                 if (new_vma->vm_ops && new_vma->vm_ops->open)
3258                         new_vma->vm_ops->open(new_vma);
3259                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
3260                 *need_rmap_locks = false;
3261         }
3262         return new_vma;
3263
3264 out_free_mempol:
3265         mpol_put(vma_policy(new_vma));
3266 out_free_vma:
3267         vm_area_free(new_vma);
3268 out:
3269         return NULL;
3270 }
3271
3272 /*
3273  * Return true if the calling process may expand its vm space by the passed
3274  * number of pages
3275  */
3276 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3277 {
3278         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3279                 return false;
3280
3281         if (is_data_mapping(flags) &&
3282             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3283                 /* Workaround for Valgrind */
3284                 if (rlimit(RLIMIT_DATA) == 0 &&
3285                     mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3286                         return true;
3287
3288                 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
3289                              current->comm, current->pid,
3290                              (mm->data_vm + npages) << PAGE_SHIFT,
3291                              rlimit(RLIMIT_DATA),
3292                              ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
3293
3294                 if (!ignore_rlimit_data)
3295                         return false;
3296         }
3297
3298         return true;
3299 }
3300
3301 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3302 {
3303         mm->total_vm += npages;
3304
3305         if (is_exec_mapping(flags))
3306                 mm->exec_vm += npages;
3307         else if (is_stack_mapping(flags))
3308                 mm->stack_vm += npages;
3309         else if (is_data_mapping(flags))
3310                 mm->data_vm += npages;
3311 }
3312
3313 static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
3314
3315 /*
3316  * Having a close hook prevents vma merging regardless of flags.
3317  */
3318 static void special_mapping_close(struct vm_area_struct *vma)
3319 {
3320 }
3321
3322 static const char *special_mapping_name(struct vm_area_struct *vma)
3323 {
3324         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3325 }
3326
3327 static int special_mapping_mremap(struct vm_area_struct *new_vma)
3328 {
3329         struct vm_special_mapping *sm = new_vma->vm_private_data;
3330
3331         if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3332                 return -EFAULT;
3333
3334         if (sm->mremap)
3335                 return sm->mremap(sm, new_vma);
3336
3337         return 0;
3338 }
3339
3340 static const struct vm_operations_struct special_mapping_vmops = {
3341         .close = special_mapping_close,
3342         .fault = special_mapping_fault,
3343         .mremap = special_mapping_mremap,
3344         .name = special_mapping_name,
3345 };
3346
3347 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3348         .close = special_mapping_close,
3349         .fault = special_mapping_fault,
3350 };
3351
3352 static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
3353 {
3354         struct vm_area_struct *vma = vmf->vma;
3355         pgoff_t pgoff;
3356         struct page **pages;
3357
3358         if (vma->vm_ops == &legacy_special_mapping_vmops) {
3359                 pages = vma->vm_private_data;
3360         } else {
3361                 struct vm_special_mapping *sm = vma->vm_private_data;
3362
3363                 if (sm->fault)
3364                         return sm->fault(sm, vmf->vma, vmf);
3365
3366                 pages = sm->pages;
3367         }
3368
3369         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3370                 pgoff--;
3371
3372         if (*pages) {
3373                 struct page *page = *pages;
3374                 get_page(page);
3375                 vmf->page = page;
3376                 return 0;
3377         }
3378
3379         return VM_FAULT_SIGBUS;
3380 }
3381
3382 static struct vm_area_struct *__install_special_mapping(
3383         struct mm_struct *mm,
3384         unsigned long addr, unsigned long len,
3385         unsigned long vm_flags, void *priv,
3386         const struct vm_operations_struct *ops)
3387 {
3388         int ret;
3389         struct vm_area_struct *vma;
3390
3391         vma = vm_area_alloc(mm);
3392         if (unlikely(vma == NULL))
3393                 return ERR_PTR(-ENOMEM);
3394
3395         vma->vm_start = addr;
3396         vma->vm_end = addr + len;
3397
3398         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3399         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3400
3401         vma->vm_ops = ops;
3402         vma->vm_private_data = priv;
3403
3404         ret = insert_vm_struct(mm, vma);
3405         if (ret)
3406                 goto out;
3407
3408         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3409
3410         perf_event_mmap(vma);
3411
3412         return vma;
3413
3414 out:
3415         vm_area_free(vma);
3416         return ERR_PTR(ret);
3417 }
3418
3419 bool vma_is_special_mapping(const struct vm_area_struct *vma,
3420         const struct vm_special_mapping *sm)
3421 {
3422         return vma->vm_private_data == sm &&
3423                 (vma->vm_ops == &special_mapping_vmops ||
3424                  vma->vm_ops == &legacy_special_mapping_vmops);
3425 }
3426
3427 /*
3428  * Called with mm->mmap_sem held for writing.
3429  * Insert a new vma covering the given region, with the given flags.
3430  * Its pages are supplied by the given array of struct page *.
3431  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3432  * The region past the last page supplied will always produce SIGBUS.
3433  * The array pointer and the pages it points to are assumed to stay alive
3434  * for as long as this mapping might exist.
3435  */
3436 struct vm_area_struct *_install_special_mapping(
3437         struct mm_struct *mm,
3438         unsigned long addr, unsigned long len,
3439         unsigned long vm_flags, const struct vm_special_mapping *spec)
3440 {
3441         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3442                                         &special_mapping_vmops);
3443 }
3444
3445 int install_special_mapping(struct mm_struct *mm,
3446                             unsigned long addr, unsigned long len,
3447                             unsigned long vm_flags, struct page **pages)
3448 {
3449         struct vm_area_struct *vma = __install_special_mapping(
3450                 mm, addr, len, vm_flags, (void *)pages,
3451                 &legacy_special_mapping_vmops);
3452
3453         return PTR_ERR_OR_ZERO(vma);
3454 }
3455
3456 static DEFINE_MUTEX(mm_all_locks_mutex);
3457
3458 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3459 {
3460         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3461                 /*
3462                  * The LSB of head.next can't change from under us
3463                  * because we hold the mm_all_locks_mutex.
3464                  */
3465                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3466                 /*
3467                  * We can safely modify head.next after taking the
3468                  * anon_vma->root->rwsem. If some other vma in this mm shares
3469                  * the same anon_vma we won't take it again.
3470                  *
3471                  * No need of atomic instructions here, head.next
3472                  * can't change from under us thanks to the
3473                  * anon_vma->root->rwsem.
3474                  */
3475                 if (__test_and_set_bit(0, (unsigned long *)
3476                                        &anon_vma->root->rb_root.rb_root.rb_node))
3477                         BUG();
3478         }
3479 }
3480
3481 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3482 {
3483         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3484                 /*
3485                  * AS_MM_ALL_LOCKS can't change from under us because
3486                  * we hold the mm_all_locks_mutex.
3487                  *
3488                  * Operations on ->flags have to be atomic because
3489                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3490                  * mm_all_locks_mutex, there may be other cpus
3491                  * changing other bitflags in parallel to us.
3492                  */
3493                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3494                         BUG();
3495                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3496         }
3497 }
3498
3499 /*
3500  * This operation locks against the VM for all pte/vma/mm related
3501  * operations that could ever happen on a certain mm. This includes
3502  * vmtruncate, try_to_unmap, and all page faults.
3503  *
3504  * The caller must take the mmap_sem in write mode before calling
3505  * mm_take_all_locks(). The caller isn't allowed to release the
3506  * mmap_sem until mm_drop_all_locks() returns.
3507  *
3508  * mmap_sem in write mode is required in order to block all operations
3509  * that could modify pagetables and free pages without need of
3510  * altering the vma layout. It's also needed in write mode to avoid new
3511  * anon_vmas to be associated with existing vmas.
3512  *
3513  * A single task can't take more than one mm_take_all_locks() in a row
3514  * or it would deadlock.
3515  *
3516  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3517  * mapping->flags avoid to take the same lock twice, if more than one
3518  * vma in this mm is backed by the same anon_vma or address_space.
3519  *
3520  * We take locks in following order, accordingly to comment at beginning
3521  * of mm/rmap.c:
3522  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3523  *     hugetlb mapping);
3524  *   - all i_mmap_rwsem locks;
3525  *   - all anon_vma->rwseml
3526  *
3527  * We can take all locks within these types randomly because the VM code
3528  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3529  * mm_all_locks_mutex.
3530  *
3531  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3532  * that may have to take thousand of locks.
3533  *
3534  * mm_take_all_locks() can fail if it's interrupted by signals.
3535  */
3536 int mm_take_all_locks(struct mm_struct *mm)
3537 {
3538         struct vm_area_struct *vma;
3539         struct anon_vma_chain *avc;
3540
3541         BUG_ON(down_read_trylock(&mm->mmap_sem));
3542
3543         mutex_lock(&mm_all_locks_mutex);
3544
3545         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3546                 if (signal_pending(current))
3547                         goto out_unlock;
3548                 if (vma->vm_file && vma->vm_file->f_mapping &&
3549                                 is_vm_hugetlb_page(vma))
3550                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3551         }
3552
3553         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3554                 if (signal_pending(current))
3555                         goto out_unlock;
3556                 if (vma->vm_file && vma->vm_file->f_mapping &&
3557                                 !is_vm_hugetlb_page(vma))
3558                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3559         }
3560
3561         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3562                 if (signal_pending(current))
3563                         goto out_unlock;
3564                 if (vma->anon_vma)
3565                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3566                                 vm_lock_anon_vma(mm, avc->anon_vma);
3567         }
3568
3569         return 0;
3570
3571 out_unlock:
3572         mm_drop_all_locks(mm);
3573         return -EINTR;
3574 }
3575
3576 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3577 {
3578         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3579                 /*
3580                  * The LSB of head.next can't change to 0 from under
3581                  * us because we hold the mm_all_locks_mutex.
3582                  *
3583                  * We must however clear the bitflag before unlocking
3584                  * the vma so the users using the anon_vma->rb_root will
3585                  * never see our bitflag.
3586                  *
3587                  * No need of atomic instructions here, head.next
3588                  * can't change from under us until we release the
3589                  * anon_vma->root->rwsem.
3590                  */
3591                 if (!__test_and_clear_bit(0, (unsigned long *)
3592                                           &anon_vma->root->rb_root.rb_root.rb_node))
3593                         BUG();
3594                 anon_vma_unlock_write(anon_vma);
3595         }
3596 }
3597
3598 static void vm_unlock_mapping(struct address_space *mapping)
3599 {
3600         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3601                 /*
3602                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3603                  * because we hold the mm_all_locks_mutex.
3604                  */
3605                 i_mmap_unlock_write(mapping);
3606                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3607                                         &mapping->flags))
3608                         BUG();
3609         }
3610 }
3611
3612 /*
3613  * The mmap_sem cannot be released by the caller until
3614  * mm_drop_all_locks() returns.
3615  */
3616 void mm_drop_all_locks(struct mm_struct *mm)
3617 {
3618         struct vm_area_struct *vma;
3619         struct anon_vma_chain *avc;
3620
3621         BUG_ON(down_read_trylock(&mm->mmap_sem));
3622         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3623
3624         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3625                 if (vma->anon_vma)
3626                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3627                                 vm_unlock_anon_vma(avc->anon_vma);
3628                 if (vma->vm_file && vma->vm_file->f_mapping)
3629                         vm_unlock_mapping(vma->vm_file->f_mapping);
3630         }
3631
3632         mutex_unlock(&mm_all_locks_mutex);
3633 }
3634
3635 /*
3636  * initialise the percpu counter for VM
3637  */
3638 void __init mmap_init(void)
3639 {
3640         int ret;
3641
3642         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3643         VM_BUG_ON(ret);
3644 }
3645
3646 /*
3647  * Initialise sysctl_user_reserve_kbytes.
3648  *
3649  * This is intended to prevent a user from starting a single memory hogging
3650  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3651  * mode.
3652  *
3653  * The default value is min(3% of free memory, 128MB)
3654  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3655  */
3656 static int init_user_reserve(void)
3657 {
3658         unsigned long free_kbytes;
3659
3660         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3661
3662         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3663         return 0;
3664 }
3665 subsys_initcall(init_user_reserve);
3666
3667 /*
3668  * Initialise sysctl_admin_reserve_kbytes.
3669  *
3670  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3671  * to log in and kill a memory hogging process.
3672  *
3673  * Systems with more than 256MB will reserve 8MB, enough to recover
3674  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3675  * only reserve 3% of free pages by default.
3676  */
3677 static int init_admin_reserve(void)
3678 {
3679         unsigned long free_kbytes;
3680
3681         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3682
3683         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3684         return 0;
3685 }
3686 subsys_initcall(init_admin_reserve);
3687
3688 /*
3689  * Reinititalise user and admin reserves if memory is added or removed.
3690  *
3691  * The default user reserve max is 128MB, and the default max for the
3692  * admin reserve is 8MB. These are usually, but not always, enough to
3693  * enable recovery from a memory hogging process using login/sshd, a shell,
3694  * and tools like top. It may make sense to increase or even disable the
3695  * reserve depending on the existence of swap or variations in the recovery
3696  * tools. So, the admin may have changed them.
3697  *
3698  * If memory is added and the reserves have been eliminated or increased above
3699  * the default max, then we'll trust the admin.
3700  *
3701  * If memory is removed and there isn't enough free memory, then we
3702  * need to reset the reserves.
3703  *
3704  * Otherwise keep the reserve set by the admin.
3705  */
3706 static int reserve_mem_notifier(struct notifier_block *nb,
3707                              unsigned long action, void *data)
3708 {
3709         unsigned long tmp, free_kbytes;
3710
3711         switch (action) {
3712         case MEM_ONLINE:
3713                 /* Default max is 128MB. Leave alone if modified by operator. */
3714                 tmp = sysctl_user_reserve_kbytes;
3715                 if (0 < tmp && tmp < (1UL << 17))
3716                         init_user_reserve();
3717
3718                 /* Default max is 8MB.  Leave alone if modified by operator. */
3719                 tmp = sysctl_admin_reserve_kbytes;
3720                 if (0 < tmp && tmp < (1UL << 13))
3721                         init_admin_reserve();
3722
3723                 break;
3724         case MEM_OFFLINE:
3725                 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3726
3727                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3728                         init_user_reserve();
3729                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3730                                 sysctl_user_reserve_kbytes);
3731                 }
3732
3733                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3734                         init_admin_reserve();
3735                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3736                                 sysctl_admin_reserve_kbytes);
3737                 }
3738                 break;
3739         default:
3740                 break;
3741         }
3742         return NOTIFY_OK;
3743 }
3744
3745 static struct notifier_block reserve_mem_nb = {
3746         .notifier_call = reserve_mem_notifier,
3747 };
3748
3749 static int __meminit init_reserve_notifier(void)
3750 {
3751         if (register_hotmemory_notifier(&reserve_mem_nb))
3752                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3753
3754         return 0;
3755 }
3756 subsys_initcall(init_reserve_notifier);