fs/exec.c

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/vmacache.h>
  30 #include <linux/stat.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/swap.h>
  33 #include <linux/string.h>
  34 #include <linux/init.h>
  35 #include <linux/sched/mm.h>
  36 #include <linux/sched/coredump.h>
  37 #include <linux/sched/signal.h>
  38 #include <linux/sched/numa_balancing.h>
  39 #include <linux/sched/task.h>
  40 #include <linux/pagemap.h>
  41 #include <linux/perf_event.h>
  42 #include <linux/highmem.h>
  43 #include <linux/spinlock.h>
  44 #include <linux/key.h>
  45 #include <linux/personality.h>
  46 #include <linux/binfmts.h>
  47 #include <linux/utsname.h>
  48 #include <linux/pid_namespace.h>
  49 #include <linux/module.h>
  50 #include <linux/namei.h>
  51 #include <linux/mount.h>
  52 #include <linux/security.h>
  53 #include <linux/syscalls.h>
  54 #include <linux/tsacct_kern.h>
  55 #include <linux/cn_proc.h>
  56 #include <linux/audit.h>
  57 #include <linux/tracehook.h>
  58 #include <linux/kmod.h>
  59 #include <linux/fsnotify.h>
  60 #include <linux/fs_struct.h>
  61 #include <linux/pipe_fs_i.h>
  62 #include <linux/oom.h>
  63 #include <linux/compat.h>
  64 #include <linux/vmalloc.h>
  65
  66 #include <linux/uaccess.h>
  67 #include <asm/mmu_context.h>
  68 #include <asm/tlb.h>
  69
  70 #include <trace/events/task.h>
  71 #include "internal.h"
  72
  73 #include <trace/events/sched.h>
  74
  75 int suid_dumpable = 0;
  76
  77 static LIST_HEAD(formats);
  78 static DEFINE_RWLOCK(binfmt_lock);
  79
  80 void __register_binfmt(struct linux_binfmt * fmt, int insert)
  81 {
  82         BUG_ON(!fmt);
  83         if (WARN_ON(!fmt->load_binary))
  84                 return;
  85         write_lock(&binfmt_lock);
  86         insert ? list_add(&fmt->lh, &formats) :
  87                  list_add_tail(&fmt->lh, &formats);
  88         write_unlock(&binfmt_lock);
  89 }
  90
  91 EXPORT_SYMBOL(__register_binfmt);
  92
  93 void unregister_binfmt(struct linux_binfmt * fmt)
  94 {
  95         write_lock(&binfmt_lock);
  96         list_del(&fmt->lh);
  97         write_unlock(&binfmt_lock);
  98 }
  99
 100 EXPORT_SYMBOL(unregister_binfmt);
 101
 102 static inline void put_binfmt(struct linux_binfmt * fmt)
 103 {
 104         module_put(fmt->module);
 105 }
 106
 107 bool path_noexec(const struct path *path)
 108 {
 109         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 110                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 111 }
 112
 113 #ifdef CONFIG_USELIB
 114 /*
 115  * Note that a shared library must be both readable and executable due to
 116  * security reasons.
 117  *
 118  * Also note that we take the address to load from from the file itself.
 119  */
 120 SYSCALL_DEFINE1(uselib, const char __user *, library)
 121 {
 122         struct linux_binfmt *fmt;
 123         struct file *file;
 124         struct filename *tmp = getname(library);
 125         int error = PTR_ERR(tmp);
 126         static const struct open_flags uselib_flags = {
 127                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 128                 .acc_mode = MAY_READ | MAY_EXEC,
 129                 .intent = LOOKUP_OPEN,
 130                 .lookup_flags = LOOKUP_FOLLOW,
 131         };
 132
 133         if (IS_ERR(tmp))
 134                 goto out;
 135
 136         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 137         putname(tmp);
 138         error = PTR_ERR(file);
 139         if (IS_ERR(file))
 140                 goto out;
 141
 142         error = -EINVAL;
 143         if (!S_ISREG(file_inode(file)->i_mode))
 144                 goto exit;
 145
 146         error = -EACCES;
 147         if (path_noexec(&file->f_path))
 148                 goto exit;
 149
 150         fsnotify_open(file);
 151
 152         error = -ENOEXEC;
 153
 154         read_lock(&binfmt_lock);
 155         list_for_each_entry(fmt, &formats, lh) {
 156                 if (!fmt->load_shlib)
 157                         continue;
 158                 if (!try_module_get(fmt->module))
 159                         continue;
 160                 read_unlock(&binfmt_lock);
 161                 error = fmt->load_shlib(file);
 162                 read_lock(&binfmt_lock);
 163                 put_binfmt(fmt);
 164                 if (error != -ENOEXEC)
 165                         break;
 166         }
 167         read_unlock(&binfmt_lock);
 168 exit:
 169         fput(file);
 170 out:
 171         return error;
 172 }
 173 #endif /* #ifdef CONFIG_USELIB */
 174
 175 #ifdef CONFIG_MMU
 176 /*
 177  * The nascent bprm->mm is not visible until exec_mmap() but it can
 178  * use a lot of memory, account these pages in current->mm temporary
 179  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 180  * change the counter back via acct_arg_size(0).
 181  */
 182 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 183 {
 184         struct mm_struct *mm = current->mm;
 185         long diff = (long)(pages - bprm->vma_pages);
 186
 187         if (!mm || !diff)
 188                 return;
 189
 190         bprm->vma_pages = pages;
 191         add_mm_counter(mm, MM_ANONPAGES, diff);
 192 }
 193
 194 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 195                 int write)
 196 {
 197         struct page *page;
 198         int ret;
 199         unsigned int gup_flags = FOLL_FORCE;
 200
 201 #ifdef CONFIG_STACK_GROWSUP
 202         if (write) {
 203                 ret = expand_downwards(bprm->vma, pos);
 204                 if (ret < 0)
 205                         return NULL;
 206         }
 207 #endif
 208
 209         if (write)
 210                 gup_flags |= FOLL_WRITE;
 211
 212         /*
 213          * We are doing an exec().  'current' is the process
 214          * doing the exec and bprm->mm is the new process's mm.
 215          */
 216         ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
 217                         &page, NULL, NULL);
 218         if (ret <= 0)
 219                 return NULL;
 220
 221         if (write) {
 222                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 223                 unsigned long ptr_size;
 224                 struct rlimit *rlim;
 225
 226                 /*
 227                  * Since the stack will hold pointers to the strings, we
 228                  * must account for them as well.
 229                  *
 230                  * The size calculation is the entire vma while each arg page is
 231                  * built, so each time we get here it's calculating how far it
 232                  * is currently (rather than each call being just the newly
 233                  * added size from the arg page).  As a result, we need to
 234                  * always add the entire size of the pointers, so that on the
 235                  * last call to get_arg_page() we'll actually have the entire
 236                  * correct size.
 237                  */
 238                 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
 239                 if (ptr_size > ULONG_MAX - size)
 240                         goto fail;
 241                 size += ptr_size;
 242
 243                 acct_arg_size(bprm, size / PAGE_SIZE);
 244
 245                 /*
 246                  * We've historically supported up to 32 pages (ARG_MAX)
 247                  * of argument strings even with small stacks
 248                  */
 249                 if (size <= ARG_MAX)
 250                         return page;
 251
 252                 /*
 253                  * Limit to 1/4-th the stack size for the argv+env strings.
 254                  * This ensures that:
 255                  *  - the remaining binfmt code will not run out of stack space,
 256                  *  - the program will have a reasonable amount of stack left
 257                  *    to work from.
 258                  */
 259                 rlim = current->signal->rlim;
 260                 if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4)
 261                         goto fail;
 262         }
 263
 264         return page;
 265
 266 fail:
 267         put_page(page);
 268         return NULL;
 269 }
 270
 271 static void put_arg_page(struct page *page)
 272 {
 273         put_page(page);
 274 }
 275
 276 static void free_arg_pages(struct linux_binprm *bprm)
 277 {
 278 }
 279
 280 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 281                 struct page *page)
 282 {
 283         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 284 }
 285
 286 static int __bprm_mm_init(struct linux_binprm *bprm)
 287 {
 288         int err;
 289         struct vm_area_struct *vma = NULL;
 290         struct mm_struct *mm = bprm->mm;
 291
 292         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 293         if (!vma)
 294                 return -ENOMEM;
 295
 296         if (down_write_killable(&mm->mmap_sem)) {
 297                 err = -EINTR;
 298                 goto err_free;
 299         }
 300         vma->vm_mm = mm;
 301
 302         /*
 303          * Place the stack at the largest stack address the architecture
 304          * supports. Later, we'll move this to an appropriate place. We don't
 305          * use STACK_TOP because that can depend on attributes which aren't
 306          * configured yet.
 307          */
 308         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 309         vma->vm_end = STACK_TOP_MAX;
 310         vma->vm_start = vma->vm_end - PAGE_SIZE;
 311         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 312         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 313         INIT_LIST_HEAD(&vma->anon_vma_chain);
 314
 315         err = insert_vm_struct(mm, vma);
 316         if (err)
 317                 goto err;
 318
 319         mm->stack_vm = mm->total_vm = 1;
 320         arch_bprm_mm_init(mm, vma);
 321         up_write(&mm->mmap_sem);
 322         bprm->p = vma->vm_end - sizeof(void *);
 323         return 0;
 324 err:
 325         up_write(&mm->mmap_sem);
 326 err_free:
 327         bprm->vma = NULL;
 328         kmem_cache_free(vm_area_cachep, vma);
 329         return err;
 330 }
 331
 332 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 333 {
 334         return len <= MAX_ARG_STRLEN;
 335 }
 336
 337 #else
 338
 339 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 340 {
 341 }
 342
 343 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 344                 int write)
 345 {
 346         struct page *page;
 347
 348         page = bprm->page[pos / PAGE_SIZE];
 349         if (!page && write) {
 350                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 351                 if (!page)
 352                         return NULL;
 353                 bprm->page[pos / PAGE_SIZE] = page;
 354         }
 355
 356         return page;
 357 }
 358
 359 static void put_arg_page(struct page *page)
 360 {
 361 }
 362
 363 static void free_arg_page(struct linux_binprm *bprm, int i)
 364 {
 365         if (bprm->page[i]) {
 366                 __free_page(bprm->page[i]);
 367                 bprm->page[i] = NULL;
 368         }
 369 }
 370
 371 static void free_arg_pages(struct linux_binprm *bprm)
 372 {
 373         int i;
 374
 375         for (i = 0; i < MAX_ARG_PAGES; i++)
 376                 free_arg_page(bprm, i);
 377 }
 378
 379 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 380                 struct page *page)
 381 {
 382 }
 383
 384 static int __bprm_mm_init(struct linux_binprm *bprm)
 385 {
 386         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 387         return 0;
 388 }
 389
 390 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 391 {
 392         return len <= bprm->p;
 393 }
 394
 395 #endif /* CONFIG_MMU */
 396
 397 /*
 398  * Create a new mm_struct and populate it with a temporary stack
 399  * vm_area_struct.  We don't have enough context at this point to set the stack
 400  * flags, permissions, and offset, so we use temporary values.  We'll update
 401  * them later in setup_arg_pages().
 402  */
 403 static int bprm_mm_init(struct linux_binprm *bprm)
 404 {
 405         int err;
 406         struct mm_struct *mm = NULL;
 407
 408         bprm->mm = mm = mm_alloc();
 409         err = -ENOMEM;
 410         if (!mm)
 411                 goto err;
 412
 413         err = __bprm_mm_init(bprm);
 414         if (err)
 415                 goto err;
 416
 417         return 0;
 418
 419 err:
 420         if (mm) {
 421                 bprm->mm = NULL;
 422                 mmdrop(mm);
 423         }
 424
 425         return err;
 426 }
 427
 428 struct user_arg_ptr {
 429 #ifdef CONFIG_COMPAT
 430         bool is_compat;
 431 #endif
 432         union {
 433                 const char __user *const __user *native;
 434 #ifdef CONFIG_COMPAT
 435                 const compat_uptr_t __user *compat;
 436 #endif
 437         } ptr;
 438 };
 439
 440 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 441 {
 442         const char __user *native;
 443
 444 #ifdef CONFIG_COMPAT
 445         if (unlikely(argv.is_compat)) {
 446                 compat_uptr_t compat;
 447
 448                 if (get_user(compat, argv.ptr.compat + nr))
 449                         return ERR_PTR(-EFAULT);
 450
 451                 return compat_ptr(compat);
 452         }
 453 #endif
 454
 455         if (get_user(native, argv.ptr.native + nr))
 456                 return ERR_PTR(-EFAULT);
 457
 458         return native;
 459 }
 460
 461 /*
 462  * count() counts the number of strings in array ARGV.
 463  */
 464 static int count(struct user_arg_ptr argv, int max)
 465 {
 466         int i = 0;
 467
 468         if (argv.ptr.native != NULL) {
 469                 for (;;) {
 470                         const char __user *p = get_user_arg_ptr(argv, i);
 471
 472                         if (!p)
 473                                 break;
 474
 475                         if (IS_ERR(p))
 476                                 return -EFAULT;
 477
 478                         if (i >= max)
 479                                 return -E2BIG;
 480                         ++i;
 481
 482                         if (fatal_signal_pending(current))
 483                                 return -ERESTARTNOHAND;
 484                         cond_resched();
 485                 }
 486         }
 487         return i;
 488 }
 489
 490 /*
 491  * 'copy_strings()' copies argument/environment strings from the old
 492  * processes's memory to the new process's stack.  The call to get_user_pages()
 493  * ensures the destination page is created and not swapped out.
 494  */
 495 static int copy_strings(int argc, struct user_arg_ptr argv,
 496                         struct linux_binprm *bprm)
 497 {
 498         struct page *kmapped_page = NULL;
 499         char *kaddr = NULL;
 500         unsigned long kpos = 0;
 501         int ret;
 502
 503         while (argc-- > 0) {
 504                 const char __user *str;
 505                 int len;
 506                 unsigned long pos;
 507
 508                 ret = -EFAULT;
 509                 str = get_user_arg_ptr(argv, argc);
 510                 if (IS_ERR(str))
 511                         goto out;
 512
 513                 len = strnlen_user(str, MAX_ARG_STRLEN);
 514                 if (!len)
 515                         goto out;
 516
 517                 ret = -E2BIG;
 518                 if (!valid_arg_len(bprm, len))
 519                         goto out;
 520
 521                 /* We're going to work our way backwords. */
 522                 pos = bprm->p;
 523                 str += len;
 524                 bprm->p -= len;
 525
 526                 while (len > 0) {
 527                         int offset, bytes_to_copy;
 528
 529                         if (fatal_signal_pending(current)) {
 530                                 ret = -ERESTARTNOHAND;
 531                                 goto out;
 532                         }
 533                         cond_resched();
 534
 535                         offset = pos % PAGE_SIZE;
 536                         if (offset == 0)
 537                                 offset = PAGE_SIZE;
 538
 539                         bytes_to_copy = offset;
 540                         if (bytes_to_copy > len)
 541                                 bytes_to_copy = len;
 542
 543                         offset -= bytes_to_copy;
 544                         pos -= bytes_to_copy;
 545                         str -= bytes_to_copy;
 546                         len -= bytes_to_copy;
 547
 548                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 549                                 struct page *page;
 550
 551                                 page = get_arg_page(bprm, pos, 1);
 552                                 if (!page) {
 553                                         ret = -E2BIG;
 554                                         goto out;
 555                                 }
 556
 557                                 if (kmapped_page) {
 558                                         flush_kernel_dcache_page(kmapped_page);
 559                                         kunmap(kmapped_page);
 560                                         put_arg_page(kmapped_page);
 561                                 }
 562                                 kmapped_page = page;
 563                                 kaddr = kmap(kmapped_page);
 564                                 kpos = pos & PAGE_MASK;
 565                                 flush_arg_page(bprm, kpos, kmapped_page);
 566                         }
 567                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 568                                 ret = -EFAULT;
 569                                 goto out;
 570                         }
 571                 }
 572         }
 573         ret = 0;
 574 out:
 575         if (kmapped_page) {
 576                 flush_kernel_dcache_page(kmapped_page);
 577                 kunmap(kmapped_page);
 578                 put_arg_page(kmapped_page);
 579         }
 580         return ret;
 581 }
 582
 583 /*
 584  * Like copy_strings, but get argv and its values from kernel memory.
 585  */
 586 int copy_strings_kernel(int argc, const char *const *__argv,
 587                         struct linux_binprm *bprm)
 588 {
 589         int r;
 590         mm_segment_t oldfs = get_fs();
 591         struct user_arg_ptr argv = {
 592                 .ptr.native = (const char __user *const  __user *)__argv,
 593         };
 594
 595         set_fs(KERNEL_DS);
 596         r = copy_strings(argc, argv, bprm);
 597         set_fs(oldfs);
 598
 599         return r;
 600 }
 601 EXPORT_SYMBOL(copy_strings_kernel);
 602
 603 #ifdef CONFIG_MMU
 604
 605 /*
 606  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 607  * the binfmt code determines where the new stack should reside, we shift it to
 608  * its final location.  The process proceeds as follows:
 609  *
 610  * 1) Use shift to calculate the new vma endpoints.
 611  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 612  *    arguments passed to subsequent functions are consistent.
 613  * 3) Move vma's page tables to the new range.
 614  * 4) Free up any cleared pgd range.
 615  * 5) Shrink the vma to cover only the new range.
 616  */
 617 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 618 {
 619         struct mm_struct *mm = vma->vm_mm;
 620         unsigned long old_start = vma->vm_start;
 621         unsigned long old_end = vma->vm_end;
 622         unsigned long length = old_end - old_start;
 623         unsigned long new_start = old_start - shift;
 624         unsigned long new_end = old_end - shift;
 625         struct mmu_gather tlb;
 626
 627         BUG_ON(new_start > new_end);
 628
 629         /*
 630          * ensure there are no vmas between where we want to go
 631          * and where we are
 632          */
 633         if (vma != find_vma(mm, new_start))
 634                 return -EFAULT;
 635
 636         /*
 637          * cover the whole range: [new_start, old_end)
 638          */
 639         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 640                 return -ENOMEM;
 641
 642         /*
 643          * move the page tables downwards, on failure we rely on
 644          * process cleanup to remove whatever mess we made.
 645          */
 646         if (length != move_page_tables(vma, old_start,
 647                                        vma, new_start, length, false))
 648                 return -ENOMEM;
 649
 650         lru_add_drain();
 651         tlb_gather_mmu(&tlb, mm, old_start, old_end);
 652         if (new_end > old_start) {
 653                 /*
 654                  * when the old and new regions overlap clear from new_end.
 655                  */
 656                 free_pgd_range(&tlb, new_end, old_end, new_end,
 657                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 658         } else {
 659                 /*
 660                  * otherwise, clean from old_start; this is done to not touch
 661                  * the address space in [new_end, old_start) some architectures
 662                  * have constraints on va-space that make this illegal (IA64) -
 663                  * for the others its just a little faster.
 664                  */
 665                 free_pgd_range(&tlb, old_start, old_end, new_end,
 666                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 667         }
 668         tlb_finish_mmu(&tlb, old_start, old_end);
 669
 670         /*
 671          * Shrink the vma to just the new range.  Always succeeds.
 672          */
 673         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 674
 675         return 0;
 676 }
 677
 678 /*
 679  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 680  * the stack is optionally relocated, and some extra space is added.
 681  */
 682 int setup_arg_pages(struct linux_binprm *bprm,
 683                     unsigned long stack_top,
 684                     int executable_stack)
 685 {
 686         unsigned long ret;
 687         unsigned long stack_shift;
 688         struct mm_struct *mm = current->mm;
 689         struct vm_area_struct *vma = bprm->vma;
 690         struct vm_area_struct *prev = NULL;
 691         unsigned long vm_flags;
 692         unsigned long stack_base;
 693         unsigned long stack_size;
 694         unsigned long stack_expand;
 695         unsigned long rlim_stack;
 696
 697 #ifdef CONFIG_STACK_GROWSUP
 698         /* Limit stack size */
 699         stack_base = rlimit_max(RLIMIT_STACK);
 700         if (stack_base > STACK_SIZE_MAX)
 701                 stack_base = STACK_SIZE_MAX;
 702
 703         /* Add space for stack randomization. */
 704         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 705
 706         /* Make sure we didn't let the argument array grow too large. */
 707         if (vma->vm_end - vma->vm_start > stack_base)
 708                 return -ENOMEM;
 709
 710         stack_base = PAGE_ALIGN(stack_top - stack_base);
 711
 712         stack_shift = vma->vm_start - stack_base;
 713         mm->arg_start = bprm->p - stack_shift;
 714         bprm->p = vma->vm_end - stack_shift;
 715 #else
 716         stack_top = arch_align_stack(stack_top);
 717         stack_top = PAGE_ALIGN(stack_top);
 718
 719         if (unlikely(stack_top < mmap_min_addr) ||
 720             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 721                 return -ENOMEM;
 722
 723         stack_shift = vma->vm_end - stack_top;
 724
 725         bprm->p -= stack_shift;
 726         mm->arg_start = bprm->p;
 727 #endif
 728
 729         if (bprm->loader)
 730                 bprm->loader -= stack_shift;
 731         bprm->exec -= stack_shift;
 732
 733         if (down_write_killable(&mm->mmap_sem))
 734                 return -EINTR;
 735
 736         vm_flags = VM_STACK_FLAGS;
 737
 738         /*
 739          * Adjust stack execute permissions; explicitly enable for
 740          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 741          * (arch default) otherwise.
 742          */
 743         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 744                 vm_flags |= VM_EXEC;
 745         else if (executable_stack == EXSTACK_DISABLE_X)
 746                 vm_flags &= ~VM_EXEC;
 747         vm_flags |= mm->def_flags;
 748         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 749
 750         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 751                         vm_flags);
 752         if (ret)
 753                 goto out_unlock;
 754         BUG_ON(prev != vma);
 755
 756         /* Move stack pages down in memory. */
 757         if (stack_shift) {
 758                 ret = shift_arg_pages(vma, stack_shift);
 759                 if (ret)
 760                         goto out_unlock;
 761         }
 762
 763         /* mprotect_fixup is overkill to remove the temporary stack flags */
 764         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 765
 766         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 767         stack_size = vma->vm_end - vma->vm_start;
 768         /*
 769          * Align this down to a page boundary as expand_stack
 770          * will align it up.
 771          */
 772         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 773 #ifdef CONFIG_STACK_GROWSUP
 774         if (stack_size + stack_expand > rlim_stack)
 775                 stack_base = vma->vm_start + rlim_stack;
 776         else
 777                 stack_base = vma->vm_end + stack_expand;
 778 #else
 779         if (stack_size + stack_expand > rlim_stack)
 780                 stack_base = vma->vm_end - rlim_stack;
 781         else
 782                 stack_base = vma->vm_start - stack_expand;
 783 #endif
 784         current->mm->start_stack = bprm->p;
 785         ret = expand_stack(vma, stack_base);
 786         if (ret)
 787                 ret = -EFAULT;
 788
 789 out_unlock:
 790         up_write(&mm->mmap_sem);
 791         return ret;
 792 }
 793 EXPORT_SYMBOL(setup_arg_pages);
 794
 795 #else
 796
 797 /*
 798  * Transfer the program arguments and environment from the holding pages
 799  * onto the stack. The provided stack pointer is adjusted accordingly.
 800  */
 801 int transfer_args_to_stack(struct linux_binprm *bprm,
 802                            unsigned long *sp_location)
 803 {
 804         unsigned long index, stop, sp;
 805         int ret = 0;
 806
 807         stop = bprm->p >> PAGE_SHIFT;
 808         sp = *sp_location;
 809
 810         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
 811                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
 812                 char *src = kmap(bprm->page[index]) + offset;
 813                 sp -= PAGE_SIZE - offset;
 814                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
 815                         ret = -EFAULT;
 816                 kunmap(bprm->page[index]);
 817                 if (ret)
 818                         goto out;
 819         }
 820
 821         *sp_location = sp;
 822
 823 out:
 824         return ret;
 825 }
 826 EXPORT_SYMBOL(transfer_args_to_stack);
 827
 828 #endif /* CONFIG_MMU */
 829
 830 static struct file *do_open_execat(int fd, struct filename *name, int flags)
 831 {
 832         struct file *file;
 833         int err;
 834         struct open_flags open_exec_flags = {
 835                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 836                 .acc_mode = MAY_EXEC,
 837                 .intent = LOOKUP_OPEN,
 838                 .lookup_flags = LOOKUP_FOLLOW,
 839         };
 840
 841         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 842                 return ERR_PTR(-EINVAL);
 843         if (flags & AT_SYMLINK_NOFOLLOW)
 844                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 845         if (flags & AT_EMPTY_PATH)
 846                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 847
 848         file = do_filp_open(fd, name, &open_exec_flags);
 849         if (IS_ERR(file))
 850                 goto out;
 851
 852         err = -EACCES;
 853         if (!S_ISREG(file_inode(file)->i_mode))
 854                 goto exit;
 855
 856         if (path_noexec(&file->f_path))
 857                 goto exit;
 858
 859         err = deny_write_access(file);
 860         if (err)
 861                 goto exit;
 862
 863         if (name->name[0] != '\0')
 864                 fsnotify_open(file);
 865
 866 out:
 867         return file;
 868
 869 exit:
 870         fput(file);
 871         return ERR_PTR(err);
 872 }
 873
 874 struct file *open_exec(const char *name)
 875 {
 876         struct filename *filename = getname_kernel(name);
 877         struct file *f = ERR_CAST(filename);
 878
 879         if (!IS_ERR(filename)) {
 880                 f = do_open_execat(AT_FDCWD, filename, 0);
 881                 putname(filename);
 882         }
 883         return f;
 884 }
 885 EXPORT_SYMBOL(open_exec);
 886
 887 int kernel_read(struct file *file, loff_t offset,
 888                 char *addr, unsigned long count)
 889 {
 890         mm_segment_t old_fs;
 891         loff_t pos = offset;
 892         int result;
 893
 894         old_fs = get_fs();
 895         set_fs(get_ds());
 896         /* The cast to a user pointer is valid due to the set_fs() */
 897         result = vfs_read(file, (void __user *)addr, count, &pos);
 898         set_fs(old_fs);
 899         return result;
 900 }
 901
 902 EXPORT_SYMBOL(kernel_read);
 903
 904 int kernel_read_file(struct file *file, void **buf, loff_t *size,
 905                      loff_t max_size, enum kernel_read_file_id id)
 906 {
 907         loff_t i_size, pos;
 908         ssize_t bytes = 0;
 909         int ret;
 910
 911         if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
 912                 return -EINVAL;
 913
 914         ret = security_kernel_read_file(file, id);
 915         if (ret)
 916                 return ret;
 917
 918         ret = deny_write_access(file);
 919         if (ret)
 920                 return ret;
 921
 922         i_size = i_size_read(file_inode(file));
 923         if (max_size > 0 && i_size > max_size) {
 924                 ret = -EFBIG;
 925                 goto out;
 926         }
 927         if (i_size <= 0) {
 928                 ret = -EINVAL;
 929                 goto out;
 930         }
 931
 932         if (id != READING_FIRMWARE_PREALLOC_BUFFER)
 933                 *buf = vmalloc(i_size);
 934         if (!*buf) {
 935                 ret = -ENOMEM;
 936                 goto out;
 937         }
 938
 939         pos = 0;
 940         while (pos < i_size) {
 941                 bytes = kernel_read(file, pos, (char *)(*buf) + pos,
 942                                     i_size - pos);
 943                 if (bytes < 0) {
 944                         ret = bytes;
 945                         goto out;
 946                 }
 947
 948                 if (bytes == 0)
 949                         break;
 950                 pos += bytes;
 951         }
 952
 953         if (pos != i_size) {
 954                 ret = -EIO;
 955                 goto out_free;
 956         }
 957
 958         ret = security_kernel_post_read_file(file, *buf, i_size, id);
 959         if (!ret)
 960                 *size = pos;
 961
 962 out_free:
 963         if (ret < 0) {
 964                 if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
 965                         vfree(*buf);
 966                         *buf = NULL;
 967                 }
 968         }
 969
 970 out:
 971         allow_write_access(file);
 972         return ret;
 973 }
 974 EXPORT_SYMBOL_GPL(kernel_read_file);
 975
 976 int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
 977                                loff_t max_size, enum kernel_read_file_id id)
 978 {
 979         struct file *file;
 980         int ret;
 981
 982         if (!path || !*path)
 983                 return -EINVAL;
 984
 985         file = filp_open(path, O_RDONLY, 0);
 986         if (IS_ERR(file))
 987                 return PTR_ERR(file);
 988
 989         ret = kernel_read_file(file, buf, size, max_size, id);
 990         fput(file);
 991         return ret;
 992 }
 993 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 994
 995 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
 996                              enum kernel_read_file_id id)
 997 {
 998         struct fd f = fdget(fd);
 999         int ret = -EBADF;
1000
1001         if (!f.file)
1002                 goto out;
1003
1004         ret = kernel_read_file(f.file, buf, size, max_size, id);
1005 out:
1006         fdput(f);
1007         return ret;
1008 }
1009 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
1010
1011 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
1012 {
1013         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
1014         if (res > 0)
1015                 flush_icache_range(addr, addr + len);
1016         return res;
1017 }
1018 EXPORT_SYMBOL(read_code);
1019
1020 static int exec_mmap(struct mm_struct *mm)
1021 {
1022         struct task_struct *tsk;
1023         struct mm_struct *old_mm, *active_mm;
1024
1025         /* Notify parent that we're no longer interested in the old VM */
1026         tsk = current;
1027         old_mm = current->mm;
1028         mm_release(tsk, old_mm);
1029
1030         if (old_mm) {
1031                 sync_mm_rss(old_mm);
1032                 /*
1033                  * Make sure that if there is a core dump in progress
1034                  * for the old mm, we get out and die instead of going
1035                  * through with the exec.  We must hold mmap_sem around
1036                  * checking core_state and changing tsk->mm.
1037                  */
1038                 down_read(&old_mm->mmap_sem);
1039                 if (unlikely(old_mm->core_state)) {
1040                         up_read(&old_mm->mmap_sem);
1041                         return -EINTR;
1042                 }
1043         }
1044         task_lock(tsk);
1045         active_mm = tsk->active_mm;
1046         tsk->mm = mm;
1047         tsk->active_mm = mm;
1048         activate_mm(active_mm, mm);
1049         tsk->mm->vmacache_seqnum = 0;
1050         vmacache_flush(tsk);
1051         task_unlock(tsk);
1052         if (old_mm) {
1053                 up_read(&old_mm->mmap_sem);
1054                 BUG_ON(active_mm != old_mm);
1055                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1056                 mm_update_next_owner(old_mm);
1057                 mmput(old_mm);
1058                 return 0;
1059         }
1060         mmdrop(active_mm);
1061         return 0;
1062 }
1063
1064 /*
1065  * This function makes sure the current process has its own signal table,
1066  * so that flush_signal_handlers can later reset the handlers without
1067  * disturbing other processes.  (Other processes might share the signal
1068  * table via the CLONE_SIGHAND option to clone().)
1069  */
1070 static int de_thread(struct task_struct *tsk)
1071 {
1072         struct signal_struct *sig = tsk->signal;
1073         struct sighand_struct *oldsighand = tsk->sighand;
1074         spinlock_t *lock = &oldsighand->siglock;
1075
1076         if (thread_group_empty(tsk))
1077                 goto no_thread_group;
1078
1079         /*
1080          * Kill all other threads in the thread group.
1081          */
1082         spin_lock_irq(lock);
1083         if (signal_group_exit(sig)) {
1084                 /*
1085                  * Another group action in progress, just
1086                  * return so that the signal is processed.
1087                  */
1088                 spin_unlock_irq(lock);
1089                 return -EAGAIN;
1090         }
1091
1092         sig->group_exit_task = tsk;
1093         sig->notify_count = zap_other_threads(tsk);
1094         if (!thread_group_leader(tsk))
1095                 sig->notify_count--;
1096
1097         while (sig->notify_count) {
1098                 __set_current_state(TASK_KILLABLE);
1099                 spin_unlock_irq(lock);
1100                 schedule();
1101                 if (unlikely(__fatal_signal_pending(tsk)))
1102                         goto killed;
1103                 spin_lock_irq(lock);
1104         }
1105         spin_unlock_irq(lock);
1106
1107         /*
1108          * At this point all other threads have exited, all we have to
1109          * do is to wait for the thread group leader to become inactive,
1110          * and to assume its PID:
1111          */
1112         if (!thread_group_leader(tsk)) {
1113                 struct task_struct *leader = tsk->group_leader;
1114
1115                 for (;;) {
1116                         cgroup_threadgroup_change_begin(tsk);
1117                         write_lock_irq(&tasklist_lock);
1118                         /*
1119                          * Do this under tasklist_lock to ensure that
1120                          * exit_notify() can't miss ->group_exit_task
1121                          */
1122                         sig->notify_count = -1;
1123                         if (likely(leader->exit_state))
1124                                 break;
1125                         __set_current_state(TASK_KILLABLE);
1126                         write_unlock_irq(&tasklist_lock);
1127                         cgroup_threadgroup_change_end(tsk);
1128                         schedule();
1129                         if (unlikely(__fatal_signal_pending(tsk)))
1130                                 goto killed;
1131                 }
1132
1133                 /*
1134                  * The only record we have of the real-time age of a
1135                  * process, regardless of execs it's done, is start_time.
1136                  * All the past CPU time is accumulated in signal_struct
1137                  * from sister threads now dead.  But in this non-leader
1138                  * exec, nothing survives from the original leader thread,
1139                  * whose birth marks the true age of this process now.
1140                  * When we take on its identity by switching to its PID, we
1141                  * also take its birthdate (always earlier than our own).
1142                  */
1143                 tsk->start_time = leader->start_time;
1144                 tsk->real_start_time = leader->real_start_time;
1145
1146                 BUG_ON(!same_thread_group(leader, tsk));
1147                 BUG_ON(has_group_leader_pid(tsk));
1148                 /*
1149                  * An exec() starts a new thread group with the
1150                  * TGID of the previous thread group. Rehash the
1151                  * two threads with a switched PID, and release
1152                  * the former thread group leader:
1153                  */
1154
1155                 /* Become a process group leader with the old leader's pid.
1156                  * The old leader becomes a thread of the this thread group.
1157                  * Note: The old leader also uses this pid until release_task
1158                  *       is called.  Odd but simple and correct.
1159                  */
1160                 tsk->pid = leader->pid;
1161                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1162                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1163                 transfer_pid(leader, tsk, PIDTYPE_SID);
1164
1165                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1166                 list_replace_init(&leader->sibling, &tsk->sibling);
1167
1168                 tsk->group_leader = tsk;
1169                 leader->group_leader = tsk;
1170
1171                 tsk->exit_signal = SIGCHLD;
1172                 leader->exit_signal = -1;
1173
1174                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1175                 leader->exit_state = EXIT_DEAD;
1176
1177                 /*
1178                  * We are going to release_task()->ptrace_unlink() silently,
1179                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1180                  * the tracer wont't block again waiting for this thread.
1181                  */
1182                 if (unlikely(leader->ptrace))
1183                         __wake_up_parent(leader, leader->parent);
1184                 write_unlock_irq(&tasklist_lock);
1185                 cgroup_threadgroup_change_end(tsk);
1186
1187                 release_task(leader);
1188         }
1189
1190         sig->group_exit_task = NULL;
1191         sig->notify_count = 0;
1192
1193 no_thread_group:
1194         /* we have changed execution domain */
1195         tsk->exit_signal = SIGCHLD;
1196
1197 #ifdef CONFIG_POSIX_TIMERS
1198         exit_itimers(sig);
1199         flush_itimer_signals();
1200 #endif
1201
1202         if (atomic_read(&oldsighand->count) != 1) {
1203                 struct sighand_struct *newsighand;
1204                 /*
1205                  * This ->sighand is shared with the CLONE_SIGHAND
1206                  * but not CLONE_THREAD task, switch to the new one.
1207                  */
1208                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1209                 if (!newsighand)
1210                         return -ENOMEM;
1211
1212                 atomic_set(&newsighand->count, 1);
1213                 memcpy(newsighand->action, oldsighand->action,
1214                        sizeof(newsighand->action));
1215
1216                 write_lock_irq(&tasklist_lock);
1217                 spin_lock(&oldsighand->siglock);
1218                 rcu_assign_pointer(tsk->sighand, newsighand);
1219                 spin_unlock(&oldsighand->siglock);
1220                 write_unlock_irq(&tasklist_lock);
1221
1222                 __cleanup_sighand(oldsighand);
1223         }
1224
1225         BUG_ON(!thread_group_leader(tsk));
1226         return 0;
1227
1228 killed:
1229         /* protects against exit_notify() and __exit_signal() */
1230         read_lock(&tasklist_lock);
1231         sig->group_exit_task = NULL;
1232         sig->notify_count = 0;
1233         read_unlock(&tasklist_lock);
1234         return -EAGAIN;
1235 }
1236
1237 char *get_task_comm(char *buf, struct task_struct *tsk)
1238 {
1239         /* buf must be at least sizeof(tsk->comm) in size */
1240         task_lock(tsk);
1241         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1242         task_unlock(tsk);
1243         return buf;
1244 }
1245 EXPORT_SYMBOL_GPL(get_task_comm);
1246
1247 /*
1248  * These functions flushes out all traces of the currently running executable
1249  * so that a new one can be started
1250  */
1251
1252 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1253 {
1254         task_lock(tsk);
1255         trace_task_rename(tsk, buf);
1256         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1257         task_unlock(tsk);
1258         perf_event_comm(tsk, exec);
1259 }
1260
1261 int flush_old_exec(struct linux_binprm * bprm)
1262 {
1263         int retval;
1264
1265         /*
1266          * Make sure we have a private signal table and that
1267          * we are unassociated from the previous thread group.
1268          */
1269         retval = de_thread(current);
1270         if (retval)
1271                 goto out;
1272
1273         /*
1274          * Must be called _before_ exec_mmap() as bprm->mm is
1275          * not visibile until then. This also enables the update
1276          * to be lockless.
1277          */
1278         set_mm_exe_file(bprm->mm, bprm->file);
1279
1280         /*
1281          * Release all of the old mmap stuff
1282          */
1283         acct_arg_size(bprm, 0);
1284         retval = exec_mmap(bprm->mm);
1285         if (retval)
1286                 goto out;
1287
1288         bprm->mm = NULL;                /* We're using it now */
1289
1290         set_fs(USER_DS);
1291         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1292                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1293         flush_thread();
1294         current->personality &= ~bprm->per_clear;
1295
1296         /*
1297          * We have to apply CLOEXEC before we change whether the process is
1298          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1299          * trying to access the should-be-closed file descriptors of a process
1300          * undergoing exec(2).
1301          */
1302         do_close_on_exec(current->files);
1303         return 0;
1304
1305 out:
1306         return retval;
1307 }
1308 EXPORT_SYMBOL(flush_old_exec);
1309
1310 void would_dump(struct linux_binprm *bprm, struct file *file)
1311 {
1312         struct inode *inode = file_inode(file);
1313         if (inode_permission(inode, MAY_READ) < 0) {
1314                 struct user_namespace *old, *user_ns;
1315                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1316
1317                 /* Ensure mm->user_ns contains the executable */
1318                 user_ns = old = bprm->mm->user_ns;
1319                 while ((user_ns != &init_user_ns) &&
1320                        !privileged_wrt_inode_uidgid(user_ns, inode))
1321                         user_ns = user_ns->parent;
1322
1323                 if (old != user_ns) {
1324                         bprm->mm->user_ns = get_user_ns(user_ns);
1325                         put_user_ns(old);
1326                 }
1327         }
1328 }
1329 EXPORT_SYMBOL(would_dump);
1330
1331 void setup_new_exec(struct linux_binprm * bprm)
1332 {
1333         arch_pick_mmap_layout(current->mm);
1334
1335         /* This is the point of no return */
1336         current->sas_ss_sp = current->sas_ss_size = 0;
1337
1338         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1339                 set_dumpable(current->mm, SUID_DUMP_USER);
1340         else
1341                 set_dumpable(current->mm, suid_dumpable);
1342
1343         arch_setup_new_exec();
1344         perf_event_exec();
1345         __set_task_comm(current, kbasename(bprm->filename), true);
1346
1347         /* Set the new mm task size. We have to do that late because it may
1348          * depend on TIF_32BIT which is only updated in flush_thread() on
1349          * some architectures like powerpc
1350          */
1351         current->mm->task_size = TASK_SIZE;
1352
1353         /* install the new credentials */
1354         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1355             !gid_eq(bprm->cred->gid, current_egid())) {
1356                 current->pdeath_signal = 0;
1357         } else {
1358                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1359                         set_dumpable(current->mm, suid_dumpable);
1360         }
1361
1362         /* An exec changes our domain. We are no longer part of the thread
1363            group */
1364         current->self_exec_id++;
1365         flush_signal_handlers(current, 0);
1366 }
1367 EXPORT_SYMBOL(setup_new_exec);
1368
1369 /*
1370  * Prepare credentials and lock ->cred_guard_mutex.
1371  * install_exec_creds() commits the new creds and drops the lock.
1372  * Or, if exec fails before, free_bprm() should release ->cred and
1373  * and unlock.
1374  */
1375 int prepare_bprm_creds(struct linux_binprm *bprm)
1376 {
1377         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1378                 return -ERESTARTNOINTR;
1379
1380         bprm->cred = prepare_exec_creds();
1381         if (likely(bprm->cred))
1382                 return 0;
1383
1384         mutex_unlock(&current->signal->cred_guard_mutex);
1385         return -ENOMEM;
1386 }
1387
1388 static void free_bprm(struct linux_binprm *bprm)
1389 {
1390         free_arg_pages(bprm);
1391         if (bprm->cred) {
1392                 mutex_unlock(&current->signal->cred_guard_mutex);
1393                 abort_creds(bprm->cred);
1394         }
1395         if (bprm->file) {
1396                 allow_write_access(bprm->file);
1397                 fput(bprm->file);
1398         }
1399         /* If a binfmt changed the interp, free it. */
1400         if (bprm->interp != bprm->filename)
1401                 kfree(bprm->interp);
1402         kfree(bprm);
1403 }
1404
1405 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1406 {
1407         /* If a binfmt changed the interp, free it first. */
1408         if (bprm->interp != bprm->filename)
1409                 kfree(bprm->interp);
1410         bprm->interp = kstrdup(interp, GFP_KERNEL);
1411         if (!bprm->interp)
1412                 return -ENOMEM;
1413         return 0;
1414 }
1415 EXPORT_SYMBOL(bprm_change_interp);
1416
1417 /*
1418  * install the new credentials for this executable
1419  */
1420 void install_exec_creds(struct linux_binprm *bprm)
1421 {
1422         security_bprm_committing_creds(bprm);
1423
1424         commit_creds(bprm->cred);
1425         bprm->cred = NULL;
1426
1427         /*
1428          * Disable monitoring for regular users
1429          * when executing setuid binaries. Must
1430          * wait until new credentials are committed
1431          * by commit_creds() above
1432          */
1433         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1434                 perf_event_exit_task(current);
1435         /*
1436          * cred_guard_mutex must be held at least to this point to prevent
1437          * ptrace_attach() from altering our determination of the task's
1438          * credentials; any time after this it may be unlocked.
1439          */
1440         security_bprm_committed_creds(bprm);
1441         mutex_unlock(&current->signal->cred_guard_mutex);
1442 }
1443 EXPORT_SYMBOL(install_exec_creds);
1444
1445 /*
1446  * determine how safe it is to execute the proposed program
1447  * - the caller must hold ->cred_guard_mutex to protect against
1448  *   PTRACE_ATTACH or seccomp thread-sync
1449  */
1450 static void check_unsafe_exec(struct linux_binprm *bprm)
1451 {
1452         struct task_struct *p = current, *t;
1453         unsigned n_fs;
1454
1455         if (p->ptrace)
1456                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1457
1458         /*
1459          * This isn't strictly necessary, but it makes it harder for LSMs to
1460          * mess up.
1461          */
1462         if (task_no_new_privs(current))
1463                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1464
1465         t = p;
1466         n_fs = 1;
1467         spin_lock(&p->fs->lock);
1468         rcu_read_lock();
1469         while_each_thread(p, t) {
1470                 if (t->fs == p->fs)
1471                         n_fs++;
1472         }
1473         rcu_read_unlock();
1474
1475         if (p->fs->users > n_fs)
1476                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1477         else
1478                 p->fs->in_exec = 1;
1479         spin_unlock(&p->fs->lock);
1480 }
1481
1482 static void bprm_fill_uid(struct linux_binprm *bprm)
1483 {
1484         struct inode *inode;
1485         unsigned int mode;
1486         kuid_t uid;
1487         kgid_t gid;
1488
1489         /*
1490          * Since this can be called multiple times (via prepare_binprm),
1491          * we must clear any previous work done when setting set[ug]id
1492          * bits from any earlier bprm->file uses (for example when run
1493          * first for a setuid script then again for its interpreter).
1494          */
1495         bprm->cred->euid = current_euid();
1496         bprm->cred->egid = current_egid();
1497
1498         if (!mnt_may_suid(bprm->file->f_path.mnt))
1499                 return;
1500
1501         if (task_no_new_privs(current))
1502                 return;
1503
1504         inode = bprm->file->f_path.dentry->d_inode;
1505         mode = READ_ONCE(inode->i_mode);
1506         if (!(mode & (S_ISUID|S_ISGID)))
1507                 return;
1508
1509         /* Be careful if suid/sgid is set */
1510         inode_lock(inode);
1511
1512         /* reload atomically mode/uid/gid now that lock held */
1513         mode = inode->i_mode;
1514         uid = inode->i_uid;
1515         gid = inode->i_gid;
1516         inode_unlock(inode);
1517
1518         /* We ignore suid/sgid if there are no mappings for them in the ns */
1519         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1520                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1521                 return;
1522
1523         if (mode & S_ISUID) {
1524                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1525                 bprm->cred->euid = uid;
1526         }
1527
1528         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1529                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1530                 bprm->cred->egid = gid;
1531         }
1532 }
1533
1534 /*
1535  * Fill the binprm structure from the inode.
1536  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1537  *
1538  * This may be called multiple times for binary chains (scripts for example).
1539  */
1540 int prepare_binprm(struct linux_binprm *bprm)
1541 {
1542         int retval;
1543
1544         bprm_fill_uid(bprm);
1545
1546         /* fill in binprm security blob */
1547         retval = security_bprm_set_creds(bprm);
1548         if (retval)
1549                 return retval;
1550         bprm->cred_prepared = 1;
1551
1552         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1553         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1554 }
1555
1556 EXPORT_SYMBOL(prepare_binprm);
1557
1558 /*
1559  * Arguments are '\0' separated strings found at the location bprm->p
1560  * points to; chop off the first by relocating brpm->p to right after
1561  * the first '\0' encountered.
1562  */
1563 int remove_arg_zero(struct linux_binprm *bprm)
1564 {
1565         int ret = 0;
1566         unsigned long offset;
1567         char *kaddr;
1568         struct page *page;
1569
1570         if (!bprm->argc)
1571                 return 0;
1572
1573         do {
1574                 offset = bprm->p & ~PAGE_MASK;
1575                 page = get_arg_page(bprm, bprm->p, 0);
1576                 if (!page) {
1577                         ret = -EFAULT;
1578                         goto out;
1579                 }
1580                 kaddr = kmap_atomic(page);
1581
1582                 for (; offset < PAGE_SIZE && kaddr[offset];
1583                                 offset++, bprm->p++)
1584                         ;
1585
1586                 kunmap_atomic(kaddr);
1587                 put_arg_page(page);
1588         } while (offset == PAGE_SIZE);
1589
1590         bprm->p++;
1591         bprm->argc--;
1592         ret = 0;
1593
1594 out:
1595         return ret;
1596 }
1597 EXPORT_SYMBOL(remove_arg_zero);
1598
1599 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1600 /*
1601  * cycle the list of binary formats handler, until one recognizes the image
1602  */
1603 int search_binary_handler(struct linux_binprm *bprm)
1604 {
1605         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1606         struct linux_binfmt *fmt;
1607         int retval;
1608
1609         /* This allows 4 levels of binfmt rewrites before failing hard. */
1610         if (bprm->recursion_depth > 5)
1611                 return -ELOOP;
1612
1613         retval = security_bprm_check(bprm);
1614         if (retval)
1615                 return retval;
1616
1617         retval = -ENOENT;
1618  retry:
1619         read_lock(&binfmt_lock);
1620         list_for_each_entry(fmt, &formats, lh) {
1621                 if (!try_module_get(fmt->module))
1622                         continue;
1623                 read_unlock(&binfmt_lock);
1624                 bprm->recursion_depth++;
1625                 retval = fmt->load_binary(bprm);
1626                 read_lock(&binfmt_lock);
1627                 put_binfmt(fmt);
1628                 bprm->recursion_depth--;
1629                 if (retval < 0 && !bprm->mm) {
1630                         /* we got to flush_old_exec() and failed after it */
1631                         read_unlock(&binfmt_lock);
1632                         force_sigsegv(SIGSEGV, current);
1633                         return retval;
1634                 }
1635                 if (retval != -ENOEXEC || !bprm->file) {
1636                         read_unlock(&binfmt_lock);
1637                         return retval;
1638                 }
1639         }
1640         read_unlock(&binfmt_lock);
1641
1642         if (need_retry) {
1643                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1644                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1645                         return retval;
1646                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1647                         return retval;
1648                 need_retry = false;
1649                 goto retry;
1650         }
1651
1652         return retval;
1653 }
1654 EXPORT_SYMBOL(search_binary_handler);
1655
1656 static int exec_binprm(struct linux_binprm *bprm)
1657 {
1658         pid_t old_pid, old_vpid;
1659         int ret;
1660
1661         /* Need to fetch pid before load_binary changes it */
1662         old_pid = current->pid;
1663         rcu_read_lock();
1664         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1665         rcu_read_unlock();
1666
1667         ret = search_binary_handler(bprm);
1668         if (ret >= 0) {
1669                 audit_bprm(bprm);
1670                 trace_sched_process_exec(current, old_pid, bprm);
1671                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1672                 proc_exec_connector(current);
1673         }
1674
1675         return ret;
1676 }
1677
1678 /*
1679  * sys_execve() executes a new program.
1680  */
1681 static int do_execveat_common(int fd, struct filename *filename,
1682                               struct user_arg_ptr argv,
1683                               struct user_arg_ptr envp,
1684                               int flags)
1685 {
1686         char *pathbuf = NULL;
1687         struct linux_binprm *bprm;
1688         struct file *file;
1689         struct files_struct *displaced;
1690         int retval;
1691
1692         if (IS_ERR(filename))
1693                 return PTR_ERR(filename);
1694
1695         /*
1696          * We move the actual failure in case of RLIMIT_NPROC excess from
1697          * set*uid() to execve() because too many poorly written programs
1698          * don't check setuid() return code.  Here we additionally recheck
1699          * whether NPROC limit is still exceeded.
1700          */
1701         if ((current->flags & PF_NPROC_EXCEEDED) &&
1702             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1703                 retval = -EAGAIN;
1704                 goto out_ret;
1705         }
1706
1707         /* We're below the limit (still or again), so we don't want to make
1708          * further execve() calls fail. */
1709         current->flags &= ~PF_NPROC_EXCEEDED;
1710
1711         retval = unshare_files(&displaced);
1712         if (retval)
1713                 goto out_ret;
1714
1715         retval = -ENOMEM;
1716         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1717         if (!bprm)
1718                 goto out_files;
1719
1720         retval = prepare_bprm_creds(bprm);
1721         if (retval)
1722                 goto out_free;
1723
1724         check_unsafe_exec(bprm);
1725         current->in_execve = 1;
1726
1727         file = do_open_execat(fd, filename, flags);
1728         retval = PTR_ERR(file);
1729         if (IS_ERR(file))
1730                 goto out_unmark;
1731
1732         sched_exec();
1733
1734         bprm->file = file;
1735         if (fd == AT_FDCWD || filename->name[0] == '/') {
1736                 bprm->filename = filename->name;
1737         } else {
1738                 if (filename->name[0] == '\0')
1739                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1740                 else
1741                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1742                                             fd, filename->name);
1743                 if (!pathbuf) {
1744                         retval = -ENOMEM;
1745                         goto out_unmark;
1746                 }
1747                 /*
1748                  * Record that a name derived from an O_CLOEXEC fd will be
1749                  * inaccessible after exec. Relies on having exclusive access to
1750                  * current->files (due to unshare_files above).
1751                  */
1752                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1753                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1754                 bprm->filename = pathbuf;
1755         }
1756         bprm->interp = bprm->filename;
1757
1758         retval = bprm_mm_init(bprm);
1759         if (retval)
1760                 goto out_unmark;
1761
1762         bprm->argc = count(argv, MAX_ARG_STRINGS);
1763         if ((retval = bprm->argc) < 0)
1764                 goto out;
1765
1766         bprm->envc = count(envp, MAX_ARG_STRINGS);
1767         if ((retval = bprm->envc) < 0)
1768                 goto out;
1769
1770         retval = prepare_binprm(bprm);
1771         if (retval < 0)
1772                 goto out;
1773
1774         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1775         if (retval < 0)
1776                 goto out;
1777
1778         bprm->exec = bprm->p;
1779         retval = copy_strings(bprm->envc, envp, bprm);
1780         if (retval < 0)
1781                 goto out;
1782
1783         retval = copy_strings(bprm->argc, argv, bprm);
1784         if (retval < 0)
1785                 goto out;
1786
1787         would_dump(bprm, bprm->file);
1788
1789         retval = exec_binprm(bprm);
1790         if (retval < 0)
1791                 goto out;
1792
1793         /* execve succeeded */
1794         current->fs->in_exec = 0;
1795         current->in_execve = 0;
1796         acct_update_integrals(current);
1797         task_numa_free(current);
1798         free_bprm(bprm);
1799         kfree(pathbuf);
1800         putname(filename);
1801         if (displaced)
1802                 put_files_struct(displaced);
1803         return retval;
1804
1805 out:
1806         if (bprm->mm) {
1807                 acct_arg_size(bprm, 0);
1808                 mmput(bprm->mm);
1809         }
1810
1811 out_unmark:
1812         current->fs->in_exec = 0;
1813         current->in_execve = 0;
1814
1815 out_free:
1816         free_bprm(bprm);
1817         kfree(pathbuf);
1818
1819 out_files:
1820         if (displaced)
1821                 reset_files_struct(displaced);
1822 out_ret:
1823         putname(filename);
1824         return retval;
1825 }
1826
1827 int do_execve(struct filename *filename,
1828         const char __user *const __user *__argv,
1829         const char __user *const __user *__envp)
1830 {
1831         struct user_arg_ptr argv = { .ptr.native = __argv };
1832         struct user_arg_ptr envp = { .ptr.native = __envp };
1833         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1834 }
1835
1836 int do_execveat(int fd, struct filename *filename,
1837                 const char __user *const __user *__argv,
1838                 const char __user *const __user *__envp,
1839                 int flags)
1840 {
1841         struct user_arg_ptr argv = { .ptr.native = __argv };
1842         struct user_arg_ptr envp = { .ptr.native = __envp };
1843
1844         return do_execveat_common(fd, filename, argv, envp, flags);
1845 }
1846
1847 #ifdef CONFIG_COMPAT
1848 static int compat_do_execve(struct filename *filename,
1849         const compat_uptr_t __user *__argv,
1850         const compat_uptr_t __user *__envp)
1851 {
1852         struct user_arg_ptr argv = {
1853                 .is_compat = true,
1854                 .ptr.compat = __argv,
1855         };
1856         struct user_arg_ptr envp = {
1857                 .is_compat = true,
1858                 .ptr.compat = __envp,
1859         };
1860         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1861 }
1862
1863 static int compat_do_execveat(int fd, struct filename *filename,
1864                               const compat_uptr_t __user *__argv,
1865                               const compat_uptr_t __user *__envp,
1866                               int flags)
1867 {
1868         struct user_arg_ptr argv = {
1869                 .is_compat = true,
1870                 .ptr.compat = __argv,
1871         };
1872         struct user_arg_ptr envp = {
1873                 .is_compat = true,
1874                 .ptr.compat = __envp,
1875         };
1876         return do_execveat_common(fd, filename, argv, envp, flags);
1877 }
1878 #endif
1879
1880 void set_binfmt(struct linux_binfmt *new)
1881 {
1882         struct mm_struct *mm = current->mm;
1883
1884         if (mm->binfmt)
1885                 module_put(mm->binfmt->module);
1886
1887         mm->binfmt = new;
1888         if (new)
1889                 __module_get(new->module);
1890 }
1891 EXPORT_SYMBOL(set_binfmt);
1892
1893 /*
1894  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1895  */
1896 void set_dumpable(struct mm_struct *mm, int value)
1897 {
1898         unsigned long old, new;
1899
1900         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1901                 return;
1902
1903         do {
1904                 old = ACCESS_ONCE(mm->flags);
1905                 new = (old & ~MMF_DUMPABLE_MASK) | value;
1906         } while (cmpxchg(&mm->flags, old, new) != old);
1907 }
1908
1909 SYSCALL_DEFINE3(execve,
1910                 const char __user *, filename,
1911                 const char __user *const __user *, argv,
1912                 const char __user *const __user *, envp)
1913 {
1914         return do_execve(getname(filename), argv, envp);
1915 }
1916
1917 SYSCALL_DEFINE5(execveat,
1918                 int, fd, const char __user *, filename,
1919                 const char __user *const __user *, argv,
1920                 const char __user *const __user *, envp,
1921                 int, flags)
1922 {
1923         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1924
1925         return do_execveat(fd,
1926                            getname_flags(filename, lookup_flags, NULL),
1927                            argv, envp, flags);
1928 }
1929
1930 #ifdef CONFIG_COMPAT
1931 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1932         const compat_uptr_t __user *, argv,
1933         const compat_uptr_t __user *, envp)
1934 {
1935         return compat_do_execve(getname(filename), argv, envp);
1936 }
1937
1938 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1939                        const char __user *, filename,
1940                        const compat_uptr_t __user *, argv,
1941                        const compat_uptr_t __user *, envp,
1942                        int,  flags)
1943 {
1944         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1945
1946         return compat_do_execveat(fd,
1947                                   getname_flags(filename, lookup_flags, NULL),
1948                                   argv, envp, flags);
1949 }
1950 #endif