kernel/fork.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/fork.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 /*
   9  *  'fork.c' contains the help-routines for the 'fork' system call
  10  * (see also entry.S and others).
  11  * Fork is rather simple, once you get the hang of it, but the memory
  12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  13  */
  14
  15 #include <linux/anon_inodes.h>
  16 #include <linux/slab.h>
  17 #include <linux/sched/autogroup.h>
  18 #include <linux/sched/mm.h>
  19 #include <linux/sched/coredump.h>
  20 #include <linux/sched/user.h>
  21 #include <linux/sched/numa_balancing.h>
  22 #include <linux/sched/stat.h>
  23 #include <linux/sched/task.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/sched/cputime.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/rtmutex.h>
  28 #include <linux/init.h>
  29 #include <linux/unistd.h>
  30 #include <linux/module.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/completion.h>
  33 #include <linux/personality.h>
  34 #include <linux/mempolicy.h>
  35 #include <linux/sem.h>
  36 #include <linux/file.h>
  37 #include <linux/fdtable.h>
  38 #include <linux/iocontext.h>
  39 #include <linux/key.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/mman.h>
  42 #include <linux/mmu_notifier.h>
  43 #include <linux/hmm.h>
  44 #include <linux/fs.h>
  45 #include <linux/mm.h>
  46 #include <linux/vmacache.h>
  47 #include <linux/nsproxy.h>
  48 #include <linux/capability.h>
  49 #include <linux/cpu.h>
  50 #include <linux/cgroup.h>
  51 #include <linux/security.h>
  52 #include <linux/hugetlb.h>
  53 #include <linux/seccomp.h>
  54 #include <linux/swap.h>
  55 #include <linux/syscalls.h>
  56 #include <linux/jiffies.h>
  57 #include <linux/futex.h>
  58 #include <linux/compat.h>
  59 #include <linux/kthread.h>
  60 #include <linux/task_io_accounting_ops.h>
  61 #include <linux/rcupdate.h>
  62 #include <linux/ptrace.h>
  63 #include <linux/mount.h>
  64 #include <linux/audit.h>
  65 #include <linux/memcontrol.h>
  66 #include <linux/ftrace.h>
  67 #include <linux/proc_fs.h>
  68 #include <linux/profile.h>
  69 #include <linux/rmap.h>
  70 #include <linux/ksm.h>
  71 #include <linux/acct.h>
  72 #include <linux/userfaultfd_k.h>
  73 #include <linux/tsacct_kern.h>
  74 #include <linux/cn_proc.h>
  75 #include <linux/freezer.h>
  76 #include <linux/delayacct.h>
  77 #include <linux/taskstats_kern.h>
  78 #include <linux/random.h>
  79 #include <linux/tty.h>
  80 #include <linux/blkdev.h>
  81 #include <linux/fs_struct.h>
  82 #include <linux/magic.h>
  83 #include <linux/perf_event.h>
  84 #include <linux/posix-timers.h>
  85 #include <linux/user-return-notifier.h>
  86 #include <linux/oom.h>
  87 #include <linux/khugepaged.h>
  88 #include <linux/signalfd.h>
  89 #include <linux/uprobes.h>
  90 #include <linux/aio.h>
  91 #include <linux/compiler.h>
  92 #include <linux/sysctl.h>
  93 #include <linux/kcov.h>
  94 #include <linux/livepatch.h>
  95 #include <linux/thread_info.h>
  96 #include <linux/stackleak.h>
  97
  98 #include <asm/pgtable.h>
  99 #include <asm/pgalloc.h>
 100 #include <linux/uaccess.h>
 101 #include <asm/mmu_context.h>
 102 #include <asm/cacheflush.h>
 103 #include <asm/tlbflush.h>
 104
 105 #include <trace/events/sched.h>
 106
 107 #define CREATE_TRACE_POINTS
 108 #include <trace/events/task.h>
 109
 110 /*
 111  * Minimum number of threads to boot the kernel
 112  */
 113 #define MIN_THREADS 20
 114
 115 /*
 116  * Maximum number of threads
 117  */
 118 #define MAX_THREADS FUTEX_TID_MASK
 119
 120 /*
 121  * Protected counters by write_lock_irq(&tasklist_lock)
 122  */
 123 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 124 int nr_threads;                 /* The idle threads do not count.. */
 125
 126 static int max_threads;         /* tunable limit on nr_threads */
 127
 128 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 129
 130 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 131
 132 #ifdef CONFIG_PROVE_RCU
 133 int lockdep_tasklist_lock_is_held(void)
 134 {
 135         return lockdep_is_held(&tasklist_lock);
 136 }
 137 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 138 #endif /* #ifdef CONFIG_PROVE_RCU */
 139
 140 int nr_processes(void)
 141 {
 142         int cpu;
 143         int total = 0;
 144
 145         for_each_possible_cpu(cpu)
 146                 total += per_cpu(process_counts, cpu);
 147
 148         return total;
 149 }
 150
 151 void __weak arch_release_task_struct(struct task_struct *tsk)
 152 {
 153 }
 154
 155 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 156 static struct kmem_cache *task_struct_cachep;
 157
 158 static inline struct task_struct *alloc_task_struct_node(int node)
 159 {
 160         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 161 }
 162
 163 static inline void free_task_struct(struct task_struct *tsk)
 164 {
 165         kmem_cache_free(task_struct_cachep, tsk);
 166 }
 167 #endif
 168
 169 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 170
 171 /*
 172  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 173  * kmemcache based allocator.
 174  */
 175 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 176
 177 #ifdef CONFIG_VMAP_STACK
 178 /*
 179  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 180  * flush.  Try to minimize the number of calls by caching stacks.
 181  */
 182 #define NR_CACHED_STACKS 2
 183 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 184
 185 static int free_vm_stack_cache(unsigned int cpu)
 186 {
 187         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
 188         int i;
 189
 190         for (i = 0; i < NR_CACHED_STACKS; i++) {
 191                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 192
 193                 if (!vm_stack)
 194                         continue;
 195
 196                 vfree(vm_stack->addr);
 197                 cached_vm_stacks[i] = NULL;
 198         }
 199
 200         return 0;
 201 }
 202 #endif
 203
 204 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 205 {
 206 #ifdef CONFIG_VMAP_STACK
 207         void *stack;
 208         int i;
 209
 210         for (i = 0; i < NR_CACHED_STACKS; i++) {
 211                 struct vm_struct *s;
 212
 213                 s = this_cpu_xchg(cached_stacks[i], NULL);
 214
 215                 if (!s)
 216                         continue;
 217
 218                 /* Clear stale pointers from reused stack. */
 219                 memset(s->addr, 0, THREAD_SIZE);
 220
 221                 tsk->stack_vm_area = s;
 222                 tsk->stack = s->addr;
 223                 return s->addr;
 224         }
 225
 226         /*
 227          * Allocated stacks are cached and later reused by new threads,
 228          * so memcg accounting is performed manually on assigning/releasing
 229          * stacks to tasks. Drop __GFP_ACCOUNT.
 230          */
 231         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
 232                                      VMALLOC_START, VMALLOC_END,
 233                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
 234                                      PAGE_KERNEL,
 235                                      0, node, __builtin_return_address(0));
 236
 237         /*
 238          * We can't call find_vm_area() in interrupt context, and
 239          * free_thread_stack() can be called in interrupt context,
 240          * so cache the vm_struct.
 241          */
 242         if (stack) {
 243                 tsk->stack_vm_area = find_vm_area(stack);
 244                 tsk->stack = stack;
 245         }
 246         return stack;
 247 #else
 248         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 249                                              THREAD_SIZE_ORDER);
 250
 251         if (likely(page)) {
 252                 tsk->stack = page_address(page);
 253                 return tsk->stack;
 254         }
 255         return NULL;
 256 #endif
 257 }
 258
 259 static inline void free_thread_stack(struct task_struct *tsk)
 260 {
 261 #ifdef CONFIG_VMAP_STACK
 262         struct vm_struct *vm = task_stack_vm_area(tsk);
 263
 264         if (vm) {
 265                 int i;
 266
 267                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 268                         mod_memcg_page_state(vm->pages[i],
 269                                              MEMCG_KERNEL_STACK_KB,
 270                                              -(int)(PAGE_SIZE / 1024));
 271
 272                         memcg_kmem_uncharge(vm->pages[i], 0);
 273                 }
 274
 275                 for (i = 0; i < NR_CACHED_STACKS; i++) {
 276                         if (this_cpu_cmpxchg(cached_stacks[i],
 277                                         NULL, tsk->stack_vm_area) != NULL)
 278                                 continue;
 279
 280                         return;
 281                 }
 282
 283                 vfree_atomic(tsk->stack);
 284                 return;
 285         }
 286 #endif
 287
 288         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 289 }
 290 # else
 291 static struct kmem_cache *thread_stack_cache;
 292
 293 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 294                                                   int node)
 295 {
 296         unsigned long *stack;
 297         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 298         tsk->stack = stack;
 299         return stack;
 300 }
 301
 302 static void free_thread_stack(struct task_struct *tsk)
 303 {
 304         kmem_cache_free(thread_stack_cache, tsk->stack);
 305 }
 306
 307 void thread_stack_cache_init(void)
 308 {
 309         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
 310                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
 311                                         THREAD_SIZE, NULL);
 312         BUG_ON(thread_stack_cache == NULL);
 313 }
 314 # endif
 315 #endif
 316
 317 /* SLAB cache for signal_struct structures (tsk->signal) */
 318 static struct kmem_cache *signal_cachep;
 319
 320 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 321 struct kmem_cache *sighand_cachep;
 322
 323 /* SLAB cache for files_struct structures (tsk->files) */
 324 struct kmem_cache *files_cachep;
 325
 326 /* SLAB cache for fs_struct structures (tsk->fs) */
 327 struct kmem_cache *fs_cachep;
 328
 329 /* SLAB cache for vm_area_struct structures */
 330 static struct kmem_cache *vm_area_cachep;
 331
 332 /* SLAB cache for mm_struct structures (tsk->mm) */
 333 static struct kmem_cache *mm_cachep;
 334
 335 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 336 {
 337         struct vm_area_struct *vma;
 338
 339         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 340         if (vma)
 341                 vma_init(vma, mm);
 342         return vma;
 343 }
 344
 345 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 346 {
 347         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 348
 349         if (new) {
 350                 *new = *orig;
 351                 INIT_LIST_HEAD(&new->anon_vma_chain);
 352         }
 353         return new;
 354 }
 355
 356 void vm_area_free(struct vm_area_struct *vma)
 357 {
 358         kmem_cache_free(vm_area_cachep, vma);
 359 }
 360
 361 static void account_kernel_stack(struct task_struct *tsk, int account)
 362 {
 363         void *stack = task_stack_page(tsk);
 364         struct vm_struct *vm = task_stack_vm_area(tsk);
 365
 366         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 367
 368         if (vm) {
 369                 int i;
 370
 371                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 372
 373                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 374                         mod_zone_page_state(page_zone(vm->pages[i]),
 375                                             NR_KERNEL_STACK_KB,
 376                                             PAGE_SIZE / 1024 * account);
 377                 }
 378         } else {
 379                 /*
 380                  * All stack pages are in the same zone and belong to the
 381                  * same memcg.
 382                  */
 383                 struct page *first_page = virt_to_page(stack);
 384
 385                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
 386                                     THREAD_SIZE / 1024 * account);
 387
 388                 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
 389                                      account * (THREAD_SIZE / 1024));
 390         }
 391 }
 392
 393 static int memcg_charge_kernel_stack(struct task_struct *tsk)
 394 {
 395 #ifdef CONFIG_VMAP_STACK
 396         struct vm_struct *vm = task_stack_vm_area(tsk);
 397         int ret;
 398
 399         if (vm) {
 400                 int i;
 401
 402                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 403                         /*
 404                          * If memcg_kmem_charge() fails, page->mem_cgroup
 405                          * pointer is NULL, and both memcg_kmem_uncharge()
 406                          * and mod_memcg_page_state() in free_thread_stack()
 407                          * will ignore this page. So it's safe.
 408                          */
 409                         ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
 410                         if (ret)
 411                                 return ret;
 412
 413                         mod_memcg_page_state(vm->pages[i],
 414                                              MEMCG_KERNEL_STACK_KB,
 415                                              PAGE_SIZE / 1024);
 416                 }
 417         }
 418 #endif
 419         return 0;
 420 }
 421
 422 static void release_task_stack(struct task_struct *tsk)
 423 {
 424         if (WARN_ON(tsk->state != TASK_DEAD))
 425                 return;  /* Better to leak the stack than to free prematurely */
 426
 427         account_kernel_stack(tsk, -1);
 428         free_thread_stack(tsk);
 429         tsk->stack = NULL;
 430 #ifdef CONFIG_VMAP_STACK
 431         tsk->stack_vm_area = NULL;
 432 #endif
 433 }
 434
 435 #ifdef CONFIG_THREAD_INFO_IN_TASK
 436 void put_task_stack(struct task_struct *tsk)
 437 {
 438         if (refcount_dec_and_test(&tsk->stack_refcount))
 439                 release_task_stack(tsk);
 440 }
 441 #endif
 442
 443 void free_task(struct task_struct *tsk)
 444 {
 445 #ifndef CONFIG_THREAD_INFO_IN_TASK
 446         /*
 447          * The task is finally done with both the stack and thread_info,
 448          * so free both.
 449          */
 450         release_task_stack(tsk);
 451 #else
 452         /*
 453          * If the task had a separate stack allocation, it should be gone
 454          * by now.
 455          */
 456         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 457 #endif
 458         rt_mutex_debug_task_free(tsk);
 459         ftrace_graph_exit_task(tsk);
 460         put_seccomp_filter(tsk);
 461         arch_release_task_struct(tsk);
 462         if (tsk->flags & PF_KTHREAD)
 463                 free_kthread_struct(tsk);
 464         free_task_struct(tsk);
 465 }
 466 EXPORT_SYMBOL(free_task);
 467
 468 #ifdef CONFIG_MMU
 469 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 470                                         struct mm_struct *oldmm)
 471 {
 472         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 473         struct rb_node **rb_link, *rb_parent;
 474         int retval;
 475         unsigned long charge;
 476         LIST_HEAD(uf);
 477
 478         uprobe_start_dup_mmap();
 479         if (down_write_killable(&oldmm->mmap_sem)) {
 480                 retval = -EINTR;
 481                 goto fail_uprobe_end;
 482         }
 483         flush_cache_dup_mm(oldmm);
 484         uprobe_dup_mmap(oldmm, mm);
 485         /*
 486          * Not linked in yet - no deadlock potential:
 487          */
 488         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 489
 490         /* No ordering required: file already has been exposed. */
 491         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 492
 493         mm->total_vm = oldmm->total_vm;
 494         mm->data_vm = oldmm->data_vm;
 495         mm->exec_vm = oldmm->exec_vm;
 496         mm->stack_vm = oldmm->stack_vm;
 497
 498         rb_link = &mm->mm_rb.rb_node;
 499         rb_parent = NULL;
 500         pprev = &mm->mmap;
 501         retval = ksm_fork(mm, oldmm);
 502         if (retval)
 503                 goto out;
 504         retval = khugepaged_fork(mm, oldmm);
 505         if (retval)
 506                 goto out;
 507
 508         prev = NULL;
 509         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 510                 struct file *file;
 511
 512                 if (mpnt->vm_flags & VM_DONTCOPY) {
 513                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 514                         continue;
 515                 }
 516                 charge = 0;
 517                 /*
 518                  * Don't duplicate many vmas if we've been oom-killed (for
 519                  * example)
 520                  */
 521                 if (fatal_signal_pending(current)) {
 522                         retval = -EINTR;
 523                         goto out;
 524                 }
 525                 if (mpnt->vm_flags & VM_ACCOUNT) {
 526                         unsigned long len = vma_pages(mpnt);
 527
 528                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 529                                 goto fail_nomem;
 530                         charge = len;
 531                 }
 532                 tmp = vm_area_dup(mpnt);
 533                 if (!tmp)
 534                         goto fail_nomem;
 535                 retval = vma_dup_policy(mpnt, tmp);
 536                 if (retval)
 537                         goto fail_nomem_policy;
 538                 tmp->vm_mm = mm;
 539                 retval = dup_userfaultfd(tmp, &uf);
 540                 if (retval)
 541                         goto fail_nomem_anon_vma_fork;
 542                 if (tmp->vm_flags & VM_WIPEONFORK) {
 543                         /* VM_WIPEONFORK gets a clean slate in the child. */
 544                         tmp->anon_vma = NULL;
 545                         if (anon_vma_prepare(tmp))
 546                                 goto fail_nomem_anon_vma_fork;
 547                 } else if (anon_vma_fork(tmp, mpnt))
 548                         goto fail_nomem_anon_vma_fork;
 549                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
 550                 tmp->vm_next = tmp->vm_prev = NULL;
 551                 file = tmp->vm_file;
 552                 if (file) {
 553                         struct inode *inode = file_inode(file);
 554                         struct address_space *mapping = file->f_mapping;
 555
 556                         get_file(file);
 557                         if (tmp->vm_flags & VM_DENYWRITE)
 558                                 atomic_dec(&inode->i_writecount);
 559                         i_mmap_lock_write(mapping);
 560                         if (tmp->vm_flags & VM_SHARED)
 561                                 atomic_inc(&mapping->i_mmap_writable);
 562                         flush_dcache_mmap_lock(mapping);
 563                         /* insert tmp into the share list, just after mpnt */
 564                         vma_interval_tree_insert_after(tmp, mpnt,
 565                                         &mapping->i_mmap);
 566                         flush_dcache_mmap_unlock(mapping);
 567                         i_mmap_unlock_write(mapping);
 568                 }
 569
 570                 /*
 571                  * Clear hugetlb-related page reserves for children. This only
 572                  * affects MAP_PRIVATE mappings. Faults generated by the child
 573                  * are not guaranteed to succeed, even if read-only
 574                  */
 575                 if (is_vm_hugetlb_page(tmp))
 576                         reset_vma_resv_huge_pages(tmp);
 577
 578                 /*
 579                  * Link in the new vma and copy the page table entries.
 580                  */
 581                 *pprev = tmp;
 582                 pprev = &tmp->vm_next;
 583                 tmp->vm_prev = prev;
 584                 prev = tmp;
 585
 586                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 587                 rb_link = &tmp->vm_rb.rb_right;
 588                 rb_parent = &tmp->vm_rb;
 589
 590                 mm->map_count++;
 591                 if (!(tmp->vm_flags & VM_WIPEONFORK))
 592                         retval = copy_page_range(mm, oldmm, mpnt);
 593
 594                 if (tmp->vm_ops && tmp->vm_ops->open)
 595                         tmp->vm_ops->open(tmp);
 596
 597                 if (retval)
 598                         goto out;
 599         }
 600         /* a new mm has just been created */
 601         retval = arch_dup_mmap(oldmm, mm);
 602 out:
 603         up_write(&mm->mmap_sem);
 604         flush_tlb_mm(oldmm);
 605         up_write(&oldmm->mmap_sem);
 606         dup_userfaultfd_complete(&uf);
 607 fail_uprobe_end:
 608         uprobe_end_dup_mmap();
 609         return retval;
 610 fail_nomem_anon_vma_fork:
 611         mpol_put(vma_policy(tmp));
 612 fail_nomem_policy:
 613         vm_area_free(tmp);
 614 fail_nomem:
 615         retval = -ENOMEM;
 616         vm_unacct_memory(charge);
 617         goto out;
 618 }
 619
 620 static inline int mm_alloc_pgd(struct mm_struct *mm)
 621 {
 622         mm->pgd = pgd_alloc(mm);
 623         if (unlikely(!mm->pgd))
 624                 return -ENOMEM;
 625         return 0;
 626 }
 627
 628 static inline void mm_free_pgd(struct mm_struct *mm)
 629 {
 630         pgd_free(mm, mm->pgd);
 631 }
 632 #else
 633 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 634 {
 635         down_write(&oldmm->mmap_sem);
 636         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 637         up_write(&oldmm->mmap_sem);
 638         return 0;
 639 }
 640 #define mm_alloc_pgd(mm)        (0)
 641 #define mm_free_pgd(mm)
 642 #endif /* CONFIG_MMU */
 643
 644 static void check_mm(struct mm_struct *mm)
 645 {
 646         int i;
 647
 648         for (i = 0; i < NR_MM_COUNTERS; i++) {
 649                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 650
 651                 if (unlikely(x))
 652                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 653                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 654         }
 655
 656         if (mm_pgtables_bytes(mm))
 657                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
 658                                 mm_pgtables_bytes(mm));
 659
 660 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 661         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 662 #endif
 663 }
 664
 665 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 666 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 667
 668 /*
 669  * Called when the last reference to the mm
 670  * is dropped: either by a lazy thread or by
 671  * mmput. Free the page directory and the mm.
 672  */
 673 void __mmdrop(struct mm_struct *mm)
 674 {
 675         BUG_ON(mm == &init_mm);
 676         WARN_ON_ONCE(mm == current->mm);
 677         WARN_ON_ONCE(mm == current->active_mm);
 678         mm_free_pgd(mm);
 679         destroy_context(mm);
 680         hmm_mm_destroy(mm);
 681         mmu_notifier_mm_destroy(mm);
 682         check_mm(mm);
 683         put_user_ns(mm->user_ns);
 684         free_mm(mm);
 685 }
 686 EXPORT_SYMBOL_GPL(__mmdrop);
 687
 688 static void mmdrop_async_fn(struct work_struct *work)
 689 {
 690         struct mm_struct *mm;
 691
 692         mm = container_of(work, struct mm_struct, async_put_work);
 693         __mmdrop(mm);
 694 }
 695
 696 static void mmdrop_async(struct mm_struct *mm)
 697 {
 698         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
 699                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
 700                 schedule_work(&mm->async_put_work);
 701         }
 702 }
 703
 704 static inline void free_signal_struct(struct signal_struct *sig)
 705 {
 706         taskstats_tgid_free(sig);
 707         sched_autogroup_exit(sig);
 708         /*
 709          * __mmdrop is not safe to call from softirq context on x86 due to
 710          * pgd_dtor so postpone it to the async context
 711          */
 712         if (sig->oom_mm)
 713                 mmdrop_async(sig->oom_mm);
 714         kmem_cache_free(signal_cachep, sig);
 715 }
 716
 717 static inline void put_signal_struct(struct signal_struct *sig)
 718 {
 719         if (refcount_dec_and_test(&sig->sigcnt))
 720                 free_signal_struct(sig);
 721 }
 722
 723 void __put_task_struct(struct task_struct *tsk)
 724 {
 725         WARN_ON(!tsk->exit_state);
 726         WARN_ON(refcount_read(&tsk->usage));
 727         WARN_ON(tsk == current);
 728
 729         cgroup_free(tsk);
 730         task_numa_free(tsk);
 731         security_task_free(tsk);
 732         exit_creds(tsk);
 733         delayacct_tsk_free(tsk);
 734         put_signal_struct(tsk->signal);
 735
 736         if (!profile_handoff_task(tsk))
 737                 free_task(tsk);
 738 }
 739 EXPORT_SYMBOL_GPL(__put_task_struct);
 740
 741 void __init __weak arch_task_cache_init(void) { }
 742
 743 /*
 744  * set_max_threads
 745  */
 746 static void set_max_threads(unsigned int max_threads_suggested)
 747 {
 748         u64 threads;
 749         unsigned long nr_pages = totalram_pages();
 750
 751         /*
 752          * The number of threads shall be limited such that the thread
 753          * structures may only consume a small part of the available memory.
 754          */
 755         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
 756                 threads = MAX_THREADS;
 757         else
 758                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
 759                                     (u64) THREAD_SIZE * 8UL);
 760
 761         if (threads > max_threads_suggested)
 762                 threads = max_threads_suggested;
 763
 764         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 765 }
 766
 767 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 768 /* Initialized by the architecture: */
 769 int arch_task_struct_size __read_mostly;
 770 #endif
 771
 772 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 773 {
 774         /* Fetch thread_struct whitelist for the architecture. */
 775         arch_thread_struct_whitelist(offset, size);
 776
 777         /*
 778          * Handle zero-sized whitelist or empty thread_struct, otherwise
 779          * adjust offset to position of thread_struct in task_struct.
 780          */
 781         if (unlikely(*size == 0))
 782                 *offset = 0;
 783         else
 784                 *offset += offsetof(struct task_struct, thread);
 785 }
 786
 787 void __init fork_init(void)
 788 {
 789         int i;
 790 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 791 #ifndef ARCH_MIN_TASKALIGN
 792 #define ARCH_MIN_TASKALIGN      0
 793 #endif
 794         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 795         unsigned long useroffset, usersize;
 796
 797         /* create a slab on which task_structs can be allocated */
 798         task_struct_whitelist(&useroffset, &usersize);
 799         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 800                         arch_task_struct_size, align,
 801                         SLAB_PANIC|SLAB_ACCOUNT,
 802                         useroffset, usersize, NULL);
 803 #endif
 804
 805         /* do the arch specific task caches init */
 806         arch_task_cache_init();
 807
 808         set_max_threads(MAX_THREADS);
 809
 810         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 811         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 812         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 813                 init_task.signal->rlim[RLIMIT_NPROC];
 814
 815         for (i = 0; i < UCOUNT_COUNTS; i++) {
 816                 init_user_ns.ucount_max[i] = max_threads/2;
 817         }
 818
 819 #ifdef CONFIG_VMAP_STACK
 820         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 821                           NULL, free_vm_stack_cache);
 822 #endif
 823
 824         lockdep_init_task(&init_task);
 825         uprobes_init();
 826 }
 827
 828 int __weak arch_dup_task_struct(struct task_struct *dst,
 829                                                struct task_struct *src)
 830 {
 831         *dst = *src;
 832         return 0;
 833 }
 834
 835 void set_task_stack_end_magic(struct task_struct *tsk)
 836 {
 837         unsigned long *stackend;
 838
 839         stackend = end_of_stack(tsk);
 840         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 841 }
 842
 843 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 844 {
 845         struct task_struct *tsk;
 846         unsigned long *stack;
 847         struct vm_struct *stack_vm_area __maybe_unused;
 848         int err;
 849
 850         if (node == NUMA_NO_NODE)
 851                 node = tsk_fork_get_node(orig);
 852         tsk = alloc_task_struct_node(node);
 853         if (!tsk)
 854                 return NULL;
 855
 856         stack = alloc_thread_stack_node(tsk, node);
 857         if (!stack)
 858                 goto free_tsk;
 859
 860         if (memcg_charge_kernel_stack(tsk))
 861                 goto free_stack;
 862
 863         stack_vm_area = task_stack_vm_area(tsk);
 864
 865         err = arch_dup_task_struct(tsk, orig);
 866
 867         /*
 868          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 869          * sure they're properly initialized before using any stack-related
 870          * functions again.
 871          */
 872         tsk->stack = stack;
 873 #ifdef CONFIG_VMAP_STACK
 874         tsk->stack_vm_area = stack_vm_area;
 875 #endif
 876 #ifdef CONFIG_THREAD_INFO_IN_TASK
 877         refcount_set(&tsk->stack_refcount, 1);
 878 #endif
 879
 880         if (err)
 881                 goto free_stack;
 882
 883 #ifdef CONFIG_SECCOMP
 884         /*
 885          * We must handle setting up seccomp filters once we're under
 886          * the sighand lock in case orig has changed between now and
 887          * then. Until then, filter must be NULL to avoid messing up
 888          * the usage counts on the error path calling free_task.
 889          */
 890         tsk->seccomp.filter = NULL;
 891 #endif
 892
 893         setup_thread_stack(tsk, orig);
 894         clear_user_return_notifier(tsk);
 895         clear_tsk_need_resched(tsk);
 896         set_task_stack_end_magic(tsk);
 897
 898 #ifdef CONFIG_STACKPROTECTOR
 899         tsk->stack_canary = get_random_canary();
 900 #endif
 901
 902         /*
 903          * One for us, one for whoever does the "release_task()" (usually
 904          * parent)
 905          */
 906         refcount_set(&tsk->usage, 2);
 907 #ifdef CONFIG_BLK_DEV_IO_TRACE
 908         tsk->btrace_seq = 0;
 909 #endif
 910         tsk->splice_pipe = NULL;
 911         tsk->task_frag.page = NULL;
 912         tsk->wake_q.next = NULL;
 913
 914         account_kernel_stack(tsk, 1);
 915
 916         kcov_task_init(tsk);
 917
 918 #ifdef CONFIG_FAULT_INJECTION
 919         tsk->fail_nth = 0;
 920 #endif
 921
 922 #ifdef CONFIG_BLK_CGROUP
 923         tsk->throttle_queue = NULL;
 924         tsk->use_memdelay = 0;
 925 #endif
 926
 927 #ifdef CONFIG_MEMCG
 928         tsk->active_memcg = NULL;
 929 #endif
 930         return tsk;
 931
 932 free_stack:
 933         free_thread_stack(tsk);
 934 free_tsk:
 935         free_task_struct(tsk);
 936         return NULL;
 937 }
 938
 939 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 940
 941 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 942
 943 static int __init coredump_filter_setup(char *s)
 944 {
 945         default_dump_filter =
 946                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 947                 MMF_DUMP_FILTER_MASK;
 948         return 1;
 949 }
 950
 951 __setup("coredump_filter=", coredump_filter_setup);
 952
 953 #include <linux/init_task.h>
 954
 955 static void mm_init_aio(struct mm_struct *mm)
 956 {
 957 #ifdef CONFIG_AIO
 958         spin_lock_init(&mm->ioctx_lock);
 959         mm->ioctx_table = NULL;
 960 #endif
 961 }
 962
 963 static __always_inline void mm_clear_owner(struct mm_struct *mm,
 964                                            struct task_struct *p)
 965 {
 966 #ifdef CONFIG_MEMCG
 967         if (mm->owner == p)
 968                 WRITE_ONCE(mm->owner, NULL);
 969 #endif
 970 }
 971
 972 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 973 {
 974 #ifdef CONFIG_MEMCG
 975         mm->owner = p;
 976 #endif
 977 }
 978
 979 static void mm_init_uprobes_state(struct mm_struct *mm)
 980 {
 981 #ifdef CONFIG_UPROBES
 982         mm->uprobes_state.xol_area = NULL;
 983 #endif
 984 }
 985
 986 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 987         struct user_namespace *user_ns)
 988 {
 989         mm->mmap = NULL;
 990         mm->mm_rb = RB_ROOT;
 991         mm->vmacache_seqnum = 0;
 992         atomic_set(&mm->mm_users, 1);
 993         atomic_set(&mm->mm_count, 1);
 994         init_rwsem(&mm->mmap_sem);
 995         INIT_LIST_HEAD(&mm->mmlist);
 996         mm->core_state = NULL;
 997         mm_pgtables_bytes_init(mm);
 998         mm->map_count = 0;
 999         mm->locked_vm = 0;
1000         atomic64_set(&mm->pinned_vm, 0);
1001         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1002         spin_lock_init(&mm->page_table_lock);
1003         spin_lock_init(&mm->arg_lock);
1004         mm_init_cpumask(mm);
1005         mm_init_aio(mm);
1006         mm_init_owner(mm, p);
1007         RCU_INIT_POINTER(mm->exe_file, NULL);
1008         mmu_notifier_mm_init(mm);
1009         hmm_mm_init(mm);
1010         init_tlb_flush_pending(mm);
1011 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1012         mm->pmd_huge_pte = NULL;
1013 #endif
1014         mm_init_uprobes_state(mm);
1015
1016         if (current->mm) {
1017                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1018                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1019         } else {
1020                 mm->flags = default_dump_filter;
1021                 mm->def_flags = 0;
1022         }
1023
1024         if (mm_alloc_pgd(mm))
1025                 goto fail_nopgd;
1026
1027         if (init_new_context(p, mm))
1028                 goto fail_nocontext;
1029
1030         mm->user_ns = get_user_ns(user_ns);
1031         return mm;
1032
1033 fail_nocontext:
1034         mm_free_pgd(mm);
1035 fail_nopgd:
1036         free_mm(mm);
1037         return NULL;
1038 }
1039
1040 /*
1041  * Allocate and initialize an mm_struct.
1042  */
1043 struct mm_struct *mm_alloc(void)
1044 {
1045         struct mm_struct *mm;
1046
1047         mm = allocate_mm();
1048         if (!mm)
1049                 return NULL;
1050
1051         memset(mm, 0, sizeof(*mm));
1052         return mm_init(mm, current, current_user_ns());
1053 }
1054
1055 static inline void __mmput(struct mm_struct *mm)
1056 {
1057         VM_BUG_ON(atomic_read(&mm->mm_users));
1058
1059         uprobe_clear_state(mm);
1060         exit_aio(mm);
1061         ksm_exit(mm);
1062         khugepaged_exit(mm); /* must run before exit_mmap */
1063         exit_mmap(mm);
1064         mm_put_huge_zero_page(mm);
1065         set_mm_exe_file(mm, NULL);
1066         if (!list_empty(&mm->mmlist)) {
1067                 spin_lock(&mmlist_lock);
1068                 list_del(&mm->mmlist);
1069                 spin_unlock(&mmlist_lock);
1070         }
1071         if (mm->binfmt)
1072                 module_put(mm->binfmt->module);
1073         mmdrop(mm);
1074 }
1075
1076 /*
1077  * Decrement the use count and release all resources for an mm.
1078  */
1079 void mmput(struct mm_struct *mm)
1080 {
1081         might_sleep();
1082
1083         if (atomic_dec_and_test(&mm->mm_users))
1084                 __mmput(mm);
1085 }
1086 EXPORT_SYMBOL_GPL(mmput);
1087
1088 #ifdef CONFIG_MMU
1089 static void mmput_async_fn(struct work_struct *work)
1090 {
1091         struct mm_struct *mm = container_of(work, struct mm_struct,
1092                                             async_put_work);
1093
1094         __mmput(mm);
1095 }
1096
1097 void mmput_async(struct mm_struct *mm)
1098 {
1099         if (atomic_dec_and_test(&mm->mm_users)) {
1100                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1101                 schedule_work(&mm->async_put_work);
1102         }
1103 }
1104 #endif
1105
1106 /**
1107  * set_mm_exe_file - change a reference to the mm's executable file
1108  *
1109  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1110  *
1111  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1112  * invocations: in mmput() nobody alive left, in execve task is single
1113  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1114  * mm->exe_file, but does so without using set_mm_exe_file() in order
1115  * to do avoid the need for any locks.
1116  */
1117 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1118 {
1119         struct file *old_exe_file;
1120
1121         /*
1122          * It is safe to dereference the exe_file without RCU as
1123          * this function is only called if nobody else can access
1124          * this mm -- see comment above for justification.
1125          */
1126         old_exe_file = rcu_dereference_raw(mm->exe_file);
1127
1128         if (new_exe_file)
1129                 get_file(new_exe_file);
1130         rcu_assign_pointer(mm->exe_file, new_exe_file);
1131         if (old_exe_file)
1132                 fput(old_exe_file);
1133 }
1134
1135 /**
1136  * get_mm_exe_file - acquire a reference to the mm's executable file
1137  *
1138  * Returns %NULL if mm has no associated executable file.
1139  * User must release file via fput().
1140  */
1141 struct file *get_mm_exe_file(struct mm_struct *mm)
1142 {
1143         struct file *exe_file;
1144
1145         rcu_read_lock();
1146         exe_file = rcu_dereference(mm->exe_file);
1147         if (exe_file && !get_file_rcu(exe_file))
1148                 exe_file = NULL;
1149         rcu_read_unlock();
1150         return exe_file;
1151 }
1152 EXPORT_SYMBOL(get_mm_exe_file);
1153
1154 /**
1155  * get_task_exe_file - acquire a reference to the task's executable file
1156  *
1157  * Returns %NULL if task's mm (if any) has no associated executable file or
1158  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1159  * User must release file via fput().
1160  */
1161 struct file *get_task_exe_file(struct task_struct *task)
1162 {
1163         struct file *exe_file = NULL;
1164         struct mm_struct *mm;
1165
1166         task_lock(task);
1167         mm = task->mm;
1168         if (mm) {
1169                 if (!(task->flags & PF_KTHREAD))
1170                         exe_file = get_mm_exe_file(mm);
1171         }
1172         task_unlock(task);
1173         return exe_file;
1174 }
1175 EXPORT_SYMBOL(get_task_exe_file);
1176
1177 /**
1178  * get_task_mm - acquire a reference to the task's mm
1179  *
1180  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1181  * this kernel workthread has transiently adopted a user mm with use_mm,
1182  * to do its AIO) is not set and if so returns a reference to it, after
1183  * bumping up the use count.  User must release the mm via mmput()
1184  * after use.  Typically used by /proc and ptrace.
1185  */
1186 struct mm_struct *get_task_mm(struct task_struct *task)
1187 {
1188         struct mm_struct *mm;
1189
1190         task_lock(task);
1191         mm = task->mm;
1192         if (mm) {
1193                 if (task->flags & PF_KTHREAD)
1194                         mm = NULL;
1195                 else
1196                         mmget(mm);
1197         }
1198         task_unlock(task);
1199         return mm;
1200 }
1201 EXPORT_SYMBOL_GPL(get_task_mm);
1202
1203 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1204 {
1205         struct mm_struct *mm;
1206         int err;
1207
1208         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1209         if (err)
1210                 return ERR_PTR(err);
1211
1212         mm = get_task_mm(task);
1213         if (mm && mm != current->mm &&
1214                         !ptrace_may_access(task, mode)) {
1215                 mmput(mm);
1216                 mm = ERR_PTR(-EACCES);
1217         }
1218         mutex_unlock(&task->signal->cred_guard_mutex);
1219
1220         return mm;
1221 }
1222
1223 static void complete_vfork_done(struct task_struct *tsk)
1224 {
1225         struct completion *vfork;
1226
1227         task_lock(tsk);
1228         vfork = tsk->vfork_done;
1229         if (likely(vfork)) {
1230                 tsk->vfork_done = NULL;
1231                 complete(vfork);
1232         }
1233         task_unlock(tsk);
1234 }
1235
1236 static int wait_for_vfork_done(struct task_struct *child,
1237                                 struct completion *vfork)
1238 {
1239         int killed;
1240
1241         freezer_do_not_count();
1242         cgroup_enter_frozen();
1243         killed = wait_for_completion_killable(vfork);
1244         cgroup_leave_frozen(false);
1245         freezer_count();
1246
1247         if (killed) {
1248                 task_lock(child);
1249                 child->vfork_done = NULL;
1250                 task_unlock(child);
1251         }
1252
1253         put_task_struct(child);
1254         return killed;
1255 }
1256
1257 /* Please note the differences between mmput and mm_release.
1258  * mmput is called whenever we stop holding onto a mm_struct,
1259  * error success whatever.
1260  *
1261  * mm_release is called after a mm_struct has been removed
1262  * from the current process.
1263  *
1264  * This difference is important for error handling, when we
1265  * only half set up a mm_struct for a new process and need to restore
1266  * the old one.  Because we mmput the new mm_struct before
1267  * restoring the old one. . .
1268  * Eric Biederman 10 January 1998
1269  */
1270 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1271 {
1272         /* Get rid of any futexes when releasing the mm */
1273 #ifdef CONFIG_FUTEX
1274         if (unlikely(tsk->robust_list)) {
1275                 exit_robust_list(tsk);
1276                 tsk->robust_list = NULL;
1277         }
1278 #ifdef CONFIG_COMPAT
1279         if (unlikely(tsk->compat_robust_list)) {
1280                 compat_exit_robust_list(tsk);
1281                 tsk->compat_robust_list = NULL;
1282         }
1283 #endif
1284         if (unlikely(!list_empty(&tsk->pi_state_list)))
1285                 exit_pi_state_list(tsk);
1286 #endif
1287
1288         uprobe_free_utask(tsk);
1289
1290         /* Get rid of any cached register state */
1291         deactivate_mm(tsk, mm);
1292
1293         /*
1294          * Signal userspace if we're not exiting with a core dump
1295          * because we want to leave the value intact for debugging
1296          * purposes.
1297          */
1298         if (tsk->clear_child_tid) {
1299                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1300                     atomic_read(&mm->mm_users) > 1) {
1301                         /*
1302                          * We don't check the error code - if userspace has
1303                          * not set up a proper pointer then tough luck.
1304                          */
1305                         put_user(0, tsk->clear_child_tid);
1306                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1307                                         1, NULL, NULL, 0, 0);
1308                 }
1309                 tsk->clear_child_tid = NULL;
1310         }
1311
1312         /*
1313          * All done, finally we can wake up parent and return this mm to him.
1314          * Also kthread_stop() uses this completion for synchronization.
1315          */
1316         if (tsk->vfork_done)
1317                 complete_vfork_done(tsk);
1318 }
1319
1320 /**
1321  * dup_mm() - duplicates an existing mm structure
1322  * @tsk: the task_struct with which the new mm will be associated.
1323  * @oldmm: the mm to duplicate.
1324  *
1325  * Allocates a new mm structure and duplicates the provided @oldmm structure
1326  * content into it.
1327  *
1328  * Return: the duplicated mm or NULL on failure.
1329  */
1330 static struct mm_struct *dup_mm(struct task_struct *tsk,
1331                                 struct mm_struct *oldmm)
1332 {
1333         struct mm_struct *mm;
1334         int err;
1335
1336         mm = allocate_mm();
1337         if (!mm)
1338                 goto fail_nomem;
1339
1340         memcpy(mm, oldmm, sizeof(*mm));
1341
1342         if (!mm_init(mm, tsk, mm->user_ns))
1343                 goto fail_nomem;
1344
1345         err = dup_mmap(mm, oldmm);
1346         if (err)
1347                 goto free_pt;
1348
1349         mm->hiwater_rss = get_mm_rss(mm);
1350         mm->hiwater_vm = mm->total_vm;
1351
1352         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1353                 goto free_pt;
1354
1355         return mm;
1356
1357 free_pt:
1358         /* don't put binfmt in mmput, we haven't got module yet */
1359         mm->binfmt = NULL;
1360         mm_init_owner(mm, NULL);
1361         mmput(mm);
1362
1363 fail_nomem:
1364         return NULL;
1365 }
1366
1367 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1368 {
1369         struct mm_struct *mm, *oldmm;
1370         int retval;
1371
1372         tsk->min_flt = tsk->maj_flt = 0;
1373         tsk->nvcsw = tsk->nivcsw = 0;
1374 #ifdef CONFIG_DETECT_HUNG_TASK
1375         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1376         tsk->last_switch_time = 0;
1377 #endif
1378
1379         tsk->mm = NULL;
1380         tsk->active_mm = NULL;
1381
1382         /*
1383          * Are we cloning a kernel thread?
1384          *
1385          * We need to steal a active VM for that..
1386          */
1387         oldmm = current->mm;
1388         if (!oldmm)
1389                 return 0;
1390
1391         /* initialize the new vmacache entries */
1392         vmacache_flush(tsk);
1393
1394         if (clone_flags & CLONE_VM) {
1395                 mmget(oldmm);
1396                 mm = oldmm;
1397                 goto good_mm;
1398         }
1399
1400         retval = -ENOMEM;
1401         mm = dup_mm(tsk, current->mm);
1402         if (!mm)
1403                 goto fail_nomem;
1404
1405 good_mm:
1406         tsk->mm = mm;
1407         tsk->active_mm = mm;
1408         return 0;
1409
1410 fail_nomem:
1411         return retval;
1412 }
1413
1414 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1415 {
1416         struct fs_struct *fs = current->fs;
1417         if (clone_flags & CLONE_FS) {
1418                 /* tsk->fs is already what we want */
1419                 spin_lock(&fs->lock);
1420                 if (fs->in_exec) {
1421                         spin_unlock(&fs->lock);
1422                         return -EAGAIN;
1423                 }
1424                 fs->users++;
1425                 spin_unlock(&fs->lock);
1426                 return 0;
1427         }
1428         tsk->fs = copy_fs_struct(fs);
1429         if (!tsk->fs)
1430                 return -ENOMEM;
1431         return 0;
1432 }
1433
1434 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1435 {
1436         struct files_struct *oldf, *newf;
1437         int error = 0;
1438
1439         /*
1440          * A background process may not have any files ...
1441          */
1442         oldf = current->files;
1443         if (!oldf)
1444                 goto out;
1445
1446         if (clone_flags & CLONE_FILES) {
1447                 atomic_inc(&oldf->count);
1448                 goto out;
1449         }
1450
1451         newf = dup_fd(oldf, &error);
1452         if (!newf)
1453                 goto out;
1454
1455         tsk->files = newf;
1456         error = 0;
1457 out:
1458         return error;
1459 }
1460
1461 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1462 {
1463 #ifdef CONFIG_BLOCK
1464         struct io_context *ioc = current->io_context;
1465         struct io_context *new_ioc;
1466
1467         if (!ioc)
1468                 return 0;
1469         /*
1470          * Share io context with parent, if CLONE_IO is set
1471          */
1472         if (clone_flags & CLONE_IO) {
1473                 ioc_task_link(ioc);
1474                 tsk->io_context = ioc;
1475         } else if (ioprio_valid(ioc->ioprio)) {
1476                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1477                 if (unlikely(!new_ioc))
1478                         return -ENOMEM;
1479
1480                 new_ioc->ioprio = ioc->ioprio;
1481                 put_io_context(new_ioc);
1482         }
1483 #endif
1484         return 0;
1485 }
1486
1487 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1488 {
1489         struct sighand_struct *sig;
1490
1491         if (clone_flags & CLONE_SIGHAND) {
1492                 refcount_inc(&current->sighand->count);
1493                 return 0;
1494         }
1495         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1496         rcu_assign_pointer(tsk->sighand, sig);
1497         if (!sig)
1498                 return -ENOMEM;
1499
1500         refcount_set(&sig->count, 1);
1501         spin_lock_irq(&current->sighand->siglock);
1502         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1503         spin_unlock_irq(&current->sighand->siglock);
1504         return 0;
1505 }
1506
1507 void __cleanup_sighand(struct sighand_struct *sighand)
1508 {
1509         if (refcount_dec_and_test(&sighand->count)) {
1510                 signalfd_cleanup(sighand);
1511                 /*
1512                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1513                  * without an RCU grace period, see __lock_task_sighand().
1514                  */
1515                 kmem_cache_free(sighand_cachep, sighand);
1516         }
1517 }
1518
1519 #ifdef CONFIG_POSIX_TIMERS
1520 /*
1521  * Initialize POSIX timer handling for a thread group.
1522  */
1523 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1524 {
1525         unsigned long cpu_limit;
1526
1527         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1528         if (cpu_limit != RLIM_INFINITY) {
1529                 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1530                 sig->cputimer.running = true;
1531         }
1532
1533         /* The timer lists. */
1534         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1535         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1536         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1537 }
1538 #else
1539 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1540 #endif
1541
1542 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1543 {
1544         struct signal_struct *sig;
1545
1546         if (clone_flags & CLONE_THREAD)
1547                 return 0;
1548
1549         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1550         tsk->signal = sig;
1551         if (!sig)
1552                 return -ENOMEM;
1553
1554         sig->nr_threads = 1;
1555         atomic_set(&sig->live, 1);
1556         refcount_set(&sig->sigcnt, 1);
1557
1558         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1559         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1560         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1561
1562         init_waitqueue_head(&sig->wait_chldexit);
1563         sig->curr_target = tsk;
1564         init_sigpending(&sig->shared_pending);
1565         INIT_HLIST_HEAD(&sig->multiprocess);
1566         seqlock_init(&sig->stats_lock);
1567         prev_cputime_init(&sig->prev_cputime);
1568
1569 #ifdef CONFIG_POSIX_TIMERS
1570         INIT_LIST_HEAD(&sig->posix_timers);
1571         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1572         sig->real_timer.function = it_real_fn;
1573 #endif
1574
1575         task_lock(current->group_leader);
1576         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1577         task_unlock(current->group_leader);
1578
1579         posix_cpu_timers_init_group(sig);
1580
1581         tty_audit_fork(sig);
1582         sched_autogroup_fork(sig);
1583
1584         sig->oom_score_adj = current->signal->oom_score_adj;
1585         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1586
1587         mutex_init(&sig->cred_guard_mutex);
1588
1589         return 0;
1590 }
1591
1592 static void copy_seccomp(struct task_struct *p)
1593 {
1594 #ifdef CONFIG_SECCOMP
1595         /*
1596          * Must be called with sighand->lock held, which is common to
1597          * all threads in the group. Holding cred_guard_mutex is not
1598          * needed because this new task is not yet running and cannot
1599          * be racing exec.
1600          */
1601         assert_spin_locked(&current->sighand->siglock);
1602
1603         /* Ref-count the new filter user, and assign it. */
1604         get_seccomp_filter(current);
1605         p->seccomp = current->seccomp;
1606
1607         /*
1608          * Explicitly enable no_new_privs here in case it got set
1609          * between the task_struct being duplicated and holding the
1610          * sighand lock. The seccomp state and nnp must be in sync.
1611          */
1612         if (task_no_new_privs(current))
1613                 task_set_no_new_privs(p);
1614
1615         /*
1616          * If the parent gained a seccomp mode after copying thread
1617          * flags and between before we held the sighand lock, we have
1618          * to manually enable the seccomp thread flag here.
1619          */
1620         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1621                 set_tsk_thread_flag(p, TIF_SECCOMP);
1622 #endif
1623 }
1624
1625 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1626 {
1627         current->clear_child_tid = tidptr;
1628
1629         return task_pid_vnr(current);
1630 }
1631
1632 static void rt_mutex_init_task(struct task_struct *p)
1633 {
1634         raw_spin_lock_init(&p->pi_lock);
1635 #ifdef CONFIG_RT_MUTEXES
1636         p->pi_waiters = RB_ROOT_CACHED;
1637         p->pi_top_task = NULL;
1638         p->pi_blocked_on = NULL;
1639 #endif
1640 }
1641
1642 #ifdef CONFIG_POSIX_TIMERS
1643 /*
1644  * Initialize POSIX timer handling for a single task.
1645  */
1646 static void posix_cpu_timers_init(struct task_struct *tsk)
1647 {
1648         tsk->cputime_expires.prof_exp = 0;
1649         tsk->cputime_expires.virt_exp = 0;
1650         tsk->cputime_expires.sched_exp = 0;
1651         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1652         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1653         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1654 }
1655 #else
1656 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1657 #endif
1658
1659 static inline void init_task_pid_links(struct task_struct *task)
1660 {
1661         enum pid_type type;
1662
1663         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1664                 INIT_HLIST_NODE(&task->pid_links[type]);
1665         }
1666 }
1667
1668 static inline void
1669 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1670 {
1671         if (type == PIDTYPE_PID)
1672                 task->thread_pid = pid;
1673         else
1674                 task->signal->pids[type] = pid;
1675 }
1676
1677 static inline void rcu_copy_process(struct task_struct *p)
1678 {
1679 #ifdef CONFIG_PREEMPT_RCU
1680         p->rcu_read_lock_nesting = 0;
1681         p->rcu_read_unlock_special.s = 0;
1682         p->rcu_blocked_node = NULL;
1683         INIT_LIST_HEAD(&p->rcu_node_entry);
1684 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1685 #ifdef CONFIG_TASKS_RCU
1686         p->rcu_tasks_holdout = false;
1687         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1688         p->rcu_tasks_idle_cpu = -1;
1689 #endif /* #ifdef CONFIG_TASKS_RCU */
1690 }
1691
1692 static int pidfd_release(struct inode *inode, struct file *file)
1693 {
1694         struct pid *pid = file->private_data;
1695
1696         file->private_data = NULL;
1697         put_pid(pid);
1698         return 0;
1699 }
1700
1701 #ifdef CONFIG_PROC_FS
1702 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1703 {
1704         struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));
1705         struct pid *pid = f->private_data;
1706
1707         seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));
1708         seq_putc(m, '\n');
1709 }
1710 #endif
1711
1712 const struct file_operations pidfd_fops = {
1713         .release = pidfd_release,
1714 #ifdef CONFIG_PROC_FS
1715         .show_fdinfo = pidfd_show_fdinfo,
1716 #endif
1717 };
1718
1719 static void __delayed_free_task(struct rcu_head *rhp)
1720 {
1721         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1722
1723         free_task(tsk);
1724 }
1725
1726 static __always_inline void delayed_free_task(struct task_struct *tsk)
1727 {
1728         if (IS_ENABLED(CONFIG_MEMCG))
1729                 call_rcu(&tsk->rcu, __delayed_free_task);
1730         else
1731                 free_task(tsk);
1732 }
1733
1734 /*
1735  * This creates a new process as a copy of the old one,
1736  * but does not actually start it yet.
1737  *
1738  * It copies the registers, and all the appropriate
1739  * parts of the process environment (as per the clone
1740  * flags). The actual kick-off is left to the caller.
1741  */
1742 static __latent_entropy struct task_struct *copy_process(
1743                                         unsigned long clone_flags,
1744                                         unsigned long stack_start,
1745                                         unsigned long stack_size,
1746                                         int __user *parent_tidptr,
1747                                         int __user *child_tidptr,
1748                                         struct pid *pid,
1749                                         int trace,
1750                                         unsigned long tls,
1751                                         int node)
1752 {
1753         int pidfd = -1, retval;
1754         struct task_struct *p;
1755         struct multiprocess_signals delayed;
1756         struct file *pidfile = NULL;
1757
1758         /*
1759          * Don't allow sharing the root directory with processes in a different
1760          * namespace
1761          */
1762         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1763                 return ERR_PTR(-EINVAL);
1764
1765         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1766                 return ERR_PTR(-EINVAL);
1767
1768         /*
1769          * Thread groups must share signals as well, and detached threads
1770          * can only be started up within the thread group.
1771          */
1772         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1773                 return ERR_PTR(-EINVAL);
1774
1775         /*
1776          * Shared signal handlers imply shared VM. By way of the above,
1777          * thread groups also imply shared VM. Blocking this case allows
1778          * for various simplifications in other code.
1779          */
1780         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1781                 return ERR_PTR(-EINVAL);
1782
1783         /*
1784          * Siblings of global init remain as zombies on exit since they are
1785          * not reaped by their parent (swapper). To solve this and to avoid
1786          * multi-rooted process trees, prevent global and container-inits
1787          * from creating siblings.
1788          */
1789         if ((clone_flags & CLONE_PARENT) &&
1790                                 current->signal->flags & SIGNAL_UNKILLABLE)
1791                 return ERR_PTR(-EINVAL);
1792
1793         /*
1794          * If the new process will be in a different pid or user namespace
1795          * do not allow it to share a thread group with the forking task.
1796          */
1797         if (clone_flags & CLONE_THREAD) {
1798                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1799                     (task_active_pid_ns(current) !=
1800                                 current->nsproxy->pid_ns_for_children))
1801                         return ERR_PTR(-EINVAL);
1802         }
1803
1804         if (clone_flags & CLONE_PIDFD) {
1805                 /*
1806                  * - CLONE_PARENT_SETTID is useless for pidfds and also
1807                  *   parent_tidptr is used to return pidfds.
1808                  * - CLONE_DETACHED is blocked so that we can potentially
1809                  *   reuse it later for CLONE_PIDFD.
1810                  * - CLONE_THREAD is blocked until someone really needs it.
1811                  */
1812                 if (clone_flags &
1813                     (CLONE_DETACHED | CLONE_PARENT_SETTID | CLONE_THREAD))
1814                         return ERR_PTR(-EINVAL);
1815         }
1816
1817         /*
1818          * Force any signals received before this point to be delivered
1819          * before the fork happens.  Collect up signals sent to multiple
1820          * processes that happen during the fork and delay them so that
1821          * they appear to happen after the fork.
1822          */
1823         sigemptyset(&delayed.signal);
1824         INIT_HLIST_NODE(&delayed.node);
1825
1826         spin_lock_irq(&current->sighand->siglock);
1827         if (!(clone_flags & CLONE_THREAD))
1828                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1829         recalc_sigpending();
1830         spin_unlock_irq(&current->sighand->siglock);
1831         retval = -ERESTARTNOINTR;
1832         if (signal_pending(current))
1833                 goto fork_out;
1834
1835         retval = -ENOMEM;
1836         p = dup_task_struct(current, node);
1837         if (!p)
1838                 goto fork_out;
1839
1840         /*
1841          * This _must_ happen before we call free_task(), i.e. before we jump
1842          * to any of the bad_fork_* labels. This is to avoid freeing
1843          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1844          * kernel threads (PF_KTHREAD).
1845          */
1846         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1847         /*
1848          * Clear TID on mm_release()?
1849          */
1850         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1851
1852         ftrace_graph_init_task(p);
1853
1854         rt_mutex_init_task(p);
1855
1856 #ifdef CONFIG_PROVE_LOCKING
1857         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1858         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1859 #endif
1860         retval = -EAGAIN;
1861         if (atomic_read(&p->real_cred->user->processes) >=
1862                         task_rlimit(p, RLIMIT_NPROC)) {
1863                 if (p->real_cred->user != INIT_USER &&
1864                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1865                         goto bad_fork_free;
1866         }
1867         current->flags &= ~PF_NPROC_EXCEEDED;
1868
1869         retval = copy_creds(p, clone_flags);
1870         if (retval < 0)
1871                 goto bad_fork_free;
1872
1873         /*
1874          * If multiple threads are within copy_process(), then this check
1875          * triggers too late. This doesn't hurt, the check is only there
1876          * to stop root fork bombs.
1877          */
1878         retval = -EAGAIN;
1879         if (nr_threads >= max_threads)
1880                 goto bad_fork_cleanup_count;
1881
1882         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1883         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1884         p->flags |= PF_FORKNOEXEC;
1885         INIT_LIST_HEAD(&p->children);
1886         INIT_LIST_HEAD(&p->sibling);
1887         rcu_copy_process(p);
1888         p->vfork_done = NULL;
1889         spin_lock_init(&p->alloc_lock);
1890
1891         init_sigpending(&p->pending);
1892
1893         p->utime = p->stime = p->gtime = 0;
1894 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1895         p->utimescaled = p->stimescaled = 0;
1896 #endif
1897         prev_cputime_init(&p->prev_cputime);
1898
1899 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1900         seqcount_init(&p->vtime.seqcount);
1901         p->vtime.starttime = 0;
1902         p->vtime.state = VTIME_INACTIVE;
1903 #endif
1904
1905 #if defined(SPLIT_RSS_COUNTING)
1906         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1907 #endif
1908
1909         p->default_timer_slack_ns = current->timer_slack_ns;
1910
1911 #ifdef CONFIG_PSI
1912         p->psi_flags = 0;
1913 #endif
1914
1915         task_io_accounting_init(&p->ioac);
1916         acct_clear_integrals(p);
1917
1918         posix_cpu_timers_init(p);
1919
1920         p->io_context = NULL;
1921         audit_set_context(p, NULL);
1922         cgroup_fork(p);
1923 #ifdef CONFIG_NUMA
1924         p->mempolicy = mpol_dup(p->mempolicy);
1925         if (IS_ERR(p->mempolicy)) {
1926                 retval = PTR_ERR(p->mempolicy);
1927                 p->mempolicy = NULL;
1928                 goto bad_fork_cleanup_threadgroup_lock;
1929         }
1930 #endif
1931 #ifdef CONFIG_CPUSETS
1932         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1933         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1934         seqcount_init(&p->mems_allowed_seq);
1935 #endif
1936 #ifdef CONFIG_TRACE_IRQFLAGS
1937         p->irq_events = 0;
1938         p->hardirqs_enabled = 0;
1939         p->hardirq_enable_ip = 0;
1940         p->hardirq_enable_event = 0;
1941         p->hardirq_disable_ip = _THIS_IP_;
1942         p->hardirq_disable_event = 0;
1943         p->softirqs_enabled = 1;
1944         p->softirq_enable_ip = _THIS_IP_;
1945         p->softirq_enable_event = 0;
1946         p->softirq_disable_ip = 0;
1947         p->softirq_disable_event = 0;
1948         p->hardirq_context = 0;
1949         p->softirq_context = 0;
1950 #endif
1951
1952         p->pagefault_disabled = 0;
1953
1954 #ifdef CONFIG_LOCKDEP
1955         p->lockdep_depth = 0; /* no locks held yet */
1956         p->curr_chain_key = 0;
1957         p->lockdep_recursion = 0;
1958         lockdep_init_task(p);
1959 #endif
1960
1961 #ifdef CONFIG_DEBUG_MUTEXES
1962         p->blocked_on = NULL; /* not blocked yet */
1963 #endif
1964 #ifdef CONFIG_BCACHE
1965         p->sequential_io        = 0;
1966         p->sequential_io_avg    = 0;
1967 #endif
1968
1969         /* Perform scheduler related setup. Assign this task to a CPU. */
1970         retval = sched_fork(clone_flags, p);
1971         if (retval)
1972                 goto bad_fork_cleanup_policy;
1973
1974         retval = perf_event_init_task(p);
1975         if (retval)
1976                 goto bad_fork_cleanup_policy;
1977         retval = audit_alloc(p);
1978         if (retval)
1979                 goto bad_fork_cleanup_perf;
1980         /* copy all the process information */
1981         shm_init_task(p);
1982         retval = security_task_alloc(p, clone_flags);
1983         if (retval)
1984                 goto bad_fork_cleanup_audit;
1985         retval = copy_semundo(clone_flags, p);
1986         if (retval)
1987                 goto bad_fork_cleanup_security;
1988         retval = copy_files(clone_flags, p);
1989         if (retval)
1990                 goto bad_fork_cleanup_semundo;
1991         retval = copy_fs(clone_flags, p);
1992         if (retval)
1993                 goto bad_fork_cleanup_files;
1994         retval = copy_sighand(clone_flags, p);
1995         if (retval)
1996                 goto bad_fork_cleanup_fs;
1997         retval = copy_signal(clone_flags, p);
1998         if (retval)
1999                 goto bad_fork_cleanup_sighand;
2000         retval = copy_mm(clone_flags, p);
2001         if (retval)
2002                 goto bad_fork_cleanup_signal;
2003         retval = copy_namespaces(clone_flags, p);
2004         if (retval)
2005                 goto bad_fork_cleanup_mm;
2006         retval = copy_io(clone_flags, p);
2007         if (retval)
2008                 goto bad_fork_cleanup_namespaces;
2009         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
2010         if (retval)
2011                 goto bad_fork_cleanup_io;
2012
2013         stackleak_task_init(p);
2014
2015         if (pid != &init_struct_pid) {
2016                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
2017                 if (IS_ERR(pid)) {
2018                         retval = PTR_ERR(pid);
2019                         goto bad_fork_cleanup_thread;
2020                 }
2021         }
2022
2023         /*
2024          * This has to happen after we've potentially unshared the file
2025          * descriptor table (so that the pidfd doesn't leak into the child
2026          * if the fd table isn't shared).
2027          */
2028         if (clone_flags & CLONE_PIDFD) {
2029                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2030                 if (retval < 0)
2031                         goto bad_fork_free_pid;
2032
2033                 pidfd = retval;
2034
2035                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2036                                               O_RDWR | O_CLOEXEC);
2037                 if (IS_ERR(pidfile)) {
2038                         put_unused_fd(pidfd);
2039                         retval = PTR_ERR(pidfile);
2040                         goto bad_fork_free_pid;
2041                 }
2042                 get_pid(pid);   /* held by pidfile now */
2043
2044                 retval = put_user(pidfd, parent_tidptr);
2045                 if (retval)
2046                         goto bad_fork_put_pidfd;
2047         }
2048
2049 #ifdef CONFIG_BLOCK
2050         p->plug = NULL;
2051 #endif
2052 #ifdef CONFIG_FUTEX
2053         p->robust_list = NULL;
2054 #ifdef CONFIG_COMPAT
2055         p->compat_robust_list = NULL;
2056 #endif
2057         INIT_LIST_HEAD(&p->pi_state_list);
2058         p->pi_state_cache = NULL;
2059 #endif
2060         /*
2061          * sigaltstack should be cleared when sharing the same VM
2062          */
2063         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2064                 sas_ss_reset(p);
2065
2066         /*
2067          * Syscall tracing and stepping should be turned off in the
2068          * child regardless of CLONE_PTRACE.
2069          */
2070         user_disable_single_step(p);
2071         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2072 #ifdef TIF_SYSCALL_EMU
2073         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2074 #endif
2075         clear_tsk_latency_tracing(p);
2076
2077         /* ok, now we should be set up.. */
2078         p->pid = pid_nr(pid);
2079         if (clone_flags & CLONE_THREAD) {
2080                 p->exit_signal = -1;
2081                 p->group_leader = current->group_leader;
2082                 p->tgid = current->tgid;
2083         } else {
2084                 if (clone_flags & CLONE_PARENT)
2085                         p->exit_signal = current->group_leader->exit_signal;
2086                 else
2087                         p->exit_signal = (clone_flags & CSIGNAL);
2088                 p->group_leader = p;
2089                 p->tgid = p->pid;
2090         }
2091
2092         p->nr_dirtied = 0;
2093         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2094         p->dirty_paused_when = 0;
2095
2096         p->pdeath_signal = 0;
2097         INIT_LIST_HEAD(&p->thread_group);
2098         p->task_works = NULL;
2099
2100         cgroup_threadgroup_change_begin(current);
2101         /*
2102          * Ensure that the cgroup subsystem policies allow the new process to be
2103          * forked. It should be noted the the new process's css_set can be changed
2104          * between here and cgroup_post_fork() if an organisation operation is in
2105          * progress.
2106          */
2107         retval = cgroup_can_fork(p);
2108         if (retval)
2109                 goto bad_fork_cgroup_threadgroup_change_end;
2110
2111         /*
2112          * From this point on we must avoid any synchronous user-space
2113          * communication until we take the tasklist-lock. In particular, we do
2114          * not want user-space to be able to predict the process start-time by
2115          * stalling fork(2) after we recorded the start_time but before it is
2116          * visible to the system.
2117          */
2118
2119         p->start_time = ktime_get_ns();
2120         p->real_start_time = ktime_get_boot_ns();
2121
2122         /*
2123          * Make it visible to the rest of the system, but dont wake it up yet.
2124          * Need tasklist lock for parent etc handling!
2125          */
2126         write_lock_irq(&tasklist_lock);
2127
2128         /* CLONE_PARENT re-uses the old parent */
2129         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2130                 p->real_parent = current->real_parent;
2131                 p->parent_exec_id = current->parent_exec_id;
2132         } else {
2133                 p->real_parent = current;
2134                 p->parent_exec_id = current->self_exec_id;
2135         }
2136
2137         klp_copy_process(p);
2138
2139         spin_lock(&current->sighand->siglock);
2140
2141         /*
2142          * Copy seccomp details explicitly here, in case they were changed
2143          * before holding sighand lock.
2144          */
2145         copy_seccomp(p);
2146
2147         rseq_fork(p, clone_flags);
2148
2149         /* Don't start children in a dying pid namespace */
2150         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2151                 retval = -ENOMEM;
2152                 goto bad_fork_cancel_cgroup;
2153         }
2154
2155         /* Let kill terminate clone/fork in the middle */
2156         if (fatal_signal_pending(current)) {
2157                 retval = -EINTR;
2158                 goto bad_fork_cancel_cgroup;
2159         }
2160
2161         /* past the last point of failure */
2162         if (pidfile)
2163                 fd_install(pidfd, pidfile);
2164
2165         init_task_pid_links(p);
2166         if (likely(p->pid)) {
2167                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2168
2169                 init_task_pid(p, PIDTYPE_PID, pid);
2170                 if (thread_group_leader(p)) {
2171                         init_task_pid(p, PIDTYPE_TGID, pid);
2172                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2173                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2174
2175                         if (is_child_reaper(pid)) {
2176                                 ns_of_pid(pid)->child_reaper = p;
2177                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2178                         }
2179                         p->signal->shared_pending.signal = delayed.signal;
2180                         p->signal->tty = tty_kref_get(current->signal->tty);
2181                         /*
2182                          * Inherit has_child_subreaper flag under the same
2183                          * tasklist_lock with adding child to the process tree
2184                          * for propagate_has_child_subreaper optimization.
2185                          */
2186                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2187                                                          p->real_parent->signal->is_child_subreaper;
2188                         list_add_tail(&p->sibling, &p->real_parent->children);
2189                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2190                         attach_pid(p, PIDTYPE_TGID);
2191                         attach_pid(p, PIDTYPE_PGID);
2192                         attach_pid(p, PIDTYPE_SID);
2193                         __this_cpu_inc(process_counts);
2194                 } else {
2195                         current->signal->nr_threads++;
2196                         atomic_inc(&current->signal->live);
2197                         refcount_inc(&current->signal->sigcnt);
2198                         task_join_group_stop(p);
2199                         list_add_tail_rcu(&p->thread_group,
2200                                           &p->group_leader->thread_group);
2201                         list_add_tail_rcu(&p->thread_node,
2202                                           &p->signal->thread_head);
2203                 }
2204                 attach_pid(p, PIDTYPE_PID);
2205                 nr_threads++;
2206         }
2207         total_forks++;
2208         hlist_del_init(&delayed.node);
2209         spin_unlock(&current->sighand->siglock);
2210         syscall_tracepoint_update(p);
2211         write_unlock_irq(&tasklist_lock);
2212
2213         proc_fork_connector(p);
2214         cgroup_post_fork(p);
2215         cgroup_threadgroup_change_end(current);
2216         perf_event_fork(p);
2217
2218         trace_task_newtask(p, clone_flags);
2219         uprobe_copy_process(p, clone_flags);
2220
2221         return p;
2222
2223 bad_fork_cancel_cgroup:
2224         spin_unlock(&current->sighand->siglock);
2225         write_unlock_irq(&tasklist_lock);
2226         cgroup_cancel_fork(p);
2227 bad_fork_cgroup_threadgroup_change_end:
2228         cgroup_threadgroup_change_end(current);
2229 bad_fork_put_pidfd:
2230         if (clone_flags & CLONE_PIDFD) {
2231                 fput(pidfile);
2232                 put_unused_fd(pidfd);
2233         }
2234 bad_fork_free_pid:
2235         if (pid != &init_struct_pid)
2236                 free_pid(pid);
2237 bad_fork_cleanup_thread:
2238         exit_thread(p);
2239 bad_fork_cleanup_io:
2240         if (p->io_context)
2241                 exit_io_context(p);
2242 bad_fork_cleanup_namespaces:
2243         exit_task_namespaces(p);
2244 bad_fork_cleanup_mm:
2245         if (p->mm) {
2246                 mm_clear_owner(p->mm, p);
2247                 mmput(p->mm);
2248         }
2249 bad_fork_cleanup_signal:
2250         if (!(clone_flags & CLONE_THREAD))
2251                 free_signal_struct(p->signal);
2252 bad_fork_cleanup_sighand:
2253         __cleanup_sighand(p->sighand);
2254 bad_fork_cleanup_fs:
2255         exit_fs(p); /* blocking */
2256 bad_fork_cleanup_files:
2257         exit_files(p); /* blocking */
2258 bad_fork_cleanup_semundo:
2259         exit_sem(p);
2260 bad_fork_cleanup_security:
2261         security_task_free(p);
2262 bad_fork_cleanup_audit:
2263         audit_free(p);
2264 bad_fork_cleanup_perf:
2265         perf_event_free_task(p);
2266 bad_fork_cleanup_policy:
2267         lockdep_free_task(p);
2268 #ifdef CONFIG_NUMA
2269         mpol_put(p->mempolicy);
2270 bad_fork_cleanup_threadgroup_lock:
2271 #endif
2272         delayacct_tsk_free(p);
2273 bad_fork_cleanup_count:
2274         atomic_dec(&p->cred->user->processes);
2275         exit_creds(p);
2276 bad_fork_free:
2277         p->state = TASK_DEAD;
2278         put_task_stack(p);
2279         delayed_free_task(p);
2280 fork_out:
2281         spin_lock_irq(&current->sighand->siglock);
2282         hlist_del_init(&delayed.node);
2283         spin_unlock_irq(&current->sighand->siglock);
2284         return ERR_PTR(retval);
2285 }
2286
2287 static inline void init_idle_pids(struct task_struct *idle)
2288 {
2289         enum pid_type type;
2290
2291         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2292                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2293                 init_task_pid(idle, type, &init_struct_pid);
2294         }
2295 }
2296
2297 struct task_struct *fork_idle(int cpu)
2298 {
2299         struct task_struct *task;
2300         task = copy_process(CLONE_VM, 0, 0, NULL, NULL, &init_struct_pid, 0, 0,
2301                             cpu_to_node(cpu));
2302         if (!IS_ERR(task)) {
2303                 init_idle_pids(task);
2304                 init_idle(task, cpu);
2305         }
2306
2307         return task;
2308 }
2309
2310 struct mm_struct *copy_init_mm(void)
2311 {
2312         return dup_mm(NULL, &init_mm);
2313 }
2314
2315 /*
2316  *  Ok, this is the main fork-routine.
2317  *
2318  * It copies the process, and if successful kick-starts
2319  * it and waits for it to finish using the VM if required.
2320  */
2321 long _do_fork(unsigned long clone_flags,
2322               unsigned long stack_start,
2323               unsigned long stack_size,
2324               int __user *parent_tidptr,
2325               int __user *child_tidptr,
2326               unsigned long tls)
2327 {
2328         struct completion vfork;
2329         struct pid *pid;
2330         struct task_struct *p;
2331         int trace = 0;
2332         long nr;
2333
2334         /*
2335          * Determine whether and which event to report to ptracer.  When
2336          * called from kernel_thread or CLONE_UNTRACED is explicitly
2337          * requested, no event is reported; otherwise, report if the event
2338          * for the type of forking is enabled.
2339          */
2340         if (!(clone_flags & CLONE_UNTRACED)) {
2341                 if (clone_flags & CLONE_VFORK)
2342                         trace = PTRACE_EVENT_VFORK;
2343                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2344                         trace = PTRACE_EVENT_CLONE;
2345                 else
2346                         trace = PTRACE_EVENT_FORK;
2347
2348                 if (likely(!ptrace_event_enabled(current, trace)))
2349                         trace = 0;
2350         }
2351
2352         p = copy_process(clone_flags, stack_start, stack_size, parent_tidptr,
2353                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2354         add_latent_entropy();
2355
2356         if (IS_ERR(p))
2357                 return PTR_ERR(p);
2358
2359         /*
2360          * Do this prior waking up the new thread - the thread pointer
2361          * might get invalid after that point, if the thread exits quickly.
2362          */
2363         trace_sched_process_fork(current, p);
2364
2365         pid = get_task_pid(p, PIDTYPE_PID);
2366         nr = pid_vnr(pid);
2367
2368         if (clone_flags & CLONE_PARENT_SETTID)
2369                 put_user(nr, parent_tidptr);
2370
2371         if (clone_flags & CLONE_VFORK) {
2372                 p->vfork_done = &vfork;
2373                 init_completion(&vfork);
2374                 get_task_struct(p);
2375         }
2376
2377         wake_up_new_task(p);
2378
2379         /* forking complete and child started to run, tell ptracer */
2380         if (unlikely(trace))
2381                 ptrace_event_pid(trace, pid);
2382
2383         if (clone_flags & CLONE_VFORK) {
2384                 if (!wait_for_vfork_done(p, &vfork))
2385                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2386         }
2387
2388         put_pid(pid);
2389         return nr;
2390 }
2391
2392 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2393 /* For compatibility with architectures that call do_fork directly rather than
2394  * using the syscall entry points below. */
2395 long do_fork(unsigned long clone_flags,
2396               unsigned long stack_start,
2397               unsigned long stack_size,
2398               int __user *parent_tidptr,
2399               int __user *child_tidptr)
2400 {
2401         return _do_fork(clone_flags, stack_start, stack_size,
2402                         parent_tidptr, child_tidptr, 0);
2403 }
2404 #endif
2405
2406 /*
2407  * Create a kernel thread.
2408  */
2409 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2410 {
2411         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2412                 (unsigned long)arg, NULL, NULL, 0);
2413 }
2414
2415 #ifdef __ARCH_WANT_SYS_FORK
2416 SYSCALL_DEFINE0(fork)
2417 {
2418 #ifdef CONFIG_MMU
2419         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2420 #else
2421         /* can not support in nommu mode */
2422         return -EINVAL;
2423 #endif
2424 }
2425 #endif
2426
2427 #ifdef __ARCH_WANT_SYS_VFORK
2428 SYSCALL_DEFINE0(vfork)
2429 {
2430         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2431                         0, NULL, NULL, 0);
2432 }
2433 #endif
2434
2435 #ifdef __ARCH_WANT_SYS_CLONE
2436 #ifdef CONFIG_CLONE_BACKWARDS
2437 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2438                  int __user *, parent_tidptr,
2439                  unsigned long, tls,
2440                  int __user *, child_tidptr)
2441 #elif defined(CONFIG_CLONE_BACKWARDS2)
2442 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2443                  int __user *, parent_tidptr,
2444                  int __user *, child_tidptr,
2445                  unsigned long, tls)
2446 #elif defined(CONFIG_CLONE_BACKWARDS3)
2447 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2448                 int, stack_size,
2449                 int __user *, parent_tidptr,
2450                 int __user *, child_tidptr,
2451                 unsigned long, tls)
2452 #else
2453 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2454                  int __user *, parent_tidptr,
2455                  int __user *, child_tidptr,
2456                  unsigned long, tls)
2457 #endif
2458 {
2459         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2460 }
2461 #endif
2462
2463 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2464 {
2465         struct task_struct *leader, *parent, *child;
2466         int res;
2467
2468         read_lock(&tasklist_lock);
2469         leader = top = top->group_leader;
2470 down:
2471         for_each_thread(leader, parent) {
2472                 list_for_each_entry(child, &parent->children, sibling) {
2473                         res = visitor(child, data);
2474                         if (res) {
2475                                 if (res < 0)
2476                                         goto out;
2477                                 leader = child;
2478                                 goto down;
2479                         }
2480 up:
2481                         ;
2482                 }
2483         }
2484
2485         if (leader != top) {
2486                 child = leader;
2487                 parent = child->real_parent;
2488                 leader = parent->group_leader;
2489                 goto up;
2490         }
2491 out:
2492         read_unlock(&tasklist_lock);
2493 }
2494
2495 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2496 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2497 #endif
2498
2499 static void sighand_ctor(void *data)
2500 {
2501         struct sighand_struct *sighand = data;
2502
2503         spin_lock_init(&sighand->siglock);
2504         init_waitqueue_head(&sighand->signalfd_wqh);
2505 }
2506
2507 void __init proc_caches_init(void)
2508 {
2509         unsigned int mm_size;
2510
2511         sighand_cachep = kmem_cache_create("sighand_cache",
2512                         sizeof(struct sighand_struct), 0,
2513                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2514                         SLAB_ACCOUNT, sighand_ctor);
2515         signal_cachep = kmem_cache_create("signal_cache",
2516                         sizeof(struct signal_struct), 0,
2517                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2518                         NULL);
2519         files_cachep = kmem_cache_create("files_cache",
2520                         sizeof(struct files_struct), 0,
2521                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2522                         NULL);
2523         fs_cachep = kmem_cache_create("fs_cache",
2524                         sizeof(struct fs_struct), 0,
2525                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2526                         NULL);
2527
2528         /*
2529          * The mm_cpumask is located at the end of mm_struct, and is
2530          * dynamically sized based on the maximum CPU number this system
2531          * can have, taking hotplug into account (nr_cpu_ids).
2532          */
2533         mm_size = sizeof(struct mm_struct) + cpumask_size();
2534
2535         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2536                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2537                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2538                         offsetof(struct mm_struct, saved_auxv),
2539                         sizeof_field(struct mm_struct, saved_auxv),
2540                         NULL);
2541         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2542         mmap_init();
2543         nsproxy_cache_init();
2544 }
2545
2546 /*
2547  * Check constraints on flags passed to the unshare system call.
2548  */
2549 static int check_unshare_flags(unsigned long unshare_flags)
2550 {
2551         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2552                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2553                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2554                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2555                 return -EINVAL;
2556         /*
2557          * Not implemented, but pretend it works if there is nothing
2558          * to unshare.  Note that unsharing the address space or the
2559          * signal handlers also need to unshare the signal queues (aka
2560          * CLONE_THREAD).
2561          */
2562         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2563                 if (!thread_group_empty(current))
2564                         return -EINVAL;
2565         }
2566         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2567                 if (refcount_read(&current->sighand->count) > 1)
2568                         return -EINVAL;
2569         }
2570         if (unshare_flags & CLONE_VM) {
2571                 if (!current_is_single_threaded())
2572                         return -EINVAL;
2573         }
2574
2575         return 0;
2576 }
2577
2578 /*
2579  * Unshare the filesystem structure if it is being shared
2580  */
2581 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2582 {
2583         struct fs_struct *fs = current->fs;
2584
2585         if (!(unshare_flags & CLONE_FS) || !fs)
2586                 return 0;
2587
2588         /* don't need lock here; in the worst case we'll do useless copy */
2589         if (fs->users == 1)
2590                 return 0;
2591
2592         *new_fsp = copy_fs_struct(fs);
2593         if (!*new_fsp)
2594                 return -ENOMEM;
2595
2596         return 0;
2597 }
2598
2599 /*
2600  * Unshare file descriptor table if it is being shared
2601  */
2602 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2603 {
2604         struct files_struct *fd = current->files;
2605         int error = 0;
2606
2607         if ((unshare_flags & CLONE_FILES) &&
2608             (fd && atomic_read(&fd->count) > 1)) {
2609                 *new_fdp = dup_fd(fd, &error);
2610                 if (!*new_fdp)
2611                         return error;
2612         }
2613
2614         return 0;
2615 }
2616
2617 /*
2618  * unshare allows a process to 'unshare' part of the process
2619  * context which was originally shared using clone.  copy_*
2620  * functions used by do_fork() cannot be used here directly
2621  * because they modify an inactive task_struct that is being
2622  * constructed. Here we are modifying the current, active,
2623  * task_struct.
2624  */
2625 int ksys_unshare(unsigned long unshare_flags)
2626 {
2627         struct fs_struct *fs, *new_fs = NULL;
2628         struct files_struct *fd, *new_fd = NULL;
2629         struct cred *new_cred = NULL;
2630         struct nsproxy *new_nsproxy = NULL;
2631         int do_sysvsem = 0;
2632         int err;
2633
2634         /*
2635          * If unsharing a user namespace must also unshare the thread group
2636          * and unshare the filesystem root and working directories.
2637          */
2638         if (unshare_flags & CLONE_NEWUSER)
2639                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2640         /*
2641          * If unsharing vm, must also unshare signal handlers.
2642          */
2643         if (unshare_flags & CLONE_VM)
2644                 unshare_flags |= CLONE_SIGHAND;
2645         /*
2646          * If unsharing a signal handlers, must also unshare the signal queues.
2647          */
2648         if (unshare_flags & CLONE_SIGHAND)
2649                 unshare_flags |= CLONE_THREAD;
2650         /*
2651          * If unsharing namespace, must also unshare filesystem information.
2652          */
2653         if (unshare_flags & CLONE_NEWNS)
2654                 unshare_flags |= CLONE_FS;
2655
2656         err = check_unshare_flags(unshare_flags);
2657         if (err)
2658                 goto bad_unshare_out;
2659         /*
2660          * CLONE_NEWIPC must also detach from the undolist: after switching
2661          * to a new ipc namespace, the semaphore arrays from the old
2662          * namespace are unreachable.
2663          */
2664         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2665                 do_sysvsem = 1;
2666         err = unshare_fs(unshare_flags, &new_fs);
2667         if (err)
2668                 goto bad_unshare_out;
2669         err = unshare_fd(unshare_flags, &new_fd);
2670         if (err)
2671                 goto bad_unshare_cleanup_fs;
2672         err = unshare_userns(unshare_flags, &new_cred);
2673         if (err)
2674                 goto bad_unshare_cleanup_fd;
2675         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2676                                          new_cred, new_fs);
2677         if (err)
2678                 goto bad_unshare_cleanup_cred;
2679
2680         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2681                 if (do_sysvsem) {
2682                         /*
2683                          * CLONE_SYSVSEM is equivalent to sys_exit().
2684                          */
2685                         exit_sem(current);
2686                 }
2687                 if (unshare_flags & CLONE_NEWIPC) {
2688                         /* Orphan segments in old ns (see sem above). */
2689                         exit_shm(current);
2690                         shm_init_task(current);
2691                 }
2692
2693                 if (new_nsproxy)
2694                         switch_task_namespaces(current, new_nsproxy);
2695
2696                 task_lock(current);
2697
2698                 if (new_fs) {
2699                         fs = current->fs;
2700                         spin_lock(&fs->lock);
2701                         current->fs = new_fs;
2702                         if (--fs->users)
2703                                 new_fs = NULL;
2704                         else
2705                                 new_fs = fs;
2706                         spin_unlock(&fs->lock);
2707                 }
2708
2709                 if (new_fd) {
2710                         fd = current->files;
2711                         current->files = new_fd;
2712                         new_fd = fd;
2713                 }
2714
2715                 task_unlock(current);
2716
2717                 if (new_cred) {
2718                         /* Install the new user namespace */
2719                         commit_creds(new_cred);
2720                         new_cred = NULL;
2721                 }
2722         }
2723
2724         perf_event_namespaces(current);
2725
2726 bad_unshare_cleanup_cred:
2727         if (new_cred)
2728                 put_cred(new_cred);
2729 bad_unshare_cleanup_fd:
2730         if (new_fd)
2731                 put_files_struct(new_fd);
2732
2733 bad_unshare_cleanup_fs:
2734         if (new_fs)
2735                 free_fs_struct(new_fs);
2736
2737 bad_unshare_out:
2738         return err;
2739 }
2740
2741 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2742 {
2743         return ksys_unshare(unshare_flags);
2744 }
2745
2746 /*
2747  *      Helper to unshare the files of the current task.
2748  *      We don't want to expose copy_files internals to
2749  *      the exec layer of the kernel.
2750  */
2751
2752 int unshare_files(struct files_struct **displaced)
2753 {
2754         struct task_struct *task = current;
2755         struct files_struct *copy = NULL;
2756         int error;
2757
2758         error = unshare_fd(CLONE_FILES, &copy);
2759         if (error || !copy) {
2760                 *displaced = NULL;
2761                 return error;
2762         }
2763         *displaced = task->files;
2764         task_lock(task);
2765         task->files = copy;
2766         task_unlock(task);
2767         return 0;
2768 }
2769
2770 int sysctl_max_threads(struct ctl_table *table, int write,
2771                        void __user *buffer, size_t *lenp, loff_t *ppos)
2772 {
2773         struct ctl_table t;
2774         int ret;
2775         int threads = max_threads;
2776         int min = MIN_THREADS;
2777         int max = MAX_THREADS;
2778
2779         t = *table;
2780         t.data = &threads;
2781         t.extra1 = &min;
2782         t.extra2 = &max;
2783
2784         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2785         if (ret || !write)
2786                 return ret;
2787
2788         set_max_threads(threads);
2789
2790         return 0;
2791 }