kernel/fork.c

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