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
 748         /*
 749          * The number of threads shall be limited such that the thread
 750          * structures may only consume a small part of the available memory.
 751          */
 752         if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
 753                 threads = MAX_THREADS;
 754         else
 755                 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
 756                                     (u64) THREAD_SIZE * 8UL);
 757
 758         if (threads > max_threads_suggested)
 759                 threads = max_threads_suggested;
 760
 761         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 762 }
 763
 764 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 765 /* Initialized by the architecture: */
 766 int arch_task_struct_size __read_mostly;
 767 #endif
 768
 769 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 770 {
 771         /* Fetch thread_struct whitelist for the architecture. */
 772         arch_thread_struct_whitelist(offset, size);
 773
 774         /*
 775          * Handle zero-sized whitelist or empty thread_struct, otherwise
 776          * adjust offset to position of thread_struct in task_struct.
 777          */
 778         if (unlikely(*size == 0))
 779                 *offset = 0;
 780         else
 781                 *offset += offsetof(struct task_struct, thread);
 782 }
 783
 784 void __init fork_init(void)
 785 {
 786         int i;
 787 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 788 #ifndef ARCH_MIN_TASKALIGN
 789 #define ARCH_MIN_TASKALIGN      0
 790 #endif
 791         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 792         unsigned long useroffset, usersize;
 793
 794         /* create a slab on which task_structs can be allocated */
 795         task_struct_whitelist(&useroffset, &usersize);
 796         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 797                         arch_task_struct_size, align,
 798                         SLAB_PANIC|SLAB_ACCOUNT,
 799                         useroffset, usersize, NULL);
 800 #endif
 801
 802         /* do the arch specific task caches init */
 803         arch_task_cache_init();
 804
 805         set_max_threads(MAX_THREADS);
 806
 807         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 808         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 809         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 810                 init_task.signal->rlim[RLIMIT_NPROC];
 811
 812         for (i = 0; i < UCOUNT_COUNTS; i++) {
 813                 init_user_ns.ucount_max[i] = max_threads/2;
 814         }
 815
 816 #ifdef CONFIG_VMAP_STACK
 817         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 818                           NULL, free_vm_stack_cache);
 819 #endif
 820
 821         lockdep_init_task(&init_task);
 822 }
 823
 824 int __weak arch_dup_task_struct(struct task_struct *dst,
 825                                                struct task_struct *src)
 826 {
 827         *dst = *src;
 828         return 0;
 829 }
 830
 831 void set_task_stack_end_magic(struct task_struct *tsk)
 832 {
 833         unsigned long *stackend;
 834
 835         stackend = end_of_stack(tsk);
 836         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 837 }
 838
 839 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 840 {
 841         struct task_struct *tsk;
 842         unsigned long *stack;
 843         struct vm_struct *stack_vm_area;
 844         int err;
 845
 846         if (node == NUMA_NO_NODE)
 847                 node = tsk_fork_get_node(orig);
 848         tsk = alloc_task_struct_node(node);
 849         if (!tsk)
 850                 return NULL;
 851
 852         stack = alloc_thread_stack_node(tsk, node);
 853         if (!stack)
 854                 goto free_tsk;
 855
 856         if (memcg_charge_kernel_stack(tsk))
 857                 goto free_stack;
 858
 859         stack_vm_area = task_stack_vm_area(tsk);
 860
 861         err = arch_dup_task_struct(tsk, orig);
 862
 863         /*
 864          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 865          * sure they're properly initialized before using any stack-related
 866          * functions again.
 867          */
 868         tsk->stack = stack;
 869 #ifdef CONFIG_VMAP_STACK
 870         tsk->stack_vm_area = stack_vm_area;
 871 #endif
 872 #ifdef CONFIG_THREAD_INFO_IN_TASK
 873         atomic_set(&tsk->stack_refcount, 1);
 874 #endif
 875
 876         if (err)
 877                 goto free_stack;
 878
 879 #ifdef CONFIG_SECCOMP
 880         /*
 881          * We must handle setting up seccomp filters once we're under
 882          * the sighand lock in case orig has changed between now and
 883          * then. Until then, filter must be NULL to avoid messing up
 884          * the usage counts on the error path calling free_task.
 885          */
 886         tsk->seccomp.filter = NULL;
 887 #endif
 888
 889         setup_thread_stack(tsk, orig);
 890         clear_user_return_notifier(tsk);
 891         clear_tsk_need_resched(tsk);
 892         set_task_stack_end_magic(tsk);
 893
 894 #ifdef CONFIG_STACKPROTECTOR
 895         tsk->stack_canary = get_random_canary();
 896 #endif
 897
 898         /*
 899          * One for us, one for whoever does the "release_task()" (usually
 900          * parent)
 901          */
 902         atomic_set(&tsk->usage, 2);
 903 #ifdef CONFIG_BLK_DEV_IO_TRACE
 904         tsk->btrace_seq = 0;
 905 #endif
 906         tsk->splice_pipe = NULL;
 907         tsk->task_frag.page = NULL;
 908         tsk->wake_q.next = NULL;
 909
 910         account_kernel_stack(tsk, 1);
 911
 912         kcov_task_init(tsk);
 913
 914 #ifdef CONFIG_FAULT_INJECTION
 915         tsk->fail_nth = 0;
 916 #endif
 917
 918 #ifdef CONFIG_BLK_CGROUP
 919         tsk->throttle_queue = NULL;
 920         tsk->use_memdelay = 0;
 921 #endif
 922
 923 #ifdef CONFIG_MEMCG
 924         tsk->active_memcg = NULL;
 925 #endif
 926         return tsk;
 927
 928 free_stack:
 929         free_thread_stack(tsk);
 930 free_tsk:
 931         free_task_struct(tsk);
 932         return NULL;
 933 }
 934
 935 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 936
 937 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 938
 939 static int __init coredump_filter_setup(char *s)
 940 {
 941         default_dump_filter =
 942                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 943                 MMF_DUMP_FILTER_MASK;
 944         return 1;
 945 }
 946
 947 __setup("coredump_filter=", coredump_filter_setup);
 948
 949 #include <linux/init_task.h>
 950
 951 static void mm_init_aio(struct mm_struct *mm)
 952 {
 953 #ifdef CONFIG_AIO
 954         spin_lock_init(&mm->ioctx_lock);
 955         mm->ioctx_table = NULL;
 956 #endif
 957 }
 958
 959 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 960 {
 961 #ifdef CONFIG_MEMCG
 962         mm->owner = p;
 963 #endif
 964 }
 965
 966 static void mm_init_uprobes_state(struct mm_struct *mm)
 967 {
 968 #ifdef CONFIG_UPROBES
 969         mm->uprobes_state.xol_area = NULL;
 970 #endif
 971 }
 972
 973 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 974         struct user_namespace *user_ns)
 975 {
 976         mm->mmap = NULL;
 977         mm->mm_rb = RB_ROOT;
 978         mm->vmacache_seqnum = 0;
 979         atomic_set(&mm->mm_users, 1);
 980         atomic_set(&mm->mm_count, 1);
 981         init_rwsem(&mm->mmap_sem);
 982         INIT_LIST_HEAD(&mm->mmlist);
 983         mm->core_state = NULL;
 984         mm_pgtables_bytes_init(mm);
 985         mm->map_count = 0;
 986         mm->locked_vm = 0;
 987         mm->pinned_vm = 0;
 988         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 989         spin_lock_init(&mm->page_table_lock);
 990         spin_lock_init(&mm->arg_lock);
 991         mm_init_cpumask(mm);
 992         mm_init_aio(mm);
 993         mm_init_owner(mm, p);
 994         RCU_INIT_POINTER(mm->exe_file, NULL);
 995         mmu_notifier_mm_init(mm);
 996         hmm_mm_init(mm);
 997         init_tlb_flush_pending(mm);
 998 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 999         mm->pmd_huge_pte = NULL;
1000 #endif
1001         mm_init_uprobes_state(mm);
1002
1003         if (current->mm) {
1004                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1005                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1006         } else {
1007                 mm->flags = default_dump_filter;
1008                 mm->def_flags = 0;
1009         }
1010
1011         if (mm_alloc_pgd(mm))
1012                 goto fail_nopgd;
1013
1014         if (init_new_context(p, mm))
1015                 goto fail_nocontext;
1016
1017         mm->user_ns = get_user_ns(user_ns);
1018         return mm;
1019
1020 fail_nocontext:
1021         mm_free_pgd(mm);
1022 fail_nopgd:
1023         free_mm(mm);
1024         return NULL;
1025 }
1026
1027 /*
1028  * Allocate and initialize an mm_struct.
1029  */
1030 struct mm_struct *mm_alloc(void)
1031 {
1032         struct mm_struct *mm;
1033
1034         mm = allocate_mm();
1035         if (!mm)
1036                 return NULL;
1037
1038         memset(mm, 0, sizeof(*mm));
1039         return mm_init(mm, current, current_user_ns());
1040 }
1041
1042 static inline void __mmput(struct mm_struct *mm)
1043 {
1044         VM_BUG_ON(atomic_read(&mm->mm_users));
1045
1046         uprobe_clear_state(mm);
1047         exit_aio(mm);
1048         ksm_exit(mm);
1049         khugepaged_exit(mm); /* must run before exit_mmap */
1050         exit_mmap(mm);
1051         mm_put_huge_zero_page(mm);
1052         set_mm_exe_file(mm, NULL);
1053         if (!list_empty(&mm->mmlist)) {
1054                 spin_lock(&mmlist_lock);
1055                 list_del(&mm->mmlist);
1056                 spin_unlock(&mmlist_lock);
1057         }
1058         if (mm->binfmt)
1059                 module_put(mm->binfmt->module);
1060         mmdrop(mm);
1061 }
1062
1063 /*
1064  * Decrement the use count and release all resources for an mm.
1065  */
1066 void mmput(struct mm_struct *mm)
1067 {
1068         might_sleep();
1069
1070         if (atomic_dec_and_test(&mm->mm_users))
1071                 __mmput(mm);
1072 }
1073 EXPORT_SYMBOL_GPL(mmput);
1074
1075 #ifdef CONFIG_MMU
1076 static void mmput_async_fn(struct work_struct *work)
1077 {
1078         struct mm_struct *mm = container_of(work, struct mm_struct,
1079                                             async_put_work);
1080
1081         __mmput(mm);
1082 }
1083
1084 void mmput_async(struct mm_struct *mm)
1085 {
1086         if (atomic_dec_and_test(&mm->mm_users)) {
1087                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1088                 schedule_work(&mm->async_put_work);
1089         }
1090 }
1091 #endif
1092
1093 /**
1094  * set_mm_exe_file - change a reference to the mm's executable file
1095  *
1096  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1097  *
1098  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1099  * invocations: in mmput() nobody alive left, in execve task is single
1100  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1101  * mm->exe_file, but does so without using set_mm_exe_file() in order
1102  * to do avoid the need for any locks.
1103  */
1104 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1105 {
1106         struct file *old_exe_file;
1107
1108         /*
1109          * It is safe to dereference the exe_file without RCU as
1110          * this function is only called if nobody else can access
1111          * this mm -- see comment above for justification.
1112          */
1113         old_exe_file = rcu_dereference_raw(mm->exe_file);
1114
1115         if (new_exe_file)
1116                 get_file(new_exe_file);
1117         rcu_assign_pointer(mm->exe_file, new_exe_file);
1118         if (old_exe_file)
1119                 fput(old_exe_file);
1120 }
1121
1122 /**
1123  * get_mm_exe_file - acquire a reference to the mm's executable file
1124  *
1125  * Returns %NULL if mm has no associated executable file.
1126  * User must release file via fput().
1127  */
1128 struct file *get_mm_exe_file(struct mm_struct *mm)
1129 {
1130         struct file *exe_file;
1131
1132         rcu_read_lock();
1133         exe_file = rcu_dereference(mm->exe_file);
1134         if (exe_file && !get_file_rcu(exe_file))
1135                 exe_file = NULL;
1136         rcu_read_unlock();
1137         return exe_file;
1138 }
1139 EXPORT_SYMBOL(get_mm_exe_file);
1140
1141 /**
1142  * get_task_exe_file - acquire a reference to the task's executable file
1143  *
1144  * Returns %NULL if task's mm (if any) has no associated executable file or
1145  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1146  * User must release file via fput().
1147  */
1148 struct file *get_task_exe_file(struct task_struct *task)
1149 {
1150         struct file *exe_file = NULL;
1151         struct mm_struct *mm;
1152
1153         task_lock(task);
1154         mm = task->mm;
1155         if (mm) {
1156                 if (!(task->flags & PF_KTHREAD))
1157                         exe_file = get_mm_exe_file(mm);
1158         }
1159         task_unlock(task);
1160         return exe_file;
1161 }
1162 EXPORT_SYMBOL(get_task_exe_file);
1163
1164 /**
1165  * get_task_mm - acquire a reference to the task's mm
1166  *
1167  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1168  * this kernel workthread has transiently adopted a user mm with use_mm,
1169  * to do its AIO) is not set and if so returns a reference to it, after
1170  * bumping up the use count.  User must release the mm via mmput()
1171  * after use.  Typically used by /proc and ptrace.
1172  */
1173 struct mm_struct *get_task_mm(struct task_struct *task)
1174 {
1175         struct mm_struct *mm;
1176
1177         task_lock(task);
1178         mm = task->mm;
1179         if (mm) {
1180                 if (task->flags & PF_KTHREAD)
1181                         mm = NULL;
1182                 else
1183                         mmget(mm);
1184         }
1185         task_unlock(task);
1186         return mm;
1187 }
1188 EXPORT_SYMBOL_GPL(get_task_mm);
1189
1190 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1191 {
1192         struct mm_struct *mm;
1193         int err;
1194
1195         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1196         if (err)
1197                 return ERR_PTR(err);
1198
1199         mm = get_task_mm(task);
1200         if (mm && mm != current->mm &&
1201                         !ptrace_may_access(task, mode)) {
1202                 mmput(mm);
1203                 mm = ERR_PTR(-EACCES);
1204         }
1205         mutex_unlock(&task->signal->cred_guard_mutex);
1206
1207         return mm;
1208 }
1209
1210 static void complete_vfork_done(struct task_struct *tsk)
1211 {
1212         struct completion *vfork;
1213
1214         task_lock(tsk);
1215         vfork = tsk->vfork_done;
1216         if (likely(vfork)) {
1217                 tsk->vfork_done = NULL;
1218                 complete(vfork);
1219         }
1220         task_unlock(tsk);
1221 }
1222
1223 static int wait_for_vfork_done(struct task_struct *child,
1224                                 struct completion *vfork)
1225 {
1226         int killed;
1227
1228         freezer_do_not_count();
1229         killed = wait_for_completion_killable(vfork);
1230         freezer_count();
1231
1232         if (killed) {
1233                 task_lock(child);
1234                 child->vfork_done = NULL;
1235                 task_unlock(child);
1236         }
1237
1238         put_task_struct(child);
1239         return killed;
1240 }
1241
1242 /* Please note the differences between mmput and mm_release.
1243  * mmput is called whenever we stop holding onto a mm_struct,
1244  * error success whatever.
1245  *
1246  * mm_release is called after a mm_struct has been removed
1247  * from the current process.
1248  *
1249  * This difference is important for error handling, when we
1250  * only half set up a mm_struct for a new process and need to restore
1251  * the old one.  Because we mmput the new mm_struct before
1252  * restoring the old one. . .
1253  * Eric Biederman 10 January 1998
1254  */
1255 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1256 {
1257         /* Get rid of any futexes when releasing the mm */
1258 #ifdef CONFIG_FUTEX
1259         if (unlikely(tsk->robust_list)) {
1260                 exit_robust_list(tsk);
1261                 tsk->robust_list = NULL;
1262         }
1263 #ifdef CONFIG_COMPAT
1264         if (unlikely(tsk->compat_robust_list)) {
1265                 compat_exit_robust_list(tsk);
1266                 tsk->compat_robust_list = NULL;
1267         }
1268 #endif
1269         if (unlikely(!list_empty(&tsk->pi_state_list)))
1270                 exit_pi_state_list(tsk);
1271 #endif
1272
1273         uprobe_free_utask(tsk);
1274
1275         /* Get rid of any cached register state */
1276         deactivate_mm(tsk, mm);
1277
1278         /*
1279          * Signal userspace if we're not exiting with a core dump
1280          * because we want to leave the value intact for debugging
1281          * purposes.
1282          */
1283         if (tsk->clear_child_tid) {
1284                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1285                     atomic_read(&mm->mm_users) > 1) {
1286                         /*
1287                          * We don't check the error code - if userspace has
1288                          * not set up a proper pointer then tough luck.
1289                          */
1290                         put_user(0, tsk->clear_child_tid);
1291                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1292                                         1, NULL, NULL, 0, 0);
1293                 }
1294                 tsk->clear_child_tid = NULL;
1295         }
1296
1297         /*
1298          * All done, finally we can wake up parent and return this mm to him.
1299          * Also kthread_stop() uses this completion for synchronization.
1300          */
1301         if (tsk->vfork_done)
1302                 complete_vfork_done(tsk);
1303 }
1304
1305 /*
1306  * Allocate a new mm structure and copy contents from the
1307  * mm structure of the passed in task structure.
1308  */
1309 static struct mm_struct *dup_mm(struct task_struct *tsk)
1310 {
1311         struct mm_struct *mm, *oldmm = current->mm;
1312         int err;
1313
1314         mm = allocate_mm();
1315         if (!mm)
1316                 goto fail_nomem;
1317
1318         memcpy(mm, oldmm, sizeof(*mm));
1319
1320         if (!mm_init(mm, tsk, mm->user_ns))
1321                 goto fail_nomem;
1322
1323         err = dup_mmap(mm, oldmm);
1324         if (err)
1325                 goto free_pt;
1326
1327         mm->hiwater_rss = get_mm_rss(mm);
1328         mm->hiwater_vm = mm->total_vm;
1329
1330         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1331                 goto free_pt;
1332
1333         return mm;
1334
1335 free_pt:
1336         /* don't put binfmt in mmput, we haven't got module yet */
1337         mm->binfmt = NULL;
1338         mmput(mm);
1339
1340 fail_nomem:
1341         return NULL;
1342 }
1343
1344 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1345 {
1346         struct mm_struct *mm, *oldmm;
1347         int retval;
1348
1349         tsk->min_flt = tsk->maj_flt = 0;
1350         tsk->nvcsw = tsk->nivcsw = 0;
1351 #ifdef CONFIG_DETECT_HUNG_TASK
1352         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1353         tsk->last_switch_time = 0;
1354 #endif
1355
1356         tsk->mm = NULL;
1357         tsk->active_mm = NULL;
1358
1359         /*
1360          * Are we cloning a kernel thread?
1361          *
1362          * We need to steal a active VM for that..
1363          */
1364         oldmm = current->mm;
1365         if (!oldmm)
1366                 return 0;
1367
1368         /* initialize the new vmacache entries */
1369         vmacache_flush(tsk);
1370
1371         if (clone_flags & CLONE_VM) {
1372                 mmget(oldmm);
1373                 mm = oldmm;
1374                 goto good_mm;
1375         }
1376
1377         retval = -ENOMEM;
1378         mm = dup_mm(tsk);
1379         if (!mm)
1380                 goto fail_nomem;
1381
1382 good_mm:
1383         tsk->mm = mm;
1384         tsk->active_mm = mm;
1385         return 0;
1386
1387 fail_nomem:
1388         return retval;
1389 }
1390
1391 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1392 {
1393         struct fs_struct *fs = current->fs;
1394         if (clone_flags & CLONE_FS) {
1395                 /* tsk->fs is already what we want */
1396                 spin_lock(&fs->lock);
1397                 if (fs->in_exec) {
1398                         spin_unlock(&fs->lock);
1399                         return -EAGAIN;
1400                 }
1401                 fs->users++;
1402                 spin_unlock(&fs->lock);
1403                 return 0;
1404         }
1405         tsk->fs = copy_fs_struct(fs);
1406         if (!tsk->fs)
1407                 return -ENOMEM;
1408         return 0;
1409 }
1410
1411 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1412 {
1413         struct files_struct *oldf, *newf;
1414         int error = 0;
1415
1416         /*
1417          * A background process may not have any files ...
1418          */
1419         oldf = current->files;
1420         if (!oldf)
1421                 goto out;
1422
1423         if (clone_flags & CLONE_FILES) {
1424                 atomic_inc(&oldf->count);
1425                 goto out;
1426         }
1427
1428         newf = dup_fd(oldf, &error);
1429         if (!newf)
1430                 goto out;
1431
1432         tsk->files = newf;
1433         error = 0;
1434 out:
1435         return error;
1436 }
1437
1438 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1439 {
1440 #ifdef CONFIG_BLOCK
1441         struct io_context *ioc = current->io_context;
1442         struct io_context *new_ioc;
1443
1444         if (!ioc)
1445                 return 0;
1446         /*
1447          * Share io context with parent, if CLONE_IO is set
1448          */
1449         if (clone_flags & CLONE_IO) {
1450                 ioc_task_link(ioc);
1451                 tsk->io_context = ioc;
1452         } else if (ioprio_valid(ioc->ioprio)) {
1453                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1454                 if (unlikely(!new_ioc))
1455                         return -ENOMEM;
1456
1457                 new_ioc->ioprio = ioc->ioprio;
1458                 put_io_context(new_ioc);
1459         }
1460 #endif
1461         return 0;
1462 }
1463
1464 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1465 {
1466         struct sighand_struct *sig;
1467
1468         if (clone_flags & CLONE_SIGHAND) {
1469                 atomic_inc(&current->sighand->count);
1470                 return 0;
1471         }
1472         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1473         rcu_assign_pointer(tsk->sighand, sig);
1474         if (!sig)
1475                 return -ENOMEM;
1476
1477         atomic_set(&sig->count, 1);
1478         spin_lock_irq(&current->sighand->siglock);
1479         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1480         spin_unlock_irq(&current->sighand->siglock);
1481         return 0;
1482 }
1483
1484 void __cleanup_sighand(struct sighand_struct *sighand)
1485 {
1486         if (atomic_dec_and_test(&sighand->count)) {
1487                 signalfd_cleanup(sighand);
1488                 /*
1489                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1490                  * without an RCU grace period, see __lock_task_sighand().
1491                  */
1492                 kmem_cache_free(sighand_cachep, sighand);
1493         }
1494 }
1495
1496 #ifdef CONFIG_POSIX_TIMERS
1497 /*
1498  * Initialize POSIX timer handling for a thread group.
1499  */
1500 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1501 {
1502         unsigned long cpu_limit;
1503
1504         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1505         if (cpu_limit != RLIM_INFINITY) {
1506                 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1507                 sig->cputimer.running = true;
1508         }
1509
1510         /* The timer lists. */
1511         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1512         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1513         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1514 }
1515 #else
1516 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1517 #endif
1518
1519 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1520 {
1521         struct signal_struct *sig;
1522
1523         if (clone_flags & CLONE_THREAD)
1524                 return 0;
1525
1526         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1527         tsk->signal = sig;
1528         if (!sig)
1529                 return -ENOMEM;
1530
1531         sig->nr_threads = 1;
1532         atomic_set(&sig->live, 1);
1533         atomic_set(&sig->sigcnt, 1);
1534
1535         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1536         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1537         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1538
1539         init_waitqueue_head(&sig->wait_chldexit);
1540         sig->curr_target = tsk;
1541         init_sigpending(&sig->shared_pending);
1542         INIT_HLIST_HEAD(&sig->multiprocess);
1543         seqlock_init(&sig->stats_lock);
1544         prev_cputime_init(&sig->prev_cputime);
1545
1546 #ifdef CONFIG_POSIX_TIMERS
1547         INIT_LIST_HEAD(&sig->posix_timers);
1548         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1549         sig->real_timer.function = it_real_fn;
1550 #endif
1551
1552         task_lock(current->group_leader);
1553         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1554         task_unlock(current->group_leader);
1555
1556         posix_cpu_timers_init_group(sig);
1557
1558         tty_audit_fork(sig);
1559         sched_autogroup_fork(sig);
1560
1561         sig->oom_score_adj = current->signal->oom_score_adj;
1562         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1563
1564         mutex_init(&sig->cred_guard_mutex);
1565
1566         return 0;
1567 }
1568
1569 static void copy_seccomp(struct task_struct *p)
1570 {
1571 #ifdef CONFIG_SECCOMP
1572         /*
1573          * Must be called with sighand->lock held, which is common to
1574          * all threads in the group. Holding cred_guard_mutex is not
1575          * needed because this new task is not yet running and cannot
1576          * be racing exec.
1577          */
1578         assert_spin_locked(&current->sighand->siglock);
1579
1580         /* Ref-count the new filter user, and assign it. */
1581         get_seccomp_filter(current);
1582         p->seccomp = current->seccomp;
1583
1584         /*
1585          * Explicitly enable no_new_privs here in case it got set
1586          * between the task_struct being duplicated and holding the
1587          * sighand lock. The seccomp state and nnp must be in sync.
1588          */
1589         if (task_no_new_privs(current))
1590                 task_set_no_new_privs(p);
1591
1592         /*
1593          * If the parent gained a seccomp mode after copying thread
1594          * flags and between before we held the sighand lock, we have
1595          * to manually enable the seccomp thread flag here.
1596          */
1597         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1598                 set_tsk_thread_flag(p, TIF_SECCOMP);
1599 #endif
1600 }
1601
1602 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1603 {
1604         current->clear_child_tid = tidptr;
1605
1606         return task_pid_vnr(current);
1607 }
1608
1609 static void rt_mutex_init_task(struct task_struct *p)
1610 {
1611         raw_spin_lock_init(&p->pi_lock);
1612 #ifdef CONFIG_RT_MUTEXES
1613         p->pi_waiters = RB_ROOT_CACHED;
1614         p->pi_top_task = NULL;
1615         p->pi_blocked_on = NULL;
1616 #endif
1617 }
1618
1619 #ifdef CONFIG_POSIX_TIMERS
1620 /*
1621  * Initialize POSIX timer handling for a single task.
1622  */
1623 static void posix_cpu_timers_init(struct task_struct *tsk)
1624 {
1625         tsk->cputime_expires.prof_exp = 0;
1626         tsk->cputime_expires.virt_exp = 0;
1627         tsk->cputime_expires.sched_exp = 0;
1628         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1629         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1630         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1631 }
1632 #else
1633 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1634 #endif
1635
1636 static inline void init_task_pid_links(struct task_struct *task)
1637 {
1638         enum pid_type type;
1639
1640         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1641                 INIT_HLIST_NODE(&task->pid_links[type]);
1642         }
1643 }
1644
1645 static inline void
1646 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1647 {
1648         if (type == PIDTYPE_PID)
1649                 task->thread_pid = pid;
1650         else
1651                 task->signal->pids[type] = pid;
1652 }
1653
1654 static inline void rcu_copy_process(struct task_struct *p)
1655 {
1656 #ifdef CONFIG_PREEMPT_RCU
1657         p->rcu_read_lock_nesting = 0;
1658         p->rcu_read_unlock_special.s = 0;
1659         p->rcu_blocked_node = NULL;
1660         INIT_LIST_HEAD(&p->rcu_node_entry);
1661 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1662 #ifdef CONFIG_TASKS_RCU
1663         p->rcu_tasks_holdout = false;
1664         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1665         p->rcu_tasks_idle_cpu = -1;
1666 #endif /* #ifdef CONFIG_TASKS_RCU */
1667 }
1668
1669 /*
1670  * This creates a new process as a copy of the old one,
1671  * but does not actually start it yet.
1672  *
1673  * It copies the registers, and all the appropriate
1674  * parts of the process environment (as per the clone
1675  * flags). The actual kick-off is left to the caller.
1676  */
1677 static __latent_entropy struct task_struct *copy_process(
1678                                         unsigned long clone_flags,
1679                                         unsigned long stack_start,
1680                                         unsigned long stack_size,
1681                                         int __user *child_tidptr,
1682                                         struct pid *pid,
1683                                         int trace,
1684                                         unsigned long tls,
1685                                         int node)
1686 {
1687         int retval;
1688         struct task_struct *p;
1689         struct multiprocess_signals delayed;
1690
1691         /*
1692          * Don't allow sharing the root directory with processes in a different
1693          * namespace
1694          */
1695         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1696                 return ERR_PTR(-EINVAL);
1697
1698         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1699                 return ERR_PTR(-EINVAL);
1700
1701         /*
1702          * Thread groups must share signals as well, and detached threads
1703          * can only be started up within the thread group.
1704          */
1705         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1706                 return ERR_PTR(-EINVAL);
1707
1708         /*
1709          * Shared signal handlers imply shared VM. By way of the above,
1710          * thread groups also imply shared VM. Blocking this case allows
1711          * for various simplifications in other code.
1712          */
1713         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1714                 return ERR_PTR(-EINVAL);
1715
1716         /*
1717          * Siblings of global init remain as zombies on exit since they are
1718          * not reaped by their parent (swapper). To solve this and to avoid
1719          * multi-rooted process trees, prevent global and container-inits
1720          * from creating siblings.
1721          */
1722         if ((clone_flags & CLONE_PARENT) &&
1723                                 current->signal->flags & SIGNAL_UNKILLABLE)
1724                 return ERR_PTR(-EINVAL);
1725
1726         /*
1727          * If the new process will be in a different pid or user namespace
1728          * do not allow it to share a thread group with the forking task.
1729          */
1730         if (clone_flags & CLONE_THREAD) {
1731                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1732                     (task_active_pid_ns(current) !=
1733                                 current->nsproxy->pid_ns_for_children))
1734                         return ERR_PTR(-EINVAL);
1735         }
1736
1737         /*
1738          * Force any signals received before this point to be delivered
1739          * before the fork happens.  Collect up signals sent to multiple
1740          * processes that happen during the fork and delay them so that
1741          * they appear to happen after the fork.
1742          */
1743         sigemptyset(&delayed.signal);
1744         INIT_HLIST_NODE(&delayed.node);
1745
1746         spin_lock_irq(&current->sighand->siglock);
1747         if (!(clone_flags & CLONE_THREAD))
1748                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1749         recalc_sigpending();
1750         spin_unlock_irq(&current->sighand->siglock);
1751         retval = -ERESTARTNOINTR;
1752         if (signal_pending(current))
1753                 goto fork_out;
1754
1755         retval = -ENOMEM;
1756         p = dup_task_struct(current, node);
1757         if (!p)
1758                 goto fork_out;
1759
1760         /*
1761          * This _must_ happen before we call free_task(), i.e. before we jump
1762          * to any of the bad_fork_* labels. This is to avoid freeing
1763          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1764          * kernel threads (PF_KTHREAD).
1765          */
1766         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1767         /*
1768          * Clear TID on mm_release()?
1769          */
1770         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1771
1772         ftrace_graph_init_task(p);
1773
1774         rt_mutex_init_task(p);
1775
1776 #ifdef CONFIG_PROVE_LOCKING
1777         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1778         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1779 #endif
1780         retval = -EAGAIN;
1781         if (atomic_read(&p->real_cred->user->processes) >=
1782                         task_rlimit(p, RLIMIT_NPROC)) {
1783                 if (p->real_cred->user != INIT_USER &&
1784                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1785                         goto bad_fork_free;
1786         }
1787         current->flags &= ~PF_NPROC_EXCEEDED;
1788
1789         retval = copy_creds(p, clone_flags);
1790         if (retval < 0)
1791                 goto bad_fork_free;
1792
1793         /*
1794          * If multiple threads are within copy_process(), then this check
1795          * triggers too late. This doesn't hurt, the check is only there
1796          * to stop root fork bombs.
1797          */
1798         retval = -EAGAIN;
1799         if (nr_threads >= max_threads)
1800                 goto bad_fork_cleanup_count;
1801
1802         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1803         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1804         p->flags |= PF_FORKNOEXEC;
1805         INIT_LIST_HEAD(&p->children);
1806         INIT_LIST_HEAD(&p->sibling);
1807         rcu_copy_process(p);
1808         p->vfork_done = NULL;
1809         spin_lock_init(&p->alloc_lock);
1810
1811         init_sigpending(&p->pending);
1812
1813         p->utime = p->stime = p->gtime = 0;
1814 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1815         p->utimescaled = p->stimescaled = 0;
1816 #endif
1817         prev_cputime_init(&p->prev_cputime);
1818
1819 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1820         seqcount_init(&p->vtime.seqcount);
1821         p->vtime.starttime = 0;
1822         p->vtime.state = VTIME_INACTIVE;
1823 #endif
1824
1825 #if defined(SPLIT_RSS_COUNTING)
1826         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1827 #endif
1828
1829         p->default_timer_slack_ns = current->timer_slack_ns;
1830
1831 #ifdef CONFIG_PSI
1832         p->psi_flags = 0;
1833 #endif
1834
1835         task_io_accounting_init(&p->ioac);
1836         acct_clear_integrals(p);
1837
1838         posix_cpu_timers_init(p);
1839
1840         p->start_time = ktime_get_ns();
1841         p->real_start_time = ktime_get_boot_ns();
1842         p->io_context = NULL;
1843         audit_set_context(p, NULL);
1844         cgroup_fork(p);
1845 #ifdef CONFIG_NUMA
1846         p->mempolicy = mpol_dup(p->mempolicy);
1847         if (IS_ERR(p->mempolicy)) {
1848                 retval = PTR_ERR(p->mempolicy);
1849                 p->mempolicy = NULL;
1850                 goto bad_fork_cleanup_threadgroup_lock;
1851         }
1852 #endif
1853 #ifdef CONFIG_CPUSETS
1854         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1855         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1856         seqcount_init(&p->mems_allowed_seq);
1857 #endif
1858 #ifdef CONFIG_TRACE_IRQFLAGS
1859         p->irq_events = 0;
1860         p->hardirqs_enabled = 0;
1861         p->hardirq_enable_ip = 0;
1862         p->hardirq_enable_event = 0;
1863         p->hardirq_disable_ip = _THIS_IP_;
1864         p->hardirq_disable_event = 0;
1865         p->softirqs_enabled = 1;
1866         p->softirq_enable_ip = _THIS_IP_;
1867         p->softirq_enable_event = 0;
1868         p->softirq_disable_ip = 0;
1869         p->softirq_disable_event = 0;
1870         p->hardirq_context = 0;
1871         p->softirq_context = 0;
1872 #endif
1873
1874         p->pagefault_disabled = 0;
1875
1876 #ifdef CONFIG_LOCKDEP
1877         p->lockdep_depth = 0; /* no locks held yet */
1878         p->curr_chain_key = 0;
1879         p->lockdep_recursion = 0;
1880         lockdep_init_task(p);
1881 #endif
1882
1883 #ifdef CONFIG_DEBUG_MUTEXES
1884         p->blocked_on = NULL; /* not blocked yet */
1885 #endif
1886 #ifdef CONFIG_BCACHE
1887         p->sequential_io        = 0;
1888         p->sequential_io_avg    = 0;
1889 #endif
1890
1891         /* Perform scheduler related setup. Assign this task to a CPU. */
1892         retval = sched_fork(clone_flags, p);
1893         if (retval)
1894                 goto bad_fork_cleanup_policy;
1895
1896         retval = perf_event_init_task(p);
1897         if (retval)
1898                 goto bad_fork_cleanup_policy;
1899         retval = audit_alloc(p);
1900         if (retval)
1901                 goto bad_fork_cleanup_perf;
1902         /* copy all the process information */
1903         shm_init_task(p);
1904         retval = security_task_alloc(p, clone_flags);
1905         if (retval)
1906                 goto bad_fork_cleanup_audit;
1907         retval = copy_semundo(clone_flags, p);
1908         if (retval)
1909                 goto bad_fork_cleanup_security;
1910         retval = copy_files(clone_flags, p);
1911         if (retval)
1912                 goto bad_fork_cleanup_semundo;
1913         retval = copy_fs(clone_flags, p);
1914         if (retval)
1915                 goto bad_fork_cleanup_files;
1916         retval = copy_sighand(clone_flags, p);
1917         if (retval)
1918                 goto bad_fork_cleanup_fs;
1919         retval = copy_signal(clone_flags, p);
1920         if (retval)
1921                 goto bad_fork_cleanup_sighand;
1922         retval = copy_mm(clone_flags, p);
1923         if (retval)
1924                 goto bad_fork_cleanup_signal;
1925         retval = copy_namespaces(clone_flags, p);
1926         if (retval)
1927                 goto bad_fork_cleanup_mm;
1928         retval = copy_io(clone_flags, p);
1929         if (retval)
1930                 goto bad_fork_cleanup_namespaces;
1931         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1932         if (retval)
1933                 goto bad_fork_cleanup_io;
1934
1935         stackleak_task_init(p);
1936
1937         if (pid != &init_struct_pid) {
1938                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1939                 if (IS_ERR(pid)) {
1940                         retval = PTR_ERR(pid);
1941                         goto bad_fork_cleanup_thread;
1942                 }
1943         }
1944
1945 #ifdef CONFIG_BLOCK
1946         p->plug = NULL;
1947 #endif
1948 #ifdef CONFIG_FUTEX
1949         p->robust_list = NULL;
1950 #ifdef CONFIG_COMPAT
1951         p->compat_robust_list = NULL;
1952 #endif
1953         INIT_LIST_HEAD(&p->pi_state_list);
1954         p->pi_state_cache = NULL;
1955 #endif
1956         /*
1957          * sigaltstack should be cleared when sharing the same VM
1958          */
1959         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1960                 sas_ss_reset(p);
1961
1962         /*
1963          * Syscall tracing and stepping should be turned off in the
1964          * child regardless of CLONE_PTRACE.
1965          */
1966         user_disable_single_step(p);
1967         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1968 #ifdef TIF_SYSCALL_EMU
1969         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1970 #endif
1971         clear_all_latency_tracing(p);
1972
1973         /* ok, now we should be set up.. */
1974         p->pid = pid_nr(pid);
1975         if (clone_flags & CLONE_THREAD) {
1976                 p->exit_signal = -1;
1977                 p->group_leader = current->group_leader;
1978                 p->tgid = current->tgid;
1979         } else {
1980                 if (clone_flags & CLONE_PARENT)
1981                         p->exit_signal = current->group_leader->exit_signal;
1982                 else
1983                         p->exit_signal = (clone_flags & CSIGNAL);
1984                 p->group_leader = p;
1985                 p->tgid = p->pid;
1986         }
1987
1988         p->nr_dirtied = 0;
1989         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1990         p->dirty_paused_when = 0;
1991
1992         p->pdeath_signal = 0;
1993         INIT_LIST_HEAD(&p->thread_group);
1994         p->task_works = NULL;
1995
1996         cgroup_threadgroup_change_begin(current);
1997         /*
1998          * Ensure that the cgroup subsystem policies allow the new process to be
1999          * forked. It should be noted the the new process's css_set can be changed
2000          * between here and cgroup_post_fork() if an organisation operation is in
2001          * progress.
2002          */
2003         retval = cgroup_can_fork(p);
2004         if (retval)
2005                 goto bad_fork_free_pid;
2006
2007         /*
2008          * Make it visible to the rest of the system, but dont wake it up yet.
2009          * Need tasklist lock for parent etc handling!
2010          */
2011         write_lock_irq(&tasklist_lock);
2012
2013         /* CLONE_PARENT re-uses the old parent */
2014         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2015                 p->real_parent = current->real_parent;
2016                 p->parent_exec_id = current->parent_exec_id;
2017         } else {
2018                 p->real_parent = current;
2019                 p->parent_exec_id = current->self_exec_id;
2020         }
2021
2022         klp_copy_process(p);
2023
2024         spin_lock(&current->sighand->siglock);
2025
2026         /*
2027          * Copy seccomp details explicitly here, in case they were changed
2028          * before holding sighand lock.
2029          */
2030         copy_seccomp(p);
2031
2032         rseq_fork(p, clone_flags);
2033
2034         /* Don't start children in a dying pid namespace */
2035         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2036                 retval = -ENOMEM;
2037                 goto bad_fork_cancel_cgroup;
2038         }
2039
2040         /* Let kill terminate clone/fork in the middle */
2041         if (fatal_signal_pending(current)) {
2042                 retval = -EINTR;
2043                 goto bad_fork_cancel_cgroup;
2044         }
2045
2046
2047         init_task_pid_links(p);
2048         if (likely(p->pid)) {
2049                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2050
2051                 init_task_pid(p, PIDTYPE_PID, pid);
2052                 if (thread_group_leader(p)) {
2053                         init_task_pid(p, PIDTYPE_TGID, pid);
2054                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2055                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2056
2057                         if (is_child_reaper(pid)) {
2058                                 ns_of_pid(pid)->child_reaper = p;
2059                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2060                         }
2061                         p->signal->shared_pending.signal = delayed.signal;
2062                         p->signal->tty = tty_kref_get(current->signal->tty);
2063                         /*
2064                          * Inherit has_child_subreaper flag under the same
2065                          * tasklist_lock with adding child to the process tree
2066                          * for propagate_has_child_subreaper optimization.
2067                          */
2068                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2069                                                          p->real_parent->signal->is_child_subreaper;
2070                         list_add_tail(&p->sibling, &p->real_parent->children);
2071                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2072                         attach_pid(p, PIDTYPE_TGID);
2073                         attach_pid(p, PIDTYPE_PGID);
2074                         attach_pid(p, PIDTYPE_SID);
2075                         __this_cpu_inc(process_counts);
2076                 } else {
2077                         current->signal->nr_threads++;
2078                         atomic_inc(&current->signal->live);
2079                         atomic_inc(&current->signal->sigcnt);
2080                         task_join_group_stop(p);
2081                         list_add_tail_rcu(&p->thread_group,
2082                                           &p->group_leader->thread_group);
2083                         list_add_tail_rcu(&p->thread_node,
2084                                           &p->signal->thread_head);
2085                 }
2086                 attach_pid(p, PIDTYPE_PID);
2087                 nr_threads++;
2088         }
2089         total_forks++;
2090         hlist_del_init(&delayed.node);
2091         spin_unlock(&current->sighand->siglock);
2092         syscall_tracepoint_update(p);
2093         write_unlock_irq(&tasklist_lock);
2094
2095         proc_fork_connector(p);
2096         cgroup_post_fork(p);
2097         cgroup_threadgroup_change_end(current);
2098         perf_event_fork(p);
2099
2100         trace_task_newtask(p, clone_flags);
2101         uprobe_copy_process(p, clone_flags);
2102
2103         return p;
2104
2105 bad_fork_cancel_cgroup:
2106         spin_unlock(&current->sighand->siglock);
2107         write_unlock_irq(&tasklist_lock);
2108         cgroup_cancel_fork(p);
2109 bad_fork_free_pid:
2110         cgroup_threadgroup_change_end(current);
2111         if (pid != &init_struct_pid)
2112                 free_pid(pid);
2113 bad_fork_cleanup_thread:
2114         exit_thread(p);
2115 bad_fork_cleanup_io:
2116         if (p->io_context)
2117                 exit_io_context(p);
2118 bad_fork_cleanup_namespaces:
2119         exit_task_namespaces(p);
2120 bad_fork_cleanup_mm:
2121         if (p->mm)
2122                 mmput(p->mm);
2123 bad_fork_cleanup_signal:
2124         if (!(clone_flags & CLONE_THREAD))
2125                 free_signal_struct(p->signal);
2126 bad_fork_cleanup_sighand:
2127         __cleanup_sighand(p->sighand);
2128 bad_fork_cleanup_fs:
2129         exit_fs(p); /* blocking */
2130 bad_fork_cleanup_files:
2131         exit_files(p); /* blocking */
2132 bad_fork_cleanup_semundo:
2133         exit_sem(p);
2134 bad_fork_cleanup_security:
2135         security_task_free(p);
2136 bad_fork_cleanup_audit:
2137         audit_free(p);
2138 bad_fork_cleanup_perf:
2139         perf_event_free_task(p);
2140 bad_fork_cleanup_policy:
2141         lockdep_free_task(p);
2142 #ifdef CONFIG_NUMA
2143         mpol_put(p->mempolicy);
2144 bad_fork_cleanup_threadgroup_lock:
2145 #endif
2146         delayacct_tsk_free(p);
2147 bad_fork_cleanup_count:
2148         atomic_dec(&p->cred->user->processes);
2149         exit_creds(p);
2150 bad_fork_free:
2151         p->state = TASK_DEAD;
2152         put_task_stack(p);
2153         free_task(p);
2154 fork_out:
2155         spin_lock_irq(&current->sighand->siglock);
2156         hlist_del_init(&delayed.node);
2157         spin_unlock_irq(&current->sighand->siglock);
2158         return ERR_PTR(retval);
2159 }
2160
2161 static inline void init_idle_pids(struct task_struct *idle)
2162 {
2163         enum pid_type type;
2164
2165         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2166                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2167                 init_task_pid(idle, type, &init_struct_pid);
2168         }
2169 }
2170
2171 struct task_struct *fork_idle(int cpu)
2172 {
2173         struct task_struct *task;
2174         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
2175                             cpu_to_node(cpu));
2176         if (!IS_ERR(task)) {
2177                 init_idle_pids(task);
2178                 init_idle(task, cpu);
2179         }
2180
2181         return task;
2182 }
2183
2184 /*
2185  *  Ok, this is the main fork-routine.
2186  *
2187  * It copies the process, and if successful kick-starts
2188  * it and waits for it to finish using the VM if required.
2189  */
2190 long _do_fork(unsigned long clone_flags,
2191               unsigned long stack_start,
2192               unsigned long stack_size,
2193               int __user *parent_tidptr,
2194               int __user *child_tidptr,
2195               unsigned long tls)
2196 {
2197         struct completion vfork;
2198         struct pid *pid;
2199         struct task_struct *p;
2200         int trace = 0;
2201         long nr;
2202
2203         /*
2204          * Determine whether and which event to report to ptracer.  When
2205          * called from kernel_thread or CLONE_UNTRACED is explicitly
2206          * requested, no event is reported; otherwise, report if the event
2207          * for the type of forking is enabled.
2208          */
2209         if (!(clone_flags & CLONE_UNTRACED)) {
2210                 if (clone_flags & CLONE_VFORK)
2211                         trace = PTRACE_EVENT_VFORK;
2212                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2213                         trace = PTRACE_EVENT_CLONE;
2214                 else
2215                         trace = PTRACE_EVENT_FORK;
2216
2217                 if (likely(!ptrace_event_enabled(current, trace)))
2218                         trace = 0;
2219         }
2220
2221         p = copy_process(clone_flags, stack_start, stack_size,
2222                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2223         add_latent_entropy();
2224
2225         if (IS_ERR(p))
2226                 return PTR_ERR(p);
2227
2228         /*
2229          * Do this prior waking up the new thread - the thread pointer
2230          * might get invalid after that point, if the thread exits quickly.
2231          */
2232         trace_sched_process_fork(current, p);
2233
2234         pid = get_task_pid(p, PIDTYPE_PID);
2235         nr = pid_vnr(pid);
2236
2237         if (clone_flags & CLONE_PARENT_SETTID)
2238                 put_user(nr, parent_tidptr);
2239
2240         if (clone_flags & CLONE_VFORK) {
2241                 p->vfork_done = &vfork;
2242                 init_completion(&vfork);
2243                 get_task_struct(p);
2244         }
2245
2246         wake_up_new_task(p);
2247
2248         /* forking complete and child started to run, tell ptracer */
2249         if (unlikely(trace))
2250                 ptrace_event_pid(trace, pid);
2251
2252         if (clone_flags & CLONE_VFORK) {
2253                 if (!wait_for_vfork_done(p, &vfork))
2254                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2255         }
2256
2257         put_pid(pid);
2258         return nr;
2259 }
2260
2261 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2262 /* For compatibility with architectures that call do_fork directly rather than
2263  * using the syscall entry points below. */
2264 long do_fork(unsigned long clone_flags,
2265               unsigned long stack_start,
2266               unsigned long stack_size,
2267               int __user *parent_tidptr,
2268               int __user *child_tidptr)
2269 {
2270         return _do_fork(clone_flags, stack_start, stack_size,
2271                         parent_tidptr, child_tidptr, 0);
2272 }
2273 #endif
2274
2275 /*
2276  * Create a kernel thread.
2277  */
2278 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2279 {
2280         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2281                 (unsigned long)arg, NULL, NULL, 0);
2282 }
2283
2284 #ifdef __ARCH_WANT_SYS_FORK
2285 SYSCALL_DEFINE0(fork)
2286 {
2287 #ifdef CONFIG_MMU
2288         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2289 #else
2290         /* can not support in nommu mode */
2291         return -EINVAL;
2292 #endif
2293 }
2294 #endif
2295
2296 #ifdef __ARCH_WANT_SYS_VFORK
2297 SYSCALL_DEFINE0(vfork)
2298 {
2299         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2300                         0, NULL, NULL, 0);
2301 }
2302 #endif
2303
2304 #ifdef __ARCH_WANT_SYS_CLONE
2305 #ifdef CONFIG_CLONE_BACKWARDS
2306 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2307                  int __user *, parent_tidptr,
2308                  unsigned long, tls,
2309                  int __user *, child_tidptr)
2310 #elif defined(CONFIG_CLONE_BACKWARDS2)
2311 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2312                  int __user *, parent_tidptr,
2313                  int __user *, child_tidptr,
2314                  unsigned long, tls)
2315 #elif defined(CONFIG_CLONE_BACKWARDS3)
2316 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2317                 int, stack_size,
2318                 int __user *, parent_tidptr,
2319                 int __user *, child_tidptr,
2320                 unsigned long, tls)
2321 #else
2322 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2323                  int __user *, parent_tidptr,
2324                  int __user *, child_tidptr,
2325                  unsigned long, tls)
2326 #endif
2327 {
2328         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2329 }
2330 #endif
2331
2332 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2333 {
2334         struct task_struct *leader, *parent, *child;
2335         int res;
2336
2337         read_lock(&tasklist_lock);
2338         leader = top = top->group_leader;
2339 down:
2340         for_each_thread(leader, parent) {
2341                 list_for_each_entry(child, &parent->children, sibling) {
2342                         res = visitor(child, data);
2343                         if (res) {
2344                                 if (res < 0)
2345                                         goto out;
2346                                 leader = child;
2347                                 goto down;
2348                         }
2349 up:
2350                         ;
2351                 }
2352         }
2353
2354         if (leader != top) {
2355                 child = leader;
2356                 parent = child->real_parent;
2357                 leader = parent->group_leader;
2358                 goto up;
2359         }
2360 out:
2361         read_unlock(&tasklist_lock);
2362 }
2363
2364 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2365 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2366 #endif
2367
2368 static void sighand_ctor(void *data)
2369 {
2370         struct sighand_struct *sighand = data;
2371
2372         spin_lock_init(&sighand->siglock);
2373         init_waitqueue_head(&sighand->signalfd_wqh);
2374 }
2375
2376 void __init proc_caches_init(void)
2377 {
2378         unsigned int mm_size;
2379
2380         sighand_cachep = kmem_cache_create("sighand_cache",
2381                         sizeof(struct sighand_struct), 0,
2382                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2383                         SLAB_ACCOUNT, sighand_ctor);
2384         signal_cachep = kmem_cache_create("signal_cache",
2385                         sizeof(struct signal_struct), 0,
2386                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2387                         NULL);
2388         files_cachep = kmem_cache_create("files_cache",
2389                         sizeof(struct files_struct), 0,
2390                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2391                         NULL);
2392         fs_cachep = kmem_cache_create("fs_cache",
2393                         sizeof(struct fs_struct), 0,
2394                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2395                         NULL);
2396
2397         /*
2398          * The mm_cpumask is located at the end of mm_struct, and is
2399          * dynamically sized based on the maximum CPU number this system
2400          * can have, taking hotplug into account (nr_cpu_ids).
2401          */
2402         mm_size = sizeof(struct mm_struct) + cpumask_size();
2403
2404         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2405                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2406                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2407                         offsetof(struct mm_struct, saved_auxv),
2408                         sizeof_field(struct mm_struct, saved_auxv),
2409                         NULL);
2410         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2411         mmap_init();
2412         nsproxy_cache_init();
2413 }
2414
2415 /*
2416  * Check constraints on flags passed to the unshare system call.
2417  */
2418 static int check_unshare_flags(unsigned long unshare_flags)
2419 {
2420         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2421                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2422                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2423                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2424                 return -EINVAL;
2425         /*
2426          * Not implemented, but pretend it works if there is nothing
2427          * to unshare.  Note that unsharing the address space or the
2428          * signal handlers also need to unshare the signal queues (aka
2429          * CLONE_THREAD).
2430          */
2431         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2432                 if (!thread_group_empty(current))
2433                         return -EINVAL;
2434         }
2435         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2436                 if (atomic_read(&current->sighand->count) > 1)
2437                         return -EINVAL;
2438         }
2439         if (unshare_flags & CLONE_VM) {
2440                 if (!current_is_single_threaded())
2441                         return -EINVAL;
2442         }
2443
2444         return 0;
2445 }
2446
2447 /*
2448  * Unshare the filesystem structure if it is being shared
2449  */
2450 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2451 {
2452         struct fs_struct *fs = current->fs;
2453
2454         if (!(unshare_flags & CLONE_FS) || !fs)
2455                 return 0;
2456
2457         /* don't need lock here; in the worst case we'll do useless copy */
2458         if (fs->users == 1)
2459                 return 0;
2460
2461         *new_fsp = copy_fs_struct(fs);
2462         if (!*new_fsp)
2463                 return -ENOMEM;
2464
2465         return 0;
2466 }
2467
2468 /*
2469  * Unshare file descriptor table if it is being shared
2470  */
2471 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2472 {
2473         struct files_struct *fd = current->files;
2474         int error = 0;
2475
2476         if ((unshare_flags & CLONE_FILES) &&
2477             (fd && atomic_read(&fd->count) > 1)) {
2478                 *new_fdp = dup_fd(fd, &error);
2479                 if (!*new_fdp)
2480                         return error;
2481         }
2482
2483         return 0;
2484 }
2485
2486 /*
2487  * unshare allows a process to 'unshare' part of the process
2488  * context which was originally shared using clone.  copy_*
2489  * functions used by do_fork() cannot be used here directly
2490  * because they modify an inactive task_struct that is being
2491  * constructed. Here we are modifying the current, active,
2492  * task_struct.
2493  */
2494 int ksys_unshare(unsigned long unshare_flags)
2495 {
2496         struct fs_struct *fs, *new_fs = NULL;
2497         struct files_struct *fd, *new_fd = NULL;
2498         struct cred *new_cred = NULL;
2499         struct nsproxy *new_nsproxy = NULL;
2500         int do_sysvsem = 0;
2501         int err;
2502
2503         /*
2504          * If unsharing a user namespace must also unshare the thread group
2505          * and unshare the filesystem root and working directories.
2506          */
2507         if (unshare_flags & CLONE_NEWUSER)
2508                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2509         /*
2510          * If unsharing vm, must also unshare signal handlers.
2511          */
2512         if (unshare_flags & CLONE_VM)
2513                 unshare_flags |= CLONE_SIGHAND;
2514         /*
2515          * If unsharing a signal handlers, must also unshare the signal queues.
2516          */
2517         if (unshare_flags & CLONE_SIGHAND)
2518                 unshare_flags |= CLONE_THREAD;
2519         /*
2520          * If unsharing namespace, must also unshare filesystem information.
2521          */
2522         if (unshare_flags & CLONE_NEWNS)
2523                 unshare_flags |= CLONE_FS;
2524
2525         err = check_unshare_flags(unshare_flags);
2526         if (err)
2527                 goto bad_unshare_out;
2528         /*
2529          * CLONE_NEWIPC must also detach from the undolist: after switching
2530          * to a new ipc namespace, the semaphore arrays from the old
2531          * namespace are unreachable.
2532          */
2533         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2534                 do_sysvsem = 1;
2535         err = unshare_fs(unshare_flags, &new_fs);
2536         if (err)
2537                 goto bad_unshare_out;
2538         err = unshare_fd(unshare_flags, &new_fd);
2539         if (err)
2540                 goto bad_unshare_cleanup_fs;
2541         err = unshare_userns(unshare_flags, &new_cred);
2542         if (err)
2543                 goto bad_unshare_cleanup_fd;
2544         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2545                                          new_cred, new_fs);
2546         if (err)
2547                 goto bad_unshare_cleanup_cred;
2548
2549         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2550                 if (do_sysvsem) {
2551                         /*
2552                          * CLONE_SYSVSEM is equivalent to sys_exit().
2553                          */
2554                         exit_sem(current);
2555                 }
2556                 if (unshare_flags & CLONE_NEWIPC) {
2557                         /* Orphan segments in old ns (see sem above). */
2558                         exit_shm(current);
2559                         shm_init_task(current);
2560                 }
2561
2562                 if (new_nsproxy)
2563                         switch_task_namespaces(current, new_nsproxy);
2564
2565                 task_lock(current);
2566
2567                 if (new_fs) {
2568                         fs = current->fs;
2569                         spin_lock(&fs->lock);
2570                         current->fs = new_fs;
2571                         if (--fs->users)
2572                                 new_fs = NULL;
2573                         else
2574                                 new_fs = fs;
2575                         spin_unlock(&fs->lock);
2576                 }
2577
2578                 if (new_fd) {
2579                         fd = current->files;
2580                         current->files = new_fd;
2581                         new_fd = fd;
2582                 }
2583
2584                 task_unlock(current);
2585
2586                 if (new_cred) {
2587                         /* Install the new user namespace */
2588                         commit_creds(new_cred);
2589                         new_cred = NULL;
2590                 }
2591         }
2592
2593         perf_event_namespaces(current);
2594
2595 bad_unshare_cleanup_cred:
2596         if (new_cred)
2597                 put_cred(new_cred);
2598 bad_unshare_cleanup_fd:
2599         if (new_fd)
2600                 put_files_struct(new_fd);
2601
2602 bad_unshare_cleanup_fs:
2603         if (new_fs)
2604                 free_fs_struct(new_fs);
2605
2606 bad_unshare_out:
2607         return err;
2608 }
2609
2610 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2611 {
2612         return ksys_unshare(unshare_flags);
2613 }
2614
2615 /*
2616  *      Helper to unshare the files of the current task.
2617  *      We don't want to expose copy_files internals to
2618  *      the exec layer of the kernel.
2619  */
2620
2621 int unshare_files(struct files_struct **displaced)
2622 {
2623         struct task_struct *task = current;
2624         struct files_struct *copy = NULL;
2625         int error;
2626
2627         error = unshare_fd(CLONE_FILES, &copy);
2628         if (error || !copy) {
2629                 *displaced = NULL;
2630                 return error;
2631         }
2632         *displaced = task->files;
2633         task_lock(task);
2634         task->files = copy;
2635         task_unlock(task);
2636         return 0;
2637 }
2638
2639 int sysctl_max_threads(struct ctl_table *table, int write,
2640                        void __user *buffer, size_t *lenp, loff_t *ppos)
2641 {
2642         struct ctl_table t;
2643         int ret;
2644         int threads = max_threads;
2645         int min = MIN_THREADS;
2646         int max = MAX_THREADS;
2647
2648         t = *table;
2649         t.data = &threads;
2650         t.extra1 = &min;
2651         t.extra2 = &max;
2652
2653         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2654         if (ret || !write)
2655                 return ret;
2656
2657         set_max_threads(threads);
2658
2659         return 0;
2660 }