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