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/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/personality.h>
  21 #include <linux/mempolicy.h>
  22 #include <linux/sem.h>
  23 #include <linux/file.h>
  24 #include <linux/fdtable.h>
  25 #include <linux/iocontext.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/mmu_notifier.h>
  30 #include <linux/fs.h>
  31 #include <linux/mm.h>
  32 #include <linux/vmacache.h>
  33 #include <linux/nsproxy.h>
  34 #include <linux/capability.h>
  35 #include <linux/cpu.h>
  36 #include <linux/cgroup.h>
  37 #include <linux/security.h>
  38 #include <linux/hugetlb.h>
  39 #include <linux/seccomp.h>
  40 #include <linux/swap.h>
  41 #include <linux/syscalls.h>
  42 #include <linux/jiffies.h>
  43 #include <linux/futex.h>
  44 #include <linux/compat.h>
  45 #include <linux/kthread.h>
  46 #include <linux/task_io_accounting_ops.h>
  47 #include <linux/rcupdate.h>
  48 #include <linux/ptrace.h>
  49 #include <linux/mount.h>
  50 #include <linux/audit.h>
  51 #include <linux/memcontrol.h>
  52 #include <linux/ftrace.h>
  53 #include <linux/proc_fs.h>
  54 #include <linux/profile.h>
  55 #include <linux/rmap.h>
  56 #include <linux/ksm.h>
  57 #include <linux/acct.h>
  58 #include <linux/tsacct_kern.h>
  59 #include <linux/cn_proc.h>
  60 #include <linux/freezer.h>
  61 #include <linux/delayacct.h>
  62 #include <linux/taskstats_kern.h>
  63 #include <linux/random.h>
  64 #include <linux/tty.h>
  65 #include <linux/blkdev.h>
  66 #include <linux/fs_struct.h>
  67 #include <linux/magic.h>
  68 #include <linux/perf_event.h>
  69 #include <linux/posix-timers.h>
  70 #include <linux/user-return-notifier.h>
  71 #include <linux/oom.h>
  72 #include <linux/khugepaged.h>
  73 #include <linux/signalfd.h>
  74 #include <linux/uprobes.h>
  75 #include <linux/aio.h>
  76 #include <linux/compiler.h>
  77
  78 #include <asm/pgtable.h>
  79 #include <asm/pgalloc.h>
  80 #include <asm/uaccess.h>
  81 #include <asm/mmu_context.h>
  82 #include <asm/cacheflush.h>
  83 #include <asm/tlbflush.h>
  84
  85 #include <trace/events/sched.h>
  86
  87 #define CREATE_TRACE_POINTS
  88 #include <trace/events/task.h>
  89
  90 /*
  91  * Protected counters by write_lock_irq(&tasklist_lock)
  92  */
  93 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  94 int nr_threads;                 /* The idle threads do not count.. */
  95
  96 int max_threads;                /* tunable limit on nr_threads */
  97
  98 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  99
 100 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 101
 102 #ifdef CONFIG_PROVE_RCU
 103 int lockdep_tasklist_lock_is_held(void)
 104 {
 105         return lockdep_is_held(&tasklist_lock);
 106 }
 107 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 108 #endif /* #ifdef CONFIG_PROVE_RCU */
 109
 110 int nr_processes(void)
 111 {
 112         int cpu;
 113         int total = 0;
 114
 115         for_each_possible_cpu(cpu)
 116                 total += per_cpu(process_counts, cpu);
 117
 118         return total;
 119 }
 120
 121 void __weak arch_release_task_struct(struct task_struct *tsk)
 122 {
 123 }
 124
 125 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 126 static struct kmem_cache *task_struct_cachep;
 127
 128 static inline struct task_struct *alloc_task_struct_node(int node)
 129 {
 130         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 131 }
 132
 133 static inline void free_task_struct(struct task_struct *tsk)
 134 {
 135         kmem_cache_free(task_struct_cachep, tsk);
 136 }
 137 #endif
 138
 139 void __weak arch_release_thread_info(struct thread_info *ti)
 140 {
 141 }
 142
 143 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 144
 145 /*
 146  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 147  * kmemcache based allocator.
 148  */
 149 # if THREAD_SIZE >= PAGE_SIZE
 150 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 151                                                   int node)
 152 {
 153         struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
 154                                                   THREAD_SIZE_ORDER);
 155
 156         return page ? page_address(page) : NULL;
 157 }
 158
 159 static inline void free_thread_info(struct thread_info *ti)
 160 {
 161         free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 162 }
 163 # else
 164 static struct kmem_cache *thread_info_cache;
 165
 166 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 167                                                   int node)
 168 {
 169         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 170 }
 171
 172 static void free_thread_info(struct thread_info *ti)
 173 {
 174         kmem_cache_free(thread_info_cache, ti);
 175 }
 176
 177 void thread_info_cache_init(void)
 178 {
 179         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 180                                               THREAD_SIZE, 0, NULL);
 181         BUG_ON(thread_info_cache == NULL);
 182 }
 183 # endif
 184 #endif
 185
 186 /* SLAB cache for signal_struct structures (tsk->signal) */
 187 static struct kmem_cache *signal_cachep;
 188
 189 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 190 struct kmem_cache *sighand_cachep;
 191
 192 /* SLAB cache for files_struct structures (tsk->files) */
 193 struct kmem_cache *files_cachep;
 194
 195 /* SLAB cache for fs_struct structures (tsk->fs) */
 196 struct kmem_cache *fs_cachep;
 197
 198 /* SLAB cache for vm_area_struct structures */
 199 struct kmem_cache *vm_area_cachep;
 200
 201 /* SLAB cache for mm_struct structures (tsk->mm) */
 202 static struct kmem_cache *mm_cachep;
 203
 204 static void account_kernel_stack(struct thread_info *ti, int account)
 205 {
 206         struct zone *zone = page_zone(virt_to_page(ti));
 207
 208         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 209 }
 210
 211 void free_task(struct task_struct *tsk)
 212 {
 213         account_kernel_stack(tsk->stack, -1);
 214         arch_release_thread_info(tsk->stack);
 215         free_thread_info(tsk->stack);
 216         rt_mutex_debug_task_free(tsk);
 217         ftrace_graph_exit_task(tsk);
 218         put_seccomp_filter(tsk);
 219         arch_release_task_struct(tsk);
 220         free_task_struct(tsk);
 221 }
 222 EXPORT_SYMBOL(free_task);
 223
 224 static inline void free_signal_struct(struct signal_struct *sig)
 225 {
 226         taskstats_tgid_free(sig);
 227         sched_autogroup_exit(sig);
 228         kmem_cache_free(signal_cachep, sig);
 229 }
 230
 231 static inline void put_signal_struct(struct signal_struct *sig)
 232 {
 233         if (atomic_dec_and_test(&sig->sigcnt))
 234                 free_signal_struct(sig);
 235 }
 236
 237 void __put_task_struct(struct task_struct *tsk)
 238 {
 239         WARN_ON(!tsk->exit_state);
 240         WARN_ON(atomic_read(&tsk->usage));
 241         WARN_ON(tsk == current);
 242
 243         task_numa_free(tsk);
 244         security_task_free(tsk);
 245         exit_creds(tsk);
 246         delayacct_tsk_free(tsk);
 247         put_signal_struct(tsk->signal);
 248
 249         if (!profile_handoff_task(tsk))
 250                 free_task(tsk);
 251 }
 252 EXPORT_SYMBOL_GPL(__put_task_struct);
 253
 254 void __init __weak arch_task_cache_init(void) { }
 255
 256 void __init fork_init(unsigned long mempages)
 257 {
 258 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 259 #ifndef ARCH_MIN_TASKALIGN
 260 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 261 #endif
 262         /* create a slab on which task_structs can be allocated */
 263         task_struct_cachep =
 264                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 265                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 266 #endif
 267
 268         /* do the arch specific task caches init */
 269         arch_task_cache_init();
 270
 271         /*
 272          * The default maximum number of threads is set to a safe
 273          * value: the thread structures can take up at most half
 274          * of memory.
 275          */
 276         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 277
 278         /*
 279          * we need to allow at least 20 threads to boot a system
 280          */
 281         if (max_threads < 20)
 282                 max_threads = 20;
 283
 284         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 285         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 286         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 287                 init_task.signal->rlim[RLIMIT_NPROC];
 288 }
 289
 290 int __weak arch_dup_task_struct(struct task_struct *dst,
 291                                                struct task_struct *src)
 292 {
 293         *dst = *src;
 294         return 0;
 295 }
 296
 297 void set_task_stack_end_magic(struct task_struct *tsk)
 298 {
 299         unsigned long *stackend;
 300
 301         stackend = end_of_stack(tsk);
 302         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 303 }
 304
 305 static struct task_struct *dup_task_struct(struct task_struct *orig)
 306 {
 307         struct task_struct *tsk;
 308         struct thread_info *ti;
 309         int node = tsk_fork_get_node(orig);
 310         int err;
 311
 312         tsk = alloc_task_struct_node(node);
 313         if (!tsk)
 314                 return NULL;
 315
 316         ti = alloc_thread_info_node(tsk, node);
 317         if (!ti)
 318                 goto free_tsk;
 319
 320         err = arch_dup_task_struct(tsk, orig);
 321         if (err)
 322                 goto free_ti;
 323
 324         tsk->stack = ti;
 325 #ifdef CONFIG_SECCOMP
 326         /*
 327          * We must handle setting up seccomp filters once we're under
 328          * the sighand lock in case orig has changed between now and
 329          * then. Until then, filter must be NULL to avoid messing up
 330          * the usage counts on the error path calling free_task.
 331          */
 332         tsk->seccomp.filter = NULL;
 333 #endif
 334
 335         setup_thread_stack(tsk, orig);
 336         clear_user_return_notifier(tsk);
 337         clear_tsk_need_resched(tsk);
 338         set_task_stack_end_magic(tsk);
 339
 340 #ifdef CONFIG_CC_STACKPROTECTOR
 341         tsk->stack_canary = get_random_int();
 342 #endif
 343
 344         /*
 345          * One for us, one for whoever does the "release_task()" (usually
 346          * parent)
 347          */
 348         atomic_set(&tsk->usage, 2);
 349 #ifdef CONFIG_BLK_DEV_IO_TRACE
 350         tsk->btrace_seq = 0;
 351 #endif
 352         tsk->splice_pipe = NULL;
 353         tsk->task_frag.page = NULL;
 354
 355         account_kernel_stack(ti, 1);
 356
 357         return tsk;
 358
 359 free_ti:
 360         free_thread_info(ti);
 361 free_tsk:
 362         free_task_struct(tsk);
 363         return NULL;
 364 }
 365
 366 #ifdef CONFIG_MMU
 367 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 368 {
 369         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 370         struct rb_node **rb_link, *rb_parent;
 371         int retval;
 372         unsigned long charge;
 373
 374         uprobe_start_dup_mmap();
 375         down_write(&oldmm->mmap_sem);
 376         flush_cache_dup_mm(oldmm);
 377         uprobe_dup_mmap(oldmm, mm);
 378         /*
 379          * Not linked in yet - no deadlock potential:
 380          */
 381         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 382
 383         mm->total_vm = oldmm->total_vm;
 384         mm->shared_vm = oldmm->shared_vm;
 385         mm->exec_vm = oldmm->exec_vm;
 386         mm->stack_vm = oldmm->stack_vm;
 387
 388         rb_link = &mm->mm_rb.rb_node;
 389         rb_parent = NULL;
 390         pprev = &mm->mmap;
 391         retval = ksm_fork(mm, oldmm);
 392         if (retval)
 393                 goto out;
 394         retval = khugepaged_fork(mm, oldmm);
 395         if (retval)
 396                 goto out;
 397
 398         prev = NULL;
 399         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 400                 struct file *file;
 401
 402                 if (mpnt->vm_flags & VM_DONTCOPY) {
 403                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 404                                                         -vma_pages(mpnt));
 405                         continue;
 406                 }
 407                 charge = 0;
 408                 if (mpnt->vm_flags & VM_ACCOUNT) {
 409                         unsigned long len = vma_pages(mpnt);
 410
 411                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 412                                 goto fail_nomem;
 413                         charge = len;
 414                 }
 415                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 416                 if (!tmp)
 417                         goto fail_nomem;
 418                 *tmp = *mpnt;
 419                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 420                 retval = vma_dup_policy(mpnt, tmp);
 421                 if (retval)
 422                         goto fail_nomem_policy;
 423                 tmp->vm_mm = mm;
 424                 if (anon_vma_fork(tmp, mpnt))
 425                         goto fail_nomem_anon_vma_fork;
 426                 tmp->vm_flags &= ~VM_LOCKED;
 427                 tmp->vm_next = tmp->vm_prev = NULL;
 428                 file = tmp->vm_file;
 429                 if (file) {
 430                         struct inode *inode = file_inode(file);
 431                         struct address_space *mapping = file->f_mapping;
 432
 433                         get_file(file);
 434                         if (tmp->vm_flags & VM_DENYWRITE)
 435                                 atomic_dec(&inode->i_writecount);
 436                         i_mmap_lock_write(mapping);
 437                         if (tmp->vm_flags & VM_SHARED)
 438                                 atomic_inc(&mapping->i_mmap_writable);
 439                         flush_dcache_mmap_lock(mapping);
 440                         /* insert tmp into the share list, just after mpnt */
 441                         vma_interval_tree_insert_after(tmp, mpnt,
 442                                         &mapping->i_mmap);
 443                         flush_dcache_mmap_unlock(mapping);
 444                         i_mmap_unlock_write(mapping);
 445                 }
 446
 447                 /*
 448                  * Clear hugetlb-related page reserves for children. This only
 449                  * affects MAP_PRIVATE mappings. Faults generated by the child
 450                  * are not guaranteed to succeed, even if read-only
 451                  */
 452                 if (is_vm_hugetlb_page(tmp))
 453                         reset_vma_resv_huge_pages(tmp);
 454
 455                 /*
 456                  * Link in the new vma and copy the page table entries.
 457                  */
 458                 *pprev = tmp;
 459                 pprev = &tmp->vm_next;
 460                 tmp->vm_prev = prev;
 461                 prev = tmp;
 462
 463                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 464                 rb_link = &tmp->vm_rb.rb_right;
 465                 rb_parent = &tmp->vm_rb;
 466
 467                 mm->map_count++;
 468                 retval = copy_page_range(mm, oldmm, mpnt);
 469
 470                 if (tmp->vm_ops && tmp->vm_ops->open)
 471                         tmp->vm_ops->open(tmp);
 472
 473                 if (retval)
 474                         goto out;
 475         }
 476         /* a new mm has just been created */
 477         arch_dup_mmap(oldmm, mm);
 478         retval = 0;
 479 out:
 480         up_write(&mm->mmap_sem);
 481         flush_tlb_mm(oldmm);
 482         up_write(&oldmm->mmap_sem);
 483         uprobe_end_dup_mmap();
 484         return retval;
 485 fail_nomem_anon_vma_fork:
 486         mpol_put(vma_policy(tmp));
 487 fail_nomem_policy:
 488         kmem_cache_free(vm_area_cachep, tmp);
 489 fail_nomem:
 490         retval = -ENOMEM;
 491         vm_unacct_memory(charge);
 492         goto out;
 493 }
 494
 495 static inline int mm_alloc_pgd(struct mm_struct *mm)
 496 {
 497         mm->pgd = pgd_alloc(mm);
 498         if (unlikely(!mm->pgd))
 499                 return -ENOMEM;
 500         return 0;
 501 }
 502
 503 static inline void mm_free_pgd(struct mm_struct *mm)
 504 {
 505         pgd_free(mm, mm->pgd);
 506 }
 507 #else
 508 #define dup_mmap(mm, oldmm)     (0)
 509 #define mm_alloc_pgd(mm)        (0)
 510 #define mm_free_pgd(mm)
 511 #endif /* CONFIG_MMU */
 512
 513 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 514
 515 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 516 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 517
 518 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 519
 520 static int __init coredump_filter_setup(char *s)
 521 {
 522         default_dump_filter =
 523                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 524                 MMF_DUMP_FILTER_MASK;
 525         return 1;
 526 }
 527
 528 __setup("coredump_filter=", coredump_filter_setup);
 529
 530 #include <linux/init_task.h>
 531
 532 static void mm_init_aio(struct mm_struct *mm)
 533 {
 534 #ifdef CONFIG_AIO
 535         spin_lock_init(&mm->ioctx_lock);
 536         mm->ioctx_table = NULL;
 537 #endif
 538 }
 539
 540 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 541 {
 542 #ifdef CONFIG_MEMCG
 543         mm->owner = p;
 544 #endif
 545 }
 546
 547 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 548 {
 549         mm->mmap = NULL;
 550         mm->mm_rb = RB_ROOT;
 551         mm->vmacache_seqnum = 0;
 552         atomic_set(&mm->mm_users, 1);
 553         atomic_set(&mm->mm_count, 1);
 554         init_rwsem(&mm->mmap_sem);
 555         INIT_LIST_HEAD(&mm->mmlist);
 556         mm->core_state = NULL;
 557         atomic_long_set(&mm->nr_ptes, 0);
 558         mm_nr_pmds_init(mm);
 559         mm->map_count = 0;
 560         mm->locked_vm = 0;
 561         mm->pinned_vm = 0;
 562         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 563         spin_lock_init(&mm->page_table_lock);
 564         mm_init_cpumask(mm);
 565         mm_init_aio(mm);
 566         mm_init_owner(mm, p);
 567         mmu_notifier_mm_init(mm);
 568         clear_tlb_flush_pending(mm);
 569 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 570         mm->pmd_huge_pte = NULL;
 571 #endif
 572
 573         if (current->mm) {
 574                 mm->flags = current->mm->flags & MMF_INIT_MASK;
 575                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 576         } else {
 577                 mm->flags = default_dump_filter;
 578                 mm->def_flags = 0;
 579         }
 580
 581         if (mm_alloc_pgd(mm))
 582                 goto fail_nopgd;
 583
 584         if (init_new_context(p, mm))
 585                 goto fail_nocontext;
 586
 587         return mm;
 588
 589 fail_nocontext:
 590         mm_free_pgd(mm);
 591 fail_nopgd:
 592         free_mm(mm);
 593         return NULL;
 594 }
 595
 596 static void check_mm(struct mm_struct *mm)
 597 {
 598         int i;
 599
 600         for (i = 0; i < NR_MM_COUNTERS; i++) {
 601                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 602
 603                 if (unlikely(x))
 604                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 605                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 606         }
 607
 608         if (atomic_long_read(&mm->nr_ptes))
 609                 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
 610                                 atomic_long_read(&mm->nr_ptes));
 611         if (mm_nr_pmds(mm))
 612                 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
 613                                 mm_nr_pmds(mm));
 614
 615 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 616         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 617 #endif
 618 }
 619
 620 /*
 621  * Allocate and initialize an mm_struct.
 622  */
 623 struct mm_struct *mm_alloc(void)
 624 {
 625         struct mm_struct *mm;
 626
 627         mm = allocate_mm();
 628         if (!mm)
 629                 return NULL;
 630
 631         memset(mm, 0, sizeof(*mm));
 632         return mm_init(mm, current);
 633 }
 634
 635 /*
 636  * Called when the last reference to the mm
 637  * is dropped: either by a lazy thread or by
 638  * mmput. Free the page directory and the mm.
 639  */
 640 void __mmdrop(struct mm_struct *mm)
 641 {
 642         BUG_ON(mm == &init_mm);
 643         mm_free_pgd(mm);
 644         destroy_context(mm);
 645         mmu_notifier_mm_destroy(mm);
 646         check_mm(mm);
 647         free_mm(mm);
 648 }
 649 EXPORT_SYMBOL_GPL(__mmdrop);
 650
 651 /*
 652  * Decrement the use count and release all resources for an mm.
 653  */
 654 void mmput(struct mm_struct *mm)
 655 {
 656         might_sleep();
 657
 658         if (atomic_dec_and_test(&mm->mm_users)) {
 659                 uprobe_clear_state(mm);
 660                 exit_aio(mm);
 661                 ksm_exit(mm);
 662                 khugepaged_exit(mm); /* must run before exit_mmap */
 663                 exit_mmap(mm);
 664                 set_mm_exe_file(mm, NULL);
 665                 if (!list_empty(&mm->mmlist)) {
 666                         spin_lock(&mmlist_lock);
 667                         list_del(&mm->mmlist);
 668                         spin_unlock(&mmlist_lock);
 669                 }
 670                 if (mm->binfmt)
 671                         module_put(mm->binfmt->module);
 672                 mmdrop(mm);
 673         }
 674 }
 675 EXPORT_SYMBOL_GPL(mmput);
 676
 677 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 678 {
 679         if (new_exe_file)
 680                 get_file(new_exe_file);
 681         if (mm->exe_file)
 682                 fput(mm->exe_file);
 683         mm->exe_file = new_exe_file;
 684 }
 685
 686 struct file *get_mm_exe_file(struct mm_struct *mm)
 687 {
 688         struct file *exe_file;
 689
 690         /* We need mmap_sem to protect against races with removal of exe_file */
 691         down_read(&mm->mmap_sem);
 692         exe_file = mm->exe_file;
 693         if (exe_file)
 694                 get_file(exe_file);
 695         up_read(&mm->mmap_sem);
 696         return exe_file;
 697 }
 698
 699 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 700 {
 701         /* It's safe to write the exe_file pointer without exe_file_lock because
 702          * this is called during fork when the task is not yet in /proc */
 703         newmm->exe_file = get_mm_exe_file(oldmm);
 704 }
 705
 706 /**
 707  * get_task_mm - acquire a reference to the task's mm
 708  *
 709  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 710  * this kernel workthread has transiently adopted a user mm with use_mm,
 711  * to do its AIO) is not set and if so returns a reference to it, after
 712  * bumping up the use count.  User must release the mm via mmput()
 713  * after use.  Typically used by /proc and ptrace.
 714  */
 715 struct mm_struct *get_task_mm(struct task_struct *task)
 716 {
 717         struct mm_struct *mm;
 718
 719         task_lock(task);
 720         mm = task->mm;
 721         if (mm) {
 722                 if (task->flags & PF_KTHREAD)
 723                         mm = NULL;
 724                 else
 725                         atomic_inc(&mm->mm_users);
 726         }
 727         task_unlock(task);
 728         return mm;
 729 }
 730 EXPORT_SYMBOL_GPL(get_task_mm);
 731
 732 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 733 {
 734         struct mm_struct *mm;
 735         int err;
 736
 737         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 738         if (err)
 739                 return ERR_PTR(err);
 740
 741         mm = get_task_mm(task);
 742         if (mm && mm != current->mm &&
 743                         !ptrace_may_access(task, mode)) {
 744                 mmput(mm);
 745                 mm = ERR_PTR(-EACCES);
 746         }
 747         mutex_unlock(&task->signal->cred_guard_mutex);
 748
 749         return mm;
 750 }
 751
 752 static void complete_vfork_done(struct task_struct *tsk)
 753 {
 754         struct completion *vfork;
 755
 756         task_lock(tsk);
 757         vfork = tsk->vfork_done;
 758         if (likely(vfork)) {
 759                 tsk->vfork_done = NULL;
 760                 complete(vfork);
 761         }
 762         task_unlock(tsk);
 763 }
 764
 765 static int wait_for_vfork_done(struct task_struct *child,
 766                                 struct completion *vfork)
 767 {
 768         int killed;
 769
 770         freezer_do_not_count();
 771         killed = wait_for_completion_killable(vfork);
 772         freezer_count();
 773
 774         if (killed) {
 775                 task_lock(child);
 776                 child->vfork_done = NULL;
 777                 task_unlock(child);
 778         }
 779
 780         put_task_struct(child);
 781         return killed;
 782 }
 783
 784 /* Please note the differences between mmput and mm_release.
 785  * mmput is called whenever we stop holding onto a mm_struct,
 786  * error success whatever.
 787  *
 788  * mm_release is called after a mm_struct has been removed
 789  * from the current process.
 790  *
 791  * This difference is important for error handling, when we
 792  * only half set up a mm_struct for a new process and need to restore
 793  * the old one.  Because we mmput the new mm_struct before
 794  * restoring the old one. . .
 795  * Eric Biederman 10 January 1998
 796  */
 797 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 798 {
 799         /* Get rid of any futexes when releasing the mm */
 800 #ifdef CONFIG_FUTEX
 801         if (unlikely(tsk->robust_list)) {
 802                 exit_robust_list(tsk);
 803                 tsk->robust_list = NULL;
 804         }
 805 #ifdef CONFIG_COMPAT
 806         if (unlikely(tsk->compat_robust_list)) {
 807                 compat_exit_robust_list(tsk);
 808                 tsk->compat_robust_list = NULL;
 809         }
 810 #endif
 811         if (unlikely(!list_empty(&tsk->pi_state_list)))
 812                 exit_pi_state_list(tsk);
 813 #endif
 814
 815         uprobe_free_utask(tsk);
 816
 817         /* Get rid of any cached register state */
 818         deactivate_mm(tsk, mm);
 819
 820         /*
 821          * If we're exiting normally, clear a user-space tid field if
 822          * requested.  We leave this alone when dying by signal, to leave
 823          * the value intact in a core dump, and to save the unnecessary
 824          * trouble, say, a killed vfork parent shouldn't touch this mm.
 825          * Userland only wants this done for a sys_exit.
 826          */
 827         if (tsk->clear_child_tid) {
 828                 if (!(tsk->flags & PF_SIGNALED) &&
 829                     atomic_read(&mm->mm_users) > 1) {
 830                         /*
 831                          * We don't check the error code - if userspace has
 832                          * not set up a proper pointer then tough luck.
 833                          */
 834                         put_user(0, tsk->clear_child_tid);
 835                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 836                                         1, NULL, NULL, 0);
 837                 }
 838                 tsk->clear_child_tid = NULL;
 839         }
 840
 841         /*
 842          * All done, finally we can wake up parent and return this mm to him.
 843          * Also kthread_stop() uses this completion for synchronization.
 844          */
 845         if (tsk->vfork_done)
 846                 complete_vfork_done(tsk);
 847 }
 848
 849 /*
 850  * Allocate a new mm structure and copy contents from the
 851  * mm structure of the passed in task structure.
 852  */
 853 static struct mm_struct *dup_mm(struct task_struct *tsk)
 854 {
 855         struct mm_struct *mm, *oldmm = current->mm;
 856         int err;
 857
 858         mm = allocate_mm();
 859         if (!mm)
 860                 goto fail_nomem;
 861
 862         memcpy(mm, oldmm, sizeof(*mm));
 863
 864         if (!mm_init(mm, tsk))
 865                 goto fail_nomem;
 866
 867         dup_mm_exe_file(oldmm, mm);
 868
 869         err = dup_mmap(mm, oldmm);
 870         if (err)
 871                 goto free_pt;
 872
 873         mm->hiwater_rss = get_mm_rss(mm);
 874         mm->hiwater_vm = mm->total_vm;
 875
 876         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 877                 goto free_pt;
 878
 879         return mm;
 880
 881 free_pt:
 882         /* don't put binfmt in mmput, we haven't got module yet */
 883         mm->binfmt = NULL;
 884         mmput(mm);
 885
 886 fail_nomem:
 887         return NULL;
 888 }
 889
 890 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 891 {
 892         struct mm_struct *mm, *oldmm;
 893         int retval;
 894
 895         tsk->min_flt = tsk->maj_flt = 0;
 896         tsk->nvcsw = tsk->nivcsw = 0;
 897 #ifdef CONFIG_DETECT_HUNG_TASK
 898         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 899 #endif
 900
 901         tsk->mm = NULL;
 902         tsk->active_mm = NULL;
 903
 904         /*
 905          * Are we cloning a kernel thread?
 906          *
 907          * We need to steal a active VM for that..
 908          */
 909         oldmm = current->mm;
 910         if (!oldmm)
 911                 return 0;
 912
 913         /* initialize the new vmacache entries */
 914         vmacache_flush(tsk);
 915
 916         if (clone_flags & CLONE_VM) {
 917                 atomic_inc(&oldmm->mm_users);
 918                 mm = oldmm;
 919                 goto good_mm;
 920         }
 921
 922         retval = -ENOMEM;
 923         mm = dup_mm(tsk);
 924         if (!mm)
 925                 goto fail_nomem;
 926
 927 good_mm:
 928         tsk->mm = mm;
 929         tsk->active_mm = mm;
 930         return 0;
 931
 932 fail_nomem:
 933         return retval;
 934 }
 935
 936 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 937 {
 938         struct fs_struct *fs = current->fs;
 939         if (clone_flags & CLONE_FS) {
 940                 /* tsk->fs is already what we want */
 941                 spin_lock(&fs->lock);
 942                 if (fs->in_exec) {
 943                         spin_unlock(&fs->lock);
 944                         return -EAGAIN;
 945                 }
 946                 fs->users++;
 947                 spin_unlock(&fs->lock);
 948                 return 0;
 949         }
 950         tsk->fs = copy_fs_struct(fs);
 951         if (!tsk->fs)
 952                 return -ENOMEM;
 953         return 0;
 954 }
 955
 956 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 957 {
 958         struct files_struct *oldf, *newf;
 959         int error = 0;
 960
 961         /*
 962          * A background process may not have any files ...
 963          */
 964         oldf = current->files;
 965         if (!oldf)
 966                 goto out;
 967
 968         if (clone_flags & CLONE_FILES) {
 969                 atomic_inc(&oldf->count);
 970                 goto out;
 971         }
 972
 973         newf = dup_fd(oldf, &error);
 974         if (!newf)
 975                 goto out;
 976
 977         tsk->files = newf;
 978         error = 0;
 979 out:
 980         return error;
 981 }
 982
 983 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 984 {
 985 #ifdef CONFIG_BLOCK
 986         struct io_context *ioc = current->io_context;
 987         struct io_context *new_ioc;
 988
 989         if (!ioc)
 990                 return 0;
 991         /*
 992          * Share io context with parent, if CLONE_IO is set
 993          */
 994         if (clone_flags & CLONE_IO) {
 995                 ioc_task_link(ioc);
 996                 tsk->io_context = ioc;
 997         } else if (ioprio_valid(ioc->ioprio)) {
 998                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 999                 if (unlikely(!new_ioc))
1000                         return -ENOMEM;
1001
1002                 new_ioc->ioprio = ioc->ioprio;
1003                 put_io_context(new_ioc);
1004         }
1005 #endif
1006         return 0;
1007 }
1008
1009 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1010 {
1011         struct sighand_struct *sig;
1012
1013         if (clone_flags & CLONE_SIGHAND) {
1014                 atomic_inc(&current->sighand->count);
1015                 return 0;
1016         }
1017         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1018         rcu_assign_pointer(tsk->sighand, sig);
1019         if (!sig)
1020                 return -ENOMEM;
1021         atomic_set(&sig->count, 1);
1022         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1023         return 0;
1024 }
1025
1026 void __cleanup_sighand(struct sighand_struct *sighand)
1027 {
1028         if (atomic_dec_and_test(&sighand->count)) {
1029                 signalfd_cleanup(sighand);
1030                 /*
1031                  * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1032                  * without an RCU grace period, see __lock_task_sighand().
1033                  */
1034                 kmem_cache_free(sighand_cachep, sighand);
1035         }
1036 }
1037
1038 /*
1039  * Initialize POSIX timer handling for a thread group.
1040  */
1041 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1042 {
1043         unsigned long cpu_limit;
1044
1045         /* Thread group counters. */
1046         thread_group_cputime_init(sig);
1047
1048         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1049         if (cpu_limit != RLIM_INFINITY) {
1050                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1051                 sig->cputimer.running = 1;
1052         }
1053
1054         /* The timer lists. */
1055         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1056         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1057         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1058 }
1059
1060 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1061 {
1062         struct signal_struct *sig;
1063
1064         if (clone_flags & CLONE_THREAD)
1065                 return 0;
1066
1067         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1068         tsk->signal = sig;
1069         if (!sig)
1070                 return -ENOMEM;
1071
1072         sig->nr_threads = 1;
1073         atomic_set(&sig->live, 1);
1074         atomic_set(&sig->sigcnt, 1);
1075
1076         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1077         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1078         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1079
1080         init_waitqueue_head(&sig->wait_chldexit);
1081         sig->curr_target = tsk;
1082         init_sigpending(&sig->shared_pending);
1083         INIT_LIST_HEAD(&sig->posix_timers);
1084         seqlock_init(&sig->stats_lock);
1085
1086         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1087         sig->real_timer.function = it_real_fn;
1088
1089         task_lock(current->group_leader);
1090         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1091         task_unlock(current->group_leader);
1092
1093         posix_cpu_timers_init_group(sig);
1094
1095         tty_audit_fork(sig);
1096         sched_autogroup_fork(sig);
1097
1098 #ifdef CONFIG_CGROUPS
1099         init_rwsem(&sig->group_rwsem);
1100 #endif
1101
1102         sig->oom_score_adj = current->signal->oom_score_adj;
1103         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1104
1105         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1106                                    current->signal->is_child_subreaper;
1107
1108         mutex_init(&sig->cred_guard_mutex);
1109
1110         return 0;
1111 }
1112
1113 static void copy_seccomp(struct task_struct *p)
1114 {
1115 #ifdef CONFIG_SECCOMP
1116         /*
1117          * Must be called with sighand->lock held, which is common to
1118          * all threads in the group. Holding cred_guard_mutex is not
1119          * needed because this new task is not yet running and cannot
1120          * be racing exec.
1121          */
1122         assert_spin_locked(&current->sighand->siglock);
1123
1124         /* Ref-count the new filter user, and assign it. */
1125         get_seccomp_filter(current);
1126         p->seccomp = current->seccomp;
1127
1128         /*
1129          * Explicitly enable no_new_privs here in case it got set
1130          * between the task_struct being duplicated and holding the
1131          * sighand lock. The seccomp state and nnp must be in sync.
1132          */
1133         if (task_no_new_privs(current))
1134                 task_set_no_new_privs(p);
1135
1136         /*
1137          * If the parent gained a seccomp mode after copying thread
1138          * flags and between before we held the sighand lock, we have
1139          * to manually enable the seccomp thread flag here.
1140          */
1141         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1142                 set_tsk_thread_flag(p, TIF_SECCOMP);
1143 #endif
1144 }
1145
1146 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1147 {
1148         current->clear_child_tid = tidptr;
1149
1150         return task_pid_vnr(current);
1151 }
1152
1153 static void rt_mutex_init_task(struct task_struct *p)
1154 {
1155         raw_spin_lock_init(&p->pi_lock);
1156 #ifdef CONFIG_RT_MUTEXES
1157         p->pi_waiters = RB_ROOT;
1158         p->pi_waiters_leftmost = NULL;
1159         p->pi_blocked_on = NULL;
1160 #endif
1161 }
1162
1163 /*
1164  * Initialize POSIX timer handling for a single task.
1165  */
1166 static void posix_cpu_timers_init(struct task_struct *tsk)
1167 {
1168         tsk->cputime_expires.prof_exp = 0;
1169         tsk->cputime_expires.virt_exp = 0;
1170         tsk->cputime_expires.sched_exp = 0;
1171         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1172         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1173         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1174 }
1175
1176 static inline void
1177 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1178 {
1179          task->pids[type].pid = pid;
1180 }
1181
1182 /*
1183  * This creates a new process as a copy of the old one,
1184  * but does not actually start it yet.
1185  *
1186  * It copies the registers, and all the appropriate
1187  * parts of the process environment (as per the clone
1188  * flags). The actual kick-off is left to the caller.
1189  */
1190 static struct task_struct *copy_process(unsigned long clone_flags,
1191                                         unsigned long stack_start,
1192                                         unsigned long stack_size,
1193                                         int __user *child_tidptr,
1194                                         struct pid *pid,
1195                                         int trace)
1196 {
1197         int retval;
1198         struct task_struct *p;
1199
1200         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1201                 return ERR_PTR(-EINVAL);
1202
1203         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1204                 return ERR_PTR(-EINVAL);
1205
1206         /*
1207          * Thread groups must share signals as well, and detached threads
1208          * can only be started up within the thread group.
1209          */
1210         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1211                 return ERR_PTR(-EINVAL);
1212
1213         /*
1214          * Shared signal handlers imply shared VM. By way of the above,
1215          * thread groups also imply shared VM. Blocking this case allows
1216          * for various simplifications in other code.
1217          */
1218         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1219                 return ERR_PTR(-EINVAL);
1220
1221         /*
1222          * Siblings of global init remain as zombies on exit since they are
1223          * not reaped by their parent (swapper). To solve this and to avoid
1224          * multi-rooted process trees, prevent global and container-inits
1225          * from creating siblings.
1226          */
1227         if ((clone_flags & CLONE_PARENT) &&
1228                                 current->signal->flags & SIGNAL_UNKILLABLE)
1229                 return ERR_PTR(-EINVAL);
1230
1231         /*
1232          * If the new process will be in a different pid or user namespace
1233          * do not allow it to share a thread group or signal handlers or
1234          * parent with the forking task.
1235          */
1236         if (clone_flags & CLONE_SIGHAND) {
1237                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1238                     (task_active_pid_ns(current) !=
1239                                 current->nsproxy->pid_ns_for_children))
1240                         return ERR_PTR(-EINVAL);
1241         }
1242
1243         retval = security_task_create(clone_flags);
1244         if (retval)
1245                 goto fork_out;
1246
1247         retval = -ENOMEM;
1248         p = dup_task_struct(current);
1249         if (!p)
1250                 goto fork_out;
1251
1252         ftrace_graph_init_task(p);
1253
1254         rt_mutex_init_task(p);
1255
1256 #ifdef CONFIG_PROVE_LOCKING
1257         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1258         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1259 #endif
1260         retval = -EAGAIN;
1261         if (atomic_read(&p->real_cred->user->processes) >=
1262                         task_rlimit(p, RLIMIT_NPROC)) {
1263                 if (p->real_cred->user != INIT_USER &&
1264                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1265                         goto bad_fork_free;
1266         }
1267         current->flags &= ~PF_NPROC_EXCEEDED;
1268
1269         retval = copy_creds(p, clone_flags);
1270         if (retval < 0)
1271                 goto bad_fork_free;
1272
1273         /*
1274          * If multiple threads are within copy_process(), then this check
1275          * triggers too late. This doesn't hurt, the check is only there
1276          * to stop root fork bombs.
1277          */
1278         retval = -EAGAIN;
1279         if (nr_threads >= max_threads)
1280                 goto bad_fork_cleanup_count;
1281
1282         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1283         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1284         p->flags |= PF_FORKNOEXEC;
1285         INIT_LIST_HEAD(&p->children);
1286         INIT_LIST_HEAD(&p->sibling);
1287         rcu_copy_process(p);
1288         p->vfork_done = NULL;
1289         spin_lock_init(&p->alloc_lock);
1290
1291         init_sigpending(&p->pending);
1292
1293         p->utime = p->stime = p->gtime = 0;
1294         p->utimescaled = p->stimescaled = 0;
1295 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1296         p->prev_cputime.utime = p->prev_cputime.stime = 0;
1297 #endif
1298 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1299         seqlock_init(&p->vtime_seqlock);
1300         p->vtime_snap = 0;
1301         p->vtime_snap_whence = VTIME_SLEEPING;
1302 #endif
1303
1304 #if defined(SPLIT_RSS_COUNTING)
1305         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1306 #endif
1307
1308         p->default_timer_slack_ns = current->timer_slack_ns;
1309
1310         task_io_accounting_init(&p->ioac);
1311         acct_clear_integrals(p);
1312
1313         posix_cpu_timers_init(p);
1314
1315         p->start_time = ktime_get_ns();
1316         p->real_start_time = ktime_get_boot_ns();
1317         p->io_context = NULL;
1318         p->audit_context = NULL;
1319         if (clone_flags & CLONE_THREAD)
1320                 threadgroup_change_begin(current);
1321         cgroup_fork(p);
1322 #ifdef CONFIG_NUMA
1323         p->mempolicy = mpol_dup(p->mempolicy);
1324         if (IS_ERR(p->mempolicy)) {
1325                 retval = PTR_ERR(p->mempolicy);
1326                 p->mempolicy = NULL;
1327                 goto bad_fork_cleanup_threadgroup_lock;
1328         }
1329 #endif
1330 #ifdef CONFIG_CPUSETS
1331         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1332         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1333         seqcount_init(&p->mems_allowed_seq);
1334 #endif
1335 #ifdef CONFIG_TRACE_IRQFLAGS
1336         p->irq_events = 0;
1337         p->hardirqs_enabled = 0;
1338         p->hardirq_enable_ip = 0;
1339         p->hardirq_enable_event = 0;
1340         p->hardirq_disable_ip = _THIS_IP_;
1341         p->hardirq_disable_event = 0;
1342         p->softirqs_enabled = 1;
1343         p->softirq_enable_ip = _THIS_IP_;
1344         p->softirq_enable_event = 0;
1345         p->softirq_disable_ip = 0;
1346         p->softirq_disable_event = 0;
1347         p->hardirq_context = 0;
1348         p->softirq_context = 0;
1349 #endif
1350 #ifdef CONFIG_LOCKDEP
1351         p->lockdep_depth = 0; /* no locks held yet */
1352         p->curr_chain_key = 0;
1353         p->lockdep_recursion = 0;
1354 #endif
1355
1356 #ifdef CONFIG_DEBUG_MUTEXES
1357         p->blocked_on = NULL; /* not blocked yet */
1358 #endif
1359 #ifdef CONFIG_BCACHE
1360         p->sequential_io        = 0;
1361         p->sequential_io_avg    = 0;
1362 #endif
1363
1364         /* Perform scheduler related setup. Assign this task to a CPU. */
1365         retval = sched_fork(clone_flags, p);
1366         if (retval)
1367                 goto bad_fork_cleanup_policy;
1368
1369         retval = perf_event_init_task(p);
1370         if (retval)
1371                 goto bad_fork_cleanup_policy;
1372         retval = audit_alloc(p);
1373         if (retval)
1374                 goto bad_fork_cleanup_perf;
1375         /* copy all the process information */
1376         shm_init_task(p);
1377         retval = copy_semundo(clone_flags, p);
1378         if (retval)
1379                 goto bad_fork_cleanup_audit;
1380         retval = copy_files(clone_flags, p);
1381         if (retval)
1382                 goto bad_fork_cleanup_semundo;
1383         retval = copy_fs(clone_flags, p);
1384         if (retval)
1385                 goto bad_fork_cleanup_files;
1386         retval = copy_sighand(clone_flags, p);
1387         if (retval)
1388                 goto bad_fork_cleanup_fs;
1389         retval = copy_signal(clone_flags, p);
1390         if (retval)
1391                 goto bad_fork_cleanup_sighand;
1392         retval = copy_mm(clone_flags, p);
1393         if (retval)
1394                 goto bad_fork_cleanup_signal;
1395         retval = copy_namespaces(clone_flags, p);
1396         if (retval)
1397                 goto bad_fork_cleanup_mm;
1398         retval = copy_io(clone_flags, p);
1399         if (retval)
1400                 goto bad_fork_cleanup_namespaces;
1401         retval = copy_thread(clone_flags, stack_start, stack_size, p);
1402         if (retval)
1403                 goto bad_fork_cleanup_io;
1404
1405         if (pid != &init_struct_pid) {
1406                 retval = -ENOMEM;
1407                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1408                 if (!pid)
1409                         goto bad_fork_cleanup_io;
1410         }
1411
1412         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1413         /*
1414          * Clear TID on mm_release()?
1415          */
1416         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1417 #ifdef CONFIG_BLOCK
1418         p->plug = NULL;
1419 #endif
1420 #ifdef CONFIG_FUTEX
1421         p->robust_list = NULL;
1422 #ifdef CONFIG_COMPAT
1423         p->compat_robust_list = NULL;
1424 #endif
1425         INIT_LIST_HEAD(&p->pi_state_list);
1426         p->pi_state_cache = NULL;
1427 #endif
1428         /*
1429          * sigaltstack should be cleared when sharing the same VM
1430          */
1431         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1432                 p->sas_ss_sp = p->sas_ss_size = 0;
1433
1434         /*
1435          * Syscall tracing and stepping should be turned off in the
1436          * child regardless of CLONE_PTRACE.
1437          */
1438         user_disable_single_step(p);
1439         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1440 #ifdef TIF_SYSCALL_EMU
1441         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1442 #endif
1443         clear_all_latency_tracing(p);
1444
1445         /* ok, now we should be set up.. */
1446         p->pid = pid_nr(pid);
1447         if (clone_flags & CLONE_THREAD) {
1448                 p->exit_signal = -1;
1449                 p->group_leader = current->group_leader;
1450                 p->tgid = current->tgid;
1451         } else {
1452                 if (clone_flags & CLONE_PARENT)
1453                         p->exit_signal = current->group_leader->exit_signal;
1454                 else
1455                         p->exit_signal = (clone_flags & CSIGNAL);
1456                 p->group_leader = p;
1457                 p->tgid = p->pid;
1458         }
1459
1460         p->nr_dirtied = 0;
1461         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1462         p->dirty_paused_when = 0;
1463
1464         p->pdeath_signal = 0;
1465         INIT_LIST_HEAD(&p->thread_group);
1466         p->task_works = NULL;
1467
1468         /*
1469          * Make it visible to the rest of the system, but dont wake it up yet.
1470          * Need tasklist lock for parent etc handling!
1471          */
1472         write_lock_irq(&tasklist_lock);
1473
1474         /* CLONE_PARENT re-uses the old parent */
1475         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1476                 p->real_parent = current->real_parent;
1477                 p->parent_exec_id = current->parent_exec_id;
1478         } else {
1479                 p->real_parent = current;
1480                 p->parent_exec_id = current->self_exec_id;
1481         }
1482
1483         spin_lock(&current->sighand->siglock);
1484
1485         /*
1486          * Copy seccomp details explicitly here, in case they were changed
1487          * before holding sighand lock.
1488          */
1489         copy_seccomp(p);
1490
1491         /*
1492          * Process group and session signals need to be delivered to just the
1493          * parent before the fork or both the parent and the child after the
1494          * fork. Restart if a signal comes in before we add the new process to
1495          * it's process group.
1496          * A fatal signal pending means that current will exit, so the new
1497          * thread can't slip out of an OOM kill (or normal SIGKILL).
1498         */
1499         recalc_sigpending();
1500         if (signal_pending(current)) {
1501                 spin_unlock(&current->sighand->siglock);
1502                 write_unlock_irq(&tasklist_lock);
1503                 retval = -ERESTARTNOINTR;
1504                 goto bad_fork_free_pid;
1505         }
1506
1507         if (likely(p->pid)) {
1508                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1509
1510                 init_task_pid(p, PIDTYPE_PID, pid);
1511                 if (thread_group_leader(p)) {
1512                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1513                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1514
1515                         if (is_child_reaper(pid)) {
1516                                 ns_of_pid(pid)->child_reaper = p;
1517                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1518                         }
1519
1520                         p->signal->leader_pid = pid;
1521                         p->signal->tty = tty_kref_get(current->signal->tty);
1522                         list_add_tail(&p->sibling, &p->real_parent->children);
1523                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1524                         attach_pid(p, PIDTYPE_PGID);
1525                         attach_pid(p, PIDTYPE_SID);
1526                         __this_cpu_inc(process_counts);
1527                 } else {
1528                         current->signal->nr_threads++;
1529                         atomic_inc(&current->signal->live);
1530                         atomic_inc(&current->signal->sigcnt);
1531                         list_add_tail_rcu(&p->thread_group,
1532                                           &p->group_leader->thread_group);
1533                         list_add_tail_rcu(&p->thread_node,
1534                                           &p->signal->thread_head);
1535                 }
1536                 attach_pid(p, PIDTYPE_PID);
1537                 nr_threads++;
1538         }
1539
1540         total_forks++;
1541         spin_unlock(&current->sighand->siglock);
1542         syscall_tracepoint_update(p);
1543         write_unlock_irq(&tasklist_lock);
1544
1545         proc_fork_connector(p);
1546         cgroup_post_fork(p);
1547         if (clone_flags & CLONE_THREAD)
1548                 threadgroup_change_end(current);
1549         perf_event_fork(p);
1550
1551         trace_task_newtask(p, clone_flags);
1552         uprobe_copy_process(p, clone_flags);
1553
1554         return p;
1555
1556 bad_fork_free_pid:
1557         if (pid != &init_struct_pid)
1558                 free_pid(pid);
1559 bad_fork_cleanup_io:
1560         if (p->io_context)
1561                 exit_io_context(p);
1562 bad_fork_cleanup_namespaces:
1563         exit_task_namespaces(p);
1564 bad_fork_cleanup_mm:
1565         if (p->mm)
1566                 mmput(p->mm);
1567 bad_fork_cleanup_signal:
1568         if (!(clone_flags & CLONE_THREAD))
1569                 free_signal_struct(p->signal);
1570 bad_fork_cleanup_sighand:
1571         __cleanup_sighand(p->sighand);
1572 bad_fork_cleanup_fs:
1573         exit_fs(p); /* blocking */
1574 bad_fork_cleanup_files:
1575         exit_files(p); /* blocking */
1576 bad_fork_cleanup_semundo:
1577         exit_sem(p);
1578 bad_fork_cleanup_audit:
1579         audit_free(p);
1580 bad_fork_cleanup_perf:
1581         perf_event_free_task(p);
1582 bad_fork_cleanup_policy:
1583 #ifdef CONFIG_NUMA
1584         mpol_put(p->mempolicy);
1585 bad_fork_cleanup_threadgroup_lock:
1586 #endif
1587         if (clone_flags & CLONE_THREAD)
1588                 threadgroup_change_end(current);
1589         delayacct_tsk_free(p);
1590 bad_fork_cleanup_count:
1591         atomic_dec(&p->cred->user->processes);
1592         exit_creds(p);
1593 bad_fork_free:
1594         free_task(p);
1595 fork_out:
1596         return ERR_PTR(retval);
1597 }
1598
1599 static inline void init_idle_pids(struct pid_link *links)
1600 {
1601         enum pid_type type;
1602
1603         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1604                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1605                 links[type].pid = &init_struct_pid;
1606         }
1607 }
1608
1609 struct task_struct *fork_idle(int cpu)
1610 {
1611         struct task_struct *task;
1612         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1613         if (!IS_ERR(task)) {
1614                 init_idle_pids(task->pids);
1615                 init_idle(task, cpu);
1616         }
1617
1618         return task;
1619 }
1620
1621 /*
1622  *  Ok, this is the main fork-routine.
1623  *
1624  * It copies the process, and if successful kick-starts
1625  * it and waits for it to finish using the VM if required.
1626  */
1627 long do_fork(unsigned long clone_flags,
1628               unsigned long stack_start,
1629               unsigned long stack_size,
1630               int __user *parent_tidptr,
1631               int __user *child_tidptr)
1632 {
1633         struct task_struct *p;
1634         int trace = 0;
1635         long nr;
1636
1637         /*
1638          * Determine whether and which event to report to ptracer.  When
1639          * called from kernel_thread or CLONE_UNTRACED is explicitly
1640          * requested, no event is reported; otherwise, report if the event
1641          * for the type of forking is enabled.
1642          */
1643         if (!(clone_flags & CLONE_UNTRACED)) {
1644                 if (clone_flags & CLONE_VFORK)
1645                         trace = PTRACE_EVENT_VFORK;
1646                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1647                         trace = PTRACE_EVENT_CLONE;
1648                 else
1649                         trace = PTRACE_EVENT_FORK;
1650
1651                 if (likely(!ptrace_event_enabled(current, trace)))
1652                         trace = 0;
1653         }
1654
1655         p = copy_process(clone_flags, stack_start, stack_size,
1656                          child_tidptr, NULL, trace);
1657         /*
1658          * Do this prior waking up the new thread - the thread pointer
1659          * might get invalid after that point, if the thread exits quickly.
1660          */
1661         if (!IS_ERR(p)) {
1662                 struct completion vfork;
1663                 struct pid *pid;
1664
1665                 trace_sched_process_fork(current, p);
1666
1667                 pid = get_task_pid(p, PIDTYPE_PID);
1668                 nr = pid_vnr(pid);
1669
1670                 if (clone_flags & CLONE_PARENT_SETTID)
1671                         put_user(nr, parent_tidptr);
1672
1673                 if (clone_flags & CLONE_VFORK) {
1674                         p->vfork_done = &vfork;
1675                         init_completion(&vfork);
1676                         get_task_struct(p);
1677                 }
1678
1679                 wake_up_new_task(p);
1680
1681                 /* forking complete and child started to run, tell ptracer */
1682                 if (unlikely(trace))
1683                         ptrace_event_pid(trace, pid);
1684
1685                 if (clone_flags & CLONE_VFORK) {
1686                         if (!wait_for_vfork_done(p, &vfork))
1687                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1688                 }
1689
1690                 put_pid(pid);
1691         } else {
1692                 nr = PTR_ERR(p);
1693         }
1694         return nr;
1695 }
1696
1697 /*
1698  * Create a kernel thread.
1699  */
1700 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1701 {
1702         return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1703                 (unsigned long)arg, NULL, NULL);
1704 }
1705
1706 #ifdef __ARCH_WANT_SYS_FORK
1707 SYSCALL_DEFINE0(fork)
1708 {
1709 #ifdef CONFIG_MMU
1710         return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1711 #else
1712         /* can not support in nommu mode */
1713         return -EINVAL;
1714 #endif
1715 }
1716 #endif
1717
1718 #ifdef __ARCH_WANT_SYS_VFORK
1719 SYSCALL_DEFINE0(vfork)
1720 {
1721         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1722                         0, NULL, NULL);
1723 }
1724 #endif
1725
1726 #ifdef __ARCH_WANT_SYS_CLONE
1727 #ifdef CONFIG_CLONE_BACKWARDS
1728 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1729                  int __user *, parent_tidptr,
1730                  int, tls_val,
1731                  int __user *, child_tidptr)
1732 #elif defined(CONFIG_CLONE_BACKWARDS2)
1733 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1734                  int __user *, parent_tidptr,
1735                  int __user *, child_tidptr,
1736                  int, tls_val)
1737 #elif defined(CONFIG_CLONE_BACKWARDS3)
1738 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1739                 int, stack_size,
1740                 int __user *, parent_tidptr,
1741                 int __user *, child_tidptr,
1742                 int, tls_val)
1743 #else
1744 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1745                  int __user *, parent_tidptr,
1746                  int __user *, child_tidptr,
1747                  int, tls_val)
1748 #endif
1749 {
1750         return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1751 }
1752 #endif
1753
1754 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1755 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1756 #endif
1757
1758 static void sighand_ctor(void *data)
1759 {
1760         struct sighand_struct *sighand = data;
1761
1762         spin_lock_init(&sighand->siglock);
1763         init_waitqueue_head(&sighand->signalfd_wqh);
1764 }
1765
1766 void __init proc_caches_init(void)
1767 {
1768         sighand_cachep = kmem_cache_create("sighand_cache",
1769                         sizeof(struct sighand_struct), 0,
1770                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1771                         SLAB_NOTRACK, sighand_ctor);
1772         signal_cachep = kmem_cache_create("signal_cache",
1773                         sizeof(struct signal_struct), 0,
1774                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1775         files_cachep = kmem_cache_create("files_cache",
1776                         sizeof(struct files_struct), 0,
1777                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1778         fs_cachep = kmem_cache_create("fs_cache",
1779                         sizeof(struct fs_struct), 0,
1780                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1781         /*
1782          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1783          * whole struct cpumask for the OFFSTACK case. We could change
1784          * this to *only* allocate as much of it as required by the
1785          * maximum number of CPU's we can ever have.  The cpumask_allocation
1786          * is at the end of the structure, exactly for that reason.
1787          */
1788         mm_cachep = kmem_cache_create("mm_struct",
1789                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1790                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1791         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1792         mmap_init();
1793         nsproxy_cache_init();
1794 }
1795
1796 /*
1797  * Check constraints on flags passed to the unshare system call.
1798  */
1799 static int check_unshare_flags(unsigned long unshare_flags)
1800 {
1801         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1802                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1803                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1804                                 CLONE_NEWUSER|CLONE_NEWPID))
1805                 return -EINVAL;
1806         /*
1807          * Not implemented, but pretend it works if there is nothing to
1808          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1809          * needs to unshare vm.
1810          */
1811         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1812                 /* FIXME: get_task_mm() increments ->mm_users */
1813                 if (atomic_read(&current->mm->mm_users) > 1)
1814                         return -EINVAL;
1815         }
1816
1817         return 0;
1818 }
1819
1820 /*
1821  * Unshare the filesystem structure if it is being shared
1822  */
1823 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1824 {
1825         struct fs_struct *fs = current->fs;
1826
1827         if (!(unshare_flags & CLONE_FS) || !fs)
1828                 return 0;
1829
1830         /* don't need lock here; in the worst case we'll do useless copy */
1831         if (fs->users == 1)
1832                 return 0;
1833
1834         *new_fsp = copy_fs_struct(fs);
1835         if (!*new_fsp)
1836                 return -ENOMEM;
1837
1838         return 0;
1839 }
1840
1841 /*
1842  * Unshare file descriptor table if it is being shared
1843  */
1844 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1845 {
1846         struct files_struct *fd = current->files;
1847         int error = 0;
1848
1849         if ((unshare_flags & CLONE_FILES) &&
1850             (fd && atomic_read(&fd->count) > 1)) {
1851                 *new_fdp = dup_fd(fd, &error);
1852                 if (!*new_fdp)
1853                         return error;
1854         }
1855
1856         return 0;
1857 }
1858
1859 /*
1860  * unshare allows a process to 'unshare' part of the process
1861  * context which was originally shared using clone.  copy_*
1862  * functions used by do_fork() cannot be used here directly
1863  * because they modify an inactive task_struct that is being
1864  * constructed. Here we are modifying the current, active,
1865  * task_struct.
1866  */
1867 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1868 {
1869         struct fs_struct *fs, *new_fs = NULL;
1870         struct files_struct *fd, *new_fd = NULL;
1871         struct cred *new_cred = NULL;
1872         struct nsproxy *new_nsproxy = NULL;
1873         int do_sysvsem = 0;
1874         int err;
1875
1876         /*
1877          * If unsharing a user namespace must also unshare the thread.
1878          */
1879         if (unshare_flags & CLONE_NEWUSER)
1880                 unshare_flags |= CLONE_THREAD | CLONE_FS;
1881         /*
1882          * If unsharing a thread from a thread group, must also unshare vm.
1883          */
1884         if (unshare_flags & CLONE_THREAD)
1885                 unshare_flags |= CLONE_VM;
1886         /*
1887          * If unsharing vm, must also unshare signal handlers.
1888          */
1889         if (unshare_flags & CLONE_VM)
1890                 unshare_flags |= CLONE_SIGHAND;
1891         /*
1892          * If unsharing namespace, must also unshare filesystem information.
1893          */
1894         if (unshare_flags & CLONE_NEWNS)
1895                 unshare_flags |= CLONE_FS;
1896
1897         err = check_unshare_flags(unshare_flags);
1898         if (err)
1899                 goto bad_unshare_out;
1900         /*
1901          * CLONE_NEWIPC must also detach from the undolist: after switching
1902          * to a new ipc namespace, the semaphore arrays from the old
1903          * namespace are unreachable.
1904          */
1905         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1906                 do_sysvsem = 1;
1907         err = unshare_fs(unshare_flags, &new_fs);
1908         if (err)
1909                 goto bad_unshare_out;
1910         err = unshare_fd(unshare_flags, &new_fd);
1911         if (err)
1912                 goto bad_unshare_cleanup_fs;
1913         err = unshare_userns(unshare_flags, &new_cred);
1914         if (err)
1915                 goto bad_unshare_cleanup_fd;
1916         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1917                                          new_cred, new_fs);
1918         if (err)
1919                 goto bad_unshare_cleanup_cred;
1920
1921         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1922                 if (do_sysvsem) {
1923                         /*
1924                          * CLONE_SYSVSEM is equivalent to sys_exit().
1925                          */
1926                         exit_sem(current);
1927                 }
1928                 if (unshare_flags & CLONE_NEWIPC) {
1929                         /* Orphan segments in old ns (see sem above). */
1930                         exit_shm(current);
1931                         shm_init_task(current);
1932                 }
1933
1934                 if (new_nsproxy)
1935                         switch_task_namespaces(current, new_nsproxy);
1936
1937                 task_lock(current);
1938
1939                 if (new_fs) {
1940                         fs = current->fs;
1941                         spin_lock(&fs->lock);
1942                         current->fs = new_fs;
1943                         if (--fs->users)
1944                                 new_fs = NULL;
1945                         else
1946                                 new_fs = fs;
1947                         spin_unlock(&fs->lock);
1948                 }
1949
1950                 if (new_fd) {
1951                         fd = current->files;
1952                         current->files = new_fd;
1953                         new_fd = fd;
1954                 }
1955
1956                 task_unlock(current);
1957
1958                 if (new_cred) {
1959                         /* Install the new user namespace */
1960                         commit_creds(new_cred);
1961                         new_cred = NULL;
1962                 }
1963         }
1964
1965 bad_unshare_cleanup_cred:
1966         if (new_cred)
1967                 put_cred(new_cred);
1968 bad_unshare_cleanup_fd:
1969         if (new_fd)
1970                 put_files_struct(new_fd);
1971
1972 bad_unshare_cleanup_fs:
1973         if (new_fs)
1974                 free_fs_struct(new_fs);
1975
1976 bad_unshare_out:
1977         return err;
1978 }
1979
1980 /*
1981  *      Helper to unshare the files of the current task.
1982  *      We don't want to expose copy_files internals to
1983  *      the exec layer of the kernel.
1984  */
1985
1986 int unshare_files(struct files_struct **displaced)
1987 {
1988         struct task_struct *task = current;
1989         struct files_struct *copy = NULL;
1990         int error;
1991
1992         error = unshare_fd(CLONE_FILES, &copy);
1993         if (error || !copy) {
1994                 *displaced = NULL;
1995                 return error;
1996         }
1997         *displaced = task->files;
1998         task_lock(task);
1999         task->files = copy;
2000         task_unlock(task);
2001         return 0;
2002 }