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/hmm.h>
  31 #include <linux/fs.h>
  32 #include <linux/nsproxy.h>
  33 #include <linux/capability.h>
  34 #include <linux/cpu.h>
  35 #include <linux/cgroup.h>
  36 #include <linux/security.h>
  37 #include <linux/hugetlb.h>
  38 #include <linux/seccomp.h>
  39 #include <linux/swap.h>
  40 #include <linux/syscalls.h>
  41 #include <linux/jiffies.h>
  42 #include <linux/futex.h>
  43 #include <linux/compat.h>
  44 #include <linux/kthread.h>
  45 #include <linux/task_io_accounting_ops.h>
  46 #include <linux/rcupdate.h>
  47 #include <linux/ptrace.h>
  48 #include <linux/mount.h>
  49 #include <linux/audit.h>
  50 #include <linux/memcontrol.h>
  51 #include <linux/ftrace.h>
  52 #include <linux/proc_fs.h>
  53 #include <linux/profile.h>
  54 #include <linux/rmap.h>
  55 #include <linux/ksm.h>
  56 #include <linux/acct.h>
  57 #include <linux/tsacct_kern.h>
  58 #include <linux/cn_proc.h>
  59 #include <linux/freezer.h>
  60 #include <linux/delayacct.h>
  61 #include <linux/taskstats_kern.h>
  62 #include <linux/random.h>
  63 #include <linux/tty.h>
  64 #include <linux/blkdev.h>
  65 #include <linux/fs_struct.h>
  66 #include <linux/magic.h>
  67 #include <linux/perf_event.h>
  68 #include <linux/posix-timers.h>
  69 #include <linux/user-return-notifier.h>
  70 #include <linux/oom.h>
  71 #include <linux/khugepaged.h>
  72 #include <linux/signalfd.h>
  73 #include <linux/uprobes.h>
  74 #include <linux/aio.h>
  75
  76 #include <asm/pgtable.h>
  77 #include <asm/pgalloc.h>
  78 #include <asm/uaccess.h>
  79 #include <asm/mmu_context.h>
  80 #include <asm/cacheflush.h>
  81 #include <asm/tlbflush.h>
  82
  83 #include <trace/events/sched.h>
  84 #include <trace/events/sys_calls.h>
  85
  86 #define CREATE_TRACE_POINTS
  87 #include <trace/events/task.h>
  88
  89 /*
  90  * Protected counters by write_lock_irq(&tasklist_lock)
  91  */
  92 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  93 int nr_threads;                 /* The idle threads do not count.. */
  94
  95 int max_threads;                /* tunable limit on nr_threads */
  96
  97 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  98
  99 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 100
 101 #ifdef CONFIG_PROVE_RCU
 102 int lockdep_tasklist_lock_is_held(void)
 103 {
 104         return lockdep_is_held(&tasklist_lock);
 105 }
 106 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 107 #endif /* #ifdef CONFIG_PROVE_RCU */
 108
 109 int nr_processes(void)
 110 {
 111         int cpu;
 112         int total = 0;
 113
 114         for_each_possible_cpu(cpu)
 115                 total += per_cpu(process_counts, cpu);
 116
 117         return total;
 118 }
 119
 120 void __weak arch_release_task_struct(struct task_struct *tsk)
 121 {
 122 }
 123
 124 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 125 static struct kmem_cache *task_struct_cachep;
 126
 127 static inline struct task_struct *alloc_task_struct_node(int node)
 128 {
 129         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 130 }
 131
 132 static inline void free_task_struct(struct task_struct *tsk)
 133 {
 134         kmem_cache_free(task_struct_cachep, tsk);
 135 }
 136 #endif
 137
 138 void __weak arch_release_thread_info(struct thread_info *ti)
 139 {
 140 }
 141
 142 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 143
 144 /*
 145  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 146  * kmemcache based allocator.
 147  */
 148 # if THREAD_SIZE >= PAGE_SIZE
 149 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 150                                                   int node)
 151 {
 152         struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
 153                                              THREAD_SIZE_ORDER);
 154
 155         return page ? page_address(page) : NULL;
 156 }
 157
 158 static inline void free_thread_info(struct thread_info *ti)
 159 {
 160         free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 161 }
 162 # else
 163 static struct kmem_cache *thread_info_cache;
 164
 165 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 166                                                   int node)
 167 {
 168         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 169 }
 170
 171 static void free_thread_info(struct thread_info *ti)
 172 {
 173         kmem_cache_free(thread_info_cache, ti);
 174 }
 175
 176 void thread_info_cache_init(void)
 177 {
 178         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 179                                               THREAD_SIZE, 0, NULL);
 180         BUG_ON(thread_info_cache == NULL);
 181 }
 182 # endif
 183 #endif
 184
 185 /* SLAB cache for signal_struct structures (tsk->signal) */
 186 static struct kmem_cache *signal_cachep;
 187
 188 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 189 struct kmem_cache *sighand_cachep;
 190
 191 /* SLAB cache for files_struct structures (tsk->files) */
 192 struct kmem_cache *files_cachep;
 193
 194 /* SLAB cache for fs_struct structures (tsk->fs) */
 195 struct kmem_cache *fs_cachep;
 196
 197 /* SLAB cache for vm_area_struct structures */
 198 struct kmem_cache *vm_area_cachep;
 199
 200 /* SLAB cache for mm_struct structures (tsk->mm) */
 201 static struct kmem_cache *mm_cachep;
 202
 203 /* Notifier list called when a task struct is freed */
 204 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 205
 206 static void account_kernel_stack(struct thread_info *ti, int account)
 207 {
 208         struct zone *zone = page_zone(virt_to_page(ti));
 209
 210         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 211 }
 212
 213 void free_task(struct task_struct *tsk)
 214 {
 215         account_kernel_stack(tsk->stack, -1);
 216         arch_release_thread_info(tsk->stack);
 217         free_thread_info(tsk->stack);
 218         rt_mutex_debug_task_free(tsk);
 219         ftrace_graph_exit_task(tsk);
 220         put_seccomp_filter(tsk);
 221         arch_release_task_struct(tsk);
 222         free_task_struct(tsk);
 223 }
 224 EXPORT_SYMBOL(free_task);
 225
 226 static inline void free_signal_struct(struct signal_struct *sig)
 227 {
 228         taskstats_tgid_free(sig);
 229         sched_autogroup_exit(sig);
 230         kmem_cache_free(signal_cachep, sig);
 231 }
 232
 233 static inline void put_signal_struct(struct signal_struct *sig)
 234 {
 235         if (atomic_dec_and_test(&sig->sigcnt))
 236                 free_signal_struct(sig);
 237 }
 238
 239 int task_free_register(struct notifier_block *n)
 240 {
 241         return atomic_notifier_chain_register(&task_free_notifier, n);
 242 }
 243 EXPORT_SYMBOL(task_free_register);
 244
 245 int task_free_unregister(struct notifier_block *n)
 246 {
 247         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 248 }
 249 EXPORT_SYMBOL(task_free_unregister);
 250
 251 void __put_task_struct(struct task_struct *tsk)
 252 {
 253         WARN_ON(!tsk->exit_state);
 254         WARN_ON(atomic_read(&tsk->usage));
 255         WARN_ON(tsk == current);
 256
 257         security_task_free(tsk);
 258         exit_creds(tsk);
 259         delayacct_tsk_free(tsk);
 260         put_signal_struct(tsk->signal);
 261
 262         atomic_notifier_call_chain(&task_free_notifier, 0, tsk);
 263         if (!profile_handoff_task(tsk))
 264                 free_task(tsk);
 265 }
 266 EXPORT_SYMBOL_GPL(__put_task_struct);
 267
 268 void __init __weak arch_task_cache_init(void) { }
 269
 270 void __init fork_init(unsigned long mempages)
 271 {
 272 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 273 #ifndef ARCH_MIN_TASKALIGN
 274 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 275 #endif
 276         /* create a slab on which task_structs can be allocated */
 277         task_struct_cachep =
 278                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 279                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 280 #endif
 281
 282         /* do the arch specific task caches init */
 283         arch_task_cache_init();
 284
 285         /*
 286          * The default maximum number of threads is set to a safe
 287          * value: the thread structures can take up at most half
 288          * of memory.
 289          */
 290         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 291
 292         /*
 293          * we need to allow at least 20 threads to boot a system
 294          */
 295         if (max_threads < 20)
 296                 max_threads = 20;
 297
 298         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 299         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 300         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 301                 init_task.signal->rlim[RLIMIT_NPROC];
 302 }
 303
 304 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 305                                                struct task_struct *src)
 306 {
 307         *dst = *src;
 308         return 0;
 309 }
 310
 311 static struct task_struct *dup_task_struct(struct task_struct *orig)
 312 {
 313         struct task_struct *tsk;
 314         struct thread_info *ti;
 315         unsigned long *stackend;
 316         int node = tsk_fork_get_node(orig);
 317         int err;
 318
 319         tsk = alloc_task_struct_node(node);
 320         if (!tsk)
 321                 return NULL;
 322
 323         ti = alloc_thread_info_node(tsk, node);
 324         if (!ti)
 325                 goto free_tsk;
 326
 327         err = arch_dup_task_struct(tsk, orig);
 328         if (err)
 329                 goto free_ti;
 330
 331         tsk->stack = ti;
 332 #ifdef CONFIG_SECCOMP
 333         /*
 334          * We must handle setting up seccomp filters once we're under
 335          * the sighand lock in case orig has changed between now and
 336          * then. Until then, filter must be NULL to avoid messing up
 337          * the usage counts on the error path calling free_task.
 338          */
 339         tsk->seccomp.filter = NULL;
 340 #endif
 341
 342         setup_thread_stack(tsk, orig);
 343         clear_user_return_notifier(tsk);
 344         clear_tsk_need_resched(tsk);
 345         stackend = end_of_stack(tsk);
 346         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 347
 348 #ifdef CONFIG_CC_STACKPROTECTOR
 349         tsk->stack_canary = get_random_int();
 350 #endif
 351
 352         /*
 353          * One for us, one for whoever does the "release_task()" (usually
 354          * parent)
 355          */
 356         atomic_set(&tsk->usage, 2);
 357 #ifdef CONFIG_BLK_DEV_IO_TRACE
 358         tsk->btrace_seq = 0;
 359 #endif
 360         tsk->splice_pipe = NULL;
 361         tsk->task_frag.page = NULL;
 362
 363         account_kernel_stack(ti, 1);
 364
 365         return tsk;
 366
 367 free_ti:
 368         free_thread_info(ti);
 369 free_tsk:
 370         free_task_struct(tsk);
 371         return NULL;
 372 }
 373
 374 #ifdef CONFIG_MMU
 375 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 376 {
 377         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 378         struct rb_node **rb_link, *rb_parent;
 379         int retval;
 380         unsigned long charge;
 381         struct mempolicy *pol;
 382
 383         uprobe_start_dup_mmap();
 384         down_write(&oldmm->mmap_sem);
 385         flush_cache_dup_mm(oldmm);
 386         uprobe_dup_mmap(oldmm, mm);
 387         /*
 388          * Not linked in yet - no deadlock potential:
 389          */
 390         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 391
 392         mm->locked_vm = 0;
 393         mm->mmap = NULL;
 394         mm->mmap_cache = NULL;
 395         mm->free_area_cache = oldmm->mmap_base;
 396         mm->cached_hole_size = ~0UL;
 397         mm->map_count = 0;
 398         cpumask_clear(mm_cpumask(mm));
 399         mm->mm_rb = RB_ROOT;
 400         rb_link = &mm->mm_rb.rb_node;
 401         rb_parent = NULL;
 402         pprev = &mm->mmap;
 403         retval = ksm_fork(mm, oldmm);
 404         if (retval)
 405                 goto out;
 406         retval = khugepaged_fork(mm, oldmm);
 407         if (retval)
 408                 goto out;
 409
 410         prev = NULL;
 411         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 412                 struct file *file;
 413
 414                 if (mpnt->vm_flags & VM_DONTCOPY) {
 415                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 416                                                         -vma_pages(mpnt));
 417                         continue;
 418                 }
 419                 charge = 0;
 420                 if (mpnt->vm_flags & VM_ACCOUNT) {
 421                         unsigned long len = vma_pages(mpnt);
 422
 423                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 424                                 goto fail_nomem;
 425                         charge = len;
 426                 }
 427                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 428                 if (!tmp)
 429                         goto fail_nomem;
 430                 *tmp = *mpnt;
 431                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 432                 pol = mpol_dup(vma_policy(mpnt));
 433                 retval = PTR_ERR(pol);
 434                 if (IS_ERR(pol))
 435                         goto fail_nomem_policy;
 436                 vma_set_policy(tmp, pol);
 437                 tmp->vm_mm = mm;
 438                 if (anon_vma_fork(tmp, mpnt))
 439                         goto fail_nomem_anon_vma_fork;
 440                 tmp->vm_flags &= ~VM_LOCKED;
 441                 tmp->vm_next = tmp->vm_prev = NULL;
 442                 file = tmp->vm_file;
 443                 if (file) {
 444                         struct inode *inode = file_inode(file);
 445                         struct address_space *mapping = file->f_mapping;
 446
 447                         get_file(file);
 448                         if (tmp->vm_flags & VM_DENYWRITE)
 449                                 atomic_dec(&inode->i_writecount);
 450                         mutex_lock(&mapping->i_mmap_mutex);
 451                         if (tmp->vm_flags & VM_SHARED)
 452                                 mapping->i_mmap_writable++;
 453                         flush_dcache_mmap_lock(mapping);
 454                         /* insert tmp into the share list, just after mpnt */
 455                         if (unlikely(tmp->vm_flags & VM_NONLINEAR))
 456                                 vma_nonlinear_insert(tmp,
 457                                                 &mapping->i_mmap_nonlinear);
 458                         else
 459                                 vma_interval_tree_insert_after(tmp, mpnt,
 460                                                         &mapping->i_mmap);
 461                         flush_dcache_mmap_unlock(mapping);
 462                         mutex_unlock(&mapping->i_mmap_mutex);
 463                 }
 464
 465                 /*
 466                  * Clear hugetlb-related page reserves for children. This only
 467                  * affects MAP_PRIVATE mappings. Faults generated by the child
 468                  * are not guaranteed to succeed, even if read-only
 469                  */
 470                 if (is_vm_hugetlb_page(tmp))
 471                         reset_vma_resv_huge_pages(tmp);
 472
 473                 /*
 474                  * Link in the new vma and copy the page table entries.
 475                  */
 476                 *pprev = tmp;
 477                 pprev = &tmp->vm_next;
 478                 tmp->vm_prev = prev;
 479                 prev = tmp;
 480
 481                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 482                 rb_link = &tmp->vm_rb.rb_right;
 483                 rb_parent = &tmp->vm_rb;
 484
 485                 mm->map_count++;
 486                 retval = copy_page_range(mm, oldmm, mpnt);
 487
 488                 if (tmp->vm_ops && tmp->vm_ops->open)
 489                         tmp->vm_ops->open(tmp);
 490
 491                 if (retval)
 492                         goto out;
 493         }
 494         /* a new mm has just been created */
 495         arch_dup_mmap(oldmm, mm);
 496         retval = 0;
 497 out:
 498         up_write(&mm->mmap_sem);
 499         flush_tlb_mm(oldmm);
 500         up_write(&oldmm->mmap_sem);
 501         uprobe_end_dup_mmap();
 502         return retval;
 503 fail_nomem_anon_vma_fork:
 504         mpol_put(pol);
 505 fail_nomem_policy:
 506         kmem_cache_free(vm_area_cachep, tmp);
 507 fail_nomem:
 508         retval = -ENOMEM;
 509         vm_unacct_memory(charge);
 510         goto out;
 511 }
 512
 513 static inline int mm_alloc_pgd(struct mm_struct *mm)
 514 {
 515         mm->pgd = pgd_alloc(mm);
 516         if (unlikely(!mm->pgd))
 517                 return -ENOMEM;
 518         return 0;
 519 }
 520
 521 static inline void mm_free_pgd(struct mm_struct *mm)
 522 {
 523         pgd_free(mm, mm->pgd);
 524 }
 525 #else
 526 #define dup_mmap(mm, oldmm)     (0)
 527 #define mm_alloc_pgd(mm)        (0)
 528 #define mm_free_pgd(mm)
 529 #endif /* CONFIG_MMU */
 530
 531 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 532
 533 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 534 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 535
 536 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 537
 538 static int __init coredump_filter_setup(char *s)
 539 {
 540         default_dump_filter =
 541                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 542                 MMF_DUMP_FILTER_MASK;
 543         return 1;
 544 }
 545
 546 __setup("coredump_filter=", coredump_filter_setup);
 547
 548 #include <linux/init_task.h>
 549
 550 static void mm_init_aio(struct mm_struct *mm)
 551 {
 552 #ifdef CONFIG_AIO
 553         spin_lock_init(&mm->ioctx_lock);
 554         INIT_HLIST_HEAD(&mm->ioctx_list);
 555 #endif
 556 }
 557
 558 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 559 {
 560         atomic_set(&mm->mm_users, 1);
 561         atomic_set(&mm->mm_count, 1);
 562         init_rwsem(&mm->mmap_sem);
 563         INIT_LIST_HEAD(&mm->mmlist);
 564         mm->flags = (current->mm) ?
 565                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 566         mm->core_state = NULL;
 567         mm->nr_ptes = 0;
 568         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 569         spin_lock_init(&mm->page_table_lock);
 570         mm->free_area_cache = TASK_UNMAPPED_BASE;
 571         mm->cached_hole_size = ~0UL;
 572         mm_init_aio(mm);
 573         mm_init_owner(mm, p);
 574         hmm_mm_init(mm);
 575         clear_tlb_flush_pending(mm);
 576
 577         if (likely(!mm_alloc_pgd(mm))) {
 578                 mm->def_flags = 0;
 579                 mmu_notifier_mm_init(mm);
 580                 return mm;
 581         }
 582
 583         free_mm(mm);
 584         return NULL;
 585 }
 586
 587 static void check_mm(struct mm_struct *mm)
 588 {
 589         int i;
 590
 591         for (i = 0; i < NR_MM_COUNTERS; i++) {
 592                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 593
 594                 if (unlikely(x))
 595                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 596                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 597         }
 598
 599 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 600         VM_BUG_ON(mm->pmd_huge_pte);
 601 #endif
 602 }
 603
 604 /*
 605  * Allocate and initialize an mm_struct.
 606  */
 607 struct mm_struct *mm_alloc(void)
 608 {
 609         struct mm_struct *mm;
 610
 611         mm = allocate_mm();
 612         if (!mm)
 613                 return NULL;
 614
 615         memset(mm, 0, sizeof(*mm));
 616         mm_init_cpumask(mm);
 617         return mm_init(mm, current);
 618 }
 619
 620 /*
 621  * Called when the last reference to the mm
 622  * is dropped: either by a lazy thread or by
 623  * mmput. Free the page directory and the mm.
 624  */
 625 void __mmdrop(struct mm_struct *mm)
 626 {
 627         BUG_ON(mm == &init_mm);
 628         mm_free_pgd(mm);
 629         destroy_context(mm);
 630         mmu_notifier_mm_destroy(mm);
 631         check_mm(mm);
 632         free_mm(mm);
 633 }
 634 EXPORT_SYMBOL_GPL(__mmdrop);
 635
 636 /*
 637  * Decrement the use count and release all resources for an mm.
 638  */
 639 void mmput(struct mm_struct *mm)
 640 {
 641         might_sleep();
 642
 643         if (atomic_dec_and_test(&mm->mm_users)) {
 644                 uprobe_clear_state(mm);
 645                 exit_aio(mm);
 646                 ksm_exit(mm);
 647                 khugepaged_exit(mm); /* must run before exit_mmap */
 648                 exit_mmap(mm);
 649                 set_mm_exe_file(mm, NULL);
 650                 if (!list_empty(&mm->mmlist)) {
 651                         spin_lock(&mmlist_lock);
 652                         list_del(&mm->mmlist);
 653                         spin_unlock(&mmlist_lock);
 654                 }
 655                 if (mm->binfmt)
 656                         module_put(mm->binfmt->module);
 657                 mmdrop(mm);
 658         }
 659 }
 660 EXPORT_SYMBOL_GPL(mmput);
 661
 662 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 663 {
 664         if (new_exe_file)
 665                 get_file(new_exe_file);
 666         if (mm->exe_file)
 667                 fput(mm->exe_file);
 668         mm->exe_file = new_exe_file;
 669 }
 670
 671 struct file *get_mm_exe_file(struct mm_struct *mm)
 672 {
 673         struct file *exe_file;
 674
 675         /* We need mmap_sem to protect against races with removal of exe_file */
 676         down_read(&mm->mmap_sem);
 677         exe_file = mm->exe_file;
 678         if (exe_file)
 679                 get_file(exe_file);
 680         up_read(&mm->mmap_sem);
 681         return exe_file;
 682 }
 683
 684 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 685 {
 686         /* It's safe to write the exe_file pointer without exe_file_lock because
 687          * this is called during fork when the task is not yet in /proc */
 688         newmm->exe_file = get_mm_exe_file(oldmm);
 689 }
 690
 691 /**
 692  * get_task_mm - acquire a reference to the task's mm
 693  *
 694  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 695  * this kernel workthread has transiently adopted a user mm with use_mm,
 696  * to do its AIO) is not set and if so returns a reference to it, after
 697  * bumping up the use count.  User must release the mm via mmput()
 698  * after use.  Typically used by /proc and ptrace.
 699  */
 700 struct mm_struct *get_task_mm(struct task_struct *task)
 701 {
 702         struct mm_struct *mm;
 703
 704         task_lock(task);
 705         mm = task->mm;
 706         if (mm) {
 707                 if (task->flags & PF_KTHREAD)
 708                         mm = NULL;
 709                 else
 710                         atomic_inc(&mm->mm_users);
 711         }
 712         task_unlock(task);
 713         return mm;
 714 }
 715 EXPORT_SYMBOL_GPL(get_task_mm);
 716
 717 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 718 {
 719         struct mm_struct *mm;
 720         int err;
 721
 722         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 723         if (err)
 724                 return ERR_PTR(err);
 725
 726         mm = get_task_mm(task);
 727         if (mm && mm != current->mm &&
 728                         !ptrace_may_access(task, mode) &&
 729                         !capable(CAP_SYS_RESOURCE)) {
 730                 mmput(mm);
 731                 mm = ERR_PTR(-EACCES);
 732         }
 733         mutex_unlock(&task->signal->cred_guard_mutex);
 734
 735         return mm;
 736 }
 737
 738 static void complete_vfork_done(struct task_struct *tsk)
 739 {
 740         struct completion *vfork;
 741
 742         task_lock(tsk);
 743         vfork = tsk->vfork_done;
 744         if (likely(vfork)) {
 745                 tsk->vfork_done = NULL;
 746                 complete(vfork);
 747         }
 748         task_unlock(tsk);
 749 }
 750
 751 static int wait_for_vfork_done(struct task_struct *child,
 752                                 struct completion *vfork)
 753 {
 754         int killed;
 755
 756         freezer_do_not_count();
 757         killed = wait_for_completion_killable(vfork);
 758         freezer_count();
 759
 760         if (killed) {
 761                 task_lock(child);
 762                 child->vfork_done = NULL;
 763                 task_unlock(child);
 764         }
 765
 766         put_task_struct(child);
 767         return killed;
 768 }
 769
 770 /* Please note the differences between mmput and mm_release.
 771  * mmput is called whenever we stop holding onto a mm_struct,
 772  * error success whatever.
 773  *
 774  * mm_release is called after a mm_struct has been removed
 775  * from the current process.
 776  *
 777  * This difference is important for error handling, when we
 778  * only half set up a mm_struct for a new process and need to restore
 779  * the old one.  Because we mmput the new mm_struct before
 780  * restoring the old one. . .
 781  * Eric Biederman 10 January 1998
 782  */
 783 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 784 {
 785         /* Get rid of any futexes when releasing the mm */
 786 #ifdef CONFIG_FUTEX
 787         if (unlikely(tsk->robust_list)) {
 788                 exit_robust_list(tsk);
 789                 tsk->robust_list = NULL;
 790         }
 791 #ifdef CONFIG_COMPAT
 792         if (unlikely(tsk->compat_robust_list)) {
 793                 compat_exit_robust_list(tsk);
 794                 tsk->compat_robust_list = NULL;
 795         }
 796 #endif
 797         if (unlikely(!list_empty(&tsk->pi_state_list)))
 798                 exit_pi_state_list(tsk);
 799 #endif
 800
 801         uprobe_free_utask(tsk);
 802
 803         /* Get rid of any cached register state */
 804         deactivate_mm(tsk, mm);
 805
 806         /*
 807          * If we're exiting normally, clear a user-space tid field if
 808          * requested.  We leave this alone when dying by signal, to leave
 809          * the value intact in a core dump, and to save the unnecessary
 810          * trouble, say, a killed vfork parent shouldn't touch this mm.
 811          * Userland only wants this done for a sys_exit.
 812          */
 813         if (tsk->clear_child_tid) {
 814                 if (!(tsk->flags & PF_SIGNALED) &&
 815                     atomic_read(&mm->mm_users) > 1) {
 816                         /*
 817                          * We don't check the error code - if userspace has
 818                          * not set up a proper pointer then tough luck.
 819                          */
 820                         put_user(0, tsk->clear_child_tid);
 821                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 822                                         1, NULL, NULL, 0);
 823                 }
 824                 tsk->clear_child_tid = NULL;
 825         }
 826
 827         /*
 828          * All done, finally we can wake up parent and return this mm to him.
 829          * Also kthread_stop() uses this completion for synchronization.
 830          */
 831         if (tsk->vfork_done)
 832                 complete_vfork_done(tsk);
 833 }
 834
 835 /*
 836  * Allocate a new mm structure and copy contents from the
 837  * mm structure of the passed in task structure.
 838  */
 839 struct mm_struct *dup_mm(struct task_struct *tsk)
 840 {
 841         struct mm_struct *mm, *oldmm = current->mm;
 842         int err;
 843
 844         if (!oldmm)
 845                 return NULL;
 846
 847         mm = allocate_mm();
 848         if (!mm)
 849                 goto fail_nomem;
 850
 851         memcpy(mm, oldmm, sizeof(*mm));
 852         mm_init_cpumask(mm);
 853
 854 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 855         mm->pmd_huge_pte = NULL;
 856 #endif
 857 #ifdef CONFIG_NUMA_BALANCING
 858         mm->first_nid = NUMA_PTE_SCAN_INIT;
 859 #endif
 860         if (!mm_init(mm, tsk))
 861                 goto fail_nomem;
 862
 863         if (init_new_context(tsk, mm))
 864                 goto fail_nocontext;
 865
 866         dup_mm_exe_file(oldmm, mm);
 867
 868         err = dup_mmap(mm, oldmm);
 869         if (err)
 870                 goto free_pt;
 871
 872         mm->hiwater_rss = get_mm_rss(mm);
 873         mm->hiwater_vm = mm->total_vm;
 874
 875         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 876                 goto free_pt;
 877
 878         return mm;
 879
 880 free_pt:
 881         /* don't put binfmt in mmput, we haven't got module yet */
 882         mm->binfmt = NULL;
 883         mmput(mm);
 884
 885 fail_nomem:
 886         return NULL;
 887
 888 fail_nocontext:
 889         /*
 890          * If init_new_context() failed, we cannot use mmput() to free the mm
 891          * because it calls destroy_context()
 892          */
 893         mm_free_pgd(mm);
 894         free_mm(mm);
 895         return NULL;
 896 }
 897
 898 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 899 {
 900         struct mm_struct *mm, *oldmm;
 901         int retval;
 902
 903         tsk->min_flt = tsk->maj_flt = 0;
 904         tsk->nvcsw = tsk->nivcsw = 0;
 905 #ifdef CONFIG_DETECT_HUNG_TASK
 906         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 907 #endif
 908
 909         tsk->mm = NULL;
 910         tsk->active_mm = NULL;
 911
 912         /*
 913          * Are we cloning a kernel thread?
 914          *
 915          * We need to steal a active VM for that..
 916          */
 917         oldmm = current->mm;
 918         if (!oldmm)
 919                 return 0;
 920
 921         if (clone_flags & CLONE_VM) {
 922                 atomic_inc(&oldmm->mm_users);
 923                 mm = oldmm;
 924                 goto good_mm;
 925         }
 926
 927         retval = -ENOMEM;
 928         mm = dup_mm(tsk);
 929         if (!mm)
 930                 goto fail_nomem;
 931
 932 good_mm:
 933         tsk->mm = mm;
 934         tsk->active_mm = mm;
 935         return 0;
 936
 937 fail_nomem:
 938         return retval;
 939 }
 940
 941 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 942 {
 943         struct fs_struct *fs = current->fs;
 944         if (clone_flags & CLONE_FS) {
 945                 /* tsk->fs is already what we want */
 946                 spin_lock(&fs->lock);
 947                 if (fs->in_exec) {
 948                         spin_unlock(&fs->lock);
 949                         return -EAGAIN;
 950                 }
 951                 fs->users++;
 952                 spin_unlock(&fs->lock);
 953                 return 0;
 954         }
 955         tsk->fs = copy_fs_struct(fs);
 956         if (!tsk->fs)
 957                 return -ENOMEM;
 958         return 0;
 959 }
 960
 961 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 962 {
 963         struct files_struct *oldf, *newf;
 964         int error = 0;
 965
 966         /*
 967          * A background process may not have any files ...
 968          */
 969         oldf = current->files;
 970         if (!oldf)
 971                 goto out;
 972
 973         if (clone_flags & CLONE_FILES) {
 974                 atomic_inc(&oldf->count);
 975                 goto out;
 976         }
 977
 978         newf = dup_fd(oldf, &error);
 979         if (!newf)
 980                 goto out;
 981
 982         tsk->files = newf;
 983         error = 0;
 984 out:
 985         return error;
 986 }
 987
 988 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 989 {
 990 #ifdef CONFIG_BLOCK
 991         struct io_context *ioc = current->io_context;
 992         struct io_context *new_ioc;
 993
 994         if (!ioc)
 995                 return 0;
 996         /*
 997          * Share io context with parent, if CLONE_IO is set
 998          */
 999         if (clone_flags & CLONE_IO) {
1000                 ioc_task_link(ioc);
1001                 tsk->io_context = ioc;
1002         } else if (ioprio_valid(ioc->ioprio)) {
1003                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1004                 if (unlikely(!new_ioc))
1005                         return -ENOMEM;
1006
1007                 new_ioc->ioprio = ioc->ioprio;
1008                 put_io_context(new_ioc);
1009         }
1010 #endif
1011         return 0;
1012 }
1013
1014 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1015 {
1016         struct sighand_struct *sig;
1017
1018         if (clone_flags & CLONE_SIGHAND) {
1019                 atomic_inc(&current->sighand->count);
1020                 return 0;
1021         }
1022         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1023         rcu_assign_pointer(tsk->sighand, sig);
1024         if (!sig)
1025                 return -ENOMEM;
1026         atomic_set(&sig->count, 1);
1027         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1028         return 0;
1029 }
1030
1031 void __cleanup_sighand(struct sighand_struct *sighand)
1032 {
1033         if (atomic_dec_and_test(&sighand->count)) {
1034                 signalfd_cleanup(sighand);
1035                 kmem_cache_free(sighand_cachep, sighand);
1036         }
1037 }
1038
1039
1040 /*
1041  * Initialize POSIX timer handling for a thread group.
1042  */
1043 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1044 {
1045         unsigned long cpu_limit;
1046
1047         /* Thread group counters. */
1048         thread_group_cputime_init(sig);
1049
1050         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1051         if (cpu_limit != RLIM_INFINITY) {
1052                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1053                 sig->cputimer.running = 1;
1054         }
1055
1056         /* The timer lists. */
1057         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1058         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1059         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1060 }
1061
1062 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1063 {
1064         struct signal_struct *sig;
1065
1066         if (clone_flags & CLONE_THREAD)
1067                 return 0;
1068
1069         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1070         tsk->signal = sig;
1071         if (!sig)
1072                 return -ENOMEM;
1073
1074         sig->nr_threads = 1;
1075         atomic_set(&sig->live, 1);
1076         atomic_set(&sig->sigcnt, 1);
1077
1078         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1079         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1080         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1081
1082         init_waitqueue_head(&sig->wait_chldexit);
1083         sig->curr_target = tsk;
1084         init_sigpending(&sig->shared_pending);
1085         INIT_LIST_HEAD(&sig->posix_timers);
1086
1087         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1088         sig->real_timer.function = it_real_fn;
1089
1090         task_lock(current->group_leader);
1091         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1092         task_unlock(current->group_leader);
1093
1094         posix_cpu_timers_init_group(sig);
1095
1096         tty_audit_fork(sig);
1097         sched_autogroup_fork(sig);
1098
1099 #ifdef CONFIG_CGROUPS
1100         init_rwsem(&sig->group_rwsem);
1101 #endif
1102
1103         sig->oom_score_adj = current->signal->oom_score_adj;
1104         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1105
1106         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1107                                    current->signal->is_child_subreaper;
1108
1109         mutex_init(&sig->cred_guard_mutex);
1110
1111         return 0;
1112 }
1113
1114 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1115 {
1116         unsigned long new_flags = p->flags;
1117
1118         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1119         new_flags |= PF_FORKNOEXEC;
1120         p->flags = new_flags;
1121 }
1122
1123 static void copy_seccomp(struct task_struct *p)
1124 {
1125 #ifdef CONFIG_SECCOMP
1126         /*
1127          * Must be called with sighand->lock held, which is common to
1128          * all threads in the group. Holding cred_guard_mutex is not
1129          * needed because this new task is not yet running and cannot
1130          * be racing exec.
1131          */
1132         assert_spin_locked(&current->sighand->siglock);
1133
1134         /* Ref-count the new filter user, and assign it. */
1135         get_seccomp_filter(current);
1136         p->seccomp = current->seccomp;
1137
1138         /*
1139          * Explicitly enable no_new_privs here in case it got set
1140          * between the task_struct being duplicated and holding the
1141          * sighand lock. The seccomp state and nnp must be in sync.
1142          */
1143         if (task_no_new_privs(current))
1144                 task_set_no_new_privs(p);
1145
1146         /*
1147          * If the parent gained a seccomp mode after copying thread
1148          * flags and between before we held the sighand lock, we have
1149          * to manually enable the seccomp thread flag here.
1150          */
1151         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1152                 set_tsk_thread_flag(p, TIF_SECCOMP);
1153 #endif
1154 }
1155
1156 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1157 {
1158         current->clear_child_tid = tidptr;
1159
1160         return task_pid_vnr(current);
1161 }
1162
1163 static void rt_mutex_init_task(struct task_struct *p)
1164 {
1165         raw_spin_lock_init(&p->pi_lock);
1166 #ifdef CONFIG_RT_MUTEXES
1167         plist_head_init(&p->pi_waiters);
1168         p->pi_blocked_on = NULL;
1169 #endif
1170 }
1171
1172 #ifdef CONFIG_MM_OWNER
1173 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1174 {
1175         mm->owner = p;
1176 }
1177 #endif /* CONFIG_MM_OWNER */
1178
1179 /*
1180  * Initialize POSIX timer handling for a single task.
1181  */
1182 static void posix_cpu_timers_init(struct task_struct *tsk)
1183 {
1184         tsk->cputime_expires.prof_exp = 0;
1185         tsk->cputime_expires.virt_exp = 0;
1186         tsk->cputime_expires.sched_exp = 0;
1187         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1188         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1189         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1190 }
1191
1192 /*
1193  * This creates a new process as a copy of the old one,
1194  * but does not actually start it yet.
1195  *
1196  * It copies the registers, and all the appropriate
1197  * parts of the process environment (as per the clone
1198  * flags). The actual kick-off is left to the caller.
1199  */
1200 static struct task_struct *copy_process(unsigned long clone_flags,
1201                                         unsigned long stack_start,
1202                                         unsigned long stack_size,
1203                                         int __user *child_tidptr,
1204                                         struct pid *pid,
1205                                         int trace)
1206 {
1207         int retval;
1208         struct task_struct *p;
1209
1210         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1211                 return ERR_PTR(-EINVAL);
1212
1213         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1214                 return ERR_PTR(-EINVAL);
1215
1216         /*
1217          * Thread groups must share signals as well, and detached threads
1218          * can only be started up within the thread group.
1219          */
1220         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1221                 return ERR_PTR(-EINVAL);
1222
1223         /*
1224          * Shared signal handlers imply shared VM. By way of the above,
1225          * thread groups also imply shared VM. Blocking this case allows
1226          * for various simplifications in other code.
1227          */
1228         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1229                 return ERR_PTR(-EINVAL);
1230
1231         /*
1232          * Siblings of global init remain as zombies on exit since they are
1233          * not reaped by their parent (swapper). To solve this and to avoid
1234          * multi-rooted process trees, prevent global and container-inits
1235          * from creating siblings.
1236          */
1237         if ((clone_flags & CLONE_PARENT) &&
1238                                 current->signal->flags & SIGNAL_UNKILLABLE)
1239                 return ERR_PTR(-EINVAL);
1240
1241         /*
1242          * If the new process will be in a different pid namespace don't
1243          * allow it to share a thread group or signal handlers with the
1244          * forking task.
1245          */
1246         if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
1247             (task_active_pid_ns(current) != current->nsproxy->pid_ns))
1248                 return ERR_PTR(-EINVAL);
1249
1250         retval = security_task_create(clone_flags);
1251         if (retval)
1252                 goto fork_out;
1253
1254         retval = -ENOMEM;
1255         p = dup_task_struct(current);
1256         if (!p)
1257                 goto fork_out;
1258
1259         ftrace_graph_init_task(p);
1260
1261         rt_mutex_init_task(p);
1262
1263 #ifdef CONFIG_PROVE_LOCKING
1264         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1265         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1266 #endif
1267         retval = -EAGAIN;
1268         if (atomic_read(&p->real_cred->user->processes) >=
1269                         task_rlimit(p, RLIMIT_NPROC)) {
1270                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1271                     p->real_cred->user != INIT_USER)
1272                         goto bad_fork_free;
1273         }
1274         current->flags &= ~PF_NPROC_EXCEEDED;
1275
1276         retval = copy_creds(p, clone_flags);
1277         if (retval < 0)
1278                 goto bad_fork_free;
1279
1280         /*
1281          * If multiple threads are within copy_process(), then this check
1282          * triggers too late. This doesn't hurt, the check is only there
1283          * to stop root fork bombs.
1284          */
1285         retval = -EAGAIN;
1286         if (nr_threads >= max_threads)
1287                 goto bad_fork_cleanup_count;
1288
1289         p->did_exec = 0;
1290         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1291         copy_flags(clone_flags, p);
1292         INIT_LIST_HEAD(&p->children);
1293         INIT_LIST_HEAD(&p->sibling);
1294         rcu_copy_process(p);
1295         p->vfork_done = NULL;
1296         spin_lock_init(&p->alloc_lock);
1297
1298         init_sigpending(&p->pending);
1299
1300         p->utime = p->stime = p->gtime = 0;
1301         p->utimescaled = p->stimescaled = 0;
1302 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1303         p->prev_cputime.utime = p->prev_cputime.stime = 0;
1304 #endif
1305 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1306         seqlock_init(&p->vtime_seqlock);
1307         p->vtime_snap = 0;
1308         p->vtime_snap_whence = VTIME_SLEEPING;
1309 #endif
1310
1311 #if defined(SPLIT_RSS_COUNTING)
1312         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1313 #endif
1314
1315         p->default_timer_slack_ns = current->timer_slack_ns;
1316
1317         task_io_accounting_init(&p->ioac);
1318         acct_clear_integrals(p);
1319
1320         posix_cpu_timers_init(p);
1321
1322         do_posix_clock_monotonic_gettime(&p->start_time);
1323         p->real_start_time = p->start_time;
1324         monotonic_to_bootbased(&p->real_start_time);
1325         p->io_context = NULL;
1326         p->audit_context = NULL;
1327         if (clone_flags & CLONE_THREAD)
1328                 threadgroup_change_begin(current);
1329         cgroup_fork(p);
1330 #ifdef CONFIG_NUMA
1331         p->mempolicy = mpol_dup(p->mempolicy);
1332         if (IS_ERR(p->mempolicy)) {
1333                 retval = PTR_ERR(p->mempolicy);
1334                 p->mempolicy = NULL;
1335                 goto bad_fork_cleanup_cgroup;
1336         }
1337         mpol_fix_fork_child_flag(p);
1338 #endif
1339 #ifdef CONFIG_CPUSETS
1340         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1341         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1342         seqcount_init(&p->mems_allowed_seq);
1343 #endif
1344 #ifdef CONFIG_TRACE_IRQFLAGS
1345         p->irq_events = 0;
1346         p->hardirqs_enabled = 0;
1347         p->hardirq_enable_ip = 0;
1348         p->hardirq_enable_event = 0;
1349         p->hardirq_disable_ip = _THIS_IP_;
1350         p->hardirq_disable_event = 0;
1351         p->softirqs_enabled = 1;
1352         p->softirq_enable_ip = _THIS_IP_;
1353         p->softirq_enable_event = 0;
1354         p->softirq_disable_ip = 0;
1355         p->softirq_disable_event = 0;
1356         p->hardirq_context = 0;
1357         p->softirq_context = 0;
1358 #endif
1359 #ifdef CONFIG_LOCKDEP
1360         p->lockdep_depth = 0; /* no locks held yet */
1361         p->curr_chain_key = 0;
1362         p->lockdep_recursion = 0;
1363 #endif
1364
1365 #ifdef CONFIG_DEBUG_MUTEXES
1366         p->blocked_on = NULL; /* not blocked yet */
1367 #endif
1368 #ifdef CONFIG_MEMCG
1369         p->memcg_batch.do_batch = 0;
1370         p->memcg_batch.memcg = NULL;
1371 #endif
1372 #ifdef CONFIG_BCACHE
1373         p->sequential_io        = 0;
1374         p->sequential_io_avg    = 0;
1375 #endif
1376
1377         /* Perform scheduler related setup. Assign this task to a CPU. */
1378         sched_fork(p);
1379
1380         retval = perf_event_init_task(p);
1381         if (retval)
1382                 goto bad_fork_cleanup_policy;
1383         retval = audit_alloc(p);
1384         if (retval)
1385                 goto bad_fork_cleanup_perf;
1386         /* copy all the process information */
1387         retval = copy_semundo(clone_flags, p);
1388         if (retval)
1389                 goto bad_fork_cleanup_audit;
1390         retval = copy_files(clone_flags, p);
1391         if (retval)
1392                 goto bad_fork_cleanup_semundo;
1393         retval = copy_fs(clone_flags, p);
1394         if (retval)
1395                 goto bad_fork_cleanup_files;
1396         retval = copy_sighand(clone_flags, p);
1397         if (retval)
1398                 goto bad_fork_cleanup_fs;
1399         retval = copy_signal(clone_flags, p);
1400         if (retval)
1401                 goto bad_fork_cleanup_sighand;
1402         retval = copy_mm(clone_flags, p);
1403         if (retval)
1404                 goto bad_fork_cleanup_signal;
1405         retval = copy_namespaces(clone_flags, p);
1406         if (retval)
1407                 goto bad_fork_cleanup_mm;
1408         retval = copy_io(clone_flags, p);
1409         if (retval)
1410                 goto bad_fork_cleanup_namespaces;
1411         retval = copy_thread(clone_flags, stack_start, stack_size, p);
1412         if (retval)
1413                 goto bad_fork_cleanup_io;
1414
1415         if (pid != &init_struct_pid) {
1416                 retval = -ENOMEM;
1417                 pid = alloc_pid(p->nsproxy->pid_ns);
1418                 if (!pid)
1419                         goto bad_fork_cleanup_io;
1420         }
1421
1422         p->pid = pid_nr(pid);
1423         p->tgid = p->pid;
1424         if (clone_flags & CLONE_THREAD)
1425                 p->tgid = current->tgid;
1426
1427         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1428         /*
1429          * Clear TID on mm_release()?
1430          */
1431         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1432 #ifdef CONFIG_BLOCK
1433         p->plug = NULL;
1434 #endif
1435 #ifdef CONFIG_FUTEX
1436         p->robust_list = NULL;
1437 #ifdef CONFIG_COMPAT
1438         p->compat_robust_list = NULL;
1439 #endif
1440         INIT_LIST_HEAD(&p->pi_state_list);
1441         p->pi_state_cache = NULL;
1442 #endif
1443         uprobe_copy_process(p);
1444         /*
1445          * sigaltstack should be cleared when sharing the same VM
1446          */
1447         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1448                 p->sas_ss_sp = p->sas_ss_size = 0;
1449
1450         /*
1451          * Syscall tracing and stepping should be turned off in the
1452          * child regardless of CLONE_PTRACE.
1453          */
1454         user_disable_single_step(p);
1455         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1456 #ifdef TIF_SYSCALL_EMU
1457         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1458 #endif
1459         clear_all_latency_tracing(p);
1460
1461         /* ok, now we should be set up.. */
1462         if (clone_flags & CLONE_THREAD)
1463                 p->exit_signal = -1;
1464         else if (clone_flags & CLONE_PARENT)
1465                 p->exit_signal = current->group_leader->exit_signal;
1466         else
1467                 p->exit_signal = (clone_flags & CSIGNAL);
1468
1469         p->pdeath_signal = 0;
1470         p->exit_state = 0;
1471
1472         p->nr_dirtied = 0;
1473         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1474         p->dirty_paused_when = 0;
1475
1476         /*
1477          * Ok, make it visible to the rest of the system.
1478          * We dont wake it up yet.
1479          */
1480         p->group_leader = p;
1481         INIT_LIST_HEAD(&p->thread_group);
1482         p->task_works = NULL;
1483
1484         /* Need tasklist lock for parent etc handling! */
1485         write_lock_irq(&tasklist_lock);
1486
1487         /* CLONE_PARENT re-uses the old parent */
1488         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1489                 p->real_parent = current->real_parent;
1490                 p->parent_exec_id = current->parent_exec_id;
1491         } else {
1492                 p->real_parent = current;
1493                 p->parent_exec_id = current->self_exec_id;
1494         }
1495
1496         spin_lock(&current->sighand->siglock);
1497
1498         /*
1499          * Copy seccomp details explicitly here, in case they were changed
1500          * before holding sighand lock.
1501          */
1502         copy_seccomp(p);
1503
1504         /*
1505          * Process group and session signals need to be delivered to just the
1506          * parent before the fork or both the parent and the child after the
1507          * fork. Restart if a signal comes in before we add the new process to
1508          * it's process group.
1509          * A fatal signal pending means that current will exit, so the new
1510          * thread can't slip out of an OOM kill (or normal SIGKILL).
1511         */
1512         recalc_sigpending();
1513         if (signal_pending(current)) {
1514                 spin_unlock(&current->sighand->siglock);
1515                 write_unlock_irq(&tasklist_lock);
1516                 retval = -ERESTARTNOINTR;
1517                 goto bad_fork_free_pid;
1518         }
1519
1520         if (likely(p->pid)) {
1521                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1522
1523                 if (thread_group_leader(p)) {
1524                         if (is_child_reaper(pid)) {
1525                                 ns_of_pid(pid)->child_reaper = p;
1526                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1527                         }
1528
1529                         p->signal->leader_pid = pid;
1530                         p->signal->tty = tty_kref_get(current->signal->tty);
1531                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1532                         attach_pid(p, PIDTYPE_SID, task_session(current));
1533                         list_add_tail(&p->sibling, &p->real_parent->children);
1534                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1535                         __this_cpu_inc(process_counts);
1536                 } else {
1537                         current->signal->nr_threads++;
1538                         atomic_inc(&current->signal->live);
1539                         atomic_inc(&current->signal->sigcnt);
1540                         p->group_leader = current->group_leader;
1541                         list_add_tail_rcu(&p->thread_group,
1542                                           &p->group_leader->thread_group);
1543                         list_add_tail_rcu(&p->thread_node,
1544                                           &p->signal->thread_head);
1545                 }
1546                 attach_pid(p, PIDTYPE_PID, pid);
1547                 nr_threads++;
1548         }
1549
1550         total_forks++;
1551         spin_unlock(&current->sighand->siglock);
1552         syscall_tracepoint_update(p);
1553         write_unlock_irq(&tasklist_lock);
1554
1555         proc_fork_connector(p);
1556         cgroup_post_fork(p);
1557         if (clone_flags & CLONE_THREAD)
1558                 threadgroup_change_end(current);
1559         perf_event_fork(p);
1560
1561         trace_task_newtask(p, clone_flags);
1562
1563         return p;
1564
1565 bad_fork_free_pid:
1566         if (pid != &init_struct_pid)
1567                 free_pid(pid);
1568 bad_fork_cleanup_io:
1569         if (p->io_context)
1570                 exit_io_context(p);
1571 bad_fork_cleanup_namespaces:
1572         exit_task_namespaces(p);
1573 bad_fork_cleanup_mm:
1574         if (p->mm)
1575                 mmput(p->mm);
1576 bad_fork_cleanup_signal:
1577         if (!(clone_flags & CLONE_THREAD))
1578                 free_signal_struct(p->signal);
1579 bad_fork_cleanup_sighand:
1580         __cleanup_sighand(p->sighand);
1581 bad_fork_cleanup_fs:
1582         exit_fs(p); /* blocking */
1583 bad_fork_cleanup_files:
1584         exit_files(p); /* blocking */
1585 bad_fork_cleanup_semundo:
1586         exit_sem(p);
1587 bad_fork_cleanup_audit:
1588         audit_free(p);
1589 bad_fork_cleanup_perf:
1590         perf_event_free_task(p);
1591 bad_fork_cleanup_policy:
1592 #ifdef CONFIG_NUMA
1593         mpol_put(p->mempolicy);
1594 bad_fork_cleanup_cgroup:
1595 #endif
1596         if (clone_flags & CLONE_THREAD)
1597                 threadgroup_change_end(current);
1598         cgroup_exit(p, 0);
1599         delayacct_tsk_free(p);
1600 bad_fork_cleanup_count:
1601         atomic_dec(&p->cred->user->processes);
1602         exit_creds(p);
1603 bad_fork_free:
1604         free_task(p);
1605 fork_out:
1606         return ERR_PTR(retval);
1607 }
1608
1609 static inline void init_idle_pids(struct pid_link *links)
1610 {
1611         enum pid_type type;
1612
1613         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1614                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1615                 links[type].pid = &init_struct_pid;
1616         }
1617 }
1618
1619 struct task_struct * __cpuinit fork_idle(int cpu)
1620 {
1621         struct task_struct *task;
1622         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1623         if (!IS_ERR(task)) {
1624                 init_idle_pids(task->pids);
1625                 init_idle(task, cpu);
1626         }
1627
1628         return task;
1629 }
1630
1631 /*
1632  *  Ok, this is the main fork-routine.
1633  *
1634  * It copies the process, and if successful kick-starts
1635  * it and waits for it to finish using the VM if required.
1636  */
1637 long do_fork(unsigned long clone_flags,
1638               unsigned long stack_start,
1639               unsigned long stack_size,
1640               int __user *parent_tidptr,
1641               int __user *child_tidptr)
1642 {
1643         struct task_struct *p;
1644         int trace = 0;
1645         long nr;
1646
1647         /*
1648          * Do some preliminary argument and permissions checking before we
1649          * actually start allocating stuff
1650          */
1651         if (clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) {
1652                 if (clone_flags & (CLONE_THREAD|CLONE_PARENT))
1653                         return -EINVAL;
1654         }
1655
1656         /*
1657          * Determine whether and which event to report to ptracer.  When
1658          * called from kernel_thread or CLONE_UNTRACED is explicitly
1659          * requested, no event is reported; otherwise, report if the event
1660          * for the type of forking is enabled.
1661          */
1662         if (!(clone_flags & CLONE_UNTRACED)) {
1663                 if (clone_flags & CLONE_VFORK)
1664                         trace = PTRACE_EVENT_VFORK;
1665                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1666                         trace = PTRACE_EVENT_CLONE;
1667                 else
1668                         trace = PTRACE_EVENT_FORK;
1669
1670                 if (likely(!ptrace_event_enabled(current, trace)))
1671                         trace = 0;
1672         }
1673
1674         p = copy_process(clone_flags, stack_start, stack_size,
1675                          child_tidptr, NULL, trace);
1676         /*
1677          * Do this prior waking up the new thread - the thread pointer
1678          * might get invalid after that point, if the thread exits quickly.
1679          */
1680         if (!IS_ERR(p)) {
1681                 struct completion vfork;
1682                 struct pid *pid;
1683
1684                 trace_sched_process_fork(current, p);
1685
1686                 pid = get_task_pid(p, PIDTYPE_PID);
1687                 nr = pid_vnr(pid);
1688
1689                 if (clone_flags & CLONE_PARENT_SETTID)
1690                         put_user(nr, parent_tidptr);
1691
1692                 if (clone_flags & CLONE_VFORK) {
1693                         p->vfork_done = &vfork;
1694                         init_completion(&vfork);
1695                         get_task_struct(p);
1696                 }
1697
1698                 wake_up_new_task(p);
1699
1700                 /* forking complete and child started to run, tell ptracer */
1701                 if (unlikely(trace))
1702                         ptrace_event_pid(trace, pid);
1703
1704                 if (clone_flags & CLONE_VFORK) {
1705                         if (!wait_for_vfork_done(p, &vfork))
1706                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1707                 }
1708
1709                 put_pid(pid);
1710         } else {
1711                 nr = PTR_ERR(p);
1712         }
1713         return nr;
1714 }
1715
1716 /*
1717  * Create a kernel thread.
1718  */
1719 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1720 {
1721         return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1722                 (unsigned long)arg, NULL, NULL);
1723 }
1724
1725 #ifdef __ARCH_WANT_SYS_FORK
1726 SYSCALL_DEFINE0(fork)
1727 {
1728 #ifdef CONFIG_MMU
1729         return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1730 #else
1731         /* can not support in nommu mode */
1732         return(-EINVAL);
1733 #endif
1734 }
1735 #endif
1736
1737 #ifdef __ARCH_WANT_SYS_VFORK
1738 SYSCALL_DEFINE0(vfork)
1739 {
1740         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1741                         0, NULL, NULL);
1742 }
1743 #endif
1744
1745 #ifdef __ARCH_WANT_SYS_CLONE
1746 #ifdef CONFIG_CLONE_BACKWARDS
1747 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1748                  int __user *, parent_tidptr,
1749                  int, tls_val,
1750                  int __user *, child_tidptr)
1751 #elif defined(CONFIG_CLONE_BACKWARDS2)
1752 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1753                  int __user *, parent_tidptr,
1754                  int __user *, child_tidptr,
1755                  int, tls_val)
1756 #elif defined(CONFIG_CLONE_BACKWARDS3)
1757 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1758                 int, stack_size,
1759                 int __user *, parent_tidptr,
1760                 int __user *, child_tidptr,
1761                 int, tls_val)
1762 #else
1763 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1764                  int __user *, parent_tidptr,
1765                  int __user *, child_tidptr,
1766                  int, tls_val)
1767 #endif
1768 {
1769         return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1770 }
1771 #endif
1772
1773 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1774 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1775 #endif
1776
1777 static void sighand_ctor(void *data)
1778 {
1779         struct sighand_struct *sighand = data;
1780
1781         spin_lock_init(&sighand->siglock);
1782         init_waitqueue_head(&sighand->signalfd_wqh);
1783 }
1784
1785 void __init proc_caches_init(void)
1786 {
1787         sighand_cachep = kmem_cache_create("sighand_cache",
1788                         sizeof(struct sighand_struct), 0,
1789                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1790                         SLAB_NOTRACK, sighand_ctor);
1791         signal_cachep = kmem_cache_create("signal_cache",
1792                         sizeof(struct signal_struct), 0,
1793                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1794         files_cachep = kmem_cache_create("files_cache",
1795                         sizeof(struct files_struct), 0,
1796                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1797         fs_cachep = kmem_cache_create("fs_cache",
1798                         sizeof(struct fs_struct), 0,
1799                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1800         /*
1801          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1802          * whole struct cpumask for the OFFSTACK case. We could change
1803          * this to *only* allocate as much of it as required by the
1804          * maximum number of CPU's we can ever have.  The cpumask_allocation
1805          * is at the end of the structure, exactly for that reason.
1806          */
1807         mm_cachep = kmem_cache_create("mm_struct",
1808                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1809                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1810         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1811         mmap_init();
1812         nsproxy_cache_init();
1813 }
1814
1815 /*
1816  * Check constraints on flags passed to the unshare system call.
1817  */
1818 static int check_unshare_flags(unsigned long unshare_flags)
1819 {
1820         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1821                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1822                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1823                                 CLONE_NEWUSER|CLONE_NEWPID))
1824                 return -EINVAL;
1825         /*
1826          * Not implemented, but pretend it works if there is nothing
1827          * to unshare.  Note that unsharing the address space or the
1828          * signal handlers also need to unshare the signal queues (aka
1829          * CLONE_THREAD).
1830          */
1831         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1832                 if (!thread_group_empty(current))
1833                         return -EINVAL;
1834         }
1835         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
1836                 if (atomic_read(&current->sighand->count) > 1)
1837                         return -EINVAL;
1838         }
1839         if (unshare_flags & CLONE_VM) {
1840                 if (!current_is_single_threaded())
1841                         return -EINVAL;
1842         }
1843
1844         return 0;
1845 }
1846
1847 /*
1848  * Unshare the filesystem structure if it is being shared
1849  */
1850 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1851 {
1852         struct fs_struct *fs = current->fs;
1853
1854         if (!(unshare_flags & CLONE_FS) || !fs)
1855                 return 0;
1856
1857         /* don't need lock here; in the worst case we'll do useless copy */
1858         if (fs->users == 1)
1859                 return 0;
1860
1861         *new_fsp = copy_fs_struct(fs);
1862         if (!*new_fsp)
1863                 return -ENOMEM;
1864
1865         return 0;
1866 }
1867
1868 /*
1869  * Unshare file descriptor table if it is being shared
1870  */
1871 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1872 {
1873         struct files_struct *fd = current->files;
1874         int error = 0;
1875
1876         if ((unshare_flags & CLONE_FILES) &&
1877             (fd && atomic_read(&fd->count) > 1)) {
1878                 *new_fdp = dup_fd(fd, &error);
1879                 if (!*new_fdp)
1880                         return error;
1881         }
1882
1883         return 0;
1884 }
1885
1886 /*
1887  * unshare allows a process to 'unshare' part of the process
1888  * context which was originally shared using clone.  copy_*
1889  * functions used by do_fork() cannot be used here directly
1890  * because they modify an inactive task_struct that is being
1891  * constructed. Here we are modifying the current, active,
1892  * task_struct.
1893  */
1894 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1895 {
1896         struct fs_struct *fs, *new_fs = NULL;
1897         struct files_struct *fd, *new_fd = NULL;
1898         struct cred *new_cred = NULL;
1899         struct nsproxy *new_nsproxy = NULL;
1900         int do_sysvsem = 0;
1901         int err;
1902
1903         /*
1904          * If unsharing a user namespace must also unshare the thread.
1905          */
1906         if (unshare_flags & CLONE_NEWUSER)
1907                 unshare_flags |= CLONE_THREAD | CLONE_FS;
1908         /*
1909          * If unsharing a pid namespace must also unshare the thread.
1910          */
1911         if (unshare_flags & CLONE_NEWPID)
1912                 unshare_flags |= CLONE_THREAD;
1913         /*
1914          * If unsharing vm, must also unshare signal handlers.
1915          */
1916         if (unshare_flags & CLONE_VM)
1917                 unshare_flags |= CLONE_SIGHAND;
1918         /*
1919          * If unsharing a signal handlers, must also unshare the signal queues.
1920          */
1921         if (unshare_flags & CLONE_SIGHAND)
1922                 unshare_flags |= CLONE_THREAD;
1923         /*
1924          * If unsharing namespace, must also unshare filesystem information.
1925          */
1926         if (unshare_flags & CLONE_NEWNS)
1927                 unshare_flags |= CLONE_FS;
1928
1929         err = check_unshare_flags(unshare_flags);
1930         if (err)
1931                 goto bad_unshare_out;
1932         /*
1933          * CLONE_NEWIPC must also detach from the undolist: after switching
1934          * to a new ipc namespace, the semaphore arrays from the old
1935          * namespace are unreachable.
1936          */
1937         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1938                 do_sysvsem = 1;
1939         err = unshare_fs(unshare_flags, &new_fs);
1940         if (err)
1941                 goto bad_unshare_out;
1942         err = unshare_fd(unshare_flags, &new_fd);
1943         if (err)
1944                 goto bad_unshare_cleanup_fs;
1945         err = unshare_userns(unshare_flags, &new_cred);
1946         if (err)
1947                 goto bad_unshare_cleanup_fd;
1948         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1949                                          new_cred, new_fs);
1950         if (err)
1951                 goto bad_unshare_cleanup_cred;
1952
1953         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1954                 if (do_sysvsem) {
1955                         /*
1956                          * CLONE_SYSVSEM is equivalent to sys_exit().
1957                          */
1958                         exit_sem(current);
1959                 }
1960
1961                 if (new_nsproxy)
1962                         switch_task_namespaces(current, new_nsproxy);
1963
1964                 task_lock(current);
1965
1966                 if (new_fs) {
1967                         fs = current->fs;
1968                         spin_lock(&fs->lock);
1969                         current->fs = new_fs;
1970                         if (--fs->users)
1971                                 new_fs = NULL;
1972                         else
1973                                 new_fs = fs;
1974                         spin_unlock(&fs->lock);
1975                 }
1976
1977                 if (new_fd) {
1978                         fd = current->files;
1979                         current->files = new_fd;
1980                         new_fd = fd;
1981                 }
1982
1983                 task_unlock(current);
1984
1985                 if (new_cred) {
1986                         /* Install the new user namespace */
1987                         commit_creds(new_cred);
1988                         new_cred = NULL;
1989                 }
1990         }
1991
1992 bad_unshare_cleanup_cred:
1993         if (new_cred)
1994                 put_cred(new_cred);
1995 bad_unshare_cleanup_fd:
1996         if (new_fd)
1997                 put_files_struct(new_fd);
1998
1999 bad_unshare_cleanup_fs:
2000         if (new_fs)
2001                 free_fs_struct(new_fs);
2002
2003 bad_unshare_out:
2004         return err;
2005 }
2006
2007 /*
2008  *      Helper to unshare the files of the current task.
2009  *      We don't want to expose copy_files internals to
2010  *      the exec layer of the kernel.
2011  */
2012
2013 int unshare_files(struct files_struct **displaced)
2014 {
2015         struct task_struct *task = current;
2016         struct files_struct *copy = NULL;
2017         int error;
2018
2019         error = unshare_fd(CLONE_FILES, &copy);
2020         if (error || !copy) {
2021                 *displaced = NULL;
2022                 return error;
2023         }
2024         *displaced = task->files;
2025         task_lock(task);
2026         task->files = copy;
2027         task_unlock(task);
2028         return 0;
2029 }