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/nsproxy.h>
  32 #include <linux/capability.h>
  33 #include <linux/cpu.h>
  34 #include <linux/cgroup.h>
  35 #include <linux/security.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/swap.h>
  38 #include <linux/syscalls.h>
  39 #include <linux/jiffies.h>
  40 #include <linux/tracehook.h>
  41 #include <linux/futex.h>
  42 #include <linux/compat.h>
  43 #include <linux/task_io_accounting_ops.h>
  44 #include <linux/rcupdate.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/mount.h>
  47 #include <linux/audit.h>
  48 #include <linux/memcontrol.h>
  49 #include <linux/ftrace.h>
  50 #include <linux/profile.h>
  51 #include <linux/rmap.h>
  52 #include <linux/ksm.h>
  53 #include <linux/acct.h>
  54 #include <linux/tsacct_kern.h>
  55 #include <linux/cn_proc.h>
  56 #include <linux/freezer.h>
  57 #include <linux/delayacct.h>
  58 #include <linux/taskstats_kern.h>
  59 #include <linux/random.h>
  60 #include <linux/tty.h>
  61 #include <linux/proc_fs.h>
  62 #include <linux/blkdev.h>
  63 #include <linux/fs_struct.h>
  64 #include <linux/magic.h>
  65 #include <linux/perf_event.h>
  66 #include <linux/posix-timers.h>
  67 #include <linux/user-return-notifier.h>
  68
  69 #include <asm/pgtable.h>
  70 #include <asm/pgalloc.h>
  71 #include <asm/uaccess.h>
  72 #include <asm/mmu_context.h>
  73 #include <asm/cacheflush.h>
  74 #include <asm/tlbflush.h>
  75
  76 #include <trace/events/sched.h>
  77
  78 /*
  79  * Protected counters by write_lock_irq(&tasklist_lock)
  80  */
  81 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  82 int nr_threads;                 /* The idle threads do not count.. */
  83
  84 int max_threads;                /* tunable limit on nr_threads */
  85
  86 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  87
  88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  89
  90 #ifdef CONFIG_PROVE_RCU
  91 int lockdep_tasklist_lock_is_held(void)
  92 {
  93         return lockdep_is_held(&tasklist_lock);
  94 }
  95 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  96 #endif /* #ifdef CONFIG_PROVE_RCU */
  97
  98 int nr_processes(void)
  99 {
 100         int cpu;
 101         int total = 0;
 102
 103         for_each_possible_cpu(cpu)
 104                 total += per_cpu(process_counts, cpu);
 105
 106         return total;
 107 }
 108
 109 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 110 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
 111 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
 112 static struct kmem_cache *task_struct_cachep;
 113 #endif
 114
 115 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 116 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 117 {
 118 #ifdef CONFIG_DEBUG_STACK_USAGE
 119         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 120 #else
 121         gfp_t mask = GFP_KERNEL;
 122 #endif
 123         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 124 }
 125
 126 static inline void free_thread_info(struct thread_info *ti)
 127 {
 128         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 129 }
 130 #endif
 131
 132 /* SLAB cache for signal_struct structures (tsk->signal) */
 133 static struct kmem_cache *signal_cachep;
 134
 135 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 136 struct kmem_cache *sighand_cachep;
 137
 138 /* SLAB cache for files_struct structures (tsk->files) */
 139 struct kmem_cache *files_cachep;
 140
 141 /* SLAB cache for fs_struct structures (tsk->fs) */
 142 struct kmem_cache *fs_cachep;
 143
 144 /* SLAB cache for vm_area_struct structures */
 145 struct kmem_cache *vm_area_cachep;
 146
 147 /* SLAB cache for mm_struct structures (tsk->mm) */
 148 static struct kmem_cache *mm_cachep;
 149
 150 static void account_kernel_stack(struct thread_info *ti, int account)
 151 {
 152         struct zone *zone = page_zone(virt_to_page(ti));
 153
 154         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 155 }
 156
 157 void free_task(struct task_struct *tsk)
 158 {
 159         prop_local_destroy_single(&tsk->dirties);
 160         account_kernel_stack(tsk->stack, -1);
 161         free_thread_info(tsk->stack);
 162         rt_mutex_debug_task_free(tsk);
 163         ftrace_graph_exit_task(tsk);
 164         free_task_struct(tsk);
 165 }
 166 EXPORT_SYMBOL(free_task);
 167
 168 static inline void free_signal_struct(struct signal_struct *sig)
 169 {
 170         kmem_cache_free(signal_cachep, sig);
 171 }
 172
 173 static inline void put_signal_struct(struct signal_struct *sig)
 174 {
 175         if (atomic_dec_and_test(&sig->sigcnt))
 176                 free_signal_struct(sig);
 177 }
 178
 179 void __put_task_struct(struct task_struct *tsk)
 180 {
 181         WARN_ON(!tsk->exit_state);
 182         WARN_ON(atomic_read(&tsk->usage));
 183         WARN_ON(tsk == current);
 184
 185         exit_creds(tsk);
 186         delayacct_tsk_free(tsk);
 187         put_signal_struct(tsk->signal);
 188
 189         if (!profile_handoff_task(tsk))
 190                 free_task(tsk);
 191 }
 192
 193 /*
 194  * macro override instead of weak attribute alias, to workaround
 195  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 196  */
 197 #ifndef arch_task_cache_init
 198 #define arch_task_cache_init()
 199 #endif
 200
 201 void __init fork_init(unsigned long mempages)
 202 {
 203 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 204 #ifndef ARCH_MIN_TASKALIGN
 205 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 206 #endif
 207         /* create a slab on which task_structs can be allocated */
 208         task_struct_cachep =
 209                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 210                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 211 #endif
 212
 213         /* do the arch specific task caches init */
 214         arch_task_cache_init();
 215
 216         /*
 217          * The default maximum number of threads is set to a safe
 218          * value: the thread structures can take up at most half
 219          * of memory.
 220          */
 221         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 222
 223         /*
 224          * we need to allow at least 20 threads to boot a system
 225          */
 226         if(max_threads < 20)
 227                 max_threads = 20;
 228
 229         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 230         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 231         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 232                 init_task.signal->rlim[RLIMIT_NPROC];
 233 }
 234
 235 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 236                                                struct task_struct *src)
 237 {
 238         *dst = *src;
 239         return 0;
 240 }
 241
 242 static struct task_struct *dup_task_struct(struct task_struct *orig)
 243 {
 244         struct task_struct *tsk;
 245         struct thread_info *ti;
 246         unsigned long *stackend;
 247
 248         int err;
 249
 250         prepare_to_copy(orig);
 251
 252         tsk = alloc_task_struct();
 253         if (!tsk)
 254                 return NULL;
 255
 256         ti = alloc_thread_info(tsk);
 257         if (!ti) {
 258                 free_task_struct(tsk);
 259                 return NULL;
 260         }
 261
 262         err = arch_dup_task_struct(tsk, orig);
 263         if (err)
 264                 goto out;
 265
 266         tsk->stack = ti;
 267
 268         err = prop_local_init_single(&tsk->dirties);
 269         if (err)
 270                 goto out;
 271
 272         setup_thread_stack(tsk, orig);
 273         clear_user_return_notifier(tsk);
 274         stackend = end_of_stack(tsk);
 275         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 276
 277 #ifdef CONFIG_CC_STACKPROTECTOR
 278         tsk->stack_canary = get_random_int();
 279 #endif
 280
 281         /* One for us, one for whoever does the "release_task()" (usually parent) */
 282         atomic_set(&tsk->usage,2);
 283         atomic_set(&tsk->fs_excl, 0);
 284 #ifdef CONFIG_BLK_DEV_IO_TRACE
 285         tsk->btrace_seq = 0;
 286 #endif
 287         tsk->splice_pipe = NULL;
 288
 289         account_kernel_stack(ti, 1);
 290
 291         return tsk;
 292
 293 out:
 294         free_thread_info(ti);
 295         free_task_struct(tsk);
 296         return NULL;
 297 }
 298
 299 #ifdef CONFIG_MMU
 300 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 301 {
 302         struct vm_area_struct *mpnt, *tmp, **pprev;
 303         struct rb_node **rb_link, *rb_parent;
 304         int retval;
 305         unsigned long charge;
 306         struct mempolicy *pol;
 307
 308         down_write(&oldmm->mmap_sem);
 309         flush_cache_dup_mm(oldmm);
 310         /*
 311          * Not linked in yet - no deadlock potential:
 312          */
 313         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 314
 315         mm->locked_vm = 0;
 316         mm->mmap = NULL;
 317         mm->mmap_cache = NULL;
 318         mm->free_area_cache = oldmm->mmap_base;
 319         mm->cached_hole_size = ~0UL;
 320         mm->map_count = 0;
 321         cpumask_clear(mm_cpumask(mm));
 322         mm->mm_rb = RB_ROOT;
 323         rb_link = &mm->mm_rb.rb_node;
 324         rb_parent = NULL;
 325         pprev = &mm->mmap;
 326         retval = ksm_fork(mm, oldmm);
 327         if (retval)
 328                 goto out;
 329
 330         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 331                 struct file *file;
 332
 333                 if (mpnt->vm_flags & VM_DONTCOPY) {
 334                         long pages = vma_pages(mpnt);
 335                         mm->total_vm -= pages;
 336                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 337                                                                 -pages);
 338                         continue;
 339                 }
 340                 charge = 0;
 341                 if (mpnt->vm_flags & VM_ACCOUNT) {
 342                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 343                         if (security_vm_enough_memory(len))
 344                                 goto fail_nomem;
 345                         charge = len;
 346                 }
 347                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 348                 if (!tmp)
 349                         goto fail_nomem;
 350                 *tmp = *mpnt;
 351                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 352                 pol = mpol_dup(vma_policy(mpnt));
 353                 retval = PTR_ERR(pol);
 354                 if (IS_ERR(pol))
 355                         goto fail_nomem_policy;
 356                 vma_set_policy(tmp, pol);
 357                 if (anon_vma_fork(tmp, mpnt))
 358                         goto fail_nomem_anon_vma_fork;
 359                 tmp->vm_flags &= ~VM_LOCKED;
 360                 tmp->vm_mm = mm;
 361                 tmp->vm_next = NULL;
 362                 file = tmp->vm_file;
 363                 if (file) {
 364                         struct inode *inode = file->f_path.dentry->d_inode;
 365                         struct address_space *mapping = file->f_mapping;
 366
 367                         get_file(file);
 368                         if (tmp->vm_flags & VM_DENYWRITE)
 369                                 atomic_dec(&inode->i_writecount);
 370                         spin_lock(&mapping->i_mmap_lock);
 371                         if (tmp->vm_flags & VM_SHARED)
 372                                 mapping->i_mmap_writable++;
 373                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 374                         flush_dcache_mmap_lock(mapping);
 375                         /* insert tmp into the share list, just after mpnt */
 376                         vma_prio_tree_add(tmp, mpnt);
 377                         flush_dcache_mmap_unlock(mapping);
 378                         spin_unlock(&mapping->i_mmap_lock);
 379                 }
 380
 381                 /*
 382                  * Clear hugetlb-related page reserves for children. This only
 383                  * affects MAP_PRIVATE mappings. Faults generated by the child
 384                  * are not guaranteed to succeed, even if read-only
 385                  */
 386                 if (is_vm_hugetlb_page(tmp))
 387                         reset_vma_resv_huge_pages(tmp);
 388
 389                 /*
 390                  * Link in the new vma and copy the page table entries.
 391                  */
 392                 *pprev = tmp;
 393                 pprev = &tmp->vm_next;
 394
 395                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 396                 rb_link = &tmp->vm_rb.rb_right;
 397                 rb_parent = &tmp->vm_rb;
 398
 399                 mm->map_count++;
 400                 retval = copy_page_range(mm, oldmm, mpnt);
 401
 402                 if (tmp->vm_ops && tmp->vm_ops->open)
 403                         tmp->vm_ops->open(tmp);
 404
 405                 if (retval)
 406                         goto out;
 407         }
 408         /* a new mm has just been created */
 409         arch_dup_mmap(oldmm, mm);
 410         retval = 0;
 411 out:
 412         up_write(&mm->mmap_sem);
 413         flush_tlb_mm(oldmm);
 414         up_write(&oldmm->mmap_sem);
 415         return retval;
 416 fail_nomem_anon_vma_fork:
 417         mpol_put(pol);
 418 fail_nomem_policy:
 419         kmem_cache_free(vm_area_cachep, tmp);
 420 fail_nomem:
 421         retval = -ENOMEM;
 422         vm_unacct_memory(charge);
 423         goto out;
 424 }
 425
 426 static inline int mm_alloc_pgd(struct mm_struct * mm)
 427 {
 428         mm->pgd = pgd_alloc(mm);
 429         if (unlikely(!mm->pgd))
 430                 return -ENOMEM;
 431         return 0;
 432 }
 433
 434 static inline void mm_free_pgd(struct mm_struct * mm)
 435 {
 436         pgd_free(mm, mm->pgd);
 437 }
 438 #else
 439 #define dup_mmap(mm, oldmm)     (0)
 440 #define mm_alloc_pgd(mm)        (0)
 441 #define mm_free_pgd(mm)
 442 #endif /* CONFIG_MMU */
 443
 444 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 445
 446 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 447 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 448
 449 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 450
 451 static int __init coredump_filter_setup(char *s)
 452 {
 453         default_dump_filter =
 454                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 455                 MMF_DUMP_FILTER_MASK;
 456         return 1;
 457 }
 458
 459 __setup("coredump_filter=", coredump_filter_setup);
 460
 461 #include <linux/init_task.h>
 462
 463 static void mm_init_aio(struct mm_struct *mm)
 464 {
 465 #ifdef CONFIG_AIO
 466         spin_lock_init(&mm->ioctx_lock);
 467         INIT_HLIST_HEAD(&mm->ioctx_list);
 468 #endif
 469 }
 470
 471 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 472 {
 473         atomic_set(&mm->mm_users, 1);
 474         atomic_set(&mm->mm_count, 1);
 475         init_rwsem(&mm->mmap_sem);
 476         INIT_LIST_HEAD(&mm->mmlist);
 477         mm->flags = (current->mm) ?
 478                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 479         mm->core_state = NULL;
 480         mm->nr_ptes = 0;
 481         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 482         spin_lock_init(&mm->page_table_lock);
 483         mm->free_area_cache = TASK_UNMAPPED_BASE;
 484         mm->cached_hole_size = ~0UL;
 485         mm_init_aio(mm);
 486         mm_init_owner(mm, p);
 487
 488         if (likely(!mm_alloc_pgd(mm))) {
 489                 mm->def_flags = 0;
 490                 mmu_notifier_mm_init(mm);
 491                 return mm;
 492         }
 493
 494         free_mm(mm);
 495         return NULL;
 496 }
 497
 498 /*
 499  * Allocate and initialize an mm_struct.
 500  */
 501 struct mm_struct * mm_alloc(void)
 502 {
 503         struct mm_struct * mm;
 504
 505         mm = allocate_mm();
 506         if (mm) {
 507                 memset(mm, 0, sizeof(*mm));
 508                 mm = mm_init(mm, current);
 509         }
 510         return mm;
 511 }
 512
 513 /*
 514  * Called when the last reference to the mm
 515  * is dropped: either by a lazy thread or by
 516  * mmput. Free the page directory and the mm.
 517  */
 518 void __mmdrop(struct mm_struct *mm)
 519 {
 520         BUG_ON(mm == &init_mm);
 521         mm_free_pgd(mm);
 522         destroy_context(mm);
 523         mmu_notifier_mm_destroy(mm);
 524         free_mm(mm);
 525 }
 526 EXPORT_SYMBOL_GPL(__mmdrop);
 527
 528 /*
 529  * Decrement the use count and release all resources for an mm.
 530  */
 531 void mmput(struct mm_struct *mm)
 532 {
 533         might_sleep();
 534
 535         if (atomic_dec_and_test(&mm->mm_users)) {
 536                 exit_aio(mm);
 537                 ksm_exit(mm);
 538                 exit_mmap(mm);
 539                 set_mm_exe_file(mm, NULL);
 540                 if (!list_empty(&mm->mmlist)) {
 541                         spin_lock(&mmlist_lock);
 542                         list_del(&mm->mmlist);
 543                         spin_unlock(&mmlist_lock);
 544                 }
 545                 put_swap_token(mm);
 546                 if (mm->binfmt)
 547                         module_put(mm->binfmt->module);
 548                 mmdrop(mm);
 549         }
 550 }
 551 EXPORT_SYMBOL_GPL(mmput);
 552
 553 /**
 554  * get_task_mm - acquire a reference to the task's mm
 555  *
 556  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 557  * this kernel workthread has transiently adopted a user mm with use_mm,
 558  * to do its AIO) is not set and if so returns a reference to it, after
 559  * bumping up the use count.  User must release the mm via mmput()
 560  * after use.  Typically used by /proc and ptrace.
 561  */
 562 struct mm_struct *get_task_mm(struct task_struct *task)
 563 {
 564         struct mm_struct *mm;
 565
 566         task_lock(task);
 567         mm = task->mm;
 568         if (mm) {
 569                 if (task->flags & PF_KTHREAD)
 570                         mm = NULL;
 571                 else
 572                         atomic_inc(&mm->mm_users);
 573         }
 574         task_unlock(task);
 575         return mm;
 576 }
 577 EXPORT_SYMBOL_GPL(get_task_mm);
 578
 579 /* Please note the differences between mmput and mm_release.
 580  * mmput is called whenever we stop holding onto a mm_struct,
 581  * error success whatever.
 582  *
 583  * mm_release is called after a mm_struct has been removed
 584  * from the current process.
 585  *
 586  * This difference is important for error handling, when we
 587  * only half set up a mm_struct for a new process and need to restore
 588  * the old one.  Because we mmput the new mm_struct before
 589  * restoring the old one. . .
 590  * Eric Biederman 10 January 1998
 591  */
 592 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 593 {
 594         struct completion *vfork_done = tsk->vfork_done;
 595
 596         /* Get rid of any futexes when releasing the mm */
 597 #ifdef CONFIG_FUTEX
 598         if (unlikely(tsk->robust_list)) {
 599                 exit_robust_list(tsk);
 600                 tsk->robust_list = NULL;
 601         }
 602 #ifdef CONFIG_COMPAT
 603         if (unlikely(tsk->compat_robust_list)) {
 604                 compat_exit_robust_list(tsk);
 605                 tsk->compat_robust_list = NULL;
 606         }
 607 #endif
 608         if (unlikely(!list_empty(&tsk->pi_state_list)))
 609                 exit_pi_state_list(tsk);
 610 #endif
 611
 612         /* Get rid of any cached register state */
 613         deactivate_mm(tsk, mm);
 614
 615         /* notify parent sleeping on vfork() */
 616         if (vfork_done) {
 617                 tsk->vfork_done = NULL;
 618                 complete(vfork_done);
 619         }
 620
 621         /*
 622          * If we're exiting normally, clear a user-space tid field if
 623          * requested.  We leave this alone when dying by signal, to leave
 624          * the value intact in a core dump, and to save the unnecessary
 625          * trouble otherwise.  Userland only wants this done for a sys_exit.
 626          */
 627         if (tsk->clear_child_tid) {
 628                 if (!(tsk->flags & PF_SIGNALED) &&
 629                     atomic_read(&mm->mm_users) > 1) {
 630                         /*
 631                          * We don't check the error code - if userspace has
 632                          * not set up a proper pointer then tough luck.
 633                          */
 634                         put_user(0, tsk->clear_child_tid);
 635                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 636                                         1, NULL, NULL, 0);
 637                 }
 638                 tsk->clear_child_tid = NULL;
 639         }
 640 }
 641
 642 /*
 643  * Allocate a new mm structure and copy contents from the
 644  * mm structure of the passed in task structure.
 645  */
 646 struct mm_struct *dup_mm(struct task_struct *tsk)
 647 {
 648         struct mm_struct *mm, *oldmm = current->mm;
 649         int err;
 650
 651         if (!oldmm)
 652                 return NULL;
 653
 654         mm = allocate_mm();
 655         if (!mm)
 656                 goto fail_nomem;
 657
 658         memcpy(mm, oldmm, sizeof(*mm));
 659
 660         /* Initializing for Swap token stuff */
 661         mm->token_priority = 0;
 662         mm->last_interval = 0;
 663
 664         if (!mm_init(mm, tsk))
 665                 goto fail_nomem;
 666
 667         if (init_new_context(tsk, mm))
 668                 goto fail_nocontext;
 669
 670         dup_mm_exe_file(oldmm, mm);
 671
 672         err = dup_mmap(mm, oldmm);
 673         if (err)
 674                 goto free_pt;
 675
 676         mm->hiwater_rss = get_mm_rss(mm);
 677         mm->hiwater_vm = mm->total_vm;
 678
 679         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 680                 goto free_pt;
 681
 682         return mm;
 683
 684 free_pt:
 685         /* don't put binfmt in mmput, we haven't got module yet */
 686         mm->binfmt = NULL;
 687         mmput(mm);
 688
 689 fail_nomem:
 690         return NULL;
 691
 692 fail_nocontext:
 693         /*
 694          * If init_new_context() failed, we cannot use mmput() to free the mm
 695          * because it calls destroy_context()
 696          */
 697         mm_free_pgd(mm);
 698         free_mm(mm);
 699         return NULL;
 700 }
 701
 702 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 703 {
 704         struct mm_struct * mm, *oldmm;
 705         int retval;
 706
 707         tsk->min_flt = tsk->maj_flt = 0;
 708         tsk->nvcsw = tsk->nivcsw = 0;
 709 #ifdef CONFIG_DETECT_HUNG_TASK
 710         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 711 #endif
 712
 713         tsk->mm = NULL;
 714         tsk->active_mm = NULL;
 715
 716         /*
 717          * Are we cloning a kernel thread?
 718          *
 719          * We need to steal a active VM for that..
 720          */
 721         oldmm = current->mm;
 722         if (!oldmm)
 723                 return 0;
 724
 725         if (clone_flags & CLONE_VM) {
 726                 atomic_inc(&oldmm->mm_users);
 727                 mm = oldmm;
 728                 goto good_mm;
 729         }
 730
 731         retval = -ENOMEM;
 732         mm = dup_mm(tsk);
 733         if (!mm)
 734                 goto fail_nomem;
 735
 736 good_mm:
 737         /* Initializing for Swap token stuff */
 738         mm->token_priority = 0;
 739         mm->last_interval = 0;
 740
 741         tsk->mm = mm;
 742         tsk->active_mm = mm;
 743         return 0;
 744
 745 fail_nomem:
 746         return retval;
 747 }
 748
 749 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 750 {
 751         struct fs_struct *fs = current->fs;
 752         if (clone_flags & CLONE_FS) {
 753                 /* tsk->fs is already what we want */
 754                 write_lock(&fs->lock);
 755                 if (fs->in_exec) {
 756                         write_unlock(&fs->lock);
 757                         return -EAGAIN;
 758                 }
 759                 fs->users++;
 760                 write_unlock(&fs->lock);
 761                 return 0;
 762         }
 763         tsk->fs = copy_fs_struct(fs);
 764         if (!tsk->fs)
 765                 return -ENOMEM;
 766         return 0;
 767 }
 768
 769 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 770 {
 771         struct files_struct *oldf, *newf;
 772         int error = 0;
 773
 774         /*
 775          * A background process may not have any files ...
 776          */
 777         oldf = current->files;
 778         if (!oldf)
 779                 goto out;
 780
 781         if (clone_flags & CLONE_FILES) {
 782                 atomic_inc(&oldf->count);
 783                 goto out;
 784         }
 785
 786         newf = dup_fd(oldf, &error);
 787         if (!newf)
 788                 goto out;
 789
 790         tsk->files = newf;
 791         error = 0;
 792 out:
 793         return error;
 794 }
 795
 796 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 797 {
 798 #ifdef CONFIG_BLOCK
 799         struct io_context *ioc = current->io_context;
 800
 801         if (!ioc)
 802                 return 0;
 803         /*
 804          * Share io context with parent, if CLONE_IO is set
 805          */
 806         if (clone_flags & CLONE_IO) {
 807                 tsk->io_context = ioc_task_link(ioc);
 808                 if (unlikely(!tsk->io_context))
 809                         return -ENOMEM;
 810         } else if (ioprio_valid(ioc->ioprio)) {
 811                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 812                 if (unlikely(!tsk->io_context))
 813                         return -ENOMEM;
 814
 815                 tsk->io_context->ioprio = ioc->ioprio;
 816         }
 817 #endif
 818         return 0;
 819 }
 820
 821 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 822 {
 823         struct sighand_struct *sig;
 824
 825         if (clone_flags & CLONE_SIGHAND) {
 826                 atomic_inc(&current->sighand->count);
 827                 return 0;
 828         }
 829         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 830         rcu_assign_pointer(tsk->sighand, sig);
 831         if (!sig)
 832                 return -ENOMEM;
 833         atomic_set(&sig->count, 1);
 834         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 835         return 0;
 836 }
 837
 838 void __cleanup_sighand(struct sighand_struct *sighand)
 839 {
 840         if (atomic_dec_and_test(&sighand->count))
 841                 kmem_cache_free(sighand_cachep, sighand);
 842 }
 843
 844
 845 /*
 846  * Initialize POSIX timer handling for a thread group.
 847  */
 848 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 849 {
 850         unsigned long cpu_limit;
 851
 852         /* Thread group counters. */
 853         thread_group_cputime_init(sig);
 854
 855         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 856         if (cpu_limit != RLIM_INFINITY) {
 857                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 858                 sig->cputimer.running = 1;
 859         }
 860
 861         /* The timer lists. */
 862         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 863         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 864         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 865 }
 866
 867 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 868 {
 869         struct signal_struct *sig;
 870
 871         if (clone_flags & CLONE_THREAD)
 872                 return 0;
 873
 874         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 875         tsk->signal = sig;
 876         if (!sig)
 877                 return -ENOMEM;
 878
 879         atomic_set(&sig->sigcnt, 1);
 880         atomic_set(&sig->count, 1);
 881         atomic_set(&sig->live, 1);
 882         init_waitqueue_head(&sig->wait_chldexit);
 883         if (clone_flags & CLONE_NEWPID)
 884                 sig->flags |= SIGNAL_UNKILLABLE;
 885         sig->curr_target = tsk;
 886         init_sigpending(&sig->shared_pending);
 887         INIT_LIST_HEAD(&sig->posix_timers);
 888
 889         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 890         sig->real_timer.function = it_real_fn;
 891
 892         task_lock(current->group_leader);
 893         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 894         task_unlock(current->group_leader);
 895
 896         posix_cpu_timers_init_group(sig);
 897
 898         tty_audit_fork(sig);
 899
 900         sig->oom_adj = current->signal->oom_adj;
 901
 902         return 0;
 903 }
 904
 905 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 906 {
 907         unsigned long new_flags = p->flags;
 908
 909         new_flags &= ~PF_SUPERPRIV;
 910         new_flags |= PF_FORKNOEXEC;
 911         new_flags |= PF_STARTING;
 912         p->flags = new_flags;
 913         clear_freeze_flag(p);
 914 }
 915
 916 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 917 {
 918         current->clear_child_tid = tidptr;
 919
 920         return task_pid_vnr(current);
 921 }
 922
 923 static void rt_mutex_init_task(struct task_struct *p)
 924 {
 925         raw_spin_lock_init(&p->pi_lock);
 926 #ifdef CONFIG_RT_MUTEXES
 927         plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
 928         p->pi_blocked_on = NULL;
 929 #endif
 930 }
 931
 932 #ifdef CONFIG_MM_OWNER
 933 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 934 {
 935         mm->owner = p;
 936 }
 937 #endif /* CONFIG_MM_OWNER */
 938
 939 /*
 940  * Initialize POSIX timer handling for a single task.
 941  */
 942 static void posix_cpu_timers_init(struct task_struct *tsk)
 943 {
 944         tsk->cputime_expires.prof_exp = cputime_zero;
 945         tsk->cputime_expires.virt_exp = cputime_zero;
 946         tsk->cputime_expires.sched_exp = 0;
 947         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 948         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 949         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 950 }
 951
 952 /*
 953  * This creates a new process as a copy of the old one,
 954  * but does not actually start it yet.
 955  *
 956  * It copies the registers, and all the appropriate
 957  * parts of the process environment (as per the clone
 958  * flags). The actual kick-off is left to the caller.
 959  */
 960 static struct task_struct *copy_process(unsigned long clone_flags,
 961                                         unsigned long stack_start,
 962                                         struct pt_regs *regs,
 963                                         unsigned long stack_size,
 964                                         int __user *child_tidptr,
 965                                         struct pid *pid,
 966                                         int trace)
 967 {
 968         int retval;
 969         struct task_struct *p;
 970         int cgroup_callbacks_done = 0;
 971
 972         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 973                 return ERR_PTR(-EINVAL);
 974
 975         /*
 976          * Thread groups must share signals as well, and detached threads
 977          * can only be started up within the thread group.
 978          */
 979         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 980                 return ERR_PTR(-EINVAL);
 981
 982         /*
 983          * Shared signal handlers imply shared VM. By way of the above,
 984          * thread groups also imply shared VM. Blocking this case allows
 985          * for various simplifications in other code.
 986          */
 987         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 988                 return ERR_PTR(-EINVAL);
 989
 990         /*
 991          * Siblings of global init remain as zombies on exit since they are
 992          * not reaped by their parent (swapper). To solve this and to avoid
 993          * multi-rooted process trees, prevent global and container-inits
 994          * from creating siblings.
 995          */
 996         if ((clone_flags & CLONE_PARENT) &&
 997                                 current->signal->flags & SIGNAL_UNKILLABLE)
 998                 return ERR_PTR(-EINVAL);
 999
1000         retval = security_task_create(clone_flags);
1001         if (retval)
1002                 goto fork_out;
1003
1004         retval = -ENOMEM;
1005         p = dup_task_struct(current);
1006         if (!p)
1007                 goto fork_out;
1008
1009         ftrace_graph_init_task(p);
1010
1011         rt_mutex_init_task(p);
1012
1013 #ifdef CONFIG_PROVE_LOCKING
1014         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1015         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1016 #endif
1017         retval = -EAGAIN;
1018         if (atomic_read(&p->real_cred->user->processes) >=
1019                         task_rlimit(p, RLIMIT_NPROC)) {
1020                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1021                     p->real_cred->user != INIT_USER)
1022                         goto bad_fork_free;
1023         }
1024
1025         retval = copy_creds(p, clone_flags);
1026         if (retval < 0)
1027                 goto bad_fork_free;
1028
1029         /*
1030          * If multiple threads are within copy_process(), then this check
1031          * triggers too late. This doesn't hurt, the check is only there
1032          * to stop root fork bombs.
1033          */
1034         retval = -EAGAIN;
1035         if (nr_threads >= max_threads)
1036                 goto bad_fork_cleanup_count;
1037
1038         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1039                 goto bad_fork_cleanup_count;
1040
1041         p->did_exec = 0;
1042         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1043         copy_flags(clone_flags, p);
1044         INIT_LIST_HEAD(&p->children);
1045         INIT_LIST_HEAD(&p->sibling);
1046         rcu_copy_process(p);
1047         p->vfork_done = NULL;
1048         spin_lock_init(&p->alloc_lock);
1049
1050         init_sigpending(&p->pending);
1051
1052         p->utime = cputime_zero;
1053         p->stime = cputime_zero;
1054         p->gtime = cputime_zero;
1055         p->utimescaled = cputime_zero;
1056         p->stimescaled = cputime_zero;
1057 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1058         p->prev_utime = cputime_zero;
1059         p->prev_stime = cputime_zero;
1060 #endif
1061 #if defined(SPLIT_RSS_COUNTING)
1062         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1063 #endif
1064
1065         p->default_timer_slack_ns = current->timer_slack_ns;
1066
1067         task_io_accounting_init(&p->ioac);
1068         acct_clear_integrals(p);
1069
1070         posix_cpu_timers_init(p);
1071
1072         p->lock_depth = -1;             /* -1 = no lock */
1073         do_posix_clock_monotonic_gettime(&p->start_time);
1074         p->real_start_time = p->start_time;
1075         monotonic_to_bootbased(&p->real_start_time);
1076         p->io_context = NULL;
1077         p->audit_context = NULL;
1078         cgroup_fork(p);
1079 #ifdef CONFIG_NUMA
1080         p->mempolicy = mpol_dup(p->mempolicy);
1081         if (IS_ERR(p->mempolicy)) {
1082                 retval = PTR_ERR(p->mempolicy);
1083                 p->mempolicy = NULL;
1084                 goto bad_fork_cleanup_cgroup;
1085         }
1086         mpol_fix_fork_child_flag(p);
1087 #endif
1088 #ifdef CONFIG_CPUSETS
1089         p->cpuset_mem_spread_rotor = node_random(p->mems_allowed);
1090         p->cpuset_slab_spread_rotor = node_random(p->mems_allowed);
1091 #endif
1092 #ifdef CONFIG_TRACE_IRQFLAGS
1093         p->irq_events = 0;
1094 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1095         p->hardirqs_enabled = 1;
1096 #else
1097         p->hardirqs_enabled = 0;
1098 #endif
1099         p->hardirq_enable_ip = 0;
1100         p->hardirq_enable_event = 0;
1101         p->hardirq_disable_ip = _THIS_IP_;
1102         p->hardirq_disable_event = 0;
1103         p->softirqs_enabled = 1;
1104         p->softirq_enable_ip = _THIS_IP_;
1105         p->softirq_enable_event = 0;
1106         p->softirq_disable_ip = 0;
1107         p->softirq_disable_event = 0;
1108         p->hardirq_context = 0;
1109         p->softirq_context = 0;
1110 #endif
1111 #ifdef CONFIG_LOCKDEP
1112         p->lockdep_depth = 0; /* no locks held yet */
1113         p->curr_chain_key = 0;
1114         p->lockdep_recursion = 0;
1115 #endif
1116
1117 #ifdef CONFIG_DEBUG_MUTEXES
1118         p->blocked_on = NULL; /* not blocked yet */
1119 #endif
1120 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1121         p->memcg_batch.do_batch = 0;
1122         p->memcg_batch.memcg = NULL;
1123 #endif
1124
1125         /* Perform scheduler related setup. Assign this task to a CPU. */
1126         sched_fork(p, clone_flags);
1127
1128         retval = perf_event_init_task(p);
1129         if (retval)
1130                 goto bad_fork_cleanup_policy;
1131
1132         if ((retval = audit_alloc(p)))
1133                 goto bad_fork_cleanup_policy;
1134         /* copy all the process information */
1135         if ((retval = copy_semundo(clone_flags, p)))
1136                 goto bad_fork_cleanup_audit;
1137         if ((retval = copy_files(clone_flags, p)))
1138                 goto bad_fork_cleanup_semundo;
1139         if ((retval = copy_fs(clone_flags, p)))
1140                 goto bad_fork_cleanup_files;
1141         if ((retval = copy_sighand(clone_flags, p)))
1142                 goto bad_fork_cleanup_fs;
1143         if ((retval = copy_signal(clone_flags, p)))
1144                 goto bad_fork_cleanup_sighand;
1145         if ((retval = copy_mm(clone_flags, p)))
1146                 goto bad_fork_cleanup_signal;
1147         if ((retval = copy_namespaces(clone_flags, p)))
1148                 goto bad_fork_cleanup_mm;
1149         if ((retval = copy_io(clone_flags, p)))
1150                 goto bad_fork_cleanup_namespaces;
1151         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1152         if (retval)
1153                 goto bad_fork_cleanup_io;
1154
1155         if (pid != &init_struct_pid) {
1156                 retval = -ENOMEM;
1157                 pid = alloc_pid(p->nsproxy->pid_ns);
1158                 if (!pid)
1159                         goto bad_fork_cleanup_io;
1160
1161                 if (clone_flags & CLONE_NEWPID) {
1162                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1163                         if (retval < 0)
1164                                 goto bad_fork_free_pid;
1165                 }
1166         }
1167
1168         p->pid = pid_nr(pid);
1169         p->tgid = p->pid;
1170         if (clone_flags & CLONE_THREAD)
1171                 p->tgid = current->tgid;
1172
1173         if (current->nsproxy != p->nsproxy) {
1174                 retval = ns_cgroup_clone(p, pid);
1175                 if (retval)
1176                         goto bad_fork_free_pid;
1177         }
1178
1179         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1180         /*
1181          * Clear TID on mm_release()?
1182          */
1183         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1184 #ifdef CONFIG_FUTEX
1185         p->robust_list = NULL;
1186 #ifdef CONFIG_COMPAT
1187         p->compat_robust_list = NULL;
1188 #endif
1189         INIT_LIST_HEAD(&p->pi_state_list);
1190         p->pi_state_cache = NULL;
1191 #endif
1192         /*
1193          * sigaltstack should be cleared when sharing the same VM
1194          */
1195         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1196                 p->sas_ss_sp = p->sas_ss_size = 0;
1197
1198         /*
1199          * Syscall tracing and stepping should be turned off in the
1200          * child regardless of CLONE_PTRACE.
1201          */
1202         user_disable_single_step(p);
1203         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1204 #ifdef TIF_SYSCALL_EMU
1205         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1206 #endif
1207         clear_all_latency_tracing(p);
1208
1209         /* ok, now we should be set up.. */
1210         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1211         p->pdeath_signal = 0;
1212         p->exit_state = 0;
1213
1214         /*
1215          * Ok, make it visible to the rest of the system.
1216          * We dont wake it up yet.
1217          */
1218         p->group_leader = p;
1219         INIT_LIST_HEAD(&p->thread_group);
1220
1221         /* Now that the task is set up, run cgroup callbacks if
1222          * necessary. We need to run them before the task is visible
1223          * on the tasklist. */
1224         cgroup_fork_callbacks(p);
1225         cgroup_callbacks_done = 1;
1226
1227         /* Need tasklist lock for parent etc handling! */
1228         write_lock_irq(&tasklist_lock);
1229
1230         /* CLONE_PARENT re-uses the old parent */
1231         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1232                 p->real_parent = current->real_parent;
1233                 p->parent_exec_id = current->parent_exec_id;
1234         } else {
1235                 p->real_parent = current;
1236                 p->parent_exec_id = current->self_exec_id;
1237         }
1238
1239         spin_lock(&current->sighand->siglock);
1240
1241         /*
1242          * Process group and session signals need to be delivered to just the
1243          * parent before the fork or both the parent and the child after the
1244          * fork. Restart if a signal comes in before we add the new process to
1245          * it's process group.
1246          * A fatal signal pending means that current will exit, so the new
1247          * thread can't slip out of an OOM kill (or normal SIGKILL).
1248          */
1249         recalc_sigpending();
1250         if (signal_pending(current)) {
1251                 spin_unlock(&current->sighand->siglock);
1252                 write_unlock_irq(&tasklist_lock);
1253                 retval = -ERESTARTNOINTR;
1254                 goto bad_fork_free_pid;
1255         }
1256
1257         if (clone_flags & CLONE_THREAD) {
1258                 atomic_inc(&current->signal->sigcnt);
1259                 atomic_inc(&current->signal->count);
1260                 atomic_inc(&current->signal->live);
1261                 p->group_leader = current->group_leader;
1262                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1263         }
1264
1265         if (likely(p->pid)) {
1266                 tracehook_finish_clone(p, clone_flags, trace);
1267
1268                 if (thread_group_leader(p)) {
1269                         if (clone_flags & CLONE_NEWPID)
1270                                 p->nsproxy->pid_ns->child_reaper = p;
1271
1272                         p->signal->leader_pid = pid;
1273                         p->signal->tty = tty_kref_get(current->signal->tty);
1274                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1275                         attach_pid(p, PIDTYPE_SID, task_session(current));
1276                         list_add_tail(&p->sibling, &p->real_parent->children);
1277                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1278                         __get_cpu_var(process_counts)++;
1279                 }
1280                 attach_pid(p, PIDTYPE_PID, pid);
1281                 nr_threads++;
1282         }
1283
1284         total_forks++;
1285         spin_unlock(&current->sighand->siglock);
1286         write_unlock_irq(&tasklist_lock);
1287         proc_fork_connector(p);
1288         cgroup_post_fork(p);
1289         perf_event_fork(p);
1290         return p;
1291
1292 bad_fork_free_pid:
1293         if (pid != &init_struct_pid)
1294                 free_pid(pid);
1295 bad_fork_cleanup_io:
1296         if (p->io_context)
1297                 exit_io_context(p);
1298 bad_fork_cleanup_namespaces:
1299         exit_task_namespaces(p);
1300 bad_fork_cleanup_mm:
1301         if (p->mm)
1302                 mmput(p->mm);
1303 bad_fork_cleanup_signal:
1304         if (!(clone_flags & CLONE_THREAD))
1305                 free_signal_struct(p->signal);
1306 bad_fork_cleanup_sighand:
1307         __cleanup_sighand(p->sighand);
1308 bad_fork_cleanup_fs:
1309         exit_fs(p); /* blocking */
1310 bad_fork_cleanup_files:
1311         exit_files(p); /* blocking */
1312 bad_fork_cleanup_semundo:
1313         exit_sem(p);
1314 bad_fork_cleanup_audit:
1315         audit_free(p);
1316 bad_fork_cleanup_policy:
1317         perf_event_free_task(p);
1318 #ifdef CONFIG_NUMA
1319         mpol_put(p->mempolicy);
1320 bad_fork_cleanup_cgroup:
1321 #endif
1322         cgroup_exit(p, cgroup_callbacks_done);
1323         delayacct_tsk_free(p);
1324         module_put(task_thread_info(p)->exec_domain->module);
1325 bad_fork_cleanup_count:
1326         atomic_dec(&p->cred->user->processes);
1327         exit_creds(p);
1328 bad_fork_free:
1329         free_task(p);
1330 fork_out:
1331         return ERR_PTR(retval);
1332 }
1333
1334 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1335 {
1336         memset(regs, 0, sizeof(struct pt_regs));
1337         return regs;
1338 }
1339
1340 struct task_struct * __cpuinit fork_idle(int cpu)
1341 {
1342         struct task_struct *task;
1343         struct pt_regs regs;
1344
1345         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1346                             &init_struct_pid, 0);
1347         if (!IS_ERR(task))
1348                 init_idle(task, cpu);
1349
1350         return task;
1351 }
1352
1353 /*
1354  *  Ok, this is the main fork-routine.
1355  *
1356  * It copies the process, and if successful kick-starts
1357  * it and waits for it to finish using the VM if required.
1358  */
1359 long do_fork(unsigned long clone_flags,
1360               unsigned long stack_start,
1361               struct pt_regs *regs,
1362               unsigned long stack_size,
1363               int __user *parent_tidptr,
1364               int __user *child_tidptr)
1365 {
1366         struct task_struct *p;
1367         int trace = 0;
1368         long nr;
1369
1370         /*
1371          * Do some preliminary argument and permissions checking before we
1372          * actually start allocating stuff
1373          */
1374         if (clone_flags & CLONE_NEWUSER) {
1375                 if (clone_flags & CLONE_THREAD)
1376                         return -EINVAL;
1377                 /* hopefully this check will go away when userns support is
1378                  * complete
1379                  */
1380                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1381                                 !capable(CAP_SETGID))
1382                         return -EPERM;
1383         }
1384
1385         /*
1386          * We hope to recycle these flags after 2.6.26
1387          */
1388         if (unlikely(clone_flags & CLONE_STOPPED)) {
1389                 static int __read_mostly count = 100;
1390
1391                 if (count > 0 && printk_ratelimit()) {
1392                         char comm[TASK_COMM_LEN];
1393
1394                         count--;
1395                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1396                                         "clone flags 0x%lx\n",
1397                                 get_task_comm(comm, current),
1398                                 clone_flags & CLONE_STOPPED);
1399                 }
1400         }
1401
1402         /*
1403          * When called from kernel_thread, don't do user tracing stuff.
1404          */
1405         if (likely(user_mode(regs)))
1406                 trace = tracehook_prepare_clone(clone_flags);
1407
1408         p = copy_process(clone_flags, stack_start, regs, stack_size,
1409                          child_tidptr, NULL, trace);
1410         /*
1411          * Do this prior waking up the new thread - the thread pointer
1412          * might get invalid after that point, if the thread exits quickly.
1413          */
1414         if (!IS_ERR(p)) {
1415                 struct completion vfork;
1416
1417                 trace_sched_process_fork(current, p);
1418
1419                 nr = task_pid_vnr(p);
1420
1421                 if (clone_flags & CLONE_PARENT_SETTID)
1422                         put_user(nr, parent_tidptr);
1423
1424                 if (clone_flags & CLONE_VFORK) {
1425                         p->vfork_done = &vfork;
1426                         init_completion(&vfork);
1427                 }
1428
1429                 audit_finish_fork(p);
1430                 tracehook_report_clone(regs, clone_flags, nr, p);
1431
1432                 /*
1433                  * We set PF_STARTING at creation in case tracing wants to
1434                  * use this to distinguish a fully live task from one that
1435                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1436                  * clear it and set the child going.
1437                  */
1438                 p->flags &= ~PF_STARTING;
1439
1440                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1441                         /*
1442                          * We'll start up with an immediate SIGSTOP.
1443                          */
1444                         sigaddset(&p->pending.signal, SIGSTOP);
1445                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1446                         __set_task_state(p, TASK_STOPPED);
1447                 } else {
1448                         wake_up_new_task(p, clone_flags);
1449                 }
1450
1451                 tracehook_report_clone_complete(trace, regs,
1452                                                 clone_flags, nr, p);
1453
1454                 if (clone_flags & CLONE_VFORK) {
1455                         freezer_do_not_count();
1456                         wait_for_completion(&vfork);
1457                         freezer_count();
1458                         tracehook_report_vfork_done(p, nr);
1459                 }
1460         } else {
1461                 nr = PTR_ERR(p);
1462         }
1463         return nr;
1464 }
1465
1466 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1467 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1468 #endif
1469
1470 static void sighand_ctor(void *data)
1471 {
1472         struct sighand_struct *sighand = data;
1473
1474         spin_lock_init(&sighand->siglock);
1475         init_waitqueue_head(&sighand->signalfd_wqh);
1476 }
1477
1478 void __init proc_caches_init(void)
1479 {
1480         sighand_cachep = kmem_cache_create("sighand_cache",
1481                         sizeof(struct sighand_struct), 0,
1482                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1483                         SLAB_NOTRACK, sighand_ctor);
1484         signal_cachep = kmem_cache_create("signal_cache",
1485                         sizeof(struct signal_struct), 0,
1486                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1487         files_cachep = kmem_cache_create("files_cache",
1488                         sizeof(struct files_struct), 0,
1489                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1490         fs_cachep = kmem_cache_create("fs_cache",
1491                         sizeof(struct fs_struct), 0,
1492                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1493         mm_cachep = kmem_cache_create("mm_struct",
1494                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1495                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1496         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1497         mmap_init();
1498 }
1499
1500 /*
1501  * Check constraints on flags passed to the unshare system call and
1502  * force unsharing of additional process context as appropriate.
1503  */
1504 static void check_unshare_flags(unsigned long *flags_ptr)
1505 {
1506         /*
1507          * If unsharing a thread from a thread group, must also
1508          * unshare vm.
1509          */
1510         if (*flags_ptr & CLONE_THREAD)
1511                 *flags_ptr |= CLONE_VM;
1512
1513         /*
1514          * If unsharing vm, must also unshare signal handlers.
1515          */
1516         if (*flags_ptr & CLONE_VM)
1517                 *flags_ptr |= CLONE_SIGHAND;
1518
1519         /*
1520          * If unsharing signal handlers and the task was created
1521          * using CLONE_THREAD, then must unshare the thread
1522          */
1523         if ((*flags_ptr & CLONE_SIGHAND) &&
1524             (atomic_read(&current->signal->count) > 1))
1525                 *flags_ptr |= CLONE_THREAD;
1526
1527         /*
1528          * If unsharing namespace, must also unshare filesystem information.
1529          */
1530         if (*flags_ptr & CLONE_NEWNS)
1531                 *flags_ptr |= CLONE_FS;
1532 }
1533
1534 /*
1535  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1536  */
1537 static int unshare_thread(unsigned long unshare_flags)
1538 {
1539         if (unshare_flags & CLONE_THREAD)
1540                 return -EINVAL;
1541
1542         return 0;
1543 }
1544
1545 /*
1546  * Unshare the filesystem structure if it is being shared
1547  */
1548 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1549 {
1550         struct fs_struct *fs = current->fs;
1551
1552         if (!(unshare_flags & CLONE_FS) || !fs)
1553                 return 0;
1554
1555         /* don't need lock here; in the worst case we'll do useless copy */
1556         if (fs->users == 1)
1557                 return 0;
1558
1559         *new_fsp = copy_fs_struct(fs);
1560         if (!*new_fsp)
1561                 return -ENOMEM;
1562
1563         return 0;
1564 }
1565
1566 /*
1567  * Unsharing of sighand is not supported yet
1568  */
1569 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1570 {
1571         struct sighand_struct *sigh = current->sighand;
1572
1573         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1574                 return -EINVAL;
1575         else
1576                 return 0;
1577 }
1578
1579 /*
1580  * Unshare vm if it is being shared
1581  */
1582 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1583 {
1584         struct mm_struct *mm = current->mm;
1585
1586         if ((unshare_flags & CLONE_VM) &&
1587             (mm && atomic_read(&mm->mm_users) > 1)) {
1588                 return -EINVAL;
1589         }
1590
1591         return 0;
1592 }
1593
1594 /*
1595  * Unshare file descriptor table if it is being shared
1596  */
1597 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1598 {
1599         struct files_struct *fd = current->files;
1600         int error = 0;
1601
1602         if ((unshare_flags & CLONE_FILES) &&
1603             (fd && atomic_read(&fd->count) > 1)) {
1604                 *new_fdp = dup_fd(fd, &error);
1605                 if (!*new_fdp)
1606                         return error;
1607         }
1608
1609         return 0;
1610 }
1611
1612 /*
1613  * unshare allows a process to 'unshare' part of the process
1614  * context which was originally shared using clone.  copy_*
1615  * functions used by do_fork() cannot be used here directly
1616  * because they modify an inactive task_struct that is being
1617  * constructed. Here we are modifying the current, active,
1618  * task_struct.
1619  */
1620 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1621 {
1622         int err = 0;
1623         struct fs_struct *fs, *new_fs = NULL;
1624         struct sighand_struct *new_sigh = NULL;
1625         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1626         struct files_struct *fd, *new_fd = NULL;
1627         struct nsproxy *new_nsproxy = NULL;
1628         int do_sysvsem = 0;
1629
1630         check_unshare_flags(&unshare_flags);
1631
1632         /* Return -EINVAL for all unsupported flags */
1633         err = -EINVAL;
1634         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1635                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1636                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1637                 goto bad_unshare_out;
1638
1639         /*
1640          * CLONE_NEWIPC must also detach from the undolist: after switching
1641          * to a new ipc namespace, the semaphore arrays from the old
1642          * namespace are unreachable.
1643          */
1644         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1645                 do_sysvsem = 1;
1646         if ((err = unshare_thread(unshare_flags)))
1647                 goto bad_unshare_out;
1648         if ((err = unshare_fs(unshare_flags, &new_fs)))
1649                 goto bad_unshare_cleanup_thread;
1650         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1651                 goto bad_unshare_cleanup_fs;
1652         if ((err = unshare_vm(unshare_flags, &new_mm)))
1653                 goto bad_unshare_cleanup_sigh;
1654         if ((err = unshare_fd(unshare_flags, &new_fd)))
1655                 goto bad_unshare_cleanup_vm;
1656         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1657                         new_fs)))
1658                 goto bad_unshare_cleanup_fd;
1659
1660         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1661                 if (do_sysvsem) {
1662                         /*
1663                          * CLONE_SYSVSEM is equivalent to sys_exit().
1664                          */
1665                         exit_sem(current);
1666                 }
1667
1668                 if (new_nsproxy) {
1669                         switch_task_namespaces(current, new_nsproxy);
1670                         new_nsproxy = NULL;
1671                 }
1672
1673                 task_lock(current);
1674
1675                 if (new_fs) {
1676                         fs = current->fs;
1677                         write_lock(&fs->lock);
1678                         current->fs = new_fs;
1679                         if (--fs->users)
1680                                 new_fs = NULL;
1681                         else
1682                                 new_fs = fs;
1683                         write_unlock(&fs->lock);
1684                 }
1685
1686                 if (new_mm) {
1687                         mm = current->mm;
1688                         active_mm = current->active_mm;
1689                         current->mm = new_mm;
1690                         current->active_mm = new_mm;
1691                         activate_mm(active_mm, new_mm);
1692                         new_mm = mm;
1693                 }
1694
1695                 if (new_fd) {
1696                         fd = current->files;
1697                         current->files = new_fd;
1698                         new_fd = fd;
1699                 }
1700
1701                 task_unlock(current);
1702         }
1703
1704         if (new_nsproxy)
1705                 put_nsproxy(new_nsproxy);
1706
1707 bad_unshare_cleanup_fd:
1708         if (new_fd)
1709                 put_files_struct(new_fd);
1710
1711 bad_unshare_cleanup_vm:
1712         if (new_mm)
1713                 mmput(new_mm);
1714
1715 bad_unshare_cleanup_sigh:
1716         if (new_sigh)
1717                 if (atomic_dec_and_test(&new_sigh->count))
1718                         kmem_cache_free(sighand_cachep, new_sigh);
1719
1720 bad_unshare_cleanup_fs:
1721         if (new_fs)
1722                 free_fs_struct(new_fs);
1723
1724 bad_unshare_cleanup_thread:
1725 bad_unshare_out:
1726         return err;
1727 }
1728
1729 /*
1730  *      Helper to unshare the files of the current task.
1731  *      We don't want to expose copy_files internals to
1732  *      the exec layer of the kernel.
1733  */
1734
1735 int unshare_files(struct files_struct **displaced)
1736 {
1737         struct task_struct *task = current;
1738         struct files_struct *copy = NULL;
1739         int error;
1740
1741         error = unshare_fd(CLONE_FILES, &copy);
1742         if (error || !copy) {
1743                 *displaced = NULL;
1744                 return error;
1745         }
1746         *displaced = task->files;
1747         task_lock(task);
1748         task->files = copy;
1749         task_unlock(task);
1750         return 0;
1751 }