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