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