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