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