kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/personality.h>
  21 #include <linux/mempolicy.h>
  22 #include <linux/sem.h>
  23 #include <linux/file.h>
  24 #include <linux/fdtable.h>
  25 #include <linux/iocontext.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/mmu_notifier.h>
  30 #include <linux/fs.h>
  31 #include <linux/nsproxy.h>
  32 #include <linux/capability.h>
  33 #include <linux/cpu.h>
  34 #include <linux/cgroup.h>
  35 #include <linux/security.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/seccomp.h>
  38 #include <linux/swap.h>
  39 #include <linux/syscalls.h>
  40 #include <linux/jiffies.h>
  41 #include <linux/futex.h>
  42 #include <linux/compat.h>
  43 #include <linux/kthread.h>
  44 #include <linux/task_io_accounting_ops.h>
  45 #include <linux/rcupdate.h>
  46 #include <linux/ptrace.h>
  47 #include <linux/mount.h>
  48 #include <linux/audit.h>
  49 #include <linux/memcontrol.h>
  50 #include <linux/ftrace.h>
  51 #include <linux/proc_fs.h>
  52 #include <linux/profile.h>
  53 #include <linux/rmap.h>
  54 #include <linux/ksm.h>
  55 #include <linux/acct.h>
  56 #include <linux/tsacct_kern.h>
  57 #include <linux/cn_proc.h>
  58 #include <linux/freezer.h>
  59 #include <linux/delayacct.h>
  60 #include <linux/taskstats_kern.h>
  61 #include <linux/random.h>
  62 #include <linux/tty.h>
  63 #include <linux/blkdev.h>
  64 #include <linux/fs_struct.h>
  65 #include <linux/magic.h>
  66 #include <linux/perf_event.h>
  67 #include <linux/posix-timers.h>
  68 #include <linux/user-return-notifier.h>
  69 #include <linux/oom.h>
  70 #include <linux/khugepaged.h>
  71 #include <linux/signalfd.h>
  72 #include <linux/uprobes.h>
  73
  74 #include <asm/pgtable.h>
  75 #include <asm/pgalloc.h>
  76 #include <asm/uaccess.h>
  77 #include <asm/mmu_context.h>
  78 #include <asm/cacheflush.h>
  79 #include <asm/tlbflush.h>
  80
  81 #include <trace/events/sched.h>
  82
  83 #define CREATE_TRACE_POINTS
  84 #include <trace/events/task.h>
  85
  86 /*
  87  * Protected counters by write_lock_irq(&tasklist_lock)
  88  */
  89 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  90 int nr_threads;                 /* The idle threads do not count.. */
  91
  92 int max_threads;                /* tunable limit on nr_threads */
  93
  94 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  95
  96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  97
  98 #ifdef CONFIG_PROVE_RCU
  99 int lockdep_tasklist_lock_is_held(void)
 100 {
 101         return lockdep_is_held(&tasklist_lock);
 102 }
 103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 104 #endif /* #ifdef CONFIG_PROVE_RCU */
 105
 106 int nr_processes(void)
 107 {
 108         int cpu;
 109         int total = 0;
 110
 111         for_each_possible_cpu(cpu)
 112                 total += per_cpu(process_counts, cpu);
 113
 114         return total;
 115 }
 116
 117 void __weak arch_release_task_struct(struct task_struct *tsk)
 118 {
 119 }
 120
 121 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 122 static struct kmem_cache *task_struct_cachep;
 123
 124 static inline struct task_struct *alloc_task_struct_node(int node)
 125 {
 126         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 127 }
 128
 129 static inline void free_task_struct(struct task_struct *tsk)
 130 {
 131         kmem_cache_free(task_struct_cachep, tsk);
 132 }
 133 #endif
 134
 135 void __weak arch_release_thread_info(struct thread_info *ti)
 136 {
 137 }
 138
 139 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 140
 141 /*
 142  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 143  * kmemcache based allocator.
 144  */
 145 # if THREAD_SIZE >= PAGE_SIZE
 146 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 147                                                   int node)
 148 {
 149         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 150                                              THREAD_SIZE_ORDER);
 151
 152         return page ? page_address(page) : NULL;
 153 }
 154
 155 static inline void free_thread_info(struct thread_info *ti)
 156 {
 157         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 158 }
 159 # else
 160 static struct kmem_cache *thread_info_cache;
 161
 162 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 163                                                   int node)
 164 {
 165         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 166 }
 167
 168 static void free_thread_info(struct thread_info *ti)
 169 {
 170         kmem_cache_free(thread_info_cache, ti);
 171 }
 172
 173 void thread_info_cache_init(void)
 174 {
 175         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 176                                               THREAD_SIZE, 0, NULL);
 177         BUG_ON(thread_info_cache == NULL);
 178 }
 179 # endif
 180 #endif
 181
 182 /* SLAB cache for signal_struct structures (tsk->signal) */
 183 static struct kmem_cache *signal_cachep;
 184
 185 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 186 struct kmem_cache *sighand_cachep;
 187
 188 /* SLAB cache for files_struct structures (tsk->files) */
 189 struct kmem_cache *files_cachep;
 190
 191 /* SLAB cache for fs_struct structures (tsk->fs) */
 192 struct kmem_cache *fs_cachep;
 193
 194 /* SLAB cache for vm_area_struct structures */
 195 struct kmem_cache *vm_area_cachep;
 196
 197 /* SLAB cache for mm_struct structures (tsk->mm) */
 198 static struct kmem_cache *mm_cachep;
 199
 200 static void account_kernel_stack(struct thread_info *ti, int account)
 201 {
 202         struct zone *zone = page_zone(virt_to_page(ti));
 203
 204         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 205 }
 206
 207 void free_task(struct task_struct *tsk)
 208 {
 209         account_kernel_stack(tsk->stack, -1);
 210         arch_release_thread_info(tsk->stack);
 211         free_thread_info(tsk->stack);
 212         rt_mutex_debug_task_free(tsk);
 213         ftrace_graph_exit_task(tsk);
 214         put_seccomp_filter(tsk);
 215         arch_release_task_struct(tsk);
 216         free_task_struct(tsk);
 217 }
 218 EXPORT_SYMBOL(free_task);
 219
 220 static inline void free_signal_struct(struct signal_struct *sig)
 221 {
 222         taskstats_tgid_free(sig);
 223         sched_autogroup_exit(sig);
 224         kmem_cache_free(signal_cachep, sig);
 225 }
 226
 227 static inline void put_signal_struct(struct signal_struct *sig)
 228 {
 229         if (atomic_dec_and_test(&sig->sigcnt))
 230                 free_signal_struct(sig);
 231 }
 232
 233 void __put_task_struct(struct task_struct *tsk)
 234 {
 235         WARN_ON(!tsk->exit_state);
 236         WARN_ON(atomic_read(&tsk->usage));
 237         WARN_ON(tsk == current);
 238
 239         security_task_free(tsk);
 240         exit_creds(tsk);
 241         delayacct_tsk_free(tsk);
 242         put_signal_struct(tsk->signal);
 243
 244         if (!profile_handoff_task(tsk))
 245                 free_task(tsk);
 246 }
 247 EXPORT_SYMBOL_GPL(__put_task_struct);
 248
 249 void __init __weak arch_task_cache_init(void) { }
 250
 251 void __init fork_init(unsigned long mempages)
 252 {
 253 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 254 #ifndef ARCH_MIN_TASKALIGN
 255 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 256 #endif
 257         /* create a slab on which task_structs can be allocated */
 258         task_struct_cachep =
 259                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 260                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 261 #endif
 262
 263         /* do the arch specific task caches init */
 264         arch_task_cache_init();
 265
 266         /*
 267          * The default maximum number of threads is set to a safe
 268          * value: the thread structures can take up at most half
 269          * of memory.
 270          */
 271         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 272
 273         /*
 274          * we need to allow at least 20 threads to boot a system
 275          */
 276         if (max_threads < 20)
 277                 max_threads = 20;
 278
 279         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 280         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 281         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 282                 init_task.signal->rlim[RLIMIT_NPROC];
 283 }
 284
 285 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 286                                                struct task_struct *src)
 287 {
 288         *dst = *src;
 289         return 0;
 290 }
 291
 292 static struct task_struct *dup_task_struct(struct task_struct *orig)
 293 {
 294         struct task_struct *tsk;
 295         struct thread_info *ti;
 296         unsigned long *stackend;
 297         int node = tsk_fork_get_node(orig);
 298         int err;
 299
 300         tsk = alloc_task_struct_node(node);
 301         if (!tsk)
 302                 return NULL;
 303
 304         ti = alloc_thread_info_node(tsk, node);
 305         if (!ti)
 306                 goto free_tsk;
 307
 308         err = arch_dup_task_struct(tsk, orig);
 309         if (err)
 310                 goto free_ti;
 311
 312         tsk->stack = ti;
 313
 314         setup_thread_stack(tsk, orig);
 315         clear_user_return_notifier(tsk);
 316         clear_tsk_need_resched(tsk);
 317         stackend = end_of_stack(tsk);
 318         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 319
 320 #ifdef CONFIG_CC_STACKPROTECTOR
 321         tsk->stack_canary = get_random_int();
 322 #endif
 323
 324         /*
 325          * One for us, one for whoever does the "release_task()" (usually
 326          * parent)
 327          */
 328         atomic_set(&tsk->usage, 2);
 329 #ifdef CONFIG_BLK_DEV_IO_TRACE
 330         tsk->btrace_seq = 0;
 331 #endif
 332         tsk->splice_pipe = NULL;
 333         tsk->task_frag.page = NULL;
 334
 335         account_kernel_stack(ti, 1);
 336
 337         return tsk;
 338
 339 free_ti:
 340         free_thread_info(ti);
 341 free_tsk:
 342         free_task_struct(tsk);
 343         return NULL;
 344 }
 345
 346 #ifdef CONFIG_MMU
 347 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 348 {
 349         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 350         struct rb_node **rb_link, *rb_parent;
 351         int retval;
 352         unsigned long charge;
 353         struct mempolicy *pol;
 354
 355         down_write(&oldmm->mmap_sem);
 356         flush_cache_dup_mm(oldmm);
 357         uprobe_dup_mmap(oldmm, mm);
 358         /*
 359          * Not linked in yet - no deadlock potential:
 360          */
 361         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 362
 363         mm->locked_vm = 0;
 364         mm->mmap = NULL;
 365         mm->mmap_cache = NULL;
 366         mm->free_area_cache = oldmm->mmap_base;
 367         mm->cached_hole_size = ~0UL;
 368         mm->map_count = 0;
 369         cpumask_clear(mm_cpumask(mm));
 370         mm->mm_rb = RB_ROOT;
 371         rb_link = &mm->mm_rb.rb_node;
 372         rb_parent = NULL;
 373         pprev = &mm->mmap;
 374         retval = ksm_fork(mm, oldmm);
 375         if (retval)
 376                 goto out;
 377         retval = khugepaged_fork(mm, oldmm);
 378         if (retval)
 379                 goto out;
 380
 381         prev = NULL;
 382         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 383                 struct file *file;
 384
 385                 if (mpnt->vm_flags & VM_DONTCOPY) {
 386                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 387                                                         -vma_pages(mpnt));
 388                         continue;
 389                 }
 390                 charge = 0;
 391                 if (mpnt->vm_flags & VM_ACCOUNT) {
 392                         unsigned long len = vma_pages(mpnt);
 393
 394                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 395                                 goto fail_nomem;
 396                         charge = len;
 397                 }
 398                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 399                 if (!tmp)
 400                         goto fail_nomem;
 401                 *tmp = *mpnt;
 402                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 403                 pol = mpol_dup(vma_policy(mpnt));
 404                 retval = PTR_ERR(pol);
 405                 if (IS_ERR(pol))
 406                         goto fail_nomem_policy;
 407                 vma_set_policy(tmp, pol);
 408                 tmp->vm_mm = mm;
 409                 if (anon_vma_fork(tmp, mpnt))
 410                         goto fail_nomem_anon_vma_fork;
 411                 tmp->vm_flags &= ~VM_LOCKED;
 412                 tmp->vm_next = tmp->vm_prev = NULL;
 413                 file = tmp->vm_file;
 414                 if (file) {
 415                         struct inode *inode = file->f_path.dentry->d_inode;
 416                         struct address_space *mapping = file->f_mapping;
 417
 418                         get_file(file);
 419                         if (tmp->vm_flags & VM_DENYWRITE)
 420                                 atomic_dec(&inode->i_writecount);
 421                         mutex_lock(&mapping->i_mmap_mutex);
 422                         if (tmp->vm_flags & VM_SHARED)
 423                                 mapping->i_mmap_writable++;
 424                         flush_dcache_mmap_lock(mapping);
 425                         /* insert tmp into the share list, just after mpnt */
 426                         vma_prio_tree_add(tmp, mpnt);
 427                         flush_dcache_mmap_unlock(mapping);
 428                         mutex_unlock(&mapping->i_mmap_mutex);
 429                 }
 430
 431                 /*
 432                  * Clear hugetlb-related page reserves for children. This only
 433                  * affects MAP_PRIVATE mappings. Faults generated by the child
 434                  * are not guaranteed to succeed, even if read-only
 435                  */
 436                 if (is_vm_hugetlb_page(tmp))
 437                         reset_vma_resv_huge_pages(tmp);
 438
 439                 /*
 440                  * Link in the new vma and copy the page table entries.
 441                  */
 442                 *pprev = tmp;
 443                 pprev = &tmp->vm_next;
 444                 tmp->vm_prev = prev;
 445                 prev = tmp;
 446
 447                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 448                 rb_link = &tmp->vm_rb.rb_right;
 449                 rb_parent = &tmp->vm_rb;
 450
 451                 mm->map_count++;
 452                 retval = copy_page_range(mm, oldmm, mpnt);
 453
 454                 if (tmp->vm_ops && tmp->vm_ops->open)
 455                         tmp->vm_ops->open(tmp);
 456
 457                 if (retval)
 458                         goto out;
 459         }
 460         /* a new mm has just been created */
 461         arch_dup_mmap(oldmm, mm);
 462         retval = 0;
 463 out:
 464         up_write(&mm->mmap_sem);
 465         flush_tlb_mm(oldmm);
 466         up_write(&oldmm->mmap_sem);
 467         return retval;
 468 fail_nomem_anon_vma_fork:
 469         mpol_put(pol);
 470 fail_nomem_policy:
 471         kmem_cache_free(vm_area_cachep, tmp);
 472 fail_nomem:
 473         retval = -ENOMEM;
 474         vm_unacct_memory(charge);
 475         goto out;
 476 }
 477
 478 static inline int mm_alloc_pgd(struct mm_struct *mm)
 479 {
 480         mm->pgd = pgd_alloc(mm);
 481         if (unlikely(!mm->pgd))
 482                 return -ENOMEM;
 483         return 0;
 484 }
 485
 486 static inline void mm_free_pgd(struct mm_struct *mm)
 487 {
 488         pgd_free(mm, mm->pgd);
 489 }
 490 #else
 491 #define dup_mmap(mm, oldmm)     (0)
 492 #define mm_alloc_pgd(mm)        (0)
 493 #define mm_free_pgd(mm)
 494 #endif /* CONFIG_MMU */
 495
 496 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 497
 498 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 499 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 500
 501 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 502
 503 static int __init coredump_filter_setup(char *s)
 504 {
 505         default_dump_filter =
 506                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 507                 MMF_DUMP_FILTER_MASK;
 508         return 1;
 509 }
 510
 511 __setup("coredump_filter=", coredump_filter_setup);
 512
 513 #include <linux/init_task.h>
 514
 515 static void mm_init_aio(struct mm_struct *mm)
 516 {
 517 #ifdef CONFIG_AIO
 518         spin_lock_init(&mm->ioctx_lock);
 519         INIT_HLIST_HEAD(&mm->ioctx_list);
 520 #endif
 521 }
 522
 523 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 524 {
 525         atomic_set(&mm->mm_users, 1);
 526         atomic_set(&mm->mm_count, 1);
 527         init_rwsem(&mm->mmap_sem);
 528         INIT_LIST_HEAD(&mm->mmlist);
 529         mm->flags = (current->mm) ?
 530                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 531         mm->core_state = NULL;
 532         mm->nr_ptes = 0;
 533         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 534         spin_lock_init(&mm->page_table_lock);
 535         mm->free_area_cache = TASK_UNMAPPED_BASE;
 536         mm->cached_hole_size = ~0UL;
 537         mm_init_aio(mm);
 538         mm_init_owner(mm, p);
 539
 540         if (likely(!mm_alloc_pgd(mm))) {
 541                 mm->def_flags = 0;
 542                 mmu_notifier_mm_init(mm);
 543                 return mm;
 544         }
 545
 546         free_mm(mm);
 547         return NULL;
 548 }
 549
 550 static void check_mm(struct mm_struct *mm)
 551 {
 552         int i;
 553
 554         for (i = 0; i < NR_MM_COUNTERS; i++) {
 555                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 556
 557                 if (unlikely(x))
 558                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 559                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 560         }
 561
 562 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 563         VM_BUG_ON(mm->pmd_huge_pte);
 564 #endif
 565 }
 566
 567 /*
 568  * Allocate and initialize an mm_struct.
 569  */
 570 struct mm_struct *mm_alloc(void)
 571 {
 572         struct mm_struct *mm;
 573
 574         mm = allocate_mm();
 575         if (!mm)
 576                 return NULL;
 577
 578         memset(mm, 0, sizeof(*mm));
 579         mm_init_cpumask(mm);
 580         return mm_init(mm, current);
 581 }
 582
 583 /*
 584  * Called when the last reference to the mm
 585  * is dropped: either by a lazy thread or by
 586  * mmput. Free the page directory and the mm.
 587  */
 588 void __mmdrop(struct mm_struct *mm)
 589 {
 590         BUG_ON(mm == &init_mm);
 591         mm_free_pgd(mm);
 592         destroy_context(mm);
 593         mmu_notifier_mm_destroy(mm);
 594         check_mm(mm);
 595         free_mm(mm);
 596 }
 597 EXPORT_SYMBOL_GPL(__mmdrop);
 598
 599 /*
 600  * Decrement the use count and release all resources for an mm.
 601  */
 602 void mmput(struct mm_struct *mm)
 603 {
 604         might_sleep();
 605
 606         if (atomic_dec_and_test(&mm->mm_users)) {
 607                 uprobe_clear_state(mm);
 608                 exit_aio(mm);
 609                 ksm_exit(mm);
 610                 khugepaged_exit(mm); /* must run before exit_mmap */
 611                 exit_mmap(mm);
 612                 set_mm_exe_file(mm, NULL);
 613                 if (!list_empty(&mm->mmlist)) {
 614                         spin_lock(&mmlist_lock);
 615                         list_del(&mm->mmlist);
 616                         spin_unlock(&mmlist_lock);
 617                 }
 618                 if (mm->binfmt)
 619                         module_put(mm->binfmt->module);
 620                 mmdrop(mm);
 621         }
 622 }
 623 EXPORT_SYMBOL_GPL(mmput);
 624
 625 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 626 {
 627         if (new_exe_file)
 628                 get_file(new_exe_file);
 629         if (mm->exe_file)
 630                 fput(mm->exe_file);
 631         mm->exe_file = new_exe_file;
 632 }
 633
 634 struct file *get_mm_exe_file(struct mm_struct *mm)
 635 {
 636         struct file *exe_file;
 637
 638         /* We need mmap_sem to protect against races with removal of exe_file */
 639         down_read(&mm->mmap_sem);
 640         exe_file = mm->exe_file;
 641         if (exe_file)
 642                 get_file(exe_file);
 643         up_read(&mm->mmap_sem);
 644         return exe_file;
 645 }
 646
 647 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 648 {
 649         /* It's safe to write the exe_file pointer without exe_file_lock because
 650          * this is called during fork when the task is not yet in /proc */
 651         newmm->exe_file = get_mm_exe_file(oldmm);
 652 }
 653
 654 /**
 655  * get_task_mm - acquire a reference to the task's mm
 656  *
 657  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 658  * this kernel workthread has transiently adopted a user mm with use_mm,
 659  * to do its AIO) is not set and if so returns a reference to it, after
 660  * bumping up the use count.  User must release the mm via mmput()
 661  * after use.  Typically used by /proc and ptrace.
 662  */
 663 struct mm_struct *get_task_mm(struct task_struct *task)
 664 {
 665         struct mm_struct *mm;
 666
 667         task_lock(task);
 668         mm = task->mm;
 669         if (mm) {
 670                 if (task->flags & PF_KTHREAD)
 671                         mm = NULL;
 672                 else
 673                         atomic_inc(&mm->mm_users);
 674         }
 675         task_unlock(task);
 676         return mm;
 677 }
 678 EXPORT_SYMBOL_GPL(get_task_mm);
 679
 680 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 681 {
 682         struct mm_struct *mm;
 683         int err;
 684
 685         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 686         if (err)
 687                 return ERR_PTR(err);
 688
 689         mm = get_task_mm(task);
 690         if (mm && mm != current->mm &&
 691                         !ptrace_may_access(task, mode)) {
 692                 mmput(mm);
 693                 mm = ERR_PTR(-EACCES);
 694         }
 695         mutex_unlock(&task->signal->cred_guard_mutex);
 696
 697         return mm;
 698 }
 699
 700 static void complete_vfork_done(struct task_struct *tsk)
 701 {
 702         struct completion *vfork;
 703
 704         task_lock(tsk);
 705         vfork = tsk->vfork_done;
 706         if (likely(vfork)) {
 707                 tsk->vfork_done = NULL;
 708                 complete(vfork);
 709         }
 710         task_unlock(tsk);
 711 }
 712
 713 static int wait_for_vfork_done(struct task_struct *child,
 714                                 struct completion *vfork)
 715 {
 716         int killed;
 717
 718         freezer_do_not_count();
 719         killed = wait_for_completion_killable(vfork);
 720         freezer_count();
 721
 722         if (killed) {
 723                 task_lock(child);
 724                 child->vfork_done = NULL;
 725                 task_unlock(child);
 726         }
 727
 728         put_task_struct(child);
 729         return killed;
 730 }
 731
 732 /* Please note the differences between mmput and mm_release.
 733  * mmput is called whenever we stop holding onto a mm_struct,
 734  * error success whatever.
 735  *
 736  * mm_release is called after a mm_struct has been removed
 737  * from the current process.
 738  *
 739  * This difference is important for error handling, when we
 740  * only half set up a mm_struct for a new process and need to restore
 741  * the old one.  Because we mmput the new mm_struct before
 742  * restoring the old one. . .
 743  * Eric Biederman 10 January 1998
 744  */
 745 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 746 {
 747         /* Get rid of any futexes when releasing the mm */
 748 #ifdef CONFIG_FUTEX
 749         if (unlikely(tsk->robust_list)) {
 750                 exit_robust_list(tsk);
 751                 tsk->robust_list = NULL;
 752         }
 753 #ifdef CONFIG_COMPAT
 754         if (unlikely(tsk->compat_robust_list)) {
 755                 compat_exit_robust_list(tsk);
 756                 tsk->compat_robust_list = NULL;
 757         }
 758 #endif
 759         if (unlikely(!list_empty(&tsk->pi_state_list)))
 760                 exit_pi_state_list(tsk);
 761 #endif
 762
 763         uprobe_free_utask(tsk);
 764
 765         /* Get rid of any cached register state */
 766         deactivate_mm(tsk, mm);
 767
 768         /*
 769          * If we're exiting normally, clear a user-space tid field if
 770          * requested.  We leave this alone when dying by signal, to leave
 771          * the value intact in a core dump, and to save the unnecessary
 772          * trouble, say, a killed vfork parent shouldn't touch this mm.
 773          * Userland only wants this done for a sys_exit.
 774          */
 775         if (tsk->clear_child_tid) {
 776                 if (!(tsk->flags & PF_SIGNALED) &&
 777                     atomic_read(&mm->mm_users) > 1) {
 778                         /*
 779                          * We don't check the error code - if userspace has
 780                          * not set up a proper pointer then tough luck.
 781                          */
 782                         put_user(0, tsk->clear_child_tid);
 783                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 784                                         1, NULL, NULL, 0);
 785                 }
 786                 tsk->clear_child_tid = NULL;
 787         }
 788
 789         /*
 790          * All done, finally we can wake up parent and return this mm to him.
 791          * Also kthread_stop() uses this completion for synchronization.
 792          */
 793         if (tsk->vfork_done)
 794                 complete_vfork_done(tsk);
 795 }
 796
 797 /*
 798  * Allocate a new mm structure and copy contents from the
 799  * mm structure of the passed in task structure.
 800  */
 801 struct mm_struct *dup_mm(struct task_struct *tsk)
 802 {
 803         struct mm_struct *mm, *oldmm = current->mm;
 804         int err;
 805
 806         if (!oldmm)
 807                 return NULL;
 808
 809         mm = allocate_mm();
 810         if (!mm)
 811                 goto fail_nomem;
 812
 813         memcpy(mm, oldmm, sizeof(*mm));
 814         mm_init_cpumask(mm);
 815
 816 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 817         mm->pmd_huge_pte = NULL;
 818 #endif
 819         if (!mm_init(mm, tsk))
 820                 goto fail_nomem;
 821
 822         if (init_new_context(tsk, mm))
 823                 goto fail_nocontext;
 824
 825         dup_mm_exe_file(oldmm, mm);
 826
 827         err = dup_mmap(mm, oldmm);
 828         if (err)
 829                 goto free_pt;
 830
 831         mm->hiwater_rss = get_mm_rss(mm);
 832         mm->hiwater_vm = mm->total_vm;
 833
 834         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 835                 goto free_pt;
 836
 837         return mm;
 838
 839 free_pt:
 840         /* don't put binfmt in mmput, we haven't got module yet */
 841         mm->binfmt = NULL;
 842         mmput(mm);
 843
 844 fail_nomem:
 845         return NULL;
 846
 847 fail_nocontext:
 848         /*
 849          * If init_new_context() failed, we cannot use mmput() to free the mm
 850          * because it calls destroy_context()
 851          */
 852         mm_free_pgd(mm);
 853         free_mm(mm);
 854         return NULL;
 855 }
 856
 857 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 858 {
 859         struct mm_struct *mm, *oldmm;
 860         int retval;
 861
 862         tsk->min_flt = tsk->maj_flt = 0;
 863         tsk->nvcsw = tsk->nivcsw = 0;
 864 #ifdef CONFIG_DETECT_HUNG_TASK
 865         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 866 #endif
 867
 868         tsk->mm = NULL;
 869         tsk->active_mm = NULL;
 870
 871         /*
 872          * Are we cloning a kernel thread?
 873          *
 874          * We need to steal a active VM for that..
 875          */
 876         oldmm = current->mm;
 877         if (!oldmm)
 878                 return 0;
 879
 880         if (clone_flags & CLONE_VM) {
 881                 atomic_inc(&oldmm->mm_users);
 882                 mm = oldmm;
 883                 goto good_mm;
 884         }
 885
 886         retval = -ENOMEM;
 887         mm = dup_mm(tsk);
 888         if (!mm)
 889                 goto fail_nomem;
 890
 891 good_mm:
 892         tsk->mm = mm;
 893         tsk->active_mm = mm;
 894         return 0;
 895
 896 fail_nomem:
 897         return retval;
 898 }
 899
 900 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 901 {
 902         struct fs_struct *fs = current->fs;
 903         if (clone_flags & CLONE_FS) {
 904                 /* tsk->fs is already what we want */
 905                 spin_lock(&fs->lock);
 906                 if (fs->in_exec) {
 907                         spin_unlock(&fs->lock);
 908                         return -EAGAIN;
 909                 }
 910                 fs->users++;
 911                 spin_unlock(&fs->lock);
 912                 return 0;
 913         }
 914         tsk->fs = copy_fs_struct(fs);
 915         if (!tsk->fs)
 916                 return -ENOMEM;
 917         return 0;
 918 }
 919
 920 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 921 {
 922         struct files_struct *oldf, *newf;
 923         int error = 0;
 924
 925         /*
 926          * A background process may not have any files ...
 927          */
 928         oldf = current->files;
 929         if (!oldf)
 930                 goto out;
 931
 932         if (clone_flags & CLONE_FILES) {
 933                 atomic_inc(&oldf->count);
 934                 goto out;
 935         }
 936
 937         newf = dup_fd(oldf, &error);
 938         if (!newf)
 939                 goto out;
 940
 941         tsk->files = newf;
 942         error = 0;
 943 out:
 944         return error;
 945 }
 946
 947 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 948 {
 949 #ifdef CONFIG_BLOCK
 950         struct io_context *ioc = current->io_context;
 951         struct io_context *new_ioc;
 952
 953         if (!ioc)
 954                 return 0;
 955         /*
 956          * Share io context with parent, if CLONE_IO is set
 957          */
 958         if (clone_flags & CLONE_IO) {
 959                 ioc_task_link(ioc);
 960                 tsk->io_context = ioc;
 961         } else if (ioprio_valid(ioc->ioprio)) {
 962                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 963                 if (unlikely(!new_ioc))
 964                         return -ENOMEM;
 965
 966                 new_ioc->ioprio = ioc->ioprio;
 967                 put_io_context(new_ioc);
 968         }
 969 #endif
 970         return 0;
 971 }
 972
 973 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 974 {
 975         struct sighand_struct *sig;
 976
 977         if (clone_flags & CLONE_SIGHAND) {
 978                 atomic_inc(&current->sighand->count);
 979                 return 0;
 980         }
 981         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 982         rcu_assign_pointer(tsk->sighand, sig);
 983         if (!sig)
 984                 return -ENOMEM;
 985         atomic_set(&sig->count, 1);
 986         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 987         return 0;
 988 }
 989
 990 void __cleanup_sighand(struct sighand_struct *sighand)
 991 {
 992         if (atomic_dec_and_test(&sighand->count)) {
 993                 signalfd_cleanup(sighand);
 994                 kmem_cache_free(sighand_cachep, sighand);
 995         }
 996 }
 997
 998
 999 /*
1000  * Initialize POSIX timer handling for a thread group.
1001  */
1002 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1003 {
1004         unsigned long cpu_limit;
1005
1006         /* Thread group counters. */
1007         thread_group_cputime_init(sig);
1008
1009         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1010         if (cpu_limit != RLIM_INFINITY) {
1011                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1012                 sig->cputimer.running = 1;
1013         }
1014
1015         /* The timer lists. */
1016         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1017         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1018         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1019 }
1020
1021 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1022 {
1023         struct signal_struct *sig;
1024
1025         if (clone_flags & CLONE_THREAD)
1026                 return 0;
1027
1028         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1029         tsk->signal = sig;
1030         if (!sig)
1031                 return -ENOMEM;
1032
1033         sig->nr_threads = 1;
1034         atomic_set(&sig->live, 1);
1035         atomic_set(&sig->sigcnt, 1);
1036         init_waitqueue_head(&sig->wait_chldexit);
1037         if (clone_flags & CLONE_NEWPID)
1038                 sig->flags |= SIGNAL_UNKILLABLE;
1039         sig->curr_target = tsk;
1040         init_sigpending(&sig->shared_pending);
1041         INIT_LIST_HEAD(&sig->posix_timers);
1042
1043         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1044         sig->real_timer.function = it_real_fn;
1045
1046         task_lock(current->group_leader);
1047         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1048         task_unlock(current->group_leader);
1049
1050         posix_cpu_timers_init_group(sig);
1051
1052         tty_audit_fork(sig);
1053         sched_autogroup_fork(sig);
1054
1055 #ifdef CONFIG_CGROUPS
1056         init_rwsem(&sig->group_rwsem);
1057 #endif
1058
1059         sig->oom_score_adj = current->signal->oom_score_adj;
1060         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1061
1062         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1063                                    current->signal->is_child_subreaper;
1064
1065         mutex_init(&sig->cred_guard_mutex);
1066
1067         return 0;
1068 }
1069
1070 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1071 {
1072         unsigned long new_flags = p->flags;
1073
1074         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1075         new_flags |= PF_FORKNOEXEC;
1076         p->flags = new_flags;
1077 }
1078
1079 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1080 {
1081         current->clear_child_tid = tidptr;
1082
1083         return task_pid_vnr(current);
1084 }
1085
1086 static void rt_mutex_init_task(struct task_struct *p)
1087 {
1088         raw_spin_lock_init(&p->pi_lock);
1089 #ifdef CONFIG_RT_MUTEXES
1090         plist_head_init(&p->pi_waiters);
1091         p->pi_blocked_on = NULL;
1092 #endif
1093 }
1094
1095 #ifdef CONFIG_MM_OWNER
1096 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1097 {
1098         mm->owner = p;
1099 }
1100 #endif /* CONFIG_MM_OWNER */
1101
1102 /*
1103  * Initialize POSIX timer handling for a single task.
1104  */
1105 static void posix_cpu_timers_init(struct task_struct *tsk)
1106 {
1107         tsk->cputime_expires.prof_exp = 0;
1108         tsk->cputime_expires.virt_exp = 0;
1109         tsk->cputime_expires.sched_exp = 0;
1110         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1111         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1112         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1113 }
1114
1115 /*
1116  * This creates a new process as a copy of the old one,
1117  * but does not actually start it yet.
1118  *
1119  * It copies the registers, and all the appropriate
1120  * parts of the process environment (as per the clone
1121  * flags). The actual kick-off is left to the caller.
1122  */
1123 static struct task_struct *copy_process(unsigned long clone_flags,
1124                                         unsigned long stack_start,
1125                                         struct pt_regs *regs,
1126                                         unsigned long stack_size,
1127                                         int __user *child_tidptr,
1128                                         struct pid *pid,
1129                                         int trace)
1130 {
1131         int retval;
1132         struct task_struct *p;
1133         int cgroup_callbacks_done = 0;
1134
1135         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1136                 return ERR_PTR(-EINVAL);
1137
1138         /*
1139          * Thread groups must share signals as well, and detached threads
1140          * can only be started up within the thread group.
1141          */
1142         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1143                 return ERR_PTR(-EINVAL);
1144
1145         /*
1146          * Shared signal handlers imply shared VM. By way of the above,
1147          * thread groups also imply shared VM. Blocking this case allows
1148          * for various simplifications in other code.
1149          */
1150         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1151                 return ERR_PTR(-EINVAL);
1152
1153         /*
1154          * Siblings of global init remain as zombies on exit since they are
1155          * not reaped by their parent (swapper). To solve this and to avoid
1156          * multi-rooted process trees, prevent global and container-inits
1157          * from creating siblings.
1158          */
1159         if ((clone_flags & CLONE_PARENT) &&
1160                                 current->signal->flags & SIGNAL_UNKILLABLE)
1161                 return ERR_PTR(-EINVAL);
1162
1163         retval = security_task_create(clone_flags);
1164         if (retval)
1165                 goto fork_out;
1166
1167         retval = -ENOMEM;
1168         p = dup_task_struct(current);
1169         if (!p)
1170                 goto fork_out;
1171
1172         ftrace_graph_init_task(p);
1173         get_seccomp_filter(p);
1174
1175         rt_mutex_init_task(p);
1176
1177 #ifdef CONFIG_PROVE_LOCKING
1178         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1179         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1180 #endif
1181         retval = -EAGAIN;
1182         if (atomic_read(&p->real_cred->user->processes) >=
1183                         task_rlimit(p, RLIMIT_NPROC)) {
1184                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1185                     p->real_cred->user != INIT_USER)
1186                         goto bad_fork_free;
1187         }
1188         current->flags &= ~PF_NPROC_EXCEEDED;
1189
1190         retval = copy_creds(p, clone_flags);
1191         if (retval < 0)
1192                 goto bad_fork_free;
1193
1194         /*
1195          * If multiple threads are within copy_process(), then this check
1196          * triggers too late. This doesn't hurt, the check is only there
1197          * to stop root fork bombs.
1198          */
1199         retval = -EAGAIN;
1200         if (nr_threads >= max_threads)
1201                 goto bad_fork_cleanup_count;
1202
1203         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1204                 goto bad_fork_cleanup_count;
1205
1206         p->did_exec = 0;
1207         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1208         copy_flags(clone_flags, p);
1209         INIT_LIST_HEAD(&p->children);
1210         INIT_LIST_HEAD(&p->sibling);
1211         rcu_copy_process(p);
1212         p->vfork_done = NULL;
1213         spin_lock_init(&p->alloc_lock);
1214
1215         init_sigpending(&p->pending);
1216
1217         p->utime = p->stime = p->gtime = 0;
1218         p->utimescaled = p->stimescaled = 0;
1219 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1220         p->prev_utime = p->prev_stime = 0;
1221 #endif
1222 #if defined(SPLIT_RSS_COUNTING)
1223         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1224 #endif
1225
1226         p->default_timer_slack_ns = current->timer_slack_ns;
1227
1228         task_io_accounting_init(&p->ioac);
1229         acct_clear_integrals(p);
1230
1231         posix_cpu_timers_init(p);
1232
1233         do_posix_clock_monotonic_gettime(&p->start_time);
1234         p->real_start_time = p->start_time;
1235         monotonic_to_bootbased(&p->real_start_time);
1236         p->io_context = NULL;
1237         p->audit_context = NULL;
1238         if (clone_flags & CLONE_THREAD)
1239                 threadgroup_change_begin(current);
1240         cgroup_fork(p);
1241 #ifdef CONFIG_NUMA
1242         p->mempolicy = mpol_dup(p->mempolicy);
1243         if (IS_ERR(p->mempolicy)) {
1244                 retval = PTR_ERR(p->mempolicy);
1245                 p->mempolicy = NULL;
1246                 goto bad_fork_cleanup_cgroup;
1247         }
1248         mpol_fix_fork_child_flag(p);
1249 #endif
1250 #ifdef CONFIG_CPUSETS
1251         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1252         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1253         seqcount_init(&p->mems_allowed_seq);
1254 #endif
1255 #ifdef CONFIG_TRACE_IRQFLAGS
1256         p->irq_events = 0;
1257         p->hardirqs_enabled = 0;
1258         p->hardirq_enable_ip = 0;
1259         p->hardirq_enable_event = 0;
1260         p->hardirq_disable_ip = _THIS_IP_;
1261         p->hardirq_disable_event = 0;
1262         p->softirqs_enabled = 1;
1263         p->softirq_enable_ip = _THIS_IP_;
1264         p->softirq_enable_event = 0;
1265         p->softirq_disable_ip = 0;
1266         p->softirq_disable_event = 0;
1267         p->hardirq_context = 0;
1268         p->softirq_context = 0;
1269 #endif
1270 #ifdef CONFIG_LOCKDEP
1271         p->lockdep_depth = 0; /* no locks held yet */
1272         p->curr_chain_key = 0;
1273         p->lockdep_recursion = 0;
1274 #endif
1275
1276 #ifdef CONFIG_DEBUG_MUTEXES
1277         p->blocked_on = NULL; /* not blocked yet */
1278 #endif
1279 #ifdef CONFIG_MEMCG
1280         p->memcg_batch.do_batch = 0;
1281         p->memcg_batch.memcg = NULL;
1282 #endif
1283
1284         /* Perform scheduler related setup. Assign this task to a CPU. */
1285         sched_fork(p);
1286
1287         retval = perf_event_init_task(p);
1288         if (retval)
1289                 goto bad_fork_cleanup_policy;
1290         retval = audit_alloc(p);
1291         if (retval)
1292                 goto bad_fork_cleanup_policy;
1293         /* copy all the process information */
1294         retval = copy_semundo(clone_flags, p);
1295         if (retval)
1296                 goto bad_fork_cleanup_audit;
1297         retval = copy_files(clone_flags, p);
1298         if (retval)
1299                 goto bad_fork_cleanup_semundo;
1300         retval = copy_fs(clone_flags, p);
1301         if (retval)
1302                 goto bad_fork_cleanup_files;
1303         retval = copy_sighand(clone_flags, p);
1304         if (retval)
1305                 goto bad_fork_cleanup_fs;
1306         retval = copy_signal(clone_flags, p);
1307         if (retval)
1308                 goto bad_fork_cleanup_sighand;
1309         retval = copy_mm(clone_flags, p);
1310         if (retval)
1311                 goto bad_fork_cleanup_signal;
1312         retval = copy_namespaces(clone_flags, p);
1313         if (retval)
1314                 goto bad_fork_cleanup_mm;
1315         retval = copy_io(clone_flags, p);
1316         if (retval)
1317                 goto bad_fork_cleanup_namespaces;
1318         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1319         if (retval)
1320                 goto bad_fork_cleanup_io;
1321
1322         if (pid != &init_struct_pid) {
1323                 retval = -ENOMEM;
1324                 pid = alloc_pid(p->nsproxy->pid_ns);
1325                 if (!pid)
1326                         goto bad_fork_cleanup_io;
1327         }
1328
1329         p->pid = pid_nr(pid);
1330         p->tgid = p->pid;
1331         if (clone_flags & CLONE_THREAD)
1332                 p->tgid = current->tgid;
1333
1334         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1335         /*
1336          * Clear TID on mm_release()?
1337          */
1338         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1339 #ifdef CONFIG_BLOCK
1340         p->plug = NULL;
1341 #endif
1342 #ifdef CONFIG_FUTEX
1343         p->robust_list = NULL;
1344 #ifdef CONFIG_COMPAT
1345         p->compat_robust_list = NULL;
1346 #endif
1347         INIT_LIST_HEAD(&p->pi_state_list);
1348         p->pi_state_cache = NULL;
1349 #endif
1350         uprobe_copy_process(p);
1351         /*
1352          * sigaltstack should be cleared when sharing the same VM
1353          */
1354         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1355                 p->sas_ss_sp = p->sas_ss_size = 0;
1356
1357         /*
1358          * Syscall tracing and stepping should be turned off in the
1359          * child regardless of CLONE_PTRACE.
1360          */
1361         user_disable_single_step(p);
1362         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1363 #ifdef TIF_SYSCALL_EMU
1364         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1365 #endif
1366         clear_all_latency_tracing(p);
1367
1368         /* ok, now we should be set up.. */
1369         if (clone_flags & CLONE_THREAD)
1370                 p->exit_signal = -1;
1371         else if (clone_flags & CLONE_PARENT)
1372                 p->exit_signal = current->group_leader->exit_signal;
1373         else
1374                 p->exit_signal = (clone_flags & CSIGNAL);
1375
1376         p->pdeath_signal = 0;
1377         p->exit_state = 0;
1378
1379         p->nr_dirtied = 0;
1380         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1381         p->dirty_paused_when = 0;
1382
1383         /*
1384          * Ok, make it visible to the rest of the system.
1385          * We dont wake it up yet.
1386          */
1387         p->group_leader = p;
1388         INIT_LIST_HEAD(&p->thread_group);
1389         p->task_works = NULL;
1390
1391         /* Now that the task is set up, run cgroup callbacks if
1392          * necessary. We need to run them before the task is visible
1393          * on the tasklist. */
1394         cgroup_fork_callbacks(p);
1395         cgroup_callbacks_done = 1;
1396
1397         /* Need tasklist lock for parent etc handling! */
1398         write_lock_irq(&tasklist_lock);
1399
1400         /* CLONE_PARENT re-uses the old parent */
1401         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1402                 p->real_parent = current->real_parent;
1403                 p->parent_exec_id = current->parent_exec_id;
1404         } else {
1405                 p->real_parent = current;
1406                 p->parent_exec_id = current->self_exec_id;
1407         }
1408
1409         spin_lock(&current->sighand->siglock);
1410
1411         /*
1412          * Process group and session signals need to be delivered to just the
1413          * parent before the fork or both the parent and the child after the
1414          * fork. Restart if a signal comes in before we add the new process to
1415          * it's process group.
1416          * A fatal signal pending means that current will exit, so the new
1417          * thread can't slip out of an OOM kill (or normal SIGKILL).
1418         */
1419         recalc_sigpending();
1420         if (signal_pending(current)) {
1421                 spin_unlock(&current->sighand->siglock);
1422                 write_unlock_irq(&tasklist_lock);
1423                 retval = -ERESTARTNOINTR;
1424                 goto bad_fork_free_pid;
1425         }
1426
1427         if (clone_flags & CLONE_THREAD) {
1428                 current->signal->nr_threads++;
1429                 atomic_inc(&current->signal->live);
1430                 atomic_inc(&current->signal->sigcnt);
1431                 p->group_leader = current->group_leader;
1432                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1433         }
1434
1435         if (likely(p->pid)) {
1436                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1437
1438                 if (thread_group_leader(p)) {
1439                         if (is_child_reaper(pid))
1440                                 p->nsproxy->pid_ns->child_reaper = p;
1441
1442                         p->signal->leader_pid = pid;
1443                         p->signal->tty = tty_kref_get(current->signal->tty);
1444                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1445                         attach_pid(p, PIDTYPE_SID, task_session(current));
1446                         list_add_tail(&p->sibling, &p->real_parent->children);
1447                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1448                         __this_cpu_inc(process_counts);
1449                 }
1450                 attach_pid(p, PIDTYPE_PID, pid);
1451                 nr_threads++;
1452         }
1453
1454         total_forks++;
1455         spin_unlock(&current->sighand->siglock);
1456         write_unlock_irq(&tasklist_lock);
1457         proc_fork_connector(p);
1458         cgroup_post_fork(p);
1459         if (clone_flags & CLONE_THREAD)
1460                 threadgroup_change_end(current);
1461         perf_event_fork(p);
1462
1463         trace_task_newtask(p, clone_flags);
1464
1465         return p;
1466
1467 bad_fork_free_pid:
1468         if (pid != &init_struct_pid)
1469                 free_pid(pid);
1470 bad_fork_cleanup_io:
1471         if (p->io_context)
1472                 exit_io_context(p);
1473 bad_fork_cleanup_namespaces:
1474         if (unlikely(clone_flags & CLONE_NEWPID))
1475                 pid_ns_release_proc(p->nsproxy->pid_ns);
1476         exit_task_namespaces(p);
1477 bad_fork_cleanup_mm:
1478         if (p->mm)
1479                 mmput(p->mm);
1480 bad_fork_cleanup_signal:
1481         if (!(clone_flags & CLONE_THREAD))
1482                 free_signal_struct(p->signal);
1483 bad_fork_cleanup_sighand:
1484         __cleanup_sighand(p->sighand);
1485 bad_fork_cleanup_fs:
1486         exit_fs(p); /* blocking */
1487 bad_fork_cleanup_files:
1488         exit_files(p); /* blocking */
1489 bad_fork_cleanup_semundo:
1490         exit_sem(p);
1491 bad_fork_cleanup_audit:
1492         audit_free(p);
1493 bad_fork_cleanup_policy:
1494         perf_event_free_task(p);
1495 #ifdef CONFIG_NUMA
1496         mpol_put(p->mempolicy);
1497 bad_fork_cleanup_cgroup:
1498 #endif
1499         if (clone_flags & CLONE_THREAD)
1500                 threadgroup_change_end(current);
1501         cgroup_exit(p, cgroup_callbacks_done);
1502         delayacct_tsk_free(p);
1503         module_put(task_thread_info(p)->exec_domain->module);
1504 bad_fork_cleanup_count:
1505         atomic_dec(&p->cred->user->processes);
1506         exit_creds(p);
1507 bad_fork_free:
1508         free_task(p);
1509 fork_out:
1510         return ERR_PTR(retval);
1511 }
1512
1513 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1514 {
1515         memset(regs, 0, sizeof(struct pt_regs));
1516         return regs;
1517 }
1518
1519 static inline void init_idle_pids(struct pid_link *links)
1520 {
1521         enum pid_type type;
1522
1523         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1524                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1525                 links[type].pid = &init_struct_pid;
1526         }
1527 }
1528
1529 struct task_struct * __cpuinit fork_idle(int cpu)
1530 {
1531         struct task_struct *task;
1532         struct pt_regs regs;
1533
1534         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1535                             &init_struct_pid, 0);
1536         if (!IS_ERR(task)) {
1537                 init_idle_pids(task->pids);
1538                 init_idle(task, cpu);
1539         }
1540
1541         return task;
1542 }
1543
1544 /*
1545  *  Ok, this is the main fork-routine.
1546  *
1547  * It copies the process, and if successful kick-starts
1548  * it and waits for it to finish using the VM if required.
1549  */
1550 long do_fork(unsigned long clone_flags,
1551               unsigned long stack_start,
1552               struct pt_regs *regs,
1553               unsigned long stack_size,
1554               int __user *parent_tidptr,
1555               int __user *child_tidptr)
1556 {
1557         struct task_struct *p;
1558         int trace = 0;
1559         long nr;
1560
1561         /*
1562          * Do some preliminary argument and permissions checking before we
1563          * actually start allocating stuff
1564          */
1565         if (clone_flags & CLONE_NEWUSER) {
1566                 if (clone_flags & CLONE_THREAD)
1567                         return -EINVAL;
1568                 /* hopefully this check will go away when userns support is
1569                  * complete
1570                  */
1571                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1572                                 !capable(CAP_SETGID))
1573                         return -EPERM;
1574         }
1575
1576         /*
1577          * Determine whether and which event to report to ptracer.  When
1578          * called from kernel_thread or CLONE_UNTRACED is explicitly
1579          * requested, no event is reported; otherwise, report if the event
1580          * for the type of forking is enabled.
1581          */
1582         if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1583                 if (clone_flags & CLONE_VFORK)
1584                         trace = PTRACE_EVENT_VFORK;
1585                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1586                         trace = PTRACE_EVENT_CLONE;
1587                 else
1588                         trace = PTRACE_EVENT_FORK;
1589
1590                 if (likely(!ptrace_event_enabled(current, trace)))
1591                         trace = 0;
1592         }
1593
1594         p = copy_process(clone_flags, stack_start, regs, stack_size,
1595                          child_tidptr, NULL, trace);
1596         /*
1597          * Do this prior waking up the new thread - the thread pointer
1598          * might get invalid after that point, if the thread exits quickly.
1599          */
1600         if (!IS_ERR(p)) {
1601                 struct completion vfork;
1602
1603                 trace_sched_process_fork(current, p);
1604
1605                 nr = task_pid_vnr(p);
1606
1607                 if (clone_flags & CLONE_PARENT_SETTID)
1608                         put_user(nr, parent_tidptr);
1609
1610                 if (clone_flags & CLONE_VFORK) {
1611                         p->vfork_done = &vfork;
1612                         init_completion(&vfork);
1613                         get_task_struct(p);
1614                 }
1615
1616                 wake_up_new_task(p);
1617
1618                 /* forking complete and child started to run, tell ptracer */
1619                 if (unlikely(trace))
1620                         ptrace_event(trace, nr);
1621
1622                 if (clone_flags & CLONE_VFORK) {
1623                         if (!wait_for_vfork_done(p, &vfork))
1624                                 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1625                 }
1626         } else {
1627                 nr = PTR_ERR(p);
1628         }
1629         return nr;
1630 }
1631
1632 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1633 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1634 #endif
1635
1636 static void sighand_ctor(void *data)
1637 {
1638         struct sighand_struct *sighand = data;
1639
1640         spin_lock_init(&sighand->siglock);
1641         init_waitqueue_head(&sighand->signalfd_wqh);
1642 }
1643
1644 void __init proc_caches_init(void)
1645 {
1646         sighand_cachep = kmem_cache_create("sighand_cache",
1647                         sizeof(struct sighand_struct), 0,
1648                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1649                         SLAB_NOTRACK, sighand_ctor);
1650         signal_cachep = kmem_cache_create("signal_cache",
1651                         sizeof(struct signal_struct), 0,
1652                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1653         files_cachep = kmem_cache_create("files_cache",
1654                         sizeof(struct files_struct), 0,
1655                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1656         fs_cachep = kmem_cache_create("fs_cache",
1657                         sizeof(struct fs_struct), 0,
1658                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1659         /*
1660          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1661          * whole struct cpumask for the OFFSTACK case. We could change
1662          * this to *only* allocate as much of it as required by the
1663          * maximum number of CPU's we can ever have.  The cpumask_allocation
1664          * is at the end of the structure, exactly for that reason.
1665          */
1666         mm_cachep = kmem_cache_create("mm_struct",
1667                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1668                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1669         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1670         mmap_init();
1671         nsproxy_cache_init();
1672 }
1673
1674 /*
1675  * Check constraints on flags passed to the unshare system call.
1676  */
1677 static int check_unshare_flags(unsigned long unshare_flags)
1678 {
1679         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1680                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1681                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1682                 return -EINVAL;
1683         /*
1684          * Not implemented, but pretend it works if there is nothing to
1685          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1686          * needs to unshare vm.
1687          */
1688         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1689                 /* FIXME: get_task_mm() increments ->mm_users */
1690                 if (atomic_read(&current->mm->mm_users) > 1)
1691                         return -EINVAL;
1692         }
1693
1694         return 0;
1695 }
1696
1697 /*
1698  * Unshare the filesystem structure if it is being shared
1699  */
1700 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1701 {
1702         struct fs_struct *fs = current->fs;
1703
1704         if (!(unshare_flags & CLONE_FS) || !fs)
1705                 return 0;
1706
1707         /* don't need lock here; in the worst case we'll do useless copy */
1708         if (fs->users == 1)
1709                 return 0;
1710
1711         *new_fsp = copy_fs_struct(fs);
1712         if (!*new_fsp)
1713                 return -ENOMEM;
1714
1715         return 0;
1716 }
1717
1718 /*
1719  * Unshare file descriptor table if it is being shared
1720  */
1721 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1722 {
1723         struct files_struct *fd = current->files;
1724         int error = 0;
1725
1726         if ((unshare_flags & CLONE_FILES) &&
1727             (fd && atomic_read(&fd->count) > 1)) {
1728                 *new_fdp = dup_fd(fd, &error);
1729                 if (!*new_fdp)
1730                         return error;
1731         }
1732
1733         return 0;
1734 }
1735
1736 /*
1737  * unshare allows a process to 'unshare' part of the process
1738  * context which was originally shared using clone.  copy_*
1739  * functions used by do_fork() cannot be used here directly
1740  * because they modify an inactive task_struct that is being
1741  * constructed. Here we are modifying the current, active,
1742  * task_struct.
1743  */
1744 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1745 {
1746         struct fs_struct *fs, *new_fs = NULL;
1747         struct files_struct *fd, *new_fd = NULL;
1748         struct nsproxy *new_nsproxy = NULL;
1749         int do_sysvsem = 0;
1750         int err;
1751
1752         err = check_unshare_flags(unshare_flags);
1753         if (err)
1754                 goto bad_unshare_out;
1755
1756         /*
1757          * If unsharing namespace, must also unshare filesystem information.
1758          */
1759         if (unshare_flags & CLONE_NEWNS)
1760                 unshare_flags |= CLONE_FS;
1761         /*
1762          * CLONE_NEWIPC must also detach from the undolist: after switching
1763          * to a new ipc namespace, the semaphore arrays from the old
1764          * namespace are unreachable.
1765          */
1766         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1767                 do_sysvsem = 1;
1768         err = unshare_fs(unshare_flags, &new_fs);
1769         if (err)
1770                 goto bad_unshare_out;
1771         err = unshare_fd(unshare_flags, &new_fd);
1772         if (err)
1773                 goto bad_unshare_cleanup_fs;
1774         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1775         if (err)
1776                 goto bad_unshare_cleanup_fd;
1777
1778         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1779                 if (do_sysvsem) {
1780                         /*
1781                          * CLONE_SYSVSEM is equivalent to sys_exit().
1782                          */
1783                         exit_sem(current);
1784                 }
1785
1786                 if (new_nsproxy) {
1787                         switch_task_namespaces(current, new_nsproxy);
1788                         new_nsproxy = NULL;
1789                 }
1790
1791                 task_lock(current);
1792
1793                 if (new_fs) {
1794                         fs = current->fs;
1795                         spin_lock(&fs->lock);
1796                         current->fs = new_fs;
1797                         if (--fs->users)
1798                                 new_fs = NULL;
1799                         else
1800                                 new_fs = fs;
1801                         spin_unlock(&fs->lock);
1802                 }
1803
1804                 if (new_fd) {
1805                         fd = current->files;
1806                         current->files = new_fd;
1807                         new_fd = fd;
1808                 }
1809
1810                 task_unlock(current);
1811         }
1812
1813         if (new_nsproxy)
1814                 put_nsproxy(new_nsproxy);
1815
1816 bad_unshare_cleanup_fd:
1817         if (new_fd)
1818                 put_files_struct(new_fd);
1819
1820 bad_unshare_cleanup_fs:
1821         if (new_fs)
1822                 free_fs_struct(new_fs);
1823
1824 bad_unshare_out:
1825         return err;
1826 }
1827
1828 /*
1829  *      Helper to unshare the files of the current task.
1830  *      We don't want to expose copy_files internals to
1831  *      the exec layer of the kernel.
1832  */
1833
1834 int unshare_files(struct files_struct **displaced)
1835 {
1836         struct task_struct *task = current;
1837         struct files_struct *copy = NULL;
1838         int error;
1839
1840         error = unshare_fd(CLONE_FILES, &copy);
1841         if (error || !copy) {
1842                 *displaced = NULL;
1843                 return error;
1844         }
1845         *displaced = task->files;
1846         task_lock(task);
1847         task->files = copy;
1848         task_unlock(task);
1849         return 0;
1850 }