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/swap.h>
  38 #include <linux/syscalls.h>
  39 #include <linux/jiffies.h>
  40 #include <linux/tracehook.h>
  41 #include <linux/futex.h>
  42 #include <linux/compat.h>
  43 #include <linux/task_io_accounting_ops.h>
  44 #include <linux/rcupdate.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/mount.h>
  47 #include <linux/audit.h>
  48 #include <linux/memcontrol.h>
  49 #include <linux/ftrace.h>
  50 #include <linux/profile.h>
  51 #include <linux/rmap.h>
  52 #include <linux/ksm.h>
  53 #include <linux/acct.h>
  54 #include <linux/tsacct_kern.h>
  55 #include <linux/cn_proc.h>
  56 #include <linux/freezer.h>
  57 #include <linux/delayacct.h>
  58 #include <linux/taskstats_kern.h>
  59 #include <linux/random.h>
  60 #include <linux/tty.h>
  61 #include <linux/proc_fs.h>
  62 #include <linux/blkdev.h>
  63 #include <linux/fs_struct.h>
  64 #include <linux/magic.h>
  65 #include <linux/perf_event.h>
  66 #include <linux/posix-timers.h>
  67 #include <linux/user-return-notifier.h>
  68
  69 #include <asm/pgtable.h>
  70 #include <asm/pgalloc.h>
  71 #include <asm/uaccess.h>
  72 #include <asm/mmu_context.h>
  73 #include <asm/cacheflush.h>
  74 #include <asm/tlbflush.h>
  75
  76 #include <trace/events/sched.h>
  77
  78 /*
  79  * Protected counters by write_lock_irq(&tasklist_lock)
  80  */
  81 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  82 int nr_threads;                 /* The idle threads do not count.. */
  83
  84 int max_threads;                /* tunable limit on nr_threads */
  85
  86 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  87
  88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  89
  90 int nr_processes(void)
  91 {
  92         int cpu;
  93         int total = 0;
  94
  95         for_each_possible_cpu(cpu)
  96                 total += per_cpu(process_counts, cpu);
  97
  98         return total;
  99 }
 100
 101 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 102 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
 103 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
 104 static struct kmem_cache *task_struct_cachep;
 105 #endif
 106
 107 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 108 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 109 {
 110 #ifdef CONFIG_DEBUG_STACK_USAGE
 111         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 112 #else
 113         gfp_t mask = GFP_KERNEL;
 114 #endif
 115         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 116 }
 117
 118 static inline void free_thread_info(struct thread_info *ti)
 119 {
 120         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 121 }
 122 #endif
 123
 124 /* SLAB cache for signal_struct structures (tsk->signal) */
 125 static struct kmem_cache *signal_cachep;
 126
 127 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 128 struct kmem_cache *sighand_cachep;
 129
 130 /* SLAB cache for files_struct structures (tsk->files) */
 131 struct kmem_cache *files_cachep;
 132
 133 /* SLAB cache for fs_struct structures (tsk->fs) */
 134 struct kmem_cache *fs_cachep;
 135
 136 /* SLAB cache for vm_area_struct structures */
 137 struct kmem_cache *vm_area_cachep;
 138
 139 /* SLAB cache for mm_struct structures (tsk->mm) */
 140 static struct kmem_cache *mm_cachep;
 141
 142 static void account_kernel_stack(struct thread_info *ti, int account)
 143 {
 144         struct zone *zone = page_zone(virt_to_page(ti));
 145
 146         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 147 }
 148
 149 void free_task(struct task_struct *tsk)
 150 {
 151         prop_local_destroy_single(&tsk->dirties);
 152         account_kernel_stack(tsk->stack, -1);
 153         free_thread_info(tsk->stack);
 154         rt_mutex_debug_task_free(tsk);
 155         ftrace_graph_exit_task(tsk);
 156         free_task_struct(tsk);
 157 }
 158 EXPORT_SYMBOL(free_task);
 159
 160 void __put_task_struct(struct task_struct *tsk)
 161 {
 162         WARN_ON(!tsk->exit_state);
 163         WARN_ON(atomic_read(&tsk->usage));
 164         WARN_ON(tsk == current);
 165
 166         exit_creds(tsk);
 167         delayacct_tsk_free(tsk);
 168
 169         if (!profile_handoff_task(tsk))
 170                 free_task(tsk);
 171 }
 172
 173 /*
 174  * macro override instead of weak attribute alias, to workaround
 175  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 176  */
 177 #ifndef arch_task_cache_init
 178 #define arch_task_cache_init()
 179 #endif
 180
 181 void __init fork_init(unsigned long mempages)
 182 {
 183 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 184 #ifndef ARCH_MIN_TASKALIGN
 185 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 186 #endif
 187         /* create a slab on which task_structs can be allocated */
 188         task_struct_cachep =
 189                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 190                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 191 #endif
 192
 193         /* do the arch specific task caches init */
 194         arch_task_cache_init();
 195
 196         /*
 197          * The default maximum number of threads is set to a safe
 198          * value: the thread structures can take up at most half
 199          * of memory.
 200          */
 201         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 202
 203         /*
 204          * we need to allow at least 20 threads to boot a system
 205          */
 206         if(max_threads < 20)
 207                 max_threads = 20;
 208
 209         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 210         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 211         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 212                 init_task.signal->rlim[RLIMIT_NPROC];
 213 }
 214
 215 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 216                                                struct task_struct *src)
 217 {
 218         *dst = *src;
 219         return 0;
 220 }
 221
 222 static struct task_struct *dup_task_struct(struct task_struct *orig)
 223 {
 224         struct task_struct *tsk;
 225         struct thread_info *ti;
 226         unsigned long *stackend;
 227
 228         int err;
 229
 230         prepare_to_copy(orig);
 231
 232         tsk = alloc_task_struct();
 233         if (!tsk)
 234                 return NULL;
 235
 236         ti = alloc_thread_info(tsk);
 237         if (!ti) {
 238                 free_task_struct(tsk);
 239                 return NULL;
 240         }
 241
 242         err = arch_dup_task_struct(tsk, orig);
 243         if (err)
 244                 goto out;
 245
 246         tsk->stack = ti;
 247
 248         err = prop_local_init_single(&tsk->dirties);
 249         if (err)
 250                 goto out;
 251
 252         setup_thread_stack(tsk, orig);
 253         clear_user_return_notifier(tsk);
 254         stackend = end_of_stack(tsk);
 255         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 256
 257 #ifdef CONFIG_CC_STACKPROTECTOR
 258         tsk->stack_canary = get_random_int();
 259 #endif
 260
 261         /* One for us, one for whoever does the "release_task()" (usually parent) */
 262         atomic_set(&tsk->usage,2);
 263         atomic_set(&tsk->fs_excl, 0);
 264 #ifdef CONFIG_BLK_DEV_IO_TRACE
 265         tsk->btrace_seq = 0;
 266 #endif
 267         tsk->splice_pipe = NULL;
 268
 269         account_kernel_stack(ti, 1);
 270
 271         return tsk;
 272
 273 out:
 274         free_thread_info(ti);
 275         free_task_struct(tsk);
 276         return NULL;
 277 }
 278
 279 #ifdef CONFIG_MMU
 280 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 281 {
 282         struct vm_area_struct *mpnt, *tmp, **pprev;
 283         struct rb_node **rb_link, *rb_parent;
 284         int retval;
 285         unsigned long charge;
 286         struct mempolicy *pol;
 287
 288         down_write(&oldmm->mmap_sem);
 289         flush_cache_dup_mm(oldmm);
 290         /*
 291          * Not linked in yet - no deadlock potential:
 292          */
 293         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 294
 295         mm->locked_vm = 0;
 296         mm->mmap = NULL;
 297         mm->mmap_cache = NULL;
 298         mm->free_area_cache = oldmm->mmap_base;
 299         mm->cached_hole_size = ~0UL;
 300         mm->map_count = 0;
 301         cpumask_clear(mm_cpumask(mm));
 302         mm->mm_rb = RB_ROOT;
 303         rb_link = &mm->mm_rb.rb_node;
 304         rb_parent = NULL;
 305         pprev = &mm->mmap;
 306         retval = ksm_fork(mm, oldmm);
 307         if (retval)
 308                 goto out;
 309
 310         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 311                 struct file *file;
 312
 313                 if (mpnt->vm_flags & VM_DONTCOPY) {
 314                         long pages = vma_pages(mpnt);
 315                         mm->total_vm -= pages;
 316                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 317                                                                 -pages);
 318                         continue;
 319                 }
 320                 charge = 0;
 321                 if (mpnt->vm_flags & VM_ACCOUNT) {
 322                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 323                         if (security_vm_enough_memory(len))
 324                                 goto fail_nomem;
 325                         charge = len;
 326                 }
 327                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 328                 if (!tmp)
 329                         goto fail_nomem;
 330                 *tmp = *mpnt;
 331                 pol = mpol_dup(vma_policy(mpnt));
 332                 retval = PTR_ERR(pol);
 333                 if (IS_ERR(pol))
 334                         goto fail_nomem_policy;
 335                 vma_set_policy(tmp, pol);
 336                 tmp->vm_flags &= ~VM_LOCKED;
 337                 tmp->vm_mm = mm;
 338                 tmp->vm_next = NULL;
 339                 anon_vma_link(tmp);
 340                 file = tmp->vm_file;
 341                 if (file) {
 342                         struct inode *inode = file->f_path.dentry->d_inode;
 343                         struct address_space *mapping = file->f_mapping;
 344
 345                         get_file(file);
 346                         if (tmp->vm_flags & VM_DENYWRITE)
 347                                 atomic_dec(&inode->i_writecount);
 348                         spin_lock(&mapping->i_mmap_lock);
 349                         if (tmp->vm_flags & VM_SHARED)
 350                                 mapping->i_mmap_writable++;
 351                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 352                         flush_dcache_mmap_lock(mapping);
 353                         /* insert tmp into the share list, just after mpnt */
 354                         vma_prio_tree_add(tmp, mpnt);
 355                         flush_dcache_mmap_unlock(mapping);
 356                         spin_unlock(&mapping->i_mmap_lock);
 357                 }
 358
 359                 /*
 360                  * Clear hugetlb-related page reserves for children. This only
 361                  * affects MAP_PRIVATE mappings. Faults generated by the child
 362                  * are not guaranteed to succeed, even if read-only
 363                  */
 364                 if (is_vm_hugetlb_page(tmp))
 365                         reset_vma_resv_huge_pages(tmp);
 366
 367                 /*
 368                  * Link in the new vma and copy the page table entries.
 369                  */
 370                 *pprev = tmp;
 371                 pprev = &tmp->vm_next;
 372
 373                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 374                 rb_link = &tmp->vm_rb.rb_right;
 375                 rb_parent = &tmp->vm_rb;
 376
 377                 mm->map_count++;
 378                 retval = copy_page_range(mm, oldmm, mpnt);
 379
 380                 if (tmp->vm_ops && tmp->vm_ops->open)
 381                         tmp->vm_ops->open(tmp);
 382
 383                 if (retval)
 384                         goto out;
 385         }
 386         /* a new mm has just been created */
 387         arch_dup_mmap(oldmm, mm);
 388         retval = 0;
 389 out:
 390         up_write(&mm->mmap_sem);
 391         flush_tlb_mm(oldmm);
 392         up_write(&oldmm->mmap_sem);
 393         return retval;
 394 fail_nomem_policy:
 395         kmem_cache_free(vm_area_cachep, tmp);
 396 fail_nomem:
 397         retval = -ENOMEM;
 398         vm_unacct_memory(charge);
 399         goto out;
 400 }
 401
 402 static inline int mm_alloc_pgd(struct mm_struct * mm)
 403 {
 404         mm->pgd = pgd_alloc(mm);
 405         if (unlikely(!mm->pgd))
 406                 return -ENOMEM;
 407         return 0;
 408 }
 409
 410 static inline void mm_free_pgd(struct mm_struct * mm)
 411 {
 412         pgd_free(mm, mm->pgd);
 413 }
 414 #else
 415 #define dup_mmap(mm, oldmm)     (0)
 416 #define mm_alloc_pgd(mm)        (0)
 417 #define mm_free_pgd(mm)
 418 #endif /* CONFIG_MMU */
 419
 420 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 421
 422 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 423 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 424
 425 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 426
 427 static int __init coredump_filter_setup(char *s)
 428 {
 429         default_dump_filter =
 430                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 431                 MMF_DUMP_FILTER_MASK;
 432         return 1;
 433 }
 434
 435 __setup("coredump_filter=", coredump_filter_setup);
 436
 437 #include <linux/init_task.h>
 438
 439 static void mm_init_aio(struct mm_struct *mm)
 440 {
 441 #ifdef CONFIG_AIO
 442         spin_lock_init(&mm->ioctx_lock);
 443         INIT_HLIST_HEAD(&mm->ioctx_list);
 444 #endif
 445 }
 446
 447 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 448 {
 449         atomic_set(&mm->mm_users, 1);
 450         atomic_set(&mm->mm_count, 1);
 451         init_rwsem(&mm->mmap_sem);
 452         INIT_LIST_HEAD(&mm->mmlist);
 453         mm->flags = (current->mm) ?
 454                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 455         mm->core_state = NULL;
 456         mm->nr_ptes = 0;
 457         set_mm_counter(mm, file_rss, 0);
 458         set_mm_counter(mm, anon_rss, 0);
 459         spin_lock_init(&mm->page_table_lock);
 460         mm->free_area_cache = TASK_UNMAPPED_BASE;
 461         mm->cached_hole_size = ~0UL;
 462         mm_init_aio(mm);
 463         mm_init_owner(mm, p);
 464
 465         if (likely(!mm_alloc_pgd(mm))) {
 466                 mm->def_flags = 0;
 467                 mmu_notifier_mm_init(mm);
 468                 return mm;
 469         }
 470
 471         free_mm(mm);
 472         return NULL;
 473 }
 474
 475 /*
 476  * Allocate and initialize an mm_struct.
 477  */
 478 struct mm_struct * mm_alloc(void)
 479 {
 480         struct mm_struct * mm;
 481
 482         mm = allocate_mm();
 483         if (mm) {
 484                 memset(mm, 0, sizeof(*mm));
 485                 mm = mm_init(mm, current);
 486         }
 487         return mm;
 488 }
 489
 490 /*
 491  * Called when the last reference to the mm
 492  * is dropped: either by a lazy thread or by
 493  * mmput. Free the page directory and the mm.
 494  */
 495 void __mmdrop(struct mm_struct *mm)
 496 {
 497         BUG_ON(mm == &init_mm);
 498         mm_free_pgd(mm);
 499         destroy_context(mm);
 500         mmu_notifier_mm_destroy(mm);
 501         free_mm(mm);
 502 }
 503 EXPORT_SYMBOL_GPL(__mmdrop);
 504
 505 /*
 506  * Decrement the use count and release all resources for an mm.
 507  */
 508 void mmput(struct mm_struct *mm)
 509 {
 510         might_sleep();
 511
 512         if (atomic_dec_and_test(&mm->mm_users)) {
 513                 exit_aio(mm);
 514                 ksm_exit(mm);
 515                 exit_mmap(mm);
 516                 set_mm_exe_file(mm, NULL);
 517                 if (!list_empty(&mm->mmlist)) {
 518                         spin_lock(&mmlist_lock);
 519                         list_del(&mm->mmlist);
 520                         spin_unlock(&mmlist_lock);
 521                 }
 522                 put_swap_token(mm);
 523                 if (mm->binfmt)
 524                         module_put(mm->binfmt->module);
 525                 mmdrop(mm);
 526         }
 527 }
 528 EXPORT_SYMBOL_GPL(mmput);
 529
 530 /**
 531  * get_task_mm - acquire a reference to the task's mm
 532  *
 533  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 534  * this kernel workthread has transiently adopted a user mm with use_mm,
 535  * to do its AIO) is not set and if so returns a reference to it, after
 536  * bumping up the use count.  User must release the mm via mmput()
 537  * after use.  Typically used by /proc and ptrace.
 538  */
 539 struct mm_struct *get_task_mm(struct task_struct *task)
 540 {
 541         struct mm_struct *mm;
 542
 543         task_lock(task);
 544         mm = task->mm;
 545         if (mm) {
 546                 if (task->flags & PF_KTHREAD)
 547                         mm = NULL;
 548                 else
 549                         atomic_inc(&mm->mm_users);
 550         }
 551         task_unlock(task);
 552         return mm;
 553 }
 554 EXPORT_SYMBOL_GPL(get_task_mm);
 555
 556 /* Please note the differences between mmput and mm_release.
 557  * mmput is called whenever we stop holding onto a mm_struct,
 558  * error success whatever.
 559  *
 560  * mm_release is called after a mm_struct has been removed
 561  * from the current process.
 562  *
 563  * This difference is important for error handling, when we
 564  * only half set up a mm_struct for a new process and need to restore
 565  * the old one.  Because we mmput the new mm_struct before
 566  * restoring the old one. . .
 567  * Eric Biederman 10 January 1998
 568  */
 569 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 570 {
 571         struct completion *vfork_done = tsk->vfork_done;
 572
 573         /* Get rid of any futexes when releasing the mm */
 574 #ifdef CONFIG_FUTEX
 575         if (unlikely(tsk->robust_list)) {
 576                 exit_robust_list(tsk);
 577                 tsk->robust_list = NULL;
 578         }
 579 #ifdef CONFIG_COMPAT
 580         if (unlikely(tsk->compat_robust_list)) {
 581                 compat_exit_robust_list(tsk);
 582                 tsk->compat_robust_list = NULL;
 583         }
 584 #endif
 585         if (unlikely(!list_empty(&tsk->pi_state_list)))
 586                 exit_pi_state_list(tsk);
 587 #endif
 588
 589         /* Get rid of any cached register state */
 590         deactivate_mm(tsk, mm);
 591
 592         /* notify parent sleeping on vfork() */
 593         if (vfork_done) {
 594                 tsk->vfork_done = NULL;
 595                 complete(vfork_done);
 596         }
 597
 598         /*
 599          * If we're exiting normally, clear a user-space tid field if
 600          * requested.  We leave this alone when dying by signal, to leave
 601          * the value intact in a core dump, and to save the unnecessary
 602          * trouble otherwise.  Userland only wants this done for a sys_exit.
 603          */
 604         if (tsk->clear_child_tid) {
 605                 if (!(tsk->flags & PF_SIGNALED) &&
 606                     atomic_read(&mm->mm_users) > 1) {
 607                         /*
 608                          * We don't check the error code - if userspace has
 609                          * not set up a proper pointer then tough luck.
 610                          */
 611                         put_user(0, tsk->clear_child_tid);
 612                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 613                                         1, NULL, NULL, 0);
 614                 }
 615                 tsk->clear_child_tid = NULL;
 616         }
 617 }
 618
 619 /*
 620  * Allocate a new mm structure and copy contents from the
 621  * mm structure of the passed in task structure.
 622  */
 623 struct mm_struct *dup_mm(struct task_struct *tsk)
 624 {
 625         struct mm_struct *mm, *oldmm = current->mm;
 626         int err;
 627
 628         if (!oldmm)
 629                 return NULL;
 630
 631         mm = allocate_mm();
 632         if (!mm)
 633                 goto fail_nomem;
 634
 635         memcpy(mm, oldmm, sizeof(*mm));
 636
 637         /* Initializing for Swap token stuff */
 638         mm->token_priority = 0;
 639         mm->last_interval = 0;
 640
 641         if (!mm_init(mm, tsk))
 642                 goto fail_nomem;
 643
 644         if (init_new_context(tsk, mm))
 645                 goto fail_nocontext;
 646
 647         dup_mm_exe_file(oldmm, mm);
 648
 649         err = dup_mmap(mm, oldmm);
 650         if (err)
 651                 goto free_pt;
 652
 653         mm->hiwater_rss = get_mm_rss(mm);
 654         mm->hiwater_vm = mm->total_vm;
 655
 656         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 657                 goto free_pt;
 658
 659         return mm;
 660
 661 free_pt:
 662         /* don't put binfmt in mmput, we haven't got module yet */
 663         mm->binfmt = NULL;
 664         mmput(mm);
 665
 666 fail_nomem:
 667         return NULL;
 668
 669 fail_nocontext:
 670         /*
 671          * If init_new_context() failed, we cannot use mmput() to free the mm
 672          * because it calls destroy_context()
 673          */
 674         mm_free_pgd(mm);
 675         free_mm(mm);
 676         return NULL;
 677 }
 678
 679 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 680 {
 681         struct mm_struct * mm, *oldmm;
 682         int retval;
 683
 684         tsk->min_flt = tsk->maj_flt = 0;
 685         tsk->nvcsw = tsk->nivcsw = 0;
 686 #ifdef CONFIG_DETECT_HUNG_TASK
 687         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 688 #endif
 689
 690         tsk->mm = NULL;
 691         tsk->active_mm = NULL;
 692
 693         /*
 694          * Are we cloning a kernel thread?
 695          *
 696          * We need to steal a active VM for that..
 697          */
 698         oldmm = current->mm;
 699         if (!oldmm)
 700                 return 0;
 701
 702         if (clone_flags & CLONE_VM) {
 703                 atomic_inc(&oldmm->mm_users);
 704                 mm = oldmm;
 705                 goto good_mm;
 706         }
 707
 708         retval = -ENOMEM;
 709         mm = dup_mm(tsk);
 710         if (!mm)
 711                 goto fail_nomem;
 712
 713 good_mm:
 714         /* Initializing for Swap token stuff */
 715         mm->token_priority = 0;
 716         mm->last_interval = 0;
 717
 718         tsk->mm = mm;
 719         tsk->active_mm = mm;
 720         return 0;
 721
 722 fail_nomem:
 723         return retval;
 724 }
 725
 726 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 727 {
 728         struct fs_struct *fs = current->fs;
 729         if (clone_flags & CLONE_FS) {
 730                 /* tsk->fs is already what we want */
 731                 write_lock(&fs->lock);
 732                 if (fs->in_exec) {
 733                         write_unlock(&fs->lock);
 734                         return -EAGAIN;
 735                 }
 736                 fs->users++;
 737                 write_unlock(&fs->lock);
 738                 return 0;
 739         }
 740         tsk->fs = copy_fs_struct(fs);
 741         if (!tsk->fs)
 742                 return -ENOMEM;
 743         return 0;
 744 }
 745
 746 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 747 {
 748         struct files_struct *oldf, *newf;
 749         int error = 0;
 750
 751         /*
 752          * A background process may not have any files ...
 753          */
 754         oldf = current->files;
 755         if (!oldf)
 756                 goto out;
 757
 758         if (clone_flags & CLONE_FILES) {
 759                 atomic_inc(&oldf->count);
 760                 goto out;
 761         }
 762
 763         newf = dup_fd(oldf, &error);
 764         if (!newf)
 765                 goto out;
 766
 767         tsk->files = newf;
 768         error = 0;
 769 out:
 770         return error;
 771 }
 772
 773 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 774 {
 775 #ifdef CONFIG_BLOCK
 776         struct io_context *ioc = current->io_context;
 777
 778         if (!ioc)
 779                 return 0;
 780         /*
 781          * Share io context with parent, if CLONE_IO is set
 782          */
 783         if (clone_flags & CLONE_IO) {
 784                 tsk->io_context = ioc_task_link(ioc);
 785                 if (unlikely(!tsk->io_context))
 786                         return -ENOMEM;
 787         } else if (ioprio_valid(ioc->ioprio)) {
 788                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 789                 if (unlikely(!tsk->io_context))
 790                         return -ENOMEM;
 791
 792                 tsk->io_context->ioprio = ioc->ioprio;
 793         }
 794 #endif
 795         return 0;
 796 }
 797
 798 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 799 {
 800         struct sighand_struct *sig;
 801
 802         if (clone_flags & CLONE_SIGHAND) {
 803                 atomic_inc(&current->sighand->count);
 804                 return 0;
 805         }
 806         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 807         rcu_assign_pointer(tsk->sighand, sig);
 808         if (!sig)
 809                 return -ENOMEM;
 810         atomic_set(&sig->count, 1);
 811         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 812         return 0;
 813 }
 814
 815 void __cleanup_sighand(struct sighand_struct *sighand)
 816 {
 817         if (atomic_dec_and_test(&sighand->count))
 818                 kmem_cache_free(sighand_cachep, sighand);
 819 }
 820
 821
 822 /*
 823  * Initialize POSIX timer handling for a thread group.
 824  */
 825 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 826 {
 827         /* Thread group counters. */
 828         thread_group_cputime_init(sig);
 829
 830         /* Expiration times and increments. */
 831         sig->it[CPUCLOCK_PROF].expires = cputime_zero;
 832         sig->it[CPUCLOCK_PROF].incr = cputime_zero;
 833         sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
 834         sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
 835
 836         /* Cached expiration times. */
 837         sig->cputime_expires.prof_exp = cputime_zero;
 838         sig->cputime_expires.virt_exp = cputime_zero;
 839         sig->cputime_expires.sched_exp = 0;
 840
 841         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 842                 sig->cputime_expires.prof_exp =
 843                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 844                 sig->cputimer.running = 1;
 845         }
 846
 847         /* The timer lists. */
 848         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 849         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 850         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 851 }
 852
 853 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 854 {
 855         struct signal_struct *sig;
 856
 857         if (clone_flags & CLONE_THREAD)
 858                 return 0;
 859
 860         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 861         tsk->signal = sig;
 862         if (!sig)
 863                 return -ENOMEM;
 864
 865         atomic_set(&sig->count, 1);
 866         atomic_set(&sig->live, 1);
 867         init_waitqueue_head(&sig->wait_chldexit);
 868         sig->flags = 0;
 869         if (clone_flags & CLONE_NEWPID)
 870                 sig->flags |= SIGNAL_UNKILLABLE;
 871         sig->group_exit_code = 0;
 872         sig->group_exit_task = NULL;
 873         sig->group_stop_count = 0;
 874         sig->curr_target = tsk;
 875         init_sigpending(&sig->shared_pending);
 876         INIT_LIST_HEAD(&sig->posix_timers);
 877
 878         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 879         sig->it_real_incr.tv64 = 0;
 880         sig->real_timer.function = it_real_fn;
 881
 882         sig->leader = 0;        /* session leadership doesn't inherit */
 883         sig->tty_old_pgrp = NULL;
 884         sig->tty = NULL;
 885
 886         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 887         sig->gtime = cputime_zero;
 888         sig->cgtime = cputime_zero;
 889 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
 890         sig->prev_utime = sig->prev_stime = cputime_zero;
 891 #endif
 892         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 893         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 894         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 895         sig->maxrss = sig->cmaxrss = 0;
 896         task_io_accounting_init(&sig->ioac);
 897         sig->sum_sched_runtime = 0;
 898         taskstats_tgid_init(sig);
 899
 900         task_lock(current->group_leader);
 901         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 902         task_unlock(current->group_leader);
 903
 904         posix_cpu_timers_init_group(sig);
 905
 906         acct_init_pacct(&sig->pacct);
 907
 908         tty_audit_fork(sig);
 909
 910         sig->oom_adj = current->signal->oom_adj;
 911
 912         return 0;
 913 }
 914
 915 void __cleanup_signal(struct signal_struct *sig)
 916 {
 917         thread_group_cputime_free(sig);
 918         tty_kref_put(sig->tty);
 919         kmem_cache_free(signal_cachep, sig);
 920 }
 921
 922 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 923 {
 924         unsigned long new_flags = p->flags;
 925
 926         new_flags &= ~PF_SUPERPRIV;
 927         new_flags |= PF_FORKNOEXEC;
 928         new_flags |= PF_STARTING;
 929         p->flags = new_flags;
 930         clear_freeze_flag(p);
 931 }
 932
 933 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 934 {
 935         current->clear_child_tid = tidptr;
 936
 937         return task_pid_vnr(current);
 938 }
 939
 940 static void rt_mutex_init_task(struct task_struct *p)
 941 {
 942         raw_spin_lock_init(&p->pi_lock);
 943 #ifdef CONFIG_RT_MUTEXES
 944         plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
 945         p->pi_blocked_on = NULL;
 946 #endif
 947 }
 948
 949 #ifdef CONFIG_MM_OWNER
 950 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 951 {
 952         mm->owner = p;
 953 }
 954 #endif /* CONFIG_MM_OWNER */
 955
 956 /*
 957  * Initialize POSIX timer handling for a single task.
 958  */
 959 static void posix_cpu_timers_init(struct task_struct *tsk)
 960 {
 961         tsk->cputime_expires.prof_exp = cputime_zero;
 962         tsk->cputime_expires.virt_exp = cputime_zero;
 963         tsk->cputime_expires.sched_exp = 0;
 964         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 965         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 966         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 967 }
 968
 969 /*
 970  * This creates a new process as a copy of the old one,
 971  * but does not actually start it yet.
 972  *
 973  * It copies the registers, and all the appropriate
 974  * parts of the process environment (as per the clone
 975  * flags). The actual kick-off is left to the caller.
 976  */
 977 static struct task_struct *copy_process(unsigned long clone_flags,
 978                                         unsigned long stack_start,
 979                                         struct pt_regs *regs,
 980                                         unsigned long stack_size,
 981                                         int __user *child_tidptr,
 982                                         struct pid *pid,
 983                                         int trace)
 984 {
 985         int retval;
 986         struct task_struct *p;
 987         int cgroup_callbacks_done = 0;
 988
 989         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 990                 return ERR_PTR(-EINVAL);
 991
 992         /*
 993          * Thread groups must share signals as well, and detached threads
 994          * can only be started up within the thread group.
 995          */
 996         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 997                 return ERR_PTR(-EINVAL);
 998
 999         /*
1000          * Shared signal handlers imply shared VM. By way of the above,
1001          * thread groups also imply shared VM. Blocking this case allows
1002          * for various simplifications in other code.
1003          */
1004         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1005                 return ERR_PTR(-EINVAL);
1006
1007         /*
1008          * Siblings of global init remain as zombies on exit since they are
1009          * not reaped by their parent (swapper). To solve this and to avoid
1010          * multi-rooted process trees, prevent global and container-inits
1011          * from creating siblings.
1012          */
1013         if ((clone_flags & CLONE_PARENT) &&
1014                                 current->signal->flags & SIGNAL_UNKILLABLE)
1015                 return ERR_PTR(-EINVAL);
1016
1017         retval = security_task_create(clone_flags);
1018         if (retval)
1019                 goto fork_out;
1020
1021         retval = -ENOMEM;
1022         p = dup_task_struct(current);
1023         if (!p)
1024                 goto fork_out;
1025
1026         ftrace_graph_init_task(p);
1027
1028         rt_mutex_init_task(p);
1029
1030 #ifdef CONFIG_PROVE_LOCKING
1031         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1032         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1033 #endif
1034         retval = -EAGAIN;
1035         if (atomic_read(&p->real_cred->user->processes) >=
1036                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1037                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1038                     p->real_cred->user != INIT_USER)
1039                         goto bad_fork_free;
1040         }
1041
1042         retval = copy_creds(p, clone_flags);
1043         if (retval < 0)
1044                 goto bad_fork_free;
1045
1046         /*
1047          * If multiple threads are within copy_process(), then this check
1048          * triggers too late. This doesn't hurt, the check is only there
1049          * to stop root fork bombs.
1050          */
1051         retval = -EAGAIN;
1052         if (nr_threads >= max_threads)
1053                 goto bad_fork_cleanup_count;
1054
1055         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1056                 goto bad_fork_cleanup_count;
1057
1058         p->did_exec = 0;
1059         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1060         copy_flags(clone_flags, p);
1061         INIT_LIST_HEAD(&p->children);
1062         INIT_LIST_HEAD(&p->sibling);
1063         rcu_copy_process(p);
1064         p->vfork_done = NULL;
1065         spin_lock_init(&p->alloc_lock);
1066
1067         init_sigpending(&p->pending);
1068
1069         p->utime = cputime_zero;
1070         p->stime = cputime_zero;
1071         p->gtime = cputime_zero;
1072         p->utimescaled = cputime_zero;
1073         p->stimescaled = cputime_zero;
1074 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1075         p->prev_utime = cputime_zero;
1076         p->prev_stime = cputime_zero;
1077 #endif
1078
1079         p->default_timer_slack_ns = current->timer_slack_ns;
1080
1081         task_io_accounting_init(&p->ioac);
1082         acct_clear_integrals(p);
1083
1084         posix_cpu_timers_init(p);
1085
1086         p->lock_depth = -1;             /* -1 = no lock */
1087         do_posix_clock_monotonic_gettime(&p->start_time);
1088         p->real_start_time = p->start_time;
1089         monotonic_to_bootbased(&p->real_start_time);
1090         p->io_context = NULL;
1091         p->audit_context = NULL;
1092         cgroup_fork(p);
1093 #ifdef CONFIG_NUMA
1094         p->mempolicy = mpol_dup(p->mempolicy);
1095         if (IS_ERR(p->mempolicy)) {
1096                 retval = PTR_ERR(p->mempolicy);
1097                 p->mempolicy = NULL;
1098                 goto bad_fork_cleanup_cgroup;
1099         }
1100         mpol_fix_fork_child_flag(p);
1101 #endif
1102 #ifdef CONFIG_TRACE_IRQFLAGS
1103         p->irq_events = 0;
1104 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1105         p->hardirqs_enabled = 1;
1106 #else
1107         p->hardirqs_enabled = 0;
1108 #endif
1109         p->hardirq_enable_ip = 0;
1110         p->hardirq_enable_event = 0;
1111         p->hardirq_disable_ip = _THIS_IP_;
1112         p->hardirq_disable_event = 0;
1113         p->softirqs_enabled = 1;
1114         p->softirq_enable_ip = _THIS_IP_;
1115         p->softirq_enable_event = 0;
1116         p->softirq_disable_ip = 0;
1117         p->softirq_disable_event = 0;
1118         p->hardirq_context = 0;
1119         p->softirq_context = 0;
1120 #endif
1121 #ifdef CONFIG_LOCKDEP
1122         p->lockdep_depth = 0; /* no locks held yet */
1123         p->curr_chain_key = 0;
1124         p->lockdep_recursion = 0;
1125 #endif
1126
1127 #ifdef CONFIG_DEBUG_MUTEXES
1128         p->blocked_on = NULL; /* not blocked yet */
1129 #endif
1130 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1131         p->memcg_batch.do_batch = 0;
1132         p->memcg_batch.memcg = NULL;
1133 #endif
1134
1135         p->bts = NULL;
1136
1137         p->stack_start = stack_start;
1138
1139         /* Perform scheduler related setup. Assign this task to a CPU. */
1140         sched_fork(p, clone_flags);
1141
1142         retval = perf_event_init_task(p);
1143         if (retval)
1144                 goto bad_fork_cleanup_policy;
1145
1146         if ((retval = audit_alloc(p)))
1147                 goto bad_fork_cleanup_policy;
1148         /* copy all the process information */
1149         if ((retval = copy_semundo(clone_flags, p)))
1150                 goto bad_fork_cleanup_audit;
1151         if ((retval = copy_files(clone_flags, p)))
1152                 goto bad_fork_cleanup_semundo;
1153         if ((retval = copy_fs(clone_flags, p)))
1154                 goto bad_fork_cleanup_files;
1155         if ((retval = copy_sighand(clone_flags, p)))
1156                 goto bad_fork_cleanup_fs;
1157         if ((retval = copy_signal(clone_flags, p)))
1158                 goto bad_fork_cleanup_sighand;
1159         if ((retval = copy_mm(clone_flags, p)))
1160                 goto bad_fork_cleanup_signal;
1161         if ((retval = copy_namespaces(clone_flags, p)))
1162                 goto bad_fork_cleanup_mm;
1163         if ((retval = copy_io(clone_flags, p)))
1164                 goto bad_fork_cleanup_namespaces;
1165         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1166         if (retval)
1167                 goto bad_fork_cleanup_io;
1168
1169         if (pid != &init_struct_pid) {
1170                 retval = -ENOMEM;
1171                 pid = alloc_pid(p->nsproxy->pid_ns);
1172                 if (!pid)
1173                         goto bad_fork_cleanup_io;
1174
1175                 if (clone_flags & CLONE_NEWPID) {
1176                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1177                         if (retval < 0)
1178                                 goto bad_fork_free_pid;
1179                 }
1180         }
1181
1182         p->pid = pid_nr(pid);
1183         p->tgid = p->pid;
1184         if (clone_flags & CLONE_THREAD)
1185                 p->tgid = current->tgid;
1186
1187         if (current->nsproxy != p->nsproxy) {
1188                 retval = ns_cgroup_clone(p, pid);
1189                 if (retval)
1190                         goto bad_fork_free_pid;
1191         }
1192
1193         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1194         /*
1195          * Clear TID on mm_release()?
1196          */
1197         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1198 #ifdef CONFIG_FUTEX
1199         p->robust_list = NULL;
1200 #ifdef CONFIG_COMPAT
1201         p->compat_robust_list = NULL;
1202 #endif
1203         INIT_LIST_HEAD(&p->pi_state_list);
1204         p->pi_state_cache = NULL;
1205 #endif
1206         /*
1207          * sigaltstack should be cleared when sharing the same VM
1208          */
1209         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1210                 p->sas_ss_sp = p->sas_ss_size = 0;
1211
1212         /*
1213          * Syscall tracing and stepping should be turned off in the
1214          * child regardless of CLONE_PTRACE.
1215          */
1216         user_disable_single_step(p);
1217         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1218 #ifdef TIF_SYSCALL_EMU
1219         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1220 #endif
1221         clear_all_latency_tracing(p);
1222
1223         /* ok, now we should be set up.. */
1224         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1225         p->pdeath_signal = 0;
1226         p->exit_state = 0;
1227
1228         /*
1229          * Ok, make it visible to the rest of the system.
1230          * We dont wake it up yet.
1231          */
1232         p->group_leader = p;
1233         INIT_LIST_HEAD(&p->thread_group);
1234
1235         /* Now that the task is set up, run cgroup callbacks if
1236          * necessary. We need to run them before the task is visible
1237          * on the tasklist. */
1238         cgroup_fork_callbacks(p);
1239         cgroup_callbacks_done = 1;
1240
1241         /* Need tasklist lock for parent etc handling! */
1242         write_lock_irq(&tasklist_lock);
1243
1244         /*
1245          * The task hasn't been attached yet, so its cpus_allowed mask will
1246          * not be changed, nor will its assigned CPU.
1247          *
1248          * The cpus_allowed mask of the parent may have changed after it was
1249          * copied first time - so re-copy it here, then check the child's CPU
1250          * to ensure it is on a valid CPU (and if not, just force it back to
1251          * parent's CPU). This avoids alot of nasty races.
1252          */
1253         p->cpus_allowed = current->cpus_allowed;
1254         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1255         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1256                         !cpu_online(task_cpu(p))))
1257                 set_task_cpu(p, smp_processor_id());
1258
1259         /* CLONE_PARENT re-uses the old parent */
1260         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1261                 p->real_parent = current->real_parent;
1262                 p->parent_exec_id = current->parent_exec_id;
1263         } else {
1264                 p->real_parent = current;
1265                 p->parent_exec_id = current->self_exec_id;
1266         }
1267
1268         spin_lock(&current->sighand->siglock);
1269
1270         /*
1271          * Process group and session signals need to be delivered to just the
1272          * parent before the fork or both the parent and the child after the
1273          * fork. Restart if a signal comes in before we add the new process to
1274          * it's process group.
1275          * A fatal signal pending means that current will exit, so the new
1276          * thread can't slip out of an OOM kill (or normal SIGKILL).
1277          */
1278         recalc_sigpending();
1279         if (signal_pending(current)) {
1280                 spin_unlock(&current->sighand->siglock);
1281                 write_unlock_irq(&tasklist_lock);
1282                 retval = -ERESTARTNOINTR;
1283                 goto bad_fork_free_pid;
1284         }
1285
1286         if (clone_flags & CLONE_THREAD) {
1287                 atomic_inc(&current->signal->count);
1288                 atomic_inc(&current->signal->live);
1289                 p->group_leader = current->group_leader;
1290                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1291         }
1292
1293         if (likely(p->pid)) {
1294                 tracehook_finish_clone(p, clone_flags, trace);
1295
1296                 if (thread_group_leader(p)) {
1297                         if (clone_flags & CLONE_NEWPID)
1298                                 p->nsproxy->pid_ns->child_reaper = p;
1299
1300                         p->signal->leader_pid = pid;
1301                         tty_kref_put(p->signal->tty);
1302                         p->signal->tty = tty_kref_get(current->signal->tty);
1303                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1304                         attach_pid(p, PIDTYPE_SID, task_session(current));
1305                         list_add_tail(&p->sibling, &p->real_parent->children);
1306                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1307                         __get_cpu_var(process_counts)++;
1308                 }
1309                 attach_pid(p, PIDTYPE_PID, pid);
1310                 nr_threads++;
1311         }
1312
1313         total_forks++;
1314         spin_unlock(&current->sighand->siglock);
1315         write_unlock_irq(&tasklist_lock);
1316         proc_fork_connector(p);
1317         cgroup_post_fork(p);
1318         perf_event_fork(p);
1319         return p;
1320
1321 bad_fork_free_pid:
1322         if (pid != &init_struct_pid)
1323                 free_pid(pid);
1324 bad_fork_cleanup_io:
1325         if (p->io_context)
1326                 exit_io_context(p);
1327 bad_fork_cleanup_namespaces:
1328         exit_task_namespaces(p);
1329 bad_fork_cleanup_mm:
1330         if (p->mm)
1331                 mmput(p->mm);
1332 bad_fork_cleanup_signal:
1333         if (!(clone_flags & CLONE_THREAD))
1334                 __cleanup_signal(p->signal);
1335 bad_fork_cleanup_sighand:
1336         __cleanup_sighand(p->sighand);
1337 bad_fork_cleanup_fs:
1338         exit_fs(p); /* blocking */
1339 bad_fork_cleanup_files:
1340         exit_files(p); /* blocking */
1341 bad_fork_cleanup_semundo:
1342         exit_sem(p);
1343 bad_fork_cleanup_audit:
1344         audit_free(p);
1345 bad_fork_cleanup_policy:
1346         perf_event_free_task(p);
1347 #ifdef CONFIG_NUMA
1348         mpol_put(p->mempolicy);
1349 bad_fork_cleanup_cgroup:
1350 #endif
1351         cgroup_exit(p, cgroup_callbacks_done);
1352         delayacct_tsk_free(p);
1353         module_put(task_thread_info(p)->exec_domain->module);
1354 bad_fork_cleanup_count:
1355         atomic_dec(&p->cred->user->processes);
1356         exit_creds(p);
1357 bad_fork_free:
1358         free_task(p);
1359 fork_out:
1360         return ERR_PTR(retval);
1361 }
1362
1363 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1364 {
1365         memset(regs, 0, sizeof(struct pt_regs));
1366         return regs;
1367 }
1368
1369 struct task_struct * __cpuinit fork_idle(int cpu)
1370 {
1371         struct task_struct *task;
1372         struct pt_regs regs;
1373
1374         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1375                             &init_struct_pid, 0);
1376         if (!IS_ERR(task))
1377                 init_idle(task, cpu);
1378
1379         return task;
1380 }
1381
1382 /*
1383  *  Ok, this is the main fork-routine.
1384  *
1385  * It copies the process, and if successful kick-starts
1386  * it and waits for it to finish using the VM if required.
1387  */
1388 long do_fork(unsigned long clone_flags,
1389               unsigned long stack_start,
1390               struct pt_regs *regs,
1391               unsigned long stack_size,
1392               int __user *parent_tidptr,
1393               int __user *child_tidptr)
1394 {
1395         struct task_struct *p;
1396         int trace = 0;
1397         long nr;
1398
1399         /*
1400          * Do some preliminary argument and permissions checking before we
1401          * actually start allocating stuff
1402          */
1403         if (clone_flags & CLONE_NEWUSER) {
1404                 if (clone_flags & CLONE_THREAD)
1405                         return -EINVAL;
1406                 /* hopefully this check will go away when userns support is
1407                  * complete
1408                  */
1409                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1410                                 !capable(CAP_SETGID))
1411                         return -EPERM;
1412         }
1413
1414         /*
1415          * We hope to recycle these flags after 2.6.26
1416          */
1417         if (unlikely(clone_flags & CLONE_STOPPED)) {
1418                 static int __read_mostly count = 100;
1419
1420                 if (count > 0 && printk_ratelimit()) {
1421                         char comm[TASK_COMM_LEN];
1422
1423                         count--;
1424                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1425                                         "clone flags 0x%lx\n",
1426                                 get_task_comm(comm, current),
1427                                 clone_flags & CLONE_STOPPED);
1428                 }
1429         }
1430
1431         /*
1432          * When called from kernel_thread, don't do user tracing stuff.
1433          */
1434         if (likely(user_mode(regs)))
1435                 trace = tracehook_prepare_clone(clone_flags);
1436
1437         p = copy_process(clone_flags, stack_start, regs, stack_size,
1438                          child_tidptr, NULL, trace);
1439         /*
1440          * Do this prior waking up the new thread - the thread pointer
1441          * might get invalid after that point, if the thread exits quickly.
1442          */
1443         if (!IS_ERR(p)) {
1444                 struct completion vfork;
1445
1446                 trace_sched_process_fork(current, p);
1447
1448                 nr = task_pid_vnr(p);
1449
1450                 if (clone_flags & CLONE_PARENT_SETTID)
1451                         put_user(nr, parent_tidptr);
1452
1453                 if (clone_flags & CLONE_VFORK) {
1454                         p->vfork_done = &vfork;
1455                         init_completion(&vfork);
1456                 }
1457
1458                 audit_finish_fork(p);
1459                 tracehook_report_clone(regs, clone_flags, nr, p);
1460
1461                 /*
1462                  * We set PF_STARTING at creation in case tracing wants to
1463                  * use this to distinguish a fully live task from one that
1464                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1465                  * clear it and set the child going.
1466                  */
1467                 p->flags &= ~PF_STARTING;
1468
1469                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1470                         /*
1471                          * We'll start up with an immediate SIGSTOP.
1472                          */
1473                         sigaddset(&p->pending.signal, SIGSTOP);
1474                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1475                         __set_task_state(p, TASK_STOPPED);
1476                 } else {
1477                         wake_up_new_task(p, clone_flags);
1478                 }
1479
1480                 tracehook_report_clone_complete(trace, regs,
1481                                                 clone_flags, nr, p);
1482
1483                 if (clone_flags & CLONE_VFORK) {
1484                         freezer_do_not_count();
1485                         wait_for_completion(&vfork);
1486                         freezer_count();
1487                         tracehook_report_vfork_done(p, nr);
1488                 }
1489         } else {
1490                 nr = PTR_ERR(p);
1491         }
1492         return nr;
1493 }
1494
1495 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1496 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1497 #endif
1498
1499 static void sighand_ctor(void *data)
1500 {
1501         struct sighand_struct *sighand = data;
1502
1503         spin_lock_init(&sighand->siglock);
1504         init_waitqueue_head(&sighand->signalfd_wqh);
1505 }
1506
1507 void __init proc_caches_init(void)
1508 {
1509         sighand_cachep = kmem_cache_create("sighand_cache",
1510                         sizeof(struct sighand_struct), 0,
1511                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1512                         SLAB_NOTRACK, sighand_ctor);
1513         signal_cachep = kmem_cache_create("signal_cache",
1514                         sizeof(struct signal_struct), 0,
1515                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1516         files_cachep = kmem_cache_create("files_cache",
1517                         sizeof(struct files_struct), 0,
1518                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1519         fs_cachep = kmem_cache_create("fs_cache",
1520                         sizeof(struct fs_struct), 0,
1521                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1522         mm_cachep = kmem_cache_create("mm_struct",
1523                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1524                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1525         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1526         mmap_init();
1527 }
1528
1529 /*
1530  * Check constraints on flags passed to the unshare system call and
1531  * force unsharing of additional process context as appropriate.
1532  */
1533 static void check_unshare_flags(unsigned long *flags_ptr)
1534 {
1535         /*
1536          * If unsharing a thread from a thread group, must also
1537          * unshare vm.
1538          */
1539         if (*flags_ptr & CLONE_THREAD)
1540                 *flags_ptr |= CLONE_VM;
1541
1542         /*
1543          * If unsharing vm, must also unshare signal handlers.
1544          */
1545         if (*flags_ptr & CLONE_VM)
1546                 *flags_ptr |= CLONE_SIGHAND;
1547
1548         /*
1549          * If unsharing signal handlers and the task was created
1550          * using CLONE_THREAD, then must unshare the thread
1551          */
1552         if ((*flags_ptr & CLONE_SIGHAND) &&
1553             (atomic_read(&current->signal->count) > 1))
1554                 *flags_ptr |= CLONE_THREAD;
1555
1556         /*
1557          * If unsharing namespace, must also unshare filesystem information.
1558          */
1559         if (*flags_ptr & CLONE_NEWNS)
1560                 *flags_ptr |= CLONE_FS;
1561 }
1562
1563 /*
1564  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1565  */
1566 static int unshare_thread(unsigned long unshare_flags)
1567 {
1568         if (unshare_flags & CLONE_THREAD)
1569                 return -EINVAL;
1570
1571         return 0;
1572 }
1573
1574 /*
1575  * Unshare the filesystem structure if it is being shared
1576  */
1577 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1578 {
1579         struct fs_struct *fs = current->fs;
1580
1581         if (!(unshare_flags & CLONE_FS) || !fs)
1582                 return 0;
1583
1584         /* don't need lock here; in the worst case we'll do useless copy */
1585         if (fs->users == 1)
1586                 return 0;
1587
1588         *new_fsp = copy_fs_struct(fs);
1589         if (!*new_fsp)
1590                 return -ENOMEM;
1591
1592         return 0;
1593 }
1594
1595 /*
1596  * Unsharing of sighand is not supported yet
1597  */
1598 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1599 {
1600         struct sighand_struct *sigh = current->sighand;
1601
1602         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1603                 return -EINVAL;
1604         else
1605                 return 0;
1606 }
1607
1608 /*
1609  * Unshare vm if it is being shared
1610  */
1611 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1612 {
1613         struct mm_struct *mm = current->mm;
1614
1615         if ((unshare_flags & CLONE_VM) &&
1616             (mm && atomic_read(&mm->mm_users) > 1)) {
1617                 return -EINVAL;
1618         }
1619
1620         return 0;
1621 }
1622
1623 /*
1624  * Unshare file descriptor table if it is being shared
1625  */
1626 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1627 {
1628         struct files_struct *fd = current->files;
1629         int error = 0;
1630
1631         if ((unshare_flags & CLONE_FILES) &&
1632             (fd && atomic_read(&fd->count) > 1)) {
1633                 *new_fdp = dup_fd(fd, &error);
1634                 if (!*new_fdp)
1635                         return error;
1636         }
1637
1638         return 0;
1639 }
1640
1641 /*
1642  * unshare allows a process to 'unshare' part of the process
1643  * context which was originally shared using clone.  copy_*
1644  * functions used by do_fork() cannot be used here directly
1645  * because they modify an inactive task_struct that is being
1646  * constructed. Here we are modifying the current, active,
1647  * task_struct.
1648  */
1649 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1650 {
1651         int err = 0;
1652         struct fs_struct *fs, *new_fs = NULL;
1653         struct sighand_struct *new_sigh = NULL;
1654         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1655         struct files_struct *fd, *new_fd = NULL;
1656         struct nsproxy *new_nsproxy = NULL;
1657         int do_sysvsem = 0;
1658
1659         check_unshare_flags(&unshare_flags);
1660
1661         /* Return -EINVAL for all unsupported flags */
1662         err = -EINVAL;
1663         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1664                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1665                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1666                 goto bad_unshare_out;
1667
1668         /*
1669          * CLONE_NEWIPC must also detach from the undolist: after switching
1670          * to a new ipc namespace, the semaphore arrays from the old
1671          * namespace are unreachable.
1672          */
1673         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1674                 do_sysvsem = 1;
1675         if ((err = unshare_thread(unshare_flags)))
1676                 goto bad_unshare_out;
1677         if ((err = unshare_fs(unshare_flags, &new_fs)))
1678                 goto bad_unshare_cleanup_thread;
1679         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1680                 goto bad_unshare_cleanup_fs;
1681         if ((err = unshare_vm(unshare_flags, &new_mm)))
1682                 goto bad_unshare_cleanup_sigh;
1683         if ((err = unshare_fd(unshare_flags, &new_fd)))
1684                 goto bad_unshare_cleanup_vm;
1685         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1686                         new_fs)))
1687                 goto bad_unshare_cleanup_fd;
1688
1689         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1690                 if (do_sysvsem) {
1691                         /*
1692                          * CLONE_SYSVSEM is equivalent to sys_exit().
1693                          */
1694                         exit_sem(current);
1695                 }
1696
1697                 if (new_nsproxy) {
1698                         switch_task_namespaces(current, new_nsproxy);
1699                         new_nsproxy = NULL;
1700                 }
1701
1702                 task_lock(current);
1703
1704                 if (new_fs) {
1705                         fs = current->fs;
1706                         write_lock(&fs->lock);
1707                         current->fs = new_fs;
1708                         if (--fs->users)
1709                                 new_fs = NULL;
1710                         else
1711                                 new_fs = fs;
1712                         write_unlock(&fs->lock);
1713                 }
1714
1715                 if (new_mm) {
1716                         mm = current->mm;
1717                         active_mm = current->active_mm;
1718                         current->mm = new_mm;
1719                         current->active_mm = new_mm;
1720                         activate_mm(active_mm, new_mm);
1721                         new_mm = mm;
1722                 }
1723
1724                 if (new_fd) {
1725                         fd = current->files;
1726                         current->files = new_fd;
1727                         new_fd = fd;
1728                 }
1729
1730                 task_unlock(current);
1731         }
1732
1733         if (new_nsproxy)
1734                 put_nsproxy(new_nsproxy);
1735
1736 bad_unshare_cleanup_fd:
1737         if (new_fd)
1738                 put_files_struct(new_fd);
1739
1740 bad_unshare_cleanup_vm:
1741         if (new_mm)
1742                 mmput(new_mm);
1743
1744 bad_unshare_cleanup_sigh:
1745         if (new_sigh)
1746                 if (atomic_dec_and_test(&new_sigh->count))
1747                         kmem_cache_free(sighand_cachep, new_sigh);
1748
1749 bad_unshare_cleanup_fs:
1750         if (new_fs)
1751                 free_fs_struct(new_fs);
1752
1753 bad_unshare_cleanup_thread:
1754 bad_unshare_out:
1755         return err;
1756 }
1757
1758 /*
1759  *      Helper to unshare the files of the current task.
1760  *      We don't want to expose copy_files internals to
1761  *      the exec layer of the kernel.
1762  */
1763
1764 int unshare_files(struct files_struct **displaced)
1765 {
1766         struct task_struct *task = current;
1767         struct files_struct *copy = NULL;
1768         int error;
1769
1770         error = unshare_fd(CLONE_FILES, &copy);
1771         if (error || !copy) {
1772                 *displaced = NULL;
1773                 return error;
1774         }
1775         *displaced = task->files;
1776         task_lock(task);
1777         task->files = copy;
1778         task_unlock(task);
1779         return 0;
1780 }