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