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/smp_lock.h>
  18 #include <linux/module.h>
  19 #include <linux/vmalloc.h>
  20 #include <linux/completion.h>
  21 #include <linux/namespace.h>
  22 #include <linux/personality.h>
  23 #include <linux/mempolicy.h>
  24 #include <linux/sem.h>
  25 #include <linux/file.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/fs.h>
  30 #include <linux/nsproxy.h>
  31 #include <linux/capability.h>
  32 #include <linux/cpu.h>
  33 #include <linux/cpuset.h>
  34 #include <linux/security.h>
  35 #include <linux/swap.h>
  36 #include <linux/syscalls.h>
  37 #include <linux/jiffies.h>
  38 #include <linux/futex.h>
  39 #include <linux/rcupdate.h>
  40 #include <linux/ptrace.h>
  41 #include <linux/mount.h>
  42 #include <linux/audit.h>
  43 #include <linux/profile.h>
  44 #include <linux/rmap.h>
  45 #include <linux/acct.h>
  46 #include <linux/tsacct_kern.h>
  47 #include <linux/cn_proc.h>
  48 #include <linux/delayacct.h>
  49 #include <linux/taskstats_kern.h>
  50 #include <linux/random.h>
  51
  52 #include <asm/pgtable.h>
  53 #include <asm/pgalloc.h>
  54 #include <asm/uaccess.h>
  55 #include <asm/mmu_context.h>
  56 #include <asm/cacheflush.h>
  57 #include <asm/tlbflush.h>
  58
  59 /*
  60  * Protected counters by write_lock_irq(&tasklist_lock)
  61  */
  62 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  63 int nr_threads;                 /* The idle threads do not count.. */
  64
  65 int max_threads;                /* tunable limit on nr_threads */
  66
  67 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  68
  69 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  70
  71 int nr_processes(void)
  72 {
  73         int cpu;
  74         int total = 0;
  75
  76         for_each_online_cpu(cpu)
  77                 total += per_cpu(process_counts, cpu);
  78
  79         return total;
  80 }
  81
  82 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  83 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  84 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  85 static kmem_cache_t *task_struct_cachep;
  86 #endif
  87
  88 /* SLAB cache for signal_struct structures (tsk->signal) */
  89 static kmem_cache_t *signal_cachep;
  90
  91 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  92 kmem_cache_t *sighand_cachep;
  93
  94 /* SLAB cache for files_struct structures (tsk->files) */
  95 kmem_cache_t *files_cachep;
  96
  97 /* SLAB cache for fs_struct structures (tsk->fs) */
  98 kmem_cache_t *fs_cachep;
  99
 100 /* SLAB cache for vm_area_struct structures */
 101 kmem_cache_t *vm_area_cachep;
 102
 103 /* SLAB cache for mm_struct structures (tsk->mm) */
 104 static kmem_cache_t *mm_cachep;
 105
 106 void free_task(struct task_struct *tsk)
 107 {
 108         free_thread_info(tsk->thread_info);
 109         rt_mutex_debug_task_free(tsk);
 110         free_task_struct(tsk);
 111 }
 112 EXPORT_SYMBOL(free_task);
 113
 114 void __put_task_struct(struct task_struct *tsk)
 115 {
 116         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
 117         WARN_ON(atomic_read(&tsk->usage));
 118         WARN_ON(tsk == current);
 119
 120         security_task_free(tsk);
 121         free_uid(tsk->user);
 122         put_group_info(tsk->group_info);
 123         delayacct_tsk_free(tsk);
 124
 125         if (!profile_handoff_task(tsk))
 126                 free_task(tsk);
 127 }
 128
 129 void __init fork_init(unsigned long mempages)
 130 {
 131 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 132 #ifndef ARCH_MIN_TASKALIGN
 133 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 134 #endif
 135         /* create a slab on which task_structs can be allocated */
 136         task_struct_cachep =
 137                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 138                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
 139 #endif
 140
 141         /*
 142          * The default maximum number of threads is set to a safe
 143          * value: the thread structures can take up at most half
 144          * of memory.
 145          */
 146         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 147
 148         /*
 149          * we need to allow at least 20 threads to boot a system
 150          */
 151         if(max_threads < 20)
 152                 max_threads = 20;
 153
 154         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 155         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 156         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 157                 init_task.signal->rlim[RLIMIT_NPROC];
 158 }
 159
 160 static struct task_struct *dup_task_struct(struct task_struct *orig)
 161 {
 162         struct task_struct *tsk;
 163         struct thread_info *ti;
 164
 165         prepare_to_copy(orig);
 166
 167         tsk = alloc_task_struct();
 168         if (!tsk)
 169                 return NULL;
 170
 171         ti = alloc_thread_info(tsk);
 172         if (!ti) {
 173                 free_task_struct(tsk);
 174                 return NULL;
 175         }
 176
 177         *tsk = *orig;
 178         tsk->thread_info = ti;
 179         setup_thread_stack(tsk, orig);
 180
 181 #ifdef CONFIG_CC_STACKPROTECTOR
 182         tsk->stack_canary = get_random_int();
 183 #endif
 184
 185         /* One for us, one for whoever does the "release_task()" (usually parent) */
 186         atomic_set(&tsk->usage,2);
 187         atomic_set(&tsk->fs_excl, 0);
 188 #ifdef CONFIG_BLK_DEV_IO_TRACE
 189         tsk->btrace_seq = 0;
 190 #endif
 191         tsk->splice_pipe = NULL;
 192         return tsk;
 193 }
 194
 195 #ifdef CONFIG_MMU
 196 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 197 {
 198         struct vm_area_struct *mpnt, *tmp, **pprev;
 199         struct rb_node **rb_link, *rb_parent;
 200         int retval;
 201         unsigned long charge;
 202         struct mempolicy *pol;
 203
 204         down_write(&oldmm->mmap_sem);
 205         flush_cache_mm(oldmm);
 206         /*
 207          * Not linked in yet - no deadlock potential:
 208          */
 209         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 210
 211         mm->locked_vm = 0;
 212         mm->mmap = NULL;
 213         mm->mmap_cache = NULL;
 214         mm->free_area_cache = oldmm->mmap_base;
 215         mm->cached_hole_size = ~0UL;
 216         mm->map_count = 0;
 217         cpus_clear(mm->cpu_vm_mask);
 218         mm->mm_rb = RB_ROOT;
 219         rb_link = &mm->mm_rb.rb_node;
 220         rb_parent = NULL;
 221         pprev = &mm->mmap;
 222
 223         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 224                 struct file *file;
 225
 226                 if (mpnt->vm_flags & VM_DONTCOPY) {
 227                         long pages = vma_pages(mpnt);
 228                         mm->total_vm -= pages;
 229                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 230                                                                 -pages);
 231                         continue;
 232                 }
 233                 charge = 0;
 234                 if (mpnt->vm_flags & VM_ACCOUNT) {
 235                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 236                         if (security_vm_enough_memory(len))
 237                                 goto fail_nomem;
 238                         charge = len;
 239                 }
 240                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 241                 if (!tmp)
 242                         goto fail_nomem;
 243                 *tmp = *mpnt;
 244                 pol = mpol_copy(vma_policy(mpnt));
 245                 retval = PTR_ERR(pol);
 246                 if (IS_ERR(pol))
 247                         goto fail_nomem_policy;
 248                 vma_set_policy(tmp, pol);
 249                 tmp->vm_flags &= ~VM_LOCKED;
 250                 tmp->vm_mm = mm;
 251                 tmp->vm_next = NULL;
 252                 anon_vma_link(tmp);
 253                 file = tmp->vm_file;
 254                 if (file) {
 255                         struct inode *inode = file->f_dentry->d_inode;
 256                         get_file(file);
 257                         if (tmp->vm_flags & VM_DENYWRITE)
 258                                 atomic_dec(&inode->i_writecount);
 259
 260                         /* insert tmp into the share list, just after mpnt */
 261                         spin_lock(&file->f_mapping->i_mmap_lock);
 262                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 263                         flush_dcache_mmap_lock(file->f_mapping);
 264                         vma_prio_tree_add(tmp, mpnt);
 265                         flush_dcache_mmap_unlock(file->f_mapping);
 266                         spin_unlock(&file->f_mapping->i_mmap_lock);
 267                 }
 268
 269                 /*
 270                  * Link in the new vma and copy the page table entries.
 271                  */
 272                 *pprev = tmp;
 273                 pprev = &tmp->vm_next;
 274
 275                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 276                 rb_link = &tmp->vm_rb.rb_right;
 277                 rb_parent = &tmp->vm_rb;
 278
 279                 mm->map_count++;
 280                 retval = copy_page_range(mm, oldmm, mpnt);
 281
 282                 if (tmp->vm_ops && tmp->vm_ops->open)
 283                         tmp->vm_ops->open(tmp);
 284
 285                 if (retval)
 286                         goto out;
 287         }
 288         retval = 0;
 289 out:
 290         up_write(&mm->mmap_sem);
 291         flush_tlb_mm(oldmm);
 292         up_write(&oldmm->mmap_sem);
 293         return retval;
 294 fail_nomem_policy:
 295         kmem_cache_free(vm_area_cachep, tmp);
 296 fail_nomem:
 297         retval = -ENOMEM;
 298         vm_unacct_memory(charge);
 299         goto out;
 300 }
 301
 302 static inline int mm_alloc_pgd(struct mm_struct * mm)
 303 {
 304         mm->pgd = pgd_alloc(mm);
 305         if (unlikely(!mm->pgd))
 306                 return -ENOMEM;
 307         return 0;
 308 }
 309
 310 static inline void mm_free_pgd(struct mm_struct * mm)
 311 {
 312         pgd_free(mm->pgd);
 313 }
 314 #else
 315 #define dup_mmap(mm, oldmm)     (0)
 316 #define mm_alloc_pgd(mm)        (0)
 317 #define mm_free_pgd(mm)
 318 #endif /* CONFIG_MMU */
 319
 320  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 321
 322 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
 323 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 324
 325 #include <linux/init_task.h>
 326
 327 static struct mm_struct * mm_init(struct mm_struct * mm)
 328 {
 329         atomic_set(&mm->mm_users, 1);
 330         atomic_set(&mm->mm_count, 1);
 331         init_rwsem(&mm->mmap_sem);
 332         INIT_LIST_HEAD(&mm->mmlist);
 333         mm->core_waiters = 0;
 334         mm->nr_ptes = 0;
 335         set_mm_counter(mm, file_rss, 0);
 336         set_mm_counter(mm, anon_rss, 0);
 337         spin_lock_init(&mm->page_table_lock);
 338         rwlock_init(&mm->ioctx_list_lock);
 339         mm->ioctx_list = NULL;
 340         mm->free_area_cache = TASK_UNMAPPED_BASE;
 341         mm->cached_hole_size = ~0UL;
 342
 343         if (likely(!mm_alloc_pgd(mm))) {
 344                 mm->def_flags = 0;
 345                 return mm;
 346         }
 347         free_mm(mm);
 348         return NULL;
 349 }
 350
 351 /*
 352  * Allocate and initialize an mm_struct.
 353  */
 354 struct mm_struct * mm_alloc(void)
 355 {
 356         struct mm_struct * mm;
 357
 358         mm = allocate_mm();
 359         if (mm) {
 360                 memset(mm, 0, sizeof(*mm));
 361                 mm = mm_init(mm);
 362         }
 363         return mm;
 364 }
 365
 366 /*
 367  * Called when the last reference to the mm
 368  * is dropped: either by a lazy thread or by
 369  * mmput. Free the page directory and the mm.
 370  */
 371 void fastcall __mmdrop(struct mm_struct *mm)
 372 {
 373         BUG_ON(mm == &init_mm);
 374         mm_free_pgd(mm);
 375         destroy_context(mm);
 376         free_mm(mm);
 377 }
 378
 379 /*
 380  * Decrement the use count and release all resources for an mm.
 381  */
 382 void mmput(struct mm_struct *mm)
 383 {
 384         might_sleep();
 385
 386         if (atomic_dec_and_test(&mm->mm_users)) {
 387                 exit_aio(mm);
 388                 exit_mmap(mm);
 389                 if (!list_empty(&mm->mmlist)) {
 390                         spin_lock(&mmlist_lock);
 391                         list_del(&mm->mmlist);
 392                         spin_unlock(&mmlist_lock);
 393                 }
 394                 put_swap_token(mm);
 395                 mmdrop(mm);
 396         }
 397 }
 398 EXPORT_SYMBOL_GPL(mmput);
 399
 400 /**
 401  * get_task_mm - acquire a reference to the task's mm
 402  *
 403  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 404  * this kernel workthread has transiently adopted a user mm with use_mm,
 405  * to do its AIO) is not set and if so returns a reference to it, after
 406  * bumping up the use count.  User must release the mm via mmput()
 407  * after use.  Typically used by /proc and ptrace.
 408  */
 409 struct mm_struct *get_task_mm(struct task_struct *task)
 410 {
 411         struct mm_struct *mm;
 412
 413         task_lock(task);
 414         mm = task->mm;
 415         if (mm) {
 416                 if (task->flags & PF_BORROWED_MM)
 417                         mm = NULL;
 418                 else
 419                         atomic_inc(&mm->mm_users);
 420         }
 421         task_unlock(task);
 422         return mm;
 423 }
 424 EXPORT_SYMBOL_GPL(get_task_mm);
 425
 426 /* Please note the differences between mmput and mm_release.
 427  * mmput is called whenever we stop holding onto a mm_struct,
 428  * error success whatever.
 429  *
 430  * mm_release is called after a mm_struct has been removed
 431  * from the current process.
 432  *
 433  * This difference is important for error handling, when we
 434  * only half set up a mm_struct for a new process and need to restore
 435  * the old one.  Because we mmput the new mm_struct before
 436  * restoring the old one. . .
 437  * Eric Biederman 10 January 1998
 438  */
 439 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 440 {
 441         struct completion *vfork_done = tsk->vfork_done;
 442
 443         /* Get rid of any cached register state */
 444         deactivate_mm(tsk, mm);
 445
 446         /* notify parent sleeping on vfork() */
 447         if (vfork_done) {
 448                 tsk->vfork_done = NULL;
 449                 complete(vfork_done);
 450         }
 451         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
 452                 u32 __user * tidptr = tsk->clear_child_tid;
 453                 tsk->clear_child_tid = NULL;
 454
 455                 /*
 456                  * We don't check the error code - if userspace has
 457                  * not set up a proper pointer then tough luck.
 458                  */
 459                 put_user(0, tidptr);
 460                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 461         }
 462 }
 463
 464 /*
 465  * Allocate a new mm structure and copy contents from the
 466  * mm structure of the passed in task structure.
 467  */
 468 static struct mm_struct *dup_mm(struct task_struct *tsk)
 469 {
 470         struct mm_struct *mm, *oldmm = current->mm;
 471         int err;
 472
 473         if (!oldmm)
 474                 return NULL;
 475
 476         mm = allocate_mm();
 477         if (!mm)
 478                 goto fail_nomem;
 479
 480         memcpy(mm, oldmm, sizeof(*mm));
 481
 482         if (!mm_init(mm))
 483                 goto fail_nomem;
 484
 485         if (init_new_context(tsk, mm))
 486                 goto fail_nocontext;
 487
 488         err = dup_mmap(mm, oldmm);
 489         if (err)
 490                 goto free_pt;
 491
 492         mm->hiwater_rss = get_mm_rss(mm);
 493         mm->hiwater_vm = mm->total_vm;
 494
 495         return mm;
 496
 497 free_pt:
 498         mmput(mm);
 499
 500 fail_nomem:
 501         return NULL;
 502
 503 fail_nocontext:
 504         /*
 505          * If init_new_context() failed, we cannot use mmput() to free the mm
 506          * because it calls destroy_context()
 507          */
 508         mm_free_pgd(mm);
 509         free_mm(mm);
 510         return NULL;
 511 }
 512
 513 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 514 {
 515         struct mm_struct * mm, *oldmm;
 516         int retval;
 517
 518         tsk->min_flt = tsk->maj_flt = 0;
 519         tsk->nvcsw = tsk->nivcsw = 0;
 520
 521         tsk->mm = NULL;
 522         tsk->active_mm = NULL;
 523
 524         /*
 525          * Are we cloning a kernel thread?
 526          *
 527          * We need to steal a active VM for that..
 528          */
 529         oldmm = current->mm;
 530         if (!oldmm)
 531                 return 0;
 532
 533         if (clone_flags & CLONE_VM) {
 534                 atomic_inc(&oldmm->mm_users);
 535                 mm = oldmm;
 536                 goto good_mm;
 537         }
 538
 539         retval = -ENOMEM;
 540         mm = dup_mm(tsk);
 541         if (!mm)
 542                 goto fail_nomem;
 543
 544 good_mm:
 545         tsk->mm = mm;
 546         tsk->active_mm = mm;
 547         return 0;
 548
 549 fail_nomem:
 550         return retval;
 551 }
 552
 553 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 554 {
 555         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 556         /* We don't need to lock fs - think why ;-) */
 557         if (fs) {
 558                 atomic_set(&fs->count, 1);
 559                 rwlock_init(&fs->lock);
 560                 fs->umask = old->umask;
 561                 read_lock(&old->lock);
 562                 fs->rootmnt = mntget(old->rootmnt);
 563                 fs->root = dget(old->root);
 564                 fs->pwdmnt = mntget(old->pwdmnt);
 565                 fs->pwd = dget(old->pwd);
 566                 if (old->altroot) {
 567                         fs->altrootmnt = mntget(old->altrootmnt);
 568                         fs->altroot = dget(old->altroot);
 569                 } else {
 570                         fs->altrootmnt = NULL;
 571                         fs->altroot = NULL;
 572                 }
 573                 read_unlock(&old->lock);
 574         }
 575         return fs;
 576 }
 577
 578 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 579 {
 580         return __copy_fs_struct(old);
 581 }
 582
 583 EXPORT_SYMBOL_GPL(copy_fs_struct);
 584
 585 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 586 {
 587         if (clone_flags & CLONE_FS) {
 588                 atomic_inc(&current->fs->count);
 589                 return 0;
 590         }
 591         tsk->fs = __copy_fs_struct(current->fs);
 592         if (!tsk->fs)
 593                 return -ENOMEM;
 594         return 0;
 595 }
 596
 597 static int count_open_files(struct fdtable *fdt)
 598 {
 599         int size = fdt->max_fdset;
 600         int i;
 601
 602         /* Find the last open fd */
 603         for (i = size/(8*sizeof(long)); i > 0; ) {
 604                 if (fdt->open_fds->fds_bits[--i])
 605                         break;
 606         }
 607         i = (i+1) * 8 * sizeof(long);
 608         return i;
 609 }
 610
 611 static struct files_struct *alloc_files(void)
 612 {
 613         struct files_struct *newf;
 614         struct fdtable *fdt;
 615
 616         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
 617         if (!newf)
 618                 goto out;
 619
 620         atomic_set(&newf->count, 1);
 621
 622         spin_lock_init(&newf->file_lock);
 623         newf->next_fd = 0;
 624         fdt = &newf->fdtab;
 625         fdt->max_fds = NR_OPEN_DEFAULT;
 626         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
 627         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 628         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 629         fdt->fd = &newf->fd_array[0];
 630         INIT_RCU_HEAD(&fdt->rcu);
 631         fdt->free_files = NULL;
 632         fdt->next = NULL;
 633         rcu_assign_pointer(newf->fdt, fdt);
 634 out:
 635         return newf;
 636 }
 637
 638 /*
 639  * Allocate a new files structure and copy contents from the
 640  * passed in files structure.
 641  * errorp will be valid only when the returned files_struct is NULL.
 642  */
 643 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 644 {
 645         struct files_struct *newf;
 646         struct file **old_fds, **new_fds;
 647         int open_files, size, i, expand;
 648         struct fdtable *old_fdt, *new_fdt;
 649
 650         *errorp = -ENOMEM;
 651         newf = alloc_files();
 652         if (!newf)
 653                 goto out;
 654
 655         spin_lock(&oldf->file_lock);
 656         old_fdt = files_fdtable(oldf);
 657         new_fdt = files_fdtable(newf);
 658         size = old_fdt->max_fdset;
 659         open_files = count_open_files(old_fdt);
 660         expand = 0;
 661
 662         /*
 663          * Check whether we need to allocate a larger fd array or fd set.
 664          * Note: we're not a clone task, so the open count won't  change.
 665          */
 666         if (open_files > new_fdt->max_fdset) {
 667                 new_fdt->max_fdset = 0;
 668                 expand = 1;
 669         }
 670         if (open_files > new_fdt->max_fds) {
 671                 new_fdt->max_fds = 0;
 672                 expand = 1;
 673         }
 674
 675         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
 676         if (expand) {
 677                 spin_unlock(&oldf->file_lock);
 678                 spin_lock(&newf->file_lock);
 679                 *errorp = expand_files(newf, open_files-1);
 680                 spin_unlock(&newf->file_lock);
 681                 if (*errorp < 0)
 682                         goto out_release;
 683                 new_fdt = files_fdtable(newf);
 684                 /*
 685                  * Reacquire the oldf lock and a pointer to its fd table
 686                  * who knows it may have a new bigger fd table. We need
 687                  * the latest pointer.
 688                  */
 689                 spin_lock(&oldf->file_lock);
 690                 open_files = count_open_files(old_fdt);
 691                 old_fdt = files_fdtable(oldf);
 692         }
 693
 694         old_fds = old_fdt->fd;
 695         new_fds = new_fdt->fd;
 696
 697         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
 698         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
 699
 700         for (i = open_files; i != 0; i--) {
 701                 struct file *f = *old_fds++;
 702                 if (f) {
 703                         get_file(f);
 704                 } else {
 705                         /*
 706                          * The fd may be claimed in the fd bitmap but not yet
 707                          * instantiated in the files array if a sibling thread
 708                          * is partway through open().  So make sure that this
 709                          * fd is available to the new process.
 710                          */
 711                         FD_CLR(open_files - i, new_fdt->open_fds);
 712                 }
 713                 rcu_assign_pointer(*new_fds++, f);
 714         }
 715         spin_unlock(&oldf->file_lock);
 716
 717         /* compute the remainder to be cleared */
 718         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 719
 720         /* This is long word aligned thus could use a optimized version */
 721         memset(new_fds, 0, size);
 722
 723         if (new_fdt->max_fdset > open_files) {
 724                 int left = (new_fdt->max_fdset-open_files)/8;
 725                 int start = open_files / (8 * sizeof(unsigned long));
 726
 727                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 728                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 729         }
 730
 731 out:
 732         return newf;
 733
 734 out_release:
 735         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
 736         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
 737         free_fd_array(new_fdt->fd, new_fdt->max_fds);
 738         kmem_cache_free(files_cachep, newf);
 739         return NULL;
 740 }
 741
 742 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 743 {
 744         struct files_struct *oldf, *newf;
 745         int error = 0;
 746
 747         /*
 748          * A background process may not have any files ...
 749          */
 750         oldf = current->files;
 751         if (!oldf)
 752                 goto out;
 753
 754         if (clone_flags & CLONE_FILES) {
 755                 atomic_inc(&oldf->count);
 756                 goto out;
 757         }
 758
 759         /*
 760          * Note: we may be using current for both targets (See exec.c)
 761          * This works because we cache current->files (old) as oldf. Don't
 762          * break this.
 763          */
 764         tsk->files = NULL;
 765         newf = dup_fd(oldf, &error);
 766         if (!newf)
 767                 goto out;
 768
 769         tsk->files = newf;
 770         error = 0;
 771 out:
 772         return error;
 773 }
 774
 775 /*
 776  *      Helper to unshare the files of the current task.
 777  *      We don't want to expose copy_files internals to
 778  *      the exec layer of the kernel.
 779  */
 780
 781 int unshare_files(void)
 782 {
 783         struct files_struct *files  = current->files;
 784         int rc;
 785
 786         BUG_ON(!files);
 787
 788         /* This can race but the race causes us to copy when we don't
 789            need to and drop the copy */
 790         if(atomic_read(&files->count) == 1)
 791         {
 792                 atomic_inc(&files->count);
 793                 return 0;
 794         }
 795         rc = copy_files(0, current);
 796         if(rc)
 797                 current->files = files;
 798         return rc;
 799 }
 800
 801 EXPORT_SYMBOL(unshare_files);
 802
 803 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 804 {
 805         struct sighand_struct *sig;
 806
 807         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 808                 atomic_inc(&current->sighand->count);
 809                 return 0;
 810         }
 811         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 812         rcu_assign_pointer(tsk->sighand, sig);
 813         if (!sig)
 814                 return -ENOMEM;
 815         atomic_set(&sig->count, 1);
 816         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 817         return 0;
 818 }
 819
 820 void __cleanup_sighand(struct sighand_struct *sighand)
 821 {
 822         if (atomic_dec_and_test(&sighand->count))
 823                 kmem_cache_free(sighand_cachep, sighand);
 824 }
 825
 826 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
 827 {
 828         struct signal_struct *sig;
 829         int ret;
 830
 831         if (clone_flags & CLONE_THREAD) {
 832                 atomic_inc(&current->signal->count);
 833                 atomic_inc(&current->signal->live);
 834                 taskstats_tgid_alloc(current);
 835                 return 0;
 836         }
 837         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 838         tsk->signal = sig;
 839         if (!sig)
 840                 return -ENOMEM;
 841
 842         ret = copy_thread_group_keys(tsk);
 843         if (ret < 0) {
 844                 kmem_cache_free(signal_cachep, sig);
 845                 return ret;
 846         }
 847
 848         atomic_set(&sig->count, 1);
 849         atomic_set(&sig->live, 1);
 850         init_waitqueue_head(&sig->wait_chldexit);
 851         sig->flags = 0;
 852         sig->group_exit_code = 0;
 853         sig->group_exit_task = NULL;
 854         sig->group_stop_count = 0;
 855         sig->curr_target = NULL;
 856         init_sigpending(&sig->shared_pending);
 857         INIT_LIST_HEAD(&sig->posix_timers);
 858
 859         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
 860         sig->it_real_incr.tv64 = 0;
 861         sig->real_timer.function = it_real_fn;
 862         sig->tsk = tsk;
 863
 864         sig->it_virt_expires = cputime_zero;
 865         sig->it_virt_incr = cputime_zero;
 866         sig->it_prof_expires = cputime_zero;
 867         sig->it_prof_incr = cputime_zero;
 868
 869         sig->leader = 0;        /* session leadership doesn't inherit */
 870         sig->tty_old_pgrp = 0;
 871
 872         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 873         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 874         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 875         sig->sched_time = 0;
 876         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 877         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 878         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 879         taskstats_tgid_init(sig);
 880
 881         task_lock(current->group_leader);
 882         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 883         task_unlock(current->group_leader);
 884
 885         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 886                 /*
 887                  * New sole thread in the process gets an expiry time
 888                  * of the whole CPU time limit.
 889                  */
 890                 tsk->it_prof_expires =
 891                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 892         }
 893         acct_init_pacct(&sig->pacct);
 894
 895         return 0;
 896 }
 897
 898 void __cleanup_signal(struct signal_struct *sig)
 899 {
 900         exit_thread_group_keys(sig);
 901         kmem_cache_free(signal_cachep, sig);
 902 }
 903
 904 static inline void cleanup_signal(struct task_struct *tsk)
 905 {
 906         struct signal_struct *sig = tsk->signal;
 907
 908         atomic_dec(&sig->live);
 909
 910         if (atomic_dec_and_test(&sig->count))
 911                 __cleanup_signal(sig);
 912 }
 913
 914 static inline 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_NOFREEZE);
 919         new_flags |= PF_FORKNOEXEC;
 920         if (!(clone_flags & CLONE_PTRACE))
 921                 p->ptrace = 0;
 922         p->flags = new_flags;
 923 }
 924
 925 asmlinkage long sys_set_tid_address(int __user *tidptr)
 926 {
 927         current->clear_child_tid = tidptr;
 928
 929         return current->pid;
 930 }
 931
 932 static inline void rt_mutex_init_task(struct task_struct *p)
 933 {
 934 #ifdef CONFIG_RT_MUTEXES
 935         spin_lock_init(&p->pi_lock);
 936         plist_head_init(&p->pi_waiters, &p->pi_lock);
 937         p->pi_blocked_on = NULL;
 938 #endif
 939 }
 940
 941 /*
 942  * This creates a new process as a copy of the old one,
 943  * but does not actually start it yet.
 944  *
 945  * It copies the registers, and all the appropriate
 946  * parts of the process environment (as per the clone
 947  * flags). The actual kick-off is left to the caller.
 948  */
 949 static struct task_struct *copy_process(unsigned long clone_flags,
 950                                         unsigned long stack_start,
 951                                         struct pt_regs *regs,
 952                                         unsigned long stack_size,
 953                                         int __user *parent_tidptr,
 954                                         int __user *child_tidptr,
 955                                         int pid)
 956 {
 957         int retval;
 958         struct task_struct *p = NULL;
 959
 960         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 961                 return ERR_PTR(-EINVAL);
 962
 963         /*
 964          * Thread groups must share signals as well, and detached threads
 965          * can only be started up within the thread group.
 966          */
 967         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 968                 return ERR_PTR(-EINVAL);
 969
 970         /*
 971          * Shared signal handlers imply shared VM. By way of the above,
 972          * thread groups also imply shared VM. Blocking this case allows
 973          * for various simplifications in other code.
 974          */
 975         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 976                 return ERR_PTR(-EINVAL);
 977
 978         retval = security_task_create(clone_flags);
 979         if (retval)
 980                 goto fork_out;
 981
 982         retval = -ENOMEM;
 983         p = dup_task_struct(current);
 984         if (!p)
 985                 goto fork_out;
 986
 987         rt_mutex_init_task(p);
 988
 989 #ifdef CONFIG_TRACE_IRQFLAGS
 990         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 991         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 992 #endif
 993         retval = -EAGAIN;
 994         if (atomic_read(&p->user->processes) >=
 995                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 996                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 997                                 p->user != &root_user)
 998                         goto bad_fork_free;
 999         }
1000
1001         atomic_inc(&p->user->__count);
1002         atomic_inc(&p->user->processes);
1003         get_group_info(p->group_info);
1004
1005         /*
1006          * If multiple threads are within copy_process(), then this check
1007          * triggers too late. This doesn't hurt, the check is only there
1008          * to stop root fork bombs.
1009          */
1010         if (nr_threads >= max_threads)
1011                 goto bad_fork_cleanup_count;
1012
1013         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1014                 goto bad_fork_cleanup_count;
1015
1016         if (p->binfmt && !try_module_get(p->binfmt->module))
1017                 goto bad_fork_cleanup_put_domain;
1018
1019         p->did_exec = 0;
1020         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1021         copy_flags(clone_flags, p);
1022         p->pid = pid;
1023         retval = -EFAULT;
1024         if (clone_flags & CLONE_PARENT_SETTID)
1025                 if (put_user(p->pid, parent_tidptr))
1026                         goto bad_fork_cleanup_delays_binfmt;
1027
1028         INIT_LIST_HEAD(&p->children);
1029         INIT_LIST_HEAD(&p->sibling);
1030         p->vfork_done = NULL;
1031         spin_lock_init(&p->alloc_lock);
1032
1033         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1034         init_sigpending(&p->pending);
1035
1036         p->utime = cputime_zero;
1037         p->stime = cputime_zero;
1038         p->sched_time = 0;
1039         p->rchar = 0;           /* I/O counter: bytes read */
1040         p->wchar = 0;           /* I/O counter: bytes written */
1041         p->syscr = 0;           /* I/O counter: read syscalls */
1042         p->syscw = 0;           /* I/O counter: write syscalls */
1043         acct_clear_integrals(p);
1044
1045         p->it_virt_expires = cputime_zero;
1046         p->it_prof_expires = cputime_zero;
1047         p->it_sched_expires = 0;
1048         INIT_LIST_HEAD(&p->cpu_timers[0]);
1049         INIT_LIST_HEAD(&p->cpu_timers[1]);
1050         INIT_LIST_HEAD(&p->cpu_timers[2]);
1051
1052         p->lock_depth = -1;             /* -1 = no lock */
1053         do_posix_clock_monotonic_gettime(&p->start_time);
1054         p->security = NULL;
1055         p->io_context = NULL;
1056         p->io_wait = NULL;
1057         p->audit_context = NULL;
1058         cpuset_fork(p);
1059 #ifdef CONFIG_NUMA
1060         p->mempolicy = mpol_copy(p->mempolicy);
1061         if (IS_ERR(p->mempolicy)) {
1062                 retval = PTR_ERR(p->mempolicy);
1063                 p->mempolicy = NULL;
1064                 goto bad_fork_cleanup_cpuset;
1065         }
1066         mpol_fix_fork_child_flag(p);
1067 #endif
1068 #ifdef CONFIG_TRACE_IRQFLAGS
1069         p->irq_events = 0;
1070 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1071         p->hardirqs_enabled = 1;
1072 #else
1073         p->hardirqs_enabled = 0;
1074 #endif
1075         p->hardirq_enable_ip = 0;
1076         p->hardirq_enable_event = 0;
1077         p->hardirq_disable_ip = _THIS_IP_;
1078         p->hardirq_disable_event = 0;
1079         p->softirqs_enabled = 1;
1080         p->softirq_enable_ip = _THIS_IP_;
1081         p->softirq_enable_event = 0;
1082         p->softirq_disable_ip = 0;
1083         p->softirq_disable_event = 0;
1084         p->hardirq_context = 0;
1085         p->softirq_context = 0;
1086 #endif
1087 #ifdef CONFIG_LOCKDEP
1088         p->lockdep_depth = 0; /* no locks held yet */
1089         p->curr_chain_key = 0;
1090         p->lockdep_recursion = 0;
1091 #endif
1092
1093 #ifdef CONFIG_DEBUG_MUTEXES
1094         p->blocked_on = NULL; /* not blocked yet */
1095 #endif
1096
1097         p->tgid = p->pid;
1098         if (clone_flags & CLONE_THREAD)
1099                 p->tgid = current->tgid;
1100
1101         if ((retval = security_task_alloc(p)))
1102                 goto bad_fork_cleanup_policy;
1103         if ((retval = audit_alloc(p)))
1104                 goto bad_fork_cleanup_security;
1105         /* copy all the process information */
1106         if ((retval = copy_semundo(clone_flags, p)))
1107                 goto bad_fork_cleanup_audit;
1108         if ((retval = copy_files(clone_flags, p)))
1109                 goto bad_fork_cleanup_semundo;
1110         if ((retval = copy_fs(clone_flags, p)))
1111                 goto bad_fork_cleanup_files;
1112         if ((retval = copy_sighand(clone_flags, p)))
1113                 goto bad_fork_cleanup_fs;
1114         if ((retval = copy_signal(clone_flags, p)))
1115                 goto bad_fork_cleanup_sighand;
1116         if ((retval = copy_mm(clone_flags, p)))
1117                 goto bad_fork_cleanup_signal;
1118         if ((retval = copy_keys(clone_flags, p)))
1119                 goto bad_fork_cleanup_mm;
1120         if ((retval = copy_namespaces(clone_flags, p)))
1121                 goto bad_fork_cleanup_keys;
1122         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1123         if (retval)
1124                 goto bad_fork_cleanup_namespaces;
1125
1126         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1127         /*
1128          * Clear TID on mm_release()?
1129          */
1130         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1131         p->robust_list = NULL;
1132 #ifdef CONFIG_COMPAT
1133         p->compat_robust_list = NULL;
1134 #endif
1135         INIT_LIST_HEAD(&p->pi_state_list);
1136         p->pi_state_cache = NULL;
1137
1138         /*
1139          * sigaltstack should be cleared when sharing the same VM
1140          */
1141         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1142                 p->sas_ss_sp = p->sas_ss_size = 0;
1143
1144         /*
1145          * Syscall tracing should be turned off in the child regardless
1146          * of CLONE_PTRACE.
1147          */
1148         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1149 #ifdef TIF_SYSCALL_EMU
1150         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1151 #endif
1152
1153         /* Our parent execution domain becomes current domain
1154            These must match for thread signalling to apply */
1155         p->parent_exec_id = p->self_exec_id;
1156
1157         /* ok, now we should be set up.. */
1158         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1159         p->pdeath_signal = 0;
1160         p->exit_state = 0;
1161
1162         /*
1163          * Ok, make it visible to the rest of the system.
1164          * We dont wake it up yet.
1165          */
1166         p->group_leader = p;
1167         INIT_LIST_HEAD(&p->thread_group);
1168         INIT_LIST_HEAD(&p->ptrace_children);
1169         INIT_LIST_HEAD(&p->ptrace_list);
1170
1171         /* Perform scheduler related setup. Assign this task to a CPU. */
1172         sched_fork(p, clone_flags);
1173
1174         /* Need tasklist lock for parent etc handling! */
1175         write_lock_irq(&tasklist_lock);
1176
1177         /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
1178         p->ioprio = current->ioprio;
1179
1180         /*
1181          * The task hasn't been attached yet, so its cpus_allowed mask will
1182          * not be changed, nor will its assigned CPU.
1183          *
1184          * The cpus_allowed mask of the parent may have changed after it was
1185          * copied first time - so re-copy it here, then check the child's CPU
1186          * to ensure it is on a valid CPU (and if not, just force it back to
1187          * parent's CPU). This avoids alot of nasty races.
1188          */
1189         p->cpus_allowed = current->cpus_allowed;
1190         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1191                         !cpu_online(task_cpu(p))))
1192                 set_task_cpu(p, smp_processor_id());
1193
1194         /* CLONE_PARENT re-uses the old parent */
1195         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1196                 p->real_parent = current->real_parent;
1197         else
1198                 p->real_parent = current;
1199         p->parent = p->real_parent;
1200
1201         spin_lock(&current->sighand->siglock);
1202
1203         /*
1204          * Process group and session signals need to be delivered to just the
1205          * parent before the fork or both the parent and the child after the
1206          * fork. Restart if a signal comes in before we add the new process to
1207          * it's process group.
1208          * A fatal signal pending means that current will exit, so the new
1209          * thread can't slip out of an OOM kill (or normal SIGKILL).
1210          */
1211         recalc_sigpending();
1212         if (signal_pending(current)) {
1213                 spin_unlock(&current->sighand->siglock);
1214                 write_unlock_irq(&tasklist_lock);
1215                 retval = -ERESTARTNOINTR;
1216                 goto bad_fork_cleanup_namespaces;
1217         }
1218
1219         if (clone_flags & CLONE_THREAD) {
1220                 p->group_leader = current->group_leader;
1221                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1222
1223                 if (!cputime_eq(current->signal->it_virt_expires,
1224                                 cputime_zero) ||
1225                     !cputime_eq(current->signal->it_prof_expires,
1226                                 cputime_zero) ||
1227                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1228                     !list_empty(&current->signal->cpu_timers[0]) ||
1229                     !list_empty(&current->signal->cpu_timers[1]) ||
1230                     !list_empty(&current->signal->cpu_timers[2])) {
1231                         /*
1232                          * Have child wake up on its first tick to check
1233                          * for process CPU timers.
1234                          */
1235                         p->it_prof_expires = jiffies_to_cputime(1);
1236                 }
1237         }
1238
1239         if (likely(p->pid)) {
1240                 add_parent(p);
1241                 if (unlikely(p->ptrace & PT_PTRACED))
1242                         __ptrace_link(p, current->parent);
1243
1244                 if (thread_group_leader(p)) {
1245                         p->signal->tty = current->signal->tty;
1246                         p->signal->pgrp = process_group(current);
1247                         p->signal->session = current->signal->session;
1248                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1249                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1250
1251                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1252                         __get_cpu_var(process_counts)++;
1253                 }
1254                 attach_pid(p, PIDTYPE_PID, p->pid);
1255                 nr_threads++;
1256         }
1257
1258         total_forks++;
1259         spin_unlock(&current->sighand->siglock);
1260         write_unlock_irq(&tasklist_lock);
1261         proc_fork_connector(p);
1262         return p;
1263
1264 bad_fork_cleanup_namespaces:
1265         exit_task_namespaces(p);
1266 bad_fork_cleanup_keys:
1267         exit_keys(p);
1268 bad_fork_cleanup_mm:
1269         if (p->mm)
1270                 mmput(p->mm);
1271 bad_fork_cleanup_signal:
1272         cleanup_signal(p);
1273 bad_fork_cleanup_sighand:
1274         __cleanup_sighand(p->sighand);
1275 bad_fork_cleanup_fs:
1276         exit_fs(p); /* blocking */
1277 bad_fork_cleanup_files:
1278         exit_files(p); /* blocking */
1279 bad_fork_cleanup_semundo:
1280         exit_sem(p);
1281 bad_fork_cleanup_audit:
1282         audit_free(p);
1283 bad_fork_cleanup_security:
1284         security_task_free(p);
1285 bad_fork_cleanup_policy:
1286 #ifdef CONFIG_NUMA
1287         mpol_free(p->mempolicy);
1288 bad_fork_cleanup_cpuset:
1289 #endif
1290         cpuset_exit(p);
1291 bad_fork_cleanup_delays_binfmt:
1292         delayacct_tsk_free(p);
1293         if (p->binfmt)
1294                 module_put(p->binfmt->module);
1295 bad_fork_cleanup_put_domain:
1296         module_put(task_thread_info(p)->exec_domain->module);
1297 bad_fork_cleanup_count:
1298         put_group_info(p->group_info);
1299         atomic_dec(&p->user->processes);
1300         free_uid(p->user);
1301 bad_fork_free:
1302         free_task(p);
1303 fork_out:
1304         return ERR_PTR(retval);
1305 }
1306
1307 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1308 {
1309         memset(regs, 0, sizeof(struct pt_regs));
1310         return regs;
1311 }
1312
1313 struct task_struct * __devinit fork_idle(int cpu)
1314 {
1315         struct task_struct *task;
1316         struct pt_regs regs;
1317
1318         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1319         if (!task)
1320                 return ERR_PTR(-ENOMEM);
1321         init_idle(task, cpu);
1322
1323         return task;
1324 }
1325
1326 static inline int fork_traceflag (unsigned clone_flags)
1327 {
1328         if (clone_flags & CLONE_UNTRACED)
1329                 return 0;
1330         else if (clone_flags & CLONE_VFORK) {
1331                 if (current->ptrace & PT_TRACE_VFORK)
1332                         return PTRACE_EVENT_VFORK;
1333         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1334                 if (current->ptrace & PT_TRACE_CLONE)
1335                         return PTRACE_EVENT_CLONE;
1336         } else if (current->ptrace & PT_TRACE_FORK)
1337                 return PTRACE_EVENT_FORK;
1338
1339         return 0;
1340 }
1341
1342 /*
1343  *  Ok, this is the main fork-routine.
1344  *
1345  * It copies the process, and if successful kick-starts
1346  * it and waits for it to finish using the VM if required.
1347  */
1348 long do_fork(unsigned long clone_flags,
1349               unsigned long stack_start,
1350               struct pt_regs *regs,
1351               unsigned long stack_size,
1352               int __user *parent_tidptr,
1353               int __user *child_tidptr)
1354 {
1355         struct task_struct *p;
1356         int trace = 0;
1357         struct pid *pid = alloc_pid();
1358         long nr;
1359
1360         if (!pid)
1361                 return -EAGAIN;
1362         nr = pid->nr;
1363         if (unlikely(current->ptrace)) {
1364                 trace = fork_traceflag (clone_flags);
1365                 if (trace)
1366                         clone_flags |= CLONE_PTRACE;
1367         }
1368
1369         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1370         /*
1371          * Do this prior waking up the new thread - the thread pointer
1372          * might get invalid after that point, if the thread exits quickly.
1373          */
1374         if (!IS_ERR(p)) {
1375                 struct completion vfork;
1376
1377                 if (clone_flags & CLONE_VFORK) {
1378                         p->vfork_done = &vfork;
1379                         init_completion(&vfork);
1380                 }
1381
1382                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1383                         /*
1384                          * We'll start up with an immediate SIGSTOP.
1385                          */
1386                         sigaddset(&p->pending.signal, SIGSTOP);
1387                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1388                 }
1389
1390                 if (!(clone_flags & CLONE_STOPPED))
1391                         wake_up_new_task(p, clone_flags);
1392                 else
1393                         p->state = TASK_STOPPED;
1394
1395                 if (unlikely (trace)) {
1396                         current->ptrace_message = nr;
1397                         ptrace_notify ((trace << 8) | SIGTRAP);
1398                 }
1399
1400                 if (clone_flags & CLONE_VFORK) {
1401                         wait_for_completion(&vfork);
1402                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1403                                 current->ptrace_message = nr;
1404                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1405                         }
1406                 }
1407         } else {
1408                 free_pid(pid);
1409                 nr = PTR_ERR(p);
1410         }
1411         return nr;
1412 }
1413
1414 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1415 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1416 #endif
1417
1418 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1419 {
1420         struct sighand_struct *sighand = data;
1421
1422         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1423                                         SLAB_CTOR_CONSTRUCTOR)
1424                 spin_lock_init(&sighand->siglock);
1425 }
1426
1427 void __init proc_caches_init(void)
1428 {
1429         sighand_cachep = kmem_cache_create("sighand_cache",
1430                         sizeof(struct sighand_struct), 0,
1431                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1432                         sighand_ctor, NULL);
1433         signal_cachep = kmem_cache_create("signal_cache",
1434                         sizeof(struct signal_struct), 0,
1435                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1436         files_cachep = kmem_cache_create("files_cache",
1437                         sizeof(struct files_struct), 0,
1438                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1439         fs_cachep = kmem_cache_create("fs_cache",
1440                         sizeof(struct fs_struct), 0,
1441                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1442         vm_area_cachep = kmem_cache_create("vm_area_struct",
1443                         sizeof(struct vm_area_struct), 0,
1444                         SLAB_PANIC, NULL, NULL);
1445         mm_cachep = kmem_cache_create("mm_struct",
1446                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1447                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1448 }
1449
1450
1451 /*
1452  * Check constraints on flags passed to the unshare system call and
1453  * force unsharing of additional process context as appropriate.
1454  */
1455 static inline void check_unshare_flags(unsigned long *flags_ptr)
1456 {
1457         /*
1458          * If unsharing a thread from a thread group, must also
1459          * unshare vm.
1460          */
1461         if (*flags_ptr & CLONE_THREAD)
1462                 *flags_ptr |= CLONE_VM;
1463
1464         /*
1465          * If unsharing vm, must also unshare signal handlers.
1466          */
1467         if (*flags_ptr & CLONE_VM)
1468                 *flags_ptr |= CLONE_SIGHAND;
1469
1470         /*
1471          * If unsharing signal handlers and the task was created
1472          * using CLONE_THREAD, then must unshare the thread
1473          */
1474         if ((*flags_ptr & CLONE_SIGHAND) &&
1475             (atomic_read(&current->signal->count) > 1))
1476                 *flags_ptr |= CLONE_THREAD;
1477
1478         /*
1479          * If unsharing namespace, must also unshare filesystem information.
1480          */
1481         if (*flags_ptr & CLONE_NEWNS)
1482                 *flags_ptr |= CLONE_FS;
1483 }
1484
1485 /*
1486  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1487  */
1488 static int unshare_thread(unsigned long unshare_flags)
1489 {
1490         if (unshare_flags & CLONE_THREAD)
1491                 return -EINVAL;
1492
1493         return 0;
1494 }
1495
1496 /*
1497  * Unshare the filesystem structure if it is being shared
1498  */
1499 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1500 {
1501         struct fs_struct *fs = current->fs;
1502
1503         if ((unshare_flags & CLONE_FS) &&
1504             (fs && atomic_read(&fs->count) > 1)) {
1505                 *new_fsp = __copy_fs_struct(current->fs);
1506                 if (!*new_fsp)
1507                         return -ENOMEM;
1508         }
1509
1510         return 0;
1511 }
1512
1513 /*
1514  * Unshare the namespace structure if it is being shared
1515  */
1516 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1517 {
1518         struct namespace *ns = current->nsproxy->namespace;
1519
1520         if ((unshare_flags & CLONE_NEWNS) && ns) {
1521                 if (!capable(CAP_SYS_ADMIN))
1522                         return -EPERM;
1523
1524                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1525                 if (!*new_nsp)
1526                         return -ENOMEM;
1527         }
1528
1529         return 0;
1530 }
1531
1532 /*
1533  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1534  * supported yet
1535  */
1536 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1537 {
1538         struct sighand_struct *sigh = current->sighand;
1539
1540         if ((unshare_flags & CLONE_SIGHAND) &&
1541             (sigh && atomic_read(&sigh->count) > 1))
1542                 return -EINVAL;
1543         else
1544                 return 0;
1545 }
1546
1547 /*
1548  * Unshare vm if it is being shared
1549  */
1550 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1551 {
1552         struct mm_struct *mm = current->mm;
1553
1554         if ((unshare_flags & CLONE_VM) &&
1555             (mm && atomic_read(&mm->mm_users) > 1)) {
1556                 return -EINVAL;
1557         }
1558
1559         return 0;
1560 }
1561
1562 /*
1563  * Unshare file descriptor table if it is being shared
1564  */
1565 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1566 {
1567         struct files_struct *fd = current->files;
1568         int error = 0;
1569
1570         if ((unshare_flags & CLONE_FILES) &&
1571             (fd && atomic_read(&fd->count) > 1)) {
1572                 *new_fdp = dup_fd(fd, &error);
1573                 if (!*new_fdp)
1574                         return error;
1575         }
1576
1577         return 0;
1578 }
1579
1580 /*
1581  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1582  * supported yet
1583  */
1584 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1585 {
1586         if (unshare_flags & CLONE_SYSVSEM)
1587                 return -EINVAL;
1588
1589         return 0;
1590 }
1591
1592 #ifndef CONFIG_IPC_NS
1593 static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns)
1594 {
1595         if (flags & CLONE_NEWIPC)
1596                 return -EINVAL;
1597
1598         return 0;
1599 }
1600 #endif
1601
1602 /*
1603  * unshare allows a process to 'unshare' part of the process
1604  * context which was originally shared using clone.  copy_*
1605  * functions used by do_fork() cannot be used here directly
1606  * because they modify an inactive task_struct that is being
1607  * constructed. Here we are modifying the current, active,
1608  * task_struct.
1609  */
1610 asmlinkage long sys_unshare(unsigned long unshare_flags)
1611 {
1612         int err = 0;
1613         struct fs_struct *fs, *new_fs = NULL;
1614         struct namespace *ns, *new_ns = NULL;
1615         struct sighand_struct *sigh, *new_sigh = NULL;
1616         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1617         struct files_struct *fd, *new_fd = NULL;
1618         struct sem_undo_list *new_ulist = NULL;
1619         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1620         struct uts_namespace *uts, *new_uts = NULL;
1621         struct ipc_namespace *ipc, *new_ipc = NULL;
1622
1623         check_unshare_flags(&unshare_flags);
1624
1625         /* Return -EINVAL for all unsupported flags */
1626         err = -EINVAL;
1627         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1628                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1629                                 CLONE_NEWUTS|CLONE_NEWIPC))
1630                 goto bad_unshare_out;
1631
1632         if ((err = unshare_thread(unshare_flags)))
1633                 goto bad_unshare_out;
1634         if ((err = unshare_fs(unshare_flags, &new_fs)))
1635                 goto bad_unshare_cleanup_thread;
1636         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1637                 goto bad_unshare_cleanup_fs;
1638         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1639                 goto bad_unshare_cleanup_ns;
1640         if ((err = unshare_vm(unshare_flags, &new_mm)))
1641                 goto bad_unshare_cleanup_sigh;
1642         if ((err = unshare_fd(unshare_flags, &new_fd)))
1643                 goto bad_unshare_cleanup_vm;
1644         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1645                 goto bad_unshare_cleanup_fd;
1646         if ((err = unshare_utsname(unshare_flags, &new_uts)))
1647                 goto bad_unshare_cleanup_semundo;
1648         if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
1649                 goto bad_unshare_cleanup_uts;
1650
1651         if (new_ns || new_uts || new_ipc) {
1652                 old_nsproxy = current->nsproxy;
1653                 new_nsproxy = dup_namespaces(old_nsproxy);
1654                 if (!new_nsproxy) {
1655                         err = -ENOMEM;
1656                         goto bad_unshare_cleanup_ipc;
1657                 }
1658         }
1659
1660         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist ||
1661                                 new_uts || new_ipc) {
1662
1663                 task_lock(current);
1664
1665                 if (new_nsproxy) {
1666                         current->nsproxy = new_nsproxy;
1667                         new_nsproxy = old_nsproxy;
1668                 }
1669
1670                 if (new_fs) {
1671                         fs = current->fs;
1672                         current->fs = new_fs;
1673                         new_fs = fs;
1674                 }
1675
1676                 if (new_ns) {
1677                         ns = current->nsproxy->namespace;
1678                         current->nsproxy->namespace = new_ns;
1679                         new_ns = ns;
1680                 }
1681
1682                 if (new_sigh) {
1683                         sigh = current->sighand;
1684                         rcu_assign_pointer(current->sighand, new_sigh);
1685                         new_sigh = sigh;
1686                 }
1687
1688                 if (new_mm) {
1689                         mm = current->mm;
1690                         active_mm = current->active_mm;
1691                         current->mm = new_mm;
1692                         current->active_mm = new_mm;
1693                         activate_mm(active_mm, new_mm);
1694                         new_mm = mm;
1695                 }
1696
1697                 if (new_fd) {
1698                         fd = current->files;
1699                         current->files = new_fd;
1700                         new_fd = fd;
1701                 }
1702
1703                 if (new_uts) {
1704                         uts = current->nsproxy->uts_ns;
1705                         current->nsproxy->uts_ns = new_uts;
1706                         new_uts = uts;
1707                 }
1708
1709                 if (new_ipc) {
1710                         ipc = current->nsproxy->ipc_ns;
1711                         current->nsproxy->ipc_ns = new_ipc;
1712                         new_ipc = ipc;
1713                 }
1714
1715                 task_unlock(current);
1716         }
1717
1718         if (new_nsproxy)
1719                 put_nsproxy(new_nsproxy);
1720
1721 bad_unshare_cleanup_ipc:
1722         if (new_ipc)
1723                 put_ipc_ns(new_ipc);
1724
1725 bad_unshare_cleanup_uts:
1726         if (new_uts)
1727                 put_uts_ns(new_uts);
1728
1729 bad_unshare_cleanup_semundo:
1730 bad_unshare_cleanup_fd:
1731         if (new_fd)
1732                 put_files_struct(new_fd);
1733
1734 bad_unshare_cleanup_vm:
1735         if (new_mm)
1736                 mmput(new_mm);
1737
1738 bad_unshare_cleanup_sigh:
1739         if (new_sigh)
1740                 if (atomic_dec_and_test(&new_sigh->count))
1741                         kmem_cache_free(sighand_cachep, new_sigh);
1742
1743 bad_unshare_cleanup_ns:
1744         if (new_ns)
1745                 put_namespace(new_ns);
1746
1747 bad_unshare_cleanup_fs:
1748         if (new_fs)
1749                 put_fs_struct(new_fs);
1750
1751 bad_unshare_cleanup_thread:
1752 bad_unshare_out:
1753         return err;
1754 }