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 struct kmem_cache *task_struct_cachep;
  86 #endif
  87
  88 /* SLAB cache for signal_struct structures (tsk->signal) */
  89 static struct kmem_cache *signal_cachep;
  90
  91 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  92 struct kmem_cache *sighand_cachep;
  93
  94 /* SLAB cache for files_struct structures (tsk->files) */
  95 struct kmem_cache *files_cachep;
  96
  97 /* SLAB cache for fs_struct structures (tsk->fs) */
  98 struct kmem_cache *fs_cachep;
  99
 100 /* SLAB cache for vm_area_struct structures */
 101 struct kmem_cache *vm_area_cachep;
 102
 103 /* SLAB cache for mm_struct structures (tsk->mm) */
 104 static struct kmem_cache *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, GFP_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, GFP_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
 452         /*
 453          * If we're exiting normally, clear a user-space tid field if
 454          * requested.  We leave this alone when dying by signal, to leave
 455          * the value intact in a core dump, and to save the unnecessary
 456          * trouble otherwise.  Userland only wants this done for a sys_exit.
 457          */
 458         if (tsk->clear_child_tid
 459             && !(tsk->flags & PF_SIGNALED)
 460             && atomic_read(&mm->mm_users) > 1) {
 461                 u32 __user * tidptr = tsk->clear_child_tid;
 462                 tsk->clear_child_tid = NULL;
 463
 464                 /*
 465                  * We don't check the error code - if userspace has
 466                  * not set up a proper pointer then tough luck.
 467                  */
 468                 put_user(0, tidptr);
 469                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 470         }
 471 }
 472
 473 /*
 474  * Allocate a new mm structure and copy contents from the
 475  * mm structure of the passed in task structure.
 476  */
 477 static struct mm_struct *dup_mm(struct task_struct *tsk)
 478 {
 479         struct mm_struct *mm, *oldmm = current->mm;
 480         int err;
 481
 482         if (!oldmm)
 483                 return NULL;
 484
 485         mm = allocate_mm();
 486         if (!mm)
 487                 goto fail_nomem;
 488
 489         memcpy(mm, oldmm, sizeof(*mm));
 490
 491         /* Initializing for Swap token stuff */
 492         mm->token_priority = 0;
 493         mm->last_interval = 0;
 494
 495         if (!mm_init(mm))
 496                 goto fail_nomem;
 497
 498         if (init_new_context(tsk, mm))
 499                 goto fail_nocontext;
 500
 501         err = dup_mmap(mm, oldmm);
 502         if (err)
 503                 goto free_pt;
 504
 505         mm->hiwater_rss = get_mm_rss(mm);
 506         mm->hiwater_vm = mm->total_vm;
 507
 508         return mm;
 509
 510 free_pt:
 511         mmput(mm);
 512
 513 fail_nomem:
 514         return NULL;
 515
 516 fail_nocontext:
 517         /*
 518          * If init_new_context() failed, we cannot use mmput() to free the mm
 519          * because it calls destroy_context()
 520          */
 521         mm_free_pgd(mm);
 522         free_mm(mm);
 523         return NULL;
 524 }
 525
 526 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 527 {
 528         struct mm_struct * mm, *oldmm;
 529         int retval;
 530
 531         tsk->min_flt = tsk->maj_flt = 0;
 532         tsk->nvcsw = tsk->nivcsw = 0;
 533
 534         tsk->mm = NULL;
 535         tsk->active_mm = NULL;
 536
 537         /*
 538          * Are we cloning a kernel thread?
 539          *
 540          * We need to steal a active VM for that..
 541          */
 542         oldmm = current->mm;
 543         if (!oldmm)
 544                 return 0;
 545
 546         if (clone_flags & CLONE_VM) {
 547                 atomic_inc(&oldmm->mm_users);
 548                 mm = oldmm;
 549                 goto good_mm;
 550         }
 551
 552         retval = -ENOMEM;
 553         mm = dup_mm(tsk);
 554         if (!mm)
 555                 goto fail_nomem;
 556
 557 good_mm:
 558         /* Initializing for Swap token stuff */
 559         mm->token_priority = 0;
 560         mm->last_interval = 0;
 561
 562         tsk->mm = mm;
 563         tsk->active_mm = mm;
 564         return 0;
 565
 566 fail_nomem:
 567         return retval;
 568 }
 569
 570 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 571 {
 572         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 573         /* We don't need to lock fs - think why ;-) */
 574         if (fs) {
 575                 atomic_set(&fs->count, 1);
 576                 rwlock_init(&fs->lock);
 577                 fs->umask = old->umask;
 578                 read_lock(&old->lock);
 579                 fs->rootmnt = mntget(old->rootmnt);
 580                 fs->root = dget(old->root);
 581                 fs->pwdmnt = mntget(old->pwdmnt);
 582                 fs->pwd = dget(old->pwd);
 583                 if (old->altroot) {
 584                         fs->altrootmnt = mntget(old->altrootmnt);
 585                         fs->altroot = dget(old->altroot);
 586                 } else {
 587                         fs->altrootmnt = NULL;
 588                         fs->altroot = NULL;
 589                 }
 590                 read_unlock(&old->lock);
 591         }
 592         return fs;
 593 }
 594
 595 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 596 {
 597         return __copy_fs_struct(old);
 598 }
 599
 600 EXPORT_SYMBOL_GPL(copy_fs_struct);
 601
 602 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 603 {
 604         if (clone_flags & CLONE_FS) {
 605                 atomic_inc(&current->fs->count);
 606                 return 0;
 607         }
 608         tsk->fs = __copy_fs_struct(current->fs);
 609         if (!tsk->fs)
 610                 return -ENOMEM;
 611         return 0;
 612 }
 613
 614 static int count_open_files(struct fdtable *fdt)
 615 {
 616         int size = fdt->max_fdset;
 617         int i;
 618
 619         /* Find the last open fd */
 620         for (i = size/(8*sizeof(long)); i > 0; ) {
 621                 if (fdt->open_fds->fds_bits[--i])
 622                         break;
 623         }
 624         i = (i+1) * 8 * sizeof(long);
 625         return i;
 626 }
 627
 628 static struct files_struct *alloc_files(void)
 629 {
 630         struct files_struct *newf;
 631         struct fdtable *fdt;
 632
 633         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 634         if (!newf)
 635                 goto out;
 636
 637         atomic_set(&newf->count, 1);
 638
 639         spin_lock_init(&newf->file_lock);
 640         newf->next_fd = 0;
 641         fdt = &newf->fdtab;
 642         fdt->max_fds = NR_OPEN_DEFAULT;
 643         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
 644         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 645         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 646         fdt->fd = &newf->fd_array[0];
 647         INIT_RCU_HEAD(&fdt->rcu);
 648         fdt->free_files = NULL;
 649         fdt->next = NULL;
 650         rcu_assign_pointer(newf->fdt, fdt);
 651 out:
 652         return newf;
 653 }
 654
 655 /*
 656  * Allocate a new files structure and copy contents from the
 657  * passed in files structure.
 658  * errorp will be valid only when the returned files_struct is NULL.
 659  */
 660 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 661 {
 662         struct files_struct *newf;
 663         struct file **old_fds, **new_fds;
 664         int open_files, size, i, expand;
 665         struct fdtable *old_fdt, *new_fdt;
 666
 667         *errorp = -ENOMEM;
 668         newf = alloc_files();
 669         if (!newf)
 670                 goto out;
 671
 672         spin_lock(&oldf->file_lock);
 673         old_fdt = files_fdtable(oldf);
 674         new_fdt = files_fdtable(newf);
 675         size = old_fdt->max_fdset;
 676         open_files = count_open_files(old_fdt);
 677         expand = 0;
 678
 679         /*
 680          * Check whether we need to allocate a larger fd array or fd set.
 681          * Note: we're not a clone task, so the open count won't  change.
 682          */
 683         if (open_files > new_fdt->max_fdset) {
 684                 new_fdt->max_fdset = 0;
 685                 expand = 1;
 686         }
 687         if (open_files > new_fdt->max_fds) {
 688                 new_fdt->max_fds = 0;
 689                 expand = 1;
 690         }
 691
 692         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
 693         if (expand) {
 694                 spin_unlock(&oldf->file_lock);
 695                 spin_lock(&newf->file_lock);
 696                 *errorp = expand_files(newf, open_files-1);
 697                 spin_unlock(&newf->file_lock);
 698                 if (*errorp < 0)
 699                         goto out_release;
 700                 new_fdt = files_fdtable(newf);
 701                 /*
 702                  * Reacquire the oldf lock and a pointer to its fd table
 703                  * who knows it may have a new bigger fd table. We need
 704                  * the latest pointer.
 705                  */
 706                 spin_lock(&oldf->file_lock);
 707                 old_fdt = files_fdtable(oldf);
 708         }
 709
 710         old_fds = old_fdt->fd;
 711         new_fds = new_fdt->fd;
 712
 713         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
 714         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
 715
 716         for (i = open_files; i != 0; i--) {
 717                 struct file *f = *old_fds++;
 718                 if (f) {
 719                         get_file(f);
 720                 } else {
 721                         /*
 722                          * The fd may be claimed in the fd bitmap but not yet
 723                          * instantiated in the files array if a sibling thread
 724                          * is partway through open().  So make sure that this
 725                          * fd is available to the new process.
 726                          */
 727                         FD_CLR(open_files - i, new_fdt->open_fds);
 728                 }
 729                 rcu_assign_pointer(*new_fds++, f);
 730         }
 731         spin_unlock(&oldf->file_lock);
 732
 733         /* compute the remainder to be cleared */
 734         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 735
 736         /* This is long word aligned thus could use a optimized version */
 737         memset(new_fds, 0, size);
 738
 739         if (new_fdt->max_fdset > open_files) {
 740                 int left = (new_fdt->max_fdset-open_files)/8;
 741                 int start = open_files / (8 * sizeof(unsigned long));
 742
 743                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 744                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 745         }
 746
 747 out:
 748         return newf;
 749
 750 out_release:
 751         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
 752         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
 753         free_fd_array(new_fdt->fd, new_fdt->max_fds);
 754         kmem_cache_free(files_cachep, newf);
 755         return NULL;
 756 }
 757
 758 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 759 {
 760         struct files_struct *oldf, *newf;
 761         int error = 0;
 762
 763         /*
 764          * A background process may not have any files ...
 765          */
 766         oldf = current->files;
 767         if (!oldf)
 768                 goto out;
 769
 770         if (clone_flags & CLONE_FILES) {
 771                 atomic_inc(&oldf->count);
 772                 goto out;
 773         }
 774
 775         /*
 776          * Note: we may be using current for both targets (See exec.c)
 777          * This works because we cache current->files (old) as oldf. Don't
 778          * break this.
 779          */
 780         tsk->files = NULL;
 781         newf = dup_fd(oldf, &error);
 782         if (!newf)
 783                 goto out;
 784
 785         tsk->files = newf;
 786         error = 0;
 787 out:
 788         return error;
 789 }
 790
 791 /*
 792  *      Helper to unshare the files of the current task.
 793  *      We don't want to expose copy_files internals to
 794  *      the exec layer of the kernel.
 795  */
 796
 797 int unshare_files(void)
 798 {
 799         struct files_struct *files  = current->files;
 800         int rc;
 801
 802         BUG_ON(!files);
 803
 804         /* This can race but the race causes us to copy when we don't
 805            need to and drop the copy */
 806         if(atomic_read(&files->count) == 1)
 807         {
 808                 atomic_inc(&files->count);
 809                 return 0;
 810         }
 811         rc = copy_files(0, current);
 812         if(rc)
 813                 current->files = files;
 814         return rc;
 815 }
 816
 817 EXPORT_SYMBOL(unshare_files);
 818
 819 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 820 {
 821         struct sighand_struct *sig;
 822
 823         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 824                 atomic_inc(&current->sighand->count);
 825                 return 0;
 826         }
 827         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 828         rcu_assign_pointer(tsk->sighand, sig);
 829         if (!sig)
 830                 return -ENOMEM;
 831         atomic_set(&sig->count, 1);
 832         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 833         return 0;
 834 }
 835
 836 void __cleanup_sighand(struct sighand_struct *sighand)
 837 {
 838         if (atomic_dec_and_test(&sighand->count))
 839                 kmem_cache_free(sighand_cachep, sighand);
 840 }
 841
 842 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
 843 {
 844         struct signal_struct *sig;
 845         int ret;
 846
 847         if (clone_flags & CLONE_THREAD) {
 848                 atomic_inc(&current->signal->count);
 849                 atomic_inc(&current->signal->live);
 850                 taskstats_tgid_alloc(current);
 851                 return 0;
 852         }
 853         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 854         tsk->signal = sig;
 855         if (!sig)
 856                 return -ENOMEM;
 857
 858         ret = copy_thread_group_keys(tsk);
 859         if (ret < 0) {
 860                 kmem_cache_free(signal_cachep, sig);
 861                 return ret;
 862         }
 863
 864         atomic_set(&sig->count, 1);
 865         atomic_set(&sig->live, 1);
 866         init_waitqueue_head(&sig->wait_chldexit);
 867         sig->flags = 0;
 868         sig->group_exit_code = 0;
 869         sig->group_exit_task = NULL;
 870         sig->group_stop_count = 0;
 871         sig->curr_target = NULL;
 872         init_sigpending(&sig->shared_pending);
 873         INIT_LIST_HEAD(&sig->posix_timers);
 874
 875         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
 876         sig->it_real_incr.tv64 = 0;
 877         sig->real_timer.function = it_real_fn;
 878         sig->tsk = tsk;
 879
 880         sig->it_virt_expires = cputime_zero;
 881         sig->it_virt_incr = cputime_zero;
 882         sig->it_prof_expires = cputime_zero;
 883         sig->it_prof_incr = cputime_zero;
 884
 885         sig->leader = 0;        /* session leadership doesn't inherit */
 886         sig->tty_old_pgrp = 0;
 887
 888         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 889         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 890         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 891         sig->sched_time = 0;
 892         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 893         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 894         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 895         taskstats_tgid_init(sig);
 896
 897         task_lock(current->group_leader);
 898         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 899         task_unlock(current->group_leader);
 900
 901         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 902                 /*
 903                  * New sole thread in the process gets an expiry time
 904                  * of the whole CPU time limit.
 905                  */
 906                 tsk->it_prof_expires =
 907                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 908         }
 909         acct_init_pacct(&sig->pacct);
 910
 911         return 0;
 912 }
 913
 914 void __cleanup_signal(struct signal_struct *sig)
 915 {
 916         exit_thread_group_keys(sig);
 917         kmem_cache_free(signal_cachep, sig);
 918 }
 919
 920 static inline void cleanup_signal(struct task_struct *tsk)
 921 {
 922         struct signal_struct *sig = tsk->signal;
 923
 924         atomic_dec(&sig->live);
 925
 926         if (atomic_dec_and_test(&sig->count))
 927                 __cleanup_signal(sig);
 928 }
 929
 930 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
 931 {
 932         unsigned long new_flags = p->flags;
 933
 934         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
 935         new_flags |= PF_FORKNOEXEC;
 936         if (!(clone_flags & CLONE_PTRACE))
 937                 p->ptrace = 0;
 938         p->flags = new_flags;
 939 }
 940
 941 asmlinkage long sys_set_tid_address(int __user *tidptr)
 942 {
 943         current->clear_child_tid = tidptr;
 944
 945         return current->pid;
 946 }
 947
 948 static inline void rt_mutex_init_task(struct task_struct *p)
 949 {
 950 #ifdef CONFIG_RT_MUTEXES
 951         spin_lock_init(&p->pi_lock);
 952         plist_head_init(&p->pi_waiters, &p->pi_lock);
 953         p->pi_blocked_on = NULL;
 954 #endif
 955 }
 956
 957 /*
 958  * This creates a new process as a copy of the old one,
 959  * but does not actually start it yet.
 960  *
 961  * It copies the registers, and all the appropriate
 962  * parts of the process environment (as per the clone
 963  * flags). The actual kick-off is left to the caller.
 964  */
 965 static struct task_struct *copy_process(unsigned long clone_flags,
 966                                         unsigned long stack_start,
 967                                         struct pt_regs *regs,
 968                                         unsigned long stack_size,
 969                                         int __user *parent_tidptr,
 970                                         int __user *child_tidptr,
 971                                         int pid)
 972 {
 973         int retval;
 974         struct task_struct *p = NULL;
 975
 976         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 977                 return ERR_PTR(-EINVAL);
 978
 979         /*
 980          * Thread groups must share signals as well, and detached threads
 981          * can only be started up within the thread group.
 982          */
 983         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 984                 return ERR_PTR(-EINVAL);
 985
 986         /*
 987          * Shared signal handlers imply shared VM. By way of the above,
 988          * thread groups also imply shared VM. Blocking this case allows
 989          * for various simplifications in other code.
 990          */
 991         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 992                 return ERR_PTR(-EINVAL);
 993
 994         retval = security_task_create(clone_flags);
 995         if (retval)
 996                 goto fork_out;
 997
 998         retval = -ENOMEM;
 999         p = dup_task_struct(current);
1000         if (!p)
1001                 goto fork_out;
1002
1003         rt_mutex_init_task(p);
1004
1005 #ifdef CONFIG_TRACE_IRQFLAGS
1006         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1007         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1008 #endif
1009         retval = -EAGAIN;
1010         if (atomic_read(&p->user->processes) >=
1011                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1012                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1013                                 p->user != &root_user)
1014                         goto bad_fork_free;
1015         }
1016
1017         atomic_inc(&p->user->__count);
1018         atomic_inc(&p->user->processes);
1019         get_group_info(p->group_info);
1020
1021         /*
1022          * If multiple threads are within copy_process(), then this check
1023          * triggers too late. This doesn't hurt, the check is only there
1024          * to stop root fork bombs.
1025          */
1026         if (nr_threads >= max_threads)
1027                 goto bad_fork_cleanup_count;
1028
1029         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1030                 goto bad_fork_cleanup_count;
1031
1032         if (p->binfmt && !try_module_get(p->binfmt->module))
1033                 goto bad_fork_cleanup_put_domain;
1034
1035         p->did_exec = 0;
1036         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1037         copy_flags(clone_flags, p);
1038         p->pid = pid;
1039         retval = -EFAULT;
1040         if (clone_flags & CLONE_PARENT_SETTID)
1041                 if (put_user(p->pid, parent_tidptr))
1042                         goto bad_fork_cleanup_delays_binfmt;
1043
1044         INIT_LIST_HEAD(&p->children);
1045         INIT_LIST_HEAD(&p->sibling);
1046         p->vfork_done = NULL;
1047         spin_lock_init(&p->alloc_lock);
1048
1049         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1050         init_sigpending(&p->pending);
1051
1052         p->utime = cputime_zero;
1053         p->stime = cputime_zero;
1054         p->sched_time = 0;
1055         p->rchar = 0;           /* I/O counter: bytes read */
1056         p->wchar = 0;           /* I/O counter: bytes written */
1057         p->syscr = 0;           /* I/O counter: read syscalls */
1058         p->syscw = 0;           /* I/O counter: write syscalls */
1059         acct_clear_integrals(p);
1060
1061         p->it_virt_expires = cputime_zero;
1062         p->it_prof_expires = cputime_zero;
1063         p->it_sched_expires = 0;
1064         INIT_LIST_HEAD(&p->cpu_timers[0]);
1065         INIT_LIST_HEAD(&p->cpu_timers[1]);
1066         INIT_LIST_HEAD(&p->cpu_timers[2]);
1067
1068         p->lock_depth = -1;             /* -1 = no lock */
1069         do_posix_clock_monotonic_gettime(&p->start_time);
1070         p->security = NULL;
1071         p->io_context = NULL;
1072         p->io_wait = NULL;
1073         p->audit_context = NULL;
1074         cpuset_fork(p);
1075 #ifdef CONFIG_NUMA
1076         p->mempolicy = mpol_copy(p->mempolicy);
1077         if (IS_ERR(p->mempolicy)) {
1078                 retval = PTR_ERR(p->mempolicy);
1079                 p->mempolicy = NULL;
1080                 goto bad_fork_cleanup_cpuset;
1081         }
1082         mpol_fix_fork_child_flag(p);
1083 #endif
1084 #ifdef CONFIG_TRACE_IRQFLAGS
1085         p->irq_events = 0;
1086 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1087         p->hardirqs_enabled = 1;
1088 #else
1089         p->hardirqs_enabled = 0;
1090 #endif
1091         p->hardirq_enable_ip = 0;
1092         p->hardirq_enable_event = 0;
1093         p->hardirq_disable_ip = _THIS_IP_;
1094         p->hardirq_disable_event = 0;
1095         p->softirqs_enabled = 1;
1096         p->softirq_enable_ip = _THIS_IP_;
1097         p->softirq_enable_event = 0;
1098         p->softirq_disable_ip = 0;
1099         p->softirq_disable_event = 0;
1100         p->hardirq_context = 0;
1101         p->softirq_context = 0;
1102 #endif
1103 #ifdef CONFIG_LOCKDEP
1104         p->lockdep_depth = 0; /* no locks held yet */
1105         p->curr_chain_key = 0;
1106         p->lockdep_recursion = 0;
1107 #endif
1108
1109 #ifdef CONFIG_DEBUG_MUTEXES
1110         p->blocked_on = NULL; /* not blocked yet */
1111 #endif
1112
1113         p->tgid = p->pid;
1114         if (clone_flags & CLONE_THREAD)
1115                 p->tgid = current->tgid;
1116
1117         if ((retval = security_task_alloc(p)))
1118                 goto bad_fork_cleanup_policy;
1119         if ((retval = audit_alloc(p)))
1120                 goto bad_fork_cleanup_security;
1121         /* copy all the process information */
1122         if ((retval = copy_semundo(clone_flags, p)))
1123                 goto bad_fork_cleanup_audit;
1124         if ((retval = copy_files(clone_flags, p)))
1125                 goto bad_fork_cleanup_semundo;
1126         if ((retval = copy_fs(clone_flags, p)))
1127                 goto bad_fork_cleanup_files;
1128         if ((retval = copy_sighand(clone_flags, p)))
1129                 goto bad_fork_cleanup_fs;
1130         if ((retval = copy_signal(clone_flags, p)))
1131                 goto bad_fork_cleanup_sighand;
1132         if ((retval = copy_mm(clone_flags, p)))
1133                 goto bad_fork_cleanup_signal;
1134         if ((retval = copy_keys(clone_flags, p)))
1135                 goto bad_fork_cleanup_mm;
1136         if ((retval = copy_namespaces(clone_flags, p)))
1137                 goto bad_fork_cleanup_keys;
1138         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1139         if (retval)
1140                 goto bad_fork_cleanup_namespaces;
1141
1142         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1143         /*
1144          * Clear TID on mm_release()?
1145          */
1146         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1147         p->robust_list = NULL;
1148 #ifdef CONFIG_COMPAT
1149         p->compat_robust_list = NULL;
1150 #endif
1151         INIT_LIST_HEAD(&p->pi_state_list);
1152         p->pi_state_cache = NULL;
1153
1154         /*
1155          * sigaltstack should be cleared when sharing the same VM
1156          */
1157         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1158                 p->sas_ss_sp = p->sas_ss_size = 0;
1159
1160         /*
1161          * Syscall tracing should be turned off in the child regardless
1162          * of CLONE_PTRACE.
1163          */
1164         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1165 #ifdef TIF_SYSCALL_EMU
1166         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1167 #endif
1168
1169         /* Our parent execution domain becomes current domain
1170            These must match for thread signalling to apply */
1171         p->parent_exec_id = p->self_exec_id;
1172
1173         /* ok, now we should be set up.. */
1174         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1175         p->pdeath_signal = 0;
1176         p->exit_state = 0;
1177
1178         /*
1179          * Ok, make it visible to the rest of the system.
1180          * We dont wake it up yet.
1181          */
1182         p->group_leader = p;
1183         INIT_LIST_HEAD(&p->thread_group);
1184         INIT_LIST_HEAD(&p->ptrace_children);
1185         INIT_LIST_HEAD(&p->ptrace_list);
1186
1187         /* Perform scheduler related setup. Assign this task to a CPU. */
1188         sched_fork(p, clone_flags);
1189
1190         /* Need tasklist lock for parent etc handling! */
1191         write_lock_irq(&tasklist_lock);
1192
1193         /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
1194         p->ioprio = current->ioprio;
1195
1196         /*
1197          * The task hasn't been attached yet, so its cpus_allowed mask will
1198          * not be changed, nor will its assigned CPU.
1199          *
1200          * The cpus_allowed mask of the parent may have changed after it was
1201          * copied first time - so re-copy it here, then check the child's CPU
1202          * to ensure it is on a valid CPU (and if not, just force it back to
1203          * parent's CPU). This avoids alot of nasty races.
1204          */
1205         p->cpus_allowed = current->cpus_allowed;
1206         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1207                         !cpu_online(task_cpu(p))))
1208                 set_task_cpu(p, smp_processor_id());
1209
1210         /* CLONE_PARENT re-uses the old parent */
1211         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1212                 p->real_parent = current->real_parent;
1213         else
1214                 p->real_parent = current;
1215         p->parent = p->real_parent;
1216
1217         spin_lock(&current->sighand->siglock);
1218
1219         /*
1220          * Process group and session signals need to be delivered to just the
1221          * parent before the fork or both the parent and the child after the
1222          * fork. Restart if a signal comes in before we add the new process to
1223          * it's process group.
1224          * A fatal signal pending means that current will exit, so the new
1225          * thread can't slip out of an OOM kill (or normal SIGKILL).
1226          */
1227         recalc_sigpending();
1228         if (signal_pending(current)) {
1229                 spin_unlock(&current->sighand->siglock);
1230                 write_unlock_irq(&tasklist_lock);
1231                 retval = -ERESTARTNOINTR;
1232                 goto bad_fork_cleanup_namespaces;
1233         }
1234
1235         if (clone_flags & CLONE_THREAD) {
1236                 p->group_leader = current->group_leader;
1237                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1238
1239                 if (!cputime_eq(current->signal->it_virt_expires,
1240                                 cputime_zero) ||
1241                     !cputime_eq(current->signal->it_prof_expires,
1242                                 cputime_zero) ||
1243                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1244                     !list_empty(&current->signal->cpu_timers[0]) ||
1245                     !list_empty(&current->signal->cpu_timers[1]) ||
1246                     !list_empty(&current->signal->cpu_timers[2])) {
1247                         /*
1248                          * Have child wake up on its first tick to check
1249                          * for process CPU timers.
1250                          */
1251                         p->it_prof_expires = jiffies_to_cputime(1);
1252                 }
1253         }
1254
1255         if (likely(p->pid)) {
1256                 add_parent(p);
1257                 if (unlikely(p->ptrace & PT_PTRACED))
1258                         __ptrace_link(p, current->parent);
1259
1260                 if (thread_group_leader(p)) {
1261                         p->signal->tty = current->signal->tty;
1262                         p->signal->pgrp = process_group(current);
1263                         p->signal->session = current->signal->session;
1264                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1265                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1266
1267                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1268                         __get_cpu_var(process_counts)++;
1269                 }
1270                 attach_pid(p, PIDTYPE_PID, p->pid);
1271                 nr_threads++;
1272         }
1273
1274         total_forks++;
1275         spin_unlock(&current->sighand->siglock);
1276         write_unlock_irq(&tasklist_lock);
1277         proc_fork_connector(p);
1278         return p;
1279
1280 bad_fork_cleanup_namespaces:
1281         exit_task_namespaces(p);
1282 bad_fork_cleanup_keys:
1283         exit_keys(p);
1284 bad_fork_cleanup_mm:
1285         if (p->mm)
1286                 mmput(p->mm);
1287 bad_fork_cleanup_signal:
1288         cleanup_signal(p);
1289 bad_fork_cleanup_sighand:
1290         __cleanup_sighand(p->sighand);
1291 bad_fork_cleanup_fs:
1292         exit_fs(p); /* blocking */
1293 bad_fork_cleanup_files:
1294         exit_files(p); /* blocking */
1295 bad_fork_cleanup_semundo:
1296         exit_sem(p);
1297 bad_fork_cleanup_audit:
1298         audit_free(p);
1299 bad_fork_cleanup_security:
1300         security_task_free(p);
1301 bad_fork_cleanup_policy:
1302 #ifdef CONFIG_NUMA
1303         mpol_free(p->mempolicy);
1304 bad_fork_cleanup_cpuset:
1305 #endif
1306         cpuset_exit(p);
1307 bad_fork_cleanup_delays_binfmt:
1308         delayacct_tsk_free(p);
1309         if (p->binfmt)
1310                 module_put(p->binfmt->module);
1311 bad_fork_cleanup_put_domain:
1312         module_put(task_thread_info(p)->exec_domain->module);
1313 bad_fork_cleanup_count:
1314         put_group_info(p->group_info);
1315         atomic_dec(&p->user->processes);
1316         free_uid(p->user);
1317 bad_fork_free:
1318         free_task(p);
1319 fork_out:
1320         return ERR_PTR(retval);
1321 }
1322
1323 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1324 {
1325         memset(regs, 0, sizeof(struct pt_regs));
1326         return regs;
1327 }
1328
1329 struct task_struct * __devinit fork_idle(int cpu)
1330 {
1331         struct task_struct *task;
1332         struct pt_regs regs;
1333
1334         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1335         if (!IS_ERR(task))
1336                 init_idle(task, cpu);
1337
1338         return task;
1339 }
1340
1341 static inline int fork_traceflag (unsigned clone_flags)
1342 {
1343         if (clone_flags & CLONE_UNTRACED)
1344                 return 0;
1345         else if (clone_flags & CLONE_VFORK) {
1346                 if (current->ptrace & PT_TRACE_VFORK)
1347                         return PTRACE_EVENT_VFORK;
1348         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1349                 if (current->ptrace & PT_TRACE_CLONE)
1350                         return PTRACE_EVENT_CLONE;
1351         } else if (current->ptrace & PT_TRACE_FORK)
1352                 return PTRACE_EVENT_FORK;
1353
1354         return 0;
1355 }
1356
1357 /*
1358  *  Ok, this is the main fork-routine.
1359  *
1360  * It copies the process, and if successful kick-starts
1361  * it and waits for it to finish using the VM if required.
1362  */
1363 long do_fork(unsigned long clone_flags,
1364               unsigned long stack_start,
1365               struct pt_regs *regs,
1366               unsigned long stack_size,
1367               int __user *parent_tidptr,
1368               int __user *child_tidptr)
1369 {
1370         struct task_struct *p;
1371         int trace = 0;
1372         struct pid *pid = alloc_pid();
1373         long nr;
1374
1375         if (!pid)
1376                 return -EAGAIN;
1377         nr = pid->nr;
1378         if (unlikely(current->ptrace)) {
1379                 trace = fork_traceflag (clone_flags);
1380                 if (trace)
1381                         clone_flags |= CLONE_PTRACE;
1382         }
1383
1384         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1385         /*
1386          * Do this prior waking up the new thread - the thread pointer
1387          * might get invalid after that point, if the thread exits quickly.
1388          */
1389         if (!IS_ERR(p)) {
1390                 struct completion vfork;
1391
1392                 if (clone_flags & CLONE_VFORK) {
1393                         p->vfork_done = &vfork;
1394                         init_completion(&vfork);
1395                 }
1396
1397                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1398                         /*
1399                          * We'll start up with an immediate SIGSTOP.
1400                          */
1401                         sigaddset(&p->pending.signal, SIGSTOP);
1402                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1403                 }
1404
1405                 if (!(clone_flags & CLONE_STOPPED))
1406                         wake_up_new_task(p, clone_flags);
1407                 else
1408                         p->state = TASK_STOPPED;
1409
1410                 if (unlikely (trace)) {
1411                         current->ptrace_message = nr;
1412                         ptrace_notify ((trace << 8) | SIGTRAP);
1413                 }
1414
1415                 if (clone_flags & CLONE_VFORK) {
1416                         wait_for_completion(&vfork);
1417                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1418                                 current->ptrace_message = nr;
1419                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1420                         }
1421                 }
1422         } else {
1423                 free_pid(pid);
1424                 nr = PTR_ERR(p);
1425         }
1426         return nr;
1427 }
1428
1429 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1430 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1431 #endif
1432
1433 static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags)
1434 {
1435         struct sighand_struct *sighand = data;
1436
1437         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1438                                         SLAB_CTOR_CONSTRUCTOR)
1439                 spin_lock_init(&sighand->siglock);
1440 }
1441
1442 void __init proc_caches_init(void)
1443 {
1444         sighand_cachep = kmem_cache_create("sighand_cache",
1445                         sizeof(struct sighand_struct), 0,
1446                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1447                         sighand_ctor, NULL);
1448         signal_cachep = kmem_cache_create("signal_cache",
1449                         sizeof(struct signal_struct), 0,
1450                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1451         files_cachep = kmem_cache_create("files_cache",
1452                         sizeof(struct files_struct), 0,
1453                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1454         fs_cachep = kmem_cache_create("fs_cache",
1455                         sizeof(struct fs_struct), 0,
1456                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1457         vm_area_cachep = kmem_cache_create("vm_area_struct",
1458                         sizeof(struct vm_area_struct), 0,
1459                         SLAB_PANIC, NULL, NULL);
1460         mm_cachep = kmem_cache_create("mm_struct",
1461                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1462                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1463 }
1464
1465
1466 /*
1467  * Check constraints on flags passed to the unshare system call and
1468  * force unsharing of additional process context as appropriate.
1469  */
1470 static inline void check_unshare_flags(unsigned long *flags_ptr)
1471 {
1472         /*
1473          * If unsharing a thread from a thread group, must also
1474          * unshare vm.
1475          */
1476         if (*flags_ptr & CLONE_THREAD)
1477                 *flags_ptr |= CLONE_VM;
1478
1479         /*
1480          * If unsharing vm, must also unshare signal handlers.
1481          */
1482         if (*flags_ptr & CLONE_VM)
1483                 *flags_ptr |= CLONE_SIGHAND;
1484
1485         /*
1486          * If unsharing signal handlers and the task was created
1487          * using CLONE_THREAD, then must unshare the thread
1488          */
1489         if ((*flags_ptr & CLONE_SIGHAND) &&
1490             (atomic_read(&current->signal->count) > 1))
1491                 *flags_ptr |= CLONE_THREAD;
1492
1493         /*
1494          * If unsharing namespace, must also unshare filesystem information.
1495          */
1496         if (*flags_ptr & CLONE_NEWNS)
1497                 *flags_ptr |= CLONE_FS;
1498 }
1499
1500 /*
1501  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1502  */
1503 static int unshare_thread(unsigned long unshare_flags)
1504 {
1505         if (unshare_flags & CLONE_THREAD)
1506                 return -EINVAL;
1507
1508         return 0;
1509 }
1510
1511 /*
1512  * Unshare the filesystem structure if it is being shared
1513  */
1514 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1515 {
1516         struct fs_struct *fs = current->fs;
1517
1518         if ((unshare_flags & CLONE_FS) &&
1519             (fs && atomic_read(&fs->count) > 1)) {
1520                 *new_fsp = __copy_fs_struct(current->fs);
1521                 if (!*new_fsp)
1522                         return -ENOMEM;
1523         }
1524
1525         return 0;
1526 }
1527
1528 /*
1529  * Unshare the namespace structure if it is being shared
1530  */
1531 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1532 {
1533         struct namespace *ns = current->nsproxy->namespace;
1534
1535         if ((unshare_flags & CLONE_NEWNS) && ns) {
1536                 if (!capable(CAP_SYS_ADMIN))
1537                         return -EPERM;
1538
1539                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1540                 if (!*new_nsp)
1541                         return -ENOMEM;
1542         }
1543
1544         return 0;
1545 }
1546
1547 /*
1548  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1549  * supported yet
1550  */
1551 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1552 {
1553         struct sighand_struct *sigh = current->sighand;
1554
1555         if ((unshare_flags & CLONE_SIGHAND) &&
1556             (sigh && atomic_read(&sigh->count) > 1))
1557                 return -EINVAL;
1558         else
1559                 return 0;
1560 }
1561
1562 /*
1563  * Unshare vm if it is being shared
1564  */
1565 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1566 {
1567         struct mm_struct *mm = current->mm;
1568
1569         if ((unshare_flags & CLONE_VM) &&
1570             (mm && atomic_read(&mm->mm_users) > 1)) {
1571                 return -EINVAL;
1572         }
1573
1574         return 0;
1575 }
1576
1577 /*
1578  * Unshare file descriptor table if it is being shared
1579  */
1580 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1581 {
1582         struct files_struct *fd = current->files;
1583         int error = 0;
1584
1585         if ((unshare_flags & CLONE_FILES) &&
1586             (fd && atomic_read(&fd->count) > 1)) {
1587                 *new_fdp = dup_fd(fd, &error);
1588                 if (!*new_fdp)
1589                         return error;
1590         }
1591
1592         return 0;
1593 }
1594
1595 /*
1596  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1597  * supported yet
1598  */
1599 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1600 {
1601         if (unshare_flags & CLONE_SYSVSEM)
1602                 return -EINVAL;
1603
1604         return 0;
1605 }
1606
1607 #ifndef CONFIG_IPC_NS
1608 static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns)
1609 {
1610         if (flags & CLONE_NEWIPC)
1611                 return -EINVAL;
1612
1613         return 0;
1614 }
1615 #endif
1616
1617 /*
1618  * unshare allows a process to 'unshare' part of the process
1619  * context which was originally shared using clone.  copy_*
1620  * functions used by do_fork() cannot be used here directly
1621  * because they modify an inactive task_struct that is being
1622  * constructed. Here we are modifying the current, active,
1623  * task_struct.
1624  */
1625 asmlinkage long sys_unshare(unsigned long unshare_flags)
1626 {
1627         int err = 0;
1628         struct fs_struct *fs, *new_fs = NULL;
1629         struct namespace *ns, *new_ns = NULL;
1630         struct sighand_struct *sigh, *new_sigh = NULL;
1631         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1632         struct files_struct *fd, *new_fd = NULL;
1633         struct sem_undo_list *new_ulist = NULL;
1634         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1635         struct uts_namespace *uts, *new_uts = NULL;
1636         struct ipc_namespace *ipc, *new_ipc = NULL;
1637
1638         check_unshare_flags(&unshare_flags);
1639
1640         /* Return -EINVAL for all unsupported flags */
1641         err = -EINVAL;
1642         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1643                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1644                                 CLONE_NEWUTS|CLONE_NEWIPC))
1645                 goto bad_unshare_out;
1646
1647         if ((err = unshare_thread(unshare_flags)))
1648                 goto bad_unshare_out;
1649         if ((err = unshare_fs(unshare_flags, &new_fs)))
1650                 goto bad_unshare_cleanup_thread;
1651         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1652                 goto bad_unshare_cleanup_fs;
1653         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1654                 goto bad_unshare_cleanup_ns;
1655         if ((err = unshare_vm(unshare_flags, &new_mm)))
1656                 goto bad_unshare_cleanup_sigh;
1657         if ((err = unshare_fd(unshare_flags, &new_fd)))
1658                 goto bad_unshare_cleanup_vm;
1659         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1660                 goto bad_unshare_cleanup_fd;
1661         if ((err = unshare_utsname(unshare_flags, &new_uts)))
1662                 goto bad_unshare_cleanup_semundo;
1663         if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
1664                 goto bad_unshare_cleanup_uts;
1665
1666         if (new_ns || new_uts || new_ipc) {
1667                 old_nsproxy = current->nsproxy;
1668                 new_nsproxy = dup_namespaces(old_nsproxy);
1669                 if (!new_nsproxy) {
1670                         err = -ENOMEM;
1671                         goto bad_unshare_cleanup_ipc;
1672                 }
1673         }
1674
1675         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist ||
1676                                 new_uts || new_ipc) {
1677
1678                 task_lock(current);
1679
1680                 if (new_nsproxy) {
1681                         current->nsproxy = new_nsproxy;
1682                         new_nsproxy = old_nsproxy;
1683                 }
1684
1685                 if (new_fs) {
1686                         fs = current->fs;
1687                         current->fs = new_fs;
1688                         new_fs = fs;
1689                 }
1690
1691                 if (new_ns) {
1692                         ns = current->nsproxy->namespace;
1693                         current->nsproxy->namespace = new_ns;
1694                         new_ns = ns;
1695                 }
1696
1697                 if (new_sigh) {
1698                         sigh = current->sighand;
1699                         rcu_assign_pointer(current->sighand, new_sigh);
1700                         new_sigh = sigh;
1701                 }
1702
1703                 if (new_mm) {
1704                         mm = current->mm;
1705                         active_mm = current->active_mm;
1706                         current->mm = new_mm;
1707                         current->active_mm = new_mm;
1708                         activate_mm(active_mm, new_mm);
1709                         new_mm = mm;
1710                 }
1711
1712                 if (new_fd) {
1713                         fd = current->files;
1714                         current->files = new_fd;
1715                         new_fd = fd;
1716                 }
1717
1718                 if (new_uts) {
1719                         uts = current->nsproxy->uts_ns;
1720                         current->nsproxy->uts_ns = new_uts;
1721                         new_uts = uts;
1722                 }
1723
1724                 if (new_ipc) {
1725                         ipc = current->nsproxy->ipc_ns;
1726                         current->nsproxy->ipc_ns = new_ipc;
1727                         new_ipc = ipc;
1728                 }
1729
1730                 task_unlock(current);
1731         }
1732
1733         if (new_nsproxy)
1734                 put_nsproxy(new_nsproxy);
1735
1736 bad_unshare_cleanup_ipc:
1737         if (new_ipc)
1738                 put_ipc_ns(new_ipc);
1739
1740 bad_unshare_cleanup_uts:
1741         if (new_uts)
1742                 put_uts_ns(new_uts);
1743
1744 bad_unshare_cleanup_semundo:
1745 bad_unshare_cleanup_fd:
1746         if (new_fd)
1747                 put_files_struct(new_fd);
1748
1749 bad_unshare_cleanup_vm:
1750         if (new_mm)
1751                 mmput(new_mm);
1752
1753 bad_unshare_cleanup_sigh:
1754         if (new_sigh)
1755                 if (atomic_dec_and_test(&new_sigh->count))
1756                         kmem_cache_free(sighand_cachep, new_sigh);
1757
1758 bad_unshare_cleanup_ns:
1759         if (new_ns)
1760                 put_namespace(new_ns);
1761
1762 bad_unshare_cleanup_fs:
1763         if (new_fs)
1764                 put_fs_struct(new_fs);
1765
1766 bad_unshare_cleanup_thread:
1767 bad_unshare_out:
1768         return err;
1769 }