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