1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/mnt_namespace.h> 21 #include <linux/personality.h> 22 #include <linux/mempolicy.h> 23 #include <linux/sem.h> 24 #include <linux/file.h> 25 #include <linux/key.h> 26 #include <linux/binfmts.h> 27 #include <linux/mman.h> 28 #include <linux/fs.h> 29 #include <linux/nsproxy.h> 30 #include <linux/capability.h> 31 #include <linux/cpu.h> 32 #include <linux/cgroup.h> 33 #include <linux/security.h> 34 #include <linux/swap.h> 35 #include <linux/syscalls.h> 36 #include <linux/jiffies.h> 37 #include <linux/futex.h> 38 #include <linux/task_io_accounting_ops.h> 39 #include <linux/rcupdate.h> 40 #include <linux/ptrace.h> 41 #include <linux/mount.h> 42 #include <linux/audit.h> 43 #include <linux/memcontrol.h> 44 #include <linux/profile.h> 45 #include <linux/rmap.h> 46 #include <linux/acct.h> 47 #include <linux/tsacct_kern.h> 48 #include <linux/cn_proc.h> 49 #include <linux/freezer.h> 50 #include <linux/delayacct.h> 51 #include <linux/taskstats_kern.h> 52 #include <linux/random.h> 53 #include <linux/tty.h> 54 #include <linux/proc_fs.h> 55 #include <linux/blkdev.h> 56 57 #include <asm/pgtable.h> 58 #include <asm/pgalloc.h> 59 #include <asm/uaccess.h> 60 #include <asm/mmu_context.h> 61 #include <asm/cacheflush.h> 62 #include <asm/tlbflush.h> 63 64 /* 65 * Protected counters by write_lock_irq(&tasklist_lock) 66 */ 67 unsigned long total_forks; /* Handle normal Linux uptimes. */ 68 int nr_threads; /* The idle threads do not count.. */ 69 70 int max_threads; /* tunable limit on nr_threads */ 71 72 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 73 74 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 75 76 int nr_processes(void) 77 { 78 int cpu; 79 int total = 0; 80 81 for_each_online_cpu(cpu) 82 total += per_cpu(process_counts, cpu); 83 84 return total; 85 } 86 87 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 88 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 89 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 90 static struct kmem_cache *task_struct_cachep; 91 #endif 92 93 /* SLAB cache for signal_struct structures (tsk->signal) */ 94 static struct kmem_cache *signal_cachep; 95 96 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 97 struct kmem_cache *sighand_cachep; 98 99 /* SLAB cache for files_struct structures (tsk->files) */ 100 struct kmem_cache *files_cachep; 101 102 /* SLAB cache for fs_struct structures (tsk->fs) */ 103 struct kmem_cache *fs_cachep; 104 105 /* SLAB cache for vm_area_struct structures */ 106 struct kmem_cache *vm_area_cachep; 107 108 /* SLAB cache for mm_struct structures (tsk->mm) */ 109 static struct kmem_cache *mm_cachep; 110 111 void free_task(struct task_struct *tsk) 112 { 113 prop_local_destroy_single(&tsk->dirties); 114 free_thread_info(tsk->stack); 115 rt_mutex_debug_task_free(tsk); 116 free_task_struct(tsk); 117 } 118 EXPORT_SYMBOL(free_task); 119 120 void __put_task_struct(struct task_struct *tsk) 121 { 122 WARN_ON(!tsk->exit_state); 123 WARN_ON(atomic_read(&tsk->usage)); 124 WARN_ON(tsk == current); 125 126 security_task_free(tsk); 127 free_uid(tsk->user); 128 put_group_info(tsk->group_info); 129 delayacct_tsk_free(tsk); 130 131 if (!profile_handoff_task(tsk)) 132 free_task(tsk); 133 } 134 135 void __init fork_init(unsigned long mempages) 136 { 137 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 138 #ifndef ARCH_MIN_TASKALIGN 139 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 140 #endif 141 /* create a slab on which task_structs can be allocated */ 142 task_struct_cachep = 143 kmem_cache_create("task_struct", sizeof(struct task_struct), 144 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 145 #endif 146 147 /* 148 * The default maximum number of threads is set to a safe 149 * value: the thread structures can take up at most half 150 * of memory. 151 */ 152 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 153 154 /* 155 * we need to allow at least 20 threads to boot a system 156 */ 157 if(max_threads < 20) 158 max_threads = 20; 159 160 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 161 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 162 init_task.signal->rlim[RLIMIT_SIGPENDING] = 163 init_task.signal->rlim[RLIMIT_NPROC]; 164 } 165 166 static struct task_struct *dup_task_struct(struct task_struct *orig) 167 { 168 struct task_struct *tsk; 169 struct thread_info *ti; 170 int err; 171 172 prepare_to_copy(orig); 173 174 tsk = alloc_task_struct(); 175 if (!tsk) 176 return NULL; 177 178 ti = alloc_thread_info(tsk); 179 if (!ti) { 180 free_task_struct(tsk); 181 return NULL; 182 } 183 184 *tsk = *orig; 185 tsk->stack = ti; 186 187 err = prop_local_init_single(&tsk->dirties); 188 if (err) { 189 free_thread_info(ti); 190 free_task_struct(tsk); 191 return NULL; 192 } 193 194 setup_thread_stack(tsk, orig); 195 196 #ifdef CONFIG_CC_STACKPROTECTOR 197 tsk->stack_canary = get_random_int(); 198 #endif 199 200 /* One for us, one for whoever does the "release_task()" (usually parent) */ 201 atomic_set(&tsk->usage,2); 202 atomic_set(&tsk->fs_excl, 0); 203 #ifdef CONFIG_BLK_DEV_IO_TRACE 204 tsk->btrace_seq = 0; 205 #endif 206 tsk->splice_pipe = NULL; 207 return tsk; 208 } 209 210 #ifdef CONFIG_MMU 211 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 212 { 213 struct vm_area_struct *mpnt, *tmp, **pprev; 214 struct rb_node **rb_link, *rb_parent; 215 int retval; 216 unsigned long charge; 217 struct mempolicy *pol; 218 219 down_write(&oldmm->mmap_sem); 220 flush_cache_dup_mm(oldmm); 221 /* 222 * Not linked in yet - no deadlock potential: 223 */ 224 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 225 226 mm->locked_vm = 0; 227 mm->mmap = NULL; 228 mm->mmap_cache = NULL; 229 mm->free_area_cache = oldmm->mmap_base; 230 mm->cached_hole_size = ~0UL; 231 mm->map_count = 0; 232 cpus_clear(mm->cpu_vm_mask); 233 mm->mm_rb = RB_ROOT; 234 rb_link = &mm->mm_rb.rb_node; 235 rb_parent = NULL; 236 pprev = &mm->mmap; 237 238 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 239 struct file *file; 240 241 if (mpnt->vm_flags & VM_DONTCOPY) { 242 long pages = vma_pages(mpnt); 243 mm->total_vm -= pages; 244 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 245 -pages); 246 continue; 247 } 248 charge = 0; 249 if (mpnt->vm_flags & VM_ACCOUNT) { 250 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 251 if (security_vm_enough_memory(len)) 252 goto fail_nomem; 253 charge = len; 254 } 255 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 256 if (!tmp) 257 goto fail_nomem; 258 *tmp = *mpnt; 259 pol = mpol_copy(vma_policy(mpnt)); 260 retval = PTR_ERR(pol); 261 if (IS_ERR(pol)) 262 goto fail_nomem_policy; 263 vma_set_policy(tmp, pol); 264 tmp->vm_flags &= ~VM_LOCKED; 265 tmp->vm_mm = mm; 266 tmp->vm_next = NULL; 267 anon_vma_link(tmp); 268 file = tmp->vm_file; 269 if (file) { 270 struct inode *inode = file->f_path.dentry->d_inode; 271 get_file(file); 272 if (tmp->vm_flags & VM_DENYWRITE) 273 atomic_dec(&inode->i_writecount); 274 275 /* insert tmp into the share list, just after mpnt */ 276 spin_lock(&file->f_mapping->i_mmap_lock); 277 tmp->vm_truncate_count = mpnt->vm_truncate_count; 278 flush_dcache_mmap_lock(file->f_mapping); 279 vma_prio_tree_add(tmp, mpnt); 280 flush_dcache_mmap_unlock(file->f_mapping); 281 spin_unlock(&file->f_mapping->i_mmap_lock); 282 } 283 284 /* 285 * Link in the new vma and copy the page table entries. 286 */ 287 *pprev = tmp; 288 pprev = &tmp->vm_next; 289 290 __vma_link_rb(mm, tmp, rb_link, rb_parent); 291 rb_link = &tmp->vm_rb.rb_right; 292 rb_parent = &tmp->vm_rb; 293 294 mm->map_count++; 295 retval = copy_page_range(mm, oldmm, mpnt); 296 297 if (tmp->vm_ops && tmp->vm_ops->open) 298 tmp->vm_ops->open(tmp); 299 300 if (retval) 301 goto out; 302 } 303 /* a new mm has just been created */ 304 arch_dup_mmap(oldmm, mm); 305 retval = 0; 306 out: 307 up_write(&mm->mmap_sem); 308 flush_tlb_mm(oldmm); 309 up_write(&oldmm->mmap_sem); 310 return retval; 311 fail_nomem_policy: 312 kmem_cache_free(vm_area_cachep, tmp); 313 fail_nomem: 314 retval = -ENOMEM; 315 vm_unacct_memory(charge); 316 goto out; 317 } 318 319 static inline int mm_alloc_pgd(struct mm_struct * mm) 320 { 321 mm->pgd = pgd_alloc(mm); 322 if (unlikely(!mm->pgd)) 323 return -ENOMEM; 324 return 0; 325 } 326 327 static inline void mm_free_pgd(struct mm_struct * mm) 328 { 329 pgd_free(mm, mm->pgd); 330 } 331 #else 332 #define dup_mmap(mm, oldmm) (0) 333 #define mm_alloc_pgd(mm) (0) 334 #define mm_free_pgd(mm) 335 #endif /* CONFIG_MMU */ 336 337 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 338 339 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 340 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 341 342 #include <linux/init_task.h> 343 344 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 345 { 346 atomic_set(&mm->mm_users, 1); 347 atomic_set(&mm->mm_count, 1); 348 init_rwsem(&mm->mmap_sem); 349 INIT_LIST_HEAD(&mm->mmlist); 350 mm->flags = (current->mm) ? current->mm->flags 351 : MMF_DUMP_FILTER_DEFAULT; 352 mm->core_waiters = 0; 353 mm->nr_ptes = 0; 354 set_mm_counter(mm, file_rss, 0); 355 set_mm_counter(mm, anon_rss, 0); 356 spin_lock_init(&mm->page_table_lock); 357 rwlock_init(&mm->ioctx_list_lock); 358 mm->ioctx_list = NULL; 359 mm->free_area_cache = TASK_UNMAPPED_BASE; 360 mm->cached_hole_size = ~0UL; 361 mm_init_cgroup(mm, p); 362 363 if (likely(!mm_alloc_pgd(mm))) { 364 mm->def_flags = 0; 365 return mm; 366 } 367 368 mm_free_cgroup(mm); 369 free_mm(mm); 370 return NULL; 371 } 372 373 /* 374 * Allocate and initialize an mm_struct. 375 */ 376 struct mm_struct * mm_alloc(void) 377 { 378 struct mm_struct * mm; 379 380 mm = allocate_mm(); 381 if (mm) { 382 memset(mm, 0, sizeof(*mm)); 383 mm = mm_init(mm, current); 384 } 385 return mm; 386 } 387 388 /* 389 * Called when the last reference to the mm 390 * is dropped: either by a lazy thread or by 391 * mmput. Free the page directory and the mm. 392 */ 393 void __mmdrop(struct mm_struct *mm) 394 { 395 BUG_ON(mm == &init_mm); 396 mm_free_pgd(mm); 397 destroy_context(mm); 398 free_mm(mm); 399 } 400 EXPORT_SYMBOL_GPL(__mmdrop); 401 402 /* 403 * Decrement the use count and release all resources for an mm. 404 */ 405 void mmput(struct mm_struct *mm) 406 { 407 might_sleep(); 408 409 if (atomic_dec_and_test(&mm->mm_users)) { 410 exit_aio(mm); 411 exit_mmap(mm); 412 if (!list_empty(&mm->mmlist)) { 413 spin_lock(&mmlist_lock); 414 list_del(&mm->mmlist); 415 spin_unlock(&mmlist_lock); 416 } 417 put_swap_token(mm); 418 mm_free_cgroup(mm); 419 mmdrop(mm); 420 } 421 } 422 EXPORT_SYMBOL_GPL(mmput); 423 424 /** 425 * get_task_mm - acquire a reference to the task's mm 426 * 427 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 428 * this kernel workthread has transiently adopted a user mm with use_mm, 429 * to do its AIO) is not set and if so returns a reference to it, after 430 * bumping up the use count. User must release the mm via mmput() 431 * after use. Typically used by /proc and ptrace. 432 */ 433 struct mm_struct *get_task_mm(struct task_struct *task) 434 { 435 struct mm_struct *mm; 436 437 task_lock(task); 438 mm = task->mm; 439 if (mm) { 440 if (task->flags & PF_BORROWED_MM) 441 mm = NULL; 442 else 443 atomic_inc(&mm->mm_users); 444 } 445 task_unlock(task); 446 return mm; 447 } 448 EXPORT_SYMBOL_GPL(get_task_mm); 449 450 /* Please note the differences between mmput and mm_release. 451 * mmput is called whenever we stop holding onto a mm_struct, 452 * error success whatever. 453 * 454 * mm_release is called after a mm_struct has been removed 455 * from the current process. 456 * 457 * This difference is important for error handling, when we 458 * only half set up a mm_struct for a new process and need to restore 459 * the old one. Because we mmput the new mm_struct before 460 * restoring the old one. . . 461 * Eric Biederman 10 January 1998 462 */ 463 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 464 { 465 struct completion *vfork_done = tsk->vfork_done; 466 467 /* Get rid of any cached register state */ 468 deactivate_mm(tsk, mm); 469 470 /* notify parent sleeping on vfork() */ 471 if (vfork_done) { 472 tsk->vfork_done = NULL; 473 complete(vfork_done); 474 } 475 476 /* 477 * If we're exiting normally, clear a user-space tid field if 478 * requested. We leave this alone when dying by signal, to leave 479 * the value intact in a core dump, and to save the unnecessary 480 * trouble otherwise. Userland only wants this done for a sys_exit. 481 */ 482 if (tsk->clear_child_tid 483 && !(tsk->flags & PF_SIGNALED) 484 && atomic_read(&mm->mm_users) > 1) { 485 u32 __user * tidptr = tsk->clear_child_tid; 486 tsk->clear_child_tid = NULL; 487 488 /* 489 * We don't check the error code - if userspace has 490 * not set up a proper pointer then tough luck. 491 */ 492 put_user(0, tidptr); 493 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 494 } 495 } 496 497 /* 498 * Allocate a new mm structure and copy contents from the 499 * mm structure of the passed in task structure. 500 */ 501 static struct mm_struct *dup_mm(struct task_struct *tsk) 502 { 503 struct mm_struct *mm, *oldmm = current->mm; 504 int err; 505 506 if (!oldmm) 507 return NULL; 508 509 mm = allocate_mm(); 510 if (!mm) 511 goto fail_nomem; 512 513 memcpy(mm, oldmm, sizeof(*mm)); 514 515 /* Initializing for Swap token stuff */ 516 mm->token_priority = 0; 517 mm->last_interval = 0; 518 519 if (!mm_init(mm, tsk)) 520 goto fail_nomem; 521 522 if (init_new_context(tsk, mm)) 523 goto fail_nocontext; 524 525 err = dup_mmap(mm, oldmm); 526 if (err) 527 goto free_pt; 528 529 mm->hiwater_rss = get_mm_rss(mm); 530 mm->hiwater_vm = mm->total_vm; 531 532 return mm; 533 534 free_pt: 535 mmput(mm); 536 537 fail_nomem: 538 return NULL; 539 540 fail_nocontext: 541 /* 542 * If init_new_context() failed, we cannot use mmput() to free the mm 543 * because it calls destroy_context() 544 */ 545 mm_free_pgd(mm); 546 free_mm(mm); 547 return NULL; 548 } 549 550 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 551 { 552 struct mm_struct * mm, *oldmm; 553 int retval; 554 555 tsk->min_flt = tsk->maj_flt = 0; 556 tsk->nvcsw = tsk->nivcsw = 0; 557 558 tsk->mm = NULL; 559 tsk->active_mm = NULL; 560 561 /* 562 * Are we cloning a kernel thread? 563 * 564 * We need to steal a active VM for that.. 565 */ 566 oldmm = current->mm; 567 if (!oldmm) 568 return 0; 569 570 if (clone_flags & CLONE_VM) { 571 atomic_inc(&oldmm->mm_users); 572 mm = oldmm; 573 goto good_mm; 574 } 575 576 retval = -ENOMEM; 577 mm = dup_mm(tsk); 578 if (!mm) 579 goto fail_nomem; 580 581 good_mm: 582 /* Initializing for Swap token stuff */ 583 mm->token_priority = 0; 584 mm->last_interval = 0; 585 586 tsk->mm = mm; 587 tsk->active_mm = mm; 588 return 0; 589 590 fail_nomem: 591 return retval; 592 } 593 594 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 595 { 596 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 597 /* We don't need to lock fs - think why ;-) */ 598 if (fs) { 599 atomic_set(&fs->count, 1); 600 rwlock_init(&fs->lock); 601 fs->umask = old->umask; 602 read_lock(&old->lock); 603 fs->root = old->root; 604 path_get(&old->root); 605 fs->pwd = old->pwd; 606 path_get(&old->pwd); 607 if (old->altroot.dentry) { 608 fs->altroot = old->altroot; 609 path_get(&old->altroot); 610 } else { 611 fs->altroot.mnt = NULL; 612 fs->altroot.dentry = NULL; 613 } 614 read_unlock(&old->lock); 615 } 616 return fs; 617 } 618 619 struct fs_struct *copy_fs_struct(struct fs_struct *old) 620 { 621 return __copy_fs_struct(old); 622 } 623 624 EXPORT_SYMBOL_GPL(copy_fs_struct); 625 626 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 627 { 628 if (clone_flags & CLONE_FS) { 629 atomic_inc(¤t->fs->count); 630 return 0; 631 } 632 tsk->fs = __copy_fs_struct(current->fs); 633 if (!tsk->fs) 634 return -ENOMEM; 635 return 0; 636 } 637 638 static int count_open_files(struct fdtable *fdt) 639 { 640 int size = fdt->max_fds; 641 int i; 642 643 /* Find the last open fd */ 644 for (i = size/(8*sizeof(long)); i > 0; ) { 645 if (fdt->open_fds->fds_bits[--i]) 646 break; 647 } 648 i = (i+1) * 8 * sizeof(long); 649 return i; 650 } 651 652 static struct files_struct *alloc_files(void) 653 { 654 struct files_struct *newf; 655 struct fdtable *fdt; 656 657 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); 658 if (!newf) 659 goto out; 660 661 atomic_set(&newf->count, 1); 662 663 spin_lock_init(&newf->file_lock); 664 newf->next_fd = 0; 665 fdt = &newf->fdtab; 666 fdt->max_fds = NR_OPEN_DEFAULT; 667 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 668 fdt->open_fds = (fd_set *)&newf->open_fds_init; 669 fdt->fd = &newf->fd_array[0]; 670 INIT_RCU_HEAD(&fdt->rcu); 671 fdt->next = NULL; 672 rcu_assign_pointer(newf->fdt, fdt); 673 out: 674 return newf; 675 } 676 677 /* 678 * Allocate a new files structure and copy contents from the 679 * passed in files structure. 680 * errorp will be valid only when the returned files_struct is NULL. 681 */ 682 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 683 { 684 struct files_struct *newf; 685 struct file **old_fds, **new_fds; 686 int open_files, size, i; 687 struct fdtable *old_fdt, *new_fdt; 688 689 *errorp = -ENOMEM; 690 newf = alloc_files(); 691 if (!newf) 692 goto out; 693 694 spin_lock(&oldf->file_lock); 695 old_fdt = files_fdtable(oldf); 696 new_fdt = files_fdtable(newf); 697 open_files = count_open_files(old_fdt); 698 699 /* 700 * Check whether we need to allocate a larger fd array and fd set. 701 * Note: we're not a clone task, so the open count won't change. 702 */ 703 if (open_files > new_fdt->max_fds) { 704 new_fdt->max_fds = 0; 705 spin_unlock(&oldf->file_lock); 706 spin_lock(&newf->file_lock); 707 *errorp = expand_files(newf, open_files-1); 708 spin_unlock(&newf->file_lock); 709 if (*errorp < 0) 710 goto out_release; 711 new_fdt = files_fdtable(newf); 712 /* 713 * Reacquire the oldf lock and a pointer to its fd table 714 * who knows it may have a new bigger fd table. We need 715 * the latest pointer. 716 */ 717 spin_lock(&oldf->file_lock); 718 old_fdt = files_fdtable(oldf); 719 } 720 721 old_fds = old_fdt->fd; 722 new_fds = new_fdt->fd; 723 724 memcpy(new_fdt->open_fds->fds_bits, 725 old_fdt->open_fds->fds_bits, open_files/8); 726 memcpy(new_fdt->close_on_exec->fds_bits, 727 old_fdt->close_on_exec->fds_bits, open_files/8); 728 729 for (i = open_files; i != 0; i--) { 730 struct file *f = *old_fds++; 731 if (f) { 732 get_file(f); 733 } else { 734 /* 735 * The fd may be claimed in the fd bitmap but not yet 736 * instantiated in the files array if a sibling thread 737 * is partway through open(). So make sure that this 738 * fd is available to the new process. 739 */ 740 FD_CLR(open_files - i, new_fdt->open_fds); 741 } 742 rcu_assign_pointer(*new_fds++, f); 743 } 744 spin_unlock(&oldf->file_lock); 745 746 /* compute the remainder to be cleared */ 747 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 748 749 /* This is long word aligned thus could use a optimized version */ 750 memset(new_fds, 0, size); 751 752 if (new_fdt->max_fds > open_files) { 753 int left = (new_fdt->max_fds-open_files)/8; 754 int start = open_files / (8 * sizeof(unsigned long)); 755 756 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 757 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 758 } 759 760 return newf; 761 762 out_release: 763 kmem_cache_free(files_cachep, newf); 764 out: 765 return NULL; 766 } 767 768 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 769 { 770 struct files_struct *oldf, *newf; 771 int error = 0; 772 773 /* 774 * A background process may not have any files ... 775 */ 776 oldf = current->files; 777 if (!oldf) 778 goto out; 779 780 if (clone_flags & CLONE_FILES) { 781 atomic_inc(&oldf->count); 782 goto out; 783 } 784 785 /* 786 * Note: we may be using current for both targets (See exec.c) 787 * This works because we cache current->files (old) as oldf. Don't 788 * break this. 789 */ 790 tsk->files = NULL; 791 newf = dup_fd(oldf, &error); 792 if (!newf) 793 goto out; 794 795 tsk->files = newf; 796 error = 0; 797 out: 798 return error; 799 } 800 801 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 802 { 803 #ifdef CONFIG_BLOCK 804 struct io_context *ioc = current->io_context; 805 806 if (!ioc) 807 return 0; 808 /* 809 * Share io context with parent, if CLONE_IO is set 810 */ 811 if (clone_flags & CLONE_IO) { 812 tsk->io_context = ioc_task_link(ioc); 813 if (unlikely(!tsk->io_context)) 814 return -ENOMEM; 815 } else if (ioprio_valid(ioc->ioprio)) { 816 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 817 if (unlikely(!tsk->io_context)) 818 return -ENOMEM; 819 820 tsk->io_context->ioprio = ioc->ioprio; 821 } 822 #endif 823 return 0; 824 } 825 826 /* 827 * Helper to unshare the files of the current task. 828 * We don't want to expose copy_files internals to 829 * the exec layer of the kernel. 830 */ 831 832 int unshare_files(void) 833 { 834 struct files_struct *files = current->files; 835 int rc; 836 837 BUG_ON(!files); 838 839 /* This can race but the race causes us to copy when we don't 840 need to and drop the copy */ 841 if(atomic_read(&files->count) == 1) 842 { 843 atomic_inc(&files->count); 844 return 0; 845 } 846 rc = copy_files(0, current); 847 if(rc) 848 current->files = files; 849 return rc; 850 } 851 852 EXPORT_SYMBOL(unshare_files); 853 854 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 855 { 856 struct sighand_struct *sig; 857 858 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 859 atomic_inc(¤t->sighand->count); 860 return 0; 861 } 862 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 863 rcu_assign_pointer(tsk->sighand, sig); 864 if (!sig) 865 return -ENOMEM; 866 atomic_set(&sig->count, 1); 867 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 868 return 0; 869 } 870 871 void __cleanup_sighand(struct sighand_struct *sighand) 872 { 873 if (atomic_dec_and_test(&sighand->count)) 874 kmem_cache_free(sighand_cachep, sighand); 875 } 876 877 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 878 { 879 struct signal_struct *sig; 880 int ret; 881 882 if (clone_flags & CLONE_THREAD) { 883 atomic_inc(¤t->signal->count); 884 atomic_inc(¤t->signal->live); 885 return 0; 886 } 887 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 888 tsk->signal = sig; 889 if (!sig) 890 return -ENOMEM; 891 892 ret = copy_thread_group_keys(tsk); 893 if (ret < 0) { 894 kmem_cache_free(signal_cachep, sig); 895 return ret; 896 } 897 898 atomic_set(&sig->count, 1); 899 atomic_set(&sig->live, 1); 900 init_waitqueue_head(&sig->wait_chldexit); 901 sig->flags = 0; 902 sig->group_exit_code = 0; 903 sig->group_exit_task = NULL; 904 sig->group_stop_count = 0; 905 sig->curr_target = NULL; 906 init_sigpending(&sig->shared_pending); 907 INIT_LIST_HEAD(&sig->posix_timers); 908 909 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 910 sig->it_real_incr.tv64 = 0; 911 sig->real_timer.function = it_real_fn; 912 913 sig->it_virt_expires = cputime_zero; 914 sig->it_virt_incr = cputime_zero; 915 sig->it_prof_expires = cputime_zero; 916 sig->it_prof_incr = cputime_zero; 917 918 sig->leader = 0; /* session leadership doesn't inherit */ 919 sig->tty_old_pgrp = NULL; 920 921 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 922 sig->gtime = cputime_zero; 923 sig->cgtime = cputime_zero; 924 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 925 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 926 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 927 sig->sum_sched_runtime = 0; 928 INIT_LIST_HEAD(&sig->cpu_timers[0]); 929 INIT_LIST_HEAD(&sig->cpu_timers[1]); 930 INIT_LIST_HEAD(&sig->cpu_timers[2]); 931 taskstats_tgid_init(sig); 932 933 task_lock(current->group_leader); 934 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 935 task_unlock(current->group_leader); 936 937 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 938 /* 939 * New sole thread in the process gets an expiry time 940 * of the whole CPU time limit. 941 */ 942 tsk->it_prof_expires = 943 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 944 } 945 acct_init_pacct(&sig->pacct); 946 947 tty_audit_fork(sig); 948 949 return 0; 950 } 951 952 void __cleanup_signal(struct signal_struct *sig) 953 { 954 exit_thread_group_keys(sig); 955 kmem_cache_free(signal_cachep, sig); 956 } 957 958 static void cleanup_signal(struct task_struct *tsk) 959 { 960 struct signal_struct *sig = tsk->signal; 961 962 atomic_dec(&sig->live); 963 964 if (atomic_dec_and_test(&sig->count)) 965 __cleanup_signal(sig); 966 } 967 968 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 969 { 970 unsigned long new_flags = p->flags; 971 972 new_flags &= ~PF_SUPERPRIV; 973 new_flags |= PF_FORKNOEXEC; 974 if (!(clone_flags & CLONE_PTRACE)) 975 p->ptrace = 0; 976 p->flags = new_flags; 977 clear_freeze_flag(p); 978 } 979 980 asmlinkage long sys_set_tid_address(int __user *tidptr) 981 { 982 current->clear_child_tid = tidptr; 983 984 return task_pid_vnr(current); 985 } 986 987 static void rt_mutex_init_task(struct task_struct *p) 988 { 989 spin_lock_init(&p->pi_lock); 990 #ifdef CONFIG_RT_MUTEXES 991 plist_head_init(&p->pi_waiters, &p->pi_lock); 992 p->pi_blocked_on = NULL; 993 #endif 994 } 995 996 /* 997 * This creates a new process as a copy of the old one, 998 * but does not actually start it yet. 999 * 1000 * It copies the registers, and all the appropriate 1001 * parts of the process environment (as per the clone 1002 * flags). The actual kick-off is left to the caller. 1003 */ 1004 static struct task_struct *copy_process(unsigned long clone_flags, 1005 unsigned long stack_start, 1006 struct pt_regs *regs, 1007 unsigned long stack_size, 1008 int __user *child_tidptr, 1009 struct pid *pid) 1010 { 1011 int retval; 1012 struct task_struct *p; 1013 int cgroup_callbacks_done = 0; 1014 1015 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1016 return ERR_PTR(-EINVAL); 1017 1018 /* 1019 * Thread groups must share signals as well, and detached threads 1020 * can only be started up within the thread group. 1021 */ 1022 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1023 return ERR_PTR(-EINVAL); 1024 1025 /* 1026 * Shared signal handlers imply shared VM. By way of the above, 1027 * thread groups also imply shared VM. Blocking this case allows 1028 * for various simplifications in other code. 1029 */ 1030 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1031 return ERR_PTR(-EINVAL); 1032 1033 retval = security_task_create(clone_flags); 1034 if (retval) 1035 goto fork_out; 1036 1037 retval = -ENOMEM; 1038 p = dup_task_struct(current); 1039 if (!p) 1040 goto fork_out; 1041 1042 rt_mutex_init_task(p); 1043 1044 #ifdef CONFIG_TRACE_IRQFLAGS 1045 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1046 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1047 #endif 1048 retval = -EAGAIN; 1049 if (atomic_read(&p->user->processes) >= 1050 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1051 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1052 p->user != current->nsproxy->user_ns->root_user) 1053 goto bad_fork_free; 1054 } 1055 1056 atomic_inc(&p->user->__count); 1057 atomic_inc(&p->user->processes); 1058 get_group_info(p->group_info); 1059 1060 /* 1061 * If multiple threads are within copy_process(), then this check 1062 * triggers too late. This doesn't hurt, the check is only there 1063 * to stop root fork bombs. 1064 */ 1065 if (nr_threads >= max_threads) 1066 goto bad_fork_cleanup_count; 1067 1068 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1069 goto bad_fork_cleanup_count; 1070 1071 if (p->binfmt && !try_module_get(p->binfmt->module)) 1072 goto bad_fork_cleanup_put_domain; 1073 1074 p->did_exec = 0; 1075 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1076 copy_flags(clone_flags, p); 1077 INIT_LIST_HEAD(&p->children); 1078 INIT_LIST_HEAD(&p->sibling); 1079 #ifdef CONFIG_PREEMPT_RCU 1080 p->rcu_read_lock_nesting = 0; 1081 p->rcu_flipctr_idx = 0; 1082 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1083 p->vfork_done = NULL; 1084 spin_lock_init(&p->alloc_lock); 1085 1086 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1087 init_sigpending(&p->pending); 1088 1089 p->utime = cputime_zero; 1090 p->stime = cputime_zero; 1091 p->gtime = cputime_zero; 1092 p->utimescaled = cputime_zero; 1093 p->stimescaled = cputime_zero; 1094 p->prev_utime = cputime_zero; 1095 p->prev_stime = cputime_zero; 1096 1097 #ifdef CONFIG_DETECT_SOFTLOCKUP 1098 p->last_switch_count = 0; 1099 p->last_switch_timestamp = 0; 1100 #endif 1101 1102 #ifdef CONFIG_TASK_XACCT 1103 p->rchar = 0; /* I/O counter: bytes read */ 1104 p->wchar = 0; /* I/O counter: bytes written */ 1105 p->syscr = 0; /* I/O counter: read syscalls */ 1106 p->syscw = 0; /* I/O counter: write syscalls */ 1107 #endif 1108 task_io_accounting_init(p); 1109 acct_clear_integrals(p); 1110 1111 p->it_virt_expires = cputime_zero; 1112 p->it_prof_expires = cputime_zero; 1113 p->it_sched_expires = 0; 1114 INIT_LIST_HEAD(&p->cpu_timers[0]); 1115 INIT_LIST_HEAD(&p->cpu_timers[1]); 1116 INIT_LIST_HEAD(&p->cpu_timers[2]); 1117 1118 p->lock_depth = -1; /* -1 = no lock */ 1119 do_posix_clock_monotonic_gettime(&p->start_time); 1120 p->real_start_time = p->start_time; 1121 monotonic_to_bootbased(&p->real_start_time); 1122 #ifdef CONFIG_SECURITY 1123 p->security = NULL; 1124 #endif 1125 p->cap_bset = current->cap_bset; 1126 p->io_context = NULL; 1127 p->audit_context = NULL; 1128 cgroup_fork(p); 1129 #ifdef CONFIG_NUMA 1130 p->mempolicy = mpol_copy(p->mempolicy); 1131 if (IS_ERR(p->mempolicy)) { 1132 retval = PTR_ERR(p->mempolicy); 1133 p->mempolicy = NULL; 1134 goto bad_fork_cleanup_cgroup; 1135 } 1136 mpol_fix_fork_child_flag(p); 1137 #endif 1138 #ifdef CONFIG_TRACE_IRQFLAGS 1139 p->irq_events = 0; 1140 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1141 p->hardirqs_enabled = 1; 1142 #else 1143 p->hardirqs_enabled = 0; 1144 #endif 1145 p->hardirq_enable_ip = 0; 1146 p->hardirq_enable_event = 0; 1147 p->hardirq_disable_ip = _THIS_IP_; 1148 p->hardirq_disable_event = 0; 1149 p->softirqs_enabled = 1; 1150 p->softirq_enable_ip = _THIS_IP_; 1151 p->softirq_enable_event = 0; 1152 p->softirq_disable_ip = 0; 1153 p->softirq_disable_event = 0; 1154 p->hardirq_context = 0; 1155 p->softirq_context = 0; 1156 #endif 1157 #ifdef CONFIG_LOCKDEP 1158 p->lockdep_depth = 0; /* no locks held yet */ 1159 p->curr_chain_key = 0; 1160 p->lockdep_recursion = 0; 1161 #endif 1162 1163 #ifdef CONFIG_DEBUG_MUTEXES 1164 p->blocked_on = NULL; /* not blocked yet */ 1165 #endif 1166 1167 /* Perform scheduler related setup. Assign this task to a CPU. */ 1168 sched_fork(p, clone_flags); 1169 1170 if ((retval = security_task_alloc(p))) 1171 goto bad_fork_cleanup_policy; 1172 if ((retval = audit_alloc(p))) 1173 goto bad_fork_cleanup_security; 1174 /* copy all the process information */ 1175 if ((retval = copy_semundo(clone_flags, p))) 1176 goto bad_fork_cleanup_audit; 1177 if ((retval = copy_files(clone_flags, p))) 1178 goto bad_fork_cleanup_semundo; 1179 if ((retval = copy_fs(clone_flags, p))) 1180 goto bad_fork_cleanup_files; 1181 if ((retval = copy_sighand(clone_flags, p))) 1182 goto bad_fork_cleanup_fs; 1183 if ((retval = copy_signal(clone_flags, p))) 1184 goto bad_fork_cleanup_sighand; 1185 if ((retval = copy_mm(clone_flags, p))) 1186 goto bad_fork_cleanup_signal; 1187 if ((retval = copy_keys(clone_flags, p))) 1188 goto bad_fork_cleanup_mm; 1189 if ((retval = copy_namespaces(clone_flags, p))) 1190 goto bad_fork_cleanup_keys; 1191 if ((retval = copy_io(clone_flags, p))) 1192 goto bad_fork_cleanup_namespaces; 1193 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1194 if (retval) 1195 goto bad_fork_cleanup_io; 1196 1197 if (pid != &init_struct_pid) { 1198 retval = -ENOMEM; 1199 pid = alloc_pid(task_active_pid_ns(p)); 1200 if (!pid) 1201 goto bad_fork_cleanup_io; 1202 1203 if (clone_flags & CLONE_NEWPID) { 1204 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1205 if (retval < 0) 1206 goto bad_fork_free_pid; 1207 } 1208 } 1209 1210 p->pid = pid_nr(pid); 1211 p->tgid = p->pid; 1212 if (clone_flags & CLONE_THREAD) 1213 p->tgid = current->tgid; 1214 1215 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1216 /* 1217 * Clear TID on mm_release()? 1218 */ 1219 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1220 #ifdef CONFIG_FUTEX 1221 p->robust_list = NULL; 1222 #ifdef CONFIG_COMPAT 1223 p->compat_robust_list = NULL; 1224 #endif 1225 INIT_LIST_HEAD(&p->pi_state_list); 1226 p->pi_state_cache = NULL; 1227 #endif 1228 /* 1229 * sigaltstack should be cleared when sharing the same VM 1230 */ 1231 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1232 p->sas_ss_sp = p->sas_ss_size = 0; 1233 1234 /* 1235 * Syscall tracing should be turned off in the child regardless 1236 * of CLONE_PTRACE. 1237 */ 1238 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1239 #ifdef TIF_SYSCALL_EMU 1240 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1241 #endif 1242 clear_all_latency_tracing(p); 1243 1244 /* Our parent execution domain becomes current domain 1245 These must match for thread signalling to apply */ 1246 p->parent_exec_id = p->self_exec_id; 1247 1248 /* ok, now we should be set up.. */ 1249 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1250 p->pdeath_signal = 0; 1251 p->exit_state = 0; 1252 1253 /* 1254 * Ok, make it visible to the rest of the system. 1255 * We dont wake it up yet. 1256 */ 1257 p->group_leader = p; 1258 INIT_LIST_HEAD(&p->thread_group); 1259 INIT_LIST_HEAD(&p->ptrace_children); 1260 INIT_LIST_HEAD(&p->ptrace_list); 1261 1262 /* Now that the task is set up, run cgroup callbacks if 1263 * necessary. We need to run them before the task is visible 1264 * on the tasklist. */ 1265 cgroup_fork_callbacks(p); 1266 cgroup_callbacks_done = 1; 1267 1268 /* Need tasklist lock for parent etc handling! */ 1269 write_lock_irq(&tasklist_lock); 1270 1271 /* 1272 * The task hasn't been attached yet, so its cpus_allowed mask will 1273 * not be changed, nor will its assigned CPU. 1274 * 1275 * The cpus_allowed mask of the parent may have changed after it was 1276 * copied first time - so re-copy it here, then check the child's CPU 1277 * to ensure it is on a valid CPU (and if not, just force it back to 1278 * parent's CPU). This avoids alot of nasty races. 1279 */ 1280 p->cpus_allowed = current->cpus_allowed; 1281 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1282 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1283 !cpu_online(task_cpu(p)))) 1284 set_task_cpu(p, smp_processor_id()); 1285 1286 /* CLONE_PARENT re-uses the old parent */ 1287 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1288 p->real_parent = current->real_parent; 1289 else 1290 p->real_parent = current; 1291 p->parent = p->real_parent; 1292 1293 spin_lock(¤t->sighand->siglock); 1294 1295 /* 1296 * Process group and session signals need to be delivered to just the 1297 * parent before the fork or both the parent and the child after the 1298 * fork. Restart if a signal comes in before we add the new process to 1299 * it's process group. 1300 * A fatal signal pending means that current will exit, so the new 1301 * thread can't slip out of an OOM kill (or normal SIGKILL). 1302 */ 1303 recalc_sigpending(); 1304 if (signal_pending(current)) { 1305 spin_unlock(¤t->sighand->siglock); 1306 write_unlock_irq(&tasklist_lock); 1307 retval = -ERESTARTNOINTR; 1308 goto bad_fork_free_pid; 1309 } 1310 1311 if (clone_flags & CLONE_THREAD) { 1312 p->group_leader = current->group_leader; 1313 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1314 1315 if (!cputime_eq(current->signal->it_virt_expires, 1316 cputime_zero) || 1317 !cputime_eq(current->signal->it_prof_expires, 1318 cputime_zero) || 1319 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1320 !list_empty(¤t->signal->cpu_timers[0]) || 1321 !list_empty(¤t->signal->cpu_timers[1]) || 1322 !list_empty(¤t->signal->cpu_timers[2])) { 1323 /* 1324 * Have child wake up on its first tick to check 1325 * for process CPU timers. 1326 */ 1327 p->it_prof_expires = jiffies_to_cputime(1); 1328 } 1329 } 1330 1331 if (likely(p->pid)) { 1332 add_parent(p); 1333 if (unlikely(p->ptrace & PT_PTRACED)) 1334 __ptrace_link(p, current->parent); 1335 1336 if (thread_group_leader(p)) { 1337 if (clone_flags & CLONE_NEWPID) 1338 p->nsproxy->pid_ns->child_reaper = p; 1339 1340 p->signal->leader_pid = pid; 1341 p->signal->tty = current->signal->tty; 1342 set_task_pgrp(p, task_pgrp_nr(current)); 1343 set_task_session(p, task_session_nr(current)); 1344 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1345 attach_pid(p, PIDTYPE_SID, task_session(current)); 1346 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1347 __get_cpu_var(process_counts)++; 1348 } 1349 attach_pid(p, PIDTYPE_PID, pid); 1350 nr_threads++; 1351 } 1352 1353 total_forks++; 1354 spin_unlock(¤t->sighand->siglock); 1355 write_unlock_irq(&tasklist_lock); 1356 proc_fork_connector(p); 1357 cgroup_post_fork(p); 1358 return p; 1359 1360 bad_fork_free_pid: 1361 if (pid != &init_struct_pid) 1362 free_pid(pid); 1363 bad_fork_cleanup_io: 1364 put_io_context(p->io_context); 1365 bad_fork_cleanup_namespaces: 1366 exit_task_namespaces(p); 1367 bad_fork_cleanup_keys: 1368 exit_keys(p); 1369 bad_fork_cleanup_mm: 1370 if (p->mm) 1371 mmput(p->mm); 1372 bad_fork_cleanup_signal: 1373 cleanup_signal(p); 1374 bad_fork_cleanup_sighand: 1375 __cleanup_sighand(p->sighand); 1376 bad_fork_cleanup_fs: 1377 exit_fs(p); /* blocking */ 1378 bad_fork_cleanup_files: 1379 exit_files(p); /* blocking */ 1380 bad_fork_cleanup_semundo: 1381 exit_sem(p); 1382 bad_fork_cleanup_audit: 1383 audit_free(p); 1384 bad_fork_cleanup_security: 1385 security_task_free(p); 1386 bad_fork_cleanup_policy: 1387 #ifdef CONFIG_NUMA 1388 mpol_free(p->mempolicy); 1389 bad_fork_cleanup_cgroup: 1390 #endif 1391 cgroup_exit(p, cgroup_callbacks_done); 1392 delayacct_tsk_free(p); 1393 if (p->binfmt) 1394 module_put(p->binfmt->module); 1395 bad_fork_cleanup_put_domain: 1396 module_put(task_thread_info(p)->exec_domain->module); 1397 bad_fork_cleanup_count: 1398 put_group_info(p->group_info); 1399 atomic_dec(&p->user->processes); 1400 free_uid(p->user); 1401 bad_fork_free: 1402 free_task(p); 1403 fork_out: 1404 return ERR_PTR(retval); 1405 } 1406 1407 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1408 { 1409 memset(regs, 0, sizeof(struct pt_regs)); 1410 return regs; 1411 } 1412 1413 struct task_struct * __cpuinit fork_idle(int cpu) 1414 { 1415 struct task_struct *task; 1416 struct pt_regs regs; 1417 1418 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1419 &init_struct_pid); 1420 if (!IS_ERR(task)) 1421 init_idle(task, cpu); 1422 1423 return task; 1424 } 1425 1426 static int fork_traceflag(unsigned clone_flags) 1427 { 1428 if (clone_flags & CLONE_UNTRACED) 1429 return 0; 1430 else if (clone_flags & CLONE_VFORK) { 1431 if (current->ptrace & PT_TRACE_VFORK) 1432 return PTRACE_EVENT_VFORK; 1433 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1434 if (current->ptrace & PT_TRACE_CLONE) 1435 return PTRACE_EVENT_CLONE; 1436 } else if (current->ptrace & PT_TRACE_FORK) 1437 return PTRACE_EVENT_FORK; 1438 1439 return 0; 1440 } 1441 1442 /* 1443 * Ok, this is the main fork-routine. 1444 * 1445 * It copies the process, and if successful kick-starts 1446 * it and waits for it to finish using the VM if required. 1447 */ 1448 long do_fork(unsigned long clone_flags, 1449 unsigned long stack_start, 1450 struct pt_regs *regs, 1451 unsigned long stack_size, 1452 int __user *parent_tidptr, 1453 int __user *child_tidptr) 1454 { 1455 struct task_struct *p; 1456 int trace = 0; 1457 long nr; 1458 1459 /* 1460 * We hope to recycle these flags after 2.6.26 1461 */ 1462 if (unlikely(clone_flags & CLONE_STOPPED)) { 1463 static int __read_mostly count = 100; 1464 1465 if (count > 0 && printk_ratelimit()) { 1466 char comm[TASK_COMM_LEN]; 1467 1468 count--; 1469 printk(KERN_INFO "fork(): process `%s' used deprecated " 1470 "clone flags 0x%lx\n", 1471 get_task_comm(comm, current), 1472 clone_flags & CLONE_STOPPED); 1473 } 1474 } 1475 1476 if (unlikely(current->ptrace)) { 1477 trace = fork_traceflag (clone_flags); 1478 if (trace) 1479 clone_flags |= CLONE_PTRACE; 1480 } 1481 1482 p = copy_process(clone_flags, stack_start, regs, stack_size, 1483 child_tidptr, NULL); 1484 /* 1485 * Do this prior waking up the new thread - the thread pointer 1486 * might get invalid after that point, if the thread exits quickly. 1487 */ 1488 if (!IS_ERR(p)) { 1489 struct completion vfork; 1490 1491 nr = task_pid_vnr(p); 1492 1493 if (clone_flags & CLONE_PARENT_SETTID) 1494 put_user(nr, parent_tidptr); 1495 1496 if (clone_flags & CLONE_VFORK) { 1497 p->vfork_done = &vfork; 1498 init_completion(&vfork); 1499 } 1500 1501 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1502 /* 1503 * We'll start up with an immediate SIGSTOP. 1504 */ 1505 sigaddset(&p->pending.signal, SIGSTOP); 1506 set_tsk_thread_flag(p, TIF_SIGPENDING); 1507 } 1508 1509 if (!(clone_flags & CLONE_STOPPED)) 1510 wake_up_new_task(p, clone_flags); 1511 else 1512 __set_task_state(p, TASK_STOPPED); 1513 1514 if (unlikely (trace)) { 1515 current->ptrace_message = nr; 1516 ptrace_notify ((trace << 8) | SIGTRAP); 1517 } 1518 1519 if (clone_flags & CLONE_VFORK) { 1520 freezer_do_not_count(); 1521 wait_for_completion(&vfork); 1522 freezer_count(); 1523 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1524 current->ptrace_message = nr; 1525 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1526 } 1527 } 1528 } else { 1529 nr = PTR_ERR(p); 1530 } 1531 return nr; 1532 } 1533 1534 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1535 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1536 #endif 1537 1538 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1539 { 1540 struct sighand_struct *sighand = data; 1541 1542 spin_lock_init(&sighand->siglock); 1543 init_waitqueue_head(&sighand->signalfd_wqh); 1544 } 1545 1546 void __init proc_caches_init(void) 1547 { 1548 sighand_cachep = kmem_cache_create("sighand_cache", 1549 sizeof(struct sighand_struct), 0, 1550 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1551 sighand_ctor); 1552 signal_cachep = kmem_cache_create("signal_cache", 1553 sizeof(struct signal_struct), 0, 1554 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1555 files_cachep = kmem_cache_create("files_cache", 1556 sizeof(struct files_struct), 0, 1557 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1558 fs_cachep = kmem_cache_create("fs_cache", 1559 sizeof(struct fs_struct), 0, 1560 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1561 vm_area_cachep = kmem_cache_create("vm_area_struct", 1562 sizeof(struct vm_area_struct), 0, 1563 SLAB_PANIC, NULL); 1564 mm_cachep = kmem_cache_create("mm_struct", 1565 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1566 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1567 } 1568 1569 /* 1570 * Check constraints on flags passed to the unshare system call and 1571 * force unsharing of additional process context as appropriate. 1572 */ 1573 static void check_unshare_flags(unsigned long *flags_ptr) 1574 { 1575 /* 1576 * If unsharing a thread from a thread group, must also 1577 * unshare vm. 1578 */ 1579 if (*flags_ptr & CLONE_THREAD) 1580 *flags_ptr |= CLONE_VM; 1581 1582 /* 1583 * If unsharing vm, must also unshare signal handlers. 1584 */ 1585 if (*flags_ptr & CLONE_VM) 1586 *flags_ptr |= CLONE_SIGHAND; 1587 1588 /* 1589 * If unsharing signal handlers and the task was created 1590 * using CLONE_THREAD, then must unshare the thread 1591 */ 1592 if ((*flags_ptr & CLONE_SIGHAND) && 1593 (atomic_read(¤t->signal->count) > 1)) 1594 *flags_ptr |= CLONE_THREAD; 1595 1596 /* 1597 * If unsharing namespace, must also unshare filesystem information. 1598 */ 1599 if (*flags_ptr & CLONE_NEWNS) 1600 *flags_ptr |= CLONE_FS; 1601 } 1602 1603 /* 1604 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1605 */ 1606 static int unshare_thread(unsigned long unshare_flags) 1607 { 1608 if (unshare_flags & CLONE_THREAD) 1609 return -EINVAL; 1610 1611 return 0; 1612 } 1613 1614 /* 1615 * Unshare the filesystem structure if it is being shared 1616 */ 1617 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1618 { 1619 struct fs_struct *fs = current->fs; 1620 1621 if ((unshare_flags & CLONE_FS) && 1622 (fs && atomic_read(&fs->count) > 1)) { 1623 *new_fsp = __copy_fs_struct(current->fs); 1624 if (!*new_fsp) 1625 return -ENOMEM; 1626 } 1627 1628 return 0; 1629 } 1630 1631 /* 1632 * Unsharing of sighand is not supported yet 1633 */ 1634 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1635 { 1636 struct sighand_struct *sigh = current->sighand; 1637 1638 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1639 return -EINVAL; 1640 else 1641 return 0; 1642 } 1643 1644 /* 1645 * Unshare vm if it is being shared 1646 */ 1647 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1648 { 1649 struct mm_struct *mm = current->mm; 1650 1651 if ((unshare_flags & CLONE_VM) && 1652 (mm && atomic_read(&mm->mm_users) > 1)) { 1653 return -EINVAL; 1654 } 1655 1656 return 0; 1657 } 1658 1659 /* 1660 * Unshare file descriptor table if it is being shared 1661 */ 1662 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1663 { 1664 struct files_struct *fd = current->files; 1665 int error = 0; 1666 1667 if ((unshare_flags & CLONE_FILES) && 1668 (fd && atomic_read(&fd->count) > 1)) { 1669 *new_fdp = dup_fd(fd, &error); 1670 if (!*new_fdp) 1671 return error; 1672 } 1673 1674 return 0; 1675 } 1676 1677 /* 1678 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1679 * supported yet 1680 */ 1681 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1682 { 1683 if (unshare_flags & CLONE_SYSVSEM) 1684 return -EINVAL; 1685 1686 return 0; 1687 } 1688 1689 /* 1690 * unshare allows a process to 'unshare' part of the process 1691 * context which was originally shared using clone. copy_* 1692 * functions used by do_fork() cannot be used here directly 1693 * because they modify an inactive task_struct that is being 1694 * constructed. Here we are modifying the current, active, 1695 * task_struct. 1696 */ 1697 asmlinkage long sys_unshare(unsigned long unshare_flags) 1698 { 1699 int err = 0; 1700 struct fs_struct *fs, *new_fs = NULL; 1701 struct sighand_struct *new_sigh = NULL; 1702 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1703 struct files_struct *fd, *new_fd = NULL; 1704 struct sem_undo_list *new_ulist = NULL; 1705 struct nsproxy *new_nsproxy = NULL; 1706 1707 check_unshare_flags(&unshare_flags); 1708 1709 /* Return -EINVAL for all unsupported flags */ 1710 err = -EINVAL; 1711 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1712 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1713 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1714 CLONE_NEWNET)) 1715 goto bad_unshare_out; 1716 1717 if ((err = unshare_thread(unshare_flags))) 1718 goto bad_unshare_out; 1719 if ((err = unshare_fs(unshare_flags, &new_fs))) 1720 goto bad_unshare_cleanup_thread; 1721 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1722 goto bad_unshare_cleanup_fs; 1723 if ((err = unshare_vm(unshare_flags, &new_mm))) 1724 goto bad_unshare_cleanup_sigh; 1725 if ((err = unshare_fd(unshare_flags, &new_fd))) 1726 goto bad_unshare_cleanup_vm; 1727 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1728 goto bad_unshare_cleanup_fd; 1729 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1730 new_fs))) 1731 goto bad_unshare_cleanup_semundo; 1732 1733 if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) { 1734 1735 if (new_nsproxy) { 1736 switch_task_namespaces(current, new_nsproxy); 1737 new_nsproxy = NULL; 1738 } 1739 1740 task_lock(current); 1741 1742 if (new_fs) { 1743 fs = current->fs; 1744 current->fs = new_fs; 1745 new_fs = fs; 1746 } 1747 1748 if (new_mm) { 1749 mm = current->mm; 1750 active_mm = current->active_mm; 1751 current->mm = new_mm; 1752 current->active_mm = new_mm; 1753 activate_mm(active_mm, new_mm); 1754 new_mm = mm; 1755 } 1756 1757 if (new_fd) { 1758 fd = current->files; 1759 current->files = new_fd; 1760 new_fd = fd; 1761 } 1762 1763 task_unlock(current); 1764 } 1765 1766 if (new_nsproxy) 1767 put_nsproxy(new_nsproxy); 1768 1769 bad_unshare_cleanup_semundo: 1770 bad_unshare_cleanup_fd: 1771 if (new_fd) 1772 put_files_struct(new_fd); 1773 1774 bad_unshare_cleanup_vm: 1775 if (new_mm) 1776 mmput(new_mm); 1777 1778 bad_unshare_cleanup_sigh: 1779 if (new_sigh) 1780 if (atomic_dec_and_test(&new_sigh->count)) 1781 kmem_cache_free(sighand_cachep, new_sigh); 1782 1783 bad_unshare_cleanup_fs: 1784 if (new_fs) 1785 put_fs_struct(new_fs); 1786 1787 bad_unshare_cleanup_thread: 1788 bad_unshare_out: 1789 return err; 1790 } 1791