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