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 /* 136 * macro override instead of weak attribute alias, to workaround 137 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 138 */ 139 #ifndef arch_task_cache_init 140 #define arch_task_cache_init() 141 #endif 142 143 void __init fork_init(unsigned long mempages) 144 { 145 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 146 #ifndef ARCH_MIN_TASKALIGN 147 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 148 #endif 149 /* create a slab on which task_structs can be allocated */ 150 task_struct_cachep = 151 kmem_cache_create("task_struct", sizeof(struct task_struct), 152 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 153 #endif 154 155 /* do the arch specific task caches init */ 156 arch_task_cache_init(); 157 158 /* 159 * The default maximum number of threads is set to a safe 160 * value: the thread structures can take up at most half 161 * of memory. 162 */ 163 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 164 165 /* 166 * we need to allow at least 20 threads to boot a system 167 */ 168 if(max_threads < 20) 169 max_threads = 20; 170 171 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 172 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 173 init_task.signal->rlim[RLIMIT_SIGPENDING] = 174 init_task.signal->rlim[RLIMIT_NPROC]; 175 } 176 177 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 178 struct task_struct *src) 179 { 180 *dst = *src; 181 return 0; 182 } 183 184 static struct task_struct *dup_task_struct(struct task_struct *orig) 185 { 186 struct task_struct *tsk; 187 struct thread_info *ti; 188 int err; 189 190 prepare_to_copy(orig); 191 192 tsk = alloc_task_struct(); 193 if (!tsk) 194 return NULL; 195 196 ti = alloc_thread_info(tsk); 197 if (!ti) { 198 free_task_struct(tsk); 199 return NULL; 200 } 201 202 err = arch_dup_task_struct(tsk, orig); 203 if (err) 204 goto out; 205 206 tsk->stack = ti; 207 208 err = prop_local_init_single(&tsk->dirties); 209 if (err) 210 goto out; 211 212 setup_thread_stack(tsk, orig); 213 214 #ifdef CONFIG_CC_STACKPROTECTOR 215 tsk->stack_canary = get_random_int(); 216 #endif 217 218 /* One for us, one for whoever does the "release_task()" (usually parent) */ 219 atomic_set(&tsk->usage,2); 220 atomic_set(&tsk->fs_excl, 0); 221 #ifdef CONFIG_BLK_DEV_IO_TRACE 222 tsk->btrace_seq = 0; 223 #endif 224 tsk->splice_pipe = NULL; 225 return tsk; 226 227 out: 228 free_thread_info(ti); 229 free_task_struct(tsk); 230 return NULL; 231 } 232 233 #ifdef CONFIG_MMU 234 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 235 { 236 struct vm_area_struct *mpnt, *tmp, **pprev; 237 struct rb_node **rb_link, *rb_parent; 238 int retval; 239 unsigned long charge; 240 struct mempolicy *pol; 241 242 down_write(&oldmm->mmap_sem); 243 flush_cache_dup_mm(oldmm); 244 /* 245 * Not linked in yet - no deadlock potential: 246 */ 247 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 248 249 mm->locked_vm = 0; 250 mm->mmap = NULL; 251 mm->mmap_cache = NULL; 252 mm->free_area_cache = oldmm->mmap_base; 253 mm->cached_hole_size = ~0UL; 254 mm->map_count = 0; 255 cpus_clear(mm->cpu_vm_mask); 256 mm->mm_rb = RB_ROOT; 257 rb_link = &mm->mm_rb.rb_node; 258 rb_parent = NULL; 259 pprev = &mm->mmap; 260 261 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 262 struct file *file; 263 264 if (mpnt->vm_flags & VM_DONTCOPY) { 265 long pages = vma_pages(mpnt); 266 mm->total_vm -= pages; 267 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 268 -pages); 269 continue; 270 } 271 charge = 0; 272 if (mpnt->vm_flags & VM_ACCOUNT) { 273 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 274 if (security_vm_enough_memory(len)) 275 goto fail_nomem; 276 charge = len; 277 } 278 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 279 if (!tmp) 280 goto fail_nomem; 281 *tmp = *mpnt; 282 pol = mpol_dup(vma_policy(mpnt)); 283 retval = PTR_ERR(pol); 284 if (IS_ERR(pol)) 285 goto fail_nomem_policy; 286 vma_set_policy(tmp, pol); 287 tmp->vm_flags &= ~VM_LOCKED; 288 tmp->vm_mm = mm; 289 tmp->vm_next = NULL; 290 anon_vma_link(tmp); 291 file = tmp->vm_file; 292 if (file) { 293 struct inode *inode = file->f_path.dentry->d_inode; 294 get_file(file); 295 if (tmp->vm_flags & VM_DENYWRITE) 296 atomic_dec(&inode->i_writecount); 297 298 /* insert tmp into the share list, just after mpnt */ 299 spin_lock(&file->f_mapping->i_mmap_lock); 300 tmp->vm_truncate_count = mpnt->vm_truncate_count; 301 flush_dcache_mmap_lock(file->f_mapping); 302 vma_prio_tree_add(tmp, mpnt); 303 flush_dcache_mmap_unlock(file->f_mapping); 304 spin_unlock(&file->f_mapping->i_mmap_lock); 305 } 306 307 /* 308 * Link in the new vma and copy the page table entries. 309 */ 310 *pprev = tmp; 311 pprev = &tmp->vm_next; 312 313 __vma_link_rb(mm, tmp, rb_link, rb_parent); 314 rb_link = &tmp->vm_rb.rb_right; 315 rb_parent = &tmp->vm_rb; 316 317 mm->map_count++; 318 retval = copy_page_range(mm, oldmm, mpnt); 319 320 if (tmp->vm_ops && tmp->vm_ops->open) 321 tmp->vm_ops->open(tmp); 322 323 if (retval) 324 goto out; 325 } 326 /* a new mm has just been created */ 327 arch_dup_mmap(oldmm, mm); 328 retval = 0; 329 out: 330 up_write(&mm->mmap_sem); 331 flush_tlb_mm(oldmm); 332 up_write(&oldmm->mmap_sem); 333 return retval; 334 fail_nomem_policy: 335 kmem_cache_free(vm_area_cachep, tmp); 336 fail_nomem: 337 retval = -ENOMEM; 338 vm_unacct_memory(charge); 339 goto out; 340 } 341 342 static inline int mm_alloc_pgd(struct mm_struct * mm) 343 { 344 mm->pgd = pgd_alloc(mm); 345 if (unlikely(!mm->pgd)) 346 return -ENOMEM; 347 return 0; 348 } 349 350 static inline void mm_free_pgd(struct mm_struct * mm) 351 { 352 pgd_free(mm, mm->pgd); 353 } 354 #else 355 #define dup_mmap(mm, oldmm) (0) 356 #define mm_alloc_pgd(mm) (0) 357 #define mm_free_pgd(mm) 358 #endif /* CONFIG_MMU */ 359 360 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 361 362 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 363 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 364 365 #include <linux/init_task.h> 366 367 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 368 { 369 atomic_set(&mm->mm_users, 1); 370 atomic_set(&mm->mm_count, 1); 371 init_rwsem(&mm->mmap_sem); 372 INIT_LIST_HEAD(&mm->mmlist); 373 mm->flags = (current->mm) ? current->mm->flags 374 : MMF_DUMP_FILTER_DEFAULT; 375 mm->core_waiters = 0; 376 mm->nr_ptes = 0; 377 set_mm_counter(mm, file_rss, 0); 378 set_mm_counter(mm, anon_rss, 0); 379 spin_lock_init(&mm->page_table_lock); 380 rwlock_init(&mm->ioctx_list_lock); 381 mm->ioctx_list = NULL; 382 mm->free_area_cache = TASK_UNMAPPED_BASE; 383 mm->cached_hole_size = ~0UL; 384 mm_init_owner(mm, p); 385 386 if (likely(!mm_alloc_pgd(mm))) { 387 mm->def_flags = 0; 388 return mm; 389 } 390 391 free_mm(mm); 392 return NULL; 393 } 394 395 /* 396 * Allocate and initialize an mm_struct. 397 */ 398 struct mm_struct * mm_alloc(void) 399 { 400 struct mm_struct * mm; 401 402 mm = allocate_mm(); 403 if (mm) { 404 memset(mm, 0, sizeof(*mm)); 405 mm = mm_init(mm, current); 406 } 407 return mm; 408 } 409 410 /* 411 * Called when the last reference to the mm 412 * is dropped: either by a lazy thread or by 413 * mmput. Free the page directory and the mm. 414 */ 415 void __mmdrop(struct mm_struct *mm) 416 { 417 BUG_ON(mm == &init_mm); 418 mm_free_pgd(mm); 419 destroy_context(mm); 420 free_mm(mm); 421 } 422 EXPORT_SYMBOL_GPL(__mmdrop); 423 424 /* 425 * Decrement the use count and release all resources for an mm. 426 */ 427 void mmput(struct mm_struct *mm) 428 { 429 might_sleep(); 430 431 if (atomic_dec_and_test(&mm->mm_users)) { 432 exit_aio(mm); 433 exit_mmap(mm); 434 set_mm_exe_file(mm, NULL); 435 if (!list_empty(&mm->mmlist)) { 436 spin_lock(&mmlist_lock); 437 list_del(&mm->mmlist); 438 spin_unlock(&mmlist_lock); 439 } 440 put_swap_token(mm); 441 mmdrop(mm); 442 } 443 } 444 EXPORT_SYMBOL_GPL(mmput); 445 446 /** 447 * get_task_mm - acquire a reference to the task's mm 448 * 449 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 450 * this kernel workthread has transiently adopted a user mm with use_mm, 451 * to do its AIO) is not set and if so returns a reference to it, after 452 * bumping up the use count. User must release the mm via mmput() 453 * after use. Typically used by /proc and ptrace. 454 */ 455 struct mm_struct *get_task_mm(struct task_struct *task) 456 { 457 struct mm_struct *mm; 458 459 task_lock(task); 460 mm = task->mm; 461 if (mm) { 462 if (task->flags & PF_BORROWED_MM) 463 mm = NULL; 464 else 465 atomic_inc(&mm->mm_users); 466 } 467 task_unlock(task); 468 return mm; 469 } 470 EXPORT_SYMBOL_GPL(get_task_mm); 471 472 /* Please note the differences between mmput and mm_release. 473 * mmput is called whenever we stop holding onto a mm_struct, 474 * error success whatever. 475 * 476 * mm_release is called after a mm_struct has been removed 477 * from the current process. 478 * 479 * This difference is important for error handling, when we 480 * only half set up a mm_struct for a new process and need to restore 481 * the old one. Because we mmput the new mm_struct before 482 * restoring the old one. . . 483 * Eric Biederman 10 January 1998 484 */ 485 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 486 { 487 struct completion *vfork_done = tsk->vfork_done; 488 489 /* Get rid of any cached register state */ 490 deactivate_mm(tsk, mm); 491 492 /* notify parent sleeping on vfork() */ 493 if (vfork_done) { 494 tsk->vfork_done = NULL; 495 complete(vfork_done); 496 } 497 498 /* 499 * If we're exiting normally, clear a user-space tid field if 500 * requested. We leave this alone when dying by signal, to leave 501 * the value intact in a core dump, and to save the unnecessary 502 * trouble otherwise. Userland only wants this done for a sys_exit. 503 */ 504 if (tsk->clear_child_tid 505 && !(tsk->flags & PF_SIGNALED) 506 && atomic_read(&mm->mm_users) > 1) { 507 u32 __user * tidptr = tsk->clear_child_tid; 508 tsk->clear_child_tid = NULL; 509 510 /* 511 * We don't check the error code - if userspace has 512 * not set up a proper pointer then tough luck. 513 */ 514 put_user(0, tidptr); 515 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 516 } 517 } 518 519 /* 520 * Allocate a new mm structure and copy contents from the 521 * mm structure of the passed in task structure. 522 */ 523 struct mm_struct *dup_mm(struct task_struct *tsk) 524 { 525 struct mm_struct *mm, *oldmm = current->mm; 526 int err; 527 528 if (!oldmm) 529 return NULL; 530 531 mm = allocate_mm(); 532 if (!mm) 533 goto fail_nomem; 534 535 memcpy(mm, oldmm, sizeof(*mm)); 536 537 /* Initializing for Swap token stuff */ 538 mm->token_priority = 0; 539 mm->last_interval = 0; 540 541 if (!mm_init(mm, tsk)) 542 goto fail_nomem; 543 544 if (init_new_context(tsk, mm)) 545 goto fail_nocontext; 546 547 dup_mm_exe_file(oldmm, mm); 548 549 err = dup_mmap(mm, oldmm); 550 if (err) 551 goto free_pt; 552 553 mm->hiwater_rss = get_mm_rss(mm); 554 mm->hiwater_vm = mm->total_vm; 555 556 return mm; 557 558 free_pt: 559 mmput(mm); 560 561 fail_nomem: 562 return NULL; 563 564 fail_nocontext: 565 /* 566 * If init_new_context() failed, we cannot use mmput() to free the mm 567 * because it calls destroy_context() 568 */ 569 mm_free_pgd(mm); 570 free_mm(mm); 571 return NULL; 572 } 573 574 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 575 { 576 struct mm_struct * mm, *oldmm; 577 int retval; 578 579 tsk->min_flt = tsk->maj_flt = 0; 580 tsk->nvcsw = tsk->nivcsw = 0; 581 582 tsk->mm = NULL; 583 tsk->active_mm = NULL; 584 585 /* 586 * Are we cloning a kernel thread? 587 * 588 * We need to steal a active VM for that.. 589 */ 590 oldmm = current->mm; 591 if (!oldmm) 592 return 0; 593 594 if (clone_flags & CLONE_VM) { 595 atomic_inc(&oldmm->mm_users); 596 mm = oldmm; 597 goto good_mm; 598 } 599 600 retval = -ENOMEM; 601 mm = dup_mm(tsk); 602 if (!mm) 603 goto fail_nomem; 604 605 good_mm: 606 /* Initializing for Swap token stuff */ 607 mm->token_priority = 0; 608 mm->last_interval = 0; 609 610 tsk->mm = mm; 611 tsk->active_mm = mm; 612 return 0; 613 614 fail_nomem: 615 return retval; 616 } 617 618 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 619 { 620 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 621 /* We don't need to lock fs - think why ;-) */ 622 if (fs) { 623 atomic_set(&fs->count, 1); 624 rwlock_init(&fs->lock); 625 fs->umask = old->umask; 626 read_lock(&old->lock); 627 fs->root = old->root; 628 path_get(&old->root); 629 fs->pwd = old->pwd; 630 path_get(&old->pwd); 631 if (old->altroot.dentry) { 632 fs->altroot = old->altroot; 633 path_get(&old->altroot); 634 } else { 635 fs->altroot.mnt = NULL; 636 fs->altroot.dentry = NULL; 637 } 638 read_unlock(&old->lock); 639 } 640 return fs; 641 } 642 643 struct fs_struct *copy_fs_struct(struct fs_struct *old) 644 { 645 return __copy_fs_struct(old); 646 } 647 648 EXPORT_SYMBOL_GPL(copy_fs_struct); 649 650 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 651 { 652 if (clone_flags & CLONE_FS) { 653 atomic_inc(¤t->fs->count); 654 return 0; 655 } 656 tsk->fs = __copy_fs_struct(current->fs); 657 if (!tsk->fs) 658 return -ENOMEM; 659 return 0; 660 } 661 662 static int count_open_files(struct fdtable *fdt) 663 { 664 int size = fdt->max_fds; 665 int i; 666 667 /* Find the last open fd */ 668 for (i = size/(8*sizeof(long)); i > 0; ) { 669 if (fdt->open_fds->fds_bits[--i]) 670 break; 671 } 672 i = (i+1) * 8 * sizeof(long); 673 return i; 674 } 675 676 static struct files_struct *alloc_files(void) 677 { 678 struct files_struct *newf; 679 struct fdtable *fdt; 680 681 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); 682 if (!newf) 683 goto out; 684 685 atomic_set(&newf->count, 1); 686 687 spin_lock_init(&newf->file_lock); 688 newf->next_fd = 0; 689 fdt = &newf->fdtab; 690 fdt->max_fds = NR_OPEN_DEFAULT; 691 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 692 fdt->open_fds = (fd_set *)&newf->open_fds_init; 693 fdt->fd = &newf->fd_array[0]; 694 INIT_RCU_HEAD(&fdt->rcu); 695 fdt->next = NULL; 696 rcu_assign_pointer(newf->fdt, fdt); 697 out: 698 return newf; 699 } 700 701 /* 702 * Allocate a new files structure and copy contents from the 703 * passed in files structure. 704 * errorp will be valid only when the returned files_struct is NULL. 705 */ 706 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 707 { 708 struct files_struct *newf; 709 struct file **old_fds, **new_fds; 710 int open_files, size, i; 711 struct fdtable *old_fdt, *new_fdt; 712 713 *errorp = -ENOMEM; 714 newf = alloc_files(); 715 if (!newf) 716 goto out; 717 718 spin_lock(&oldf->file_lock); 719 old_fdt = files_fdtable(oldf); 720 new_fdt = files_fdtable(newf); 721 open_files = count_open_files(old_fdt); 722 723 /* 724 * Check whether we need to allocate a larger fd array and fd set. 725 * Note: we're not a clone task, so the open count won't change. 726 */ 727 if (open_files > new_fdt->max_fds) { 728 new_fdt->max_fds = 0; 729 spin_unlock(&oldf->file_lock); 730 spin_lock(&newf->file_lock); 731 *errorp = expand_files(newf, open_files-1); 732 spin_unlock(&newf->file_lock); 733 if (*errorp < 0) 734 goto out_release; 735 new_fdt = files_fdtable(newf); 736 /* 737 * Reacquire the oldf lock and a pointer to its fd table 738 * who knows it may have a new bigger fd table. We need 739 * the latest pointer. 740 */ 741 spin_lock(&oldf->file_lock); 742 old_fdt = files_fdtable(oldf); 743 } 744 745 old_fds = old_fdt->fd; 746 new_fds = new_fdt->fd; 747 748 memcpy(new_fdt->open_fds->fds_bits, 749 old_fdt->open_fds->fds_bits, open_files/8); 750 memcpy(new_fdt->close_on_exec->fds_bits, 751 old_fdt->close_on_exec->fds_bits, open_files/8); 752 753 for (i = open_files; i != 0; i--) { 754 struct file *f = *old_fds++; 755 if (f) { 756 get_file(f); 757 } else { 758 /* 759 * The fd may be claimed in the fd bitmap but not yet 760 * instantiated in the files array if a sibling thread 761 * is partway through open(). So make sure that this 762 * fd is available to the new process. 763 */ 764 FD_CLR(open_files - i, new_fdt->open_fds); 765 } 766 rcu_assign_pointer(*new_fds++, f); 767 } 768 spin_unlock(&oldf->file_lock); 769 770 /* compute the remainder to be cleared */ 771 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 772 773 /* This is long word aligned thus could use a optimized version */ 774 memset(new_fds, 0, size); 775 776 if (new_fdt->max_fds > open_files) { 777 int left = (new_fdt->max_fds-open_files)/8; 778 int start = open_files / (8 * sizeof(unsigned long)); 779 780 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 781 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 782 } 783 784 return newf; 785 786 out_release: 787 kmem_cache_free(files_cachep, newf); 788 out: 789 return NULL; 790 } 791 792 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 793 { 794 struct files_struct *oldf, *newf; 795 int error = 0; 796 797 /* 798 * A background process may not have any files ... 799 */ 800 oldf = current->files; 801 if (!oldf) 802 goto out; 803 804 if (clone_flags & CLONE_FILES) { 805 atomic_inc(&oldf->count); 806 goto out; 807 } 808 809 newf = dup_fd(oldf, &error); 810 if (!newf) 811 goto out; 812 813 tsk->files = newf; 814 error = 0; 815 out: 816 return error; 817 } 818 819 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 820 { 821 #ifdef CONFIG_BLOCK 822 struct io_context *ioc = current->io_context; 823 824 if (!ioc) 825 return 0; 826 /* 827 * Share io context with parent, if CLONE_IO is set 828 */ 829 if (clone_flags & CLONE_IO) { 830 tsk->io_context = ioc_task_link(ioc); 831 if (unlikely(!tsk->io_context)) 832 return -ENOMEM; 833 } else if (ioprio_valid(ioc->ioprio)) { 834 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 835 if (unlikely(!tsk->io_context)) 836 return -ENOMEM; 837 838 tsk->io_context->ioprio = ioc->ioprio; 839 } 840 #endif 841 return 0; 842 } 843 844 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 845 { 846 struct sighand_struct *sig; 847 848 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 849 atomic_inc(¤t->sighand->count); 850 return 0; 851 } 852 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 853 rcu_assign_pointer(tsk->sighand, sig); 854 if (!sig) 855 return -ENOMEM; 856 atomic_set(&sig->count, 1); 857 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 858 return 0; 859 } 860 861 void __cleanup_sighand(struct sighand_struct *sighand) 862 { 863 if (atomic_dec_and_test(&sighand->count)) 864 kmem_cache_free(sighand_cachep, sighand); 865 } 866 867 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 868 { 869 struct signal_struct *sig; 870 int ret; 871 872 if (clone_flags & CLONE_THREAD) { 873 atomic_inc(¤t->signal->count); 874 atomic_inc(¤t->signal->live); 875 return 0; 876 } 877 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 878 tsk->signal = sig; 879 if (!sig) 880 return -ENOMEM; 881 882 ret = copy_thread_group_keys(tsk); 883 if (ret < 0) { 884 kmem_cache_free(signal_cachep, sig); 885 return ret; 886 } 887 888 atomic_set(&sig->count, 1); 889 atomic_set(&sig->live, 1); 890 init_waitqueue_head(&sig->wait_chldexit); 891 sig->flags = 0; 892 sig->group_exit_code = 0; 893 sig->group_exit_task = NULL; 894 sig->group_stop_count = 0; 895 sig->curr_target = tsk; 896 init_sigpending(&sig->shared_pending); 897 INIT_LIST_HEAD(&sig->posix_timers); 898 899 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 900 sig->it_real_incr.tv64 = 0; 901 sig->real_timer.function = it_real_fn; 902 903 sig->it_virt_expires = cputime_zero; 904 sig->it_virt_incr = cputime_zero; 905 sig->it_prof_expires = cputime_zero; 906 sig->it_prof_incr = cputime_zero; 907 908 sig->leader = 0; /* session leadership doesn't inherit */ 909 sig->tty_old_pgrp = NULL; 910 911 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 912 sig->gtime = cputime_zero; 913 sig->cgtime = cputime_zero; 914 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 915 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 916 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 917 sig->sum_sched_runtime = 0; 918 INIT_LIST_HEAD(&sig->cpu_timers[0]); 919 INIT_LIST_HEAD(&sig->cpu_timers[1]); 920 INIT_LIST_HEAD(&sig->cpu_timers[2]); 921 taskstats_tgid_init(sig); 922 923 task_lock(current->group_leader); 924 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 925 task_unlock(current->group_leader); 926 927 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 928 /* 929 * New sole thread in the process gets an expiry time 930 * of the whole CPU time limit. 931 */ 932 tsk->it_prof_expires = 933 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 934 } 935 acct_init_pacct(&sig->pacct); 936 937 tty_audit_fork(sig); 938 939 return 0; 940 } 941 942 void __cleanup_signal(struct signal_struct *sig) 943 { 944 exit_thread_group_keys(sig); 945 kmem_cache_free(signal_cachep, sig); 946 } 947 948 static void cleanup_signal(struct task_struct *tsk) 949 { 950 struct signal_struct *sig = tsk->signal; 951 952 atomic_dec(&sig->live); 953 954 if (atomic_dec_and_test(&sig->count)) 955 __cleanup_signal(sig); 956 } 957 958 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 959 { 960 unsigned long new_flags = p->flags; 961 962 new_flags &= ~PF_SUPERPRIV; 963 new_flags |= PF_FORKNOEXEC; 964 if (!(clone_flags & CLONE_PTRACE)) 965 p->ptrace = 0; 966 p->flags = new_flags; 967 clear_freeze_flag(p); 968 } 969 970 asmlinkage long sys_set_tid_address(int __user *tidptr) 971 { 972 current->clear_child_tid = tidptr; 973 974 return task_pid_vnr(current); 975 } 976 977 static void rt_mutex_init_task(struct task_struct *p) 978 { 979 spin_lock_init(&p->pi_lock); 980 #ifdef CONFIG_RT_MUTEXES 981 plist_head_init(&p->pi_waiters, &p->pi_lock); 982 p->pi_blocked_on = NULL; 983 #endif 984 } 985 986 #ifdef CONFIG_MM_OWNER 987 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 988 { 989 mm->owner = p; 990 } 991 #endif /* CONFIG_MM_OWNER */ 992 993 /* 994 * This creates a new process as a copy of the old one, 995 * but does not actually start it yet. 996 * 997 * It copies the registers, and all the appropriate 998 * parts of the process environment (as per the clone 999 * flags). The actual kick-off is left to the caller. 1000 */ 1001 static struct task_struct *copy_process(unsigned long clone_flags, 1002 unsigned long stack_start, 1003 struct pt_regs *regs, 1004 unsigned long stack_size, 1005 int __user *child_tidptr, 1006 struct pid *pid) 1007 { 1008 int retval; 1009 struct task_struct *p; 1010 int cgroup_callbacks_done = 0; 1011 1012 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1013 return ERR_PTR(-EINVAL); 1014 1015 /* 1016 * Thread groups must share signals as well, and detached threads 1017 * can only be started up within the thread group. 1018 */ 1019 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1020 return ERR_PTR(-EINVAL); 1021 1022 /* 1023 * Shared signal handlers imply shared VM. By way of the above, 1024 * thread groups also imply shared VM. Blocking this case allows 1025 * for various simplifications in other code. 1026 */ 1027 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1028 return ERR_PTR(-EINVAL); 1029 1030 retval = security_task_create(clone_flags); 1031 if (retval) 1032 goto fork_out; 1033 1034 retval = -ENOMEM; 1035 p = dup_task_struct(current); 1036 if (!p) 1037 goto fork_out; 1038 1039 rt_mutex_init_task(p); 1040 1041 #ifdef CONFIG_TRACE_IRQFLAGS 1042 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1043 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1044 #endif 1045 retval = -EAGAIN; 1046 if (atomic_read(&p->user->processes) >= 1047 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1048 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1049 p->user != current->nsproxy->user_ns->root_user) 1050 goto bad_fork_free; 1051 } 1052 1053 atomic_inc(&p->user->__count); 1054 atomic_inc(&p->user->processes); 1055 get_group_info(p->group_info); 1056 1057 /* 1058 * If multiple threads are within copy_process(), then this check 1059 * triggers too late. This doesn't hurt, the check is only there 1060 * to stop root fork bombs. 1061 */ 1062 if (nr_threads >= max_threads) 1063 goto bad_fork_cleanup_count; 1064 1065 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1066 goto bad_fork_cleanup_count; 1067 1068 if (p->binfmt && !try_module_get(p->binfmt->module)) 1069 goto bad_fork_cleanup_put_domain; 1070 1071 p->did_exec = 0; 1072 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1073 copy_flags(clone_flags, p); 1074 INIT_LIST_HEAD(&p->children); 1075 INIT_LIST_HEAD(&p->sibling); 1076 #ifdef CONFIG_PREEMPT_RCU 1077 p->rcu_read_lock_nesting = 0; 1078 p->rcu_flipctr_idx = 0; 1079 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1080 p->vfork_done = NULL; 1081 spin_lock_init(&p->alloc_lock); 1082 1083 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1084 init_sigpending(&p->pending); 1085 1086 p->utime = cputime_zero; 1087 p->stime = cputime_zero; 1088 p->gtime = cputime_zero; 1089 p->utimescaled = cputime_zero; 1090 p->stimescaled = cputime_zero; 1091 p->prev_utime = cputime_zero; 1092 p->prev_stime = cputime_zero; 1093 1094 #ifdef CONFIG_DETECT_SOFTLOCKUP 1095 p->last_switch_count = 0; 1096 p->last_switch_timestamp = 0; 1097 #endif 1098 1099 #ifdef CONFIG_TASK_XACCT 1100 p->rchar = 0; /* I/O counter: bytes read */ 1101 p->wchar = 0; /* I/O counter: bytes written */ 1102 p->syscr = 0; /* I/O counter: read syscalls */ 1103 p->syscw = 0; /* I/O counter: write syscalls */ 1104 #endif 1105 task_io_accounting_init(p); 1106 acct_clear_integrals(p); 1107 1108 p->it_virt_expires = cputime_zero; 1109 p->it_prof_expires = cputime_zero; 1110 p->it_sched_expires = 0; 1111 INIT_LIST_HEAD(&p->cpu_timers[0]); 1112 INIT_LIST_HEAD(&p->cpu_timers[1]); 1113 INIT_LIST_HEAD(&p->cpu_timers[2]); 1114 1115 p->lock_depth = -1; /* -1 = no lock */ 1116 do_posix_clock_monotonic_gettime(&p->start_time); 1117 p->real_start_time = p->start_time; 1118 monotonic_to_bootbased(&p->real_start_time); 1119 #ifdef CONFIG_SECURITY 1120 p->security = NULL; 1121 #endif 1122 p->cap_bset = current->cap_bset; 1123 p->io_context = NULL; 1124 p->audit_context = NULL; 1125 cgroup_fork(p); 1126 #ifdef CONFIG_NUMA 1127 p->mempolicy = mpol_dup(p->mempolicy); 1128 if (IS_ERR(p->mempolicy)) { 1129 retval = PTR_ERR(p->mempolicy); 1130 p->mempolicy = NULL; 1131 goto bad_fork_cleanup_cgroup; 1132 } 1133 mpol_fix_fork_child_flag(p); 1134 #endif 1135 #ifdef CONFIG_TRACE_IRQFLAGS 1136 p->irq_events = 0; 1137 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1138 p->hardirqs_enabled = 1; 1139 #else 1140 p->hardirqs_enabled = 0; 1141 #endif 1142 p->hardirq_enable_ip = 0; 1143 p->hardirq_enable_event = 0; 1144 p->hardirq_disable_ip = _THIS_IP_; 1145 p->hardirq_disable_event = 0; 1146 p->softirqs_enabled = 1; 1147 p->softirq_enable_ip = _THIS_IP_; 1148 p->softirq_enable_event = 0; 1149 p->softirq_disable_ip = 0; 1150 p->softirq_disable_event = 0; 1151 p->hardirq_context = 0; 1152 p->softirq_context = 0; 1153 #endif 1154 #ifdef CONFIG_LOCKDEP 1155 p->lockdep_depth = 0; /* no locks held yet */ 1156 p->curr_chain_key = 0; 1157 p->lockdep_recursion = 0; 1158 #endif 1159 1160 #ifdef CONFIG_DEBUG_MUTEXES 1161 p->blocked_on = NULL; /* not blocked yet */ 1162 #endif 1163 1164 /* Perform scheduler related setup. Assign this task to a CPU. */ 1165 sched_fork(p, clone_flags); 1166 1167 if ((retval = security_task_alloc(p))) 1168 goto bad_fork_cleanup_policy; 1169 if ((retval = audit_alloc(p))) 1170 goto bad_fork_cleanup_security; 1171 /* copy all the process information */ 1172 if ((retval = copy_semundo(clone_flags, p))) 1173 goto bad_fork_cleanup_audit; 1174 if ((retval = copy_files(clone_flags, p))) 1175 goto bad_fork_cleanup_semundo; 1176 if ((retval = copy_fs(clone_flags, p))) 1177 goto bad_fork_cleanup_files; 1178 if ((retval = copy_sighand(clone_flags, p))) 1179 goto bad_fork_cleanup_fs; 1180 if ((retval = copy_signal(clone_flags, p))) 1181 goto bad_fork_cleanup_sighand; 1182 if ((retval = copy_mm(clone_flags, p))) 1183 goto bad_fork_cleanup_signal; 1184 if ((retval = copy_keys(clone_flags, p))) 1185 goto bad_fork_cleanup_mm; 1186 if ((retval = copy_namespaces(clone_flags, p))) 1187 goto bad_fork_cleanup_keys; 1188 if ((retval = copy_io(clone_flags, p))) 1189 goto bad_fork_cleanup_namespaces; 1190 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1191 if (retval) 1192 goto bad_fork_cleanup_io; 1193 1194 if (pid != &init_struct_pid) { 1195 retval = -ENOMEM; 1196 pid = alloc_pid(task_active_pid_ns(p)); 1197 if (!pid) 1198 goto bad_fork_cleanup_io; 1199 1200 if (clone_flags & CLONE_NEWPID) { 1201 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1202 if (retval < 0) 1203 goto bad_fork_free_pid; 1204 } 1205 } 1206 1207 p->pid = pid_nr(pid); 1208 p->tgid = p->pid; 1209 if (clone_flags & CLONE_THREAD) 1210 p->tgid = current->tgid; 1211 1212 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1213 /* 1214 * Clear TID on mm_release()? 1215 */ 1216 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1217 #ifdef CONFIG_FUTEX 1218 p->robust_list = NULL; 1219 #ifdef CONFIG_COMPAT 1220 p->compat_robust_list = NULL; 1221 #endif 1222 INIT_LIST_HEAD(&p->pi_state_list); 1223 p->pi_state_cache = NULL; 1224 #endif 1225 /* 1226 * sigaltstack should be cleared when sharing the same VM 1227 */ 1228 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1229 p->sas_ss_sp = p->sas_ss_size = 0; 1230 1231 /* 1232 * Syscall tracing should be turned off in the child regardless 1233 * of CLONE_PTRACE. 1234 */ 1235 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1236 #ifdef TIF_SYSCALL_EMU 1237 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1238 #endif 1239 clear_all_latency_tracing(p); 1240 1241 /* Our parent execution domain becomes current domain 1242 These must match for thread signalling to apply */ 1243 p->parent_exec_id = p->self_exec_id; 1244 1245 /* ok, now we should be set up.. */ 1246 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1247 p->pdeath_signal = 0; 1248 p->exit_state = 0; 1249 1250 /* 1251 * Ok, make it visible to the rest of the system. 1252 * We dont wake it up yet. 1253 */ 1254 p->group_leader = p; 1255 INIT_LIST_HEAD(&p->thread_group); 1256 INIT_LIST_HEAD(&p->ptrace_children); 1257 INIT_LIST_HEAD(&p->ptrace_list); 1258 1259 /* Now that the task is set up, run cgroup callbacks if 1260 * necessary. We need to run them before the task is visible 1261 * on the tasklist. */ 1262 cgroup_fork_callbacks(p); 1263 cgroup_callbacks_done = 1; 1264 1265 /* Need tasklist lock for parent etc handling! */ 1266 write_lock_irq(&tasklist_lock); 1267 1268 /* 1269 * The task hasn't been attached yet, so its cpus_allowed mask will 1270 * not be changed, nor will its assigned CPU. 1271 * 1272 * The cpus_allowed mask of the parent may have changed after it was 1273 * copied first time - so re-copy it here, then check the child's CPU 1274 * to ensure it is on a valid CPU (and if not, just force it back to 1275 * parent's CPU). This avoids alot of nasty races. 1276 */ 1277 p->cpus_allowed = current->cpus_allowed; 1278 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1279 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1280 !cpu_online(task_cpu(p)))) 1281 set_task_cpu(p, smp_processor_id()); 1282 1283 /* CLONE_PARENT re-uses the old parent */ 1284 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1285 p->real_parent = current->real_parent; 1286 else 1287 p->real_parent = current; 1288 p->parent = p->real_parent; 1289 1290 spin_lock(¤t->sighand->siglock); 1291 1292 /* 1293 * Process group and session signals need to be delivered to just the 1294 * parent before the fork or both the parent and the child after the 1295 * fork. Restart if a signal comes in before we add the new process to 1296 * it's process group. 1297 * A fatal signal pending means that current will exit, so the new 1298 * thread can't slip out of an OOM kill (or normal SIGKILL). 1299 */ 1300 recalc_sigpending(); 1301 if (signal_pending(current)) { 1302 spin_unlock(¤t->sighand->siglock); 1303 write_unlock_irq(&tasklist_lock); 1304 retval = -ERESTARTNOINTR; 1305 goto bad_fork_free_pid; 1306 } 1307 1308 if (clone_flags & CLONE_THREAD) { 1309 p->group_leader = current->group_leader; 1310 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1311 1312 if (!cputime_eq(current->signal->it_virt_expires, 1313 cputime_zero) || 1314 !cputime_eq(current->signal->it_prof_expires, 1315 cputime_zero) || 1316 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1317 !list_empty(¤t->signal->cpu_timers[0]) || 1318 !list_empty(¤t->signal->cpu_timers[1]) || 1319 !list_empty(¤t->signal->cpu_timers[2])) { 1320 /* 1321 * Have child wake up on its first tick to check 1322 * for process CPU timers. 1323 */ 1324 p->it_prof_expires = jiffies_to_cputime(1); 1325 } 1326 } 1327 1328 if (likely(p->pid)) { 1329 add_parent(p); 1330 if (unlikely(p->ptrace & PT_PTRACED)) 1331 __ptrace_link(p, current->parent); 1332 1333 if (thread_group_leader(p)) { 1334 if (clone_flags & CLONE_NEWPID) 1335 p->nsproxy->pid_ns->child_reaper = p; 1336 1337 p->signal->leader_pid = pid; 1338 p->signal->tty = current->signal->tty; 1339 set_task_pgrp(p, task_pgrp_nr(current)); 1340 set_task_session(p, task_session_nr(current)); 1341 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1342 attach_pid(p, PIDTYPE_SID, task_session(current)); 1343 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1344 __get_cpu_var(process_counts)++; 1345 } 1346 attach_pid(p, PIDTYPE_PID, pid); 1347 nr_threads++; 1348 } 1349 1350 total_forks++; 1351 spin_unlock(¤t->sighand->siglock); 1352 write_unlock_irq(&tasklist_lock); 1353 proc_fork_connector(p); 1354 cgroup_post_fork(p); 1355 return p; 1356 1357 bad_fork_free_pid: 1358 if (pid != &init_struct_pid) 1359 free_pid(pid); 1360 bad_fork_cleanup_io: 1361 put_io_context(p->io_context); 1362 bad_fork_cleanup_namespaces: 1363 exit_task_namespaces(p); 1364 bad_fork_cleanup_keys: 1365 exit_keys(p); 1366 bad_fork_cleanup_mm: 1367 if (p->mm) 1368 mmput(p->mm); 1369 bad_fork_cleanup_signal: 1370 cleanup_signal(p); 1371 bad_fork_cleanup_sighand: 1372 __cleanup_sighand(p->sighand); 1373 bad_fork_cleanup_fs: 1374 exit_fs(p); /* blocking */ 1375 bad_fork_cleanup_files: 1376 exit_files(p); /* blocking */ 1377 bad_fork_cleanup_semundo: 1378 exit_sem(p); 1379 bad_fork_cleanup_audit: 1380 audit_free(p); 1381 bad_fork_cleanup_security: 1382 security_task_free(p); 1383 bad_fork_cleanup_policy: 1384 #ifdef CONFIG_NUMA 1385 mpol_put(p->mempolicy); 1386 bad_fork_cleanup_cgroup: 1387 #endif 1388 cgroup_exit(p, cgroup_callbacks_done); 1389 delayacct_tsk_free(p); 1390 if (p->binfmt) 1391 module_put(p->binfmt->module); 1392 bad_fork_cleanup_put_domain: 1393 module_put(task_thread_info(p)->exec_domain->module); 1394 bad_fork_cleanup_count: 1395 put_group_info(p->group_info); 1396 atomic_dec(&p->user->processes); 1397 free_uid(p->user); 1398 bad_fork_free: 1399 free_task(p); 1400 fork_out: 1401 return ERR_PTR(retval); 1402 } 1403 1404 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1405 { 1406 memset(regs, 0, sizeof(struct pt_regs)); 1407 return regs; 1408 } 1409 1410 struct task_struct * __cpuinit fork_idle(int cpu) 1411 { 1412 struct task_struct *task; 1413 struct pt_regs regs; 1414 1415 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1416 &init_struct_pid); 1417 if (!IS_ERR(task)) 1418 init_idle(task, cpu); 1419 1420 return task; 1421 } 1422 1423 static int fork_traceflag(unsigned clone_flags) 1424 { 1425 if (clone_flags & CLONE_UNTRACED) 1426 return 0; 1427 else if (clone_flags & CLONE_VFORK) { 1428 if (current->ptrace & PT_TRACE_VFORK) 1429 return PTRACE_EVENT_VFORK; 1430 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1431 if (current->ptrace & PT_TRACE_CLONE) 1432 return PTRACE_EVENT_CLONE; 1433 } else if (current->ptrace & PT_TRACE_FORK) 1434 return PTRACE_EVENT_FORK; 1435 1436 return 0; 1437 } 1438 1439 /* 1440 * Ok, this is the main fork-routine. 1441 * 1442 * It copies the process, and if successful kick-starts 1443 * it and waits for it to finish using the VM if required. 1444 */ 1445 long do_fork(unsigned long clone_flags, 1446 unsigned long stack_start, 1447 struct pt_regs *regs, 1448 unsigned long stack_size, 1449 int __user *parent_tidptr, 1450 int __user *child_tidptr) 1451 { 1452 struct task_struct *p; 1453 int trace = 0; 1454 long nr; 1455 1456 /* 1457 * We hope to recycle these flags after 2.6.26 1458 */ 1459 if (unlikely(clone_flags & CLONE_STOPPED)) { 1460 static int __read_mostly count = 100; 1461 1462 if (count > 0 && printk_ratelimit()) { 1463 char comm[TASK_COMM_LEN]; 1464 1465 count--; 1466 printk(KERN_INFO "fork(): process `%s' used deprecated " 1467 "clone flags 0x%lx\n", 1468 get_task_comm(comm, current), 1469 clone_flags & CLONE_STOPPED); 1470 } 1471 } 1472 1473 if (unlikely(current->ptrace)) { 1474 trace = fork_traceflag (clone_flags); 1475 if (trace) 1476 clone_flags |= CLONE_PTRACE; 1477 } 1478 1479 p = copy_process(clone_flags, stack_start, regs, stack_size, 1480 child_tidptr, NULL); 1481 /* 1482 * Do this prior waking up the new thread - the thread pointer 1483 * might get invalid after that point, if the thread exits quickly. 1484 */ 1485 if (!IS_ERR(p)) { 1486 struct completion vfork; 1487 1488 nr = task_pid_vnr(p); 1489 1490 if (clone_flags & CLONE_PARENT_SETTID) 1491 put_user(nr, parent_tidptr); 1492 1493 if (clone_flags & CLONE_VFORK) { 1494 p->vfork_done = &vfork; 1495 init_completion(&vfork); 1496 } 1497 1498 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1499 /* 1500 * We'll start up with an immediate SIGSTOP. 1501 */ 1502 sigaddset(&p->pending.signal, SIGSTOP); 1503 set_tsk_thread_flag(p, TIF_SIGPENDING); 1504 } 1505 1506 if (!(clone_flags & CLONE_STOPPED)) 1507 wake_up_new_task(p, clone_flags); 1508 else 1509 __set_task_state(p, TASK_STOPPED); 1510 1511 if (unlikely (trace)) { 1512 current->ptrace_message = nr; 1513 ptrace_notify ((trace << 8) | SIGTRAP); 1514 } 1515 1516 if (clone_flags & CLONE_VFORK) { 1517 freezer_do_not_count(); 1518 wait_for_completion(&vfork); 1519 freezer_count(); 1520 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1521 current->ptrace_message = nr; 1522 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1523 } 1524 } 1525 } else { 1526 nr = PTR_ERR(p); 1527 } 1528 return nr; 1529 } 1530 1531 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1532 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1533 #endif 1534 1535 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1536 { 1537 struct sighand_struct *sighand = data; 1538 1539 spin_lock_init(&sighand->siglock); 1540 init_waitqueue_head(&sighand->signalfd_wqh); 1541 } 1542 1543 void __init proc_caches_init(void) 1544 { 1545 sighand_cachep = kmem_cache_create("sighand_cache", 1546 sizeof(struct sighand_struct), 0, 1547 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1548 sighand_ctor); 1549 signal_cachep = kmem_cache_create("signal_cache", 1550 sizeof(struct signal_struct), 0, 1551 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1552 files_cachep = kmem_cache_create("files_cache", 1553 sizeof(struct files_struct), 0, 1554 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1555 fs_cachep = kmem_cache_create("fs_cache", 1556 sizeof(struct fs_struct), 0, 1557 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1558 vm_area_cachep = kmem_cache_create("vm_area_struct", 1559 sizeof(struct vm_area_struct), 0, 1560 SLAB_PANIC, NULL); 1561 mm_cachep = kmem_cache_create("mm_struct", 1562 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1563 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1564 } 1565 1566 /* 1567 * Check constraints on flags passed to the unshare system call and 1568 * force unsharing of additional process context as appropriate. 1569 */ 1570 static void check_unshare_flags(unsigned long *flags_ptr) 1571 { 1572 /* 1573 * If unsharing a thread from a thread group, must also 1574 * unshare vm. 1575 */ 1576 if (*flags_ptr & CLONE_THREAD) 1577 *flags_ptr |= CLONE_VM; 1578 1579 /* 1580 * If unsharing vm, must also unshare signal handlers. 1581 */ 1582 if (*flags_ptr & CLONE_VM) 1583 *flags_ptr |= CLONE_SIGHAND; 1584 1585 /* 1586 * If unsharing signal handlers and the task was created 1587 * using CLONE_THREAD, then must unshare the thread 1588 */ 1589 if ((*flags_ptr & CLONE_SIGHAND) && 1590 (atomic_read(¤t->signal->count) > 1)) 1591 *flags_ptr |= CLONE_THREAD; 1592 1593 /* 1594 * If unsharing namespace, must also unshare filesystem information. 1595 */ 1596 if (*flags_ptr & CLONE_NEWNS) 1597 *flags_ptr |= CLONE_FS; 1598 } 1599 1600 /* 1601 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1602 */ 1603 static int unshare_thread(unsigned long unshare_flags) 1604 { 1605 if (unshare_flags & CLONE_THREAD) 1606 return -EINVAL; 1607 1608 return 0; 1609 } 1610 1611 /* 1612 * Unshare the filesystem structure if it is being shared 1613 */ 1614 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1615 { 1616 struct fs_struct *fs = current->fs; 1617 1618 if ((unshare_flags & CLONE_FS) && 1619 (fs && atomic_read(&fs->count) > 1)) { 1620 *new_fsp = __copy_fs_struct(current->fs); 1621 if (!*new_fsp) 1622 return -ENOMEM; 1623 } 1624 1625 return 0; 1626 } 1627 1628 /* 1629 * Unsharing of sighand is not supported yet 1630 */ 1631 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1632 { 1633 struct sighand_struct *sigh = current->sighand; 1634 1635 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1636 return -EINVAL; 1637 else 1638 return 0; 1639 } 1640 1641 /* 1642 * Unshare vm if it is being shared 1643 */ 1644 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1645 { 1646 struct mm_struct *mm = current->mm; 1647 1648 if ((unshare_flags & CLONE_VM) && 1649 (mm && atomic_read(&mm->mm_users) > 1)) { 1650 return -EINVAL; 1651 } 1652 1653 return 0; 1654 } 1655 1656 /* 1657 * Unshare file descriptor table if it is being shared 1658 */ 1659 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1660 { 1661 struct files_struct *fd = current->files; 1662 int error = 0; 1663 1664 if ((unshare_flags & CLONE_FILES) && 1665 (fd && atomic_read(&fd->count) > 1)) { 1666 *new_fdp = dup_fd(fd, &error); 1667 if (!*new_fdp) 1668 return error; 1669 } 1670 1671 return 0; 1672 } 1673 1674 /* 1675 * unshare allows a process to 'unshare' part of the process 1676 * context which was originally shared using clone. copy_* 1677 * functions used by do_fork() cannot be used here directly 1678 * because they modify an inactive task_struct that is being 1679 * constructed. Here we are modifying the current, active, 1680 * task_struct. 1681 */ 1682 asmlinkage long sys_unshare(unsigned long unshare_flags) 1683 { 1684 int err = 0; 1685 struct fs_struct *fs, *new_fs = NULL; 1686 struct sighand_struct *new_sigh = NULL; 1687 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1688 struct files_struct *fd, *new_fd = NULL; 1689 struct nsproxy *new_nsproxy = NULL; 1690 int do_sysvsem = 0; 1691 1692 check_unshare_flags(&unshare_flags); 1693 1694 /* Return -EINVAL for all unsupported flags */ 1695 err = -EINVAL; 1696 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1697 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1698 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1699 CLONE_NEWNET)) 1700 goto bad_unshare_out; 1701 1702 /* 1703 * CLONE_NEWIPC must also detach from the undolist: after switching 1704 * to a new ipc namespace, the semaphore arrays from the old 1705 * namespace are unreachable. 1706 */ 1707 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1708 do_sysvsem = 1; 1709 if ((err = unshare_thread(unshare_flags))) 1710 goto bad_unshare_out; 1711 if ((err = unshare_fs(unshare_flags, &new_fs))) 1712 goto bad_unshare_cleanup_thread; 1713 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1714 goto bad_unshare_cleanup_fs; 1715 if ((err = unshare_vm(unshare_flags, &new_mm))) 1716 goto bad_unshare_cleanup_sigh; 1717 if ((err = unshare_fd(unshare_flags, &new_fd))) 1718 goto bad_unshare_cleanup_vm; 1719 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1720 new_fs))) 1721 goto bad_unshare_cleanup_fd; 1722 1723 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1724 if (do_sysvsem) { 1725 /* 1726 * CLONE_SYSVSEM is equivalent to sys_exit(). 1727 */ 1728 exit_sem(current); 1729 } 1730 1731 if (new_nsproxy) { 1732 switch_task_namespaces(current, new_nsproxy); 1733 new_nsproxy = NULL; 1734 } 1735 1736 task_lock(current); 1737 1738 if (new_fs) { 1739 fs = current->fs; 1740 current->fs = new_fs; 1741 new_fs = fs; 1742 } 1743 1744 if (new_mm) { 1745 mm = current->mm; 1746 active_mm = current->active_mm; 1747 current->mm = new_mm; 1748 current->active_mm = new_mm; 1749 activate_mm(active_mm, new_mm); 1750 new_mm = mm; 1751 } 1752 1753 if (new_fd) { 1754 fd = current->files; 1755 current->files = new_fd; 1756 new_fd = fd; 1757 } 1758 1759 task_unlock(current); 1760 } 1761 1762 if (new_nsproxy) 1763 put_nsproxy(new_nsproxy); 1764 1765 bad_unshare_cleanup_fd: 1766 if (new_fd) 1767 put_files_struct(new_fd); 1768 1769 bad_unshare_cleanup_vm: 1770 if (new_mm) 1771 mmput(new_mm); 1772 1773 bad_unshare_cleanup_sigh: 1774 if (new_sigh) 1775 if (atomic_dec_and_test(&new_sigh->count)) 1776 kmem_cache_free(sighand_cachep, new_sigh); 1777 1778 bad_unshare_cleanup_fs: 1779 if (new_fs) 1780 put_fs_struct(new_fs); 1781 1782 bad_unshare_cleanup_thread: 1783 bad_unshare_out: 1784 return err; 1785 } 1786 1787 /* 1788 * Helper to unshare the files of the current task. 1789 * We don't want to expose copy_files internals to 1790 * the exec layer of the kernel. 1791 */ 1792 1793 int unshare_files(struct files_struct **displaced) 1794 { 1795 struct task_struct *task = current; 1796 struct files_struct *copy = NULL; 1797 int error; 1798 1799 error = unshare_fd(CLONE_FILES, ©); 1800 if (error || !copy) { 1801 *displaced = NULL; 1802 return error; 1803 } 1804 *displaced = task->files; 1805 task_lock(task); 1806 task->files = copy; 1807 task_unlock(task); 1808 return 0; 1809 } 1810