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/fdtable.h> 26 #include <linux/iocontext.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/mmu_notifier.h> 31 #include <linux/fs.h> 32 #include <linux/nsproxy.h> 33 #include <linux/capability.h> 34 #include <linux/cpu.h> 35 #include <linux/cgroup.h> 36 #include <linux/security.h> 37 #include <linux/hugetlb.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/tracehook.h> 42 #include <linux/futex.h> 43 #include <linux/compat.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/acct.h> 53 #include <linux/tsacct_kern.h> 54 #include <linux/cn_proc.h> 55 #include <linux/freezer.h> 56 #include <linux/delayacct.h> 57 #include <linux/taskstats_kern.h> 58 #include <linux/random.h> 59 #include <linux/tty.h> 60 #include <linux/proc_fs.h> 61 #include <linux/blkdev.h> 62 #include <trace/sched.h> 63 64 #include <asm/pgtable.h> 65 #include <asm/pgalloc.h> 66 #include <asm/uaccess.h> 67 #include <asm/mmu_context.h> 68 #include <asm/cacheflush.h> 69 #include <asm/tlbflush.h> 70 71 /* 72 * Protected counters by write_lock_irq(&tasklist_lock) 73 */ 74 unsigned long total_forks; /* Handle normal Linux uptimes. */ 75 int nr_threads; /* The idle threads do not count.. */ 76 77 int max_threads; /* tunable limit on nr_threads */ 78 79 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 80 81 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 82 83 int nr_processes(void) 84 { 85 int cpu; 86 int total = 0; 87 88 for_each_online_cpu(cpu) 89 total += per_cpu(process_counts, cpu); 90 91 return total; 92 } 93 94 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 95 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 96 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 97 static struct kmem_cache *task_struct_cachep; 98 #endif 99 100 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 101 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 102 { 103 #ifdef CONFIG_DEBUG_STACK_USAGE 104 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 105 #else 106 gfp_t mask = GFP_KERNEL; 107 #endif 108 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 109 } 110 111 static inline void free_thread_info(struct thread_info *ti) 112 { 113 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 114 } 115 #endif 116 117 /* SLAB cache for signal_struct structures (tsk->signal) */ 118 static struct kmem_cache *signal_cachep; 119 120 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 121 struct kmem_cache *sighand_cachep; 122 123 /* SLAB cache for files_struct structures (tsk->files) */ 124 struct kmem_cache *files_cachep; 125 126 /* SLAB cache for fs_struct structures (tsk->fs) */ 127 struct kmem_cache *fs_cachep; 128 129 /* SLAB cache for vm_area_struct structures */ 130 struct kmem_cache *vm_area_cachep; 131 132 /* SLAB cache for mm_struct structures (tsk->mm) */ 133 static struct kmem_cache *mm_cachep; 134 135 void free_task(struct task_struct *tsk) 136 { 137 prop_local_destroy_single(&tsk->dirties); 138 free_thread_info(tsk->stack); 139 rt_mutex_debug_task_free(tsk); 140 free_task_struct(tsk); 141 } 142 EXPORT_SYMBOL(free_task); 143 144 void __put_task_struct(struct task_struct *tsk) 145 { 146 WARN_ON(!tsk->exit_state); 147 WARN_ON(atomic_read(&tsk->usage)); 148 WARN_ON(tsk == current); 149 150 security_task_free(tsk); 151 free_uid(tsk->user); 152 put_group_info(tsk->group_info); 153 delayacct_tsk_free(tsk); 154 155 if (!profile_handoff_task(tsk)) 156 free_task(tsk); 157 } 158 159 /* 160 * macro override instead of weak attribute alias, to workaround 161 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 162 */ 163 #ifndef arch_task_cache_init 164 #define arch_task_cache_init() 165 #endif 166 167 void __init fork_init(unsigned long mempages) 168 { 169 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 170 #ifndef ARCH_MIN_TASKALIGN 171 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 172 #endif 173 /* create a slab on which task_structs can be allocated */ 174 task_struct_cachep = 175 kmem_cache_create("task_struct", sizeof(struct task_struct), 176 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 177 #endif 178 179 /* do the arch specific task caches init */ 180 arch_task_cache_init(); 181 182 /* 183 * The default maximum number of threads is set to a safe 184 * value: the thread structures can take up at most half 185 * of memory. 186 */ 187 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 188 189 /* 190 * we need to allow at least 20 threads to boot a system 191 */ 192 if(max_threads < 20) 193 max_threads = 20; 194 195 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 196 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 197 init_task.signal->rlim[RLIMIT_SIGPENDING] = 198 init_task.signal->rlim[RLIMIT_NPROC]; 199 } 200 201 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 202 struct task_struct *src) 203 { 204 *dst = *src; 205 return 0; 206 } 207 208 static struct task_struct *dup_task_struct(struct task_struct *orig) 209 { 210 struct task_struct *tsk; 211 struct thread_info *ti; 212 int err; 213 214 prepare_to_copy(orig); 215 216 tsk = alloc_task_struct(); 217 if (!tsk) 218 return NULL; 219 220 ti = alloc_thread_info(tsk); 221 if (!ti) { 222 free_task_struct(tsk); 223 return NULL; 224 } 225 226 err = arch_dup_task_struct(tsk, orig); 227 if (err) 228 goto out; 229 230 tsk->stack = ti; 231 232 err = prop_local_init_single(&tsk->dirties); 233 if (err) 234 goto out; 235 236 setup_thread_stack(tsk, orig); 237 238 #ifdef CONFIG_CC_STACKPROTECTOR 239 tsk->stack_canary = get_random_int(); 240 #endif 241 242 /* One for us, one for whoever does the "release_task()" (usually parent) */ 243 atomic_set(&tsk->usage,2); 244 atomic_set(&tsk->fs_excl, 0); 245 #ifdef CONFIG_BLK_DEV_IO_TRACE 246 tsk->btrace_seq = 0; 247 #endif 248 tsk->splice_pipe = NULL; 249 return tsk; 250 251 out: 252 free_thread_info(ti); 253 free_task_struct(tsk); 254 return NULL; 255 } 256 257 #ifdef CONFIG_MMU 258 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 259 { 260 struct vm_area_struct *mpnt, *tmp, **pprev; 261 struct rb_node **rb_link, *rb_parent; 262 int retval; 263 unsigned long charge; 264 struct mempolicy *pol; 265 266 down_write(&oldmm->mmap_sem); 267 flush_cache_dup_mm(oldmm); 268 /* 269 * Not linked in yet - no deadlock potential: 270 */ 271 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 272 273 mm->locked_vm = 0; 274 mm->mmap = NULL; 275 mm->mmap_cache = NULL; 276 mm->free_area_cache = oldmm->mmap_base; 277 mm->cached_hole_size = ~0UL; 278 mm->map_count = 0; 279 cpus_clear(mm->cpu_vm_mask); 280 mm->mm_rb = RB_ROOT; 281 rb_link = &mm->mm_rb.rb_node; 282 rb_parent = NULL; 283 pprev = &mm->mmap; 284 285 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 286 struct file *file; 287 288 if (mpnt->vm_flags & VM_DONTCOPY) { 289 long pages = vma_pages(mpnt); 290 mm->total_vm -= pages; 291 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 292 -pages); 293 continue; 294 } 295 charge = 0; 296 if (mpnt->vm_flags & VM_ACCOUNT) { 297 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 298 if (security_vm_enough_memory(len)) 299 goto fail_nomem; 300 charge = len; 301 } 302 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 303 if (!tmp) 304 goto fail_nomem; 305 *tmp = *mpnt; 306 pol = mpol_dup(vma_policy(mpnt)); 307 retval = PTR_ERR(pol); 308 if (IS_ERR(pol)) 309 goto fail_nomem_policy; 310 vma_set_policy(tmp, pol); 311 tmp->vm_flags &= ~VM_LOCKED; 312 tmp->vm_mm = mm; 313 tmp->vm_next = NULL; 314 anon_vma_link(tmp); 315 file = tmp->vm_file; 316 if (file) { 317 struct inode *inode = file->f_path.dentry->d_inode; 318 struct address_space *mapping = file->f_mapping; 319 320 get_file(file); 321 if (tmp->vm_flags & VM_DENYWRITE) 322 atomic_dec(&inode->i_writecount); 323 spin_lock(&mapping->i_mmap_lock); 324 if (tmp->vm_flags & VM_SHARED) 325 mapping->i_mmap_writable++; 326 tmp->vm_truncate_count = mpnt->vm_truncate_count; 327 flush_dcache_mmap_lock(mapping); 328 /* insert tmp into the share list, just after mpnt */ 329 vma_prio_tree_add(tmp, mpnt); 330 flush_dcache_mmap_unlock(mapping); 331 spin_unlock(&mapping->i_mmap_lock); 332 } 333 334 /* 335 * Clear hugetlb-related page reserves for children. This only 336 * affects MAP_PRIVATE mappings. Faults generated by the child 337 * are not guaranteed to succeed, even if read-only 338 */ 339 if (is_vm_hugetlb_page(tmp)) 340 reset_vma_resv_huge_pages(tmp); 341 342 /* 343 * Link in the new vma and copy the page table entries. 344 */ 345 *pprev = tmp; 346 pprev = &tmp->vm_next; 347 348 __vma_link_rb(mm, tmp, rb_link, rb_parent); 349 rb_link = &tmp->vm_rb.rb_right; 350 rb_parent = &tmp->vm_rb; 351 352 mm->map_count++; 353 retval = copy_page_range(mm, oldmm, mpnt); 354 355 if (tmp->vm_ops && tmp->vm_ops->open) 356 tmp->vm_ops->open(tmp); 357 358 if (retval) 359 goto out; 360 } 361 /* a new mm has just been created */ 362 arch_dup_mmap(oldmm, mm); 363 retval = 0; 364 out: 365 up_write(&mm->mmap_sem); 366 flush_tlb_mm(oldmm); 367 up_write(&oldmm->mmap_sem); 368 return retval; 369 fail_nomem_policy: 370 kmem_cache_free(vm_area_cachep, tmp); 371 fail_nomem: 372 retval = -ENOMEM; 373 vm_unacct_memory(charge); 374 goto out; 375 } 376 377 static inline int mm_alloc_pgd(struct mm_struct * mm) 378 { 379 mm->pgd = pgd_alloc(mm); 380 if (unlikely(!mm->pgd)) 381 return -ENOMEM; 382 return 0; 383 } 384 385 static inline void mm_free_pgd(struct mm_struct * mm) 386 { 387 pgd_free(mm, mm->pgd); 388 } 389 #else 390 #define dup_mmap(mm, oldmm) (0) 391 #define mm_alloc_pgd(mm) (0) 392 #define mm_free_pgd(mm) 393 #endif /* CONFIG_MMU */ 394 395 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 396 397 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 398 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 399 400 #include <linux/init_task.h> 401 402 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 403 { 404 atomic_set(&mm->mm_users, 1); 405 atomic_set(&mm->mm_count, 1); 406 init_rwsem(&mm->mmap_sem); 407 INIT_LIST_HEAD(&mm->mmlist); 408 mm->flags = (current->mm) ? current->mm->flags 409 : MMF_DUMP_FILTER_DEFAULT; 410 mm->core_state = NULL; 411 mm->nr_ptes = 0; 412 set_mm_counter(mm, file_rss, 0); 413 set_mm_counter(mm, anon_rss, 0); 414 spin_lock_init(&mm->page_table_lock); 415 rwlock_init(&mm->ioctx_list_lock); 416 mm->ioctx_list = NULL; 417 mm->free_area_cache = TASK_UNMAPPED_BASE; 418 mm->cached_hole_size = ~0UL; 419 mm_init_owner(mm, p); 420 421 if (likely(!mm_alloc_pgd(mm))) { 422 mm->def_flags = 0; 423 mmu_notifier_mm_init(mm); 424 return mm; 425 } 426 427 free_mm(mm); 428 return NULL; 429 } 430 431 /* 432 * Allocate and initialize an mm_struct. 433 */ 434 struct mm_struct * mm_alloc(void) 435 { 436 struct mm_struct * mm; 437 438 mm = allocate_mm(); 439 if (mm) { 440 memset(mm, 0, sizeof(*mm)); 441 mm = mm_init(mm, current); 442 } 443 return mm; 444 } 445 446 /* 447 * Called when the last reference to the mm 448 * is dropped: either by a lazy thread or by 449 * mmput. Free the page directory and the mm. 450 */ 451 void __mmdrop(struct mm_struct *mm) 452 { 453 BUG_ON(mm == &init_mm); 454 mm_free_pgd(mm); 455 destroy_context(mm); 456 mmu_notifier_mm_destroy(mm); 457 free_mm(mm); 458 } 459 EXPORT_SYMBOL_GPL(__mmdrop); 460 461 /* 462 * Decrement the use count and release all resources for an mm. 463 */ 464 void mmput(struct mm_struct *mm) 465 { 466 might_sleep(); 467 468 if (atomic_dec_and_test(&mm->mm_users)) { 469 exit_aio(mm); 470 exit_mmap(mm); 471 set_mm_exe_file(mm, NULL); 472 if (!list_empty(&mm->mmlist)) { 473 spin_lock(&mmlist_lock); 474 list_del(&mm->mmlist); 475 spin_unlock(&mmlist_lock); 476 } 477 put_swap_token(mm); 478 mmdrop(mm); 479 } 480 } 481 EXPORT_SYMBOL_GPL(mmput); 482 483 /** 484 * get_task_mm - acquire a reference to the task's mm 485 * 486 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 487 * this kernel workthread has transiently adopted a user mm with use_mm, 488 * to do its AIO) is not set and if so returns a reference to it, after 489 * bumping up the use count. User must release the mm via mmput() 490 * after use. Typically used by /proc and ptrace. 491 */ 492 struct mm_struct *get_task_mm(struct task_struct *task) 493 { 494 struct mm_struct *mm; 495 496 task_lock(task); 497 mm = task->mm; 498 if (mm) { 499 if (task->flags & PF_KTHREAD) 500 mm = NULL; 501 else 502 atomic_inc(&mm->mm_users); 503 } 504 task_unlock(task); 505 return mm; 506 } 507 EXPORT_SYMBOL_GPL(get_task_mm); 508 509 /* Please note the differences between mmput and mm_release. 510 * mmput is called whenever we stop holding onto a mm_struct, 511 * error success whatever. 512 * 513 * mm_release is called after a mm_struct has been removed 514 * from the current process. 515 * 516 * This difference is important for error handling, when we 517 * only half set up a mm_struct for a new process and need to restore 518 * the old one. Because we mmput the new mm_struct before 519 * restoring the old one. . . 520 * Eric Biederman 10 January 1998 521 */ 522 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 523 { 524 struct completion *vfork_done = tsk->vfork_done; 525 526 /* Get rid of any futexes when releasing the mm */ 527 #ifdef CONFIG_FUTEX 528 if (unlikely(tsk->robust_list)) 529 exit_robust_list(tsk); 530 #ifdef CONFIG_COMPAT 531 if (unlikely(tsk->compat_robust_list)) 532 compat_exit_robust_list(tsk); 533 #endif 534 #endif 535 536 /* Get rid of any cached register state */ 537 deactivate_mm(tsk, mm); 538 539 /* notify parent sleeping on vfork() */ 540 if (vfork_done) { 541 tsk->vfork_done = NULL; 542 complete(vfork_done); 543 } 544 545 /* 546 * If we're exiting normally, clear a user-space tid field if 547 * requested. We leave this alone when dying by signal, to leave 548 * the value intact in a core dump, and to save the unnecessary 549 * trouble otherwise. Userland only wants this done for a sys_exit. 550 */ 551 if (tsk->clear_child_tid 552 && !(tsk->flags & PF_SIGNALED) 553 && atomic_read(&mm->mm_users) > 1) { 554 u32 __user * tidptr = tsk->clear_child_tid; 555 tsk->clear_child_tid = NULL; 556 557 /* 558 * We don't check the error code - if userspace has 559 * not set up a proper pointer then tough luck. 560 */ 561 put_user(0, tidptr); 562 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 563 } 564 } 565 566 /* 567 * Allocate a new mm structure and copy contents from the 568 * mm structure of the passed in task structure. 569 */ 570 struct mm_struct *dup_mm(struct task_struct *tsk) 571 { 572 struct mm_struct *mm, *oldmm = current->mm; 573 int err; 574 575 if (!oldmm) 576 return NULL; 577 578 mm = allocate_mm(); 579 if (!mm) 580 goto fail_nomem; 581 582 memcpy(mm, oldmm, sizeof(*mm)); 583 584 /* Initializing for Swap token stuff */ 585 mm->token_priority = 0; 586 mm->last_interval = 0; 587 588 if (!mm_init(mm, tsk)) 589 goto fail_nomem; 590 591 if (init_new_context(tsk, mm)) 592 goto fail_nocontext; 593 594 dup_mm_exe_file(oldmm, mm); 595 596 err = dup_mmap(mm, oldmm); 597 if (err) 598 goto free_pt; 599 600 mm->hiwater_rss = get_mm_rss(mm); 601 mm->hiwater_vm = mm->total_vm; 602 603 return mm; 604 605 free_pt: 606 mmput(mm); 607 608 fail_nomem: 609 return NULL; 610 611 fail_nocontext: 612 /* 613 * If init_new_context() failed, we cannot use mmput() to free the mm 614 * because it calls destroy_context() 615 */ 616 mm_free_pgd(mm); 617 free_mm(mm); 618 return NULL; 619 } 620 621 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 622 { 623 struct mm_struct * mm, *oldmm; 624 int retval; 625 626 tsk->min_flt = tsk->maj_flt = 0; 627 tsk->nvcsw = tsk->nivcsw = 0; 628 629 tsk->mm = NULL; 630 tsk->active_mm = NULL; 631 632 /* 633 * Are we cloning a kernel thread? 634 * 635 * We need to steal a active VM for that.. 636 */ 637 oldmm = current->mm; 638 if (!oldmm) 639 return 0; 640 641 if (clone_flags & CLONE_VM) { 642 atomic_inc(&oldmm->mm_users); 643 mm = oldmm; 644 goto good_mm; 645 } 646 647 retval = -ENOMEM; 648 mm = dup_mm(tsk); 649 if (!mm) 650 goto fail_nomem; 651 652 good_mm: 653 /* Initializing for Swap token stuff */ 654 mm->token_priority = 0; 655 mm->last_interval = 0; 656 657 tsk->mm = mm; 658 tsk->active_mm = mm; 659 return 0; 660 661 fail_nomem: 662 return retval; 663 } 664 665 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 666 { 667 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 668 /* We don't need to lock fs - think why ;-) */ 669 if (fs) { 670 atomic_set(&fs->count, 1); 671 rwlock_init(&fs->lock); 672 fs->umask = old->umask; 673 read_lock(&old->lock); 674 fs->root = old->root; 675 path_get(&old->root); 676 fs->pwd = old->pwd; 677 path_get(&old->pwd); 678 read_unlock(&old->lock); 679 } 680 return fs; 681 } 682 683 struct fs_struct *copy_fs_struct(struct fs_struct *old) 684 { 685 return __copy_fs_struct(old); 686 } 687 688 EXPORT_SYMBOL_GPL(copy_fs_struct); 689 690 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 691 { 692 if (clone_flags & CLONE_FS) { 693 atomic_inc(¤t->fs->count); 694 return 0; 695 } 696 tsk->fs = __copy_fs_struct(current->fs); 697 if (!tsk->fs) 698 return -ENOMEM; 699 return 0; 700 } 701 702 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 703 { 704 struct files_struct *oldf, *newf; 705 int error = 0; 706 707 /* 708 * A background process may not have any files ... 709 */ 710 oldf = current->files; 711 if (!oldf) 712 goto out; 713 714 if (clone_flags & CLONE_FILES) { 715 atomic_inc(&oldf->count); 716 goto out; 717 } 718 719 newf = dup_fd(oldf, &error); 720 if (!newf) 721 goto out; 722 723 tsk->files = newf; 724 error = 0; 725 out: 726 return error; 727 } 728 729 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 730 { 731 #ifdef CONFIG_BLOCK 732 struct io_context *ioc = current->io_context; 733 734 if (!ioc) 735 return 0; 736 /* 737 * Share io context with parent, if CLONE_IO is set 738 */ 739 if (clone_flags & CLONE_IO) { 740 tsk->io_context = ioc_task_link(ioc); 741 if (unlikely(!tsk->io_context)) 742 return -ENOMEM; 743 } else if (ioprio_valid(ioc->ioprio)) { 744 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 745 if (unlikely(!tsk->io_context)) 746 return -ENOMEM; 747 748 tsk->io_context->ioprio = ioc->ioprio; 749 } 750 #endif 751 return 0; 752 } 753 754 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 755 { 756 struct sighand_struct *sig; 757 758 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 759 atomic_inc(¤t->sighand->count); 760 return 0; 761 } 762 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 763 rcu_assign_pointer(tsk->sighand, sig); 764 if (!sig) 765 return -ENOMEM; 766 atomic_set(&sig->count, 1); 767 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 768 return 0; 769 } 770 771 void __cleanup_sighand(struct sighand_struct *sighand) 772 { 773 if (atomic_dec_and_test(&sighand->count)) 774 kmem_cache_free(sighand_cachep, sighand); 775 } 776 777 778 /* 779 * Initialize POSIX timer handling for a thread group. 780 */ 781 static void posix_cpu_timers_init_group(struct signal_struct *sig) 782 { 783 /* Thread group counters. */ 784 thread_group_cputime_init(sig); 785 786 /* Expiration times and increments. */ 787 sig->it_virt_expires = cputime_zero; 788 sig->it_virt_incr = cputime_zero; 789 sig->it_prof_expires = cputime_zero; 790 sig->it_prof_incr = cputime_zero; 791 792 /* Cached expiration times. */ 793 sig->cputime_expires.prof_exp = cputime_zero; 794 sig->cputime_expires.virt_exp = cputime_zero; 795 sig->cputime_expires.sched_exp = 0; 796 797 /* The timer lists. */ 798 INIT_LIST_HEAD(&sig->cpu_timers[0]); 799 INIT_LIST_HEAD(&sig->cpu_timers[1]); 800 INIT_LIST_HEAD(&sig->cpu_timers[2]); 801 } 802 803 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 804 { 805 struct signal_struct *sig; 806 int ret; 807 808 if (clone_flags & CLONE_THREAD) { 809 ret = thread_group_cputime_clone_thread(current); 810 if (likely(!ret)) { 811 atomic_inc(¤t->signal->count); 812 atomic_inc(¤t->signal->live); 813 } 814 return ret; 815 } 816 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 817 tsk->signal = sig; 818 if (!sig) 819 return -ENOMEM; 820 821 ret = copy_thread_group_keys(tsk); 822 if (ret < 0) { 823 kmem_cache_free(signal_cachep, sig); 824 return ret; 825 } 826 827 atomic_set(&sig->count, 1); 828 atomic_set(&sig->live, 1); 829 init_waitqueue_head(&sig->wait_chldexit); 830 sig->flags = 0; 831 sig->group_exit_code = 0; 832 sig->group_exit_task = NULL; 833 sig->group_stop_count = 0; 834 sig->curr_target = tsk; 835 init_sigpending(&sig->shared_pending); 836 INIT_LIST_HEAD(&sig->posix_timers); 837 838 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 839 sig->it_real_incr.tv64 = 0; 840 sig->real_timer.function = it_real_fn; 841 842 sig->leader = 0; /* session leadership doesn't inherit */ 843 sig->tty_old_pgrp = NULL; 844 sig->tty = NULL; 845 846 sig->cutime = sig->cstime = cputime_zero; 847 sig->gtime = cputime_zero; 848 sig->cgtime = cputime_zero; 849 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 850 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 851 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 852 task_io_accounting_init(&sig->ioac); 853 taskstats_tgid_init(sig); 854 855 task_lock(current->group_leader); 856 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 857 task_unlock(current->group_leader); 858 859 posix_cpu_timers_init_group(sig); 860 861 acct_init_pacct(&sig->pacct); 862 863 tty_audit_fork(sig); 864 865 return 0; 866 } 867 868 void __cleanup_signal(struct signal_struct *sig) 869 { 870 thread_group_cputime_free(sig); 871 exit_thread_group_keys(sig); 872 tty_kref_put(sig->tty); 873 kmem_cache_free(signal_cachep, sig); 874 } 875 876 static void cleanup_signal(struct task_struct *tsk) 877 { 878 struct signal_struct *sig = tsk->signal; 879 880 atomic_dec(&sig->live); 881 882 if (atomic_dec_and_test(&sig->count)) 883 __cleanup_signal(sig); 884 } 885 886 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 887 { 888 unsigned long new_flags = p->flags; 889 890 new_flags &= ~PF_SUPERPRIV; 891 new_flags |= PF_FORKNOEXEC; 892 new_flags |= PF_STARTING; 893 p->flags = new_flags; 894 clear_freeze_flag(p); 895 } 896 897 asmlinkage long sys_set_tid_address(int __user *tidptr) 898 { 899 current->clear_child_tid = tidptr; 900 901 return task_pid_vnr(current); 902 } 903 904 static void rt_mutex_init_task(struct task_struct *p) 905 { 906 spin_lock_init(&p->pi_lock); 907 #ifdef CONFIG_RT_MUTEXES 908 plist_head_init(&p->pi_waiters, &p->pi_lock); 909 p->pi_blocked_on = NULL; 910 #endif 911 } 912 913 #ifdef CONFIG_MM_OWNER 914 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 915 { 916 mm->owner = p; 917 } 918 #endif /* CONFIG_MM_OWNER */ 919 920 /* 921 * Initialize POSIX timer handling for a single task. 922 */ 923 static void posix_cpu_timers_init(struct task_struct *tsk) 924 { 925 tsk->cputime_expires.prof_exp = cputime_zero; 926 tsk->cputime_expires.virt_exp = cputime_zero; 927 tsk->cputime_expires.sched_exp = 0; 928 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 929 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 930 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 931 } 932 933 /* 934 * This creates a new process as a copy of the old one, 935 * but does not actually start it yet. 936 * 937 * It copies the registers, and all the appropriate 938 * parts of the process environment (as per the clone 939 * flags). The actual kick-off is left to the caller. 940 */ 941 static struct task_struct *copy_process(unsigned long clone_flags, 942 unsigned long stack_start, 943 struct pt_regs *regs, 944 unsigned long stack_size, 945 int __user *child_tidptr, 946 struct pid *pid, 947 int trace) 948 { 949 int retval; 950 struct task_struct *p; 951 int cgroup_callbacks_done = 0; 952 953 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 954 return ERR_PTR(-EINVAL); 955 956 /* 957 * Thread groups must share signals as well, and detached threads 958 * can only be started up within the thread group. 959 */ 960 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 961 return ERR_PTR(-EINVAL); 962 963 /* 964 * Shared signal handlers imply shared VM. By way of the above, 965 * thread groups also imply shared VM. Blocking this case allows 966 * for various simplifications in other code. 967 */ 968 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 969 return ERR_PTR(-EINVAL); 970 971 retval = security_task_create(clone_flags); 972 if (retval) 973 goto fork_out; 974 975 retval = -ENOMEM; 976 p = dup_task_struct(current); 977 if (!p) 978 goto fork_out; 979 980 rt_mutex_init_task(p); 981 982 #ifdef CONFIG_PROVE_LOCKING 983 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 984 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 985 #endif 986 retval = -EAGAIN; 987 if (atomic_read(&p->user->processes) >= 988 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 989 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 990 p->user != current->nsproxy->user_ns->root_user) 991 goto bad_fork_free; 992 } 993 994 atomic_inc(&p->user->__count); 995 atomic_inc(&p->user->processes); 996 get_group_info(p->group_info); 997 998 /* 999 * If multiple threads are within copy_process(), then this check 1000 * triggers too late. This doesn't hurt, the check is only there 1001 * to stop root fork bombs. 1002 */ 1003 if (nr_threads >= max_threads) 1004 goto bad_fork_cleanup_count; 1005 1006 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1007 goto bad_fork_cleanup_count; 1008 1009 if (p->binfmt && !try_module_get(p->binfmt->module)) 1010 goto bad_fork_cleanup_put_domain; 1011 1012 p->did_exec = 0; 1013 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1014 copy_flags(clone_flags, p); 1015 INIT_LIST_HEAD(&p->children); 1016 INIT_LIST_HEAD(&p->sibling); 1017 #ifdef CONFIG_PREEMPT_RCU 1018 p->rcu_read_lock_nesting = 0; 1019 p->rcu_flipctr_idx = 0; 1020 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1021 p->vfork_done = NULL; 1022 spin_lock_init(&p->alloc_lock); 1023 1024 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1025 init_sigpending(&p->pending); 1026 1027 p->utime = cputime_zero; 1028 p->stime = cputime_zero; 1029 p->gtime = cputime_zero; 1030 p->utimescaled = cputime_zero; 1031 p->stimescaled = cputime_zero; 1032 p->prev_utime = cputime_zero; 1033 p->prev_stime = cputime_zero; 1034 1035 p->default_timer_slack_ns = current->timer_slack_ns; 1036 1037 #ifdef CONFIG_DETECT_SOFTLOCKUP 1038 p->last_switch_count = 0; 1039 p->last_switch_timestamp = 0; 1040 #endif 1041 1042 task_io_accounting_init(&p->ioac); 1043 acct_clear_integrals(p); 1044 1045 posix_cpu_timers_init(p); 1046 1047 p->lock_depth = -1; /* -1 = no lock */ 1048 do_posix_clock_monotonic_gettime(&p->start_time); 1049 p->real_start_time = p->start_time; 1050 monotonic_to_bootbased(&p->real_start_time); 1051 #ifdef CONFIG_SECURITY 1052 p->security = NULL; 1053 #endif 1054 p->cap_bset = current->cap_bset; 1055 p->io_context = NULL; 1056 p->audit_context = NULL; 1057 cgroup_fork(p); 1058 #ifdef CONFIG_NUMA 1059 p->mempolicy = mpol_dup(p->mempolicy); 1060 if (IS_ERR(p->mempolicy)) { 1061 retval = PTR_ERR(p->mempolicy); 1062 p->mempolicy = NULL; 1063 goto bad_fork_cleanup_cgroup; 1064 } 1065 mpol_fix_fork_child_flag(p); 1066 #endif 1067 #ifdef CONFIG_TRACE_IRQFLAGS 1068 p->irq_events = 0; 1069 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1070 p->hardirqs_enabled = 1; 1071 #else 1072 p->hardirqs_enabled = 0; 1073 #endif 1074 p->hardirq_enable_ip = 0; 1075 p->hardirq_enable_event = 0; 1076 p->hardirq_disable_ip = _THIS_IP_; 1077 p->hardirq_disable_event = 0; 1078 p->softirqs_enabled = 1; 1079 p->softirq_enable_ip = _THIS_IP_; 1080 p->softirq_enable_event = 0; 1081 p->softirq_disable_ip = 0; 1082 p->softirq_disable_event = 0; 1083 p->hardirq_context = 0; 1084 p->softirq_context = 0; 1085 #endif 1086 #ifdef CONFIG_LOCKDEP 1087 p->lockdep_depth = 0; /* no locks held yet */ 1088 p->curr_chain_key = 0; 1089 p->lockdep_recursion = 0; 1090 #endif 1091 1092 #ifdef CONFIG_DEBUG_MUTEXES 1093 p->blocked_on = NULL; /* not blocked yet */ 1094 #endif 1095 1096 /* Perform scheduler related setup. Assign this task to a CPU. */ 1097 sched_fork(p, clone_flags); 1098 1099 if ((retval = security_task_alloc(p))) 1100 goto bad_fork_cleanup_policy; 1101 if ((retval = audit_alloc(p))) 1102 goto bad_fork_cleanup_security; 1103 /* copy all the process information */ 1104 if ((retval = copy_semundo(clone_flags, p))) 1105 goto bad_fork_cleanup_audit; 1106 if ((retval = copy_files(clone_flags, p))) 1107 goto bad_fork_cleanup_semundo; 1108 if ((retval = copy_fs(clone_flags, p))) 1109 goto bad_fork_cleanup_files; 1110 if ((retval = copy_sighand(clone_flags, p))) 1111 goto bad_fork_cleanup_fs; 1112 if ((retval = copy_signal(clone_flags, p))) 1113 goto bad_fork_cleanup_sighand; 1114 if ((retval = copy_mm(clone_flags, p))) 1115 goto bad_fork_cleanup_signal; 1116 if ((retval = copy_keys(clone_flags, p))) 1117 goto bad_fork_cleanup_mm; 1118 if ((retval = copy_namespaces(clone_flags, p))) 1119 goto bad_fork_cleanup_keys; 1120 if ((retval = copy_io(clone_flags, p))) 1121 goto bad_fork_cleanup_namespaces; 1122 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1123 if (retval) 1124 goto bad_fork_cleanup_io; 1125 1126 if (pid != &init_struct_pid) { 1127 retval = -ENOMEM; 1128 pid = alloc_pid(task_active_pid_ns(p)); 1129 if (!pid) 1130 goto bad_fork_cleanup_io; 1131 1132 if (clone_flags & CLONE_NEWPID) { 1133 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1134 if (retval < 0) 1135 goto bad_fork_free_pid; 1136 } 1137 } 1138 1139 p->pid = pid_nr(pid); 1140 p->tgid = p->pid; 1141 if (clone_flags & CLONE_THREAD) 1142 p->tgid = current->tgid; 1143 1144 if (current->nsproxy != p->nsproxy) { 1145 retval = ns_cgroup_clone(p, pid); 1146 if (retval) 1147 goto bad_fork_free_pid; 1148 } 1149 1150 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1151 /* 1152 * Clear TID on mm_release()? 1153 */ 1154 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1155 #ifdef CONFIG_FUTEX 1156 p->robust_list = NULL; 1157 #ifdef CONFIG_COMPAT 1158 p->compat_robust_list = NULL; 1159 #endif 1160 INIT_LIST_HEAD(&p->pi_state_list); 1161 p->pi_state_cache = NULL; 1162 #endif 1163 /* 1164 * sigaltstack should be cleared when sharing the same VM 1165 */ 1166 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1167 p->sas_ss_sp = p->sas_ss_size = 0; 1168 1169 /* 1170 * Syscall tracing should be turned off in the child regardless 1171 * of CLONE_PTRACE. 1172 */ 1173 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1174 #ifdef TIF_SYSCALL_EMU 1175 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1176 #endif 1177 clear_all_latency_tracing(p); 1178 1179 /* Our parent execution domain becomes current domain 1180 These must match for thread signalling to apply */ 1181 p->parent_exec_id = p->self_exec_id; 1182 1183 /* ok, now we should be set up.. */ 1184 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1185 p->pdeath_signal = 0; 1186 p->exit_state = 0; 1187 1188 /* 1189 * Ok, make it visible to the rest of the system. 1190 * We dont wake it up yet. 1191 */ 1192 p->group_leader = p; 1193 INIT_LIST_HEAD(&p->thread_group); 1194 1195 /* Now that the task is set up, run cgroup callbacks if 1196 * necessary. We need to run them before the task is visible 1197 * on the tasklist. */ 1198 cgroup_fork_callbacks(p); 1199 cgroup_callbacks_done = 1; 1200 1201 /* Need tasklist lock for parent etc handling! */ 1202 write_lock_irq(&tasklist_lock); 1203 1204 /* 1205 * The task hasn't been attached yet, so its cpus_allowed mask will 1206 * not be changed, nor will its assigned CPU. 1207 * 1208 * The cpus_allowed mask of the parent may have changed after it was 1209 * copied first time - so re-copy it here, then check the child's CPU 1210 * to ensure it is on a valid CPU (and if not, just force it back to 1211 * parent's CPU). This avoids alot of nasty races. 1212 */ 1213 p->cpus_allowed = current->cpus_allowed; 1214 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1215 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1216 !cpu_online(task_cpu(p)))) 1217 set_task_cpu(p, smp_processor_id()); 1218 1219 /* CLONE_PARENT re-uses the old parent */ 1220 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1221 p->real_parent = current->real_parent; 1222 else 1223 p->real_parent = current; 1224 1225 spin_lock(¤t->sighand->siglock); 1226 1227 /* 1228 * Process group and session signals need to be delivered to just the 1229 * parent before the fork or both the parent and the child after the 1230 * fork. Restart if a signal comes in before we add the new process to 1231 * it's process group. 1232 * A fatal signal pending means that current will exit, so the new 1233 * thread can't slip out of an OOM kill (or normal SIGKILL). 1234 */ 1235 recalc_sigpending(); 1236 if (signal_pending(current)) { 1237 spin_unlock(¤t->sighand->siglock); 1238 write_unlock_irq(&tasklist_lock); 1239 retval = -ERESTARTNOINTR; 1240 goto bad_fork_free_pid; 1241 } 1242 1243 if (clone_flags & CLONE_THREAD) { 1244 p->group_leader = current->group_leader; 1245 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1246 } 1247 1248 if (likely(p->pid)) { 1249 list_add_tail(&p->sibling, &p->real_parent->children); 1250 tracehook_finish_clone(p, clone_flags, trace); 1251 1252 if (thread_group_leader(p)) { 1253 if (clone_flags & CLONE_NEWPID) 1254 p->nsproxy->pid_ns->child_reaper = p; 1255 1256 p->signal->leader_pid = pid; 1257 tty_kref_put(p->signal->tty); 1258 p->signal->tty = tty_kref_get(current->signal->tty); 1259 set_task_pgrp(p, task_pgrp_nr(current)); 1260 set_task_session(p, task_session_nr(current)); 1261 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1262 attach_pid(p, PIDTYPE_SID, task_session(current)); 1263 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1264 __get_cpu_var(process_counts)++; 1265 } 1266 attach_pid(p, PIDTYPE_PID, pid); 1267 nr_threads++; 1268 } 1269 1270 total_forks++; 1271 spin_unlock(¤t->sighand->siglock); 1272 write_unlock_irq(&tasklist_lock); 1273 proc_fork_connector(p); 1274 cgroup_post_fork(p); 1275 return p; 1276 1277 bad_fork_free_pid: 1278 if (pid != &init_struct_pid) 1279 free_pid(pid); 1280 bad_fork_cleanup_io: 1281 put_io_context(p->io_context); 1282 bad_fork_cleanup_namespaces: 1283 exit_task_namespaces(p); 1284 bad_fork_cleanup_keys: 1285 exit_keys(p); 1286 bad_fork_cleanup_mm: 1287 if (p->mm) 1288 mmput(p->mm); 1289 bad_fork_cleanup_signal: 1290 cleanup_signal(p); 1291 bad_fork_cleanup_sighand: 1292 __cleanup_sighand(p->sighand); 1293 bad_fork_cleanup_fs: 1294 exit_fs(p); /* blocking */ 1295 bad_fork_cleanup_files: 1296 exit_files(p); /* blocking */ 1297 bad_fork_cleanup_semundo: 1298 exit_sem(p); 1299 bad_fork_cleanup_audit: 1300 audit_free(p); 1301 bad_fork_cleanup_security: 1302 security_task_free(p); 1303 bad_fork_cleanup_policy: 1304 #ifdef CONFIG_NUMA 1305 mpol_put(p->mempolicy); 1306 bad_fork_cleanup_cgroup: 1307 #endif 1308 cgroup_exit(p, cgroup_callbacks_done); 1309 delayacct_tsk_free(p); 1310 if (p->binfmt) 1311 module_put(p->binfmt->module); 1312 bad_fork_cleanup_put_domain: 1313 module_put(task_thread_info(p)->exec_domain->module); 1314 bad_fork_cleanup_count: 1315 put_group_info(p->group_info); 1316 atomic_dec(&p->user->processes); 1317 free_uid(p->user); 1318 bad_fork_free: 1319 free_task(p); 1320 fork_out: 1321 return ERR_PTR(retval); 1322 } 1323 1324 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1325 { 1326 memset(regs, 0, sizeof(struct pt_regs)); 1327 return regs; 1328 } 1329 1330 struct task_struct * __cpuinit fork_idle(int cpu) 1331 { 1332 struct task_struct *task; 1333 struct pt_regs regs; 1334 1335 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1336 &init_struct_pid, 0); 1337 if (!IS_ERR(task)) 1338 init_idle(task, cpu); 1339 1340 return task; 1341 } 1342 1343 /* 1344 * Ok, this is the main fork-routine. 1345 * 1346 * It copies the process, and if successful kick-starts 1347 * it and waits for it to finish using the VM if required. 1348 */ 1349 long do_fork(unsigned long clone_flags, 1350 unsigned long stack_start, 1351 struct pt_regs *regs, 1352 unsigned long stack_size, 1353 int __user *parent_tidptr, 1354 int __user *child_tidptr) 1355 { 1356 struct task_struct *p; 1357 int trace = 0; 1358 long nr; 1359 1360 /* 1361 * We hope to recycle these flags after 2.6.26 1362 */ 1363 if (unlikely(clone_flags & CLONE_STOPPED)) { 1364 static int __read_mostly count = 100; 1365 1366 if (count > 0 && printk_ratelimit()) { 1367 char comm[TASK_COMM_LEN]; 1368 1369 count--; 1370 printk(KERN_INFO "fork(): process `%s' used deprecated " 1371 "clone flags 0x%lx\n", 1372 get_task_comm(comm, current), 1373 clone_flags & CLONE_STOPPED); 1374 } 1375 } 1376 1377 /* 1378 * When called from kernel_thread, don't do user tracing stuff. 1379 */ 1380 if (likely(user_mode(regs))) 1381 trace = tracehook_prepare_clone(clone_flags); 1382 1383 p = copy_process(clone_flags, stack_start, regs, stack_size, 1384 child_tidptr, NULL, trace); 1385 /* 1386 * Do this prior waking up the new thread - the thread pointer 1387 * might get invalid after that point, if the thread exits quickly. 1388 */ 1389 if (!IS_ERR(p)) { 1390 struct completion vfork; 1391 1392 trace_sched_process_fork(current, p); 1393 1394 nr = task_pid_vnr(p); 1395 1396 if (clone_flags & CLONE_PARENT_SETTID) 1397 put_user(nr, parent_tidptr); 1398 1399 if (clone_flags & CLONE_VFORK) { 1400 p->vfork_done = &vfork; 1401 init_completion(&vfork); 1402 } 1403 1404 audit_finish_fork(p); 1405 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1406 1407 /* 1408 * We set PF_STARTING at creation in case tracing wants to 1409 * use this to distinguish a fully live task from one that 1410 * hasn't gotten to tracehook_report_clone() yet. Now we 1411 * clear it and set the child going. 1412 */ 1413 p->flags &= ~PF_STARTING; 1414 1415 if (unlikely(clone_flags & CLONE_STOPPED)) { 1416 /* 1417 * We'll start up with an immediate SIGSTOP. 1418 */ 1419 sigaddset(&p->pending.signal, SIGSTOP); 1420 set_tsk_thread_flag(p, TIF_SIGPENDING); 1421 __set_task_state(p, TASK_STOPPED); 1422 } else { 1423 wake_up_new_task(p, clone_flags); 1424 } 1425 1426 tracehook_report_clone_complete(trace, regs, 1427 clone_flags, nr, p); 1428 1429 if (clone_flags & CLONE_VFORK) { 1430 freezer_do_not_count(); 1431 wait_for_completion(&vfork); 1432 freezer_count(); 1433 tracehook_report_vfork_done(p, nr); 1434 } 1435 } else { 1436 nr = PTR_ERR(p); 1437 } 1438 return nr; 1439 } 1440 1441 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1442 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1443 #endif 1444 1445 static void sighand_ctor(void *data) 1446 { 1447 struct sighand_struct *sighand = data; 1448 1449 spin_lock_init(&sighand->siglock); 1450 init_waitqueue_head(&sighand->signalfd_wqh); 1451 } 1452 1453 void __init proc_caches_init(void) 1454 { 1455 sighand_cachep = kmem_cache_create("sighand_cache", 1456 sizeof(struct sighand_struct), 0, 1457 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1458 sighand_ctor); 1459 signal_cachep = kmem_cache_create("signal_cache", 1460 sizeof(struct signal_struct), 0, 1461 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1462 files_cachep = kmem_cache_create("files_cache", 1463 sizeof(struct files_struct), 0, 1464 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1465 fs_cachep = kmem_cache_create("fs_cache", 1466 sizeof(struct fs_struct), 0, 1467 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1468 vm_area_cachep = kmem_cache_create("vm_area_struct", 1469 sizeof(struct vm_area_struct), 0, 1470 SLAB_PANIC, NULL); 1471 mm_cachep = kmem_cache_create("mm_struct", 1472 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1473 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1474 } 1475 1476 /* 1477 * Check constraints on flags passed to the unshare system call and 1478 * force unsharing of additional process context as appropriate. 1479 */ 1480 static void check_unshare_flags(unsigned long *flags_ptr) 1481 { 1482 /* 1483 * If unsharing a thread from a thread group, must also 1484 * unshare vm. 1485 */ 1486 if (*flags_ptr & CLONE_THREAD) 1487 *flags_ptr |= CLONE_VM; 1488 1489 /* 1490 * If unsharing vm, must also unshare signal handlers. 1491 */ 1492 if (*flags_ptr & CLONE_VM) 1493 *flags_ptr |= CLONE_SIGHAND; 1494 1495 /* 1496 * If unsharing signal handlers and the task was created 1497 * using CLONE_THREAD, then must unshare the thread 1498 */ 1499 if ((*flags_ptr & CLONE_SIGHAND) && 1500 (atomic_read(¤t->signal->count) > 1)) 1501 *flags_ptr |= CLONE_THREAD; 1502 1503 /* 1504 * If unsharing namespace, must also unshare filesystem information. 1505 */ 1506 if (*flags_ptr & CLONE_NEWNS) 1507 *flags_ptr |= CLONE_FS; 1508 } 1509 1510 /* 1511 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1512 */ 1513 static int unshare_thread(unsigned long unshare_flags) 1514 { 1515 if (unshare_flags & CLONE_THREAD) 1516 return -EINVAL; 1517 1518 return 0; 1519 } 1520 1521 /* 1522 * Unshare the filesystem structure if it is being shared 1523 */ 1524 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1525 { 1526 struct fs_struct *fs = current->fs; 1527 1528 if ((unshare_flags & CLONE_FS) && 1529 (fs && atomic_read(&fs->count) > 1)) { 1530 *new_fsp = __copy_fs_struct(current->fs); 1531 if (!*new_fsp) 1532 return -ENOMEM; 1533 } 1534 1535 return 0; 1536 } 1537 1538 /* 1539 * Unsharing of sighand is not supported yet 1540 */ 1541 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1542 { 1543 struct sighand_struct *sigh = current->sighand; 1544 1545 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1546 return -EINVAL; 1547 else 1548 return 0; 1549 } 1550 1551 /* 1552 * Unshare vm if it is being shared 1553 */ 1554 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1555 { 1556 struct mm_struct *mm = current->mm; 1557 1558 if ((unshare_flags & CLONE_VM) && 1559 (mm && atomic_read(&mm->mm_users) > 1)) { 1560 return -EINVAL; 1561 } 1562 1563 return 0; 1564 } 1565 1566 /* 1567 * Unshare file descriptor table if it is being shared 1568 */ 1569 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1570 { 1571 struct files_struct *fd = current->files; 1572 int error = 0; 1573 1574 if ((unshare_flags & CLONE_FILES) && 1575 (fd && atomic_read(&fd->count) > 1)) { 1576 *new_fdp = dup_fd(fd, &error); 1577 if (!*new_fdp) 1578 return error; 1579 } 1580 1581 return 0; 1582 } 1583 1584 /* 1585 * unshare allows a process to 'unshare' part of the process 1586 * context which was originally shared using clone. copy_* 1587 * functions used by do_fork() cannot be used here directly 1588 * because they modify an inactive task_struct that is being 1589 * constructed. Here we are modifying the current, active, 1590 * task_struct. 1591 */ 1592 asmlinkage long sys_unshare(unsigned long unshare_flags) 1593 { 1594 int err = 0; 1595 struct fs_struct *fs, *new_fs = NULL; 1596 struct sighand_struct *new_sigh = NULL; 1597 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1598 struct files_struct *fd, *new_fd = NULL; 1599 struct nsproxy *new_nsproxy = NULL; 1600 int do_sysvsem = 0; 1601 1602 check_unshare_flags(&unshare_flags); 1603 1604 /* Return -EINVAL for all unsupported flags */ 1605 err = -EINVAL; 1606 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1607 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1608 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1609 CLONE_NEWNET)) 1610 goto bad_unshare_out; 1611 1612 /* 1613 * CLONE_NEWIPC must also detach from the undolist: after switching 1614 * to a new ipc namespace, the semaphore arrays from the old 1615 * namespace are unreachable. 1616 */ 1617 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1618 do_sysvsem = 1; 1619 if ((err = unshare_thread(unshare_flags))) 1620 goto bad_unshare_out; 1621 if ((err = unshare_fs(unshare_flags, &new_fs))) 1622 goto bad_unshare_cleanup_thread; 1623 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1624 goto bad_unshare_cleanup_fs; 1625 if ((err = unshare_vm(unshare_flags, &new_mm))) 1626 goto bad_unshare_cleanup_sigh; 1627 if ((err = unshare_fd(unshare_flags, &new_fd))) 1628 goto bad_unshare_cleanup_vm; 1629 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1630 new_fs))) 1631 goto bad_unshare_cleanup_fd; 1632 1633 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1634 if (do_sysvsem) { 1635 /* 1636 * CLONE_SYSVSEM is equivalent to sys_exit(). 1637 */ 1638 exit_sem(current); 1639 } 1640 1641 if (new_nsproxy) { 1642 switch_task_namespaces(current, new_nsproxy); 1643 new_nsproxy = NULL; 1644 } 1645 1646 task_lock(current); 1647 1648 if (new_fs) { 1649 fs = current->fs; 1650 current->fs = new_fs; 1651 new_fs = fs; 1652 } 1653 1654 if (new_mm) { 1655 mm = current->mm; 1656 active_mm = current->active_mm; 1657 current->mm = new_mm; 1658 current->active_mm = new_mm; 1659 activate_mm(active_mm, new_mm); 1660 new_mm = mm; 1661 } 1662 1663 if (new_fd) { 1664 fd = current->files; 1665 current->files = new_fd; 1666 new_fd = fd; 1667 } 1668 1669 task_unlock(current); 1670 } 1671 1672 if (new_nsproxy) 1673 put_nsproxy(new_nsproxy); 1674 1675 bad_unshare_cleanup_fd: 1676 if (new_fd) 1677 put_files_struct(new_fd); 1678 1679 bad_unshare_cleanup_vm: 1680 if (new_mm) 1681 mmput(new_mm); 1682 1683 bad_unshare_cleanup_sigh: 1684 if (new_sigh) 1685 if (atomic_dec_and_test(&new_sigh->count)) 1686 kmem_cache_free(sighand_cachep, new_sigh); 1687 1688 bad_unshare_cleanup_fs: 1689 if (new_fs) 1690 put_fs_struct(new_fs); 1691 1692 bad_unshare_cleanup_thread: 1693 bad_unshare_out: 1694 return err; 1695 } 1696 1697 /* 1698 * Helper to unshare the files of the current task. 1699 * We don't want to expose copy_files internals to 1700 * the exec layer of the kernel. 1701 */ 1702 1703 int unshare_files(struct files_struct **displaced) 1704 { 1705 struct task_struct *task = current; 1706 struct files_struct *copy = NULL; 1707 int error; 1708 1709 error = unshare_fd(CLONE_FILES, ©); 1710 if (error || !copy) { 1711 *displaced = NULL; 1712 return error; 1713 } 1714 *displaced = task->files; 1715 task_lock(task); 1716 task->files = copy; 1717 task_unlock(task); 1718 return 0; 1719 } 1720