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/ftrace.h> 51 #include <linux/profile.h> 52 #include <linux/rmap.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <trace/sched.h> 64 #include <linux/magic.h> 65 66 #include <asm/pgtable.h> 67 #include <asm/pgalloc.h> 68 #include <asm/uaccess.h> 69 #include <asm/mmu_context.h> 70 #include <asm/cacheflush.h> 71 #include <asm/tlbflush.h> 72 73 /* 74 * Protected counters by write_lock_irq(&tasklist_lock) 75 */ 76 unsigned long total_forks; /* Handle normal Linux uptimes. */ 77 int nr_threads; /* The idle threads do not count.. */ 78 79 int max_threads; /* tunable limit on nr_threads */ 80 81 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 82 83 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 84 85 DEFINE_TRACE(sched_process_fork); 86 87 int nr_processes(void) 88 { 89 int cpu; 90 int total = 0; 91 92 for_each_online_cpu(cpu) 93 total += per_cpu(process_counts, cpu); 94 95 return total; 96 } 97 98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 99 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 100 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 101 static struct kmem_cache *task_struct_cachep; 102 #endif 103 104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 106 { 107 #ifdef CONFIG_DEBUG_STACK_USAGE 108 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 109 #else 110 gfp_t mask = GFP_KERNEL; 111 #endif 112 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 113 } 114 115 static inline void free_thread_info(struct thread_info *ti) 116 { 117 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 118 } 119 #endif 120 121 /* SLAB cache for signal_struct structures (tsk->signal) */ 122 static struct kmem_cache *signal_cachep; 123 124 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 125 struct kmem_cache *sighand_cachep; 126 127 /* SLAB cache for files_struct structures (tsk->files) */ 128 struct kmem_cache *files_cachep; 129 130 /* SLAB cache for fs_struct structures (tsk->fs) */ 131 struct kmem_cache *fs_cachep; 132 133 /* SLAB cache for vm_area_struct structures */ 134 struct kmem_cache *vm_area_cachep; 135 136 /* SLAB cache for mm_struct structures (tsk->mm) */ 137 static struct kmem_cache *mm_cachep; 138 139 void free_task(struct task_struct *tsk) 140 { 141 prop_local_destroy_single(&tsk->dirties); 142 free_thread_info(tsk->stack); 143 rt_mutex_debug_task_free(tsk); 144 ftrace_graph_exit_task(tsk); 145 free_task_struct(tsk); 146 } 147 EXPORT_SYMBOL(free_task); 148 149 void __put_task_struct(struct task_struct *tsk) 150 { 151 WARN_ON(!tsk->exit_state); 152 WARN_ON(atomic_read(&tsk->usage)); 153 WARN_ON(tsk == current); 154 155 put_cred(tsk->real_cred); 156 put_cred(tsk->cred); 157 delayacct_tsk_free(tsk); 158 159 if (!profile_handoff_task(tsk)) 160 free_task(tsk); 161 } 162 163 /* 164 * macro override instead of weak attribute alias, to workaround 165 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 166 */ 167 #ifndef arch_task_cache_init 168 #define arch_task_cache_init() 169 #endif 170 171 void __init fork_init(unsigned long mempages) 172 { 173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 174 #ifndef ARCH_MIN_TASKALIGN 175 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 176 #endif 177 /* create a slab on which task_structs can be allocated */ 178 task_struct_cachep = 179 kmem_cache_create("task_struct", sizeof(struct task_struct), 180 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 181 #endif 182 183 /* do the arch specific task caches init */ 184 arch_task_cache_init(); 185 186 /* 187 * The default maximum number of threads is set to a safe 188 * value: the thread structures can take up at most half 189 * of memory. 190 */ 191 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 192 193 /* 194 * we need to allow at least 20 threads to boot a system 195 */ 196 if(max_threads < 20) 197 max_threads = 20; 198 199 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 200 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 201 init_task.signal->rlim[RLIMIT_SIGPENDING] = 202 init_task.signal->rlim[RLIMIT_NPROC]; 203 } 204 205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 206 struct task_struct *src) 207 { 208 *dst = *src; 209 return 0; 210 } 211 212 static struct task_struct *dup_task_struct(struct task_struct *orig) 213 { 214 struct task_struct *tsk; 215 struct thread_info *ti; 216 unsigned long *stackend; 217 218 int err; 219 220 prepare_to_copy(orig); 221 222 tsk = alloc_task_struct(); 223 if (!tsk) 224 return NULL; 225 226 ti = alloc_thread_info(tsk); 227 if (!ti) { 228 free_task_struct(tsk); 229 return NULL; 230 } 231 232 err = arch_dup_task_struct(tsk, orig); 233 if (err) 234 goto out; 235 236 tsk->stack = ti; 237 238 err = prop_local_init_single(&tsk->dirties); 239 if (err) 240 goto out; 241 242 setup_thread_stack(tsk, orig); 243 stackend = end_of_stack(tsk); 244 *stackend = STACK_END_MAGIC; /* for overflow detection */ 245 246 #ifdef CONFIG_CC_STACKPROTECTOR 247 tsk->stack_canary = get_random_int(); 248 #endif 249 250 /* One for us, one for whoever does the "release_task()" (usually parent) */ 251 atomic_set(&tsk->usage,2); 252 atomic_set(&tsk->fs_excl, 0); 253 #ifdef CONFIG_BLK_DEV_IO_TRACE 254 tsk->btrace_seq = 0; 255 #endif 256 tsk->splice_pipe = NULL; 257 return tsk; 258 259 out: 260 free_thread_info(ti); 261 free_task_struct(tsk); 262 return NULL; 263 } 264 265 #ifdef CONFIG_MMU 266 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 267 { 268 struct vm_area_struct *mpnt, *tmp, **pprev; 269 struct rb_node **rb_link, *rb_parent; 270 int retval; 271 unsigned long charge; 272 struct mempolicy *pol; 273 274 down_write(&oldmm->mmap_sem); 275 flush_cache_dup_mm(oldmm); 276 /* 277 * Not linked in yet - no deadlock potential: 278 */ 279 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 280 281 mm->locked_vm = 0; 282 mm->mmap = NULL; 283 mm->mmap_cache = NULL; 284 mm->free_area_cache = oldmm->mmap_base; 285 mm->cached_hole_size = ~0UL; 286 mm->map_count = 0; 287 cpumask_clear(mm_cpumask(mm)); 288 mm->mm_rb = RB_ROOT; 289 rb_link = &mm->mm_rb.rb_node; 290 rb_parent = NULL; 291 pprev = &mm->mmap; 292 293 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 294 struct file *file; 295 296 if (mpnt->vm_flags & VM_DONTCOPY) { 297 long pages = vma_pages(mpnt); 298 mm->total_vm -= pages; 299 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 300 -pages); 301 continue; 302 } 303 charge = 0; 304 if (mpnt->vm_flags & VM_ACCOUNT) { 305 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 306 if (security_vm_enough_memory(len)) 307 goto fail_nomem; 308 charge = len; 309 } 310 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 311 if (!tmp) 312 goto fail_nomem; 313 *tmp = *mpnt; 314 pol = mpol_dup(vma_policy(mpnt)); 315 retval = PTR_ERR(pol); 316 if (IS_ERR(pol)) 317 goto fail_nomem_policy; 318 vma_set_policy(tmp, pol); 319 tmp->vm_flags &= ~VM_LOCKED; 320 tmp->vm_mm = mm; 321 tmp->vm_next = NULL; 322 anon_vma_link(tmp); 323 file = tmp->vm_file; 324 if (file) { 325 struct inode *inode = file->f_path.dentry->d_inode; 326 struct address_space *mapping = file->f_mapping; 327 328 get_file(file); 329 if (tmp->vm_flags & VM_DENYWRITE) 330 atomic_dec(&inode->i_writecount); 331 spin_lock(&mapping->i_mmap_lock); 332 if (tmp->vm_flags & VM_SHARED) 333 mapping->i_mmap_writable++; 334 tmp->vm_truncate_count = mpnt->vm_truncate_count; 335 flush_dcache_mmap_lock(mapping); 336 /* insert tmp into the share list, just after mpnt */ 337 vma_prio_tree_add(tmp, mpnt); 338 flush_dcache_mmap_unlock(mapping); 339 spin_unlock(&mapping->i_mmap_lock); 340 } 341 342 /* 343 * Clear hugetlb-related page reserves for children. This only 344 * affects MAP_PRIVATE mappings. Faults generated by the child 345 * are not guaranteed to succeed, even if read-only 346 */ 347 if (is_vm_hugetlb_page(tmp)) 348 reset_vma_resv_huge_pages(tmp); 349 350 /* 351 * Link in the new vma and copy the page table entries. 352 */ 353 *pprev = tmp; 354 pprev = &tmp->vm_next; 355 356 __vma_link_rb(mm, tmp, rb_link, rb_parent); 357 rb_link = &tmp->vm_rb.rb_right; 358 rb_parent = &tmp->vm_rb; 359 360 mm->map_count++; 361 retval = copy_page_range(mm, oldmm, mpnt); 362 363 if (tmp->vm_ops && tmp->vm_ops->open) 364 tmp->vm_ops->open(tmp); 365 366 if (retval) 367 goto out; 368 } 369 /* a new mm has just been created */ 370 arch_dup_mmap(oldmm, mm); 371 retval = 0; 372 out: 373 up_write(&mm->mmap_sem); 374 flush_tlb_mm(oldmm); 375 up_write(&oldmm->mmap_sem); 376 return retval; 377 fail_nomem_policy: 378 kmem_cache_free(vm_area_cachep, tmp); 379 fail_nomem: 380 retval = -ENOMEM; 381 vm_unacct_memory(charge); 382 goto out; 383 } 384 385 static inline int mm_alloc_pgd(struct mm_struct * mm) 386 { 387 mm->pgd = pgd_alloc(mm); 388 if (unlikely(!mm->pgd)) 389 return -ENOMEM; 390 return 0; 391 } 392 393 static inline void mm_free_pgd(struct mm_struct * mm) 394 { 395 pgd_free(mm, mm->pgd); 396 } 397 #else 398 #define dup_mmap(mm, oldmm) (0) 399 #define mm_alloc_pgd(mm) (0) 400 #define mm_free_pgd(mm) 401 #endif /* CONFIG_MMU */ 402 403 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 404 405 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 406 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 407 408 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 409 410 static int __init coredump_filter_setup(char *s) 411 { 412 default_dump_filter = 413 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 414 MMF_DUMP_FILTER_MASK; 415 return 1; 416 } 417 418 __setup("coredump_filter=", coredump_filter_setup); 419 420 #include <linux/init_task.h> 421 422 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 423 { 424 atomic_set(&mm->mm_users, 1); 425 atomic_set(&mm->mm_count, 1); 426 init_rwsem(&mm->mmap_sem); 427 INIT_LIST_HEAD(&mm->mmlist); 428 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter; 429 mm->core_state = NULL; 430 mm->nr_ptes = 0; 431 set_mm_counter(mm, file_rss, 0); 432 set_mm_counter(mm, anon_rss, 0); 433 spin_lock_init(&mm->page_table_lock); 434 spin_lock_init(&mm->ioctx_lock); 435 INIT_HLIST_HEAD(&mm->ioctx_list); 436 mm->free_area_cache = TASK_UNMAPPED_BASE; 437 mm->cached_hole_size = ~0UL; 438 mm_init_owner(mm, p); 439 440 if (likely(!mm_alloc_pgd(mm))) { 441 mm->def_flags = 0; 442 mmu_notifier_mm_init(mm); 443 return mm; 444 } 445 446 free_mm(mm); 447 return NULL; 448 } 449 450 /* 451 * Allocate and initialize an mm_struct. 452 */ 453 struct mm_struct * mm_alloc(void) 454 { 455 struct mm_struct * mm; 456 457 mm = allocate_mm(); 458 if (mm) { 459 memset(mm, 0, sizeof(*mm)); 460 mm = mm_init(mm, current); 461 } 462 return mm; 463 } 464 465 /* 466 * Called when the last reference to the mm 467 * is dropped: either by a lazy thread or by 468 * mmput. Free the page directory and the mm. 469 */ 470 void __mmdrop(struct mm_struct *mm) 471 { 472 BUG_ON(mm == &init_mm); 473 mm_free_pgd(mm); 474 destroy_context(mm); 475 mmu_notifier_mm_destroy(mm); 476 free_mm(mm); 477 } 478 EXPORT_SYMBOL_GPL(__mmdrop); 479 480 /* 481 * Decrement the use count and release all resources for an mm. 482 */ 483 void mmput(struct mm_struct *mm) 484 { 485 might_sleep(); 486 487 if (atomic_dec_and_test(&mm->mm_users)) { 488 exit_aio(mm); 489 exit_mmap(mm); 490 set_mm_exe_file(mm, NULL); 491 if (!list_empty(&mm->mmlist)) { 492 spin_lock(&mmlist_lock); 493 list_del(&mm->mmlist); 494 spin_unlock(&mmlist_lock); 495 } 496 put_swap_token(mm); 497 mmdrop(mm); 498 } 499 } 500 EXPORT_SYMBOL_GPL(mmput); 501 502 /** 503 * get_task_mm - acquire a reference to the task's mm 504 * 505 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 506 * this kernel workthread has transiently adopted a user mm with use_mm, 507 * to do its AIO) is not set and if so returns a reference to it, after 508 * bumping up the use count. User must release the mm via mmput() 509 * after use. Typically used by /proc and ptrace. 510 */ 511 struct mm_struct *get_task_mm(struct task_struct *task) 512 { 513 struct mm_struct *mm; 514 515 task_lock(task); 516 mm = task->mm; 517 if (mm) { 518 if (task->flags & PF_KTHREAD) 519 mm = NULL; 520 else 521 atomic_inc(&mm->mm_users); 522 } 523 task_unlock(task); 524 return mm; 525 } 526 EXPORT_SYMBOL_GPL(get_task_mm); 527 528 /* Please note the differences between mmput and mm_release. 529 * mmput is called whenever we stop holding onto a mm_struct, 530 * error success whatever. 531 * 532 * mm_release is called after a mm_struct has been removed 533 * from the current process. 534 * 535 * This difference is important for error handling, when we 536 * only half set up a mm_struct for a new process and need to restore 537 * the old one. Because we mmput the new mm_struct before 538 * restoring the old one. . . 539 * Eric Biederman 10 January 1998 540 */ 541 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 542 { 543 struct completion *vfork_done = tsk->vfork_done; 544 545 /* Get rid of any futexes when releasing the mm */ 546 #ifdef CONFIG_FUTEX 547 if (unlikely(tsk->robust_list)) 548 exit_robust_list(tsk); 549 #ifdef CONFIG_COMPAT 550 if (unlikely(tsk->compat_robust_list)) 551 compat_exit_robust_list(tsk); 552 #endif 553 #endif 554 555 /* Get rid of any cached register state */ 556 deactivate_mm(tsk, mm); 557 558 /* notify parent sleeping on vfork() */ 559 if (vfork_done) { 560 tsk->vfork_done = NULL; 561 complete(vfork_done); 562 } 563 564 /* 565 * If we're exiting normally, clear a user-space tid field if 566 * requested. We leave this alone when dying by signal, to leave 567 * the value intact in a core dump, and to save the unnecessary 568 * trouble otherwise. Userland only wants this done for a sys_exit. 569 */ 570 if (tsk->clear_child_tid 571 && !(tsk->flags & PF_SIGNALED) 572 && atomic_read(&mm->mm_users) > 1) { 573 u32 __user * tidptr = tsk->clear_child_tid; 574 tsk->clear_child_tid = NULL; 575 576 /* 577 * We don't check the error code - if userspace has 578 * not set up a proper pointer then tough luck. 579 */ 580 put_user(0, tidptr); 581 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 582 } 583 } 584 585 /* 586 * Allocate a new mm structure and copy contents from the 587 * mm structure of the passed in task structure. 588 */ 589 struct mm_struct *dup_mm(struct task_struct *tsk) 590 { 591 struct mm_struct *mm, *oldmm = current->mm; 592 int err; 593 594 if (!oldmm) 595 return NULL; 596 597 mm = allocate_mm(); 598 if (!mm) 599 goto fail_nomem; 600 601 memcpy(mm, oldmm, sizeof(*mm)); 602 603 /* Initializing for Swap token stuff */ 604 mm->token_priority = 0; 605 mm->last_interval = 0; 606 607 if (!mm_init(mm, tsk)) 608 goto fail_nomem; 609 610 if (init_new_context(tsk, mm)) 611 goto fail_nocontext; 612 613 dup_mm_exe_file(oldmm, mm); 614 615 err = dup_mmap(mm, oldmm); 616 if (err) 617 goto free_pt; 618 619 mm->hiwater_rss = get_mm_rss(mm); 620 mm->hiwater_vm = mm->total_vm; 621 622 return mm; 623 624 free_pt: 625 mmput(mm); 626 627 fail_nomem: 628 return NULL; 629 630 fail_nocontext: 631 /* 632 * If init_new_context() failed, we cannot use mmput() to free the mm 633 * because it calls destroy_context() 634 */ 635 mm_free_pgd(mm); 636 free_mm(mm); 637 return NULL; 638 } 639 640 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 641 { 642 struct mm_struct * mm, *oldmm; 643 int retval; 644 645 tsk->min_flt = tsk->maj_flt = 0; 646 tsk->nvcsw = tsk->nivcsw = 0; 647 648 tsk->mm = NULL; 649 tsk->active_mm = NULL; 650 651 /* 652 * Are we cloning a kernel thread? 653 * 654 * We need to steal a active VM for that.. 655 */ 656 oldmm = current->mm; 657 if (!oldmm) 658 return 0; 659 660 if (clone_flags & CLONE_VM) { 661 atomic_inc(&oldmm->mm_users); 662 mm = oldmm; 663 goto good_mm; 664 } 665 666 retval = -ENOMEM; 667 mm = dup_mm(tsk); 668 if (!mm) 669 goto fail_nomem; 670 671 good_mm: 672 /* Initializing for Swap token stuff */ 673 mm->token_priority = 0; 674 mm->last_interval = 0; 675 676 tsk->mm = mm; 677 tsk->active_mm = mm; 678 return 0; 679 680 fail_nomem: 681 return retval; 682 } 683 684 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 685 { 686 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 687 /* We don't need to lock fs - think why ;-) */ 688 if (fs) { 689 atomic_set(&fs->count, 1); 690 rwlock_init(&fs->lock); 691 fs->umask = old->umask; 692 read_lock(&old->lock); 693 fs->root = old->root; 694 path_get(&old->root); 695 fs->pwd = old->pwd; 696 path_get(&old->pwd); 697 read_unlock(&old->lock); 698 } 699 return fs; 700 } 701 702 struct fs_struct *copy_fs_struct(struct fs_struct *old) 703 { 704 return __copy_fs_struct(old); 705 } 706 707 EXPORT_SYMBOL_GPL(copy_fs_struct); 708 709 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 710 { 711 if (clone_flags & CLONE_FS) { 712 atomic_inc(¤t->fs->count); 713 return 0; 714 } 715 tsk->fs = __copy_fs_struct(current->fs); 716 if (!tsk->fs) 717 return -ENOMEM; 718 return 0; 719 } 720 721 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 722 { 723 struct files_struct *oldf, *newf; 724 int error = 0; 725 726 /* 727 * A background process may not have any files ... 728 */ 729 oldf = current->files; 730 if (!oldf) 731 goto out; 732 733 if (clone_flags & CLONE_FILES) { 734 atomic_inc(&oldf->count); 735 goto out; 736 } 737 738 newf = dup_fd(oldf, &error); 739 if (!newf) 740 goto out; 741 742 tsk->files = newf; 743 error = 0; 744 out: 745 return error; 746 } 747 748 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 749 { 750 #ifdef CONFIG_BLOCK 751 struct io_context *ioc = current->io_context; 752 753 if (!ioc) 754 return 0; 755 /* 756 * Share io context with parent, if CLONE_IO is set 757 */ 758 if (clone_flags & CLONE_IO) { 759 tsk->io_context = ioc_task_link(ioc); 760 if (unlikely(!tsk->io_context)) 761 return -ENOMEM; 762 } else if (ioprio_valid(ioc->ioprio)) { 763 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 764 if (unlikely(!tsk->io_context)) 765 return -ENOMEM; 766 767 tsk->io_context->ioprio = ioc->ioprio; 768 } 769 #endif 770 return 0; 771 } 772 773 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 774 { 775 struct sighand_struct *sig; 776 777 if (clone_flags & CLONE_SIGHAND) { 778 atomic_inc(¤t->sighand->count); 779 return 0; 780 } 781 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 782 rcu_assign_pointer(tsk->sighand, sig); 783 if (!sig) 784 return -ENOMEM; 785 atomic_set(&sig->count, 1); 786 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 787 return 0; 788 } 789 790 void __cleanup_sighand(struct sighand_struct *sighand) 791 { 792 if (atomic_dec_and_test(&sighand->count)) 793 kmem_cache_free(sighand_cachep, sighand); 794 } 795 796 797 /* 798 * Initialize POSIX timer handling for a thread group. 799 */ 800 static void posix_cpu_timers_init_group(struct signal_struct *sig) 801 { 802 /* Thread group counters. */ 803 thread_group_cputime_init(sig); 804 805 /* Expiration times and increments. */ 806 sig->it_virt_expires = cputime_zero; 807 sig->it_virt_incr = cputime_zero; 808 sig->it_prof_expires = cputime_zero; 809 sig->it_prof_incr = cputime_zero; 810 811 /* Cached expiration times. */ 812 sig->cputime_expires.prof_exp = cputime_zero; 813 sig->cputime_expires.virt_exp = cputime_zero; 814 sig->cputime_expires.sched_exp = 0; 815 816 /* The timer lists. */ 817 INIT_LIST_HEAD(&sig->cpu_timers[0]); 818 INIT_LIST_HEAD(&sig->cpu_timers[1]); 819 INIT_LIST_HEAD(&sig->cpu_timers[2]); 820 } 821 822 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 823 { 824 struct signal_struct *sig; 825 826 if (clone_flags & CLONE_THREAD) { 827 atomic_inc(¤t->signal->count); 828 atomic_inc(¤t->signal->live); 829 return 0; 830 } 831 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 832 833 if (sig) 834 posix_cpu_timers_init_group(sig); 835 836 tsk->signal = sig; 837 if (!sig) 838 return -ENOMEM; 839 840 atomic_set(&sig->count, 1); 841 atomic_set(&sig->live, 1); 842 init_waitqueue_head(&sig->wait_chldexit); 843 sig->flags = 0; 844 sig->group_exit_code = 0; 845 sig->group_exit_task = NULL; 846 sig->group_stop_count = 0; 847 sig->curr_target = tsk; 848 init_sigpending(&sig->shared_pending); 849 INIT_LIST_HEAD(&sig->posix_timers); 850 851 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 852 sig->it_real_incr.tv64 = 0; 853 sig->real_timer.function = it_real_fn; 854 855 sig->leader = 0; /* session leadership doesn't inherit */ 856 sig->tty_old_pgrp = NULL; 857 sig->tty = NULL; 858 859 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 860 sig->gtime = cputime_zero; 861 sig->cgtime = cputime_zero; 862 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 863 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 864 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 865 task_io_accounting_init(&sig->ioac); 866 sig->sum_sched_runtime = 0; 867 taskstats_tgid_init(sig); 868 869 task_lock(current->group_leader); 870 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 871 task_unlock(current->group_leader); 872 873 acct_init_pacct(&sig->pacct); 874 875 tty_audit_fork(sig); 876 877 return 0; 878 } 879 880 void __cleanup_signal(struct signal_struct *sig) 881 { 882 thread_group_cputime_free(sig); 883 tty_kref_put(sig->tty); 884 kmem_cache_free(signal_cachep, sig); 885 } 886 887 static void cleanup_signal(struct task_struct *tsk) 888 { 889 struct signal_struct *sig = tsk->signal; 890 891 atomic_dec(&sig->live); 892 893 if (atomic_dec_and_test(&sig->count)) 894 __cleanup_signal(sig); 895 } 896 897 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 898 { 899 unsigned long new_flags = p->flags; 900 901 new_flags &= ~PF_SUPERPRIV; 902 new_flags |= PF_FORKNOEXEC; 903 new_flags |= PF_STARTING; 904 p->flags = new_flags; 905 clear_freeze_flag(p); 906 } 907 908 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 909 { 910 current->clear_child_tid = tidptr; 911 912 return task_pid_vnr(current); 913 } 914 915 static void rt_mutex_init_task(struct task_struct *p) 916 { 917 spin_lock_init(&p->pi_lock); 918 #ifdef CONFIG_RT_MUTEXES 919 plist_head_init(&p->pi_waiters, &p->pi_lock); 920 p->pi_blocked_on = NULL; 921 #endif 922 } 923 924 #ifdef CONFIG_MM_OWNER 925 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 926 { 927 mm->owner = p; 928 } 929 #endif /* CONFIG_MM_OWNER */ 930 931 /* 932 * Initialize POSIX timer handling for a single task. 933 */ 934 static void posix_cpu_timers_init(struct task_struct *tsk) 935 { 936 tsk->cputime_expires.prof_exp = cputime_zero; 937 tsk->cputime_expires.virt_exp = cputime_zero; 938 tsk->cputime_expires.sched_exp = 0; 939 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 940 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 941 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 942 } 943 944 /* 945 * This creates a new process as a copy of the old one, 946 * but does not actually start it yet. 947 * 948 * It copies the registers, and all the appropriate 949 * parts of the process environment (as per the clone 950 * flags). The actual kick-off is left to the caller. 951 */ 952 static struct task_struct *copy_process(unsigned long clone_flags, 953 unsigned long stack_start, 954 struct pt_regs *regs, 955 unsigned long stack_size, 956 int __user *child_tidptr, 957 struct pid *pid, 958 int trace) 959 { 960 int retval; 961 struct task_struct *p; 962 int cgroup_callbacks_done = 0; 963 964 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 965 return ERR_PTR(-EINVAL); 966 967 /* 968 * Thread groups must share signals as well, and detached threads 969 * can only be started up within the thread group. 970 */ 971 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 972 return ERR_PTR(-EINVAL); 973 974 /* 975 * Shared signal handlers imply shared VM. By way of the above, 976 * thread groups also imply shared VM. Blocking this case allows 977 * for various simplifications in other code. 978 */ 979 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 980 return ERR_PTR(-EINVAL); 981 982 retval = security_task_create(clone_flags); 983 if (retval) 984 goto fork_out; 985 986 retval = -ENOMEM; 987 p = dup_task_struct(current); 988 if (!p) 989 goto fork_out; 990 991 rt_mutex_init_task(p); 992 993 #ifdef CONFIG_PROVE_LOCKING 994 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 995 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 996 #endif 997 retval = -EAGAIN; 998 if (atomic_read(&p->real_cred->user->processes) >= 999 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1000 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1001 p->real_cred->user != INIT_USER) 1002 goto bad_fork_free; 1003 } 1004 1005 retval = copy_creds(p, clone_flags); 1006 if (retval < 0) 1007 goto bad_fork_free; 1008 1009 /* 1010 * If multiple threads are within copy_process(), then this check 1011 * triggers too late. This doesn't hurt, the check is only there 1012 * to stop root fork bombs. 1013 */ 1014 retval = -EAGAIN; 1015 if (nr_threads >= max_threads) 1016 goto bad_fork_cleanup_count; 1017 1018 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1019 goto bad_fork_cleanup_count; 1020 1021 if (p->binfmt && !try_module_get(p->binfmt->module)) 1022 goto bad_fork_cleanup_put_domain; 1023 1024 p->did_exec = 0; 1025 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1026 copy_flags(clone_flags, p); 1027 INIT_LIST_HEAD(&p->children); 1028 INIT_LIST_HEAD(&p->sibling); 1029 #ifdef CONFIG_PREEMPT_RCU 1030 p->rcu_read_lock_nesting = 0; 1031 p->rcu_flipctr_idx = 0; 1032 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1033 p->vfork_done = NULL; 1034 spin_lock_init(&p->alloc_lock); 1035 1036 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1037 init_sigpending(&p->pending); 1038 1039 p->utime = cputime_zero; 1040 p->stime = cputime_zero; 1041 p->gtime = cputime_zero; 1042 p->utimescaled = cputime_zero; 1043 p->stimescaled = cputime_zero; 1044 p->prev_utime = cputime_zero; 1045 p->prev_stime = cputime_zero; 1046 1047 p->default_timer_slack_ns = current->timer_slack_ns; 1048 1049 #ifdef CONFIG_DETECT_SOFTLOCKUP 1050 p->last_switch_count = 0; 1051 p->last_switch_timestamp = 0; 1052 #endif 1053 1054 task_io_accounting_init(&p->ioac); 1055 acct_clear_integrals(p); 1056 1057 posix_cpu_timers_init(p); 1058 1059 p->lock_depth = -1; /* -1 = no lock */ 1060 do_posix_clock_monotonic_gettime(&p->start_time); 1061 p->real_start_time = p->start_time; 1062 monotonic_to_bootbased(&p->real_start_time); 1063 p->io_context = NULL; 1064 p->audit_context = NULL; 1065 cgroup_fork(p); 1066 #ifdef CONFIG_NUMA 1067 p->mempolicy = mpol_dup(p->mempolicy); 1068 if (IS_ERR(p->mempolicy)) { 1069 retval = PTR_ERR(p->mempolicy); 1070 p->mempolicy = NULL; 1071 goto bad_fork_cleanup_cgroup; 1072 } 1073 mpol_fix_fork_child_flag(p); 1074 #endif 1075 #ifdef CONFIG_TRACE_IRQFLAGS 1076 p->irq_events = 0; 1077 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1078 p->hardirqs_enabled = 1; 1079 #else 1080 p->hardirqs_enabled = 0; 1081 #endif 1082 p->hardirq_enable_ip = 0; 1083 p->hardirq_enable_event = 0; 1084 p->hardirq_disable_ip = _THIS_IP_; 1085 p->hardirq_disable_event = 0; 1086 p->softirqs_enabled = 1; 1087 p->softirq_enable_ip = _THIS_IP_; 1088 p->softirq_enable_event = 0; 1089 p->softirq_disable_ip = 0; 1090 p->softirq_disable_event = 0; 1091 p->hardirq_context = 0; 1092 p->softirq_context = 0; 1093 #endif 1094 #ifdef CONFIG_LOCKDEP 1095 p->lockdep_depth = 0; /* no locks held yet */ 1096 p->curr_chain_key = 0; 1097 p->lockdep_recursion = 0; 1098 #endif 1099 1100 #ifdef CONFIG_DEBUG_MUTEXES 1101 p->blocked_on = NULL; /* not blocked yet */ 1102 #endif 1103 if (unlikely(current->ptrace)) 1104 ptrace_fork(p, clone_flags); 1105 1106 /* Perform scheduler related setup. Assign this task to a CPU. */ 1107 sched_fork(p, clone_flags); 1108 1109 if ((retval = audit_alloc(p))) 1110 goto bad_fork_cleanup_policy; 1111 /* copy all the process information */ 1112 if ((retval = copy_semundo(clone_flags, p))) 1113 goto bad_fork_cleanup_audit; 1114 if ((retval = copy_files(clone_flags, p))) 1115 goto bad_fork_cleanup_semundo; 1116 if ((retval = copy_fs(clone_flags, p))) 1117 goto bad_fork_cleanup_files; 1118 if ((retval = copy_sighand(clone_flags, p))) 1119 goto bad_fork_cleanup_fs; 1120 if ((retval = copy_signal(clone_flags, p))) 1121 goto bad_fork_cleanup_sighand; 1122 if ((retval = copy_mm(clone_flags, p))) 1123 goto bad_fork_cleanup_signal; 1124 if ((retval = copy_namespaces(clone_flags, p))) 1125 goto bad_fork_cleanup_mm; 1126 if ((retval = copy_io(clone_flags, p))) 1127 goto bad_fork_cleanup_namespaces; 1128 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1129 if (retval) 1130 goto bad_fork_cleanup_io; 1131 1132 if (pid != &init_struct_pid) { 1133 retval = -ENOMEM; 1134 pid = alloc_pid(p->nsproxy->pid_ns); 1135 if (!pid) 1136 goto bad_fork_cleanup_io; 1137 1138 if (clone_flags & CLONE_NEWPID) { 1139 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1140 if (retval < 0) 1141 goto bad_fork_free_pid; 1142 } 1143 } 1144 1145 ftrace_graph_init_task(p); 1146 1147 p->pid = pid_nr(pid); 1148 p->tgid = p->pid; 1149 if (clone_flags & CLONE_THREAD) 1150 p->tgid = current->tgid; 1151 1152 if (current->nsproxy != p->nsproxy) { 1153 retval = ns_cgroup_clone(p, pid); 1154 if (retval) 1155 goto bad_fork_free_graph; 1156 } 1157 1158 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1159 /* 1160 * Clear TID on mm_release()? 1161 */ 1162 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1163 #ifdef CONFIG_FUTEX 1164 p->robust_list = NULL; 1165 #ifdef CONFIG_COMPAT 1166 p->compat_robust_list = NULL; 1167 #endif 1168 INIT_LIST_HEAD(&p->pi_state_list); 1169 p->pi_state_cache = NULL; 1170 #endif 1171 /* 1172 * sigaltstack should be cleared when sharing the same VM 1173 */ 1174 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1175 p->sas_ss_sp = p->sas_ss_size = 0; 1176 1177 /* 1178 * Syscall tracing should be turned off in the child regardless 1179 * of CLONE_PTRACE. 1180 */ 1181 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1182 #ifdef TIF_SYSCALL_EMU 1183 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1184 #endif 1185 clear_all_latency_tracing(p); 1186 1187 /* ok, now we should be set up.. */ 1188 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1189 p->pdeath_signal = 0; 1190 p->exit_state = 0; 1191 1192 /* 1193 * Ok, make it visible to the rest of the system. 1194 * We dont wake it up yet. 1195 */ 1196 p->group_leader = p; 1197 INIT_LIST_HEAD(&p->thread_group); 1198 1199 /* Now that the task is set up, run cgroup callbacks if 1200 * necessary. We need to run them before the task is visible 1201 * on the tasklist. */ 1202 cgroup_fork_callbacks(p); 1203 cgroup_callbacks_done = 1; 1204 1205 /* Need tasklist lock for parent etc handling! */ 1206 write_lock_irq(&tasklist_lock); 1207 1208 /* 1209 * The task hasn't been attached yet, so its cpus_allowed mask will 1210 * not be changed, nor will its assigned CPU. 1211 * 1212 * The cpus_allowed mask of the parent may have changed after it was 1213 * copied first time - so re-copy it here, then check the child's CPU 1214 * to ensure it is on a valid CPU (and if not, just force it back to 1215 * parent's CPU). This avoids alot of nasty races. 1216 */ 1217 p->cpus_allowed = current->cpus_allowed; 1218 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1219 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1220 !cpu_online(task_cpu(p)))) 1221 set_task_cpu(p, smp_processor_id()); 1222 1223 /* CLONE_PARENT re-uses the old parent */ 1224 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1225 p->real_parent = current->real_parent; 1226 p->parent_exec_id = current->parent_exec_id; 1227 } else { 1228 p->real_parent = current; 1229 p->parent_exec_id = current->self_exec_id; 1230 } 1231 1232 spin_lock(¤t->sighand->siglock); 1233 1234 /* 1235 * Process group and session signals need to be delivered to just the 1236 * parent before the fork or both the parent and the child after the 1237 * fork. Restart if a signal comes in before we add the new process to 1238 * it's process group. 1239 * A fatal signal pending means that current will exit, so the new 1240 * thread can't slip out of an OOM kill (or normal SIGKILL). 1241 */ 1242 recalc_sigpending(); 1243 if (signal_pending(current)) { 1244 spin_unlock(¤t->sighand->siglock); 1245 write_unlock_irq(&tasklist_lock); 1246 retval = -ERESTARTNOINTR; 1247 goto bad_fork_free_graph; 1248 } 1249 1250 if (clone_flags & CLONE_THREAD) { 1251 p->group_leader = current->group_leader; 1252 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1253 } 1254 1255 if (likely(p->pid)) { 1256 list_add_tail(&p->sibling, &p->real_parent->children); 1257 tracehook_finish_clone(p, clone_flags, trace); 1258 1259 if (thread_group_leader(p)) { 1260 if (clone_flags & CLONE_NEWPID) 1261 p->nsproxy->pid_ns->child_reaper = p; 1262 1263 p->signal->leader_pid = pid; 1264 tty_kref_put(p->signal->tty); 1265 p->signal->tty = tty_kref_get(current->signal->tty); 1266 set_task_pgrp(p, task_pgrp_nr(current)); 1267 set_task_session(p, task_session_nr(current)); 1268 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1269 attach_pid(p, PIDTYPE_SID, task_session(current)); 1270 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1271 __get_cpu_var(process_counts)++; 1272 } 1273 attach_pid(p, PIDTYPE_PID, pid); 1274 nr_threads++; 1275 } 1276 1277 total_forks++; 1278 spin_unlock(¤t->sighand->siglock); 1279 write_unlock_irq(&tasklist_lock); 1280 proc_fork_connector(p); 1281 cgroup_post_fork(p); 1282 return p; 1283 1284 bad_fork_free_graph: 1285 ftrace_graph_exit_task(p); 1286 bad_fork_free_pid: 1287 if (pid != &init_struct_pid) 1288 free_pid(pid); 1289 bad_fork_cleanup_io: 1290 put_io_context(p->io_context); 1291 bad_fork_cleanup_namespaces: 1292 exit_task_namespaces(p); 1293 bad_fork_cleanup_mm: 1294 if (p->mm) 1295 mmput(p->mm); 1296 bad_fork_cleanup_signal: 1297 cleanup_signal(p); 1298 bad_fork_cleanup_sighand: 1299 __cleanup_sighand(p->sighand); 1300 bad_fork_cleanup_fs: 1301 exit_fs(p); /* blocking */ 1302 bad_fork_cleanup_files: 1303 exit_files(p); /* blocking */ 1304 bad_fork_cleanup_semundo: 1305 exit_sem(p); 1306 bad_fork_cleanup_audit: 1307 audit_free(p); 1308 bad_fork_cleanup_policy: 1309 #ifdef CONFIG_NUMA 1310 mpol_put(p->mempolicy); 1311 bad_fork_cleanup_cgroup: 1312 #endif 1313 cgroup_exit(p, cgroup_callbacks_done); 1314 delayacct_tsk_free(p); 1315 if (p->binfmt) 1316 module_put(p->binfmt->module); 1317 bad_fork_cleanup_put_domain: 1318 module_put(task_thread_info(p)->exec_domain->module); 1319 bad_fork_cleanup_count: 1320 atomic_dec(&p->cred->user->processes); 1321 put_cred(p->real_cred); 1322 put_cred(p->cred); 1323 bad_fork_free: 1324 free_task(p); 1325 fork_out: 1326 return ERR_PTR(retval); 1327 } 1328 1329 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1330 { 1331 memset(regs, 0, sizeof(struct pt_regs)); 1332 return regs; 1333 } 1334 1335 struct task_struct * __cpuinit fork_idle(int cpu) 1336 { 1337 struct task_struct *task; 1338 struct pt_regs regs; 1339 1340 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1341 &init_struct_pid, 0); 1342 if (!IS_ERR(task)) 1343 init_idle(task, cpu); 1344 1345 return task; 1346 } 1347 1348 /* 1349 * Ok, this is the main fork-routine. 1350 * 1351 * It copies the process, and if successful kick-starts 1352 * it and waits for it to finish using the VM if required. 1353 */ 1354 long do_fork(unsigned long clone_flags, 1355 unsigned long stack_start, 1356 struct pt_regs *regs, 1357 unsigned long stack_size, 1358 int __user *parent_tidptr, 1359 int __user *child_tidptr) 1360 { 1361 struct task_struct *p; 1362 int trace = 0; 1363 long nr; 1364 1365 /* 1366 * Do some preliminary argument and permissions checking before we 1367 * actually start allocating stuff 1368 */ 1369 if (clone_flags & CLONE_NEWUSER) { 1370 if (clone_flags & CLONE_THREAD) 1371 return -EINVAL; 1372 /* hopefully this check will go away when userns support is 1373 * complete 1374 */ 1375 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1376 !capable(CAP_SETGID)) 1377 return -EPERM; 1378 } 1379 1380 /* 1381 * We hope to recycle these flags after 2.6.26 1382 */ 1383 if (unlikely(clone_flags & CLONE_STOPPED)) { 1384 static int __read_mostly count = 100; 1385 1386 if (count > 0 && printk_ratelimit()) { 1387 char comm[TASK_COMM_LEN]; 1388 1389 count--; 1390 printk(KERN_INFO "fork(): process `%s' used deprecated " 1391 "clone flags 0x%lx\n", 1392 get_task_comm(comm, current), 1393 clone_flags & CLONE_STOPPED); 1394 } 1395 } 1396 1397 /* 1398 * When called from kernel_thread, don't do user tracing stuff. 1399 */ 1400 if (likely(user_mode(regs))) 1401 trace = tracehook_prepare_clone(clone_flags); 1402 1403 p = copy_process(clone_flags, stack_start, regs, stack_size, 1404 child_tidptr, NULL, trace); 1405 /* 1406 * Do this prior waking up the new thread - the thread pointer 1407 * might get invalid after that point, if the thread exits quickly. 1408 */ 1409 if (!IS_ERR(p)) { 1410 struct completion vfork; 1411 1412 trace_sched_process_fork(current, p); 1413 1414 nr = task_pid_vnr(p); 1415 1416 if (clone_flags & CLONE_PARENT_SETTID) 1417 put_user(nr, parent_tidptr); 1418 1419 if (clone_flags & CLONE_VFORK) { 1420 p->vfork_done = &vfork; 1421 init_completion(&vfork); 1422 } 1423 1424 audit_finish_fork(p); 1425 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1426 1427 /* 1428 * We set PF_STARTING at creation in case tracing wants to 1429 * use this to distinguish a fully live task from one that 1430 * hasn't gotten to tracehook_report_clone() yet. Now we 1431 * clear it and set the child going. 1432 */ 1433 p->flags &= ~PF_STARTING; 1434 1435 if (unlikely(clone_flags & CLONE_STOPPED)) { 1436 /* 1437 * We'll start up with an immediate SIGSTOP. 1438 */ 1439 sigaddset(&p->pending.signal, SIGSTOP); 1440 set_tsk_thread_flag(p, TIF_SIGPENDING); 1441 __set_task_state(p, TASK_STOPPED); 1442 } else { 1443 wake_up_new_task(p, clone_flags); 1444 } 1445 1446 tracehook_report_clone_complete(trace, regs, 1447 clone_flags, nr, p); 1448 1449 if (clone_flags & CLONE_VFORK) { 1450 freezer_do_not_count(); 1451 wait_for_completion(&vfork); 1452 freezer_count(); 1453 tracehook_report_vfork_done(p, nr); 1454 } 1455 } else { 1456 nr = PTR_ERR(p); 1457 } 1458 return nr; 1459 } 1460 1461 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1462 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1463 #endif 1464 1465 static void sighand_ctor(void *data) 1466 { 1467 struct sighand_struct *sighand = data; 1468 1469 spin_lock_init(&sighand->siglock); 1470 init_waitqueue_head(&sighand->signalfd_wqh); 1471 } 1472 1473 void __init proc_caches_init(void) 1474 { 1475 sighand_cachep = kmem_cache_create("sighand_cache", 1476 sizeof(struct sighand_struct), 0, 1477 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1478 sighand_ctor); 1479 signal_cachep = kmem_cache_create("signal_cache", 1480 sizeof(struct signal_struct), 0, 1481 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1482 files_cachep = kmem_cache_create("files_cache", 1483 sizeof(struct files_struct), 0, 1484 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1485 fs_cachep = kmem_cache_create("fs_cache", 1486 sizeof(struct fs_struct), 0, 1487 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1488 mm_cachep = kmem_cache_create("mm_struct", 1489 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1490 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1491 mmap_init(); 1492 } 1493 1494 /* 1495 * Check constraints on flags passed to the unshare system call and 1496 * force unsharing of additional process context as appropriate. 1497 */ 1498 static void check_unshare_flags(unsigned long *flags_ptr) 1499 { 1500 /* 1501 * If unsharing a thread from a thread group, must also 1502 * unshare vm. 1503 */ 1504 if (*flags_ptr & CLONE_THREAD) 1505 *flags_ptr |= CLONE_VM; 1506 1507 /* 1508 * If unsharing vm, must also unshare signal handlers. 1509 */ 1510 if (*flags_ptr & CLONE_VM) 1511 *flags_ptr |= CLONE_SIGHAND; 1512 1513 /* 1514 * If unsharing signal handlers and the task was created 1515 * using CLONE_THREAD, then must unshare the thread 1516 */ 1517 if ((*flags_ptr & CLONE_SIGHAND) && 1518 (atomic_read(¤t->signal->count) > 1)) 1519 *flags_ptr |= CLONE_THREAD; 1520 1521 /* 1522 * If unsharing namespace, must also unshare filesystem information. 1523 */ 1524 if (*flags_ptr & CLONE_NEWNS) 1525 *flags_ptr |= CLONE_FS; 1526 } 1527 1528 /* 1529 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1530 */ 1531 static int unshare_thread(unsigned long unshare_flags) 1532 { 1533 if (unshare_flags & CLONE_THREAD) 1534 return -EINVAL; 1535 1536 return 0; 1537 } 1538 1539 /* 1540 * Unshare the filesystem structure if it is being shared 1541 */ 1542 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1543 { 1544 struct fs_struct *fs = current->fs; 1545 1546 if ((unshare_flags & CLONE_FS) && 1547 (fs && atomic_read(&fs->count) > 1)) { 1548 *new_fsp = __copy_fs_struct(current->fs); 1549 if (!*new_fsp) 1550 return -ENOMEM; 1551 } 1552 1553 return 0; 1554 } 1555 1556 /* 1557 * Unsharing of sighand is not supported yet 1558 */ 1559 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1560 { 1561 struct sighand_struct *sigh = current->sighand; 1562 1563 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1564 return -EINVAL; 1565 else 1566 return 0; 1567 } 1568 1569 /* 1570 * Unshare vm if it is being shared 1571 */ 1572 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1573 { 1574 struct mm_struct *mm = current->mm; 1575 1576 if ((unshare_flags & CLONE_VM) && 1577 (mm && atomic_read(&mm->mm_users) > 1)) { 1578 return -EINVAL; 1579 } 1580 1581 return 0; 1582 } 1583 1584 /* 1585 * Unshare file descriptor table if it is being shared 1586 */ 1587 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1588 { 1589 struct files_struct *fd = current->files; 1590 int error = 0; 1591 1592 if ((unshare_flags & CLONE_FILES) && 1593 (fd && atomic_read(&fd->count) > 1)) { 1594 *new_fdp = dup_fd(fd, &error); 1595 if (!*new_fdp) 1596 return error; 1597 } 1598 1599 return 0; 1600 } 1601 1602 /* 1603 * unshare allows a process to 'unshare' part of the process 1604 * context which was originally shared using clone. copy_* 1605 * functions used by do_fork() cannot be used here directly 1606 * because they modify an inactive task_struct that is being 1607 * constructed. Here we are modifying the current, active, 1608 * task_struct. 1609 */ 1610 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1611 { 1612 int err = 0; 1613 struct fs_struct *fs, *new_fs = NULL; 1614 struct sighand_struct *new_sigh = NULL; 1615 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1616 struct files_struct *fd, *new_fd = NULL; 1617 struct nsproxy *new_nsproxy = NULL; 1618 int do_sysvsem = 0; 1619 1620 check_unshare_flags(&unshare_flags); 1621 1622 /* Return -EINVAL for all unsupported flags */ 1623 err = -EINVAL; 1624 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1625 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1626 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1627 goto bad_unshare_out; 1628 1629 /* 1630 * CLONE_NEWIPC must also detach from the undolist: after switching 1631 * to a new ipc namespace, the semaphore arrays from the old 1632 * namespace are unreachable. 1633 */ 1634 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1635 do_sysvsem = 1; 1636 if ((err = unshare_thread(unshare_flags))) 1637 goto bad_unshare_out; 1638 if ((err = unshare_fs(unshare_flags, &new_fs))) 1639 goto bad_unshare_cleanup_thread; 1640 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1641 goto bad_unshare_cleanup_fs; 1642 if ((err = unshare_vm(unshare_flags, &new_mm))) 1643 goto bad_unshare_cleanup_sigh; 1644 if ((err = unshare_fd(unshare_flags, &new_fd))) 1645 goto bad_unshare_cleanup_vm; 1646 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1647 new_fs))) 1648 goto bad_unshare_cleanup_fd; 1649 1650 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1651 if (do_sysvsem) { 1652 /* 1653 * CLONE_SYSVSEM is equivalent to sys_exit(). 1654 */ 1655 exit_sem(current); 1656 } 1657 1658 if (new_nsproxy) { 1659 switch_task_namespaces(current, new_nsproxy); 1660 new_nsproxy = NULL; 1661 } 1662 1663 task_lock(current); 1664 1665 if (new_fs) { 1666 fs = current->fs; 1667 current->fs = new_fs; 1668 new_fs = fs; 1669 } 1670 1671 if (new_mm) { 1672 mm = current->mm; 1673 active_mm = current->active_mm; 1674 current->mm = new_mm; 1675 current->active_mm = new_mm; 1676 activate_mm(active_mm, new_mm); 1677 new_mm = mm; 1678 } 1679 1680 if (new_fd) { 1681 fd = current->files; 1682 current->files = new_fd; 1683 new_fd = fd; 1684 } 1685 1686 task_unlock(current); 1687 } 1688 1689 if (new_nsproxy) 1690 put_nsproxy(new_nsproxy); 1691 1692 bad_unshare_cleanup_fd: 1693 if (new_fd) 1694 put_files_struct(new_fd); 1695 1696 bad_unshare_cleanup_vm: 1697 if (new_mm) 1698 mmput(new_mm); 1699 1700 bad_unshare_cleanup_sigh: 1701 if (new_sigh) 1702 if (atomic_dec_and_test(&new_sigh->count)) 1703 kmem_cache_free(sighand_cachep, new_sigh); 1704 1705 bad_unshare_cleanup_fs: 1706 if (new_fs) 1707 put_fs_struct(new_fs); 1708 1709 bad_unshare_cleanup_thread: 1710 bad_unshare_out: 1711 return err; 1712 } 1713 1714 /* 1715 * Helper to unshare the files of the current task. 1716 * We don't want to expose copy_files internals to 1717 * the exec layer of the kernel. 1718 */ 1719 1720 int unshare_files(struct files_struct **displaced) 1721 { 1722 struct task_struct *task = current; 1723 struct files_struct *copy = NULL; 1724 int error; 1725 1726 error = unshare_fd(CLONE_FILES, ©); 1727 if (error || !copy) { 1728 *displaced = NULL; 1729 return error; 1730 } 1731 *displaced = task->files; 1732 task_lock(task); 1733 task->files = copy; 1734 task_unlock(task); 1735 return 0; 1736 } 1737