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/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/ksm.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 <linux/fs_struct.h> 64 #include <linux/magic.h> 65 #include <linux/perf_event.h> 66 #include <linux/posix-timers.h> 67 68 #include <asm/pgtable.h> 69 #include <asm/pgalloc.h> 70 #include <asm/uaccess.h> 71 #include <asm/mmu_context.h> 72 #include <asm/cacheflush.h> 73 #include <asm/tlbflush.h> 74 75 #include <trace/events/sched.h> 76 77 /* 78 * Protected counters by write_lock_irq(&tasklist_lock) 79 */ 80 unsigned long total_forks; /* Handle normal Linux uptimes. */ 81 int nr_threads; /* The idle threads do not count.. */ 82 83 int max_threads; /* tunable limit on nr_threads */ 84 85 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 86 87 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 88 89 int nr_processes(void) 90 { 91 int cpu; 92 int total = 0; 93 94 for_each_online_cpu(cpu) 95 total += per_cpu(process_counts, cpu); 96 97 return total; 98 } 99 100 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 101 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 102 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 103 static struct kmem_cache *task_struct_cachep; 104 #endif 105 106 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 107 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 108 { 109 #ifdef CONFIG_DEBUG_STACK_USAGE 110 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 111 #else 112 gfp_t mask = GFP_KERNEL; 113 #endif 114 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 115 } 116 117 static inline void free_thread_info(struct thread_info *ti) 118 { 119 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 120 } 121 #endif 122 123 /* SLAB cache for signal_struct structures (tsk->signal) */ 124 static struct kmem_cache *signal_cachep; 125 126 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 127 struct kmem_cache *sighand_cachep; 128 129 /* SLAB cache for files_struct structures (tsk->files) */ 130 struct kmem_cache *files_cachep; 131 132 /* SLAB cache for fs_struct structures (tsk->fs) */ 133 struct kmem_cache *fs_cachep; 134 135 /* SLAB cache for vm_area_struct structures */ 136 struct kmem_cache *vm_area_cachep; 137 138 /* SLAB cache for mm_struct structures (tsk->mm) */ 139 static struct kmem_cache *mm_cachep; 140 141 static void account_kernel_stack(struct thread_info *ti, int account) 142 { 143 struct zone *zone = page_zone(virt_to_page(ti)); 144 145 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 146 } 147 148 void free_task(struct task_struct *tsk) 149 { 150 prop_local_destroy_single(&tsk->dirties); 151 account_kernel_stack(tsk->stack, -1); 152 free_thread_info(tsk->stack); 153 rt_mutex_debug_task_free(tsk); 154 ftrace_graph_exit_task(tsk); 155 free_task_struct(tsk); 156 } 157 EXPORT_SYMBOL(free_task); 158 159 void __put_task_struct(struct task_struct *tsk) 160 { 161 WARN_ON(!tsk->exit_state); 162 WARN_ON(atomic_read(&tsk->usage)); 163 WARN_ON(tsk == current); 164 165 exit_creds(tsk); 166 delayacct_tsk_free(tsk); 167 168 if (!profile_handoff_task(tsk)) 169 free_task(tsk); 170 } 171 172 /* 173 * macro override instead of weak attribute alias, to workaround 174 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 175 */ 176 #ifndef arch_task_cache_init 177 #define arch_task_cache_init() 178 #endif 179 180 void __init fork_init(unsigned long mempages) 181 { 182 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 183 #ifndef ARCH_MIN_TASKALIGN 184 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 185 #endif 186 /* create a slab on which task_structs can be allocated */ 187 task_struct_cachep = 188 kmem_cache_create("task_struct", sizeof(struct task_struct), 189 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 190 #endif 191 192 /* do the arch specific task caches init */ 193 arch_task_cache_init(); 194 195 /* 196 * The default maximum number of threads is set to a safe 197 * value: the thread structures can take up at most half 198 * of memory. 199 */ 200 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 201 202 /* 203 * we need to allow at least 20 threads to boot a system 204 */ 205 if(max_threads < 20) 206 max_threads = 20; 207 208 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 209 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 210 init_task.signal->rlim[RLIMIT_SIGPENDING] = 211 init_task.signal->rlim[RLIMIT_NPROC]; 212 } 213 214 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 215 struct task_struct *src) 216 { 217 *dst = *src; 218 return 0; 219 } 220 221 static struct task_struct *dup_task_struct(struct task_struct *orig) 222 { 223 struct task_struct *tsk; 224 struct thread_info *ti; 225 unsigned long *stackend; 226 227 int err; 228 229 prepare_to_copy(orig); 230 231 tsk = alloc_task_struct(); 232 if (!tsk) 233 return NULL; 234 235 ti = alloc_thread_info(tsk); 236 if (!ti) { 237 free_task_struct(tsk); 238 return NULL; 239 } 240 241 err = arch_dup_task_struct(tsk, orig); 242 if (err) 243 goto out; 244 245 tsk->stack = ti; 246 247 err = prop_local_init_single(&tsk->dirties); 248 if (err) 249 goto out; 250 251 setup_thread_stack(tsk, orig); 252 stackend = end_of_stack(tsk); 253 *stackend = STACK_END_MAGIC; /* for overflow detection */ 254 255 #ifdef CONFIG_CC_STACKPROTECTOR 256 tsk->stack_canary = get_random_int(); 257 #endif 258 259 /* One for us, one for whoever does the "release_task()" (usually parent) */ 260 atomic_set(&tsk->usage,2); 261 atomic_set(&tsk->fs_excl, 0); 262 #ifdef CONFIG_BLK_DEV_IO_TRACE 263 tsk->btrace_seq = 0; 264 #endif 265 tsk->splice_pipe = NULL; 266 267 account_kernel_stack(ti, 1); 268 269 return tsk; 270 271 out: 272 free_thread_info(ti); 273 free_task_struct(tsk); 274 return NULL; 275 } 276 277 #ifdef CONFIG_MMU 278 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 279 { 280 struct vm_area_struct *mpnt, *tmp, **pprev; 281 struct rb_node **rb_link, *rb_parent; 282 int retval; 283 unsigned long charge; 284 struct mempolicy *pol; 285 286 down_write(&oldmm->mmap_sem); 287 flush_cache_dup_mm(oldmm); 288 /* 289 * Not linked in yet - no deadlock potential: 290 */ 291 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 292 293 mm->locked_vm = 0; 294 mm->mmap = NULL; 295 mm->mmap_cache = NULL; 296 mm->free_area_cache = oldmm->mmap_base; 297 mm->cached_hole_size = ~0UL; 298 mm->map_count = 0; 299 cpumask_clear(mm_cpumask(mm)); 300 mm->mm_rb = RB_ROOT; 301 rb_link = &mm->mm_rb.rb_node; 302 rb_parent = NULL; 303 pprev = &mm->mmap; 304 retval = ksm_fork(mm, oldmm); 305 if (retval) 306 goto out; 307 308 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 309 struct file *file; 310 311 if (mpnt->vm_flags & VM_DONTCOPY) { 312 long pages = vma_pages(mpnt); 313 mm->total_vm -= pages; 314 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 315 -pages); 316 continue; 317 } 318 charge = 0; 319 if (mpnt->vm_flags & VM_ACCOUNT) { 320 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 321 if (security_vm_enough_memory(len)) 322 goto fail_nomem; 323 charge = len; 324 } 325 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 326 if (!tmp) 327 goto fail_nomem; 328 *tmp = *mpnt; 329 pol = mpol_dup(vma_policy(mpnt)); 330 retval = PTR_ERR(pol); 331 if (IS_ERR(pol)) 332 goto fail_nomem_policy; 333 vma_set_policy(tmp, pol); 334 tmp->vm_flags &= ~VM_LOCKED; 335 tmp->vm_mm = mm; 336 tmp->vm_next = NULL; 337 anon_vma_link(tmp); 338 file = tmp->vm_file; 339 if (file) { 340 struct inode *inode = file->f_path.dentry->d_inode; 341 struct address_space *mapping = file->f_mapping; 342 343 get_file(file); 344 if (tmp->vm_flags & VM_DENYWRITE) 345 atomic_dec(&inode->i_writecount); 346 spin_lock(&mapping->i_mmap_lock); 347 if (tmp->vm_flags & VM_SHARED) 348 mapping->i_mmap_writable++; 349 tmp->vm_truncate_count = mpnt->vm_truncate_count; 350 flush_dcache_mmap_lock(mapping); 351 /* insert tmp into the share list, just after mpnt */ 352 vma_prio_tree_add(tmp, mpnt); 353 flush_dcache_mmap_unlock(mapping); 354 spin_unlock(&mapping->i_mmap_lock); 355 } 356 357 /* 358 * Clear hugetlb-related page reserves for children. This only 359 * affects MAP_PRIVATE mappings. Faults generated by the child 360 * are not guaranteed to succeed, even if read-only 361 */ 362 if (is_vm_hugetlb_page(tmp)) 363 reset_vma_resv_huge_pages(tmp); 364 365 /* 366 * Link in the new vma and copy the page table entries. 367 */ 368 *pprev = tmp; 369 pprev = &tmp->vm_next; 370 371 __vma_link_rb(mm, tmp, rb_link, rb_parent); 372 rb_link = &tmp->vm_rb.rb_right; 373 rb_parent = &tmp->vm_rb; 374 375 mm->map_count++; 376 retval = copy_page_range(mm, oldmm, mpnt); 377 378 if (tmp->vm_ops && tmp->vm_ops->open) 379 tmp->vm_ops->open(tmp); 380 381 if (retval) 382 goto out; 383 } 384 /* a new mm has just been created */ 385 arch_dup_mmap(oldmm, mm); 386 retval = 0; 387 out: 388 up_write(&mm->mmap_sem); 389 flush_tlb_mm(oldmm); 390 up_write(&oldmm->mmap_sem); 391 return retval; 392 fail_nomem_policy: 393 kmem_cache_free(vm_area_cachep, tmp); 394 fail_nomem: 395 retval = -ENOMEM; 396 vm_unacct_memory(charge); 397 goto out; 398 } 399 400 static inline int mm_alloc_pgd(struct mm_struct * mm) 401 { 402 mm->pgd = pgd_alloc(mm); 403 if (unlikely(!mm->pgd)) 404 return -ENOMEM; 405 return 0; 406 } 407 408 static inline void mm_free_pgd(struct mm_struct * mm) 409 { 410 pgd_free(mm, mm->pgd); 411 } 412 #else 413 #define dup_mmap(mm, oldmm) (0) 414 #define mm_alloc_pgd(mm) (0) 415 #define mm_free_pgd(mm) 416 #endif /* CONFIG_MMU */ 417 418 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 419 420 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 421 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 422 423 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 424 425 static int __init coredump_filter_setup(char *s) 426 { 427 default_dump_filter = 428 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 429 MMF_DUMP_FILTER_MASK; 430 return 1; 431 } 432 433 __setup("coredump_filter=", coredump_filter_setup); 434 435 #include <linux/init_task.h> 436 437 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 438 { 439 atomic_set(&mm->mm_users, 1); 440 atomic_set(&mm->mm_count, 1); 441 init_rwsem(&mm->mmap_sem); 442 INIT_LIST_HEAD(&mm->mmlist); 443 mm->flags = (current->mm) ? 444 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 445 mm->core_state = NULL; 446 mm->nr_ptes = 0; 447 set_mm_counter(mm, file_rss, 0); 448 set_mm_counter(mm, anon_rss, 0); 449 spin_lock_init(&mm->page_table_lock); 450 spin_lock_init(&mm->ioctx_lock); 451 INIT_HLIST_HEAD(&mm->ioctx_list); 452 mm->free_area_cache = TASK_UNMAPPED_BASE; 453 mm->cached_hole_size = ~0UL; 454 mm_init_owner(mm, p); 455 456 if (likely(!mm_alloc_pgd(mm))) { 457 mm->def_flags = 0; 458 mmu_notifier_mm_init(mm); 459 return mm; 460 } 461 462 free_mm(mm); 463 return NULL; 464 } 465 466 /* 467 * Allocate and initialize an mm_struct. 468 */ 469 struct mm_struct * mm_alloc(void) 470 { 471 struct mm_struct * mm; 472 473 mm = allocate_mm(); 474 if (mm) { 475 memset(mm, 0, sizeof(*mm)); 476 mm = mm_init(mm, current); 477 } 478 return mm; 479 } 480 481 /* 482 * Called when the last reference to the mm 483 * is dropped: either by a lazy thread or by 484 * mmput. Free the page directory and the mm. 485 */ 486 void __mmdrop(struct mm_struct *mm) 487 { 488 BUG_ON(mm == &init_mm); 489 mm_free_pgd(mm); 490 destroy_context(mm); 491 mmu_notifier_mm_destroy(mm); 492 free_mm(mm); 493 } 494 EXPORT_SYMBOL_GPL(__mmdrop); 495 496 /* 497 * Decrement the use count and release all resources for an mm. 498 */ 499 void mmput(struct mm_struct *mm) 500 { 501 might_sleep(); 502 503 if (atomic_dec_and_test(&mm->mm_users)) { 504 exit_aio(mm); 505 ksm_exit(mm); 506 exit_mmap(mm); 507 set_mm_exe_file(mm, NULL); 508 if (!list_empty(&mm->mmlist)) { 509 spin_lock(&mmlist_lock); 510 list_del(&mm->mmlist); 511 spin_unlock(&mmlist_lock); 512 } 513 put_swap_token(mm); 514 mmdrop(mm); 515 } 516 } 517 EXPORT_SYMBOL_GPL(mmput); 518 519 /** 520 * get_task_mm - acquire a reference to the task's mm 521 * 522 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 523 * this kernel workthread has transiently adopted a user mm with use_mm, 524 * to do its AIO) is not set and if so returns a reference to it, after 525 * bumping up the use count. User must release the mm via mmput() 526 * after use. Typically used by /proc and ptrace. 527 */ 528 struct mm_struct *get_task_mm(struct task_struct *task) 529 { 530 struct mm_struct *mm; 531 532 task_lock(task); 533 mm = task->mm; 534 if (mm) { 535 if (task->flags & PF_KTHREAD) 536 mm = NULL; 537 else 538 atomic_inc(&mm->mm_users); 539 } 540 task_unlock(task); 541 return mm; 542 } 543 EXPORT_SYMBOL_GPL(get_task_mm); 544 545 /* Please note the differences between mmput and mm_release. 546 * mmput is called whenever we stop holding onto a mm_struct, 547 * error success whatever. 548 * 549 * mm_release is called after a mm_struct has been removed 550 * from the current process. 551 * 552 * This difference is important for error handling, when we 553 * only half set up a mm_struct for a new process and need to restore 554 * the old one. Because we mmput the new mm_struct before 555 * restoring the old one. . . 556 * Eric Biederman 10 January 1998 557 */ 558 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 559 { 560 struct completion *vfork_done = tsk->vfork_done; 561 562 /* Get rid of any futexes when releasing the mm */ 563 #ifdef CONFIG_FUTEX 564 if (unlikely(tsk->robust_list)) 565 exit_robust_list(tsk); 566 #ifdef CONFIG_COMPAT 567 if (unlikely(tsk->compat_robust_list)) 568 compat_exit_robust_list(tsk); 569 #endif 570 #endif 571 572 /* Get rid of any cached register state */ 573 deactivate_mm(tsk, mm); 574 575 /* notify parent sleeping on vfork() */ 576 if (vfork_done) { 577 tsk->vfork_done = NULL; 578 complete(vfork_done); 579 } 580 581 /* 582 * If we're exiting normally, clear a user-space tid field if 583 * requested. We leave this alone when dying by signal, to leave 584 * the value intact in a core dump, and to save the unnecessary 585 * trouble otherwise. Userland only wants this done for a sys_exit. 586 */ 587 if (tsk->clear_child_tid) { 588 if (!(tsk->flags & PF_SIGNALED) && 589 atomic_read(&mm->mm_users) > 1) { 590 /* 591 * We don't check the error code - if userspace has 592 * not set up a proper pointer then tough luck. 593 */ 594 put_user(0, tsk->clear_child_tid); 595 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 596 1, NULL, NULL, 0); 597 } 598 tsk->clear_child_tid = NULL; 599 } 600 } 601 602 /* 603 * Allocate a new mm structure and copy contents from the 604 * mm structure of the passed in task structure. 605 */ 606 struct mm_struct *dup_mm(struct task_struct *tsk) 607 { 608 struct mm_struct *mm, *oldmm = current->mm; 609 int err; 610 611 if (!oldmm) 612 return NULL; 613 614 mm = allocate_mm(); 615 if (!mm) 616 goto fail_nomem; 617 618 memcpy(mm, oldmm, sizeof(*mm)); 619 620 /* Initializing for Swap token stuff */ 621 mm->token_priority = 0; 622 mm->last_interval = 0; 623 624 if (!mm_init(mm, tsk)) 625 goto fail_nomem; 626 627 if (init_new_context(tsk, mm)) 628 goto fail_nocontext; 629 630 dup_mm_exe_file(oldmm, mm); 631 632 err = dup_mmap(mm, oldmm); 633 if (err) 634 goto free_pt; 635 636 mm->hiwater_rss = get_mm_rss(mm); 637 mm->hiwater_vm = mm->total_vm; 638 639 return mm; 640 641 free_pt: 642 mmput(mm); 643 644 fail_nomem: 645 return NULL; 646 647 fail_nocontext: 648 /* 649 * If init_new_context() failed, we cannot use mmput() to free the mm 650 * because it calls destroy_context() 651 */ 652 mm_free_pgd(mm); 653 free_mm(mm); 654 return NULL; 655 } 656 657 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 658 { 659 struct mm_struct * mm, *oldmm; 660 int retval; 661 662 tsk->min_flt = tsk->maj_flt = 0; 663 tsk->nvcsw = tsk->nivcsw = 0; 664 #ifdef CONFIG_DETECT_HUNG_TASK 665 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 666 #endif 667 668 tsk->mm = NULL; 669 tsk->active_mm = NULL; 670 671 /* 672 * Are we cloning a kernel thread? 673 * 674 * We need to steal a active VM for that.. 675 */ 676 oldmm = current->mm; 677 if (!oldmm) 678 return 0; 679 680 if (clone_flags & CLONE_VM) { 681 atomic_inc(&oldmm->mm_users); 682 mm = oldmm; 683 goto good_mm; 684 } 685 686 retval = -ENOMEM; 687 mm = dup_mm(tsk); 688 if (!mm) 689 goto fail_nomem; 690 691 good_mm: 692 /* Initializing for Swap token stuff */ 693 mm->token_priority = 0; 694 mm->last_interval = 0; 695 696 tsk->mm = mm; 697 tsk->active_mm = mm; 698 return 0; 699 700 fail_nomem: 701 return retval; 702 } 703 704 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 705 { 706 struct fs_struct *fs = current->fs; 707 if (clone_flags & CLONE_FS) { 708 /* tsk->fs is already what we want */ 709 write_lock(&fs->lock); 710 if (fs->in_exec) { 711 write_unlock(&fs->lock); 712 return -EAGAIN; 713 } 714 fs->users++; 715 write_unlock(&fs->lock); 716 return 0; 717 } 718 tsk->fs = copy_fs_struct(fs); 719 if (!tsk->fs) 720 return -ENOMEM; 721 return 0; 722 } 723 724 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 725 { 726 struct files_struct *oldf, *newf; 727 int error = 0; 728 729 /* 730 * A background process may not have any files ... 731 */ 732 oldf = current->files; 733 if (!oldf) 734 goto out; 735 736 if (clone_flags & CLONE_FILES) { 737 atomic_inc(&oldf->count); 738 goto out; 739 } 740 741 newf = dup_fd(oldf, &error); 742 if (!newf) 743 goto out; 744 745 tsk->files = newf; 746 error = 0; 747 out: 748 return error; 749 } 750 751 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 752 { 753 #ifdef CONFIG_BLOCK 754 struct io_context *ioc = current->io_context; 755 756 if (!ioc) 757 return 0; 758 /* 759 * Share io context with parent, if CLONE_IO is set 760 */ 761 if (clone_flags & CLONE_IO) { 762 tsk->io_context = ioc_task_link(ioc); 763 if (unlikely(!tsk->io_context)) 764 return -ENOMEM; 765 } else if (ioprio_valid(ioc->ioprio)) { 766 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 767 if (unlikely(!tsk->io_context)) 768 return -ENOMEM; 769 770 tsk->io_context->ioprio = ioc->ioprio; 771 } 772 #endif 773 return 0; 774 } 775 776 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 777 { 778 struct sighand_struct *sig; 779 780 if (clone_flags & CLONE_SIGHAND) { 781 atomic_inc(¤t->sighand->count); 782 return 0; 783 } 784 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 785 rcu_assign_pointer(tsk->sighand, sig); 786 if (!sig) 787 return -ENOMEM; 788 atomic_set(&sig->count, 1); 789 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 790 return 0; 791 } 792 793 void __cleanup_sighand(struct sighand_struct *sighand) 794 { 795 if (atomic_dec_and_test(&sighand->count)) 796 kmem_cache_free(sighand_cachep, sighand); 797 } 798 799 800 /* 801 * Initialize POSIX timer handling for a thread group. 802 */ 803 static void posix_cpu_timers_init_group(struct signal_struct *sig) 804 { 805 /* Thread group counters. */ 806 thread_group_cputime_init(sig); 807 808 /* Expiration times and increments. */ 809 sig->it[CPUCLOCK_PROF].expires = cputime_zero; 810 sig->it[CPUCLOCK_PROF].incr = cputime_zero; 811 sig->it[CPUCLOCK_VIRT].expires = cputime_zero; 812 sig->it[CPUCLOCK_VIRT].incr = cputime_zero; 813 814 /* Cached expiration times. */ 815 sig->cputime_expires.prof_exp = cputime_zero; 816 sig->cputime_expires.virt_exp = cputime_zero; 817 sig->cputime_expires.sched_exp = 0; 818 819 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 820 sig->cputime_expires.prof_exp = 821 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 822 sig->cputimer.running = 1; 823 } 824 825 /* The timer lists. */ 826 INIT_LIST_HEAD(&sig->cpu_timers[0]); 827 INIT_LIST_HEAD(&sig->cpu_timers[1]); 828 INIT_LIST_HEAD(&sig->cpu_timers[2]); 829 } 830 831 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 832 { 833 struct signal_struct *sig; 834 835 if (clone_flags & CLONE_THREAD) 836 return 0; 837 838 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 839 tsk->signal = sig; 840 if (!sig) 841 return -ENOMEM; 842 843 atomic_set(&sig->count, 1); 844 atomic_set(&sig->live, 1); 845 init_waitqueue_head(&sig->wait_chldexit); 846 sig->flags = 0; 847 if (clone_flags & CLONE_NEWPID) 848 sig->flags |= SIGNAL_UNKILLABLE; 849 sig->group_exit_code = 0; 850 sig->group_exit_task = NULL; 851 sig->group_stop_count = 0; 852 sig->curr_target = tsk; 853 init_sigpending(&sig->shared_pending); 854 INIT_LIST_HEAD(&sig->posix_timers); 855 856 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 857 sig->it_real_incr.tv64 = 0; 858 sig->real_timer.function = it_real_fn; 859 860 sig->leader = 0; /* session leadership doesn't inherit */ 861 sig->tty_old_pgrp = NULL; 862 sig->tty = NULL; 863 864 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 865 sig->gtime = cputime_zero; 866 sig->cgtime = cputime_zero; 867 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 868 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 869 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 870 sig->maxrss = sig->cmaxrss = 0; 871 task_io_accounting_init(&sig->ioac); 872 sig->sum_sched_runtime = 0; 873 taskstats_tgid_init(sig); 874 875 task_lock(current->group_leader); 876 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 877 task_unlock(current->group_leader); 878 879 posix_cpu_timers_init_group(sig); 880 881 acct_init_pacct(&sig->pacct); 882 883 tty_audit_fork(sig); 884 885 sig->oom_adj = current->signal->oom_adj; 886 887 return 0; 888 } 889 890 void __cleanup_signal(struct signal_struct *sig) 891 { 892 thread_group_cputime_free(sig); 893 tty_kref_put(sig->tty); 894 kmem_cache_free(signal_cachep, 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 ftrace_graph_init_task(p); 992 993 rt_mutex_init_task(p); 994 995 #ifdef CONFIG_PROVE_LOCKING 996 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 997 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 998 #endif 999 retval = -EAGAIN; 1000 if (atomic_read(&p->real_cred->user->processes) >= 1001 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1002 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1003 p->real_cred->user != INIT_USER) 1004 goto bad_fork_free; 1005 } 1006 1007 retval = copy_creds(p, clone_flags); 1008 if (retval < 0) 1009 goto bad_fork_free; 1010 1011 /* 1012 * If multiple threads are within copy_process(), then this check 1013 * triggers too late. This doesn't hurt, the check is only there 1014 * to stop root fork bombs. 1015 */ 1016 retval = -EAGAIN; 1017 if (nr_threads >= max_threads) 1018 goto bad_fork_cleanup_count; 1019 1020 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1021 goto bad_fork_cleanup_count; 1022 1023 if (p->binfmt && !try_module_get(p->binfmt->module)) 1024 goto bad_fork_cleanup_put_domain; 1025 1026 p->did_exec = 0; 1027 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1028 copy_flags(clone_flags, p); 1029 INIT_LIST_HEAD(&p->children); 1030 INIT_LIST_HEAD(&p->sibling); 1031 rcu_copy_process(p); 1032 p->vfork_done = NULL; 1033 spin_lock_init(&p->alloc_lock); 1034 1035 init_sigpending(&p->pending); 1036 1037 p->utime = cputime_zero; 1038 p->stime = cputime_zero; 1039 p->gtime = cputime_zero; 1040 p->utimescaled = cputime_zero; 1041 p->stimescaled = cputime_zero; 1042 p->prev_utime = cputime_zero; 1043 p->prev_stime = cputime_zero; 1044 1045 p->default_timer_slack_ns = current->timer_slack_ns; 1046 1047 task_io_accounting_init(&p->ioac); 1048 acct_clear_integrals(p); 1049 1050 posix_cpu_timers_init(p); 1051 1052 p->lock_depth = -1; /* -1 = no lock */ 1053 do_posix_clock_monotonic_gettime(&p->start_time); 1054 p->real_start_time = p->start_time; 1055 monotonic_to_bootbased(&p->real_start_time); 1056 p->io_context = NULL; 1057 p->audit_context = NULL; 1058 cgroup_fork(p); 1059 #ifdef CONFIG_NUMA 1060 p->mempolicy = mpol_dup(p->mempolicy); 1061 if (IS_ERR(p->mempolicy)) { 1062 retval = PTR_ERR(p->mempolicy); 1063 p->mempolicy = NULL; 1064 goto bad_fork_cleanup_cgroup; 1065 } 1066 mpol_fix_fork_child_flag(p); 1067 #endif 1068 #ifdef CONFIG_TRACE_IRQFLAGS 1069 p->irq_events = 0; 1070 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1071 p->hardirqs_enabled = 1; 1072 #else 1073 p->hardirqs_enabled = 0; 1074 #endif 1075 p->hardirq_enable_ip = 0; 1076 p->hardirq_enable_event = 0; 1077 p->hardirq_disable_ip = _THIS_IP_; 1078 p->hardirq_disable_event = 0; 1079 p->softirqs_enabled = 1; 1080 p->softirq_enable_ip = _THIS_IP_; 1081 p->softirq_enable_event = 0; 1082 p->softirq_disable_ip = 0; 1083 p->softirq_disable_event = 0; 1084 p->hardirq_context = 0; 1085 p->softirq_context = 0; 1086 #endif 1087 #ifdef CONFIG_LOCKDEP 1088 p->lockdep_depth = 0; /* no locks held yet */ 1089 p->curr_chain_key = 0; 1090 p->lockdep_recursion = 0; 1091 #endif 1092 1093 #ifdef CONFIG_DEBUG_MUTEXES 1094 p->blocked_on = NULL; /* not blocked yet */ 1095 #endif 1096 1097 p->bts = NULL; 1098 1099 p->stack_start = stack_start; 1100 1101 /* Perform scheduler related setup. Assign this task to a CPU. */ 1102 sched_fork(p, clone_flags); 1103 1104 retval = perf_event_init_task(p); 1105 if (retval) 1106 goto bad_fork_cleanup_policy; 1107 1108 if ((retval = audit_alloc(p))) 1109 goto bad_fork_cleanup_policy; 1110 /* copy all the process information */ 1111 if ((retval = copy_semundo(clone_flags, p))) 1112 goto bad_fork_cleanup_audit; 1113 if ((retval = copy_files(clone_flags, p))) 1114 goto bad_fork_cleanup_semundo; 1115 if ((retval = copy_fs(clone_flags, p))) 1116 goto bad_fork_cleanup_files; 1117 if ((retval = copy_sighand(clone_flags, p))) 1118 goto bad_fork_cleanup_fs; 1119 if ((retval = copy_signal(clone_flags, p))) 1120 goto bad_fork_cleanup_sighand; 1121 if ((retval = copy_mm(clone_flags, p))) 1122 goto bad_fork_cleanup_signal; 1123 if ((retval = copy_namespaces(clone_flags, p))) 1124 goto bad_fork_cleanup_mm; 1125 if ((retval = copy_io(clone_flags, p))) 1126 goto bad_fork_cleanup_namespaces; 1127 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1128 if (retval) 1129 goto bad_fork_cleanup_io; 1130 1131 if (pid != &init_struct_pid) { 1132 retval = -ENOMEM; 1133 pid = alloc_pid(p->nsproxy->pid_ns); 1134 if (!pid) 1135 goto bad_fork_cleanup_io; 1136 1137 if (clone_flags & CLONE_NEWPID) { 1138 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1139 if (retval < 0) 1140 goto bad_fork_free_pid; 1141 } 1142 } 1143 1144 p->pid = pid_nr(pid); 1145 p->tgid = p->pid; 1146 if (clone_flags & CLONE_THREAD) 1147 p->tgid = current->tgid; 1148 1149 if (current->nsproxy != p->nsproxy) { 1150 retval = ns_cgroup_clone(p, pid); 1151 if (retval) 1152 goto bad_fork_free_pid; 1153 } 1154 1155 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1156 /* 1157 * Clear TID on mm_release()? 1158 */ 1159 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1160 #ifdef CONFIG_FUTEX 1161 p->robust_list = NULL; 1162 #ifdef CONFIG_COMPAT 1163 p->compat_robust_list = NULL; 1164 #endif 1165 INIT_LIST_HEAD(&p->pi_state_list); 1166 p->pi_state_cache = NULL; 1167 #endif 1168 /* 1169 * sigaltstack should be cleared when sharing the same VM 1170 */ 1171 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1172 p->sas_ss_sp = p->sas_ss_size = 0; 1173 1174 /* 1175 * Syscall tracing should be turned off in the child regardless 1176 * of CLONE_PTRACE. 1177 */ 1178 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1179 #ifdef TIF_SYSCALL_EMU 1180 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1181 #endif 1182 clear_all_latency_tracing(p); 1183 1184 /* ok, now we should be set up.. */ 1185 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1186 p->pdeath_signal = 0; 1187 p->exit_state = 0; 1188 1189 /* 1190 * Ok, make it visible to the rest of the system. 1191 * We dont wake it up yet. 1192 */ 1193 p->group_leader = p; 1194 INIT_LIST_HEAD(&p->thread_group); 1195 1196 /* Now that the task is set up, run cgroup callbacks if 1197 * necessary. We need to run them before the task is visible 1198 * on the tasklist. */ 1199 cgroup_fork_callbacks(p); 1200 cgroup_callbacks_done = 1; 1201 1202 /* Need tasklist lock for parent etc handling! */ 1203 write_lock_irq(&tasklist_lock); 1204 1205 /* 1206 * The task hasn't been attached yet, so its cpus_allowed mask will 1207 * not be changed, nor will its assigned CPU. 1208 * 1209 * The cpus_allowed mask of the parent may have changed after it was 1210 * copied first time - so re-copy it here, then check the child's CPU 1211 * to ensure it is on a valid CPU (and if not, just force it back to 1212 * parent's CPU). This avoids alot of nasty races. 1213 */ 1214 p->cpus_allowed = current->cpus_allowed; 1215 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1216 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1217 !cpu_online(task_cpu(p)))) 1218 set_task_cpu(p, smp_processor_id()); 1219 1220 /* CLONE_PARENT re-uses the old parent */ 1221 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1222 p->real_parent = current->real_parent; 1223 p->parent_exec_id = current->parent_exec_id; 1224 } else { 1225 p->real_parent = current; 1226 p->parent_exec_id = current->self_exec_id; 1227 } 1228 1229 spin_lock(¤t->sighand->siglock); 1230 1231 /* 1232 * Process group and session signals need to be delivered to just the 1233 * parent before the fork or both the parent and the child after the 1234 * fork. Restart if a signal comes in before we add the new process to 1235 * it's process group. 1236 * A fatal signal pending means that current will exit, so the new 1237 * thread can't slip out of an OOM kill (or normal SIGKILL). 1238 */ 1239 recalc_sigpending(); 1240 if (signal_pending(current)) { 1241 spin_unlock(¤t->sighand->siglock); 1242 write_unlock_irq(&tasklist_lock); 1243 retval = -ERESTARTNOINTR; 1244 goto bad_fork_free_pid; 1245 } 1246 1247 if (clone_flags & CLONE_THREAD) { 1248 atomic_inc(¤t->signal->count); 1249 atomic_inc(¤t->signal->live); 1250 p->group_leader = current->group_leader; 1251 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1252 } 1253 1254 if (likely(p->pid)) { 1255 list_add_tail(&p->sibling, &p->real_parent->children); 1256 tracehook_finish_clone(p, clone_flags, trace); 1257 1258 if (thread_group_leader(p)) { 1259 if (clone_flags & CLONE_NEWPID) 1260 p->nsproxy->pid_ns->child_reaper = p; 1261 1262 p->signal->leader_pid = pid; 1263 tty_kref_put(p->signal->tty); 1264 p->signal->tty = tty_kref_get(current->signal->tty); 1265 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1266 attach_pid(p, PIDTYPE_SID, task_session(current)); 1267 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1268 __get_cpu_var(process_counts)++; 1269 } 1270 attach_pid(p, PIDTYPE_PID, pid); 1271 nr_threads++; 1272 } 1273 1274 total_forks++; 1275 spin_unlock(¤t->sighand->siglock); 1276 write_unlock_irq(&tasklist_lock); 1277 proc_fork_connector(p); 1278 cgroup_post_fork(p); 1279 perf_event_fork(p); 1280 return p; 1281 1282 bad_fork_free_pid: 1283 if (pid != &init_struct_pid) 1284 free_pid(pid); 1285 bad_fork_cleanup_io: 1286 put_io_context(p->io_context); 1287 bad_fork_cleanup_namespaces: 1288 exit_task_namespaces(p); 1289 bad_fork_cleanup_mm: 1290 if (p->mm) 1291 mmput(p->mm); 1292 bad_fork_cleanup_signal: 1293 if (!(clone_flags & CLONE_THREAD)) 1294 __cleanup_signal(p->signal); 1295 bad_fork_cleanup_sighand: 1296 __cleanup_sighand(p->sighand); 1297 bad_fork_cleanup_fs: 1298 exit_fs(p); /* blocking */ 1299 bad_fork_cleanup_files: 1300 exit_files(p); /* blocking */ 1301 bad_fork_cleanup_semundo: 1302 exit_sem(p); 1303 bad_fork_cleanup_audit: 1304 audit_free(p); 1305 bad_fork_cleanup_policy: 1306 perf_event_free_task(p); 1307 #ifdef CONFIG_NUMA 1308 mpol_put(p->mempolicy); 1309 bad_fork_cleanup_cgroup: 1310 #endif 1311 cgroup_exit(p, cgroup_callbacks_done); 1312 delayacct_tsk_free(p); 1313 if (p->binfmt) 1314 module_put(p->binfmt->module); 1315 bad_fork_cleanup_put_domain: 1316 module_put(task_thread_info(p)->exec_domain->module); 1317 bad_fork_cleanup_count: 1318 atomic_dec(&p->cred->user->processes); 1319 exit_creds(p); 1320 bad_fork_free: 1321 free_task(p); 1322 fork_out: 1323 return ERR_PTR(retval); 1324 } 1325 1326 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1327 { 1328 memset(regs, 0, sizeof(struct pt_regs)); 1329 return regs; 1330 } 1331 1332 struct task_struct * __cpuinit fork_idle(int cpu) 1333 { 1334 struct task_struct *task; 1335 struct pt_regs regs; 1336 1337 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1338 &init_struct_pid, 0); 1339 if (!IS_ERR(task)) 1340 init_idle(task, cpu); 1341 1342 return task; 1343 } 1344 1345 /* 1346 * Ok, this is the main fork-routine. 1347 * 1348 * It copies the process, and if successful kick-starts 1349 * it and waits for it to finish using the VM if required. 1350 */ 1351 long do_fork(unsigned long clone_flags, 1352 unsigned long stack_start, 1353 struct pt_regs *regs, 1354 unsigned long stack_size, 1355 int __user *parent_tidptr, 1356 int __user *child_tidptr) 1357 { 1358 struct task_struct *p; 1359 int trace = 0; 1360 long nr; 1361 1362 /* 1363 * Do some preliminary argument and permissions checking before we 1364 * actually start allocating stuff 1365 */ 1366 if (clone_flags & CLONE_NEWUSER) { 1367 if (clone_flags & CLONE_THREAD) 1368 return -EINVAL; 1369 /* hopefully this check will go away when userns support is 1370 * complete 1371 */ 1372 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1373 !capable(CAP_SETGID)) 1374 return -EPERM; 1375 } 1376 1377 /* 1378 * We hope to recycle these flags after 2.6.26 1379 */ 1380 if (unlikely(clone_flags & CLONE_STOPPED)) { 1381 static int __read_mostly count = 100; 1382 1383 if (count > 0 && printk_ratelimit()) { 1384 char comm[TASK_COMM_LEN]; 1385 1386 count--; 1387 printk(KERN_INFO "fork(): process `%s' used deprecated " 1388 "clone flags 0x%lx\n", 1389 get_task_comm(comm, current), 1390 clone_flags & CLONE_STOPPED); 1391 } 1392 } 1393 1394 /* 1395 * When called from kernel_thread, don't do user tracing stuff. 1396 */ 1397 if (likely(user_mode(regs))) 1398 trace = tracehook_prepare_clone(clone_flags); 1399 1400 p = copy_process(clone_flags, stack_start, regs, stack_size, 1401 child_tidptr, NULL, trace); 1402 /* 1403 * Do this prior waking up the new thread - the thread pointer 1404 * might get invalid after that point, if the thread exits quickly. 1405 */ 1406 if (!IS_ERR(p)) { 1407 struct completion vfork; 1408 1409 trace_sched_process_fork(current, p); 1410 1411 nr = task_pid_vnr(p); 1412 1413 if (clone_flags & CLONE_PARENT_SETTID) 1414 put_user(nr, parent_tidptr); 1415 1416 if (clone_flags & CLONE_VFORK) { 1417 p->vfork_done = &vfork; 1418 init_completion(&vfork); 1419 } 1420 1421 audit_finish_fork(p); 1422 tracehook_report_clone(regs, clone_flags, nr, p); 1423 1424 /* 1425 * We set PF_STARTING at creation in case tracing wants to 1426 * use this to distinguish a fully live task from one that 1427 * hasn't gotten to tracehook_report_clone() yet. Now we 1428 * clear it and set the child going. 1429 */ 1430 p->flags &= ~PF_STARTING; 1431 1432 if (unlikely(clone_flags & CLONE_STOPPED)) { 1433 /* 1434 * We'll start up with an immediate SIGSTOP. 1435 */ 1436 sigaddset(&p->pending.signal, SIGSTOP); 1437 set_tsk_thread_flag(p, TIF_SIGPENDING); 1438 __set_task_state(p, TASK_STOPPED); 1439 } else { 1440 wake_up_new_task(p, clone_flags); 1441 } 1442 1443 tracehook_report_clone_complete(trace, regs, 1444 clone_flags, nr, p); 1445 1446 if (clone_flags & CLONE_VFORK) { 1447 freezer_do_not_count(); 1448 wait_for_completion(&vfork); 1449 freezer_count(); 1450 tracehook_report_vfork_done(p, nr); 1451 } 1452 } else { 1453 nr = PTR_ERR(p); 1454 } 1455 return nr; 1456 } 1457 1458 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1459 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1460 #endif 1461 1462 static void sighand_ctor(void *data) 1463 { 1464 struct sighand_struct *sighand = data; 1465 1466 spin_lock_init(&sighand->siglock); 1467 init_waitqueue_head(&sighand->signalfd_wqh); 1468 } 1469 1470 void __init proc_caches_init(void) 1471 { 1472 sighand_cachep = kmem_cache_create("sighand_cache", 1473 sizeof(struct sighand_struct), 0, 1474 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1475 SLAB_NOTRACK, sighand_ctor); 1476 signal_cachep = kmem_cache_create("signal_cache", 1477 sizeof(struct signal_struct), 0, 1478 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1479 files_cachep = kmem_cache_create("files_cache", 1480 sizeof(struct files_struct), 0, 1481 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1482 fs_cachep = kmem_cache_create("fs_cache", 1483 sizeof(struct fs_struct), 0, 1484 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1485 mm_cachep = kmem_cache_create("mm_struct", 1486 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1487 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1488 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1489 mmap_init(); 1490 } 1491 1492 /* 1493 * Check constraints on flags passed to the unshare system call and 1494 * force unsharing of additional process context as appropriate. 1495 */ 1496 static void check_unshare_flags(unsigned long *flags_ptr) 1497 { 1498 /* 1499 * If unsharing a thread from a thread group, must also 1500 * unshare vm. 1501 */ 1502 if (*flags_ptr & CLONE_THREAD) 1503 *flags_ptr |= CLONE_VM; 1504 1505 /* 1506 * If unsharing vm, must also unshare signal handlers. 1507 */ 1508 if (*flags_ptr & CLONE_VM) 1509 *flags_ptr |= CLONE_SIGHAND; 1510 1511 /* 1512 * If unsharing signal handlers and the task was created 1513 * using CLONE_THREAD, then must unshare the thread 1514 */ 1515 if ((*flags_ptr & CLONE_SIGHAND) && 1516 (atomic_read(¤t->signal->count) > 1)) 1517 *flags_ptr |= CLONE_THREAD; 1518 1519 /* 1520 * If unsharing namespace, must also unshare filesystem information. 1521 */ 1522 if (*flags_ptr & CLONE_NEWNS) 1523 *flags_ptr |= CLONE_FS; 1524 } 1525 1526 /* 1527 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1528 */ 1529 static int unshare_thread(unsigned long unshare_flags) 1530 { 1531 if (unshare_flags & CLONE_THREAD) 1532 return -EINVAL; 1533 1534 return 0; 1535 } 1536 1537 /* 1538 * Unshare the filesystem structure if it is being shared 1539 */ 1540 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1541 { 1542 struct fs_struct *fs = current->fs; 1543 1544 if (!(unshare_flags & CLONE_FS) || !fs) 1545 return 0; 1546 1547 /* don't need lock here; in the worst case we'll do useless copy */ 1548 if (fs->users == 1) 1549 return 0; 1550 1551 *new_fsp = copy_fs_struct(fs); 1552 if (!*new_fsp) 1553 return -ENOMEM; 1554 1555 return 0; 1556 } 1557 1558 /* 1559 * Unsharing of sighand is not supported yet 1560 */ 1561 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1562 { 1563 struct sighand_struct *sigh = current->sighand; 1564 1565 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1566 return -EINVAL; 1567 else 1568 return 0; 1569 } 1570 1571 /* 1572 * Unshare vm if it is being shared 1573 */ 1574 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1575 { 1576 struct mm_struct *mm = current->mm; 1577 1578 if ((unshare_flags & CLONE_VM) && 1579 (mm && atomic_read(&mm->mm_users) > 1)) { 1580 return -EINVAL; 1581 } 1582 1583 return 0; 1584 } 1585 1586 /* 1587 * Unshare file descriptor table if it is being shared 1588 */ 1589 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1590 { 1591 struct files_struct *fd = current->files; 1592 int error = 0; 1593 1594 if ((unshare_flags & CLONE_FILES) && 1595 (fd && atomic_read(&fd->count) > 1)) { 1596 *new_fdp = dup_fd(fd, &error); 1597 if (!*new_fdp) 1598 return error; 1599 } 1600 1601 return 0; 1602 } 1603 1604 /* 1605 * unshare allows a process to 'unshare' part of the process 1606 * context which was originally shared using clone. copy_* 1607 * functions used by do_fork() cannot be used here directly 1608 * because they modify an inactive task_struct that is being 1609 * constructed. Here we are modifying the current, active, 1610 * task_struct. 1611 */ 1612 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1613 { 1614 int err = 0; 1615 struct fs_struct *fs, *new_fs = NULL; 1616 struct sighand_struct *new_sigh = NULL; 1617 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1618 struct files_struct *fd, *new_fd = NULL; 1619 struct nsproxy *new_nsproxy = NULL; 1620 int do_sysvsem = 0; 1621 1622 check_unshare_flags(&unshare_flags); 1623 1624 /* Return -EINVAL for all unsupported flags */ 1625 err = -EINVAL; 1626 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1627 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1628 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1629 goto bad_unshare_out; 1630 1631 /* 1632 * CLONE_NEWIPC must also detach from the undolist: after switching 1633 * to a new ipc namespace, the semaphore arrays from the old 1634 * namespace are unreachable. 1635 */ 1636 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1637 do_sysvsem = 1; 1638 if ((err = unshare_thread(unshare_flags))) 1639 goto bad_unshare_out; 1640 if ((err = unshare_fs(unshare_flags, &new_fs))) 1641 goto bad_unshare_cleanup_thread; 1642 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1643 goto bad_unshare_cleanup_fs; 1644 if ((err = unshare_vm(unshare_flags, &new_mm))) 1645 goto bad_unshare_cleanup_sigh; 1646 if ((err = unshare_fd(unshare_flags, &new_fd))) 1647 goto bad_unshare_cleanup_vm; 1648 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1649 new_fs))) 1650 goto bad_unshare_cleanup_fd; 1651 1652 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1653 if (do_sysvsem) { 1654 /* 1655 * CLONE_SYSVSEM is equivalent to sys_exit(). 1656 */ 1657 exit_sem(current); 1658 } 1659 1660 if (new_nsproxy) { 1661 switch_task_namespaces(current, new_nsproxy); 1662 new_nsproxy = NULL; 1663 } 1664 1665 task_lock(current); 1666 1667 if (new_fs) { 1668 fs = current->fs; 1669 write_lock(&fs->lock); 1670 current->fs = new_fs; 1671 if (--fs->users) 1672 new_fs = NULL; 1673 else 1674 new_fs = fs; 1675 write_unlock(&fs->lock); 1676 } 1677 1678 if (new_mm) { 1679 mm = current->mm; 1680 active_mm = current->active_mm; 1681 current->mm = new_mm; 1682 current->active_mm = new_mm; 1683 activate_mm(active_mm, new_mm); 1684 new_mm = mm; 1685 } 1686 1687 if (new_fd) { 1688 fd = current->files; 1689 current->files = new_fd; 1690 new_fd = fd; 1691 } 1692 1693 task_unlock(current); 1694 } 1695 1696 if (new_nsproxy) 1697 put_nsproxy(new_nsproxy); 1698 1699 bad_unshare_cleanup_fd: 1700 if (new_fd) 1701 put_files_struct(new_fd); 1702 1703 bad_unshare_cleanup_vm: 1704 if (new_mm) 1705 mmput(new_mm); 1706 1707 bad_unshare_cleanup_sigh: 1708 if (new_sigh) 1709 if (atomic_dec_and_test(&new_sigh->count)) 1710 kmem_cache_free(sighand_cachep, new_sigh); 1711 1712 bad_unshare_cleanup_fs: 1713 if (new_fs) 1714 free_fs_struct(new_fs); 1715 1716 bad_unshare_cleanup_thread: 1717 bad_unshare_out: 1718 return err; 1719 } 1720 1721 /* 1722 * Helper to unshare the files of the current task. 1723 * We don't want to expose copy_files internals to 1724 * the exec layer of the kernel. 1725 */ 1726 1727 int unshare_files(struct files_struct **displaced) 1728 { 1729 struct task_struct *task = current; 1730 struct files_struct *copy = NULL; 1731 int error; 1732 1733 error = unshare_fd(CLONE_FILES, ©); 1734 if (error || !copy) { 1735 *displaced = NULL; 1736 return error; 1737 } 1738 *displaced = task->files; 1739 task_lock(task); 1740 task->files = copy; 1741 task_unlock(task); 1742 return 0; 1743 } 1744