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 67 #include <asm/pgtable.h> 68 #include <asm/pgalloc.h> 69 #include <asm/uaccess.h> 70 #include <asm/mmu_context.h> 71 #include <asm/cacheflush.h> 72 #include <asm/tlbflush.h> 73 74 #include <trace/events/sched.h> 75 76 /* 77 * Protected counters by write_lock_irq(&tasklist_lock) 78 */ 79 unsigned long total_forks; /* Handle normal Linux uptimes. */ 80 int nr_threads; /* The idle threads do not count.. */ 81 82 int max_threads; /* tunable limit on nr_threads */ 83 84 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 85 86 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 87 88 int nr_processes(void) 89 { 90 int cpu; 91 int total = 0; 92 93 for_each_online_cpu(cpu) 94 total += per_cpu(process_counts, cpu); 95 96 return total; 97 } 98 99 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 100 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 101 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 102 static struct kmem_cache *task_struct_cachep; 103 #endif 104 105 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 106 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 107 { 108 #ifdef CONFIG_DEBUG_STACK_USAGE 109 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 110 #else 111 gfp_t mask = GFP_KERNEL; 112 #endif 113 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 114 } 115 116 static inline void free_thread_info(struct thread_info *ti) 117 { 118 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 119 } 120 #endif 121 122 /* SLAB cache for signal_struct structures (tsk->signal) */ 123 static struct kmem_cache *signal_cachep; 124 125 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 126 struct kmem_cache *sighand_cachep; 127 128 /* SLAB cache for files_struct structures (tsk->files) */ 129 struct kmem_cache *files_cachep; 130 131 /* SLAB cache for fs_struct structures (tsk->fs) */ 132 struct kmem_cache *fs_cachep; 133 134 /* SLAB cache for vm_area_struct structures */ 135 struct kmem_cache *vm_area_cachep; 136 137 /* SLAB cache for mm_struct structures (tsk->mm) */ 138 static struct kmem_cache *mm_cachep; 139 140 static void account_kernel_stack(struct thread_info *ti, int account) 141 { 142 struct zone *zone = page_zone(virt_to_page(ti)); 143 144 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 145 } 146 147 void free_task(struct task_struct *tsk) 148 { 149 prop_local_destroy_single(&tsk->dirties); 150 account_kernel_stack(tsk->stack, -1); 151 free_thread_info(tsk->stack); 152 rt_mutex_debug_task_free(tsk); 153 ftrace_graph_exit_task(tsk); 154 free_task_struct(tsk); 155 } 156 EXPORT_SYMBOL(free_task); 157 158 void __put_task_struct(struct task_struct *tsk) 159 { 160 WARN_ON(!tsk->exit_state); 161 WARN_ON(atomic_read(&tsk->usage)); 162 WARN_ON(tsk == current); 163 164 exit_creds(tsk); 165 delayacct_tsk_free(tsk); 166 167 if (!profile_handoff_task(tsk)) 168 free_task(tsk); 169 } 170 171 /* 172 * macro override instead of weak attribute alias, to workaround 173 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 174 */ 175 #ifndef arch_task_cache_init 176 #define arch_task_cache_init() 177 #endif 178 179 void __init fork_init(unsigned long mempages) 180 { 181 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 182 #ifndef ARCH_MIN_TASKALIGN 183 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 184 #endif 185 /* create a slab on which task_structs can be allocated */ 186 task_struct_cachep = 187 kmem_cache_create("task_struct", sizeof(struct task_struct), 188 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 189 #endif 190 191 /* do the arch specific task caches init */ 192 arch_task_cache_init(); 193 194 /* 195 * The default maximum number of threads is set to a safe 196 * value: the thread structures can take up at most half 197 * of memory. 198 */ 199 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 200 201 /* 202 * we need to allow at least 20 threads to boot a system 203 */ 204 if(max_threads < 20) 205 max_threads = 20; 206 207 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 208 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 209 init_task.signal->rlim[RLIMIT_SIGPENDING] = 210 init_task.signal->rlim[RLIMIT_NPROC]; 211 } 212 213 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 214 struct task_struct *src) 215 { 216 *dst = *src; 217 return 0; 218 } 219 220 static struct task_struct *dup_task_struct(struct task_struct *orig) 221 { 222 struct task_struct *tsk; 223 struct thread_info *ti; 224 unsigned long *stackend; 225 226 int err; 227 228 prepare_to_copy(orig); 229 230 tsk = alloc_task_struct(); 231 if (!tsk) 232 return NULL; 233 234 ti = alloc_thread_info(tsk); 235 if (!ti) { 236 free_task_struct(tsk); 237 return NULL; 238 } 239 240 err = arch_dup_task_struct(tsk, orig); 241 if (err) 242 goto out; 243 244 tsk->stack = ti; 245 246 err = prop_local_init_single(&tsk->dirties); 247 if (err) 248 goto out; 249 250 setup_thread_stack(tsk, orig); 251 stackend = end_of_stack(tsk); 252 *stackend = STACK_END_MAGIC; /* for overflow detection */ 253 254 #ifdef CONFIG_CC_STACKPROTECTOR 255 tsk->stack_canary = get_random_int(); 256 #endif 257 258 /* One for us, one for whoever does the "release_task()" (usually parent) */ 259 atomic_set(&tsk->usage,2); 260 atomic_set(&tsk->fs_excl, 0); 261 #ifdef CONFIG_BLK_DEV_IO_TRACE 262 tsk->btrace_seq = 0; 263 #endif 264 tsk->splice_pipe = NULL; 265 266 account_kernel_stack(ti, 1); 267 268 return tsk; 269 270 out: 271 free_thread_info(ti); 272 free_task_struct(tsk); 273 return NULL; 274 } 275 276 #ifdef CONFIG_MMU 277 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 278 { 279 struct vm_area_struct *mpnt, *tmp, **pprev; 280 struct rb_node **rb_link, *rb_parent; 281 int retval; 282 unsigned long charge; 283 struct mempolicy *pol; 284 285 down_write(&oldmm->mmap_sem); 286 flush_cache_dup_mm(oldmm); 287 /* 288 * Not linked in yet - no deadlock potential: 289 */ 290 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 291 292 mm->locked_vm = 0; 293 mm->mmap = NULL; 294 mm->mmap_cache = NULL; 295 mm->free_area_cache = oldmm->mmap_base; 296 mm->cached_hole_size = ~0UL; 297 mm->map_count = 0; 298 cpumask_clear(mm_cpumask(mm)); 299 mm->mm_rb = RB_ROOT; 300 rb_link = &mm->mm_rb.rb_node; 301 rb_parent = NULL; 302 pprev = &mm->mmap; 303 retval = ksm_fork(mm, oldmm); 304 if (retval) 305 goto out; 306 307 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 308 struct file *file; 309 310 if (mpnt->vm_flags & VM_DONTCOPY) { 311 long pages = vma_pages(mpnt); 312 mm->total_vm -= pages; 313 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 314 -pages); 315 continue; 316 } 317 charge = 0; 318 if (mpnt->vm_flags & VM_ACCOUNT) { 319 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 320 if (security_vm_enough_memory(len)) 321 goto fail_nomem; 322 charge = len; 323 } 324 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 325 if (!tmp) 326 goto fail_nomem; 327 *tmp = *mpnt; 328 pol = mpol_dup(vma_policy(mpnt)); 329 retval = PTR_ERR(pol); 330 if (IS_ERR(pol)) 331 goto fail_nomem_policy; 332 vma_set_policy(tmp, pol); 333 tmp->vm_flags &= ~VM_LOCKED; 334 tmp->vm_mm = mm; 335 tmp->vm_next = NULL; 336 anon_vma_link(tmp); 337 file = tmp->vm_file; 338 if (file) { 339 struct inode *inode = file->f_path.dentry->d_inode; 340 struct address_space *mapping = file->f_mapping; 341 342 get_file(file); 343 if (tmp->vm_flags & VM_DENYWRITE) 344 atomic_dec(&inode->i_writecount); 345 spin_lock(&mapping->i_mmap_lock); 346 if (tmp->vm_flags & VM_SHARED) 347 mapping->i_mmap_writable++; 348 tmp->vm_truncate_count = mpnt->vm_truncate_count; 349 flush_dcache_mmap_lock(mapping); 350 /* insert tmp into the share list, just after mpnt */ 351 vma_prio_tree_add(tmp, mpnt); 352 flush_dcache_mmap_unlock(mapping); 353 spin_unlock(&mapping->i_mmap_lock); 354 } 355 356 /* 357 * Clear hugetlb-related page reserves for children. This only 358 * affects MAP_PRIVATE mappings. Faults generated by the child 359 * are not guaranteed to succeed, even if read-only 360 */ 361 if (is_vm_hugetlb_page(tmp)) 362 reset_vma_resv_huge_pages(tmp); 363 364 /* 365 * Link in the new vma and copy the page table entries. 366 */ 367 *pprev = tmp; 368 pprev = &tmp->vm_next; 369 370 __vma_link_rb(mm, tmp, rb_link, rb_parent); 371 rb_link = &tmp->vm_rb.rb_right; 372 rb_parent = &tmp->vm_rb; 373 374 mm->map_count++; 375 retval = copy_page_range(mm, oldmm, mpnt); 376 377 if (tmp->vm_ops && tmp->vm_ops->open) 378 tmp->vm_ops->open(tmp); 379 380 if (retval) 381 goto out; 382 } 383 /* a new mm has just been created */ 384 arch_dup_mmap(oldmm, mm); 385 retval = 0; 386 out: 387 up_write(&mm->mmap_sem); 388 flush_tlb_mm(oldmm); 389 up_write(&oldmm->mmap_sem); 390 return retval; 391 fail_nomem_policy: 392 kmem_cache_free(vm_area_cachep, tmp); 393 fail_nomem: 394 retval = -ENOMEM; 395 vm_unacct_memory(charge); 396 goto out; 397 } 398 399 static inline int mm_alloc_pgd(struct mm_struct * mm) 400 { 401 mm->pgd = pgd_alloc(mm); 402 if (unlikely(!mm->pgd)) 403 return -ENOMEM; 404 return 0; 405 } 406 407 static inline void mm_free_pgd(struct mm_struct * mm) 408 { 409 pgd_free(mm, mm->pgd); 410 } 411 #else 412 #define dup_mmap(mm, oldmm) (0) 413 #define mm_alloc_pgd(mm) (0) 414 #define mm_free_pgd(mm) 415 #endif /* CONFIG_MMU */ 416 417 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 418 419 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 420 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 421 422 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 423 424 static int __init coredump_filter_setup(char *s) 425 { 426 default_dump_filter = 427 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 428 MMF_DUMP_FILTER_MASK; 429 return 1; 430 } 431 432 __setup("coredump_filter=", coredump_filter_setup); 433 434 #include <linux/init_task.h> 435 436 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 437 { 438 atomic_set(&mm->mm_users, 1); 439 atomic_set(&mm->mm_count, 1); 440 init_rwsem(&mm->mmap_sem); 441 INIT_LIST_HEAD(&mm->mmlist); 442 mm->flags = (current->mm) ? 443 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 444 mm->core_state = NULL; 445 mm->nr_ptes = 0; 446 set_mm_counter(mm, file_rss, 0); 447 set_mm_counter(mm, anon_rss, 0); 448 spin_lock_init(&mm->page_table_lock); 449 spin_lock_init(&mm->ioctx_lock); 450 INIT_HLIST_HEAD(&mm->ioctx_list); 451 mm->free_area_cache = TASK_UNMAPPED_BASE; 452 mm->cached_hole_size = ~0UL; 453 mm_init_owner(mm, p); 454 455 if (likely(!mm_alloc_pgd(mm))) { 456 mm->def_flags = 0; 457 mmu_notifier_mm_init(mm); 458 return mm; 459 } 460 461 free_mm(mm); 462 return NULL; 463 } 464 465 /* 466 * Allocate and initialize an mm_struct. 467 */ 468 struct mm_struct * mm_alloc(void) 469 { 470 struct mm_struct * mm; 471 472 mm = allocate_mm(); 473 if (mm) { 474 memset(mm, 0, sizeof(*mm)); 475 mm = mm_init(mm, current); 476 } 477 return mm; 478 } 479 480 /* 481 * Called when the last reference to the mm 482 * is dropped: either by a lazy thread or by 483 * mmput. Free the page directory and the mm. 484 */ 485 void __mmdrop(struct mm_struct *mm) 486 { 487 BUG_ON(mm == &init_mm); 488 mm_free_pgd(mm); 489 destroy_context(mm); 490 mmu_notifier_mm_destroy(mm); 491 free_mm(mm); 492 } 493 EXPORT_SYMBOL_GPL(__mmdrop); 494 495 /* 496 * Decrement the use count and release all resources for an mm. 497 */ 498 void mmput(struct mm_struct *mm) 499 { 500 might_sleep(); 501 502 if (atomic_dec_and_test(&mm->mm_users)) { 503 exit_aio(mm); 504 ksm_exit(mm); 505 exit_mmap(mm); 506 set_mm_exe_file(mm, NULL); 507 if (!list_empty(&mm->mmlist)) { 508 spin_lock(&mmlist_lock); 509 list_del(&mm->mmlist); 510 spin_unlock(&mmlist_lock); 511 } 512 put_swap_token(mm); 513 mmdrop(mm); 514 } 515 } 516 EXPORT_SYMBOL_GPL(mmput); 517 518 /** 519 * get_task_mm - acquire a reference to the task's mm 520 * 521 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 522 * this kernel workthread has transiently adopted a user mm with use_mm, 523 * to do its AIO) is not set and if so returns a reference to it, after 524 * bumping up the use count. User must release the mm via mmput() 525 * after use. Typically used by /proc and ptrace. 526 */ 527 struct mm_struct *get_task_mm(struct task_struct *task) 528 { 529 struct mm_struct *mm; 530 531 task_lock(task); 532 mm = task->mm; 533 if (mm) { 534 if (task->flags & PF_KTHREAD) 535 mm = NULL; 536 else 537 atomic_inc(&mm->mm_users); 538 } 539 task_unlock(task); 540 return mm; 541 } 542 EXPORT_SYMBOL_GPL(get_task_mm); 543 544 /* Please note the differences between mmput and mm_release. 545 * mmput is called whenever we stop holding onto a mm_struct, 546 * error success whatever. 547 * 548 * mm_release is called after a mm_struct has been removed 549 * from the current process. 550 * 551 * This difference is important for error handling, when we 552 * only half set up a mm_struct for a new process and need to restore 553 * the old one. Because we mmput the new mm_struct before 554 * restoring the old one. . . 555 * Eric Biederman 10 January 1998 556 */ 557 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 558 { 559 struct completion *vfork_done = tsk->vfork_done; 560 561 /* Get rid of any futexes when releasing the mm */ 562 #ifdef CONFIG_FUTEX 563 if (unlikely(tsk->robust_list)) 564 exit_robust_list(tsk); 565 #ifdef CONFIG_COMPAT 566 if (unlikely(tsk->compat_robust_list)) 567 compat_exit_robust_list(tsk); 568 #endif 569 #endif 570 571 /* Get rid of any cached register state */ 572 deactivate_mm(tsk, mm); 573 574 /* notify parent sleeping on vfork() */ 575 if (vfork_done) { 576 tsk->vfork_done = NULL; 577 complete(vfork_done); 578 } 579 580 /* 581 * If we're exiting normally, clear a user-space tid field if 582 * requested. We leave this alone when dying by signal, to leave 583 * the value intact in a core dump, and to save the unnecessary 584 * trouble otherwise. Userland only wants this done for a sys_exit. 585 */ 586 if (tsk->clear_child_tid) { 587 if (!(tsk->flags & PF_SIGNALED) && 588 atomic_read(&mm->mm_users) > 1) { 589 /* 590 * We don't check the error code - if userspace has 591 * not set up a proper pointer then tough luck. 592 */ 593 put_user(0, tsk->clear_child_tid); 594 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 595 1, NULL, NULL, 0); 596 } 597 tsk->clear_child_tid = NULL; 598 } 599 } 600 601 /* 602 * Allocate a new mm structure and copy contents from the 603 * mm structure of the passed in task structure. 604 */ 605 struct mm_struct *dup_mm(struct task_struct *tsk) 606 { 607 struct mm_struct *mm, *oldmm = current->mm; 608 int err; 609 610 if (!oldmm) 611 return NULL; 612 613 mm = allocate_mm(); 614 if (!mm) 615 goto fail_nomem; 616 617 memcpy(mm, oldmm, sizeof(*mm)); 618 619 /* Initializing for Swap token stuff */ 620 mm->token_priority = 0; 621 mm->last_interval = 0; 622 623 if (!mm_init(mm, tsk)) 624 goto fail_nomem; 625 626 if (init_new_context(tsk, mm)) 627 goto fail_nocontext; 628 629 dup_mm_exe_file(oldmm, mm); 630 631 err = dup_mmap(mm, oldmm); 632 if (err) 633 goto free_pt; 634 635 mm->hiwater_rss = get_mm_rss(mm); 636 mm->hiwater_vm = mm->total_vm; 637 638 return mm; 639 640 free_pt: 641 mmput(mm); 642 643 fail_nomem: 644 return NULL; 645 646 fail_nocontext: 647 /* 648 * If init_new_context() failed, we cannot use mmput() to free the mm 649 * because it calls destroy_context() 650 */ 651 mm_free_pgd(mm); 652 free_mm(mm); 653 return NULL; 654 } 655 656 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 657 { 658 struct mm_struct * mm, *oldmm; 659 int retval; 660 661 tsk->min_flt = tsk->maj_flt = 0; 662 tsk->nvcsw = tsk->nivcsw = 0; 663 #ifdef CONFIG_DETECT_HUNG_TASK 664 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 665 #endif 666 667 tsk->mm = NULL; 668 tsk->active_mm = NULL; 669 670 /* 671 * Are we cloning a kernel thread? 672 * 673 * We need to steal a active VM for that.. 674 */ 675 oldmm = current->mm; 676 if (!oldmm) 677 return 0; 678 679 if (clone_flags & CLONE_VM) { 680 atomic_inc(&oldmm->mm_users); 681 mm = oldmm; 682 goto good_mm; 683 } 684 685 retval = -ENOMEM; 686 mm = dup_mm(tsk); 687 if (!mm) 688 goto fail_nomem; 689 690 good_mm: 691 /* Initializing for Swap token stuff */ 692 mm->token_priority = 0; 693 mm->last_interval = 0; 694 695 tsk->mm = mm; 696 tsk->active_mm = mm; 697 return 0; 698 699 fail_nomem: 700 return retval; 701 } 702 703 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 704 { 705 struct fs_struct *fs = current->fs; 706 if (clone_flags & CLONE_FS) { 707 /* tsk->fs is already what we want */ 708 write_lock(&fs->lock); 709 if (fs->in_exec) { 710 write_unlock(&fs->lock); 711 return -EAGAIN; 712 } 713 fs->users++; 714 write_unlock(&fs->lock); 715 return 0; 716 } 717 tsk->fs = copy_fs_struct(fs); 718 if (!tsk->fs) 719 return -ENOMEM; 720 return 0; 721 } 722 723 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 724 { 725 struct files_struct *oldf, *newf; 726 int error = 0; 727 728 /* 729 * A background process may not have any files ... 730 */ 731 oldf = current->files; 732 if (!oldf) 733 goto out; 734 735 if (clone_flags & CLONE_FILES) { 736 atomic_inc(&oldf->count); 737 goto out; 738 } 739 740 newf = dup_fd(oldf, &error); 741 if (!newf) 742 goto out; 743 744 tsk->files = newf; 745 error = 0; 746 out: 747 return error; 748 } 749 750 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 751 { 752 #ifdef CONFIG_BLOCK 753 struct io_context *ioc = current->io_context; 754 755 if (!ioc) 756 return 0; 757 /* 758 * Share io context with parent, if CLONE_IO is set 759 */ 760 if (clone_flags & CLONE_IO) { 761 tsk->io_context = ioc_task_link(ioc); 762 if (unlikely(!tsk->io_context)) 763 return -ENOMEM; 764 } else if (ioprio_valid(ioc->ioprio)) { 765 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 766 if (unlikely(!tsk->io_context)) 767 return -ENOMEM; 768 769 tsk->io_context->ioprio = ioc->ioprio; 770 } 771 #endif 772 return 0; 773 } 774 775 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 776 { 777 struct sighand_struct *sig; 778 779 if (clone_flags & CLONE_SIGHAND) { 780 atomic_inc(¤t->sighand->count); 781 return 0; 782 } 783 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 784 rcu_assign_pointer(tsk->sighand, sig); 785 if (!sig) 786 return -ENOMEM; 787 atomic_set(&sig->count, 1); 788 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 789 return 0; 790 } 791 792 void __cleanup_sighand(struct sighand_struct *sighand) 793 { 794 if (atomic_dec_and_test(&sighand->count)) 795 kmem_cache_free(sighand_cachep, sighand); 796 } 797 798 799 /* 800 * Initialize POSIX timer handling for a thread group. 801 */ 802 static void posix_cpu_timers_init_group(struct signal_struct *sig) 803 { 804 /* Thread group counters. */ 805 thread_group_cputime_init(sig); 806 807 /* Expiration times and increments. */ 808 sig->it_virt_expires = cputime_zero; 809 sig->it_virt_incr = cputime_zero; 810 sig->it_prof_expires = cputime_zero; 811 sig->it_prof_incr = cputime_zero; 812 813 /* Cached expiration times. */ 814 sig->cputime_expires.prof_exp = cputime_zero; 815 sig->cputime_expires.virt_exp = cputime_zero; 816 sig->cputime_expires.sched_exp = 0; 817 818 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 819 sig->cputime_expires.prof_exp = 820 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 821 sig->cputimer.running = 1; 822 } 823 824 /* The timer lists. */ 825 INIT_LIST_HEAD(&sig->cpu_timers[0]); 826 INIT_LIST_HEAD(&sig->cpu_timers[1]); 827 INIT_LIST_HEAD(&sig->cpu_timers[2]); 828 } 829 830 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 831 { 832 struct signal_struct *sig; 833 834 if (clone_flags & CLONE_THREAD) 835 return 0; 836 837 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 838 tsk->signal = sig; 839 if (!sig) 840 return -ENOMEM; 841 842 atomic_set(&sig->count, 1); 843 atomic_set(&sig->live, 1); 844 init_waitqueue_head(&sig->wait_chldexit); 845 sig->flags = 0; 846 if (clone_flags & CLONE_NEWPID) 847 sig->flags |= SIGNAL_UNKILLABLE; 848 sig->group_exit_code = 0; 849 sig->group_exit_task = NULL; 850 sig->group_stop_count = 0; 851 sig->curr_target = tsk; 852 init_sigpending(&sig->shared_pending); 853 INIT_LIST_HEAD(&sig->posix_timers); 854 855 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 856 sig->it_real_incr.tv64 = 0; 857 sig->real_timer.function = it_real_fn; 858 859 sig->leader = 0; /* session leadership doesn't inherit */ 860 sig->tty_old_pgrp = NULL; 861 sig->tty = NULL; 862 863 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 864 sig->gtime = cputime_zero; 865 sig->cgtime = cputime_zero; 866 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 867 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 868 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 869 task_io_accounting_init(&sig->ioac); 870 sig->sum_sched_runtime = 0; 871 taskstats_tgid_init(sig); 872 873 task_lock(current->group_leader); 874 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 875 task_unlock(current->group_leader); 876 877 posix_cpu_timers_init_group(sig); 878 879 acct_init_pacct(&sig->pacct); 880 881 tty_audit_fork(sig); 882 883 return 0; 884 } 885 886 void __cleanup_signal(struct signal_struct *sig) 887 { 888 thread_group_cputime_free(sig); 889 tty_kref_put(sig->tty); 890 kmem_cache_free(signal_cachep, sig); 891 } 892 893 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 894 { 895 unsigned long new_flags = p->flags; 896 897 new_flags &= ~PF_SUPERPRIV; 898 new_flags |= PF_FORKNOEXEC; 899 new_flags |= PF_STARTING; 900 p->flags = new_flags; 901 clear_freeze_flag(p); 902 } 903 904 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 905 { 906 current->clear_child_tid = tidptr; 907 908 return task_pid_vnr(current); 909 } 910 911 static void rt_mutex_init_task(struct task_struct *p) 912 { 913 spin_lock_init(&p->pi_lock); 914 #ifdef CONFIG_RT_MUTEXES 915 plist_head_init(&p->pi_waiters, &p->pi_lock); 916 p->pi_blocked_on = NULL; 917 #endif 918 } 919 920 #ifdef CONFIG_MM_OWNER 921 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 922 { 923 mm->owner = p; 924 } 925 #endif /* CONFIG_MM_OWNER */ 926 927 /* 928 * Initialize POSIX timer handling for a single task. 929 */ 930 static void posix_cpu_timers_init(struct task_struct *tsk) 931 { 932 tsk->cputime_expires.prof_exp = cputime_zero; 933 tsk->cputime_expires.virt_exp = cputime_zero; 934 tsk->cputime_expires.sched_exp = 0; 935 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 936 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 937 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 938 } 939 940 /* 941 * This creates a new process as a copy of the old one, 942 * but does not actually start it yet. 943 * 944 * It copies the registers, and all the appropriate 945 * parts of the process environment (as per the clone 946 * flags). The actual kick-off is left to the caller. 947 */ 948 static struct task_struct *copy_process(unsigned long clone_flags, 949 unsigned long stack_start, 950 struct pt_regs *regs, 951 unsigned long stack_size, 952 int __user *child_tidptr, 953 struct pid *pid, 954 int trace) 955 { 956 int retval; 957 struct task_struct *p; 958 int cgroup_callbacks_done = 0; 959 960 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 961 return ERR_PTR(-EINVAL); 962 963 /* 964 * Thread groups must share signals as well, and detached threads 965 * can only be started up within the thread group. 966 */ 967 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 968 return ERR_PTR(-EINVAL); 969 970 /* 971 * Shared signal handlers imply shared VM. By way of the above, 972 * thread groups also imply shared VM. Blocking this case allows 973 * for various simplifications in other code. 974 */ 975 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 976 return ERR_PTR(-EINVAL); 977 978 retval = security_task_create(clone_flags); 979 if (retval) 980 goto fork_out; 981 982 retval = -ENOMEM; 983 p = dup_task_struct(current); 984 if (!p) 985 goto fork_out; 986 987 ftrace_graph_init_task(p); 988 989 rt_mutex_init_task(p); 990 991 #ifdef CONFIG_PROVE_LOCKING 992 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 993 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 994 #endif 995 retval = -EAGAIN; 996 if (atomic_read(&p->real_cred->user->processes) >= 997 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 998 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 999 p->real_cred->user != INIT_USER) 1000 goto bad_fork_free; 1001 } 1002 1003 retval = copy_creds(p, clone_flags); 1004 if (retval < 0) 1005 goto bad_fork_free; 1006 1007 /* 1008 * If multiple threads are within copy_process(), then this check 1009 * triggers too late. This doesn't hurt, the check is only there 1010 * to stop root fork bombs. 1011 */ 1012 retval = -EAGAIN; 1013 if (nr_threads >= max_threads) 1014 goto bad_fork_cleanup_count; 1015 1016 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1017 goto bad_fork_cleanup_count; 1018 1019 if (p->binfmt && !try_module_get(p->binfmt->module)) 1020 goto bad_fork_cleanup_put_domain; 1021 1022 p->did_exec = 0; 1023 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1024 copy_flags(clone_flags, p); 1025 INIT_LIST_HEAD(&p->children); 1026 INIT_LIST_HEAD(&p->sibling); 1027 rcu_copy_process(p); 1028 p->vfork_done = NULL; 1029 spin_lock_init(&p->alloc_lock); 1030 1031 init_sigpending(&p->pending); 1032 1033 p->utime = cputime_zero; 1034 p->stime = cputime_zero; 1035 p->gtime = cputime_zero; 1036 p->utimescaled = cputime_zero; 1037 p->stimescaled = cputime_zero; 1038 p->prev_utime = cputime_zero; 1039 p->prev_stime = cputime_zero; 1040 1041 p->default_timer_slack_ns = current->timer_slack_ns; 1042 1043 task_io_accounting_init(&p->ioac); 1044 acct_clear_integrals(p); 1045 1046 posix_cpu_timers_init(p); 1047 1048 p->lock_depth = -1; /* -1 = no lock */ 1049 do_posix_clock_monotonic_gettime(&p->start_time); 1050 p->real_start_time = p->start_time; 1051 monotonic_to_bootbased(&p->real_start_time); 1052 p->io_context = NULL; 1053 p->audit_context = NULL; 1054 cgroup_fork(p); 1055 #ifdef CONFIG_NUMA 1056 p->mempolicy = mpol_dup(p->mempolicy); 1057 if (IS_ERR(p->mempolicy)) { 1058 retval = PTR_ERR(p->mempolicy); 1059 p->mempolicy = NULL; 1060 goto bad_fork_cleanup_cgroup; 1061 } 1062 mpol_fix_fork_child_flag(p); 1063 #endif 1064 #ifdef CONFIG_TRACE_IRQFLAGS 1065 p->irq_events = 0; 1066 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1067 p->hardirqs_enabled = 1; 1068 #else 1069 p->hardirqs_enabled = 0; 1070 #endif 1071 p->hardirq_enable_ip = 0; 1072 p->hardirq_enable_event = 0; 1073 p->hardirq_disable_ip = _THIS_IP_; 1074 p->hardirq_disable_event = 0; 1075 p->softirqs_enabled = 1; 1076 p->softirq_enable_ip = _THIS_IP_; 1077 p->softirq_enable_event = 0; 1078 p->softirq_disable_ip = 0; 1079 p->softirq_disable_event = 0; 1080 p->hardirq_context = 0; 1081 p->softirq_context = 0; 1082 #endif 1083 #ifdef CONFIG_LOCKDEP 1084 p->lockdep_depth = 0; /* no locks held yet */ 1085 p->curr_chain_key = 0; 1086 p->lockdep_recursion = 0; 1087 #endif 1088 1089 #ifdef CONFIG_DEBUG_MUTEXES 1090 p->blocked_on = NULL; /* not blocked yet */ 1091 #endif 1092 1093 p->bts = NULL; 1094 1095 /* Perform scheduler related setup. Assign this task to a CPU. */ 1096 sched_fork(p, clone_flags); 1097 1098 retval = perf_event_init_task(p); 1099 if (retval) 1100 goto bad_fork_cleanup_policy; 1101 1102 if ((retval = audit_alloc(p))) 1103 goto bad_fork_cleanup_policy; 1104 /* copy all the process information */ 1105 if ((retval = copy_semundo(clone_flags, p))) 1106 goto bad_fork_cleanup_audit; 1107 if ((retval = copy_files(clone_flags, p))) 1108 goto bad_fork_cleanup_semundo; 1109 if ((retval = copy_fs(clone_flags, p))) 1110 goto bad_fork_cleanup_files; 1111 if ((retval = copy_sighand(clone_flags, p))) 1112 goto bad_fork_cleanup_fs; 1113 if ((retval = copy_signal(clone_flags, p))) 1114 goto bad_fork_cleanup_sighand; 1115 if ((retval = copy_mm(clone_flags, p))) 1116 goto bad_fork_cleanup_signal; 1117 if ((retval = copy_namespaces(clone_flags, p))) 1118 goto bad_fork_cleanup_mm; 1119 if ((retval = copy_io(clone_flags, p))) 1120 goto bad_fork_cleanup_namespaces; 1121 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1122 if (retval) 1123 goto bad_fork_cleanup_io; 1124 1125 if (pid != &init_struct_pid) { 1126 retval = -ENOMEM; 1127 pid = alloc_pid(p->nsproxy->pid_ns); 1128 if (!pid) 1129 goto bad_fork_cleanup_io; 1130 1131 if (clone_flags & CLONE_NEWPID) { 1132 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1133 if (retval < 0) 1134 goto bad_fork_free_pid; 1135 } 1136 } 1137 1138 p->pid = pid_nr(pid); 1139 p->tgid = p->pid; 1140 if (clone_flags & CLONE_THREAD) 1141 p->tgid = current->tgid; 1142 1143 if (current->nsproxy != p->nsproxy) { 1144 retval = ns_cgroup_clone(p, pid); 1145 if (retval) 1146 goto bad_fork_free_pid; 1147 } 1148 1149 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1150 /* 1151 * Clear TID on mm_release()? 1152 */ 1153 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1154 #ifdef CONFIG_FUTEX 1155 p->robust_list = NULL; 1156 #ifdef CONFIG_COMPAT 1157 p->compat_robust_list = NULL; 1158 #endif 1159 INIT_LIST_HEAD(&p->pi_state_list); 1160 p->pi_state_cache = NULL; 1161 #endif 1162 /* 1163 * sigaltstack should be cleared when sharing the same VM 1164 */ 1165 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1166 p->sas_ss_sp = p->sas_ss_size = 0; 1167 1168 /* 1169 * Syscall tracing should be turned off in the child regardless 1170 * of CLONE_PTRACE. 1171 */ 1172 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1173 #ifdef TIF_SYSCALL_EMU 1174 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1175 #endif 1176 clear_all_latency_tracing(p); 1177 1178 /* ok, now we should be set up.. */ 1179 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1180 p->pdeath_signal = 0; 1181 p->exit_state = 0; 1182 1183 /* 1184 * Ok, make it visible to the rest of the system. 1185 * We dont wake it up yet. 1186 */ 1187 p->group_leader = p; 1188 INIT_LIST_HEAD(&p->thread_group); 1189 1190 /* Now that the task is set up, run cgroup callbacks if 1191 * necessary. We need to run them before the task is visible 1192 * on the tasklist. */ 1193 cgroup_fork_callbacks(p); 1194 cgroup_callbacks_done = 1; 1195 1196 /* Need tasklist lock for parent etc handling! */ 1197 write_lock_irq(&tasklist_lock); 1198 1199 /* 1200 * The task hasn't been attached yet, so its cpus_allowed mask will 1201 * not be changed, nor will its assigned CPU. 1202 * 1203 * The cpus_allowed mask of the parent may have changed after it was 1204 * copied first time - so re-copy it here, then check the child's CPU 1205 * to ensure it is on a valid CPU (and if not, just force it back to 1206 * parent's CPU). This avoids alot of nasty races. 1207 */ 1208 p->cpus_allowed = current->cpus_allowed; 1209 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1210 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1211 !cpu_online(task_cpu(p)))) 1212 set_task_cpu(p, smp_processor_id()); 1213 1214 /* CLONE_PARENT re-uses the old parent */ 1215 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1216 p->real_parent = current->real_parent; 1217 p->parent_exec_id = current->parent_exec_id; 1218 } else { 1219 p->real_parent = current; 1220 p->parent_exec_id = current->self_exec_id; 1221 } 1222 1223 spin_lock(¤t->sighand->siglock); 1224 1225 /* 1226 * Process group and session signals need to be delivered to just the 1227 * parent before the fork or both the parent and the child after the 1228 * fork. Restart if a signal comes in before we add the new process to 1229 * it's process group. 1230 * A fatal signal pending means that current will exit, so the new 1231 * thread can't slip out of an OOM kill (or normal SIGKILL). 1232 */ 1233 recalc_sigpending(); 1234 if (signal_pending(current)) { 1235 spin_unlock(¤t->sighand->siglock); 1236 write_unlock_irq(&tasklist_lock); 1237 retval = -ERESTARTNOINTR; 1238 goto bad_fork_free_pid; 1239 } 1240 1241 if (clone_flags & CLONE_THREAD) { 1242 atomic_inc(¤t->signal->count); 1243 atomic_inc(¤t->signal->live); 1244 p->group_leader = current->group_leader; 1245 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1246 } 1247 1248 if (likely(p->pid)) { 1249 list_add_tail(&p->sibling, &p->real_parent->children); 1250 tracehook_finish_clone(p, clone_flags, trace); 1251 1252 if (thread_group_leader(p)) { 1253 if (clone_flags & CLONE_NEWPID) 1254 p->nsproxy->pid_ns->child_reaper = p; 1255 1256 p->signal->leader_pid = pid; 1257 tty_kref_put(p->signal->tty); 1258 p->signal->tty = tty_kref_get(current->signal->tty); 1259 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1260 attach_pid(p, PIDTYPE_SID, task_session(current)); 1261 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1262 __get_cpu_var(process_counts)++; 1263 } 1264 attach_pid(p, PIDTYPE_PID, pid); 1265 nr_threads++; 1266 } 1267 1268 total_forks++; 1269 spin_unlock(¤t->sighand->siglock); 1270 write_unlock_irq(&tasklist_lock); 1271 proc_fork_connector(p); 1272 cgroup_post_fork(p); 1273 perf_event_fork(p); 1274 return p; 1275 1276 bad_fork_free_pid: 1277 if (pid != &init_struct_pid) 1278 free_pid(pid); 1279 bad_fork_cleanup_io: 1280 put_io_context(p->io_context); 1281 bad_fork_cleanup_namespaces: 1282 exit_task_namespaces(p); 1283 bad_fork_cleanup_mm: 1284 if (p->mm) 1285 mmput(p->mm); 1286 bad_fork_cleanup_signal: 1287 if (!(clone_flags & CLONE_THREAD)) 1288 __cleanup_signal(p->signal); 1289 bad_fork_cleanup_sighand: 1290 __cleanup_sighand(p->sighand); 1291 bad_fork_cleanup_fs: 1292 exit_fs(p); /* blocking */ 1293 bad_fork_cleanup_files: 1294 exit_files(p); /* blocking */ 1295 bad_fork_cleanup_semundo: 1296 exit_sem(p); 1297 bad_fork_cleanup_audit: 1298 audit_free(p); 1299 bad_fork_cleanup_policy: 1300 perf_event_free_task(p); 1301 #ifdef CONFIG_NUMA 1302 mpol_put(p->mempolicy); 1303 bad_fork_cleanup_cgroup: 1304 #endif 1305 cgroup_exit(p, cgroup_callbacks_done); 1306 delayacct_tsk_free(p); 1307 if (p->binfmt) 1308 module_put(p->binfmt->module); 1309 bad_fork_cleanup_put_domain: 1310 module_put(task_thread_info(p)->exec_domain->module); 1311 bad_fork_cleanup_count: 1312 atomic_dec(&p->cred->user->processes); 1313 exit_creds(p); 1314 bad_fork_free: 1315 free_task(p); 1316 fork_out: 1317 return ERR_PTR(retval); 1318 } 1319 1320 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1321 { 1322 memset(regs, 0, sizeof(struct pt_regs)); 1323 return regs; 1324 } 1325 1326 struct task_struct * __cpuinit fork_idle(int cpu) 1327 { 1328 struct task_struct *task; 1329 struct pt_regs regs; 1330 1331 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1332 &init_struct_pid, 0); 1333 if (!IS_ERR(task)) 1334 init_idle(task, cpu); 1335 1336 return task; 1337 } 1338 1339 /* 1340 * Ok, this is the main fork-routine. 1341 * 1342 * It copies the process, and if successful kick-starts 1343 * it and waits for it to finish using the VM if required. 1344 */ 1345 long do_fork(unsigned long clone_flags, 1346 unsigned long stack_start, 1347 struct pt_regs *regs, 1348 unsigned long stack_size, 1349 int __user *parent_tidptr, 1350 int __user *child_tidptr) 1351 { 1352 struct task_struct *p; 1353 int trace = 0; 1354 long nr; 1355 1356 /* 1357 * Do some preliminary argument and permissions checking before we 1358 * actually start allocating stuff 1359 */ 1360 if (clone_flags & CLONE_NEWUSER) { 1361 if (clone_flags & CLONE_THREAD) 1362 return -EINVAL; 1363 /* hopefully this check will go away when userns support is 1364 * complete 1365 */ 1366 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1367 !capable(CAP_SETGID)) 1368 return -EPERM; 1369 } 1370 1371 /* 1372 * We hope to recycle these flags after 2.6.26 1373 */ 1374 if (unlikely(clone_flags & CLONE_STOPPED)) { 1375 static int __read_mostly count = 100; 1376 1377 if (count > 0 && printk_ratelimit()) { 1378 char comm[TASK_COMM_LEN]; 1379 1380 count--; 1381 printk(KERN_INFO "fork(): process `%s' used deprecated " 1382 "clone flags 0x%lx\n", 1383 get_task_comm(comm, current), 1384 clone_flags & CLONE_STOPPED); 1385 } 1386 } 1387 1388 /* 1389 * When called from kernel_thread, don't do user tracing stuff. 1390 */ 1391 if (likely(user_mode(regs))) 1392 trace = tracehook_prepare_clone(clone_flags); 1393 1394 p = copy_process(clone_flags, stack_start, regs, stack_size, 1395 child_tidptr, NULL, trace); 1396 /* 1397 * Do this prior waking up the new thread - the thread pointer 1398 * might get invalid after that point, if the thread exits quickly. 1399 */ 1400 if (!IS_ERR(p)) { 1401 struct completion vfork; 1402 1403 trace_sched_process_fork(current, p); 1404 1405 nr = task_pid_vnr(p); 1406 1407 if (clone_flags & CLONE_PARENT_SETTID) 1408 put_user(nr, parent_tidptr); 1409 1410 if (clone_flags & CLONE_VFORK) { 1411 p->vfork_done = &vfork; 1412 init_completion(&vfork); 1413 } 1414 1415 audit_finish_fork(p); 1416 tracehook_report_clone(regs, clone_flags, nr, p); 1417 1418 /* 1419 * We set PF_STARTING at creation in case tracing wants to 1420 * use this to distinguish a fully live task from one that 1421 * hasn't gotten to tracehook_report_clone() yet. Now we 1422 * clear it and set the child going. 1423 */ 1424 p->flags &= ~PF_STARTING; 1425 1426 if (unlikely(clone_flags & CLONE_STOPPED)) { 1427 /* 1428 * We'll start up with an immediate SIGSTOP. 1429 */ 1430 sigaddset(&p->pending.signal, SIGSTOP); 1431 set_tsk_thread_flag(p, TIF_SIGPENDING); 1432 __set_task_state(p, TASK_STOPPED); 1433 } else { 1434 wake_up_new_task(p, clone_flags); 1435 } 1436 1437 tracehook_report_clone_complete(trace, regs, 1438 clone_flags, nr, p); 1439 1440 if (clone_flags & CLONE_VFORK) { 1441 freezer_do_not_count(); 1442 wait_for_completion(&vfork); 1443 freezer_count(); 1444 tracehook_report_vfork_done(p, nr); 1445 } 1446 } else { 1447 nr = PTR_ERR(p); 1448 } 1449 return nr; 1450 } 1451 1452 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1453 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1454 #endif 1455 1456 static void sighand_ctor(void *data) 1457 { 1458 struct sighand_struct *sighand = data; 1459 1460 spin_lock_init(&sighand->siglock); 1461 init_waitqueue_head(&sighand->signalfd_wqh); 1462 } 1463 1464 void __init proc_caches_init(void) 1465 { 1466 sighand_cachep = kmem_cache_create("sighand_cache", 1467 sizeof(struct sighand_struct), 0, 1468 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1469 SLAB_NOTRACK, sighand_ctor); 1470 signal_cachep = kmem_cache_create("signal_cache", 1471 sizeof(struct signal_struct), 0, 1472 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1473 files_cachep = kmem_cache_create("files_cache", 1474 sizeof(struct files_struct), 0, 1475 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1476 fs_cachep = kmem_cache_create("fs_cache", 1477 sizeof(struct fs_struct), 0, 1478 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1479 mm_cachep = kmem_cache_create("mm_struct", 1480 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1481 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1482 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1483 mmap_init(); 1484 } 1485 1486 /* 1487 * Check constraints on flags passed to the unshare system call and 1488 * force unsharing of additional process context as appropriate. 1489 */ 1490 static void check_unshare_flags(unsigned long *flags_ptr) 1491 { 1492 /* 1493 * If unsharing a thread from a thread group, must also 1494 * unshare vm. 1495 */ 1496 if (*flags_ptr & CLONE_THREAD) 1497 *flags_ptr |= CLONE_VM; 1498 1499 /* 1500 * If unsharing vm, must also unshare signal handlers. 1501 */ 1502 if (*flags_ptr & CLONE_VM) 1503 *flags_ptr |= CLONE_SIGHAND; 1504 1505 /* 1506 * If unsharing signal handlers and the task was created 1507 * using CLONE_THREAD, then must unshare the thread 1508 */ 1509 if ((*flags_ptr & CLONE_SIGHAND) && 1510 (atomic_read(¤t->signal->count) > 1)) 1511 *flags_ptr |= CLONE_THREAD; 1512 1513 /* 1514 * If unsharing namespace, must also unshare filesystem information. 1515 */ 1516 if (*flags_ptr & CLONE_NEWNS) 1517 *flags_ptr |= CLONE_FS; 1518 } 1519 1520 /* 1521 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1522 */ 1523 static int unshare_thread(unsigned long unshare_flags) 1524 { 1525 if (unshare_flags & CLONE_THREAD) 1526 return -EINVAL; 1527 1528 return 0; 1529 } 1530 1531 /* 1532 * Unshare the filesystem structure if it is being shared 1533 */ 1534 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1535 { 1536 struct fs_struct *fs = current->fs; 1537 1538 if (!(unshare_flags & CLONE_FS) || !fs) 1539 return 0; 1540 1541 /* don't need lock here; in the worst case we'll do useless copy */ 1542 if (fs->users == 1) 1543 return 0; 1544 1545 *new_fsp = copy_fs_struct(fs); 1546 if (!*new_fsp) 1547 return -ENOMEM; 1548 1549 return 0; 1550 } 1551 1552 /* 1553 * Unsharing of sighand is not supported yet 1554 */ 1555 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1556 { 1557 struct sighand_struct *sigh = current->sighand; 1558 1559 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1560 return -EINVAL; 1561 else 1562 return 0; 1563 } 1564 1565 /* 1566 * Unshare vm if it is being shared 1567 */ 1568 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1569 { 1570 struct mm_struct *mm = current->mm; 1571 1572 if ((unshare_flags & CLONE_VM) && 1573 (mm && atomic_read(&mm->mm_users) > 1)) { 1574 return -EINVAL; 1575 } 1576 1577 return 0; 1578 } 1579 1580 /* 1581 * Unshare file descriptor table if it is being shared 1582 */ 1583 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1584 { 1585 struct files_struct *fd = current->files; 1586 int error = 0; 1587 1588 if ((unshare_flags & CLONE_FILES) && 1589 (fd && atomic_read(&fd->count) > 1)) { 1590 *new_fdp = dup_fd(fd, &error); 1591 if (!*new_fdp) 1592 return error; 1593 } 1594 1595 return 0; 1596 } 1597 1598 /* 1599 * unshare allows a process to 'unshare' part of the process 1600 * context which was originally shared using clone. copy_* 1601 * functions used by do_fork() cannot be used here directly 1602 * because they modify an inactive task_struct that is being 1603 * constructed. Here we are modifying the current, active, 1604 * task_struct. 1605 */ 1606 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1607 { 1608 int err = 0; 1609 struct fs_struct *fs, *new_fs = NULL; 1610 struct sighand_struct *new_sigh = NULL; 1611 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1612 struct files_struct *fd, *new_fd = NULL; 1613 struct nsproxy *new_nsproxy = NULL; 1614 int do_sysvsem = 0; 1615 1616 check_unshare_flags(&unshare_flags); 1617 1618 /* Return -EINVAL for all unsupported flags */ 1619 err = -EINVAL; 1620 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1621 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1622 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1623 goto bad_unshare_out; 1624 1625 /* 1626 * CLONE_NEWIPC must also detach from the undolist: after switching 1627 * to a new ipc namespace, the semaphore arrays from the old 1628 * namespace are unreachable. 1629 */ 1630 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1631 do_sysvsem = 1; 1632 if ((err = unshare_thread(unshare_flags))) 1633 goto bad_unshare_out; 1634 if ((err = unshare_fs(unshare_flags, &new_fs))) 1635 goto bad_unshare_cleanup_thread; 1636 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1637 goto bad_unshare_cleanup_fs; 1638 if ((err = unshare_vm(unshare_flags, &new_mm))) 1639 goto bad_unshare_cleanup_sigh; 1640 if ((err = unshare_fd(unshare_flags, &new_fd))) 1641 goto bad_unshare_cleanup_vm; 1642 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1643 new_fs))) 1644 goto bad_unshare_cleanup_fd; 1645 1646 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1647 if (do_sysvsem) { 1648 /* 1649 * CLONE_SYSVSEM is equivalent to sys_exit(). 1650 */ 1651 exit_sem(current); 1652 } 1653 1654 if (new_nsproxy) { 1655 switch_task_namespaces(current, new_nsproxy); 1656 new_nsproxy = NULL; 1657 } 1658 1659 task_lock(current); 1660 1661 if (new_fs) { 1662 fs = current->fs; 1663 write_lock(&fs->lock); 1664 current->fs = new_fs; 1665 if (--fs->users) 1666 new_fs = NULL; 1667 else 1668 new_fs = fs; 1669 write_unlock(&fs->lock); 1670 } 1671 1672 if (new_mm) { 1673 mm = current->mm; 1674 active_mm = current->active_mm; 1675 current->mm = new_mm; 1676 current->active_mm = new_mm; 1677 activate_mm(active_mm, new_mm); 1678 new_mm = mm; 1679 } 1680 1681 if (new_fd) { 1682 fd = current->files; 1683 current->files = new_fd; 1684 new_fd = fd; 1685 } 1686 1687 task_unlock(current); 1688 } 1689 1690 if (new_nsproxy) 1691 put_nsproxy(new_nsproxy); 1692 1693 bad_unshare_cleanup_fd: 1694 if (new_fd) 1695 put_files_struct(new_fd); 1696 1697 bad_unshare_cleanup_vm: 1698 if (new_mm) 1699 mmput(new_mm); 1700 1701 bad_unshare_cleanup_sigh: 1702 if (new_sigh) 1703 if (atomic_dec_and_test(&new_sigh->count)) 1704 kmem_cache_free(sighand_cachep, new_sigh); 1705 1706 bad_unshare_cleanup_fs: 1707 if (new_fs) 1708 free_fs_struct(new_fs); 1709 1710 bad_unshare_cleanup_thread: 1711 bad_unshare_out: 1712 return err; 1713 } 1714 1715 /* 1716 * Helper to unshare the files of the current task. 1717 * We don't want to expose copy_files internals to 1718 * the exec layer of the kernel. 1719 */ 1720 1721 int unshare_files(struct files_struct **displaced) 1722 { 1723 struct task_struct *task = current; 1724 struct files_struct *copy = NULL; 1725 int error; 1726 1727 error = unshare_fd(CLONE_FILES, ©); 1728 if (error || !copy) { 1729 *displaced = NULL; 1730 return error; 1731 } 1732 *displaced = task->files; 1733 task_lock(task); 1734 task->files = copy; 1735 task_unlock(task); 1736 return 0; 1737 } 1738