1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/mnt_namespace.h> 21 #include <linux/personality.h> 22 #include <linux/mempolicy.h> 23 #include <linux/sem.h> 24 #include <linux/file.h> 25 #include <linux/fdtable.h> 26 #include <linux/iocontext.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/mmu_notifier.h> 31 #include <linux/fs.h> 32 #include <linux/nsproxy.h> 33 #include <linux/capability.h> 34 #include <linux/cpu.h> 35 #include <linux/cgroup.h> 36 #include <linux/security.h> 37 #include <linux/hugetlb.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/tracehook.h> 42 #include <linux/futex.h> 43 #include <linux/compat.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/profile.h> 52 #include <linux/rmap.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <trace/sched.h> 64 65 #include <asm/pgtable.h> 66 #include <asm/pgalloc.h> 67 #include <asm/uaccess.h> 68 #include <asm/mmu_context.h> 69 #include <asm/cacheflush.h> 70 #include <asm/tlbflush.h> 71 72 /* 73 * Protected counters by write_lock_irq(&tasklist_lock) 74 */ 75 unsigned long total_forks; /* Handle normal Linux uptimes. */ 76 int nr_threads; /* The idle threads do not count.. */ 77 78 int max_threads; /* tunable limit on nr_threads */ 79 80 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 81 82 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 83 84 DEFINE_TRACE(sched_process_fork); 85 86 int nr_processes(void) 87 { 88 int cpu; 89 int total = 0; 90 91 for_each_online_cpu(cpu) 92 total += per_cpu(process_counts, cpu); 93 94 return total; 95 } 96 97 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 98 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 99 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 100 static struct kmem_cache *task_struct_cachep; 101 #endif 102 103 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 104 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 105 { 106 #ifdef CONFIG_DEBUG_STACK_USAGE 107 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 108 #else 109 gfp_t mask = GFP_KERNEL; 110 #endif 111 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 112 } 113 114 static inline void free_thread_info(struct thread_info *ti) 115 { 116 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 117 } 118 #endif 119 120 /* SLAB cache for signal_struct structures (tsk->signal) */ 121 static struct kmem_cache *signal_cachep; 122 123 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 124 struct kmem_cache *sighand_cachep; 125 126 /* SLAB cache for files_struct structures (tsk->files) */ 127 struct kmem_cache *files_cachep; 128 129 /* SLAB cache for fs_struct structures (tsk->fs) */ 130 struct kmem_cache *fs_cachep; 131 132 /* SLAB cache for vm_area_struct structures */ 133 struct kmem_cache *vm_area_cachep; 134 135 /* SLAB cache for mm_struct structures (tsk->mm) */ 136 static struct kmem_cache *mm_cachep; 137 138 void free_task(struct task_struct *tsk) 139 { 140 prop_local_destroy_single(&tsk->dirties); 141 free_thread_info(tsk->stack); 142 rt_mutex_debug_task_free(tsk); 143 ftrace_graph_exit_task(tsk); 144 free_task_struct(tsk); 145 } 146 EXPORT_SYMBOL(free_task); 147 148 void __put_task_struct(struct task_struct *tsk) 149 { 150 WARN_ON(!tsk->exit_state); 151 WARN_ON(atomic_read(&tsk->usage)); 152 WARN_ON(tsk == current); 153 154 security_task_free(tsk); 155 free_uid(tsk->user); 156 put_group_info(tsk->group_info); 157 delayacct_tsk_free(tsk); 158 159 if (!profile_handoff_task(tsk)) 160 free_task(tsk); 161 } 162 163 /* 164 * macro override instead of weak attribute alias, to workaround 165 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 166 */ 167 #ifndef arch_task_cache_init 168 #define arch_task_cache_init() 169 #endif 170 171 void __init fork_init(unsigned long mempages) 172 { 173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 174 #ifndef ARCH_MIN_TASKALIGN 175 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 176 #endif 177 /* create a slab on which task_structs can be allocated */ 178 task_struct_cachep = 179 kmem_cache_create("task_struct", sizeof(struct task_struct), 180 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 181 #endif 182 183 /* do the arch specific task caches init */ 184 arch_task_cache_init(); 185 186 /* 187 * The default maximum number of threads is set to a safe 188 * value: the thread structures can take up at most half 189 * of memory. 190 */ 191 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 192 193 /* 194 * we need to allow at least 20 threads to boot a system 195 */ 196 if(max_threads < 20) 197 max_threads = 20; 198 199 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 200 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 201 init_task.signal->rlim[RLIMIT_SIGPENDING] = 202 init_task.signal->rlim[RLIMIT_NPROC]; 203 } 204 205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 206 struct task_struct *src) 207 { 208 *dst = *src; 209 return 0; 210 } 211 212 static struct task_struct *dup_task_struct(struct task_struct *orig) 213 { 214 struct task_struct *tsk; 215 struct thread_info *ti; 216 int err; 217 218 prepare_to_copy(orig); 219 220 tsk = alloc_task_struct(); 221 if (!tsk) 222 return NULL; 223 224 ti = alloc_thread_info(tsk); 225 if (!ti) { 226 free_task_struct(tsk); 227 return NULL; 228 } 229 230 err = arch_dup_task_struct(tsk, orig); 231 if (err) 232 goto out; 233 234 tsk->stack = ti; 235 236 err = prop_local_init_single(&tsk->dirties); 237 if (err) 238 goto out; 239 240 setup_thread_stack(tsk, orig); 241 242 #ifdef CONFIG_CC_STACKPROTECTOR 243 tsk->stack_canary = get_random_int(); 244 #endif 245 246 /* One for us, one for whoever does the "release_task()" (usually parent) */ 247 atomic_set(&tsk->usage,2); 248 atomic_set(&tsk->fs_excl, 0); 249 #ifdef CONFIG_BLK_DEV_IO_TRACE 250 tsk->btrace_seq = 0; 251 #endif 252 tsk->splice_pipe = NULL; 253 return tsk; 254 255 out: 256 free_thread_info(ti); 257 free_task_struct(tsk); 258 return NULL; 259 } 260 261 #ifdef CONFIG_MMU 262 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 263 { 264 struct vm_area_struct *mpnt, *tmp, **pprev; 265 struct rb_node **rb_link, *rb_parent; 266 int retval; 267 unsigned long charge; 268 struct mempolicy *pol; 269 270 down_write(&oldmm->mmap_sem); 271 flush_cache_dup_mm(oldmm); 272 /* 273 * Not linked in yet - no deadlock potential: 274 */ 275 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 276 277 mm->locked_vm = 0; 278 mm->mmap = NULL; 279 mm->mmap_cache = NULL; 280 mm->free_area_cache = oldmm->mmap_base; 281 mm->cached_hole_size = ~0UL; 282 mm->map_count = 0; 283 cpus_clear(mm->cpu_vm_mask); 284 mm->mm_rb = RB_ROOT; 285 rb_link = &mm->mm_rb.rb_node; 286 rb_parent = NULL; 287 pprev = &mm->mmap; 288 289 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 290 struct file *file; 291 292 if (mpnt->vm_flags & VM_DONTCOPY) { 293 long pages = vma_pages(mpnt); 294 mm->total_vm -= pages; 295 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 296 -pages); 297 continue; 298 } 299 charge = 0; 300 if (mpnt->vm_flags & VM_ACCOUNT) { 301 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 302 if (security_vm_enough_memory(len)) 303 goto fail_nomem; 304 charge = len; 305 } 306 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 307 if (!tmp) 308 goto fail_nomem; 309 *tmp = *mpnt; 310 pol = mpol_dup(vma_policy(mpnt)); 311 retval = PTR_ERR(pol); 312 if (IS_ERR(pol)) 313 goto fail_nomem_policy; 314 vma_set_policy(tmp, pol); 315 tmp->vm_flags &= ~VM_LOCKED; 316 tmp->vm_mm = mm; 317 tmp->vm_next = NULL; 318 anon_vma_link(tmp); 319 file = tmp->vm_file; 320 if (file) { 321 struct inode *inode = file->f_path.dentry->d_inode; 322 struct address_space *mapping = file->f_mapping; 323 324 get_file(file); 325 if (tmp->vm_flags & VM_DENYWRITE) 326 atomic_dec(&inode->i_writecount); 327 spin_lock(&mapping->i_mmap_lock); 328 if (tmp->vm_flags & VM_SHARED) 329 mapping->i_mmap_writable++; 330 tmp->vm_truncate_count = mpnt->vm_truncate_count; 331 flush_dcache_mmap_lock(mapping); 332 /* insert tmp into the share list, just after mpnt */ 333 vma_prio_tree_add(tmp, mpnt); 334 flush_dcache_mmap_unlock(mapping); 335 spin_unlock(&mapping->i_mmap_lock); 336 } 337 338 /* 339 * Clear hugetlb-related page reserves for children. This only 340 * affects MAP_PRIVATE mappings. Faults generated by the child 341 * are not guaranteed to succeed, even if read-only 342 */ 343 if (is_vm_hugetlb_page(tmp)) 344 reset_vma_resv_huge_pages(tmp); 345 346 /* 347 * Link in the new vma and copy the page table entries. 348 */ 349 *pprev = tmp; 350 pprev = &tmp->vm_next; 351 352 __vma_link_rb(mm, tmp, rb_link, rb_parent); 353 rb_link = &tmp->vm_rb.rb_right; 354 rb_parent = &tmp->vm_rb; 355 356 mm->map_count++; 357 retval = copy_page_range(mm, oldmm, mpnt); 358 359 if (tmp->vm_ops && tmp->vm_ops->open) 360 tmp->vm_ops->open(tmp); 361 362 if (retval) 363 goto out; 364 } 365 /* a new mm has just been created */ 366 arch_dup_mmap(oldmm, mm); 367 retval = 0; 368 out: 369 up_write(&mm->mmap_sem); 370 flush_tlb_mm(oldmm); 371 up_write(&oldmm->mmap_sem); 372 return retval; 373 fail_nomem_policy: 374 kmem_cache_free(vm_area_cachep, tmp); 375 fail_nomem: 376 retval = -ENOMEM; 377 vm_unacct_memory(charge); 378 goto out; 379 } 380 381 static inline int mm_alloc_pgd(struct mm_struct * mm) 382 { 383 mm->pgd = pgd_alloc(mm); 384 if (unlikely(!mm->pgd)) 385 return -ENOMEM; 386 return 0; 387 } 388 389 static inline void mm_free_pgd(struct mm_struct * mm) 390 { 391 pgd_free(mm, mm->pgd); 392 } 393 #else 394 #define dup_mmap(mm, oldmm) (0) 395 #define mm_alloc_pgd(mm) (0) 396 #define mm_free_pgd(mm) 397 #endif /* CONFIG_MMU */ 398 399 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 400 401 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 402 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 403 404 #include <linux/init_task.h> 405 406 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 407 { 408 atomic_set(&mm->mm_users, 1); 409 atomic_set(&mm->mm_count, 1); 410 init_rwsem(&mm->mmap_sem); 411 INIT_LIST_HEAD(&mm->mmlist); 412 mm->flags = (current->mm) ? current->mm->flags 413 : MMF_DUMP_FILTER_DEFAULT; 414 mm->core_state = NULL; 415 mm->nr_ptes = 0; 416 set_mm_counter(mm, file_rss, 0); 417 set_mm_counter(mm, anon_rss, 0); 418 spin_lock_init(&mm->page_table_lock); 419 rwlock_init(&mm->ioctx_list_lock); 420 mm->ioctx_list = NULL; 421 mm->free_area_cache = TASK_UNMAPPED_BASE; 422 mm->cached_hole_size = ~0UL; 423 mm_init_owner(mm, p); 424 425 if (likely(!mm_alloc_pgd(mm))) { 426 mm->def_flags = 0; 427 mmu_notifier_mm_init(mm); 428 return mm; 429 } 430 431 free_mm(mm); 432 return NULL; 433 } 434 435 /* 436 * Allocate and initialize an mm_struct. 437 */ 438 struct mm_struct * mm_alloc(void) 439 { 440 struct mm_struct * mm; 441 442 mm = allocate_mm(); 443 if (mm) { 444 memset(mm, 0, sizeof(*mm)); 445 mm = mm_init(mm, current); 446 } 447 return mm; 448 } 449 450 /* 451 * Called when the last reference to the mm 452 * is dropped: either by a lazy thread or by 453 * mmput. Free the page directory and the mm. 454 */ 455 void __mmdrop(struct mm_struct *mm) 456 { 457 BUG_ON(mm == &init_mm); 458 mm_free_pgd(mm); 459 destroy_context(mm); 460 mmu_notifier_mm_destroy(mm); 461 free_mm(mm); 462 } 463 EXPORT_SYMBOL_GPL(__mmdrop); 464 465 /* 466 * Decrement the use count and release all resources for an mm. 467 */ 468 void mmput(struct mm_struct *mm) 469 { 470 might_sleep(); 471 472 if (atomic_dec_and_test(&mm->mm_users)) { 473 exit_aio(mm); 474 exit_mmap(mm); 475 set_mm_exe_file(mm, NULL); 476 if (!list_empty(&mm->mmlist)) { 477 spin_lock(&mmlist_lock); 478 list_del(&mm->mmlist); 479 spin_unlock(&mmlist_lock); 480 } 481 put_swap_token(mm); 482 mmdrop(mm); 483 } 484 } 485 EXPORT_SYMBOL_GPL(mmput); 486 487 /** 488 * get_task_mm - acquire a reference to the task's mm 489 * 490 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 491 * this kernel workthread has transiently adopted a user mm with use_mm, 492 * to do its AIO) is not set and if so returns a reference to it, after 493 * bumping up the use count. User must release the mm via mmput() 494 * after use. Typically used by /proc and ptrace. 495 */ 496 struct mm_struct *get_task_mm(struct task_struct *task) 497 { 498 struct mm_struct *mm; 499 500 task_lock(task); 501 mm = task->mm; 502 if (mm) { 503 if (task->flags & PF_KTHREAD) 504 mm = NULL; 505 else 506 atomic_inc(&mm->mm_users); 507 } 508 task_unlock(task); 509 return mm; 510 } 511 EXPORT_SYMBOL_GPL(get_task_mm); 512 513 /* Please note the differences between mmput and mm_release. 514 * mmput is called whenever we stop holding onto a mm_struct, 515 * error success whatever. 516 * 517 * mm_release is called after a mm_struct has been removed 518 * from the current process. 519 * 520 * This difference is important for error handling, when we 521 * only half set up a mm_struct for a new process and need to restore 522 * the old one. Because we mmput the new mm_struct before 523 * restoring the old one. . . 524 * Eric Biederman 10 January 1998 525 */ 526 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 527 { 528 struct completion *vfork_done = tsk->vfork_done; 529 530 /* Get rid of any futexes when releasing the mm */ 531 #ifdef CONFIG_FUTEX 532 if (unlikely(tsk->robust_list)) 533 exit_robust_list(tsk); 534 #ifdef CONFIG_COMPAT 535 if (unlikely(tsk->compat_robust_list)) 536 compat_exit_robust_list(tsk); 537 #endif 538 #endif 539 540 /* Get rid of any cached register state */ 541 deactivate_mm(tsk, mm); 542 543 /* notify parent sleeping on vfork() */ 544 if (vfork_done) { 545 tsk->vfork_done = NULL; 546 complete(vfork_done); 547 } 548 549 /* 550 * If we're exiting normally, clear a user-space tid field if 551 * requested. We leave this alone when dying by signal, to leave 552 * the value intact in a core dump, and to save the unnecessary 553 * trouble otherwise. Userland only wants this done for a sys_exit. 554 */ 555 if (tsk->clear_child_tid 556 && !(tsk->flags & PF_SIGNALED) 557 && atomic_read(&mm->mm_users) > 1) { 558 u32 __user * tidptr = tsk->clear_child_tid; 559 tsk->clear_child_tid = NULL; 560 561 /* 562 * We don't check the error code - if userspace has 563 * not set up a proper pointer then tough luck. 564 */ 565 put_user(0, tidptr); 566 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 567 } 568 } 569 570 /* 571 * Allocate a new mm structure and copy contents from the 572 * mm structure of the passed in task structure. 573 */ 574 struct mm_struct *dup_mm(struct task_struct *tsk) 575 { 576 struct mm_struct *mm, *oldmm = current->mm; 577 int err; 578 579 if (!oldmm) 580 return NULL; 581 582 mm = allocate_mm(); 583 if (!mm) 584 goto fail_nomem; 585 586 memcpy(mm, oldmm, sizeof(*mm)); 587 588 /* Initializing for Swap token stuff */ 589 mm->token_priority = 0; 590 mm->last_interval = 0; 591 592 if (!mm_init(mm, tsk)) 593 goto fail_nomem; 594 595 if (init_new_context(tsk, mm)) 596 goto fail_nocontext; 597 598 dup_mm_exe_file(oldmm, mm); 599 600 err = dup_mmap(mm, oldmm); 601 if (err) 602 goto free_pt; 603 604 mm->hiwater_rss = get_mm_rss(mm); 605 mm->hiwater_vm = mm->total_vm; 606 607 return mm; 608 609 free_pt: 610 mmput(mm); 611 612 fail_nomem: 613 return NULL; 614 615 fail_nocontext: 616 /* 617 * If init_new_context() failed, we cannot use mmput() to free the mm 618 * because it calls destroy_context() 619 */ 620 mm_free_pgd(mm); 621 free_mm(mm); 622 return NULL; 623 } 624 625 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 626 { 627 struct mm_struct * mm, *oldmm; 628 int retval; 629 630 tsk->min_flt = tsk->maj_flt = 0; 631 tsk->nvcsw = tsk->nivcsw = 0; 632 633 tsk->mm = NULL; 634 tsk->active_mm = NULL; 635 636 /* 637 * Are we cloning a kernel thread? 638 * 639 * We need to steal a active VM for that.. 640 */ 641 oldmm = current->mm; 642 if (!oldmm) 643 return 0; 644 645 if (clone_flags & CLONE_VM) { 646 atomic_inc(&oldmm->mm_users); 647 mm = oldmm; 648 goto good_mm; 649 } 650 651 retval = -ENOMEM; 652 mm = dup_mm(tsk); 653 if (!mm) 654 goto fail_nomem; 655 656 good_mm: 657 /* Initializing for Swap token stuff */ 658 mm->token_priority = 0; 659 mm->last_interval = 0; 660 661 tsk->mm = mm; 662 tsk->active_mm = mm; 663 return 0; 664 665 fail_nomem: 666 return retval; 667 } 668 669 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 670 { 671 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 672 /* We don't need to lock fs - think why ;-) */ 673 if (fs) { 674 atomic_set(&fs->count, 1); 675 rwlock_init(&fs->lock); 676 fs->umask = old->umask; 677 read_lock(&old->lock); 678 fs->root = old->root; 679 path_get(&old->root); 680 fs->pwd = old->pwd; 681 path_get(&old->pwd); 682 read_unlock(&old->lock); 683 } 684 return fs; 685 } 686 687 struct fs_struct *copy_fs_struct(struct fs_struct *old) 688 { 689 return __copy_fs_struct(old); 690 } 691 692 EXPORT_SYMBOL_GPL(copy_fs_struct); 693 694 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 695 { 696 if (clone_flags & CLONE_FS) { 697 atomic_inc(¤t->fs->count); 698 return 0; 699 } 700 tsk->fs = __copy_fs_struct(current->fs); 701 if (!tsk->fs) 702 return -ENOMEM; 703 return 0; 704 } 705 706 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 707 { 708 struct files_struct *oldf, *newf; 709 int error = 0; 710 711 /* 712 * A background process may not have any files ... 713 */ 714 oldf = current->files; 715 if (!oldf) 716 goto out; 717 718 if (clone_flags & CLONE_FILES) { 719 atomic_inc(&oldf->count); 720 goto out; 721 } 722 723 newf = dup_fd(oldf, &error); 724 if (!newf) 725 goto out; 726 727 tsk->files = newf; 728 error = 0; 729 out: 730 return error; 731 } 732 733 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 734 { 735 #ifdef CONFIG_BLOCK 736 struct io_context *ioc = current->io_context; 737 738 if (!ioc) 739 return 0; 740 /* 741 * Share io context with parent, if CLONE_IO is set 742 */ 743 if (clone_flags & CLONE_IO) { 744 tsk->io_context = ioc_task_link(ioc); 745 if (unlikely(!tsk->io_context)) 746 return -ENOMEM; 747 } else if (ioprio_valid(ioc->ioprio)) { 748 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 749 if (unlikely(!tsk->io_context)) 750 return -ENOMEM; 751 752 tsk->io_context->ioprio = ioc->ioprio; 753 } 754 #endif 755 return 0; 756 } 757 758 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 759 { 760 struct sighand_struct *sig; 761 762 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 763 atomic_inc(¤t->sighand->count); 764 return 0; 765 } 766 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 767 rcu_assign_pointer(tsk->sighand, sig); 768 if (!sig) 769 return -ENOMEM; 770 atomic_set(&sig->count, 1); 771 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 772 return 0; 773 } 774 775 void __cleanup_sighand(struct sighand_struct *sighand) 776 { 777 if (atomic_dec_and_test(&sighand->count)) 778 kmem_cache_free(sighand_cachep, sighand); 779 } 780 781 782 /* 783 * Initialize POSIX timer handling for a thread group. 784 */ 785 static void posix_cpu_timers_init_group(struct signal_struct *sig) 786 { 787 /* Thread group counters. */ 788 thread_group_cputime_init(sig); 789 790 /* Expiration times and increments. */ 791 sig->it_virt_expires = cputime_zero; 792 sig->it_virt_incr = cputime_zero; 793 sig->it_prof_expires = cputime_zero; 794 sig->it_prof_incr = cputime_zero; 795 796 /* Cached expiration times. */ 797 sig->cputime_expires.prof_exp = cputime_zero; 798 sig->cputime_expires.virt_exp = cputime_zero; 799 sig->cputime_expires.sched_exp = 0; 800 801 /* The timer lists. */ 802 INIT_LIST_HEAD(&sig->cpu_timers[0]); 803 INIT_LIST_HEAD(&sig->cpu_timers[1]); 804 INIT_LIST_HEAD(&sig->cpu_timers[2]); 805 } 806 807 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 808 { 809 struct signal_struct *sig; 810 int ret; 811 812 if (clone_flags & CLONE_THREAD) { 813 ret = thread_group_cputime_clone_thread(current); 814 if (likely(!ret)) { 815 atomic_inc(¤t->signal->count); 816 atomic_inc(¤t->signal->live); 817 } 818 return ret; 819 } 820 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 821 tsk->signal = sig; 822 if (!sig) 823 return -ENOMEM; 824 825 ret = copy_thread_group_keys(tsk); 826 if (ret < 0) { 827 kmem_cache_free(signal_cachep, sig); 828 return ret; 829 } 830 831 atomic_set(&sig->count, 1); 832 atomic_set(&sig->live, 1); 833 init_waitqueue_head(&sig->wait_chldexit); 834 sig->flags = 0; 835 sig->group_exit_code = 0; 836 sig->group_exit_task = NULL; 837 sig->group_stop_count = 0; 838 sig->curr_target = tsk; 839 init_sigpending(&sig->shared_pending); 840 INIT_LIST_HEAD(&sig->posix_timers); 841 842 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 843 sig->it_real_incr.tv64 = 0; 844 sig->real_timer.function = it_real_fn; 845 846 sig->leader = 0; /* session leadership doesn't inherit */ 847 sig->tty_old_pgrp = NULL; 848 sig->tty = NULL; 849 850 sig->cutime = sig->cstime = cputime_zero; 851 sig->gtime = cputime_zero; 852 sig->cgtime = cputime_zero; 853 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 854 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 855 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 856 task_io_accounting_init(&sig->ioac); 857 taskstats_tgid_init(sig); 858 859 task_lock(current->group_leader); 860 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 861 task_unlock(current->group_leader); 862 863 posix_cpu_timers_init_group(sig); 864 865 acct_init_pacct(&sig->pacct); 866 867 tty_audit_fork(sig); 868 869 return 0; 870 } 871 872 void __cleanup_signal(struct signal_struct *sig) 873 { 874 thread_group_cputime_free(sig); 875 exit_thread_group_keys(sig); 876 tty_kref_put(sig->tty); 877 kmem_cache_free(signal_cachep, sig); 878 } 879 880 static void cleanup_signal(struct task_struct *tsk) 881 { 882 struct signal_struct *sig = tsk->signal; 883 884 atomic_dec(&sig->live); 885 886 if (atomic_dec_and_test(&sig->count)) 887 __cleanup_signal(sig); 888 } 889 890 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 891 { 892 unsigned long new_flags = p->flags; 893 894 new_flags &= ~PF_SUPERPRIV; 895 new_flags |= PF_FORKNOEXEC; 896 new_flags |= PF_STARTING; 897 p->flags = new_flags; 898 clear_freeze_flag(p); 899 } 900 901 asmlinkage long sys_set_tid_address(int __user *tidptr) 902 { 903 current->clear_child_tid = tidptr; 904 905 return task_pid_vnr(current); 906 } 907 908 static void rt_mutex_init_task(struct task_struct *p) 909 { 910 spin_lock_init(&p->pi_lock); 911 #ifdef CONFIG_RT_MUTEXES 912 plist_head_init(&p->pi_waiters, &p->pi_lock); 913 p->pi_blocked_on = NULL; 914 #endif 915 } 916 917 #ifdef CONFIG_MM_OWNER 918 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 919 { 920 mm->owner = p; 921 } 922 #endif /* CONFIG_MM_OWNER */ 923 924 /* 925 * Initialize POSIX timer handling for a single task. 926 */ 927 static void posix_cpu_timers_init(struct task_struct *tsk) 928 { 929 tsk->cputime_expires.prof_exp = cputime_zero; 930 tsk->cputime_expires.virt_exp = cputime_zero; 931 tsk->cputime_expires.sched_exp = 0; 932 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 933 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 934 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 935 } 936 937 /* 938 * This creates a new process as a copy of the old one, 939 * but does not actually start it yet. 940 * 941 * It copies the registers, and all the appropriate 942 * parts of the process environment (as per the clone 943 * flags). The actual kick-off is left to the caller. 944 */ 945 static struct task_struct *copy_process(unsigned long clone_flags, 946 unsigned long stack_start, 947 struct pt_regs *regs, 948 unsigned long stack_size, 949 int __user *child_tidptr, 950 struct pid *pid, 951 int trace) 952 { 953 int retval; 954 struct task_struct *p; 955 int cgroup_callbacks_done = 0; 956 957 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 958 return ERR_PTR(-EINVAL); 959 960 /* 961 * Thread groups must share signals as well, and detached threads 962 * can only be started up within the thread group. 963 */ 964 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 965 return ERR_PTR(-EINVAL); 966 967 /* 968 * Shared signal handlers imply shared VM. By way of the above, 969 * thread groups also imply shared VM. Blocking this case allows 970 * for various simplifications in other code. 971 */ 972 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 973 return ERR_PTR(-EINVAL); 974 975 retval = security_task_create(clone_flags); 976 if (retval) 977 goto fork_out; 978 979 retval = -ENOMEM; 980 p = dup_task_struct(current); 981 if (!p) 982 goto fork_out; 983 984 rt_mutex_init_task(p); 985 986 #ifdef CONFIG_PROVE_LOCKING 987 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 988 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 989 #endif 990 retval = -EAGAIN; 991 if (atomic_read(&p->user->processes) >= 992 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 993 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 994 p->user != current->nsproxy->user_ns->root_user) 995 goto bad_fork_free; 996 } 997 998 atomic_inc(&p->user->__count); 999 atomic_inc(&p->user->processes); 1000 get_group_info(p->group_info); 1001 1002 /* 1003 * If multiple threads are within copy_process(), then this check 1004 * triggers too late. This doesn't hurt, the check is only there 1005 * to stop root fork bombs. 1006 */ 1007 if (nr_threads >= max_threads) 1008 goto bad_fork_cleanup_count; 1009 1010 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1011 goto bad_fork_cleanup_count; 1012 1013 if (p->binfmt && !try_module_get(p->binfmt->module)) 1014 goto bad_fork_cleanup_put_domain; 1015 1016 p->did_exec = 0; 1017 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1018 copy_flags(clone_flags, p); 1019 INIT_LIST_HEAD(&p->children); 1020 INIT_LIST_HEAD(&p->sibling); 1021 #ifdef CONFIG_PREEMPT_RCU 1022 p->rcu_read_lock_nesting = 0; 1023 p->rcu_flipctr_idx = 0; 1024 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1025 p->vfork_done = NULL; 1026 spin_lock_init(&p->alloc_lock); 1027 1028 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1029 init_sigpending(&p->pending); 1030 1031 p->utime = cputime_zero; 1032 p->stime = cputime_zero; 1033 p->gtime = cputime_zero; 1034 p->utimescaled = cputime_zero; 1035 p->stimescaled = cputime_zero; 1036 p->prev_utime = cputime_zero; 1037 p->prev_stime = cputime_zero; 1038 1039 p->default_timer_slack_ns = current->timer_slack_ns; 1040 1041 #ifdef CONFIG_DETECT_SOFTLOCKUP 1042 p->last_switch_count = 0; 1043 p->last_switch_timestamp = 0; 1044 #endif 1045 1046 task_io_accounting_init(&p->ioac); 1047 acct_clear_integrals(p); 1048 1049 posix_cpu_timers_init(p); 1050 1051 p->lock_depth = -1; /* -1 = no lock */ 1052 do_posix_clock_monotonic_gettime(&p->start_time); 1053 p->real_start_time = p->start_time; 1054 monotonic_to_bootbased(&p->real_start_time); 1055 #ifdef CONFIG_SECURITY 1056 p->security = NULL; 1057 #endif 1058 p->cap_bset = current->cap_bset; 1059 p->io_context = NULL; 1060 p->audit_context = NULL; 1061 cgroup_fork(p); 1062 #ifdef CONFIG_NUMA 1063 p->mempolicy = mpol_dup(p->mempolicy); 1064 if (IS_ERR(p->mempolicy)) { 1065 retval = PTR_ERR(p->mempolicy); 1066 p->mempolicy = NULL; 1067 goto bad_fork_cleanup_cgroup; 1068 } 1069 mpol_fix_fork_child_flag(p); 1070 #endif 1071 #ifdef CONFIG_TRACE_IRQFLAGS 1072 p->irq_events = 0; 1073 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1074 p->hardirqs_enabled = 1; 1075 #else 1076 p->hardirqs_enabled = 0; 1077 #endif 1078 p->hardirq_enable_ip = 0; 1079 p->hardirq_enable_event = 0; 1080 p->hardirq_disable_ip = _THIS_IP_; 1081 p->hardirq_disable_event = 0; 1082 p->softirqs_enabled = 1; 1083 p->softirq_enable_ip = _THIS_IP_; 1084 p->softirq_enable_event = 0; 1085 p->softirq_disable_ip = 0; 1086 p->softirq_disable_event = 0; 1087 p->hardirq_context = 0; 1088 p->softirq_context = 0; 1089 #endif 1090 #ifdef CONFIG_LOCKDEP 1091 p->lockdep_depth = 0; /* no locks held yet */ 1092 p->curr_chain_key = 0; 1093 p->lockdep_recursion = 0; 1094 #endif 1095 1096 #ifdef CONFIG_DEBUG_MUTEXES 1097 p->blocked_on = NULL; /* not blocked yet */ 1098 #endif 1099 1100 /* Perform scheduler related setup. Assign this task to a CPU. */ 1101 sched_fork(p, clone_flags); 1102 1103 if ((retval = security_task_alloc(p))) 1104 goto bad_fork_cleanup_policy; 1105 if ((retval = audit_alloc(p))) 1106 goto bad_fork_cleanup_security; 1107 /* copy all the process information */ 1108 if ((retval = copy_semundo(clone_flags, p))) 1109 goto bad_fork_cleanup_audit; 1110 if ((retval = copy_files(clone_flags, p))) 1111 goto bad_fork_cleanup_semundo; 1112 if ((retval = copy_fs(clone_flags, p))) 1113 goto bad_fork_cleanup_files; 1114 if ((retval = copy_sighand(clone_flags, p))) 1115 goto bad_fork_cleanup_fs; 1116 if ((retval = copy_signal(clone_flags, p))) 1117 goto bad_fork_cleanup_sighand; 1118 if ((retval = copy_mm(clone_flags, p))) 1119 goto bad_fork_cleanup_signal; 1120 if ((retval = copy_keys(clone_flags, p))) 1121 goto bad_fork_cleanup_mm; 1122 if ((retval = copy_namespaces(clone_flags, p))) 1123 goto bad_fork_cleanup_keys; 1124 if ((retval = copy_io(clone_flags, p))) 1125 goto bad_fork_cleanup_namespaces; 1126 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1127 if (retval) 1128 goto bad_fork_cleanup_io; 1129 1130 if (pid != &init_struct_pid) { 1131 retval = -ENOMEM; 1132 pid = alloc_pid(task_active_pid_ns(p)); 1133 if (!pid) 1134 goto bad_fork_cleanup_io; 1135 1136 if (clone_flags & CLONE_NEWPID) { 1137 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1138 if (retval < 0) 1139 goto bad_fork_free_pid; 1140 } 1141 } 1142 1143 ftrace_graph_init_task(p); 1144 1145 p->pid = pid_nr(pid); 1146 p->tgid = p->pid; 1147 if (clone_flags & CLONE_THREAD) 1148 p->tgid = current->tgid; 1149 1150 if (current->nsproxy != p->nsproxy) { 1151 retval = ns_cgroup_clone(p, pid); 1152 if (retval) 1153 goto bad_fork_free_graph; 1154 } 1155 1156 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1157 /* 1158 * Clear TID on mm_release()? 1159 */ 1160 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1161 #ifdef CONFIG_FUTEX 1162 p->robust_list = NULL; 1163 #ifdef CONFIG_COMPAT 1164 p->compat_robust_list = NULL; 1165 #endif 1166 INIT_LIST_HEAD(&p->pi_state_list); 1167 p->pi_state_cache = NULL; 1168 #endif 1169 /* 1170 * sigaltstack should be cleared when sharing the same VM 1171 */ 1172 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1173 p->sas_ss_sp = p->sas_ss_size = 0; 1174 1175 /* 1176 * Syscall tracing should be turned off in the child regardless 1177 * of CLONE_PTRACE. 1178 */ 1179 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1180 #ifdef TIF_SYSCALL_EMU 1181 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1182 #endif 1183 clear_all_latency_tracing(p); 1184 1185 /* Our parent execution domain becomes current domain 1186 These must match for thread signalling to apply */ 1187 p->parent_exec_id = p->self_exec_id; 1188 1189 /* ok, now we should be set up.. */ 1190 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1191 p->pdeath_signal = 0; 1192 p->exit_state = 0; 1193 1194 /* 1195 * Ok, make it visible to the rest of the system. 1196 * We dont wake it up yet. 1197 */ 1198 p->group_leader = p; 1199 INIT_LIST_HEAD(&p->thread_group); 1200 1201 /* Now that the task is set up, run cgroup callbacks if 1202 * necessary. We need to run them before the task is visible 1203 * on the tasklist. */ 1204 cgroup_fork_callbacks(p); 1205 cgroup_callbacks_done = 1; 1206 1207 /* Need tasklist lock for parent etc handling! */ 1208 write_lock_irq(&tasklist_lock); 1209 1210 /* 1211 * The task hasn't been attached yet, so its cpus_allowed mask will 1212 * not be changed, nor will its assigned CPU. 1213 * 1214 * The cpus_allowed mask of the parent may have changed after it was 1215 * copied first time - so re-copy it here, then check the child's CPU 1216 * to ensure it is on a valid CPU (and if not, just force it back to 1217 * parent's CPU). This avoids alot of nasty races. 1218 */ 1219 p->cpus_allowed = current->cpus_allowed; 1220 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1221 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1222 !cpu_online(task_cpu(p)))) 1223 set_task_cpu(p, smp_processor_id()); 1224 1225 /* CLONE_PARENT re-uses the old parent */ 1226 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1227 p->real_parent = current->real_parent; 1228 else 1229 p->real_parent = current; 1230 1231 spin_lock(¤t->sighand->siglock); 1232 1233 /* 1234 * Process group and session signals need to be delivered to just the 1235 * parent before the fork or both the parent and the child after the 1236 * fork. Restart if a signal comes in before we add the new process to 1237 * it's process group. 1238 * A fatal signal pending means that current will exit, so the new 1239 * thread can't slip out of an OOM kill (or normal SIGKILL). 1240 */ 1241 recalc_sigpending(); 1242 if (signal_pending(current)) { 1243 spin_unlock(¤t->sighand->siglock); 1244 write_unlock_irq(&tasklist_lock); 1245 retval = -ERESTARTNOINTR; 1246 goto bad_fork_free_graph; 1247 } 1248 1249 if (clone_flags & CLONE_THREAD) { 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 set_task_pgrp(p, task_pgrp_nr(current)); 1266 set_task_session(p, task_session_nr(current)); 1267 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1268 attach_pid(p, PIDTYPE_SID, task_session(current)); 1269 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1270 __get_cpu_var(process_counts)++; 1271 } 1272 attach_pid(p, PIDTYPE_PID, pid); 1273 nr_threads++; 1274 } 1275 1276 total_forks++; 1277 spin_unlock(¤t->sighand->siglock); 1278 write_unlock_irq(&tasklist_lock); 1279 proc_fork_connector(p); 1280 cgroup_post_fork(p); 1281 return p; 1282 1283 bad_fork_free_graph: 1284 ftrace_graph_exit_task(p); 1285 bad_fork_free_pid: 1286 if (pid != &init_struct_pid) 1287 free_pid(pid); 1288 bad_fork_cleanup_io: 1289 put_io_context(p->io_context); 1290 bad_fork_cleanup_namespaces: 1291 exit_task_namespaces(p); 1292 bad_fork_cleanup_keys: 1293 exit_keys(p); 1294 bad_fork_cleanup_mm: 1295 if (p->mm) 1296 mmput(p->mm); 1297 bad_fork_cleanup_signal: 1298 cleanup_signal(p); 1299 bad_fork_cleanup_sighand: 1300 __cleanup_sighand(p->sighand); 1301 bad_fork_cleanup_fs: 1302 exit_fs(p); /* blocking */ 1303 bad_fork_cleanup_files: 1304 exit_files(p); /* blocking */ 1305 bad_fork_cleanup_semundo: 1306 exit_sem(p); 1307 bad_fork_cleanup_audit: 1308 audit_free(p); 1309 bad_fork_cleanup_security: 1310 security_task_free(p); 1311 bad_fork_cleanup_policy: 1312 #ifdef CONFIG_NUMA 1313 mpol_put(p->mempolicy); 1314 bad_fork_cleanup_cgroup: 1315 #endif 1316 cgroup_exit(p, cgroup_callbacks_done); 1317 delayacct_tsk_free(p); 1318 if (p->binfmt) 1319 module_put(p->binfmt->module); 1320 bad_fork_cleanup_put_domain: 1321 module_put(task_thread_info(p)->exec_domain->module); 1322 bad_fork_cleanup_count: 1323 put_group_info(p->group_info); 1324 atomic_dec(&p->user->processes); 1325 free_uid(p->user); 1326 bad_fork_free: 1327 free_task(p); 1328 fork_out: 1329 return ERR_PTR(retval); 1330 } 1331 1332 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1333 { 1334 memset(regs, 0, sizeof(struct pt_regs)); 1335 return regs; 1336 } 1337 1338 struct task_struct * __cpuinit fork_idle(int cpu) 1339 { 1340 struct task_struct *task; 1341 struct pt_regs regs; 1342 1343 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1344 &init_struct_pid, 0); 1345 if (!IS_ERR(task)) 1346 init_idle(task, cpu); 1347 1348 return task; 1349 } 1350 1351 /* 1352 * Ok, this is the main fork-routine. 1353 * 1354 * It copies the process, and if successful kick-starts 1355 * it and waits for it to finish using the VM if required. 1356 */ 1357 long do_fork(unsigned long clone_flags, 1358 unsigned long stack_start, 1359 struct pt_regs *regs, 1360 unsigned long stack_size, 1361 int __user *parent_tidptr, 1362 int __user *child_tidptr) 1363 { 1364 struct task_struct *p; 1365 int trace = 0; 1366 long nr; 1367 1368 /* 1369 * We hope to recycle these flags after 2.6.26 1370 */ 1371 if (unlikely(clone_flags & CLONE_STOPPED)) { 1372 static int __read_mostly count = 100; 1373 1374 if (count > 0 && printk_ratelimit()) { 1375 char comm[TASK_COMM_LEN]; 1376 1377 count--; 1378 printk(KERN_INFO "fork(): process `%s' used deprecated " 1379 "clone flags 0x%lx\n", 1380 get_task_comm(comm, current), 1381 clone_flags & CLONE_STOPPED); 1382 } 1383 } 1384 1385 /* 1386 * When called from kernel_thread, don't do user tracing stuff. 1387 */ 1388 if (likely(user_mode(regs))) 1389 trace = tracehook_prepare_clone(clone_flags); 1390 1391 p = copy_process(clone_flags, stack_start, regs, stack_size, 1392 child_tidptr, NULL, trace); 1393 /* 1394 * Do this prior waking up the new thread - the thread pointer 1395 * might get invalid after that point, if the thread exits quickly. 1396 */ 1397 if (!IS_ERR(p)) { 1398 struct completion vfork; 1399 1400 trace_sched_process_fork(current, p); 1401 1402 nr = task_pid_vnr(p); 1403 1404 if (clone_flags & CLONE_PARENT_SETTID) 1405 put_user(nr, parent_tidptr); 1406 1407 if (clone_flags & CLONE_VFORK) { 1408 p->vfork_done = &vfork; 1409 init_completion(&vfork); 1410 } 1411 1412 audit_finish_fork(p); 1413 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1414 1415 /* 1416 * We set PF_STARTING at creation in case tracing wants to 1417 * use this to distinguish a fully live task from one that 1418 * hasn't gotten to tracehook_report_clone() yet. Now we 1419 * clear it and set the child going. 1420 */ 1421 p->flags &= ~PF_STARTING; 1422 1423 if (unlikely(clone_flags & CLONE_STOPPED)) { 1424 /* 1425 * We'll start up with an immediate SIGSTOP. 1426 */ 1427 sigaddset(&p->pending.signal, SIGSTOP); 1428 set_tsk_thread_flag(p, TIF_SIGPENDING); 1429 __set_task_state(p, TASK_STOPPED); 1430 } else { 1431 wake_up_new_task(p, clone_flags); 1432 } 1433 1434 tracehook_report_clone_complete(trace, regs, 1435 clone_flags, nr, p); 1436 1437 if (clone_flags & CLONE_VFORK) { 1438 freezer_do_not_count(); 1439 wait_for_completion(&vfork); 1440 freezer_count(); 1441 tracehook_report_vfork_done(p, nr); 1442 } 1443 } else { 1444 nr = PTR_ERR(p); 1445 } 1446 return nr; 1447 } 1448 1449 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1450 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1451 #endif 1452 1453 static void sighand_ctor(void *data) 1454 { 1455 struct sighand_struct *sighand = data; 1456 1457 spin_lock_init(&sighand->siglock); 1458 init_waitqueue_head(&sighand->signalfd_wqh); 1459 } 1460 1461 void __init proc_caches_init(void) 1462 { 1463 sighand_cachep = kmem_cache_create("sighand_cache", 1464 sizeof(struct sighand_struct), 0, 1465 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1466 sighand_ctor); 1467 signal_cachep = kmem_cache_create("signal_cache", 1468 sizeof(struct signal_struct), 0, 1469 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1470 files_cachep = kmem_cache_create("files_cache", 1471 sizeof(struct files_struct), 0, 1472 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1473 fs_cachep = kmem_cache_create("fs_cache", 1474 sizeof(struct fs_struct), 0, 1475 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1476 vm_area_cachep = kmem_cache_create("vm_area_struct", 1477 sizeof(struct vm_area_struct), 0, 1478 SLAB_PANIC, NULL); 1479 mm_cachep = kmem_cache_create("mm_struct", 1480 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1481 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1482 } 1483 1484 /* 1485 * Check constraints on flags passed to the unshare system call and 1486 * force unsharing of additional process context as appropriate. 1487 */ 1488 static void check_unshare_flags(unsigned long *flags_ptr) 1489 { 1490 /* 1491 * If unsharing a thread from a thread group, must also 1492 * unshare vm. 1493 */ 1494 if (*flags_ptr & CLONE_THREAD) 1495 *flags_ptr |= CLONE_VM; 1496 1497 /* 1498 * If unsharing vm, must also unshare signal handlers. 1499 */ 1500 if (*flags_ptr & CLONE_VM) 1501 *flags_ptr |= CLONE_SIGHAND; 1502 1503 /* 1504 * If unsharing signal handlers and the task was created 1505 * using CLONE_THREAD, then must unshare the thread 1506 */ 1507 if ((*flags_ptr & CLONE_SIGHAND) && 1508 (atomic_read(¤t->signal->count) > 1)) 1509 *flags_ptr |= CLONE_THREAD; 1510 1511 /* 1512 * If unsharing namespace, must also unshare filesystem information. 1513 */ 1514 if (*flags_ptr & CLONE_NEWNS) 1515 *flags_ptr |= CLONE_FS; 1516 } 1517 1518 /* 1519 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1520 */ 1521 static int unshare_thread(unsigned long unshare_flags) 1522 { 1523 if (unshare_flags & CLONE_THREAD) 1524 return -EINVAL; 1525 1526 return 0; 1527 } 1528 1529 /* 1530 * Unshare the filesystem structure if it is being shared 1531 */ 1532 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1533 { 1534 struct fs_struct *fs = current->fs; 1535 1536 if ((unshare_flags & CLONE_FS) && 1537 (fs && atomic_read(&fs->count) > 1)) { 1538 *new_fsp = __copy_fs_struct(current->fs); 1539 if (!*new_fsp) 1540 return -ENOMEM; 1541 } 1542 1543 return 0; 1544 } 1545 1546 /* 1547 * Unsharing of sighand is not supported yet 1548 */ 1549 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1550 { 1551 struct sighand_struct *sigh = current->sighand; 1552 1553 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1554 return -EINVAL; 1555 else 1556 return 0; 1557 } 1558 1559 /* 1560 * Unshare vm if it is being shared 1561 */ 1562 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1563 { 1564 struct mm_struct *mm = current->mm; 1565 1566 if ((unshare_flags & CLONE_VM) && 1567 (mm && atomic_read(&mm->mm_users) > 1)) { 1568 return -EINVAL; 1569 } 1570 1571 return 0; 1572 } 1573 1574 /* 1575 * Unshare file descriptor table if it is being shared 1576 */ 1577 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1578 { 1579 struct files_struct *fd = current->files; 1580 int error = 0; 1581 1582 if ((unshare_flags & CLONE_FILES) && 1583 (fd && atomic_read(&fd->count) > 1)) { 1584 *new_fdp = dup_fd(fd, &error); 1585 if (!*new_fdp) 1586 return error; 1587 } 1588 1589 return 0; 1590 } 1591 1592 /* 1593 * unshare allows a process to 'unshare' part of the process 1594 * context which was originally shared using clone. copy_* 1595 * functions used by do_fork() cannot be used here directly 1596 * because they modify an inactive task_struct that is being 1597 * constructed. Here we are modifying the current, active, 1598 * task_struct. 1599 */ 1600 asmlinkage long sys_unshare(unsigned long unshare_flags) 1601 { 1602 int err = 0; 1603 struct fs_struct *fs, *new_fs = NULL; 1604 struct sighand_struct *new_sigh = NULL; 1605 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1606 struct files_struct *fd, *new_fd = NULL; 1607 struct nsproxy *new_nsproxy = NULL; 1608 int do_sysvsem = 0; 1609 1610 check_unshare_flags(&unshare_flags); 1611 1612 /* Return -EINVAL for all unsupported flags */ 1613 err = -EINVAL; 1614 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1615 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1616 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1617 CLONE_NEWNET)) 1618 goto bad_unshare_out; 1619 1620 /* 1621 * CLONE_NEWIPC must also detach from the undolist: after switching 1622 * to a new ipc namespace, the semaphore arrays from the old 1623 * namespace are unreachable. 1624 */ 1625 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1626 do_sysvsem = 1; 1627 if ((err = unshare_thread(unshare_flags))) 1628 goto bad_unshare_out; 1629 if ((err = unshare_fs(unshare_flags, &new_fs))) 1630 goto bad_unshare_cleanup_thread; 1631 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1632 goto bad_unshare_cleanup_fs; 1633 if ((err = unshare_vm(unshare_flags, &new_mm))) 1634 goto bad_unshare_cleanup_sigh; 1635 if ((err = unshare_fd(unshare_flags, &new_fd))) 1636 goto bad_unshare_cleanup_vm; 1637 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1638 new_fs))) 1639 goto bad_unshare_cleanup_fd; 1640 1641 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1642 if (do_sysvsem) { 1643 /* 1644 * CLONE_SYSVSEM is equivalent to sys_exit(). 1645 */ 1646 exit_sem(current); 1647 } 1648 1649 if (new_nsproxy) { 1650 switch_task_namespaces(current, new_nsproxy); 1651 new_nsproxy = NULL; 1652 } 1653 1654 task_lock(current); 1655 1656 if (new_fs) { 1657 fs = current->fs; 1658 current->fs = new_fs; 1659 new_fs = fs; 1660 } 1661 1662 if (new_mm) { 1663 mm = current->mm; 1664 active_mm = current->active_mm; 1665 current->mm = new_mm; 1666 current->active_mm = new_mm; 1667 activate_mm(active_mm, new_mm); 1668 new_mm = mm; 1669 } 1670 1671 if (new_fd) { 1672 fd = current->files; 1673 current->files = new_fd; 1674 new_fd = fd; 1675 } 1676 1677 task_unlock(current); 1678 } 1679 1680 if (new_nsproxy) 1681 put_nsproxy(new_nsproxy); 1682 1683 bad_unshare_cleanup_fd: 1684 if (new_fd) 1685 put_files_struct(new_fd); 1686 1687 bad_unshare_cleanup_vm: 1688 if (new_mm) 1689 mmput(new_mm); 1690 1691 bad_unshare_cleanup_sigh: 1692 if (new_sigh) 1693 if (atomic_dec_and_test(&new_sigh->count)) 1694 kmem_cache_free(sighand_cachep, new_sigh); 1695 1696 bad_unshare_cleanup_fs: 1697 if (new_fs) 1698 put_fs_struct(new_fs); 1699 1700 bad_unshare_cleanup_thread: 1701 bad_unshare_out: 1702 return err; 1703 } 1704 1705 /* 1706 * Helper to unshare the files of the current task. 1707 * We don't want to expose copy_files internals to 1708 * the exec layer of the kernel. 1709 */ 1710 1711 int unshare_files(struct files_struct **displaced) 1712 { 1713 struct task_struct *task = current; 1714 struct files_struct *copy = NULL; 1715 int error; 1716 1717 error = unshare_fd(CLONE_FILES, ©); 1718 if (error || !copy) { 1719 *displaced = NULL; 1720 return error; 1721 } 1722 *displaced = task->files; 1723 task_lock(task); 1724 task->files = copy; 1725 task_unlock(task); 1726 return 0; 1727 } 1728