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