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/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/profile.h> 50 #include <linux/rmap.h> 51 #include <linux/acct.h> 52 #include <linux/tsacct_kern.h> 53 #include <linux/cn_proc.h> 54 #include <linux/freezer.h> 55 #include <linux/delayacct.h> 56 #include <linux/taskstats_kern.h> 57 #include <linux/random.h> 58 #include <linux/tty.h> 59 #include <linux/proc_fs.h> 60 #include <linux/blkdev.h> 61 #include <trace/sched.h> 62 63 #include <asm/pgtable.h> 64 #include <asm/pgalloc.h> 65 #include <asm/uaccess.h> 66 #include <asm/mmu_context.h> 67 #include <asm/cacheflush.h> 68 #include <asm/tlbflush.h> 69 70 /* 71 * Protected counters by write_lock_irq(&tasklist_lock) 72 */ 73 unsigned long total_forks; /* Handle normal Linux uptimes. */ 74 int nr_threads; /* The idle threads do not count.. */ 75 76 int max_threads; /* tunable limit on nr_threads */ 77 78 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 79 80 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 81 82 int nr_processes(void) 83 { 84 int cpu; 85 int total = 0; 86 87 for_each_online_cpu(cpu) 88 total += per_cpu(process_counts, cpu); 89 90 return total; 91 } 92 93 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 94 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 95 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 96 static struct kmem_cache *task_struct_cachep; 97 #endif 98 99 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 100 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 101 { 102 #ifdef CONFIG_DEBUG_STACK_USAGE 103 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 104 #else 105 gfp_t mask = GFP_KERNEL; 106 #endif 107 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 108 } 109 110 static inline void free_thread_info(struct thread_info *ti) 111 { 112 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 113 } 114 #endif 115 116 /* SLAB cache for signal_struct structures (tsk->signal) */ 117 static struct kmem_cache *signal_cachep; 118 119 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 120 struct kmem_cache *sighand_cachep; 121 122 /* SLAB cache for files_struct structures (tsk->files) */ 123 struct kmem_cache *files_cachep; 124 125 /* SLAB cache for fs_struct structures (tsk->fs) */ 126 struct kmem_cache *fs_cachep; 127 128 /* SLAB cache for vm_area_struct structures */ 129 struct kmem_cache *vm_area_cachep; 130 131 /* SLAB cache for mm_struct structures (tsk->mm) */ 132 static struct kmem_cache *mm_cachep; 133 134 void free_task(struct task_struct *tsk) 135 { 136 prop_local_destroy_single(&tsk->dirties); 137 free_thread_info(tsk->stack); 138 rt_mutex_debug_task_free(tsk); 139 free_task_struct(tsk); 140 } 141 EXPORT_SYMBOL(free_task); 142 143 void __put_task_struct(struct task_struct *tsk) 144 { 145 WARN_ON(!tsk->exit_state); 146 WARN_ON(atomic_read(&tsk->usage)); 147 WARN_ON(tsk == current); 148 149 security_task_free(tsk); 150 free_uid(tsk->user); 151 put_group_info(tsk->group_info); 152 delayacct_tsk_free(tsk); 153 154 if (!profile_handoff_task(tsk)) 155 free_task(tsk); 156 } 157 158 /* 159 * macro override instead of weak attribute alias, to workaround 160 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 161 */ 162 #ifndef arch_task_cache_init 163 #define arch_task_cache_init() 164 #endif 165 166 void __init fork_init(unsigned long mempages) 167 { 168 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 169 #ifndef ARCH_MIN_TASKALIGN 170 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 171 #endif 172 /* create a slab on which task_structs can be allocated */ 173 task_struct_cachep = 174 kmem_cache_create("task_struct", sizeof(struct task_struct), 175 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 176 #endif 177 178 /* do the arch specific task caches init */ 179 arch_task_cache_init(); 180 181 /* 182 * The default maximum number of threads is set to a safe 183 * value: the thread structures can take up at most half 184 * of memory. 185 */ 186 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 187 188 /* 189 * we need to allow at least 20 threads to boot a system 190 */ 191 if(max_threads < 20) 192 max_threads = 20; 193 194 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 195 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 196 init_task.signal->rlim[RLIMIT_SIGPENDING] = 197 init_task.signal->rlim[RLIMIT_NPROC]; 198 } 199 200 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 201 struct task_struct *src) 202 { 203 *dst = *src; 204 return 0; 205 } 206 207 static struct task_struct *dup_task_struct(struct task_struct *orig) 208 { 209 struct task_struct *tsk; 210 struct thread_info *ti; 211 int err; 212 213 prepare_to_copy(orig); 214 215 tsk = alloc_task_struct(); 216 if (!tsk) 217 return NULL; 218 219 ti = alloc_thread_info(tsk); 220 if (!ti) { 221 free_task_struct(tsk); 222 return NULL; 223 } 224 225 err = arch_dup_task_struct(tsk, orig); 226 if (err) 227 goto out; 228 229 tsk->stack = ti; 230 231 err = prop_local_init_single(&tsk->dirties); 232 if (err) 233 goto out; 234 235 setup_thread_stack(tsk, orig); 236 237 #ifdef CONFIG_CC_STACKPROTECTOR 238 tsk->stack_canary = get_random_int(); 239 #endif 240 241 /* One for us, one for whoever does the "release_task()" (usually parent) */ 242 atomic_set(&tsk->usage,2); 243 atomic_set(&tsk->fs_excl, 0); 244 #ifdef CONFIG_BLK_DEV_IO_TRACE 245 tsk->btrace_seq = 0; 246 #endif 247 tsk->splice_pipe = NULL; 248 return tsk; 249 250 out: 251 free_thread_info(ti); 252 free_task_struct(tsk); 253 return NULL; 254 } 255 256 #ifdef CONFIG_MMU 257 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 258 { 259 struct vm_area_struct *mpnt, *tmp, **pprev; 260 struct rb_node **rb_link, *rb_parent; 261 int retval; 262 unsigned long charge; 263 struct mempolicy *pol; 264 265 down_write(&oldmm->mmap_sem); 266 flush_cache_dup_mm(oldmm); 267 /* 268 * Not linked in yet - no deadlock potential: 269 */ 270 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 271 272 mm->locked_vm = 0; 273 mm->mmap = NULL; 274 mm->mmap_cache = NULL; 275 mm->free_area_cache = oldmm->mmap_base; 276 mm->cached_hole_size = ~0UL; 277 mm->map_count = 0; 278 cpus_clear(mm->cpu_vm_mask); 279 mm->mm_rb = RB_ROOT; 280 rb_link = &mm->mm_rb.rb_node; 281 rb_parent = NULL; 282 pprev = &mm->mmap; 283 284 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 285 struct file *file; 286 287 if (mpnt->vm_flags & VM_DONTCOPY) { 288 long pages = vma_pages(mpnt); 289 mm->total_vm -= pages; 290 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 291 -pages); 292 continue; 293 } 294 charge = 0; 295 if (mpnt->vm_flags & VM_ACCOUNT) { 296 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 297 if (security_vm_enough_memory(len)) 298 goto fail_nomem; 299 charge = len; 300 } 301 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 302 if (!tmp) 303 goto fail_nomem; 304 *tmp = *mpnt; 305 pol = mpol_dup(vma_policy(mpnt)); 306 retval = PTR_ERR(pol); 307 if (IS_ERR(pol)) 308 goto fail_nomem_policy; 309 vma_set_policy(tmp, pol); 310 tmp->vm_flags &= ~VM_LOCKED; 311 tmp->vm_mm = mm; 312 tmp->vm_next = NULL; 313 anon_vma_link(tmp); 314 file = tmp->vm_file; 315 if (file) { 316 struct inode *inode = file->f_path.dentry->d_inode; 317 get_file(file); 318 if (tmp->vm_flags & VM_DENYWRITE) 319 atomic_dec(&inode->i_writecount); 320 321 /* insert tmp into the share list, just after mpnt */ 322 spin_lock(&file->f_mapping->i_mmap_lock); 323 tmp->vm_truncate_count = mpnt->vm_truncate_count; 324 flush_dcache_mmap_lock(file->f_mapping); 325 vma_prio_tree_add(tmp, mpnt); 326 flush_dcache_mmap_unlock(file->f_mapping); 327 spin_unlock(&file->f_mapping->i_mmap_lock); 328 } 329 330 /* 331 * Clear hugetlb-related page reserves for children. This only 332 * affects MAP_PRIVATE mappings. Faults generated by the child 333 * are not guaranteed to succeed, even if read-only 334 */ 335 if (is_vm_hugetlb_page(tmp)) 336 reset_vma_resv_huge_pages(tmp); 337 338 /* 339 * Link in the new vma and copy the page table entries. 340 */ 341 *pprev = tmp; 342 pprev = &tmp->vm_next; 343 344 __vma_link_rb(mm, tmp, rb_link, rb_parent); 345 rb_link = &tmp->vm_rb.rb_right; 346 rb_parent = &tmp->vm_rb; 347 348 mm->map_count++; 349 retval = copy_page_range(mm, oldmm, mpnt); 350 351 if (tmp->vm_ops && tmp->vm_ops->open) 352 tmp->vm_ops->open(tmp); 353 354 if (retval) 355 goto out; 356 } 357 /* a new mm has just been created */ 358 arch_dup_mmap(oldmm, mm); 359 retval = 0; 360 out: 361 up_write(&mm->mmap_sem); 362 flush_tlb_mm(oldmm); 363 up_write(&oldmm->mmap_sem); 364 return retval; 365 fail_nomem_policy: 366 kmem_cache_free(vm_area_cachep, tmp); 367 fail_nomem: 368 retval = -ENOMEM; 369 vm_unacct_memory(charge); 370 goto out; 371 } 372 373 static inline int mm_alloc_pgd(struct mm_struct * mm) 374 { 375 mm->pgd = pgd_alloc(mm); 376 if (unlikely(!mm->pgd)) 377 return -ENOMEM; 378 return 0; 379 } 380 381 static inline void mm_free_pgd(struct mm_struct * mm) 382 { 383 pgd_free(mm, mm->pgd); 384 } 385 #else 386 #define dup_mmap(mm, oldmm) (0) 387 #define mm_alloc_pgd(mm) (0) 388 #define mm_free_pgd(mm) 389 #endif /* CONFIG_MMU */ 390 391 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 392 393 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 394 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 395 396 #include <linux/init_task.h> 397 398 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 399 { 400 atomic_set(&mm->mm_users, 1); 401 atomic_set(&mm->mm_count, 1); 402 init_rwsem(&mm->mmap_sem); 403 INIT_LIST_HEAD(&mm->mmlist); 404 mm->flags = (current->mm) ? current->mm->flags 405 : MMF_DUMP_FILTER_DEFAULT; 406 mm->core_state = NULL; 407 mm->nr_ptes = 0; 408 set_mm_counter(mm, file_rss, 0); 409 set_mm_counter(mm, anon_rss, 0); 410 spin_lock_init(&mm->page_table_lock); 411 rwlock_init(&mm->ioctx_list_lock); 412 mm->ioctx_list = NULL; 413 mm->free_area_cache = TASK_UNMAPPED_BASE; 414 mm->cached_hole_size = ~0UL; 415 mm_init_owner(mm, p); 416 417 if (likely(!mm_alloc_pgd(mm))) { 418 mm->def_flags = 0; 419 mmu_notifier_mm_init(mm); 420 return mm; 421 } 422 423 free_mm(mm); 424 return NULL; 425 } 426 427 /* 428 * Allocate and initialize an mm_struct. 429 */ 430 struct mm_struct * mm_alloc(void) 431 { 432 struct mm_struct * mm; 433 434 mm = allocate_mm(); 435 if (mm) { 436 memset(mm, 0, sizeof(*mm)); 437 mm = mm_init(mm, current); 438 } 439 return mm; 440 } 441 442 /* 443 * Called when the last reference to the mm 444 * is dropped: either by a lazy thread or by 445 * mmput. Free the page directory and the mm. 446 */ 447 void __mmdrop(struct mm_struct *mm) 448 { 449 BUG_ON(mm == &init_mm); 450 mm_free_pgd(mm); 451 destroy_context(mm); 452 mmu_notifier_mm_destroy(mm); 453 free_mm(mm); 454 } 455 EXPORT_SYMBOL_GPL(__mmdrop); 456 457 /* 458 * Decrement the use count and release all resources for an mm. 459 */ 460 void mmput(struct mm_struct *mm) 461 { 462 might_sleep(); 463 464 if (atomic_dec_and_test(&mm->mm_users)) { 465 exit_aio(mm); 466 exit_mmap(mm); 467 set_mm_exe_file(mm, NULL); 468 if (!list_empty(&mm->mmlist)) { 469 spin_lock(&mmlist_lock); 470 list_del(&mm->mmlist); 471 spin_unlock(&mmlist_lock); 472 } 473 put_swap_token(mm); 474 mmdrop(mm); 475 } 476 } 477 EXPORT_SYMBOL_GPL(mmput); 478 479 /** 480 * get_task_mm - acquire a reference to the task's mm 481 * 482 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 483 * this kernel workthread has transiently adopted a user mm with use_mm, 484 * to do its AIO) is not set and if so returns a reference to it, after 485 * bumping up the use count. User must release the mm via mmput() 486 * after use. Typically used by /proc and ptrace. 487 */ 488 struct mm_struct *get_task_mm(struct task_struct *task) 489 { 490 struct mm_struct *mm; 491 492 task_lock(task); 493 mm = task->mm; 494 if (mm) { 495 if (task->flags & PF_KTHREAD) 496 mm = NULL; 497 else 498 atomic_inc(&mm->mm_users); 499 } 500 task_unlock(task); 501 return mm; 502 } 503 EXPORT_SYMBOL_GPL(get_task_mm); 504 505 /* Please note the differences between mmput and mm_release. 506 * mmput is called whenever we stop holding onto a mm_struct, 507 * error success whatever. 508 * 509 * mm_release is called after a mm_struct has been removed 510 * from the current process. 511 * 512 * This difference is important for error handling, when we 513 * only half set up a mm_struct for a new process and need to restore 514 * the old one. Because we mmput the new mm_struct before 515 * restoring the old one. . . 516 * Eric Biederman 10 January 1998 517 */ 518 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 519 { 520 struct completion *vfork_done = tsk->vfork_done; 521 522 /* Get rid of any cached register state */ 523 deactivate_mm(tsk, mm); 524 525 /* notify parent sleeping on vfork() */ 526 if (vfork_done) { 527 tsk->vfork_done = NULL; 528 complete(vfork_done); 529 } 530 531 /* 532 * If we're exiting normally, clear a user-space tid field if 533 * requested. We leave this alone when dying by signal, to leave 534 * the value intact in a core dump, and to save the unnecessary 535 * trouble otherwise. Userland only wants this done for a sys_exit. 536 */ 537 if (tsk->clear_child_tid 538 && !(tsk->flags & PF_SIGNALED) 539 && atomic_read(&mm->mm_users) > 1) { 540 u32 __user * tidptr = tsk->clear_child_tid; 541 tsk->clear_child_tid = NULL; 542 543 /* 544 * We don't check the error code - if userspace has 545 * not set up a proper pointer then tough luck. 546 */ 547 put_user(0, tidptr); 548 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 549 } 550 } 551 552 /* 553 * Allocate a new mm structure and copy contents from the 554 * mm structure of the passed in task structure. 555 */ 556 struct mm_struct *dup_mm(struct task_struct *tsk) 557 { 558 struct mm_struct *mm, *oldmm = current->mm; 559 int err; 560 561 if (!oldmm) 562 return NULL; 563 564 mm = allocate_mm(); 565 if (!mm) 566 goto fail_nomem; 567 568 memcpy(mm, oldmm, sizeof(*mm)); 569 570 /* Initializing for Swap token stuff */ 571 mm->token_priority = 0; 572 mm->last_interval = 0; 573 574 if (!mm_init(mm, tsk)) 575 goto fail_nomem; 576 577 if (init_new_context(tsk, mm)) 578 goto fail_nocontext; 579 580 dup_mm_exe_file(oldmm, mm); 581 582 err = dup_mmap(mm, oldmm); 583 if (err) 584 goto free_pt; 585 586 mm->hiwater_rss = get_mm_rss(mm); 587 mm->hiwater_vm = mm->total_vm; 588 589 return mm; 590 591 free_pt: 592 mmput(mm); 593 594 fail_nomem: 595 return NULL; 596 597 fail_nocontext: 598 /* 599 * If init_new_context() failed, we cannot use mmput() to free the mm 600 * because it calls destroy_context() 601 */ 602 mm_free_pgd(mm); 603 free_mm(mm); 604 return NULL; 605 } 606 607 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 608 { 609 struct mm_struct * mm, *oldmm; 610 int retval; 611 612 tsk->min_flt = tsk->maj_flt = 0; 613 tsk->nvcsw = tsk->nivcsw = 0; 614 615 tsk->mm = NULL; 616 tsk->active_mm = NULL; 617 618 /* 619 * Are we cloning a kernel thread? 620 * 621 * We need to steal a active VM for that.. 622 */ 623 oldmm = current->mm; 624 if (!oldmm) 625 return 0; 626 627 if (clone_flags & CLONE_VM) { 628 atomic_inc(&oldmm->mm_users); 629 mm = oldmm; 630 goto good_mm; 631 } 632 633 retval = -ENOMEM; 634 mm = dup_mm(tsk); 635 if (!mm) 636 goto fail_nomem; 637 638 good_mm: 639 /* Initializing for Swap token stuff */ 640 mm->token_priority = 0; 641 mm->last_interval = 0; 642 643 tsk->mm = mm; 644 tsk->active_mm = mm; 645 return 0; 646 647 fail_nomem: 648 return retval; 649 } 650 651 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 652 { 653 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 654 /* We don't need to lock fs - think why ;-) */ 655 if (fs) { 656 atomic_set(&fs->count, 1); 657 rwlock_init(&fs->lock); 658 fs->umask = old->umask; 659 read_lock(&old->lock); 660 fs->root = old->root; 661 path_get(&old->root); 662 fs->pwd = old->pwd; 663 path_get(&old->pwd); 664 read_unlock(&old->lock); 665 } 666 return fs; 667 } 668 669 struct fs_struct *copy_fs_struct(struct fs_struct *old) 670 { 671 return __copy_fs_struct(old); 672 } 673 674 EXPORT_SYMBOL_GPL(copy_fs_struct); 675 676 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 677 { 678 if (clone_flags & CLONE_FS) { 679 atomic_inc(¤t->fs->count); 680 return 0; 681 } 682 tsk->fs = __copy_fs_struct(current->fs); 683 if (!tsk->fs) 684 return -ENOMEM; 685 return 0; 686 } 687 688 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 689 { 690 struct files_struct *oldf, *newf; 691 int error = 0; 692 693 /* 694 * A background process may not have any files ... 695 */ 696 oldf = current->files; 697 if (!oldf) 698 goto out; 699 700 if (clone_flags & CLONE_FILES) { 701 atomic_inc(&oldf->count); 702 goto out; 703 } 704 705 newf = dup_fd(oldf, &error); 706 if (!newf) 707 goto out; 708 709 tsk->files = newf; 710 error = 0; 711 out: 712 return error; 713 } 714 715 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 716 { 717 #ifdef CONFIG_BLOCK 718 struct io_context *ioc = current->io_context; 719 720 if (!ioc) 721 return 0; 722 /* 723 * Share io context with parent, if CLONE_IO is set 724 */ 725 if (clone_flags & CLONE_IO) { 726 tsk->io_context = ioc_task_link(ioc); 727 if (unlikely(!tsk->io_context)) 728 return -ENOMEM; 729 } else if (ioprio_valid(ioc->ioprio)) { 730 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 731 if (unlikely(!tsk->io_context)) 732 return -ENOMEM; 733 734 tsk->io_context->ioprio = ioc->ioprio; 735 } 736 #endif 737 return 0; 738 } 739 740 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 741 { 742 struct sighand_struct *sig; 743 744 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 745 atomic_inc(¤t->sighand->count); 746 return 0; 747 } 748 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 749 rcu_assign_pointer(tsk->sighand, sig); 750 if (!sig) 751 return -ENOMEM; 752 atomic_set(&sig->count, 1); 753 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 754 return 0; 755 } 756 757 void __cleanup_sighand(struct sighand_struct *sighand) 758 { 759 if (atomic_dec_and_test(&sighand->count)) 760 kmem_cache_free(sighand_cachep, sighand); 761 } 762 763 764 /* 765 * Initialize POSIX timer handling for a thread group. 766 */ 767 static void posix_cpu_timers_init_group(struct signal_struct *sig) 768 { 769 /* Thread group counters. */ 770 thread_group_cputime_init(sig); 771 772 /* Expiration times and increments. */ 773 sig->it_virt_expires = cputime_zero; 774 sig->it_virt_incr = cputime_zero; 775 sig->it_prof_expires = cputime_zero; 776 sig->it_prof_incr = cputime_zero; 777 778 /* Cached expiration times. */ 779 sig->cputime_expires.prof_exp = cputime_zero; 780 sig->cputime_expires.virt_exp = cputime_zero; 781 sig->cputime_expires.sched_exp = 0; 782 783 /* The timer lists. */ 784 INIT_LIST_HEAD(&sig->cpu_timers[0]); 785 INIT_LIST_HEAD(&sig->cpu_timers[1]); 786 INIT_LIST_HEAD(&sig->cpu_timers[2]); 787 } 788 789 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 790 { 791 struct signal_struct *sig; 792 int ret; 793 794 if (clone_flags & CLONE_THREAD) { 795 ret = thread_group_cputime_clone_thread(current); 796 if (likely(!ret)) { 797 atomic_inc(¤t->signal->count); 798 atomic_inc(¤t->signal->live); 799 } 800 return ret; 801 } 802 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 803 tsk->signal = sig; 804 if (!sig) 805 return -ENOMEM; 806 807 ret = copy_thread_group_keys(tsk); 808 if (ret < 0) { 809 kmem_cache_free(signal_cachep, sig); 810 return ret; 811 } 812 813 atomic_set(&sig->count, 1); 814 atomic_set(&sig->live, 1); 815 init_waitqueue_head(&sig->wait_chldexit); 816 sig->flags = 0; 817 sig->group_exit_code = 0; 818 sig->group_exit_task = NULL; 819 sig->group_stop_count = 0; 820 sig->curr_target = tsk; 821 init_sigpending(&sig->shared_pending); 822 INIT_LIST_HEAD(&sig->posix_timers); 823 824 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 825 sig->it_real_incr.tv64 = 0; 826 sig->real_timer.function = it_real_fn; 827 828 sig->leader = 0; /* session leadership doesn't inherit */ 829 sig->tty_old_pgrp = NULL; 830 sig->tty = NULL; 831 832 sig->cutime = sig->cstime = cputime_zero; 833 sig->gtime = cputime_zero; 834 sig->cgtime = cputime_zero; 835 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 836 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 837 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 838 task_io_accounting_init(&sig->ioac); 839 taskstats_tgid_init(sig); 840 841 task_lock(current->group_leader); 842 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 843 task_unlock(current->group_leader); 844 845 posix_cpu_timers_init_group(sig); 846 847 acct_init_pacct(&sig->pacct); 848 849 tty_audit_fork(sig); 850 851 return 0; 852 } 853 854 void __cleanup_signal(struct signal_struct *sig) 855 { 856 thread_group_cputime_free(sig); 857 exit_thread_group_keys(sig); 858 tty_kref_put(sig->tty); 859 kmem_cache_free(signal_cachep, sig); 860 } 861 862 static void cleanup_signal(struct task_struct *tsk) 863 { 864 struct signal_struct *sig = tsk->signal; 865 866 atomic_dec(&sig->live); 867 868 if (atomic_dec_and_test(&sig->count)) 869 __cleanup_signal(sig); 870 } 871 872 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 873 { 874 unsigned long new_flags = p->flags; 875 876 new_flags &= ~PF_SUPERPRIV; 877 new_flags |= PF_FORKNOEXEC; 878 new_flags |= PF_STARTING; 879 p->flags = new_flags; 880 clear_freeze_flag(p); 881 } 882 883 asmlinkage long sys_set_tid_address(int __user *tidptr) 884 { 885 current->clear_child_tid = tidptr; 886 887 return task_pid_vnr(current); 888 } 889 890 static void rt_mutex_init_task(struct task_struct *p) 891 { 892 spin_lock_init(&p->pi_lock); 893 #ifdef CONFIG_RT_MUTEXES 894 plist_head_init(&p->pi_waiters, &p->pi_lock); 895 p->pi_blocked_on = NULL; 896 #endif 897 } 898 899 #ifdef CONFIG_MM_OWNER 900 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 901 { 902 mm->owner = p; 903 } 904 #endif /* CONFIG_MM_OWNER */ 905 906 /* 907 * Initialize POSIX timer handling for a single task. 908 */ 909 static void posix_cpu_timers_init(struct task_struct *tsk) 910 { 911 tsk->cputime_expires.prof_exp = cputime_zero; 912 tsk->cputime_expires.virt_exp = cputime_zero; 913 tsk->cputime_expires.sched_exp = 0; 914 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 915 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 916 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 917 } 918 919 /* 920 * This creates a new process as a copy of the old one, 921 * but does not actually start it yet. 922 * 923 * It copies the registers, and all the appropriate 924 * parts of the process environment (as per the clone 925 * flags). The actual kick-off is left to the caller. 926 */ 927 static struct task_struct *copy_process(unsigned long clone_flags, 928 unsigned long stack_start, 929 struct pt_regs *regs, 930 unsigned long stack_size, 931 int __user *child_tidptr, 932 struct pid *pid, 933 int trace) 934 { 935 int retval; 936 struct task_struct *p; 937 int cgroup_callbacks_done = 0; 938 939 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 940 return ERR_PTR(-EINVAL); 941 942 /* 943 * Thread groups must share signals as well, and detached threads 944 * can only be started up within the thread group. 945 */ 946 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 947 return ERR_PTR(-EINVAL); 948 949 /* 950 * Shared signal handlers imply shared VM. By way of the above, 951 * thread groups also imply shared VM. Blocking this case allows 952 * for various simplifications in other code. 953 */ 954 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 955 return ERR_PTR(-EINVAL); 956 957 retval = security_task_create(clone_flags); 958 if (retval) 959 goto fork_out; 960 961 retval = -ENOMEM; 962 p = dup_task_struct(current); 963 if (!p) 964 goto fork_out; 965 966 rt_mutex_init_task(p); 967 968 #ifdef CONFIG_PROVE_LOCKING 969 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 970 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 971 #endif 972 retval = -EAGAIN; 973 if (atomic_read(&p->user->processes) >= 974 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 975 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 976 p->user != current->nsproxy->user_ns->root_user) 977 goto bad_fork_free; 978 } 979 980 atomic_inc(&p->user->__count); 981 atomic_inc(&p->user->processes); 982 get_group_info(p->group_info); 983 984 /* 985 * If multiple threads are within copy_process(), then this check 986 * triggers too late. This doesn't hurt, the check is only there 987 * to stop root fork bombs. 988 */ 989 if (nr_threads >= max_threads) 990 goto bad_fork_cleanup_count; 991 992 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 993 goto bad_fork_cleanup_count; 994 995 if (p->binfmt && !try_module_get(p->binfmt->module)) 996 goto bad_fork_cleanup_put_domain; 997 998 p->did_exec = 0; 999 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1000 copy_flags(clone_flags, p); 1001 INIT_LIST_HEAD(&p->children); 1002 INIT_LIST_HEAD(&p->sibling); 1003 #ifdef CONFIG_PREEMPT_RCU 1004 p->rcu_read_lock_nesting = 0; 1005 p->rcu_flipctr_idx = 0; 1006 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1007 p->vfork_done = NULL; 1008 spin_lock_init(&p->alloc_lock); 1009 1010 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1011 init_sigpending(&p->pending); 1012 1013 p->utime = cputime_zero; 1014 p->stime = cputime_zero; 1015 p->gtime = cputime_zero; 1016 p->utimescaled = cputime_zero; 1017 p->stimescaled = cputime_zero; 1018 p->prev_utime = cputime_zero; 1019 p->prev_stime = cputime_zero; 1020 1021 #ifdef CONFIG_DETECT_SOFTLOCKUP 1022 p->last_switch_count = 0; 1023 p->last_switch_timestamp = 0; 1024 #endif 1025 1026 task_io_accounting_init(&p->ioac); 1027 acct_clear_integrals(p); 1028 1029 posix_cpu_timers_init(p); 1030 1031 p->lock_depth = -1; /* -1 = no lock */ 1032 do_posix_clock_monotonic_gettime(&p->start_time); 1033 p->real_start_time = p->start_time; 1034 monotonic_to_bootbased(&p->real_start_time); 1035 #ifdef CONFIG_SECURITY 1036 p->security = NULL; 1037 #endif 1038 p->cap_bset = current->cap_bset; 1039 p->io_context = NULL; 1040 p->audit_context = NULL; 1041 cgroup_fork(p); 1042 #ifdef CONFIG_NUMA 1043 p->mempolicy = mpol_dup(p->mempolicy); 1044 if (IS_ERR(p->mempolicy)) { 1045 retval = PTR_ERR(p->mempolicy); 1046 p->mempolicy = NULL; 1047 goto bad_fork_cleanup_cgroup; 1048 } 1049 mpol_fix_fork_child_flag(p); 1050 #endif 1051 #ifdef CONFIG_TRACE_IRQFLAGS 1052 p->irq_events = 0; 1053 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1054 p->hardirqs_enabled = 1; 1055 #else 1056 p->hardirqs_enabled = 0; 1057 #endif 1058 p->hardirq_enable_ip = 0; 1059 p->hardirq_enable_event = 0; 1060 p->hardirq_disable_ip = _THIS_IP_; 1061 p->hardirq_disable_event = 0; 1062 p->softirqs_enabled = 1; 1063 p->softirq_enable_ip = _THIS_IP_; 1064 p->softirq_enable_event = 0; 1065 p->softirq_disable_ip = 0; 1066 p->softirq_disable_event = 0; 1067 p->hardirq_context = 0; 1068 p->softirq_context = 0; 1069 #endif 1070 #ifdef CONFIG_LOCKDEP 1071 p->lockdep_depth = 0; /* no locks held yet */ 1072 p->curr_chain_key = 0; 1073 p->lockdep_recursion = 0; 1074 #endif 1075 1076 #ifdef CONFIG_DEBUG_MUTEXES 1077 p->blocked_on = NULL; /* not blocked yet */ 1078 #endif 1079 1080 /* Perform scheduler related setup. Assign this task to a CPU. */ 1081 sched_fork(p, clone_flags); 1082 1083 if ((retval = security_task_alloc(p))) 1084 goto bad_fork_cleanup_policy; 1085 if ((retval = audit_alloc(p))) 1086 goto bad_fork_cleanup_security; 1087 /* copy all the process information */ 1088 if ((retval = copy_semundo(clone_flags, p))) 1089 goto bad_fork_cleanup_audit; 1090 if ((retval = copy_files(clone_flags, p))) 1091 goto bad_fork_cleanup_semundo; 1092 if ((retval = copy_fs(clone_flags, p))) 1093 goto bad_fork_cleanup_files; 1094 if ((retval = copy_sighand(clone_flags, p))) 1095 goto bad_fork_cleanup_fs; 1096 if ((retval = copy_signal(clone_flags, p))) 1097 goto bad_fork_cleanup_sighand; 1098 if ((retval = copy_mm(clone_flags, p))) 1099 goto bad_fork_cleanup_signal; 1100 if ((retval = copy_keys(clone_flags, p))) 1101 goto bad_fork_cleanup_mm; 1102 if ((retval = copy_namespaces(clone_flags, p))) 1103 goto bad_fork_cleanup_keys; 1104 if ((retval = copy_io(clone_flags, p))) 1105 goto bad_fork_cleanup_namespaces; 1106 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1107 if (retval) 1108 goto bad_fork_cleanup_io; 1109 1110 if (pid != &init_struct_pid) { 1111 retval = -ENOMEM; 1112 pid = alloc_pid(task_active_pid_ns(p)); 1113 if (!pid) 1114 goto bad_fork_cleanup_io; 1115 1116 if (clone_flags & CLONE_NEWPID) { 1117 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1118 if (retval < 0) 1119 goto bad_fork_free_pid; 1120 } 1121 } 1122 1123 p->pid = pid_nr(pid); 1124 p->tgid = p->pid; 1125 if (clone_flags & CLONE_THREAD) 1126 p->tgid = current->tgid; 1127 1128 if (current->nsproxy != p->nsproxy) { 1129 retval = ns_cgroup_clone(p, pid); 1130 if (retval) 1131 goto bad_fork_free_pid; 1132 } 1133 1134 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1135 /* 1136 * Clear TID on mm_release()? 1137 */ 1138 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1139 #ifdef CONFIG_FUTEX 1140 p->robust_list = NULL; 1141 #ifdef CONFIG_COMPAT 1142 p->compat_robust_list = NULL; 1143 #endif 1144 INIT_LIST_HEAD(&p->pi_state_list); 1145 p->pi_state_cache = NULL; 1146 #endif 1147 /* 1148 * sigaltstack should be cleared when sharing the same VM 1149 */ 1150 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1151 p->sas_ss_sp = p->sas_ss_size = 0; 1152 1153 /* 1154 * Syscall tracing should be turned off in the child regardless 1155 * of CLONE_PTRACE. 1156 */ 1157 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1158 #ifdef TIF_SYSCALL_EMU 1159 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1160 #endif 1161 clear_all_latency_tracing(p); 1162 1163 /* Our parent execution domain becomes current domain 1164 These must match for thread signalling to apply */ 1165 p->parent_exec_id = p->self_exec_id; 1166 1167 /* ok, now we should be set up.. */ 1168 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1169 p->pdeath_signal = 0; 1170 p->exit_state = 0; 1171 1172 /* 1173 * Ok, make it visible to the rest of the system. 1174 * We dont wake it up yet. 1175 */ 1176 p->group_leader = p; 1177 INIT_LIST_HEAD(&p->thread_group); 1178 1179 /* Now that the task is set up, run cgroup callbacks if 1180 * necessary. We need to run them before the task is visible 1181 * on the tasklist. */ 1182 cgroup_fork_callbacks(p); 1183 cgroup_callbacks_done = 1; 1184 1185 /* Need tasklist lock for parent etc handling! */ 1186 write_lock_irq(&tasklist_lock); 1187 1188 /* 1189 * The task hasn't been attached yet, so its cpus_allowed mask will 1190 * not be changed, nor will its assigned CPU. 1191 * 1192 * The cpus_allowed mask of the parent may have changed after it was 1193 * copied first time - so re-copy it here, then check the child's CPU 1194 * to ensure it is on a valid CPU (and if not, just force it back to 1195 * parent's CPU). This avoids alot of nasty races. 1196 */ 1197 p->cpus_allowed = current->cpus_allowed; 1198 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1199 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1200 !cpu_online(task_cpu(p)))) 1201 set_task_cpu(p, smp_processor_id()); 1202 1203 /* CLONE_PARENT re-uses the old parent */ 1204 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1205 p->real_parent = current->real_parent; 1206 else 1207 p->real_parent = current; 1208 1209 spin_lock(¤t->sighand->siglock); 1210 1211 /* 1212 * Process group and session signals need to be delivered to just the 1213 * parent before the fork or both the parent and the child after the 1214 * fork. Restart if a signal comes in before we add the new process to 1215 * it's process group. 1216 * A fatal signal pending means that current will exit, so the new 1217 * thread can't slip out of an OOM kill (or normal SIGKILL). 1218 */ 1219 recalc_sigpending(); 1220 if (signal_pending(current)) { 1221 spin_unlock(¤t->sighand->siglock); 1222 write_unlock_irq(&tasklist_lock); 1223 retval = -ERESTARTNOINTR; 1224 goto bad_fork_free_pid; 1225 } 1226 1227 if (clone_flags & CLONE_THREAD) { 1228 p->group_leader = current->group_leader; 1229 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1230 } 1231 1232 if (likely(p->pid)) { 1233 list_add_tail(&p->sibling, &p->real_parent->children); 1234 tracehook_finish_clone(p, clone_flags, trace); 1235 1236 if (thread_group_leader(p)) { 1237 if (clone_flags & CLONE_NEWPID) 1238 p->nsproxy->pid_ns->child_reaper = p; 1239 1240 p->signal->leader_pid = pid; 1241 tty_kref_put(p->signal->tty); 1242 p->signal->tty = tty_kref_get(current->signal->tty); 1243 set_task_pgrp(p, task_pgrp_nr(current)); 1244 set_task_session(p, task_session_nr(current)); 1245 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1246 attach_pid(p, PIDTYPE_SID, task_session(current)); 1247 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1248 __get_cpu_var(process_counts)++; 1249 } 1250 attach_pid(p, PIDTYPE_PID, pid); 1251 nr_threads++; 1252 } 1253 1254 total_forks++; 1255 spin_unlock(¤t->sighand->siglock); 1256 write_unlock_irq(&tasklist_lock); 1257 proc_fork_connector(p); 1258 cgroup_post_fork(p); 1259 return p; 1260 1261 bad_fork_free_pid: 1262 if (pid != &init_struct_pid) 1263 free_pid(pid); 1264 bad_fork_cleanup_io: 1265 put_io_context(p->io_context); 1266 bad_fork_cleanup_namespaces: 1267 exit_task_namespaces(p); 1268 bad_fork_cleanup_keys: 1269 exit_keys(p); 1270 bad_fork_cleanup_mm: 1271 if (p->mm) 1272 mmput(p->mm); 1273 bad_fork_cleanup_signal: 1274 cleanup_signal(p); 1275 bad_fork_cleanup_sighand: 1276 __cleanup_sighand(p->sighand); 1277 bad_fork_cleanup_fs: 1278 exit_fs(p); /* blocking */ 1279 bad_fork_cleanup_files: 1280 exit_files(p); /* blocking */ 1281 bad_fork_cleanup_semundo: 1282 exit_sem(p); 1283 bad_fork_cleanup_audit: 1284 audit_free(p); 1285 bad_fork_cleanup_security: 1286 security_task_free(p); 1287 bad_fork_cleanup_policy: 1288 #ifdef CONFIG_NUMA 1289 mpol_put(p->mempolicy); 1290 bad_fork_cleanup_cgroup: 1291 #endif 1292 cgroup_exit(p, cgroup_callbacks_done); 1293 delayacct_tsk_free(p); 1294 if (p->binfmt) 1295 module_put(p->binfmt->module); 1296 bad_fork_cleanup_put_domain: 1297 module_put(task_thread_info(p)->exec_domain->module); 1298 bad_fork_cleanup_count: 1299 put_group_info(p->group_info); 1300 atomic_dec(&p->user->processes); 1301 free_uid(p->user); 1302 bad_fork_free: 1303 free_task(p); 1304 fork_out: 1305 return ERR_PTR(retval); 1306 } 1307 1308 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1309 { 1310 memset(regs, 0, sizeof(struct pt_regs)); 1311 return regs; 1312 } 1313 1314 struct task_struct * __cpuinit fork_idle(int cpu) 1315 { 1316 struct task_struct *task; 1317 struct pt_regs regs; 1318 1319 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1320 &init_struct_pid, 0); 1321 if (!IS_ERR(task)) 1322 init_idle(task, cpu); 1323 1324 return task; 1325 } 1326 1327 /* 1328 * Ok, this is the main fork-routine. 1329 * 1330 * It copies the process, and if successful kick-starts 1331 * it and waits for it to finish using the VM if required. 1332 */ 1333 long do_fork(unsigned long clone_flags, 1334 unsigned long stack_start, 1335 struct pt_regs *regs, 1336 unsigned long stack_size, 1337 int __user *parent_tidptr, 1338 int __user *child_tidptr) 1339 { 1340 struct task_struct *p; 1341 int trace = 0; 1342 long nr; 1343 1344 /* 1345 * We hope to recycle these flags after 2.6.26 1346 */ 1347 if (unlikely(clone_flags & CLONE_STOPPED)) { 1348 static int __read_mostly count = 100; 1349 1350 if (count > 0 && printk_ratelimit()) { 1351 char comm[TASK_COMM_LEN]; 1352 1353 count--; 1354 printk(KERN_INFO "fork(): process `%s' used deprecated " 1355 "clone flags 0x%lx\n", 1356 get_task_comm(comm, current), 1357 clone_flags & CLONE_STOPPED); 1358 } 1359 } 1360 1361 /* 1362 * When called from kernel_thread, don't do user tracing stuff. 1363 */ 1364 if (likely(user_mode(regs))) 1365 trace = tracehook_prepare_clone(clone_flags); 1366 1367 p = copy_process(clone_flags, stack_start, regs, stack_size, 1368 child_tidptr, NULL, trace); 1369 /* 1370 * Do this prior waking up the new thread - the thread pointer 1371 * might get invalid after that point, if the thread exits quickly. 1372 */ 1373 if (!IS_ERR(p)) { 1374 struct completion vfork; 1375 1376 trace_sched_process_fork(current, p); 1377 1378 nr = task_pid_vnr(p); 1379 1380 if (clone_flags & CLONE_PARENT_SETTID) 1381 put_user(nr, parent_tidptr); 1382 1383 if (clone_flags & CLONE_VFORK) { 1384 p->vfork_done = &vfork; 1385 init_completion(&vfork); 1386 } 1387 1388 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1389 1390 /* 1391 * We set PF_STARTING at creation in case tracing wants to 1392 * use this to distinguish a fully live task from one that 1393 * hasn't gotten to tracehook_report_clone() yet. Now we 1394 * clear it and set the child going. 1395 */ 1396 p->flags &= ~PF_STARTING; 1397 1398 if (unlikely(clone_flags & CLONE_STOPPED)) { 1399 /* 1400 * We'll start up with an immediate SIGSTOP. 1401 */ 1402 sigaddset(&p->pending.signal, SIGSTOP); 1403 set_tsk_thread_flag(p, TIF_SIGPENDING); 1404 __set_task_state(p, TASK_STOPPED); 1405 } else { 1406 wake_up_new_task(p, clone_flags); 1407 } 1408 1409 tracehook_report_clone_complete(trace, regs, 1410 clone_flags, nr, p); 1411 1412 if (clone_flags & CLONE_VFORK) { 1413 freezer_do_not_count(); 1414 wait_for_completion(&vfork); 1415 freezer_count(); 1416 tracehook_report_vfork_done(p, nr); 1417 } 1418 } else { 1419 nr = PTR_ERR(p); 1420 } 1421 return nr; 1422 } 1423 1424 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1425 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1426 #endif 1427 1428 static void sighand_ctor(void *data) 1429 { 1430 struct sighand_struct *sighand = data; 1431 1432 spin_lock_init(&sighand->siglock); 1433 init_waitqueue_head(&sighand->signalfd_wqh); 1434 } 1435 1436 void __init proc_caches_init(void) 1437 { 1438 sighand_cachep = kmem_cache_create("sighand_cache", 1439 sizeof(struct sighand_struct), 0, 1440 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1441 sighand_ctor); 1442 signal_cachep = kmem_cache_create("signal_cache", 1443 sizeof(struct signal_struct), 0, 1444 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1445 files_cachep = kmem_cache_create("files_cache", 1446 sizeof(struct files_struct), 0, 1447 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1448 fs_cachep = kmem_cache_create("fs_cache", 1449 sizeof(struct fs_struct), 0, 1450 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1451 vm_area_cachep = kmem_cache_create("vm_area_struct", 1452 sizeof(struct vm_area_struct), 0, 1453 SLAB_PANIC, NULL); 1454 mm_cachep = kmem_cache_create("mm_struct", 1455 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1456 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1457 } 1458 1459 /* 1460 * Check constraints on flags passed to the unshare system call and 1461 * force unsharing of additional process context as appropriate. 1462 */ 1463 static void check_unshare_flags(unsigned long *flags_ptr) 1464 { 1465 /* 1466 * If unsharing a thread from a thread group, must also 1467 * unshare vm. 1468 */ 1469 if (*flags_ptr & CLONE_THREAD) 1470 *flags_ptr |= CLONE_VM; 1471 1472 /* 1473 * If unsharing vm, must also unshare signal handlers. 1474 */ 1475 if (*flags_ptr & CLONE_VM) 1476 *flags_ptr |= CLONE_SIGHAND; 1477 1478 /* 1479 * If unsharing signal handlers and the task was created 1480 * using CLONE_THREAD, then must unshare the thread 1481 */ 1482 if ((*flags_ptr & CLONE_SIGHAND) && 1483 (atomic_read(¤t->signal->count) > 1)) 1484 *flags_ptr |= CLONE_THREAD; 1485 1486 /* 1487 * If unsharing namespace, must also unshare filesystem information. 1488 */ 1489 if (*flags_ptr & CLONE_NEWNS) 1490 *flags_ptr |= CLONE_FS; 1491 } 1492 1493 /* 1494 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1495 */ 1496 static int unshare_thread(unsigned long unshare_flags) 1497 { 1498 if (unshare_flags & CLONE_THREAD) 1499 return -EINVAL; 1500 1501 return 0; 1502 } 1503 1504 /* 1505 * Unshare the filesystem structure if it is being shared 1506 */ 1507 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1508 { 1509 struct fs_struct *fs = current->fs; 1510 1511 if ((unshare_flags & CLONE_FS) && 1512 (fs && atomic_read(&fs->count) > 1)) { 1513 *new_fsp = __copy_fs_struct(current->fs); 1514 if (!*new_fsp) 1515 return -ENOMEM; 1516 } 1517 1518 return 0; 1519 } 1520 1521 /* 1522 * Unsharing of sighand is not supported yet 1523 */ 1524 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1525 { 1526 struct sighand_struct *sigh = current->sighand; 1527 1528 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1529 return -EINVAL; 1530 else 1531 return 0; 1532 } 1533 1534 /* 1535 * Unshare vm if it is being shared 1536 */ 1537 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1538 { 1539 struct mm_struct *mm = current->mm; 1540 1541 if ((unshare_flags & CLONE_VM) && 1542 (mm && atomic_read(&mm->mm_users) > 1)) { 1543 return -EINVAL; 1544 } 1545 1546 return 0; 1547 } 1548 1549 /* 1550 * Unshare file descriptor table if it is being shared 1551 */ 1552 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1553 { 1554 struct files_struct *fd = current->files; 1555 int error = 0; 1556 1557 if ((unshare_flags & CLONE_FILES) && 1558 (fd && atomic_read(&fd->count) > 1)) { 1559 *new_fdp = dup_fd(fd, &error); 1560 if (!*new_fdp) 1561 return error; 1562 } 1563 1564 return 0; 1565 } 1566 1567 /* 1568 * unshare allows a process to 'unshare' part of the process 1569 * context which was originally shared using clone. copy_* 1570 * functions used by do_fork() cannot be used here directly 1571 * because they modify an inactive task_struct that is being 1572 * constructed. Here we are modifying the current, active, 1573 * task_struct. 1574 */ 1575 asmlinkage long sys_unshare(unsigned long unshare_flags) 1576 { 1577 int err = 0; 1578 struct fs_struct *fs, *new_fs = NULL; 1579 struct sighand_struct *new_sigh = NULL; 1580 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1581 struct files_struct *fd, *new_fd = NULL; 1582 struct nsproxy *new_nsproxy = NULL; 1583 int do_sysvsem = 0; 1584 1585 check_unshare_flags(&unshare_flags); 1586 1587 /* Return -EINVAL for all unsupported flags */ 1588 err = -EINVAL; 1589 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1590 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1591 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1592 CLONE_NEWNET)) 1593 goto bad_unshare_out; 1594 1595 /* 1596 * CLONE_NEWIPC must also detach from the undolist: after switching 1597 * to a new ipc namespace, the semaphore arrays from the old 1598 * namespace are unreachable. 1599 */ 1600 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1601 do_sysvsem = 1; 1602 if ((err = unshare_thread(unshare_flags))) 1603 goto bad_unshare_out; 1604 if ((err = unshare_fs(unshare_flags, &new_fs))) 1605 goto bad_unshare_cleanup_thread; 1606 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1607 goto bad_unshare_cleanup_fs; 1608 if ((err = unshare_vm(unshare_flags, &new_mm))) 1609 goto bad_unshare_cleanup_sigh; 1610 if ((err = unshare_fd(unshare_flags, &new_fd))) 1611 goto bad_unshare_cleanup_vm; 1612 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1613 new_fs))) 1614 goto bad_unshare_cleanup_fd; 1615 1616 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1617 if (do_sysvsem) { 1618 /* 1619 * CLONE_SYSVSEM is equivalent to sys_exit(). 1620 */ 1621 exit_sem(current); 1622 } 1623 1624 if (new_nsproxy) { 1625 switch_task_namespaces(current, new_nsproxy); 1626 new_nsproxy = NULL; 1627 } 1628 1629 task_lock(current); 1630 1631 if (new_fs) { 1632 fs = current->fs; 1633 current->fs = new_fs; 1634 new_fs = fs; 1635 } 1636 1637 if (new_mm) { 1638 mm = current->mm; 1639 active_mm = current->active_mm; 1640 current->mm = new_mm; 1641 current->active_mm = new_mm; 1642 activate_mm(active_mm, new_mm); 1643 new_mm = mm; 1644 } 1645 1646 if (new_fd) { 1647 fd = current->files; 1648 current->files = new_fd; 1649 new_fd = fd; 1650 } 1651 1652 task_unlock(current); 1653 } 1654 1655 if (new_nsproxy) 1656 put_nsproxy(new_nsproxy); 1657 1658 bad_unshare_cleanup_fd: 1659 if (new_fd) 1660 put_files_struct(new_fd); 1661 1662 bad_unshare_cleanup_vm: 1663 if (new_mm) 1664 mmput(new_mm); 1665 1666 bad_unshare_cleanup_sigh: 1667 if (new_sigh) 1668 if (atomic_dec_and_test(&new_sigh->count)) 1669 kmem_cache_free(sighand_cachep, new_sigh); 1670 1671 bad_unshare_cleanup_fs: 1672 if (new_fs) 1673 put_fs_struct(new_fs); 1674 1675 bad_unshare_cleanup_thread: 1676 bad_unshare_out: 1677 return err; 1678 } 1679 1680 /* 1681 * Helper to unshare the files of the current task. 1682 * We don't want to expose copy_files internals to 1683 * the exec layer of the kernel. 1684 */ 1685 1686 int unshare_files(struct files_struct **displaced) 1687 { 1688 struct task_struct *task = current; 1689 struct files_struct *copy = NULL; 1690 int error; 1691 1692 error = unshare_fd(CLONE_FILES, ©); 1693 if (error || !copy) { 1694 *displaced = NULL; 1695 return error; 1696 } 1697 *displaced = task->files; 1698 task_lock(task); 1699 task->files = copy; 1700 task_unlock(task); 1701 return 0; 1702 } 1703