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/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/task_io_accounting_ops.h> 43 #include <linux/rcupdate.h> 44 #include <linux/ptrace.h> 45 #include <linux/mount.h> 46 #include <linux/audit.h> 47 #include <linux/memcontrol.h> 48 #include <linux/profile.h> 49 #include <linux/rmap.h> 50 #include <linux/acct.h> 51 #include <linux/tsacct_kern.h> 52 #include <linux/cn_proc.h> 53 #include <linux/freezer.h> 54 #include <linux/delayacct.h> 55 #include <linux/taskstats_kern.h> 56 #include <linux/random.h> 57 #include <linux/tty.h> 58 #include <linux/proc_fs.h> 59 #include <linux/blkdev.h> 60 61 #include <asm/pgtable.h> 62 #include <asm/pgalloc.h> 63 #include <asm/uaccess.h> 64 #include <asm/mmu_context.h> 65 #include <asm/cacheflush.h> 66 #include <asm/tlbflush.h> 67 68 /* 69 * Protected counters by write_lock_irq(&tasklist_lock) 70 */ 71 unsigned long total_forks; /* Handle normal Linux uptimes. */ 72 int nr_threads; /* The idle threads do not count.. */ 73 74 int max_threads; /* tunable limit on nr_threads */ 75 76 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 77 78 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 79 80 int nr_processes(void) 81 { 82 int cpu; 83 int total = 0; 84 85 for_each_online_cpu(cpu) 86 total += per_cpu(process_counts, cpu); 87 88 return total; 89 } 90 91 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 92 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 93 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 94 static struct kmem_cache *task_struct_cachep; 95 #endif 96 97 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 98 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 99 { 100 #ifdef CONFIG_DEBUG_STACK_USAGE 101 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 102 #else 103 gfp_t mask = GFP_KERNEL; 104 #endif 105 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 106 } 107 108 static inline void free_thread_info(struct thread_info *ti) 109 { 110 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 111 } 112 #endif 113 114 /* SLAB cache for signal_struct structures (tsk->signal) */ 115 static struct kmem_cache *signal_cachep; 116 117 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 118 struct kmem_cache *sighand_cachep; 119 120 /* SLAB cache for files_struct structures (tsk->files) */ 121 struct kmem_cache *files_cachep; 122 123 /* SLAB cache for fs_struct structures (tsk->fs) */ 124 struct kmem_cache *fs_cachep; 125 126 /* SLAB cache for vm_area_struct structures */ 127 struct kmem_cache *vm_area_cachep; 128 129 /* SLAB cache for mm_struct structures (tsk->mm) */ 130 static struct kmem_cache *mm_cachep; 131 132 void free_task(struct task_struct *tsk) 133 { 134 prop_local_destroy_single(&tsk->dirties); 135 free_thread_info(tsk->stack); 136 rt_mutex_debug_task_free(tsk); 137 free_task_struct(tsk); 138 } 139 EXPORT_SYMBOL(free_task); 140 141 void __put_task_struct(struct task_struct *tsk) 142 { 143 WARN_ON(!tsk->exit_state); 144 WARN_ON(atomic_read(&tsk->usage)); 145 WARN_ON(tsk == current); 146 147 security_task_free(tsk); 148 free_uid(tsk->user); 149 put_group_info(tsk->group_info); 150 delayacct_tsk_free(tsk); 151 152 if (!profile_handoff_task(tsk)) 153 free_task(tsk); 154 } 155 156 /* 157 * macro override instead of weak attribute alias, to workaround 158 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 159 */ 160 #ifndef arch_task_cache_init 161 #define arch_task_cache_init() 162 #endif 163 164 void __init fork_init(unsigned long mempages) 165 { 166 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 167 #ifndef ARCH_MIN_TASKALIGN 168 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 169 #endif 170 /* create a slab on which task_structs can be allocated */ 171 task_struct_cachep = 172 kmem_cache_create("task_struct", sizeof(struct task_struct), 173 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 174 #endif 175 176 /* do the arch specific task caches init */ 177 arch_task_cache_init(); 178 179 /* 180 * The default maximum number of threads is set to a safe 181 * value: the thread structures can take up at most half 182 * of memory. 183 */ 184 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 185 186 /* 187 * we need to allow at least 20 threads to boot a system 188 */ 189 if(max_threads < 20) 190 max_threads = 20; 191 192 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 193 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 194 init_task.signal->rlim[RLIMIT_SIGPENDING] = 195 init_task.signal->rlim[RLIMIT_NPROC]; 196 } 197 198 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 199 struct task_struct *src) 200 { 201 *dst = *src; 202 return 0; 203 } 204 205 static struct task_struct *dup_task_struct(struct task_struct *orig) 206 { 207 struct task_struct *tsk; 208 struct thread_info *ti; 209 int err; 210 211 prepare_to_copy(orig); 212 213 tsk = alloc_task_struct(); 214 if (!tsk) 215 return NULL; 216 217 ti = alloc_thread_info(tsk); 218 if (!ti) { 219 free_task_struct(tsk); 220 return NULL; 221 } 222 223 err = arch_dup_task_struct(tsk, orig); 224 if (err) 225 goto out; 226 227 tsk->stack = ti; 228 229 err = prop_local_init_single(&tsk->dirties); 230 if (err) 231 goto out; 232 233 setup_thread_stack(tsk, orig); 234 235 #ifdef CONFIG_CC_STACKPROTECTOR 236 tsk->stack_canary = get_random_int(); 237 #endif 238 239 /* One for us, one for whoever does the "release_task()" (usually parent) */ 240 atomic_set(&tsk->usage,2); 241 atomic_set(&tsk->fs_excl, 0); 242 #ifdef CONFIG_BLK_DEV_IO_TRACE 243 tsk->btrace_seq = 0; 244 #endif 245 tsk->splice_pipe = NULL; 246 return tsk; 247 248 out: 249 free_thread_info(ti); 250 free_task_struct(tsk); 251 return NULL; 252 } 253 254 #ifdef CONFIG_MMU 255 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 256 { 257 struct vm_area_struct *mpnt, *tmp, **pprev; 258 struct rb_node **rb_link, *rb_parent; 259 int retval; 260 unsigned long charge; 261 struct mempolicy *pol; 262 263 down_write(&oldmm->mmap_sem); 264 flush_cache_dup_mm(oldmm); 265 /* 266 * Not linked in yet - no deadlock potential: 267 */ 268 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 269 270 mm->locked_vm = 0; 271 mm->mmap = NULL; 272 mm->mmap_cache = NULL; 273 mm->free_area_cache = oldmm->mmap_base; 274 mm->cached_hole_size = ~0UL; 275 mm->map_count = 0; 276 cpus_clear(mm->cpu_vm_mask); 277 mm->mm_rb = RB_ROOT; 278 rb_link = &mm->mm_rb.rb_node; 279 rb_parent = NULL; 280 pprev = &mm->mmap; 281 282 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 283 struct file *file; 284 285 if (mpnt->vm_flags & VM_DONTCOPY) { 286 long pages = vma_pages(mpnt); 287 mm->total_vm -= pages; 288 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 289 -pages); 290 continue; 291 } 292 charge = 0; 293 if (mpnt->vm_flags & VM_ACCOUNT) { 294 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 295 if (security_vm_enough_memory(len)) 296 goto fail_nomem; 297 charge = len; 298 } 299 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 300 if (!tmp) 301 goto fail_nomem; 302 *tmp = *mpnt; 303 pol = mpol_dup(vma_policy(mpnt)); 304 retval = PTR_ERR(pol); 305 if (IS_ERR(pol)) 306 goto fail_nomem_policy; 307 vma_set_policy(tmp, pol); 308 tmp->vm_flags &= ~VM_LOCKED; 309 tmp->vm_mm = mm; 310 tmp->vm_next = NULL; 311 anon_vma_link(tmp); 312 file = tmp->vm_file; 313 if (file) { 314 struct inode *inode = file->f_path.dentry->d_inode; 315 get_file(file); 316 if (tmp->vm_flags & VM_DENYWRITE) 317 atomic_dec(&inode->i_writecount); 318 319 /* insert tmp into the share list, just after mpnt */ 320 spin_lock(&file->f_mapping->i_mmap_lock); 321 tmp->vm_truncate_count = mpnt->vm_truncate_count; 322 flush_dcache_mmap_lock(file->f_mapping); 323 vma_prio_tree_add(tmp, mpnt); 324 flush_dcache_mmap_unlock(file->f_mapping); 325 spin_unlock(&file->f_mapping->i_mmap_lock); 326 } 327 328 /* 329 * Clear hugetlb-related page reserves for children. This only 330 * affects MAP_PRIVATE mappings. Faults generated by the child 331 * are not guaranteed to succeed, even if read-only 332 */ 333 if (is_vm_hugetlb_page(tmp)) 334 reset_vma_resv_huge_pages(tmp); 335 336 /* 337 * Link in the new vma and copy the page table entries. 338 */ 339 *pprev = tmp; 340 pprev = &tmp->vm_next; 341 342 __vma_link_rb(mm, tmp, rb_link, rb_parent); 343 rb_link = &tmp->vm_rb.rb_right; 344 rb_parent = &tmp->vm_rb; 345 346 mm->map_count++; 347 retval = copy_page_range(mm, oldmm, mpnt); 348 349 if (tmp->vm_ops && tmp->vm_ops->open) 350 tmp->vm_ops->open(tmp); 351 352 if (retval) 353 goto out; 354 } 355 /* a new mm has just been created */ 356 arch_dup_mmap(oldmm, mm); 357 retval = 0; 358 out: 359 up_write(&mm->mmap_sem); 360 flush_tlb_mm(oldmm); 361 up_write(&oldmm->mmap_sem); 362 return retval; 363 fail_nomem_policy: 364 kmem_cache_free(vm_area_cachep, tmp); 365 fail_nomem: 366 retval = -ENOMEM; 367 vm_unacct_memory(charge); 368 goto out; 369 } 370 371 static inline int mm_alloc_pgd(struct mm_struct * mm) 372 { 373 mm->pgd = pgd_alloc(mm); 374 if (unlikely(!mm->pgd)) 375 return -ENOMEM; 376 return 0; 377 } 378 379 static inline void mm_free_pgd(struct mm_struct * mm) 380 { 381 pgd_free(mm, mm->pgd); 382 } 383 #else 384 #define dup_mmap(mm, oldmm) (0) 385 #define mm_alloc_pgd(mm) (0) 386 #define mm_free_pgd(mm) 387 #endif /* CONFIG_MMU */ 388 389 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 390 391 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 392 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 393 394 #include <linux/init_task.h> 395 396 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 397 { 398 atomic_set(&mm->mm_users, 1); 399 atomic_set(&mm->mm_count, 1); 400 init_rwsem(&mm->mmap_sem); 401 INIT_LIST_HEAD(&mm->mmlist); 402 mm->flags = (current->mm) ? current->mm->flags 403 : MMF_DUMP_FILTER_DEFAULT; 404 mm->core_state = NULL; 405 mm->nr_ptes = 0; 406 set_mm_counter(mm, file_rss, 0); 407 set_mm_counter(mm, anon_rss, 0); 408 spin_lock_init(&mm->page_table_lock); 409 rwlock_init(&mm->ioctx_list_lock); 410 mm->ioctx_list = NULL; 411 mm->free_area_cache = TASK_UNMAPPED_BASE; 412 mm->cached_hole_size = ~0UL; 413 mm_init_owner(mm, p); 414 415 if (likely(!mm_alloc_pgd(mm))) { 416 mm->def_flags = 0; 417 return mm; 418 } 419 420 free_mm(mm); 421 return NULL; 422 } 423 424 /* 425 * Allocate and initialize an mm_struct. 426 */ 427 struct mm_struct * mm_alloc(void) 428 { 429 struct mm_struct * mm; 430 431 mm = allocate_mm(); 432 if (mm) { 433 memset(mm, 0, sizeof(*mm)); 434 mm = mm_init(mm, current); 435 } 436 return mm; 437 } 438 439 /* 440 * Called when the last reference to the mm 441 * is dropped: either by a lazy thread or by 442 * mmput. Free the page directory and the mm. 443 */ 444 void __mmdrop(struct mm_struct *mm) 445 { 446 BUG_ON(mm == &init_mm); 447 mm_free_pgd(mm); 448 destroy_context(mm); 449 free_mm(mm); 450 } 451 EXPORT_SYMBOL_GPL(__mmdrop); 452 453 /* 454 * Decrement the use count and release all resources for an mm. 455 */ 456 void mmput(struct mm_struct *mm) 457 { 458 might_sleep(); 459 460 if (atomic_dec_and_test(&mm->mm_users)) { 461 exit_aio(mm); 462 exit_mmap(mm); 463 set_mm_exe_file(mm, NULL); 464 if (!list_empty(&mm->mmlist)) { 465 spin_lock(&mmlist_lock); 466 list_del(&mm->mmlist); 467 spin_unlock(&mmlist_lock); 468 } 469 put_swap_token(mm); 470 mmdrop(mm); 471 } 472 } 473 EXPORT_SYMBOL_GPL(mmput); 474 475 /** 476 * get_task_mm - acquire a reference to the task's mm 477 * 478 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 479 * this kernel workthread has transiently adopted a user mm with use_mm, 480 * to do its AIO) is not set and if so returns a reference to it, after 481 * bumping up the use count. User must release the mm via mmput() 482 * after use. Typically used by /proc and ptrace. 483 */ 484 struct mm_struct *get_task_mm(struct task_struct *task) 485 { 486 struct mm_struct *mm; 487 488 task_lock(task); 489 mm = task->mm; 490 if (mm) { 491 if (task->flags & PF_KTHREAD) 492 mm = NULL; 493 else 494 atomic_inc(&mm->mm_users); 495 } 496 task_unlock(task); 497 return mm; 498 } 499 EXPORT_SYMBOL_GPL(get_task_mm); 500 501 /* Please note the differences between mmput and mm_release. 502 * mmput is called whenever we stop holding onto a mm_struct, 503 * error success whatever. 504 * 505 * mm_release is called after a mm_struct has been removed 506 * from the current process. 507 * 508 * This difference is important for error handling, when we 509 * only half set up a mm_struct for a new process and need to restore 510 * the old one. Because we mmput the new mm_struct before 511 * restoring the old one. . . 512 * Eric Biederman 10 January 1998 513 */ 514 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 515 { 516 struct completion *vfork_done = tsk->vfork_done; 517 518 /* Get rid of any cached register state */ 519 deactivate_mm(tsk, mm); 520 521 /* notify parent sleeping on vfork() */ 522 if (vfork_done) { 523 tsk->vfork_done = NULL; 524 complete(vfork_done); 525 } 526 527 /* 528 * If we're exiting normally, clear a user-space tid field if 529 * requested. We leave this alone when dying by signal, to leave 530 * the value intact in a core dump, and to save the unnecessary 531 * trouble otherwise. Userland only wants this done for a sys_exit. 532 */ 533 if (tsk->clear_child_tid 534 && !(tsk->flags & PF_SIGNALED) 535 && atomic_read(&mm->mm_users) > 1) { 536 u32 __user * tidptr = tsk->clear_child_tid; 537 tsk->clear_child_tid = NULL; 538 539 /* 540 * We don't check the error code - if userspace has 541 * not set up a proper pointer then tough luck. 542 */ 543 put_user(0, tidptr); 544 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 545 } 546 } 547 548 /* 549 * Allocate a new mm structure and copy contents from the 550 * mm structure of the passed in task structure. 551 */ 552 struct mm_struct *dup_mm(struct task_struct *tsk) 553 { 554 struct mm_struct *mm, *oldmm = current->mm; 555 int err; 556 557 if (!oldmm) 558 return NULL; 559 560 mm = allocate_mm(); 561 if (!mm) 562 goto fail_nomem; 563 564 memcpy(mm, oldmm, sizeof(*mm)); 565 566 /* Initializing for Swap token stuff */ 567 mm->token_priority = 0; 568 mm->last_interval = 0; 569 570 if (!mm_init(mm, tsk)) 571 goto fail_nomem; 572 573 if (init_new_context(tsk, mm)) 574 goto fail_nocontext; 575 576 dup_mm_exe_file(oldmm, mm); 577 578 err = dup_mmap(mm, oldmm); 579 if (err) 580 goto free_pt; 581 582 mm->hiwater_rss = get_mm_rss(mm); 583 mm->hiwater_vm = mm->total_vm; 584 585 return mm; 586 587 free_pt: 588 mmput(mm); 589 590 fail_nomem: 591 return NULL; 592 593 fail_nocontext: 594 /* 595 * If init_new_context() failed, we cannot use mmput() to free the mm 596 * because it calls destroy_context() 597 */ 598 mm_free_pgd(mm); 599 free_mm(mm); 600 return NULL; 601 } 602 603 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 604 { 605 struct mm_struct * mm, *oldmm; 606 int retval; 607 608 tsk->min_flt = tsk->maj_flt = 0; 609 tsk->nvcsw = tsk->nivcsw = 0; 610 611 tsk->mm = NULL; 612 tsk->active_mm = NULL; 613 614 /* 615 * Are we cloning a kernel thread? 616 * 617 * We need to steal a active VM for that.. 618 */ 619 oldmm = current->mm; 620 if (!oldmm) 621 return 0; 622 623 if (clone_flags & CLONE_VM) { 624 atomic_inc(&oldmm->mm_users); 625 mm = oldmm; 626 goto good_mm; 627 } 628 629 retval = -ENOMEM; 630 mm = dup_mm(tsk); 631 if (!mm) 632 goto fail_nomem; 633 634 good_mm: 635 /* Initializing for Swap token stuff */ 636 mm->token_priority = 0; 637 mm->last_interval = 0; 638 639 tsk->mm = mm; 640 tsk->active_mm = mm; 641 return 0; 642 643 fail_nomem: 644 return retval; 645 } 646 647 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 648 { 649 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 650 /* We don't need to lock fs - think why ;-) */ 651 if (fs) { 652 atomic_set(&fs->count, 1); 653 rwlock_init(&fs->lock); 654 fs->umask = old->umask; 655 read_lock(&old->lock); 656 fs->root = old->root; 657 path_get(&old->root); 658 fs->pwd = old->pwd; 659 path_get(&old->pwd); 660 read_unlock(&old->lock); 661 } 662 return fs; 663 } 664 665 struct fs_struct *copy_fs_struct(struct fs_struct *old) 666 { 667 return __copy_fs_struct(old); 668 } 669 670 EXPORT_SYMBOL_GPL(copy_fs_struct); 671 672 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 673 { 674 if (clone_flags & CLONE_FS) { 675 atomic_inc(¤t->fs->count); 676 return 0; 677 } 678 tsk->fs = __copy_fs_struct(current->fs); 679 if (!tsk->fs) 680 return -ENOMEM; 681 return 0; 682 } 683 684 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 685 { 686 struct files_struct *oldf, *newf; 687 int error = 0; 688 689 /* 690 * A background process may not have any files ... 691 */ 692 oldf = current->files; 693 if (!oldf) 694 goto out; 695 696 if (clone_flags & CLONE_FILES) { 697 atomic_inc(&oldf->count); 698 goto out; 699 } 700 701 newf = dup_fd(oldf, &error); 702 if (!newf) 703 goto out; 704 705 tsk->files = newf; 706 error = 0; 707 out: 708 return error; 709 } 710 711 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 712 { 713 #ifdef CONFIG_BLOCK 714 struct io_context *ioc = current->io_context; 715 716 if (!ioc) 717 return 0; 718 /* 719 * Share io context with parent, if CLONE_IO is set 720 */ 721 if (clone_flags & CLONE_IO) { 722 tsk->io_context = ioc_task_link(ioc); 723 if (unlikely(!tsk->io_context)) 724 return -ENOMEM; 725 } else if (ioprio_valid(ioc->ioprio)) { 726 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 727 if (unlikely(!tsk->io_context)) 728 return -ENOMEM; 729 730 tsk->io_context->ioprio = ioc->ioprio; 731 } 732 #endif 733 return 0; 734 } 735 736 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 737 { 738 struct sighand_struct *sig; 739 740 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 741 atomic_inc(¤t->sighand->count); 742 return 0; 743 } 744 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 745 rcu_assign_pointer(tsk->sighand, sig); 746 if (!sig) 747 return -ENOMEM; 748 atomic_set(&sig->count, 1); 749 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 750 return 0; 751 } 752 753 void __cleanup_sighand(struct sighand_struct *sighand) 754 { 755 if (atomic_dec_and_test(&sighand->count)) 756 kmem_cache_free(sighand_cachep, sighand); 757 } 758 759 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 760 { 761 struct signal_struct *sig; 762 int ret; 763 764 if (clone_flags & CLONE_THREAD) { 765 atomic_inc(¤t->signal->count); 766 atomic_inc(¤t->signal->live); 767 return 0; 768 } 769 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 770 tsk->signal = sig; 771 if (!sig) 772 return -ENOMEM; 773 774 ret = copy_thread_group_keys(tsk); 775 if (ret < 0) { 776 kmem_cache_free(signal_cachep, sig); 777 return ret; 778 } 779 780 atomic_set(&sig->count, 1); 781 atomic_set(&sig->live, 1); 782 init_waitqueue_head(&sig->wait_chldexit); 783 sig->flags = 0; 784 sig->group_exit_code = 0; 785 sig->group_exit_task = NULL; 786 sig->group_stop_count = 0; 787 sig->curr_target = tsk; 788 init_sigpending(&sig->shared_pending); 789 INIT_LIST_HEAD(&sig->posix_timers); 790 791 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 792 sig->it_real_incr.tv64 = 0; 793 sig->real_timer.function = it_real_fn; 794 795 sig->it_virt_expires = cputime_zero; 796 sig->it_virt_incr = cputime_zero; 797 sig->it_prof_expires = cputime_zero; 798 sig->it_prof_incr = cputime_zero; 799 800 sig->leader = 0; /* session leadership doesn't inherit */ 801 sig->tty_old_pgrp = NULL; 802 803 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 804 sig->gtime = cputime_zero; 805 sig->cgtime = cputime_zero; 806 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 807 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 808 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 809 task_io_accounting_init(&sig->ioac); 810 sig->sum_sched_runtime = 0; 811 INIT_LIST_HEAD(&sig->cpu_timers[0]); 812 INIT_LIST_HEAD(&sig->cpu_timers[1]); 813 INIT_LIST_HEAD(&sig->cpu_timers[2]); 814 taskstats_tgid_init(sig); 815 816 task_lock(current->group_leader); 817 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 818 task_unlock(current->group_leader); 819 820 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 821 /* 822 * New sole thread in the process gets an expiry time 823 * of the whole CPU time limit. 824 */ 825 tsk->it_prof_expires = 826 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 827 } 828 acct_init_pacct(&sig->pacct); 829 830 tty_audit_fork(sig); 831 832 return 0; 833 } 834 835 void __cleanup_signal(struct signal_struct *sig) 836 { 837 exit_thread_group_keys(sig); 838 kmem_cache_free(signal_cachep, sig); 839 } 840 841 static void cleanup_signal(struct task_struct *tsk) 842 { 843 struct signal_struct *sig = tsk->signal; 844 845 atomic_dec(&sig->live); 846 847 if (atomic_dec_and_test(&sig->count)) 848 __cleanup_signal(sig); 849 } 850 851 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 852 { 853 unsigned long new_flags = p->flags; 854 855 new_flags &= ~PF_SUPERPRIV; 856 new_flags |= PF_FORKNOEXEC; 857 new_flags |= PF_STARTING; 858 p->flags = new_flags; 859 clear_freeze_flag(p); 860 } 861 862 asmlinkage long sys_set_tid_address(int __user *tidptr) 863 { 864 current->clear_child_tid = tidptr; 865 866 return task_pid_vnr(current); 867 } 868 869 static void rt_mutex_init_task(struct task_struct *p) 870 { 871 spin_lock_init(&p->pi_lock); 872 #ifdef CONFIG_RT_MUTEXES 873 plist_head_init(&p->pi_waiters, &p->pi_lock); 874 p->pi_blocked_on = NULL; 875 #endif 876 } 877 878 #ifdef CONFIG_MM_OWNER 879 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 880 { 881 mm->owner = p; 882 } 883 #endif /* CONFIG_MM_OWNER */ 884 885 /* 886 * This creates a new process as a copy of the old one, 887 * but does not actually start it yet. 888 * 889 * It copies the registers, and all the appropriate 890 * parts of the process environment (as per the clone 891 * flags). The actual kick-off is left to the caller. 892 */ 893 static struct task_struct *copy_process(unsigned long clone_flags, 894 unsigned long stack_start, 895 struct pt_regs *regs, 896 unsigned long stack_size, 897 int __user *child_tidptr, 898 struct pid *pid, 899 int trace) 900 { 901 int retval; 902 struct task_struct *p; 903 int cgroup_callbacks_done = 0; 904 905 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 906 return ERR_PTR(-EINVAL); 907 908 /* 909 * Thread groups must share signals as well, and detached threads 910 * can only be started up within the thread group. 911 */ 912 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 913 return ERR_PTR(-EINVAL); 914 915 /* 916 * Shared signal handlers imply shared VM. By way of the above, 917 * thread groups also imply shared VM. Blocking this case allows 918 * for various simplifications in other code. 919 */ 920 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 921 return ERR_PTR(-EINVAL); 922 923 retval = security_task_create(clone_flags); 924 if (retval) 925 goto fork_out; 926 927 retval = -ENOMEM; 928 p = dup_task_struct(current); 929 if (!p) 930 goto fork_out; 931 932 rt_mutex_init_task(p); 933 934 #ifdef CONFIG_PROVE_LOCKING 935 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 936 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 937 #endif 938 retval = -EAGAIN; 939 if (atomic_read(&p->user->processes) >= 940 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 941 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 942 p->user != current->nsproxy->user_ns->root_user) 943 goto bad_fork_free; 944 } 945 946 atomic_inc(&p->user->__count); 947 atomic_inc(&p->user->processes); 948 get_group_info(p->group_info); 949 950 /* 951 * If multiple threads are within copy_process(), then this check 952 * triggers too late. This doesn't hurt, the check is only there 953 * to stop root fork bombs. 954 */ 955 if (nr_threads >= max_threads) 956 goto bad_fork_cleanup_count; 957 958 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 959 goto bad_fork_cleanup_count; 960 961 if (p->binfmt && !try_module_get(p->binfmt->module)) 962 goto bad_fork_cleanup_put_domain; 963 964 p->did_exec = 0; 965 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 966 copy_flags(clone_flags, p); 967 INIT_LIST_HEAD(&p->children); 968 INIT_LIST_HEAD(&p->sibling); 969 #ifdef CONFIG_PREEMPT_RCU 970 p->rcu_read_lock_nesting = 0; 971 p->rcu_flipctr_idx = 0; 972 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 973 p->vfork_done = NULL; 974 spin_lock_init(&p->alloc_lock); 975 976 clear_tsk_thread_flag(p, TIF_SIGPENDING); 977 init_sigpending(&p->pending); 978 979 p->utime = cputime_zero; 980 p->stime = cputime_zero; 981 p->gtime = cputime_zero; 982 p->utimescaled = cputime_zero; 983 p->stimescaled = cputime_zero; 984 p->prev_utime = cputime_zero; 985 p->prev_stime = cputime_zero; 986 987 #ifdef CONFIG_DETECT_SOFTLOCKUP 988 p->last_switch_count = 0; 989 p->last_switch_timestamp = 0; 990 #endif 991 992 task_io_accounting_init(&p->ioac); 993 acct_clear_integrals(p); 994 995 p->it_virt_expires = cputime_zero; 996 p->it_prof_expires = cputime_zero; 997 p->it_sched_expires = 0; 998 INIT_LIST_HEAD(&p->cpu_timers[0]); 999 INIT_LIST_HEAD(&p->cpu_timers[1]); 1000 INIT_LIST_HEAD(&p->cpu_timers[2]); 1001 1002 p->lock_depth = -1; /* -1 = no lock */ 1003 do_posix_clock_monotonic_gettime(&p->start_time); 1004 p->real_start_time = p->start_time; 1005 monotonic_to_bootbased(&p->real_start_time); 1006 #ifdef CONFIG_SECURITY 1007 p->security = NULL; 1008 #endif 1009 p->cap_bset = current->cap_bset; 1010 p->io_context = NULL; 1011 p->audit_context = NULL; 1012 cgroup_fork(p); 1013 #ifdef CONFIG_NUMA 1014 p->mempolicy = mpol_dup(p->mempolicy); 1015 if (IS_ERR(p->mempolicy)) { 1016 retval = PTR_ERR(p->mempolicy); 1017 p->mempolicy = NULL; 1018 goto bad_fork_cleanup_cgroup; 1019 } 1020 mpol_fix_fork_child_flag(p); 1021 #endif 1022 #ifdef CONFIG_TRACE_IRQFLAGS 1023 p->irq_events = 0; 1024 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1025 p->hardirqs_enabled = 1; 1026 #else 1027 p->hardirqs_enabled = 0; 1028 #endif 1029 p->hardirq_enable_ip = 0; 1030 p->hardirq_enable_event = 0; 1031 p->hardirq_disable_ip = _THIS_IP_; 1032 p->hardirq_disable_event = 0; 1033 p->softirqs_enabled = 1; 1034 p->softirq_enable_ip = _THIS_IP_; 1035 p->softirq_enable_event = 0; 1036 p->softirq_disable_ip = 0; 1037 p->softirq_disable_event = 0; 1038 p->hardirq_context = 0; 1039 p->softirq_context = 0; 1040 #endif 1041 #ifdef CONFIG_LOCKDEP 1042 p->lockdep_depth = 0; /* no locks held yet */ 1043 p->curr_chain_key = 0; 1044 p->lockdep_recursion = 0; 1045 #endif 1046 1047 #ifdef CONFIG_DEBUG_MUTEXES 1048 p->blocked_on = NULL; /* not blocked yet */ 1049 #endif 1050 1051 /* Perform scheduler related setup. Assign this task to a CPU. */ 1052 sched_fork(p, clone_flags); 1053 1054 if ((retval = security_task_alloc(p))) 1055 goto bad_fork_cleanup_policy; 1056 if ((retval = audit_alloc(p))) 1057 goto bad_fork_cleanup_security; 1058 /* copy all the process information */ 1059 if ((retval = copy_semundo(clone_flags, p))) 1060 goto bad_fork_cleanup_audit; 1061 if ((retval = copy_files(clone_flags, p))) 1062 goto bad_fork_cleanup_semundo; 1063 if ((retval = copy_fs(clone_flags, p))) 1064 goto bad_fork_cleanup_files; 1065 if ((retval = copy_sighand(clone_flags, p))) 1066 goto bad_fork_cleanup_fs; 1067 if ((retval = copy_signal(clone_flags, p))) 1068 goto bad_fork_cleanup_sighand; 1069 if ((retval = copy_mm(clone_flags, p))) 1070 goto bad_fork_cleanup_signal; 1071 if ((retval = copy_keys(clone_flags, p))) 1072 goto bad_fork_cleanup_mm; 1073 if ((retval = copy_namespaces(clone_flags, p))) 1074 goto bad_fork_cleanup_keys; 1075 if ((retval = copy_io(clone_flags, p))) 1076 goto bad_fork_cleanup_namespaces; 1077 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1078 if (retval) 1079 goto bad_fork_cleanup_io; 1080 1081 if (pid != &init_struct_pid) { 1082 retval = -ENOMEM; 1083 pid = alloc_pid(task_active_pid_ns(p)); 1084 if (!pid) 1085 goto bad_fork_cleanup_io; 1086 1087 if (clone_flags & CLONE_NEWPID) { 1088 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1089 if (retval < 0) 1090 goto bad_fork_free_pid; 1091 } 1092 } 1093 1094 p->pid = pid_nr(pid); 1095 p->tgid = p->pid; 1096 if (clone_flags & CLONE_THREAD) 1097 p->tgid = current->tgid; 1098 1099 if (current->nsproxy != p->nsproxy) { 1100 retval = ns_cgroup_clone(p, pid); 1101 if (retval) 1102 goto bad_fork_free_pid; 1103 } 1104 1105 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1106 /* 1107 * Clear TID on mm_release()? 1108 */ 1109 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1110 #ifdef CONFIG_FUTEX 1111 p->robust_list = NULL; 1112 #ifdef CONFIG_COMPAT 1113 p->compat_robust_list = NULL; 1114 #endif 1115 INIT_LIST_HEAD(&p->pi_state_list); 1116 p->pi_state_cache = NULL; 1117 #endif 1118 /* 1119 * sigaltstack should be cleared when sharing the same VM 1120 */ 1121 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1122 p->sas_ss_sp = p->sas_ss_size = 0; 1123 1124 /* 1125 * Syscall tracing should be turned off in the child regardless 1126 * of CLONE_PTRACE. 1127 */ 1128 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1129 #ifdef TIF_SYSCALL_EMU 1130 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1131 #endif 1132 clear_all_latency_tracing(p); 1133 1134 /* Our parent execution domain becomes current domain 1135 These must match for thread signalling to apply */ 1136 p->parent_exec_id = p->self_exec_id; 1137 1138 /* ok, now we should be set up.. */ 1139 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1140 p->pdeath_signal = 0; 1141 p->exit_state = 0; 1142 1143 /* 1144 * Ok, make it visible to the rest of the system. 1145 * We dont wake it up yet. 1146 */ 1147 p->group_leader = p; 1148 INIT_LIST_HEAD(&p->thread_group); 1149 1150 /* Now that the task is set up, run cgroup callbacks if 1151 * necessary. We need to run them before the task is visible 1152 * on the tasklist. */ 1153 cgroup_fork_callbacks(p); 1154 cgroup_callbacks_done = 1; 1155 1156 /* Need tasklist lock for parent etc handling! */ 1157 write_lock_irq(&tasklist_lock); 1158 1159 /* 1160 * The task hasn't been attached yet, so its cpus_allowed mask will 1161 * not be changed, nor will its assigned CPU. 1162 * 1163 * The cpus_allowed mask of the parent may have changed after it was 1164 * copied first time - so re-copy it here, then check the child's CPU 1165 * to ensure it is on a valid CPU (and if not, just force it back to 1166 * parent's CPU). This avoids alot of nasty races. 1167 */ 1168 p->cpus_allowed = current->cpus_allowed; 1169 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1170 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1171 !cpu_online(task_cpu(p)))) 1172 set_task_cpu(p, smp_processor_id()); 1173 1174 /* CLONE_PARENT re-uses the old parent */ 1175 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1176 p->real_parent = current->real_parent; 1177 else 1178 p->real_parent = current; 1179 1180 spin_lock(¤t->sighand->siglock); 1181 1182 /* 1183 * Process group and session signals need to be delivered to just the 1184 * parent before the fork or both the parent and the child after the 1185 * fork. Restart if a signal comes in before we add the new process to 1186 * it's process group. 1187 * A fatal signal pending means that current will exit, so the new 1188 * thread can't slip out of an OOM kill (or normal SIGKILL). 1189 */ 1190 recalc_sigpending(); 1191 if (signal_pending(current)) { 1192 spin_unlock(¤t->sighand->siglock); 1193 write_unlock_irq(&tasklist_lock); 1194 retval = -ERESTARTNOINTR; 1195 goto bad_fork_free_pid; 1196 } 1197 1198 if (clone_flags & CLONE_THREAD) { 1199 p->group_leader = current->group_leader; 1200 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1201 1202 if (!cputime_eq(current->signal->it_virt_expires, 1203 cputime_zero) || 1204 !cputime_eq(current->signal->it_prof_expires, 1205 cputime_zero) || 1206 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1207 !list_empty(¤t->signal->cpu_timers[0]) || 1208 !list_empty(¤t->signal->cpu_timers[1]) || 1209 !list_empty(¤t->signal->cpu_timers[2])) { 1210 /* 1211 * Have child wake up on its first tick to check 1212 * for process CPU timers. 1213 */ 1214 p->it_prof_expires = jiffies_to_cputime(1); 1215 } 1216 } 1217 1218 if (likely(p->pid)) { 1219 list_add_tail(&p->sibling, &p->real_parent->children); 1220 tracehook_finish_clone(p, clone_flags, trace); 1221 1222 if (thread_group_leader(p)) { 1223 if (clone_flags & CLONE_NEWPID) 1224 p->nsproxy->pid_ns->child_reaper = p; 1225 1226 p->signal->leader_pid = pid; 1227 p->signal->tty = current->signal->tty; 1228 set_task_pgrp(p, task_pgrp_nr(current)); 1229 set_task_session(p, task_session_nr(current)); 1230 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1231 attach_pid(p, PIDTYPE_SID, task_session(current)); 1232 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1233 __get_cpu_var(process_counts)++; 1234 } 1235 attach_pid(p, PIDTYPE_PID, pid); 1236 nr_threads++; 1237 } 1238 1239 total_forks++; 1240 spin_unlock(¤t->sighand->siglock); 1241 write_unlock_irq(&tasklist_lock); 1242 proc_fork_connector(p); 1243 cgroup_post_fork(p); 1244 return p; 1245 1246 bad_fork_free_pid: 1247 if (pid != &init_struct_pid) 1248 free_pid(pid); 1249 bad_fork_cleanup_io: 1250 put_io_context(p->io_context); 1251 bad_fork_cleanup_namespaces: 1252 exit_task_namespaces(p); 1253 bad_fork_cleanup_keys: 1254 exit_keys(p); 1255 bad_fork_cleanup_mm: 1256 if (p->mm) 1257 mmput(p->mm); 1258 bad_fork_cleanup_signal: 1259 cleanup_signal(p); 1260 bad_fork_cleanup_sighand: 1261 __cleanup_sighand(p->sighand); 1262 bad_fork_cleanup_fs: 1263 exit_fs(p); /* blocking */ 1264 bad_fork_cleanup_files: 1265 exit_files(p); /* blocking */ 1266 bad_fork_cleanup_semundo: 1267 exit_sem(p); 1268 bad_fork_cleanup_audit: 1269 audit_free(p); 1270 bad_fork_cleanup_security: 1271 security_task_free(p); 1272 bad_fork_cleanup_policy: 1273 #ifdef CONFIG_NUMA 1274 mpol_put(p->mempolicy); 1275 bad_fork_cleanup_cgroup: 1276 #endif 1277 cgroup_exit(p, cgroup_callbacks_done); 1278 delayacct_tsk_free(p); 1279 if (p->binfmt) 1280 module_put(p->binfmt->module); 1281 bad_fork_cleanup_put_domain: 1282 module_put(task_thread_info(p)->exec_domain->module); 1283 bad_fork_cleanup_count: 1284 put_group_info(p->group_info); 1285 atomic_dec(&p->user->processes); 1286 free_uid(p->user); 1287 bad_fork_free: 1288 free_task(p); 1289 fork_out: 1290 return ERR_PTR(retval); 1291 } 1292 1293 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1294 { 1295 memset(regs, 0, sizeof(struct pt_regs)); 1296 return regs; 1297 } 1298 1299 struct task_struct * __cpuinit fork_idle(int cpu) 1300 { 1301 struct task_struct *task; 1302 struct pt_regs regs; 1303 1304 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1305 &init_struct_pid, 0); 1306 if (!IS_ERR(task)) 1307 init_idle(task, cpu); 1308 1309 return task; 1310 } 1311 1312 /* 1313 * Ok, this is the main fork-routine. 1314 * 1315 * It copies the process, and if successful kick-starts 1316 * it and waits for it to finish using the VM if required. 1317 */ 1318 long do_fork(unsigned long clone_flags, 1319 unsigned long stack_start, 1320 struct pt_regs *regs, 1321 unsigned long stack_size, 1322 int __user *parent_tidptr, 1323 int __user *child_tidptr) 1324 { 1325 struct task_struct *p; 1326 int trace = 0; 1327 long nr; 1328 1329 /* 1330 * We hope to recycle these flags after 2.6.26 1331 */ 1332 if (unlikely(clone_flags & CLONE_STOPPED)) { 1333 static int __read_mostly count = 100; 1334 1335 if (count > 0 && printk_ratelimit()) { 1336 char comm[TASK_COMM_LEN]; 1337 1338 count--; 1339 printk(KERN_INFO "fork(): process `%s' used deprecated " 1340 "clone flags 0x%lx\n", 1341 get_task_comm(comm, current), 1342 clone_flags & CLONE_STOPPED); 1343 } 1344 } 1345 1346 /* 1347 * When called from kernel_thread, don't do user tracing stuff. 1348 */ 1349 if (likely(user_mode(regs))) 1350 trace = tracehook_prepare_clone(clone_flags); 1351 1352 p = copy_process(clone_flags, stack_start, regs, stack_size, 1353 child_tidptr, NULL, trace); 1354 /* 1355 * Do this prior waking up the new thread - the thread pointer 1356 * might get invalid after that point, if the thread exits quickly. 1357 */ 1358 if (!IS_ERR(p)) { 1359 struct completion vfork; 1360 1361 nr = task_pid_vnr(p); 1362 1363 if (clone_flags & CLONE_PARENT_SETTID) 1364 put_user(nr, parent_tidptr); 1365 1366 if (clone_flags & CLONE_VFORK) { 1367 p->vfork_done = &vfork; 1368 init_completion(&vfork); 1369 } 1370 1371 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1372 1373 /* 1374 * We set PF_STARTING at creation in case tracing wants to 1375 * use this to distinguish a fully live task from one that 1376 * hasn't gotten to tracehook_report_clone() yet. Now we 1377 * clear it and set the child going. 1378 */ 1379 p->flags &= ~PF_STARTING; 1380 1381 if (unlikely(clone_flags & CLONE_STOPPED)) { 1382 /* 1383 * We'll start up with an immediate SIGSTOP. 1384 */ 1385 sigaddset(&p->pending.signal, SIGSTOP); 1386 set_tsk_thread_flag(p, TIF_SIGPENDING); 1387 __set_task_state(p, TASK_STOPPED); 1388 } else { 1389 wake_up_new_task(p, clone_flags); 1390 } 1391 1392 tracehook_report_clone_complete(trace, regs, 1393 clone_flags, nr, p); 1394 1395 if (clone_flags & CLONE_VFORK) { 1396 freezer_do_not_count(); 1397 wait_for_completion(&vfork); 1398 freezer_count(); 1399 tracehook_report_vfork_done(p, nr); 1400 } 1401 } else { 1402 nr = PTR_ERR(p); 1403 } 1404 return nr; 1405 } 1406 1407 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1408 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1409 #endif 1410 1411 static void sighand_ctor(void *data) 1412 { 1413 struct sighand_struct *sighand = data; 1414 1415 spin_lock_init(&sighand->siglock); 1416 init_waitqueue_head(&sighand->signalfd_wqh); 1417 } 1418 1419 void __init proc_caches_init(void) 1420 { 1421 sighand_cachep = kmem_cache_create("sighand_cache", 1422 sizeof(struct sighand_struct), 0, 1423 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1424 sighand_ctor); 1425 signal_cachep = kmem_cache_create("signal_cache", 1426 sizeof(struct signal_struct), 0, 1427 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1428 files_cachep = kmem_cache_create("files_cache", 1429 sizeof(struct files_struct), 0, 1430 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1431 fs_cachep = kmem_cache_create("fs_cache", 1432 sizeof(struct fs_struct), 0, 1433 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1434 vm_area_cachep = kmem_cache_create("vm_area_struct", 1435 sizeof(struct vm_area_struct), 0, 1436 SLAB_PANIC, NULL); 1437 mm_cachep = kmem_cache_create("mm_struct", 1438 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1439 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1440 } 1441 1442 /* 1443 * Check constraints on flags passed to the unshare system call and 1444 * force unsharing of additional process context as appropriate. 1445 */ 1446 static void check_unshare_flags(unsigned long *flags_ptr) 1447 { 1448 /* 1449 * If unsharing a thread from a thread group, must also 1450 * unshare vm. 1451 */ 1452 if (*flags_ptr & CLONE_THREAD) 1453 *flags_ptr |= CLONE_VM; 1454 1455 /* 1456 * If unsharing vm, must also unshare signal handlers. 1457 */ 1458 if (*flags_ptr & CLONE_VM) 1459 *flags_ptr |= CLONE_SIGHAND; 1460 1461 /* 1462 * If unsharing signal handlers and the task was created 1463 * using CLONE_THREAD, then must unshare the thread 1464 */ 1465 if ((*flags_ptr & CLONE_SIGHAND) && 1466 (atomic_read(¤t->signal->count) > 1)) 1467 *flags_ptr |= CLONE_THREAD; 1468 1469 /* 1470 * If unsharing namespace, must also unshare filesystem information. 1471 */ 1472 if (*flags_ptr & CLONE_NEWNS) 1473 *flags_ptr |= CLONE_FS; 1474 } 1475 1476 /* 1477 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1478 */ 1479 static int unshare_thread(unsigned long unshare_flags) 1480 { 1481 if (unshare_flags & CLONE_THREAD) 1482 return -EINVAL; 1483 1484 return 0; 1485 } 1486 1487 /* 1488 * Unshare the filesystem structure if it is being shared 1489 */ 1490 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1491 { 1492 struct fs_struct *fs = current->fs; 1493 1494 if ((unshare_flags & CLONE_FS) && 1495 (fs && atomic_read(&fs->count) > 1)) { 1496 *new_fsp = __copy_fs_struct(current->fs); 1497 if (!*new_fsp) 1498 return -ENOMEM; 1499 } 1500 1501 return 0; 1502 } 1503 1504 /* 1505 * Unsharing of sighand is not supported yet 1506 */ 1507 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1508 { 1509 struct sighand_struct *sigh = current->sighand; 1510 1511 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1512 return -EINVAL; 1513 else 1514 return 0; 1515 } 1516 1517 /* 1518 * Unshare vm if it is being shared 1519 */ 1520 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1521 { 1522 struct mm_struct *mm = current->mm; 1523 1524 if ((unshare_flags & CLONE_VM) && 1525 (mm && atomic_read(&mm->mm_users) > 1)) { 1526 return -EINVAL; 1527 } 1528 1529 return 0; 1530 } 1531 1532 /* 1533 * Unshare file descriptor table if it is being shared 1534 */ 1535 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1536 { 1537 struct files_struct *fd = current->files; 1538 int error = 0; 1539 1540 if ((unshare_flags & CLONE_FILES) && 1541 (fd && atomic_read(&fd->count) > 1)) { 1542 *new_fdp = dup_fd(fd, &error); 1543 if (!*new_fdp) 1544 return error; 1545 } 1546 1547 return 0; 1548 } 1549 1550 /* 1551 * unshare allows a process to 'unshare' part of the process 1552 * context which was originally shared using clone. copy_* 1553 * functions used by do_fork() cannot be used here directly 1554 * because they modify an inactive task_struct that is being 1555 * constructed. Here we are modifying the current, active, 1556 * task_struct. 1557 */ 1558 asmlinkage long sys_unshare(unsigned long unshare_flags) 1559 { 1560 int err = 0; 1561 struct fs_struct *fs, *new_fs = NULL; 1562 struct sighand_struct *new_sigh = NULL; 1563 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1564 struct files_struct *fd, *new_fd = NULL; 1565 struct nsproxy *new_nsproxy = NULL; 1566 int do_sysvsem = 0; 1567 1568 check_unshare_flags(&unshare_flags); 1569 1570 /* Return -EINVAL for all unsupported flags */ 1571 err = -EINVAL; 1572 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1573 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1574 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1575 CLONE_NEWNET)) 1576 goto bad_unshare_out; 1577 1578 /* 1579 * CLONE_NEWIPC must also detach from the undolist: after switching 1580 * to a new ipc namespace, the semaphore arrays from the old 1581 * namespace are unreachable. 1582 */ 1583 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1584 do_sysvsem = 1; 1585 if ((err = unshare_thread(unshare_flags))) 1586 goto bad_unshare_out; 1587 if ((err = unshare_fs(unshare_flags, &new_fs))) 1588 goto bad_unshare_cleanup_thread; 1589 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1590 goto bad_unshare_cleanup_fs; 1591 if ((err = unshare_vm(unshare_flags, &new_mm))) 1592 goto bad_unshare_cleanup_sigh; 1593 if ((err = unshare_fd(unshare_flags, &new_fd))) 1594 goto bad_unshare_cleanup_vm; 1595 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1596 new_fs))) 1597 goto bad_unshare_cleanup_fd; 1598 1599 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1600 if (do_sysvsem) { 1601 /* 1602 * CLONE_SYSVSEM is equivalent to sys_exit(). 1603 */ 1604 exit_sem(current); 1605 } 1606 1607 if (new_nsproxy) { 1608 switch_task_namespaces(current, new_nsproxy); 1609 new_nsproxy = NULL; 1610 } 1611 1612 task_lock(current); 1613 1614 if (new_fs) { 1615 fs = current->fs; 1616 current->fs = new_fs; 1617 new_fs = fs; 1618 } 1619 1620 if (new_mm) { 1621 mm = current->mm; 1622 active_mm = current->active_mm; 1623 current->mm = new_mm; 1624 current->active_mm = new_mm; 1625 activate_mm(active_mm, new_mm); 1626 new_mm = mm; 1627 } 1628 1629 if (new_fd) { 1630 fd = current->files; 1631 current->files = new_fd; 1632 new_fd = fd; 1633 } 1634 1635 task_unlock(current); 1636 } 1637 1638 if (new_nsproxy) 1639 put_nsproxy(new_nsproxy); 1640 1641 bad_unshare_cleanup_fd: 1642 if (new_fd) 1643 put_files_struct(new_fd); 1644 1645 bad_unshare_cleanup_vm: 1646 if (new_mm) 1647 mmput(new_mm); 1648 1649 bad_unshare_cleanup_sigh: 1650 if (new_sigh) 1651 if (atomic_dec_and_test(&new_sigh->count)) 1652 kmem_cache_free(sighand_cachep, new_sigh); 1653 1654 bad_unshare_cleanup_fs: 1655 if (new_fs) 1656 put_fs_struct(new_fs); 1657 1658 bad_unshare_cleanup_thread: 1659 bad_unshare_out: 1660 return err; 1661 } 1662 1663 /* 1664 * Helper to unshare the files of the current task. 1665 * We don't want to expose copy_files internals to 1666 * the exec layer of the kernel. 1667 */ 1668 1669 int unshare_files(struct files_struct **displaced) 1670 { 1671 struct task_struct *task = current; 1672 struct files_struct *copy = NULL; 1673 int error; 1674 1675 error = unshare_fd(CLONE_FILES, ©); 1676 if (error || !copy) { 1677 *displaced = NULL; 1678 return error; 1679 } 1680 *displaced = task->files; 1681 task_lock(task); 1682 task->files = copy; 1683 task_unlock(task); 1684 return 0; 1685 } 1686