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/futex.h> 41 #include <linux/task_io_accounting_ops.h> 42 #include <linux/rcupdate.h> 43 #include <linux/ptrace.h> 44 #include <linux/mount.h> 45 #include <linux/audit.h> 46 #include <linux/memcontrol.h> 47 #include <linux/profile.h> 48 #include <linux/rmap.h> 49 #include <linux/acct.h> 50 #include <linux/tsacct_kern.h> 51 #include <linux/cn_proc.h> 52 #include <linux/freezer.h> 53 #include <linux/delayacct.h> 54 #include <linux/taskstats_kern.h> 55 #include <linux/random.h> 56 #include <linux/tty.h> 57 #include <linux/proc_fs.h> 58 #include <linux/blkdev.h> 59 60 #include <asm/pgtable.h> 61 #include <asm/pgalloc.h> 62 #include <asm/uaccess.h> 63 #include <asm/mmu_context.h> 64 #include <asm/cacheflush.h> 65 #include <asm/tlbflush.h> 66 67 /* 68 * Protected counters by write_lock_irq(&tasklist_lock) 69 */ 70 unsigned long total_forks; /* Handle normal Linux uptimes. */ 71 int nr_threads; /* The idle threads do not count.. */ 72 73 int max_threads; /* tunable limit on nr_threads */ 74 75 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 76 77 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 78 79 int nr_processes(void) 80 { 81 int cpu; 82 int total = 0; 83 84 for_each_online_cpu(cpu) 85 total += per_cpu(process_counts, cpu); 86 87 return total; 88 } 89 90 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 91 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 92 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 93 static struct kmem_cache *task_struct_cachep; 94 #endif 95 96 /* SLAB cache for signal_struct structures (tsk->signal) */ 97 static struct kmem_cache *signal_cachep; 98 99 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 100 struct kmem_cache *sighand_cachep; 101 102 /* SLAB cache for files_struct structures (tsk->files) */ 103 struct kmem_cache *files_cachep; 104 105 /* SLAB cache for fs_struct structures (tsk->fs) */ 106 struct kmem_cache *fs_cachep; 107 108 /* SLAB cache for vm_area_struct structures */ 109 struct kmem_cache *vm_area_cachep; 110 111 /* SLAB cache for mm_struct structures (tsk->mm) */ 112 static struct kmem_cache *mm_cachep; 113 114 void free_task(struct task_struct *tsk) 115 { 116 prop_local_destroy_single(&tsk->dirties); 117 free_thread_info(tsk->stack); 118 rt_mutex_debug_task_free(tsk); 119 free_task_struct(tsk); 120 } 121 EXPORT_SYMBOL(free_task); 122 123 void __put_task_struct(struct task_struct *tsk) 124 { 125 WARN_ON(!tsk->exit_state); 126 WARN_ON(atomic_read(&tsk->usage)); 127 WARN_ON(tsk == current); 128 129 security_task_free(tsk); 130 free_uid(tsk->user); 131 put_group_info(tsk->group_info); 132 delayacct_tsk_free(tsk); 133 134 if (!profile_handoff_task(tsk)) 135 free_task(tsk); 136 } 137 138 /* 139 * macro override instead of weak attribute alias, to workaround 140 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 141 */ 142 #ifndef arch_task_cache_init 143 #define arch_task_cache_init() 144 #endif 145 146 void __init fork_init(unsigned long mempages) 147 { 148 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 149 #ifndef ARCH_MIN_TASKALIGN 150 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 151 #endif 152 /* create a slab on which task_structs can be allocated */ 153 task_struct_cachep = 154 kmem_cache_create("task_struct", sizeof(struct task_struct), 155 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 156 #endif 157 158 /* do the arch specific task caches init */ 159 arch_task_cache_init(); 160 161 /* 162 * The default maximum number of threads is set to a safe 163 * value: the thread structures can take up at most half 164 * of memory. 165 */ 166 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 167 168 /* 169 * we need to allow at least 20 threads to boot a system 170 */ 171 if(max_threads < 20) 172 max_threads = 20; 173 174 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 175 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 176 init_task.signal->rlim[RLIMIT_SIGPENDING] = 177 init_task.signal->rlim[RLIMIT_NPROC]; 178 } 179 180 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 181 struct task_struct *src) 182 { 183 *dst = *src; 184 return 0; 185 } 186 187 static struct task_struct *dup_task_struct(struct task_struct *orig) 188 { 189 struct task_struct *tsk; 190 struct thread_info *ti; 191 int err; 192 193 prepare_to_copy(orig); 194 195 tsk = alloc_task_struct(); 196 if (!tsk) 197 return NULL; 198 199 ti = alloc_thread_info(tsk); 200 if (!ti) { 201 free_task_struct(tsk); 202 return NULL; 203 } 204 205 err = arch_dup_task_struct(tsk, orig); 206 if (err) 207 goto out; 208 209 tsk->stack = ti; 210 211 err = prop_local_init_single(&tsk->dirties); 212 if (err) 213 goto out; 214 215 setup_thread_stack(tsk, orig); 216 217 #ifdef CONFIG_CC_STACKPROTECTOR 218 tsk->stack_canary = get_random_int(); 219 #endif 220 221 /* One for us, one for whoever does the "release_task()" (usually parent) */ 222 atomic_set(&tsk->usage,2); 223 atomic_set(&tsk->fs_excl, 0); 224 #ifdef CONFIG_BLK_DEV_IO_TRACE 225 tsk->btrace_seq = 0; 226 #endif 227 tsk->splice_pipe = NULL; 228 return tsk; 229 230 out: 231 free_thread_info(ti); 232 free_task_struct(tsk); 233 return NULL; 234 } 235 236 #ifdef CONFIG_MMU 237 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 238 { 239 struct vm_area_struct *mpnt, *tmp, **pprev; 240 struct rb_node **rb_link, *rb_parent; 241 int retval; 242 unsigned long charge; 243 struct mempolicy *pol; 244 245 down_write(&oldmm->mmap_sem); 246 flush_cache_dup_mm(oldmm); 247 /* 248 * Not linked in yet - no deadlock potential: 249 */ 250 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 251 252 mm->locked_vm = 0; 253 mm->mmap = NULL; 254 mm->mmap_cache = NULL; 255 mm->free_area_cache = oldmm->mmap_base; 256 mm->cached_hole_size = ~0UL; 257 mm->map_count = 0; 258 cpus_clear(mm->cpu_vm_mask); 259 mm->mm_rb = RB_ROOT; 260 rb_link = &mm->mm_rb.rb_node; 261 rb_parent = NULL; 262 pprev = &mm->mmap; 263 264 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 265 struct file *file; 266 267 if (mpnt->vm_flags & VM_DONTCOPY) { 268 long pages = vma_pages(mpnt); 269 mm->total_vm -= pages; 270 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 271 -pages); 272 continue; 273 } 274 charge = 0; 275 if (mpnt->vm_flags & VM_ACCOUNT) { 276 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 277 if (security_vm_enough_memory(len)) 278 goto fail_nomem; 279 charge = len; 280 } 281 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 282 if (!tmp) 283 goto fail_nomem; 284 *tmp = *mpnt; 285 pol = mpol_dup(vma_policy(mpnt)); 286 retval = PTR_ERR(pol); 287 if (IS_ERR(pol)) 288 goto fail_nomem_policy; 289 vma_set_policy(tmp, pol); 290 tmp->vm_flags &= ~VM_LOCKED; 291 tmp->vm_mm = mm; 292 tmp->vm_next = NULL; 293 anon_vma_link(tmp); 294 file = tmp->vm_file; 295 if (file) { 296 struct inode *inode = file->f_path.dentry->d_inode; 297 get_file(file); 298 if (tmp->vm_flags & VM_DENYWRITE) 299 atomic_dec(&inode->i_writecount); 300 301 /* insert tmp into the share list, just after mpnt */ 302 spin_lock(&file->f_mapping->i_mmap_lock); 303 tmp->vm_truncate_count = mpnt->vm_truncate_count; 304 flush_dcache_mmap_lock(file->f_mapping); 305 vma_prio_tree_add(tmp, mpnt); 306 flush_dcache_mmap_unlock(file->f_mapping); 307 spin_unlock(&file->f_mapping->i_mmap_lock); 308 } 309 310 /* 311 * Clear hugetlb-related page reserves for children. This only 312 * affects MAP_PRIVATE mappings. Faults generated by the child 313 * are not guaranteed to succeed, even if read-only 314 */ 315 if (is_vm_hugetlb_page(tmp)) 316 reset_vma_resv_huge_pages(tmp); 317 318 /* 319 * Link in the new vma and copy the page table entries. 320 */ 321 *pprev = tmp; 322 pprev = &tmp->vm_next; 323 324 __vma_link_rb(mm, tmp, rb_link, rb_parent); 325 rb_link = &tmp->vm_rb.rb_right; 326 rb_parent = &tmp->vm_rb; 327 328 mm->map_count++; 329 retval = copy_page_range(mm, oldmm, mpnt); 330 331 if (tmp->vm_ops && tmp->vm_ops->open) 332 tmp->vm_ops->open(tmp); 333 334 if (retval) 335 goto out; 336 } 337 /* a new mm has just been created */ 338 arch_dup_mmap(oldmm, mm); 339 retval = 0; 340 out: 341 up_write(&mm->mmap_sem); 342 flush_tlb_mm(oldmm); 343 up_write(&oldmm->mmap_sem); 344 return retval; 345 fail_nomem_policy: 346 kmem_cache_free(vm_area_cachep, tmp); 347 fail_nomem: 348 retval = -ENOMEM; 349 vm_unacct_memory(charge); 350 goto out; 351 } 352 353 static inline int mm_alloc_pgd(struct mm_struct * mm) 354 { 355 mm->pgd = pgd_alloc(mm); 356 if (unlikely(!mm->pgd)) 357 return -ENOMEM; 358 return 0; 359 } 360 361 static inline void mm_free_pgd(struct mm_struct * mm) 362 { 363 pgd_free(mm, mm->pgd); 364 } 365 #else 366 #define dup_mmap(mm, oldmm) (0) 367 #define mm_alloc_pgd(mm) (0) 368 #define mm_free_pgd(mm) 369 #endif /* CONFIG_MMU */ 370 371 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 372 373 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 374 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 375 376 #include <linux/init_task.h> 377 378 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 379 { 380 atomic_set(&mm->mm_users, 1); 381 atomic_set(&mm->mm_count, 1); 382 init_rwsem(&mm->mmap_sem); 383 INIT_LIST_HEAD(&mm->mmlist); 384 mm->flags = (current->mm) ? current->mm->flags 385 : MMF_DUMP_FILTER_DEFAULT; 386 mm->core_waiters = 0; 387 mm->nr_ptes = 0; 388 set_mm_counter(mm, file_rss, 0); 389 set_mm_counter(mm, anon_rss, 0); 390 spin_lock_init(&mm->page_table_lock); 391 rwlock_init(&mm->ioctx_list_lock); 392 mm->ioctx_list = NULL; 393 mm->free_area_cache = TASK_UNMAPPED_BASE; 394 mm->cached_hole_size = ~0UL; 395 mm_init_owner(mm, p); 396 397 if (likely(!mm_alloc_pgd(mm))) { 398 mm->def_flags = 0; 399 return mm; 400 } 401 402 free_mm(mm); 403 return NULL; 404 } 405 406 /* 407 * Allocate and initialize an mm_struct. 408 */ 409 struct mm_struct * mm_alloc(void) 410 { 411 struct mm_struct * mm; 412 413 mm = allocate_mm(); 414 if (mm) { 415 memset(mm, 0, sizeof(*mm)); 416 mm = mm_init(mm, current); 417 } 418 return mm; 419 } 420 421 /* 422 * Called when the last reference to the mm 423 * is dropped: either by a lazy thread or by 424 * mmput. Free the page directory and the mm. 425 */ 426 void __mmdrop(struct mm_struct *mm) 427 { 428 BUG_ON(mm == &init_mm); 429 mm_free_pgd(mm); 430 destroy_context(mm); 431 free_mm(mm); 432 } 433 EXPORT_SYMBOL_GPL(__mmdrop); 434 435 /* 436 * Decrement the use count and release all resources for an mm. 437 */ 438 void mmput(struct mm_struct *mm) 439 { 440 might_sleep(); 441 442 if (atomic_dec_and_test(&mm->mm_users)) { 443 exit_aio(mm); 444 exit_mmap(mm); 445 set_mm_exe_file(mm, NULL); 446 if (!list_empty(&mm->mmlist)) { 447 spin_lock(&mmlist_lock); 448 list_del(&mm->mmlist); 449 spin_unlock(&mmlist_lock); 450 } 451 put_swap_token(mm); 452 mmdrop(mm); 453 } 454 } 455 EXPORT_SYMBOL_GPL(mmput); 456 457 /** 458 * get_task_mm - acquire a reference to the task's mm 459 * 460 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 461 * this kernel workthread has transiently adopted a user mm with use_mm, 462 * to do its AIO) is not set and if so returns a reference to it, after 463 * bumping up the use count. User must release the mm via mmput() 464 * after use. Typically used by /proc and ptrace. 465 */ 466 struct mm_struct *get_task_mm(struct task_struct *task) 467 { 468 struct mm_struct *mm; 469 470 task_lock(task); 471 mm = task->mm; 472 if (mm) { 473 if (task->flags & PF_BORROWED_MM) 474 mm = NULL; 475 else 476 atomic_inc(&mm->mm_users); 477 } 478 task_unlock(task); 479 return mm; 480 } 481 EXPORT_SYMBOL_GPL(get_task_mm); 482 483 /* Please note the differences between mmput and mm_release. 484 * mmput is called whenever we stop holding onto a mm_struct, 485 * error success whatever. 486 * 487 * mm_release is called after a mm_struct has been removed 488 * from the current process. 489 * 490 * This difference is important for error handling, when we 491 * only half set up a mm_struct for a new process and need to restore 492 * the old one. Because we mmput the new mm_struct before 493 * restoring the old one. . . 494 * Eric Biederman 10 January 1998 495 */ 496 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 497 { 498 struct completion *vfork_done = tsk->vfork_done; 499 500 /* Get rid of any cached register state */ 501 deactivate_mm(tsk, mm); 502 503 /* notify parent sleeping on vfork() */ 504 if (vfork_done) { 505 tsk->vfork_done = NULL; 506 complete(vfork_done); 507 } 508 509 /* 510 * If we're exiting normally, clear a user-space tid field if 511 * requested. We leave this alone when dying by signal, to leave 512 * the value intact in a core dump, and to save the unnecessary 513 * trouble otherwise. Userland only wants this done for a sys_exit. 514 */ 515 if (tsk->clear_child_tid 516 && !(tsk->flags & PF_SIGNALED) 517 && atomic_read(&mm->mm_users) > 1) { 518 u32 __user * tidptr = tsk->clear_child_tid; 519 tsk->clear_child_tid = NULL; 520 521 /* 522 * We don't check the error code - if userspace has 523 * not set up a proper pointer then tough luck. 524 */ 525 put_user(0, tidptr); 526 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 527 } 528 } 529 530 /* 531 * Allocate a new mm structure and copy contents from the 532 * mm structure of the passed in task structure. 533 */ 534 struct mm_struct *dup_mm(struct task_struct *tsk) 535 { 536 struct mm_struct *mm, *oldmm = current->mm; 537 int err; 538 539 if (!oldmm) 540 return NULL; 541 542 mm = allocate_mm(); 543 if (!mm) 544 goto fail_nomem; 545 546 memcpy(mm, oldmm, sizeof(*mm)); 547 548 /* Initializing for Swap token stuff */ 549 mm->token_priority = 0; 550 mm->last_interval = 0; 551 552 if (!mm_init(mm, tsk)) 553 goto fail_nomem; 554 555 if (init_new_context(tsk, mm)) 556 goto fail_nocontext; 557 558 dup_mm_exe_file(oldmm, mm); 559 560 err = dup_mmap(mm, oldmm); 561 if (err) 562 goto free_pt; 563 564 mm->hiwater_rss = get_mm_rss(mm); 565 mm->hiwater_vm = mm->total_vm; 566 567 return mm; 568 569 free_pt: 570 mmput(mm); 571 572 fail_nomem: 573 return NULL; 574 575 fail_nocontext: 576 /* 577 * If init_new_context() failed, we cannot use mmput() to free the mm 578 * because it calls destroy_context() 579 */ 580 mm_free_pgd(mm); 581 free_mm(mm); 582 return NULL; 583 } 584 585 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 586 { 587 struct mm_struct * mm, *oldmm; 588 int retval; 589 590 tsk->min_flt = tsk->maj_flt = 0; 591 tsk->nvcsw = tsk->nivcsw = 0; 592 593 tsk->mm = NULL; 594 tsk->active_mm = NULL; 595 596 /* 597 * Are we cloning a kernel thread? 598 * 599 * We need to steal a active VM for that.. 600 */ 601 oldmm = current->mm; 602 if (!oldmm) 603 return 0; 604 605 if (clone_flags & CLONE_VM) { 606 atomic_inc(&oldmm->mm_users); 607 mm = oldmm; 608 goto good_mm; 609 } 610 611 retval = -ENOMEM; 612 mm = dup_mm(tsk); 613 if (!mm) 614 goto fail_nomem; 615 616 good_mm: 617 /* Initializing for Swap token stuff */ 618 mm->token_priority = 0; 619 mm->last_interval = 0; 620 621 tsk->mm = mm; 622 tsk->active_mm = mm; 623 return 0; 624 625 fail_nomem: 626 return retval; 627 } 628 629 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 630 { 631 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 632 /* We don't need to lock fs - think why ;-) */ 633 if (fs) { 634 atomic_set(&fs->count, 1); 635 rwlock_init(&fs->lock); 636 fs->umask = old->umask; 637 read_lock(&old->lock); 638 fs->root = old->root; 639 path_get(&old->root); 640 fs->pwd = old->pwd; 641 path_get(&old->pwd); 642 if (old->altroot.dentry) { 643 fs->altroot = old->altroot; 644 path_get(&old->altroot); 645 } else { 646 fs->altroot.mnt = NULL; 647 fs->altroot.dentry = NULL; 648 } 649 read_unlock(&old->lock); 650 } 651 return fs; 652 } 653 654 struct fs_struct *copy_fs_struct(struct fs_struct *old) 655 { 656 return __copy_fs_struct(old); 657 } 658 659 EXPORT_SYMBOL_GPL(copy_fs_struct); 660 661 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 662 { 663 if (clone_flags & CLONE_FS) { 664 atomic_inc(¤t->fs->count); 665 return 0; 666 } 667 tsk->fs = __copy_fs_struct(current->fs); 668 if (!tsk->fs) 669 return -ENOMEM; 670 return 0; 671 } 672 673 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 674 { 675 struct files_struct *oldf, *newf; 676 int error = 0; 677 678 /* 679 * A background process may not have any files ... 680 */ 681 oldf = current->files; 682 if (!oldf) 683 goto out; 684 685 if (clone_flags & CLONE_FILES) { 686 atomic_inc(&oldf->count); 687 goto out; 688 } 689 690 newf = dup_fd(oldf, &error); 691 if (!newf) 692 goto out; 693 694 tsk->files = newf; 695 error = 0; 696 out: 697 return error; 698 } 699 700 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 701 { 702 #ifdef CONFIG_BLOCK 703 struct io_context *ioc = current->io_context; 704 705 if (!ioc) 706 return 0; 707 /* 708 * Share io context with parent, if CLONE_IO is set 709 */ 710 if (clone_flags & CLONE_IO) { 711 tsk->io_context = ioc_task_link(ioc); 712 if (unlikely(!tsk->io_context)) 713 return -ENOMEM; 714 } else if (ioprio_valid(ioc->ioprio)) { 715 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 716 if (unlikely(!tsk->io_context)) 717 return -ENOMEM; 718 719 tsk->io_context->ioprio = ioc->ioprio; 720 } 721 #endif 722 return 0; 723 } 724 725 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 726 { 727 struct sighand_struct *sig; 728 729 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 730 atomic_inc(¤t->sighand->count); 731 return 0; 732 } 733 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 734 rcu_assign_pointer(tsk->sighand, sig); 735 if (!sig) 736 return -ENOMEM; 737 atomic_set(&sig->count, 1); 738 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 739 return 0; 740 } 741 742 void __cleanup_sighand(struct sighand_struct *sighand) 743 { 744 if (atomic_dec_and_test(&sighand->count)) 745 kmem_cache_free(sighand_cachep, sighand); 746 } 747 748 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 749 { 750 struct signal_struct *sig; 751 int ret; 752 753 if (clone_flags & CLONE_THREAD) { 754 atomic_inc(¤t->signal->count); 755 atomic_inc(¤t->signal->live); 756 return 0; 757 } 758 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 759 tsk->signal = sig; 760 if (!sig) 761 return -ENOMEM; 762 763 ret = copy_thread_group_keys(tsk); 764 if (ret < 0) { 765 kmem_cache_free(signal_cachep, sig); 766 return ret; 767 } 768 769 atomic_set(&sig->count, 1); 770 atomic_set(&sig->live, 1); 771 init_waitqueue_head(&sig->wait_chldexit); 772 sig->flags = 0; 773 sig->group_exit_code = 0; 774 sig->group_exit_task = NULL; 775 sig->group_stop_count = 0; 776 sig->curr_target = tsk; 777 init_sigpending(&sig->shared_pending); 778 INIT_LIST_HEAD(&sig->posix_timers); 779 780 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 781 sig->it_real_incr.tv64 = 0; 782 sig->real_timer.function = it_real_fn; 783 784 sig->it_virt_expires = cputime_zero; 785 sig->it_virt_incr = cputime_zero; 786 sig->it_prof_expires = cputime_zero; 787 sig->it_prof_incr = cputime_zero; 788 789 sig->leader = 0; /* session leadership doesn't inherit */ 790 sig->tty_old_pgrp = NULL; 791 792 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 793 sig->gtime = cputime_zero; 794 sig->cgtime = cputime_zero; 795 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 796 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 797 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 798 sig->sum_sched_runtime = 0; 799 INIT_LIST_HEAD(&sig->cpu_timers[0]); 800 INIT_LIST_HEAD(&sig->cpu_timers[1]); 801 INIT_LIST_HEAD(&sig->cpu_timers[2]); 802 taskstats_tgid_init(sig); 803 804 task_lock(current->group_leader); 805 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 806 task_unlock(current->group_leader); 807 808 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 809 /* 810 * New sole thread in the process gets an expiry time 811 * of the whole CPU time limit. 812 */ 813 tsk->it_prof_expires = 814 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 815 } 816 acct_init_pacct(&sig->pacct); 817 818 tty_audit_fork(sig); 819 820 return 0; 821 } 822 823 void __cleanup_signal(struct signal_struct *sig) 824 { 825 exit_thread_group_keys(sig); 826 kmem_cache_free(signal_cachep, sig); 827 } 828 829 static void cleanup_signal(struct task_struct *tsk) 830 { 831 struct signal_struct *sig = tsk->signal; 832 833 atomic_dec(&sig->live); 834 835 if (atomic_dec_and_test(&sig->count)) 836 __cleanup_signal(sig); 837 } 838 839 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 840 { 841 unsigned long new_flags = p->flags; 842 843 new_flags &= ~PF_SUPERPRIV; 844 new_flags |= PF_FORKNOEXEC; 845 if (!(clone_flags & CLONE_PTRACE)) 846 p->ptrace = 0; 847 p->flags = new_flags; 848 clear_freeze_flag(p); 849 } 850 851 asmlinkage long sys_set_tid_address(int __user *tidptr) 852 { 853 current->clear_child_tid = tidptr; 854 855 return task_pid_vnr(current); 856 } 857 858 static void rt_mutex_init_task(struct task_struct *p) 859 { 860 spin_lock_init(&p->pi_lock); 861 #ifdef CONFIG_RT_MUTEXES 862 plist_head_init(&p->pi_waiters, &p->pi_lock); 863 p->pi_blocked_on = NULL; 864 #endif 865 } 866 867 #ifdef CONFIG_MM_OWNER 868 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 869 { 870 mm->owner = p; 871 } 872 #endif /* CONFIG_MM_OWNER */ 873 874 /* 875 * This creates a new process as a copy of the old one, 876 * but does not actually start it yet. 877 * 878 * It copies the registers, and all the appropriate 879 * parts of the process environment (as per the clone 880 * flags). The actual kick-off is left to the caller. 881 */ 882 static struct task_struct *copy_process(unsigned long clone_flags, 883 unsigned long stack_start, 884 struct pt_regs *regs, 885 unsigned long stack_size, 886 int __user *child_tidptr, 887 struct pid *pid) 888 { 889 int retval; 890 struct task_struct *p; 891 int cgroup_callbacks_done = 0; 892 893 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 894 return ERR_PTR(-EINVAL); 895 896 /* 897 * Thread groups must share signals as well, and detached threads 898 * can only be started up within the thread group. 899 */ 900 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 901 return ERR_PTR(-EINVAL); 902 903 /* 904 * Shared signal handlers imply shared VM. By way of the above, 905 * thread groups also imply shared VM. Blocking this case allows 906 * for various simplifications in other code. 907 */ 908 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 909 return ERR_PTR(-EINVAL); 910 911 retval = security_task_create(clone_flags); 912 if (retval) 913 goto fork_out; 914 915 retval = -ENOMEM; 916 p = dup_task_struct(current); 917 if (!p) 918 goto fork_out; 919 920 rt_mutex_init_task(p); 921 922 #ifdef CONFIG_PROVE_LOCKING 923 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 924 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 925 #endif 926 retval = -EAGAIN; 927 if (atomic_read(&p->user->processes) >= 928 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 929 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 930 p->user != current->nsproxy->user_ns->root_user) 931 goto bad_fork_free; 932 } 933 934 atomic_inc(&p->user->__count); 935 atomic_inc(&p->user->processes); 936 get_group_info(p->group_info); 937 938 /* 939 * If multiple threads are within copy_process(), then this check 940 * triggers too late. This doesn't hurt, the check is only there 941 * to stop root fork bombs. 942 */ 943 if (nr_threads >= max_threads) 944 goto bad_fork_cleanup_count; 945 946 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 947 goto bad_fork_cleanup_count; 948 949 if (p->binfmt && !try_module_get(p->binfmt->module)) 950 goto bad_fork_cleanup_put_domain; 951 952 p->did_exec = 0; 953 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 954 copy_flags(clone_flags, p); 955 INIT_LIST_HEAD(&p->children); 956 INIT_LIST_HEAD(&p->sibling); 957 #ifdef CONFIG_PREEMPT_RCU 958 p->rcu_read_lock_nesting = 0; 959 p->rcu_flipctr_idx = 0; 960 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 961 p->vfork_done = NULL; 962 spin_lock_init(&p->alloc_lock); 963 964 clear_tsk_thread_flag(p, TIF_SIGPENDING); 965 init_sigpending(&p->pending); 966 967 p->utime = cputime_zero; 968 p->stime = cputime_zero; 969 p->gtime = cputime_zero; 970 p->utimescaled = cputime_zero; 971 p->stimescaled = cputime_zero; 972 p->prev_utime = cputime_zero; 973 p->prev_stime = cputime_zero; 974 975 #ifdef CONFIG_DETECT_SOFTLOCKUP 976 p->last_switch_count = 0; 977 p->last_switch_timestamp = 0; 978 #endif 979 980 #ifdef CONFIG_TASK_XACCT 981 p->rchar = 0; /* I/O counter: bytes read */ 982 p->wchar = 0; /* I/O counter: bytes written */ 983 p->syscr = 0; /* I/O counter: read syscalls */ 984 p->syscw = 0; /* I/O counter: write syscalls */ 985 #endif 986 task_io_accounting_init(p); 987 acct_clear_integrals(p); 988 989 p->it_virt_expires = cputime_zero; 990 p->it_prof_expires = cputime_zero; 991 p->it_sched_expires = 0; 992 INIT_LIST_HEAD(&p->cpu_timers[0]); 993 INIT_LIST_HEAD(&p->cpu_timers[1]); 994 INIT_LIST_HEAD(&p->cpu_timers[2]); 995 996 p->lock_depth = -1; /* -1 = no lock */ 997 do_posix_clock_monotonic_gettime(&p->start_time); 998 p->real_start_time = p->start_time; 999 monotonic_to_bootbased(&p->real_start_time); 1000 #ifdef CONFIG_SECURITY 1001 p->security = NULL; 1002 #endif 1003 p->cap_bset = current->cap_bset; 1004 p->io_context = NULL; 1005 p->audit_context = NULL; 1006 cgroup_fork(p); 1007 #ifdef CONFIG_NUMA 1008 p->mempolicy = mpol_dup(p->mempolicy); 1009 if (IS_ERR(p->mempolicy)) { 1010 retval = PTR_ERR(p->mempolicy); 1011 p->mempolicy = NULL; 1012 goto bad_fork_cleanup_cgroup; 1013 } 1014 mpol_fix_fork_child_flag(p); 1015 #endif 1016 #ifdef CONFIG_TRACE_IRQFLAGS 1017 p->irq_events = 0; 1018 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1019 p->hardirqs_enabled = 1; 1020 #else 1021 p->hardirqs_enabled = 0; 1022 #endif 1023 p->hardirq_enable_ip = 0; 1024 p->hardirq_enable_event = 0; 1025 p->hardirq_disable_ip = _THIS_IP_; 1026 p->hardirq_disable_event = 0; 1027 p->softirqs_enabled = 1; 1028 p->softirq_enable_ip = _THIS_IP_; 1029 p->softirq_enable_event = 0; 1030 p->softirq_disable_ip = 0; 1031 p->softirq_disable_event = 0; 1032 p->hardirq_context = 0; 1033 p->softirq_context = 0; 1034 #endif 1035 #ifdef CONFIG_LOCKDEP 1036 p->lockdep_depth = 0; /* no locks held yet */ 1037 p->curr_chain_key = 0; 1038 p->lockdep_recursion = 0; 1039 #endif 1040 1041 #ifdef CONFIG_DEBUG_MUTEXES 1042 p->blocked_on = NULL; /* not blocked yet */ 1043 #endif 1044 1045 /* Perform scheduler related setup. Assign this task to a CPU. */ 1046 sched_fork(p, clone_flags); 1047 1048 if ((retval = security_task_alloc(p))) 1049 goto bad_fork_cleanup_policy; 1050 if ((retval = audit_alloc(p))) 1051 goto bad_fork_cleanup_security; 1052 /* copy all the process information */ 1053 if ((retval = copy_semundo(clone_flags, p))) 1054 goto bad_fork_cleanup_audit; 1055 if ((retval = copy_files(clone_flags, p))) 1056 goto bad_fork_cleanup_semundo; 1057 if ((retval = copy_fs(clone_flags, p))) 1058 goto bad_fork_cleanup_files; 1059 if ((retval = copy_sighand(clone_flags, p))) 1060 goto bad_fork_cleanup_fs; 1061 if ((retval = copy_signal(clone_flags, p))) 1062 goto bad_fork_cleanup_sighand; 1063 if ((retval = copy_mm(clone_flags, p))) 1064 goto bad_fork_cleanup_signal; 1065 if ((retval = copy_keys(clone_flags, p))) 1066 goto bad_fork_cleanup_mm; 1067 if ((retval = copy_namespaces(clone_flags, p))) 1068 goto bad_fork_cleanup_keys; 1069 if ((retval = copy_io(clone_flags, p))) 1070 goto bad_fork_cleanup_namespaces; 1071 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1072 if (retval) 1073 goto bad_fork_cleanup_io; 1074 1075 if (pid != &init_struct_pid) { 1076 retval = -ENOMEM; 1077 pid = alloc_pid(task_active_pid_ns(p)); 1078 if (!pid) 1079 goto bad_fork_cleanup_io; 1080 1081 if (clone_flags & CLONE_NEWPID) { 1082 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1083 if (retval < 0) 1084 goto bad_fork_free_pid; 1085 } 1086 } 1087 1088 p->pid = pid_nr(pid); 1089 p->tgid = p->pid; 1090 if (clone_flags & CLONE_THREAD) 1091 p->tgid = current->tgid; 1092 1093 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1094 /* 1095 * Clear TID on mm_release()? 1096 */ 1097 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1098 #ifdef CONFIG_FUTEX 1099 p->robust_list = NULL; 1100 #ifdef CONFIG_COMPAT 1101 p->compat_robust_list = NULL; 1102 #endif 1103 INIT_LIST_HEAD(&p->pi_state_list); 1104 p->pi_state_cache = NULL; 1105 #endif 1106 /* 1107 * sigaltstack should be cleared when sharing the same VM 1108 */ 1109 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1110 p->sas_ss_sp = p->sas_ss_size = 0; 1111 1112 /* 1113 * Syscall tracing should be turned off in the child regardless 1114 * of CLONE_PTRACE. 1115 */ 1116 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1117 #ifdef TIF_SYSCALL_EMU 1118 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1119 #endif 1120 clear_all_latency_tracing(p); 1121 1122 /* Our parent execution domain becomes current domain 1123 These must match for thread signalling to apply */ 1124 p->parent_exec_id = p->self_exec_id; 1125 1126 /* ok, now we should be set up.. */ 1127 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1128 p->pdeath_signal = 0; 1129 p->exit_state = 0; 1130 1131 /* 1132 * Ok, make it visible to the rest of the system. 1133 * We dont wake it up yet. 1134 */ 1135 p->group_leader = p; 1136 INIT_LIST_HEAD(&p->thread_group); 1137 INIT_LIST_HEAD(&p->ptrace_entry); 1138 INIT_LIST_HEAD(&p->ptraced); 1139 1140 /* Now that the task is set up, run cgroup callbacks if 1141 * necessary. We need to run them before the task is visible 1142 * on the tasklist. */ 1143 cgroup_fork_callbacks(p); 1144 cgroup_callbacks_done = 1; 1145 1146 /* Need tasklist lock for parent etc handling! */ 1147 write_lock_irq(&tasklist_lock); 1148 1149 /* 1150 * The task hasn't been attached yet, so its cpus_allowed mask will 1151 * not be changed, nor will its assigned CPU. 1152 * 1153 * The cpus_allowed mask of the parent may have changed after it was 1154 * copied first time - so re-copy it here, then check the child's CPU 1155 * to ensure it is on a valid CPU (and if not, just force it back to 1156 * parent's CPU). This avoids alot of nasty races. 1157 */ 1158 p->cpus_allowed = current->cpus_allowed; 1159 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1160 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1161 !cpu_online(task_cpu(p)))) 1162 set_task_cpu(p, smp_processor_id()); 1163 1164 /* CLONE_PARENT re-uses the old parent */ 1165 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1166 p->real_parent = current->real_parent; 1167 else 1168 p->real_parent = current; 1169 p->parent = p->real_parent; 1170 1171 spin_lock(¤t->sighand->siglock); 1172 1173 /* 1174 * Process group and session signals need to be delivered to just the 1175 * parent before the fork or both the parent and the child after the 1176 * fork. Restart if a signal comes in before we add the new process to 1177 * it's process group. 1178 * A fatal signal pending means that current will exit, so the new 1179 * thread can't slip out of an OOM kill (or normal SIGKILL). 1180 */ 1181 recalc_sigpending(); 1182 if (signal_pending(current)) { 1183 spin_unlock(¤t->sighand->siglock); 1184 write_unlock_irq(&tasklist_lock); 1185 retval = -ERESTARTNOINTR; 1186 goto bad_fork_free_pid; 1187 } 1188 1189 if (clone_flags & CLONE_THREAD) { 1190 p->group_leader = current->group_leader; 1191 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1192 1193 if (!cputime_eq(current->signal->it_virt_expires, 1194 cputime_zero) || 1195 !cputime_eq(current->signal->it_prof_expires, 1196 cputime_zero) || 1197 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1198 !list_empty(¤t->signal->cpu_timers[0]) || 1199 !list_empty(¤t->signal->cpu_timers[1]) || 1200 !list_empty(¤t->signal->cpu_timers[2])) { 1201 /* 1202 * Have child wake up on its first tick to check 1203 * for process CPU timers. 1204 */ 1205 p->it_prof_expires = jiffies_to_cputime(1); 1206 } 1207 } 1208 1209 if (likely(p->pid)) { 1210 list_add_tail(&p->sibling, &p->real_parent->children); 1211 if (unlikely(p->ptrace & PT_PTRACED)) 1212 __ptrace_link(p, current->parent); 1213 1214 if (thread_group_leader(p)) { 1215 if (clone_flags & CLONE_NEWPID) 1216 p->nsproxy->pid_ns->child_reaper = p; 1217 1218 p->signal->leader_pid = pid; 1219 p->signal->tty = current->signal->tty; 1220 set_task_pgrp(p, task_pgrp_nr(current)); 1221 set_task_session(p, task_session_nr(current)); 1222 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1223 attach_pid(p, PIDTYPE_SID, task_session(current)); 1224 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1225 __get_cpu_var(process_counts)++; 1226 } 1227 attach_pid(p, PIDTYPE_PID, pid); 1228 nr_threads++; 1229 } 1230 1231 total_forks++; 1232 spin_unlock(¤t->sighand->siglock); 1233 write_unlock_irq(&tasklist_lock); 1234 proc_fork_connector(p); 1235 cgroup_post_fork(p); 1236 return p; 1237 1238 bad_fork_free_pid: 1239 if (pid != &init_struct_pid) 1240 free_pid(pid); 1241 bad_fork_cleanup_io: 1242 put_io_context(p->io_context); 1243 bad_fork_cleanup_namespaces: 1244 exit_task_namespaces(p); 1245 bad_fork_cleanup_keys: 1246 exit_keys(p); 1247 bad_fork_cleanup_mm: 1248 if (p->mm) 1249 mmput(p->mm); 1250 bad_fork_cleanup_signal: 1251 cleanup_signal(p); 1252 bad_fork_cleanup_sighand: 1253 __cleanup_sighand(p->sighand); 1254 bad_fork_cleanup_fs: 1255 exit_fs(p); /* blocking */ 1256 bad_fork_cleanup_files: 1257 exit_files(p); /* blocking */ 1258 bad_fork_cleanup_semundo: 1259 exit_sem(p); 1260 bad_fork_cleanup_audit: 1261 audit_free(p); 1262 bad_fork_cleanup_security: 1263 security_task_free(p); 1264 bad_fork_cleanup_policy: 1265 #ifdef CONFIG_NUMA 1266 mpol_put(p->mempolicy); 1267 bad_fork_cleanup_cgroup: 1268 #endif 1269 cgroup_exit(p, cgroup_callbacks_done); 1270 delayacct_tsk_free(p); 1271 if (p->binfmt) 1272 module_put(p->binfmt->module); 1273 bad_fork_cleanup_put_domain: 1274 module_put(task_thread_info(p)->exec_domain->module); 1275 bad_fork_cleanup_count: 1276 put_group_info(p->group_info); 1277 atomic_dec(&p->user->processes); 1278 free_uid(p->user); 1279 bad_fork_free: 1280 free_task(p); 1281 fork_out: 1282 return ERR_PTR(retval); 1283 } 1284 1285 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1286 { 1287 memset(regs, 0, sizeof(struct pt_regs)); 1288 return regs; 1289 } 1290 1291 struct task_struct * __cpuinit fork_idle(int cpu) 1292 { 1293 struct task_struct *task; 1294 struct pt_regs regs; 1295 1296 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1297 &init_struct_pid); 1298 if (!IS_ERR(task)) 1299 init_idle(task, cpu); 1300 1301 return task; 1302 } 1303 1304 static int fork_traceflag(unsigned clone_flags) 1305 { 1306 if (clone_flags & CLONE_UNTRACED) 1307 return 0; 1308 else if (clone_flags & CLONE_VFORK) { 1309 if (current->ptrace & PT_TRACE_VFORK) 1310 return PTRACE_EVENT_VFORK; 1311 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1312 if (current->ptrace & PT_TRACE_CLONE) 1313 return PTRACE_EVENT_CLONE; 1314 } else if (current->ptrace & PT_TRACE_FORK) 1315 return PTRACE_EVENT_FORK; 1316 1317 return 0; 1318 } 1319 1320 /* 1321 * Ok, this is the main fork-routine. 1322 * 1323 * It copies the process, and if successful kick-starts 1324 * it and waits for it to finish using the VM if required. 1325 */ 1326 long do_fork(unsigned long clone_flags, 1327 unsigned long stack_start, 1328 struct pt_regs *regs, 1329 unsigned long stack_size, 1330 int __user *parent_tidptr, 1331 int __user *child_tidptr) 1332 { 1333 struct task_struct *p; 1334 int trace = 0; 1335 long nr; 1336 1337 /* 1338 * We hope to recycle these flags after 2.6.26 1339 */ 1340 if (unlikely(clone_flags & CLONE_STOPPED)) { 1341 static int __read_mostly count = 100; 1342 1343 if (count > 0 && printk_ratelimit()) { 1344 char comm[TASK_COMM_LEN]; 1345 1346 count--; 1347 printk(KERN_INFO "fork(): process `%s' used deprecated " 1348 "clone flags 0x%lx\n", 1349 get_task_comm(comm, current), 1350 clone_flags & CLONE_STOPPED); 1351 } 1352 } 1353 1354 if (unlikely(current->ptrace)) { 1355 trace = fork_traceflag (clone_flags); 1356 if (trace) 1357 clone_flags |= CLONE_PTRACE; 1358 } 1359 1360 p = copy_process(clone_flags, stack_start, regs, stack_size, 1361 child_tidptr, NULL); 1362 /* 1363 * Do this prior waking up the new thread - the thread pointer 1364 * might get invalid after that point, if the thread exits quickly. 1365 */ 1366 if (!IS_ERR(p)) { 1367 struct completion vfork; 1368 1369 nr = task_pid_vnr(p); 1370 1371 if (clone_flags & CLONE_PARENT_SETTID) 1372 put_user(nr, parent_tidptr); 1373 1374 if (clone_flags & CLONE_VFORK) { 1375 p->vfork_done = &vfork; 1376 init_completion(&vfork); 1377 } 1378 1379 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1380 /* 1381 * We'll start up with an immediate SIGSTOP. 1382 */ 1383 sigaddset(&p->pending.signal, SIGSTOP); 1384 set_tsk_thread_flag(p, TIF_SIGPENDING); 1385 } 1386 1387 if (!(clone_flags & CLONE_STOPPED)) 1388 wake_up_new_task(p, clone_flags); 1389 else 1390 __set_task_state(p, TASK_STOPPED); 1391 1392 if (unlikely (trace)) { 1393 current->ptrace_message = nr; 1394 ptrace_notify ((trace << 8) | SIGTRAP); 1395 } 1396 1397 if (clone_flags & CLONE_VFORK) { 1398 freezer_do_not_count(); 1399 wait_for_completion(&vfork); 1400 freezer_count(); 1401 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1402 current->ptrace_message = nr; 1403 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1404 } 1405 } 1406 } else { 1407 nr = PTR_ERR(p); 1408 } 1409 return nr; 1410 } 1411 1412 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1413 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1414 #endif 1415 1416 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1417 { 1418 struct sighand_struct *sighand = data; 1419 1420 spin_lock_init(&sighand->siglock); 1421 init_waitqueue_head(&sighand->signalfd_wqh); 1422 } 1423 1424 void __init proc_caches_init(void) 1425 { 1426 sighand_cachep = kmem_cache_create("sighand_cache", 1427 sizeof(struct sighand_struct), 0, 1428 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1429 sighand_ctor); 1430 signal_cachep = kmem_cache_create("signal_cache", 1431 sizeof(struct signal_struct), 0, 1432 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1433 files_cachep = kmem_cache_create("files_cache", 1434 sizeof(struct files_struct), 0, 1435 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1436 fs_cachep = kmem_cache_create("fs_cache", 1437 sizeof(struct fs_struct), 0, 1438 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1439 vm_area_cachep = kmem_cache_create("vm_area_struct", 1440 sizeof(struct vm_area_struct), 0, 1441 SLAB_PANIC, NULL); 1442 mm_cachep = kmem_cache_create("mm_struct", 1443 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1444 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1445 } 1446 1447 /* 1448 * Check constraints on flags passed to the unshare system call and 1449 * force unsharing of additional process context as appropriate. 1450 */ 1451 static void check_unshare_flags(unsigned long *flags_ptr) 1452 { 1453 /* 1454 * If unsharing a thread from a thread group, must also 1455 * unshare vm. 1456 */ 1457 if (*flags_ptr & CLONE_THREAD) 1458 *flags_ptr |= CLONE_VM; 1459 1460 /* 1461 * If unsharing vm, must also unshare signal handlers. 1462 */ 1463 if (*flags_ptr & CLONE_VM) 1464 *flags_ptr |= CLONE_SIGHAND; 1465 1466 /* 1467 * If unsharing signal handlers and the task was created 1468 * using CLONE_THREAD, then must unshare the thread 1469 */ 1470 if ((*flags_ptr & CLONE_SIGHAND) && 1471 (atomic_read(¤t->signal->count) > 1)) 1472 *flags_ptr |= CLONE_THREAD; 1473 1474 /* 1475 * If unsharing namespace, must also unshare filesystem information. 1476 */ 1477 if (*flags_ptr & CLONE_NEWNS) 1478 *flags_ptr |= CLONE_FS; 1479 } 1480 1481 /* 1482 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1483 */ 1484 static int unshare_thread(unsigned long unshare_flags) 1485 { 1486 if (unshare_flags & CLONE_THREAD) 1487 return -EINVAL; 1488 1489 return 0; 1490 } 1491 1492 /* 1493 * Unshare the filesystem structure if it is being shared 1494 */ 1495 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1496 { 1497 struct fs_struct *fs = current->fs; 1498 1499 if ((unshare_flags & CLONE_FS) && 1500 (fs && atomic_read(&fs->count) > 1)) { 1501 *new_fsp = __copy_fs_struct(current->fs); 1502 if (!*new_fsp) 1503 return -ENOMEM; 1504 } 1505 1506 return 0; 1507 } 1508 1509 /* 1510 * Unsharing of sighand is not supported yet 1511 */ 1512 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1513 { 1514 struct sighand_struct *sigh = current->sighand; 1515 1516 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1517 return -EINVAL; 1518 else 1519 return 0; 1520 } 1521 1522 /* 1523 * Unshare vm if it is being shared 1524 */ 1525 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1526 { 1527 struct mm_struct *mm = current->mm; 1528 1529 if ((unshare_flags & CLONE_VM) && 1530 (mm && atomic_read(&mm->mm_users) > 1)) { 1531 return -EINVAL; 1532 } 1533 1534 return 0; 1535 } 1536 1537 /* 1538 * Unshare file descriptor table if it is being shared 1539 */ 1540 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1541 { 1542 struct files_struct *fd = current->files; 1543 int error = 0; 1544 1545 if ((unshare_flags & CLONE_FILES) && 1546 (fd && atomic_read(&fd->count) > 1)) { 1547 *new_fdp = dup_fd(fd, &error); 1548 if (!*new_fdp) 1549 return error; 1550 } 1551 1552 return 0; 1553 } 1554 1555 /* 1556 * unshare allows a process to 'unshare' part of the process 1557 * context which was originally shared using clone. copy_* 1558 * functions used by do_fork() cannot be used here directly 1559 * because they modify an inactive task_struct that is being 1560 * constructed. Here we are modifying the current, active, 1561 * task_struct. 1562 */ 1563 asmlinkage long sys_unshare(unsigned long unshare_flags) 1564 { 1565 int err = 0; 1566 struct fs_struct *fs, *new_fs = NULL; 1567 struct sighand_struct *new_sigh = NULL; 1568 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1569 struct files_struct *fd, *new_fd = NULL; 1570 struct nsproxy *new_nsproxy = NULL; 1571 int do_sysvsem = 0; 1572 1573 check_unshare_flags(&unshare_flags); 1574 1575 /* Return -EINVAL for all unsupported flags */ 1576 err = -EINVAL; 1577 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1578 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1579 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1580 CLONE_NEWNET)) 1581 goto bad_unshare_out; 1582 1583 /* 1584 * CLONE_NEWIPC must also detach from the undolist: after switching 1585 * to a new ipc namespace, the semaphore arrays from the old 1586 * namespace are unreachable. 1587 */ 1588 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1589 do_sysvsem = 1; 1590 if ((err = unshare_thread(unshare_flags))) 1591 goto bad_unshare_out; 1592 if ((err = unshare_fs(unshare_flags, &new_fs))) 1593 goto bad_unshare_cleanup_thread; 1594 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1595 goto bad_unshare_cleanup_fs; 1596 if ((err = unshare_vm(unshare_flags, &new_mm))) 1597 goto bad_unshare_cleanup_sigh; 1598 if ((err = unshare_fd(unshare_flags, &new_fd))) 1599 goto bad_unshare_cleanup_vm; 1600 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1601 new_fs))) 1602 goto bad_unshare_cleanup_fd; 1603 1604 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1605 if (do_sysvsem) { 1606 /* 1607 * CLONE_SYSVSEM is equivalent to sys_exit(). 1608 */ 1609 exit_sem(current); 1610 } 1611 1612 if (new_nsproxy) { 1613 switch_task_namespaces(current, new_nsproxy); 1614 new_nsproxy = NULL; 1615 } 1616 1617 task_lock(current); 1618 1619 if (new_fs) { 1620 fs = current->fs; 1621 current->fs = new_fs; 1622 new_fs = fs; 1623 } 1624 1625 if (new_mm) { 1626 mm = current->mm; 1627 active_mm = current->active_mm; 1628 current->mm = new_mm; 1629 current->active_mm = new_mm; 1630 activate_mm(active_mm, new_mm); 1631 new_mm = mm; 1632 } 1633 1634 if (new_fd) { 1635 fd = current->files; 1636 current->files = new_fd; 1637 new_fd = fd; 1638 } 1639 1640 task_unlock(current); 1641 } 1642 1643 if (new_nsproxy) 1644 put_nsproxy(new_nsproxy); 1645 1646 bad_unshare_cleanup_fd: 1647 if (new_fd) 1648 put_files_struct(new_fd); 1649 1650 bad_unshare_cleanup_vm: 1651 if (new_mm) 1652 mmput(new_mm); 1653 1654 bad_unshare_cleanup_sigh: 1655 if (new_sigh) 1656 if (atomic_dec_and_test(&new_sigh->count)) 1657 kmem_cache_free(sighand_cachep, new_sigh); 1658 1659 bad_unshare_cleanup_fs: 1660 if (new_fs) 1661 put_fs_struct(new_fs); 1662 1663 bad_unshare_cleanup_thread: 1664 bad_unshare_out: 1665 return err; 1666 } 1667 1668 /* 1669 * Helper to unshare the files of the current task. 1670 * We don't want to expose copy_files internals to 1671 * the exec layer of the kernel. 1672 */ 1673 1674 int unshare_files(struct files_struct **displaced) 1675 { 1676 struct task_struct *task = current; 1677 struct files_struct *copy = NULL; 1678 int error; 1679 1680 error = unshare_fd(CLONE_FILES, ©); 1681 if (error || !copy) { 1682 *displaced = NULL; 1683 return error; 1684 } 1685 *displaced = task->files; 1686 task_lock(task); 1687 task->files = copy; 1688 task_unlock(task); 1689 return 0; 1690 } 1691