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 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 97 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 98 { 99 #ifdef CONFIG_DEBUG_STACK_USAGE 100 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 101 #else 102 gfp_t mask = GFP_KERNEL; 103 #endif 104 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 105 } 106 107 static inline void free_thread_info(struct thread_info *ti) 108 { 109 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 110 } 111 #endif 112 113 /* SLAB cache for signal_struct structures (tsk->signal) */ 114 static struct kmem_cache *signal_cachep; 115 116 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 117 struct kmem_cache *sighand_cachep; 118 119 /* SLAB cache for files_struct structures (tsk->files) */ 120 struct kmem_cache *files_cachep; 121 122 /* SLAB cache for fs_struct structures (tsk->fs) */ 123 struct kmem_cache *fs_cachep; 124 125 /* SLAB cache for vm_area_struct structures */ 126 struct kmem_cache *vm_area_cachep; 127 128 /* SLAB cache for mm_struct structures (tsk->mm) */ 129 static struct kmem_cache *mm_cachep; 130 131 void free_task(struct task_struct *tsk) 132 { 133 prop_local_destroy_single(&tsk->dirties); 134 free_thread_info(tsk->stack); 135 rt_mutex_debug_task_free(tsk); 136 free_task_struct(tsk); 137 } 138 EXPORT_SYMBOL(free_task); 139 140 void __put_task_struct(struct task_struct *tsk) 141 { 142 WARN_ON(!tsk->exit_state); 143 WARN_ON(atomic_read(&tsk->usage)); 144 WARN_ON(tsk == current); 145 146 security_task_free(tsk); 147 free_uid(tsk->user); 148 put_group_info(tsk->group_info); 149 delayacct_tsk_free(tsk); 150 151 if (!profile_handoff_task(tsk)) 152 free_task(tsk); 153 } 154 155 /* 156 * macro override instead of weak attribute alias, to workaround 157 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 158 */ 159 #ifndef arch_task_cache_init 160 #define arch_task_cache_init() 161 #endif 162 163 void __init fork_init(unsigned long mempages) 164 { 165 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 166 #ifndef ARCH_MIN_TASKALIGN 167 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 168 #endif 169 /* create a slab on which task_structs can be allocated */ 170 task_struct_cachep = 171 kmem_cache_create("task_struct", sizeof(struct task_struct), 172 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 173 #endif 174 175 /* do the arch specific task caches init */ 176 arch_task_cache_init(); 177 178 /* 179 * The default maximum number of threads is set to a safe 180 * value: the thread structures can take up at most half 181 * of memory. 182 */ 183 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 184 185 /* 186 * we need to allow at least 20 threads to boot a system 187 */ 188 if(max_threads < 20) 189 max_threads = 20; 190 191 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 192 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 193 init_task.signal->rlim[RLIMIT_SIGPENDING] = 194 init_task.signal->rlim[RLIMIT_NPROC]; 195 } 196 197 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 198 struct task_struct *src) 199 { 200 *dst = *src; 201 return 0; 202 } 203 204 static struct task_struct *dup_task_struct(struct task_struct *orig) 205 { 206 struct task_struct *tsk; 207 struct thread_info *ti; 208 int err; 209 210 prepare_to_copy(orig); 211 212 tsk = alloc_task_struct(); 213 if (!tsk) 214 return NULL; 215 216 ti = alloc_thread_info(tsk); 217 if (!ti) { 218 free_task_struct(tsk); 219 return NULL; 220 } 221 222 err = arch_dup_task_struct(tsk, orig); 223 if (err) 224 goto out; 225 226 tsk->stack = ti; 227 228 err = prop_local_init_single(&tsk->dirties); 229 if (err) 230 goto out; 231 232 setup_thread_stack(tsk, orig); 233 234 #ifdef CONFIG_CC_STACKPROTECTOR 235 tsk->stack_canary = get_random_int(); 236 #endif 237 238 /* One for us, one for whoever does the "release_task()" (usually parent) */ 239 atomic_set(&tsk->usage,2); 240 atomic_set(&tsk->fs_excl, 0); 241 #ifdef CONFIG_BLK_DEV_IO_TRACE 242 tsk->btrace_seq = 0; 243 #endif 244 tsk->splice_pipe = NULL; 245 return tsk; 246 247 out: 248 free_thread_info(ti); 249 free_task_struct(tsk); 250 return NULL; 251 } 252 253 #ifdef CONFIG_MMU 254 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 255 { 256 struct vm_area_struct *mpnt, *tmp, **pprev; 257 struct rb_node **rb_link, *rb_parent; 258 int retval; 259 unsigned long charge; 260 struct mempolicy *pol; 261 262 down_write(&oldmm->mmap_sem); 263 flush_cache_dup_mm(oldmm); 264 /* 265 * Not linked in yet - no deadlock potential: 266 */ 267 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 268 269 mm->locked_vm = 0; 270 mm->mmap = NULL; 271 mm->mmap_cache = NULL; 272 mm->free_area_cache = oldmm->mmap_base; 273 mm->cached_hole_size = ~0UL; 274 mm->map_count = 0; 275 cpus_clear(mm->cpu_vm_mask); 276 mm->mm_rb = RB_ROOT; 277 rb_link = &mm->mm_rb.rb_node; 278 rb_parent = NULL; 279 pprev = &mm->mmap; 280 281 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 282 struct file *file; 283 284 if (mpnt->vm_flags & VM_DONTCOPY) { 285 long pages = vma_pages(mpnt); 286 mm->total_vm -= pages; 287 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 288 -pages); 289 continue; 290 } 291 charge = 0; 292 if (mpnt->vm_flags & VM_ACCOUNT) { 293 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 294 if (security_vm_enough_memory(len)) 295 goto fail_nomem; 296 charge = len; 297 } 298 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 299 if (!tmp) 300 goto fail_nomem; 301 *tmp = *mpnt; 302 pol = mpol_dup(vma_policy(mpnt)); 303 retval = PTR_ERR(pol); 304 if (IS_ERR(pol)) 305 goto fail_nomem_policy; 306 vma_set_policy(tmp, pol); 307 tmp->vm_flags &= ~VM_LOCKED; 308 tmp->vm_mm = mm; 309 tmp->vm_next = NULL; 310 anon_vma_link(tmp); 311 file = tmp->vm_file; 312 if (file) { 313 struct inode *inode = file->f_path.dentry->d_inode; 314 get_file(file); 315 if (tmp->vm_flags & VM_DENYWRITE) 316 atomic_dec(&inode->i_writecount); 317 318 /* insert tmp into the share list, just after mpnt */ 319 spin_lock(&file->f_mapping->i_mmap_lock); 320 tmp->vm_truncate_count = mpnt->vm_truncate_count; 321 flush_dcache_mmap_lock(file->f_mapping); 322 vma_prio_tree_add(tmp, mpnt); 323 flush_dcache_mmap_unlock(file->f_mapping); 324 spin_unlock(&file->f_mapping->i_mmap_lock); 325 } 326 327 /* 328 * Clear hugetlb-related page reserves for children. This only 329 * affects MAP_PRIVATE mappings. Faults generated by the child 330 * are not guaranteed to succeed, even if read-only 331 */ 332 if (is_vm_hugetlb_page(tmp)) 333 reset_vma_resv_huge_pages(tmp); 334 335 /* 336 * Link in the new vma and copy the page table entries. 337 */ 338 *pprev = tmp; 339 pprev = &tmp->vm_next; 340 341 __vma_link_rb(mm, tmp, rb_link, rb_parent); 342 rb_link = &tmp->vm_rb.rb_right; 343 rb_parent = &tmp->vm_rb; 344 345 mm->map_count++; 346 retval = copy_page_range(mm, oldmm, mpnt); 347 348 if (tmp->vm_ops && tmp->vm_ops->open) 349 tmp->vm_ops->open(tmp); 350 351 if (retval) 352 goto out; 353 } 354 /* a new mm has just been created */ 355 arch_dup_mmap(oldmm, mm); 356 retval = 0; 357 out: 358 up_write(&mm->mmap_sem); 359 flush_tlb_mm(oldmm); 360 up_write(&oldmm->mmap_sem); 361 return retval; 362 fail_nomem_policy: 363 kmem_cache_free(vm_area_cachep, tmp); 364 fail_nomem: 365 retval = -ENOMEM; 366 vm_unacct_memory(charge); 367 goto out; 368 } 369 370 static inline int mm_alloc_pgd(struct mm_struct * mm) 371 { 372 mm->pgd = pgd_alloc(mm); 373 if (unlikely(!mm->pgd)) 374 return -ENOMEM; 375 return 0; 376 } 377 378 static inline void mm_free_pgd(struct mm_struct * mm) 379 { 380 pgd_free(mm, mm->pgd); 381 } 382 #else 383 #define dup_mmap(mm, oldmm) (0) 384 #define mm_alloc_pgd(mm) (0) 385 #define mm_free_pgd(mm) 386 #endif /* CONFIG_MMU */ 387 388 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 389 390 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 391 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 392 393 #include <linux/init_task.h> 394 395 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 396 { 397 atomic_set(&mm->mm_users, 1); 398 atomic_set(&mm->mm_count, 1); 399 init_rwsem(&mm->mmap_sem); 400 INIT_LIST_HEAD(&mm->mmlist); 401 mm->flags = (current->mm) ? current->mm->flags 402 : MMF_DUMP_FILTER_DEFAULT; 403 mm->core_waiters = 0; 404 mm->nr_ptes = 0; 405 set_mm_counter(mm, file_rss, 0); 406 set_mm_counter(mm, anon_rss, 0); 407 spin_lock_init(&mm->page_table_lock); 408 rwlock_init(&mm->ioctx_list_lock); 409 mm->ioctx_list = NULL; 410 mm->free_area_cache = TASK_UNMAPPED_BASE; 411 mm->cached_hole_size = ~0UL; 412 mm_init_owner(mm, p); 413 414 if (likely(!mm_alloc_pgd(mm))) { 415 mm->def_flags = 0; 416 return mm; 417 } 418 419 free_mm(mm); 420 return NULL; 421 } 422 423 /* 424 * Allocate and initialize an mm_struct. 425 */ 426 struct mm_struct * mm_alloc(void) 427 { 428 struct mm_struct * mm; 429 430 mm = allocate_mm(); 431 if (mm) { 432 memset(mm, 0, sizeof(*mm)); 433 mm = mm_init(mm, current); 434 } 435 return mm; 436 } 437 438 /* 439 * Called when the last reference to the mm 440 * is dropped: either by a lazy thread or by 441 * mmput. Free the page directory and the mm. 442 */ 443 void __mmdrop(struct mm_struct *mm) 444 { 445 BUG_ON(mm == &init_mm); 446 mm_free_pgd(mm); 447 destroy_context(mm); 448 free_mm(mm); 449 } 450 EXPORT_SYMBOL_GPL(__mmdrop); 451 452 /* 453 * Decrement the use count and release all resources for an mm. 454 */ 455 void mmput(struct mm_struct *mm) 456 { 457 might_sleep(); 458 459 if (atomic_dec_and_test(&mm->mm_users)) { 460 exit_aio(mm); 461 exit_mmap(mm); 462 set_mm_exe_file(mm, NULL); 463 if (!list_empty(&mm->mmlist)) { 464 spin_lock(&mmlist_lock); 465 list_del(&mm->mmlist); 466 spin_unlock(&mmlist_lock); 467 } 468 put_swap_token(mm); 469 mmdrop(mm); 470 } 471 } 472 EXPORT_SYMBOL_GPL(mmput); 473 474 /** 475 * get_task_mm - acquire a reference to the task's mm 476 * 477 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 478 * this kernel workthread has transiently adopted a user mm with use_mm, 479 * to do its AIO) is not set and if so returns a reference to it, after 480 * bumping up the use count. User must release the mm via mmput() 481 * after use. Typically used by /proc and ptrace. 482 */ 483 struct mm_struct *get_task_mm(struct task_struct *task) 484 { 485 struct mm_struct *mm; 486 487 task_lock(task); 488 mm = task->mm; 489 if (mm) { 490 if (task->flags & PF_BORROWED_MM) 491 mm = NULL; 492 else 493 atomic_inc(&mm->mm_users); 494 } 495 task_unlock(task); 496 return mm; 497 } 498 EXPORT_SYMBOL_GPL(get_task_mm); 499 500 /* Please note the differences between mmput and mm_release. 501 * mmput is called whenever we stop holding onto a mm_struct, 502 * error success whatever. 503 * 504 * mm_release is called after a mm_struct has been removed 505 * from the current process. 506 * 507 * This difference is important for error handling, when we 508 * only half set up a mm_struct for a new process and need to restore 509 * the old one. Because we mmput the new mm_struct before 510 * restoring the old one. . . 511 * Eric Biederman 10 January 1998 512 */ 513 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 514 { 515 struct completion *vfork_done = tsk->vfork_done; 516 517 /* Get rid of any cached register state */ 518 deactivate_mm(tsk, mm); 519 520 /* notify parent sleeping on vfork() */ 521 if (vfork_done) { 522 tsk->vfork_done = NULL; 523 complete(vfork_done); 524 } 525 526 /* 527 * If we're exiting normally, clear a user-space tid field if 528 * requested. We leave this alone when dying by signal, to leave 529 * the value intact in a core dump, and to save the unnecessary 530 * trouble otherwise. Userland only wants this done for a sys_exit. 531 */ 532 if (tsk->clear_child_tid 533 && !(tsk->flags & PF_SIGNALED) 534 && atomic_read(&mm->mm_users) > 1) { 535 u32 __user * tidptr = tsk->clear_child_tid; 536 tsk->clear_child_tid = NULL; 537 538 /* 539 * We don't check the error code - if userspace has 540 * not set up a proper pointer then tough luck. 541 */ 542 put_user(0, tidptr); 543 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 544 } 545 } 546 547 /* 548 * Allocate a new mm structure and copy contents from the 549 * mm structure of the passed in task structure. 550 */ 551 struct mm_struct *dup_mm(struct task_struct *tsk) 552 { 553 struct mm_struct *mm, *oldmm = current->mm; 554 int err; 555 556 if (!oldmm) 557 return NULL; 558 559 mm = allocate_mm(); 560 if (!mm) 561 goto fail_nomem; 562 563 memcpy(mm, oldmm, sizeof(*mm)); 564 565 /* Initializing for Swap token stuff */ 566 mm->token_priority = 0; 567 mm->last_interval = 0; 568 569 if (!mm_init(mm, tsk)) 570 goto fail_nomem; 571 572 if (init_new_context(tsk, mm)) 573 goto fail_nocontext; 574 575 dup_mm_exe_file(oldmm, mm); 576 577 err = dup_mmap(mm, oldmm); 578 if (err) 579 goto free_pt; 580 581 mm->hiwater_rss = get_mm_rss(mm); 582 mm->hiwater_vm = mm->total_vm; 583 584 return mm; 585 586 free_pt: 587 mmput(mm); 588 589 fail_nomem: 590 return NULL; 591 592 fail_nocontext: 593 /* 594 * If init_new_context() failed, we cannot use mmput() to free the mm 595 * because it calls destroy_context() 596 */ 597 mm_free_pgd(mm); 598 free_mm(mm); 599 return NULL; 600 } 601 602 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 603 { 604 struct mm_struct * mm, *oldmm; 605 int retval; 606 607 tsk->min_flt = tsk->maj_flt = 0; 608 tsk->nvcsw = tsk->nivcsw = 0; 609 610 tsk->mm = NULL; 611 tsk->active_mm = NULL; 612 613 /* 614 * Are we cloning a kernel thread? 615 * 616 * We need to steal a active VM for that.. 617 */ 618 oldmm = current->mm; 619 if (!oldmm) 620 return 0; 621 622 if (clone_flags & CLONE_VM) { 623 atomic_inc(&oldmm->mm_users); 624 mm = oldmm; 625 goto good_mm; 626 } 627 628 retval = -ENOMEM; 629 mm = dup_mm(tsk); 630 if (!mm) 631 goto fail_nomem; 632 633 good_mm: 634 /* Initializing for Swap token stuff */ 635 mm->token_priority = 0; 636 mm->last_interval = 0; 637 638 tsk->mm = mm; 639 tsk->active_mm = mm; 640 return 0; 641 642 fail_nomem: 643 return retval; 644 } 645 646 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 647 { 648 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 649 /* We don't need to lock fs - think why ;-) */ 650 if (fs) { 651 atomic_set(&fs->count, 1); 652 rwlock_init(&fs->lock); 653 fs->umask = old->umask; 654 read_lock(&old->lock); 655 fs->root = old->root; 656 path_get(&old->root); 657 fs->pwd = old->pwd; 658 path_get(&old->pwd); 659 if (old->altroot.dentry) { 660 fs->altroot = old->altroot; 661 path_get(&old->altroot); 662 } else { 663 fs->altroot.mnt = NULL; 664 fs->altroot.dentry = NULL; 665 } 666 read_unlock(&old->lock); 667 } 668 return fs; 669 } 670 671 struct fs_struct *copy_fs_struct(struct fs_struct *old) 672 { 673 return __copy_fs_struct(old); 674 } 675 676 EXPORT_SYMBOL_GPL(copy_fs_struct); 677 678 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 679 { 680 if (clone_flags & CLONE_FS) { 681 atomic_inc(¤t->fs->count); 682 return 0; 683 } 684 tsk->fs = __copy_fs_struct(current->fs); 685 if (!tsk->fs) 686 return -ENOMEM; 687 return 0; 688 } 689 690 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 691 { 692 struct files_struct *oldf, *newf; 693 int error = 0; 694 695 /* 696 * A background process may not have any files ... 697 */ 698 oldf = current->files; 699 if (!oldf) 700 goto out; 701 702 if (clone_flags & CLONE_FILES) { 703 atomic_inc(&oldf->count); 704 goto out; 705 } 706 707 newf = dup_fd(oldf, &error); 708 if (!newf) 709 goto out; 710 711 tsk->files = newf; 712 error = 0; 713 out: 714 return error; 715 } 716 717 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 718 { 719 #ifdef CONFIG_BLOCK 720 struct io_context *ioc = current->io_context; 721 722 if (!ioc) 723 return 0; 724 /* 725 * Share io context with parent, if CLONE_IO is set 726 */ 727 if (clone_flags & CLONE_IO) { 728 tsk->io_context = ioc_task_link(ioc); 729 if (unlikely(!tsk->io_context)) 730 return -ENOMEM; 731 } else if (ioprio_valid(ioc->ioprio)) { 732 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 733 if (unlikely(!tsk->io_context)) 734 return -ENOMEM; 735 736 tsk->io_context->ioprio = ioc->ioprio; 737 } 738 #endif 739 return 0; 740 } 741 742 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 743 { 744 struct sighand_struct *sig; 745 746 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 747 atomic_inc(¤t->sighand->count); 748 return 0; 749 } 750 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 751 rcu_assign_pointer(tsk->sighand, sig); 752 if (!sig) 753 return -ENOMEM; 754 atomic_set(&sig->count, 1); 755 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 756 return 0; 757 } 758 759 void __cleanup_sighand(struct sighand_struct *sighand) 760 { 761 if (atomic_dec_and_test(&sighand->count)) 762 kmem_cache_free(sighand_cachep, sighand); 763 } 764 765 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 766 { 767 struct signal_struct *sig; 768 int ret; 769 770 if (clone_flags & CLONE_THREAD) { 771 atomic_inc(¤t->signal->count); 772 atomic_inc(¤t->signal->live); 773 return 0; 774 } 775 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 776 tsk->signal = sig; 777 if (!sig) 778 return -ENOMEM; 779 780 ret = copy_thread_group_keys(tsk); 781 if (ret < 0) { 782 kmem_cache_free(signal_cachep, sig); 783 return ret; 784 } 785 786 atomic_set(&sig->count, 1); 787 atomic_set(&sig->live, 1); 788 init_waitqueue_head(&sig->wait_chldexit); 789 sig->flags = 0; 790 sig->group_exit_code = 0; 791 sig->group_exit_task = NULL; 792 sig->group_stop_count = 0; 793 sig->curr_target = tsk; 794 init_sigpending(&sig->shared_pending); 795 INIT_LIST_HEAD(&sig->posix_timers); 796 797 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 798 sig->it_real_incr.tv64 = 0; 799 sig->real_timer.function = it_real_fn; 800 801 sig->it_virt_expires = cputime_zero; 802 sig->it_virt_incr = cputime_zero; 803 sig->it_prof_expires = cputime_zero; 804 sig->it_prof_incr = cputime_zero; 805 806 sig->leader = 0; /* session leadership doesn't inherit */ 807 sig->tty_old_pgrp = NULL; 808 809 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 810 sig->gtime = cputime_zero; 811 sig->cgtime = cputime_zero; 812 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 813 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 814 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 815 sig->sum_sched_runtime = 0; 816 INIT_LIST_HEAD(&sig->cpu_timers[0]); 817 INIT_LIST_HEAD(&sig->cpu_timers[1]); 818 INIT_LIST_HEAD(&sig->cpu_timers[2]); 819 taskstats_tgid_init(sig); 820 821 task_lock(current->group_leader); 822 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 823 task_unlock(current->group_leader); 824 825 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 826 /* 827 * New sole thread in the process gets an expiry time 828 * of the whole CPU time limit. 829 */ 830 tsk->it_prof_expires = 831 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 832 } 833 acct_init_pacct(&sig->pacct); 834 835 tty_audit_fork(sig); 836 837 return 0; 838 } 839 840 void __cleanup_signal(struct signal_struct *sig) 841 { 842 exit_thread_group_keys(sig); 843 kmem_cache_free(signal_cachep, sig); 844 } 845 846 static void cleanup_signal(struct task_struct *tsk) 847 { 848 struct signal_struct *sig = tsk->signal; 849 850 atomic_dec(&sig->live); 851 852 if (atomic_dec_and_test(&sig->count)) 853 __cleanup_signal(sig); 854 } 855 856 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 857 { 858 unsigned long new_flags = p->flags; 859 860 new_flags &= ~PF_SUPERPRIV; 861 new_flags |= PF_FORKNOEXEC; 862 if (!(clone_flags & CLONE_PTRACE)) 863 p->ptrace = 0; 864 p->flags = new_flags; 865 clear_freeze_flag(p); 866 } 867 868 asmlinkage long sys_set_tid_address(int __user *tidptr) 869 { 870 current->clear_child_tid = tidptr; 871 872 return task_pid_vnr(current); 873 } 874 875 static void rt_mutex_init_task(struct task_struct *p) 876 { 877 spin_lock_init(&p->pi_lock); 878 #ifdef CONFIG_RT_MUTEXES 879 plist_head_init(&p->pi_waiters, &p->pi_lock); 880 p->pi_blocked_on = NULL; 881 #endif 882 } 883 884 #ifdef CONFIG_MM_OWNER 885 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 886 { 887 mm->owner = p; 888 } 889 #endif /* CONFIG_MM_OWNER */ 890 891 /* 892 * This creates a new process as a copy of the old one, 893 * but does not actually start it yet. 894 * 895 * It copies the registers, and all the appropriate 896 * parts of the process environment (as per the clone 897 * flags). The actual kick-off is left to the caller. 898 */ 899 static struct task_struct *copy_process(unsigned long clone_flags, 900 unsigned long stack_start, 901 struct pt_regs *regs, 902 unsigned long stack_size, 903 int __user *child_tidptr, 904 struct pid *pid) 905 { 906 int retval; 907 struct task_struct *p; 908 int cgroup_callbacks_done = 0; 909 910 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 911 return ERR_PTR(-EINVAL); 912 913 /* 914 * Thread groups must share signals as well, and detached threads 915 * can only be started up within the thread group. 916 */ 917 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 918 return ERR_PTR(-EINVAL); 919 920 /* 921 * Shared signal handlers imply shared VM. By way of the above, 922 * thread groups also imply shared VM. Blocking this case allows 923 * for various simplifications in other code. 924 */ 925 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 926 return ERR_PTR(-EINVAL); 927 928 retval = security_task_create(clone_flags); 929 if (retval) 930 goto fork_out; 931 932 retval = -ENOMEM; 933 p = dup_task_struct(current); 934 if (!p) 935 goto fork_out; 936 937 rt_mutex_init_task(p); 938 939 #ifdef CONFIG_PROVE_LOCKING 940 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 941 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 942 #endif 943 retval = -EAGAIN; 944 if (atomic_read(&p->user->processes) >= 945 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 946 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 947 p->user != current->nsproxy->user_ns->root_user) 948 goto bad_fork_free; 949 } 950 951 atomic_inc(&p->user->__count); 952 atomic_inc(&p->user->processes); 953 get_group_info(p->group_info); 954 955 /* 956 * If multiple threads are within copy_process(), then this check 957 * triggers too late. This doesn't hurt, the check is only there 958 * to stop root fork bombs. 959 */ 960 if (nr_threads >= max_threads) 961 goto bad_fork_cleanup_count; 962 963 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 964 goto bad_fork_cleanup_count; 965 966 if (p->binfmt && !try_module_get(p->binfmt->module)) 967 goto bad_fork_cleanup_put_domain; 968 969 p->did_exec = 0; 970 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 971 copy_flags(clone_flags, p); 972 INIT_LIST_HEAD(&p->children); 973 INIT_LIST_HEAD(&p->sibling); 974 #ifdef CONFIG_PREEMPT_RCU 975 p->rcu_read_lock_nesting = 0; 976 p->rcu_flipctr_idx = 0; 977 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 978 p->vfork_done = NULL; 979 spin_lock_init(&p->alloc_lock); 980 981 clear_tsk_thread_flag(p, TIF_SIGPENDING); 982 init_sigpending(&p->pending); 983 984 p->utime = cputime_zero; 985 p->stime = cputime_zero; 986 p->gtime = cputime_zero; 987 p->utimescaled = cputime_zero; 988 p->stimescaled = cputime_zero; 989 p->prev_utime = cputime_zero; 990 p->prev_stime = cputime_zero; 991 992 #ifdef CONFIG_DETECT_SOFTLOCKUP 993 p->last_switch_count = 0; 994 p->last_switch_timestamp = 0; 995 #endif 996 997 #ifdef CONFIG_TASK_XACCT 998 p->rchar = 0; /* I/O counter: bytes read */ 999 p->wchar = 0; /* I/O counter: bytes written */ 1000 p->syscr = 0; /* I/O counter: read syscalls */ 1001 p->syscw = 0; /* I/O counter: write syscalls */ 1002 #endif 1003 task_io_accounting_init(p); 1004 acct_clear_integrals(p); 1005 1006 p->it_virt_expires = cputime_zero; 1007 p->it_prof_expires = cputime_zero; 1008 p->it_sched_expires = 0; 1009 INIT_LIST_HEAD(&p->cpu_timers[0]); 1010 INIT_LIST_HEAD(&p->cpu_timers[1]); 1011 INIT_LIST_HEAD(&p->cpu_timers[2]); 1012 1013 p->lock_depth = -1; /* -1 = no lock */ 1014 do_posix_clock_monotonic_gettime(&p->start_time); 1015 p->real_start_time = p->start_time; 1016 monotonic_to_bootbased(&p->real_start_time); 1017 #ifdef CONFIG_SECURITY 1018 p->security = NULL; 1019 #endif 1020 p->cap_bset = current->cap_bset; 1021 p->io_context = NULL; 1022 p->audit_context = NULL; 1023 cgroup_fork(p); 1024 #ifdef CONFIG_NUMA 1025 p->mempolicy = mpol_dup(p->mempolicy); 1026 if (IS_ERR(p->mempolicy)) { 1027 retval = PTR_ERR(p->mempolicy); 1028 p->mempolicy = NULL; 1029 goto bad_fork_cleanup_cgroup; 1030 } 1031 mpol_fix_fork_child_flag(p); 1032 #endif 1033 #ifdef CONFIG_TRACE_IRQFLAGS 1034 p->irq_events = 0; 1035 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1036 p->hardirqs_enabled = 1; 1037 #else 1038 p->hardirqs_enabled = 0; 1039 #endif 1040 p->hardirq_enable_ip = 0; 1041 p->hardirq_enable_event = 0; 1042 p->hardirq_disable_ip = _THIS_IP_; 1043 p->hardirq_disable_event = 0; 1044 p->softirqs_enabled = 1; 1045 p->softirq_enable_ip = _THIS_IP_; 1046 p->softirq_enable_event = 0; 1047 p->softirq_disable_ip = 0; 1048 p->softirq_disable_event = 0; 1049 p->hardirq_context = 0; 1050 p->softirq_context = 0; 1051 #endif 1052 #ifdef CONFIG_LOCKDEP 1053 p->lockdep_depth = 0; /* no locks held yet */ 1054 p->curr_chain_key = 0; 1055 p->lockdep_recursion = 0; 1056 #endif 1057 1058 #ifdef CONFIG_DEBUG_MUTEXES 1059 p->blocked_on = NULL; /* not blocked yet */ 1060 #endif 1061 1062 /* Perform scheduler related setup. Assign this task to a CPU. */ 1063 sched_fork(p, clone_flags); 1064 1065 if ((retval = security_task_alloc(p))) 1066 goto bad_fork_cleanup_policy; 1067 if ((retval = audit_alloc(p))) 1068 goto bad_fork_cleanup_security; 1069 /* copy all the process information */ 1070 if ((retval = copy_semundo(clone_flags, p))) 1071 goto bad_fork_cleanup_audit; 1072 if ((retval = copy_files(clone_flags, p))) 1073 goto bad_fork_cleanup_semundo; 1074 if ((retval = copy_fs(clone_flags, p))) 1075 goto bad_fork_cleanup_files; 1076 if ((retval = copy_sighand(clone_flags, p))) 1077 goto bad_fork_cleanup_fs; 1078 if ((retval = copy_signal(clone_flags, p))) 1079 goto bad_fork_cleanup_sighand; 1080 if ((retval = copy_mm(clone_flags, p))) 1081 goto bad_fork_cleanup_signal; 1082 if ((retval = copy_keys(clone_flags, p))) 1083 goto bad_fork_cleanup_mm; 1084 if ((retval = copy_namespaces(clone_flags, p))) 1085 goto bad_fork_cleanup_keys; 1086 if ((retval = copy_io(clone_flags, p))) 1087 goto bad_fork_cleanup_namespaces; 1088 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1089 if (retval) 1090 goto bad_fork_cleanup_io; 1091 1092 if (pid != &init_struct_pid) { 1093 retval = -ENOMEM; 1094 pid = alloc_pid(task_active_pid_ns(p)); 1095 if (!pid) 1096 goto bad_fork_cleanup_io; 1097 1098 if (clone_flags & CLONE_NEWPID) { 1099 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1100 if (retval < 0) 1101 goto bad_fork_free_pid; 1102 } 1103 } 1104 1105 p->pid = pid_nr(pid); 1106 p->tgid = p->pid; 1107 if (clone_flags & CLONE_THREAD) 1108 p->tgid = current->tgid; 1109 1110 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1111 /* 1112 * Clear TID on mm_release()? 1113 */ 1114 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1115 #ifdef CONFIG_FUTEX 1116 p->robust_list = NULL; 1117 #ifdef CONFIG_COMPAT 1118 p->compat_robust_list = NULL; 1119 #endif 1120 INIT_LIST_HEAD(&p->pi_state_list); 1121 p->pi_state_cache = NULL; 1122 #endif 1123 /* 1124 * sigaltstack should be cleared when sharing the same VM 1125 */ 1126 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1127 p->sas_ss_sp = p->sas_ss_size = 0; 1128 1129 /* 1130 * Syscall tracing should be turned off in the child regardless 1131 * of CLONE_PTRACE. 1132 */ 1133 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1134 #ifdef TIF_SYSCALL_EMU 1135 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1136 #endif 1137 clear_all_latency_tracing(p); 1138 1139 /* Our parent execution domain becomes current domain 1140 These must match for thread signalling to apply */ 1141 p->parent_exec_id = p->self_exec_id; 1142 1143 /* ok, now we should be set up.. */ 1144 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1145 p->pdeath_signal = 0; 1146 p->exit_state = 0; 1147 1148 /* 1149 * Ok, make it visible to the rest of the system. 1150 * We dont wake it up yet. 1151 */ 1152 p->group_leader = p; 1153 INIT_LIST_HEAD(&p->thread_group); 1154 INIT_LIST_HEAD(&p->ptrace_entry); 1155 INIT_LIST_HEAD(&p->ptraced); 1156 1157 /* Now that the task is set up, run cgroup callbacks if 1158 * necessary. We need to run them before the task is visible 1159 * on the tasklist. */ 1160 cgroup_fork_callbacks(p); 1161 cgroup_callbacks_done = 1; 1162 1163 /* Need tasklist lock for parent etc handling! */ 1164 write_lock_irq(&tasklist_lock); 1165 1166 /* 1167 * The task hasn't been attached yet, so its cpus_allowed mask will 1168 * not be changed, nor will its assigned CPU. 1169 * 1170 * The cpus_allowed mask of the parent may have changed after it was 1171 * copied first time - so re-copy it here, then check the child's CPU 1172 * to ensure it is on a valid CPU (and if not, just force it back to 1173 * parent's CPU). This avoids alot of nasty races. 1174 */ 1175 p->cpus_allowed = current->cpus_allowed; 1176 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1177 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1178 !cpu_online(task_cpu(p)))) 1179 set_task_cpu(p, smp_processor_id()); 1180 1181 /* CLONE_PARENT re-uses the old parent */ 1182 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1183 p->real_parent = current->real_parent; 1184 else 1185 p->real_parent = current; 1186 p->parent = p->real_parent; 1187 1188 spin_lock(¤t->sighand->siglock); 1189 1190 /* 1191 * Process group and session signals need to be delivered to just the 1192 * parent before the fork or both the parent and the child after the 1193 * fork. Restart if a signal comes in before we add the new process to 1194 * it's process group. 1195 * A fatal signal pending means that current will exit, so the new 1196 * thread can't slip out of an OOM kill (or normal SIGKILL). 1197 */ 1198 recalc_sigpending(); 1199 if (signal_pending(current)) { 1200 spin_unlock(¤t->sighand->siglock); 1201 write_unlock_irq(&tasklist_lock); 1202 retval = -ERESTARTNOINTR; 1203 goto bad_fork_free_pid; 1204 } 1205 1206 if (clone_flags & CLONE_THREAD) { 1207 p->group_leader = current->group_leader; 1208 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1209 1210 if (!cputime_eq(current->signal->it_virt_expires, 1211 cputime_zero) || 1212 !cputime_eq(current->signal->it_prof_expires, 1213 cputime_zero) || 1214 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1215 !list_empty(¤t->signal->cpu_timers[0]) || 1216 !list_empty(¤t->signal->cpu_timers[1]) || 1217 !list_empty(¤t->signal->cpu_timers[2])) { 1218 /* 1219 * Have child wake up on its first tick to check 1220 * for process CPU timers. 1221 */ 1222 p->it_prof_expires = jiffies_to_cputime(1); 1223 } 1224 } 1225 1226 if (likely(p->pid)) { 1227 list_add_tail(&p->sibling, &p->real_parent->children); 1228 if (unlikely(p->ptrace & PT_PTRACED)) 1229 __ptrace_link(p, current->parent); 1230 1231 if (thread_group_leader(p)) { 1232 if (clone_flags & CLONE_NEWPID) 1233 p->nsproxy->pid_ns->child_reaper = p; 1234 1235 p->signal->leader_pid = pid; 1236 p->signal->tty = current->signal->tty; 1237 set_task_pgrp(p, task_pgrp_nr(current)); 1238 set_task_session(p, task_session_nr(current)); 1239 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1240 attach_pid(p, PIDTYPE_SID, task_session(current)); 1241 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1242 __get_cpu_var(process_counts)++; 1243 } 1244 attach_pid(p, PIDTYPE_PID, pid); 1245 nr_threads++; 1246 } 1247 1248 total_forks++; 1249 spin_unlock(¤t->sighand->siglock); 1250 write_unlock_irq(&tasklist_lock); 1251 proc_fork_connector(p); 1252 cgroup_post_fork(p); 1253 return p; 1254 1255 bad_fork_free_pid: 1256 if (pid != &init_struct_pid) 1257 free_pid(pid); 1258 bad_fork_cleanup_io: 1259 put_io_context(p->io_context); 1260 bad_fork_cleanup_namespaces: 1261 exit_task_namespaces(p); 1262 bad_fork_cleanup_keys: 1263 exit_keys(p); 1264 bad_fork_cleanup_mm: 1265 if (p->mm) 1266 mmput(p->mm); 1267 bad_fork_cleanup_signal: 1268 cleanup_signal(p); 1269 bad_fork_cleanup_sighand: 1270 __cleanup_sighand(p->sighand); 1271 bad_fork_cleanup_fs: 1272 exit_fs(p); /* blocking */ 1273 bad_fork_cleanup_files: 1274 exit_files(p); /* blocking */ 1275 bad_fork_cleanup_semundo: 1276 exit_sem(p); 1277 bad_fork_cleanup_audit: 1278 audit_free(p); 1279 bad_fork_cleanup_security: 1280 security_task_free(p); 1281 bad_fork_cleanup_policy: 1282 #ifdef CONFIG_NUMA 1283 mpol_put(p->mempolicy); 1284 bad_fork_cleanup_cgroup: 1285 #endif 1286 cgroup_exit(p, cgroup_callbacks_done); 1287 delayacct_tsk_free(p); 1288 if (p->binfmt) 1289 module_put(p->binfmt->module); 1290 bad_fork_cleanup_put_domain: 1291 module_put(task_thread_info(p)->exec_domain->module); 1292 bad_fork_cleanup_count: 1293 put_group_info(p->group_info); 1294 atomic_dec(&p->user->processes); 1295 free_uid(p->user); 1296 bad_fork_free: 1297 free_task(p); 1298 fork_out: 1299 return ERR_PTR(retval); 1300 } 1301 1302 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1303 { 1304 memset(regs, 0, sizeof(struct pt_regs)); 1305 return regs; 1306 } 1307 1308 struct task_struct * __cpuinit fork_idle(int cpu) 1309 { 1310 struct task_struct *task; 1311 struct pt_regs regs; 1312 1313 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1314 &init_struct_pid); 1315 if (!IS_ERR(task)) 1316 init_idle(task, cpu); 1317 1318 return task; 1319 } 1320 1321 static int fork_traceflag(unsigned clone_flags) 1322 { 1323 if (clone_flags & CLONE_UNTRACED) 1324 return 0; 1325 else if (clone_flags & CLONE_VFORK) { 1326 if (current->ptrace & PT_TRACE_VFORK) 1327 return PTRACE_EVENT_VFORK; 1328 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1329 if (current->ptrace & PT_TRACE_CLONE) 1330 return PTRACE_EVENT_CLONE; 1331 } else if (current->ptrace & PT_TRACE_FORK) 1332 return PTRACE_EVENT_FORK; 1333 1334 return 0; 1335 } 1336 1337 /* 1338 * Ok, this is the main fork-routine. 1339 * 1340 * It copies the process, and if successful kick-starts 1341 * it and waits for it to finish using the VM if required. 1342 */ 1343 long do_fork(unsigned long clone_flags, 1344 unsigned long stack_start, 1345 struct pt_regs *regs, 1346 unsigned long stack_size, 1347 int __user *parent_tidptr, 1348 int __user *child_tidptr) 1349 { 1350 struct task_struct *p; 1351 int trace = 0; 1352 long nr; 1353 1354 /* 1355 * We hope to recycle these flags after 2.6.26 1356 */ 1357 if (unlikely(clone_flags & CLONE_STOPPED)) { 1358 static int __read_mostly count = 100; 1359 1360 if (count > 0 && printk_ratelimit()) { 1361 char comm[TASK_COMM_LEN]; 1362 1363 count--; 1364 printk(KERN_INFO "fork(): process `%s' used deprecated " 1365 "clone flags 0x%lx\n", 1366 get_task_comm(comm, current), 1367 clone_flags & CLONE_STOPPED); 1368 } 1369 } 1370 1371 if (unlikely(current->ptrace)) { 1372 trace = fork_traceflag (clone_flags); 1373 if (trace) 1374 clone_flags |= CLONE_PTRACE; 1375 } 1376 1377 p = copy_process(clone_flags, stack_start, regs, stack_size, 1378 child_tidptr, NULL); 1379 /* 1380 * Do this prior waking up the new thread - the thread pointer 1381 * might get invalid after that point, if the thread exits quickly. 1382 */ 1383 if (!IS_ERR(p)) { 1384 struct completion vfork; 1385 1386 nr = task_pid_vnr(p); 1387 1388 if (clone_flags & CLONE_PARENT_SETTID) 1389 put_user(nr, parent_tidptr); 1390 1391 if (clone_flags & CLONE_VFORK) { 1392 p->vfork_done = &vfork; 1393 init_completion(&vfork); 1394 } 1395 1396 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1397 /* 1398 * We'll start up with an immediate SIGSTOP. 1399 */ 1400 sigaddset(&p->pending.signal, SIGSTOP); 1401 set_tsk_thread_flag(p, TIF_SIGPENDING); 1402 } 1403 1404 if (!(clone_flags & CLONE_STOPPED)) 1405 wake_up_new_task(p, clone_flags); 1406 else 1407 __set_task_state(p, TASK_STOPPED); 1408 1409 if (unlikely (trace)) { 1410 current->ptrace_message = nr; 1411 ptrace_notify ((trace << 8) | SIGTRAP); 1412 } 1413 1414 if (clone_flags & CLONE_VFORK) { 1415 freezer_do_not_count(); 1416 wait_for_completion(&vfork); 1417 freezer_count(); 1418 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1419 current->ptrace_message = nr; 1420 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1421 } 1422 } 1423 } else { 1424 nr = PTR_ERR(p); 1425 } 1426 return nr; 1427 } 1428 1429 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1430 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1431 #endif 1432 1433 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1434 { 1435 struct sighand_struct *sighand = data; 1436 1437 spin_lock_init(&sighand->siglock); 1438 init_waitqueue_head(&sighand->signalfd_wqh); 1439 } 1440 1441 void __init proc_caches_init(void) 1442 { 1443 sighand_cachep = kmem_cache_create("sighand_cache", 1444 sizeof(struct sighand_struct), 0, 1445 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1446 sighand_ctor); 1447 signal_cachep = kmem_cache_create("signal_cache", 1448 sizeof(struct signal_struct), 0, 1449 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1450 files_cachep = kmem_cache_create("files_cache", 1451 sizeof(struct files_struct), 0, 1452 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1453 fs_cachep = kmem_cache_create("fs_cache", 1454 sizeof(struct fs_struct), 0, 1455 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1456 vm_area_cachep = kmem_cache_create("vm_area_struct", 1457 sizeof(struct vm_area_struct), 0, 1458 SLAB_PANIC, NULL); 1459 mm_cachep = kmem_cache_create("mm_struct", 1460 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1461 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1462 } 1463 1464 /* 1465 * Check constraints on flags passed to the unshare system call and 1466 * force unsharing of additional process context as appropriate. 1467 */ 1468 static void check_unshare_flags(unsigned long *flags_ptr) 1469 { 1470 /* 1471 * If unsharing a thread from a thread group, must also 1472 * unshare vm. 1473 */ 1474 if (*flags_ptr & CLONE_THREAD) 1475 *flags_ptr |= CLONE_VM; 1476 1477 /* 1478 * If unsharing vm, must also unshare signal handlers. 1479 */ 1480 if (*flags_ptr & CLONE_VM) 1481 *flags_ptr |= CLONE_SIGHAND; 1482 1483 /* 1484 * If unsharing signal handlers and the task was created 1485 * using CLONE_THREAD, then must unshare the thread 1486 */ 1487 if ((*flags_ptr & CLONE_SIGHAND) && 1488 (atomic_read(¤t->signal->count) > 1)) 1489 *flags_ptr |= CLONE_THREAD; 1490 1491 /* 1492 * If unsharing namespace, must also unshare filesystem information. 1493 */ 1494 if (*flags_ptr & CLONE_NEWNS) 1495 *flags_ptr |= CLONE_FS; 1496 } 1497 1498 /* 1499 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1500 */ 1501 static int unshare_thread(unsigned long unshare_flags) 1502 { 1503 if (unshare_flags & CLONE_THREAD) 1504 return -EINVAL; 1505 1506 return 0; 1507 } 1508 1509 /* 1510 * Unshare the filesystem structure if it is being shared 1511 */ 1512 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1513 { 1514 struct fs_struct *fs = current->fs; 1515 1516 if ((unshare_flags & CLONE_FS) && 1517 (fs && atomic_read(&fs->count) > 1)) { 1518 *new_fsp = __copy_fs_struct(current->fs); 1519 if (!*new_fsp) 1520 return -ENOMEM; 1521 } 1522 1523 return 0; 1524 } 1525 1526 /* 1527 * Unsharing of sighand is not supported yet 1528 */ 1529 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1530 { 1531 struct sighand_struct *sigh = current->sighand; 1532 1533 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1534 return -EINVAL; 1535 else 1536 return 0; 1537 } 1538 1539 /* 1540 * Unshare vm if it is being shared 1541 */ 1542 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1543 { 1544 struct mm_struct *mm = current->mm; 1545 1546 if ((unshare_flags & CLONE_VM) && 1547 (mm && atomic_read(&mm->mm_users) > 1)) { 1548 return -EINVAL; 1549 } 1550 1551 return 0; 1552 } 1553 1554 /* 1555 * Unshare file descriptor table if it is being shared 1556 */ 1557 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1558 { 1559 struct files_struct *fd = current->files; 1560 int error = 0; 1561 1562 if ((unshare_flags & CLONE_FILES) && 1563 (fd && atomic_read(&fd->count) > 1)) { 1564 *new_fdp = dup_fd(fd, &error); 1565 if (!*new_fdp) 1566 return error; 1567 } 1568 1569 return 0; 1570 } 1571 1572 /* 1573 * unshare allows a process to 'unshare' part of the process 1574 * context which was originally shared using clone. copy_* 1575 * functions used by do_fork() cannot be used here directly 1576 * because they modify an inactive task_struct that is being 1577 * constructed. Here we are modifying the current, active, 1578 * task_struct. 1579 */ 1580 asmlinkage long sys_unshare(unsigned long unshare_flags) 1581 { 1582 int err = 0; 1583 struct fs_struct *fs, *new_fs = NULL; 1584 struct sighand_struct *new_sigh = NULL; 1585 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1586 struct files_struct *fd, *new_fd = NULL; 1587 struct nsproxy *new_nsproxy = NULL; 1588 int do_sysvsem = 0; 1589 1590 check_unshare_flags(&unshare_flags); 1591 1592 /* Return -EINVAL for all unsupported flags */ 1593 err = -EINVAL; 1594 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1595 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1596 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1597 CLONE_NEWNET)) 1598 goto bad_unshare_out; 1599 1600 /* 1601 * CLONE_NEWIPC must also detach from the undolist: after switching 1602 * to a new ipc namespace, the semaphore arrays from the old 1603 * namespace are unreachable. 1604 */ 1605 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1606 do_sysvsem = 1; 1607 if ((err = unshare_thread(unshare_flags))) 1608 goto bad_unshare_out; 1609 if ((err = unshare_fs(unshare_flags, &new_fs))) 1610 goto bad_unshare_cleanup_thread; 1611 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1612 goto bad_unshare_cleanup_fs; 1613 if ((err = unshare_vm(unshare_flags, &new_mm))) 1614 goto bad_unshare_cleanup_sigh; 1615 if ((err = unshare_fd(unshare_flags, &new_fd))) 1616 goto bad_unshare_cleanup_vm; 1617 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1618 new_fs))) 1619 goto bad_unshare_cleanup_fd; 1620 1621 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1622 if (do_sysvsem) { 1623 /* 1624 * CLONE_SYSVSEM is equivalent to sys_exit(). 1625 */ 1626 exit_sem(current); 1627 } 1628 1629 if (new_nsproxy) { 1630 switch_task_namespaces(current, new_nsproxy); 1631 new_nsproxy = NULL; 1632 } 1633 1634 task_lock(current); 1635 1636 if (new_fs) { 1637 fs = current->fs; 1638 current->fs = new_fs; 1639 new_fs = fs; 1640 } 1641 1642 if (new_mm) { 1643 mm = current->mm; 1644 active_mm = current->active_mm; 1645 current->mm = new_mm; 1646 current->active_mm = new_mm; 1647 activate_mm(active_mm, new_mm); 1648 new_mm = mm; 1649 } 1650 1651 if (new_fd) { 1652 fd = current->files; 1653 current->files = new_fd; 1654 new_fd = fd; 1655 } 1656 1657 task_unlock(current); 1658 } 1659 1660 if (new_nsproxy) 1661 put_nsproxy(new_nsproxy); 1662 1663 bad_unshare_cleanup_fd: 1664 if (new_fd) 1665 put_files_struct(new_fd); 1666 1667 bad_unshare_cleanup_vm: 1668 if (new_mm) 1669 mmput(new_mm); 1670 1671 bad_unshare_cleanup_sigh: 1672 if (new_sigh) 1673 if (atomic_dec_and_test(&new_sigh->count)) 1674 kmem_cache_free(sighand_cachep, new_sigh); 1675 1676 bad_unshare_cleanup_fs: 1677 if (new_fs) 1678 put_fs_struct(new_fs); 1679 1680 bad_unshare_cleanup_thread: 1681 bad_unshare_out: 1682 return err; 1683 } 1684 1685 /* 1686 * Helper to unshare the files of the current task. 1687 * We don't want to expose copy_files internals to 1688 * the exec layer of the kernel. 1689 */ 1690 1691 int unshare_files(struct files_struct **displaced) 1692 { 1693 struct task_struct *task = current; 1694 struct files_struct *copy = NULL; 1695 int error; 1696 1697 error = unshare_fd(CLONE_FILES, ©); 1698 if (error || !copy) { 1699 *displaced = NULL; 1700 return error; 1701 } 1702 *displaced = task->files; 1703 task_lock(task); 1704 task->files = copy; 1705 task_unlock(task); 1706 return 0; 1707 } 1708