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/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/ksm.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <linux/fs_struct.h> 64 #include <linux/magic.h> 65 #include <linux/perf_event.h> 66 #include <linux/posix-timers.h> 67 #include <linux/user-return-notifier.h> 68 69 #include <asm/pgtable.h> 70 #include <asm/pgalloc.h> 71 #include <asm/uaccess.h> 72 #include <asm/mmu_context.h> 73 #include <asm/cacheflush.h> 74 #include <asm/tlbflush.h> 75 76 #include <trace/events/sched.h> 77 78 /* 79 * Protected counters by write_lock_irq(&tasklist_lock) 80 */ 81 unsigned long total_forks; /* Handle normal Linux uptimes. */ 82 int nr_threads; /* The idle threads do not count.. */ 83 84 int max_threads; /* tunable limit on nr_threads */ 85 86 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 87 88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 89 EXPORT_SYMBOL_GPL(tasklist_lock); 90 91 int nr_processes(void) 92 { 93 int cpu; 94 int total = 0; 95 96 for_each_possible_cpu(cpu) 97 total += per_cpu(process_counts, cpu); 98 99 return total; 100 } 101 102 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 103 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 104 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 105 static struct kmem_cache *task_struct_cachep; 106 #endif 107 108 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 109 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 110 { 111 #ifdef CONFIG_DEBUG_STACK_USAGE 112 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 113 #else 114 gfp_t mask = GFP_KERNEL; 115 #endif 116 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 117 } 118 119 static inline void free_thread_info(struct thread_info *ti) 120 { 121 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 122 } 123 #endif 124 125 /* SLAB cache for signal_struct structures (tsk->signal) */ 126 static struct kmem_cache *signal_cachep; 127 128 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 129 struct kmem_cache *sighand_cachep; 130 131 /* SLAB cache for files_struct structures (tsk->files) */ 132 struct kmem_cache *files_cachep; 133 134 /* SLAB cache for fs_struct structures (tsk->fs) */ 135 struct kmem_cache *fs_cachep; 136 137 /* SLAB cache for vm_area_struct structures */ 138 struct kmem_cache *vm_area_cachep; 139 140 /* SLAB cache for mm_struct structures (tsk->mm) */ 141 static struct kmem_cache *mm_cachep; 142 143 static void account_kernel_stack(struct thread_info *ti, int account) 144 { 145 struct zone *zone = page_zone(virt_to_page(ti)); 146 147 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 148 } 149 150 void free_task(struct task_struct *tsk) 151 { 152 prop_local_destroy_single(&tsk->dirties); 153 account_kernel_stack(tsk->stack, -1); 154 free_thread_info(tsk->stack); 155 rt_mutex_debug_task_free(tsk); 156 ftrace_graph_exit_task(tsk); 157 free_task_struct(tsk); 158 } 159 EXPORT_SYMBOL(free_task); 160 161 void __put_task_struct(struct task_struct *tsk) 162 { 163 WARN_ON(!tsk->exit_state); 164 WARN_ON(atomic_read(&tsk->usage)); 165 WARN_ON(tsk == current); 166 167 exit_creds(tsk); 168 delayacct_tsk_free(tsk); 169 170 if (!profile_handoff_task(tsk)) 171 free_task(tsk); 172 } 173 174 /* 175 * macro override instead of weak attribute alias, to workaround 176 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 177 */ 178 #ifndef arch_task_cache_init 179 #define arch_task_cache_init() 180 #endif 181 182 void __init fork_init(unsigned long mempages) 183 { 184 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 185 #ifndef ARCH_MIN_TASKALIGN 186 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 187 #endif 188 /* create a slab on which task_structs can be allocated */ 189 task_struct_cachep = 190 kmem_cache_create("task_struct", sizeof(struct task_struct), 191 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 192 #endif 193 194 /* do the arch specific task caches init */ 195 arch_task_cache_init(); 196 197 /* 198 * The default maximum number of threads is set to a safe 199 * value: the thread structures can take up at most half 200 * of memory. 201 */ 202 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 203 204 /* 205 * we need to allow at least 20 threads to boot a system 206 */ 207 if(max_threads < 20) 208 max_threads = 20; 209 210 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 211 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 212 init_task.signal->rlim[RLIMIT_SIGPENDING] = 213 init_task.signal->rlim[RLIMIT_NPROC]; 214 } 215 216 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 217 struct task_struct *src) 218 { 219 *dst = *src; 220 return 0; 221 } 222 223 static struct task_struct *dup_task_struct(struct task_struct *orig) 224 { 225 struct task_struct *tsk; 226 struct thread_info *ti; 227 unsigned long *stackend; 228 229 int err; 230 231 prepare_to_copy(orig); 232 233 tsk = alloc_task_struct(); 234 if (!tsk) 235 return NULL; 236 237 ti = alloc_thread_info(tsk); 238 if (!ti) { 239 free_task_struct(tsk); 240 return NULL; 241 } 242 243 err = arch_dup_task_struct(tsk, orig); 244 if (err) 245 goto out; 246 247 tsk->stack = ti; 248 249 err = prop_local_init_single(&tsk->dirties); 250 if (err) 251 goto out; 252 253 setup_thread_stack(tsk, orig); 254 clear_user_return_notifier(tsk); 255 stackend = end_of_stack(tsk); 256 *stackend = STACK_END_MAGIC; /* for overflow detection */ 257 258 #ifdef CONFIG_CC_STACKPROTECTOR 259 tsk->stack_canary = get_random_int(); 260 #endif 261 262 /* One for us, one for whoever does the "release_task()" (usually parent) */ 263 atomic_set(&tsk->usage,2); 264 atomic_set(&tsk->fs_excl, 0); 265 #ifdef CONFIG_BLK_DEV_IO_TRACE 266 tsk->btrace_seq = 0; 267 #endif 268 tsk->splice_pipe = NULL; 269 270 account_kernel_stack(ti, 1); 271 272 return tsk; 273 274 out: 275 free_thread_info(ti); 276 free_task_struct(tsk); 277 return NULL; 278 } 279 280 #ifdef CONFIG_MMU 281 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 282 { 283 struct vm_area_struct *mpnt, *tmp, **pprev; 284 struct rb_node **rb_link, *rb_parent; 285 int retval; 286 unsigned long charge; 287 struct mempolicy *pol; 288 289 down_write(&oldmm->mmap_sem); 290 flush_cache_dup_mm(oldmm); 291 /* 292 * Not linked in yet - no deadlock potential: 293 */ 294 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 295 296 mm->locked_vm = 0; 297 mm->mmap = NULL; 298 mm->mmap_cache = NULL; 299 mm->free_area_cache = oldmm->mmap_base; 300 mm->cached_hole_size = ~0UL; 301 mm->map_count = 0; 302 cpumask_clear(mm_cpumask(mm)); 303 mm->mm_rb = RB_ROOT; 304 rb_link = &mm->mm_rb.rb_node; 305 rb_parent = NULL; 306 pprev = &mm->mmap; 307 retval = ksm_fork(mm, oldmm); 308 if (retval) 309 goto out; 310 311 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 312 struct file *file; 313 314 if (mpnt->vm_flags & VM_DONTCOPY) { 315 long pages = vma_pages(mpnt); 316 mm->total_vm -= pages; 317 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 318 -pages); 319 continue; 320 } 321 charge = 0; 322 if (mpnt->vm_flags & VM_ACCOUNT) { 323 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 324 if (security_vm_enough_memory(len)) 325 goto fail_nomem; 326 charge = len; 327 } 328 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 329 if (!tmp) 330 goto fail_nomem; 331 *tmp = *mpnt; 332 pol = mpol_dup(vma_policy(mpnt)); 333 retval = PTR_ERR(pol); 334 if (IS_ERR(pol)) 335 goto fail_nomem_policy; 336 vma_set_policy(tmp, pol); 337 tmp->vm_flags &= ~VM_LOCKED; 338 tmp->vm_mm = mm; 339 tmp->vm_next = NULL; 340 anon_vma_link(tmp); 341 file = tmp->vm_file; 342 if (file) { 343 struct inode *inode = file->f_path.dentry->d_inode; 344 struct address_space *mapping = file->f_mapping; 345 346 get_file(file); 347 if (tmp->vm_flags & VM_DENYWRITE) 348 atomic_dec(&inode->i_writecount); 349 spin_lock(&mapping->i_mmap_lock); 350 if (tmp->vm_flags & VM_SHARED) 351 mapping->i_mmap_writable++; 352 tmp->vm_truncate_count = mpnt->vm_truncate_count; 353 flush_dcache_mmap_lock(mapping); 354 /* insert tmp into the share list, just after mpnt */ 355 vma_prio_tree_add(tmp, mpnt); 356 flush_dcache_mmap_unlock(mapping); 357 spin_unlock(&mapping->i_mmap_lock); 358 } 359 360 /* 361 * Clear hugetlb-related page reserves for children. This only 362 * affects MAP_PRIVATE mappings. Faults generated by the child 363 * are not guaranteed to succeed, even if read-only 364 */ 365 if (is_vm_hugetlb_page(tmp)) 366 reset_vma_resv_huge_pages(tmp); 367 368 /* 369 * Link in the new vma and copy the page table entries. 370 */ 371 *pprev = tmp; 372 pprev = &tmp->vm_next; 373 374 __vma_link_rb(mm, tmp, rb_link, rb_parent); 375 rb_link = &tmp->vm_rb.rb_right; 376 rb_parent = &tmp->vm_rb; 377 378 mm->map_count++; 379 retval = copy_page_range(mm, oldmm, mpnt); 380 381 if (tmp->vm_ops && tmp->vm_ops->open) 382 tmp->vm_ops->open(tmp); 383 384 if (retval) 385 goto out; 386 } 387 /* a new mm has just been created */ 388 arch_dup_mmap(oldmm, mm); 389 retval = 0; 390 out: 391 up_write(&mm->mmap_sem); 392 flush_tlb_mm(oldmm); 393 up_write(&oldmm->mmap_sem); 394 return retval; 395 fail_nomem_policy: 396 kmem_cache_free(vm_area_cachep, tmp); 397 fail_nomem: 398 retval = -ENOMEM; 399 vm_unacct_memory(charge); 400 goto out; 401 } 402 403 static inline int mm_alloc_pgd(struct mm_struct * mm) 404 { 405 mm->pgd = pgd_alloc(mm); 406 if (unlikely(!mm->pgd)) 407 return -ENOMEM; 408 return 0; 409 } 410 411 static inline void mm_free_pgd(struct mm_struct * mm) 412 { 413 pgd_free(mm, mm->pgd); 414 } 415 #else 416 #define dup_mmap(mm, oldmm) (0) 417 #define mm_alloc_pgd(mm) (0) 418 #define mm_free_pgd(mm) 419 #endif /* CONFIG_MMU */ 420 421 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 422 423 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 424 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 425 426 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 427 428 static int __init coredump_filter_setup(char *s) 429 { 430 default_dump_filter = 431 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 432 MMF_DUMP_FILTER_MASK; 433 return 1; 434 } 435 436 __setup("coredump_filter=", coredump_filter_setup); 437 438 #include <linux/init_task.h> 439 440 static void mm_init_aio(struct mm_struct *mm) 441 { 442 #ifdef CONFIG_AIO 443 spin_lock_init(&mm->ioctx_lock); 444 INIT_HLIST_HEAD(&mm->ioctx_list); 445 #endif 446 } 447 448 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 449 { 450 atomic_set(&mm->mm_users, 1); 451 atomic_set(&mm->mm_count, 1); 452 init_rwsem(&mm->mmap_sem); 453 INIT_LIST_HEAD(&mm->mmlist); 454 mm->flags = (current->mm) ? 455 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 456 mm->core_state = NULL; 457 mm->nr_ptes = 0; 458 set_mm_counter(mm, file_rss, 0); 459 set_mm_counter(mm, anon_rss, 0); 460 spin_lock_init(&mm->page_table_lock); 461 mm->free_area_cache = TASK_UNMAPPED_BASE; 462 mm->cached_hole_size = ~0UL; 463 mm_init_aio(mm); 464 mm_init_owner(mm, p); 465 466 if (likely(!mm_alloc_pgd(mm))) { 467 mm->def_flags = 0; 468 mmu_notifier_mm_init(mm); 469 return mm; 470 } 471 472 free_mm(mm); 473 return NULL; 474 } 475 476 /* 477 * Allocate and initialize an mm_struct. 478 */ 479 struct mm_struct * mm_alloc(void) 480 { 481 struct mm_struct * mm; 482 483 mm = allocate_mm(); 484 if (mm) { 485 memset(mm, 0, sizeof(*mm)); 486 mm = mm_init(mm, current); 487 } 488 return mm; 489 } 490 491 /* 492 * Called when the last reference to the mm 493 * is dropped: either by a lazy thread or by 494 * mmput. Free the page directory and the mm. 495 */ 496 void __mmdrop(struct mm_struct *mm) 497 { 498 BUG_ON(mm == &init_mm); 499 mm_free_pgd(mm); 500 destroy_context(mm); 501 mmu_notifier_mm_destroy(mm); 502 free_mm(mm); 503 } 504 EXPORT_SYMBOL_GPL(__mmdrop); 505 506 /* 507 * Decrement the use count and release all resources for an mm. 508 */ 509 void mmput(struct mm_struct *mm) 510 { 511 might_sleep(); 512 513 if (atomic_dec_and_test(&mm->mm_users)) { 514 exit_aio(mm); 515 ksm_exit(mm); 516 exit_mmap(mm); 517 set_mm_exe_file(mm, NULL); 518 if (!list_empty(&mm->mmlist)) { 519 spin_lock(&mmlist_lock); 520 list_del(&mm->mmlist); 521 spin_unlock(&mmlist_lock); 522 } 523 put_swap_token(mm); 524 if (mm->binfmt) 525 module_put(mm->binfmt->module); 526 mmdrop(mm); 527 } 528 } 529 EXPORT_SYMBOL_GPL(mmput); 530 531 /** 532 * get_task_mm - acquire a reference to the task's mm 533 * 534 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 535 * this kernel workthread has transiently adopted a user mm with use_mm, 536 * to do its AIO) is not set and if so returns a reference to it, after 537 * bumping up the use count. User must release the mm via mmput() 538 * after use. Typically used by /proc and ptrace. 539 */ 540 struct mm_struct *get_task_mm(struct task_struct *task) 541 { 542 struct mm_struct *mm; 543 544 task_lock(task); 545 mm = task->mm; 546 if (mm) { 547 if (task->flags & PF_KTHREAD) 548 mm = NULL; 549 else 550 atomic_inc(&mm->mm_users); 551 } 552 task_unlock(task); 553 return mm; 554 } 555 EXPORT_SYMBOL_GPL(get_task_mm); 556 557 /* Please note the differences between mmput and mm_release. 558 * mmput is called whenever we stop holding onto a mm_struct, 559 * error success whatever. 560 * 561 * mm_release is called after a mm_struct has been removed 562 * from the current process. 563 * 564 * This difference is important for error handling, when we 565 * only half set up a mm_struct for a new process and need to restore 566 * the old one. Because we mmput the new mm_struct before 567 * restoring the old one. . . 568 * Eric Biederman 10 January 1998 569 */ 570 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 571 { 572 struct completion *vfork_done = tsk->vfork_done; 573 574 /* Get rid of any futexes when releasing the mm */ 575 #ifdef CONFIG_FUTEX 576 if (unlikely(tsk->robust_list)) { 577 exit_robust_list(tsk); 578 tsk->robust_list = NULL; 579 } 580 #ifdef CONFIG_COMPAT 581 if (unlikely(tsk->compat_robust_list)) { 582 compat_exit_robust_list(tsk); 583 tsk->compat_robust_list = NULL; 584 } 585 #endif 586 if (unlikely(!list_empty(&tsk->pi_state_list))) 587 exit_pi_state_list(tsk); 588 #endif 589 590 /* Get rid of any cached register state */ 591 deactivate_mm(tsk, mm); 592 593 /* notify parent sleeping on vfork() */ 594 if (vfork_done) { 595 tsk->vfork_done = NULL; 596 complete(vfork_done); 597 } 598 599 /* 600 * If we're exiting normally, clear a user-space tid field if 601 * requested. We leave this alone when dying by signal, to leave 602 * the value intact in a core dump, and to save the unnecessary 603 * trouble otherwise. Userland only wants this done for a sys_exit. 604 */ 605 if (tsk->clear_child_tid) { 606 if (!(tsk->flags & PF_SIGNALED) && 607 atomic_read(&mm->mm_users) > 1) { 608 /* 609 * We don't check the error code - if userspace has 610 * not set up a proper pointer then tough luck. 611 */ 612 put_user(0, tsk->clear_child_tid); 613 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 614 1, NULL, NULL, 0); 615 } 616 tsk->clear_child_tid = NULL; 617 } 618 } 619 620 /* 621 * Allocate a new mm structure and copy contents from the 622 * mm structure of the passed in task structure. 623 */ 624 struct mm_struct *dup_mm(struct task_struct *tsk) 625 { 626 struct mm_struct *mm, *oldmm = current->mm; 627 int err; 628 629 if (!oldmm) 630 return NULL; 631 632 mm = allocate_mm(); 633 if (!mm) 634 goto fail_nomem; 635 636 memcpy(mm, oldmm, sizeof(*mm)); 637 638 /* Initializing for Swap token stuff */ 639 mm->token_priority = 0; 640 mm->last_interval = 0; 641 642 if (!mm_init(mm, tsk)) 643 goto fail_nomem; 644 645 if (init_new_context(tsk, mm)) 646 goto fail_nocontext; 647 648 dup_mm_exe_file(oldmm, mm); 649 650 err = dup_mmap(mm, oldmm); 651 if (err) 652 goto free_pt; 653 654 mm->hiwater_rss = get_mm_rss(mm); 655 mm->hiwater_vm = mm->total_vm; 656 657 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 658 goto free_pt; 659 660 return mm; 661 662 free_pt: 663 /* don't put binfmt in mmput, we haven't got module yet */ 664 mm->binfmt = NULL; 665 mmput(mm); 666 667 fail_nomem: 668 return NULL; 669 670 fail_nocontext: 671 /* 672 * If init_new_context() failed, we cannot use mmput() to free the mm 673 * because it calls destroy_context() 674 */ 675 mm_free_pgd(mm); 676 free_mm(mm); 677 return NULL; 678 } 679 680 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 681 { 682 struct mm_struct * mm, *oldmm; 683 int retval; 684 685 tsk->min_flt = tsk->maj_flt = 0; 686 tsk->nvcsw = tsk->nivcsw = 0; 687 #ifdef CONFIG_DETECT_HUNG_TASK 688 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 689 #endif 690 691 tsk->mm = NULL; 692 tsk->active_mm = NULL; 693 694 /* 695 * Are we cloning a kernel thread? 696 * 697 * We need to steal a active VM for that.. 698 */ 699 oldmm = current->mm; 700 if (!oldmm) 701 return 0; 702 703 if (clone_flags & CLONE_VM) { 704 atomic_inc(&oldmm->mm_users); 705 mm = oldmm; 706 goto good_mm; 707 } 708 709 retval = -ENOMEM; 710 mm = dup_mm(tsk); 711 if (!mm) 712 goto fail_nomem; 713 714 good_mm: 715 /* Initializing for Swap token stuff */ 716 mm->token_priority = 0; 717 mm->last_interval = 0; 718 719 tsk->mm = mm; 720 tsk->active_mm = mm; 721 return 0; 722 723 fail_nomem: 724 return retval; 725 } 726 727 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 728 { 729 struct fs_struct *fs = current->fs; 730 if (clone_flags & CLONE_FS) { 731 /* tsk->fs is already what we want */ 732 write_lock(&fs->lock); 733 if (fs->in_exec) { 734 write_unlock(&fs->lock); 735 return -EAGAIN; 736 } 737 fs->users++; 738 write_unlock(&fs->lock); 739 return 0; 740 } 741 tsk->fs = copy_fs_struct(fs); 742 if (!tsk->fs) 743 return -ENOMEM; 744 return 0; 745 } 746 747 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 748 { 749 struct files_struct *oldf, *newf; 750 int error = 0; 751 752 /* 753 * A background process may not have any files ... 754 */ 755 oldf = current->files; 756 if (!oldf) 757 goto out; 758 759 if (clone_flags & CLONE_FILES) { 760 atomic_inc(&oldf->count); 761 goto out; 762 } 763 764 newf = dup_fd(oldf, &error); 765 if (!newf) 766 goto out; 767 768 tsk->files = newf; 769 error = 0; 770 out: 771 return error; 772 } 773 774 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 775 { 776 #ifdef CONFIG_BLOCK 777 struct io_context *ioc = current->io_context; 778 779 if (!ioc) 780 return 0; 781 /* 782 * Share io context with parent, if CLONE_IO is set 783 */ 784 if (clone_flags & CLONE_IO) { 785 tsk->io_context = ioc_task_link(ioc); 786 if (unlikely(!tsk->io_context)) 787 return -ENOMEM; 788 } else if (ioprio_valid(ioc->ioprio)) { 789 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 790 if (unlikely(!tsk->io_context)) 791 return -ENOMEM; 792 793 tsk->io_context->ioprio = ioc->ioprio; 794 } 795 #endif 796 return 0; 797 } 798 799 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 800 { 801 struct sighand_struct *sig; 802 803 if (clone_flags & CLONE_SIGHAND) { 804 atomic_inc(¤t->sighand->count); 805 return 0; 806 } 807 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 808 rcu_assign_pointer(tsk->sighand, sig); 809 if (!sig) 810 return -ENOMEM; 811 atomic_set(&sig->count, 1); 812 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 813 return 0; 814 } 815 816 void __cleanup_sighand(struct sighand_struct *sighand) 817 { 818 if (atomic_dec_and_test(&sighand->count)) 819 kmem_cache_free(sighand_cachep, sighand); 820 } 821 822 823 /* 824 * Initialize POSIX timer handling for a thread group. 825 */ 826 static void posix_cpu_timers_init_group(struct signal_struct *sig) 827 { 828 /* Thread group counters. */ 829 thread_group_cputime_init(sig); 830 831 /* Expiration times and increments. */ 832 sig->it[CPUCLOCK_PROF].expires = cputime_zero; 833 sig->it[CPUCLOCK_PROF].incr = cputime_zero; 834 sig->it[CPUCLOCK_VIRT].expires = cputime_zero; 835 sig->it[CPUCLOCK_VIRT].incr = cputime_zero; 836 837 /* Cached expiration times. */ 838 sig->cputime_expires.prof_exp = cputime_zero; 839 sig->cputime_expires.virt_exp = cputime_zero; 840 sig->cputime_expires.sched_exp = 0; 841 842 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 843 sig->cputime_expires.prof_exp = 844 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 845 sig->cputimer.running = 1; 846 } 847 848 /* The timer lists. */ 849 INIT_LIST_HEAD(&sig->cpu_timers[0]); 850 INIT_LIST_HEAD(&sig->cpu_timers[1]); 851 INIT_LIST_HEAD(&sig->cpu_timers[2]); 852 } 853 854 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 855 { 856 struct signal_struct *sig; 857 858 if (clone_flags & CLONE_THREAD) 859 return 0; 860 861 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 862 tsk->signal = sig; 863 if (!sig) 864 return -ENOMEM; 865 866 atomic_set(&sig->count, 1); 867 atomic_set(&sig->live, 1); 868 init_waitqueue_head(&sig->wait_chldexit); 869 sig->flags = 0; 870 if (clone_flags & CLONE_NEWPID) 871 sig->flags |= SIGNAL_UNKILLABLE; 872 sig->group_exit_code = 0; 873 sig->group_exit_task = NULL; 874 sig->group_stop_count = 0; 875 sig->curr_target = tsk; 876 init_sigpending(&sig->shared_pending); 877 INIT_LIST_HEAD(&sig->posix_timers); 878 879 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 880 sig->it_real_incr.tv64 = 0; 881 sig->real_timer.function = it_real_fn; 882 883 sig->leader = 0; /* session leadership doesn't inherit */ 884 sig->tty_old_pgrp = NULL; 885 sig->tty = NULL; 886 887 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 888 sig->gtime = cputime_zero; 889 sig->cgtime = cputime_zero; 890 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 891 sig->prev_utime = sig->prev_stime = cputime_zero; 892 #endif 893 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 894 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 895 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 896 sig->maxrss = sig->cmaxrss = 0; 897 task_io_accounting_init(&sig->ioac); 898 sig->sum_sched_runtime = 0; 899 taskstats_tgid_init(sig); 900 901 task_lock(current->group_leader); 902 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 903 task_unlock(current->group_leader); 904 905 posix_cpu_timers_init_group(sig); 906 907 acct_init_pacct(&sig->pacct); 908 909 tty_audit_fork(sig); 910 911 sig->oom_adj = current->signal->oom_adj; 912 913 return 0; 914 } 915 916 void __cleanup_signal(struct signal_struct *sig) 917 { 918 thread_group_cputime_free(sig); 919 tty_kref_put(sig->tty); 920 kmem_cache_free(signal_cachep, sig); 921 } 922 923 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 924 { 925 unsigned long new_flags = p->flags; 926 927 new_flags &= ~PF_SUPERPRIV; 928 new_flags |= PF_FORKNOEXEC; 929 new_flags |= PF_STARTING; 930 p->flags = new_flags; 931 clear_freeze_flag(p); 932 } 933 934 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 935 { 936 current->clear_child_tid = tidptr; 937 938 return task_pid_vnr(current); 939 } 940 941 static void rt_mutex_init_task(struct task_struct *p) 942 { 943 raw_spin_lock_init(&p->pi_lock); 944 #ifdef CONFIG_RT_MUTEXES 945 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 946 p->pi_blocked_on = NULL; 947 #endif 948 } 949 950 #ifdef CONFIG_MM_OWNER 951 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 952 { 953 mm->owner = p; 954 } 955 #endif /* CONFIG_MM_OWNER */ 956 957 /* 958 * Initialize POSIX timer handling for a single task. 959 */ 960 static void posix_cpu_timers_init(struct task_struct *tsk) 961 { 962 tsk->cputime_expires.prof_exp = cputime_zero; 963 tsk->cputime_expires.virt_exp = cputime_zero; 964 tsk->cputime_expires.sched_exp = 0; 965 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 966 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 967 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 968 } 969 970 /* 971 * This creates a new process as a copy of the old one, 972 * but does not actually start it yet. 973 * 974 * It copies the registers, and all the appropriate 975 * parts of the process environment (as per the clone 976 * flags). The actual kick-off is left to the caller. 977 */ 978 static struct task_struct *copy_process(unsigned long clone_flags, 979 unsigned long stack_start, 980 struct pt_regs *regs, 981 unsigned long stack_size, 982 int __user *child_tidptr, 983 struct pid *pid, 984 int trace) 985 { 986 int retval; 987 struct task_struct *p; 988 int cgroup_callbacks_done = 0; 989 990 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 991 return ERR_PTR(-EINVAL); 992 993 /* 994 * Thread groups must share signals as well, and detached threads 995 * can only be started up within the thread group. 996 */ 997 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 998 return ERR_PTR(-EINVAL); 999 1000 /* 1001 * Shared signal handlers imply shared VM. By way of the above, 1002 * thread groups also imply shared VM. Blocking this case allows 1003 * for various simplifications in other code. 1004 */ 1005 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1006 return ERR_PTR(-EINVAL); 1007 1008 /* 1009 * Siblings of global init remain as zombies on exit since they are 1010 * not reaped by their parent (swapper). To solve this and to avoid 1011 * multi-rooted process trees, prevent global and container-inits 1012 * from creating siblings. 1013 */ 1014 if ((clone_flags & CLONE_PARENT) && 1015 current->signal->flags & SIGNAL_UNKILLABLE) 1016 return ERR_PTR(-EINVAL); 1017 1018 retval = security_task_create(clone_flags); 1019 if (retval) 1020 goto fork_out; 1021 1022 retval = -ENOMEM; 1023 p = dup_task_struct(current); 1024 if (!p) 1025 goto fork_out; 1026 1027 ftrace_graph_init_task(p); 1028 1029 rt_mutex_init_task(p); 1030 1031 #ifdef CONFIG_PROVE_LOCKING 1032 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1033 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1034 #endif 1035 retval = -EAGAIN; 1036 if (atomic_read(&p->real_cred->user->processes) >= 1037 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1038 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1039 p->real_cred->user != INIT_USER) 1040 goto bad_fork_free; 1041 } 1042 1043 retval = copy_creds(p, clone_flags); 1044 if (retval < 0) 1045 goto bad_fork_free; 1046 1047 /* 1048 * If multiple threads are within copy_process(), then this check 1049 * triggers too late. This doesn't hurt, the check is only there 1050 * to stop root fork bombs. 1051 */ 1052 retval = -EAGAIN; 1053 if (nr_threads >= max_threads) 1054 goto bad_fork_cleanup_count; 1055 1056 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1057 goto bad_fork_cleanup_count; 1058 1059 p->did_exec = 0; 1060 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1061 copy_flags(clone_flags, p); 1062 INIT_LIST_HEAD(&p->children); 1063 INIT_LIST_HEAD(&p->sibling); 1064 rcu_copy_process(p); 1065 p->vfork_done = NULL; 1066 spin_lock_init(&p->alloc_lock); 1067 1068 init_sigpending(&p->pending); 1069 1070 p->utime = cputime_zero; 1071 p->stime = cputime_zero; 1072 p->gtime = cputime_zero; 1073 p->utimescaled = cputime_zero; 1074 p->stimescaled = cputime_zero; 1075 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1076 p->prev_utime = cputime_zero; 1077 p->prev_stime = cputime_zero; 1078 #endif 1079 1080 p->default_timer_slack_ns = current->timer_slack_ns; 1081 1082 task_io_accounting_init(&p->ioac); 1083 acct_clear_integrals(p); 1084 1085 posix_cpu_timers_init(p); 1086 1087 p->lock_depth = -1; /* -1 = no lock */ 1088 do_posix_clock_monotonic_gettime(&p->start_time); 1089 p->real_start_time = p->start_time; 1090 monotonic_to_bootbased(&p->real_start_time); 1091 p->io_context = NULL; 1092 p->audit_context = NULL; 1093 cgroup_fork(p); 1094 #ifdef CONFIG_NUMA 1095 p->mempolicy = mpol_dup(p->mempolicy); 1096 if (IS_ERR(p->mempolicy)) { 1097 retval = PTR_ERR(p->mempolicy); 1098 p->mempolicy = NULL; 1099 goto bad_fork_cleanup_cgroup; 1100 } 1101 mpol_fix_fork_child_flag(p); 1102 #endif 1103 #ifdef CONFIG_TRACE_IRQFLAGS 1104 p->irq_events = 0; 1105 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1106 p->hardirqs_enabled = 1; 1107 #else 1108 p->hardirqs_enabled = 0; 1109 #endif 1110 p->hardirq_enable_ip = 0; 1111 p->hardirq_enable_event = 0; 1112 p->hardirq_disable_ip = _THIS_IP_; 1113 p->hardirq_disable_event = 0; 1114 p->softirqs_enabled = 1; 1115 p->softirq_enable_ip = _THIS_IP_; 1116 p->softirq_enable_event = 0; 1117 p->softirq_disable_ip = 0; 1118 p->softirq_disable_event = 0; 1119 p->hardirq_context = 0; 1120 p->softirq_context = 0; 1121 #endif 1122 #ifdef CONFIG_LOCKDEP 1123 p->lockdep_depth = 0; /* no locks held yet */ 1124 p->curr_chain_key = 0; 1125 p->lockdep_recursion = 0; 1126 #endif 1127 1128 #ifdef CONFIG_DEBUG_MUTEXES 1129 p->blocked_on = NULL; /* not blocked yet */ 1130 #endif 1131 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1132 p->memcg_batch.do_batch = 0; 1133 p->memcg_batch.memcg = NULL; 1134 #endif 1135 1136 p->bts = NULL; 1137 1138 p->stack_start = stack_start; 1139 1140 /* Perform scheduler related setup. Assign this task to a CPU. */ 1141 sched_fork(p, clone_flags); 1142 1143 retval = perf_event_init_task(p); 1144 if (retval) 1145 goto bad_fork_cleanup_policy; 1146 1147 if ((retval = audit_alloc(p))) 1148 goto bad_fork_cleanup_policy; 1149 /* copy all the process information */ 1150 if ((retval = copy_semundo(clone_flags, p))) 1151 goto bad_fork_cleanup_audit; 1152 if ((retval = copy_files(clone_flags, p))) 1153 goto bad_fork_cleanup_semundo; 1154 if ((retval = copy_fs(clone_flags, p))) 1155 goto bad_fork_cleanup_files; 1156 if ((retval = copy_sighand(clone_flags, p))) 1157 goto bad_fork_cleanup_fs; 1158 if ((retval = copy_signal(clone_flags, p))) 1159 goto bad_fork_cleanup_sighand; 1160 if ((retval = copy_mm(clone_flags, p))) 1161 goto bad_fork_cleanup_signal; 1162 if ((retval = copy_namespaces(clone_flags, p))) 1163 goto bad_fork_cleanup_mm; 1164 if ((retval = copy_io(clone_flags, p))) 1165 goto bad_fork_cleanup_namespaces; 1166 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1167 if (retval) 1168 goto bad_fork_cleanup_io; 1169 1170 if (pid != &init_struct_pid) { 1171 retval = -ENOMEM; 1172 pid = alloc_pid(p->nsproxy->pid_ns); 1173 if (!pid) 1174 goto bad_fork_cleanup_io; 1175 1176 if (clone_flags & CLONE_NEWPID) { 1177 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1178 if (retval < 0) 1179 goto bad_fork_free_pid; 1180 } 1181 } 1182 1183 p->pid = pid_nr(pid); 1184 p->tgid = p->pid; 1185 if (clone_flags & CLONE_THREAD) 1186 p->tgid = current->tgid; 1187 1188 if (current->nsproxy != p->nsproxy) { 1189 retval = ns_cgroup_clone(p, pid); 1190 if (retval) 1191 goto bad_fork_free_pid; 1192 } 1193 1194 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1195 /* 1196 * Clear TID on mm_release()? 1197 */ 1198 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1199 #ifdef CONFIG_FUTEX 1200 p->robust_list = NULL; 1201 #ifdef CONFIG_COMPAT 1202 p->compat_robust_list = NULL; 1203 #endif 1204 INIT_LIST_HEAD(&p->pi_state_list); 1205 p->pi_state_cache = NULL; 1206 #endif 1207 /* 1208 * sigaltstack should be cleared when sharing the same VM 1209 */ 1210 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1211 p->sas_ss_sp = p->sas_ss_size = 0; 1212 1213 /* 1214 * Syscall tracing and stepping should be turned off in the 1215 * child regardless of CLONE_PTRACE. 1216 */ 1217 user_disable_single_step(p); 1218 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1219 #ifdef TIF_SYSCALL_EMU 1220 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1221 #endif 1222 clear_all_latency_tracing(p); 1223 1224 /* ok, now we should be set up.. */ 1225 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1226 p->pdeath_signal = 0; 1227 p->exit_state = 0; 1228 1229 /* 1230 * Ok, make it visible to the rest of the system. 1231 * We dont wake it up yet. 1232 */ 1233 p->group_leader = p; 1234 INIT_LIST_HEAD(&p->thread_group); 1235 1236 /* Now that the task is set up, run cgroup callbacks if 1237 * necessary. We need to run them before the task is visible 1238 * on the tasklist. */ 1239 cgroup_fork_callbacks(p); 1240 cgroup_callbacks_done = 1; 1241 1242 /* Need tasklist lock for parent etc handling! */ 1243 write_lock_irq(&tasklist_lock); 1244 1245 /* CLONE_PARENT re-uses the old parent */ 1246 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1247 p->real_parent = current->real_parent; 1248 p->parent_exec_id = current->parent_exec_id; 1249 } else { 1250 p->real_parent = current; 1251 p->parent_exec_id = current->self_exec_id; 1252 } 1253 1254 spin_lock(¤t->sighand->siglock); 1255 1256 /* 1257 * Process group and session signals need to be delivered to just the 1258 * parent before the fork or both the parent and the child after the 1259 * fork. Restart if a signal comes in before we add the new process to 1260 * it's process group. 1261 * A fatal signal pending means that current will exit, so the new 1262 * thread can't slip out of an OOM kill (or normal SIGKILL). 1263 */ 1264 recalc_sigpending(); 1265 if (signal_pending(current)) { 1266 spin_unlock(¤t->sighand->siglock); 1267 write_unlock_irq(&tasklist_lock); 1268 retval = -ERESTARTNOINTR; 1269 goto bad_fork_free_pid; 1270 } 1271 1272 if (clone_flags & CLONE_THREAD) { 1273 atomic_inc(¤t->signal->count); 1274 atomic_inc(¤t->signal->live); 1275 p->group_leader = current->group_leader; 1276 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1277 } 1278 1279 if (likely(p->pid)) { 1280 tracehook_finish_clone(p, clone_flags, trace); 1281 1282 if (thread_group_leader(p)) { 1283 if (clone_flags & CLONE_NEWPID) 1284 p->nsproxy->pid_ns->child_reaper = p; 1285 1286 p->signal->leader_pid = pid; 1287 tty_kref_put(p->signal->tty); 1288 p->signal->tty = tty_kref_get(current->signal->tty); 1289 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1290 attach_pid(p, PIDTYPE_SID, task_session(current)); 1291 list_add_tail(&p->sibling, &p->real_parent->children); 1292 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1293 __get_cpu_var(process_counts)++; 1294 } 1295 attach_pid(p, PIDTYPE_PID, pid); 1296 nr_threads++; 1297 } 1298 1299 total_forks++; 1300 spin_unlock(¤t->sighand->siglock); 1301 write_unlock_irq(&tasklist_lock); 1302 proc_fork_connector(p); 1303 cgroup_post_fork(p); 1304 perf_event_fork(p); 1305 return p; 1306 1307 bad_fork_free_pid: 1308 if (pid != &init_struct_pid) 1309 free_pid(pid); 1310 bad_fork_cleanup_io: 1311 if (p->io_context) 1312 exit_io_context(p); 1313 bad_fork_cleanup_namespaces: 1314 exit_task_namespaces(p); 1315 bad_fork_cleanup_mm: 1316 if (p->mm) 1317 mmput(p->mm); 1318 bad_fork_cleanup_signal: 1319 if (!(clone_flags & CLONE_THREAD)) 1320 __cleanup_signal(p->signal); 1321 bad_fork_cleanup_sighand: 1322 __cleanup_sighand(p->sighand); 1323 bad_fork_cleanup_fs: 1324 exit_fs(p); /* blocking */ 1325 bad_fork_cleanup_files: 1326 exit_files(p); /* blocking */ 1327 bad_fork_cleanup_semundo: 1328 exit_sem(p); 1329 bad_fork_cleanup_audit: 1330 audit_free(p); 1331 bad_fork_cleanup_policy: 1332 perf_event_free_task(p); 1333 #ifdef CONFIG_NUMA 1334 mpol_put(p->mempolicy); 1335 bad_fork_cleanup_cgroup: 1336 #endif 1337 cgroup_exit(p, cgroup_callbacks_done); 1338 delayacct_tsk_free(p); 1339 module_put(task_thread_info(p)->exec_domain->module); 1340 bad_fork_cleanup_count: 1341 atomic_dec(&p->cred->user->processes); 1342 exit_creds(p); 1343 bad_fork_free: 1344 free_task(p); 1345 fork_out: 1346 return ERR_PTR(retval); 1347 } 1348 1349 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1350 { 1351 memset(regs, 0, sizeof(struct pt_regs)); 1352 return regs; 1353 } 1354 1355 struct task_struct * __cpuinit fork_idle(int cpu) 1356 { 1357 struct task_struct *task; 1358 struct pt_regs regs; 1359 1360 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1361 &init_struct_pid, 0); 1362 if (!IS_ERR(task)) 1363 init_idle(task, cpu); 1364 1365 return task; 1366 } 1367 1368 /* 1369 * Ok, this is the main fork-routine. 1370 * 1371 * It copies the process, and if successful kick-starts 1372 * it and waits for it to finish using the VM if required. 1373 */ 1374 long do_fork(unsigned long clone_flags, 1375 unsigned long stack_start, 1376 struct pt_regs *regs, 1377 unsigned long stack_size, 1378 int __user *parent_tidptr, 1379 int __user *child_tidptr) 1380 { 1381 struct task_struct *p; 1382 int trace = 0; 1383 long nr; 1384 1385 /* 1386 * Do some preliminary argument and permissions checking before we 1387 * actually start allocating stuff 1388 */ 1389 if (clone_flags & CLONE_NEWUSER) { 1390 if (clone_flags & CLONE_THREAD) 1391 return -EINVAL; 1392 /* hopefully this check will go away when userns support is 1393 * complete 1394 */ 1395 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1396 !capable(CAP_SETGID)) 1397 return -EPERM; 1398 } 1399 1400 /* 1401 * We hope to recycle these flags after 2.6.26 1402 */ 1403 if (unlikely(clone_flags & CLONE_STOPPED)) { 1404 static int __read_mostly count = 100; 1405 1406 if (count > 0 && printk_ratelimit()) { 1407 char comm[TASK_COMM_LEN]; 1408 1409 count--; 1410 printk(KERN_INFO "fork(): process `%s' used deprecated " 1411 "clone flags 0x%lx\n", 1412 get_task_comm(comm, current), 1413 clone_flags & CLONE_STOPPED); 1414 } 1415 } 1416 1417 /* 1418 * When called from kernel_thread, don't do user tracing stuff. 1419 */ 1420 if (likely(user_mode(regs))) 1421 trace = tracehook_prepare_clone(clone_flags); 1422 1423 p = copy_process(clone_flags, stack_start, regs, stack_size, 1424 child_tidptr, NULL, trace); 1425 /* 1426 * Do this prior waking up the new thread - the thread pointer 1427 * might get invalid after that point, if the thread exits quickly. 1428 */ 1429 if (!IS_ERR(p)) { 1430 struct completion vfork; 1431 1432 trace_sched_process_fork(current, p); 1433 1434 nr = task_pid_vnr(p); 1435 1436 if (clone_flags & CLONE_PARENT_SETTID) 1437 put_user(nr, parent_tidptr); 1438 1439 if (clone_flags & CLONE_VFORK) { 1440 p->vfork_done = &vfork; 1441 init_completion(&vfork); 1442 } 1443 1444 audit_finish_fork(p); 1445 tracehook_report_clone(regs, clone_flags, nr, p); 1446 1447 /* 1448 * We set PF_STARTING at creation in case tracing wants to 1449 * use this to distinguish a fully live task from one that 1450 * hasn't gotten to tracehook_report_clone() yet. Now we 1451 * clear it and set the child going. 1452 */ 1453 p->flags &= ~PF_STARTING; 1454 1455 if (unlikely(clone_flags & CLONE_STOPPED)) { 1456 /* 1457 * We'll start up with an immediate SIGSTOP. 1458 */ 1459 sigaddset(&p->pending.signal, SIGSTOP); 1460 set_tsk_thread_flag(p, TIF_SIGPENDING); 1461 __set_task_state(p, TASK_STOPPED); 1462 } else { 1463 wake_up_new_task(p, clone_flags); 1464 } 1465 1466 tracehook_report_clone_complete(trace, regs, 1467 clone_flags, nr, p); 1468 1469 if (clone_flags & CLONE_VFORK) { 1470 freezer_do_not_count(); 1471 wait_for_completion(&vfork); 1472 freezer_count(); 1473 tracehook_report_vfork_done(p, nr); 1474 } 1475 } else { 1476 nr = PTR_ERR(p); 1477 } 1478 return nr; 1479 } 1480 1481 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1482 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1483 #endif 1484 1485 static void sighand_ctor(void *data) 1486 { 1487 struct sighand_struct *sighand = data; 1488 1489 spin_lock_init(&sighand->siglock); 1490 init_waitqueue_head(&sighand->signalfd_wqh); 1491 } 1492 1493 void __init proc_caches_init(void) 1494 { 1495 sighand_cachep = kmem_cache_create("sighand_cache", 1496 sizeof(struct sighand_struct), 0, 1497 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1498 SLAB_NOTRACK, sighand_ctor); 1499 signal_cachep = kmem_cache_create("signal_cache", 1500 sizeof(struct signal_struct), 0, 1501 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1502 files_cachep = kmem_cache_create("files_cache", 1503 sizeof(struct files_struct), 0, 1504 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1505 fs_cachep = kmem_cache_create("fs_cache", 1506 sizeof(struct fs_struct), 0, 1507 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1508 mm_cachep = kmem_cache_create("mm_struct", 1509 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1510 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1511 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1512 mmap_init(); 1513 } 1514 1515 /* 1516 * Check constraints on flags passed to the unshare system call and 1517 * force unsharing of additional process context as appropriate. 1518 */ 1519 static void check_unshare_flags(unsigned long *flags_ptr) 1520 { 1521 /* 1522 * If unsharing a thread from a thread group, must also 1523 * unshare vm. 1524 */ 1525 if (*flags_ptr & CLONE_THREAD) 1526 *flags_ptr |= CLONE_VM; 1527 1528 /* 1529 * If unsharing vm, must also unshare signal handlers. 1530 */ 1531 if (*flags_ptr & CLONE_VM) 1532 *flags_ptr |= CLONE_SIGHAND; 1533 1534 /* 1535 * If unsharing signal handlers and the task was created 1536 * using CLONE_THREAD, then must unshare the thread 1537 */ 1538 if ((*flags_ptr & CLONE_SIGHAND) && 1539 (atomic_read(¤t->signal->count) > 1)) 1540 *flags_ptr |= CLONE_THREAD; 1541 1542 /* 1543 * If unsharing namespace, must also unshare filesystem information. 1544 */ 1545 if (*flags_ptr & CLONE_NEWNS) 1546 *flags_ptr |= CLONE_FS; 1547 } 1548 1549 /* 1550 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1551 */ 1552 static int unshare_thread(unsigned long unshare_flags) 1553 { 1554 if (unshare_flags & CLONE_THREAD) 1555 return -EINVAL; 1556 1557 return 0; 1558 } 1559 1560 /* 1561 * Unshare the filesystem structure if it is being shared 1562 */ 1563 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1564 { 1565 struct fs_struct *fs = current->fs; 1566 1567 if (!(unshare_flags & CLONE_FS) || !fs) 1568 return 0; 1569 1570 /* don't need lock here; in the worst case we'll do useless copy */ 1571 if (fs->users == 1) 1572 return 0; 1573 1574 *new_fsp = copy_fs_struct(fs); 1575 if (!*new_fsp) 1576 return -ENOMEM; 1577 1578 return 0; 1579 } 1580 1581 /* 1582 * Unsharing of sighand is not supported yet 1583 */ 1584 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1585 { 1586 struct sighand_struct *sigh = current->sighand; 1587 1588 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1589 return -EINVAL; 1590 else 1591 return 0; 1592 } 1593 1594 /* 1595 * Unshare vm if it is being shared 1596 */ 1597 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1598 { 1599 struct mm_struct *mm = current->mm; 1600 1601 if ((unshare_flags & CLONE_VM) && 1602 (mm && atomic_read(&mm->mm_users) > 1)) { 1603 return -EINVAL; 1604 } 1605 1606 return 0; 1607 } 1608 1609 /* 1610 * Unshare file descriptor table if it is being shared 1611 */ 1612 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1613 { 1614 struct files_struct *fd = current->files; 1615 int error = 0; 1616 1617 if ((unshare_flags & CLONE_FILES) && 1618 (fd && atomic_read(&fd->count) > 1)) { 1619 *new_fdp = dup_fd(fd, &error); 1620 if (!*new_fdp) 1621 return error; 1622 } 1623 1624 return 0; 1625 } 1626 1627 /* 1628 * unshare allows a process to 'unshare' part of the process 1629 * context which was originally shared using clone. copy_* 1630 * functions used by do_fork() cannot be used here directly 1631 * because they modify an inactive task_struct that is being 1632 * constructed. Here we are modifying the current, active, 1633 * task_struct. 1634 */ 1635 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1636 { 1637 int err = 0; 1638 struct fs_struct *fs, *new_fs = NULL; 1639 struct sighand_struct *new_sigh = NULL; 1640 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1641 struct files_struct *fd, *new_fd = NULL; 1642 struct nsproxy *new_nsproxy = NULL; 1643 int do_sysvsem = 0; 1644 1645 check_unshare_flags(&unshare_flags); 1646 1647 /* Return -EINVAL for all unsupported flags */ 1648 err = -EINVAL; 1649 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1650 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1651 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1652 goto bad_unshare_out; 1653 1654 /* 1655 * CLONE_NEWIPC must also detach from the undolist: after switching 1656 * to a new ipc namespace, the semaphore arrays from the old 1657 * namespace are unreachable. 1658 */ 1659 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1660 do_sysvsem = 1; 1661 if ((err = unshare_thread(unshare_flags))) 1662 goto bad_unshare_out; 1663 if ((err = unshare_fs(unshare_flags, &new_fs))) 1664 goto bad_unshare_cleanup_thread; 1665 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1666 goto bad_unshare_cleanup_fs; 1667 if ((err = unshare_vm(unshare_flags, &new_mm))) 1668 goto bad_unshare_cleanup_sigh; 1669 if ((err = unshare_fd(unshare_flags, &new_fd))) 1670 goto bad_unshare_cleanup_vm; 1671 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1672 new_fs))) 1673 goto bad_unshare_cleanup_fd; 1674 1675 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1676 if (do_sysvsem) { 1677 /* 1678 * CLONE_SYSVSEM is equivalent to sys_exit(). 1679 */ 1680 exit_sem(current); 1681 } 1682 1683 if (new_nsproxy) { 1684 switch_task_namespaces(current, new_nsproxy); 1685 new_nsproxy = NULL; 1686 } 1687 1688 task_lock(current); 1689 1690 if (new_fs) { 1691 fs = current->fs; 1692 write_lock(&fs->lock); 1693 current->fs = new_fs; 1694 if (--fs->users) 1695 new_fs = NULL; 1696 else 1697 new_fs = fs; 1698 write_unlock(&fs->lock); 1699 } 1700 1701 if (new_mm) { 1702 mm = current->mm; 1703 active_mm = current->active_mm; 1704 current->mm = new_mm; 1705 current->active_mm = new_mm; 1706 activate_mm(active_mm, new_mm); 1707 new_mm = mm; 1708 } 1709 1710 if (new_fd) { 1711 fd = current->files; 1712 current->files = new_fd; 1713 new_fd = fd; 1714 } 1715 1716 task_unlock(current); 1717 } 1718 1719 if (new_nsproxy) 1720 put_nsproxy(new_nsproxy); 1721 1722 bad_unshare_cleanup_fd: 1723 if (new_fd) 1724 put_files_struct(new_fd); 1725 1726 bad_unshare_cleanup_vm: 1727 if (new_mm) 1728 mmput(new_mm); 1729 1730 bad_unshare_cleanup_sigh: 1731 if (new_sigh) 1732 if (atomic_dec_and_test(&new_sigh->count)) 1733 kmem_cache_free(sighand_cachep, new_sigh); 1734 1735 bad_unshare_cleanup_fs: 1736 if (new_fs) 1737 free_fs_struct(new_fs); 1738 1739 bad_unshare_cleanup_thread: 1740 bad_unshare_out: 1741 return err; 1742 } 1743 1744 /* 1745 * Helper to unshare the files of the current task. 1746 * We don't want to expose copy_files internals to 1747 * the exec layer of the kernel. 1748 */ 1749 1750 int unshare_files(struct files_struct **displaced) 1751 { 1752 struct task_struct *task = current; 1753 struct files_struct *copy = NULL; 1754 int error; 1755 1756 error = unshare_fd(CLONE_FILES, ©); 1757 if (error || !copy) { 1758 *displaced = NULL; 1759 return error; 1760 } 1761 *displaced = task->files; 1762 task_lock(task); 1763 task->files = copy; 1764 task_unlock(task); 1765 return 0; 1766 } 1767