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