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 int nr_processes(void) 91 { 92 int cpu; 93 int total = 0; 94 95 for_each_possible_cpu(cpu) 96 total += per_cpu(process_counts, cpu); 97 98 return total; 99 } 100 101 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 102 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 103 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 104 static struct kmem_cache *task_struct_cachep; 105 #endif 106 107 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 108 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 109 { 110 #ifdef CONFIG_DEBUG_STACK_USAGE 111 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 112 #else 113 gfp_t mask = GFP_KERNEL; 114 #endif 115 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 116 } 117 118 static inline void free_thread_info(struct thread_info *ti) 119 { 120 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 121 } 122 #endif 123 124 /* SLAB cache for signal_struct structures (tsk->signal) */ 125 static struct kmem_cache *signal_cachep; 126 127 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 128 struct kmem_cache *sighand_cachep; 129 130 /* SLAB cache for files_struct structures (tsk->files) */ 131 struct kmem_cache *files_cachep; 132 133 /* SLAB cache for fs_struct structures (tsk->fs) */ 134 struct kmem_cache *fs_cachep; 135 136 /* SLAB cache for vm_area_struct structures */ 137 struct kmem_cache *vm_area_cachep; 138 139 /* SLAB cache for mm_struct structures (tsk->mm) */ 140 static struct kmem_cache *mm_cachep; 141 142 static void account_kernel_stack(struct thread_info *ti, int account) 143 { 144 struct zone *zone = page_zone(virt_to_page(ti)); 145 146 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 147 } 148 149 void free_task(struct task_struct *tsk) 150 { 151 prop_local_destroy_single(&tsk->dirties); 152 account_kernel_stack(tsk->stack, -1); 153 free_thread_info(tsk->stack); 154 rt_mutex_debug_task_free(tsk); 155 ftrace_graph_exit_task(tsk); 156 free_task_struct(tsk); 157 } 158 EXPORT_SYMBOL(free_task); 159 160 void __put_task_struct(struct task_struct *tsk) 161 { 162 WARN_ON(!tsk->exit_state); 163 WARN_ON(atomic_read(&tsk->usage)); 164 WARN_ON(tsk == current); 165 166 exit_creds(tsk); 167 delayacct_tsk_free(tsk); 168 169 if (!profile_handoff_task(tsk)) 170 free_task(tsk); 171 } 172 173 /* 174 * macro override instead of weak attribute alias, to workaround 175 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 176 */ 177 #ifndef arch_task_cache_init 178 #define arch_task_cache_init() 179 #endif 180 181 void __init fork_init(unsigned long mempages) 182 { 183 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 184 #ifndef ARCH_MIN_TASKALIGN 185 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 186 #endif 187 /* create a slab on which task_structs can be allocated */ 188 task_struct_cachep = 189 kmem_cache_create("task_struct", sizeof(struct task_struct), 190 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 191 #endif 192 193 /* do the arch specific task caches init */ 194 arch_task_cache_init(); 195 196 /* 197 * The default maximum number of threads is set to a safe 198 * value: the thread structures can take up at most half 199 * of memory. 200 */ 201 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 202 203 /* 204 * we need to allow at least 20 threads to boot a system 205 */ 206 if(max_threads < 20) 207 max_threads = 20; 208 209 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 210 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 211 init_task.signal->rlim[RLIMIT_SIGPENDING] = 212 init_task.signal->rlim[RLIMIT_NPROC]; 213 } 214 215 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 216 struct task_struct *src) 217 { 218 *dst = *src; 219 return 0; 220 } 221 222 static struct task_struct *dup_task_struct(struct task_struct *orig) 223 { 224 struct task_struct *tsk; 225 struct thread_info *ti; 226 unsigned long *stackend; 227 228 int err; 229 230 prepare_to_copy(orig); 231 232 tsk = alloc_task_struct(); 233 if (!tsk) 234 return NULL; 235 236 ti = alloc_thread_info(tsk); 237 if (!ti) { 238 free_task_struct(tsk); 239 return NULL; 240 } 241 242 err = arch_dup_task_struct(tsk, orig); 243 if (err) 244 goto out; 245 246 tsk->stack = ti; 247 248 err = prop_local_init_single(&tsk->dirties); 249 if (err) 250 goto out; 251 252 setup_thread_stack(tsk, orig); 253 clear_user_return_notifier(tsk); 254 stackend = end_of_stack(tsk); 255 *stackend = STACK_END_MAGIC; /* for overflow detection */ 256 257 #ifdef CONFIG_CC_STACKPROTECTOR 258 tsk->stack_canary = get_random_int(); 259 #endif 260 261 /* One for us, one for whoever does the "release_task()" (usually parent) */ 262 atomic_set(&tsk->usage,2); 263 atomic_set(&tsk->fs_excl, 0); 264 #ifdef CONFIG_BLK_DEV_IO_TRACE 265 tsk->btrace_seq = 0; 266 #endif 267 tsk->splice_pipe = NULL; 268 269 account_kernel_stack(ti, 1); 270 271 return tsk; 272 273 out: 274 free_thread_info(ti); 275 free_task_struct(tsk); 276 return NULL; 277 } 278 279 #ifdef CONFIG_MMU 280 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 281 { 282 struct vm_area_struct *mpnt, *tmp, **pprev; 283 struct rb_node **rb_link, *rb_parent; 284 int retval; 285 unsigned long charge; 286 struct mempolicy *pol; 287 288 down_write(&oldmm->mmap_sem); 289 flush_cache_dup_mm(oldmm); 290 /* 291 * Not linked in yet - no deadlock potential: 292 */ 293 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 294 295 mm->locked_vm = 0; 296 mm->mmap = NULL; 297 mm->mmap_cache = NULL; 298 mm->free_area_cache = oldmm->mmap_base; 299 mm->cached_hole_size = ~0UL; 300 mm->map_count = 0; 301 cpumask_clear(mm_cpumask(mm)); 302 mm->mm_rb = RB_ROOT; 303 rb_link = &mm->mm_rb.rb_node; 304 rb_parent = NULL; 305 pprev = &mm->mmap; 306 retval = ksm_fork(mm, oldmm); 307 if (retval) 308 goto out; 309 310 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 311 struct file *file; 312 313 if (mpnt->vm_flags & VM_DONTCOPY) { 314 long pages = vma_pages(mpnt); 315 mm->total_vm -= pages; 316 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 317 -pages); 318 continue; 319 } 320 charge = 0; 321 if (mpnt->vm_flags & VM_ACCOUNT) { 322 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 323 if (security_vm_enough_memory(len)) 324 goto fail_nomem; 325 charge = len; 326 } 327 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 328 if (!tmp) 329 goto fail_nomem; 330 *tmp = *mpnt; 331 pol = mpol_dup(vma_policy(mpnt)); 332 retval = PTR_ERR(pol); 333 if (IS_ERR(pol)) 334 goto fail_nomem_policy; 335 vma_set_policy(tmp, pol); 336 tmp->vm_flags &= ~VM_LOCKED; 337 tmp->vm_mm = mm; 338 tmp->vm_next = NULL; 339 anon_vma_link(tmp); 340 file = tmp->vm_file; 341 if (file) { 342 struct inode *inode = file->f_path.dentry->d_inode; 343 struct address_space *mapping = file->f_mapping; 344 345 get_file(file); 346 if (tmp->vm_flags & VM_DENYWRITE) 347 atomic_dec(&inode->i_writecount); 348 spin_lock(&mapping->i_mmap_lock); 349 if (tmp->vm_flags & VM_SHARED) 350 mapping->i_mmap_writable++; 351 tmp->vm_truncate_count = mpnt->vm_truncate_count; 352 flush_dcache_mmap_lock(mapping); 353 /* insert tmp into the share list, just after mpnt */ 354 vma_prio_tree_add(tmp, mpnt); 355 flush_dcache_mmap_unlock(mapping); 356 spin_unlock(&mapping->i_mmap_lock); 357 } 358 359 /* 360 * Clear hugetlb-related page reserves for children. This only 361 * affects MAP_PRIVATE mappings. Faults generated by the child 362 * are not guaranteed to succeed, even if read-only 363 */ 364 if (is_vm_hugetlb_page(tmp)) 365 reset_vma_resv_huge_pages(tmp); 366 367 /* 368 * Link in the new vma and copy the page table entries. 369 */ 370 *pprev = tmp; 371 pprev = &tmp->vm_next; 372 373 __vma_link_rb(mm, tmp, rb_link, rb_parent); 374 rb_link = &tmp->vm_rb.rb_right; 375 rb_parent = &tmp->vm_rb; 376 377 mm->map_count++; 378 retval = copy_page_range(mm, oldmm, mpnt); 379 380 if (tmp->vm_ops && tmp->vm_ops->open) 381 tmp->vm_ops->open(tmp); 382 383 if (retval) 384 goto out; 385 } 386 /* a new mm has just been created */ 387 arch_dup_mmap(oldmm, mm); 388 retval = 0; 389 out: 390 up_write(&mm->mmap_sem); 391 flush_tlb_mm(oldmm); 392 up_write(&oldmm->mmap_sem); 393 return retval; 394 fail_nomem_policy: 395 kmem_cache_free(vm_area_cachep, tmp); 396 fail_nomem: 397 retval = -ENOMEM; 398 vm_unacct_memory(charge); 399 goto out; 400 } 401 402 static inline int mm_alloc_pgd(struct mm_struct * mm) 403 { 404 mm->pgd = pgd_alloc(mm); 405 if (unlikely(!mm->pgd)) 406 return -ENOMEM; 407 return 0; 408 } 409 410 static inline void mm_free_pgd(struct mm_struct * mm) 411 { 412 pgd_free(mm, mm->pgd); 413 } 414 #else 415 #define dup_mmap(mm, oldmm) (0) 416 #define mm_alloc_pgd(mm) (0) 417 #define mm_free_pgd(mm) 418 #endif /* CONFIG_MMU */ 419 420 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 421 422 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 423 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 424 425 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 426 427 static int __init coredump_filter_setup(char *s) 428 { 429 default_dump_filter = 430 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 431 MMF_DUMP_FILTER_MASK; 432 return 1; 433 } 434 435 __setup("coredump_filter=", coredump_filter_setup); 436 437 #include <linux/init_task.h> 438 439 static void mm_init_aio(struct mm_struct *mm) 440 { 441 #ifdef CONFIG_AIO 442 spin_lock_init(&mm->ioctx_lock); 443 INIT_HLIST_HEAD(&mm->ioctx_list); 444 #endif 445 } 446 447 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 448 { 449 atomic_set(&mm->mm_users, 1); 450 atomic_set(&mm->mm_count, 1); 451 init_rwsem(&mm->mmap_sem); 452 INIT_LIST_HEAD(&mm->mmlist); 453 mm->flags = (current->mm) ? 454 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 455 mm->core_state = NULL; 456 mm->nr_ptes = 0; 457 set_mm_counter(mm, file_rss, 0); 458 set_mm_counter(mm, anon_rss, 0); 459 spin_lock_init(&mm->page_table_lock); 460 mm->free_area_cache = TASK_UNMAPPED_BASE; 461 mm->cached_hole_size = ~0UL; 462 mm_init_aio(mm); 463 mm_init_owner(mm, p); 464 465 if (likely(!mm_alloc_pgd(mm))) { 466 mm->def_flags = 0; 467 mmu_notifier_mm_init(mm); 468 return mm; 469 } 470 471 free_mm(mm); 472 return NULL; 473 } 474 475 /* 476 * Allocate and initialize an mm_struct. 477 */ 478 struct mm_struct * mm_alloc(void) 479 { 480 struct mm_struct * mm; 481 482 mm = allocate_mm(); 483 if (mm) { 484 memset(mm, 0, sizeof(*mm)); 485 mm = mm_init(mm, current); 486 } 487 return mm; 488 } 489 490 /* 491 * Called when the last reference to the mm 492 * is dropped: either by a lazy thread or by 493 * mmput. Free the page directory and the mm. 494 */ 495 void __mmdrop(struct mm_struct *mm) 496 { 497 BUG_ON(mm == &init_mm); 498 mm_free_pgd(mm); 499 destroy_context(mm); 500 mmu_notifier_mm_destroy(mm); 501 free_mm(mm); 502 } 503 EXPORT_SYMBOL_GPL(__mmdrop); 504 505 /* 506 * Decrement the use count and release all resources for an mm. 507 */ 508 void mmput(struct mm_struct *mm) 509 { 510 might_sleep(); 511 512 if (atomic_dec_and_test(&mm->mm_users)) { 513 exit_aio(mm); 514 ksm_exit(mm); 515 exit_mmap(mm); 516 set_mm_exe_file(mm, NULL); 517 if (!list_empty(&mm->mmlist)) { 518 spin_lock(&mmlist_lock); 519 list_del(&mm->mmlist); 520 spin_unlock(&mmlist_lock); 521 } 522 put_swap_token(mm); 523 if (mm->binfmt) 524 module_put(mm->binfmt->module); 525 mmdrop(mm); 526 } 527 } 528 EXPORT_SYMBOL_GPL(mmput); 529 530 /** 531 * get_task_mm - acquire a reference to the task's mm 532 * 533 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 534 * this kernel workthread has transiently adopted a user mm with use_mm, 535 * to do its AIO) is not set and if so returns a reference to it, after 536 * bumping up the use count. User must release the mm via mmput() 537 * after use. Typically used by /proc and ptrace. 538 */ 539 struct mm_struct *get_task_mm(struct task_struct *task) 540 { 541 struct mm_struct *mm; 542 543 task_lock(task); 544 mm = task->mm; 545 if (mm) { 546 if (task->flags & PF_KTHREAD) 547 mm = NULL; 548 else 549 atomic_inc(&mm->mm_users); 550 } 551 task_unlock(task); 552 return mm; 553 } 554 EXPORT_SYMBOL_GPL(get_task_mm); 555 556 /* Please note the differences between mmput and mm_release. 557 * mmput is called whenever we stop holding onto a mm_struct, 558 * error success whatever. 559 * 560 * mm_release is called after a mm_struct has been removed 561 * from the current process. 562 * 563 * This difference is important for error handling, when we 564 * only half set up a mm_struct for a new process and need to restore 565 * the old one. Because we mmput the new mm_struct before 566 * restoring the old one. . . 567 * Eric Biederman 10 January 1998 568 */ 569 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 570 { 571 struct completion *vfork_done = tsk->vfork_done; 572 573 /* Get rid of any futexes when releasing the mm */ 574 #ifdef CONFIG_FUTEX 575 if (unlikely(tsk->robust_list)) { 576 exit_robust_list(tsk); 577 tsk->robust_list = NULL; 578 } 579 #ifdef CONFIG_COMPAT 580 if (unlikely(tsk->compat_robust_list)) { 581 compat_exit_robust_list(tsk); 582 tsk->compat_robust_list = NULL; 583 } 584 #endif 585 if (unlikely(!list_empty(&tsk->pi_state_list))) 586 exit_pi_state_list(tsk); 587 #endif 588 589 /* Get rid of any cached register state */ 590 deactivate_mm(tsk, mm); 591 592 /* notify parent sleeping on vfork() */ 593 if (vfork_done) { 594 tsk->vfork_done = NULL; 595 complete(vfork_done); 596 } 597 598 /* 599 * If we're exiting normally, clear a user-space tid field if 600 * requested. We leave this alone when dying by signal, to leave 601 * the value intact in a core dump, and to save the unnecessary 602 * trouble otherwise. Userland only wants this done for a sys_exit. 603 */ 604 if (tsk->clear_child_tid) { 605 if (!(tsk->flags & PF_SIGNALED) && 606 atomic_read(&mm->mm_users) > 1) { 607 /* 608 * We don't check the error code - if userspace has 609 * not set up a proper pointer then tough luck. 610 */ 611 put_user(0, tsk->clear_child_tid); 612 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 613 1, NULL, NULL, 0); 614 } 615 tsk->clear_child_tid = NULL; 616 } 617 } 618 619 /* 620 * Allocate a new mm structure and copy contents from the 621 * mm structure of the passed in task structure. 622 */ 623 struct mm_struct *dup_mm(struct task_struct *tsk) 624 { 625 struct mm_struct *mm, *oldmm = current->mm; 626 int err; 627 628 if (!oldmm) 629 return NULL; 630 631 mm = allocate_mm(); 632 if (!mm) 633 goto fail_nomem; 634 635 memcpy(mm, oldmm, sizeof(*mm)); 636 637 /* Initializing for Swap token stuff */ 638 mm->token_priority = 0; 639 mm->last_interval = 0; 640 641 if (!mm_init(mm, tsk)) 642 goto fail_nomem; 643 644 if (init_new_context(tsk, mm)) 645 goto fail_nocontext; 646 647 dup_mm_exe_file(oldmm, mm); 648 649 err = dup_mmap(mm, oldmm); 650 if (err) 651 goto free_pt; 652 653 mm->hiwater_rss = get_mm_rss(mm); 654 mm->hiwater_vm = mm->total_vm; 655 656 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 657 goto free_pt; 658 659 return mm; 660 661 free_pt: 662 /* don't put binfmt in mmput, we haven't got module yet */ 663 mm->binfmt = NULL; 664 mmput(mm); 665 666 fail_nomem: 667 return NULL; 668 669 fail_nocontext: 670 /* 671 * If init_new_context() failed, we cannot use mmput() to free the mm 672 * because it calls destroy_context() 673 */ 674 mm_free_pgd(mm); 675 free_mm(mm); 676 return NULL; 677 } 678 679 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 680 { 681 struct mm_struct * mm, *oldmm; 682 int retval; 683 684 tsk->min_flt = tsk->maj_flt = 0; 685 tsk->nvcsw = tsk->nivcsw = 0; 686 #ifdef CONFIG_DETECT_HUNG_TASK 687 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 688 #endif 689 690 tsk->mm = NULL; 691 tsk->active_mm = NULL; 692 693 /* 694 * Are we cloning a kernel thread? 695 * 696 * We need to steal a active VM for that.. 697 */ 698 oldmm = current->mm; 699 if (!oldmm) 700 return 0; 701 702 if (clone_flags & CLONE_VM) { 703 atomic_inc(&oldmm->mm_users); 704 mm = oldmm; 705 goto good_mm; 706 } 707 708 retval = -ENOMEM; 709 mm = dup_mm(tsk); 710 if (!mm) 711 goto fail_nomem; 712 713 good_mm: 714 /* Initializing for Swap token stuff */ 715 mm->token_priority = 0; 716 mm->last_interval = 0; 717 718 tsk->mm = mm; 719 tsk->active_mm = mm; 720 return 0; 721 722 fail_nomem: 723 return retval; 724 } 725 726 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 727 { 728 struct fs_struct *fs = current->fs; 729 if (clone_flags & CLONE_FS) { 730 /* tsk->fs is already what we want */ 731 write_lock(&fs->lock); 732 if (fs->in_exec) { 733 write_unlock(&fs->lock); 734 return -EAGAIN; 735 } 736 fs->users++; 737 write_unlock(&fs->lock); 738 return 0; 739 } 740 tsk->fs = copy_fs_struct(fs); 741 if (!tsk->fs) 742 return -ENOMEM; 743 return 0; 744 } 745 746 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 747 { 748 struct files_struct *oldf, *newf; 749 int error = 0; 750 751 /* 752 * A background process may not have any files ... 753 */ 754 oldf = current->files; 755 if (!oldf) 756 goto out; 757 758 if (clone_flags & CLONE_FILES) { 759 atomic_inc(&oldf->count); 760 goto out; 761 } 762 763 newf = dup_fd(oldf, &error); 764 if (!newf) 765 goto out; 766 767 tsk->files = newf; 768 error = 0; 769 out: 770 return error; 771 } 772 773 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 774 { 775 #ifdef CONFIG_BLOCK 776 struct io_context *ioc = current->io_context; 777 778 if (!ioc) 779 return 0; 780 /* 781 * Share io context with parent, if CLONE_IO is set 782 */ 783 if (clone_flags & CLONE_IO) { 784 tsk->io_context = ioc_task_link(ioc); 785 if (unlikely(!tsk->io_context)) 786 return -ENOMEM; 787 } else if (ioprio_valid(ioc->ioprio)) { 788 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 789 if (unlikely(!tsk->io_context)) 790 return -ENOMEM; 791 792 tsk->io_context->ioprio = ioc->ioprio; 793 } 794 #endif 795 return 0; 796 } 797 798 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 799 { 800 struct sighand_struct *sig; 801 802 if (clone_flags & CLONE_SIGHAND) { 803 atomic_inc(¤t->sighand->count); 804 return 0; 805 } 806 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 807 rcu_assign_pointer(tsk->sighand, sig); 808 if (!sig) 809 return -ENOMEM; 810 atomic_set(&sig->count, 1); 811 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 812 return 0; 813 } 814 815 void __cleanup_sighand(struct sighand_struct *sighand) 816 { 817 if (atomic_dec_and_test(&sighand->count)) 818 kmem_cache_free(sighand_cachep, sighand); 819 } 820 821 822 /* 823 * Initialize POSIX timer handling for a thread group. 824 */ 825 static void posix_cpu_timers_init_group(struct signal_struct *sig) 826 { 827 /* Thread group counters. */ 828 thread_group_cputime_init(sig); 829 830 /* Expiration times and increments. */ 831 sig->it[CPUCLOCK_PROF].expires = cputime_zero; 832 sig->it[CPUCLOCK_PROF].incr = cputime_zero; 833 sig->it[CPUCLOCK_VIRT].expires = cputime_zero; 834 sig->it[CPUCLOCK_VIRT].incr = cputime_zero; 835 836 /* Cached expiration times. */ 837 sig->cputime_expires.prof_exp = cputime_zero; 838 sig->cputime_expires.virt_exp = cputime_zero; 839 sig->cputime_expires.sched_exp = 0; 840 841 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 842 sig->cputime_expires.prof_exp = 843 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 844 sig->cputimer.running = 1; 845 } 846 847 /* The timer lists. */ 848 INIT_LIST_HEAD(&sig->cpu_timers[0]); 849 INIT_LIST_HEAD(&sig->cpu_timers[1]); 850 INIT_LIST_HEAD(&sig->cpu_timers[2]); 851 } 852 853 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 854 { 855 struct signal_struct *sig; 856 857 if (clone_flags & CLONE_THREAD) 858 return 0; 859 860 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 861 tsk->signal = sig; 862 if (!sig) 863 return -ENOMEM; 864 865 atomic_set(&sig->count, 1); 866 atomic_set(&sig->live, 1); 867 init_waitqueue_head(&sig->wait_chldexit); 868 sig->flags = 0; 869 if (clone_flags & CLONE_NEWPID) 870 sig->flags |= SIGNAL_UNKILLABLE; 871 sig->group_exit_code = 0; 872 sig->group_exit_task = NULL; 873 sig->group_stop_count = 0; 874 sig->curr_target = tsk; 875 init_sigpending(&sig->shared_pending); 876 INIT_LIST_HEAD(&sig->posix_timers); 877 878 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 879 sig->it_real_incr.tv64 = 0; 880 sig->real_timer.function = it_real_fn; 881 882 sig->leader = 0; /* session leadership doesn't inherit */ 883 sig->tty_old_pgrp = NULL; 884 sig->tty = NULL; 885 886 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 887 sig->gtime = cputime_zero; 888 sig->cgtime = cputime_zero; 889 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 890 sig->prev_utime = sig->prev_stime = cputime_zero; 891 #endif 892 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 893 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 894 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 895 sig->maxrss = sig->cmaxrss = 0; 896 task_io_accounting_init(&sig->ioac); 897 sig->sum_sched_runtime = 0; 898 taskstats_tgid_init(sig); 899 900 task_lock(current->group_leader); 901 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 902 task_unlock(current->group_leader); 903 904 posix_cpu_timers_init_group(sig); 905 906 acct_init_pacct(&sig->pacct); 907 908 tty_audit_fork(sig); 909 910 sig->oom_adj = current->signal->oom_adj; 911 912 return 0; 913 } 914 915 void __cleanup_signal(struct signal_struct *sig) 916 { 917 thread_group_cputime_free(sig); 918 tty_kref_put(sig->tty); 919 kmem_cache_free(signal_cachep, sig); 920 } 921 922 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 923 { 924 unsigned long new_flags = p->flags; 925 926 new_flags &= ~PF_SUPERPRIV; 927 new_flags |= PF_FORKNOEXEC; 928 new_flags |= PF_STARTING; 929 p->flags = new_flags; 930 clear_freeze_flag(p); 931 } 932 933 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 934 { 935 current->clear_child_tid = tidptr; 936 937 return task_pid_vnr(current); 938 } 939 940 static void rt_mutex_init_task(struct task_struct *p) 941 { 942 raw_spin_lock_init(&p->pi_lock); 943 #ifdef CONFIG_RT_MUTEXES 944 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 945 p->pi_blocked_on = NULL; 946 #endif 947 } 948 949 #ifdef CONFIG_MM_OWNER 950 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 951 { 952 mm->owner = p; 953 } 954 #endif /* CONFIG_MM_OWNER */ 955 956 /* 957 * Initialize POSIX timer handling for a single task. 958 */ 959 static void posix_cpu_timers_init(struct task_struct *tsk) 960 { 961 tsk->cputime_expires.prof_exp = cputime_zero; 962 tsk->cputime_expires.virt_exp = cputime_zero; 963 tsk->cputime_expires.sched_exp = 0; 964 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 965 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 966 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 967 } 968 969 /* 970 * This creates a new process as a copy of the old one, 971 * but does not actually start it yet. 972 * 973 * It copies the registers, and all the appropriate 974 * parts of the process environment (as per the clone 975 * flags). The actual kick-off is left to the caller. 976 */ 977 static struct task_struct *copy_process(unsigned long clone_flags, 978 unsigned long stack_start, 979 struct pt_regs *regs, 980 unsigned long stack_size, 981 int __user *child_tidptr, 982 struct pid *pid, 983 int trace) 984 { 985 int retval; 986 struct task_struct *p; 987 int cgroup_callbacks_done = 0; 988 989 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 990 return ERR_PTR(-EINVAL); 991 992 /* 993 * Thread groups must share signals as well, and detached threads 994 * can only be started up within the thread group. 995 */ 996 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 997 return ERR_PTR(-EINVAL); 998 999 /* 1000 * Shared signal handlers imply shared VM. By way of the above, 1001 * thread groups also imply shared VM. Blocking this case allows 1002 * for various simplifications in other code. 1003 */ 1004 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1005 return ERR_PTR(-EINVAL); 1006 1007 /* 1008 * Siblings of global init remain as zombies on exit since they are 1009 * not reaped by their parent (swapper). To solve this and to avoid 1010 * multi-rooted process trees, prevent global and container-inits 1011 * from creating siblings. 1012 */ 1013 if ((clone_flags & CLONE_PARENT) && 1014 current->signal->flags & SIGNAL_UNKILLABLE) 1015 return ERR_PTR(-EINVAL); 1016 1017 retval = security_task_create(clone_flags); 1018 if (retval) 1019 goto fork_out; 1020 1021 retval = -ENOMEM; 1022 p = dup_task_struct(current); 1023 if (!p) 1024 goto fork_out; 1025 1026 ftrace_graph_init_task(p); 1027 1028 rt_mutex_init_task(p); 1029 1030 #ifdef CONFIG_PROVE_LOCKING 1031 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1032 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1033 #endif 1034 retval = -EAGAIN; 1035 if (atomic_read(&p->real_cred->user->processes) >= 1036 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1037 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1038 p->real_cred->user != INIT_USER) 1039 goto bad_fork_free; 1040 } 1041 1042 retval = copy_creds(p, clone_flags); 1043 if (retval < 0) 1044 goto bad_fork_free; 1045 1046 /* 1047 * If multiple threads are within copy_process(), then this check 1048 * triggers too late. This doesn't hurt, the check is only there 1049 * to stop root fork bombs. 1050 */ 1051 retval = -EAGAIN; 1052 if (nr_threads >= max_threads) 1053 goto bad_fork_cleanup_count; 1054 1055 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1056 goto bad_fork_cleanup_count; 1057 1058 p->did_exec = 0; 1059 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1060 copy_flags(clone_flags, p); 1061 INIT_LIST_HEAD(&p->children); 1062 INIT_LIST_HEAD(&p->sibling); 1063 rcu_copy_process(p); 1064 p->vfork_done = NULL; 1065 spin_lock_init(&p->alloc_lock); 1066 1067 init_sigpending(&p->pending); 1068 1069 p->utime = cputime_zero; 1070 p->stime = cputime_zero; 1071 p->gtime = cputime_zero; 1072 p->utimescaled = cputime_zero; 1073 p->stimescaled = cputime_zero; 1074 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1075 p->prev_utime = cputime_zero; 1076 p->prev_stime = cputime_zero; 1077 #endif 1078 1079 p->default_timer_slack_ns = current->timer_slack_ns; 1080 1081 task_io_accounting_init(&p->ioac); 1082 acct_clear_integrals(p); 1083 1084 posix_cpu_timers_init(p); 1085 1086 p->lock_depth = -1; /* -1 = no lock */ 1087 do_posix_clock_monotonic_gettime(&p->start_time); 1088 p->real_start_time = p->start_time; 1089 monotonic_to_bootbased(&p->real_start_time); 1090 p->io_context = NULL; 1091 p->audit_context = NULL; 1092 cgroup_fork(p); 1093 #ifdef CONFIG_NUMA 1094 p->mempolicy = mpol_dup(p->mempolicy); 1095 if (IS_ERR(p->mempolicy)) { 1096 retval = PTR_ERR(p->mempolicy); 1097 p->mempolicy = NULL; 1098 goto bad_fork_cleanup_cgroup; 1099 } 1100 mpol_fix_fork_child_flag(p); 1101 #endif 1102 #ifdef CONFIG_TRACE_IRQFLAGS 1103 p->irq_events = 0; 1104 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1105 p->hardirqs_enabled = 1; 1106 #else 1107 p->hardirqs_enabled = 0; 1108 #endif 1109 p->hardirq_enable_ip = 0; 1110 p->hardirq_enable_event = 0; 1111 p->hardirq_disable_ip = _THIS_IP_; 1112 p->hardirq_disable_event = 0; 1113 p->softirqs_enabled = 1; 1114 p->softirq_enable_ip = _THIS_IP_; 1115 p->softirq_enable_event = 0; 1116 p->softirq_disable_ip = 0; 1117 p->softirq_disable_event = 0; 1118 p->hardirq_context = 0; 1119 p->softirq_context = 0; 1120 #endif 1121 #ifdef CONFIG_LOCKDEP 1122 p->lockdep_depth = 0; /* no locks held yet */ 1123 p->curr_chain_key = 0; 1124 p->lockdep_recursion = 0; 1125 #endif 1126 1127 #ifdef CONFIG_DEBUG_MUTEXES 1128 p->blocked_on = NULL; /* not blocked yet */ 1129 #endif 1130 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1131 p->memcg_batch.do_batch = 0; 1132 p->memcg_batch.memcg = NULL; 1133 #endif 1134 1135 p->bts = NULL; 1136 1137 p->stack_start = stack_start; 1138 1139 /* Perform scheduler related setup. Assign this task to a CPU. */ 1140 sched_fork(p, clone_flags); 1141 1142 retval = perf_event_init_task(p); 1143 if (retval) 1144 goto bad_fork_cleanup_policy; 1145 1146 if ((retval = audit_alloc(p))) 1147 goto bad_fork_cleanup_policy; 1148 /* copy all the process information */ 1149 if ((retval = copy_semundo(clone_flags, p))) 1150 goto bad_fork_cleanup_audit; 1151 if ((retval = copy_files(clone_flags, p))) 1152 goto bad_fork_cleanup_semundo; 1153 if ((retval = copy_fs(clone_flags, p))) 1154 goto bad_fork_cleanup_files; 1155 if ((retval = copy_sighand(clone_flags, p))) 1156 goto bad_fork_cleanup_fs; 1157 if ((retval = copy_signal(clone_flags, p))) 1158 goto bad_fork_cleanup_sighand; 1159 if ((retval = copy_mm(clone_flags, p))) 1160 goto bad_fork_cleanup_signal; 1161 if ((retval = copy_namespaces(clone_flags, p))) 1162 goto bad_fork_cleanup_mm; 1163 if ((retval = copy_io(clone_flags, p))) 1164 goto bad_fork_cleanup_namespaces; 1165 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1166 if (retval) 1167 goto bad_fork_cleanup_io; 1168 1169 if (pid != &init_struct_pid) { 1170 retval = -ENOMEM; 1171 pid = alloc_pid(p->nsproxy->pid_ns); 1172 if (!pid) 1173 goto bad_fork_cleanup_io; 1174 1175 if (clone_flags & CLONE_NEWPID) { 1176 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1177 if (retval < 0) 1178 goto bad_fork_free_pid; 1179 } 1180 } 1181 1182 p->pid = pid_nr(pid); 1183 p->tgid = p->pid; 1184 if (clone_flags & CLONE_THREAD) 1185 p->tgid = current->tgid; 1186 1187 if (current->nsproxy != p->nsproxy) { 1188 retval = ns_cgroup_clone(p, pid); 1189 if (retval) 1190 goto bad_fork_free_pid; 1191 } 1192 1193 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1194 /* 1195 * Clear TID on mm_release()? 1196 */ 1197 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1198 #ifdef CONFIG_FUTEX 1199 p->robust_list = NULL; 1200 #ifdef CONFIG_COMPAT 1201 p->compat_robust_list = NULL; 1202 #endif 1203 INIT_LIST_HEAD(&p->pi_state_list); 1204 p->pi_state_cache = NULL; 1205 #endif 1206 /* 1207 * sigaltstack should be cleared when sharing the same VM 1208 */ 1209 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1210 p->sas_ss_sp = p->sas_ss_size = 0; 1211 1212 /* 1213 * Syscall tracing and stepping should be turned off in the 1214 * child regardless of CLONE_PTRACE. 1215 */ 1216 user_disable_single_step(p); 1217 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1218 #ifdef TIF_SYSCALL_EMU 1219 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1220 #endif 1221 clear_all_latency_tracing(p); 1222 1223 /* ok, now we should be set up.. */ 1224 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1225 p->pdeath_signal = 0; 1226 p->exit_state = 0; 1227 1228 /* 1229 * Ok, make it visible to the rest of the system. 1230 * We dont wake it up yet. 1231 */ 1232 p->group_leader = p; 1233 INIT_LIST_HEAD(&p->thread_group); 1234 1235 /* Now that the task is set up, run cgroup callbacks if 1236 * necessary. We need to run them before the task is visible 1237 * on the tasklist. */ 1238 cgroup_fork_callbacks(p); 1239 cgroup_callbacks_done = 1; 1240 1241 /* Need tasklist lock for parent etc handling! */ 1242 write_lock_irq(&tasklist_lock); 1243 1244 /* 1245 * The task hasn't been attached yet, so its cpus_allowed mask will 1246 * not be changed, nor will its assigned CPU. 1247 * 1248 * The cpus_allowed mask of the parent may have changed after it was 1249 * copied first time - so re-copy it here, then check the child's CPU 1250 * to ensure it is on a valid CPU (and if not, just force it back to 1251 * parent's CPU). This avoids alot of nasty races. 1252 */ 1253 p->cpus_allowed = current->cpus_allowed; 1254 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1255 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1256 !cpu_online(task_cpu(p)))) 1257 set_task_cpu(p, smp_processor_id()); 1258 1259 /* CLONE_PARENT re-uses the old parent */ 1260 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1261 p->real_parent = current->real_parent; 1262 p->parent_exec_id = current->parent_exec_id; 1263 } else { 1264 p->real_parent = current; 1265 p->parent_exec_id = current->self_exec_id; 1266 } 1267 1268 spin_lock(¤t->sighand->siglock); 1269 1270 /* 1271 * Process group and session signals need to be delivered to just the 1272 * parent before the fork or both the parent and the child after the 1273 * fork. Restart if a signal comes in before we add the new process to 1274 * it's process group. 1275 * A fatal signal pending means that current will exit, so the new 1276 * thread can't slip out of an OOM kill (or normal SIGKILL). 1277 */ 1278 recalc_sigpending(); 1279 if (signal_pending(current)) { 1280 spin_unlock(¤t->sighand->siglock); 1281 write_unlock_irq(&tasklist_lock); 1282 retval = -ERESTARTNOINTR; 1283 goto bad_fork_free_pid; 1284 } 1285 1286 if (clone_flags & CLONE_THREAD) { 1287 atomic_inc(¤t->signal->count); 1288 atomic_inc(¤t->signal->live); 1289 p->group_leader = current->group_leader; 1290 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1291 } 1292 1293 if (likely(p->pid)) { 1294 tracehook_finish_clone(p, clone_flags, trace); 1295 1296 if (thread_group_leader(p)) { 1297 if (clone_flags & CLONE_NEWPID) 1298 p->nsproxy->pid_ns->child_reaper = p; 1299 1300 p->signal->leader_pid = pid; 1301 tty_kref_put(p->signal->tty); 1302 p->signal->tty = tty_kref_get(current->signal->tty); 1303 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1304 attach_pid(p, PIDTYPE_SID, task_session(current)); 1305 list_add_tail(&p->sibling, &p->real_parent->children); 1306 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1307 __get_cpu_var(process_counts)++; 1308 } 1309 attach_pid(p, PIDTYPE_PID, pid); 1310 nr_threads++; 1311 } 1312 1313 total_forks++; 1314 spin_unlock(¤t->sighand->siglock); 1315 write_unlock_irq(&tasklist_lock); 1316 proc_fork_connector(p); 1317 cgroup_post_fork(p); 1318 perf_event_fork(p); 1319 return p; 1320 1321 bad_fork_free_pid: 1322 if (pid != &init_struct_pid) 1323 free_pid(pid); 1324 bad_fork_cleanup_io: 1325 if (p->io_context) 1326 exit_io_context(p); 1327 bad_fork_cleanup_namespaces: 1328 exit_task_namespaces(p); 1329 bad_fork_cleanup_mm: 1330 if (p->mm) 1331 mmput(p->mm); 1332 bad_fork_cleanup_signal: 1333 if (!(clone_flags & CLONE_THREAD)) 1334 __cleanup_signal(p->signal); 1335 bad_fork_cleanup_sighand: 1336 __cleanup_sighand(p->sighand); 1337 bad_fork_cleanup_fs: 1338 exit_fs(p); /* blocking */ 1339 bad_fork_cleanup_files: 1340 exit_files(p); /* blocking */ 1341 bad_fork_cleanup_semundo: 1342 exit_sem(p); 1343 bad_fork_cleanup_audit: 1344 audit_free(p); 1345 bad_fork_cleanup_policy: 1346 perf_event_free_task(p); 1347 #ifdef CONFIG_NUMA 1348 mpol_put(p->mempolicy); 1349 bad_fork_cleanup_cgroup: 1350 #endif 1351 cgroup_exit(p, cgroup_callbacks_done); 1352 delayacct_tsk_free(p); 1353 module_put(task_thread_info(p)->exec_domain->module); 1354 bad_fork_cleanup_count: 1355 atomic_dec(&p->cred->user->processes); 1356 exit_creds(p); 1357 bad_fork_free: 1358 free_task(p); 1359 fork_out: 1360 return ERR_PTR(retval); 1361 } 1362 1363 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1364 { 1365 memset(regs, 0, sizeof(struct pt_regs)); 1366 return regs; 1367 } 1368 1369 struct task_struct * __cpuinit fork_idle(int cpu) 1370 { 1371 struct task_struct *task; 1372 struct pt_regs regs; 1373 1374 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1375 &init_struct_pid, 0); 1376 if (!IS_ERR(task)) 1377 init_idle(task, cpu); 1378 1379 return task; 1380 } 1381 1382 /* 1383 * Ok, this is the main fork-routine. 1384 * 1385 * It copies the process, and if successful kick-starts 1386 * it and waits for it to finish using the VM if required. 1387 */ 1388 long do_fork(unsigned long clone_flags, 1389 unsigned long stack_start, 1390 struct pt_regs *regs, 1391 unsigned long stack_size, 1392 int __user *parent_tidptr, 1393 int __user *child_tidptr) 1394 { 1395 struct task_struct *p; 1396 int trace = 0; 1397 long nr; 1398 1399 /* 1400 * Do some preliminary argument and permissions checking before we 1401 * actually start allocating stuff 1402 */ 1403 if (clone_flags & CLONE_NEWUSER) { 1404 if (clone_flags & CLONE_THREAD) 1405 return -EINVAL; 1406 /* hopefully this check will go away when userns support is 1407 * complete 1408 */ 1409 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1410 !capable(CAP_SETGID)) 1411 return -EPERM; 1412 } 1413 1414 /* 1415 * We hope to recycle these flags after 2.6.26 1416 */ 1417 if (unlikely(clone_flags & CLONE_STOPPED)) { 1418 static int __read_mostly count = 100; 1419 1420 if (count > 0 && printk_ratelimit()) { 1421 char comm[TASK_COMM_LEN]; 1422 1423 count--; 1424 printk(KERN_INFO "fork(): process `%s' used deprecated " 1425 "clone flags 0x%lx\n", 1426 get_task_comm(comm, current), 1427 clone_flags & CLONE_STOPPED); 1428 } 1429 } 1430 1431 /* 1432 * When called from kernel_thread, don't do user tracing stuff. 1433 */ 1434 if (likely(user_mode(regs))) 1435 trace = tracehook_prepare_clone(clone_flags); 1436 1437 p = copy_process(clone_flags, stack_start, regs, stack_size, 1438 child_tidptr, NULL, trace); 1439 /* 1440 * Do this prior waking up the new thread - the thread pointer 1441 * might get invalid after that point, if the thread exits quickly. 1442 */ 1443 if (!IS_ERR(p)) { 1444 struct completion vfork; 1445 1446 trace_sched_process_fork(current, p); 1447 1448 nr = task_pid_vnr(p); 1449 1450 if (clone_flags & CLONE_PARENT_SETTID) 1451 put_user(nr, parent_tidptr); 1452 1453 if (clone_flags & CLONE_VFORK) { 1454 p->vfork_done = &vfork; 1455 init_completion(&vfork); 1456 } 1457 1458 audit_finish_fork(p); 1459 tracehook_report_clone(regs, clone_flags, nr, p); 1460 1461 /* 1462 * We set PF_STARTING at creation in case tracing wants to 1463 * use this to distinguish a fully live task from one that 1464 * hasn't gotten to tracehook_report_clone() yet. Now we 1465 * clear it and set the child going. 1466 */ 1467 p->flags &= ~PF_STARTING; 1468 1469 if (unlikely(clone_flags & CLONE_STOPPED)) { 1470 /* 1471 * We'll start up with an immediate SIGSTOP. 1472 */ 1473 sigaddset(&p->pending.signal, SIGSTOP); 1474 set_tsk_thread_flag(p, TIF_SIGPENDING); 1475 __set_task_state(p, TASK_STOPPED); 1476 } else { 1477 wake_up_new_task(p, clone_flags); 1478 } 1479 1480 tracehook_report_clone_complete(trace, regs, 1481 clone_flags, nr, p); 1482 1483 if (clone_flags & CLONE_VFORK) { 1484 freezer_do_not_count(); 1485 wait_for_completion(&vfork); 1486 freezer_count(); 1487 tracehook_report_vfork_done(p, nr); 1488 } 1489 } else { 1490 nr = PTR_ERR(p); 1491 } 1492 return nr; 1493 } 1494 1495 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1496 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1497 #endif 1498 1499 static void sighand_ctor(void *data) 1500 { 1501 struct sighand_struct *sighand = data; 1502 1503 spin_lock_init(&sighand->siglock); 1504 init_waitqueue_head(&sighand->signalfd_wqh); 1505 } 1506 1507 void __init proc_caches_init(void) 1508 { 1509 sighand_cachep = kmem_cache_create("sighand_cache", 1510 sizeof(struct sighand_struct), 0, 1511 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1512 SLAB_NOTRACK, sighand_ctor); 1513 signal_cachep = kmem_cache_create("signal_cache", 1514 sizeof(struct signal_struct), 0, 1515 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1516 files_cachep = kmem_cache_create("files_cache", 1517 sizeof(struct files_struct), 0, 1518 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1519 fs_cachep = kmem_cache_create("fs_cache", 1520 sizeof(struct fs_struct), 0, 1521 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1522 mm_cachep = kmem_cache_create("mm_struct", 1523 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1524 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1525 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1526 mmap_init(); 1527 } 1528 1529 /* 1530 * Check constraints on flags passed to the unshare system call and 1531 * force unsharing of additional process context as appropriate. 1532 */ 1533 static void check_unshare_flags(unsigned long *flags_ptr) 1534 { 1535 /* 1536 * If unsharing a thread from a thread group, must also 1537 * unshare vm. 1538 */ 1539 if (*flags_ptr & CLONE_THREAD) 1540 *flags_ptr |= CLONE_VM; 1541 1542 /* 1543 * If unsharing vm, must also unshare signal handlers. 1544 */ 1545 if (*flags_ptr & CLONE_VM) 1546 *flags_ptr |= CLONE_SIGHAND; 1547 1548 /* 1549 * If unsharing signal handlers and the task was created 1550 * using CLONE_THREAD, then must unshare the thread 1551 */ 1552 if ((*flags_ptr & CLONE_SIGHAND) && 1553 (atomic_read(¤t->signal->count) > 1)) 1554 *flags_ptr |= CLONE_THREAD; 1555 1556 /* 1557 * If unsharing namespace, must also unshare filesystem information. 1558 */ 1559 if (*flags_ptr & CLONE_NEWNS) 1560 *flags_ptr |= CLONE_FS; 1561 } 1562 1563 /* 1564 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1565 */ 1566 static int unshare_thread(unsigned long unshare_flags) 1567 { 1568 if (unshare_flags & CLONE_THREAD) 1569 return -EINVAL; 1570 1571 return 0; 1572 } 1573 1574 /* 1575 * Unshare the filesystem structure if it is being shared 1576 */ 1577 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1578 { 1579 struct fs_struct *fs = current->fs; 1580 1581 if (!(unshare_flags & CLONE_FS) || !fs) 1582 return 0; 1583 1584 /* don't need lock here; in the worst case we'll do useless copy */ 1585 if (fs->users == 1) 1586 return 0; 1587 1588 *new_fsp = copy_fs_struct(fs); 1589 if (!*new_fsp) 1590 return -ENOMEM; 1591 1592 return 0; 1593 } 1594 1595 /* 1596 * Unsharing of sighand is not supported yet 1597 */ 1598 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1599 { 1600 struct sighand_struct *sigh = current->sighand; 1601 1602 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1603 return -EINVAL; 1604 else 1605 return 0; 1606 } 1607 1608 /* 1609 * Unshare vm if it is being shared 1610 */ 1611 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1612 { 1613 struct mm_struct *mm = current->mm; 1614 1615 if ((unshare_flags & CLONE_VM) && 1616 (mm && atomic_read(&mm->mm_users) > 1)) { 1617 return -EINVAL; 1618 } 1619 1620 return 0; 1621 } 1622 1623 /* 1624 * Unshare file descriptor table if it is being shared 1625 */ 1626 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1627 { 1628 struct files_struct *fd = current->files; 1629 int error = 0; 1630 1631 if ((unshare_flags & CLONE_FILES) && 1632 (fd && atomic_read(&fd->count) > 1)) { 1633 *new_fdp = dup_fd(fd, &error); 1634 if (!*new_fdp) 1635 return error; 1636 } 1637 1638 return 0; 1639 } 1640 1641 /* 1642 * unshare allows a process to 'unshare' part of the process 1643 * context which was originally shared using clone. copy_* 1644 * functions used by do_fork() cannot be used here directly 1645 * because they modify an inactive task_struct that is being 1646 * constructed. Here we are modifying the current, active, 1647 * task_struct. 1648 */ 1649 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1650 { 1651 int err = 0; 1652 struct fs_struct *fs, *new_fs = NULL; 1653 struct sighand_struct *new_sigh = NULL; 1654 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1655 struct files_struct *fd, *new_fd = NULL; 1656 struct nsproxy *new_nsproxy = NULL; 1657 int do_sysvsem = 0; 1658 1659 check_unshare_flags(&unshare_flags); 1660 1661 /* Return -EINVAL for all unsupported flags */ 1662 err = -EINVAL; 1663 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1664 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1665 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1666 goto bad_unshare_out; 1667 1668 /* 1669 * CLONE_NEWIPC must also detach from the undolist: after switching 1670 * to a new ipc namespace, the semaphore arrays from the old 1671 * namespace are unreachable. 1672 */ 1673 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1674 do_sysvsem = 1; 1675 if ((err = unshare_thread(unshare_flags))) 1676 goto bad_unshare_out; 1677 if ((err = unshare_fs(unshare_flags, &new_fs))) 1678 goto bad_unshare_cleanup_thread; 1679 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1680 goto bad_unshare_cleanup_fs; 1681 if ((err = unshare_vm(unshare_flags, &new_mm))) 1682 goto bad_unshare_cleanup_sigh; 1683 if ((err = unshare_fd(unshare_flags, &new_fd))) 1684 goto bad_unshare_cleanup_vm; 1685 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1686 new_fs))) 1687 goto bad_unshare_cleanup_fd; 1688 1689 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1690 if (do_sysvsem) { 1691 /* 1692 * CLONE_SYSVSEM is equivalent to sys_exit(). 1693 */ 1694 exit_sem(current); 1695 } 1696 1697 if (new_nsproxy) { 1698 switch_task_namespaces(current, new_nsproxy); 1699 new_nsproxy = NULL; 1700 } 1701 1702 task_lock(current); 1703 1704 if (new_fs) { 1705 fs = current->fs; 1706 write_lock(&fs->lock); 1707 current->fs = new_fs; 1708 if (--fs->users) 1709 new_fs = NULL; 1710 else 1711 new_fs = fs; 1712 write_unlock(&fs->lock); 1713 } 1714 1715 if (new_mm) { 1716 mm = current->mm; 1717 active_mm = current->active_mm; 1718 current->mm = new_mm; 1719 current->active_mm = new_mm; 1720 activate_mm(active_mm, new_mm); 1721 new_mm = mm; 1722 } 1723 1724 if (new_fd) { 1725 fd = current->files; 1726 current->files = new_fd; 1727 new_fd = fd; 1728 } 1729 1730 task_unlock(current); 1731 } 1732 1733 if (new_nsproxy) 1734 put_nsproxy(new_nsproxy); 1735 1736 bad_unshare_cleanup_fd: 1737 if (new_fd) 1738 put_files_struct(new_fd); 1739 1740 bad_unshare_cleanup_vm: 1741 if (new_mm) 1742 mmput(new_mm); 1743 1744 bad_unshare_cleanup_sigh: 1745 if (new_sigh) 1746 if (atomic_dec_and_test(&new_sigh->count)) 1747 kmem_cache_free(sighand_cachep, new_sigh); 1748 1749 bad_unshare_cleanup_fs: 1750 if (new_fs) 1751 free_fs_struct(new_fs); 1752 1753 bad_unshare_cleanup_thread: 1754 bad_unshare_out: 1755 return err; 1756 } 1757 1758 /* 1759 * Helper to unshare the files of the current task. 1760 * We don't want to expose copy_files internals to 1761 * the exec layer of the kernel. 1762 */ 1763 1764 int unshare_files(struct files_struct **displaced) 1765 { 1766 struct task_struct *task = current; 1767 struct files_struct *copy = NULL; 1768 int error; 1769 1770 error = unshare_fd(CLONE_FILES, ©); 1771 if (error || !copy) { 1772 *displaced = NULL; 1773 return error; 1774 } 1775 *displaced = task->files; 1776 task_lock(task); 1777 task->files = copy; 1778 task_unlock(task); 1779 return 0; 1780 } 1781