1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/ksm.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <linux/fs_struct.h> 64 #include <linux/magic.h> 65 #include <linux/perf_event.h> 66 #include <linux/posix-timers.h> 67 #include <linux/user-return-notifier.h> 68 69 #include <asm/pgtable.h> 70 #include <asm/pgalloc.h> 71 #include <asm/uaccess.h> 72 #include <asm/mmu_context.h> 73 #include <asm/cacheflush.h> 74 #include <asm/tlbflush.h> 75 76 #include <trace/events/sched.h> 77 78 /* 79 * Protected counters by write_lock_irq(&tasklist_lock) 80 */ 81 unsigned long total_forks; /* Handle normal Linux uptimes. */ 82 int nr_threads; /* The idle threads do not count.. */ 83 84 int max_threads; /* tunable limit on nr_threads */ 85 86 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 87 88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 89 EXPORT_SYMBOL_GPL(tasklist_lock); 90 91 int nr_processes(void) 92 { 93 int cpu; 94 int total = 0; 95 96 for_each_possible_cpu(cpu) 97 total += per_cpu(process_counts, cpu); 98 99 return total; 100 } 101 102 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 103 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 104 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 105 static struct kmem_cache *task_struct_cachep; 106 #endif 107 108 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 109 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 110 { 111 #ifdef CONFIG_DEBUG_STACK_USAGE 112 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 113 #else 114 gfp_t mask = GFP_KERNEL; 115 #endif 116 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 117 } 118 119 static inline void free_thread_info(struct thread_info *ti) 120 { 121 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 122 } 123 #endif 124 125 /* SLAB cache for signal_struct structures (tsk->signal) */ 126 static struct kmem_cache *signal_cachep; 127 128 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 129 struct kmem_cache *sighand_cachep; 130 131 /* SLAB cache for files_struct structures (tsk->files) */ 132 struct kmem_cache *files_cachep; 133 134 /* SLAB cache for fs_struct structures (tsk->fs) */ 135 struct kmem_cache *fs_cachep; 136 137 /* SLAB cache for vm_area_struct structures */ 138 struct kmem_cache *vm_area_cachep; 139 140 /* SLAB cache for mm_struct structures (tsk->mm) */ 141 static struct kmem_cache *mm_cachep; 142 143 static void account_kernel_stack(struct thread_info *ti, int account) 144 { 145 struct zone *zone = page_zone(virt_to_page(ti)); 146 147 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 148 } 149 150 void free_task(struct task_struct *tsk) 151 { 152 prop_local_destroy_single(&tsk->dirties); 153 account_kernel_stack(tsk->stack, -1); 154 free_thread_info(tsk->stack); 155 rt_mutex_debug_task_free(tsk); 156 ftrace_graph_exit_task(tsk); 157 free_task_struct(tsk); 158 } 159 EXPORT_SYMBOL(free_task); 160 161 void __put_task_struct(struct task_struct *tsk) 162 { 163 WARN_ON(!tsk->exit_state); 164 WARN_ON(atomic_read(&tsk->usage)); 165 WARN_ON(tsk == current); 166 167 exit_creds(tsk); 168 delayacct_tsk_free(tsk); 169 170 if (!profile_handoff_task(tsk)) 171 free_task(tsk); 172 } 173 174 /* 175 * macro override instead of weak attribute alias, to workaround 176 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 177 */ 178 #ifndef arch_task_cache_init 179 #define arch_task_cache_init() 180 #endif 181 182 void __init fork_init(unsigned long mempages) 183 { 184 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 185 #ifndef ARCH_MIN_TASKALIGN 186 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 187 #endif 188 /* create a slab on which task_structs can be allocated */ 189 task_struct_cachep = 190 kmem_cache_create("task_struct", sizeof(struct task_struct), 191 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 192 #endif 193 194 /* do the arch specific task caches init */ 195 arch_task_cache_init(); 196 197 /* 198 * The default maximum number of threads is set to a safe 199 * value: the thread structures can take up at most half 200 * of memory. 201 */ 202 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 203 204 /* 205 * we need to allow at least 20 threads to boot a system 206 */ 207 if(max_threads < 20) 208 max_threads = 20; 209 210 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 211 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 212 init_task.signal->rlim[RLIMIT_SIGPENDING] = 213 init_task.signal->rlim[RLIMIT_NPROC]; 214 } 215 216 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 217 struct task_struct *src) 218 { 219 *dst = *src; 220 return 0; 221 } 222 223 static struct task_struct *dup_task_struct(struct task_struct *orig) 224 { 225 struct task_struct *tsk; 226 struct thread_info *ti; 227 unsigned long *stackend; 228 229 int err; 230 231 prepare_to_copy(orig); 232 233 tsk = alloc_task_struct(); 234 if (!tsk) 235 return NULL; 236 237 ti = alloc_thread_info(tsk); 238 if (!ti) { 239 free_task_struct(tsk); 240 return NULL; 241 } 242 243 err = arch_dup_task_struct(tsk, orig); 244 if (err) 245 goto out; 246 247 tsk->stack = ti; 248 249 err = prop_local_init_single(&tsk->dirties); 250 if (err) 251 goto out; 252 253 setup_thread_stack(tsk, orig); 254 clear_user_return_notifier(tsk); 255 stackend = end_of_stack(tsk); 256 *stackend = STACK_END_MAGIC; /* for overflow detection */ 257 258 #ifdef CONFIG_CC_STACKPROTECTOR 259 tsk->stack_canary = get_random_int(); 260 #endif 261 262 /* One for us, one for whoever does the "release_task()" (usually parent) */ 263 atomic_set(&tsk->usage,2); 264 atomic_set(&tsk->fs_excl, 0); 265 #ifdef CONFIG_BLK_DEV_IO_TRACE 266 tsk->btrace_seq = 0; 267 #endif 268 tsk->splice_pipe = NULL; 269 270 account_kernel_stack(ti, 1); 271 272 return tsk; 273 274 out: 275 free_thread_info(ti); 276 free_task_struct(tsk); 277 return NULL; 278 } 279 280 #ifdef CONFIG_MMU 281 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 282 { 283 struct vm_area_struct *mpnt, *tmp, **pprev; 284 struct rb_node **rb_link, *rb_parent; 285 int retval; 286 unsigned long charge; 287 struct mempolicy *pol; 288 289 down_write(&oldmm->mmap_sem); 290 flush_cache_dup_mm(oldmm); 291 /* 292 * Not linked in yet - no deadlock potential: 293 */ 294 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 295 296 mm->locked_vm = 0; 297 mm->mmap = NULL; 298 mm->mmap_cache = NULL; 299 mm->free_area_cache = oldmm->mmap_base; 300 mm->cached_hole_size = ~0UL; 301 mm->map_count = 0; 302 cpumask_clear(mm_cpumask(mm)); 303 mm->mm_rb = RB_ROOT; 304 rb_link = &mm->mm_rb.rb_node; 305 rb_parent = NULL; 306 pprev = &mm->mmap; 307 retval = ksm_fork(mm, oldmm); 308 if (retval) 309 goto out; 310 311 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 312 struct file *file; 313 314 if (mpnt->vm_flags & VM_DONTCOPY) { 315 long pages = vma_pages(mpnt); 316 mm->total_vm -= pages; 317 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 318 -pages); 319 continue; 320 } 321 charge = 0; 322 if (mpnt->vm_flags & VM_ACCOUNT) { 323 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 324 if (security_vm_enough_memory(len)) 325 goto fail_nomem; 326 charge = len; 327 } 328 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 329 if (!tmp) 330 goto fail_nomem; 331 *tmp = *mpnt; 332 INIT_LIST_HEAD(&tmp->anon_vma_chain); 333 pol = mpol_dup(vma_policy(mpnt)); 334 retval = PTR_ERR(pol); 335 if (IS_ERR(pol)) 336 goto fail_nomem_policy; 337 vma_set_policy(tmp, pol); 338 if (anon_vma_fork(tmp, mpnt)) 339 goto fail_nomem_anon_vma_fork; 340 tmp->vm_flags &= ~VM_LOCKED; 341 tmp->vm_mm = mm; 342 tmp->vm_next = NULL; 343 file = tmp->vm_file; 344 if (file) { 345 struct inode *inode = file->f_path.dentry->d_inode; 346 struct address_space *mapping = file->f_mapping; 347 348 get_file(file); 349 if (tmp->vm_flags & VM_DENYWRITE) 350 atomic_dec(&inode->i_writecount); 351 spin_lock(&mapping->i_mmap_lock); 352 if (tmp->vm_flags & VM_SHARED) 353 mapping->i_mmap_writable++; 354 tmp->vm_truncate_count = mpnt->vm_truncate_count; 355 flush_dcache_mmap_lock(mapping); 356 /* insert tmp into the share list, just after mpnt */ 357 vma_prio_tree_add(tmp, mpnt); 358 flush_dcache_mmap_unlock(mapping); 359 spin_unlock(&mapping->i_mmap_lock); 360 } 361 362 /* 363 * Clear hugetlb-related page reserves for children. This only 364 * affects MAP_PRIVATE mappings. Faults generated by the child 365 * are not guaranteed to succeed, even if read-only 366 */ 367 if (is_vm_hugetlb_page(tmp)) 368 reset_vma_resv_huge_pages(tmp); 369 370 /* 371 * Link in the new vma and copy the page table entries. 372 */ 373 *pprev = tmp; 374 pprev = &tmp->vm_next; 375 376 __vma_link_rb(mm, tmp, rb_link, rb_parent); 377 rb_link = &tmp->vm_rb.rb_right; 378 rb_parent = &tmp->vm_rb; 379 380 mm->map_count++; 381 retval = copy_page_range(mm, oldmm, mpnt); 382 383 if (tmp->vm_ops && tmp->vm_ops->open) 384 tmp->vm_ops->open(tmp); 385 386 if (retval) 387 goto out; 388 } 389 /* a new mm has just been created */ 390 arch_dup_mmap(oldmm, mm); 391 retval = 0; 392 out: 393 up_write(&mm->mmap_sem); 394 flush_tlb_mm(oldmm); 395 up_write(&oldmm->mmap_sem); 396 return retval; 397 fail_nomem_anon_vma_fork: 398 mpol_put(pol); 399 fail_nomem_policy: 400 kmem_cache_free(vm_area_cachep, tmp); 401 fail_nomem: 402 retval = -ENOMEM; 403 vm_unacct_memory(charge); 404 goto out; 405 } 406 407 static inline int mm_alloc_pgd(struct mm_struct * mm) 408 { 409 mm->pgd = pgd_alloc(mm); 410 if (unlikely(!mm->pgd)) 411 return -ENOMEM; 412 return 0; 413 } 414 415 static inline void mm_free_pgd(struct mm_struct * mm) 416 { 417 pgd_free(mm, mm->pgd); 418 } 419 #else 420 #define dup_mmap(mm, oldmm) (0) 421 #define mm_alloc_pgd(mm) (0) 422 #define mm_free_pgd(mm) 423 #endif /* CONFIG_MMU */ 424 425 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 426 427 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 428 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 429 430 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 431 432 static int __init coredump_filter_setup(char *s) 433 { 434 default_dump_filter = 435 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 436 MMF_DUMP_FILTER_MASK; 437 return 1; 438 } 439 440 __setup("coredump_filter=", coredump_filter_setup); 441 442 #include <linux/init_task.h> 443 444 static void mm_init_aio(struct mm_struct *mm) 445 { 446 #ifdef CONFIG_AIO 447 spin_lock_init(&mm->ioctx_lock); 448 INIT_HLIST_HEAD(&mm->ioctx_list); 449 #endif 450 } 451 452 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 453 { 454 atomic_set(&mm->mm_users, 1); 455 atomic_set(&mm->mm_count, 1); 456 init_rwsem(&mm->mmap_sem); 457 INIT_LIST_HEAD(&mm->mmlist); 458 mm->flags = (current->mm) ? 459 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 460 mm->core_state = NULL; 461 mm->nr_ptes = 0; 462 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 463 spin_lock_init(&mm->page_table_lock); 464 mm->free_area_cache = TASK_UNMAPPED_BASE; 465 mm->cached_hole_size = ~0UL; 466 mm_init_aio(mm); 467 mm_init_owner(mm, p); 468 469 if (likely(!mm_alloc_pgd(mm))) { 470 mm->def_flags = 0; 471 mmu_notifier_mm_init(mm); 472 return mm; 473 } 474 475 free_mm(mm); 476 return NULL; 477 } 478 479 /* 480 * Allocate and initialize an mm_struct. 481 */ 482 struct mm_struct * mm_alloc(void) 483 { 484 struct mm_struct * mm; 485 486 mm = allocate_mm(); 487 if (mm) { 488 memset(mm, 0, sizeof(*mm)); 489 mm = mm_init(mm, current); 490 } 491 return mm; 492 } 493 494 /* 495 * Called when the last reference to the mm 496 * is dropped: either by a lazy thread or by 497 * mmput. Free the page directory and the mm. 498 */ 499 void __mmdrop(struct mm_struct *mm) 500 { 501 BUG_ON(mm == &init_mm); 502 mm_free_pgd(mm); 503 destroy_context(mm); 504 mmu_notifier_mm_destroy(mm); 505 free_mm(mm); 506 } 507 EXPORT_SYMBOL_GPL(__mmdrop); 508 509 /* 510 * Decrement the use count and release all resources for an mm. 511 */ 512 void mmput(struct mm_struct *mm) 513 { 514 might_sleep(); 515 516 if (atomic_dec_and_test(&mm->mm_users)) { 517 exit_aio(mm); 518 ksm_exit(mm); 519 exit_mmap(mm); 520 set_mm_exe_file(mm, NULL); 521 if (!list_empty(&mm->mmlist)) { 522 spin_lock(&mmlist_lock); 523 list_del(&mm->mmlist); 524 spin_unlock(&mmlist_lock); 525 } 526 put_swap_token(mm); 527 if (mm->binfmt) 528 module_put(mm->binfmt->module); 529 mmdrop(mm); 530 } 531 } 532 EXPORT_SYMBOL_GPL(mmput); 533 534 /** 535 * get_task_mm - acquire a reference to the task's mm 536 * 537 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 538 * this kernel workthread has transiently adopted a user mm with use_mm, 539 * to do its AIO) is not set and if so returns a reference to it, after 540 * bumping up the use count. User must release the mm via mmput() 541 * after use. Typically used by /proc and ptrace. 542 */ 543 struct mm_struct *get_task_mm(struct task_struct *task) 544 { 545 struct mm_struct *mm; 546 547 task_lock(task); 548 mm = task->mm; 549 if (mm) { 550 if (task->flags & PF_KTHREAD) 551 mm = NULL; 552 else 553 atomic_inc(&mm->mm_users); 554 } 555 task_unlock(task); 556 return mm; 557 } 558 EXPORT_SYMBOL_GPL(get_task_mm); 559 560 /* Please note the differences between mmput and mm_release. 561 * mmput is called whenever we stop holding onto a mm_struct, 562 * error success whatever. 563 * 564 * mm_release is called after a mm_struct has been removed 565 * from the current process. 566 * 567 * This difference is important for error handling, when we 568 * only half set up a mm_struct for a new process and need to restore 569 * the old one. Because we mmput the new mm_struct before 570 * restoring the old one. . . 571 * Eric Biederman 10 January 1998 572 */ 573 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 574 { 575 struct completion *vfork_done = tsk->vfork_done; 576 577 /* Get rid of any futexes when releasing the mm */ 578 #ifdef CONFIG_FUTEX 579 if (unlikely(tsk->robust_list)) { 580 exit_robust_list(tsk); 581 tsk->robust_list = NULL; 582 } 583 #ifdef CONFIG_COMPAT 584 if (unlikely(tsk->compat_robust_list)) { 585 compat_exit_robust_list(tsk); 586 tsk->compat_robust_list = NULL; 587 } 588 #endif 589 if (unlikely(!list_empty(&tsk->pi_state_list))) 590 exit_pi_state_list(tsk); 591 #endif 592 593 /* Get rid of any cached register state */ 594 deactivate_mm(tsk, mm); 595 596 /* notify parent sleeping on vfork() */ 597 if (vfork_done) { 598 tsk->vfork_done = NULL; 599 complete(vfork_done); 600 } 601 602 /* 603 * If we're exiting normally, clear a user-space tid field if 604 * requested. We leave this alone when dying by signal, to leave 605 * the value intact in a core dump, and to save the unnecessary 606 * trouble otherwise. Userland only wants this done for a sys_exit. 607 */ 608 if (tsk->clear_child_tid) { 609 if (!(tsk->flags & PF_SIGNALED) && 610 atomic_read(&mm->mm_users) > 1) { 611 /* 612 * We don't check the error code - if userspace has 613 * not set up a proper pointer then tough luck. 614 */ 615 put_user(0, tsk->clear_child_tid); 616 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 617 1, NULL, NULL, 0); 618 } 619 tsk->clear_child_tid = NULL; 620 } 621 } 622 623 /* 624 * Allocate a new mm structure and copy contents from the 625 * mm structure of the passed in task structure. 626 */ 627 struct mm_struct *dup_mm(struct task_struct *tsk) 628 { 629 struct mm_struct *mm, *oldmm = current->mm; 630 int err; 631 632 if (!oldmm) 633 return NULL; 634 635 mm = allocate_mm(); 636 if (!mm) 637 goto fail_nomem; 638 639 memcpy(mm, oldmm, sizeof(*mm)); 640 641 /* Initializing for Swap token stuff */ 642 mm->token_priority = 0; 643 mm->last_interval = 0; 644 645 if (!mm_init(mm, tsk)) 646 goto fail_nomem; 647 648 if (init_new_context(tsk, mm)) 649 goto fail_nocontext; 650 651 dup_mm_exe_file(oldmm, mm); 652 653 err = dup_mmap(mm, oldmm); 654 if (err) 655 goto free_pt; 656 657 mm->hiwater_rss = get_mm_rss(mm); 658 mm->hiwater_vm = mm->total_vm; 659 660 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 661 goto free_pt; 662 663 return mm; 664 665 free_pt: 666 /* don't put binfmt in mmput, we haven't got module yet */ 667 mm->binfmt = NULL; 668 mmput(mm); 669 670 fail_nomem: 671 return NULL; 672 673 fail_nocontext: 674 /* 675 * If init_new_context() failed, we cannot use mmput() to free the mm 676 * because it calls destroy_context() 677 */ 678 mm_free_pgd(mm); 679 free_mm(mm); 680 return NULL; 681 } 682 683 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 684 { 685 struct mm_struct * mm, *oldmm; 686 int retval; 687 688 tsk->min_flt = tsk->maj_flt = 0; 689 tsk->nvcsw = tsk->nivcsw = 0; 690 #ifdef CONFIG_DETECT_HUNG_TASK 691 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 692 #endif 693 694 tsk->mm = NULL; 695 tsk->active_mm = NULL; 696 697 /* 698 * Are we cloning a kernel thread? 699 * 700 * We need to steal a active VM for that.. 701 */ 702 oldmm = current->mm; 703 if (!oldmm) 704 return 0; 705 706 if (clone_flags & CLONE_VM) { 707 atomic_inc(&oldmm->mm_users); 708 mm = oldmm; 709 goto good_mm; 710 } 711 712 retval = -ENOMEM; 713 mm = dup_mm(tsk); 714 if (!mm) 715 goto fail_nomem; 716 717 good_mm: 718 /* Initializing for Swap token stuff */ 719 mm->token_priority = 0; 720 mm->last_interval = 0; 721 722 tsk->mm = mm; 723 tsk->active_mm = mm; 724 return 0; 725 726 fail_nomem: 727 return retval; 728 } 729 730 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 731 { 732 struct fs_struct *fs = current->fs; 733 if (clone_flags & CLONE_FS) { 734 /* tsk->fs is already what we want */ 735 write_lock(&fs->lock); 736 if (fs->in_exec) { 737 write_unlock(&fs->lock); 738 return -EAGAIN; 739 } 740 fs->users++; 741 write_unlock(&fs->lock); 742 return 0; 743 } 744 tsk->fs = copy_fs_struct(fs); 745 if (!tsk->fs) 746 return -ENOMEM; 747 return 0; 748 } 749 750 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 751 { 752 struct files_struct *oldf, *newf; 753 int error = 0; 754 755 /* 756 * A background process may not have any files ... 757 */ 758 oldf = current->files; 759 if (!oldf) 760 goto out; 761 762 if (clone_flags & CLONE_FILES) { 763 atomic_inc(&oldf->count); 764 goto out; 765 } 766 767 newf = dup_fd(oldf, &error); 768 if (!newf) 769 goto out; 770 771 tsk->files = newf; 772 error = 0; 773 out: 774 return error; 775 } 776 777 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 778 { 779 #ifdef CONFIG_BLOCK 780 struct io_context *ioc = current->io_context; 781 782 if (!ioc) 783 return 0; 784 /* 785 * Share io context with parent, if CLONE_IO is set 786 */ 787 if (clone_flags & CLONE_IO) { 788 tsk->io_context = ioc_task_link(ioc); 789 if (unlikely(!tsk->io_context)) 790 return -ENOMEM; 791 } else if (ioprio_valid(ioc->ioprio)) { 792 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 793 if (unlikely(!tsk->io_context)) 794 return -ENOMEM; 795 796 tsk->io_context->ioprio = ioc->ioprio; 797 } 798 #endif 799 return 0; 800 } 801 802 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 803 { 804 struct sighand_struct *sig; 805 806 if (clone_flags & CLONE_SIGHAND) { 807 atomic_inc(¤t->sighand->count); 808 return 0; 809 } 810 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 811 rcu_assign_pointer(tsk->sighand, sig); 812 if (!sig) 813 return -ENOMEM; 814 atomic_set(&sig->count, 1); 815 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 816 return 0; 817 } 818 819 void __cleanup_sighand(struct sighand_struct *sighand) 820 { 821 if (atomic_dec_and_test(&sighand->count)) 822 kmem_cache_free(sighand_cachep, sighand); 823 } 824 825 826 /* 827 * Initialize POSIX timer handling for a thread group. 828 */ 829 static void posix_cpu_timers_init_group(struct signal_struct *sig) 830 { 831 unsigned long cpu_limit; 832 833 /* Thread group counters. */ 834 thread_group_cputime_init(sig); 835 836 /* Expiration times and increments. */ 837 sig->it[CPUCLOCK_PROF].expires = cputime_zero; 838 sig->it[CPUCLOCK_PROF].incr = cputime_zero; 839 sig->it[CPUCLOCK_VIRT].expires = cputime_zero; 840 sig->it[CPUCLOCK_VIRT].incr = cputime_zero; 841 842 /* Cached expiration times. */ 843 sig->cputime_expires.prof_exp = cputime_zero; 844 sig->cputime_expires.virt_exp = cputime_zero; 845 sig->cputime_expires.sched_exp = 0; 846 847 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 848 if (cpu_limit != RLIM_INFINITY) { 849 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 850 sig->cputimer.running = 1; 851 } 852 853 /* The timer lists. */ 854 INIT_LIST_HEAD(&sig->cpu_timers[0]); 855 INIT_LIST_HEAD(&sig->cpu_timers[1]); 856 INIT_LIST_HEAD(&sig->cpu_timers[2]); 857 } 858 859 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 860 { 861 struct signal_struct *sig; 862 863 if (clone_flags & CLONE_THREAD) 864 return 0; 865 866 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 867 tsk->signal = sig; 868 if (!sig) 869 return -ENOMEM; 870 871 atomic_set(&sig->count, 1); 872 atomic_set(&sig->live, 1); 873 init_waitqueue_head(&sig->wait_chldexit); 874 sig->flags = 0; 875 if (clone_flags & CLONE_NEWPID) 876 sig->flags |= SIGNAL_UNKILLABLE; 877 sig->group_exit_code = 0; 878 sig->group_exit_task = NULL; 879 sig->group_stop_count = 0; 880 sig->curr_target = tsk; 881 init_sigpending(&sig->shared_pending); 882 INIT_LIST_HEAD(&sig->posix_timers); 883 884 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 885 sig->it_real_incr.tv64 = 0; 886 sig->real_timer.function = it_real_fn; 887 888 sig->leader = 0; /* session leadership doesn't inherit */ 889 sig->tty_old_pgrp = NULL; 890 sig->tty = NULL; 891 892 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 893 sig->gtime = cputime_zero; 894 sig->cgtime = cputime_zero; 895 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 896 sig->prev_utime = sig->prev_stime = cputime_zero; 897 #endif 898 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 899 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 900 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 901 sig->maxrss = sig->cmaxrss = 0; 902 task_io_accounting_init(&sig->ioac); 903 sig->sum_sched_runtime = 0; 904 taskstats_tgid_init(sig); 905 906 task_lock(current->group_leader); 907 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 908 task_unlock(current->group_leader); 909 910 posix_cpu_timers_init_group(sig); 911 912 acct_init_pacct(&sig->pacct); 913 914 tty_audit_fork(sig); 915 916 sig->oom_adj = current->signal->oom_adj; 917 918 return 0; 919 } 920 921 void __cleanup_signal(struct signal_struct *sig) 922 { 923 thread_group_cputime_free(sig); 924 tty_kref_put(sig->tty); 925 kmem_cache_free(signal_cachep, sig); 926 } 927 928 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 929 { 930 unsigned long new_flags = p->flags; 931 932 new_flags &= ~PF_SUPERPRIV; 933 new_flags |= PF_FORKNOEXEC; 934 new_flags |= PF_STARTING; 935 p->flags = new_flags; 936 clear_freeze_flag(p); 937 } 938 939 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 940 { 941 current->clear_child_tid = tidptr; 942 943 return task_pid_vnr(current); 944 } 945 946 static void rt_mutex_init_task(struct task_struct *p) 947 { 948 raw_spin_lock_init(&p->pi_lock); 949 #ifdef CONFIG_RT_MUTEXES 950 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 951 p->pi_blocked_on = NULL; 952 #endif 953 } 954 955 #ifdef CONFIG_MM_OWNER 956 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 957 { 958 mm->owner = p; 959 } 960 #endif /* CONFIG_MM_OWNER */ 961 962 /* 963 * Initialize POSIX timer handling for a single task. 964 */ 965 static void posix_cpu_timers_init(struct task_struct *tsk) 966 { 967 tsk->cputime_expires.prof_exp = cputime_zero; 968 tsk->cputime_expires.virt_exp = cputime_zero; 969 tsk->cputime_expires.sched_exp = 0; 970 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 971 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 972 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 973 } 974 975 /* 976 * This creates a new process as a copy of the old one, 977 * but does not actually start it yet. 978 * 979 * It copies the registers, and all the appropriate 980 * parts of the process environment (as per the clone 981 * flags). The actual kick-off is left to the caller. 982 */ 983 static struct task_struct *copy_process(unsigned long clone_flags, 984 unsigned long stack_start, 985 struct pt_regs *regs, 986 unsigned long stack_size, 987 int __user *child_tidptr, 988 struct pid *pid, 989 int trace) 990 { 991 int retval; 992 struct task_struct *p; 993 int cgroup_callbacks_done = 0; 994 995 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 996 return ERR_PTR(-EINVAL); 997 998 /* 999 * Thread groups must share signals as well, and detached threads 1000 * can only be started up within the thread group. 1001 */ 1002 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1003 return ERR_PTR(-EINVAL); 1004 1005 /* 1006 * Shared signal handlers imply shared VM. By way of the above, 1007 * thread groups also imply shared VM. Blocking this case allows 1008 * for various simplifications in other code. 1009 */ 1010 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1011 return ERR_PTR(-EINVAL); 1012 1013 /* 1014 * Siblings of global init remain as zombies on exit since they are 1015 * not reaped by their parent (swapper). To solve this and to avoid 1016 * multi-rooted process trees, prevent global and container-inits 1017 * from creating siblings. 1018 */ 1019 if ((clone_flags & CLONE_PARENT) && 1020 current->signal->flags & SIGNAL_UNKILLABLE) 1021 return ERR_PTR(-EINVAL); 1022 1023 retval = security_task_create(clone_flags); 1024 if (retval) 1025 goto fork_out; 1026 1027 retval = -ENOMEM; 1028 p = dup_task_struct(current); 1029 if (!p) 1030 goto fork_out; 1031 1032 ftrace_graph_init_task(p); 1033 1034 rt_mutex_init_task(p); 1035 1036 #ifdef CONFIG_PROVE_LOCKING 1037 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1038 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1039 #endif 1040 retval = -EAGAIN; 1041 if (atomic_read(&p->real_cred->user->processes) >= 1042 task_rlimit(p, RLIMIT_NPROC)) { 1043 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1044 p->real_cred->user != INIT_USER) 1045 goto bad_fork_free; 1046 } 1047 1048 retval = copy_creds(p, clone_flags); 1049 if (retval < 0) 1050 goto bad_fork_free; 1051 1052 /* 1053 * If multiple threads are within copy_process(), then this check 1054 * triggers too late. This doesn't hurt, the check is only there 1055 * to stop root fork bombs. 1056 */ 1057 retval = -EAGAIN; 1058 if (nr_threads >= max_threads) 1059 goto bad_fork_cleanup_count; 1060 1061 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1062 goto bad_fork_cleanup_count; 1063 1064 p->did_exec = 0; 1065 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1066 copy_flags(clone_flags, p); 1067 INIT_LIST_HEAD(&p->children); 1068 INIT_LIST_HEAD(&p->sibling); 1069 rcu_copy_process(p); 1070 p->vfork_done = NULL; 1071 spin_lock_init(&p->alloc_lock); 1072 1073 init_sigpending(&p->pending); 1074 1075 p->utime = cputime_zero; 1076 p->stime = cputime_zero; 1077 p->gtime = cputime_zero; 1078 p->utimescaled = cputime_zero; 1079 p->stimescaled = cputime_zero; 1080 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1081 p->prev_utime = cputime_zero; 1082 p->prev_stime = cputime_zero; 1083 #endif 1084 1085 p->default_timer_slack_ns = current->timer_slack_ns; 1086 1087 task_io_accounting_init(&p->ioac); 1088 acct_clear_integrals(p); 1089 1090 posix_cpu_timers_init(p); 1091 1092 p->lock_depth = -1; /* -1 = no lock */ 1093 do_posix_clock_monotonic_gettime(&p->start_time); 1094 p->real_start_time = p->start_time; 1095 monotonic_to_bootbased(&p->real_start_time); 1096 p->io_context = NULL; 1097 p->audit_context = NULL; 1098 cgroup_fork(p); 1099 #ifdef CONFIG_NUMA 1100 p->mempolicy = mpol_dup(p->mempolicy); 1101 if (IS_ERR(p->mempolicy)) { 1102 retval = PTR_ERR(p->mempolicy); 1103 p->mempolicy = NULL; 1104 goto bad_fork_cleanup_cgroup; 1105 } 1106 mpol_fix_fork_child_flag(p); 1107 #endif 1108 #ifdef CONFIG_TRACE_IRQFLAGS 1109 p->irq_events = 0; 1110 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1111 p->hardirqs_enabled = 1; 1112 #else 1113 p->hardirqs_enabled = 0; 1114 #endif 1115 p->hardirq_enable_ip = 0; 1116 p->hardirq_enable_event = 0; 1117 p->hardirq_disable_ip = _THIS_IP_; 1118 p->hardirq_disable_event = 0; 1119 p->softirqs_enabled = 1; 1120 p->softirq_enable_ip = _THIS_IP_; 1121 p->softirq_enable_event = 0; 1122 p->softirq_disable_ip = 0; 1123 p->softirq_disable_event = 0; 1124 p->hardirq_context = 0; 1125 p->softirq_context = 0; 1126 #endif 1127 #ifdef CONFIG_LOCKDEP 1128 p->lockdep_depth = 0; /* no locks held yet */ 1129 p->curr_chain_key = 0; 1130 p->lockdep_recursion = 0; 1131 #endif 1132 1133 #ifdef CONFIG_DEBUG_MUTEXES 1134 p->blocked_on = NULL; /* not blocked yet */ 1135 #endif 1136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1137 p->memcg_batch.do_batch = 0; 1138 p->memcg_batch.memcg = NULL; 1139 #endif 1140 1141 p->bts = NULL; 1142 1143 p->stack_start = stack_start; 1144 1145 /* Perform scheduler related setup. Assign this task to a CPU. */ 1146 sched_fork(p, clone_flags); 1147 1148 retval = perf_event_init_task(p); 1149 if (retval) 1150 goto bad_fork_cleanup_policy; 1151 1152 if ((retval = audit_alloc(p))) 1153 goto bad_fork_cleanup_policy; 1154 /* copy all the process information */ 1155 if ((retval = copy_semundo(clone_flags, p))) 1156 goto bad_fork_cleanup_audit; 1157 if ((retval = copy_files(clone_flags, p))) 1158 goto bad_fork_cleanup_semundo; 1159 if ((retval = copy_fs(clone_flags, p))) 1160 goto bad_fork_cleanup_files; 1161 if ((retval = copy_sighand(clone_flags, p))) 1162 goto bad_fork_cleanup_fs; 1163 if ((retval = copy_signal(clone_flags, p))) 1164 goto bad_fork_cleanup_sighand; 1165 if ((retval = copy_mm(clone_flags, p))) 1166 goto bad_fork_cleanup_signal; 1167 if ((retval = copy_namespaces(clone_flags, p))) 1168 goto bad_fork_cleanup_mm; 1169 if ((retval = copy_io(clone_flags, p))) 1170 goto bad_fork_cleanup_namespaces; 1171 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1172 if (retval) 1173 goto bad_fork_cleanup_io; 1174 1175 if (pid != &init_struct_pid) { 1176 retval = -ENOMEM; 1177 pid = alloc_pid(p->nsproxy->pid_ns); 1178 if (!pid) 1179 goto bad_fork_cleanup_io; 1180 1181 if (clone_flags & CLONE_NEWPID) { 1182 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1183 if (retval < 0) 1184 goto bad_fork_free_pid; 1185 } 1186 } 1187 1188 p->pid = pid_nr(pid); 1189 p->tgid = p->pid; 1190 if (clone_flags & CLONE_THREAD) 1191 p->tgid = current->tgid; 1192 1193 if (current->nsproxy != p->nsproxy) { 1194 retval = ns_cgroup_clone(p, pid); 1195 if (retval) 1196 goto bad_fork_free_pid; 1197 } 1198 1199 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1200 /* 1201 * Clear TID on mm_release()? 1202 */ 1203 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1204 #ifdef CONFIG_FUTEX 1205 p->robust_list = NULL; 1206 #ifdef CONFIG_COMPAT 1207 p->compat_robust_list = NULL; 1208 #endif 1209 INIT_LIST_HEAD(&p->pi_state_list); 1210 p->pi_state_cache = NULL; 1211 #endif 1212 /* 1213 * sigaltstack should be cleared when sharing the same VM 1214 */ 1215 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1216 p->sas_ss_sp = p->sas_ss_size = 0; 1217 1218 /* 1219 * Syscall tracing and stepping should be turned off in the 1220 * child regardless of CLONE_PTRACE. 1221 */ 1222 user_disable_single_step(p); 1223 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1224 #ifdef TIF_SYSCALL_EMU 1225 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1226 #endif 1227 clear_all_latency_tracing(p); 1228 1229 /* ok, now we should be set up.. */ 1230 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1231 p->pdeath_signal = 0; 1232 p->exit_state = 0; 1233 1234 /* 1235 * Ok, make it visible to the rest of the system. 1236 * We dont wake it up yet. 1237 */ 1238 p->group_leader = p; 1239 INIT_LIST_HEAD(&p->thread_group); 1240 1241 /* Now that the task is set up, run cgroup callbacks if 1242 * necessary. We need to run them before the task is visible 1243 * on the tasklist. */ 1244 cgroup_fork_callbacks(p); 1245 cgroup_callbacks_done = 1; 1246 1247 /* Need tasklist lock for parent etc handling! */ 1248 write_lock_irq(&tasklist_lock); 1249 1250 /* CLONE_PARENT re-uses the old parent */ 1251 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1252 p->real_parent = current->real_parent; 1253 p->parent_exec_id = current->parent_exec_id; 1254 } else { 1255 p->real_parent = current; 1256 p->parent_exec_id = current->self_exec_id; 1257 } 1258 1259 spin_lock(¤t->sighand->siglock); 1260 1261 /* 1262 * Process group and session signals need to be delivered to just the 1263 * parent before the fork or both the parent and the child after the 1264 * fork. Restart if a signal comes in before we add the new process to 1265 * it's process group. 1266 * A fatal signal pending means that current will exit, so the new 1267 * thread can't slip out of an OOM kill (or normal SIGKILL). 1268 */ 1269 recalc_sigpending(); 1270 if (signal_pending(current)) { 1271 spin_unlock(¤t->sighand->siglock); 1272 write_unlock_irq(&tasklist_lock); 1273 retval = -ERESTARTNOINTR; 1274 goto bad_fork_free_pid; 1275 } 1276 1277 if (clone_flags & CLONE_THREAD) { 1278 atomic_inc(¤t->signal->count); 1279 atomic_inc(¤t->signal->live); 1280 p->group_leader = current->group_leader; 1281 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1282 } 1283 1284 if (likely(p->pid)) { 1285 tracehook_finish_clone(p, clone_flags, trace); 1286 1287 if (thread_group_leader(p)) { 1288 if (clone_flags & CLONE_NEWPID) 1289 p->nsproxy->pid_ns->child_reaper = p; 1290 1291 p->signal->leader_pid = pid; 1292 tty_kref_put(p->signal->tty); 1293 p->signal->tty = tty_kref_get(current->signal->tty); 1294 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1295 attach_pid(p, PIDTYPE_SID, task_session(current)); 1296 list_add_tail(&p->sibling, &p->real_parent->children); 1297 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1298 __get_cpu_var(process_counts)++; 1299 } 1300 attach_pid(p, PIDTYPE_PID, pid); 1301 nr_threads++; 1302 } 1303 1304 total_forks++; 1305 spin_unlock(¤t->sighand->siglock); 1306 write_unlock_irq(&tasklist_lock); 1307 proc_fork_connector(p); 1308 cgroup_post_fork(p); 1309 perf_event_fork(p); 1310 return p; 1311 1312 bad_fork_free_pid: 1313 if (pid != &init_struct_pid) 1314 free_pid(pid); 1315 bad_fork_cleanup_io: 1316 if (p->io_context) 1317 exit_io_context(p); 1318 bad_fork_cleanup_namespaces: 1319 exit_task_namespaces(p); 1320 bad_fork_cleanup_mm: 1321 if (p->mm) 1322 mmput(p->mm); 1323 bad_fork_cleanup_signal: 1324 if (!(clone_flags & CLONE_THREAD)) 1325 __cleanup_signal(p->signal); 1326 bad_fork_cleanup_sighand: 1327 __cleanup_sighand(p->sighand); 1328 bad_fork_cleanup_fs: 1329 exit_fs(p); /* blocking */ 1330 bad_fork_cleanup_files: 1331 exit_files(p); /* blocking */ 1332 bad_fork_cleanup_semundo: 1333 exit_sem(p); 1334 bad_fork_cleanup_audit: 1335 audit_free(p); 1336 bad_fork_cleanup_policy: 1337 perf_event_free_task(p); 1338 #ifdef CONFIG_NUMA 1339 mpol_put(p->mempolicy); 1340 bad_fork_cleanup_cgroup: 1341 #endif 1342 cgroup_exit(p, cgroup_callbacks_done); 1343 delayacct_tsk_free(p); 1344 module_put(task_thread_info(p)->exec_domain->module); 1345 bad_fork_cleanup_count: 1346 atomic_dec(&p->cred->user->processes); 1347 exit_creds(p); 1348 bad_fork_free: 1349 free_task(p); 1350 fork_out: 1351 return ERR_PTR(retval); 1352 } 1353 1354 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1355 { 1356 memset(regs, 0, sizeof(struct pt_regs)); 1357 return regs; 1358 } 1359 1360 struct task_struct * __cpuinit fork_idle(int cpu) 1361 { 1362 struct task_struct *task; 1363 struct pt_regs regs; 1364 1365 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1366 &init_struct_pid, 0); 1367 if (!IS_ERR(task)) 1368 init_idle(task, cpu); 1369 1370 return task; 1371 } 1372 1373 /* 1374 * Ok, this is the main fork-routine. 1375 * 1376 * It copies the process, and if successful kick-starts 1377 * it and waits for it to finish using the VM if required. 1378 */ 1379 long do_fork(unsigned long clone_flags, 1380 unsigned long stack_start, 1381 struct pt_regs *regs, 1382 unsigned long stack_size, 1383 int __user *parent_tidptr, 1384 int __user *child_tidptr) 1385 { 1386 struct task_struct *p; 1387 int trace = 0; 1388 long nr; 1389 1390 /* 1391 * Do some preliminary argument and permissions checking before we 1392 * actually start allocating stuff 1393 */ 1394 if (clone_flags & CLONE_NEWUSER) { 1395 if (clone_flags & CLONE_THREAD) 1396 return -EINVAL; 1397 /* hopefully this check will go away when userns support is 1398 * complete 1399 */ 1400 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1401 !capable(CAP_SETGID)) 1402 return -EPERM; 1403 } 1404 1405 /* 1406 * We hope to recycle these flags after 2.6.26 1407 */ 1408 if (unlikely(clone_flags & CLONE_STOPPED)) { 1409 static int __read_mostly count = 100; 1410 1411 if (count > 0 && printk_ratelimit()) { 1412 char comm[TASK_COMM_LEN]; 1413 1414 count--; 1415 printk(KERN_INFO "fork(): process `%s' used deprecated " 1416 "clone flags 0x%lx\n", 1417 get_task_comm(comm, current), 1418 clone_flags & CLONE_STOPPED); 1419 } 1420 } 1421 1422 /* 1423 * When called from kernel_thread, don't do user tracing stuff. 1424 */ 1425 if (likely(user_mode(regs))) 1426 trace = tracehook_prepare_clone(clone_flags); 1427 1428 p = copy_process(clone_flags, stack_start, regs, stack_size, 1429 child_tidptr, NULL, trace); 1430 /* 1431 * Do this prior waking up the new thread - the thread pointer 1432 * might get invalid after that point, if the thread exits quickly. 1433 */ 1434 if (!IS_ERR(p)) { 1435 struct completion vfork; 1436 1437 trace_sched_process_fork(current, p); 1438 1439 nr = task_pid_vnr(p); 1440 1441 if (clone_flags & CLONE_PARENT_SETTID) 1442 put_user(nr, parent_tidptr); 1443 1444 if (clone_flags & CLONE_VFORK) { 1445 p->vfork_done = &vfork; 1446 init_completion(&vfork); 1447 } 1448 1449 audit_finish_fork(p); 1450 tracehook_report_clone(regs, clone_flags, nr, p); 1451 1452 /* 1453 * We set PF_STARTING at creation in case tracing wants to 1454 * use this to distinguish a fully live task from one that 1455 * hasn't gotten to tracehook_report_clone() yet. Now we 1456 * clear it and set the child going. 1457 */ 1458 p->flags &= ~PF_STARTING; 1459 1460 if (unlikely(clone_flags & CLONE_STOPPED)) { 1461 /* 1462 * We'll start up with an immediate SIGSTOP. 1463 */ 1464 sigaddset(&p->pending.signal, SIGSTOP); 1465 set_tsk_thread_flag(p, TIF_SIGPENDING); 1466 __set_task_state(p, TASK_STOPPED); 1467 } else { 1468 wake_up_new_task(p, clone_flags); 1469 } 1470 1471 tracehook_report_clone_complete(trace, regs, 1472 clone_flags, nr, p); 1473 1474 if (clone_flags & CLONE_VFORK) { 1475 freezer_do_not_count(); 1476 wait_for_completion(&vfork); 1477 freezer_count(); 1478 tracehook_report_vfork_done(p, nr); 1479 } 1480 } else { 1481 nr = PTR_ERR(p); 1482 } 1483 return nr; 1484 } 1485 1486 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1487 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1488 #endif 1489 1490 static void sighand_ctor(void *data) 1491 { 1492 struct sighand_struct *sighand = data; 1493 1494 spin_lock_init(&sighand->siglock); 1495 init_waitqueue_head(&sighand->signalfd_wqh); 1496 } 1497 1498 void __init proc_caches_init(void) 1499 { 1500 sighand_cachep = kmem_cache_create("sighand_cache", 1501 sizeof(struct sighand_struct), 0, 1502 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1503 SLAB_NOTRACK, sighand_ctor); 1504 signal_cachep = kmem_cache_create("signal_cache", 1505 sizeof(struct signal_struct), 0, 1506 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1507 files_cachep = kmem_cache_create("files_cache", 1508 sizeof(struct files_struct), 0, 1509 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1510 fs_cachep = kmem_cache_create("fs_cache", 1511 sizeof(struct fs_struct), 0, 1512 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1513 mm_cachep = kmem_cache_create("mm_struct", 1514 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1515 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1516 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1517 mmap_init(); 1518 } 1519 1520 /* 1521 * Check constraints on flags passed to the unshare system call and 1522 * force unsharing of additional process context as appropriate. 1523 */ 1524 static void check_unshare_flags(unsigned long *flags_ptr) 1525 { 1526 /* 1527 * If unsharing a thread from a thread group, must also 1528 * unshare vm. 1529 */ 1530 if (*flags_ptr & CLONE_THREAD) 1531 *flags_ptr |= CLONE_VM; 1532 1533 /* 1534 * If unsharing vm, must also unshare signal handlers. 1535 */ 1536 if (*flags_ptr & CLONE_VM) 1537 *flags_ptr |= CLONE_SIGHAND; 1538 1539 /* 1540 * If unsharing signal handlers and the task was created 1541 * using CLONE_THREAD, then must unshare the thread 1542 */ 1543 if ((*flags_ptr & CLONE_SIGHAND) && 1544 (atomic_read(¤t->signal->count) > 1)) 1545 *flags_ptr |= CLONE_THREAD; 1546 1547 /* 1548 * If unsharing namespace, must also unshare filesystem information. 1549 */ 1550 if (*flags_ptr & CLONE_NEWNS) 1551 *flags_ptr |= CLONE_FS; 1552 } 1553 1554 /* 1555 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1556 */ 1557 static int unshare_thread(unsigned long unshare_flags) 1558 { 1559 if (unshare_flags & CLONE_THREAD) 1560 return -EINVAL; 1561 1562 return 0; 1563 } 1564 1565 /* 1566 * Unshare the filesystem structure if it is being shared 1567 */ 1568 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1569 { 1570 struct fs_struct *fs = current->fs; 1571 1572 if (!(unshare_flags & CLONE_FS) || !fs) 1573 return 0; 1574 1575 /* don't need lock here; in the worst case we'll do useless copy */ 1576 if (fs->users == 1) 1577 return 0; 1578 1579 *new_fsp = copy_fs_struct(fs); 1580 if (!*new_fsp) 1581 return -ENOMEM; 1582 1583 return 0; 1584 } 1585 1586 /* 1587 * Unsharing of sighand is not supported yet 1588 */ 1589 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1590 { 1591 struct sighand_struct *sigh = current->sighand; 1592 1593 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1594 return -EINVAL; 1595 else 1596 return 0; 1597 } 1598 1599 /* 1600 * Unshare vm if it is being shared 1601 */ 1602 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1603 { 1604 struct mm_struct *mm = current->mm; 1605 1606 if ((unshare_flags & CLONE_VM) && 1607 (mm && atomic_read(&mm->mm_users) > 1)) { 1608 return -EINVAL; 1609 } 1610 1611 return 0; 1612 } 1613 1614 /* 1615 * Unshare file descriptor table if it is being shared 1616 */ 1617 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1618 { 1619 struct files_struct *fd = current->files; 1620 int error = 0; 1621 1622 if ((unshare_flags & CLONE_FILES) && 1623 (fd && atomic_read(&fd->count) > 1)) { 1624 *new_fdp = dup_fd(fd, &error); 1625 if (!*new_fdp) 1626 return error; 1627 } 1628 1629 return 0; 1630 } 1631 1632 /* 1633 * unshare allows a process to 'unshare' part of the process 1634 * context which was originally shared using clone. copy_* 1635 * functions used by do_fork() cannot be used here directly 1636 * because they modify an inactive task_struct that is being 1637 * constructed. Here we are modifying the current, active, 1638 * task_struct. 1639 */ 1640 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1641 { 1642 int err = 0; 1643 struct fs_struct *fs, *new_fs = NULL; 1644 struct sighand_struct *new_sigh = NULL; 1645 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1646 struct files_struct *fd, *new_fd = NULL; 1647 struct nsproxy *new_nsproxy = NULL; 1648 int do_sysvsem = 0; 1649 1650 check_unshare_flags(&unshare_flags); 1651 1652 /* Return -EINVAL for all unsupported flags */ 1653 err = -EINVAL; 1654 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1655 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1656 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1657 goto bad_unshare_out; 1658 1659 /* 1660 * CLONE_NEWIPC must also detach from the undolist: after switching 1661 * to a new ipc namespace, the semaphore arrays from the old 1662 * namespace are unreachable. 1663 */ 1664 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1665 do_sysvsem = 1; 1666 if ((err = unshare_thread(unshare_flags))) 1667 goto bad_unshare_out; 1668 if ((err = unshare_fs(unshare_flags, &new_fs))) 1669 goto bad_unshare_cleanup_thread; 1670 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1671 goto bad_unshare_cleanup_fs; 1672 if ((err = unshare_vm(unshare_flags, &new_mm))) 1673 goto bad_unshare_cleanup_sigh; 1674 if ((err = unshare_fd(unshare_flags, &new_fd))) 1675 goto bad_unshare_cleanup_vm; 1676 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1677 new_fs))) 1678 goto bad_unshare_cleanup_fd; 1679 1680 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1681 if (do_sysvsem) { 1682 /* 1683 * CLONE_SYSVSEM is equivalent to sys_exit(). 1684 */ 1685 exit_sem(current); 1686 } 1687 1688 if (new_nsproxy) { 1689 switch_task_namespaces(current, new_nsproxy); 1690 new_nsproxy = NULL; 1691 } 1692 1693 task_lock(current); 1694 1695 if (new_fs) { 1696 fs = current->fs; 1697 write_lock(&fs->lock); 1698 current->fs = new_fs; 1699 if (--fs->users) 1700 new_fs = NULL; 1701 else 1702 new_fs = fs; 1703 write_unlock(&fs->lock); 1704 } 1705 1706 if (new_mm) { 1707 mm = current->mm; 1708 active_mm = current->active_mm; 1709 current->mm = new_mm; 1710 current->active_mm = new_mm; 1711 activate_mm(active_mm, new_mm); 1712 new_mm = mm; 1713 } 1714 1715 if (new_fd) { 1716 fd = current->files; 1717 current->files = new_fd; 1718 new_fd = fd; 1719 } 1720 1721 task_unlock(current); 1722 } 1723 1724 if (new_nsproxy) 1725 put_nsproxy(new_nsproxy); 1726 1727 bad_unshare_cleanup_fd: 1728 if (new_fd) 1729 put_files_struct(new_fd); 1730 1731 bad_unshare_cleanup_vm: 1732 if (new_mm) 1733 mmput(new_mm); 1734 1735 bad_unshare_cleanup_sigh: 1736 if (new_sigh) 1737 if (atomic_dec_and_test(&new_sigh->count)) 1738 kmem_cache_free(sighand_cachep, new_sigh); 1739 1740 bad_unshare_cleanup_fs: 1741 if (new_fs) 1742 free_fs_struct(new_fs); 1743 1744 bad_unshare_cleanup_thread: 1745 bad_unshare_out: 1746 return err; 1747 } 1748 1749 /* 1750 * Helper to unshare the files of the current task. 1751 * We don't want to expose copy_files internals to 1752 * the exec layer of the kernel. 1753 */ 1754 1755 int unshare_files(struct files_struct **displaced) 1756 { 1757 struct task_struct *task = current; 1758 struct files_struct *copy = NULL; 1759 int error; 1760 1761 error = unshare_fd(CLONE_FILES, ©); 1762 if (error || !copy) { 1763 *displaced = NULL; 1764 return error; 1765 } 1766 *displaced = task->files; 1767 task_lock(task); 1768 task->files = copy; 1769 task_unlock(task); 1770 return 0; 1771 } 1772