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