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 #include <linux/oom.h> 69 70 #include <asm/pgtable.h> 71 #include <asm/pgalloc.h> 72 #include <asm/uaccess.h> 73 #include <asm/mmu_context.h> 74 #include <asm/cacheflush.h> 75 #include <asm/tlbflush.h> 76 77 #include <trace/events/sched.h> 78 79 /* 80 * Protected counters by write_lock_irq(&tasklist_lock) 81 */ 82 unsigned long total_forks; /* Handle normal Linux uptimes. */ 83 int nr_threads; /* The idle threads do not count.. */ 84 85 int max_threads; /* tunable limit on nr_threads */ 86 87 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 88 89 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 90 91 #ifdef CONFIG_PROVE_RCU 92 int lockdep_tasklist_lock_is_held(void) 93 { 94 return lockdep_is_held(&tasklist_lock); 95 } 96 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 97 #endif /* #ifdef CONFIG_PROVE_RCU */ 98 99 int nr_processes(void) 100 { 101 int cpu; 102 int total = 0; 103 104 for_each_possible_cpu(cpu) 105 total += per_cpu(process_counts, cpu); 106 107 return total; 108 } 109 110 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 111 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 112 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 113 static struct kmem_cache *task_struct_cachep; 114 #endif 115 116 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 117 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 118 { 119 #ifdef CONFIG_DEBUG_STACK_USAGE 120 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 121 #else 122 gfp_t mask = GFP_KERNEL; 123 #endif 124 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 125 } 126 127 static inline void free_thread_info(struct thread_info *ti) 128 { 129 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 130 } 131 #endif 132 133 /* SLAB cache for signal_struct structures (tsk->signal) */ 134 static struct kmem_cache *signal_cachep; 135 136 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 137 struct kmem_cache *sighand_cachep; 138 139 /* SLAB cache for files_struct structures (tsk->files) */ 140 struct kmem_cache *files_cachep; 141 142 /* SLAB cache for fs_struct structures (tsk->fs) */ 143 struct kmem_cache *fs_cachep; 144 145 /* SLAB cache for vm_area_struct structures */ 146 struct kmem_cache *vm_area_cachep; 147 148 /* SLAB cache for mm_struct structures (tsk->mm) */ 149 static struct kmem_cache *mm_cachep; 150 151 static void account_kernel_stack(struct thread_info *ti, int account) 152 { 153 struct zone *zone = page_zone(virt_to_page(ti)); 154 155 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 156 } 157 158 void free_task(struct task_struct *tsk) 159 { 160 prop_local_destroy_single(&tsk->dirties); 161 account_kernel_stack(tsk->stack, -1); 162 free_thread_info(tsk->stack); 163 rt_mutex_debug_task_free(tsk); 164 ftrace_graph_exit_task(tsk); 165 free_task_struct(tsk); 166 } 167 EXPORT_SYMBOL(free_task); 168 169 static inline void free_signal_struct(struct signal_struct *sig) 170 { 171 taskstats_tgid_free(sig); 172 kmem_cache_free(signal_cachep, sig); 173 } 174 175 static inline void put_signal_struct(struct signal_struct *sig) 176 { 177 if (atomic_dec_and_test(&sig->sigcnt)) 178 free_signal_struct(sig); 179 } 180 181 void __put_task_struct(struct task_struct *tsk) 182 { 183 WARN_ON(!tsk->exit_state); 184 WARN_ON(atomic_read(&tsk->usage)); 185 WARN_ON(tsk == current); 186 187 exit_creds(tsk); 188 delayacct_tsk_free(tsk); 189 put_signal_struct(tsk->signal); 190 191 if (!profile_handoff_task(tsk)) 192 free_task(tsk); 193 } 194 195 /* 196 * macro override instead of weak attribute alias, to workaround 197 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 198 */ 199 #ifndef arch_task_cache_init 200 #define arch_task_cache_init() 201 #endif 202 203 void __init fork_init(unsigned long mempages) 204 { 205 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 206 #ifndef ARCH_MIN_TASKALIGN 207 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 208 #endif 209 /* create a slab on which task_structs can be allocated */ 210 task_struct_cachep = 211 kmem_cache_create("task_struct", sizeof(struct task_struct), 212 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 213 #endif 214 215 /* do the arch specific task caches init */ 216 arch_task_cache_init(); 217 218 /* 219 * The default maximum number of threads is set to a safe 220 * value: the thread structures can take up at most half 221 * of memory. 222 */ 223 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 224 225 /* 226 * we need to allow at least 20 threads to boot a system 227 */ 228 if(max_threads < 20) 229 max_threads = 20; 230 231 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 232 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 233 init_task.signal->rlim[RLIMIT_SIGPENDING] = 234 init_task.signal->rlim[RLIMIT_NPROC]; 235 } 236 237 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 238 struct task_struct *src) 239 { 240 *dst = *src; 241 return 0; 242 } 243 244 static struct task_struct *dup_task_struct(struct task_struct *orig) 245 { 246 struct task_struct *tsk; 247 struct thread_info *ti; 248 unsigned long *stackend; 249 250 int err; 251 252 prepare_to_copy(orig); 253 254 tsk = alloc_task_struct(); 255 if (!tsk) 256 return NULL; 257 258 ti = alloc_thread_info(tsk); 259 if (!ti) { 260 free_task_struct(tsk); 261 return NULL; 262 } 263 264 err = arch_dup_task_struct(tsk, orig); 265 if (err) 266 goto out; 267 268 tsk->stack = ti; 269 270 err = prop_local_init_single(&tsk->dirties); 271 if (err) 272 goto out; 273 274 setup_thread_stack(tsk, orig); 275 clear_user_return_notifier(tsk); 276 clear_tsk_need_resched(tsk); 277 stackend = end_of_stack(tsk); 278 *stackend = STACK_END_MAGIC; /* for overflow detection */ 279 280 #ifdef CONFIG_CC_STACKPROTECTOR 281 tsk->stack_canary = get_random_int(); 282 #endif 283 284 /* One for us, one for whoever does the "release_task()" (usually parent) */ 285 atomic_set(&tsk->usage,2); 286 atomic_set(&tsk->fs_excl, 0); 287 #ifdef CONFIG_BLK_DEV_IO_TRACE 288 tsk->btrace_seq = 0; 289 #endif 290 tsk->splice_pipe = NULL; 291 292 account_kernel_stack(ti, 1); 293 294 return tsk; 295 296 out: 297 free_thread_info(ti); 298 free_task_struct(tsk); 299 return NULL; 300 } 301 302 #ifdef CONFIG_MMU 303 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 304 { 305 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 306 struct rb_node **rb_link, *rb_parent; 307 int retval; 308 unsigned long charge; 309 struct mempolicy *pol; 310 311 down_write(&oldmm->mmap_sem); 312 flush_cache_dup_mm(oldmm); 313 /* 314 * Not linked in yet - no deadlock potential: 315 */ 316 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 317 318 mm->locked_vm = 0; 319 mm->mmap = NULL; 320 mm->mmap_cache = NULL; 321 mm->free_area_cache = oldmm->mmap_base; 322 mm->cached_hole_size = ~0UL; 323 mm->map_count = 0; 324 cpumask_clear(mm_cpumask(mm)); 325 mm->mm_rb = RB_ROOT; 326 rb_link = &mm->mm_rb.rb_node; 327 rb_parent = NULL; 328 pprev = &mm->mmap; 329 retval = ksm_fork(mm, oldmm); 330 if (retval) 331 goto out; 332 333 prev = NULL; 334 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 335 struct file *file; 336 337 if (mpnt->vm_flags & VM_DONTCOPY) { 338 long pages = vma_pages(mpnt); 339 mm->total_vm -= pages; 340 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 341 -pages); 342 continue; 343 } 344 charge = 0; 345 if (mpnt->vm_flags & VM_ACCOUNT) { 346 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 347 if (security_vm_enough_memory(len)) 348 goto fail_nomem; 349 charge = len; 350 } 351 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 352 if (!tmp) 353 goto fail_nomem; 354 *tmp = *mpnt; 355 INIT_LIST_HEAD(&tmp->anon_vma_chain); 356 pol = mpol_dup(vma_policy(mpnt)); 357 retval = PTR_ERR(pol); 358 if (IS_ERR(pol)) 359 goto fail_nomem_policy; 360 vma_set_policy(tmp, pol); 361 tmp->vm_mm = mm; 362 if (anon_vma_fork(tmp, mpnt)) 363 goto fail_nomem_anon_vma_fork; 364 tmp->vm_flags &= ~VM_LOCKED; 365 tmp->vm_next = tmp->vm_prev = NULL; 366 file = tmp->vm_file; 367 if (file) { 368 struct inode *inode = file->f_path.dentry->d_inode; 369 struct address_space *mapping = file->f_mapping; 370 371 get_file(file); 372 if (tmp->vm_flags & VM_DENYWRITE) 373 atomic_dec(&inode->i_writecount); 374 spin_lock(&mapping->i_mmap_lock); 375 if (tmp->vm_flags & VM_SHARED) 376 mapping->i_mmap_writable++; 377 tmp->vm_truncate_count = mpnt->vm_truncate_count; 378 flush_dcache_mmap_lock(mapping); 379 /* insert tmp into the share list, just after mpnt */ 380 vma_prio_tree_add(tmp, mpnt); 381 flush_dcache_mmap_unlock(mapping); 382 spin_unlock(&mapping->i_mmap_lock); 383 } 384 385 /* 386 * Clear hugetlb-related page reserves for children. This only 387 * affects MAP_PRIVATE mappings. Faults generated by the child 388 * are not guaranteed to succeed, even if read-only 389 */ 390 if (is_vm_hugetlb_page(tmp)) 391 reset_vma_resv_huge_pages(tmp); 392 393 /* 394 * Link in the new vma and copy the page table entries. 395 */ 396 *pprev = tmp; 397 pprev = &tmp->vm_next; 398 tmp->vm_prev = prev; 399 prev = tmp; 400 401 __vma_link_rb(mm, tmp, rb_link, rb_parent); 402 rb_link = &tmp->vm_rb.rb_right; 403 rb_parent = &tmp->vm_rb; 404 405 mm->map_count++; 406 retval = copy_page_range(mm, oldmm, mpnt); 407 408 if (tmp->vm_ops && tmp->vm_ops->open) 409 tmp->vm_ops->open(tmp); 410 411 if (retval) 412 goto out; 413 } 414 /* a new mm has just been created */ 415 arch_dup_mmap(oldmm, mm); 416 retval = 0; 417 out: 418 up_write(&mm->mmap_sem); 419 flush_tlb_mm(oldmm); 420 up_write(&oldmm->mmap_sem); 421 return retval; 422 fail_nomem_anon_vma_fork: 423 mpol_put(pol); 424 fail_nomem_policy: 425 kmem_cache_free(vm_area_cachep, tmp); 426 fail_nomem: 427 retval = -ENOMEM; 428 vm_unacct_memory(charge); 429 goto out; 430 } 431 432 static inline int mm_alloc_pgd(struct mm_struct * mm) 433 { 434 mm->pgd = pgd_alloc(mm); 435 if (unlikely(!mm->pgd)) 436 return -ENOMEM; 437 return 0; 438 } 439 440 static inline void mm_free_pgd(struct mm_struct * mm) 441 { 442 pgd_free(mm, mm->pgd); 443 } 444 #else 445 #define dup_mmap(mm, oldmm) (0) 446 #define mm_alloc_pgd(mm) (0) 447 #define mm_free_pgd(mm) 448 #endif /* CONFIG_MMU */ 449 450 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 451 452 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 453 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 454 455 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 456 457 static int __init coredump_filter_setup(char *s) 458 { 459 default_dump_filter = 460 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 461 MMF_DUMP_FILTER_MASK; 462 return 1; 463 } 464 465 __setup("coredump_filter=", coredump_filter_setup); 466 467 #include <linux/init_task.h> 468 469 static void mm_init_aio(struct mm_struct *mm) 470 { 471 #ifdef CONFIG_AIO 472 spin_lock_init(&mm->ioctx_lock); 473 INIT_HLIST_HEAD(&mm->ioctx_list); 474 #endif 475 } 476 477 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 478 { 479 atomic_set(&mm->mm_users, 1); 480 atomic_set(&mm->mm_count, 1); 481 init_rwsem(&mm->mmap_sem); 482 INIT_LIST_HEAD(&mm->mmlist); 483 mm->flags = (current->mm) ? 484 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 485 mm->core_state = NULL; 486 mm->nr_ptes = 0; 487 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 488 spin_lock_init(&mm->page_table_lock); 489 mm->free_area_cache = TASK_UNMAPPED_BASE; 490 mm->cached_hole_size = ~0UL; 491 mm_init_aio(mm); 492 mm_init_owner(mm, p); 493 atomic_set(&mm->oom_disable_count, 0); 494 495 if (likely(!mm_alloc_pgd(mm))) { 496 mm->def_flags = 0; 497 mmu_notifier_mm_init(mm); 498 return mm; 499 } 500 501 free_mm(mm); 502 return NULL; 503 } 504 505 /* 506 * Allocate and initialize an mm_struct. 507 */ 508 struct mm_struct * mm_alloc(void) 509 { 510 struct mm_struct * mm; 511 512 mm = allocate_mm(); 513 if (mm) { 514 memset(mm, 0, sizeof(*mm)); 515 mm = mm_init(mm, current); 516 } 517 return mm; 518 } 519 520 /* 521 * Called when the last reference to the mm 522 * is dropped: either by a lazy thread or by 523 * mmput. Free the page directory and the mm. 524 */ 525 void __mmdrop(struct mm_struct *mm) 526 { 527 BUG_ON(mm == &init_mm); 528 mm_free_pgd(mm); 529 destroy_context(mm); 530 mmu_notifier_mm_destroy(mm); 531 free_mm(mm); 532 } 533 EXPORT_SYMBOL_GPL(__mmdrop); 534 535 /* 536 * Decrement the use count and release all resources for an mm. 537 */ 538 void mmput(struct mm_struct *mm) 539 { 540 might_sleep(); 541 542 if (atomic_dec_and_test(&mm->mm_users)) { 543 exit_aio(mm); 544 ksm_exit(mm); 545 exit_mmap(mm); 546 set_mm_exe_file(mm, NULL); 547 if (!list_empty(&mm->mmlist)) { 548 spin_lock(&mmlist_lock); 549 list_del(&mm->mmlist); 550 spin_unlock(&mmlist_lock); 551 } 552 put_swap_token(mm); 553 if (mm->binfmt) 554 module_put(mm->binfmt->module); 555 mmdrop(mm); 556 } 557 } 558 EXPORT_SYMBOL_GPL(mmput); 559 560 /** 561 * get_task_mm - acquire a reference to the task's mm 562 * 563 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 564 * this kernel workthread has transiently adopted a user mm with use_mm, 565 * to do its AIO) is not set and if so returns a reference to it, after 566 * bumping up the use count. User must release the mm via mmput() 567 * after use. Typically used by /proc and ptrace. 568 */ 569 struct mm_struct *get_task_mm(struct task_struct *task) 570 { 571 struct mm_struct *mm; 572 573 task_lock(task); 574 mm = task->mm; 575 if (mm) { 576 if (task->flags & PF_KTHREAD) 577 mm = NULL; 578 else 579 atomic_inc(&mm->mm_users); 580 } 581 task_unlock(task); 582 return mm; 583 } 584 EXPORT_SYMBOL_GPL(get_task_mm); 585 586 /* Please note the differences between mmput and mm_release. 587 * mmput is called whenever we stop holding onto a mm_struct, 588 * error success whatever. 589 * 590 * mm_release is called after a mm_struct has been removed 591 * from the current process. 592 * 593 * This difference is important for error handling, when we 594 * only half set up a mm_struct for a new process and need to restore 595 * the old one. Because we mmput the new mm_struct before 596 * restoring the old one. . . 597 * Eric Biederman 10 January 1998 598 */ 599 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 600 { 601 struct completion *vfork_done = tsk->vfork_done; 602 603 /* Get rid of any futexes when releasing the mm */ 604 #ifdef CONFIG_FUTEX 605 if (unlikely(tsk->robust_list)) { 606 exit_robust_list(tsk); 607 tsk->robust_list = NULL; 608 } 609 #ifdef CONFIG_COMPAT 610 if (unlikely(tsk->compat_robust_list)) { 611 compat_exit_robust_list(tsk); 612 tsk->compat_robust_list = NULL; 613 } 614 #endif 615 if (unlikely(!list_empty(&tsk->pi_state_list))) 616 exit_pi_state_list(tsk); 617 #endif 618 619 /* Get rid of any cached register state */ 620 deactivate_mm(tsk, mm); 621 622 /* notify parent sleeping on vfork() */ 623 if (vfork_done) { 624 tsk->vfork_done = NULL; 625 complete(vfork_done); 626 } 627 628 /* 629 * If we're exiting normally, clear a user-space tid field if 630 * requested. We leave this alone when dying by signal, to leave 631 * the value intact in a core dump, and to save the unnecessary 632 * trouble otherwise. Userland only wants this done for a sys_exit. 633 */ 634 if (tsk->clear_child_tid) { 635 if (!(tsk->flags & PF_SIGNALED) && 636 atomic_read(&mm->mm_users) > 1) { 637 /* 638 * We don't check the error code - if userspace has 639 * not set up a proper pointer then tough luck. 640 */ 641 put_user(0, tsk->clear_child_tid); 642 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 643 1, NULL, NULL, 0); 644 } 645 tsk->clear_child_tid = NULL; 646 } 647 } 648 649 /* 650 * Allocate a new mm structure and copy contents from the 651 * mm structure of the passed in task structure. 652 */ 653 struct mm_struct *dup_mm(struct task_struct *tsk) 654 { 655 struct mm_struct *mm, *oldmm = current->mm; 656 int err; 657 658 if (!oldmm) 659 return NULL; 660 661 mm = allocate_mm(); 662 if (!mm) 663 goto fail_nomem; 664 665 memcpy(mm, oldmm, sizeof(*mm)); 666 667 /* Initializing for Swap token stuff */ 668 mm->token_priority = 0; 669 mm->last_interval = 0; 670 671 if (!mm_init(mm, tsk)) 672 goto fail_nomem; 673 674 if (init_new_context(tsk, mm)) 675 goto fail_nocontext; 676 677 dup_mm_exe_file(oldmm, mm); 678 679 err = dup_mmap(mm, oldmm); 680 if (err) 681 goto free_pt; 682 683 mm->hiwater_rss = get_mm_rss(mm); 684 mm->hiwater_vm = mm->total_vm; 685 686 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 687 goto free_pt; 688 689 return mm; 690 691 free_pt: 692 /* don't put binfmt in mmput, we haven't got module yet */ 693 mm->binfmt = NULL; 694 mmput(mm); 695 696 fail_nomem: 697 return NULL; 698 699 fail_nocontext: 700 /* 701 * If init_new_context() failed, we cannot use mmput() to free the mm 702 * because it calls destroy_context() 703 */ 704 mm_free_pgd(mm); 705 free_mm(mm); 706 return NULL; 707 } 708 709 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 710 { 711 struct mm_struct * mm, *oldmm; 712 int retval; 713 714 tsk->min_flt = tsk->maj_flt = 0; 715 tsk->nvcsw = tsk->nivcsw = 0; 716 #ifdef CONFIG_DETECT_HUNG_TASK 717 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 718 #endif 719 720 tsk->mm = NULL; 721 tsk->active_mm = NULL; 722 723 /* 724 * Are we cloning a kernel thread? 725 * 726 * We need to steal a active VM for that.. 727 */ 728 oldmm = current->mm; 729 if (!oldmm) 730 return 0; 731 732 if (clone_flags & CLONE_VM) { 733 atomic_inc(&oldmm->mm_users); 734 mm = oldmm; 735 goto good_mm; 736 } 737 738 retval = -ENOMEM; 739 mm = dup_mm(tsk); 740 if (!mm) 741 goto fail_nomem; 742 743 good_mm: 744 /* Initializing for Swap token stuff */ 745 mm->token_priority = 0; 746 mm->last_interval = 0; 747 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 748 atomic_inc(&mm->oom_disable_count); 749 750 tsk->mm = mm; 751 tsk->active_mm = mm; 752 return 0; 753 754 fail_nomem: 755 return retval; 756 } 757 758 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 759 { 760 struct fs_struct *fs = current->fs; 761 if (clone_flags & CLONE_FS) { 762 /* tsk->fs is already what we want */ 763 spin_lock(&fs->lock); 764 if (fs->in_exec) { 765 spin_unlock(&fs->lock); 766 return -EAGAIN; 767 } 768 fs->users++; 769 spin_unlock(&fs->lock); 770 return 0; 771 } 772 tsk->fs = copy_fs_struct(fs); 773 if (!tsk->fs) 774 return -ENOMEM; 775 return 0; 776 } 777 778 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 779 { 780 struct files_struct *oldf, *newf; 781 int error = 0; 782 783 /* 784 * A background process may not have any files ... 785 */ 786 oldf = current->files; 787 if (!oldf) 788 goto out; 789 790 if (clone_flags & CLONE_FILES) { 791 atomic_inc(&oldf->count); 792 goto out; 793 } 794 795 newf = dup_fd(oldf, &error); 796 if (!newf) 797 goto out; 798 799 tsk->files = newf; 800 error = 0; 801 out: 802 return error; 803 } 804 805 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 806 { 807 #ifdef CONFIG_BLOCK 808 struct io_context *ioc = current->io_context; 809 810 if (!ioc) 811 return 0; 812 /* 813 * Share io context with parent, if CLONE_IO is set 814 */ 815 if (clone_flags & CLONE_IO) { 816 tsk->io_context = ioc_task_link(ioc); 817 if (unlikely(!tsk->io_context)) 818 return -ENOMEM; 819 } else if (ioprio_valid(ioc->ioprio)) { 820 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 821 if (unlikely(!tsk->io_context)) 822 return -ENOMEM; 823 824 tsk->io_context->ioprio = ioc->ioprio; 825 } 826 #endif 827 return 0; 828 } 829 830 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 831 { 832 struct sighand_struct *sig; 833 834 if (clone_flags & CLONE_SIGHAND) { 835 atomic_inc(¤t->sighand->count); 836 return 0; 837 } 838 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 839 rcu_assign_pointer(tsk->sighand, sig); 840 if (!sig) 841 return -ENOMEM; 842 atomic_set(&sig->count, 1); 843 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 844 return 0; 845 } 846 847 void __cleanup_sighand(struct sighand_struct *sighand) 848 { 849 if (atomic_dec_and_test(&sighand->count)) 850 kmem_cache_free(sighand_cachep, sighand); 851 } 852 853 854 /* 855 * Initialize POSIX timer handling for a thread group. 856 */ 857 static void posix_cpu_timers_init_group(struct signal_struct *sig) 858 { 859 unsigned long cpu_limit; 860 861 /* Thread group counters. */ 862 thread_group_cputime_init(sig); 863 864 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 865 if (cpu_limit != RLIM_INFINITY) { 866 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 867 sig->cputimer.running = 1; 868 } 869 870 /* The timer lists. */ 871 INIT_LIST_HEAD(&sig->cpu_timers[0]); 872 INIT_LIST_HEAD(&sig->cpu_timers[1]); 873 INIT_LIST_HEAD(&sig->cpu_timers[2]); 874 } 875 876 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 877 { 878 struct signal_struct *sig; 879 880 if (clone_flags & CLONE_THREAD) 881 return 0; 882 883 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 884 tsk->signal = sig; 885 if (!sig) 886 return -ENOMEM; 887 888 sig->nr_threads = 1; 889 atomic_set(&sig->live, 1); 890 atomic_set(&sig->sigcnt, 1); 891 init_waitqueue_head(&sig->wait_chldexit); 892 if (clone_flags & CLONE_NEWPID) 893 sig->flags |= SIGNAL_UNKILLABLE; 894 sig->curr_target = tsk; 895 init_sigpending(&sig->shared_pending); 896 INIT_LIST_HEAD(&sig->posix_timers); 897 898 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 899 sig->real_timer.function = it_real_fn; 900 901 task_lock(current->group_leader); 902 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 903 task_unlock(current->group_leader); 904 905 posix_cpu_timers_init_group(sig); 906 907 tty_audit_fork(sig); 908 909 sig->oom_adj = current->signal->oom_adj; 910 sig->oom_score_adj = current->signal->oom_score_adj; 911 912 mutex_init(&sig->cred_guard_mutex); 913 914 return 0; 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 | PF_WQ_WORKER); 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 raw_spin_lock_init(&p->pi_lock); 938 #ifdef CONFIG_RT_MUTEXES 939 plist_head_init_raw(&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 task_rlimit(p, RLIMIT_NPROC)) { 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 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1070 p->prev_utime = cputime_zero; 1071 p->prev_stime = cputime_zero; 1072 #endif 1073 #if defined(SPLIT_RSS_COUNTING) 1074 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1075 #endif 1076 1077 p->default_timer_slack_ns = current->timer_slack_ns; 1078 1079 task_io_accounting_init(&p->ioac); 1080 acct_clear_integrals(p); 1081 1082 posix_cpu_timers_init(p); 1083 1084 p->lock_depth = -1; /* -1 = no lock */ 1085 do_posix_clock_monotonic_gettime(&p->start_time); 1086 p->real_start_time = p->start_time; 1087 monotonic_to_bootbased(&p->real_start_time); 1088 p->io_context = NULL; 1089 p->audit_context = NULL; 1090 cgroup_fork(p); 1091 #ifdef CONFIG_NUMA 1092 p->mempolicy = mpol_dup(p->mempolicy); 1093 if (IS_ERR(p->mempolicy)) { 1094 retval = PTR_ERR(p->mempolicy); 1095 p->mempolicy = NULL; 1096 goto bad_fork_cleanup_cgroup; 1097 } 1098 mpol_fix_fork_child_flag(p); 1099 #endif 1100 #ifdef CONFIG_TRACE_IRQFLAGS 1101 p->irq_events = 0; 1102 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1103 p->hardirqs_enabled = 1; 1104 #else 1105 p->hardirqs_enabled = 0; 1106 #endif 1107 p->hardirq_enable_ip = 0; 1108 p->hardirq_enable_event = 0; 1109 p->hardirq_disable_ip = _THIS_IP_; 1110 p->hardirq_disable_event = 0; 1111 p->softirqs_enabled = 1; 1112 p->softirq_enable_ip = _THIS_IP_; 1113 p->softirq_enable_event = 0; 1114 p->softirq_disable_ip = 0; 1115 p->softirq_disable_event = 0; 1116 p->hardirq_context = 0; 1117 p->softirq_context = 0; 1118 #endif 1119 #ifdef CONFIG_LOCKDEP 1120 p->lockdep_depth = 0; /* no locks held yet */ 1121 p->curr_chain_key = 0; 1122 p->lockdep_recursion = 0; 1123 #endif 1124 1125 #ifdef CONFIG_DEBUG_MUTEXES 1126 p->blocked_on = NULL; /* not blocked yet */ 1127 #endif 1128 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1129 p->memcg_batch.do_batch = 0; 1130 p->memcg_batch.memcg = NULL; 1131 #endif 1132 1133 /* Perform scheduler related setup. Assign this task to a CPU. */ 1134 sched_fork(p, clone_flags); 1135 1136 retval = perf_event_init_task(p); 1137 if (retval) 1138 goto bad_fork_cleanup_policy; 1139 1140 if ((retval = audit_alloc(p))) 1141 goto bad_fork_cleanup_policy; 1142 /* copy all the process information */ 1143 if ((retval = copy_semundo(clone_flags, p))) 1144 goto bad_fork_cleanup_audit; 1145 if ((retval = copy_files(clone_flags, p))) 1146 goto bad_fork_cleanup_semundo; 1147 if ((retval = copy_fs(clone_flags, p))) 1148 goto bad_fork_cleanup_files; 1149 if ((retval = copy_sighand(clone_flags, p))) 1150 goto bad_fork_cleanup_fs; 1151 if ((retval = copy_signal(clone_flags, p))) 1152 goto bad_fork_cleanup_sighand; 1153 if ((retval = copy_mm(clone_flags, p))) 1154 goto bad_fork_cleanup_signal; 1155 if ((retval = copy_namespaces(clone_flags, p))) 1156 goto bad_fork_cleanup_mm; 1157 if ((retval = copy_io(clone_flags, p))) 1158 goto bad_fork_cleanup_namespaces; 1159 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1160 if (retval) 1161 goto bad_fork_cleanup_io; 1162 1163 if (pid != &init_struct_pid) { 1164 retval = -ENOMEM; 1165 pid = alloc_pid(p->nsproxy->pid_ns); 1166 if (!pid) 1167 goto bad_fork_cleanup_io; 1168 1169 if (clone_flags & CLONE_NEWPID) { 1170 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1171 if (retval < 0) 1172 goto bad_fork_free_pid; 1173 } 1174 } 1175 1176 p->pid = pid_nr(pid); 1177 p->tgid = p->pid; 1178 if (clone_flags & CLONE_THREAD) 1179 p->tgid = current->tgid; 1180 1181 if (current->nsproxy != p->nsproxy) { 1182 retval = ns_cgroup_clone(p, pid); 1183 if (retval) 1184 goto bad_fork_free_pid; 1185 } 1186 1187 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1188 /* 1189 * Clear TID on mm_release()? 1190 */ 1191 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1192 #ifdef CONFIG_FUTEX 1193 p->robust_list = NULL; 1194 #ifdef CONFIG_COMPAT 1195 p->compat_robust_list = NULL; 1196 #endif 1197 INIT_LIST_HEAD(&p->pi_state_list); 1198 p->pi_state_cache = NULL; 1199 #endif 1200 /* 1201 * sigaltstack should be cleared when sharing the same VM 1202 */ 1203 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1204 p->sas_ss_sp = p->sas_ss_size = 0; 1205 1206 /* 1207 * Syscall tracing and stepping should be turned off in the 1208 * child regardless of CLONE_PTRACE. 1209 */ 1210 user_disable_single_step(p); 1211 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1212 #ifdef TIF_SYSCALL_EMU 1213 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1214 #endif 1215 clear_all_latency_tracing(p); 1216 1217 /* ok, now we should be set up.. */ 1218 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1219 p->pdeath_signal = 0; 1220 p->exit_state = 0; 1221 1222 /* 1223 * Ok, make it visible to the rest of the system. 1224 * We dont wake it up yet. 1225 */ 1226 p->group_leader = p; 1227 INIT_LIST_HEAD(&p->thread_group); 1228 1229 /* Now that the task is set up, run cgroup callbacks if 1230 * necessary. We need to run them before the task is visible 1231 * on the tasklist. */ 1232 cgroup_fork_callbacks(p); 1233 cgroup_callbacks_done = 1; 1234 1235 /* Need tasklist lock for parent etc handling! */ 1236 write_lock_irq(&tasklist_lock); 1237 1238 /* CLONE_PARENT re-uses the old parent */ 1239 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1240 p->real_parent = current->real_parent; 1241 p->parent_exec_id = current->parent_exec_id; 1242 } else { 1243 p->real_parent = current; 1244 p->parent_exec_id = current->self_exec_id; 1245 } 1246 1247 spin_lock(¤t->sighand->siglock); 1248 1249 /* 1250 * Process group and session signals need to be delivered to just the 1251 * parent before the fork or both the parent and the child after the 1252 * fork. Restart if a signal comes in before we add the new process to 1253 * it's process group. 1254 * A fatal signal pending means that current will exit, so the new 1255 * thread can't slip out of an OOM kill (or normal SIGKILL). 1256 */ 1257 recalc_sigpending(); 1258 if (signal_pending(current)) { 1259 spin_unlock(¤t->sighand->siglock); 1260 write_unlock_irq(&tasklist_lock); 1261 retval = -ERESTARTNOINTR; 1262 goto bad_fork_free_pid; 1263 } 1264 1265 if (clone_flags & CLONE_THREAD) { 1266 current->signal->nr_threads++; 1267 atomic_inc(¤t->signal->live); 1268 atomic_inc(¤t->signal->sigcnt); 1269 p->group_leader = current->group_leader; 1270 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1271 } 1272 1273 if (likely(p->pid)) { 1274 tracehook_finish_clone(p, clone_flags, trace); 1275 1276 if (thread_group_leader(p)) { 1277 if (clone_flags & CLONE_NEWPID) 1278 p->nsproxy->pid_ns->child_reaper = p; 1279 1280 p->signal->leader_pid = pid; 1281 p->signal->tty = tty_kref_get(current->signal->tty); 1282 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1283 attach_pid(p, PIDTYPE_SID, task_session(current)); 1284 list_add_tail(&p->sibling, &p->real_parent->children); 1285 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1286 __get_cpu_var(process_counts)++; 1287 } 1288 attach_pid(p, PIDTYPE_PID, pid); 1289 nr_threads++; 1290 } 1291 1292 total_forks++; 1293 spin_unlock(¤t->sighand->siglock); 1294 write_unlock_irq(&tasklist_lock); 1295 proc_fork_connector(p); 1296 cgroup_post_fork(p); 1297 perf_event_fork(p); 1298 return p; 1299 1300 bad_fork_free_pid: 1301 if (pid != &init_struct_pid) 1302 free_pid(pid); 1303 bad_fork_cleanup_io: 1304 if (p->io_context) 1305 exit_io_context(p); 1306 bad_fork_cleanup_namespaces: 1307 exit_task_namespaces(p); 1308 bad_fork_cleanup_mm: 1309 if (p->mm) { 1310 task_lock(p); 1311 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 1312 atomic_dec(&p->mm->oom_disable_count); 1313 task_unlock(p); 1314 mmput(p->mm); 1315 } 1316 bad_fork_cleanup_signal: 1317 if (!(clone_flags & CLONE_THREAD)) 1318 free_signal_struct(p->signal); 1319 bad_fork_cleanup_sighand: 1320 __cleanup_sighand(p->sighand); 1321 bad_fork_cleanup_fs: 1322 exit_fs(p); /* blocking */ 1323 bad_fork_cleanup_files: 1324 exit_files(p); /* blocking */ 1325 bad_fork_cleanup_semundo: 1326 exit_sem(p); 1327 bad_fork_cleanup_audit: 1328 audit_free(p); 1329 bad_fork_cleanup_policy: 1330 perf_event_free_task(p); 1331 #ifdef CONFIG_NUMA 1332 mpol_put(p->mempolicy); 1333 bad_fork_cleanup_cgroup: 1334 #endif 1335 cgroup_exit(p, cgroup_callbacks_done); 1336 delayacct_tsk_free(p); 1337 module_put(task_thread_info(p)->exec_domain->module); 1338 bad_fork_cleanup_count: 1339 atomic_dec(&p->cred->user->processes); 1340 exit_creds(p); 1341 bad_fork_free: 1342 free_task(p); 1343 fork_out: 1344 return ERR_PTR(retval); 1345 } 1346 1347 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1348 { 1349 memset(regs, 0, sizeof(struct pt_regs)); 1350 return regs; 1351 } 1352 1353 static inline void init_idle_pids(struct pid_link *links) 1354 { 1355 enum pid_type type; 1356 1357 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1358 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1359 links[type].pid = &init_struct_pid; 1360 } 1361 } 1362 1363 struct task_struct * __cpuinit fork_idle(int cpu) 1364 { 1365 struct task_struct *task; 1366 struct pt_regs regs; 1367 1368 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1369 &init_struct_pid, 0); 1370 if (!IS_ERR(task)) { 1371 init_idle_pids(task->pids); 1372 init_idle(task, cpu); 1373 } 1374 1375 return task; 1376 } 1377 1378 /* 1379 * Ok, this is the main fork-routine. 1380 * 1381 * It copies the process, and if successful kick-starts 1382 * it and waits for it to finish using the VM if required. 1383 */ 1384 long do_fork(unsigned long clone_flags, 1385 unsigned long stack_start, 1386 struct pt_regs *regs, 1387 unsigned long stack_size, 1388 int __user *parent_tidptr, 1389 int __user *child_tidptr) 1390 { 1391 struct task_struct *p; 1392 int trace = 0; 1393 long nr; 1394 1395 /* 1396 * Do some preliminary argument and permissions checking before we 1397 * actually start allocating stuff 1398 */ 1399 if (clone_flags & CLONE_NEWUSER) { 1400 if (clone_flags & CLONE_THREAD) 1401 return -EINVAL; 1402 /* hopefully this check will go away when userns support is 1403 * complete 1404 */ 1405 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1406 !capable(CAP_SETGID)) 1407 return -EPERM; 1408 } 1409 1410 /* 1411 * We hope to recycle these flags after 2.6.26 1412 */ 1413 if (unlikely(clone_flags & CLONE_STOPPED)) { 1414 static int __read_mostly count = 100; 1415 1416 if (count > 0 && printk_ratelimit()) { 1417 char comm[TASK_COMM_LEN]; 1418 1419 count--; 1420 printk(KERN_INFO "fork(): process `%s' used deprecated " 1421 "clone flags 0x%lx\n", 1422 get_task_comm(comm, current), 1423 clone_flags & CLONE_STOPPED); 1424 } 1425 } 1426 1427 /* 1428 * When called from kernel_thread, don't do user tracing stuff. 1429 */ 1430 if (likely(user_mode(regs))) 1431 trace = tracehook_prepare_clone(clone_flags); 1432 1433 p = copy_process(clone_flags, stack_start, regs, stack_size, 1434 child_tidptr, NULL, trace); 1435 /* 1436 * Do this prior waking up the new thread - the thread pointer 1437 * might get invalid after that point, if the thread exits quickly. 1438 */ 1439 if (!IS_ERR(p)) { 1440 struct completion vfork; 1441 1442 trace_sched_process_fork(current, p); 1443 1444 nr = task_pid_vnr(p); 1445 1446 if (clone_flags & CLONE_PARENT_SETTID) 1447 put_user(nr, parent_tidptr); 1448 1449 if (clone_flags & CLONE_VFORK) { 1450 p->vfork_done = &vfork; 1451 init_completion(&vfork); 1452 } 1453 1454 audit_finish_fork(p); 1455 tracehook_report_clone(regs, clone_flags, nr, p); 1456 1457 /* 1458 * We set PF_STARTING at creation in case tracing wants to 1459 * use this to distinguish a fully live task from one that 1460 * hasn't gotten to tracehook_report_clone() yet. Now we 1461 * clear it and set the child going. 1462 */ 1463 p->flags &= ~PF_STARTING; 1464 1465 if (unlikely(clone_flags & CLONE_STOPPED)) { 1466 /* 1467 * We'll start up with an immediate SIGSTOP. 1468 */ 1469 sigaddset(&p->pending.signal, SIGSTOP); 1470 set_tsk_thread_flag(p, TIF_SIGPENDING); 1471 __set_task_state(p, TASK_STOPPED); 1472 } else { 1473 wake_up_new_task(p, clone_flags); 1474 } 1475 1476 tracehook_report_clone_complete(trace, regs, 1477 clone_flags, nr, p); 1478 1479 if (clone_flags & CLONE_VFORK) { 1480 freezer_do_not_count(); 1481 wait_for_completion(&vfork); 1482 freezer_count(); 1483 tracehook_report_vfork_done(p, nr); 1484 } 1485 } else { 1486 nr = PTR_ERR(p); 1487 } 1488 return nr; 1489 } 1490 1491 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1492 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1493 #endif 1494 1495 static void sighand_ctor(void *data) 1496 { 1497 struct sighand_struct *sighand = data; 1498 1499 spin_lock_init(&sighand->siglock); 1500 init_waitqueue_head(&sighand->signalfd_wqh); 1501 } 1502 1503 void __init proc_caches_init(void) 1504 { 1505 sighand_cachep = kmem_cache_create("sighand_cache", 1506 sizeof(struct sighand_struct), 0, 1507 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1508 SLAB_NOTRACK, sighand_ctor); 1509 signal_cachep = kmem_cache_create("signal_cache", 1510 sizeof(struct signal_struct), 0, 1511 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1512 files_cachep = kmem_cache_create("files_cache", 1513 sizeof(struct files_struct), 0, 1514 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1515 fs_cachep = kmem_cache_create("fs_cache", 1516 sizeof(struct fs_struct), 0, 1517 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1518 mm_cachep = kmem_cache_create("mm_struct", 1519 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1520 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1521 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1522 mmap_init(); 1523 } 1524 1525 /* 1526 * Check constraints on flags passed to the unshare system call and 1527 * force unsharing of additional process context as appropriate. 1528 */ 1529 static void check_unshare_flags(unsigned long *flags_ptr) 1530 { 1531 /* 1532 * If unsharing a thread from a thread group, must also 1533 * unshare vm. 1534 */ 1535 if (*flags_ptr & CLONE_THREAD) 1536 *flags_ptr |= CLONE_VM; 1537 1538 /* 1539 * If unsharing vm, must also unshare signal handlers. 1540 */ 1541 if (*flags_ptr & CLONE_VM) 1542 *flags_ptr |= CLONE_SIGHAND; 1543 1544 /* 1545 * If unsharing namespace, must also unshare filesystem information. 1546 */ 1547 if (*flags_ptr & CLONE_NEWNS) 1548 *flags_ptr |= CLONE_FS; 1549 } 1550 1551 /* 1552 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1553 */ 1554 static int unshare_thread(unsigned long unshare_flags) 1555 { 1556 if (unshare_flags & CLONE_THREAD) 1557 return -EINVAL; 1558 1559 return 0; 1560 } 1561 1562 /* 1563 * Unshare the filesystem structure if it is being shared 1564 */ 1565 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1566 { 1567 struct fs_struct *fs = current->fs; 1568 1569 if (!(unshare_flags & CLONE_FS) || !fs) 1570 return 0; 1571 1572 /* don't need lock here; in the worst case we'll do useless copy */ 1573 if (fs->users == 1) 1574 return 0; 1575 1576 *new_fsp = copy_fs_struct(fs); 1577 if (!*new_fsp) 1578 return -ENOMEM; 1579 1580 return 0; 1581 } 1582 1583 /* 1584 * Unsharing of sighand is not supported yet 1585 */ 1586 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1587 { 1588 struct sighand_struct *sigh = current->sighand; 1589 1590 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1591 return -EINVAL; 1592 else 1593 return 0; 1594 } 1595 1596 /* 1597 * Unshare vm if it is being shared 1598 */ 1599 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1600 { 1601 struct mm_struct *mm = current->mm; 1602 1603 if ((unshare_flags & CLONE_VM) && 1604 (mm && atomic_read(&mm->mm_users) > 1)) { 1605 return -EINVAL; 1606 } 1607 1608 return 0; 1609 } 1610 1611 /* 1612 * Unshare file descriptor table if it is being shared 1613 */ 1614 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1615 { 1616 struct files_struct *fd = current->files; 1617 int error = 0; 1618 1619 if ((unshare_flags & CLONE_FILES) && 1620 (fd && atomic_read(&fd->count) > 1)) { 1621 *new_fdp = dup_fd(fd, &error); 1622 if (!*new_fdp) 1623 return error; 1624 } 1625 1626 return 0; 1627 } 1628 1629 /* 1630 * unshare allows a process to 'unshare' part of the process 1631 * context which was originally shared using clone. copy_* 1632 * functions used by do_fork() cannot be used here directly 1633 * because they modify an inactive task_struct that is being 1634 * constructed. Here we are modifying the current, active, 1635 * task_struct. 1636 */ 1637 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1638 { 1639 int err = 0; 1640 struct fs_struct *fs, *new_fs = NULL; 1641 struct sighand_struct *new_sigh = NULL; 1642 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1643 struct files_struct *fd, *new_fd = NULL; 1644 struct nsproxy *new_nsproxy = NULL; 1645 int do_sysvsem = 0; 1646 1647 check_unshare_flags(&unshare_flags); 1648 1649 /* Return -EINVAL for all unsupported flags */ 1650 err = -EINVAL; 1651 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1652 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1653 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1654 goto bad_unshare_out; 1655 1656 /* 1657 * CLONE_NEWIPC must also detach from the undolist: after switching 1658 * to a new ipc namespace, the semaphore arrays from the old 1659 * namespace are unreachable. 1660 */ 1661 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1662 do_sysvsem = 1; 1663 if ((err = unshare_thread(unshare_flags))) 1664 goto bad_unshare_out; 1665 if ((err = unshare_fs(unshare_flags, &new_fs))) 1666 goto bad_unshare_cleanup_thread; 1667 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1668 goto bad_unshare_cleanup_fs; 1669 if ((err = unshare_vm(unshare_flags, &new_mm))) 1670 goto bad_unshare_cleanup_sigh; 1671 if ((err = unshare_fd(unshare_flags, &new_fd))) 1672 goto bad_unshare_cleanup_vm; 1673 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1674 new_fs))) 1675 goto bad_unshare_cleanup_fd; 1676 1677 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1678 if (do_sysvsem) { 1679 /* 1680 * CLONE_SYSVSEM is equivalent to sys_exit(). 1681 */ 1682 exit_sem(current); 1683 } 1684 1685 if (new_nsproxy) { 1686 switch_task_namespaces(current, new_nsproxy); 1687 new_nsproxy = NULL; 1688 } 1689 1690 task_lock(current); 1691 1692 if (new_fs) { 1693 fs = current->fs; 1694 spin_lock(&fs->lock); 1695 current->fs = new_fs; 1696 if (--fs->users) 1697 new_fs = NULL; 1698 else 1699 new_fs = fs; 1700 spin_unlock(&fs->lock); 1701 } 1702 1703 if (new_mm) { 1704 mm = current->mm; 1705 active_mm = current->active_mm; 1706 current->mm = new_mm; 1707 current->active_mm = new_mm; 1708 if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { 1709 atomic_dec(&mm->oom_disable_count); 1710 atomic_inc(&new_mm->oom_disable_count); 1711 } 1712 activate_mm(active_mm, new_mm); 1713 new_mm = mm; 1714 } 1715 1716 if (new_fd) { 1717 fd = current->files; 1718 current->files = new_fd; 1719 new_fd = fd; 1720 } 1721 1722 task_unlock(current); 1723 } 1724 1725 if (new_nsproxy) 1726 put_nsproxy(new_nsproxy); 1727 1728 bad_unshare_cleanup_fd: 1729 if (new_fd) 1730 put_files_struct(new_fd); 1731 1732 bad_unshare_cleanup_vm: 1733 if (new_mm) 1734 mmput(new_mm); 1735 1736 bad_unshare_cleanup_sigh: 1737 if (new_sigh) 1738 if (atomic_dec_and_test(&new_sigh->count)) 1739 kmem_cache_free(sighand_cachep, new_sigh); 1740 1741 bad_unshare_cleanup_fs: 1742 if (new_fs) 1743 free_fs_struct(new_fs); 1744 1745 bad_unshare_cleanup_thread: 1746 bad_unshare_out: 1747 return err; 1748 } 1749 1750 /* 1751 * Helper to unshare the files of the current task. 1752 * We don't want to expose copy_files internals to 1753 * the exec layer of the kernel. 1754 */ 1755 1756 int unshare_files(struct files_struct **displaced) 1757 { 1758 struct task_struct *task = current; 1759 struct files_struct *copy = NULL; 1760 int error; 1761 1762 error = unshare_fd(CLONE_FILES, ©); 1763 if (error || !copy) { 1764 *displaced = NULL; 1765 return error; 1766 } 1767 *displaced = task->files; 1768 task_lock(task); 1769 task->files = copy; 1770 task_unlock(task); 1771 return 0; 1772 } 1773