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/seccomp.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/kthread.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/proc_fs.h> 52 #include <linux/profile.h> 53 #include <linux/rmap.h> 54 #include <linux/ksm.h> 55 #include <linux/acct.h> 56 #include <linux/tsacct_kern.h> 57 #include <linux/cn_proc.h> 58 #include <linux/freezer.h> 59 #include <linux/delayacct.h> 60 #include <linux/taskstats_kern.h> 61 #include <linux/random.h> 62 #include <linux/tty.h> 63 #include <linux/blkdev.h> 64 #include <linux/fs_struct.h> 65 #include <linux/magic.h> 66 #include <linux/perf_event.h> 67 #include <linux/posix-timers.h> 68 #include <linux/user-return-notifier.h> 69 #include <linux/oom.h> 70 #include <linux/khugepaged.h> 71 #include <linux/signalfd.h> 72 #include <linux/uprobes.h> 73 74 #include <asm/pgtable.h> 75 #include <asm/pgalloc.h> 76 #include <asm/uaccess.h> 77 #include <asm/mmu_context.h> 78 #include <asm/cacheflush.h> 79 #include <asm/tlbflush.h> 80 81 #include <trace/events/sched.h> 82 83 #define CREATE_TRACE_POINTS 84 #include <trace/events/task.h> 85 86 /* 87 * Protected counters by write_lock_irq(&tasklist_lock) 88 */ 89 unsigned long total_forks; /* Handle normal Linux uptimes. */ 90 int nr_threads; /* The idle threads do not count.. */ 91 92 int max_threads; /* tunable limit on nr_threads */ 93 94 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 95 96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 97 98 #ifdef CONFIG_PROVE_RCU 99 int lockdep_tasklist_lock_is_held(void) 100 { 101 return lockdep_is_held(&tasklist_lock); 102 } 103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 104 #endif /* #ifdef CONFIG_PROVE_RCU */ 105 106 int nr_processes(void) 107 { 108 int cpu; 109 int total = 0; 110 111 for_each_possible_cpu(cpu) 112 total += per_cpu(process_counts, cpu); 113 114 return total; 115 } 116 117 void __weak arch_release_task_struct(struct task_struct *tsk) 118 { 119 } 120 121 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 122 static struct kmem_cache *task_struct_cachep; 123 124 static inline struct task_struct *alloc_task_struct_node(int node) 125 { 126 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 127 } 128 129 static inline void free_task_struct(struct task_struct *tsk) 130 { 131 kmem_cache_free(task_struct_cachep, tsk); 132 } 133 #endif 134 135 void __weak arch_release_thread_info(struct thread_info *ti) 136 { 137 } 138 139 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 140 141 /* 142 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 143 * kmemcache based allocator. 144 */ 145 # if THREAD_SIZE >= PAGE_SIZE 146 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 147 int node) 148 { 149 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 150 THREAD_SIZE_ORDER); 151 152 return page ? page_address(page) : NULL; 153 } 154 155 static inline void free_thread_info(struct thread_info *ti) 156 { 157 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 158 } 159 # else 160 static struct kmem_cache *thread_info_cache; 161 162 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 163 int node) 164 { 165 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 166 } 167 168 static void free_thread_info(struct thread_info *ti) 169 { 170 kmem_cache_free(thread_info_cache, ti); 171 } 172 173 void thread_info_cache_init(void) 174 { 175 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 176 THREAD_SIZE, 0, NULL); 177 BUG_ON(thread_info_cache == NULL); 178 } 179 # endif 180 #endif 181 182 /* SLAB cache for signal_struct structures (tsk->signal) */ 183 static struct kmem_cache *signal_cachep; 184 185 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 186 struct kmem_cache *sighand_cachep; 187 188 /* SLAB cache for files_struct structures (tsk->files) */ 189 struct kmem_cache *files_cachep; 190 191 /* SLAB cache for fs_struct structures (tsk->fs) */ 192 struct kmem_cache *fs_cachep; 193 194 /* SLAB cache for vm_area_struct structures */ 195 struct kmem_cache *vm_area_cachep; 196 197 /* SLAB cache for mm_struct structures (tsk->mm) */ 198 static struct kmem_cache *mm_cachep; 199 200 static void account_kernel_stack(struct thread_info *ti, int account) 201 { 202 struct zone *zone = page_zone(virt_to_page(ti)); 203 204 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 205 } 206 207 void free_task(struct task_struct *tsk) 208 { 209 account_kernel_stack(tsk->stack, -1); 210 arch_release_thread_info(tsk->stack); 211 free_thread_info(tsk->stack); 212 rt_mutex_debug_task_free(tsk); 213 ftrace_graph_exit_task(tsk); 214 put_seccomp_filter(tsk); 215 arch_release_task_struct(tsk); 216 free_task_struct(tsk); 217 } 218 EXPORT_SYMBOL(free_task); 219 220 static inline void free_signal_struct(struct signal_struct *sig) 221 { 222 taskstats_tgid_free(sig); 223 sched_autogroup_exit(sig); 224 kmem_cache_free(signal_cachep, sig); 225 } 226 227 static inline void put_signal_struct(struct signal_struct *sig) 228 { 229 if (atomic_dec_and_test(&sig->sigcnt)) 230 free_signal_struct(sig); 231 } 232 233 void __put_task_struct(struct task_struct *tsk) 234 { 235 WARN_ON(!tsk->exit_state); 236 WARN_ON(atomic_read(&tsk->usage)); 237 WARN_ON(tsk == current); 238 239 security_task_free(tsk); 240 exit_creds(tsk); 241 delayacct_tsk_free(tsk); 242 put_signal_struct(tsk->signal); 243 244 if (!profile_handoff_task(tsk)) 245 free_task(tsk); 246 } 247 EXPORT_SYMBOL_GPL(__put_task_struct); 248 249 void __init __weak arch_task_cache_init(void) { } 250 251 void __init fork_init(unsigned long mempages) 252 { 253 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 254 #ifndef ARCH_MIN_TASKALIGN 255 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 256 #endif 257 /* create a slab on which task_structs can be allocated */ 258 task_struct_cachep = 259 kmem_cache_create("task_struct", sizeof(struct task_struct), 260 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 261 #endif 262 263 /* do the arch specific task caches init */ 264 arch_task_cache_init(); 265 266 /* 267 * The default maximum number of threads is set to a safe 268 * value: the thread structures can take up at most half 269 * of memory. 270 */ 271 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 272 273 /* 274 * we need to allow at least 20 threads to boot a system 275 */ 276 if (max_threads < 20) 277 max_threads = 20; 278 279 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 280 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 281 init_task.signal->rlim[RLIMIT_SIGPENDING] = 282 init_task.signal->rlim[RLIMIT_NPROC]; 283 } 284 285 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 286 struct task_struct *src) 287 { 288 *dst = *src; 289 return 0; 290 } 291 292 static struct task_struct *dup_task_struct(struct task_struct *orig) 293 { 294 struct task_struct *tsk; 295 struct thread_info *ti; 296 unsigned long *stackend; 297 int node = tsk_fork_get_node(orig); 298 int err; 299 300 tsk = alloc_task_struct_node(node); 301 if (!tsk) 302 return NULL; 303 304 ti = alloc_thread_info_node(tsk, node); 305 if (!ti) 306 goto free_tsk; 307 308 err = arch_dup_task_struct(tsk, orig); 309 if (err) 310 goto free_ti; 311 312 tsk->stack = ti; 313 314 setup_thread_stack(tsk, orig); 315 clear_user_return_notifier(tsk); 316 clear_tsk_need_resched(tsk); 317 stackend = end_of_stack(tsk); 318 *stackend = STACK_END_MAGIC; /* for overflow detection */ 319 320 #ifdef CONFIG_CC_STACKPROTECTOR 321 tsk->stack_canary = get_random_int(); 322 #endif 323 324 /* 325 * One for us, one for whoever does the "release_task()" (usually 326 * parent) 327 */ 328 atomic_set(&tsk->usage, 2); 329 #ifdef CONFIG_BLK_DEV_IO_TRACE 330 tsk->btrace_seq = 0; 331 #endif 332 tsk->splice_pipe = NULL; 333 tsk->task_frag.page = NULL; 334 335 account_kernel_stack(ti, 1); 336 337 return tsk; 338 339 free_ti: 340 free_thread_info(ti); 341 free_tsk: 342 free_task_struct(tsk); 343 return NULL; 344 } 345 346 #ifdef CONFIG_MMU 347 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 348 { 349 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 350 struct rb_node **rb_link, *rb_parent; 351 int retval; 352 unsigned long charge; 353 struct mempolicy *pol; 354 355 down_write(&oldmm->mmap_sem); 356 flush_cache_dup_mm(oldmm); 357 uprobe_dup_mmap(oldmm, mm); 358 /* 359 * Not linked in yet - no deadlock potential: 360 */ 361 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 362 363 mm->locked_vm = 0; 364 mm->mmap = NULL; 365 mm->mmap_cache = NULL; 366 mm->free_area_cache = oldmm->mmap_base; 367 mm->cached_hole_size = ~0UL; 368 mm->map_count = 0; 369 cpumask_clear(mm_cpumask(mm)); 370 mm->mm_rb = RB_ROOT; 371 rb_link = &mm->mm_rb.rb_node; 372 rb_parent = NULL; 373 pprev = &mm->mmap; 374 retval = ksm_fork(mm, oldmm); 375 if (retval) 376 goto out; 377 retval = khugepaged_fork(mm, oldmm); 378 if (retval) 379 goto out; 380 381 prev = NULL; 382 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 383 struct file *file; 384 385 if (mpnt->vm_flags & VM_DONTCOPY) { 386 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 387 -vma_pages(mpnt)); 388 continue; 389 } 390 charge = 0; 391 if (mpnt->vm_flags & VM_ACCOUNT) { 392 unsigned long len = vma_pages(mpnt); 393 394 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 395 goto fail_nomem; 396 charge = len; 397 } 398 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 399 if (!tmp) 400 goto fail_nomem; 401 *tmp = *mpnt; 402 INIT_LIST_HEAD(&tmp->anon_vma_chain); 403 pol = mpol_dup(vma_policy(mpnt)); 404 retval = PTR_ERR(pol); 405 if (IS_ERR(pol)) 406 goto fail_nomem_policy; 407 vma_set_policy(tmp, pol); 408 tmp->vm_mm = mm; 409 if (anon_vma_fork(tmp, mpnt)) 410 goto fail_nomem_anon_vma_fork; 411 tmp->vm_flags &= ~VM_LOCKED; 412 tmp->vm_next = tmp->vm_prev = NULL; 413 file = tmp->vm_file; 414 if (file) { 415 struct inode *inode = file->f_path.dentry->d_inode; 416 struct address_space *mapping = file->f_mapping; 417 418 get_file(file); 419 if (tmp->vm_flags & VM_DENYWRITE) 420 atomic_dec(&inode->i_writecount); 421 mutex_lock(&mapping->i_mmap_mutex); 422 if (tmp->vm_flags & VM_SHARED) 423 mapping->i_mmap_writable++; 424 flush_dcache_mmap_lock(mapping); 425 /* insert tmp into the share list, just after mpnt */ 426 if (unlikely(tmp->vm_flags & VM_NONLINEAR)) 427 vma_nonlinear_insert(tmp, 428 &mapping->i_mmap_nonlinear); 429 else 430 vma_interval_tree_insert_after(tmp, mpnt, 431 &mapping->i_mmap); 432 flush_dcache_mmap_unlock(mapping); 433 mutex_unlock(&mapping->i_mmap_mutex); 434 } 435 436 /* 437 * Clear hugetlb-related page reserves for children. This only 438 * affects MAP_PRIVATE mappings. Faults generated by the child 439 * are not guaranteed to succeed, even if read-only 440 */ 441 if (is_vm_hugetlb_page(tmp)) 442 reset_vma_resv_huge_pages(tmp); 443 444 /* 445 * Link in the new vma and copy the page table entries. 446 */ 447 *pprev = tmp; 448 pprev = &tmp->vm_next; 449 tmp->vm_prev = prev; 450 prev = tmp; 451 452 __vma_link_rb(mm, tmp, rb_link, rb_parent); 453 rb_link = &tmp->vm_rb.rb_right; 454 rb_parent = &tmp->vm_rb; 455 456 mm->map_count++; 457 retval = copy_page_range(mm, oldmm, mpnt); 458 459 if (tmp->vm_ops && tmp->vm_ops->open) 460 tmp->vm_ops->open(tmp); 461 462 if (retval) 463 goto out; 464 } 465 /* a new mm has just been created */ 466 arch_dup_mmap(oldmm, mm); 467 retval = 0; 468 out: 469 up_write(&mm->mmap_sem); 470 flush_tlb_mm(oldmm); 471 up_write(&oldmm->mmap_sem); 472 return retval; 473 fail_nomem_anon_vma_fork: 474 mpol_put(pol); 475 fail_nomem_policy: 476 kmem_cache_free(vm_area_cachep, tmp); 477 fail_nomem: 478 retval = -ENOMEM; 479 vm_unacct_memory(charge); 480 goto out; 481 } 482 483 static inline int mm_alloc_pgd(struct mm_struct *mm) 484 { 485 mm->pgd = pgd_alloc(mm); 486 if (unlikely(!mm->pgd)) 487 return -ENOMEM; 488 return 0; 489 } 490 491 static inline void mm_free_pgd(struct mm_struct *mm) 492 { 493 pgd_free(mm, mm->pgd); 494 } 495 #else 496 #define dup_mmap(mm, oldmm) (0) 497 #define mm_alloc_pgd(mm) (0) 498 #define mm_free_pgd(mm) 499 #endif /* CONFIG_MMU */ 500 501 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 502 503 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 504 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 505 506 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 507 508 static int __init coredump_filter_setup(char *s) 509 { 510 default_dump_filter = 511 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 512 MMF_DUMP_FILTER_MASK; 513 return 1; 514 } 515 516 __setup("coredump_filter=", coredump_filter_setup); 517 518 #include <linux/init_task.h> 519 520 static void mm_init_aio(struct mm_struct *mm) 521 { 522 #ifdef CONFIG_AIO 523 spin_lock_init(&mm->ioctx_lock); 524 INIT_HLIST_HEAD(&mm->ioctx_list); 525 #endif 526 } 527 528 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 529 { 530 atomic_set(&mm->mm_users, 1); 531 atomic_set(&mm->mm_count, 1); 532 init_rwsem(&mm->mmap_sem); 533 INIT_LIST_HEAD(&mm->mmlist); 534 mm->flags = (current->mm) ? 535 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 536 mm->core_state = NULL; 537 mm->nr_ptes = 0; 538 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 539 spin_lock_init(&mm->page_table_lock); 540 mm->free_area_cache = TASK_UNMAPPED_BASE; 541 mm->cached_hole_size = ~0UL; 542 mm_init_aio(mm); 543 mm_init_owner(mm, p); 544 545 if (likely(!mm_alloc_pgd(mm))) { 546 mm->def_flags = 0; 547 mmu_notifier_mm_init(mm); 548 return mm; 549 } 550 551 free_mm(mm); 552 return NULL; 553 } 554 555 static void check_mm(struct mm_struct *mm) 556 { 557 int i; 558 559 for (i = 0; i < NR_MM_COUNTERS; i++) { 560 long x = atomic_long_read(&mm->rss_stat.count[i]); 561 562 if (unlikely(x)) 563 printk(KERN_ALERT "BUG: Bad rss-counter state " 564 "mm:%p idx:%d val:%ld\n", mm, i, x); 565 } 566 567 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 568 VM_BUG_ON(mm->pmd_huge_pte); 569 #endif 570 } 571 572 /* 573 * Allocate and initialize an mm_struct. 574 */ 575 struct mm_struct *mm_alloc(void) 576 { 577 struct mm_struct *mm; 578 579 mm = allocate_mm(); 580 if (!mm) 581 return NULL; 582 583 memset(mm, 0, sizeof(*mm)); 584 mm_init_cpumask(mm); 585 return mm_init(mm, current); 586 } 587 588 /* 589 * Called when the last reference to the mm 590 * is dropped: either by a lazy thread or by 591 * mmput. Free the page directory and the mm. 592 */ 593 void __mmdrop(struct mm_struct *mm) 594 { 595 BUG_ON(mm == &init_mm); 596 mm_free_pgd(mm); 597 destroy_context(mm); 598 mmu_notifier_mm_destroy(mm); 599 check_mm(mm); 600 free_mm(mm); 601 } 602 EXPORT_SYMBOL_GPL(__mmdrop); 603 604 /* 605 * Decrement the use count and release all resources for an mm. 606 */ 607 void mmput(struct mm_struct *mm) 608 { 609 might_sleep(); 610 611 if (atomic_dec_and_test(&mm->mm_users)) { 612 uprobe_clear_state(mm); 613 exit_aio(mm); 614 ksm_exit(mm); 615 khugepaged_exit(mm); /* must run before exit_mmap */ 616 exit_mmap(mm); 617 set_mm_exe_file(mm, NULL); 618 if (!list_empty(&mm->mmlist)) { 619 spin_lock(&mmlist_lock); 620 list_del(&mm->mmlist); 621 spin_unlock(&mmlist_lock); 622 } 623 if (mm->binfmt) 624 module_put(mm->binfmt->module); 625 mmdrop(mm); 626 } 627 } 628 EXPORT_SYMBOL_GPL(mmput); 629 630 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 631 { 632 if (new_exe_file) 633 get_file(new_exe_file); 634 if (mm->exe_file) 635 fput(mm->exe_file); 636 mm->exe_file = new_exe_file; 637 } 638 639 struct file *get_mm_exe_file(struct mm_struct *mm) 640 { 641 struct file *exe_file; 642 643 /* We need mmap_sem to protect against races with removal of exe_file */ 644 down_read(&mm->mmap_sem); 645 exe_file = mm->exe_file; 646 if (exe_file) 647 get_file(exe_file); 648 up_read(&mm->mmap_sem); 649 return exe_file; 650 } 651 652 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 653 { 654 /* It's safe to write the exe_file pointer without exe_file_lock because 655 * this is called during fork when the task is not yet in /proc */ 656 newmm->exe_file = get_mm_exe_file(oldmm); 657 } 658 659 /** 660 * get_task_mm - acquire a reference to the task's mm 661 * 662 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 663 * this kernel workthread has transiently adopted a user mm with use_mm, 664 * to do its AIO) is not set and if so returns a reference to it, after 665 * bumping up the use count. User must release the mm via mmput() 666 * after use. Typically used by /proc and ptrace. 667 */ 668 struct mm_struct *get_task_mm(struct task_struct *task) 669 { 670 struct mm_struct *mm; 671 672 task_lock(task); 673 mm = task->mm; 674 if (mm) { 675 if (task->flags & PF_KTHREAD) 676 mm = NULL; 677 else 678 atomic_inc(&mm->mm_users); 679 } 680 task_unlock(task); 681 return mm; 682 } 683 EXPORT_SYMBOL_GPL(get_task_mm); 684 685 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 686 { 687 struct mm_struct *mm; 688 int err; 689 690 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 691 if (err) 692 return ERR_PTR(err); 693 694 mm = get_task_mm(task); 695 if (mm && mm != current->mm && 696 !ptrace_may_access(task, mode)) { 697 mmput(mm); 698 mm = ERR_PTR(-EACCES); 699 } 700 mutex_unlock(&task->signal->cred_guard_mutex); 701 702 return mm; 703 } 704 705 static void complete_vfork_done(struct task_struct *tsk) 706 { 707 struct completion *vfork; 708 709 task_lock(tsk); 710 vfork = tsk->vfork_done; 711 if (likely(vfork)) { 712 tsk->vfork_done = NULL; 713 complete(vfork); 714 } 715 task_unlock(tsk); 716 } 717 718 static int wait_for_vfork_done(struct task_struct *child, 719 struct completion *vfork) 720 { 721 int killed; 722 723 freezer_do_not_count(); 724 killed = wait_for_completion_killable(vfork); 725 freezer_count(); 726 727 if (killed) { 728 task_lock(child); 729 child->vfork_done = NULL; 730 task_unlock(child); 731 } 732 733 put_task_struct(child); 734 return killed; 735 } 736 737 /* Please note the differences between mmput and mm_release. 738 * mmput is called whenever we stop holding onto a mm_struct, 739 * error success whatever. 740 * 741 * mm_release is called after a mm_struct has been removed 742 * from the current process. 743 * 744 * This difference is important for error handling, when we 745 * only half set up a mm_struct for a new process and need to restore 746 * the old one. Because we mmput the new mm_struct before 747 * restoring the old one. . . 748 * Eric Biederman 10 January 1998 749 */ 750 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 751 { 752 /* Get rid of any futexes when releasing the mm */ 753 #ifdef CONFIG_FUTEX 754 if (unlikely(tsk->robust_list)) { 755 exit_robust_list(tsk); 756 tsk->robust_list = NULL; 757 } 758 #ifdef CONFIG_COMPAT 759 if (unlikely(tsk->compat_robust_list)) { 760 compat_exit_robust_list(tsk); 761 tsk->compat_robust_list = NULL; 762 } 763 #endif 764 if (unlikely(!list_empty(&tsk->pi_state_list))) 765 exit_pi_state_list(tsk); 766 #endif 767 768 uprobe_free_utask(tsk); 769 770 /* Get rid of any cached register state */ 771 deactivate_mm(tsk, mm); 772 773 /* 774 * If we're exiting normally, clear a user-space tid field if 775 * requested. We leave this alone when dying by signal, to leave 776 * the value intact in a core dump, and to save the unnecessary 777 * trouble, say, a killed vfork parent shouldn't touch this mm. 778 * Userland only wants this done for a sys_exit. 779 */ 780 if (tsk->clear_child_tid) { 781 if (!(tsk->flags & PF_SIGNALED) && 782 atomic_read(&mm->mm_users) > 1) { 783 /* 784 * We don't check the error code - if userspace has 785 * not set up a proper pointer then tough luck. 786 */ 787 put_user(0, tsk->clear_child_tid); 788 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 789 1, NULL, NULL, 0); 790 } 791 tsk->clear_child_tid = NULL; 792 } 793 794 /* 795 * All done, finally we can wake up parent and return this mm to him. 796 * Also kthread_stop() uses this completion for synchronization. 797 */ 798 if (tsk->vfork_done) 799 complete_vfork_done(tsk); 800 } 801 802 /* 803 * Allocate a new mm structure and copy contents from the 804 * mm structure of the passed in task structure. 805 */ 806 struct mm_struct *dup_mm(struct task_struct *tsk) 807 { 808 struct mm_struct *mm, *oldmm = current->mm; 809 int err; 810 811 if (!oldmm) 812 return NULL; 813 814 mm = allocate_mm(); 815 if (!mm) 816 goto fail_nomem; 817 818 memcpy(mm, oldmm, sizeof(*mm)); 819 mm_init_cpumask(mm); 820 821 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 822 mm->pmd_huge_pte = NULL; 823 #endif 824 if (!mm_init(mm, tsk)) 825 goto fail_nomem; 826 827 if (init_new_context(tsk, mm)) 828 goto fail_nocontext; 829 830 dup_mm_exe_file(oldmm, mm); 831 832 err = dup_mmap(mm, oldmm); 833 if (err) 834 goto free_pt; 835 836 mm->hiwater_rss = get_mm_rss(mm); 837 mm->hiwater_vm = mm->total_vm; 838 839 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 840 goto free_pt; 841 842 return mm; 843 844 free_pt: 845 /* don't put binfmt in mmput, we haven't got module yet */ 846 mm->binfmt = NULL; 847 mmput(mm); 848 849 fail_nomem: 850 return NULL; 851 852 fail_nocontext: 853 /* 854 * If init_new_context() failed, we cannot use mmput() to free the mm 855 * because it calls destroy_context() 856 */ 857 mm_free_pgd(mm); 858 free_mm(mm); 859 return NULL; 860 } 861 862 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 863 { 864 struct mm_struct *mm, *oldmm; 865 int retval; 866 867 tsk->min_flt = tsk->maj_flt = 0; 868 tsk->nvcsw = tsk->nivcsw = 0; 869 #ifdef CONFIG_DETECT_HUNG_TASK 870 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 871 #endif 872 873 tsk->mm = NULL; 874 tsk->active_mm = NULL; 875 876 /* 877 * Are we cloning a kernel thread? 878 * 879 * We need to steal a active VM for that.. 880 */ 881 oldmm = current->mm; 882 if (!oldmm) 883 return 0; 884 885 if (clone_flags & CLONE_VM) { 886 atomic_inc(&oldmm->mm_users); 887 mm = oldmm; 888 goto good_mm; 889 } 890 891 retval = -ENOMEM; 892 mm = dup_mm(tsk); 893 if (!mm) 894 goto fail_nomem; 895 896 good_mm: 897 tsk->mm = mm; 898 tsk->active_mm = mm; 899 return 0; 900 901 fail_nomem: 902 return retval; 903 } 904 905 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 906 { 907 struct fs_struct *fs = current->fs; 908 if (clone_flags & CLONE_FS) { 909 /* tsk->fs is already what we want */ 910 spin_lock(&fs->lock); 911 if (fs->in_exec) { 912 spin_unlock(&fs->lock); 913 return -EAGAIN; 914 } 915 fs->users++; 916 spin_unlock(&fs->lock); 917 return 0; 918 } 919 tsk->fs = copy_fs_struct(fs); 920 if (!tsk->fs) 921 return -ENOMEM; 922 return 0; 923 } 924 925 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 926 { 927 struct files_struct *oldf, *newf; 928 int error = 0; 929 930 /* 931 * A background process may not have any files ... 932 */ 933 oldf = current->files; 934 if (!oldf) 935 goto out; 936 937 if (clone_flags & CLONE_FILES) { 938 atomic_inc(&oldf->count); 939 goto out; 940 } 941 942 newf = dup_fd(oldf, &error); 943 if (!newf) 944 goto out; 945 946 tsk->files = newf; 947 error = 0; 948 out: 949 return error; 950 } 951 952 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 953 { 954 #ifdef CONFIG_BLOCK 955 struct io_context *ioc = current->io_context; 956 struct io_context *new_ioc; 957 958 if (!ioc) 959 return 0; 960 /* 961 * Share io context with parent, if CLONE_IO is set 962 */ 963 if (clone_flags & CLONE_IO) { 964 ioc_task_link(ioc); 965 tsk->io_context = ioc; 966 } else if (ioprio_valid(ioc->ioprio)) { 967 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 968 if (unlikely(!new_ioc)) 969 return -ENOMEM; 970 971 new_ioc->ioprio = ioc->ioprio; 972 put_io_context(new_ioc); 973 } 974 #endif 975 return 0; 976 } 977 978 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 979 { 980 struct sighand_struct *sig; 981 982 if (clone_flags & CLONE_SIGHAND) { 983 atomic_inc(¤t->sighand->count); 984 return 0; 985 } 986 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 987 rcu_assign_pointer(tsk->sighand, sig); 988 if (!sig) 989 return -ENOMEM; 990 atomic_set(&sig->count, 1); 991 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 992 return 0; 993 } 994 995 void __cleanup_sighand(struct sighand_struct *sighand) 996 { 997 if (atomic_dec_and_test(&sighand->count)) { 998 signalfd_cleanup(sighand); 999 kmem_cache_free(sighand_cachep, sighand); 1000 } 1001 } 1002 1003 1004 /* 1005 * Initialize POSIX timer handling for a thread group. 1006 */ 1007 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1008 { 1009 unsigned long cpu_limit; 1010 1011 /* Thread group counters. */ 1012 thread_group_cputime_init(sig); 1013 1014 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1015 if (cpu_limit != RLIM_INFINITY) { 1016 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1017 sig->cputimer.running = 1; 1018 } 1019 1020 /* The timer lists. */ 1021 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1022 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1023 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1024 } 1025 1026 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1027 { 1028 struct signal_struct *sig; 1029 1030 if (clone_flags & CLONE_THREAD) 1031 return 0; 1032 1033 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1034 tsk->signal = sig; 1035 if (!sig) 1036 return -ENOMEM; 1037 1038 sig->nr_threads = 1; 1039 atomic_set(&sig->live, 1); 1040 atomic_set(&sig->sigcnt, 1); 1041 init_waitqueue_head(&sig->wait_chldexit); 1042 if (clone_flags & CLONE_NEWPID) 1043 sig->flags |= SIGNAL_UNKILLABLE; 1044 sig->curr_target = tsk; 1045 init_sigpending(&sig->shared_pending); 1046 INIT_LIST_HEAD(&sig->posix_timers); 1047 1048 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1049 sig->real_timer.function = it_real_fn; 1050 1051 task_lock(current->group_leader); 1052 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1053 task_unlock(current->group_leader); 1054 1055 posix_cpu_timers_init_group(sig); 1056 1057 tty_audit_fork(sig); 1058 sched_autogroup_fork(sig); 1059 1060 #ifdef CONFIG_CGROUPS 1061 init_rwsem(&sig->group_rwsem); 1062 #endif 1063 1064 sig->oom_score_adj = current->signal->oom_score_adj; 1065 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1066 1067 sig->has_child_subreaper = current->signal->has_child_subreaper || 1068 current->signal->is_child_subreaper; 1069 1070 mutex_init(&sig->cred_guard_mutex); 1071 1072 return 0; 1073 } 1074 1075 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1076 { 1077 unsigned long new_flags = p->flags; 1078 1079 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1080 new_flags |= PF_FORKNOEXEC; 1081 p->flags = new_flags; 1082 } 1083 1084 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1085 { 1086 current->clear_child_tid = tidptr; 1087 1088 return task_pid_vnr(current); 1089 } 1090 1091 static void rt_mutex_init_task(struct task_struct *p) 1092 { 1093 raw_spin_lock_init(&p->pi_lock); 1094 #ifdef CONFIG_RT_MUTEXES 1095 plist_head_init(&p->pi_waiters); 1096 p->pi_blocked_on = NULL; 1097 #endif 1098 } 1099 1100 #ifdef CONFIG_MM_OWNER 1101 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1102 { 1103 mm->owner = p; 1104 } 1105 #endif /* CONFIG_MM_OWNER */ 1106 1107 /* 1108 * Initialize POSIX timer handling for a single task. 1109 */ 1110 static void posix_cpu_timers_init(struct task_struct *tsk) 1111 { 1112 tsk->cputime_expires.prof_exp = 0; 1113 tsk->cputime_expires.virt_exp = 0; 1114 tsk->cputime_expires.sched_exp = 0; 1115 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1116 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1117 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1118 } 1119 1120 /* 1121 * This creates a new process as a copy of the old one, 1122 * but does not actually start it yet. 1123 * 1124 * It copies the registers, and all the appropriate 1125 * parts of the process environment (as per the clone 1126 * flags). The actual kick-off is left to the caller. 1127 */ 1128 static struct task_struct *copy_process(unsigned long clone_flags, 1129 unsigned long stack_start, 1130 unsigned long stack_size, 1131 int __user *child_tidptr, 1132 struct pid *pid, 1133 int trace) 1134 { 1135 int retval; 1136 struct task_struct *p; 1137 int cgroup_callbacks_done = 0; 1138 1139 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1140 return ERR_PTR(-EINVAL); 1141 1142 /* 1143 * Thread groups must share signals as well, and detached threads 1144 * can only be started up within the thread group. 1145 */ 1146 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1147 return ERR_PTR(-EINVAL); 1148 1149 /* 1150 * Shared signal handlers imply shared VM. By way of the above, 1151 * thread groups also imply shared VM. Blocking this case allows 1152 * for various simplifications in other code. 1153 */ 1154 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1155 return ERR_PTR(-EINVAL); 1156 1157 /* 1158 * Siblings of global init remain as zombies on exit since they are 1159 * not reaped by their parent (swapper). To solve this and to avoid 1160 * multi-rooted process trees, prevent global and container-inits 1161 * from creating siblings. 1162 */ 1163 if ((clone_flags & CLONE_PARENT) && 1164 current->signal->flags & SIGNAL_UNKILLABLE) 1165 return ERR_PTR(-EINVAL); 1166 1167 retval = security_task_create(clone_flags); 1168 if (retval) 1169 goto fork_out; 1170 1171 retval = -ENOMEM; 1172 p = dup_task_struct(current); 1173 if (!p) 1174 goto fork_out; 1175 1176 ftrace_graph_init_task(p); 1177 get_seccomp_filter(p); 1178 1179 rt_mutex_init_task(p); 1180 1181 #ifdef CONFIG_PROVE_LOCKING 1182 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1183 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1184 #endif 1185 retval = -EAGAIN; 1186 if (atomic_read(&p->real_cred->user->processes) >= 1187 task_rlimit(p, RLIMIT_NPROC)) { 1188 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1189 p->real_cred->user != INIT_USER) 1190 goto bad_fork_free; 1191 } 1192 current->flags &= ~PF_NPROC_EXCEEDED; 1193 1194 retval = copy_creds(p, clone_flags); 1195 if (retval < 0) 1196 goto bad_fork_free; 1197 1198 /* 1199 * If multiple threads are within copy_process(), then this check 1200 * triggers too late. This doesn't hurt, the check is only there 1201 * to stop root fork bombs. 1202 */ 1203 retval = -EAGAIN; 1204 if (nr_threads >= max_threads) 1205 goto bad_fork_cleanup_count; 1206 1207 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1208 goto bad_fork_cleanup_count; 1209 1210 p->did_exec = 0; 1211 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1212 copy_flags(clone_flags, p); 1213 INIT_LIST_HEAD(&p->children); 1214 INIT_LIST_HEAD(&p->sibling); 1215 rcu_copy_process(p); 1216 p->vfork_done = NULL; 1217 spin_lock_init(&p->alloc_lock); 1218 1219 init_sigpending(&p->pending); 1220 1221 p->utime = p->stime = p->gtime = 0; 1222 p->utimescaled = p->stimescaled = 0; 1223 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1224 p->prev_utime = p->prev_stime = 0; 1225 #endif 1226 #if defined(SPLIT_RSS_COUNTING) 1227 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1228 #endif 1229 1230 p->default_timer_slack_ns = current->timer_slack_ns; 1231 1232 task_io_accounting_init(&p->ioac); 1233 acct_clear_integrals(p); 1234 1235 posix_cpu_timers_init(p); 1236 1237 do_posix_clock_monotonic_gettime(&p->start_time); 1238 p->real_start_time = p->start_time; 1239 monotonic_to_bootbased(&p->real_start_time); 1240 p->io_context = NULL; 1241 p->audit_context = NULL; 1242 if (clone_flags & CLONE_THREAD) 1243 threadgroup_change_begin(current); 1244 cgroup_fork(p); 1245 #ifdef CONFIG_NUMA 1246 p->mempolicy = mpol_dup(p->mempolicy); 1247 if (IS_ERR(p->mempolicy)) { 1248 retval = PTR_ERR(p->mempolicy); 1249 p->mempolicy = NULL; 1250 goto bad_fork_cleanup_cgroup; 1251 } 1252 mpol_fix_fork_child_flag(p); 1253 #endif 1254 #ifdef CONFIG_CPUSETS 1255 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1256 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1257 seqcount_init(&p->mems_allowed_seq); 1258 #endif 1259 #ifdef CONFIG_TRACE_IRQFLAGS 1260 p->irq_events = 0; 1261 p->hardirqs_enabled = 0; 1262 p->hardirq_enable_ip = 0; 1263 p->hardirq_enable_event = 0; 1264 p->hardirq_disable_ip = _THIS_IP_; 1265 p->hardirq_disable_event = 0; 1266 p->softirqs_enabled = 1; 1267 p->softirq_enable_ip = _THIS_IP_; 1268 p->softirq_enable_event = 0; 1269 p->softirq_disable_ip = 0; 1270 p->softirq_disable_event = 0; 1271 p->hardirq_context = 0; 1272 p->softirq_context = 0; 1273 #endif 1274 #ifdef CONFIG_LOCKDEP 1275 p->lockdep_depth = 0; /* no locks held yet */ 1276 p->curr_chain_key = 0; 1277 p->lockdep_recursion = 0; 1278 #endif 1279 1280 #ifdef CONFIG_DEBUG_MUTEXES 1281 p->blocked_on = NULL; /* not blocked yet */ 1282 #endif 1283 #ifdef CONFIG_MEMCG 1284 p->memcg_batch.do_batch = 0; 1285 p->memcg_batch.memcg = NULL; 1286 #endif 1287 1288 /* Perform scheduler related setup. Assign this task to a CPU. */ 1289 sched_fork(p); 1290 1291 retval = perf_event_init_task(p); 1292 if (retval) 1293 goto bad_fork_cleanup_policy; 1294 retval = audit_alloc(p); 1295 if (retval) 1296 goto bad_fork_cleanup_policy; 1297 /* copy all the process information */ 1298 retval = copy_semundo(clone_flags, p); 1299 if (retval) 1300 goto bad_fork_cleanup_audit; 1301 retval = copy_files(clone_flags, p); 1302 if (retval) 1303 goto bad_fork_cleanup_semundo; 1304 retval = copy_fs(clone_flags, p); 1305 if (retval) 1306 goto bad_fork_cleanup_files; 1307 retval = copy_sighand(clone_flags, p); 1308 if (retval) 1309 goto bad_fork_cleanup_fs; 1310 retval = copy_signal(clone_flags, p); 1311 if (retval) 1312 goto bad_fork_cleanup_sighand; 1313 retval = copy_mm(clone_flags, p); 1314 if (retval) 1315 goto bad_fork_cleanup_signal; 1316 retval = copy_namespaces(clone_flags, p); 1317 if (retval) 1318 goto bad_fork_cleanup_mm; 1319 retval = copy_io(clone_flags, p); 1320 if (retval) 1321 goto bad_fork_cleanup_namespaces; 1322 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1323 if (retval) 1324 goto bad_fork_cleanup_io; 1325 1326 if (pid != &init_struct_pid) { 1327 retval = -ENOMEM; 1328 pid = alloc_pid(p->nsproxy->pid_ns); 1329 if (!pid) 1330 goto bad_fork_cleanup_io; 1331 } 1332 1333 p->pid = pid_nr(pid); 1334 p->tgid = p->pid; 1335 if (clone_flags & CLONE_THREAD) 1336 p->tgid = current->tgid; 1337 1338 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1339 /* 1340 * Clear TID on mm_release()? 1341 */ 1342 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1343 #ifdef CONFIG_BLOCK 1344 p->plug = NULL; 1345 #endif 1346 #ifdef CONFIG_FUTEX 1347 p->robust_list = NULL; 1348 #ifdef CONFIG_COMPAT 1349 p->compat_robust_list = NULL; 1350 #endif 1351 INIT_LIST_HEAD(&p->pi_state_list); 1352 p->pi_state_cache = NULL; 1353 #endif 1354 uprobe_copy_process(p); 1355 /* 1356 * sigaltstack should be cleared when sharing the same VM 1357 */ 1358 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1359 p->sas_ss_sp = p->sas_ss_size = 0; 1360 1361 /* 1362 * Syscall tracing and stepping should be turned off in the 1363 * child regardless of CLONE_PTRACE. 1364 */ 1365 user_disable_single_step(p); 1366 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1367 #ifdef TIF_SYSCALL_EMU 1368 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1369 #endif 1370 clear_all_latency_tracing(p); 1371 1372 /* ok, now we should be set up.. */ 1373 if (clone_flags & CLONE_THREAD) 1374 p->exit_signal = -1; 1375 else if (clone_flags & CLONE_PARENT) 1376 p->exit_signal = current->group_leader->exit_signal; 1377 else 1378 p->exit_signal = (clone_flags & CSIGNAL); 1379 1380 p->pdeath_signal = 0; 1381 p->exit_state = 0; 1382 1383 p->nr_dirtied = 0; 1384 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1385 p->dirty_paused_when = 0; 1386 1387 /* 1388 * Ok, make it visible to the rest of the system. 1389 * We dont wake it up yet. 1390 */ 1391 p->group_leader = p; 1392 INIT_LIST_HEAD(&p->thread_group); 1393 p->task_works = NULL; 1394 1395 /* Now that the task is set up, run cgroup callbacks if 1396 * necessary. We need to run them before the task is visible 1397 * on the tasklist. */ 1398 cgroup_fork_callbacks(p); 1399 cgroup_callbacks_done = 1; 1400 1401 /* Need tasklist lock for parent etc handling! */ 1402 write_lock_irq(&tasklist_lock); 1403 1404 /* CLONE_PARENT re-uses the old parent */ 1405 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1406 p->real_parent = current->real_parent; 1407 p->parent_exec_id = current->parent_exec_id; 1408 } else { 1409 p->real_parent = current; 1410 p->parent_exec_id = current->self_exec_id; 1411 } 1412 1413 spin_lock(¤t->sighand->siglock); 1414 1415 /* 1416 * Process group and session signals need to be delivered to just the 1417 * parent before the fork or both the parent and the child after the 1418 * fork. Restart if a signal comes in before we add the new process to 1419 * it's process group. 1420 * A fatal signal pending means that current will exit, so the new 1421 * thread can't slip out of an OOM kill (or normal SIGKILL). 1422 */ 1423 recalc_sigpending(); 1424 if (signal_pending(current)) { 1425 spin_unlock(¤t->sighand->siglock); 1426 write_unlock_irq(&tasklist_lock); 1427 retval = -ERESTARTNOINTR; 1428 goto bad_fork_free_pid; 1429 } 1430 1431 if (clone_flags & CLONE_THREAD) { 1432 current->signal->nr_threads++; 1433 atomic_inc(¤t->signal->live); 1434 atomic_inc(¤t->signal->sigcnt); 1435 p->group_leader = current->group_leader; 1436 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1437 } 1438 1439 if (likely(p->pid)) { 1440 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1441 1442 if (thread_group_leader(p)) { 1443 if (is_child_reaper(pid)) 1444 p->nsproxy->pid_ns->child_reaper = p; 1445 1446 p->signal->leader_pid = pid; 1447 p->signal->tty = tty_kref_get(current->signal->tty); 1448 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1449 attach_pid(p, PIDTYPE_SID, task_session(current)); 1450 list_add_tail(&p->sibling, &p->real_parent->children); 1451 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1452 __this_cpu_inc(process_counts); 1453 } 1454 attach_pid(p, PIDTYPE_PID, pid); 1455 nr_threads++; 1456 } 1457 1458 total_forks++; 1459 spin_unlock(¤t->sighand->siglock); 1460 write_unlock_irq(&tasklist_lock); 1461 proc_fork_connector(p); 1462 cgroup_post_fork(p); 1463 if (clone_flags & CLONE_THREAD) 1464 threadgroup_change_end(current); 1465 perf_event_fork(p); 1466 1467 trace_task_newtask(p, clone_flags); 1468 1469 return p; 1470 1471 bad_fork_free_pid: 1472 if (pid != &init_struct_pid) 1473 free_pid(pid); 1474 bad_fork_cleanup_io: 1475 if (p->io_context) 1476 exit_io_context(p); 1477 bad_fork_cleanup_namespaces: 1478 if (unlikely(clone_flags & CLONE_NEWPID)) 1479 pid_ns_release_proc(p->nsproxy->pid_ns); 1480 exit_task_namespaces(p); 1481 bad_fork_cleanup_mm: 1482 if (p->mm) 1483 mmput(p->mm); 1484 bad_fork_cleanup_signal: 1485 if (!(clone_flags & CLONE_THREAD)) 1486 free_signal_struct(p->signal); 1487 bad_fork_cleanup_sighand: 1488 __cleanup_sighand(p->sighand); 1489 bad_fork_cleanup_fs: 1490 exit_fs(p); /* blocking */ 1491 bad_fork_cleanup_files: 1492 exit_files(p); /* blocking */ 1493 bad_fork_cleanup_semundo: 1494 exit_sem(p); 1495 bad_fork_cleanup_audit: 1496 audit_free(p); 1497 bad_fork_cleanup_policy: 1498 perf_event_free_task(p); 1499 #ifdef CONFIG_NUMA 1500 mpol_put(p->mempolicy); 1501 bad_fork_cleanup_cgroup: 1502 #endif 1503 if (clone_flags & CLONE_THREAD) 1504 threadgroup_change_end(current); 1505 cgroup_exit(p, cgroup_callbacks_done); 1506 delayacct_tsk_free(p); 1507 module_put(task_thread_info(p)->exec_domain->module); 1508 bad_fork_cleanup_count: 1509 atomic_dec(&p->cred->user->processes); 1510 exit_creds(p); 1511 bad_fork_free: 1512 free_task(p); 1513 fork_out: 1514 return ERR_PTR(retval); 1515 } 1516 1517 static inline void init_idle_pids(struct pid_link *links) 1518 { 1519 enum pid_type type; 1520 1521 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1522 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1523 links[type].pid = &init_struct_pid; 1524 } 1525 } 1526 1527 struct task_struct * __cpuinit fork_idle(int cpu) 1528 { 1529 struct task_struct *task; 1530 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1531 if (!IS_ERR(task)) { 1532 init_idle_pids(task->pids); 1533 init_idle(task, cpu); 1534 } 1535 1536 return task; 1537 } 1538 1539 /* 1540 * Ok, this is the main fork-routine. 1541 * 1542 * It copies the process, and if successful kick-starts 1543 * it and waits for it to finish using the VM if required. 1544 */ 1545 long do_fork(unsigned long clone_flags, 1546 unsigned long stack_start, 1547 unsigned long stack_size, 1548 int __user *parent_tidptr, 1549 int __user *child_tidptr) 1550 { 1551 struct task_struct *p; 1552 int trace = 0; 1553 long nr; 1554 1555 /* 1556 * Do some preliminary argument and permissions checking before we 1557 * actually start allocating stuff 1558 */ 1559 if (clone_flags & CLONE_NEWUSER) { 1560 if (clone_flags & CLONE_THREAD) 1561 return -EINVAL; 1562 /* hopefully this check will go away when userns support is 1563 * complete 1564 */ 1565 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1566 !capable(CAP_SETGID)) 1567 return -EPERM; 1568 } 1569 1570 /* 1571 * Determine whether and which event to report to ptracer. When 1572 * called from kernel_thread or CLONE_UNTRACED is explicitly 1573 * requested, no event is reported; otherwise, report if the event 1574 * for the type of forking is enabled. 1575 */ 1576 if (!(clone_flags & CLONE_UNTRACED)) { 1577 if (clone_flags & CLONE_VFORK) 1578 trace = PTRACE_EVENT_VFORK; 1579 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1580 trace = PTRACE_EVENT_CLONE; 1581 else 1582 trace = PTRACE_EVENT_FORK; 1583 1584 if (likely(!ptrace_event_enabled(current, trace))) 1585 trace = 0; 1586 } 1587 1588 p = copy_process(clone_flags, stack_start, stack_size, 1589 child_tidptr, NULL, trace); 1590 /* 1591 * Do this prior waking up the new thread - the thread pointer 1592 * might get invalid after that point, if the thread exits quickly. 1593 */ 1594 if (!IS_ERR(p)) { 1595 struct completion vfork; 1596 1597 trace_sched_process_fork(current, p); 1598 1599 nr = task_pid_vnr(p); 1600 1601 if (clone_flags & CLONE_PARENT_SETTID) 1602 put_user(nr, parent_tidptr); 1603 1604 if (clone_flags & CLONE_VFORK) { 1605 p->vfork_done = &vfork; 1606 init_completion(&vfork); 1607 get_task_struct(p); 1608 } 1609 1610 wake_up_new_task(p); 1611 1612 /* forking complete and child started to run, tell ptracer */ 1613 if (unlikely(trace)) 1614 ptrace_event(trace, nr); 1615 1616 if (clone_flags & CLONE_VFORK) { 1617 if (!wait_for_vfork_done(p, &vfork)) 1618 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1619 } 1620 } else { 1621 nr = PTR_ERR(p); 1622 } 1623 return nr; 1624 } 1625 1626 /* 1627 * Create a kernel thread. 1628 */ 1629 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1630 { 1631 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1632 (unsigned long)arg, NULL, NULL); 1633 } 1634 1635 #ifdef __ARCH_WANT_SYS_FORK 1636 SYSCALL_DEFINE0(fork) 1637 { 1638 #ifdef CONFIG_MMU 1639 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1640 #else 1641 /* can not support in nommu mode */ 1642 return(-EINVAL); 1643 #endif 1644 } 1645 #endif 1646 1647 #ifdef __ARCH_WANT_SYS_VFORK 1648 SYSCALL_DEFINE0(vfork) 1649 { 1650 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1651 0, NULL, NULL); 1652 } 1653 #endif 1654 1655 #ifdef __ARCH_WANT_SYS_CLONE 1656 #ifdef CONFIG_CLONE_BACKWARDS 1657 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1658 int __user *, parent_tidptr, 1659 int, tls_val, 1660 int __user *, child_tidptr) 1661 #elif defined(CONFIG_CLONE_BACKWARDS2) 1662 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1663 int __user *, parent_tidptr, 1664 int __user *, child_tidptr, 1665 int, tls_val) 1666 #else 1667 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1668 int __user *, parent_tidptr, 1669 int __user *, child_tidptr, 1670 int, tls_val) 1671 #endif 1672 { 1673 return do_fork(clone_flags, newsp, 0, 1674 parent_tidptr, child_tidptr); 1675 } 1676 #endif 1677 1678 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1679 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1680 #endif 1681 1682 static void sighand_ctor(void *data) 1683 { 1684 struct sighand_struct *sighand = data; 1685 1686 spin_lock_init(&sighand->siglock); 1687 init_waitqueue_head(&sighand->signalfd_wqh); 1688 } 1689 1690 void __init proc_caches_init(void) 1691 { 1692 sighand_cachep = kmem_cache_create("sighand_cache", 1693 sizeof(struct sighand_struct), 0, 1694 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1695 SLAB_NOTRACK, sighand_ctor); 1696 signal_cachep = kmem_cache_create("signal_cache", 1697 sizeof(struct signal_struct), 0, 1698 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1699 files_cachep = kmem_cache_create("files_cache", 1700 sizeof(struct files_struct), 0, 1701 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1702 fs_cachep = kmem_cache_create("fs_cache", 1703 sizeof(struct fs_struct), 0, 1704 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1705 /* 1706 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1707 * whole struct cpumask for the OFFSTACK case. We could change 1708 * this to *only* allocate as much of it as required by the 1709 * maximum number of CPU's we can ever have. The cpumask_allocation 1710 * is at the end of the structure, exactly for that reason. 1711 */ 1712 mm_cachep = kmem_cache_create("mm_struct", 1713 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1714 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1715 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1716 mmap_init(); 1717 nsproxy_cache_init(); 1718 } 1719 1720 /* 1721 * Check constraints on flags passed to the unshare system call. 1722 */ 1723 static int check_unshare_flags(unsigned long unshare_flags) 1724 { 1725 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1726 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1727 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1728 return -EINVAL; 1729 /* 1730 * Not implemented, but pretend it works if there is nothing to 1731 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1732 * needs to unshare vm. 1733 */ 1734 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1735 /* FIXME: get_task_mm() increments ->mm_users */ 1736 if (atomic_read(¤t->mm->mm_users) > 1) 1737 return -EINVAL; 1738 } 1739 1740 return 0; 1741 } 1742 1743 /* 1744 * Unshare the filesystem structure if it is being shared 1745 */ 1746 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1747 { 1748 struct fs_struct *fs = current->fs; 1749 1750 if (!(unshare_flags & CLONE_FS) || !fs) 1751 return 0; 1752 1753 /* don't need lock here; in the worst case we'll do useless copy */ 1754 if (fs->users == 1) 1755 return 0; 1756 1757 *new_fsp = copy_fs_struct(fs); 1758 if (!*new_fsp) 1759 return -ENOMEM; 1760 1761 return 0; 1762 } 1763 1764 /* 1765 * Unshare file descriptor table if it is being shared 1766 */ 1767 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1768 { 1769 struct files_struct *fd = current->files; 1770 int error = 0; 1771 1772 if ((unshare_flags & CLONE_FILES) && 1773 (fd && atomic_read(&fd->count) > 1)) { 1774 *new_fdp = dup_fd(fd, &error); 1775 if (!*new_fdp) 1776 return error; 1777 } 1778 1779 return 0; 1780 } 1781 1782 /* 1783 * unshare allows a process to 'unshare' part of the process 1784 * context which was originally shared using clone. copy_* 1785 * functions used by do_fork() cannot be used here directly 1786 * because they modify an inactive task_struct that is being 1787 * constructed. Here we are modifying the current, active, 1788 * task_struct. 1789 */ 1790 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1791 { 1792 struct fs_struct *fs, *new_fs = NULL; 1793 struct files_struct *fd, *new_fd = NULL; 1794 struct nsproxy *new_nsproxy = NULL; 1795 int do_sysvsem = 0; 1796 int err; 1797 1798 err = check_unshare_flags(unshare_flags); 1799 if (err) 1800 goto bad_unshare_out; 1801 1802 /* 1803 * If unsharing namespace, must also unshare filesystem information. 1804 */ 1805 if (unshare_flags & CLONE_NEWNS) 1806 unshare_flags |= CLONE_FS; 1807 /* 1808 * CLONE_NEWIPC must also detach from the undolist: after switching 1809 * to a new ipc namespace, the semaphore arrays from the old 1810 * namespace are unreachable. 1811 */ 1812 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1813 do_sysvsem = 1; 1814 err = unshare_fs(unshare_flags, &new_fs); 1815 if (err) 1816 goto bad_unshare_out; 1817 err = unshare_fd(unshare_flags, &new_fd); 1818 if (err) 1819 goto bad_unshare_cleanup_fs; 1820 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1821 if (err) 1822 goto bad_unshare_cleanup_fd; 1823 1824 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1825 if (do_sysvsem) { 1826 /* 1827 * CLONE_SYSVSEM is equivalent to sys_exit(). 1828 */ 1829 exit_sem(current); 1830 } 1831 1832 if (new_nsproxy) { 1833 switch_task_namespaces(current, new_nsproxy); 1834 new_nsproxy = NULL; 1835 } 1836 1837 task_lock(current); 1838 1839 if (new_fs) { 1840 fs = current->fs; 1841 spin_lock(&fs->lock); 1842 current->fs = new_fs; 1843 if (--fs->users) 1844 new_fs = NULL; 1845 else 1846 new_fs = fs; 1847 spin_unlock(&fs->lock); 1848 } 1849 1850 if (new_fd) { 1851 fd = current->files; 1852 current->files = new_fd; 1853 new_fd = fd; 1854 } 1855 1856 task_unlock(current); 1857 } 1858 1859 if (new_nsproxy) 1860 put_nsproxy(new_nsproxy); 1861 1862 bad_unshare_cleanup_fd: 1863 if (new_fd) 1864 put_files_struct(new_fd); 1865 1866 bad_unshare_cleanup_fs: 1867 if (new_fs) 1868 free_fs_struct(new_fs); 1869 1870 bad_unshare_out: 1871 return err; 1872 } 1873 1874 /* 1875 * Helper to unshare the files of the current task. 1876 * We don't want to expose copy_files internals to 1877 * the exec layer of the kernel. 1878 */ 1879 1880 int unshare_files(struct files_struct **displaced) 1881 { 1882 struct task_struct *task = current; 1883 struct files_struct *copy = NULL; 1884 int error; 1885 1886 error = unshare_fd(CLONE_FILES, ©); 1887 if (error || !copy) { 1888 *displaced = NULL; 1889 return error; 1890 } 1891 *displaced = task->files; 1892 task_lock(task); 1893 task->files = copy; 1894 task_unlock(task); 1895 return 0; 1896 } 1897