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