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 #include <linux/aio.h> 74 75 #include <asm/pgtable.h> 76 #include <asm/pgalloc.h> 77 #include <asm/uaccess.h> 78 #include <asm/mmu_context.h> 79 #include <asm/cacheflush.h> 80 #include <asm/tlbflush.h> 81 82 #include <trace/events/sched.h> 83 84 #define CREATE_TRACE_POINTS 85 #include <trace/events/task.h> 86 87 /* 88 * Protected counters by write_lock_irq(&tasklist_lock) 89 */ 90 unsigned long total_forks; /* Handle normal Linux uptimes. */ 91 int nr_threads; /* The idle threads do not count.. */ 92 93 int max_threads; /* tunable limit on nr_threads */ 94 95 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 96 97 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 98 99 #ifdef CONFIG_PROVE_RCU 100 int lockdep_tasklist_lock_is_held(void) 101 { 102 return lockdep_is_held(&tasklist_lock); 103 } 104 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 105 #endif /* #ifdef CONFIG_PROVE_RCU */ 106 107 int nr_processes(void) 108 { 109 int cpu; 110 int total = 0; 111 112 for_each_possible_cpu(cpu) 113 total += per_cpu(process_counts, cpu); 114 115 return total; 116 } 117 118 void __weak arch_release_task_struct(struct task_struct *tsk) 119 { 120 } 121 122 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 123 static struct kmem_cache *task_struct_cachep; 124 125 static inline struct task_struct *alloc_task_struct_node(int node) 126 { 127 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 128 } 129 130 static inline void free_task_struct(struct task_struct *tsk) 131 { 132 kmem_cache_free(task_struct_cachep, tsk); 133 } 134 #endif 135 136 void __weak arch_release_thread_info(struct thread_info *ti) 137 { 138 } 139 140 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 141 142 /* 143 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 144 * kmemcache based allocator. 145 */ 146 # if THREAD_SIZE >= PAGE_SIZE 147 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 148 int node) 149 { 150 struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED, 151 THREAD_SIZE_ORDER); 152 153 return page ? page_address(page) : NULL; 154 } 155 156 static inline void free_thread_info(struct thread_info *ti) 157 { 158 free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); 159 } 160 # else 161 static struct kmem_cache *thread_info_cache; 162 163 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 164 int node) 165 { 166 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 167 } 168 169 static void free_thread_info(struct thread_info *ti) 170 { 171 kmem_cache_free(thread_info_cache, ti); 172 } 173 174 void thread_info_cache_init(void) 175 { 176 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 177 THREAD_SIZE, 0, NULL); 178 BUG_ON(thread_info_cache == NULL); 179 } 180 # endif 181 #endif 182 183 /* SLAB cache for signal_struct structures (tsk->signal) */ 184 static struct kmem_cache *signal_cachep; 185 186 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 187 struct kmem_cache *sighand_cachep; 188 189 /* SLAB cache for files_struct structures (tsk->files) */ 190 struct kmem_cache *files_cachep; 191 192 /* SLAB cache for fs_struct structures (tsk->fs) */ 193 struct kmem_cache *fs_cachep; 194 195 /* SLAB cache for vm_area_struct structures */ 196 struct kmem_cache *vm_area_cachep; 197 198 /* SLAB cache for mm_struct structures (tsk->mm) */ 199 static struct kmem_cache *mm_cachep; 200 201 static void account_kernel_stack(struct thread_info *ti, int account) 202 { 203 struct zone *zone = page_zone(virt_to_page(ti)); 204 205 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 206 } 207 208 void free_task(struct task_struct *tsk) 209 { 210 account_kernel_stack(tsk->stack, -1); 211 arch_release_thread_info(tsk->stack); 212 free_thread_info(tsk->stack); 213 rt_mutex_debug_task_free(tsk); 214 ftrace_graph_exit_task(tsk); 215 put_seccomp_filter(tsk); 216 arch_release_task_struct(tsk); 217 free_task_struct(tsk); 218 } 219 EXPORT_SYMBOL(free_task); 220 221 static inline void free_signal_struct(struct signal_struct *sig) 222 { 223 taskstats_tgid_free(sig); 224 sched_autogroup_exit(sig); 225 kmem_cache_free(signal_cachep, sig); 226 } 227 228 static inline void put_signal_struct(struct signal_struct *sig) 229 { 230 if (atomic_dec_and_test(&sig->sigcnt)) 231 free_signal_struct(sig); 232 } 233 234 void __put_task_struct(struct task_struct *tsk) 235 { 236 WARN_ON(!tsk->exit_state); 237 WARN_ON(atomic_read(&tsk->usage)); 238 WARN_ON(tsk == current); 239 240 security_task_free(tsk); 241 exit_creds(tsk); 242 delayacct_tsk_free(tsk); 243 put_signal_struct(tsk->signal); 244 245 if (!profile_handoff_task(tsk)) 246 free_task(tsk); 247 } 248 EXPORT_SYMBOL_GPL(__put_task_struct); 249 250 void __init __weak arch_task_cache_init(void) { } 251 252 void __init fork_init(unsigned long mempages) 253 { 254 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 255 #ifndef ARCH_MIN_TASKALIGN 256 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 257 #endif 258 /* create a slab on which task_structs can be allocated */ 259 task_struct_cachep = 260 kmem_cache_create("task_struct", sizeof(struct task_struct), 261 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 262 #endif 263 264 /* do the arch specific task caches init */ 265 arch_task_cache_init(); 266 267 /* 268 * The default maximum number of threads is set to a safe 269 * value: the thread structures can take up at most half 270 * of memory. 271 */ 272 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 273 274 /* 275 * we need to allow at least 20 threads to boot a system 276 */ 277 if (max_threads < 20) 278 max_threads = 20; 279 280 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 281 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 282 init_task.signal->rlim[RLIMIT_SIGPENDING] = 283 init_task.signal->rlim[RLIMIT_NPROC]; 284 } 285 286 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 287 struct task_struct *src) 288 { 289 *dst = *src; 290 return 0; 291 } 292 293 static struct task_struct *dup_task_struct(struct task_struct *orig) 294 { 295 struct task_struct *tsk; 296 struct thread_info *ti; 297 unsigned long *stackend; 298 int node = tsk_fork_get_node(orig); 299 int err; 300 301 tsk = alloc_task_struct_node(node); 302 if (!tsk) 303 return NULL; 304 305 ti = alloc_thread_info_node(tsk, node); 306 if (!ti) 307 goto free_tsk; 308 309 err = arch_dup_task_struct(tsk, orig); 310 if (err) 311 goto free_ti; 312 313 tsk->stack = ti; 314 315 setup_thread_stack(tsk, orig); 316 clear_user_return_notifier(tsk); 317 clear_tsk_need_resched(tsk); 318 stackend = end_of_stack(tsk); 319 *stackend = STACK_END_MAGIC; /* for overflow detection */ 320 321 #ifdef CONFIG_CC_STACKPROTECTOR 322 tsk->stack_canary = get_random_int(); 323 #endif 324 325 /* 326 * One for us, one for whoever does the "release_task()" (usually 327 * parent) 328 */ 329 atomic_set(&tsk->usage, 2); 330 #ifdef CONFIG_BLK_DEV_IO_TRACE 331 tsk->btrace_seq = 0; 332 #endif 333 tsk->splice_pipe = NULL; 334 tsk->task_frag.page = NULL; 335 336 account_kernel_stack(ti, 1); 337 338 return tsk; 339 340 free_ti: 341 free_thread_info(ti); 342 free_tsk: 343 free_task_struct(tsk); 344 return NULL; 345 } 346 347 #ifdef CONFIG_MMU 348 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 349 { 350 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 351 struct rb_node **rb_link, *rb_parent; 352 int retval; 353 unsigned long charge; 354 355 uprobe_start_dup_mmap(); 356 down_write(&oldmm->mmap_sem); 357 flush_cache_dup_mm(oldmm); 358 uprobe_dup_mmap(oldmm, mm); 359 /* 360 * Not linked in yet - no deadlock potential: 361 */ 362 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 363 364 mm->locked_vm = 0; 365 mm->mmap = NULL; 366 mm->mmap_cache = NULL; 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 retval = vma_dup_policy(mpnt, tmp); 403 if (retval) 404 goto fail_nomem_policy; 405 tmp->vm_mm = mm; 406 if (anon_vma_fork(tmp, mpnt)) 407 goto fail_nomem_anon_vma_fork; 408 tmp->vm_flags &= ~VM_LOCKED; 409 tmp->vm_next = tmp->vm_prev = NULL; 410 file = tmp->vm_file; 411 if (file) { 412 struct inode *inode = file_inode(file); 413 struct address_space *mapping = file->f_mapping; 414 415 get_file(file); 416 if (tmp->vm_flags & VM_DENYWRITE) 417 atomic_dec(&inode->i_writecount); 418 mutex_lock(&mapping->i_mmap_mutex); 419 if (tmp->vm_flags & VM_SHARED) 420 mapping->i_mmap_writable++; 421 flush_dcache_mmap_lock(mapping); 422 /* insert tmp into the share list, just after mpnt */ 423 if (unlikely(tmp->vm_flags & VM_NONLINEAR)) 424 vma_nonlinear_insert(tmp, 425 &mapping->i_mmap_nonlinear); 426 else 427 vma_interval_tree_insert_after(tmp, mpnt, 428 &mapping->i_mmap); 429 flush_dcache_mmap_unlock(mapping); 430 mutex_unlock(&mapping->i_mmap_mutex); 431 } 432 433 /* 434 * Clear hugetlb-related page reserves for children. This only 435 * affects MAP_PRIVATE mappings. Faults generated by the child 436 * are not guaranteed to succeed, even if read-only 437 */ 438 if (is_vm_hugetlb_page(tmp)) 439 reset_vma_resv_huge_pages(tmp); 440 441 /* 442 * Link in the new vma and copy the page table entries. 443 */ 444 *pprev = tmp; 445 pprev = &tmp->vm_next; 446 tmp->vm_prev = prev; 447 prev = tmp; 448 449 __vma_link_rb(mm, tmp, rb_link, rb_parent); 450 rb_link = &tmp->vm_rb.rb_right; 451 rb_parent = &tmp->vm_rb; 452 453 mm->map_count++; 454 retval = copy_page_range(mm, oldmm, mpnt); 455 456 if (tmp->vm_ops && tmp->vm_ops->open) 457 tmp->vm_ops->open(tmp); 458 459 if (retval) 460 goto out; 461 } 462 /* a new mm has just been created */ 463 arch_dup_mmap(oldmm, mm); 464 retval = 0; 465 out: 466 up_write(&mm->mmap_sem); 467 flush_tlb_mm(oldmm); 468 up_write(&oldmm->mmap_sem); 469 uprobe_end_dup_mmap(); 470 return retval; 471 fail_nomem_anon_vma_fork: 472 mpol_put(vma_policy(tmp)); 473 fail_nomem_policy: 474 kmem_cache_free(vm_area_cachep, tmp); 475 fail_nomem: 476 retval = -ENOMEM; 477 vm_unacct_memory(charge); 478 goto out; 479 } 480 481 static inline int mm_alloc_pgd(struct mm_struct *mm) 482 { 483 mm->pgd = pgd_alloc(mm); 484 if (unlikely(!mm->pgd)) 485 return -ENOMEM; 486 return 0; 487 } 488 489 static inline void mm_free_pgd(struct mm_struct *mm) 490 { 491 pgd_free(mm, mm->pgd); 492 } 493 #else 494 #define dup_mmap(mm, oldmm) (0) 495 #define mm_alloc_pgd(mm) (0) 496 #define mm_free_pgd(mm) 497 #endif /* CONFIG_MMU */ 498 499 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 500 501 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 502 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 503 504 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 505 506 static int __init coredump_filter_setup(char *s) 507 { 508 default_dump_filter = 509 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 510 MMF_DUMP_FILTER_MASK; 511 return 1; 512 } 513 514 __setup("coredump_filter=", coredump_filter_setup); 515 516 #include <linux/init_task.h> 517 518 static void mm_init_aio(struct mm_struct *mm) 519 { 520 #ifdef CONFIG_AIO 521 spin_lock_init(&mm->ioctx_lock); 522 mm->ioctx_table = NULL; 523 #endif 524 } 525 526 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 527 { 528 atomic_set(&mm->mm_users, 1); 529 atomic_set(&mm->mm_count, 1); 530 init_rwsem(&mm->mmap_sem); 531 INIT_LIST_HEAD(&mm->mmlist); 532 mm->flags = (current->mm) ? 533 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 534 mm->core_state = NULL; 535 atomic_long_set(&mm->nr_ptes, 0); 536 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 537 spin_lock_init(&mm->page_table_lock); 538 mm_init_aio(mm); 539 mm_init_owner(mm, p); 540 clear_tlb_flush_pending(mm); 541 542 if (likely(!mm_alloc_pgd(mm))) { 543 mm->def_flags = 0; 544 mmu_notifier_mm_init(mm); 545 return mm; 546 } 547 548 free_mm(mm); 549 return NULL; 550 } 551 552 static void check_mm(struct mm_struct *mm) 553 { 554 int i; 555 556 for (i = 0; i < NR_MM_COUNTERS; i++) { 557 long x = atomic_long_read(&mm->rss_stat.count[i]); 558 559 if (unlikely(x)) 560 printk(KERN_ALERT "BUG: Bad rss-counter state " 561 "mm:%p idx:%d val:%ld\n", mm, i, x); 562 } 563 564 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 565 VM_BUG_ON(mm->pmd_huge_pte); 566 #endif 567 } 568 569 /* 570 * Allocate and initialize an mm_struct. 571 */ 572 struct mm_struct *mm_alloc(void) 573 { 574 struct mm_struct *mm; 575 576 mm = allocate_mm(); 577 if (!mm) 578 return NULL; 579 580 memset(mm, 0, sizeof(*mm)); 581 mm_init_cpumask(mm); 582 return mm_init(mm, current); 583 } 584 585 /* 586 * Called when the last reference to the mm 587 * is dropped: either by a lazy thread or by 588 * mmput. Free the page directory and the mm. 589 */ 590 void __mmdrop(struct mm_struct *mm) 591 { 592 BUG_ON(mm == &init_mm); 593 mm_free_pgd(mm); 594 destroy_context(mm); 595 mmu_notifier_mm_destroy(mm); 596 check_mm(mm); 597 free_mm(mm); 598 } 599 EXPORT_SYMBOL_GPL(__mmdrop); 600 601 /* 602 * Decrement the use count and release all resources for an mm. 603 */ 604 void mmput(struct mm_struct *mm) 605 { 606 might_sleep(); 607 608 if (atomic_dec_and_test(&mm->mm_users)) { 609 uprobe_clear_state(mm); 610 exit_aio(mm); 611 ksm_exit(mm); 612 khugepaged_exit(mm); /* must run before exit_mmap */ 613 exit_mmap(mm); 614 set_mm_exe_file(mm, NULL); 615 if (!list_empty(&mm->mmlist)) { 616 spin_lock(&mmlist_lock); 617 list_del(&mm->mmlist); 618 spin_unlock(&mmlist_lock); 619 } 620 if (mm->binfmt) 621 module_put(mm->binfmt->module); 622 mmdrop(mm); 623 } 624 } 625 EXPORT_SYMBOL_GPL(mmput); 626 627 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 628 { 629 if (new_exe_file) 630 get_file(new_exe_file); 631 if (mm->exe_file) 632 fput(mm->exe_file); 633 mm->exe_file = new_exe_file; 634 } 635 636 struct file *get_mm_exe_file(struct mm_struct *mm) 637 { 638 struct file *exe_file; 639 640 /* We need mmap_sem to protect against races with removal of exe_file */ 641 down_read(&mm->mmap_sem); 642 exe_file = mm->exe_file; 643 if (exe_file) 644 get_file(exe_file); 645 up_read(&mm->mmap_sem); 646 return exe_file; 647 } 648 649 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 650 { 651 /* It's safe to write the exe_file pointer without exe_file_lock because 652 * this is called during fork when the task is not yet in /proc */ 653 newmm->exe_file = get_mm_exe_file(oldmm); 654 } 655 656 /** 657 * get_task_mm - acquire a reference to the task's mm 658 * 659 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 660 * this kernel workthread has transiently adopted a user mm with use_mm, 661 * to do its AIO) is not set and if so returns a reference to it, after 662 * bumping up the use count. User must release the mm via mmput() 663 * after use. Typically used by /proc and ptrace. 664 */ 665 struct mm_struct *get_task_mm(struct task_struct *task) 666 { 667 struct mm_struct *mm; 668 669 task_lock(task); 670 mm = task->mm; 671 if (mm) { 672 if (task->flags & PF_KTHREAD) 673 mm = NULL; 674 else 675 atomic_inc(&mm->mm_users); 676 } 677 task_unlock(task); 678 return mm; 679 } 680 EXPORT_SYMBOL_GPL(get_task_mm); 681 682 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 683 { 684 struct mm_struct *mm; 685 int err; 686 687 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 688 if (err) 689 return ERR_PTR(err); 690 691 mm = get_task_mm(task); 692 if (mm && mm != current->mm && 693 !ptrace_may_access(task, mode)) { 694 mmput(mm); 695 mm = ERR_PTR(-EACCES); 696 } 697 mutex_unlock(&task->signal->cred_guard_mutex); 698 699 return mm; 700 } 701 702 static void complete_vfork_done(struct task_struct *tsk) 703 { 704 struct completion *vfork; 705 706 task_lock(tsk); 707 vfork = tsk->vfork_done; 708 if (likely(vfork)) { 709 tsk->vfork_done = NULL; 710 complete(vfork); 711 } 712 task_unlock(tsk); 713 } 714 715 static int wait_for_vfork_done(struct task_struct *child, 716 struct completion *vfork) 717 { 718 int killed; 719 720 freezer_do_not_count(); 721 killed = wait_for_completion_killable(vfork); 722 freezer_count(); 723 724 if (killed) { 725 task_lock(child); 726 child->vfork_done = NULL; 727 task_unlock(child); 728 } 729 730 put_task_struct(child); 731 return killed; 732 } 733 734 /* Please note the differences between mmput and mm_release. 735 * mmput is called whenever we stop holding onto a mm_struct, 736 * error success whatever. 737 * 738 * mm_release is called after a mm_struct has been removed 739 * from the current process. 740 * 741 * This difference is important for error handling, when we 742 * only half set up a mm_struct for a new process and need to restore 743 * the old one. Because we mmput the new mm_struct before 744 * restoring the old one. . . 745 * Eric Biederman 10 January 1998 746 */ 747 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 748 { 749 /* Get rid of any futexes when releasing the mm */ 750 #ifdef CONFIG_FUTEX 751 if (unlikely(tsk->robust_list)) { 752 exit_robust_list(tsk); 753 tsk->robust_list = NULL; 754 } 755 #ifdef CONFIG_COMPAT 756 if (unlikely(tsk->compat_robust_list)) { 757 compat_exit_robust_list(tsk); 758 tsk->compat_robust_list = NULL; 759 } 760 #endif 761 if (unlikely(!list_empty(&tsk->pi_state_list))) 762 exit_pi_state_list(tsk); 763 #endif 764 765 uprobe_free_utask(tsk); 766 767 /* Get rid of any cached register state */ 768 deactivate_mm(tsk, mm); 769 770 /* 771 * If we're exiting normally, clear a user-space tid field if 772 * requested. We leave this alone when dying by signal, to leave 773 * the value intact in a core dump, and to save the unnecessary 774 * trouble, say, a killed vfork parent shouldn't touch this mm. 775 * Userland only wants this done for a sys_exit. 776 */ 777 if (tsk->clear_child_tid) { 778 if (!(tsk->flags & PF_SIGNALED) && 779 atomic_read(&mm->mm_users) > 1) { 780 /* 781 * We don't check the error code - if userspace has 782 * not set up a proper pointer then tough luck. 783 */ 784 put_user(0, tsk->clear_child_tid); 785 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 786 1, NULL, NULL, 0); 787 } 788 tsk->clear_child_tid = NULL; 789 } 790 791 /* 792 * All done, finally we can wake up parent and return this mm to him. 793 * Also kthread_stop() uses this completion for synchronization. 794 */ 795 if (tsk->vfork_done) 796 complete_vfork_done(tsk); 797 } 798 799 /* 800 * Allocate a new mm structure and copy contents from the 801 * mm structure of the passed in task structure. 802 */ 803 struct mm_struct *dup_mm(struct task_struct *tsk) 804 { 805 struct mm_struct *mm, *oldmm = current->mm; 806 int err; 807 808 if (!oldmm) 809 return NULL; 810 811 mm = allocate_mm(); 812 if (!mm) 813 goto fail_nomem; 814 815 memcpy(mm, oldmm, sizeof(*mm)); 816 mm_init_cpumask(mm); 817 818 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 819 mm->pmd_huge_pte = NULL; 820 #endif 821 if (!mm_init(mm, tsk)) 822 goto fail_nomem; 823 824 if (init_new_context(tsk, mm)) 825 goto fail_nocontext; 826 827 dup_mm_exe_file(oldmm, mm); 828 829 err = dup_mmap(mm, oldmm); 830 if (err) 831 goto free_pt; 832 833 mm->hiwater_rss = get_mm_rss(mm); 834 mm->hiwater_vm = mm->total_vm; 835 836 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 837 goto free_pt; 838 839 return mm; 840 841 free_pt: 842 /* don't put binfmt in mmput, we haven't got module yet */ 843 mm->binfmt = NULL; 844 mmput(mm); 845 846 fail_nomem: 847 return NULL; 848 849 fail_nocontext: 850 /* 851 * If init_new_context() failed, we cannot use mmput() to free the mm 852 * because it calls destroy_context() 853 */ 854 mm_free_pgd(mm); 855 free_mm(mm); 856 return NULL; 857 } 858 859 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 860 { 861 struct mm_struct *mm, *oldmm; 862 int retval; 863 864 tsk->min_flt = tsk->maj_flt = 0; 865 tsk->nvcsw = tsk->nivcsw = 0; 866 #ifdef CONFIG_DETECT_HUNG_TASK 867 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 868 #endif 869 870 tsk->mm = NULL; 871 tsk->active_mm = NULL; 872 873 /* 874 * Are we cloning a kernel thread? 875 * 876 * We need to steal a active VM for that.. 877 */ 878 oldmm = current->mm; 879 if (!oldmm) 880 return 0; 881 882 if (clone_flags & CLONE_VM) { 883 atomic_inc(&oldmm->mm_users); 884 mm = oldmm; 885 goto good_mm; 886 } 887 888 retval = -ENOMEM; 889 mm = dup_mm(tsk); 890 if (!mm) 891 goto fail_nomem; 892 893 good_mm: 894 tsk->mm = mm; 895 tsk->active_mm = mm; 896 return 0; 897 898 fail_nomem: 899 return retval; 900 } 901 902 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 903 { 904 struct fs_struct *fs = current->fs; 905 if (clone_flags & CLONE_FS) { 906 /* tsk->fs is already what we want */ 907 spin_lock(&fs->lock); 908 if (fs->in_exec) { 909 spin_unlock(&fs->lock); 910 return -EAGAIN; 911 } 912 fs->users++; 913 spin_unlock(&fs->lock); 914 return 0; 915 } 916 tsk->fs = copy_fs_struct(fs); 917 if (!tsk->fs) 918 return -ENOMEM; 919 return 0; 920 } 921 922 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 923 { 924 struct files_struct *oldf, *newf; 925 int error = 0; 926 927 /* 928 * A background process may not have any files ... 929 */ 930 oldf = current->files; 931 if (!oldf) 932 goto out; 933 934 if (clone_flags & CLONE_FILES) { 935 atomic_inc(&oldf->count); 936 goto out; 937 } 938 939 newf = dup_fd(oldf, &error); 940 if (!newf) 941 goto out; 942 943 tsk->files = newf; 944 error = 0; 945 out: 946 return error; 947 } 948 949 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 950 { 951 #ifdef CONFIG_BLOCK 952 struct io_context *ioc = current->io_context; 953 struct io_context *new_ioc; 954 955 if (!ioc) 956 return 0; 957 /* 958 * Share io context with parent, if CLONE_IO is set 959 */ 960 if (clone_flags & CLONE_IO) { 961 ioc_task_link(ioc); 962 tsk->io_context = ioc; 963 } else if (ioprio_valid(ioc->ioprio)) { 964 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 965 if (unlikely(!new_ioc)) 966 return -ENOMEM; 967 968 new_ioc->ioprio = ioc->ioprio; 969 put_io_context(new_ioc); 970 } 971 #endif 972 return 0; 973 } 974 975 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 976 { 977 struct sighand_struct *sig; 978 979 if (clone_flags & CLONE_SIGHAND) { 980 atomic_inc(¤t->sighand->count); 981 return 0; 982 } 983 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 984 rcu_assign_pointer(tsk->sighand, sig); 985 if (!sig) 986 return -ENOMEM; 987 atomic_set(&sig->count, 1); 988 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 989 return 0; 990 } 991 992 void __cleanup_sighand(struct sighand_struct *sighand) 993 { 994 if (atomic_dec_and_test(&sighand->count)) { 995 signalfd_cleanup(sighand); 996 kmem_cache_free(sighand_cachep, sighand); 997 } 998 } 999 1000 1001 /* 1002 * Initialize POSIX timer handling for a thread group. 1003 */ 1004 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1005 { 1006 unsigned long cpu_limit; 1007 1008 /* Thread group counters. */ 1009 thread_group_cputime_init(sig); 1010 1011 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1012 if (cpu_limit != RLIM_INFINITY) { 1013 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1014 sig->cputimer.running = 1; 1015 } 1016 1017 /* The timer lists. */ 1018 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1019 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1020 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1021 } 1022 1023 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1024 { 1025 struct signal_struct *sig; 1026 1027 if (clone_flags & CLONE_THREAD) 1028 return 0; 1029 1030 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1031 tsk->signal = sig; 1032 if (!sig) 1033 return -ENOMEM; 1034 1035 sig->nr_threads = 1; 1036 atomic_set(&sig->live, 1); 1037 atomic_set(&sig->sigcnt, 1); 1038 init_waitqueue_head(&sig->wait_chldexit); 1039 sig->curr_target = tsk; 1040 init_sigpending(&sig->shared_pending); 1041 INIT_LIST_HEAD(&sig->posix_timers); 1042 1043 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1044 sig->real_timer.function = it_real_fn; 1045 1046 task_lock(current->group_leader); 1047 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1048 task_unlock(current->group_leader); 1049 1050 posix_cpu_timers_init_group(sig); 1051 1052 tty_audit_fork(sig); 1053 sched_autogroup_fork(sig); 1054 1055 #ifdef CONFIG_CGROUPS 1056 init_rwsem(&sig->group_rwsem); 1057 #endif 1058 1059 sig->oom_score_adj = current->signal->oom_score_adj; 1060 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1061 1062 sig->has_child_subreaper = current->signal->has_child_subreaper || 1063 current->signal->is_child_subreaper; 1064 1065 mutex_init(&sig->cred_guard_mutex); 1066 1067 return 0; 1068 } 1069 1070 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1071 { 1072 unsigned long new_flags = p->flags; 1073 1074 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1075 new_flags |= PF_FORKNOEXEC; 1076 p->flags = new_flags; 1077 } 1078 1079 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1080 { 1081 current->clear_child_tid = tidptr; 1082 1083 return task_pid_vnr(current); 1084 } 1085 1086 static void rt_mutex_init_task(struct task_struct *p) 1087 { 1088 raw_spin_lock_init(&p->pi_lock); 1089 #ifdef CONFIG_RT_MUTEXES 1090 plist_head_init(&p->pi_waiters); 1091 p->pi_blocked_on = NULL; 1092 #endif 1093 } 1094 1095 #ifdef CONFIG_MM_OWNER 1096 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1097 { 1098 mm->owner = p; 1099 } 1100 #endif /* CONFIG_MM_OWNER */ 1101 1102 /* 1103 * Initialize POSIX timer handling for a single task. 1104 */ 1105 static void posix_cpu_timers_init(struct task_struct *tsk) 1106 { 1107 tsk->cputime_expires.prof_exp = 0; 1108 tsk->cputime_expires.virt_exp = 0; 1109 tsk->cputime_expires.sched_exp = 0; 1110 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1111 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1112 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1113 } 1114 1115 static inline void 1116 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1117 { 1118 task->pids[type].pid = pid; 1119 } 1120 1121 /* 1122 * This creates a new process as a copy of the old one, 1123 * but does not actually start it yet. 1124 * 1125 * It copies the registers, and all the appropriate 1126 * parts of the process environment (as per the clone 1127 * flags). The actual kick-off is left to the caller. 1128 */ 1129 static struct task_struct *copy_process(unsigned long clone_flags, 1130 unsigned long stack_start, 1131 unsigned long stack_size, 1132 int __user *child_tidptr, 1133 struct pid *pid, 1134 int trace) 1135 { 1136 int retval; 1137 struct task_struct *p; 1138 1139 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1140 return ERR_PTR(-EINVAL); 1141 1142 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1143 return ERR_PTR(-EINVAL); 1144 1145 /* 1146 * Thread groups must share signals as well, and detached threads 1147 * can only be started up within the thread group. 1148 */ 1149 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1150 return ERR_PTR(-EINVAL); 1151 1152 /* 1153 * Shared signal handlers imply shared VM. By way of the above, 1154 * thread groups also imply shared VM. Blocking this case allows 1155 * for various simplifications in other code. 1156 */ 1157 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1158 return ERR_PTR(-EINVAL); 1159 1160 /* 1161 * Siblings of global init remain as zombies on exit since they are 1162 * not reaped by their parent (swapper). To solve this and to avoid 1163 * multi-rooted process trees, prevent global and container-inits 1164 * from creating siblings. 1165 */ 1166 if ((clone_flags & CLONE_PARENT) && 1167 current->signal->flags & SIGNAL_UNKILLABLE) 1168 return ERR_PTR(-EINVAL); 1169 1170 /* 1171 * If the new process will be in a different pid or user namespace 1172 * do not allow it to share a thread group or signal handlers or 1173 * parent with the forking task. 1174 */ 1175 if (clone_flags & (CLONE_SIGHAND | CLONE_PARENT)) { 1176 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1177 (task_active_pid_ns(current) != 1178 current->nsproxy->pid_ns_for_children)) 1179 return ERR_PTR(-EINVAL); 1180 } 1181 1182 retval = security_task_create(clone_flags); 1183 if (retval) 1184 goto fork_out; 1185 1186 retval = -ENOMEM; 1187 p = dup_task_struct(current); 1188 if (!p) 1189 goto fork_out; 1190 1191 ftrace_graph_init_task(p); 1192 get_seccomp_filter(p); 1193 1194 rt_mutex_init_task(p); 1195 1196 #ifdef CONFIG_PROVE_LOCKING 1197 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1198 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1199 #endif 1200 retval = -EAGAIN; 1201 if (atomic_read(&p->real_cred->user->processes) >= 1202 task_rlimit(p, RLIMIT_NPROC)) { 1203 if (p->real_cred->user != INIT_USER && 1204 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1205 goto bad_fork_free; 1206 } 1207 current->flags &= ~PF_NPROC_EXCEEDED; 1208 1209 retval = copy_creds(p, clone_flags); 1210 if (retval < 0) 1211 goto bad_fork_free; 1212 1213 /* 1214 * If multiple threads are within copy_process(), then this check 1215 * triggers too late. This doesn't hurt, the check is only there 1216 * to stop root fork bombs. 1217 */ 1218 retval = -EAGAIN; 1219 if (nr_threads >= max_threads) 1220 goto bad_fork_cleanup_count; 1221 1222 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1223 goto bad_fork_cleanup_count; 1224 1225 p->did_exec = 0; 1226 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1227 copy_flags(clone_flags, p); 1228 INIT_LIST_HEAD(&p->children); 1229 INIT_LIST_HEAD(&p->sibling); 1230 rcu_copy_process(p); 1231 p->vfork_done = NULL; 1232 spin_lock_init(&p->alloc_lock); 1233 1234 init_sigpending(&p->pending); 1235 1236 p->utime = p->stime = p->gtime = 0; 1237 p->utimescaled = p->stimescaled = 0; 1238 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1239 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1240 #endif 1241 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1242 seqlock_init(&p->vtime_seqlock); 1243 p->vtime_snap = 0; 1244 p->vtime_snap_whence = VTIME_SLEEPING; 1245 #endif 1246 1247 #if defined(SPLIT_RSS_COUNTING) 1248 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1249 #endif 1250 1251 p->default_timer_slack_ns = current->timer_slack_ns; 1252 1253 task_io_accounting_init(&p->ioac); 1254 acct_clear_integrals(p); 1255 1256 posix_cpu_timers_init(p); 1257 1258 do_posix_clock_monotonic_gettime(&p->start_time); 1259 p->real_start_time = p->start_time; 1260 monotonic_to_bootbased(&p->real_start_time); 1261 p->io_context = NULL; 1262 p->audit_context = NULL; 1263 if (clone_flags & CLONE_THREAD) 1264 threadgroup_change_begin(current); 1265 cgroup_fork(p); 1266 #ifdef CONFIG_NUMA 1267 p->mempolicy = mpol_dup(p->mempolicy); 1268 if (IS_ERR(p->mempolicy)) { 1269 retval = PTR_ERR(p->mempolicy); 1270 p->mempolicy = NULL; 1271 goto bad_fork_cleanup_cgroup; 1272 } 1273 mpol_fix_fork_child_flag(p); 1274 #endif 1275 #ifdef CONFIG_CPUSETS 1276 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1277 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1278 seqcount_init(&p->mems_allowed_seq); 1279 #endif 1280 #ifdef CONFIG_TRACE_IRQFLAGS 1281 p->irq_events = 0; 1282 p->hardirqs_enabled = 0; 1283 p->hardirq_enable_ip = 0; 1284 p->hardirq_enable_event = 0; 1285 p->hardirq_disable_ip = _THIS_IP_; 1286 p->hardirq_disable_event = 0; 1287 p->softirqs_enabled = 1; 1288 p->softirq_enable_ip = _THIS_IP_; 1289 p->softirq_enable_event = 0; 1290 p->softirq_disable_ip = 0; 1291 p->softirq_disable_event = 0; 1292 p->hardirq_context = 0; 1293 p->softirq_context = 0; 1294 #endif 1295 #ifdef CONFIG_LOCKDEP 1296 p->lockdep_depth = 0; /* no locks held yet */ 1297 p->curr_chain_key = 0; 1298 p->lockdep_recursion = 0; 1299 #endif 1300 1301 #ifdef CONFIG_DEBUG_MUTEXES 1302 p->blocked_on = NULL; /* not blocked yet */ 1303 #endif 1304 #ifdef CONFIG_MEMCG 1305 p->memcg_batch.do_batch = 0; 1306 p->memcg_batch.memcg = NULL; 1307 #endif 1308 #ifdef CONFIG_BCACHE 1309 p->sequential_io = 0; 1310 p->sequential_io_avg = 0; 1311 #endif 1312 1313 /* Perform scheduler related setup. Assign this task to a CPU. */ 1314 sched_fork(clone_flags, p); 1315 1316 retval = perf_event_init_task(p); 1317 if (retval) 1318 goto bad_fork_cleanup_policy; 1319 retval = audit_alloc(p); 1320 if (retval) 1321 goto bad_fork_cleanup_policy; 1322 /* copy all the process information */ 1323 retval = copy_semundo(clone_flags, p); 1324 if (retval) 1325 goto bad_fork_cleanup_audit; 1326 retval = copy_files(clone_flags, p); 1327 if (retval) 1328 goto bad_fork_cleanup_semundo; 1329 retval = copy_fs(clone_flags, p); 1330 if (retval) 1331 goto bad_fork_cleanup_files; 1332 retval = copy_sighand(clone_flags, p); 1333 if (retval) 1334 goto bad_fork_cleanup_fs; 1335 retval = copy_signal(clone_flags, p); 1336 if (retval) 1337 goto bad_fork_cleanup_sighand; 1338 retval = copy_mm(clone_flags, p); 1339 if (retval) 1340 goto bad_fork_cleanup_signal; 1341 retval = copy_namespaces(clone_flags, p); 1342 if (retval) 1343 goto bad_fork_cleanup_mm; 1344 retval = copy_io(clone_flags, p); 1345 if (retval) 1346 goto bad_fork_cleanup_namespaces; 1347 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1348 if (retval) 1349 goto bad_fork_cleanup_io; 1350 1351 if (pid != &init_struct_pid) { 1352 retval = -ENOMEM; 1353 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1354 if (!pid) 1355 goto bad_fork_cleanup_io; 1356 } 1357 1358 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1359 /* 1360 * Clear TID on mm_release()? 1361 */ 1362 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1363 #ifdef CONFIG_BLOCK 1364 p->plug = NULL; 1365 #endif 1366 #ifdef CONFIG_FUTEX 1367 p->robust_list = NULL; 1368 #ifdef CONFIG_COMPAT 1369 p->compat_robust_list = NULL; 1370 #endif 1371 INIT_LIST_HEAD(&p->pi_state_list); 1372 p->pi_state_cache = NULL; 1373 #endif 1374 /* 1375 * sigaltstack should be cleared when sharing the same VM 1376 */ 1377 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1378 p->sas_ss_sp = p->sas_ss_size = 0; 1379 1380 /* 1381 * Syscall tracing and stepping should be turned off in the 1382 * child regardless of CLONE_PTRACE. 1383 */ 1384 user_disable_single_step(p); 1385 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1386 #ifdef TIF_SYSCALL_EMU 1387 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1388 #endif 1389 clear_all_latency_tracing(p); 1390 1391 /* ok, now we should be set up.. */ 1392 p->pid = pid_nr(pid); 1393 if (clone_flags & CLONE_THREAD) { 1394 p->exit_signal = -1; 1395 p->group_leader = current->group_leader; 1396 p->tgid = current->tgid; 1397 } else { 1398 if (clone_flags & CLONE_PARENT) 1399 p->exit_signal = current->group_leader->exit_signal; 1400 else 1401 p->exit_signal = (clone_flags & CSIGNAL); 1402 p->group_leader = p; 1403 p->tgid = p->pid; 1404 } 1405 1406 p->pdeath_signal = 0; 1407 p->exit_state = 0; 1408 1409 p->nr_dirtied = 0; 1410 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1411 p->dirty_paused_when = 0; 1412 1413 INIT_LIST_HEAD(&p->thread_group); 1414 p->task_works = NULL; 1415 1416 /* 1417 * Make it visible to the rest of the system, but dont wake it up yet. 1418 * Need tasklist lock for parent etc handling! 1419 */ 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 (likely(p->pid)) { 1450 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1451 1452 init_task_pid(p, PIDTYPE_PID, pid); 1453 if (thread_group_leader(p)) { 1454 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1455 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1456 1457 if (is_child_reaper(pid)) { 1458 ns_of_pid(pid)->child_reaper = p; 1459 p->signal->flags |= SIGNAL_UNKILLABLE; 1460 } 1461 1462 p->signal->leader_pid = pid; 1463 p->signal->tty = tty_kref_get(current->signal->tty); 1464 list_add_tail(&p->sibling, &p->real_parent->children); 1465 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1466 attach_pid(p, PIDTYPE_PGID); 1467 attach_pid(p, PIDTYPE_SID); 1468 __this_cpu_inc(process_counts); 1469 } else { 1470 current->signal->nr_threads++; 1471 atomic_inc(¤t->signal->live); 1472 atomic_inc(¤t->signal->sigcnt); 1473 list_add_tail_rcu(&p->thread_group, 1474 &p->group_leader->thread_group); 1475 } 1476 attach_pid(p, PIDTYPE_PID); 1477 nr_threads++; 1478 } 1479 1480 total_forks++; 1481 spin_unlock(¤t->sighand->siglock); 1482 write_unlock_irq(&tasklist_lock); 1483 proc_fork_connector(p); 1484 cgroup_post_fork(p); 1485 if (clone_flags & CLONE_THREAD) 1486 threadgroup_change_end(current); 1487 perf_event_fork(p); 1488 1489 trace_task_newtask(p, clone_flags); 1490 uprobe_copy_process(p, clone_flags); 1491 1492 return p; 1493 1494 bad_fork_free_pid: 1495 if (pid != &init_struct_pid) 1496 free_pid(pid); 1497 bad_fork_cleanup_io: 1498 if (p->io_context) 1499 exit_io_context(p); 1500 bad_fork_cleanup_namespaces: 1501 exit_task_namespaces(p); 1502 bad_fork_cleanup_mm: 1503 if (p->mm) 1504 mmput(p->mm); 1505 bad_fork_cleanup_signal: 1506 if (!(clone_flags & CLONE_THREAD)) 1507 free_signal_struct(p->signal); 1508 bad_fork_cleanup_sighand: 1509 __cleanup_sighand(p->sighand); 1510 bad_fork_cleanup_fs: 1511 exit_fs(p); /* blocking */ 1512 bad_fork_cleanup_files: 1513 exit_files(p); /* blocking */ 1514 bad_fork_cleanup_semundo: 1515 exit_sem(p); 1516 bad_fork_cleanup_audit: 1517 audit_free(p); 1518 bad_fork_cleanup_policy: 1519 perf_event_free_task(p); 1520 #ifdef CONFIG_NUMA 1521 mpol_put(p->mempolicy); 1522 bad_fork_cleanup_cgroup: 1523 #endif 1524 if (clone_flags & CLONE_THREAD) 1525 threadgroup_change_end(current); 1526 cgroup_exit(p, 0); 1527 delayacct_tsk_free(p); 1528 module_put(task_thread_info(p)->exec_domain->module); 1529 bad_fork_cleanup_count: 1530 atomic_dec(&p->cred->user->processes); 1531 exit_creds(p); 1532 bad_fork_free: 1533 free_task(p); 1534 fork_out: 1535 return ERR_PTR(retval); 1536 } 1537 1538 static inline void init_idle_pids(struct pid_link *links) 1539 { 1540 enum pid_type type; 1541 1542 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1543 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1544 links[type].pid = &init_struct_pid; 1545 } 1546 } 1547 1548 struct task_struct *fork_idle(int cpu) 1549 { 1550 struct task_struct *task; 1551 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1552 if (!IS_ERR(task)) { 1553 init_idle_pids(task->pids); 1554 init_idle(task, cpu); 1555 } 1556 1557 return task; 1558 } 1559 1560 /* 1561 * Ok, this is the main fork-routine. 1562 * 1563 * It copies the process, and if successful kick-starts 1564 * it and waits for it to finish using the VM if required. 1565 */ 1566 long do_fork(unsigned long clone_flags, 1567 unsigned long stack_start, 1568 unsigned long stack_size, 1569 int __user *parent_tidptr, 1570 int __user *child_tidptr) 1571 { 1572 struct task_struct *p; 1573 int trace = 0; 1574 long nr; 1575 1576 /* 1577 * Determine whether and which event to report to ptracer. When 1578 * called from kernel_thread or CLONE_UNTRACED is explicitly 1579 * requested, no event is reported; otherwise, report if the event 1580 * for the type of forking is enabled. 1581 */ 1582 if (!(clone_flags & CLONE_UNTRACED)) { 1583 if (clone_flags & CLONE_VFORK) 1584 trace = PTRACE_EVENT_VFORK; 1585 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1586 trace = PTRACE_EVENT_CLONE; 1587 else 1588 trace = PTRACE_EVENT_FORK; 1589 1590 if (likely(!ptrace_event_enabled(current, trace))) 1591 trace = 0; 1592 } 1593 1594 p = copy_process(clone_flags, stack_start, stack_size, 1595 child_tidptr, NULL, trace); 1596 /* 1597 * Do this prior waking up the new thread - the thread pointer 1598 * might get invalid after that point, if the thread exits quickly. 1599 */ 1600 if (!IS_ERR(p)) { 1601 struct completion vfork; 1602 1603 trace_sched_process_fork(current, p); 1604 1605 nr = task_pid_vnr(p); 1606 1607 if (clone_flags & CLONE_PARENT_SETTID) 1608 put_user(nr, parent_tidptr); 1609 1610 if (clone_flags & CLONE_VFORK) { 1611 p->vfork_done = &vfork; 1612 init_completion(&vfork); 1613 get_task_struct(p); 1614 } 1615 1616 wake_up_new_task(p); 1617 1618 /* forking complete and child started to run, tell ptracer */ 1619 if (unlikely(trace)) 1620 ptrace_event(trace, nr); 1621 1622 if (clone_flags & CLONE_VFORK) { 1623 if (!wait_for_vfork_done(p, &vfork)) 1624 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1625 } 1626 } else { 1627 nr = PTR_ERR(p); 1628 } 1629 return nr; 1630 } 1631 1632 /* 1633 * Create a kernel thread. 1634 */ 1635 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1636 { 1637 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1638 (unsigned long)arg, NULL, NULL); 1639 } 1640 1641 #ifdef __ARCH_WANT_SYS_FORK 1642 SYSCALL_DEFINE0(fork) 1643 { 1644 #ifdef CONFIG_MMU 1645 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1646 #else 1647 /* can not support in nommu mode */ 1648 return(-EINVAL); 1649 #endif 1650 } 1651 #endif 1652 1653 #ifdef __ARCH_WANT_SYS_VFORK 1654 SYSCALL_DEFINE0(vfork) 1655 { 1656 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1657 0, NULL, NULL); 1658 } 1659 #endif 1660 1661 #ifdef __ARCH_WANT_SYS_CLONE 1662 #ifdef CONFIG_CLONE_BACKWARDS 1663 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1664 int __user *, parent_tidptr, 1665 int, tls_val, 1666 int __user *, child_tidptr) 1667 #elif defined(CONFIG_CLONE_BACKWARDS2) 1668 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1669 int __user *, parent_tidptr, 1670 int __user *, child_tidptr, 1671 int, tls_val) 1672 #elif defined(CONFIG_CLONE_BACKWARDS3) 1673 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1674 int, stack_size, 1675 int __user *, parent_tidptr, 1676 int __user *, child_tidptr, 1677 int, tls_val) 1678 #else 1679 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1680 int __user *, parent_tidptr, 1681 int __user *, child_tidptr, 1682 int, tls_val) 1683 #endif 1684 { 1685 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1686 } 1687 #endif 1688 1689 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1690 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1691 #endif 1692 1693 static void sighand_ctor(void *data) 1694 { 1695 struct sighand_struct *sighand = data; 1696 1697 spin_lock_init(&sighand->siglock); 1698 init_waitqueue_head(&sighand->signalfd_wqh); 1699 } 1700 1701 void __init proc_caches_init(void) 1702 { 1703 sighand_cachep = kmem_cache_create("sighand_cache", 1704 sizeof(struct sighand_struct), 0, 1705 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1706 SLAB_NOTRACK, sighand_ctor); 1707 signal_cachep = kmem_cache_create("signal_cache", 1708 sizeof(struct signal_struct), 0, 1709 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1710 files_cachep = kmem_cache_create("files_cache", 1711 sizeof(struct files_struct), 0, 1712 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1713 fs_cachep = kmem_cache_create("fs_cache", 1714 sizeof(struct fs_struct), 0, 1715 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1716 /* 1717 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1718 * whole struct cpumask for the OFFSTACK case. We could change 1719 * this to *only* allocate as much of it as required by the 1720 * maximum number of CPU's we can ever have. The cpumask_allocation 1721 * is at the end of the structure, exactly for that reason. 1722 */ 1723 mm_cachep = kmem_cache_create("mm_struct", 1724 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1725 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1726 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1727 mmap_init(); 1728 nsproxy_cache_init(); 1729 } 1730 1731 /* 1732 * Check constraints on flags passed to the unshare system call. 1733 */ 1734 static int check_unshare_flags(unsigned long unshare_flags) 1735 { 1736 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1737 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1738 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1739 CLONE_NEWUSER|CLONE_NEWPID)) 1740 return -EINVAL; 1741 /* 1742 * Not implemented, but pretend it works if there is nothing to 1743 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1744 * needs to unshare vm. 1745 */ 1746 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1747 /* FIXME: get_task_mm() increments ->mm_users */ 1748 if (atomic_read(¤t->mm->mm_users) > 1) 1749 return -EINVAL; 1750 } 1751 1752 return 0; 1753 } 1754 1755 /* 1756 * Unshare the filesystem structure if it is being shared 1757 */ 1758 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1759 { 1760 struct fs_struct *fs = current->fs; 1761 1762 if (!(unshare_flags & CLONE_FS) || !fs) 1763 return 0; 1764 1765 /* don't need lock here; in the worst case we'll do useless copy */ 1766 if (fs->users == 1) 1767 return 0; 1768 1769 *new_fsp = copy_fs_struct(fs); 1770 if (!*new_fsp) 1771 return -ENOMEM; 1772 1773 return 0; 1774 } 1775 1776 /* 1777 * Unshare file descriptor table if it is being shared 1778 */ 1779 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1780 { 1781 struct files_struct *fd = current->files; 1782 int error = 0; 1783 1784 if ((unshare_flags & CLONE_FILES) && 1785 (fd && atomic_read(&fd->count) > 1)) { 1786 *new_fdp = dup_fd(fd, &error); 1787 if (!*new_fdp) 1788 return error; 1789 } 1790 1791 return 0; 1792 } 1793 1794 /* 1795 * unshare allows a process to 'unshare' part of the process 1796 * context which was originally shared using clone. copy_* 1797 * functions used by do_fork() cannot be used here directly 1798 * because they modify an inactive task_struct that is being 1799 * constructed. Here we are modifying the current, active, 1800 * task_struct. 1801 */ 1802 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1803 { 1804 struct fs_struct *fs, *new_fs = NULL; 1805 struct files_struct *fd, *new_fd = NULL; 1806 struct cred *new_cred = NULL; 1807 struct nsproxy *new_nsproxy = NULL; 1808 int do_sysvsem = 0; 1809 int err; 1810 1811 /* 1812 * If unsharing a user namespace must also unshare the thread. 1813 */ 1814 if (unshare_flags & CLONE_NEWUSER) 1815 unshare_flags |= CLONE_THREAD | CLONE_FS; 1816 /* 1817 * If unsharing a thread from a thread group, must also unshare vm. 1818 */ 1819 if (unshare_flags & CLONE_THREAD) 1820 unshare_flags |= CLONE_VM; 1821 /* 1822 * If unsharing vm, must also unshare signal handlers. 1823 */ 1824 if (unshare_flags & CLONE_VM) 1825 unshare_flags |= CLONE_SIGHAND; 1826 /* 1827 * If unsharing namespace, must also unshare filesystem information. 1828 */ 1829 if (unshare_flags & CLONE_NEWNS) 1830 unshare_flags |= CLONE_FS; 1831 1832 err = check_unshare_flags(unshare_flags); 1833 if (err) 1834 goto bad_unshare_out; 1835 /* 1836 * CLONE_NEWIPC must also detach from the undolist: after switching 1837 * to a new ipc namespace, the semaphore arrays from the old 1838 * namespace are unreachable. 1839 */ 1840 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1841 do_sysvsem = 1; 1842 err = unshare_fs(unshare_flags, &new_fs); 1843 if (err) 1844 goto bad_unshare_out; 1845 err = unshare_fd(unshare_flags, &new_fd); 1846 if (err) 1847 goto bad_unshare_cleanup_fs; 1848 err = unshare_userns(unshare_flags, &new_cred); 1849 if (err) 1850 goto bad_unshare_cleanup_fd; 1851 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1852 new_cred, new_fs); 1853 if (err) 1854 goto bad_unshare_cleanup_cred; 1855 1856 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1857 if (do_sysvsem) { 1858 /* 1859 * CLONE_SYSVSEM is equivalent to sys_exit(). 1860 */ 1861 exit_sem(current); 1862 } 1863 1864 if (new_nsproxy) 1865 switch_task_namespaces(current, new_nsproxy); 1866 1867 task_lock(current); 1868 1869 if (new_fs) { 1870 fs = current->fs; 1871 spin_lock(&fs->lock); 1872 current->fs = new_fs; 1873 if (--fs->users) 1874 new_fs = NULL; 1875 else 1876 new_fs = fs; 1877 spin_unlock(&fs->lock); 1878 } 1879 1880 if (new_fd) { 1881 fd = current->files; 1882 current->files = new_fd; 1883 new_fd = fd; 1884 } 1885 1886 task_unlock(current); 1887 1888 if (new_cred) { 1889 /* Install the new user namespace */ 1890 commit_creds(new_cred); 1891 new_cred = NULL; 1892 } 1893 } 1894 1895 bad_unshare_cleanup_cred: 1896 if (new_cred) 1897 put_cred(new_cred); 1898 bad_unshare_cleanup_fd: 1899 if (new_fd) 1900 put_files_struct(new_fd); 1901 1902 bad_unshare_cleanup_fs: 1903 if (new_fs) 1904 free_fs_struct(new_fs); 1905 1906 bad_unshare_out: 1907 return err; 1908 } 1909 1910 /* 1911 * Helper to unshare the files of the current task. 1912 * We don't want to expose copy_files internals to 1913 * the exec layer of the kernel. 1914 */ 1915 1916 int unshare_files(struct files_struct **displaced) 1917 { 1918 struct task_struct *task = current; 1919 struct files_struct *copy = NULL; 1920 int error; 1921 1922 error = unshare_fd(CLONE_FILES, ©); 1923 if (error || !copy) { 1924 *displaced = NULL; 1925 return error; 1926 } 1927 *displaced = task->files; 1928 task_lock(task); 1929 task->files = copy; 1930 task_unlock(task); 1931 return 0; 1932 } 1933