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/mm.h> 32 #include <linux/vmacache.h> 33 #include <linux/nsproxy.h> 34 #include <linux/capability.h> 35 #include <linux/cpu.h> 36 #include <linux/cgroup.h> 37 #include <linux/security.h> 38 #include <linux/hugetlb.h> 39 #include <linux/seccomp.h> 40 #include <linux/swap.h> 41 #include <linux/syscalls.h> 42 #include <linux/jiffies.h> 43 #include <linux/futex.h> 44 #include <linux/compat.h> 45 #include <linux/kthread.h> 46 #include <linux/task_io_accounting_ops.h> 47 #include <linux/rcupdate.h> 48 #include <linux/ptrace.h> 49 #include <linux/mount.h> 50 #include <linux/audit.h> 51 #include <linux/memcontrol.h> 52 #include <linux/ftrace.h> 53 #include <linux/proc_fs.h> 54 #include <linux/profile.h> 55 #include <linux/rmap.h> 56 #include <linux/ksm.h> 57 #include <linux/acct.h> 58 #include <linux/tsacct_kern.h> 59 #include <linux/cn_proc.h> 60 #include <linux/freezer.h> 61 #include <linux/delayacct.h> 62 #include <linux/taskstats_kern.h> 63 #include <linux/random.h> 64 #include <linux/tty.h> 65 #include <linux/blkdev.h> 66 #include <linux/fs_struct.h> 67 #include <linux/magic.h> 68 #include <linux/perf_event.h> 69 #include <linux/posix-timers.h> 70 #include <linux/user-return-notifier.h> 71 #include <linux/oom.h> 72 #include <linux/khugepaged.h> 73 #include <linux/signalfd.h> 74 #include <linux/uprobes.h> 75 #include <linux/aio.h> 76 #include <linux/compiler.h> 77 78 #include <asm/pgtable.h> 79 #include <asm/pgalloc.h> 80 #include <asm/uaccess.h> 81 #include <asm/mmu_context.h> 82 #include <asm/cacheflush.h> 83 #include <asm/tlbflush.h> 84 85 #include <trace/events/sched.h> 86 87 #define CREATE_TRACE_POINTS 88 #include <trace/events/task.h> 89 90 /* 91 * Protected counters by write_lock_irq(&tasklist_lock) 92 */ 93 unsigned long total_forks; /* Handle normal Linux uptimes. */ 94 int nr_threads; /* The idle threads do not count.. */ 95 96 int max_threads; /* tunable limit on nr_threads */ 97 98 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 99 100 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 101 102 #ifdef CONFIG_PROVE_RCU 103 int lockdep_tasklist_lock_is_held(void) 104 { 105 return lockdep_is_held(&tasklist_lock); 106 } 107 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 108 #endif /* #ifdef CONFIG_PROVE_RCU */ 109 110 int nr_processes(void) 111 { 112 int cpu; 113 int total = 0; 114 115 for_each_possible_cpu(cpu) 116 total += per_cpu(process_counts, cpu); 117 118 return total; 119 } 120 121 void __weak arch_release_task_struct(struct task_struct *tsk) 122 { 123 } 124 125 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 126 static struct kmem_cache *task_struct_cachep; 127 128 static inline struct task_struct *alloc_task_struct_node(int node) 129 { 130 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 131 } 132 133 static inline void free_task_struct(struct task_struct *tsk) 134 { 135 kmem_cache_free(task_struct_cachep, tsk); 136 } 137 #endif 138 139 void __weak arch_release_thread_info(struct thread_info *ti) 140 { 141 } 142 143 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 144 145 /* 146 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 147 * kmemcache based allocator. 148 */ 149 # if THREAD_SIZE >= PAGE_SIZE 150 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 151 int node) 152 { 153 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP, 154 THREAD_SIZE_ORDER); 155 156 return page ? page_address(page) : NULL; 157 } 158 159 static inline void free_thread_info(struct thread_info *ti) 160 { 161 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); 162 } 163 # else 164 static struct kmem_cache *thread_info_cache; 165 166 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 167 int node) 168 { 169 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 170 } 171 172 static void free_thread_info(struct thread_info *ti) 173 { 174 kmem_cache_free(thread_info_cache, ti); 175 } 176 177 void thread_info_cache_init(void) 178 { 179 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 180 THREAD_SIZE, 0, NULL); 181 BUG_ON(thread_info_cache == NULL); 182 } 183 # endif 184 #endif 185 186 /* SLAB cache for signal_struct structures (tsk->signal) */ 187 static struct kmem_cache *signal_cachep; 188 189 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 190 struct kmem_cache *sighand_cachep; 191 192 /* SLAB cache for files_struct structures (tsk->files) */ 193 struct kmem_cache *files_cachep; 194 195 /* SLAB cache for fs_struct structures (tsk->fs) */ 196 struct kmem_cache *fs_cachep; 197 198 /* SLAB cache for vm_area_struct structures */ 199 struct kmem_cache *vm_area_cachep; 200 201 /* SLAB cache for mm_struct structures (tsk->mm) */ 202 static struct kmem_cache *mm_cachep; 203 204 static void account_kernel_stack(struct thread_info *ti, int account) 205 { 206 struct zone *zone = page_zone(virt_to_page(ti)); 207 208 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 209 } 210 211 void free_task(struct task_struct *tsk) 212 { 213 account_kernel_stack(tsk->stack, -1); 214 arch_release_thread_info(tsk->stack); 215 free_thread_info(tsk->stack); 216 rt_mutex_debug_task_free(tsk); 217 ftrace_graph_exit_task(tsk); 218 put_seccomp_filter(tsk); 219 arch_release_task_struct(tsk); 220 free_task_struct(tsk); 221 } 222 EXPORT_SYMBOL(free_task); 223 224 static inline void free_signal_struct(struct signal_struct *sig) 225 { 226 taskstats_tgid_free(sig); 227 sched_autogroup_exit(sig); 228 kmem_cache_free(signal_cachep, sig); 229 } 230 231 static inline void put_signal_struct(struct signal_struct *sig) 232 { 233 if (atomic_dec_and_test(&sig->sigcnt)) 234 free_signal_struct(sig); 235 } 236 237 void __put_task_struct(struct task_struct *tsk) 238 { 239 WARN_ON(!tsk->exit_state); 240 WARN_ON(atomic_read(&tsk->usage)); 241 WARN_ON(tsk == current); 242 243 task_numa_free(tsk); 244 security_task_free(tsk); 245 exit_creds(tsk); 246 delayacct_tsk_free(tsk); 247 put_signal_struct(tsk->signal); 248 249 if (!profile_handoff_task(tsk)) 250 free_task(tsk); 251 } 252 EXPORT_SYMBOL_GPL(__put_task_struct); 253 254 void __init __weak arch_task_cache_init(void) { } 255 256 void __init fork_init(unsigned long mempages) 257 { 258 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 259 #ifndef ARCH_MIN_TASKALIGN 260 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 261 #endif 262 /* create a slab on which task_structs can be allocated */ 263 task_struct_cachep = 264 kmem_cache_create("task_struct", sizeof(struct task_struct), 265 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 266 #endif 267 268 /* do the arch specific task caches init */ 269 arch_task_cache_init(); 270 271 /* 272 * The default maximum number of threads is set to a safe 273 * value: the thread structures can take up at most half 274 * of memory. 275 */ 276 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 277 278 /* 279 * we need to allow at least 20 threads to boot a system 280 */ 281 if (max_threads < 20) 282 max_threads = 20; 283 284 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 285 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 286 init_task.signal->rlim[RLIMIT_SIGPENDING] = 287 init_task.signal->rlim[RLIMIT_NPROC]; 288 } 289 290 int __weak arch_dup_task_struct(struct task_struct *dst, 291 struct task_struct *src) 292 { 293 *dst = *src; 294 return 0; 295 } 296 297 static struct task_struct *dup_task_struct(struct task_struct *orig) 298 { 299 struct task_struct *tsk; 300 struct thread_info *ti; 301 unsigned long *stackend; 302 int node = tsk_fork_get_node(orig); 303 int err; 304 305 tsk = alloc_task_struct_node(node); 306 if (!tsk) 307 return NULL; 308 309 ti = alloc_thread_info_node(tsk, node); 310 if (!ti) 311 goto free_tsk; 312 313 err = arch_dup_task_struct(tsk, orig); 314 if (err) 315 goto free_ti; 316 317 tsk->stack = ti; 318 319 setup_thread_stack(tsk, orig); 320 clear_user_return_notifier(tsk); 321 clear_tsk_need_resched(tsk); 322 stackend = end_of_stack(tsk); 323 *stackend = STACK_END_MAGIC; /* for overflow detection */ 324 325 #ifdef CONFIG_CC_STACKPROTECTOR 326 tsk->stack_canary = get_random_int(); 327 #endif 328 329 /* 330 * One for us, one for whoever does the "release_task()" (usually 331 * parent) 332 */ 333 atomic_set(&tsk->usage, 2); 334 #ifdef CONFIG_BLK_DEV_IO_TRACE 335 tsk->btrace_seq = 0; 336 #endif 337 tsk->splice_pipe = NULL; 338 tsk->task_frag.page = NULL; 339 340 account_kernel_stack(ti, 1); 341 342 return tsk; 343 344 free_ti: 345 free_thread_info(ti); 346 free_tsk: 347 free_task_struct(tsk); 348 return NULL; 349 } 350 351 #ifdef CONFIG_MMU 352 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 353 { 354 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 355 struct rb_node **rb_link, *rb_parent; 356 int retval; 357 unsigned long charge; 358 359 uprobe_start_dup_mmap(); 360 down_write(&oldmm->mmap_sem); 361 flush_cache_dup_mm(oldmm); 362 uprobe_dup_mmap(oldmm, mm); 363 /* 364 * Not linked in yet - no deadlock potential: 365 */ 366 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 367 368 mm->locked_vm = 0; 369 mm->mmap = NULL; 370 mm->vmacache_seqnum = 0; 371 mm->map_count = 0; 372 cpumask_clear(mm_cpumask(mm)); 373 mm->mm_rb = RB_ROOT; 374 rb_link = &mm->mm_rb.rb_node; 375 rb_parent = NULL; 376 pprev = &mm->mmap; 377 retval = ksm_fork(mm, oldmm); 378 if (retval) 379 goto out; 380 retval = khugepaged_fork(mm, oldmm); 381 if (retval) 382 goto out; 383 384 prev = NULL; 385 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 386 struct file *file; 387 388 if (mpnt->vm_flags & VM_DONTCOPY) { 389 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 390 -vma_pages(mpnt)); 391 continue; 392 } 393 charge = 0; 394 if (mpnt->vm_flags & VM_ACCOUNT) { 395 unsigned long len = vma_pages(mpnt); 396 397 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 398 goto fail_nomem; 399 charge = len; 400 } 401 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 402 if (!tmp) 403 goto fail_nomem; 404 *tmp = *mpnt; 405 INIT_LIST_HEAD(&tmp->anon_vma_chain); 406 retval = vma_dup_policy(mpnt, tmp); 407 if (retval) 408 goto fail_nomem_policy; 409 tmp->vm_mm = mm; 410 if (anon_vma_fork(tmp, mpnt)) 411 goto fail_nomem_anon_vma_fork; 412 tmp->vm_flags &= ~VM_LOCKED; 413 tmp->vm_next = tmp->vm_prev = NULL; 414 file = tmp->vm_file; 415 if (file) { 416 struct inode *inode = file_inode(file); 417 struct address_space *mapping = file->f_mapping; 418 419 get_file(file); 420 if (tmp->vm_flags & VM_DENYWRITE) 421 atomic_dec(&inode->i_writecount); 422 mutex_lock(&mapping->i_mmap_mutex); 423 if (tmp->vm_flags & VM_SHARED) 424 mapping->i_mmap_writable++; 425 flush_dcache_mmap_lock(mapping); 426 /* insert tmp into the share list, just after mpnt */ 427 if (unlikely(tmp->vm_flags & VM_NONLINEAR)) 428 vma_nonlinear_insert(tmp, 429 &mapping->i_mmap_nonlinear); 430 else 431 vma_interval_tree_insert_after(tmp, mpnt, 432 &mapping->i_mmap); 433 flush_dcache_mmap_unlock(mapping); 434 mutex_unlock(&mapping->i_mmap_mutex); 435 } 436 437 /* 438 * Clear hugetlb-related page reserves for children. This only 439 * affects MAP_PRIVATE mappings. Faults generated by the child 440 * are not guaranteed to succeed, even if read-only 441 */ 442 if (is_vm_hugetlb_page(tmp)) 443 reset_vma_resv_huge_pages(tmp); 444 445 /* 446 * Link in the new vma and copy the page table entries. 447 */ 448 *pprev = tmp; 449 pprev = &tmp->vm_next; 450 tmp->vm_prev = prev; 451 prev = tmp; 452 453 __vma_link_rb(mm, tmp, rb_link, rb_parent); 454 rb_link = &tmp->vm_rb.rb_right; 455 rb_parent = &tmp->vm_rb; 456 457 mm->map_count++; 458 retval = copy_page_range(mm, oldmm, mpnt); 459 460 if (tmp->vm_ops && tmp->vm_ops->open) 461 tmp->vm_ops->open(tmp); 462 463 if (retval) 464 goto out; 465 } 466 /* a new mm has just been created */ 467 arch_dup_mmap(oldmm, mm); 468 retval = 0; 469 out: 470 up_write(&mm->mmap_sem); 471 flush_tlb_mm(oldmm); 472 up_write(&oldmm->mmap_sem); 473 uprobe_end_dup_mmap(); 474 return retval; 475 fail_nomem_anon_vma_fork: 476 mpol_put(vma_policy(tmp)); 477 fail_nomem_policy: 478 kmem_cache_free(vm_area_cachep, tmp); 479 fail_nomem: 480 retval = -ENOMEM; 481 vm_unacct_memory(charge); 482 goto out; 483 } 484 485 static inline int mm_alloc_pgd(struct mm_struct *mm) 486 { 487 mm->pgd = pgd_alloc(mm); 488 if (unlikely(!mm->pgd)) 489 return -ENOMEM; 490 return 0; 491 } 492 493 static inline void mm_free_pgd(struct mm_struct *mm) 494 { 495 pgd_free(mm, mm->pgd); 496 } 497 #else 498 #define dup_mmap(mm, oldmm) (0) 499 #define mm_alloc_pgd(mm) (0) 500 #define mm_free_pgd(mm) 501 #endif /* CONFIG_MMU */ 502 503 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 504 505 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 506 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 507 508 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 509 510 static int __init coredump_filter_setup(char *s) 511 { 512 default_dump_filter = 513 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 514 MMF_DUMP_FILTER_MASK; 515 return 1; 516 } 517 518 __setup("coredump_filter=", coredump_filter_setup); 519 520 #include <linux/init_task.h> 521 522 static void mm_init_aio(struct mm_struct *mm) 523 { 524 #ifdef CONFIG_AIO 525 spin_lock_init(&mm->ioctx_lock); 526 mm->ioctx_table = NULL; 527 #endif 528 } 529 530 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 531 { 532 atomic_set(&mm->mm_users, 1); 533 atomic_set(&mm->mm_count, 1); 534 init_rwsem(&mm->mmap_sem); 535 INIT_LIST_HEAD(&mm->mmlist); 536 mm->core_state = NULL; 537 atomic_long_set(&mm->nr_ptes, 0); 538 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 539 spin_lock_init(&mm->page_table_lock); 540 mm_init_aio(mm); 541 mm_init_owner(mm, p); 542 clear_tlb_flush_pending(mm); 543 544 if (current->mm) { 545 mm->flags = current->mm->flags & MMF_INIT_MASK; 546 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 547 } else { 548 mm->flags = default_dump_filter; 549 mm->def_flags = 0; 550 } 551 552 if (likely(!mm_alloc_pgd(mm))) { 553 mmu_notifier_mm_init(mm); 554 return mm; 555 } 556 557 free_mm(mm); 558 return NULL; 559 } 560 561 static void check_mm(struct mm_struct *mm) 562 { 563 int i; 564 565 for (i = 0; i < NR_MM_COUNTERS; i++) { 566 long x = atomic_long_read(&mm->rss_stat.count[i]); 567 568 if (unlikely(x)) 569 printk(KERN_ALERT "BUG: Bad rss-counter state " 570 "mm:%p idx:%d val:%ld\n", mm, i, x); 571 } 572 573 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 574 VM_BUG_ON(mm->pmd_huge_pte); 575 #endif 576 } 577 578 /* 579 * Allocate and initialize an mm_struct. 580 */ 581 struct mm_struct *mm_alloc(void) 582 { 583 struct mm_struct *mm; 584 585 mm = allocate_mm(); 586 if (!mm) 587 return NULL; 588 589 memset(mm, 0, sizeof(*mm)); 590 mm_init_cpumask(mm); 591 return mm_init(mm, current); 592 } 593 594 /* 595 * Called when the last reference to the mm 596 * is dropped: either by a lazy thread or by 597 * mmput. Free the page directory and the mm. 598 */ 599 void __mmdrop(struct mm_struct *mm) 600 { 601 BUG_ON(mm == &init_mm); 602 mm_free_pgd(mm); 603 destroy_context(mm); 604 mmu_notifier_mm_destroy(mm); 605 check_mm(mm); 606 free_mm(mm); 607 } 608 EXPORT_SYMBOL_GPL(__mmdrop); 609 610 /* 611 * Decrement the use count and release all resources for an mm. 612 */ 613 void mmput(struct mm_struct *mm) 614 { 615 might_sleep(); 616 617 if (atomic_dec_and_test(&mm->mm_users)) { 618 uprobe_clear_state(mm); 619 exit_aio(mm); 620 ksm_exit(mm); 621 khugepaged_exit(mm); /* must run before exit_mmap */ 622 exit_mmap(mm); 623 set_mm_exe_file(mm, NULL); 624 if (!list_empty(&mm->mmlist)) { 625 spin_lock(&mmlist_lock); 626 list_del(&mm->mmlist); 627 spin_unlock(&mmlist_lock); 628 } 629 if (mm->binfmt) 630 module_put(mm->binfmt->module); 631 mmdrop(mm); 632 } 633 } 634 EXPORT_SYMBOL_GPL(mmput); 635 636 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 637 { 638 if (new_exe_file) 639 get_file(new_exe_file); 640 if (mm->exe_file) 641 fput(mm->exe_file); 642 mm->exe_file = new_exe_file; 643 } 644 645 struct file *get_mm_exe_file(struct mm_struct *mm) 646 { 647 struct file *exe_file; 648 649 /* We need mmap_sem to protect against races with removal of exe_file */ 650 down_read(&mm->mmap_sem); 651 exe_file = mm->exe_file; 652 if (exe_file) 653 get_file(exe_file); 654 up_read(&mm->mmap_sem); 655 return exe_file; 656 } 657 658 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 659 { 660 /* It's safe to write the exe_file pointer without exe_file_lock because 661 * this is called during fork when the task is not yet in /proc */ 662 newmm->exe_file = get_mm_exe_file(oldmm); 663 } 664 665 /** 666 * get_task_mm - acquire a reference to the task's mm 667 * 668 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 669 * this kernel workthread has transiently adopted a user mm with use_mm, 670 * to do its AIO) is not set and if so returns a reference to it, after 671 * bumping up the use count. User must release the mm via mmput() 672 * after use. Typically used by /proc and ptrace. 673 */ 674 struct mm_struct *get_task_mm(struct task_struct *task) 675 { 676 struct mm_struct *mm; 677 678 task_lock(task); 679 mm = task->mm; 680 if (mm) { 681 if (task->flags & PF_KTHREAD) 682 mm = NULL; 683 else 684 atomic_inc(&mm->mm_users); 685 } 686 task_unlock(task); 687 return mm; 688 } 689 EXPORT_SYMBOL_GPL(get_task_mm); 690 691 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 692 { 693 struct mm_struct *mm; 694 int err; 695 696 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 697 if (err) 698 return ERR_PTR(err); 699 700 mm = get_task_mm(task); 701 if (mm && mm != current->mm && 702 !ptrace_may_access(task, mode)) { 703 mmput(mm); 704 mm = ERR_PTR(-EACCES); 705 } 706 mutex_unlock(&task->signal->cred_guard_mutex); 707 708 return mm; 709 } 710 711 static void complete_vfork_done(struct task_struct *tsk) 712 { 713 struct completion *vfork; 714 715 task_lock(tsk); 716 vfork = tsk->vfork_done; 717 if (likely(vfork)) { 718 tsk->vfork_done = NULL; 719 complete(vfork); 720 } 721 task_unlock(tsk); 722 } 723 724 static int wait_for_vfork_done(struct task_struct *child, 725 struct completion *vfork) 726 { 727 int killed; 728 729 freezer_do_not_count(); 730 killed = wait_for_completion_killable(vfork); 731 freezer_count(); 732 733 if (killed) { 734 task_lock(child); 735 child->vfork_done = NULL; 736 task_unlock(child); 737 } 738 739 put_task_struct(child); 740 return killed; 741 } 742 743 /* Please note the differences between mmput and mm_release. 744 * mmput is called whenever we stop holding onto a mm_struct, 745 * error success whatever. 746 * 747 * mm_release is called after a mm_struct has been removed 748 * from the current process. 749 * 750 * This difference is important for error handling, when we 751 * only half set up a mm_struct for a new process and need to restore 752 * the old one. Because we mmput the new mm_struct before 753 * restoring the old one. . . 754 * Eric Biederman 10 January 1998 755 */ 756 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 757 { 758 /* Get rid of any futexes when releasing the mm */ 759 #ifdef CONFIG_FUTEX 760 if (unlikely(tsk->robust_list)) { 761 exit_robust_list(tsk); 762 tsk->robust_list = NULL; 763 } 764 #ifdef CONFIG_COMPAT 765 if (unlikely(tsk->compat_robust_list)) { 766 compat_exit_robust_list(tsk); 767 tsk->compat_robust_list = NULL; 768 } 769 #endif 770 if (unlikely(!list_empty(&tsk->pi_state_list))) 771 exit_pi_state_list(tsk); 772 #endif 773 774 uprobe_free_utask(tsk); 775 776 /* Get rid of any cached register state */ 777 deactivate_mm(tsk, mm); 778 779 /* 780 * If we're exiting normally, clear a user-space tid field if 781 * requested. We leave this alone when dying by signal, to leave 782 * the value intact in a core dump, and to save the unnecessary 783 * trouble, say, a killed vfork parent shouldn't touch this mm. 784 * Userland only wants this done for a sys_exit. 785 */ 786 if (tsk->clear_child_tid) { 787 if (!(tsk->flags & PF_SIGNALED) && 788 atomic_read(&mm->mm_users) > 1) { 789 /* 790 * We don't check the error code - if userspace has 791 * not set up a proper pointer then tough luck. 792 */ 793 put_user(0, tsk->clear_child_tid); 794 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 795 1, NULL, NULL, 0); 796 } 797 tsk->clear_child_tid = NULL; 798 } 799 800 /* 801 * All done, finally we can wake up parent and return this mm to him. 802 * Also kthread_stop() uses this completion for synchronization. 803 */ 804 if (tsk->vfork_done) 805 complete_vfork_done(tsk); 806 } 807 808 /* 809 * Allocate a new mm structure and copy contents from the 810 * mm structure of the passed in task structure. 811 */ 812 static struct mm_struct *dup_mm(struct task_struct *tsk) 813 { 814 struct mm_struct *mm, *oldmm = current->mm; 815 int err; 816 817 mm = allocate_mm(); 818 if (!mm) 819 goto fail_nomem; 820 821 memcpy(mm, oldmm, sizeof(*mm)); 822 mm_init_cpumask(mm); 823 824 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 825 mm->pmd_huge_pte = NULL; 826 #endif 827 if (!mm_init(mm, tsk)) 828 goto fail_nomem; 829 830 if (init_new_context(tsk, mm)) 831 goto fail_nocontext; 832 833 dup_mm_exe_file(oldmm, mm); 834 835 err = dup_mmap(mm, oldmm); 836 if (err) 837 goto free_pt; 838 839 mm->hiwater_rss = get_mm_rss(mm); 840 mm->hiwater_vm = mm->total_vm; 841 842 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 843 goto free_pt; 844 845 return mm; 846 847 free_pt: 848 /* don't put binfmt in mmput, we haven't got module yet */ 849 mm->binfmt = NULL; 850 mmput(mm); 851 852 fail_nomem: 853 return NULL; 854 855 fail_nocontext: 856 /* 857 * If init_new_context() failed, we cannot use mmput() to free the mm 858 * because it calls destroy_context() 859 */ 860 mm_free_pgd(mm); 861 free_mm(mm); 862 return NULL; 863 } 864 865 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 866 { 867 struct mm_struct *mm, *oldmm; 868 int retval; 869 870 tsk->min_flt = tsk->maj_flt = 0; 871 tsk->nvcsw = tsk->nivcsw = 0; 872 #ifdef CONFIG_DETECT_HUNG_TASK 873 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 874 #endif 875 876 tsk->mm = NULL; 877 tsk->active_mm = NULL; 878 879 /* 880 * Are we cloning a kernel thread? 881 * 882 * We need to steal a active VM for that.. 883 */ 884 oldmm = current->mm; 885 if (!oldmm) 886 return 0; 887 888 /* initialize the new vmacache entries */ 889 vmacache_flush(tsk); 890 891 if (clone_flags & CLONE_VM) { 892 atomic_inc(&oldmm->mm_users); 893 mm = oldmm; 894 goto good_mm; 895 } 896 897 retval = -ENOMEM; 898 mm = dup_mm(tsk); 899 if (!mm) 900 goto fail_nomem; 901 902 good_mm: 903 tsk->mm = mm; 904 tsk->active_mm = mm; 905 return 0; 906 907 fail_nomem: 908 return retval; 909 } 910 911 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 912 { 913 struct fs_struct *fs = current->fs; 914 if (clone_flags & CLONE_FS) { 915 /* tsk->fs is already what we want */ 916 spin_lock(&fs->lock); 917 if (fs->in_exec) { 918 spin_unlock(&fs->lock); 919 return -EAGAIN; 920 } 921 fs->users++; 922 spin_unlock(&fs->lock); 923 return 0; 924 } 925 tsk->fs = copy_fs_struct(fs); 926 if (!tsk->fs) 927 return -ENOMEM; 928 return 0; 929 } 930 931 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 932 { 933 struct files_struct *oldf, *newf; 934 int error = 0; 935 936 /* 937 * A background process may not have any files ... 938 */ 939 oldf = current->files; 940 if (!oldf) 941 goto out; 942 943 if (clone_flags & CLONE_FILES) { 944 atomic_inc(&oldf->count); 945 goto out; 946 } 947 948 newf = dup_fd(oldf, &error); 949 if (!newf) 950 goto out; 951 952 tsk->files = newf; 953 error = 0; 954 out: 955 return error; 956 } 957 958 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 959 { 960 #ifdef CONFIG_BLOCK 961 struct io_context *ioc = current->io_context; 962 struct io_context *new_ioc; 963 964 if (!ioc) 965 return 0; 966 /* 967 * Share io context with parent, if CLONE_IO is set 968 */ 969 if (clone_flags & CLONE_IO) { 970 ioc_task_link(ioc); 971 tsk->io_context = ioc; 972 } else if (ioprio_valid(ioc->ioprio)) { 973 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 974 if (unlikely(!new_ioc)) 975 return -ENOMEM; 976 977 new_ioc->ioprio = ioc->ioprio; 978 put_io_context(new_ioc); 979 } 980 #endif 981 return 0; 982 } 983 984 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 985 { 986 struct sighand_struct *sig; 987 988 if (clone_flags & CLONE_SIGHAND) { 989 atomic_inc(¤t->sighand->count); 990 return 0; 991 } 992 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 993 rcu_assign_pointer(tsk->sighand, sig); 994 if (!sig) 995 return -ENOMEM; 996 atomic_set(&sig->count, 1); 997 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 998 return 0; 999 } 1000 1001 void __cleanup_sighand(struct sighand_struct *sighand) 1002 { 1003 if (atomic_dec_and_test(&sighand->count)) { 1004 signalfd_cleanup(sighand); 1005 kmem_cache_free(sighand_cachep, sighand); 1006 } 1007 } 1008 1009 1010 /* 1011 * Initialize POSIX timer handling for a thread group. 1012 */ 1013 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1014 { 1015 unsigned long cpu_limit; 1016 1017 /* Thread group counters. */ 1018 thread_group_cputime_init(sig); 1019 1020 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1021 if (cpu_limit != RLIM_INFINITY) { 1022 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1023 sig->cputimer.running = 1; 1024 } 1025 1026 /* The timer lists. */ 1027 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1028 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1029 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1030 } 1031 1032 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1033 { 1034 struct signal_struct *sig; 1035 1036 if (clone_flags & CLONE_THREAD) 1037 return 0; 1038 1039 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1040 tsk->signal = sig; 1041 if (!sig) 1042 return -ENOMEM; 1043 1044 sig->nr_threads = 1; 1045 atomic_set(&sig->live, 1); 1046 atomic_set(&sig->sigcnt, 1); 1047 1048 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1049 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1050 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1051 1052 init_waitqueue_head(&sig->wait_chldexit); 1053 sig->curr_target = tsk; 1054 init_sigpending(&sig->shared_pending); 1055 INIT_LIST_HEAD(&sig->posix_timers); 1056 1057 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1058 sig->real_timer.function = it_real_fn; 1059 1060 task_lock(current->group_leader); 1061 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1062 task_unlock(current->group_leader); 1063 1064 posix_cpu_timers_init_group(sig); 1065 1066 tty_audit_fork(sig); 1067 sched_autogroup_fork(sig); 1068 1069 #ifdef CONFIG_CGROUPS 1070 init_rwsem(&sig->group_rwsem); 1071 #endif 1072 1073 sig->oom_score_adj = current->signal->oom_score_adj; 1074 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1075 1076 sig->has_child_subreaper = current->signal->has_child_subreaper || 1077 current->signal->is_child_subreaper; 1078 1079 mutex_init(&sig->cred_guard_mutex); 1080 1081 return 0; 1082 } 1083 1084 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1085 { 1086 current->clear_child_tid = tidptr; 1087 1088 return task_pid_vnr(current); 1089 } 1090 1091 static void rt_mutex_init_task(struct task_struct *p) 1092 { 1093 raw_spin_lock_init(&p->pi_lock); 1094 #ifdef CONFIG_RT_MUTEXES 1095 p->pi_waiters = RB_ROOT; 1096 p->pi_waiters_leftmost = NULL; 1097 p->pi_blocked_on = NULL; 1098 p->pi_top_task = NULL; 1099 #endif 1100 } 1101 1102 #ifdef CONFIG_MEMCG 1103 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1104 { 1105 mm->owner = p; 1106 } 1107 #endif /* CONFIG_MEMCG */ 1108 1109 /* 1110 * Initialize POSIX timer handling for a single task. 1111 */ 1112 static void posix_cpu_timers_init(struct task_struct *tsk) 1113 { 1114 tsk->cputime_expires.prof_exp = 0; 1115 tsk->cputime_expires.virt_exp = 0; 1116 tsk->cputime_expires.sched_exp = 0; 1117 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1118 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1119 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1120 } 1121 1122 static inline void 1123 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1124 { 1125 task->pids[type].pid = pid; 1126 } 1127 1128 /* 1129 * This creates a new process as a copy of the old one, 1130 * but does not actually start it yet. 1131 * 1132 * It copies the registers, and all the appropriate 1133 * parts of the process environment (as per the clone 1134 * flags). The actual kick-off is left to the caller. 1135 */ 1136 static struct task_struct *copy_process(unsigned long clone_flags, 1137 unsigned long stack_start, 1138 unsigned long stack_size, 1139 int __user *child_tidptr, 1140 struct pid *pid, 1141 int trace) 1142 { 1143 int retval; 1144 struct task_struct *p; 1145 1146 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1147 return ERR_PTR(-EINVAL); 1148 1149 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1150 return ERR_PTR(-EINVAL); 1151 1152 /* 1153 * Thread groups must share signals as well, and detached threads 1154 * can only be started up within the thread group. 1155 */ 1156 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1157 return ERR_PTR(-EINVAL); 1158 1159 /* 1160 * Shared signal handlers imply shared VM. By way of the above, 1161 * thread groups also imply shared VM. Blocking this case allows 1162 * for various simplifications in other code. 1163 */ 1164 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1165 return ERR_PTR(-EINVAL); 1166 1167 /* 1168 * Siblings of global init remain as zombies on exit since they are 1169 * not reaped by their parent (swapper). To solve this and to avoid 1170 * multi-rooted process trees, prevent global and container-inits 1171 * from creating siblings. 1172 */ 1173 if ((clone_flags & CLONE_PARENT) && 1174 current->signal->flags & SIGNAL_UNKILLABLE) 1175 return ERR_PTR(-EINVAL); 1176 1177 /* 1178 * If the new process will be in a different pid or user namespace 1179 * do not allow it to share a thread group or signal handlers or 1180 * parent with the forking task. 1181 */ 1182 if (clone_flags & CLONE_SIGHAND) { 1183 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1184 (task_active_pid_ns(current) != 1185 current->nsproxy->pid_ns_for_children)) 1186 return ERR_PTR(-EINVAL); 1187 } 1188 1189 retval = security_task_create(clone_flags); 1190 if (retval) 1191 goto fork_out; 1192 1193 retval = -ENOMEM; 1194 p = dup_task_struct(current); 1195 if (!p) 1196 goto fork_out; 1197 1198 ftrace_graph_init_task(p); 1199 get_seccomp_filter(p); 1200 1201 rt_mutex_init_task(p); 1202 1203 #ifdef CONFIG_PROVE_LOCKING 1204 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1205 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1206 #endif 1207 retval = -EAGAIN; 1208 if (atomic_read(&p->real_cred->user->processes) >= 1209 task_rlimit(p, RLIMIT_NPROC)) { 1210 if (p->real_cred->user != INIT_USER && 1211 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1212 goto bad_fork_free; 1213 } 1214 current->flags &= ~PF_NPROC_EXCEEDED; 1215 1216 retval = copy_creds(p, clone_flags); 1217 if (retval < 0) 1218 goto bad_fork_free; 1219 1220 /* 1221 * If multiple threads are within copy_process(), then this check 1222 * triggers too late. This doesn't hurt, the check is only there 1223 * to stop root fork bombs. 1224 */ 1225 retval = -EAGAIN; 1226 if (nr_threads >= max_threads) 1227 goto bad_fork_cleanup_count; 1228 1229 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1230 goto bad_fork_cleanup_count; 1231 1232 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1233 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1234 p->flags |= PF_FORKNOEXEC; 1235 INIT_LIST_HEAD(&p->children); 1236 INIT_LIST_HEAD(&p->sibling); 1237 rcu_copy_process(p); 1238 p->vfork_done = NULL; 1239 spin_lock_init(&p->alloc_lock); 1240 1241 init_sigpending(&p->pending); 1242 1243 p->utime = p->stime = p->gtime = 0; 1244 p->utimescaled = p->stimescaled = 0; 1245 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1246 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1247 #endif 1248 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1249 seqlock_init(&p->vtime_seqlock); 1250 p->vtime_snap = 0; 1251 p->vtime_snap_whence = VTIME_SLEEPING; 1252 #endif 1253 1254 #if defined(SPLIT_RSS_COUNTING) 1255 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1256 #endif 1257 1258 p->default_timer_slack_ns = current->timer_slack_ns; 1259 1260 task_io_accounting_init(&p->ioac); 1261 acct_clear_integrals(p); 1262 1263 posix_cpu_timers_init(p); 1264 1265 do_posix_clock_monotonic_gettime(&p->start_time); 1266 p->real_start_time = p->start_time; 1267 monotonic_to_bootbased(&p->real_start_time); 1268 p->io_context = NULL; 1269 p->audit_context = NULL; 1270 if (clone_flags & CLONE_THREAD) 1271 threadgroup_change_begin(current); 1272 cgroup_fork(p); 1273 #ifdef CONFIG_NUMA 1274 p->mempolicy = mpol_dup(p->mempolicy); 1275 if (IS_ERR(p->mempolicy)) { 1276 retval = PTR_ERR(p->mempolicy); 1277 p->mempolicy = NULL; 1278 goto bad_fork_cleanup_threadgroup_lock; 1279 } 1280 #endif 1281 #ifdef CONFIG_CPUSETS 1282 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1283 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1284 seqcount_init(&p->mems_allowed_seq); 1285 #endif 1286 #ifdef CONFIG_TRACE_IRQFLAGS 1287 p->irq_events = 0; 1288 p->hardirqs_enabled = 0; 1289 p->hardirq_enable_ip = 0; 1290 p->hardirq_enable_event = 0; 1291 p->hardirq_disable_ip = _THIS_IP_; 1292 p->hardirq_disable_event = 0; 1293 p->softirqs_enabled = 1; 1294 p->softirq_enable_ip = _THIS_IP_; 1295 p->softirq_enable_event = 0; 1296 p->softirq_disable_ip = 0; 1297 p->softirq_disable_event = 0; 1298 p->hardirq_context = 0; 1299 p->softirq_context = 0; 1300 #endif 1301 #ifdef CONFIG_LOCKDEP 1302 p->lockdep_depth = 0; /* no locks held yet */ 1303 p->curr_chain_key = 0; 1304 p->lockdep_recursion = 0; 1305 #endif 1306 1307 #ifdef CONFIG_DEBUG_MUTEXES 1308 p->blocked_on = NULL; /* not blocked yet */ 1309 #endif 1310 #ifdef CONFIG_MEMCG 1311 p->memcg_batch.do_batch = 0; 1312 p->memcg_batch.memcg = NULL; 1313 #endif 1314 #ifdef CONFIG_BCACHE 1315 p->sequential_io = 0; 1316 p->sequential_io_avg = 0; 1317 #endif 1318 1319 /* Perform scheduler related setup. Assign this task to a CPU. */ 1320 retval = sched_fork(clone_flags, p); 1321 if (retval) 1322 goto bad_fork_cleanup_policy; 1323 1324 retval = perf_event_init_task(p); 1325 if (retval) 1326 goto bad_fork_cleanup_policy; 1327 retval = audit_alloc(p); 1328 if (retval) 1329 goto bad_fork_cleanup_policy; 1330 /* copy all the process information */ 1331 retval = copy_semundo(clone_flags, p); 1332 if (retval) 1333 goto bad_fork_cleanup_audit; 1334 retval = copy_files(clone_flags, p); 1335 if (retval) 1336 goto bad_fork_cleanup_semundo; 1337 retval = copy_fs(clone_flags, p); 1338 if (retval) 1339 goto bad_fork_cleanup_files; 1340 retval = copy_sighand(clone_flags, p); 1341 if (retval) 1342 goto bad_fork_cleanup_fs; 1343 retval = copy_signal(clone_flags, p); 1344 if (retval) 1345 goto bad_fork_cleanup_sighand; 1346 retval = copy_mm(clone_flags, p); 1347 if (retval) 1348 goto bad_fork_cleanup_signal; 1349 retval = copy_namespaces(clone_flags, p); 1350 if (retval) 1351 goto bad_fork_cleanup_mm; 1352 retval = copy_io(clone_flags, p); 1353 if (retval) 1354 goto bad_fork_cleanup_namespaces; 1355 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1356 if (retval) 1357 goto bad_fork_cleanup_io; 1358 1359 if (pid != &init_struct_pid) { 1360 retval = -ENOMEM; 1361 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1362 if (!pid) 1363 goto bad_fork_cleanup_io; 1364 } 1365 1366 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1367 /* 1368 * Clear TID on mm_release()? 1369 */ 1370 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1371 #ifdef CONFIG_BLOCK 1372 p->plug = NULL; 1373 #endif 1374 #ifdef CONFIG_FUTEX 1375 p->robust_list = NULL; 1376 #ifdef CONFIG_COMPAT 1377 p->compat_robust_list = NULL; 1378 #endif 1379 INIT_LIST_HEAD(&p->pi_state_list); 1380 p->pi_state_cache = NULL; 1381 #endif 1382 /* 1383 * sigaltstack should be cleared when sharing the same VM 1384 */ 1385 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1386 p->sas_ss_sp = p->sas_ss_size = 0; 1387 1388 /* 1389 * Syscall tracing and stepping should be turned off in the 1390 * child regardless of CLONE_PTRACE. 1391 */ 1392 user_disable_single_step(p); 1393 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1394 #ifdef TIF_SYSCALL_EMU 1395 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1396 #endif 1397 clear_all_latency_tracing(p); 1398 1399 /* ok, now we should be set up.. */ 1400 p->pid = pid_nr(pid); 1401 if (clone_flags & CLONE_THREAD) { 1402 p->exit_signal = -1; 1403 p->group_leader = current->group_leader; 1404 p->tgid = current->tgid; 1405 } else { 1406 if (clone_flags & CLONE_PARENT) 1407 p->exit_signal = current->group_leader->exit_signal; 1408 else 1409 p->exit_signal = (clone_flags & CSIGNAL); 1410 p->group_leader = p; 1411 p->tgid = p->pid; 1412 } 1413 1414 p->nr_dirtied = 0; 1415 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1416 p->dirty_paused_when = 0; 1417 1418 p->pdeath_signal = 0; 1419 INIT_LIST_HEAD(&p->thread_group); 1420 p->task_works = NULL; 1421 1422 /* 1423 * Make it visible to the rest of the system, but dont wake it up yet. 1424 * Need tasklist lock for parent etc handling! 1425 */ 1426 write_lock_irq(&tasklist_lock); 1427 1428 /* CLONE_PARENT re-uses the old parent */ 1429 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1430 p->real_parent = current->real_parent; 1431 p->parent_exec_id = current->parent_exec_id; 1432 } else { 1433 p->real_parent = current; 1434 p->parent_exec_id = current->self_exec_id; 1435 } 1436 1437 spin_lock(¤t->sighand->siglock); 1438 1439 /* 1440 * Process group and session signals need to be delivered to just the 1441 * parent before the fork or both the parent and the child after the 1442 * fork. Restart if a signal comes in before we add the new process to 1443 * it's process group. 1444 * A fatal signal pending means that current will exit, so the new 1445 * thread can't slip out of an OOM kill (or normal SIGKILL). 1446 */ 1447 recalc_sigpending(); 1448 if (signal_pending(current)) { 1449 spin_unlock(¤t->sighand->siglock); 1450 write_unlock_irq(&tasklist_lock); 1451 retval = -ERESTARTNOINTR; 1452 goto bad_fork_free_pid; 1453 } 1454 1455 if (likely(p->pid)) { 1456 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1457 1458 init_task_pid(p, PIDTYPE_PID, pid); 1459 if (thread_group_leader(p)) { 1460 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1461 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1462 1463 if (is_child_reaper(pid)) { 1464 ns_of_pid(pid)->child_reaper = p; 1465 p->signal->flags |= SIGNAL_UNKILLABLE; 1466 } 1467 1468 p->signal->leader_pid = pid; 1469 p->signal->tty = tty_kref_get(current->signal->tty); 1470 list_add_tail(&p->sibling, &p->real_parent->children); 1471 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1472 attach_pid(p, PIDTYPE_PGID); 1473 attach_pid(p, PIDTYPE_SID); 1474 __this_cpu_inc(process_counts); 1475 } else { 1476 current->signal->nr_threads++; 1477 atomic_inc(¤t->signal->live); 1478 atomic_inc(¤t->signal->sigcnt); 1479 list_add_tail_rcu(&p->thread_group, 1480 &p->group_leader->thread_group); 1481 list_add_tail_rcu(&p->thread_node, 1482 &p->signal->thread_head); 1483 } 1484 attach_pid(p, PIDTYPE_PID); 1485 nr_threads++; 1486 } 1487 1488 total_forks++; 1489 spin_unlock(¤t->sighand->siglock); 1490 write_unlock_irq(&tasklist_lock); 1491 proc_fork_connector(p); 1492 cgroup_post_fork(p); 1493 if (clone_flags & CLONE_THREAD) 1494 threadgroup_change_end(current); 1495 perf_event_fork(p); 1496 1497 trace_task_newtask(p, clone_flags); 1498 uprobe_copy_process(p, clone_flags); 1499 1500 return p; 1501 1502 bad_fork_free_pid: 1503 if (pid != &init_struct_pid) 1504 free_pid(pid); 1505 bad_fork_cleanup_io: 1506 if (p->io_context) 1507 exit_io_context(p); 1508 bad_fork_cleanup_namespaces: 1509 exit_task_namespaces(p); 1510 bad_fork_cleanup_mm: 1511 if (p->mm) 1512 mmput(p->mm); 1513 bad_fork_cleanup_signal: 1514 if (!(clone_flags & CLONE_THREAD)) 1515 free_signal_struct(p->signal); 1516 bad_fork_cleanup_sighand: 1517 __cleanup_sighand(p->sighand); 1518 bad_fork_cleanup_fs: 1519 exit_fs(p); /* blocking */ 1520 bad_fork_cleanup_files: 1521 exit_files(p); /* blocking */ 1522 bad_fork_cleanup_semundo: 1523 exit_sem(p); 1524 bad_fork_cleanup_audit: 1525 audit_free(p); 1526 bad_fork_cleanup_policy: 1527 perf_event_free_task(p); 1528 #ifdef CONFIG_NUMA 1529 mpol_put(p->mempolicy); 1530 bad_fork_cleanup_threadgroup_lock: 1531 #endif 1532 if (clone_flags & CLONE_THREAD) 1533 threadgroup_change_end(current); 1534 delayacct_tsk_free(p); 1535 module_put(task_thread_info(p)->exec_domain->module); 1536 bad_fork_cleanup_count: 1537 atomic_dec(&p->cred->user->processes); 1538 exit_creds(p); 1539 bad_fork_free: 1540 free_task(p); 1541 fork_out: 1542 return ERR_PTR(retval); 1543 } 1544 1545 static inline void init_idle_pids(struct pid_link *links) 1546 { 1547 enum pid_type type; 1548 1549 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1550 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1551 links[type].pid = &init_struct_pid; 1552 } 1553 } 1554 1555 struct task_struct *fork_idle(int cpu) 1556 { 1557 struct task_struct *task; 1558 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1559 if (!IS_ERR(task)) { 1560 init_idle_pids(task->pids); 1561 init_idle(task, cpu); 1562 } 1563 1564 return task; 1565 } 1566 1567 /* 1568 * Ok, this is the main fork-routine. 1569 * 1570 * It copies the process, and if successful kick-starts 1571 * it and waits for it to finish using the VM if required. 1572 */ 1573 long do_fork(unsigned long clone_flags, 1574 unsigned long stack_start, 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 * Determine whether and which event to report to ptracer. When 1585 * called from kernel_thread or CLONE_UNTRACED is explicitly 1586 * requested, no event is reported; otherwise, report if the event 1587 * for the type of forking is enabled. 1588 */ 1589 if (!(clone_flags & CLONE_UNTRACED)) { 1590 if (clone_flags & CLONE_VFORK) 1591 trace = PTRACE_EVENT_VFORK; 1592 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1593 trace = PTRACE_EVENT_CLONE; 1594 else 1595 trace = PTRACE_EVENT_FORK; 1596 1597 if (likely(!ptrace_event_enabled(current, trace))) 1598 trace = 0; 1599 } 1600 1601 p = copy_process(clone_flags, stack_start, stack_size, 1602 child_tidptr, NULL, trace); 1603 /* 1604 * Do this prior waking up the new thread - the thread pointer 1605 * might get invalid after that point, if the thread exits quickly. 1606 */ 1607 if (!IS_ERR(p)) { 1608 struct completion vfork; 1609 struct pid *pid; 1610 1611 trace_sched_process_fork(current, p); 1612 1613 pid = get_task_pid(p, PIDTYPE_PID); 1614 nr = pid_vnr(pid); 1615 1616 if (clone_flags & CLONE_PARENT_SETTID) 1617 put_user(nr, parent_tidptr); 1618 1619 if (clone_flags & CLONE_VFORK) { 1620 p->vfork_done = &vfork; 1621 init_completion(&vfork); 1622 get_task_struct(p); 1623 } 1624 1625 wake_up_new_task(p); 1626 1627 /* forking complete and child started to run, tell ptracer */ 1628 if (unlikely(trace)) 1629 ptrace_event_pid(trace, pid); 1630 1631 if (clone_flags & CLONE_VFORK) { 1632 if (!wait_for_vfork_done(p, &vfork)) 1633 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1634 } 1635 1636 put_pid(pid); 1637 } else { 1638 nr = PTR_ERR(p); 1639 } 1640 return nr; 1641 } 1642 1643 /* 1644 * Create a kernel thread. 1645 */ 1646 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1647 { 1648 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1649 (unsigned long)arg, NULL, NULL); 1650 } 1651 1652 #ifdef __ARCH_WANT_SYS_FORK 1653 SYSCALL_DEFINE0(fork) 1654 { 1655 #ifdef CONFIG_MMU 1656 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1657 #else 1658 /* can not support in nommu mode */ 1659 return -EINVAL; 1660 #endif 1661 } 1662 #endif 1663 1664 #ifdef __ARCH_WANT_SYS_VFORK 1665 SYSCALL_DEFINE0(vfork) 1666 { 1667 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1668 0, NULL, NULL); 1669 } 1670 #endif 1671 1672 #ifdef __ARCH_WANT_SYS_CLONE 1673 #ifdef CONFIG_CLONE_BACKWARDS 1674 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1675 int __user *, parent_tidptr, 1676 int, tls_val, 1677 int __user *, child_tidptr) 1678 #elif defined(CONFIG_CLONE_BACKWARDS2) 1679 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1680 int __user *, parent_tidptr, 1681 int __user *, child_tidptr, 1682 int, tls_val) 1683 #elif defined(CONFIG_CLONE_BACKWARDS3) 1684 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1685 int, stack_size, 1686 int __user *, parent_tidptr, 1687 int __user *, child_tidptr, 1688 int, tls_val) 1689 #else 1690 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1691 int __user *, parent_tidptr, 1692 int __user *, child_tidptr, 1693 int, tls_val) 1694 #endif 1695 { 1696 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1697 } 1698 #endif 1699 1700 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1701 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1702 #endif 1703 1704 static void sighand_ctor(void *data) 1705 { 1706 struct sighand_struct *sighand = data; 1707 1708 spin_lock_init(&sighand->siglock); 1709 init_waitqueue_head(&sighand->signalfd_wqh); 1710 } 1711 1712 void __init proc_caches_init(void) 1713 { 1714 sighand_cachep = kmem_cache_create("sighand_cache", 1715 sizeof(struct sighand_struct), 0, 1716 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1717 SLAB_NOTRACK, sighand_ctor); 1718 signal_cachep = kmem_cache_create("signal_cache", 1719 sizeof(struct signal_struct), 0, 1720 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1721 files_cachep = kmem_cache_create("files_cache", 1722 sizeof(struct files_struct), 0, 1723 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1724 fs_cachep = kmem_cache_create("fs_cache", 1725 sizeof(struct fs_struct), 0, 1726 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1727 /* 1728 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1729 * whole struct cpumask for the OFFSTACK case. We could change 1730 * this to *only* allocate as much of it as required by the 1731 * maximum number of CPU's we can ever have. The cpumask_allocation 1732 * is at the end of the structure, exactly for that reason. 1733 */ 1734 mm_cachep = kmem_cache_create("mm_struct", 1735 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1736 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1737 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1738 mmap_init(); 1739 nsproxy_cache_init(); 1740 } 1741 1742 /* 1743 * Check constraints on flags passed to the unshare system call. 1744 */ 1745 static int check_unshare_flags(unsigned long unshare_flags) 1746 { 1747 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1748 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1749 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1750 CLONE_NEWUSER|CLONE_NEWPID)) 1751 return -EINVAL; 1752 /* 1753 * Not implemented, but pretend it works if there is nothing to 1754 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1755 * needs to unshare vm. 1756 */ 1757 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1758 /* FIXME: get_task_mm() increments ->mm_users */ 1759 if (atomic_read(¤t->mm->mm_users) > 1) 1760 return -EINVAL; 1761 } 1762 1763 return 0; 1764 } 1765 1766 /* 1767 * Unshare the filesystem structure if it is being shared 1768 */ 1769 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1770 { 1771 struct fs_struct *fs = current->fs; 1772 1773 if (!(unshare_flags & CLONE_FS) || !fs) 1774 return 0; 1775 1776 /* don't need lock here; in the worst case we'll do useless copy */ 1777 if (fs->users == 1) 1778 return 0; 1779 1780 *new_fsp = copy_fs_struct(fs); 1781 if (!*new_fsp) 1782 return -ENOMEM; 1783 1784 return 0; 1785 } 1786 1787 /* 1788 * Unshare file descriptor table if it is being shared 1789 */ 1790 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1791 { 1792 struct files_struct *fd = current->files; 1793 int error = 0; 1794 1795 if ((unshare_flags & CLONE_FILES) && 1796 (fd && atomic_read(&fd->count) > 1)) { 1797 *new_fdp = dup_fd(fd, &error); 1798 if (!*new_fdp) 1799 return error; 1800 } 1801 1802 return 0; 1803 } 1804 1805 /* 1806 * unshare allows a process to 'unshare' part of the process 1807 * context which was originally shared using clone. copy_* 1808 * functions used by do_fork() cannot be used here directly 1809 * because they modify an inactive task_struct that is being 1810 * constructed. Here we are modifying the current, active, 1811 * task_struct. 1812 */ 1813 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1814 { 1815 struct fs_struct *fs, *new_fs = NULL; 1816 struct files_struct *fd, *new_fd = NULL; 1817 struct cred *new_cred = NULL; 1818 struct nsproxy *new_nsproxy = NULL; 1819 int do_sysvsem = 0; 1820 int err; 1821 1822 /* 1823 * If unsharing a user namespace must also unshare the thread. 1824 */ 1825 if (unshare_flags & CLONE_NEWUSER) 1826 unshare_flags |= CLONE_THREAD | CLONE_FS; 1827 /* 1828 * If unsharing a thread from a thread group, must also unshare vm. 1829 */ 1830 if (unshare_flags & CLONE_THREAD) 1831 unshare_flags |= CLONE_VM; 1832 /* 1833 * If unsharing vm, must also unshare signal handlers. 1834 */ 1835 if (unshare_flags & CLONE_VM) 1836 unshare_flags |= CLONE_SIGHAND; 1837 /* 1838 * If unsharing namespace, must also unshare filesystem information. 1839 */ 1840 if (unshare_flags & CLONE_NEWNS) 1841 unshare_flags |= CLONE_FS; 1842 1843 err = check_unshare_flags(unshare_flags); 1844 if (err) 1845 goto bad_unshare_out; 1846 /* 1847 * CLONE_NEWIPC must also detach from the undolist: after switching 1848 * to a new ipc namespace, the semaphore arrays from the old 1849 * namespace are unreachable. 1850 */ 1851 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1852 do_sysvsem = 1; 1853 err = unshare_fs(unshare_flags, &new_fs); 1854 if (err) 1855 goto bad_unshare_out; 1856 err = unshare_fd(unshare_flags, &new_fd); 1857 if (err) 1858 goto bad_unshare_cleanup_fs; 1859 err = unshare_userns(unshare_flags, &new_cred); 1860 if (err) 1861 goto bad_unshare_cleanup_fd; 1862 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1863 new_cred, new_fs); 1864 if (err) 1865 goto bad_unshare_cleanup_cred; 1866 1867 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1868 if (do_sysvsem) { 1869 /* 1870 * CLONE_SYSVSEM is equivalent to sys_exit(). 1871 */ 1872 exit_sem(current); 1873 } 1874 1875 if (new_nsproxy) 1876 switch_task_namespaces(current, new_nsproxy); 1877 1878 task_lock(current); 1879 1880 if (new_fs) { 1881 fs = current->fs; 1882 spin_lock(&fs->lock); 1883 current->fs = new_fs; 1884 if (--fs->users) 1885 new_fs = NULL; 1886 else 1887 new_fs = fs; 1888 spin_unlock(&fs->lock); 1889 } 1890 1891 if (new_fd) { 1892 fd = current->files; 1893 current->files = new_fd; 1894 new_fd = fd; 1895 } 1896 1897 task_unlock(current); 1898 1899 if (new_cred) { 1900 /* Install the new user namespace */ 1901 commit_creds(new_cred); 1902 new_cred = NULL; 1903 } 1904 } 1905 1906 bad_unshare_cleanup_cred: 1907 if (new_cred) 1908 put_cred(new_cred); 1909 bad_unshare_cleanup_fd: 1910 if (new_fd) 1911 put_files_struct(new_fd); 1912 1913 bad_unshare_cleanup_fs: 1914 if (new_fs) 1915 free_fs_struct(new_fs); 1916 1917 bad_unshare_out: 1918 return err; 1919 } 1920 1921 /* 1922 * Helper to unshare the files of the current task. 1923 * We don't want to expose copy_files internals to 1924 * the exec layer of the kernel. 1925 */ 1926 1927 int unshare_files(struct files_struct **displaced) 1928 { 1929 struct task_struct *task = current; 1930 struct files_struct *copy = NULL; 1931 int error; 1932 1933 error = unshare_fd(CLONE_FILES, ©); 1934 if (error || !copy) { 1935 *displaced = NULL; 1936 return error; 1937 } 1938 *displaced = task->files; 1939 task_lock(task); 1940 task->files = copy; 1941 task_unlock(task); 1942 return 0; 1943 } 1944