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 task_numa_free(tsk); 241 security_task_free(tsk); 242 exit_creds(tsk); 243 delayacct_tsk_free(tsk); 244 put_signal_struct(tsk->signal); 245 246 if (!profile_handoff_task(tsk)) 247 free_task(tsk); 248 } 249 EXPORT_SYMBOL_GPL(__put_task_struct); 250 251 void __init __weak arch_task_cache_init(void) { } 252 253 void __init fork_init(unsigned long mempages) 254 { 255 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 256 #ifndef ARCH_MIN_TASKALIGN 257 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 258 #endif 259 /* create a slab on which task_structs can be allocated */ 260 task_struct_cachep = 261 kmem_cache_create("task_struct", sizeof(struct task_struct), 262 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 263 #endif 264 265 /* do the arch specific task caches init */ 266 arch_task_cache_init(); 267 268 /* 269 * The default maximum number of threads is set to a safe 270 * value: the thread structures can take up at most half 271 * of memory. 272 */ 273 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 274 275 /* 276 * we need to allow at least 20 threads to boot a system 277 */ 278 if (max_threads < 20) 279 max_threads = 20; 280 281 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 282 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 283 init_task.signal->rlim[RLIMIT_SIGPENDING] = 284 init_task.signal->rlim[RLIMIT_NPROC]; 285 } 286 287 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 288 struct task_struct *src) 289 { 290 *dst = *src; 291 return 0; 292 } 293 294 static struct task_struct *dup_task_struct(struct task_struct *orig) 295 { 296 struct task_struct *tsk; 297 struct thread_info *ti; 298 unsigned long *stackend; 299 int node = tsk_fork_get_node(orig); 300 int err; 301 302 tsk = alloc_task_struct_node(node); 303 if (!tsk) 304 return NULL; 305 306 ti = alloc_thread_info_node(tsk, node); 307 if (!ti) 308 goto free_tsk; 309 310 err = arch_dup_task_struct(tsk, orig); 311 if (err) 312 goto free_ti; 313 314 tsk->stack = ti; 315 316 setup_thread_stack(tsk, orig); 317 clear_user_return_notifier(tsk); 318 clear_tsk_need_resched(tsk); 319 stackend = end_of_stack(tsk); 320 *stackend = STACK_END_MAGIC; /* for overflow detection */ 321 322 #ifdef CONFIG_CC_STACKPROTECTOR 323 tsk->stack_canary = get_random_int(); 324 #endif 325 326 /* 327 * One for us, one for whoever does the "release_task()" (usually 328 * parent) 329 */ 330 atomic_set(&tsk->usage, 2); 331 #ifdef CONFIG_BLK_DEV_IO_TRACE 332 tsk->btrace_seq = 0; 333 #endif 334 tsk->splice_pipe = NULL; 335 tsk->task_frag.page = NULL; 336 337 account_kernel_stack(ti, 1); 338 339 return tsk; 340 341 free_ti: 342 free_thread_info(ti); 343 free_tsk: 344 free_task_struct(tsk); 345 return NULL; 346 } 347 348 #ifdef CONFIG_MMU 349 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 350 { 351 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 352 struct rb_node **rb_link, *rb_parent; 353 int retval; 354 unsigned long charge; 355 356 uprobe_start_dup_mmap(); 357 down_write(&oldmm->mmap_sem); 358 flush_cache_dup_mm(oldmm); 359 uprobe_dup_mmap(oldmm, mm); 360 /* 361 * Not linked in yet - no deadlock potential: 362 */ 363 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 364 365 mm->locked_vm = 0; 366 mm->mmap = NULL; 367 mm->mmap_cache = NULL; 368 mm->map_count = 0; 369 cpumask_clear(mm_cpumask(mm)); 370 mm->mm_rb = RB_ROOT; 371 rb_link = &mm->mm_rb.rb_node; 372 rb_parent = NULL; 373 pprev = &mm->mmap; 374 retval = ksm_fork(mm, oldmm); 375 if (retval) 376 goto out; 377 retval = khugepaged_fork(mm, oldmm); 378 if (retval) 379 goto out; 380 381 prev = NULL; 382 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 383 struct file *file; 384 385 if (mpnt->vm_flags & VM_DONTCOPY) { 386 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 387 -vma_pages(mpnt)); 388 continue; 389 } 390 charge = 0; 391 if (mpnt->vm_flags & VM_ACCOUNT) { 392 unsigned long len = vma_pages(mpnt); 393 394 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 395 goto fail_nomem; 396 charge = len; 397 } 398 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 399 if (!tmp) 400 goto fail_nomem; 401 *tmp = *mpnt; 402 INIT_LIST_HEAD(&tmp->anon_vma_chain); 403 retval = vma_dup_policy(mpnt, tmp); 404 if (retval) 405 goto fail_nomem_policy; 406 tmp->vm_mm = mm; 407 if (anon_vma_fork(tmp, mpnt)) 408 goto fail_nomem_anon_vma_fork; 409 tmp->vm_flags &= ~VM_LOCKED; 410 tmp->vm_next = tmp->vm_prev = NULL; 411 file = tmp->vm_file; 412 if (file) { 413 struct inode *inode = file_inode(file); 414 struct address_space *mapping = file->f_mapping; 415 416 get_file(file); 417 if (tmp->vm_flags & VM_DENYWRITE) 418 atomic_dec(&inode->i_writecount); 419 mutex_lock(&mapping->i_mmap_mutex); 420 if (tmp->vm_flags & VM_SHARED) 421 mapping->i_mmap_writable++; 422 flush_dcache_mmap_lock(mapping); 423 /* insert tmp into the share list, just after mpnt */ 424 if (unlikely(tmp->vm_flags & VM_NONLINEAR)) 425 vma_nonlinear_insert(tmp, 426 &mapping->i_mmap_nonlinear); 427 else 428 vma_interval_tree_insert_after(tmp, mpnt, 429 &mapping->i_mmap); 430 flush_dcache_mmap_unlock(mapping); 431 mutex_unlock(&mapping->i_mmap_mutex); 432 } 433 434 /* 435 * Clear hugetlb-related page reserves for children. This only 436 * affects MAP_PRIVATE mappings. Faults generated by the child 437 * are not guaranteed to succeed, even if read-only 438 */ 439 if (is_vm_hugetlb_page(tmp)) 440 reset_vma_resv_huge_pages(tmp); 441 442 /* 443 * Link in the new vma and copy the page table entries. 444 */ 445 *pprev = tmp; 446 pprev = &tmp->vm_next; 447 tmp->vm_prev = prev; 448 prev = tmp; 449 450 __vma_link_rb(mm, tmp, rb_link, rb_parent); 451 rb_link = &tmp->vm_rb.rb_right; 452 rb_parent = &tmp->vm_rb; 453 454 mm->map_count++; 455 retval = copy_page_range(mm, oldmm, mpnt); 456 457 if (tmp->vm_ops && tmp->vm_ops->open) 458 tmp->vm_ops->open(tmp); 459 460 if (retval) 461 goto out; 462 } 463 /* a new mm has just been created */ 464 arch_dup_mmap(oldmm, mm); 465 retval = 0; 466 out: 467 up_write(&mm->mmap_sem); 468 flush_tlb_mm(oldmm); 469 up_write(&oldmm->mmap_sem); 470 uprobe_end_dup_mmap(); 471 return retval; 472 fail_nomem_anon_vma_fork: 473 mpol_put(vma_policy(tmp)); 474 fail_nomem_policy: 475 kmem_cache_free(vm_area_cachep, tmp); 476 fail_nomem: 477 retval = -ENOMEM; 478 vm_unacct_memory(charge); 479 goto out; 480 } 481 482 static inline int mm_alloc_pgd(struct mm_struct *mm) 483 { 484 mm->pgd = pgd_alloc(mm); 485 if (unlikely(!mm->pgd)) 486 return -ENOMEM; 487 return 0; 488 } 489 490 static inline void mm_free_pgd(struct mm_struct *mm) 491 { 492 pgd_free(mm, mm->pgd); 493 } 494 #else 495 #define dup_mmap(mm, oldmm) (0) 496 #define mm_alloc_pgd(mm) (0) 497 #define mm_free_pgd(mm) 498 #endif /* CONFIG_MMU */ 499 500 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 501 502 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 503 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 504 505 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 506 507 static int __init coredump_filter_setup(char *s) 508 { 509 default_dump_filter = 510 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 511 MMF_DUMP_FILTER_MASK; 512 return 1; 513 } 514 515 __setup("coredump_filter=", coredump_filter_setup); 516 517 #include <linux/init_task.h> 518 519 static void mm_init_aio(struct mm_struct *mm) 520 { 521 #ifdef CONFIG_AIO 522 spin_lock_init(&mm->ioctx_lock); 523 mm->ioctx_table = NULL; 524 #endif 525 } 526 527 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 528 { 529 atomic_set(&mm->mm_users, 1); 530 atomic_set(&mm->mm_count, 1); 531 init_rwsem(&mm->mmap_sem); 532 INIT_LIST_HEAD(&mm->mmlist); 533 mm->flags = (current->mm) ? 534 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 535 mm->core_state = NULL; 536 atomic_long_set(&mm->nr_ptes, 0); 537 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 538 spin_lock_init(&mm->page_table_lock); 539 mm_init_aio(mm); 540 mm_init_owner(mm, p); 541 clear_tlb_flush_pending(mm); 542 543 if (likely(!mm_alloc_pgd(mm))) { 544 mm->def_flags = 0; 545 mmu_notifier_mm_init(mm); 546 return mm; 547 } 548 549 free_mm(mm); 550 return NULL; 551 } 552 553 static void check_mm(struct mm_struct *mm) 554 { 555 int i; 556 557 for (i = 0; i < NR_MM_COUNTERS; i++) { 558 long x = atomic_long_read(&mm->rss_stat.count[i]); 559 560 if (unlikely(x)) 561 printk(KERN_ALERT "BUG: Bad rss-counter state " 562 "mm:%p idx:%d val:%ld\n", mm, i, x); 563 } 564 565 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 566 VM_BUG_ON(mm->pmd_huge_pte); 567 #endif 568 } 569 570 /* 571 * Allocate and initialize an mm_struct. 572 */ 573 struct mm_struct *mm_alloc(void) 574 { 575 struct mm_struct *mm; 576 577 mm = allocate_mm(); 578 if (!mm) 579 return NULL; 580 581 memset(mm, 0, sizeof(*mm)); 582 mm_init_cpumask(mm); 583 return mm_init(mm, current); 584 } 585 586 /* 587 * Called when the last reference to the mm 588 * is dropped: either by a lazy thread or by 589 * mmput. Free the page directory and the mm. 590 */ 591 void __mmdrop(struct mm_struct *mm) 592 { 593 BUG_ON(mm == &init_mm); 594 mm_free_pgd(mm); 595 destroy_context(mm); 596 mmu_notifier_mm_destroy(mm); 597 check_mm(mm); 598 free_mm(mm); 599 } 600 EXPORT_SYMBOL_GPL(__mmdrop); 601 602 /* 603 * Decrement the use count and release all resources for an mm. 604 */ 605 void mmput(struct mm_struct *mm) 606 { 607 might_sleep(); 608 609 if (atomic_dec_and_test(&mm->mm_users)) { 610 uprobe_clear_state(mm); 611 exit_aio(mm); 612 ksm_exit(mm); 613 khugepaged_exit(mm); /* must run before exit_mmap */ 614 exit_mmap(mm); 615 set_mm_exe_file(mm, NULL); 616 if (!list_empty(&mm->mmlist)) { 617 spin_lock(&mmlist_lock); 618 list_del(&mm->mmlist); 619 spin_unlock(&mmlist_lock); 620 } 621 if (mm->binfmt) 622 module_put(mm->binfmt->module); 623 mmdrop(mm); 624 } 625 } 626 EXPORT_SYMBOL_GPL(mmput); 627 628 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 629 { 630 if (new_exe_file) 631 get_file(new_exe_file); 632 if (mm->exe_file) 633 fput(mm->exe_file); 634 mm->exe_file = new_exe_file; 635 } 636 637 struct file *get_mm_exe_file(struct mm_struct *mm) 638 { 639 struct file *exe_file; 640 641 /* We need mmap_sem to protect against races with removal of exe_file */ 642 down_read(&mm->mmap_sem); 643 exe_file = mm->exe_file; 644 if (exe_file) 645 get_file(exe_file); 646 up_read(&mm->mmap_sem); 647 return exe_file; 648 } 649 650 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 651 { 652 /* It's safe to write the exe_file pointer without exe_file_lock because 653 * this is called during fork when the task is not yet in /proc */ 654 newmm->exe_file = get_mm_exe_file(oldmm); 655 } 656 657 /** 658 * get_task_mm - acquire a reference to the task's mm 659 * 660 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 661 * this kernel workthread has transiently adopted a user mm with use_mm, 662 * to do its AIO) is not set and if so returns a reference to it, after 663 * bumping up the use count. User must release the mm via mmput() 664 * after use. Typically used by /proc and ptrace. 665 */ 666 struct mm_struct *get_task_mm(struct task_struct *task) 667 { 668 struct mm_struct *mm; 669 670 task_lock(task); 671 mm = task->mm; 672 if (mm) { 673 if (task->flags & PF_KTHREAD) 674 mm = NULL; 675 else 676 atomic_inc(&mm->mm_users); 677 } 678 task_unlock(task); 679 return mm; 680 } 681 EXPORT_SYMBOL_GPL(get_task_mm); 682 683 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 684 { 685 struct mm_struct *mm; 686 int err; 687 688 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 689 if (err) 690 return ERR_PTR(err); 691 692 mm = get_task_mm(task); 693 if (mm && mm != current->mm && 694 !ptrace_may_access(task, mode)) { 695 mmput(mm); 696 mm = ERR_PTR(-EACCES); 697 } 698 mutex_unlock(&task->signal->cred_guard_mutex); 699 700 return mm; 701 } 702 703 static void complete_vfork_done(struct task_struct *tsk) 704 { 705 struct completion *vfork; 706 707 task_lock(tsk); 708 vfork = tsk->vfork_done; 709 if (likely(vfork)) { 710 tsk->vfork_done = NULL; 711 complete(vfork); 712 } 713 task_unlock(tsk); 714 } 715 716 static int wait_for_vfork_done(struct task_struct *child, 717 struct completion *vfork) 718 { 719 int killed; 720 721 freezer_do_not_count(); 722 killed = wait_for_completion_killable(vfork); 723 freezer_count(); 724 725 if (killed) { 726 task_lock(child); 727 child->vfork_done = NULL; 728 task_unlock(child); 729 } 730 731 put_task_struct(child); 732 return killed; 733 } 734 735 /* Please note the differences between mmput and mm_release. 736 * mmput is called whenever we stop holding onto a mm_struct, 737 * error success whatever. 738 * 739 * mm_release is called after a mm_struct has been removed 740 * from the current process. 741 * 742 * This difference is important for error handling, when we 743 * only half set up a mm_struct for a new process and need to restore 744 * the old one. Because we mmput the new mm_struct before 745 * restoring the old one. . . 746 * Eric Biederman 10 January 1998 747 */ 748 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 749 { 750 /* Get rid of any futexes when releasing the mm */ 751 #ifdef CONFIG_FUTEX 752 if (unlikely(tsk->robust_list)) { 753 exit_robust_list(tsk); 754 tsk->robust_list = NULL; 755 } 756 #ifdef CONFIG_COMPAT 757 if (unlikely(tsk->compat_robust_list)) { 758 compat_exit_robust_list(tsk); 759 tsk->compat_robust_list = NULL; 760 } 761 #endif 762 if (unlikely(!list_empty(&tsk->pi_state_list))) 763 exit_pi_state_list(tsk); 764 #endif 765 766 uprobe_free_utask(tsk); 767 768 /* Get rid of any cached register state */ 769 deactivate_mm(tsk, mm); 770 771 /* 772 * If we're exiting normally, clear a user-space tid field if 773 * requested. We leave this alone when dying by signal, to leave 774 * the value intact in a core dump, and to save the unnecessary 775 * trouble, say, a killed vfork parent shouldn't touch this mm. 776 * Userland only wants this done for a sys_exit. 777 */ 778 if (tsk->clear_child_tid) { 779 if (!(tsk->flags & PF_SIGNALED) && 780 atomic_read(&mm->mm_users) > 1) { 781 /* 782 * We don't check the error code - if userspace has 783 * not set up a proper pointer then tough luck. 784 */ 785 put_user(0, tsk->clear_child_tid); 786 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 787 1, NULL, NULL, 0); 788 } 789 tsk->clear_child_tid = NULL; 790 } 791 792 /* 793 * All done, finally we can wake up parent and return this mm to him. 794 * Also kthread_stop() uses this completion for synchronization. 795 */ 796 if (tsk->vfork_done) 797 complete_vfork_done(tsk); 798 } 799 800 /* 801 * Allocate a new mm structure and copy contents from the 802 * mm structure of the passed in task structure. 803 */ 804 static struct mm_struct *dup_mm(struct task_struct *tsk) 805 { 806 struct mm_struct *mm, *oldmm = current->mm; 807 int err; 808 809 mm = allocate_mm(); 810 if (!mm) 811 goto fail_nomem; 812 813 memcpy(mm, oldmm, sizeof(*mm)); 814 mm_init_cpumask(mm); 815 816 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 817 mm->pmd_huge_pte = NULL; 818 #endif 819 if (!mm_init(mm, tsk)) 820 goto fail_nomem; 821 822 if (init_new_context(tsk, mm)) 823 goto fail_nocontext; 824 825 dup_mm_exe_file(oldmm, mm); 826 827 err = dup_mmap(mm, oldmm); 828 if (err) 829 goto free_pt; 830 831 mm->hiwater_rss = get_mm_rss(mm); 832 mm->hiwater_vm = mm->total_vm; 833 834 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 835 goto free_pt; 836 837 return mm; 838 839 free_pt: 840 /* don't put binfmt in mmput, we haven't got module yet */ 841 mm->binfmt = NULL; 842 mmput(mm); 843 844 fail_nomem: 845 return NULL; 846 847 fail_nocontext: 848 /* 849 * If init_new_context() failed, we cannot use mmput() to free the mm 850 * because it calls destroy_context() 851 */ 852 mm_free_pgd(mm); 853 free_mm(mm); 854 return NULL; 855 } 856 857 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 858 { 859 struct mm_struct *mm, *oldmm; 860 int retval; 861 862 tsk->min_flt = tsk->maj_flt = 0; 863 tsk->nvcsw = tsk->nivcsw = 0; 864 #ifdef CONFIG_DETECT_HUNG_TASK 865 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 866 #endif 867 868 tsk->mm = NULL; 869 tsk->active_mm = NULL; 870 871 /* 872 * Are we cloning a kernel thread? 873 * 874 * We need to steal a active VM for that.. 875 */ 876 oldmm = current->mm; 877 if (!oldmm) 878 return 0; 879 880 if (clone_flags & CLONE_VM) { 881 atomic_inc(&oldmm->mm_users); 882 mm = oldmm; 883 goto good_mm; 884 } 885 886 retval = -ENOMEM; 887 mm = dup_mm(tsk); 888 if (!mm) 889 goto fail_nomem; 890 891 good_mm: 892 tsk->mm = mm; 893 tsk->active_mm = mm; 894 return 0; 895 896 fail_nomem: 897 return retval; 898 } 899 900 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 901 { 902 struct fs_struct *fs = current->fs; 903 if (clone_flags & CLONE_FS) { 904 /* tsk->fs is already what we want */ 905 spin_lock(&fs->lock); 906 if (fs->in_exec) { 907 spin_unlock(&fs->lock); 908 return -EAGAIN; 909 } 910 fs->users++; 911 spin_unlock(&fs->lock); 912 return 0; 913 } 914 tsk->fs = copy_fs_struct(fs); 915 if (!tsk->fs) 916 return -ENOMEM; 917 return 0; 918 } 919 920 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 921 { 922 struct files_struct *oldf, *newf; 923 int error = 0; 924 925 /* 926 * A background process may not have any files ... 927 */ 928 oldf = current->files; 929 if (!oldf) 930 goto out; 931 932 if (clone_flags & CLONE_FILES) { 933 atomic_inc(&oldf->count); 934 goto out; 935 } 936 937 newf = dup_fd(oldf, &error); 938 if (!newf) 939 goto out; 940 941 tsk->files = newf; 942 error = 0; 943 out: 944 return error; 945 } 946 947 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 948 { 949 #ifdef CONFIG_BLOCK 950 struct io_context *ioc = current->io_context; 951 struct io_context *new_ioc; 952 953 if (!ioc) 954 return 0; 955 /* 956 * Share io context with parent, if CLONE_IO is set 957 */ 958 if (clone_flags & CLONE_IO) { 959 ioc_task_link(ioc); 960 tsk->io_context = ioc; 961 } else if (ioprio_valid(ioc->ioprio)) { 962 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 963 if (unlikely(!new_ioc)) 964 return -ENOMEM; 965 966 new_ioc->ioprio = ioc->ioprio; 967 put_io_context(new_ioc); 968 } 969 #endif 970 return 0; 971 } 972 973 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 974 { 975 struct sighand_struct *sig; 976 977 if (clone_flags & CLONE_SIGHAND) { 978 atomic_inc(¤t->sighand->count); 979 return 0; 980 } 981 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 982 rcu_assign_pointer(tsk->sighand, sig); 983 if (!sig) 984 return -ENOMEM; 985 atomic_set(&sig->count, 1); 986 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 987 return 0; 988 } 989 990 void __cleanup_sighand(struct sighand_struct *sighand) 991 { 992 if (atomic_dec_and_test(&sighand->count)) { 993 signalfd_cleanup(sighand); 994 kmem_cache_free(sighand_cachep, sighand); 995 } 996 } 997 998 999 /* 1000 * Initialize POSIX timer handling for a thread group. 1001 */ 1002 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1003 { 1004 unsigned long cpu_limit; 1005 1006 /* Thread group counters. */ 1007 thread_group_cputime_init(sig); 1008 1009 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1010 if (cpu_limit != RLIM_INFINITY) { 1011 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1012 sig->cputimer.running = 1; 1013 } 1014 1015 /* The timer lists. */ 1016 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1017 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1018 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1019 } 1020 1021 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1022 { 1023 struct signal_struct *sig; 1024 1025 if (clone_flags & CLONE_THREAD) 1026 return 0; 1027 1028 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1029 tsk->signal = sig; 1030 if (!sig) 1031 return -ENOMEM; 1032 1033 sig->nr_threads = 1; 1034 atomic_set(&sig->live, 1); 1035 atomic_set(&sig->sigcnt, 1); 1036 1037 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1038 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1039 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1040 1041 init_waitqueue_head(&sig->wait_chldexit); 1042 sig->curr_target = tsk; 1043 init_sigpending(&sig->shared_pending); 1044 INIT_LIST_HEAD(&sig->posix_timers); 1045 1046 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1047 sig->real_timer.function = it_real_fn; 1048 1049 task_lock(current->group_leader); 1050 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1051 task_unlock(current->group_leader); 1052 1053 posix_cpu_timers_init_group(sig); 1054 1055 tty_audit_fork(sig); 1056 sched_autogroup_fork(sig); 1057 1058 #ifdef CONFIG_CGROUPS 1059 init_rwsem(&sig->group_rwsem); 1060 #endif 1061 1062 sig->oom_score_adj = current->signal->oom_score_adj; 1063 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1064 1065 sig->has_child_subreaper = current->signal->has_child_subreaper || 1066 current->signal->is_child_subreaper; 1067 1068 mutex_init(&sig->cred_guard_mutex); 1069 1070 return 0; 1071 } 1072 1073 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1074 { 1075 unsigned long new_flags = p->flags; 1076 1077 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1078 new_flags |= PF_FORKNOEXEC; 1079 p->flags = new_flags; 1080 } 1081 1082 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1083 { 1084 current->clear_child_tid = tidptr; 1085 1086 return task_pid_vnr(current); 1087 } 1088 1089 static void rt_mutex_init_task(struct task_struct *p) 1090 { 1091 raw_spin_lock_init(&p->pi_lock); 1092 #ifdef CONFIG_RT_MUTEXES 1093 p->pi_waiters = RB_ROOT; 1094 p->pi_waiters_leftmost = NULL; 1095 p->pi_blocked_on = NULL; 1096 p->pi_top_task = NULL; 1097 #endif 1098 } 1099 1100 #ifdef CONFIG_MM_OWNER 1101 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1102 { 1103 mm->owner = p; 1104 } 1105 #endif /* CONFIG_MM_OWNER */ 1106 1107 /* 1108 * Initialize POSIX timer handling for a single task. 1109 */ 1110 static void posix_cpu_timers_init(struct task_struct *tsk) 1111 { 1112 tsk->cputime_expires.prof_exp = 0; 1113 tsk->cputime_expires.virt_exp = 0; 1114 tsk->cputime_expires.sched_exp = 0; 1115 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1116 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1117 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1118 } 1119 1120 static inline void 1121 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1122 { 1123 task->pids[type].pid = pid; 1124 } 1125 1126 /* 1127 * This creates a new process as a copy of the old one, 1128 * but does not actually start it yet. 1129 * 1130 * It copies the registers, and all the appropriate 1131 * parts of the process environment (as per the clone 1132 * flags). The actual kick-off is left to the caller. 1133 */ 1134 static struct task_struct *copy_process(unsigned long clone_flags, 1135 unsigned long stack_start, 1136 unsigned long stack_size, 1137 int __user *child_tidptr, 1138 struct pid *pid, 1139 int trace) 1140 { 1141 int retval; 1142 struct task_struct *p; 1143 1144 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1145 return ERR_PTR(-EINVAL); 1146 1147 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1148 return ERR_PTR(-EINVAL); 1149 1150 /* 1151 * Thread groups must share signals as well, and detached threads 1152 * can only be started up within the thread group. 1153 */ 1154 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1155 return ERR_PTR(-EINVAL); 1156 1157 /* 1158 * Shared signal handlers imply shared VM. By way of the above, 1159 * thread groups also imply shared VM. Blocking this case allows 1160 * for various simplifications in other code. 1161 */ 1162 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1163 return ERR_PTR(-EINVAL); 1164 1165 /* 1166 * Siblings of global init remain as zombies on exit since they are 1167 * not reaped by their parent (swapper). To solve this and to avoid 1168 * multi-rooted process trees, prevent global and container-inits 1169 * from creating siblings. 1170 */ 1171 if ((clone_flags & CLONE_PARENT) && 1172 current->signal->flags & SIGNAL_UNKILLABLE) 1173 return ERR_PTR(-EINVAL); 1174 1175 /* 1176 * If the new process will be in a different pid or user namespace 1177 * do not allow it to share a thread group or signal handlers or 1178 * parent with the forking task. 1179 */ 1180 if (clone_flags & CLONE_SIGHAND) { 1181 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1182 (task_active_pid_ns(current) != 1183 current->nsproxy->pid_ns_for_children)) 1184 return ERR_PTR(-EINVAL); 1185 } 1186 1187 retval = security_task_create(clone_flags); 1188 if (retval) 1189 goto fork_out; 1190 1191 retval = -ENOMEM; 1192 p = dup_task_struct(current); 1193 if (!p) 1194 goto fork_out; 1195 1196 ftrace_graph_init_task(p); 1197 get_seccomp_filter(p); 1198 1199 rt_mutex_init_task(p); 1200 1201 #ifdef CONFIG_PROVE_LOCKING 1202 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1203 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1204 #endif 1205 retval = -EAGAIN; 1206 if (atomic_read(&p->real_cred->user->processes) >= 1207 task_rlimit(p, RLIMIT_NPROC)) { 1208 if (p->real_cred->user != INIT_USER && 1209 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1210 goto bad_fork_free; 1211 } 1212 current->flags &= ~PF_NPROC_EXCEEDED; 1213 1214 retval = copy_creds(p, clone_flags); 1215 if (retval < 0) 1216 goto bad_fork_free; 1217 1218 /* 1219 * If multiple threads are within copy_process(), then this check 1220 * triggers too late. This doesn't hurt, the check is only there 1221 * to stop root fork bombs. 1222 */ 1223 retval = -EAGAIN; 1224 if (nr_threads >= max_threads) 1225 goto bad_fork_cleanup_count; 1226 1227 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1228 goto bad_fork_cleanup_count; 1229 1230 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1231 copy_flags(clone_flags, p); 1232 INIT_LIST_HEAD(&p->children); 1233 INIT_LIST_HEAD(&p->sibling); 1234 rcu_copy_process(p); 1235 p->vfork_done = NULL; 1236 spin_lock_init(&p->alloc_lock); 1237 1238 init_sigpending(&p->pending); 1239 1240 p->utime = p->stime = p->gtime = 0; 1241 p->utimescaled = p->stimescaled = 0; 1242 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1243 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1244 #endif 1245 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1246 seqlock_init(&p->vtime_seqlock); 1247 p->vtime_snap = 0; 1248 p->vtime_snap_whence = VTIME_SLEEPING; 1249 #endif 1250 1251 #if defined(SPLIT_RSS_COUNTING) 1252 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1253 #endif 1254 1255 p->default_timer_slack_ns = current->timer_slack_ns; 1256 1257 task_io_accounting_init(&p->ioac); 1258 acct_clear_integrals(p); 1259 1260 posix_cpu_timers_init(p); 1261 1262 do_posix_clock_monotonic_gettime(&p->start_time); 1263 p->real_start_time = p->start_time; 1264 monotonic_to_bootbased(&p->real_start_time); 1265 p->io_context = NULL; 1266 p->audit_context = NULL; 1267 if (clone_flags & CLONE_THREAD) 1268 threadgroup_change_begin(current); 1269 cgroup_fork(p); 1270 #ifdef CONFIG_NUMA 1271 p->mempolicy = mpol_dup(p->mempolicy); 1272 if (IS_ERR(p->mempolicy)) { 1273 retval = PTR_ERR(p->mempolicy); 1274 p->mempolicy = NULL; 1275 goto bad_fork_cleanup_cgroup; 1276 } 1277 mpol_fix_fork_child_flag(p); 1278 #endif 1279 #ifdef CONFIG_CPUSETS 1280 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1281 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1282 seqcount_init(&p->mems_allowed_seq); 1283 #endif 1284 #ifdef CONFIG_TRACE_IRQFLAGS 1285 p->irq_events = 0; 1286 p->hardirqs_enabled = 0; 1287 p->hardirq_enable_ip = 0; 1288 p->hardirq_enable_event = 0; 1289 p->hardirq_disable_ip = _THIS_IP_; 1290 p->hardirq_disable_event = 0; 1291 p->softirqs_enabled = 1; 1292 p->softirq_enable_ip = _THIS_IP_; 1293 p->softirq_enable_event = 0; 1294 p->softirq_disable_ip = 0; 1295 p->softirq_disable_event = 0; 1296 p->hardirq_context = 0; 1297 p->softirq_context = 0; 1298 #endif 1299 #ifdef CONFIG_LOCKDEP 1300 p->lockdep_depth = 0; /* no locks held yet */ 1301 p->curr_chain_key = 0; 1302 p->lockdep_recursion = 0; 1303 #endif 1304 1305 #ifdef CONFIG_DEBUG_MUTEXES 1306 p->blocked_on = NULL; /* not blocked yet */ 1307 #endif 1308 #ifdef CONFIG_MEMCG 1309 p->memcg_batch.do_batch = 0; 1310 p->memcg_batch.memcg = NULL; 1311 #endif 1312 #ifdef CONFIG_BCACHE 1313 p->sequential_io = 0; 1314 p->sequential_io_avg = 0; 1315 #endif 1316 1317 /* Perform scheduler related setup. Assign this task to a CPU. */ 1318 retval = sched_fork(clone_flags, p); 1319 if (retval) 1320 goto bad_fork_cleanup_policy; 1321 1322 retval = perf_event_init_task(p); 1323 if (retval) 1324 goto bad_fork_cleanup_policy; 1325 retval = audit_alloc(p); 1326 if (retval) 1327 goto bad_fork_cleanup_policy; 1328 /* copy all the process information */ 1329 retval = copy_semundo(clone_flags, p); 1330 if (retval) 1331 goto bad_fork_cleanup_audit; 1332 retval = copy_files(clone_flags, p); 1333 if (retval) 1334 goto bad_fork_cleanup_semundo; 1335 retval = copy_fs(clone_flags, p); 1336 if (retval) 1337 goto bad_fork_cleanup_files; 1338 retval = copy_sighand(clone_flags, p); 1339 if (retval) 1340 goto bad_fork_cleanup_fs; 1341 retval = copy_signal(clone_flags, p); 1342 if (retval) 1343 goto bad_fork_cleanup_sighand; 1344 retval = copy_mm(clone_flags, p); 1345 if (retval) 1346 goto bad_fork_cleanup_signal; 1347 retval = copy_namespaces(clone_flags, p); 1348 if (retval) 1349 goto bad_fork_cleanup_mm; 1350 retval = copy_io(clone_flags, p); 1351 if (retval) 1352 goto bad_fork_cleanup_namespaces; 1353 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1354 if (retval) 1355 goto bad_fork_cleanup_io; 1356 1357 if (pid != &init_struct_pid) { 1358 retval = -ENOMEM; 1359 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1360 if (!pid) 1361 goto bad_fork_cleanup_io; 1362 } 1363 1364 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1365 /* 1366 * Clear TID on mm_release()? 1367 */ 1368 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1369 #ifdef CONFIG_BLOCK 1370 p->plug = NULL; 1371 #endif 1372 #ifdef CONFIG_FUTEX 1373 p->robust_list = NULL; 1374 #ifdef CONFIG_COMPAT 1375 p->compat_robust_list = NULL; 1376 #endif 1377 INIT_LIST_HEAD(&p->pi_state_list); 1378 p->pi_state_cache = NULL; 1379 #endif 1380 /* 1381 * sigaltstack should be cleared when sharing the same VM 1382 */ 1383 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1384 p->sas_ss_sp = p->sas_ss_size = 0; 1385 1386 /* 1387 * Syscall tracing and stepping should be turned off in the 1388 * child regardless of CLONE_PTRACE. 1389 */ 1390 user_disable_single_step(p); 1391 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1392 #ifdef TIF_SYSCALL_EMU 1393 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1394 #endif 1395 clear_all_latency_tracing(p); 1396 1397 /* ok, now we should be set up.. */ 1398 p->pid = pid_nr(pid); 1399 if (clone_flags & CLONE_THREAD) { 1400 p->exit_signal = -1; 1401 p->group_leader = current->group_leader; 1402 p->tgid = current->tgid; 1403 } else { 1404 if (clone_flags & CLONE_PARENT) 1405 p->exit_signal = current->group_leader->exit_signal; 1406 else 1407 p->exit_signal = (clone_flags & CSIGNAL); 1408 p->group_leader = p; 1409 p->tgid = p->pid; 1410 } 1411 1412 p->nr_dirtied = 0; 1413 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1414 p->dirty_paused_when = 0; 1415 1416 p->pdeath_signal = 0; 1417 INIT_LIST_HEAD(&p->thread_group); 1418 p->task_works = NULL; 1419 1420 /* 1421 * Make it visible to the rest of the system, but dont wake it up yet. 1422 * Need tasklist lock for parent etc handling! 1423 */ 1424 write_lock_irq(&tasklist_lock); 1425 1426 /* CLONE_PARENT re-uses the old parent */ 1427 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1428 p->real_parent = current->real_parent; 1429 p->parent_exec_id = current->parent_exec_id; 1430 } else { 1431 p->real_parent = current; 1432 p->parent_exec_id = current->self_exec_id; 1433 } 1434 1435 spin_lock(¤t->sighand->siglock); 1436 1437 /* 1438 * Process group and session signals need to be delivered to just the 1439 * parent before the fork or both the parent and the child after the 1440 * fork. Restart if a signal comes in before we add the new process to 1441 * it's process group. 1442 * A fatal signal pending means that current will exit, so the new 1443 * thread can't slip out of an OOM kill (or normal SIGKILL). 1444 */ 1445 recalc_sigpending(); 1446 if (signal_pending(current)) { 1447 spin_unlock(¤t->sighand->siglock); 1448 write_unlock_irq(&tasklist_lock); 1449 retval = -ERESTARTNOINTR; 1450 goto bad_fork_free_pid; 1451 } 1452 1453 if (likely(p->pid)) { 1454 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1455 1456 init_task_pid(p, PIDTYPE_PID, pid); 1457 if (thread_group_leader(p)) { 1458 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1459 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1460 1461 if (is_child_reaper(pid)) { 1462 ns_of_pid(pid)->child_reaper = p; 1463 p->signal->flags |= SIGNAL_UNKILLABLE; 1464 } 1465 1466 p->signal->leader_pid = pid; 1467 p->signal->tty = tty_kref_get(current->signal->tty); 1468 list_add_tail(&p->sibling, &p->real_parent->children); 1469 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1470 attach_pid(p, PIDTYPE_PGID); 1471 attach_pid(p, PIDTYPE_SID); 1472 __this_cpu_inc(process_counts); 1473 } else { 1474 current->signal->nr_threads++; 1475 atomic_inc(¤t->signal->live); 1476 atomic_inc(¤t->signal->sigcnt); 1477 list_add_tail_rcu(&p->thread_group, 1478 &p->group_leader->thread_group); 1479 list_add_tail_rcu(&p->thread_node, 1480 &p->signal->thread_head); 1481 } 1482 attach_pid(p, PIDTYPE_PID); 1483 nr_threads++; 1484 } 1485 1486 total_forks++; 1487 spin_unlock(¤t->sighand->siglock); 1488 write_unlock_irq(&tasklist_lock); 1489 proc_fork_connector(p); 1490 cgroup_post_fork(p); 1491 if (clone_flags & CLONE_THREAD) 1492 threadgroup_change_end(current); 1493 perf_event_fork(p); 1494 1495 trace_task_newtask(p, clone_flags); 1496 uprobe_copy_process(p, clone_flags); 1497 1498 return p; 1499 1500 bad_fork_free_pid: 1501 if (pid != &init_struct_pid) 1502 free_pid(pid); 1503 bad_fork_cleanup_io: 1504 if (p->io_context) 1505 exit_io_context(p); 1506 bad_fork_cleanup_namespaces: 1507 exit_task_namespaces(p); 1508 bad_fork_cleanup_mm: 1509 if (p->mm) 1510 mmput(p->mm); 1511 bad_fork_cleanup_signal: 1512 if (!(clone_flags & CLONE_THREAD)) 1513 free_signal_struct(p->signal); 1514 bad_fork_cleanup_sighand: 1515 __cleanup_sighand(p->sighand); 1516 bad_fork_cleanup_fs: 1517 exit_fs(p); /* blocking */ 1518 bad_fork_cleanup_files: 1519 exit_files(p); /* blocking */ 1520 bad_fork_cleanup_semundo: 1521 exit_sem(p); 1522 bad_fork_cleanup_audit: 1523 audit_free(p); 1524 bad_fork_cleanup_policy: 1525 perf_event_free_task(p); 1526 #ifdef CONFIG_NUMA 1527 mpol_put(p->mempolicy); 1528 bad_fork_cleanup_cgroup: 1529 #endif 1530 if (clone_flags & CLONE_THREAD) 1531 threadgroup_change_end(current); 1532 cgroup_exit(p, 0); 1533 delayacct_tsk_free(p); 1534 module_put(task_thread_info(p)->exec_domain->module); 1535 bad_fork_cleanup_count: 1536 atomic_dec(&p->cred->user->processes); 1537 exit_creds(p); 1538 bad_fork_free: 1539 free_task(p); 1540 fork_out: 1541 return ERR_PTR(retval); 1542 } 1543 1544 static inline void init_idle_pids(struct pid_link *links) 1545 { 1546 enum pid_type type; 1547 1548 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1549 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1550 links[type].pid = &init_struct_pid; 1551 } 1552 } 1553 1554 struct task_struct *fork_idle(int cpu) 1555 { 1556 struct task_struct *task; 1557 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1558 if (!IS_ERR(task)) { 1559 init_idle_pids(task->pids); 1560 init_idle(task, cpu); 1561 } 1562 1563 return task; 1564 } 1565 1566 /* 1567 * Ok, this is the main fork-routine. 1568 * 1569 * It copies the process, and if successful kick-starts 1570 * it and waits for it to finish using the VM if required. 1571 */ 1572 long do_fork(unsigned long clone_flags, 1573 unsigned long stack_start, 1574 unsigned long stack_size, 1575 int __user *parent_tidptr, 1576 int __user *child_tidptr) 1577 { 1578 struct task_struct *p; 1579 int trace = 0; 1580 long nr; 1581 1582 /* 1583 * Determine whether and which event to report to ptracer. When 1584 * called from kernel_thread or CLONE_UNTRACED is explicitly 1585 * requested, no event is reported; otherwise, report if the event 1586 * for the type of forking is enabled. 1587 */ 1588 if (!(clone_flags & CLONE_UNTRACED)) { 1589 if (clone_flags & CLONE_VFORK) 1590 trace = PTRACE_EVENT_VFORK; 1591 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1592 trace = PTRACE_EVENT_CLONE; 1593 else 1594 trace = PTRACE_EVENT_FORK; 1595 1596 if (likely(!ptrace_event_enabled(current, trace))) 1597 trace = 0; 1598 } 1599 1600 p = copy_process(clone_flags, stack_start, stack_size, 1601 child_tidptr, NULL, trace); 1602 /* 1603 * Do this prior waking up the new thread - the thread pointer 1604 * might get invalid after that point, if the thread exits quickly. 1605 */ 1606 if (!IS_ERR(p)) { 1607 struct completion vfork; 1608 1609 trace_sched_process_fork(current, p); 1610 1611 nr = task_pid_vnr(p); 1612 1613 if (clone_flags & CLONE_PARENT_SETTID) 1614 put_user(nr, parent_tidptr); 1615 1616 if (clone_flags & CLONE_VFORK) { 1617 p->vfork_done = &vfork; 1618 init_completion(&vfork); 1619 get_task_struct(p); 1620 } 1621 1622 wake_up_new_task(p); 1623 1624 /* forking complete and child started to run, tell ptracer */ 1625 if (unlikely(trace)) 1626 ptrace_event(trace, nr); 1627 1628 if (clone_flags & CLONE_VFORK) { 1629 if (!wait_for_vfork_done(p, &vfork)) 1630 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1631 } 1632 } else { 1633 nr = PTR_ERR(p); 1634 } 1635 return nr; 1636 } 1637 1638 /* 1639 * Create a kernel thread. 1640 */ 1641 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1642 { 1643 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1644 (unsigned long)arg, NULL, NULL); 1645 } 1646 1647 #ifdef __ARCH_WANT_SYS_FORK 1648 SYSCALL_DEFINE0(fork) 1649 { 1650 #ifdef CONFIG_MMU 1651 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1652 #else 1653 /* can not support in nommu mode */ 1654 return -EINVAL; 1655 #endif 1656 } 1657 #endif 1658 1659 #ifdef __ARCH_WANT_SYS_VFORK 1660 SYSCALL_DEFINE0(vfork) 1661 { 1662 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1663 0, NULL, NULL); 1664 } 1665 #endif 1666 1667 #ifdef __ARCH_WANT_SYS_CLONE 1668 #ifdef CONFIG_CLONE_BACKWARDS 1669 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1670 int __user *, parent_tidptr, 1671 int, tls_val, 1672 int __user *, child_tidptr) 1673 #elif defined(CONFIG_CLONE_BACKWARDS2) 1674 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1675 int __user *, parent_tidptr, 1676 int __user *, child_tidptr, 1677 int, tls_val) 1678 #elif defined(CONFIG_CLONE_BACKWARDS3) 1679 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1680 int, stack_size, 1681 int __user *, parent_tidptr, 1682 int __user *, child_tidptr, 1683 int, tls_val) 1684 #else 1685 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1686 int __user *, parent_tidptr, 1687 int __user *, child_tidptr, 1688 int, tls_val) 1689 #endif 1690 { 1691 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1692 } 1693 #endif 1694 1695 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1696 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1697 #endif 1698 1699 static void sighand_ctor(void *data) 1700 { 1701 struct sighand_struct *sighand = data; 1702 1703 spin_lock_init(&sighand->siglock); 1704 init_waitqueue_head(&sighand->signalfd_wqh); 1705 } 1706 1707 void __init proc_caches_init(void) 1708 { 1709 sighand_cachep = kmem_cache_create("sighand_cache", 1710 sizeof(struct sighand_struct), 0, 1711 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1712 SLAB_NOTRACK, sighand_ctor); 1713 signal_cachep = kmem_cache_create("signal_cache", 1714 sizeof(struct signal_struct), 0, 1715 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1716 files_cachep = kmem_cache_create("files_cache", 1717 sizeof(struct files_struct), 0, 1718 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1719 fs_cachep = kmem_cache_create("fs_cache", 1720 sizeof(struct fs_struct), 0, 1721 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1722 /* 1723 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1724 * whole struct cpumask for the OFFSTACK case. We could change 1725 * this to *only* allocate as much of it as required by the 1726 * maximum number of CPU's we can ever have. The cpumask_allocation 1727 * is at the end of the structure, exactly for that reason. 1728 */ 1729 mm_cachep = kmem_cache_create("mm_struct", 1730 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1731 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1732 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1733 mmap_init(); 1734 nsproxy_cache_init(); 1735 } 1736 1737 /* 1738 * Check constraints on flags passed to the unshare system call. 1739 */ 1740 static int check_unshare_flags(unsigned long unshare_flags) 1741 { 1742 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1743 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1744 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1745 CLONE_NEWUSER|CLONE_NEWPID)) 1746 return -EINVAL; 1747 /* 1748 * Not implemented, but pretend it works if there is nothing to 1749 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1750 * needs to unshare vm. 1751 */ 1752 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1753 /* FIXME: get_task_mm() increments ->mm_users */ 1754 if (atomic_read(¤t->mm->mm_users) > 1) 1755 return -EINVAL; 1756 } 1757 1758 return 0; 1759 } 1760 1761 /* 1762 * Unshare the filesystem structure if it is being shared 1763 */ 1764 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1765 { 1766 struct fs_struct *fs = current->fs; 1767 1768 if (!(unshare_flags & CLONE_FS) || !fs) 1769 return 0; 1770 1771 /* don't need lock here; in the worst case we'll do useless copy */ 1772 if (fs->users == 1) 1773 return 0; 1774 1775 *new_fsp = copy_fs_struct(fs); 1776 if (!*new_fsp) 1777 return -ENOMEM; 1778 1779 return 0; 1780 } 1781 1782 /* 1783 * Unshare file descriptor table if it is being shared 1784 */ 1785 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1786 { 1787 struct files_struct *fd = current->files; 1788 int error = 0; 1789 1790 if ((unshare_flags & CLONE_FILES) && 1791 (fd && atomic_read(&fd->count) > 1)) { 1792 *new_fdp = dup_fd(fd, &error); 1793 if (!*new_fdp) 1794 return error; 1795 } 1796 1797 return 0; 1798 } 1799 1800 /* 1801 * unshare allows a process to 'unshare' part of the process 1802 * context which was originally shared using clone. copy_* 1803 * functions used by do_fork() cannot be used here directly 1804 * because they modify an inactive task_struct that is being 1805 * constructed. Here we are modifying the current, active, 1806 * task_struct. 1807 */ 1808 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1809 { 1810 struct fs_struct *fs, *new_fs = NULL; 1811 struct files_struct *fd, *new_fd = NULL; 1812 struct cred *new_cred = NULL; 1813 struct nsproxy *new_nsproxy = NULL; 1814 int do_sysvsem = 0; 1815 int err; 1816 1817 /* 1818 * If unsharing a user namespace must also unshare the thread. 1819 */ 1820 if (unshare_flags & CLONE_NEWUSER) 1821 unshare_flags |= CLONE_THREAD | CLONE_FS; 1822 /* 1823 * If unsharing a thread from a thread group, must also unshare vm. 1824 */ 1825 if (unshare_flags & CLONE_THREAD) 1826 unshare_flags |= CLONE_VM; 1827 /* 1828 * If unsharing vm, must also unshare signal handlers. 1829 */ 1830 if (unshare_flags & CLONE_VM) 1831 unshare_flags |= CLONE_SIGHAND; 1832 /* 1833 * If unsharing namespace, must also unshare filesystem information. 1834 */ 1835 if (unshare_flags & CLONE_NEWNS) 1836 unshare_flags |= CLONE_FS; 1837 1838 err = check_unshare_flags(unshare_flags); 1839 if (err) 1840 goto bad_unshare_out; 1841 /* 1842 * CLONE_NEWIPC must also detach from the undolist: after switching 1843 * to a new ipc namespace, the semaphore arrays from the old 1844 * namespace are unreachable. 1845 */ 1846 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1847 do_sysvsem = 1; 1848 err = unshare_fs(unshare_flags, &new_fs); 1849 if (err) 1850 goto bad_unshare_out; 1851 err = unshare_fd(unshare_flags, &new_fd); 1852 if (err) 1853 goto bad_unshare_cleanup_fs; 1854 err = unshare_userns(unshare_flags, &new_cred); 1855 if (err) 1856 goto bad_unshare_cleanup_fd; 1857 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1858 new_cred, new_fs); 1859 if (err) 1860 goto bad_unshare_cleanup_cred; 1861 1862 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1863 if (do_sysvsem) { 1864 /* 1865 * CLONE_SYSVSEM is equivalent to sys_exit(). 1866 */ 1867 exit_sem(current); 1868 } 1869 1870 if (new_nsproxy) 1871 switch_task_namespaces(current, new_nsproxy); 1872 1873 task_lock(current); 1874 1875 if (new_fs) { 1876 fs = current->fs; 1877 spin_lock(&fs->lock); 1878 current->fs = new_fs; 1879 if (--fs->users) 1880 new_fs = NULL; 1881 else 1882 new_fs = fs; 1883 spin_unlock(&fs->lock); 1884 } 1885 1886 if (new_fd) { 1887 fd = current->files; 1888 current->files = new_fd; 1889 new_fd = fd; 1890 } 1891 1892 task_unlock(current); 1893 1894 if (new_cred) { 1895 /* Install the new user namespace */ 1896 commit_creds(new_cred); 1897 new_cred = NULL; 1898 } 1899 } 1900 1901 bad_unshare_cleanup_cred: 1902 if (new_cred) 1903 put_cred(new_cred); 1904 bad_unshare_cleanup_fd: 1905 if (new_fd) 1906 put_files_struct(new_fd); 1907 1908 bad_unshare_cleanup_fs: 1909 if (new_fs) 1910 free_fs_struct(new_fs); 1911 1912 bad_unshare_out: 1913 return err; 1914 } 1915 1916 /* 1917 * Helper to unshare the files of the current task. 1918 * We don't want to expose copy_files internals to 1919 * the exec layer of the kernel. 1920 */ 1921 1922 int unshare_files(struct files_struct **displaced) 1923 { 1924 struct task_struct *task = current; 1925 struct files_struct *copy = NULL; 1926 int error; 1927 1928 error = unshare_fd(CLONE_FILES, ©); 1929 if (error || !copy) { 1930 *displaced = NULL; 1931 return error; 1932 } 1933 *displaced = task->files; 1934 task_lock(task); 1935 task->files = copy; 1936 task_unlock(task); 1937 return 0; 1938 } 1939