1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/seccomp.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/kthread.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/proc_fs.h> 52 #include <linux/profile.h> 53 #include <linux/rmap.h> 54 #include <linux/ksm.h> 55 #include <linux/acct.h> 56 #include <linux/tsacct_kern.h> 57 #include <linux/cn_proc.h> 58 #include <linux/freezer.h> 59 #include <linux/delayacct.h> 60 #include <linux/taskstats_kern.h> 61 #include <linux/random.h> 62 #include <linux/tty.h> 63 #include <linux/blkdev.h> 64 #include <linux/fs_struct.h> 65 #include <linux/magic.h> 66 #include <linux/perf_event.h> 67 #include <linux/posix-timers.h> 68 #include <linux/user-return-notifier.h> 69 #include <linux/oom.h> 70 #include <linux/khugepaged.h> 71 #include <linux/signalfd.h> 72 #include <linux/uprobes.h> 73 #include <linux/aio.h> 74 75 #include <asm/pgtable.h> 76 #include <asm/pgalloc.h> 77 #include <asm/uaccess.h> 78 #include <asm/mmu_context.h> 79 #include <asm/cacheflush.h> 80 #include <asm/tlbflush.h> 81 82 #include <trace/events/sched.h> 83 84 #define CREATE_TRACE_POINTS 85 #include <trace/events/task.h> 86 87 /* 88 * Protected counters by write_lock_irq(&tasklist_lock) 89 */ 90 unsigned long total_forks; /* Handle normal Linux uptimes. */ 91 int nr_threads; /* The idle threads do not count.. */ 92 93 int max_threads; /* tunable limit on nr_threads */ 94 95 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 96 97 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 98 99 #ifdef CONFIG_PROVE_RCU 100 int lockdep_tasklist_lock_is_held(void) 101 { 102 return lockdep_is_held(&tasklist_lock); 103 } 104 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 105 #endif /* #ifdef CONFIG_PROVE_RCU */ 106 107 int nr_processes(void) 108 { 109 int cpu; 110 int total = 0; 111 112 for_each_possible_cpu(cpu) 113 total += per_cpu(process_counts, cpu); 114 115 return total; 116 } 117 118 void __weak arch_release_task_struct(struct task_struct *tsk) 119 { 120 } 121 122 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 123 static struct kmem_cache *task_struct_cachep; 124 125 static inline struct task_struct *alloc_task_struct_node(int node) 126 { 127 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 128 } 129 130 static inline void free_task_struct(struct task_struct *tsk) 131 { 132 kmem_cache_free(task_struct_cachep, tsk); 133 } 134 #endif 135 136 void __weak arch_release_thread_info(struct thread_info *ti) 137 { 138 } 139 140 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 141 142 /* 143 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 144 * kmemcache based allocator. 145 */ 146 # if THREAD_SIZE >= PAGE_SIZE 147 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 148 int node) 149 { 150 struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED, 151 THREAD_SIZE_ORDER); 152 153 return page ? page_address(page) : NULL; 154 } 155 156 static inline void free_thread_info(struct thread_info *ti) 157 { 158 free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); 159 } 160 # else 161 static struct kmem_cache *thread_info_cache; 162 163 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 164 int node) 165 { 166 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 167 } 168 169 static void free_thread_info(struct thread_info *ti) 170 { 171 kmem_cache_free(thread_info_cache, ti); 172 } 173 174 void thread_info_cache_init(void) 175 { 176 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 177 THREAD_SIZE, 0, NULL); 178 BUG_ON(thread_info_cache == NULL); 179 } 180 # endif 181 #endif 182 183 /* SLAB cache for signal_struct structures (tsk->signal) */ 184 static struct kmem_cache *signal_cachep; 185 186 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 187 struct kmem_cache *sighand_cachep; 188 189 /* SLAB cache for files_struct structures (tsk->files) */ 190 struct kmem_cache *files_cachep; 191 192 /* SLAB cache for fs_struct structures (tsk->fs) */ 193 struct kmem_cache *fs_cachep; 194 195 /* SLAB cache for vm_area_struct structures */ 196 struct kmem_cache *vm_area_cachep; 197 198 /* SLAB cache for mm_struct structures (tsk->mm) */ 199 static struct kmem_cache *mm_cachep; 200 201 static void account_kernel_stack(struct thread_info *ti, int account) 202 { 203 struct zone *zone = page_zone(virt_to_page(ti)); 204 205 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 206 } 207 208 void free_task(struct task_struct *tsk) 209 { 210 account_kernel_stack(tsk->stack, -1); 211 arch_release_thread_info(tsk->stack); 212 free_thread_info(tsk->stack); 213 rt_mutex_debug_task_free(tsk); 214 ftrace_graph_exit_task(tsk); 215 put_seccomp_filter(tsk); 216 arch_release_task_struct(tsk); 217 free_task_struct(tsk); 218 } 219 EXPORT_SYMBOL(free_task); 220 221 static inline void free_signal_struct(struct signal_struct *sig) 222 { 223 taskstats_tgid_free(sig); 224 sched_autogroup_exit(sig); 225 kmem_cache_free(signal_cachep, sig); 226 } 227 228 static inline void put_signal_struct(struct signal_struct *sig) 229 { 230 if (atomic_dec_and_test(&sig->sigcnt)) 231 free_signal_struct(sig); 232 } 233 234 void __put_task_struct(struct task_struct *tsk) 235 { 236 WARN_ON(!tsk->exit_state); 237 WARN_ON(atomic_read(&tsk->usage)); 238 WARN_ON(tsk == current); 239 240 security_task_free(tsk); 241 exit_creds(tsk); 242 delayacct_tsk_free(tsk); 243 put_signal_struct(tsk->signal); 244 245 if (!profile_handoff_task(tsk)) 246 free_task(tsk); 247 } 248 EXPORT_SYMBOL_GPL(__put_task_struct); 249 250 void __init __weak arch_task_cache_init(void) { } 251 252 void __init fork_init(unsigned long mempages) 253 { 254 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 255 #ifndef ARCH_MIN_TASKALIGN 256 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 257 #endif 258 /* create a slab on which task_structs can be allocated */ 259 task_struct_cachep = 260 kmem_cache_create("task_struct", sizeof(struct task_struct), 261 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 262 #endif 263 264 /* do the arch specific task caches init */ 265 arch_task_cache_init(); 266 267 /* 268 * The default maximum number of threads is set to a safe 269 * value: the thread structures can take up at most half 270 * of memory. 271 */ 272 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 273 274 /* 275 * we need to allow at least 20 threads to boot a system 276 */ 277 if (max_threads < 20) 278 max_threads = 20; 279 280 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 281 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 282 init_task.signal->rlim[RLIMIT_SIGPENDING] = 283 init_task.signal->rlim[RLIMIT_NPROC]; 284 } 285 286 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 287 struct task_struct *src) 288 { 289 *dst = *src; 290 return 0; 291 } 292 293 static struct task_struct *dup_task_struct(struct task_struct *orig) 294 { 295 struct task_struct *tsk; 296 struct thread_info *ti; 297 unsigned long *stackend; 298 int node = tsk_fork_get_node(orig); 299 int err; 300 301 tsk = alloc_task_struct_node(node); 302 if (!tsk) 303 return NULL; 304 305 ti = alloc_thread_info_node(tsk, node); 306 if (!ti) 307 goto free_tsk; 308 309 err = arch_dup_task_struct(tsk, orig); 310 if (err) 311 goto free_ti; 312 313 tsk->stack = ti; 314 315 setup_thread_stack(tsk, orig); 316 clear_user_return_notifier(tsk); 317 clear_tsk_need_resched(tsk); 318 stackend = end_of_stack(tsk); 319 *stackend = STACK_END_MAGIC; /* for overflow detection */ 320 321 #ifdef CONFIG_CC_STACKPROTECTOR 322 tsk->stack_canary = get_random_int(); 323 #endif 324 325 /* 326 * One for us, one for whoever does the "release_task()" (usually 327 * parent) 328 */ 329 atomic_set(&tsk->usage, 2); 330 #ifdef CONFIG_BLK_DEV_IO_TRACE 331 tsk->btrace_seq = 0; 332 #endif 333 tsk->splice_pipe = NULL; 334 tsk->task_frag.page = NULL; 335 336 account_kernel_stack(ti, 1); 337 338 return tsk; 339 340 free_ti: 341 free_thread_info(ti); 342 free_tsk: 343 free_task_struct(tsk); 344 return NULL; 345 } 346 347 #ifdef CONFIG_MMU 348 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 349 { 350 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 351 struct rb_node **rb_link, *rb_parent; 352 int retval; 353 unsigned long charge; 354 355 uprobe_start_dup_mmap(); 356 down_write(&oldmm->mmap_sem); 357 flush_cache_dup_mm(oldmm); 358 uprobe_dup_mmap(oldmm, mm); 359 /* 360 * Not linked in yet - no deadlock potential: 361 */ 362 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 363 364 mm->locked_vm = 0; 365 mm->mmap = NULL; 366 mm->mmap_cache = NULL; 367 mm->map_count = 0; 368 cpumask_clear(mm_cpumask(mm)); 369 mm->mm_rb = RB_ROOT; 370 rb_link = &mm->mm_rb.rb_node; 371 rb_parent = NULL; 372 pprev = &mm->mmap; 373 retval = ksm_fork(mm, oldmm); 374 if (retval) 375 goto out; 376 retval = khugepaged_fork(mm, oldmm); 377 if (retval) 378 goto out; 379 380 prev = NULL; 381 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 382 struct file *file; 383 384 if (mpnt->vm_flags & VM_DONTCOPY) { 385 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 386 -vma_pages(mpnt)); 387 continue; 388 } 389 charge = 0; 390 if (mpnt->vm_flags & VM_ACCOUNT) { 391 unsigned long len = vma_pages(mpnt); 392 393 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 394 goto fail_nomem; 395 charge = len; 396 } 397 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 398 if (!tmp) 399 goto fail_nomem; 400 *tmp = *mpnt; 401 INIT_LIST_HEAD(&tmp->anon_vma_chain); 402 retval = vma_dup_policy(mpnt, tmp); 403 if (retval) 404 goto fail_nomem_policy; 405 tmp->vm_mm = mm; 406 if (anon_vma_fork(tmp, mpnt)) 407 goto fail_nomem_anon_vma_fork; 408 tmp->vm_flags &= ~VM_LOCKED; 409 tmp->vm_next = tmp->vm_prev = NULL; 410 file = tmp->vm_file; 411 if (file) { 412 struct inode *inode = file_inode(file); 413 struct address_space *mapping = file->f_mapping; 414 415 get_file(file); 416 if (tmp->vm_flags & VM_DENYWRITE) 417 atomic_dec(&inode->i_writecount); 418 mutex_lock(&mapping->i_mmap_mutex); 419 if (tmp->vm_flags & VM_SHARED) 420 mapping->i_mmap_writable++; 421 flush_dcache_mmap_lock(mapping); 422 /* insert tmp into the share list, just after mpnt */ 423 if (unlikely(tmp->vm_flags & VM_NONLINEAR)) 424 vma_nonlinear_insert(tmp, 425 &mapping->i_mmap_nonlinear); 426 else 427 vma_interval_tree_insert_after(tmp, mpnt, 428 &mapping->i_mmap); 429 flush_dcache_mmap_unlock(mapping); 430 mutex_unlock(&mapping->i_mmap_mutex); 431 } 432 433 /* 434 * Clear hugetlb-related page reserves for children. This only 435 * affects MAP_PRIVATE mappings. Faults generated by the child 436 * are not guaranteed to succeed, even if read-only 437 */ 438 if (is_vm_hugetlb_page(tmp)) 439 reset_vma_resv_huge_pages(tmp); 440 441 /* 442 * Link in the new vma and copy the page table entries. 443 */ 444 *pprev = tmp; 445 pprev = &tmp->vm_next; 446 tmp->vm_prev = prev; 447 prev = tmp; 448 449 __vma_link_rb(mm, tmp, rb_link, rb_parent); 450 rb_link = &tmp->vm_rb.rb_right; 451 rb_parent = &tmp->vm_rb; 452 453 mm->map_count++; 454 retval = copy_page_range(mm, oldmm, mpnt); 455 456 if (tmp->vm_ops && tmp->vm_ops->open) 457 tmp->vm_ops->open(tmp); 458 459 if (retval) 460 goto out; 461 } 462 /* a new mm has just been created */ 463 arch_dup_mmap(oldmm, mm); 464 retval = 0; 465 out: 466 up_write(&mm->mmap_sem); 467 flush_tlb_mm(oldmm); 468 up_write(&oldmm->mmap_sem); 469 uprobe_end_dup_mmap(); 470 return retval; 471 fail_nomem_anon_vma_fork: 472 mpol_put(vma_policy(tmp)); 473 fail_nomem_policy: 474 kmem_cache_free(vm_area_cachep, tmp); 475 fail_nomem: 476 retval = -ENOMEM; 477 vm_unacct_memory(charge); 478 goto out; 479 } 480 481 static inline int mm_alloc_pgd(struct mm_struct *mm) 482 { 483 mm->pgd = pgd_alloc(mm); 484 if (unlikely(!mm->pgd)) 485 return -ENOMEM; 486 return 0; 487 } 488 489 static inline void mm_free_pgd(struct mm_struct *mm) 490 { 491 pgd_free(mm, mm->pgd); 492 } 493 #else 494 #define dup_mmap(mm, oldmm) (0) 495 #define mm_alloc_pgd(mm) (0) 496 #define mm_free_pgd(mm) 497 #endif /* CONFIG_MMU */ 498 499 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 500 501 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 502 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 503 504 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 505 506 static int __init coredump_filter_setup(char *s) 507 { 508 default_dump_filter = 509 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 510 MMF_DUMP_FILTER_MASK; 511 return 1; 512 } 513 514 __setup("coredump_filter=", coredump_filter_setup); 515 516 #include <linux/init_task.h> 517 518 static void mm_init_aio(struct mm_struct *mm) 519 { 520 #ifdef CONFIG_AIO 521 spin_lock_init(&mm->ioctx_lock); 522 mm->ioctx_table = NULL; 523 #endif 524 } 525 526 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 527 { 528 atomic_set(&mm->mm_users, 1); 529 atomic_set(&mm->mm_count, 1); 530 init_rwsem(&mm->mmap_sem); 531 INIT_LIST_HEAD(&mm->mmlist); 532 mm->flags = (current->mm) ? 533 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 534 mm->core_state = NULL; 535 atomic_long_set(&mm->nr_ptes, 0); 536 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 537 spin_lock_init(&mm->page_table_lock); 538 mm_init_aio(mm); 539 mm_init_owner(mm, p); 540 clear_tlb_flush_pending(mm); 541 542 if (likely(!mm_alloc_pgd(mm))) { 543 mm->def_flags = 0; 544 mmu_notifier_mm_init(mm); 545 return mm; 546 } 547 548 free_mm(mm); 549 return NULL; 550 } 551 552 static void check_mm(struct mm_struct *mm) 553 { 554 int i; 555 556 for (i = 0; i < NR_MM_COUNTERS; i++) { 557 long x = atomic_long_read(&mm->rss_stat.count[i]); 558 559 if (unlikely(x)) 560 printk(KERN_ALERT "BUG: Bad rss-counter state " 561 "mm:%p idx:%d val:%ld\n", mm, i, x); 562 } 563 564 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 565 VM_BUG_ON(mm->pmd_huge_pte); 566 #endif 567 } 568 569 /* 570 * Allocate and initialize an mm_struct. 571 */ 572 struct mm_struct *mm_alloc(void) 573 { 574 struct mm_struct *mm; 575 576 mm = allocate_mm(); 577 if (!mm) 578 return NULL; 579 580 memset(mm, 0, sizeof(*mm)); 581 mm_init_cpumask(mm); 582 return mm_init(mm, current); 583 } 584 585 /* 586 * Called when the last reference to the mm 587 * is dropped: either by a lazy thread or by 588 * mmput. Free the page directory and the mm. 589 */ 590 void __mmdrop(struct mm_struct *mm) 591 { 592 BUG_ON(mm == &init_mm); 593 mm_free_pgd(mm); 594 destroy_context(mm); 595 mmu_notifier_mm_destroy(mm); 596 check_mm(mm); 597 free_mm(mm); 598 } 599 EXPORT_SYMBOL_GPL(__mmdrop); 600 601 /* 602 * Decrement the use count and release all resources for an mm. 603 */ 604 void mmput(struct mm_struct *mm) 605 { 606 might_sleep(); 607 608 if (atomic_dec_and_test(&mm->mm_users)) { 609 uprobe_clear_state(mm); 610 exit_aio(mm); 611 ksm_exit(mm); 612 khugepaged_exit(mm); /* must run before exit_mmap */ 613 exit_mmap(mm); 614 set_mm_exe_file(mm, NULL); 615 if (!list_empty(&mm->mmlist)) { 616 spin_lock(&mmlist_lock); 617 list_del(&mm->mmlist); 618 spin_unlock(&mmlist_lock); 619 } 620 if (mm->binfmt) 621 module_put(mm->binfmt->module); 622 mmdrop(mm); 623 } 624 } 625 EXPORT_SYMBOL_GPL(mmput); 626 627 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 628 { 629 if (new_exe_file) 630 get_file(new_exe_file); 631 if (mm->exe_file) 632 fput(mm->exe_file); 633 mm->exe_file = new_exe_file; 634 } 635 636 struct file *get_mm_exe_file(struct mm_struct *mm) 637 { 638 struct file *exe_file; 639 640 /* We need mmap_sem to protect against races with removal of exe_file */ 641 down_read(&mm->mmap_sem); 642 exe_file = mm->exe_file; 643 if (exe_file) 644 get_file(exe_file); 645 up_read(&mm->mmap_sem); 646 return exe_file; 647 } 648 649 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 650 { 651 /* It's safe to write the exe_file pointer without exe_file_lock because 652 * this is called during fork when the task is not yet in /proc */ 653 newmm->exe_file = get_mm_exe_file(oldmm); 654 } 655 656 /** 657 * get_task_mm - acquire a reference to the task's mm 658 * 659 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 660 * this kernel workthread has transiently adopted a user mm with use_mm, 661 * to do its AIO) is not set and if so returns a reference to it, after 662 * bumping up the use count. User must release the mm via mmput() 663 * after use. Typically used by /proc and ptrace. 664 */ 665 struct mm_struct *get_task_mm(struct task_struct *task) 666 { 667 struct mm_struct *mm; 668 669 task_lock(task); 670 mm = task->mm; 671 if (mm) { 672 if (task->flags & PF_KTHREAD) 673 mm = NULL; 674 else 675 atomic_inc(&mm->mm_users); 676 } 677 task_unlock(task); 678 return mm; 679 } 680 EXPORT_SYMBOL_GPL(get_task_mm); 681 682 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 683 { 684 struct mm_struct *mm; 685 int err; 686 687 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 688 if (err) 689 return ERR_PTR(err); 690 691 mm = get_task_mm(task); 692 if (mm && mm != current->mm && 693 !ptrace_may_access(task, mode)) { 694 mmput(mm); 695 mm = ERR_PTR(-EACCES); 696 } 697 mutex_unlock(&task->signal->cred_guard_mutex); 698 699 return mm; 700 } 701 702 static void complete_vfork_done(struct task_struct *tsk) 703 { 704 struct completion *vfork; 705 706 task_lock(tsk); 707 vfork = tsk->vfork_done; 708 if (likely(vfork)) { 709 tsk->vfork_done = NULL; 710 complete(vfork); 711 } 712 task_unlock(tsk); 713 } 714 715 static int wait_for_vfork_done(struct task_struct *child, 716 struct completion *vfork) 717 { 718 int killed; 719 720 freezer_do_not_count(); 721 killed = wait_for_completion_killable(vfork); 722 freezer_count(); 723 724 if (killed) { 725 task_lock(child); 726 child->vfork_done = NULL; 727 task_unlock(child); 728 } 729 730 put_task_struct(child); 731 return killed; 732 } 733 734 /* Please note the differences between mmput and mm_release. 735 * mmput is called whenever we stop holding onto a mm_struct, 736 * error success whatever. 737 * 738 * mm_release is called after a mm_struct has been removed 739 * from the current process. 740 * 741 * This difference is important for error handling, when we 742 * only half set up a mm_struct for a new process and need to restore 743 * the old one. Because we mmput the new mm_struct before 744 * restoring the old one. . . 745 * Eric Biederman 10 January 1998 746 */ 747 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 748 { 749 /* Get rid of any futexes when releasing the mm */ 750 #ifdef CONFIG_FUTEX 751 if (unlikely(tsk->robust_list)) { 752 exit_robust_list(tsk); 753 tsk->robust_list = NULL; 754 } 755 #ifdef CONFIG_COMPAT 756 if (unlikely(tsk->compat_robust_list)) { 757 compat_exit_robust_list(tsk); 758 tsk->compat_robust_list = NULL; 759 } 760 #endif 761 if (unlikely(!list_empty(&tsk->pi_state_list))) 762 exit_pi_state_list(tsk); 763 #endif 764 765 uprobe_free_utask(tsk); 766 767 /* Get rid of any cached register state */ 768 deactivate_mm(tsk, mm); 769 770 /* 771 * If we're exiting normally, clear a user-space tid field if 772 * requested. We leave this alone when dying by signal, to leave 773 * the value intact in a core dump, and to save the unnecessary 774 * trouble, say, a killed vfork parent shouldn't touch this mm. 775 * Userland only wants this done for a sys_exit. 776 */ 777 if (tsk->clear_child_tid) { 778 if (!(tsk->flags & PF_SIGNALED) && 779 atomic_read(&mm->mm_users) > 1) { 780 /* 781 * We don't check the error code - if userspace has 782 * not set up a proper pointer then tough luck. 783 */ 784 put_user(0, tsk->clear_child_tid); 785 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 786 1, NULL, NULL, 0); 787 } 788 tsk->clear_child_tid = NULL; 789 } 790 791 /* 792 * All done, finally we can wake up parent and return this mm to him. 793 * Also kthread_stop() uses this completion for synchronization. 794 */ 795 if (tsk->vfork_done) 796 complete_vfork_done(tsk); 797 } 798 799 /* 800 * Allocate a new mm structure and copy contents from the 801 * mm structure of the passed in task structure. 802 */ 803 static struct mm_struct *dup_mm(struct task_struct *tsk) 804 { 805 struct mm_struct *mm, *oldmm = current->mm; 806 int err; 807 808 mm = allocate_mm(); 809 if (!mm) 810 goto fail_nomem; 811 812 memcpy(mm, oldmm, sizeof(*mm)); 813 mm_init_cpumask(mm); 814 815 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 816 mm->pmd_huge_pte = NULL; 817 #endif 818 if (!mm_init(mm, tsk)) 819 goto fail_nomem; 820 821 if (init_new_context(tsk, mm)) 822 goto fail_nocontext; 823 824 dup_mm_exe_file(oldmm, mm); 825 826 err = dup_mmap(mm, oldmm); 827 if (err) 828 goto free_pt; 829 830 mm->hiwater_rss = get_mm_rss(mm); 831 mm->hiwater_vm = mm->total_vm; 832 833 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 834 goto free_pt; 835 836 return mm; 837 838 free_pt: 839 /* don't put binfmt in mmput, we haven't got module yet */ 840 mm->binfmt = NULL; 841 mmput(mm); 842 843 fail_nomem: 844 return NULL; 845 846 fail_nocontext: 847 /* 848 * If init_new_context() failed, we cannot use mmput() to free the mm 849 * because it calls destroy_context() 850 */ 851 mm_free_pgd(mm); 852 free_mm(mm); 853 return NULL; 854 } 855 856 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 857 { 858 struct mm_struct *mm, *oldmm; 859 int retval; 860 861 tsk->min_flt = tsk->maj_flt = 0; 862 tsk->nvcsw = tsk->nivcsw = 0; 863 #ifdef CONFIG_DETECT_HUNG_TASK 864 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 865 #endif 866 867 tsk->mm = NULL; 868 tsk->active_mm = NULL; 869 870 /* 871 * Are we cloning a kernel thread? 872 * 873 * We need to steal a active VM for that.. 874 */ 875 oldmm = current->mm; 876 if (!oldmm) 877 return 0; 878 879 if (clone_flags & CLONE_VM) { 880 atomic_inc(&oldmm->mm_users); 881 mm = oldmm; 882 goto good_mm; 883 } 884 885 retval = -ENOMEM; 886 mm = dup_mm(tsk); 887 if (!mm) 888 goto fail_nomem; 889 890 good_mm: 891 tsk->mm = mm; 892 tsk->active_mm = mm; 893 return 0; 894 895 fail_nomem: 896 return retval; 897 } 898 899 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 900 { 901 struct fs_struct *fs = current->fs; 902 if (clone_flags & CLONE_FS) { 903 /* tsk->fs is already what we want */ 904 spin_lock(&fs->lock); 905 if (fs->in_exec) { 906 spin_unlock(&fs->lock); 907 return -EAGAIN; 908 } 909 fs->users++; 910 spin_unlock(&fs->lock); 911 return 0; 912 } 913 tsk->fs = copy_fs_struct(fs); 914 if (!tsk->fs) 915 return -ENOMEM; 916 return 0; 917 } 918 919 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 920 { 921 struct files_struct *oldf, *newf; 922 int error = 0; 923 924 /* 925 * A background process may not have any files ... 926 */ 927 oldf = current->files; 928 if (!oldf) 929 goto out; 930 931 if (clone_flags & CLONE_FILES) { 932 atomic_inc(&oldf->count); 933 goto out; 934 } 935 936 newf = dup_fd(oldf, &error); 937 if (!newf) 938 goto out; 939 940 tsk->files = newf; 941 error = 0; 942 out: 943 return error; 944 } 945 946 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 947 { 948 #ifdef CONFIG_BLOCK 949 struct io_context *ioc = current->io_context; 950 struct io_context *new_ioc; 951 952 if (!ioc) 953 return 0; 954 /* 955 * Share io context with parent, if CLONE_IO is set 956 */ 957 if (clone_flags & CLONE_IO) { 958 ioc_task_link(ioc); 959 tsk->io_context = ioc; 960 } else if (ioprio_valid(ioc->ioprio)) { 961 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 962 if (unlikely(!new_ioc)) 963 return -ENOMEM; 964 965 new_ioc->ioprio = ioc->ioprio; 966 put_io_context(new_ioc); 967 } 968 #endif 969 return 0; 970 } 971 972 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 973 { 974 struct sighand_struct *sig; 975 976 if (clone_flags & CLONE_SIGHAND) { 977 atomic_inc(¤t->sighand->count); 978 return 0; 979 } 980 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 981 rcu_assign_pointer(tsk->sighand, sig); 982 if (!sig) 983 return -ENOMEM; 984 atomic_set(&sig->count, 1); 985 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 986 return 0; 987 } 988 989 void __cleanup_sighand(struct sighand_struct *sighand) 990 { 991 if (atomic_dec_and_test(&sighand->count)) { 992 signalfd_cleanup(sighand); 993 kmem_cache_free(sighand_cachep, sighand); 994 } 995 } 996 997 998 /* 999 * Initialize POSIX timer handling for a thread group. 1000 */ 1001 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1002 { 1003 unsigned long cpu_limit; 1004 1005 /* Thread group counters. */ 1006 thread_group_cputime_init(sig); 1007 1008 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1009 if (cpu_limit != RLIM_INFINITY) { 1010 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1011 sig->cputimer.running = 1; 1012 } 1013 1014 /* The timer lists. */ 1015 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1016 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1017 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1018 } 1019 1020 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1021 { 1022 struct signal_struct *sig; 1023 1024 if (clone_flags & CLONE_THREAD) 1025 return 0; 1026 1027 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1028 tsk->signal = sig; 1029 if (!sig) 1030 return -ENOMEM; 1031 1032 sig->nr_threads = 1; 1033 atomic_set(&sig->live, 1); 1034 atomic_set(&sig->sigcnt, 1); 1035 1036 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1037 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1038 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1039 1040 init_waitqueue_head(&sig->wait_chldexit); 1041 sig->curr_target = tsk; 1042 init_sigpending(&sig->shared_pending); 1043 INIT_LIST_HEAD(&sig->posix_timers); 1044 1045 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1046 sig->real_timer.function = it_real_fn; 1047 1048 task_lock(current->group_leader); 1049 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1050 task_unlock(current->group_leader); 1051 1052 posix_cpu_timers_init_group(sig); 1053 1054 tty_audit_fork(sig); 1055 sched_autogroup_fork(sig); 1056 1057 #ifdef CONFIG_CGROUPS 1058 init_rwsem(&sig->group_rwsem); 1059 #endif 1060 1061 sig->oom_score_adj = current->signal->oom_score_adj; 1062 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1063 1064 sig->has_child_subreaper = current->signal->has_child_subreaper || 1065 current->signal->is_child_subreaper; 1066 1067 mutex_init(&sig->cred_guard_mutex); 1068 1069 return 0; 1070 } 1071 1072 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1073 { 1074 unsigned long new_flags = p->flags; 1075 1076 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1077 new_flags |= PF_FORKNOEXEC; 1078 p->flags = new_flags; 1079 } 1080 1081 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1082 { 1083 current->clear_child_tid = tidptr; 1084 1085 return task_pid_vnr(current); 1086 } 1087 1088 static void rt_mutex_init_task(struct task_struct *p) 1089 { 1090 raw_spin_lock_init(&p->pi_lock); 1091 #ifdef CONFIG_RT_MUTEXES 1092 p->pi_waiters = RB_ROOT; 1093 p->pi_waiters_leftmost = NULL; 1094 p->pi_blocked_on = NULL; 1095 p->pi_top_task = NULL; 1096 #endif 1097 } 1098 1099 #ifdef CONFIG_MM_OWNER 1100 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1101 { 1102 mm->owner = p; 1103 } 1104 #endif /* CONFIG_MM_OWNER */ 1105 1106 /* 1107 * Initialize POSIX timer handling for a single task. 1108 */ 1109 static void posix_cpu_timers_init(struct task_struct *tsk) 1110 { 1111 tsk->cputime_expires.prof_exp = 0; 1112 tsk->cputime_expires.virt_exp = 0; 1113 tsk->cputime_expires.sched_exp = 0; 1114 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1115 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1116 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1117 } 1118 1119 static inline void 1120 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1121 { 1122 task->pids[type].pid = pid; 1123 } 1124 1125 /* 1126 * This creates a new process as a copy of the old one, 1127 * but does not actually start it yet. 1128 * 1129 * It copies the registers, and all the appropriate 1130 * parts of the process environment (as per the clone 1131 * flags). The actual kick-off is left to the caller. 1132 */ 1133 static struct task_struct *copy_process(unsigned long clone_flags, 1134 unsigned long stack_start, 1135 unsigned long stack_size, 1136 int __user *child_tidptr, 1137 struct pid *pid, 1138 int trace) 1139 { 1140 int retval; 1141 struct task_struct *p; 1142 1143 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1144 return ERR_PTR(-EINVAL); 1145 1146 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1147 return ERR_PTR(-EINVAL); 1148 1149 /* 1150 * Thread groups must share signals as well, and detached threads 1151 * can only be started up within the thread group. 1152 */ 1153 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1154 return ERR_PTR(-EINVAL); 1155 1156 /* 1157 * Shared signal handlers imply shared VM. By way of the above, 1158 * thread groups also imply shared VM. Blocking this case allows 1159 * for various simplifications in other code. 1160 */ 1161 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1162 return ERR_PTR(-EINVAL); 1163 1164 /* 1165 * Siblings of global init remain as zombies on exit since they are 1166 * not reaped by their parent (swapper). To solve this and to avoid 1167 * multi-rooted process trees, prevent global and container-inits 1168 * from creating siblings. 1169 */ 1170 if ((clone_flags & CLONE_PARENT) && 1171 current->signal->flags & SIGNAL_UNKILLABLE) 1172 return ERR_PTR(-EINVAL); 1173 1174 /* 1175 * If the new process will be in a different pid or user namespace 1176 * do not allow it to share a thread group or signal handlers or 1177 * parent with the forking task. 1178 */ 1179 if (clone_flags & CLONE_SIGHAND) { 1180 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1181 (task_active_pid_ns(current) != 1182 current->nsproxy->pid_ns_for_children)) 1183 return ERR_PTR(-EINVAL); 1184 } 1185 1186 retval = security_task_create(clone_flags); 1187 if (retval) 1188 goto fork_out; 1189 1190 retval = -ENOMEM; 1191 p = dup_task_struct(current); 1192 if (!p) 1193 goto fork_out; 1194 1195 ftrace_graph_init_task(p); 1196 get_seccomp_filter(p); 1197 1198 rt_mutex_init_task(p); 1199 1200 #ifdef CONFIG_PROVE_LOCKING 1201 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1202 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1203 #endif 1204 retval = -EAGAIN; 1205 if (atomic_read(&p->real_cred->user->processes) >= 1206 task_rlimit(p, RLIMIT_NPROC)) { 1207 if (p->real_cred->user != INIT_USER && 1208 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1209 goto bad_fork_free; 1210 } 1211 current->flags &= ~PF_NPROC_EXCEEDED; 1212 1213 retval = copy_creds(p, clone_flags); 1214 if (retval < 0) 1215 goto bad_fork_free; 1216 1217 /* 1218 * If multiple threads are within copy_process(), then this check 1219 * triggers too late. This doesn't hurt, the check is only there 1220 * to stop root fork bombs. 1221 */ 1222 retval = -EAGAIN; 1223 if (nr_threads >= max_threads) 1224 goto bad_fork_cleanup_count; 1225 1226 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1227 goto bad_fork_cleanup_count; 1228 1229 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1230 copy_flags(clone_flags, p); 1231 INIT_LIST_HEAD(&p->children); 1232 INIT_LIST_HEAD(&p->sibling); 1233 rcu_copy_process(p); 1234 p->vfork_done = NULL; 1235 spin_lock_init(&p->alloc_lock); 1236 1237 init_sigpending(&p->pending); 1238 1239 p->utime = p->stime = p->gtime = 0; 1240 p->utimescaled = p->stimescaled = 0; 1241 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1242 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1243 #endif 1244 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1245 seqlock_init(&p->vtime_seqlock); 1246 p->vtime_snap = 0; 1247 p->vtime_snap_whence = VTIME_SLEEPING; 1248 #endif 1249 1250 #if defined(SPLIT_RSS_COUNTING) 1251 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1252 #endif 1253 1254 p->default_timer_slack_ns = current->timer_slack_ns; 1255 1256 task_io_accounting_init(&p->ioac); 1257 acct_clear_integrals(p); 1258 1259 posix_cpu_timers_init(p); 1260 1261 do_posix_clock_monotonic_gettime(&p->start_time); 1262 p->real_start_time = p->start_time; 1263 monotonic_to_bootbased(&p->real_start_time); 1264 p->io_context = NULL; 1265 p->audit_context = NULL; 1266 if (clone_flags & CLONE_THREAD) 1267 threadgroup_change_begin(current); 1268 cgroup_fork(p); 1269 #ifdef CONFIG_NUMA 1270 p->mempolicy = mpol_dup(p->mempolicy); 1271 if (IS_ERR(p->mempolicy)) { 1272 retval = PTR_ERR(p->mempolicy); 1273 p->mempolicy = NULL; 1274 goto bad_fork_cleanup_cgroup; 1275 } 1276 mpol_fix_fork_child_flag(p); 1277 #endif 1278 #ifdef CONFIG_CPUSETS 1279 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1280 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1281 seqcount_init(&p->mems_allowed_seq); 1282 #endif 1283 #ifdef CONFIG_TRACE_IRQFLAGS 1284 p->irq_events = 0; 1285 p->hardirqs_enabled = 0; 1286 p->hardirq_enable_ip = 0; 1287 p->hardirq_enable_event = 0; 1288 p->hardirq_disable_ip = _THIS_IP_; 1289 p->hardirq_disable_event = 0; 1290 p->softirqs_enabled = 1; 1291 p->softirq_enable_ip = _THIS_IP_; 1292 p->softirq_enable_event = 0; 1293 p->softirq_disable_ip = 0; 1294 p->softirq_disable_event = 0; 1295 p->hardirq_context = 0; 1296 p->softirq_context = 0; 1297 #endif 1298 #ifdef CONFIG_LOCKDEP 1299 p->lockdep_depth = 0; /* no locks held yet */ 1300 p->curr_chain_key = 0; 1301 p->lockdep_recursion = 0; 1302 #endif 1303 1304 #ifdef CONFIG_DEBUG_MUTEXES 1305 p->blocked_on = NULL; /* not blocked yet */ 1306 #endif 1307 #ifdef CONFIG_MEMCG 1308 p->memcg_batch.do_batch = 0; 1309 p->memcg_batch.memcg = NULL; 1310 #endif 1311 #ifdef CONFIG_BCACHE 1312 p->sequential_io = 0; 1313 p->sequential_io_avg = 0; 1314 #endif 1315 1316 /* Perform scheduler related setup. Assign this task to a CPU. */ 1317 retval = sched_fork(clone_flags, p); 1318 if (retval) 1319 goto bad_fork_cleanup_policy; 1320 1321 retval = perf_event_init_task(p); 1322 if (retval) 1323 goto bad_fork_cleanup_policy; 1324 retval = audit_alloc(p); 1325 if (retval) 1326 goto bad_fork_cleanup_policy; 1327 /* copy all the process information */ 1328 retval = copy_semundo(clone_flags, p); 1329 if (retval) 1330 goto bad_fork_cleanup_audit; 1331 retval = copy_files(clone_flags, p); 1332 if (retval) 1333 goto bad_fork_cleanup_semundo; 1334 retval = copy_fs(clone_flags, p); 1335 if (retval) 1336 goto bad_fork_cleanup_files; 1337 retval = copy_sighand(clone_flags, p); 1338 if (retval) 1339 goto bad_fork_cleanup_fs; 1340 retval = copy_signal(clone_flags, p); 1341 if (retval) 1342 goto bad_fork_cleanup_sighand; 1343 retval = copy_mm(clone_flags, p); 1344 if (retval) 1345 goto bad_fork_cleanup_signal; 1346 retval = copy_namespaces(clone_flags, p); 1347 if (retval) 1348 goto bad_fork_cleanup_mm; 1349 retval = copy_io(clone_flags, p); 1350 if (retval) 1351 goto bad_fork_cleanup_namespaces; 1352 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1353 if (retval) 1354 goto bad_fork_cleanup_io; 1355 1356 if (pid != &init_struct_pid) { 1357 retval = -ENOMEM; 1358 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1359 if (!pid) 1360 goto bad_fork_cleanup_io; 1361 } 1362 1363 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1364 /* 1365 * Clear TID on mm_release()? 1366 */ 1367 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1368 #ifdef CONFIG_BLOCK 1369 p->plug = NULL; 1370 #endif 1371 #ifdef CONFIG_FUTEX 1372 p->robust_list = NULL; 1373 #ifdef CONFIG_COMPAT 1374 p->compat_robust_list = NULL; 1375 #endif 1376 INIT_LIST_HEAD(&p->pi_state_list); 1377 p->pi_state_cache = NULL; 1378 #endif 1379 /* 1380 * sigaltstack should be cleared when sharing the same VM 1381 */ 1382 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1383 p->sas_ss_sp = p->sas_ss_size = 0; 1384 1385 /* 1386 * Syscall tracing and stepping should be turned off in the 1387 * child regardless of CLONE_PTRACE. 1388 */ 1389 user_disable_single_step(p); 1390 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1391 #ifdef TIF_SYSCALL_EMU 1392 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1393 #endif 1394 clear_all_latency_tracing(p); 1395 1396 /* ok, now we should be set up.. */ 1397 p->pid = pid_nr(pid); 1398 if (clone_flags & CLONE_THREAD) { 1399 p->exit_signal = -1; 1400 p->group_leader = current->group_leader; 1401 p->tgid = current->tgid; 1402 } else { 1403 if (clone_flags & CLONE_PARENT) 1404 p->exit_signal = current->group_leader->exit_signal; 1405 else 1406 p->exit_signal = (clone_flags & CSIGNAL); 1407 p->group_leader = p; 1408 p->tgid = p->pid; 1409 } 1410 1411 p->nr_dirtied = 0; 1412 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1413 p->dirty_paused_when = 0; 1414 1415 p->pdeath_signal = 0; 1416 INIT_LIST_HEAD(&p->thread_group); 1417 p->task_works = NULL; 1418 1419 /* 1420 * Make it visible to the rest of the system, but dont wake it up yet. 1421 * Need tasklist lock for parent etc handling! 1422 */ 1423 write_lock_irq(&tasklist_lock); 1424 1425 /* CLONE_PARENT re-uses the old parent */ 1426 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1427 p->real_parent = current->real_parent; 1428 p->parent_exec_id = current->parent_exec_id; 1429 } else { 1430 p->real_parent = current; 1431 p->parent_exec_id = current->self_exec_id; 1432 } 1433 1434 spin_lock(¤t->sighand->siglock); 1435 1436 /* 1437 * Process group and session signals need to be delivered to just the 1438 * parent before the fork or both the parent and the child after the 1439 * fork. Restart if a signal comes in before we add the new process to 1440 * it's process group. 1441 * A fatal signal pending means that current will exit, so the new 1442 * thread can't slip out of an OOM kill (or normal SIGKILL). 1443 */ 1444 recalc_sigpending(); 1445 if (signal_pending(current)) { 1446 spin_unlock(¤t->sighand->siglock); 1447 write_unlock_irq(&tasklist_lock); 1448 retval = -ERESTARTNOINTR; 1449 goto bad_fork_free_pid; 1450 } 1451 1452 if (likely(p->pid)) { 1453 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1454 1455 init_task_pid(p, PIDTYPE_PID, pid); 1456 if (thread_group_leader(p)) { 1457 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1458 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1459 1460 if (is_child_reaper(pid)) { 1461 ns_of_pid(pid)->child_reaper = p; 1462 p->signal->flags |= SIGNAL_UNKILLABLE; 1463 } 1464 1465 p->signal->leader_pid = pid; 1466 p->signal->tty = tty_kref_get(current->signal->tty); 1467 list_add_tail(&p->sibling, &p->real_parent->children); 1468 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1469 attach_pid(p, PIDTYPE_PGID); 1470 attach_pid(p, PIDTYPE_SID); 1471 __this_cpu_inc(process_counts); 1472 } else { 1473 current->signal->nr_threads++; 1474 atomic_inc(¤t->signal->live); 1475 atomic_inc(¤t->signal->sigcnt); 1476 list_add_tail_rcu(&p->thread_group, 1477 &p->group_leader->thread_group); 1478 list_add_tail_rcu(&p->thread_node, 1479 &p->signal->thread_head); 1480 } 1481 attach_pid(p, PIDTYPE_PID); 1482 nr_threads++; 1483 } 1484 1485 total_forks++; 1486 spin_unlock(¤t->sighand->siglock); 1487 write_unlock_irq(&tasklist_lock); 1488 proc_fork_connector(p); 1489 cgroup_post_fork(p); 1490 if (clone_flags & CLONE_THREAD) 1491 threadgroup_change_end(current); 1492 perf_event_fork(p); 1493 1494 trace_task_newtask(p, clone_flags); 1495 uprobe_copy_process(p, clone_flags); 1496 1497 return p; 1498 1499 bad_fork_free_pid: 1500 if (pid != &init_struct_pid) 1501 free_pid(pid); 1502 bad_fork_cleanup_io: 1503 if (p->io_context) 1504 exit_io_context(p); 1505 bad_fork_cleanup_namespaces: 1506 exit_task_namespaces(p); 1507 bad_fork_cleanup_mm: 1508 if (p->mm) 1509 mmput(p->mm); 1510 bad_fork_cleanup_signal: 1511 if (!(clone_flags & CLONE_THREAD)) 1512 free_signal_struct(p->signal); 1513 bad_fork_cleanup_sighand: 1514 __cleanup_sighand(p->sighand); 1515 bad_fork_cleanup_fs: 1516 exit_fs(p); /* blocking */ 1517 bad_fork_cleanup_files: 1518 exit_files(p); /* blocking */ 1519 bad_fork_cleanup_semundo: 1520 exit_sem(p); 1521 bad_fork_cleanup_audit: 1522 audit_free(p); 1523 bad_fork_cleanup_policy: 1524 perf_event_free_task(p); 1525 #ifdef CONFIG_NUMA 1526 mpol_put(p->mempolicy); 1527 bad_fork_cleanup_cgroup: 1528 #endif 1529 if (clone_flags & CLONE_THREAD) 1530 threadgroup_change_end(current); 1531 cgroup_exit(p, 0); 1532 delayacct_tsk_free(p); 1533 module_put(task_thread_info(p)->exec_domain->module); 1534 bad_fork_cleanup_count: 1535 atomic_dec(&p->cred->user->processes); 1536 exit_creds(p); 1537 bad_fork_free: 1538 free_task(p); 1539 fork_out: 1540 return ERR_PTR(retval); 1541 } 1542 1543 static inline void init_idle_pids(struct pid_link *links) 1544 { 1545 enum pid_type type; 1546 1547 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1548 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1549 links[type].pid = &init_struct_pid; 1550 } 1551 } 1552 1553 struct task_struct *fork_idle(int cpu) 1554 { 1555 struct task_struct *task; 1556 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1557 if (!IS_ERR(task)) { 1558 init_idle_pids(task->pids); 1559 init_idle(task, cpu); 1560 } 1561 1562 return task; 1563 } 1564 1565 /* 1566 * Ok, this is the main fork-routine. 1567 * 1568 * It copies the process, and if successful kick-starts 1569 * it and waits for it to finish using the VM if required. 1570 */ 1571 long do_fork(unsigned long clone_flags, 1572 unsigned long stack_start, 1573 unsigned long stack_size, 1574 int __user *parent_tidptr, 1575 int __user *child_tidptr) 1576 { 1577 struct task_struct *p; 1578 int trace = 0; 1579 long nr; 1580 1581 /* 1582 * Determine whether and which event to report to ptracer. When 1583 * called from kernel_thread or CLONE_UNTRACED is explicitly 1584 * requested, no event is reported; otherwise, report if the event 1585 * for the type of forking is enabled. 1586 */ 1587 if (!(clone_flags & CLONE_UNTRACED)) { 1588 if (clone_flags & CLONE_VFORK) 1589 trace = PTRACE_EVENT_VFORK; 1590 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1591 trace = PTRACE_EVENT_CLONE; 1592 else 1593 trace = PTRACE_EVENT_FORK; 1594 1595 if (likely(!ptrace_event_enabled(current, trace))) 1596 trace = 0; 1597 } 1598 1599 p = copy_process(clone_flags, stack_start, stack_size, 1600 child_tidptr, NULL, trace); 1601 /* 1602 * Do this prior waking up the new thread - the thread pointer 1603 * might get invalid after that point, if the thread exits quickly. 1604 */ 1605 if (!IS_ERR(p)) { 1606 struct completion vfork; 1607 1608 trace_sched_process_fork(current, p); 1609 1610 nr = task_pid_vnr(p); 1611 1612 if (clone_flags & CLONE_PARENT_SETTID) 1613 put_user(nr, parent_tidptr); 1614 1615 if (clone_flags & CLONE_VFORK) { 1616 p->vfork_done = &vfork; 1617 init_completion(&vfork); 1618 get_task_struct(p); 1619 } 1620 1621 wake_up_new_task(p); 1622 1623 /* forking complete and child started to run, tell ptracer */ 1624 if (unlikely(trace)) 1625 ptrace_event(trace, nr); 1626 1627 if (clone_flags & CLONE_VFORK) { 1628 if (!wait_for_vfork_done(p, &vfork)) 1629 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1630 } 1631 } else { 1632 nr = PTR_ERR(p); 1633 } 1634 return nr; 1635 } 1636 1637 /* 1638 * Create a kernel thread. 1639 */ 1640 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1641 { 1642 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1643 (unsigned long)arg, NULL, NULL); 1644 } 1645 1646 #ifdef __ARCH_WANT_SYS_FORK 1647 SYSCALL_DEFINE0(fork) 1648 { 1649 #ifdef CONFIG_MMU 1650 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1651 #else 1652 /* can not support in nommu mode */ 1653 return -EINVAL; 1654 #endif 1655 } 1656 #endif 1657 1658 #ifdef __ARCH_WANT_SYS_VFORK 1659 SYSCALL_DEFINE0(vfork) 1660 { 1661 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1662 0, NULL, NULL); 1663 } 1664 #endif 1665 1666 #ifdef __ARCH_WANT_SYS_CLONE 1667 #ifdef CONFIG_CLONE_BACKWARDS 1668 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1669 int __user *, parent_tidptr, 1670 int, tls_val, 1671 int __user *, child_tidptr) 1672 #elif defined(CONFIG_CLONE_BACKWARDS2) 1673 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1674 int __user *, parent_tidptr, 1675 int __user *, child_tidptr, 1676 int, tls_val) 1677 #elif defined(CONFIG_CLONE_BACKWARDS3) 1678 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1679 int, stack_size, 1680 int __user *, parent_tidptr, 1681 int __user *, child_tidptr, 1682 int, tls_val) 1683 #else 1684 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1685 int __user *, parent_tidptr, 1686 int __user *, child_tidptr, 1687 int, tls_val) 1688 #endif 1689 { 1690 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1691 } 1692 #endif 1693 1694 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1695 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1696 #endif 1697 1698 static void sighand_ctor(void *data) 1699 { 1700 struct sighand_struct *sighand = data; 1701 1702 spin_lock_init(&sighand->siglock); 1703 init_waitqueue_head(&sighand->signalfd_wqh); 1704 } 1705 1706 void __init proc_caches_init(void) 1707 { 1708 sighand_cachep = kmem_cache_create("sighand_cache", 1709 sizeof(struct sighand_struct), 0, 1710 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1711 SLAB_NOTRACK, sighand_ctor); 1712 signal_cachep = kmem_cache_create("signal_cache", 1713 sizeof(struct signal_struct), 0, 1714 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1715 files_cachep = kmem_cache_create("files_cache", 1716 sizeof(struct files_struct), 0, 1717 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1718 fs_cachep = kmem_cache_create("fs_cache", 1719 sizeof(struct fs_struct), 0, 1720 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1721 /* 1722 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1723 * whole struct cpumask for the OFFSTACK case. We could change 1724 * this to *only* allocate as much of it as required by the 1725 * maximum number of CPU's we can ever have. The cpumask_allocation 1726 * is at the end of the structure, exactly for that reason. 1727 */ 1728 mm_cachep = kmem_cache_create("mm_struct", 1729 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1730 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1731 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1732 mmap_init(); 1733 nsproxy_cache_init(); 1734 } 1735 1736 /* 1737 * Check constraints on flags passed to the unshare system call. 1738 */ 1739 static int check_unshare_flags(unsigned long unshare_flags) 1740 { 1741 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1742 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1743 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1744 CLONE_NEWUSER|CLONE_NEWPID)) 1745 return -EINVAL; 1746 /* 1747 * Not implemented, but pretend it works if there is nothing to 1748 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1749 * needs to unshare vm. 1750 */ 1751 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1752 /* FIXME: get_task_mm() increments ->mm_users */ 1753 if (atomic_read(¤t->mm->mm_users) > 1) 1754 return -EINVAL; 1755 } 1756 1757 return 0; 1758 } 1759 1760 /* 1761 * Unshare the filesystem structure if it is being shared 1762 */ 1763 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1764 { 1765 struct fs_struct *fs = current->fs; 1766 1767 if (!(unshare_flags & CLONE_FS) || !fs) 1768 return 0; 1769 1770 /* don't need lock here; in the worst case we'll do useless copy */ 1771 if (fs->users == 1) 1772 return 0; 1773 1774 *new_fsp = copy_fs_struct(fs); 1775 if (!*new_fsp) 1776 return -ENOMEM; 1777 1778 return 0; 1779 } 1780 1781 /* 1782 * Unshare file descriptor table if it is being shared 1783 */ 1784 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1785 { 1786 struct files_struct *fd = current->files; 1787 int error = 0; 1788 1789 if ((unshare_flags & CLONE_FILES) && 1790 (fd && atomic_read(&fd->count) > 1)) { 1791 *new_fdp = dup_fd(fd, &error); 1792 if (!*new_fdp) 1793 return error; 1794 } 1795 1796 return 0; 1797 } 1798 1799 /* 1800 * unshare allows a process to 'unshare' part of the process 1801 * context which was originally shared using clone. copy_* 1802 * functions used by do_fork() cannot be used here directly 1803 * because they modify an inactive task_struct that is being 1804 * constructed. Here we are modifying the current, active, 1805 * task_struct. 1806 */ 1807 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1808 { 1809 struct fs_struct *fs, *new_fs = NULL; 1810 struct files_struct *fd, *new_fd = NULL; 1811 struct cred *new_cred = NULL; 1812 struct nsproxy *new_nsproxy = NULL; 1813 int do_sysvsem = 0; 1814 int err; 1815 1816 /* 1817 * If unsharing a user namespace must also unshare the thread. 1818 */ 1819 if (unshare_flags & CLONE_NEWUSER) 1820 unshare_flags |= CLONE_THREAD | CLONE_FS; 1821 /* 1822 * If unsharing a thread from a thread group, must also unshare vm. 1823 */ 1824 if (unshare_flags & CLONE_THREAD) 1825 unshare_flags |= CLONE_VM; 1826 /* 1827 * If unsharing vm, must also unshare signal handlers. 1828 */ 1829 if (unshare_flags & CLONE_VM) 1830 unshare_flags |= CLONE_SIGHAND; 1831 /* 1832 * If unsharing namespace, must also unshare filesystem information. 1833 */ 1834 if (unshare_flags & CLONE_NEWNS) 1835 unshare_flags |= CLONE_FS; 1836 1837 err = check_unshare_flags(unshare_flags); 1838 if (err) 1839 goto bad_unshare_out; 1840 /* 1841 * CLONE_NEWIPC must also detach from the undolist: after switching 1842 * to a new ipc namespace, the semaphore arrays from the old 1843 * namespace are unreachable. 1844 */ 1845 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1846 do_sysvsem = 1; 1847 err = unshare_fs(unshare_flags, &new_fs); 1848 if (err) 1849 goto bad_unshare_out; 1850 err = unshare_fd(unshare_flags, &new_fd); 1851 if (err) 1852 goto bad_unshare_cleanup_fs; 1853 err = unshare_userns(unshare_flags, &new_cred); 1854 if (err) 1855 goto bad_unshare_cleanup_fd; 1856 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1857 new_cred, new_fs); 1858 if (err) 1859 goto bad_unshare_cleanup_cred; 1860 1861 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1862 if (do_sysvsem) { 1863 /* 1864 * CLONE_SYSVSEM is equivalent to sys_exit(). 1865 */ 1866 exit_sem(current); 1867 } 1868 1869 if (new_nsproxy) 1870 switch_task_namespaces(current, new_nsproxy); 1871 1872 task_lock(current); 1873 1874 if (new_fs) { 1875 fs = current->fs; 1876 spin_lock(&fs->lock); 1877 current->fs = new_fs; 1878 if (--fs->users) 1879 new_fs = NULL; 1880 else 1881 new_fs = fs; 1882 spin_unlock(&fs->lock); 1883 } 1884 1885 if (new_fd) { 1886 fd = current->files; 1887 current->files = new_fd; 1888 new_fd = fd; 1889 } 1890 1891 task_unlock(current); 1892 1893 if (new_cred) { 1894 /* Install the new user namespace */ 1895 commit_creds(new_cred); 1896 new_cred = NULL; 1897 } 1898 } 1899 1900 bad_unshare_cleanup_cred: 1901 if (new_cred) 1902 put_cred(new_cred); 1903 bad_unshare_cleanup_fd: 1904 if (new_fd) 1905 put_files_struct(new_fd); 1906 1907 bad_unshare_cleanup_fs: 1908 if (new_fs) 1909 free_fs_struct(new_fs); 1910 1911 bad_unshare_out: 1912 return err; 1913 } 1914 1915 /* 1916 * Helper to unshare the files of the current task. 1917 * We don't want to expose copy_files internals to 1918 * the exec layer of the kernel. 1919 */ 1920 1921 int unshare_files(struct files_struct **displaced) 1922 { 1923 struct task_struct *task = current; 1924 struct files_struct *copy = NULL; 1925 int error; 1926 1927 error = unshare_fd(CLONE_FILES, ©); 1928 if (error || !copy) { 1929 *displaced = NULL; 1930 return error; 1931 } 1932 *displaced = task->files; 1933 task_lock(task); 1934 task->files = copy; 1935 task_unlock(task); 1936 return 0; 1937 } 1938