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