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/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/futex.h> 41 #include <linux/compat.h> 42 #include <linux/kthread.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/ksm.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/blkdev.h> 62 #include <linux/fs_struct.h> 63 #include <linux/magic.h> 64 #include <linux/perf_event.h> 65 #include <linux/posix-timers.h> 66 #include <linux/user-return-notifier.h> 67 #include <linux/oom.h> 68 #include <linux/khugepaged.h> 69 #include <linux/signalfd.h> 70 71 #include <asm/pgtable.h> 72 #include <asm/pgalloc.h> 73 #include <asm/uaccess.h> 74 #include <asm/mmu_context.h> 75 #include <asm/cacheflush.h> 76 #include <asm/tlbflush.h> 77 78 #include <trace/events/sched.h> 79 80 #define CREATE_TRACE_POINTS 81 #include <trace/events/task.h> 82 83 /* 84 * Protected counters by write_lock_irq(&tasklist_lock) 85 */ 86 unsigned long total_forks; /* Handle normal Linux uptimes. */ 87 int nr_threads; /* The idle threads do not count.. */ 88 89 int max_threads; /* tunable limit on nr_threads */ 90 91 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 92 93 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 94 95 #ifdef CONFIG_PROVE_RCU 96 int lockdep_tasklist_lock_is_held(void) 97 { 98 return lockdep_is_held(&tasklist_lock); 99 } 100 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 101 #endif /* #ifdef CONFIG_PROVE_RCU */ 102 103 int nr_processes(void) 104 { 105 int cpu; 106 int total = 0; 107 108 for_each_possible_cpu(cpu) 109 total += per_cpu(process_counts, cpu); 110 111 return total; 112 } 113 114 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 115 # define alloc_task_struct_node(node) \ 116 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node) 117 # define free_task_struct(tsk) \ 118 kmem_cache_free(task_struct_cachep, (tsk)) 119 static struct kmem_cache *task_struct_cachep; 120 #endif 121 122 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 123 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 124 int node) 125 { 126 #ifdef CONFIG_DEBUG_STACK_USAGE 127 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 128 #else 129 gfp_t mask = GFP_KERNEL; 130 #endif 131 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER); 132 133 return page ? page_address(page) : NULL; 134 } 135 136 static inline void free_thread_info(struct thread_info *ti) 137 { 138 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 139 } 140 #endif 141 142 /* SLAB cache for signal_struct structures (tsk->signal) */ 143 static struct kmem_cache *signal_cachep; 144 145 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 146 struct kmem_cache *sighand_cachep; 147 148 /* SLAB cache for files_struct structures (tsk->files) */ 149 struct kmem_cache *files_cachep; 150 151 /* SLAB cache for fs_struct structures (tsk->fs) */ 152 struct kmem_cache *fs_cachep; 153 154 /* SLAB cache for vm_area_struct structures */ 155 struct kmem_cache *vm_area_cachep; 156 157 /* SLAB cache for mm_struct structures (tsk->mm) */ 158 static struct kmem_cache *mm_cachep; 159 160 static void account_kernel_stack(struct thread_info *ti, int account) 161 { 162 struct zone *zone = page_zone(virt_to_page(ti)); 163 164 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 165 } 166 167 void free_task(struct task_struct *tsk) 168 { 169 account_kernel_stack(tsk->stack, -1); 170 free_thread_info(tsk->stack); 171 rt_mutex_debug_task_free(tsk); 172 ftrace_graph_exit_task(tsk); 173 free_task_struct(tsk); 174 } 175 EXPORT_SYMBOL(free_task); 176 177 static inline void free_signal_struct(struct signal_struct *sig) 178 { 179 taskstats_tgid_free(sig); 180 sched_autogroup_exit(sig); 181 kmem_cache_free(signal_cachep, sig); 182 } 183 184 static inline void put_signal_struct(struct signal_struct *sig) 185 { 186 if (atomic_dec_and_test(&sig->sigcnt)) 187 free_signal_struct(sig); 188 } 189 190 void __put_task_struct(struct task_struct *tsk) 191 { 192 WARN_ON(!tsk->exit_state); 193 WARN_ON(atomic_read(&tsk->usage)); 194 WARN_ON(tsk == current); 195 196 security_task_free(tsk); 197 exit_creds(tsk); 198 delayacct_tsk_free(tsk); 199 put_signal_struct(tsk->signal); 200 201 if (!profile_handoff_task(tsk)) 202 free_task(tsk); 203 } 204 EXPORT_SYMBOL_GPL(__put_task_struct); 205 206 /* 207 * macro override instead of weak attribute alias, to workaround 208 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 209 */ 210 #ifndef arch_task_cache_init 211 #define arch_task_cache_init() 212 #endif 213 214 void __init fork_init(unsigned long mempages) 215 { 216 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 217 #ifndef ARCH_MIN_TASKALIGN 218 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 219 #endif 220 /* create a slab on which task_structs can be allocated */ 221 task_struct_cachep = 222 kmem_cache_create("task_struct", sizeof(struct task_struct), 223 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 224 #endif 225 226 /* do the arch specific task caches init */ 227 arch_task_cache_init(); 228 229 /* 230 * The default maximum number of threads is set to a safe 231 * value: the thread structures can take up at most half 232 * of memory. 233 */ 234 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 235 236 /* 237 * we need to allow at least 20 threads to boot a system 238 */ 239 if (max_threads < 20) 240 max_threads = 20; 241 242 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 243 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 244 init_task.signal->rlim[RLIMIT_SIGPENDING] = 245 init_task.signal->rlim[RLIMIT_NPROC]; 246 } 247 248 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 249 struct task_struct *src) 250 { 251 *dst = *src; 252 return 0; 253 } 254 255 static struct task_struct *dup_task_struct(struct task_struct *orig) 256 { 257 struct task_struct *tsk; 258 struct thread_info *ti; 259 unsigned long *stackend; 260 int node = tsk_fork_get_node(orig); 261 int err; 262 263 prepare_to_copy(orig); 264 265 tsk = alloc_task_struct_node(node); 266 if (!tsk) 267 return NULL; 268 269 ti = alloc_thread_info_node(tsk, node); 270 if (!ti) { 271 free_task_struct(tsk); 272 return NULL; 273 } 274 275 err = arch_dup_task_struct(tsk, orig); 276 if (err) 277 goto out; 278 279 tsk->stack = ti; 280 281 setup_thread_stack(tsk, orig); 282 clear_user_return_notifier(tsk); 283 clear_tsk_need_resched(tsk); 284 stackend = end_of_stack(tsk); 285 *stackend = STACK_END_MAGIC; /* for overflow detection */ 286 287 #ifdef CONFIG_CC_STACKPROTECTOR 288 tsk->stack_canary = get_random_int(); 289 #endif 290 291 /* 292 * One for us, one for whoever does the "release_task()" (usually 293 * parent) 294 */ 295 atomic_set(&tsk->usage, 2); 296 #ifdef CONFIG_BLK_DEV_IO_TRACE 297 tsk->btrace_seq = 0; 298 #endif 299 tsk->splice_pipe = NULL; 300 301 account_kernel_stack(ti, 1); 302 303 return tsk; 304 305 out: 306 free_thread_info(ti); 307 free_task_struct(tsk); 308 return NULL; 309 } 310 311 #ifdef CONFIG_MMU 312 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 313 { 314 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 315 struct rb_node **rb_link, *rb_parent; 316 int retval; 317 unsigned long charge; 318 struct mempolicy *pol; 319 320 down_write(&oldmm->mmap_sem); 321 flush_cache_dup_mm(oldmm); 322 /* 323 * Not linked in yet - no deadlock potential: 324 */ 325 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 326 327 mm->locked_vm = 0; 328 mm->mmap = NULL; 329 mm->mmap_cache = NULL; 330 mm->free_area_cache = oldmm->mmap_base; 331 mm->cached_hole_size = ~0UL; 332 mm->map_count = 0; 333 cpumask_clear(mm_cpumask(mm)); 334 mm->mm_rb = RB_ROOT; 335 rb_link = &mm->mm_rb.rb_node; 336 rb_parent = NULL; 337 pprev = &mm->mmap; 338 retval = ksm_fork(mm, oldmm); 339 if (retval) 340 goto out; 341 retval = khugepaged_fork(mm, oldmm); 342 if (retval) 343 goto out; 344 345 prev = NULL; 346 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 347 struct file *file; 348 349 if (mpnt->vm_flags & VM_DONTCOPY) { 350 long pages = vma_pages(mpnt); 351 mm->total_vm -= pages; 352 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 353 -pages); 354 continue; 355 } 356 charge = 0; 357 if (mpnt->vm_flags & VM_ACCOUNT) { 358 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 359 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 360 goto fail_nomem; 361 charge = len; 362 } 363 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 364 if (!tmp) 365 goto fail_nomem; 366 *tmp = *mpnt; 367 INIT_LIST_HEAD(&tmp->anon_vma_chain); 368 pol = mpol_dup(vma_policy(mpnt)); 369 retval = PTR_ERR(pol); 370 if (IS_ERR(pol)) 371 goto fail_nomem_policy; 372 vma_set_policy(tmp, pol); 373 tmp->vm_mm = mm; 374 if (anon_vma_fork(tmp, mpnt)) 375 goto fail_nomem_anon_vma_fork; 376 tmp->vm_flags &= ~VM_LOCKED; 377 tmp->vm_next = tmp->vm_prev = NULL; 378 file = tmp->vm_file; 379 if (file) { 380 struct inode *inode = file->f_path.dentry->d_inode; 381 struct address_space *mapping = file->f_mapping; 382 383 get_file(file); 384 if (tmp->vm_flags & VM_DENYWRITE) 385 atomic_dec(&inode->i_writecount); 386 mutex_lock(&mapping->i_mmap_mutex); 387 if (tmp->vm_flags & VM_SHARED) 388 mapping->i_mmap_writable++; 389 flush_dcache_mmap_lock(mapping); 390 /* insert tmp into the share list, just after mpnt */ 391 vma_prio_tree_add(tmp, mpnt); 392 flush_dcache_mmap_unlock(mapping); 393 mutex_unlock(&mapping->i_mmap_mutex); 394 } 395 396 /* 397 * Clear hugetlb-related page reserves for children. This only 398 * affects MAP_PRIVATE mappings. Faults generated by the child 399 * are not guaranteed to succeed, even if read-only 400 */ 401 if (is_vm_hugetlb_page(tmp)) 402 reset_vma_resv_huge_pages(tmp); 403 404 /* 405 * Link in the new vma and copy the page table entries. 406 */ 407 *pprev = tmp; 408 pprev = &tmp->vm_next; 409 tmp->vm_prev = prev; 410 prev = tmp; 411 412 __vma_link_rb(mm, tmp, rb_link, rb_parent); 413 rb_link = &tmp->vm_rb.rb_right; 414 rb_parent = &tmp->vm_rb; 415 416 mm->map_count++; 417 retval = copy_page_range(mm, oldmm, mpnt); 418 419 if (tmp->vm_ops && tmp->vm_ops->open) 420 tmp->vm_ops->open(tmp); 421 422 if (retval) 423 goto out; 424 } 425 /* a new mm has just been created */ 426 arch_dup_mmap(oldmm, mm); 427 retval = 0; 428 out: 429 up_write(&mm->mmap_sem); 430 flush_tlb_mm(oldmm); 431 up_write(&oldmm->mmap_sem); 432 return retval; 433 fail_nomem_anon_vma_fork: 434 mpol_put(pol); 435 fail_nomem_policy: 436 kmem_cache_free(vm_area_cachep, tmp); 437 fail_nomem: 438 retval = -ENOMEM; 439 vm_unacct_memory(charge); 440 goto out; 441 } 442 443 static inline int mm_alloc_pgd(struct mm_struct *mm) 444 { 445 mm->pgd = pgd_alloc(mm); 446 if (unlikely(!mm->pgd)) 447 return -ENOMEM; 448 return 0; 449 } 450 451 static inline void mm_free_pgd(struct mm_struct *mm) 452 { 453 pgd_free(mm, mm->pgd); 454 } 455 #else 456 #define dup_mmap(mm, oldmm) (0) 457 #define mm_alloc_pgd(mm) (0) 458 #define mm_free_pgd(mm) 459 #endif /* CONFIG_MMU */ 460 461 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 462 463 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 464 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 465 466 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 467 468 static int __init coredump_filter_setup(char *s) 469 { 470 default_dump_filter = 471 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 472 MMF_DUMP_FILTER_MASK; 473 return 1; 474 } 475 476 __setup("coredump_filter=", coredump_filter_setup); 477 478 #include <linux/init_task.h> 479 480 static void mm_init_aio(struct mm_struct *mm) 481 { 482 #ifdef CONFIG_AIO 483 spin_lock_init(&mm->ioctx_lock); 484 INIT_HLIST_HEAD(&mm->ioctx_list); 485 #endif 486 } 487 488 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 489 { 490 atomic_set(&mm->mm_users, 1); 491 atomic_set(&mm->mm_count, 1); 492 init_rwsem(&mm->mmap_sem); 493 INIT_LIST_HEAD(&mm->mmlist); 494 mm->flags = (current->mm) ? 495 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 496 mm->core_state = NULL; 497 mm->nr_ptes = 0; 498 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 499 spin_lock_init(&mm->page_table_lock); 500 mm->free_area_cache = TASK_UNMAPPED_BASE; 501 mm->cached_hole_size = ~0UL; 502 mm_init_aio(mm); 503 mm_init_owner(mm, p); 504 505 if (likely(!mm_alloc_pgd(mm))) { 506 mm->def_flags = 0; 507 mmu_notifier_mm_init(mm); 508 return mm; 509 } 510 511 free_mm(mm); 512 return NULL; 513 } 514 515 static void check_mm(struct mm_struct *mm) 516 { 517 int i; 518 519 for (i = 0; i < NR_MM_COUNTERS; i++) { 520 long x = atomic_long_read(&mm->rss_stat.count[i]); 521 522 if (unlikely(x)) 523 printk(KERN_ALERT "BUG: Bad rss-counter state " 524 "mm:%p idx:%d val:%ld\n", mm, i, x); 525 } 526 527 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 528 VM_BUG_ON(mm->pmd_huge_pte); 529 #endif 530 } 531 532 /* 533 * Allocate and initialize an mm_struct. 534 */ 535 struct mm_struct *mm_alloc(void) 536 { 537 struct mm_struct *mm; 538 539 mm = allocate_mm(); 540 if (!mm) 541 return NULL; 542 543 memset(mm, 0, sizeof(*mm)); 544 mm_init_cpumask(mm); 545 return mm_init(mm, current); 546 } 547 548 /* 549 * Called when the last reference to the mm 550 * is dropped: either by a lazy thread or by 551 * mmput. Free the page directory and the mm. 552 */ 553 void __mmdrop(struct mm_struct *mm) 554 { 555 BUG_ON(mm == &init_mm); 556 mm_free_pgd(mm); 557 destroy_context(mm); 558 mmu_notifier_mm_destroy(mm); 559 check_mm(mm); 560 free_mm(mm); 561 } 562 EXPORT_SYMBOL_GPL(__mmdrop); 563 564 /* 565 * Decrement the use count and release all resources for an mm. 566 */ 567 void mmput(struct mm_struct *mm) 568 { 569 might_sleep(); 570 571 if (atomic_dec_and_test(&mm->mm_users)) { 572 exit_aio(mm); 573 ksm_exit(mm); 574 khugepaged_exit(mm); /* must run before exit_mmap */ 575 exit_mmap(mm); 576 set_mm_exe_file(mm, NULL); 577 if (!list_empty(&mm->mmlist)) { 578 spin_lock(&mmlist_lock); 579 list_del(&mm->mmlist); 580 spin_unlock(&mmlist_lock); 581 } 582 put_swap_token(mm); 583 if (mm->binfmt) 584 module_put(mm->binfmt->module); 585 mmdrop(mm); 586 } 587 } 588 EXPORT_SYMBOL_GPL(mmput); 589 590 /* 591 * We added or removed a vma mapping the executable. The vmas are only mapped 592 * during exec and are not mapped with the mmap system call. 593 * Callers must hold down_write() on the mm's mmap_sem for these 594 */ 595 void added_exe_file_vma(struct mm_struct *mm) 596 { 597 mm->num_exe_file_vmas++; 598 } 599 600 void removed_exe_file_vma(struct mm_struct *mm) 601 { 602 mm->num_exe_file_vmas--; 603 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 604 fput(mm->exe_file); 605 mm->exe_file = NULL; 606 } 607 608 } 609 610 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 611 { 612 if (new_exe_file) 613 get_file(new_exe_file); 614 if (mm->exe_file) 615 fput(mm->exe_file); 616 mm->exe_file = new_exe_file; 617 mm->num_exe_file_vmas = 0; 618 } 619 620 struct file *get_mm_exe_file(struct mm_struct *mm) 621 { 622 struct file *exe_file; 623 624 /* We need mmap_sem to protect against races with removal of 625 * VM_EXECUTABLE vmas */ 626 down_read(&mm->mmap_sem); 627 exe_file = mm->exe_file; 628 if (exe_file) 629 get_file(exe_file); 630 up_read(&mm->mmap_sem); 631 return exe_file; 632 } 633 634 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 635 { 636 /* It's safe to write the exe_file pointer without exe_file_lock because 637 * this is called during fork when the task is not yet in /proc */ 638 newmm->exe_file = get_mm_exe_file(oldmm); 639 } 640 641 /** 642 * get_task_mm - acquire a reference to the task's mm 643 * 644 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 645 * this kernel workthread has transiently adopted a user mm with use_mm, 646 * to do its AIO) is not set and if so returns a reference to it, after 647 * bumping up the use count. User must release the mm via mmput() 648 * after use. Typically used by /proc and ptrace. 649 */ 650 struct mm_struct *get_task_mm(struct task_struct *task) 651 { 652 struct mm_struct *mm; 653 654 task_lock(task); 655 mm = task->mm; 656 if (mm) { 657 if (task->flags & PF_KTHREAD) 658 mm = NULL; 659 else 660 atomic_inc(&mm->mm_users); 661 } 662 task_unlock(task); 663 return mm; 664 } 665 EXPORT_SYMBOL_GPL(get_task_mm); 666 667 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 668 { 669 struct mm_struct *mm; 670 int err; 671 672 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 673 if (err) 674 return ERR_PTR(err); 675 676 mm = get_task_mm(task); 677 if (mm && mm != current->mm && 678 !ptrace_may_access(task, mode)) { 679 mmput(mm); 680 mm = ERR_PTR(-EACCES); 681 } 682 mutex_unlock(&task->signal->cred_guard_mutex); 683 684 return mm; 685 } 686 687 static void complete_vfork_done(struct task_struct *tsk) 688 { 689 struct completion *vfork; 690 691 task_lock(tsk); 692 vfork = tsk->vfork_done; 693 if (likely(vfork)) { 694 tsk->vfork_done = NULL; 695 complete(vfork); 696 } 697 task_unlock(tsk); 698 } 699 700 static int wait_for_vfork_done(struct task_struct *child, 701 struct completion *vfork) 702 { 703 int killed; 704 705 freezer_do_not_count(); 706 killed = wait_for_completion_killable(vfork); 707 freezer_count(); 708 709 if (killed) { 710 task_lock(child); 711 child->vfork_done = NULL; 712 task_unlock(child); 713 } 714 715 put_task_struct(child); 716 return killed; 717 } 718 719 /* Please note the differences between mmput and mm_release. 720 * mmput is called whenever we stop holding onto a mm_struct, 721 * error success whatever. 722 * 723 * mm_release is called after a mm_struct has been removed 724 * from the current process. 725 * 726 * This difference is important for error handling, when we 727 * only half set up a mm_struct for a new process and need to restore 728 * the old one. Because we mmput the new mm_struct before 729 * restoring the old one. . . 730 * Eric Biederman 10 January 1998 731 */ 732 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 733 { 734 /* Get rid of any futexes when releasing the mm */ 735 #ifdef CONFIG_FUTEX 736 if (unlikely(tsk->robust_list)) { 737 exit_robust_list(tsk); 738 tsk->robust_list = NULL; 739 } 740 #ifdef CONFIG_COMPAT 741 if (unlikely(tsk->compat_robust_list)) { 742 compat_exit_robust_list(tsk); 743 tsk->compat_robust_list = NULL; 744 } 745 #endif 746 if (unlikely(!list_empty(&tsk->pi_state_list))) 747 exit_pi_state_list(tsk); 748 #endif 749 750 /* Get rid of any cached register state */ 751 deactivate_mm(tsk, mm); 752 753 if (tsk->vfork_done) 754 complete_vfork_done(tsk); 755 756 /* 757 * If we're exiting normally, clear a user-space tid field if 758 * requested. We leave this alone when dying by signal, to leave 759 * the value intact in a core dump, and to save the unnecessary 760 * trouble, say, a killed vfork parent shouldn't touch this mm. 761 * Userland only wants this done for a sys_exit. 762 */ 763 if (tsk->clear_child_tid) { 764 if (!(tsk->flags & PF_SIGNALED) && 765 atomic_read(&mm->mm_users) > 1) { 766 /* 767 * We don't check the error code - if userspace has 768 * not set up a proper pointer then tough luck. 769 */ 770 put_user(0, tsk->clear_child_tid); 771 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 772 1, NULL, NULL, 0); 773 } 774 tsk->clear_child_tid = NULL; 775 } 776 } 777 778 /* 779 * Allocate a new mm structure and copy contents from the 780 * mm structure of the passed in task structure. 781 */ 782 struct mm_struct *dup_mm(struct task_struct *tsk) 783 { 784 struct mm_struct *mm, *oldmm = current->mm; 785 int err; 786 787 if (!oldmm) 788 return NULL; 789 790 mm = allocate_mm(); 791 if (!mm) 792 goto fail_nomem; 793 794 memcpy(mm, oldmm, sizeof(*mm)); 795 mm_init_cpumask(mm); 796 797 /* Initializing for Swap token stuff */ 798 mm->token_priority = 0; 799 mm->last_interval = 0; 800 801 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 802 mm->pmd_huge_pte = NULL; 803 #endif 804 805 if (!mm_init(mm, tsk)) 806 goto fail_nomem; 807 808 if (init_new_context(tsk, mm)) 809 goto fail_nocontext; 810 811 dup_mm_exe_file(oldmm, mm); 812 813 err = dup_mmap(mm, oldmm); 814 if (err) 815 goto free_pt; 816 817 mm->hiwater_rss = get_mm_rss(mm); 818 mm->hiwater_vm = mm->total_vm; 819 820 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 821 goto free_pt; 822 823 return mm; 824 825 free_pt: 826 /* don't put binfmt in mmput, we haven't got module yet */ 827 mm->binfmt = NULL; 828 mmput(mm); 829 830 fail_nomem: 831 return NULL; 832 833 fail_nocontext: 834 /* 835 * If init_new_context() failed, we cannot use mmput() to free the mm 836 * because it calls destroy_context() 837 */ 838 mm_free_pgd(mm); 839 free_mm(mm); 840 return NULL; 841 } 842 843 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 844 { 845 struct mm_struct *mm, *oldmm; 846 int retval; 847 848 tsk->min_flt = tsk->maj_flt = 0; 849 tsk->nvcsw = tsk->nivcsw = 0; 850 #ifdef CONFIG_DETECT_HUNG_TASK 851 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 852 #endif 853 854 tsk->mm = NULL; 855 tsk->active_mm = NULL; 856 857 /* 858 * Are we cloning a kernel thread? 859 * 860 * We need to steal a active VM for that.. 861 */ 862 oldmm = current->mm; 863 if (!oldmm) 864 return 0; 865 866 if (clone_flags & CLONE_VM) { 867 atomic_inc(&oldmm->mm_users); 868 mm = oldmm; 869 goto good_mm; 870 } 871 872 retval = -ENOMEM; 873 mm = dup_mm(tsk); 874 if (!mm) 875 goto fail_nomem; 876 877 good_mm: 878 /* Initializing for Swap token stuff */ 879 mm->token_priority = 0; 880 mm->last_interval = 0; 881 882 tsk->mm = mm; 883 tsk->active_mm = mm; 884 return 0; 885 886 fail_nomem: 887 return retval; 888 } 889 890 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 891 { 892 struct fs_struct *fs = current->fs; 893 if (clone_flags & CLONE_FS) { 894 /* tsk->fs is already what we want */ 895 spin_lock(&fs->lock); 896 if (fs->in_exec) { 897 spin_unlock(&fs->lock); 898 return -EAGAIN; 899 } 900 fs->users++; 901 spin_unlock(&fs->lock); 902 return 0; 903 } 904 tsk->fs = copy_fs_struct(fs); 905 if (!tsk->fs) 906 return -ENOMEM; 907 return 0; 908 } 909 910 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 911 { 912 struct files_struct *oldf, *newf; 913 int error = 0; 914 915 /* 916 * A background process may not have any files ... 917 */ 918 oldf = current->files; 919 if (!oldf) 920 goto out; 921 922 if (clone_flags & CLONE_FILES) { 923 atomic_inc(&oldf->count); 924 goto out; 925 } 926 927 newf = dup_fd(oldf, &error); 928 if (!newf) 929 goto out; 930 931 tsk->files = newf; 932 error = 0; 933 out: 934 return error; 935 } 936 937 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 938 { 939 #ifdef CONFIG_BLOCK 940 struct io_context *ioc = current->io_context; 941 struct io_context *new_ioc; 942 943 if (!ioc) 944 return 0; 945 /* 946 * Share io context with parent, if CLONE_IO is set 947 */ 948 if (clone_flags & CLONE_IO) { 949 tsk->io_context = ioc_task_link(ioc); 950 if (unlikely(!tsk->io_context)) 951 return -ENOMEM; 952 } else if (ioprio_valid(ioc->ioprio)) { 953 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 954 if (unlikely(!new_ioc)) 955 return -ENOMEM; 956 957 new_ioc->ioprio = ioc->ioprio; 958 put_io_context(new_ioc); 959 } 960 #endif 961 return 0; 962 } 963 964 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 965 { 966 struct sighand_struct *sig; 967 968 if (clone_flags & CLONE_SIGHAND) { 969 atomic_inc(¤t->sighand->count); 970 return 0; 971 } 972 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 973 rcu_assign_pointer(tsk->sighand, sig); 974 if (!sig) 975 return -ENOMEM; 976 atomic_set(&sig->count, 1); 977 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 978 return 0; 979 } 980 981 void __cleanup_sighand(struct sighand_struct *sighand) 982 { 983 if (atomic_dec_and_test(&sighand->count)) { 984 signalfd_cleanup(sighand); 985 kmem_cache_free(sighand_cachep, sighand); 986 } 987 } 988 989 990 /* 991 * Initialize POSIX timer handling for a thread group. 992 */ 993 static void posix_cpu_timers_init_group(struct signal_struct *sig) 994 { 995 unsigned long cpu_limit; 996 997 /* Thread group counters. */ 998 thread_group_cputime_init(sig); 999 1000 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1001 if (cpu_limit != RLIM_INFINITY) { 1002 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1003 sig->cputimer.running = 1; 1004 } 1005 1006 /* The timer lists. */ 1007 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1008 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1009 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1010 } 1011 1012 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1013 { 1014 struct signal_struct *sig; 1015 1016 if (clone_flags & CLONE_THREAD) 1017 return 0; 1018 1019 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1020 tsk->signal = sig; 1021 if (!sig) 1022 return -ENOMEM; 1023 1024 sig->nr_threads = 1; 1025 atomic_set(&sig->live, 1); 1026 atomic_set(&sig->sigcnt, 1); 1027 init_waitqueue_head(&sig->wait_chldexit); 1028 if (clone_flags & CLONE_NEWPID) 1029 sig->flags |= SIGNAL_UNKILLABLE; 1030 sig->curr_target = tsk; 1031 init_sigpending(&sig->shared_pending); 1032 INIT_LIST_HEAD(&sig->posix_timers); 1033 1034 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1035 sig->real_timer.function = it_real_fn; 1036 1037 task_lock(current->group_leader); 1038 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1039 task_unlock(current->group_leader); 1040 1041 posix_cpu_timers_init_group(sig); 1042 1043 tty_audit_fork(sig); 1044 sched_autogroup_fork(sig); 1045 1046 #ifdef CONFIG_CGROUPS 1047 init_rwsem(&sig->group_rwsem); 1048 #endif 1049 1050 sig->oom_adj = current->signal->oom_adj; 1051 sig->oom_score_adj = current->signal->oom_score_adj; 1052 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1053 1054 sig->has_child_subreaper = current->signal->has_child_subreaper || 1055 current->signal->is_child_subreaper; 1056 1057 mutex_init(&sig->cred_guard_mutex); 1058 1059 return 0; 1060 } 1061 1062 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1063 { 1064 unsigned long new_flags = p->flags; 1065 1066 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1067 new_flags |= PF_FORKNOEXEC; 1068 p->flags = new_flags; 1069 } 1070 1071 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1072 { 1073 current->clear_child_tid = tidptr; 1074 1075 return task_pid_vnr(current); 1076 } 1077 1078 static void rt_mutex_init_task(struct task_struct *p) 1079 { 1080 raw_spin_lock_init(&p->pi_lock); 1081 #ifdef CONFIG_RT_MUTEXES 1082 plist_head_init(&p->pi_waiters); 1083 p->pi_blocked_on = NULL; 1084 #endif 1085 } 1086 1087 #ifdef CONFIG_MM_OWNER 1088 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1089 { 1090 mm->owner = p; 1091 } 1092 #endif /* CONFIG_MM_OWNER */ 1093 1094 /* 1095 * Initialize POSIX timer handling for a single task. 1096 */ 1097 static void posix_cpu_timers_init(struct task_struct *tsk) 1098 { 1099 tsk->cputime_expires.prof_exp = 0; 1100 tsk->cputime_expires.virt_exp = 0; 1101 tsk->cputime_expires.sched_exp = 0; 1102 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1103 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1104 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1105 } 1106 1107 /* 1108 * This creates a new process as a copy of the old one, 1109 * but does not actually start it yet. 1110 * 1111 * It copies the registers, and all the appropriate 1112 * parts of the process environment (as per the clone 1113 * flags). The actual kick-off is left to the caller. 1114 */ 1115 static struct task_struct *copy_process(unsigned long clone_flags, 1116 unsigned long stack_start, 1117 struct pt_regs *regs, 1118 unsigned long stack_size, 1119 int __user *child_tidptr, 1120 struct pid *pid, 1121 int trace) 1122 { 1123 int retval; 1124 struct task_struct *p; 1125 int cgroup_callbacks_done = 0; 1126 1127 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1128 return ERR_PTR(-EINVAL); 1129 1130 /* 1131 * Thread groups must share signals as well, and detached threads 1132 * can only be started up within the thread group. 1133 */ 1134 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1135 return ERR_PTR(-EINVAL); 1136 1137 /* 1138 * Shared signal handlers imply shared VM. By way of the above, 1139 * thread groups also imply shared VM. Blocking this case allows 1140 * for various simplifications in other code. 1141 */ 1142 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1143 return ERR_PTR(-EINVAL); 1144 1145 /* 1146 * Siblings of global init remain as zombies on exit since they are 1147 * not reaped by their parent (swapper). To solve this and to avoid 1148 * multi-rooted process trees, prevent global and container-inits 1149 * from creating siblings. 1150 */ 1151 if ((clone_flags & CLONE_PARENT) && 1152 current->signal->flags & SIGNAL_UNKILLABLE) 1153 return ERR_PTR(-EINVAL); 1154 1155 retval = security_task_create(clone_flags); 1156 if (retval) 1157 goto fork_out; 1158 1159 retval = -ENOMEM; 1160 p = dup_task_struct(current); 1161 if (!p) 1162 goto fork_out; 1163 1164 ftrace_graph_init_task(p); 1165 1166 rt_mutex_init_task(p); 1167 1168 #ifdef CONFIG_PROVE_LOCKING 1169 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1170 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1171 #endif 1172 retval = -EAGAIN; 1173 if (atomic_read(&p->real_cred->user->processes) >= 1174 task_rlimit(p, RLIMIT_NPROC)) { 1175 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1176 p->real_cred->user != INIT_USER) 1177 goto bad_fork_free; 1178 } 1179 current->flags &= ~PF_NPROC_EXCEEDED; 1180 1181 retval = copy_creds(p, clone_flags); 1182 if (retval < 0) 1183 goto bad_fork_free; 1184 1185 /* 1186 * If multiple threads are within copy_process(), then this check 1187 * triggers too late. This doesn't hurt, the check is only there 1188 * to stop root fork bombs. 1189 */ 1190 retval = -EAGAIN; 1191 if (nr_threads >= max_threads) 1192 goto bad_fork_cleanup_count; 1193 1194 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1195 goto bad_fork_cleanup_count; 1196 1197 p->did_exec = 0; 1198 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1199 copy_flags(clone_flags, p); 1200 INIT_LIST_HEAD(&p->children); 1201 INIT_LIST_HEAD(&p->sibling); 1202 rcu_copy_process(p); 1203 p->vfork_done = NULL; 1204 spin_lock_init(&p->alloc_lock); 1205 1206 init_sigpending(&p->pending); 1207 1208 p->utime = p->stime = p->gtime = 0; 1209 p->utimescaled = p->stimescaled = 0; 1210 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1211 p->prev_utime = p->prev_stime = 0; 1212 #endif 1213 #if defined(SPLIT_RSS_COUNTING) 1214 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1215 #endif 1216 1217 p->default_timer_slack_ns = current->timer_slack_ns; 1218 1219 task_io_accounting_init(&p->ioac); 1220 acct_clear_integrals(p); 1221 1222 posix_cpu_timers_init(p); 1223 1224 do_posix_clock_monotonic_gettime(&p->start_time); 1225 p->real_start_time = p->start_time; 1226 monotonic_to_bootbased(&p->real_start_time); 1227 p->io_context = NULL; 1228 p->audit_context = NULL; 1229 if (clone_flags & CLONE_THREAD) 1230 threadgroup_change_begin(current); 1231 cgroup_fork(p); 1232 #ifdef CONFIG_NUMA 1233 p->mempolicy = mpol_dup(p->mempolicy); 1234 if (IS_ERR(p->mempolicy)) { 1235 retval = PTR_ERR(p->mempolicy); 1236 p->mempolicy = NULL; 1237 goto bad_fork_cleanup_cgroup; 1238 } 1239 mpol_fix_fork_child_flag(p); 1240 #endif 1241 #ifdef CONFIG_CPUSETS 1242 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1243 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1244 seqcount_init(&p->mems_allowed_seq); 1245 #endif 1246 #ifdef CONFIG_TRACE_IRQFLAGS 1247 p->irq_events = 0; 1248 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1249 p->hardirqs_enabled = 1; 1250 #else 1251 p->hardirqs_enabled = 0; 1252 #endif 1253 p->hardirq_enable_ip = 0; 1254 p->hardirq_enable_event = 0; 1255 p->hardirq_disable_ip = _THIS_IP_; 1256 p->hardirq_disable_event = 0; 1257 p->softirqs_enabled = 1; 1258 p->softirq_enable_ip = _THIS_IP_; 1259 p->softirq_enable_event = 0; 1260 p->softirq_disable_ip = 0; 1261 p->softirq_disable_event = 0; 1262 p->hardirq_context = 0; 1263 p->softirq_context = 0; 1264 #endif 1265 #ifdef CONFIG_LOCKDEP 1266 p->lockdep_depth = 0; /* no locks held yet */ 1267 p->curr_chain_key = 0; 1268 p->lockdep_recursion = 0; 1269 #endif 1270 1271 #ifdef CONFIG_DEBUG_MUTEXES 1272 p->blocked_on = NULL; /* not blocked yet */ 1273 #endif 1274 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1275 p->memcg_batch.do_batch = 0; 1276 p->memcg_batch.memcg = NULL; 1277 #endif 1278 1279 /* Perform scheduler related setup. Assign this task to a CPU. */ 1280 sched_fork(p); 1281 1282 retval = perf_event_init_task(p); 1283 if (retval) 1284 goto bad_fork_cleanup_policy; 1285 retval = audit_alloc(p); 1286 if (retval) 1287 goto bad_fork_cleanup_policy; 1288 /* copy all the process information */ 1289 retval = copy_semundo(clone_flags, p); 1290 if (retval) 1291 goto bad_fork_cleanup_audit; 1292 retval = copy_files(clone_flags, p); 1293 if (retval) 1294 goto bad_fork_cleanup_semundo; 1295 retval = copy_fs(clone_flags, p); 1296 if (retval) 1297 goto bad_fork_cleanup_files; 1298 retval = copy_sighand(clone_flags, p); 1299 if (retval) 1300 goto bad_fork_cleanup_fs; 1301 retval = copy_signal(clone_flags, p); 1302 if (retval) 1303 goto bad_fork_cleanup_sighand; 1304 retval = copy_mm(clone_flags, p); 1305 if (retval) 1306 goto bad_fork_cleanup_signal; 1307 retval = copy_namespaces(clone_flags, p); 1308 if (retval) 1309 goto bad_fork_cleanup_mm; 1310 retval = copy_io(clone_flags, p); 1311 if (retval) 1312 goto bad_fork_cleanup_namespaces; 1313 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1314 if (retval) 1315 goto bad_fork_cleanup_io; 1316 1317 if (pid != &init_struct_pid) { 1318 retval = -ENOMEM; 1319 pid = alloc_pid(p->nsproxy->pid_ns); 1320 if (!pid) 1321 goto bad_fork_cleanup_io; 1322 } 1323 1324 p->pid = pid_nr(pid); 1325 p->tgid = p->pid; 1326 if (clone_flags & CLONE_THREAD) 1327 p->tgid = current->tgid; 1328 1329 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1330 /* 1331 * Clear TID on mm_release()? 1332 */ 1333 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1334 #ifdef CONFIG_BLOCK 1335 p->plug = NULL; 1336 #endif 1337 #ifdef CONFIG_FUTEX 1338 p->robust_list = NULL; 1339 #ifdef CONFIG_COMPAT 1340 p->compat_robust_list = NULL; 1341 #endif 1342 INIT_LIST_HEAD(&p->pi_state_list); 1343 p->pi_state_cache = NULL; 1344 #endif 1345 /* 1346 * sigaltstack should be cleared when sharing the same VM 1347 */ 1348 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1349 p->sas_ss_sp = p->sas_ss_size = 0; 1350 1351 /* 1352 * Syscall tracing and stepping should be turned off in the 1353 * child regardless of CLONE_PTRACE. 1354 */ 1355 user_disable_single_step(p); 1356 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1357 #ifdef TIF_SYSCALL_EMU 1358 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1359 #endif 1360 clear_all_latency_tracing(p); 1361 1362 /* ok, now we should be set up.. */ 1363 if (clone_flags & CLONE_THREAD) 1364 p->exit_signal = -1; 1365 else if (clone_flags & CLONE_PARENT) 1366 p->exit_signal = current->group_leader->exit_signal; 1367 else 1368 p->exit_signal = (clone_flags & CSIGNAL); 1369 1370 p->pdeath_signal = 0; 1371 p->exit_state = 0; 1372 1373 p->nr_dirtied = 0; 1374 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1375 p->dirty_paused_when = 0; 1376 1377 /* 1378 * Ok, make it visible to the rest of the system. 1379 * We dont wake it up yet. 1380 */ 1381 p->group_leader = p; 1382 INIT_LIST_HEAD(&p->thread_group); 1383 1384 /* Now that the task is set up, run cgroup callbacks if 1385 * necessary. We need to run them before the task is visible 1386 * on the tasklist. */ 1387 cgroup_fork_callbacks(p); 1388 cgroup_callbacks_done = 1; 1389 1390 /* Need tasklist lock for parent etc handling! */ 1391 write_lock_irq(&tasklist_lock); 1392 1393 /* CLONE_PARENT re-uses the old parent */ 1394 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1395 p->real_parent = current->real_parent; 1396 p->parent_exec_id = current->parent_exec_id; 1397 } else { 1398 p->real_parent = current; 1399 p->parent_exec_id = current->self_exec_id; 1400 } 1401 1402 spin_lock(¤t->sighand->siglock); 1403 1404 /* 1405 * Process group and session signals need to be delivered to just the 1406 * parent before the fork or both the parent and the child after the 1407 * fork. Restart if a signal comes in before we add the new process to 1408 * it's process group. 1409 * A fatal signal pending means that current will exit, so the new 1410 * thread can't slip out of an OOM kill (or normal SIGKILL). 1411 */ 1412 recalc_sigpending(); 1413 if (signal_pending(current)) { 1414 spin_unlock(¤t->sighand->siglock); 1415 write_unlock_irq(&tasklist_lock); 1416 retval = -ERESTARTNOINTR; 1417 goto bad_fork_free_pid; 1418 } 1419 1420 if (clone_flags & CLONE_THREAD) { 1421 current->signal->nr_threads++; 1422 atomic_inc(¤t->signal->live); 1423 atomic_inc(¤t->signal->sigcnt); 1424 p->group_leader = current->group_leader; 1425 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1426 } 1427 1428 if (likely(p->pid)) { 1429 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1430 1431 if (thread_group_leader(p)) { 1432 if (is_child_reaper(pid)) 1433 p->nsproxy->pid_ns->child_reaper = p; 1434 1435 p->signal->leader_pid = pid; 1436 p->signal->tty = tty_kref_get(current->signal->tty); 1437 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1438 attach_pid(p, PIDTYPE_SID, task_session(current)); 1439 list_add_tail(&p->sibling, &p->real_parent->children); 1440 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1441 __this_cpu_inc(process_counts); 1442 } 1443 attach_pid(p, PIDTYPE_PID, pid); 1444 nr_threads++; 1445 } 1446 1447 total_forks++; 1448 spin_unlock(¤t->sighand->siglock); 1449 write_unlock_irq(&tasklist_lock); 1450 proc_fork_connector(p); 1451 cgroup_post_fork(p); 1452 if (clone_flags & CLONE_THREAD) 1453 threadgroup_change_end(current); 1454 perf_event_fork(p); 1455 1456 trace_task_newtask(p, clone_flags); 1457 1458 return p; 1459 1460 bad_fork_free_pid: 1461 if (pid != &init_struct_pid) 1462 free_pid(pid); 1463 bad_fork_cleanup_io: 1464 if (p->io_context) 1465 exit_io_context(p); 1466 bad_fork_cleanup_namespaces: 1467 exit_task_namespaces(p); 1468 bad_fork_cleanup_mm: 1469 if (p->mm) 1470 mmput(p->mm); 1471 bad_fork_cleanup_signal: 1472 if (!(clone_flags & CLONE_THREAD)) 1473 free_signal_struct(p->signal); 1474 bad_fork_cleanup_sighand: 1475 __cleanup_sighand(p->sighand); 1476 bad_fork_cleanup_fs: 1477 exit_fs(p); /* blocking */ 1478 bad_fork_cleanup_files: 1479 exit_files(p); /* blocking */ 1480 bad_fork_cleanup_semundo: 1481 exit_sem(p); 1482 bad_fork_cleanup_audit: 1483 audit_free(p); 1484 bad_fork_cleanup_policy: 1485 perf_event_free_task(p); 1486 #ifdef CONFIG_NUMA 1487 mpol_put(p->mempolicy); 1488 bad_fork_cleanup_cgroup: 1489 #endif 1490 if (clone_flags & CLONE_THREAD) 1491 threadgroup_change_end(current); 1492 cgroup_exit(p, cgroup_callbacks_done); 1493 delayacct_tsk_free(p); 1494 module_put(task_thread_info(p)->exec_domain->module); 1495 bad_fork_cleanup_count: 1496 atomic_dec(&p->cred->user->processes); 1497 exit_creds(p); 1498 bad_fork_free: 1499 free_task(p); 1500 fork_out: 1501 return ERR_PTR(retval); 1502 } 1503 1504 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1505 { 1506 memset(regs, 0, sizeof(struct pt_regs)); 1507 return regs; 1508 } 1509 1510 static inline void init_idle_pids(struct pid_link *links) 1511 { 1512 enum pid_type type; 1513 1514 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1515 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1516 links[type].pid = &init_struct_pid; 1517 } 1518 } 1519 1520 struct task_struct * __cpuinit fork_idle(int cpu) 1521 { 1522 struct task_struct *task; 1523 struct pt_regs regs; 1524 1525 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1526 &init_struct_pid, 0); 1527 if (!IS_ERR(task)) { 1528 init_idle_pids(task->pids); 1529 init_idle(task, cpu); 1530 } 1531 1532 return task; 1533 } 1534 1535 /* 1536 * Ok, this is the main fork-routine. 1537 * 1538 * It copies the process, and if successful kick-starts 1539 * it and waits for it to finish using the VM if required. 1540 */ 1541 long do_fork(unsigned long clone_flags, 1542 unsigned long stack_start, 1543 struct pt_regs *regs, 1544 unsigned long stack_size, 1545 int __user *parent_tidptr, 1546 int __user *child_tidptr) 1547 { 1548 struct task_struct *p; 1549 int trace = 0; 1550 long nr; 1551 1552 /* 1553 * Do some preliminary argument and permissions checking before we 1554 * actually start allocating stuff 1555 */ 1556 if (clone_flags & CLONE_NEWUSER) { 1557 if (clone_flags & CLONE_THREAD) 1558 return -EINVAL; 1559 /* hopefully this check will go away when userns support is 1560 * complete 1561 */ 1562 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1563 !capable(CAP_SETGID)) 1564 return -EPERM; 1565 } 1566 1567 /* 1568 * Determine whether and which event to report to ptracer. When 1569 * called from kernel_thread or CLONE_UNTRACED is explicitly 1570 * requested, no event is reported; otherwise, report if the event 1571 * for the type of forking is enabled. 1572 */ 1573 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1574 if (clone_flags & CLONE_VFORK) 1575 trace = PTRACE_EVENT_VFORK; 1576 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1577 trace = PTRACE_EVENT_CLONE; 1578 else 1579 trace = PTRACE_EVENT_FORK; 1580 1581 if (likely(!ptrace_event_enabled(current, trace))) 1582 trace = 0; 1583 } 1584 1585 p = copy_process(clone_flags, stack_start, regs, stack_size, 1586 child_tidptr, NULL, trace); 1587 /* 1588 * Do this prior waking up the new thread - the thread pointer 1589 * might get invalid after that point, if the thread exits quickly. 1590 */ 1591 if (!IS_ERR(p)) { 1592 struct completion vfork; 1593 1594 trace_sched_process_fork(current, p); 1595 1596 nr = task_pid_vnr(p); 1597 1598 if (clone_flags & CLONE_PARENT_SETTID) 1599 put_user(nr, parent_tidptr); 1600 1601 if (clone_flags & CLONE_VFORK) { 1602 p->vfork_done = &vfork; 1603 init_completion(&vfork); 1604 get_task_struct(p); 1605 } 1606 1607 wake_up_new_task(p); 1608 1609 /* forking complete and child started to run, tell ptracer */ 1610 if (unlikely(trace)) 1611 ptrace_event(trace, nr); 1612 1613 if (clone_flags & CLONE_VFORK) { 1614 if (!wait_for_vfork_done(p, &vfork)) 1615 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1616 } 1617 } else { 1618 nr = PTR_ERR(p); 1619 } 1620 return nr; 1621 } 1622 1623 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1624 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1625 #endif 1626 1627 static void sighand_ctor(void *data) 1628 { 1629 struct sighand_struct *sighand = data; 1630 1631 spin_lock_init(&sighand->siglock); 1632 init_waitqueue_head(&sighand->signalfd_wqh); 1633 } 1634 1635 void __init proc_caches_init(void) 1636 { 1637 sighand_cachep = kmem_cache_create("sighand_cache", 1638 sizeof(struct sighand_struct), 0, 1639 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1640 SLAB_NOTRACK, sighand_ctor); 1641 signal_cachep = kmem_cache_create("signal_cache", 1642 sizeof(struct signal_struct), 0, 1643 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1644 files_cachep = kmem_cache_create("files_cache", 1645 sizeof(struct files_struct), 0, 1646 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1647 fs_cachep = kmem_cache_create("fs_cache", 1648 sizeof(struct fs_struct), 0, 1649 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1650 /* 1651 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1652 * whole struct cpumask for the OFFSTACK case. We could change 1653 * this to *only* allocate as much of it as required by the 1654 * maximum number of CPU's we can ever have. The cpumask_allocation 1655 * is at the end of the structure, exactly for that reason. 1656 */ 1657 mm_cachep = kmem_cache_create("mm_struct", 1658 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1659 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1660 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1661 mmap_init(); 1662 nsproxy_cache_init(); 1663 } 1664 1665 /* 1666 * Check constraints on flags passed to the unshare system call. 1667 */ 1668 static int check_unshare_flags(unsigned long unshare_flags) 1669 { 1670 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1671 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1672 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1673 return -EINVAL; 1674 /* 1675 * Not implemented, but pretend it works if there is nothing to 1676 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1677 * needs to unshare vm. 1678 */ 1679 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1680 /* FIXME: get_task_mm() increments ->mm_users */ 1681 if (atomic_read(¤t->mm->mm_users) > 1) 1682 return -EINVAL; 1683 } 1684 1685 return 0; 1686 } 1687 1688 /* 1689 * Unshare the filesystem structure if it is being shared 1690 */ 1691 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1692 { 1693 struct fs_struct *fs = current->fs; 1694 1695 if (!(unshare_flags & CLONE_FS) || !fs) 1696 return 0; 1697 1698 /* don't need lock here; in the worst case we'll do useless copy */ 1699 if (fs->users == 1) 1700 return 0; 1701 1702 *new_fsp = copy_fs_struct(fs); 1703 if (!*new_fsp) 1704 return -ENOMEM; 1705 1706 return 0; 1707 } 1708 1709 /* 1710 * Unshare file descriptor table if it is being shared 1711 */ 1712 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1713 { 1714 struct files_struct *fd = current->files; 1715 int error = 0; 1716 1717 if ((unshare_flags & CLONE_FILES) && 1718 (fd && atomic_read(&fd->count) > 1)) { 1719 *new_fdp = dup_fd(fd, &error); 1720 if (!*new_fdp) 1721 return error; 1722 } 1723 1724 return 0; 1725 } 1726 1727 /* 1728 * unshare allows a process to 'unshare' part of the process 1729 * context which was originally shared using clone. copy_* 1730 * functions used by do_fork() cannot be used here directly 1731 * because they modify an inactive task_struct that is being 1732 * constructed. Here we are modifying the current, active, 1733 * task_struct. 1734 */ 1735 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1736 { 1737 struct fs_struct *fs, *new_fs = NULL; 1738 struct files_struct *fd, *new_fd = NULL; 1739 struct nsproxy *new_nsproxy = NULL; 1740 int do_sysvsem = 0; 1741 int err; 1742 1743 err = check_unshare_flags(unshare_flags); 1744 if (err) 1745 goto bad_unshare_out; 1746 1747 /* 1748 * If unsharing namespace, must also unshare filesystem information. 1749 */ 1750 if (unshare_flags & CLONE_NEWNS) 1751 unshare_flags |= CLONE_FS; 1752 /* 1753 * CLONE_NEWIPC must also detach from the undolist: after switching 1754 * to a new ipc namespace, the semaphore arrays from the old 1755 * namespace are unreachable. 1756 */ 1757 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1758 do_sysvsem = 1; 1759 err = unshare_fs(unshare_flags, &new_fs); 1760 if (err) 1761 goto bad_unshare_out; 1762 err = unshare_fd(unshare_flags, &new_fd); 1763 if (err) 1764 goto bad_unshare_cleanup_fs; 1765 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1766 if (err) 1767 goto bad_unshare_cleanup_fd; 1768 1769 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1770 if (do_sysvsem) { 1771 /* 1772 * CLONE_SYSVSEM is equivalent to sys_exit(). 1773 */ 1774 exit_sem(current); 1775 } 1776 1777 if (new_nsproxy) { 1778 switch_task_namespaces(current, new_nsproxy); 1779 new_nsproxy = NULL; 1780 } 1781 1782 task_lock(current); 1783 1784 if (new_fs) { 1785 fs = current->fs; 1786 spin_lock(&fs->lock); 1787 current->fs = new_fs; 1788 if (--fs->users) 1789 new_fs = NULL; 1790 else 1791 new_fs = fs; 1792 spin_unlock(&fs->lock); 1793 } 1794 1795 if (new_fd) { 1796 fd = current->files; 1797 current->files = new_fd; 1798 new_fd = fd; 1799 } 1800 1801 task_unlock(current); 1802 } 1803 1804 if (new_nsproxy) 1805 put_nsproxy(new_nsproxy); 1806 1807 bad_unshare_cleanup_fd: 1808 if (new_fd) 1809 put_files_struct(new_fd); 1810 1811 bad_unshare_cleanup_fs: 1812 if (new_fs) 1813 free_fs_struct(new_fs); 1814 1815 bad_unshare_out: 1816 return err; 1817 } 1818 1819 /* 1820 * Helper to unshare the files of the current task. 1821 * We don't want to expose copy_files internals to 1822 * the exec layer of the kernel. 1823 */ 1824 1825 int unshare_files(struct files_struct **displaced) 1826 { 1827 struct task_struct *task = current; 1828 struct files_struct *copy = NULL; 1829 int error; 1830 1831 error = unshare_fd(CLONE_FILES, ©); 1832 if (error || !copy) { 1833 *displaced = NULL; 1834 return error; 1835 } 1836 *displaced = task->files; 1837 task_lock(task); 1838 task->files = copy; 1839 task_unlock(task); 1840 return 0; 1841 } 1842