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