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