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/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/compat.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/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <linux/fs_struct.h> 64 #include <linux/magic.h> 65 #include <linux/perf_event.h> 66 #include <linux/posix-timers.h> 67 #include <linux/user-return-notifier.h> 68 #include <linux/oom.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() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 112 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 113 static struct kmem_cache *task_struct_cachep; 114 #endif 115 116 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 117 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 118 { 119 #ifdef CONFIG_DEBUG_STACK_USAGE 120 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 121 #else 122 gfp_t mask = GFP_KERNEL; 123 #endif 124 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 125 } 126 127 static inline void free_thread_info(struct thread_info *ti) 128 { 129 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 130 } 131 #endif 132 133 /* SLAB cache for signal_struct structures (tsk->signal) */ 134 static struct kmem_cache *signal_cachep; 135 136 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 137 struct kmem_cache *sighand_cachep; 138 139 /* SLAB cache for files_struct structures (tsk->files) */ 140 struct kmem_cache *files_cachep; 141 142 /* SLAB cache for fs_struct structures (tsk->fs) */ 143 struct kmem_cache *fs_cachep; 144 145 /* SLAB cache for vm_area_struct structures */ 146 struct kmem_cache *vm_area_cachep; 147 148 /* SLAB cache for mm_struct structures (tsk->mm) */ 149 static struct kmem_cache *mm_cachep; 150 151 static void account_kernel_stack(struct thread_info *ti, int account) 152 { 153 struct zone *zone = page_zone(virt_to_page(ti)); 154 155 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 156 } 157 158 void free_task(struct task_struct *tsk) 159 { 160 prop_local_destroy_single(&tsk->dirties); 161 account_kernel_stack(tsk->stack, -1); 162 free_thread_info(tsk->stack); 163 rt_mutex_debug_task_free(tsk); 164 ftrace_graph_exit_task(tsk); 165 free_task_struct(tsk); 166 } 167 EXPORT_SYMBOL(free_task); 168 169 static inline void free_signal_struct(struct signal_struct *sig) 170 { 171 taskstats_tgid_free(sig); 172 sched_autogroup_exit(sig); 173 kmem_cache_free(signal_cachep, sig); 174 } 175 176 static inline void put_signal_struct(struct signal_struct *sig) 177 { 178 if (atomic_dec_and_test(&sig->sigcnt)) 179 free_signal_struct(sig); 180 } 181 182 void __put_task_struct(struct task_struct *tsk) 183 { 184 WARN_ON(!tsk->exit_state); 185 WARN_ON(atomic_read(&tsk->usage)); 186 WARN_ON(tsk == current); 187 188 exit_creds(tsk); 189 delayacct_tsk_free(tsk); 190 put_signal_struct(tsk->signal); 191 192 if (!profile_handoff_task(tsk)) 193 free_task(tsk); 194 } 195 196 /* 197 * macro override instead of weak attribute alias, to workaround 198 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 199 */ 200 #ifndef arch_task_cache_init 201 #define arch_task_cache_init() 202 #endif 203 204 void __init fork_init(unsigned long mempages) 205 { 206 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 207 #ifndef ARCH_MIN_TASKALIGN 208 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 209 #endif 210 /* create a slab on which task_structs can be allocated */ 211 task_struct_cachep = 212 kmem_cache_create("task_struct", sizeof(struct task_struct), 213 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 214 #endif 215 216 /* do the arch specific task caches init */ 217 arch_task_cache_init(); 218 219 /* 220 * The default maximum number of threads is set to a safe 221 * value: the thread structures can take up at most half 222 * of memory. 223 */ 224 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 225 226 /* 227 * we need to allow at least 20 threads to boot a system 228 */ 229 if(max_threads < 20) 230 max_threads = 20; 231 232 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 233 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 234 init_task.signal->rlim[RLIMIT_SIGPENDING] = 235 init_task.signal->rlim[RLIMIT_NPROC]; 236 } 237 238 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 239 struct task_struct *src) 240 { 241 *dst = *src; 242 return 0; 243 } 244 245 static struct task_struct *dup_task_struct(struct task_struct *orig) 246 { 247 struct task_struct *tsk; 248 struct thread_info *ti; 249 unsigned long *stackend; 250 251 int err; 252 253 prepare_to_copy(orig); 254 255 tsk = alloc_task_struct(); 256 if (!tsk) 257 return NULL; 258 259 ti = alloc_thread_info(tsk); 260 if (!ti) { 261 free_task_struct(tsk); 262 return NULL; 263 } 264 265 err = arch_dup_task_struct(tsk, orig); 266 if (err) 267 goto out; 268 269 tsk->stack = ti; 270 271 err = prop_local_init_single(&tsk->dirties); 272 if (err) 273 goto out; 274 275 setup_thread_stack(tsk, orig); 276 clear_user_return_notifier(tsk); 277 clear_tsk_need_resched(tsk); 278 stackend = end_of_stack(tsk); 279 *stackend = STACK_END_MAGIC; /* for overflow detection */ 280 281 #ifdef CONFIG_CC_STACKPROTECTOR 282 tsk->stack_canary = get_random_int(); 283 #endif 284 285 /* One for us, one for whoever does the "release_task()" (usually parent) */ 286 atomic_set(&tsk->usage,2); 287 atomic_set(&tsk->fs_excl, 0); 288 #ifdef CONFIG_BLK_DEV_IO_TRACE 289 tsk->btrace_seq = 0; 290 #endif 291 tsk->splice_pipe = NULL; 292 293 account_kernel_stack(ti, 1); 294 295 return tsk; 296 297 out: 298 free_thread_info(ti); 299 free_task_struct(tsk); 300 return NULL; 301 } 302 303 #ifdef CONFIG_MMU 304 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 305 { 306 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 307 struct rb_node **rb_link, *rb_parent; 308 int retval; 309 unsigned long charge; 310 struct mempolicy *pol; 311 312 down_write(&oldmm->mmap_sem); 313 flush_cache_dup_mm(oldmm); 314 /* 315 * Not linked in yet - no deadlock potential: 316 */ 317 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 318 319 mm->locked_vm = 0; 320 mm->mmap = NULL; 321 mm->mmap_cache = NULL; 322 mm->free_area_cache = oldmm->mmap_base; 323 mm->cached_hole_size = ~0UL; 324 mm->map_count = 0; 325 cpumask_clear(mm_cpumask(mm)); 326 mm->mm_rb = RB_ROOT; 327 rb_link = &mm->mm_rb.rb_node; 328 rb_parent = NULL; 329 pprev = &mm->mmap; 330 retval = ksm_fork(mm, oldmm); 331 if (retval) 332 goto out; 333 334 prev = NULL; 335 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 336 struct file *file; 337 338 if (mpnt->vm_flags & VM_DONTCOPY) { 339 long pages = vma_pages(mpnt); 340 mm->total_vm -= pages; 341 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 342 -pages); 343 continue; 344 } 345 charge = 0; 346 if (mpnt->vm_flags & VM_ACCOUNT) { 347 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 348 if (security_vm_enough_memory(len)) 349 goto fail_nomem; 350 charge = len; 351 } 352 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 353 if (!tmp) 354 goto fail_nomem; 355 *tmp = *mpnt; 356 INIT_LIST_HEAD(&tmp->anon_vma_chain); 357 pol = mpol_dup(vma_policy(mpnt)); 358 retval = PTR_ERR(pol); 359 if (IS_ERR(pol)) 360 goto fail_nomem_policy; 361 vma_set_policy(tmp, pol); 362 tmp->vm_mm = mm; 363 if (anon_vma_fork(tmp, mpnt)) 364 goto fail_nomem_anon_vma_fork; 365 tmp->vm_flags &= ~VM_LOCKED; 366 tmp->vm_next = tmp->vm_prev = NULL; 367 file = tmp->vm_file; 368 if (file) { 369 struct inode *inode = file->f_path.dentry->d_inode; 370 struct address_space *mapping = file->f_mapping; 371 372 get_file(file); 373 if (tmp->vm_flags & VM_DENYWRITE) 374 atomic_dec(&inode->i_writecount); 375 spin_lock(&mapping->i_mmap_lock); 376 if (tmp->vm_flags & VM_SHARED) 377 mapping->i_mmap_writable++; 378 tmp->vm_truncate_count = mpnt->vm_truncate_count; 379 flush_dcache_mmap_lock(mapping); 380 /* insert tmp into the share list, just after mpnt */ 381 vma_prio_tree_add(tmp, mpnt); 382 flush_dcache_mmap_unlock(mapping); 383 spin_unlock(&mapping->i_mmap_lock); 384 } 385 386 /* 387 * Clear hugetlb-related page reserves for children. This only 388 * affects MAP_PRIVATE mappings. Faults generated by the child 389 * are not guaranteed to succeed, even if read-only 390 */ 391 if (is_vm_hugetlb_page(tmp)) 392 reset_vma_resv_huge_pages(tmp); 393 394 /* 395 * Link in the new vma and copy the page table entries. 396 */ 397 *pprev = tmp; 398 pprev = &tmp->vm_next; 399 tmp->vm_prev = prev; 400 prev = tmp; 401 402 __vma_link_rb(mm, tmp, rb_link, rb_parent); 403 rb_link = &tmp->vm_rb.rb_right; 404 rb_parent = &tmp->vm_rb; 405 406 mm->map_count++; 407 retval = copy_page_range(mm, oldmm, mpnt); 408 409 if (tmp->vm_ops && tmp->vm_ops->open) 410 tmp->vm_ops->open(tmp); 411 412 if (retval) 413 goto out; 414 } 415 /* a new mm has just been created */ 416 arch_dup_mmap(oldmm, mm); 417 retval = 0; 418 out: 419 up_write(&mm->mmap_sem); 420 flush_tlb_mm(oldmm); 421 up_write(&oldmm->mmap_sem); 422 return retval; 423 fail_nomem_anon_vma_fork: 424 mpol_put(pol); 425 fail_nomem_policy: 426 kmem_cache_free(vm_area_cachep, tmp); 427 fail_nomem: 428 retval = -ENOMEM; 429 vm_unacct_memory(charge); 430 goto out; 431 } 432 433 static inline int mm_alloc_pgd(struct mm_struct * mm) 434 { 435 mm->pgd = pgd_alloc(mm); 436 if (unlikely(!mm->pgd)) 437 return -ENOMEM; 438 return 0; 439 } 440 441 static inline void mm_free_pgd(struct mm_struct * mm) 442 { 443 pgd_free(mm, mm->pgd); 444 } 445 #else 446 #define dup_mmap(mm, oldmm) (0) 447 #define mm_alloc_pgd(mm) (0) 448 #define mm_free_pgd(mm) 449 #endif /* CONFIG_MMU */ 450 451 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 452 453 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 454 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 455 456 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 457 458 static int __init coredump_filter_setup(char *s) 459 { 460 default_dump_filter = 461 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 462 MMF_DUMP_FILTER_MASK; 463 return 1; 464 } 465 466 __setup("coredump_filter=", coredump_filter_setup); 467 468 #include <linux/init_task.h> 469 470 static void mm_init_aio(struct mm_struct *mm) 471 { 472 #ifdef CONFIG_AIO 473 spin_lock_init(&mm->ioctx_lock); 474 INIT_HLIST_HEAD(&mm->ioctx_list); 475 #endif 476 } 477 478 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 479 { 480 atomic_set(&mm->mm_users, 1); 481 atomic_set(&mm->mm_count, 1); 482 init_rwsem(&mm->mmap_sem); 483 INIT_LIST_HEAD(&mm->mmlist); 484 mm->flags = (current->mm) ? 485 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 486 mm->core_state = NULL; 487 mm->nr_ptes = 0; 488 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 489 spin_lock_init(&mm->page_table_lock); 490 mm->free_area_cache = TASK_UNMAPPED_BASE; 491 mm->cached_hole_size = ~0UL; 492 mm_init_aio(mm); 493 mm_init_owner(mm, p); 494 atomic_set(&mm->oom_disable_count, 0); 495 496 if (likely(!mm_alloc_pgd(mm))) { 497 mm->def_flags = 0; 498 mmu_notifier_mm_init(mm); 499 return mm; 500 } 501 502 free_mm(mm); 503 return NULL; 504 } 505 506 /* 507 * Allocate and initialize an mm_struct. 508 */ 509 struct mm_struct * mm_alloc(void) 510 { 511 struct mm_struct * mm; 512 513 mm = allocate_mm(); 514 if (mm) { 515 memset(mm, 0, sizeof(*mm)); 516 mm = mm_init(mm, current); 517 } 518 return mm; 519 } 520 521 /* 522 * Called when the last reference to the mm 523 * is dropped: either by a lazy thread or by 524 * mmput. Free the page directory and the mm. 525 */ 526 void __mmdrop(struct mm_struct *mm) 527 { 528 BUG_ON(mm == &init_mm); 529 mm_free_pgd(mm); 530 destroy_context(mm); 531 mmu_notifier_mm_destroy(mm); 532 free_mm(mm); 533 } 534 EXPORT_SYMBOL_GPL(__mmdrop); 535 536 /* 537 * Decrement the use count and release all resources for an mm. 538 */ 539 void mmput(struct mm_struct *mm) 540 { 541 might_sleep(); 542 543 if (atomic_dec_and_test(&mm->mm_users)) { 544 exit_aio(mm); 545 ksm_exit(mm); 546 exit_mmap(mm); 547 set_mm_exe_file(mm, NULL); 548 if (!list_empty(&mm->mmlist)) { 549 spin_lock(&mmlist_lock); 550 list_del(&mm->mmlist); 551 spin_unlock(&mmlist_lock); 552 } 553 put_swap_token(mm); 554 if (mm->binfmt) 555 module_put(mm->binfmt->module); 556 mmdrop(mm); 557 } 558 } 559 EXPORT_SYMBOL_GPL(mmput); 560 561 /** 562 * get_task_mm - acquire a reference to the task's mm 563 * 564 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 565 * this kernel workthread has transiently adopted a user mm with use_mm, 566 * to do its AIO) is not set and if so returns a reference to it, after 567 * bumping up the use count. User must release the mm via mmput() 568 * after use. Typically used by /proc and ptrace. 569 */ 570 struct mm_struct *get_task_mm(struct task_struct *task) 571 { 572 struct mm_struct *mm; 573 574 task_lock(task); 575 mm = task->mm; 576 if (mm) { 577 if (task->flags & PF_KTHREAD) 578 mm = NULL; 579 else 580 atomic_inc(&mm->mm_users); 581 } 582 task_unlock(task); 583 return mm; 584 } 585 EXPORT_SYMBOL_GPL(get_task_mm); 586 587 /* Please note the differences between mmput and mm_release. 588 * mmput is called whenever we stop holding onto a mm_struct, 589 * error success whatever. 590 * 591 * mm_release is called after a mm_struct has been removed 592 * from the current process. 593 * 594 * This difference is important for error handling, when we 595 * only half set up a mm_struct for a new process and need to restore 596 * the old one. Because we mmput the new mm_struct before 597 * restoring the old one. . . 598 * Eric Biederman 10 January 1998 599 */ 600 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 601 { 602 struct completion *vfork_done = tsk->vfork_done; 603 604 /* Get rid of any futexes when releasing the mm */ 605 #ifdef CONFIG_FUTEX 606 if (unlikely(tsk->robust_list)) { 607 exit_robust_list(tsk); 608 tsk->robust_list = NULL; 609 } 610 #ifdef CONFIG_COMPAT 611 if (unlikely(tsk->compat_robust_list)) { 612 compat_exit_robust_list(tsk); 613 tsk->compat_robust_list = NULL; 614 } 615 #endif 616 if (unlikely(!list_empty(&tsk->pi_state_list))) 617 exit_pi_state_list(tsk); 618 #endif 619 620 /* Get rid of any cached register state */ 621 deactivate_mm(tsk, mm); 622 623 /* notify parent sleeping on vfork() */ 624 if (vfork_done) { 625 tsk->vfork_done = NULL; 626 complete(vfork_done); 627 } 628 629 /* 630 * If we're exiting normally, clear a user-space tid field if 631 * requested. We leave this alone when dying by signal, to leave 632 * the value intact in a core dump, and to save the unnecessary 633 * trouble otherwise. Userland only wants this done for a sys_exit. 634 */ 635 if (tsk->clear_child_tid) { 636 if (!(tsk->flags & PF_SIGNALED) && 637 atomic_read(&mm->mm_users) > 1) { 638 /* 639 * We don't check the error code - if userspace has 640 * not set up a proper pointer then tough luck. 641 */ 642 put_user(0, tsk->clear_child_tid); 643 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 644 1, NULL, NULL, 0); 645 } 646 tsk->clear_child_tid = NULL; 647 } 648 } 649 650 /* 651 * Allocate a new mm structure and copy contents from the 652 * mm structure of the passed in task structure. 653 */ 654 struct mm_struct *dup_mm(struct task_struct *tsk) 655 { 656 struct mm_struct *mm, *oldmm = current->mm; 657 int err; 658 659 if (!oldmm) 660 return NULL; 661 662 mm = allocate_mm(); 663 if (!mm) 664 goto fail_nomem; 665 666 memcpy(mm, oldmm, sizeof(*mm)); 667 668 /* Initializing for Swap token stuff */ 669 mm->token_priority = 0; 670 mm->last_interval = 0; 671 672 if (!mm_init(mm, tsk)) 673 goto fail_nomem; 674 675 if (init_new_context(tsk, mm)) 676 goto fail_nocontext; 677 678 dup_mm_exe_file(oldmm, mm); 679 680 err = dup_mmap(mm, oldmm); 681 if (err) 682 goto free_pt; 683 684 mm->hiwater_rss = get_mm_rss(mm); 685 mm->hiwater_vm = mm->total_vm; 686 687 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 688 goto free_pt; 689 690 return mm; 691 692 free_pt: 693 /* don't put binfmt in mmput, we haven't got module yet */ 694 mm->binfmt = NULL; 695 mmput(mm); 696 697 fail_nomem: 698 return NULL; 699 700 fail_nocontext: 701 /* 702 * If init_new_context() failed, we cannot use mmput() to free the mm 703 * because it calls destroy_context() 704 */ 705 mm_free_pgd(mm); 706 free_mm(mm); 707 return NULL; 708 } 709 710 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 711 { 712 struct mm_struct * mm, *oldmm; 713 int retval; 714 715 tsk->min_flt = tsk->maj_flt = 0; 716 tsk->nvcsw = tsk->nivcsw = 0; 717 #ifdef CONFIG_DETECT_HUNG_TASK 718 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 719 #endif 720 721 tsk->mm = NULL; 722 tsk->active_mm = NULL; 723 724 /* 725 * Are we cloning a kernel thread? 726 * 727 * We need to steal a active VM for that.. 728 */ 729 oldmm = current->mm; 730 if (!oldmm) 731 return 0; 732 733 if (clone_flags & CLONE_VM) { 734 atomic_inc(&oldmm->mm_users); 735 mm = oldmm; 736 goto good_mm; 737 } 738 739 retval = -ENOMEM; 740 mm = dup_mm(tsk); 741 if (!mm) 742 goto fail_nomem; 743 744 good_mm: 745 /* Initializing for Swap token stuff */ 746 mm->token_priority = 0; 747 mm->last_interval = 0; 748 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 749 atomic_inc(&mm->oom_disable_count); 750 751 tsk->mm = mm; 752 tsk->active_mm = mm; 753 return 0; 754 755 fail_nomem: 756 return retval; 757 } 758 759 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 760 { 761 struct fs_struct *fs = current->fs; 762 if (clone_flags & CLONE_FS) { 763 /* tsk->fs is already what we want */ 764 spin_lock(&fs->lock); 765 if (fs->in_exec) { 766 spin_unlock(&fs->lock); 767 return -EAGAIN; 768 } 769 fs->users++; 770 spin_unlock(&fs->lock); 771 return 0; 772 } 773 tsk->fs = copy_fs_struct(fs); 774 if (!tsk->fs) 775 return -ENOMEM; 776 return 0; 777 } 778 779 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 780 { 781 struct files_struct *oldf, *newf; 782 int error = 0; 783 784 /* 785 * A background process may not have any files ... 786 */ 787 oldf = current->files; 788 if (!oldf) 789 goto out; 790 791 if (clone_flags & CLONE_FILES) { 792 atomic_inc(&oldf->count); 793 goto out; 794 } 795 796 newf = dup_fd(oldf, &error); 797 if (!newf) 798 goto out; 799 800 tsk->files = newf; 801 error = 0; 802 out: 803 return error; 804 } 805 806 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 807 { 808 #ifdef CONFIG_BLOCK 809 struct io_context *ioc = current->io_context; 810 811 if (!ioc) 812 return 0; 813 /* 814 * Share io context with parent, if CLONE_IO is set 815 */ 816 if (clone_flags & CLONE_IO) { 817 tsk->io_context = ioc_task_link(ioc); 818 if (unlikely(!tsk->io_context)) 819 return -ENOMEM; 820 } else if (ioprio_valid(ioc->ioprio)) { 821 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 822 if (unlikely(!tsk->io_context)) 823 return -ENOMEM; 824 825 tsk->io_context->ioprio = ioc->ioprio; 826 } 827 #endif 828 return 0; 829 } 830 831 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 832 { 833 struct sighand_struct *sig; 834 835 if (clone_flags & CLONE_SIGHAND) { 836 atomic_inc(¤t->sighand->count); 837 return 0; 838 } 839 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 840 rcu_assign_pointer(tsk->sighand, sig); 841 if (!sig) 842 return -ENOMEM; 843 atomic_set(&sig->count, 1); 844 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 845 return 0; 846 } 847 848 void __cleanup_sighand(struct sighand_struct *sighand) 849 { 850 if (atomic_dec_and_test(&sighand->count)) 851 kmem_cache_free(sighand_cachep, sighand); 852 } 853 854 855 /* 856 * Initialize POSIX timer handling for a thread group. 857 */ 858 static void posix_cpu_timers_init_group(struct signal_struct *sig) 859 { 860 unsigned long cpu_limit; 861 862 /* Thread group counters. */ 863 thread_group_cputime_init(sig); 864 865 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 866 if (cpu_limit != RLIM_INFINITY) { 867 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 868 sig->cputimer.running = 1; 869 } 870 871 /* The timer lists. */ 872 INIT_LIST_HEAD(&sig->cpu_timers[0]); 873 INIT_LIST_HEAD(&sig->cpu_timers[1]); 874 INIT_LIST_HEAD(&sig->cpu_timers[2]); 875 } 876 877 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 878 { 879 struct signal_struct *sig; 880 881 if (clone_flags & CLONE_THREAD) 882 return 0; 883 884 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 885 tsk->signal = sig; 886 if (!sig) 887 return -ENOMEM; 888 889 sig->nr_threads = 1; 890 atomic_set(&sig->live, 1); 891 atomic_set(&sig->sigcnt, 1); 892 init_waitqueue_head(&sig->wait_chldexit); 893 if (clone_flags & CLONE_NEWPID) 894 sig->flags |= SIGNAL_UNKILLABLE; 895 sig->curr_target = tsk; 896 init_sigpending(&sig->shared_pending); 897 INIT_LIST_HEAD(&sig->posix_timers); 898 899 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 900 sig->real_timer.function = it_real_fn; 901 902 task_lock(current->group_leader); 903 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 904 task_unlock(current->group_leader); 905 906 posix_cpu_timers_init_group(sig); 907 908 tty_audit_fork(sig); 909 sched_autogroup_fork(sig); 910 911 sig->oom_adj = current->signal->oom_adj; 912 sig->oom_score_adj = current->signal->oom_score_adj; 913 914 mutex_init(&sig->cred_guard_mutex); 915 916 return 0; 917 } 918 919 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 920 { 921 unsigned long new_flags = p->flags; 922 923 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 924 new_flags |= PF_FORKNOEXEC; 925 new_flags |= PF_STARTING; 926 p->flags = new_flags; 927 clear_freeze_flag(p); 928 } 929 930 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 931 { 932 current->clear_child_tid = tidptr; 933 934 return task_pid_vnr(current); 935 } 936 937 static void rt_mutex_init_task(struct task_struct *p) 938 { 939 raw_spin_lock_init(&p->pi_lock); 940 #ifdef CONFIG_RT_MUTEXES 941 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 942 p->pi_blocked_on = NULL; 943 #endif 944 } 945 946 #ifdef CONFIG_MM_OWNER 947 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 948 { 949 mm->owner = p; 950 } 951 #endif /* CONFIG_MM_OWNER */ 952 953 /* 954 * Initialize POSIX timer handling for a single task. 955 */ 956 static void posix_cpu_timers_init(struct task_struct *tsk) 957 { 958 tsk->cputime_expires.prof_exp = cputime_zero; 959 tsk->cputime_expires.virt_exp = cputime_zero; 960 tsk->cputime_expires.sched_exp = 0; 961 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 962 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 963 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 964 } 965 966 /* 967 * This creates a new process as a copy of the old one, 968 * but does not actually start it yet. 969 * 970 * It copies the registers, and all the appropriate 971 * parts of the process environment (as per the clone 972 * flags). The actual kick-off is left to the caller. 973 */ 974 static struct task_struct *copy_process(unsigned long clone_flags, 975 unsigned long stack_start, 976 struct pt_regs *regs, 977 unsigned long stack_size, 978 int __user *child_tidptr, 979 struct pid *pid, 980 int trace) 981 { 982 int retval; 983 struct task_struct *p; 984 int cgroup_callbacks_done = 0; 985 986 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 987 return ERR_PTR(-EINVAL); 988 989 /* 990 * Thread groups must share signals as well, and detached threads 991 * can only be started up within the thread group. 992 */ 993 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 994 return ERR_PTR(-EINVAL); 995 996 /* 997 * Shared signal handlers imply shared VM. By way of the above, 998 * thread groups also imply shared VM. Blocking this case allows 999 * for various simplifications in other code. 1000 */ 1001 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1002 return ERR_PTR(-EINVAL); 1003 1004 /* 1005 * Siblings of global init remain as zombies on exit since they are 1006 * not reaped by their parent (swapper). To solve this and to avoid 1007 * multi-rooted process trees, prevent global and container-inits 1008 * from creating siblings. 1009 */ 1010 if ((clone_flags & CLONE_PARENT) && 1011 current->signal->flags & SIGNAL_UNKILLABLE) 1012 return ERR_PTR(-EINVAL); 1013 1014 retval = security_task_create(clone_flags); 1015 if (retval) 1016 goto fork_out; 1017 1018 retval = -ENOMEM; 1019 p = dup_task_struct(current); 1020 if (!p) 1021 goto fork_out; 1022 1023 ftrace_graph_init_task(p); 1024 1025 rt_mutex_init_task(p); 1026 1027 #ifdef CONFIG_PROVE_LOCKING 1028 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1029 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1030 #endif 1031 retval = -EAGAIN; 1032 if (atomic_read(&p->real_cred->user->processes) >= 1033 task_rlimit(p, RLIMIT_NPROC)) { 1034 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1035 p->real_cred->user != INIT_USER) 1036 goto bad_fork_free; 1037 } 1038 1039 retval = copy_creds(p, clone_flags); 1040 if (retval < 0) 1041 goto bad_fork_free; 1042 1043 /* 1044 * If multiple threads are within copy_process(), then this check 1045 * triggers too late. This doesn't hurt, the check is only there 1046 * to stop root fork bombs. 1047 */ 1048 retval = -EAGAIN; 1049 if (nr_threads >= max_threads) 1050 goto bad_fork_cleanup_count; 1051 1052 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1053 goto bad_fork_cleanup_count; 1054 1055 p->did_exec = 0; 1056 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1057 copy_flags(clone_flags, p); 1058 INIT_LIST_HEAD(&p->children); 1059 INIT_LIST_HEAD(&p->sibling); 1060 rcu_copy_process(p); 1061 p->vfork_done = NULL; 1062 spin_lock_init(&p->alloc_lock); 1063 1064 init_sigpending(&p->pending); 1065 1066 p->utime = cputime_zero; 1067 p->stime = cputime_zero; 1068 p->gtime = cputime_zero; 1069 p->utimescaled = cputime_zero; 1070 p->stimescaled = cputime_zero; 1071 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1072 p->prev_utime = cputime_zero; 1073 p->prev_stime = cputime_zero; 1074 #endif 1075 #if defined(SPLIT_RSS_COUNTING) 1076 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1077 #endif 1078 1079 p->default_timer_slack_ns = current->timer_slack_ns; 1080 1081 task_io_accounting_init(&p->ioac); 1082 acct_clear_integrals(p); 1083 1084 posix_cpu_timers_init(p); 1085 1086 p->lock_depth = -1; /* -1 = no lock */ 1087 do_posix_clock_monotonic_gettime(&p->start_time); 1088 p->real_start_time = p->start_time; 1089 monotonic_to_bootbased(&p->real_start_time); 1090 p->io_context = NULL; 1091 p->audit_context = NULL; 1092 cgroup_fork(p); 1093 #ifdef CONFIG_NUMA 1094 p->mempolicy = mpol_dup(p->mempolicy); 1095 if (IS_ERR(p->mempolicy)) { 1096 retval = PTR_ERR(p->mempolicy); 1097 p->mempolicy = NULL; 1098 goto bad_fork_cleanup_cgroup; 1099 } 1100 mpol_fix_fork_child_flag(p); 1101 #endif 1102 #ifdef CONFIG_TRACE_IRQFLAGS 1103 p->irq_events = 0; 1104 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1105 p->hardirqs_enabled = 1; 1106 #else 1107 p->hardirqs_enabled = 0; 1108 #endif 1109 p->hardirq_enable_ip = 0; 1110 p->hardirq_enable_event = 0; 1111 p->hardirq_disable_ip = _THIS_IP_; 1112 p->hardirq_disable_event = 0; 1113 p->softirqs_enabled = 1; 1114 p->softirq_enable_ip = _THIS_IP_; 1115 p->softirq_enable_event = 0; 1116 p->softirq_disable_ip = 0; 1117 p->softirq_disable_event = 0; 1118 p->hardirq_context = 0; 1119 p->softirq_context = 0; 1120 #endif 1121 #ifdef CONFIG_LOCKDEP 1122 p->lockdep_depth = 0; /* no locks held yet */ 1123 p->curr_chain_key = 0; 1124 p->lockdep_recursion = 0; 1125 #endif 1126 1127 #ifdef CONFIG_DEBUG_MUTEXES 1128 p->blocked_on = NULL; /* not blocked yet */ 1129 #endif 1130 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1131 p->memcg_batch.do_batch = 0; 1132 p->memcg_batch.memcg = NULL; 1133 #endif 1134 1135 /* Perform scheduler related setup. Assign this task to a CPU. */ 1136 sched_fork(p, clone_flags); 1137 1138 retval = perf_event_init_task(p); 1139 if (retval) 1140 goto bad_fork_cleanup_policy; 1141 1142 if ((retval = audit_alloc(p))) 1143 goto bad_fork_cleanup_policy; 1144 /* copy all the process information */ 1145 if ((retval = copy_semundo(clone_flags, p))) 1146 goto bad_fork_cleanup_audit; 1147 if ((retval = copy_files(clone_flags, p))) 1148 goto bad_fork_cleanup_semundo; 1149 if ((retval = copy_fs(clone_flags, p))) 1150 goto bad_fork_cleanup_files; 1151 if ((retval = copy_sighand(clone_flags, p))) 1152 goto bad_fork_cleanup_fs; 1153 if ((retval = copy_signal(clone_flags, p))) 1154 goto bad_fork_cleanup_sighand; 1155 if ((retval = copy_mm(clone_flags, p))) 1156 goto bad_fork_cleanup_signal; 1157 if ((retval = copy_namespaces(clone_flags, p))) 1158 goto bad_fork_cleanup_mm; 1159 if ((retval = copy_io(clone_flags, p))) 1160 goto bad_fork_cleanup_namespaces; 1161 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1162 if (retval) 1163 goto bad_fork_cleanup_io; 1164 1165 if (pid != &init_struct_pid) { 1166 retval = -ENOMEM; 1167 pid = alloc_pid(p->nsproxy->pid_ns); 1168 if (!pid) 1169 goto bad_fork_cleanup_io; 1170 1171 if (clone_flags & CLONE_NEWPID) { 1172 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1173 if (retval < 0) 1174 goto bad_fork_free_pid; 1175 } 1176 } 1177 1178 p->pid = pid_nr(pid); 1179 p->tgid = p->pid; 1180 if (clone_flags & CLONE_THREAD) 1181 p->tgid = current->tgid; 1182 1183 if (current->nsproxy != p->nsproxy) { 1184 retval = ns_cgroup_clone(p, pid); 1185 if (retval) 1186 goto bad_fork_free_pid; 1187 } 1188 1189 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1190 /* 1191 * Clear TID on mm_release()? 1192 */ 1193 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1194 #ifdef CONFIG_FUTEX 1195 p->robust_list = NULL; 1196 #ifdef CONFIG_COMPAT 1197 p->compat_robust_list = NULL; 1198 #endif 1199 INIT_LIST_HEAD(&p->pi_state_list); 1200 p->pi_state_cache = NULL; 1201 #endif 1202 /* 1203 * sigaltstack should be cleared when sharing the same VM 1204 */ 1205 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1206 p->sas_ss_sp = p->sas_ss_size = 0; 1207 1208 /* 1209 * Syscall tracing and stepping should be turned off in the 1210 * child regardless of CLONE_PTRACE. 1211 */ 1212 user_disable_single_step(p); 1213 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1214 #ifdef TIF_SYSCALL_EMU 1215 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1216 #endif 1217 clear_all_latency_tracing(p); 1218 1219 /* ok, now we should be set up.. */ 1220 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1221 p->pdeath_signal = 0; 1222 p->exit_state = 0; 1223 1224 /* 1225 * Ok, make it visible to the rest of the system. 1226 * We dont wake it up yet. 1227 */ 1228 p->group_leader = p; 1229 INIT_LIST_HEAD(&p->thread_group); 1230 1231 /* Now that the task is set up, run cgroup callbacks if 1232 * necessary. We need to run them before the task is visible 1233 * on the tasklist. */ 1234 cgroup_fork_callbacks(p); 1235 cgroup_callbacks_done = 1; 1236 1237 /* Need tasklist lock for parent etc handling! */ 1238 write_lock_irq(&tasklist_lock); 1239 1240 /* CLONE_PARENT re-uses the old parent */ 1241 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1242 p->real_parent = current->real_parent; 1243 p->parent_exec_id = current->parent_exec_id; 1244 } else { 1245 p->real_parent = current; 1246 p->parent_exec_id = current->self_exec_id; 1247 } 1248 1249 spin_lock(¤t->sighand->siglock); 1250 1251 /* 1252 * Process group and session signals need to be delivered to just the 1253 * parent before the fork or both the parent and the child after the 1254 * fork. Restart if a signal comes in before we add the new process to 1255 * it's process group. 1256 * A fatal signal pending means that current will exit, so the new 1257 * thread can't slip out of an OOM kill (or normal SIGKILL). 1258 */ 1259 recalc_sigpending(); 1260 if (signal_pending(current)) { 1261 spin_unlock(¤t->sighand->siglock); 1262 write_unlock_irq(&tasklist_lock); 1263 retval = -ERESTARTNOINTR; 1264 goto bad_fork_free_pid; 1265 } 1266 1267 if (clone_flags & CLONE_THREAD) { 1268 current->signal->nr_threads++; 1269 atomic_inc(¤t->signal->live); 1270 atomic_inc(¤t->signal->sigcnt); 1271 p->group_leader = current->group_leader; 1272 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1273 } 1274 1275 if (likely(p->pid)) { 1276 tracehook_finish_clone(p, clone_flags, trace); 1277 1278 if (thread_group_leader(p)) { 1279 if (clone_flags & CLONE_NEWPID) 1280 p->nsproxy->pid_ns->child_reaper = p; 1281 1282 p->signal->leader_pid = pid; 1283 p->signal->tty = tty_kref_get(current->signal->tty); 1284 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1285 attach_pid(p, PIDTYPE_SID, task_session(current)); 1286 list_add_tail(&p->sibling, &p->real_parent->children); 1287 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1288 __this_cpu_inc(process_counts); 1289 } 1290 attach_pid(p, PIDTYPE_PID, pid); 1291 nr_threads++; 1292 } 1293 1294 total_forks++; 1295 spin_unlock(¤t->sighand->siglock); 1296 write_unlock_irq(&tasklist_lock); 1297 proc_fork_connector(p); 1298 cgroup_post_fork(p); 1299 perf_event_fork(p); 1300 return p; 1301 1302 bad_fork_free_pid: 1303 if (pid != &init_struct_pid) 1304 free_pid(pid); 1305 bad_fork_cleanup_io: 1306 if (p->io_context) 1307 exit_io_context(p); 1308 bad_fork_cleanup_namespaces: 1309 exit_task_namespaces(p); 1310 bad_fork_cleanup_mm: 1311 if (p->mm) { 1312 task_lock(p); 1313 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 1314 atomic_dec(&p->mm->oom_disable_count); 1315 task_unlock(p); 1316 mmput(p->mm); 1317 } 1318 bad_fork_cleanup_signal: 1319 if (!(clone_flags & CLONE_THREAD)) 1320 free_signal_struct(p->signal); 1321 bad_fork_cleanup_sighand: 1322 __cleanup_sighand(p->sighand); 1323 bad_fork_cleanup_fs: 1324 exit_fs(p); /* blocking */ 1325 bad_fork_cleanup_files: 1326 exit_files(p); /* blocking */ 1327 bad_fork_cleanup_semundo: 1328 exit_sem(p); 1329 bad_fork_cleanup_audit: 1330 audit_free(p); 1331 bad_fork_cleanup_policy: 1332 perf_event_free_task(p); 1333 #ifdef CONFIG_NUMA 1334 mpol_put(p->mempolicy); 1335 bad_fork_cleanup_cgroup: 1336 #endif 1337 cgroup_exit(p, cgroup_callbacks_done); 1338 delayacct_tsk_free(p); 1339 module_put(task_thread_info(p)->exec_domain->module); 1340 bad_fork_cleanup_count: 1341 atomic_dec(&p->cred->user->processes); 1342 exit_creds(p); 1343 bad_fork_free: 1344 free_task(p); 1345 fork_out: 1346 return ERR_PTR(retval); 1347 } 1348 1349 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1350 { 1351 memset(regs, 0, sizeof(struct pt_regs)); 1352 return regs; 1353 } 1354 1355 static inline void init_idle_pids(struct pid_link *links) 1356 { 1357 enum pid_type type; 1358 1359 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1360 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1361 links[type].pid = &init_struct_pid; 1362 } 1363 } 1364 1365 struct task_struct * __cpuinit fork_idle(int cpu) 1366 { 1367 struct task_struct *task; 1368 struct pt_regs regs; 1369 1370 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1371 &init_struct_pid, 0); 1372 if (!IS_ERR(task)) { 1373 init_idle_pids(task->pids); 1374 init_idle(task, cpu); 1375 } 1376 1377 return task; 1378 } 1379 1380 /* 1381 * Ok, this is the main fork-routine. 1382 * 1383 * It copies the process, and if successful kick-starts 1384 * it and waits for it to finish using the VM if required. 1385 */ 1386 long do_fork(unsigned long clone_flags, 1387 unsigned long stack_start, 1388 struct pt_regs *regs, 1389 unsigned long stack_size, 1390 int __user *parent_tidptr, 1391 int __user *child_tidptr) 1392 { 1393 struct task_struct *p; 1394 int trace = 0; 1395 long nr; 1396 1397 /* 1398 * Do some preliminary argument and permissions checking before we 1399 * actually start allocating stuff 1400 */ 1401 if (clone_flags & CLONE_NEWUSER) { 1402 if (clone_flags & CLONE_THREAD) 1403 return -EINVAL; 1404 /* hopefully this check will go away when userns support is 1405 * complete 1406 */ 1407 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1408 !capable(CAP_SETGID)) 1409 return -EPERM; 1410 } 1411 1412 /* 1413 * We hope to recycle these flags after 2.6.26 1414 */ 1415 if (unlikely(clone_flags & CLONE_STOPPED)) { 1416 static int __read_mostly count = 100; 1417 1418 if (count > 0 && printk_ratelimit()) { 1419 char comm[TASK_COMM_LEN]; 1420 1421 count--; 1422 printk(KERN_INFO "fork(): process `%s' used deprecated " 1423 "clone flags 0x%lx\n", 1424 get_task_comm(comm, current), 1425 clone_flags & CLONE_STOPPED); 1426 } 1427 } 1428 1429 /* 1430 * When called from kernel_thread, don't do user tracing stuff. 1431 */ 1432 if (likely(user_mode(regs))) 1433 trace = tracehook_prepare_clone(clone_flags); 1434 1435 p = copy_process(clone_flags, stack_start, regs, stack_size, 1436 child_tidptr, NULL, trace); 1437 /* 1438 * Do this prior waking up the new thread - the thread pointer 1439 * might get invalid after that point, if the thread exits quickly. 1440 */ 1441 if (!IS_ERR(p)) { 1442 struct completion vfork; 1443 1444 trace_sched_process_fork(current, p); 1445 1446 nr = task_pid_vnr(p); 1447 1448 if (clone_flags & CLONE_PARENT_SETTID) 1449 put_user(nr, parent_tidptr); 1450 1451 if (clone_flags & CLONE_VFORK) { 1452 p->vfork_done = &vfork; 1453 init_completion(&vfork); 1454 } 1455 1456 audit_finish_fork(p); 1457 tracehook_report_clone(regs, clone_flags, nr, p); 1458 1459 /* 1460 * We set PF_STARTING at creation in case tracing wants to 1461 * use this to distinguish a fully live task from one that 1462 * hasn't gotten to tracehook_report_clone() yet. Now we 1463 * clear it and set the child going. 1464 */ 1465 p->flags &= ~PF_STARTING; 1466 1467 if (unlikely(clone_flags & CLONE_STOPPED)) { 1468 /* 1469 * We'll start up with an immediate SIGSTOP. 1470 */ 1471 sigaddset(&p->pending.signal, SIGSTOP); 1472 set_tsk_thread_flag(p, TIF_SIGPENDING); 1473 __set_task_state(p, TASK_STOPPED); 1474 } else { 1475 wake_up_new_task(p, clone_flags); 1476 } 1477 1478 tracehook_report_clone_complete(trace, regs, 1479 clone_flags, nr, p); 1480 1481 if (clone_flags & CLONE_VFORK) { 1482 freezer_do_not_count(); 1483 wait_for_completion(&vfork); 1484 freezer_count(); 1485 tracehook_report_vfork_done(p, nr); 1486 } 1487 } else { 1488 nr = PTR_ERR(p); 1489 } 1490 return nr; 1491 } 1492 1493 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1494 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1495 #endif 1496 1497 static void sighand_ctor(void *data) 1498 { 1499 struct sighand_struct *sighand = data; 1500 1501 spin_lock_init(&sighand->siglock); 1502 init_waitqueue_head(&sighand->signalfd_wqh); 1503 } 1504 1505 void __init proc_caches_init(void) 1506 { 1507 sighand_cachep = kmem_cache_create("sighand_cache", 1508 sizeof(struct sighand_struct), 0, 1509 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1510 SLAB_NOTRACK, sighand_ctor); 1511 signal_cachep = kmem_cache_create("signal_cache", 1512 sizeof(struct signal_struct), 0, 1513 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1514 files_cachep = kmem_cache_create("files_cache", 1515 sizeof(struct files_struct), 0, 1516 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1517 fs_cachep = kmem_cache_create("fs_cache", 1518 sizeof(struct fs_struct), 0, 1519 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1520 mm_cachep = kmem_cache_create("mm_struct", 1521 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1522 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1523 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1524 mmap_init(); 1525 } 1526 1527 /* 1528 * Check constraints on flags passed to the unshare system call and 1529 * force unsharing of additional process context as appropriate. 1530 */ 1531 static void check_unshare_flags(unsigned long *flags_ptr) 1532 { 1533 /* 1534 * If unsharing a thread from a thread group, must also 1535 * unshare vm. 1536 */ 1537 if (*flags_ptr & CLONE_THREAD) 1538 *flags_ptr |= CLONE_VM; 1539 1540 /* 1541 * If unsharing vm, must also unshare signal handlers. 1542 */ 1543 if (*flags_ptr & CLONE_VM) 1544 *flags_ptr |= CLONE_SIGHAND; 1545 1546 /* 1547 * If unsharing namespace, must also unshare filesystem information. 1548 */ 1549 if (*flags_ptr & CLONE_NEWNS) 1550 *flags_ptr |= CLONE_FS; 1551 } 1552 1553 /* 1554 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1555 */ 1556 static int unshare_thread(unsigned long unshare_flags) 1557 { 1558 if (unshare_flags & CLONE_THREAD) 1559 return -EINVAL; 1560 1561 return 0; 1562 } 1563 1564 /* 1565 * Unshare the filesystem structure if it is being shared 1566 */ 1567 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1568 { 1569 struct fs_struct *fs = current->fs; 1570 1571 if (!(unshare_flags & CLONE_FS) || !fs) 1572 return 0; 1573 1574 /* don't need lock here; in the worst case we'll do useless copy */ 1575 if (fs->users == 1) 1576 return 0; 1577 1578 *new_fsp = copy_fs_struct(fs); 1579 if (!*new_fsp) 1580 return -ENOMEM; 1581 1582 return 0; 1583 } 1584 1585 /* 1586 * Unsharing of sighand is not supported yet 1587 */ 1588 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1589 { 1590 struct sighand_struct *sigh = current->sighand; 1591 1592 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1593 return -EINVAL; 1594 else 1595 return 0; 1596 } 1597 1598 /* 1599 * Unshare vm if it is being shared 1600 */ 1601 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1602 { 1603 struct mm_struct *mm = current->mm; 1604 1605 if ((unshare_flags & CLONE_VM) && 1606 (mm && atomic_read(&mm->mm_users) > 1)) { 1607 return -EINVAL; 1608 } 1609 1610 return 0; 1611 } 1612 1613 /* 1614 * Unshare file descriptor table if it is being shared 1615 */ 1616 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1617 { 1618 struct files_struct *fd = current->files; 1619 int error = 0; 1620 1621 if ((unshare_flags & CLONE_FILES) && 1622 (fd && atomic_read(&fd->count) > 1)) { 1623 *new_fdp = dup_fd(fd, &error); 1624 if (!*new_fdp) 1625 return error; 1626 } 1627 1628 return 0; 1629 } 1630 1631 /* 1632 * unshare allows a process to 'unshare' part of the process 1633 * context which was originally shared using clone. copy_* 1634 * functions used by do_fork() cannot be used here directly 1635 * because they modify an inactive task_struct that is being 1636 * constructed. Here we are modifying the current, active, 1637 * task_struct. 1638 */ 1639 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1640 { 1641 int err = 0; 1642 struct fs_struct *fs, *new_fs = NULL; 1643 struct sighand_struct *new_sigh = NULL; 1644 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1645 struct files_struct *fd, *new_fd = NULL; 1646 struct nsproxy *new_nsproxy = NULL; 1647 int do_sysvsem = 0; 1648 1649 check_unshare_flags(&unshare_flags); 1650 1651 /* Return -EINVAL for all unsupported flags */ 1652 err = -EINVAL; 1653 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1654 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1655 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1656 goto bad_unshare_out; 1657 1658 /* 1659 * CLONE_NEWIPC must also detach from the undolist: after switching 1660 * to a new ipc namespace, the semaphore arrays from the old 1661 * namespace are unreachable. 1662 */ 1663 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1664 do_sysvsem = 1; 1665 if ((err = unshare_thread(unshare_flags))) 1666 goto bad_unshare_out; 1667 if ((err = unshare_fs(unshare_flags, &new_fs))) 1668 goto bad_unshare_cleanup_thread; 1669 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1670 goto bad_unshare_cleanup_fs; 1671 if ((err = unshare_vm(unshare_flags, &new_mm))) 1672 goto bad_unshare_cleanup_sigh; 1673 if ((err = unshare_fd(unshare_flags, &new_fd))) 1674 goto bad_unshare_cleanup_vm; 1675 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1676 new_fs))) 1677 goto bad_unshare_cleanup_fd; 1678 1679 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1680 if (do_sysvsem) { 1681 /* 1682 * CLONE_SYSVSEM is equivalent to sys_exit(). 1683 */ 1684 exit_sem(current); 1685 } 1686 1687 if (new_nsproxy) { 1688 switch_task_namespaces(current, new_nsproxy); 1689 new_nsproxy = NULL; 1690 } 1691 1692 task_lock(current); 1693 1694 if (new_fs) { 1695 fs = current->fs; 1696 spin_lock(&fs->lock); 1697 current->fs = new_fs; 1698 if (--fs->users) 1699 new_fs = NULL; 1700 else 1701 new_fs = fs; 1702 spin_unlock(&fs->lock); 1703 } 1704 1705 if (new_mm) { 1706 mm = current->mm; 1707 active_mm = current->active_mm; 1708 current->mm = new_mm; 1709 current->active_mm = new_mm; 1710 if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { 1711 atomic_dec(&mm->oom_disable_count); 1712 atomic_inc(&new_mm->oom_disable_count); 1713 } 1714 activate_mm(active_mm, new_mm); 1715 new_mm = mm; 1716 } 1717 1718 if (new_fd) { 1719 fd = current->files; 1720 current->files = new_fd; 1721 new_fd = fd; 1722 } 1723 1724 task_unlock(current); 1725 } 1726 1727 if (new_nsproxy) 1728 put_nsproxy(new_nsproxy); 1729 1730 bad_unshare_cleanup_fd: 1731 if (new_fd) 1732 put_files_struct(new_fd); 1733 1734 bad_unshare_cleanup_vm: 1735 if (new_mm) 1736 mmput(new_mm); 1737 1738 bad_unshare_cleanup_sigh: 1739 if (new_sigh) 1740 if (atomic_dec_and_test(&new_sigh->count)) 1741 kmem_cache_free(sighand_cachep, new_sigh); 1742 1743 bad_unshare_cleanup_fs: 1744 if (new_fs) 1745 free_fs_struct(new_fs); 1746 1747 bad_unshare_cleanup_thread: 1748 bad_unshare_out: 1749 return err; 1750 } 1751 1752 /* 1753 * Helper to unshare the files of the current task. 1754 * We don't want to expose copy_files internals to 1755 * the exec layer of the kernel. 1756 */ 1757 1758 int unshare_files(struct files_struct **displaced) 1759 { 1760 struct task_struct *task = current; 1761 struct files_struct *copy = NULL; 1762 int error; 1763 1764 error = unshare_fd(CLONE_FILES, ©); 1765 if (error || !copy) { 1766 *displaced = NULL; 1767 return error; 1768 } 1769 *displaced = task->files; 1770 task_lock(task); 1771 task->files = copy; 1772 task_unlock(task); 1773 return 0; 1774 } 1775