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