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 69 #include <asm/pgtable.h> 70 #include <asm/pgalloc.h> 71 #include <asm/uaccess.h> 72 #include <asm/mmu_context.h> 73 #include <asm/cacheflush.h> 74 #include <asm/tlbflush.h> 75 76 #include <trace/events/sched.h> 77 78 /* 79 * Protected counters by write_lock_irq(&tasklist_lock) 80 */ 81 unsigned long total_forks; /* Handle normal Linux uptimes. */ 82 int nr_threads; /* The idle threads do not count.. */ 83 84 int max_threads; /* tunable limit on nr_threads */ 85 86 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 87 88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 89 90 #ifdef CONFIG_PROVE_RCU 91 int lockdep_tasklist_lock_is_held(void) 92 { 93 return lockdep_is_held(&tasklist_lock); 94 } 95 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 96 #endif /* #ifdef CONFIG_PROVE_RCU */ 97 98 int nr_processes(void) 99 { 100 int cpu; 101 int total = 0; 102 103 for_each_possible_cpu(cpu) 104 total += per_cpu(process_counts, cpu); 105 106 return total; 107 } 108 109 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 110 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 111 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 112 static struct kmem_cache *task_struct_cachep; 113 #endif 114 115 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 116 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 117 { 118 #ifdef CONFIG_DEBUG_STACK_USAGE 119 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 120 #else 121 gfp_t mask = GFP_KERNEL; 122 #endif 123 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 124 } 125 126 static inline void free_thread_info(struct thread_info *ti) 127 { 128 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 129 } 130 #endif 131 132 /* SLAB cache for signal_struct structures (tsk->signal) */ 133 static struct kmem_cache *signal_cachep; 134 135 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 136 struct kmem_cache *sighand_cachep; 137 138 /* SLAB cache for files_struct structures (tsk->files) */ 139 struct kmem_cache *files_cachep; 140 141 /* SLAB cache for fs_struct structures (tsk->fs) */ 142 struct kmem_cache *fs_cachep; 143 144 /* SLAB cache for vm_area_struct structures */ 145 struct kmem_cache *vm_area_cachep; 146 147 /* SLAB cache for mm_struct structures (tsk->mm) */ 148 static struct kmem_cache *mm_cachep; 149 150 static void account_kernel_stack(struct thread_info *ti, int account) 151 { 152 struct zone *zone = page_zone(virt_to_page(ti)); 153 154 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 155 } 156 157 void free_task(struct task_struct *tsk) 158 { 159 prop_local_destroy_single(&tsk->dirties); 160 account_kernel_stack(tsk->stack, -1); 161 free_thread_info(tsk->stack); 162 rt_mutex_debug_task_free(tsk); 163 ftrace_graph_exit_task(tsk); 164 free_task_struct(tsk); 165 } 166 EXPORT_SYMBOL(free_task); 167 168 static inline void free_signal_struct(struct signal_struct *sig) 169 { 170 taskstats_tgid_free(sig); 171 kmem_cache_free(signal_cachep, sig); 172 } 173 174 static inline void put_signal_struct(struct signal_struct *sig) 175 { 176 if (atomic_dec_and_test(&sig->sigcnt)) 177 free_signal_struct(sig); 178 } 179 180 void __put_task_struct(struct task_struct *tsk) 181 { 182 WARN_ON(!tsk->exit_state); 183 WARN_ON(atomic_read(&tsk->usage)); 184 WARN_ON(tsk == current); 185 186 exit_creds(tsk); 187 delayacct_tsk_free(tsk); 188 put_signal_struct(tsk->signal); 189 190 if (!profile_handoff_task(tsk)) 191 free_task(tsk); 192 } 193 194 /* 195 * macro override instead of weak attribute alias, to workaround 196 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 197 */ 198 #ifndef arch_task_cache_init 199 #define arch_task_cache_init() 200 #endif 201 202 void __init fork_init(unsigned long mempages) 203 { 204 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 205 #ifndef ARCH_MIN_TASKALIGN 206 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 207 #endif 208 /* create a slab on which task_structs can be allocated */ 209 task_struct_cachep = 210 kmem_cache_create("task_struct", sizeof(struct task_struct), 211 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 212 #endif 213 214 /* do the arch specific task caches init */ 215 arch_task_cache_init(); 216 217 /* 218 * The default maximum number of threads is set to a safe 219 * value: the thread structures can take up at most half 220 * of memory. 221 */ 222 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 223 224 /* 225 * we need to allow at least 20 threads to boot a system 226 */ 227 if(max_threads < 20) 228 max_threads = 20; 229 230 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 231 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 232 init_task.signal->rlim[RLIMIT_SIGPENDING] = 233 init_task.signal->rlim[RLIMIT_NPROC]; 234 } 235 236 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 237 struct task_struct *src) 238 { 239 *dst = *src; 240 return 0; 241 } 242 243 static struct task_struct *dup_task_struct(struct task_struct *orig) 244 { 245 struct task_struct *tsk; 246 struct thread_info *ti; 247 unsigned long *stackend; 248 249 int err; 250 251 prepare_to_copy(orig); 252 253 tsk = alloc_task_struct(); 254 if (!tsk) 255 return NULL; 256 257 ti = alloc_thread_info(tsk); 258 if (!ti) { 259 free_task_struct(tsk); 260 return NULL; 261 } 262 263 err = arch_dup_task_struct(tsk, orig); 264 if (err) 265 goto out; 266 267 tsk->stack = ti; 268 269 err = prop_local_init_single(&tsk->dirties); 270 if (err) 271 goto out; 272 273 setup_thread_stack(tsk, orig); 274 clear_user_return_notifier(tsk); 275 stackend = end_of_stack(tsk); 276 *stackend = STACK_END_MAGIC; /* for overflow detection */ 277 278 #ifdef CONFIG_CC_STACKPROTECTOR 279 tsk->stack_canary = get_random_int(); 280 #endif 281 282 /* One for us, one for whoever does the "release_task()" (usually parent) */ 283 atomic_set(&tsk->usage,2); 284 atomic_set(&tsk->fs_excl, 0); 285 #ifdef CONFIG_BLK_DEV_IO_TRACE 286 tsk->btrace_seq = 0; 287 #endif 288 tsk->splice_pipe = NULL; 289 290 account_kernel_stack(ti, 1); 291 292 return tsk; 293 294 out: 295 free_thread_info(ti); 296 free_task_struct(tsk); 297 return NULL; 298 } 299 300 #ifdef CONFIG_MMU 301 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 302 { 303 struct vm_area_struct *mpnt, *tmp, **pprev; 304 struct rb_node **rb_link, *rb_parent; 305 int retval; 306 unsigned long charge; 307 struct mempolicy *pol; 308 309 down_write(&oldmm->mmap_sem); 310 flush_cache_dup_mm(oldmm); 311 /* 312 * Not linked in yet - no deadlock potential: 313 */ 314 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 315 316 mm->locked_vm = 0; 317 mm->mmap = NULL; 318 mm->mmap_cache = NULL; 319 mm->free_area_cache = oldmm->mmap_base; 320 mm->cached_hole_size = ~0UL; 321 mm->map_count = 0; 322 cpumask_clear(mm_cpumask(mm)); 323 mm->mm_rb = RB_ROOT; 324 rb_link = &mm->mm_rb.rb_node; 325 rb_parent = NULL; 326 pprev = &mm->mmap; 327 retval = ksm_fork(mm, oldmm); 328 if (retval) 329 goto out; 330 331 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 332 struct file *file; 333 334 if (mpnt->vm_flags & VM_DONTCOPY) { 335 long pages = vma_pages(mpnt); 336 mm->total_vm -= pages; 337 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 338 -pages); 339 continue; 340 } 341 charge = 0; 342 if (mpnt->vm_flags & VM_ACCOUNT) { 343 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 344 if (security_vm_enough_memory(len)) 345 goto fail_nomem; 346 charge = len; 347 } 348 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 349 if (!tmp) 350 goto fail_nomem; 351 *tmp = *mpnt; 352 INIT_LIST_HEAD(&tmp->anon_vma_chain); 353 pol = mpol_dup(vma_policy(mpnt)); 354 retval = PTR_ERR(pol); 355 if (IS_ERR(pol)) 356 goto fail_nomem_policy; 357 vma_set_policy(tmp, pol); 358 if (anon_vma_fork(tmp, mpnt)) 359 goto fail_nomem_anon_vma_fork; 360 tmp->vm_flags &= ~VM_LOCKED; 361 tmp->vm_mm = mm; 362 tmp->vm_next = NULL; 363 file = tmp->vm_file; 364 if (file) { 365 struct inode *inode = file->f_path.dentry->d_inode; 366 struct address_space *mapping = file->f_mapping; 367 368 get_file(file); 369 if (tmp->vm_flags & VM_DENYWRITE) 370 atomic_dec(&inode->i_writecount); 371 spin_lock(&mapping->i_mmap_lock); 372 if (tmp->vm_flags & VM_SHARED) 373 mapping->i_mmap_writable++; 374 tmp->vm_truncate_count = mpnt->vm_truncate_count; 375 flush_dcache_mmap_lock(mapping); 376 /* insert tmp into the share list, just after mpnt */ 377 vma_prio_tree_add(tmp, mpnt); 378 flush_dcache_mmap_unlock(mapping); 379 spin_unlock(&mapping->i_mmap_lock); 380 } 381 382 /* 383 * Clear hugetlb-related page reserves for children. This only 384 * affects MAP_PRIVATE mappings. Faults generated by the child 385 * are not guaranteed to succeed, even if read-only 386 */ 387 if (is_vm_hugetlb_page(tmp)) 388 reset_vma_resv_huge_pages(tmp); 389 390 /* 391 * Link in the new vma and copy the page table entries. 392 */ 393 *pprev = tmp; 394 pprev = &tmp->vm_next; 395 396 __vma_link_rb(mm, tmp, rb_link, rb_parent); 397 rb_link = &tmp->vm_rb.rb_right; 398 rb_parent = &tmp->vm_rb; 399 400 mm->map_count++; 401 retval = copy_page_range(mm, oldmm, mpnt); 402 403 if (tmp->vm_ops && tmp->vm_ops->open) 404 tmp->vm_ops->open(tmp); 405 406 if (retval) 407 goto out; 408 } 409 /* a new mm has just been created */ 410 arch_dup_mmap(oldmm, mm); 411 retval = 0; 412 out: 413 up_write(&mm->mmap_sem); 414 flush_tlb_mm(oldmm); 415 up_write(&oldmm->mmap_sem); 416 return retval; 417 fail_nomem_anon_vma_fork: 418 mpol_put(pol); 419 fail_nomem_policy: 420 kmem_cache_free(vm_area_cachep, tmp); 421 fail_nomem: 422 retval = -ENOMEM; 423 vm_unacct_memory(charge); 424 goto out; 425 } 426 427 static inline int mm_alloc_pgd(struct mm_struct * mm) 428 { 429 mm->pgd = pgd_alloc(mm); 430 if (unlikely(!mm->pgd)) 431 return -ENOMEM; 432 return 0; 433 } 434 435 static inline void mm_free_pgd(struct mm_struct * mm) 436 { 437 pgd_free(mm, mm->pgd); 438 } 439 #else 440 #define dup_mmap(mm, oldmm) (0) 441 #define mm_alloc_pgd(mm) (0) 442 #define mm_free_pgd(mm) 443 #endif /* CONFIG_MMU */ 444 445 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 446 447 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 448 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 449 450 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 451 452 static int __init coredump_filter_setup(char *s) 453 { 454 default_dump_filter = 455 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 456 MMF_DUMP_FILTER_MASK; 457 return 1; 458 } 459 460 __setup("coredump_filter=", coredump_filter_setup); 461 462 #include <linux/init_task.h> 463 464 static void mm_init_aio(struct mm_struct *mm) 465 { 466 #ifdef CONFIG_AIO 467 spin_lock_init(&mm->ioctx_lock); 468 INIT_HLIST_HEAD(&mm->ioctx_list); 469 #endif 470 } 471 472 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 473 { 474 atomic_set(&mm->mm_users, 1); 475 atomic_set(&mm->mm_count, 1); 476 init_rwsem(&mm->mmap_sem); 477 INIT_LIST_HEAD(&mm->mmlist); 478 mm->flags = (current->mm) ? 479 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 480 mm->core_state = NULL; 481 mm->nr_ptes = 0; 482 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 483 spin_lock_init(&mm->page_table_lock); 484 mm->free_area_cache = TASK_UNMAPPED_BASE; 485 mm->cached_hole_size = ~0UL; 486 mm_init_aio(mm); 487 mm_init_owner(mm, p); 488 489 if (likely(!mm_alloc_pgd(mm))) { 490 mm->def_flags = 0; 491 mmu_notifier_mm_init(mm); 492 return mm; 493 } 494 495 free_mm(mm); 496 return NULL; 497 } 498 499 /* 500 * Allocate and initialize an mm_struct. 501 */ 502 struct mm_struct * mm_alloc(void) 503 { 504 struct mm_struct * mm; 505 506 mm = allocate_mm(); 507 if (mm) { 508 memset(mm, 0, sizeof(*mm)); 509 mm = mm_init(mm, current); 510 } 511 return mm; 512 } 513 514 /* 515 * Called when the last reference to the mm 516 * is dropped: either by a lazy thread or by 517 * mmput. Free the page directory and the mm. 518 */ 519 void __mmdrop(struct mm_struct *mm) 520 { 521 BUG_ON(mm == &init_mm); 522 mm_free_pgd(mm); 523 destroy_context(mm); 524 mmu_notifier_mm_destroy(mm); 525 free_mm(mm); 526 } 527 EXPORT_SYMBOL_GPL(__mmdrop); 528 529 /* 530 * Decrement the use count and release all resources for an mm. 531 */ 532 void mmput(struct mm_struct *mm) 533 { 534 might_sleep(); 535 536 if (atomic_dec_and_test(&mm->mm_users)) { 537 exit_aio(mm); 538 ksm_exit(mm); 539 exit_mmap(mm); 540 set_mm_exe_file(mm, NULL); 541 if (!list_empty(&mm->mmlist)) { 542 spin_lock(&mmlist_lock); 543 list_del(&mm->mmlist); 544 spin_unlock(&mmlist_lock); 545 } 546 put_swap_token(mm); 547 if (mm->binfmt) 548 module_put(mm->binfmt->module); 549 mmdrop(mm); 550 } 551 } 552 EXPORT_SYMBOL_GPL(mmput); 553 554 /** 555 * get_task_mm - acquire a reference to the task's mm 556 * 557 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 558 * this kernel workthread has transiently adopted a user mm with use_mm, 559 * to do its AIO) is not set and if so returns a reference to it, after 560 * bumping up the use count. User must release the mm via mmput() 561 * after use. Typically used by /proc and ptrace. 562 */ 563 struct mm_struct *get_task_mm(struct task_struct *task) 564 { 565 struct mm_struct *mm; 566 567 task_lock(task); 568 mm = task->mm; 569 if (mm) { 570 if (task->flags & PF_KTHREAD) 571 mm = NULL; 572 else 573 atomic_inc(&mm->mm_users); 574 } 575 task_unlock(task); 576 return mm; 577 } 578 EXPORT_SYMBOL_GPL(get_task_mm); 579 580 /* Please note the differences between mmput and mm_release. 581 * mmput is called whenever we stop holding onto a mm_struct, 582 * error success whatever. 583 * 584 * mm_release is called after a mm_struct has been removed 585 * from the current process. 586 * 587 * This difference is important for error handling, when we 588 * only half set up a mm_struct for a new process and need to restore 589 * the old one. Because we mmput the new mm_struct before 590 * restoring the old one. . . 591 * Eric Biederman 10 January 1998 592 */ 593 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 594 { 595 struct completion *vfork_done = tsk->vfork_done; 596 597 /* Get rid of any futexes when releasing the mm */ 598 #ifdef CONFIG_FUTEX 599 if (unlikely(tsk->robust_list)) { 600 exit_robust_list(tsk); 601 tsk->robust_list = NULL; 602 } 603 #ifdef CONFIG_COMPAT 604 if (unlikely(tsk->compat_robust_list)) { 605 compat_exit_robust_list(tsk); 606 tsk->compat_robust_list = NULL; 607 } 608 #endif 609 if (unlikely(!list_empty(&tsk->pi_state_list))) 610 exit_pi_state_list(tsk); 611 #endif 612 613 /* Get rid of any cached register state */ 614 deactivate_mm(tsk, mm); 615 616 /* notify parent sleeping on vfork() */ 617 if (vfork_done) { 618 tsk->vfork_done = NULL; 619 complete(vfork_done); 620 } 621 622 /* 623 * If we're exiting normally, clear a user-space tid field if 624 * requested. We leave this alone when dying by signal, to leave 625 * the value intact in a core dump, and to save the unnecessary 626 * trouble otherwise. Userland only wants this done for a sys_exit. 627 */ 628 if (tsk->clear_child_tid) { 629 if (!(tsk->flags & PF_SIGNALED) && 630 atomic_read(&mm->mm_users) > 1) { 631 /* 632 * We don't check the error code - if userspace has 633 * not set up a proper pointer then tough luck. 634 */ 635 put_user(0, tsk->clear_child_tid); 636 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 637 1, NULL, NULL, 0); 638 } 639 tsk->clear_child_tid = NULL; 640 } 641 } 642 643 /* 644 * Allocate a new mm structure and copy contents from the 645 * mm structure of the passed in task structure. 646 */ 647 struct mm_struct *dup_mm(struct task_struct *tsk) 648 { 649 struct mm_struct *mm, *oldmm = current->mm; 650 int err; 651 652 if (!oldmm) 653 return NULL; 654 655 mm = allocate_mm(); 656 if (!mm) 657 goto fail_nomem; 658 659 memcpy(mm, oldmm, sizeof(*mm)); 660 661 /* Initializing for Swap token stuff */ 662 mm->token_priority = 0; 663 mm->last_interval = 0; 664 665 if (!mm_init(mm, tsk)) 666 goto fail_nomem; 667 668 if (init_new_context(tsk, mm)) 669 goto fail_nocontext; 670 671 dup_mm_exe_file(oldmm, mm); 672 673 err = dup_mmap(mm, oldmm); 674 if (err) 675 goto free_pt; 676 677 mm->hiwater_rss = get_mm_rss(mm); 678 mm->hiwater_vm = mm->total_vm; 679 680 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 681 goto free_pt; 682 683 return mm; 684 685 free_pt: 686 /* don't put binfmt in mmput, we haven't got module yet */ 687 mm->binfmt = NULL; 688 mmput(mm); 689 690 fail_nomem: 691 return NULL; 692 693 fail_nocontext: 694 /* 695 * If init_new_context() failed, we cannot use mmput() to free the mm 696 * because it calls destroy_context() 697 */ 698 mm_free_pgd(mm); 699 free_mm(mm); 700 return NULL; 701 } 702 703 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 704 { 705 struct mm_struct * mm, *oldmm; 706 int retval; 707 708 tsk->min_flt = tsk->maj_flt = 0; 709 tsk->nvcsw = tsk->nivcsw = 0; 710 #ifdef CONFIG_DETECT_HUNG_TASK 711 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 712 #endif 713 714 tsk->mm = NULL; 715 tsk->active_mm = NULL; 716 717 /* 718 * Are we cloning a kernel thread? 719 * 720 * We need to steal a active VM for that.. 721 */ 722 oldmm = current->mm; 723 if (!oldmm) 724 return 0; 725 726 if (clone_flags & CLONE_VM) { 727 atomic_inc(&oldmm->mm_users); 728 mm = oldmm; 729 goto good_mm; 730 } 731 732 retval = -ENOMEM; 733 mm = dup_mm(tsk); 734 if (!mm) 735 goto fail_nomem; 736 737 good_mm: 738 /* Initializing for Swap token stuff */ 739 mm->token_priority = 0; 740 mm->last_interval = 0; 741 742 tsk->mm = mm; 743 tsk->active_mm = mm; 744 return 0; 745 746 fail_nomem: 747 return retval; 748 } 749 750 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 751 { 752 struct fs_struct *fs = current->fs; 753 if (clone_flags & CLONE_FS) { 754 /* tsk->fs is already what we want */ 755 write_lock(&fs->lock); 756 if (fs->in_exec) { 757 write_unlock(&fs->lock); 758 return -EAGAIN; 759 } 760 fs->users++; 761 write_unlock(&fs->lock); 762 return 0; 763 } 764 tsk->fs = copy_fs_struct(fs); 765 if (!tsk->fs) 766 return -ENOMEM; 767 return 0; 768 } 769 770 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 771 { 772 struct files_struct *oldf, *newf; 773 int error = 0; 774 775 /* 776 * A background process may not have any files ... 777 */ 778 oldf = current->files; 779 if (!oldf) 780 goto out; 781 782 if (clone_flags & CLONE_FILES) { 783 atomic_inc(&oldf->count); 784 goto out; 785 } 786 787 newf = dup_fd(oldf, &error); 788 if (!newf) 789 goto out; 790 791 tsk->files = newf; 792 error = 0; 793 out: 794 return error; 795 } 796 797 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 798 { 799 #ifdef CONFIG_BLOCK 800 struct io_context *ioc = current->io_context; 801 802 if (!ioc) 803 return 0; 804 /* 805 * Share io context with parent, if CLONE_IO is set 806 */ 807 if (clone_flags & CLONE_IO) { 808 tsk->io_context = ioc_task_link(ioc); 809 if (unlikely(!tsk->io_context)) 810 return -ENOMEM; 811 } else if (ioprio_valid(ioc->ioprio)) { 812 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 813 if (unlikely(!tsk->io_context)) 814 return -ENOMEM; 815 816 tsk->io_context->ioprio = ioc->ioprio; 817 } 818 #endif 819 return 0; 820 } 821 822 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 823 { 824 struct sighand_struct *sig; 825 826 if (clone_flags & CLONE_SIGHAND) { 827 atomic_inc(¤t->sighand->count); 828 return 0; 829 } 830 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 831 rcu_assign_pointer(tsk->sighand, sig); 832 if (!sig) 833 return -ENOMEM; 834 atomic_set(&sig->count, 1); 835 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 836 return 0; 837 } 838 839 void __cleanup_sighand(struct sighand_struct *sighand) 840 { 841 if (atomic_dec_and_test(&sighand->count)) 842 kmem_cache_free(sighand_cachep, sighand); 843 } 844 845 846 /* 847 * Initialize POSIX timer handling for a thread group. 848 */ 849 static void posix_cpu_timers_init_group(struct signal_struct *sig) 850 { 851 unsigned long cpu_limit; 852 853 /* Thread group counters. */ 854 thread_group_cputime_init(sig); 855 856 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 857 if (cpu_limit != RLIM_INFINITY) { 858 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 859 sig->cputimer.running = 1; 860 } 861 862 /* The timer lists. */ 863 INIT_LIST_HEAD(&sig->cpu_timers[0]); 864 INIT_LIST_HEAD(&sig->cpu_timers[1]); 865 INIT_LIST_HEAD(&sig->cpu_timers[2]); 866 } 867 868 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 869 { 870 struct signal_struct *sig; 871 872 if (clone_flags & CLONE_THREAD) 873 return 0; 874 875 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 876 tsk->signal = sig; 877 if (!sig) 878 return -ENOMEM; 879 880 sig->nr_threads = 1; 881 atomic_set(&sig->live, 1); 882 atomic_set(&sig->sigcnt, 1); 883 init_waitqueue_head(&sig->wait_chldexit); 884 if (clone_flags & CLONE_NEWPID) 885 sig->flags |= SIGNAL_UNKILLABLE; 886 sig->curr_target = tsk; 887 init_sigpending(&sig->shared_pending); 888 INIT_LIST_HEAD(&sig->posix_timers); 889 890 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 891 sig->real_timer.function = it_real_fn; 892 893 task_lock(current->group_leader); 894 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 895 task_unlock(current->group_leader); 896 897 posix_cpu_timers_init_group(sig); 898 899 tty_audit_fork(sig); 900 901 sig->oom_adj = current->signal->oom_adj; 902 903 return 0; 904 } 905 906 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 907 { 908 unsigned long new_flags = p->flags; 909 910 new_flags &= ~PF_SUPERPRIV; 911 new_flags |= PF_FORKNOEXEC; 912 new_flags |= PF_STARTING; 913 p->flags = new_flags; 914 clear_freeze_flag(p); 915 } 916 917 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 918 { 919 current->clear_child_tid = tidptr; 920 921 return task_pid_vnr(current); 922 } 923 924 static void rt_mutex_init_task(struct task_struct *p) 925 { 926 raw_spin_lock_init(&p->pi_lock); 927 #ifdef CONFIG_RT_MUTEXES 928 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 929 p->pi_blocked_on = NULL; 930 #endif 931 } 932 933 #ifdef CONFIG_MM_OWNER 934 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 935 { 936 mm->owner = p; 937 } 938 #endif /* CONFIG_MM_OWNER */ 939 940 /* 941 * Initialize POSIX timer handling for a single task. 942 */ 943 static void posix_cpu_timers_init(struct task_struct *tsk) 944 { 945 tsk->cputime_expires.prof_exp = cputime_zero; 946 tsk->cputime_expires.virt_exp = cputime_zero; 947 tsk->cputime_expires.sched_exp = 0; 948 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 949 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 950 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 951 } 952 953 /* 954 * This creates a new process as a copy of the old one, 955 * but does not actually start it yet. 956 * 957 * It copies the registers, and all the appropriate 958 * parts of the process environment (as per the clone 959 * flags). The actual kick-off is left to the caller. 960 */ 961 static struct task_struct *copy_process(unsigned long clone_flags, 962 unsigned long stack_start, 963 struct pt_regs *regs, 964 unsigned long stack_size, 965 int __user *child_tidptr, 966 struct pid *pid, 967 int trace) 968 { 969 int retval; 970 struct task_struct *p; 971 int cgroup_callbacks_done = 0; 972 973 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 974 return ERR_PTR(-EINVAL); 975 976 /* 977 * Thread groups must share signals as well, and detached threads 978 * can only be started up within the thread group. 979 */ 980 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 981 return ERR_PTR(-EINVAL); 982 983 /* 984 * Shared signal handlers imply shared VM. By way of the above, 985 * thread groups also imply shared VM. Blocking this case allows 986 * for various simplifications in other code. 987 */ 988 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 989 return ERR_PTR(-EINVAL); 990 991 /* 992 * Siblings of global init remain as zombies on exit since they are 993 * not reaped by their parent (swapper). To solve this and to avoid 994 * multi-rooted process trees, prevent global and container-inits 995 * from creating siblings. 996 */ 997 if ((clone_flags & CLONE_PARENT) && 998 current->signal->flags & SIGNAL_UNKILLABLE) 999 return ERR_PTR(-EINVAL); 1000 1001 retval = security_task_create(clone_flags); 1002 if (retval) 1003 goto fork_out; 1004 1005 retval = -ENOMEM; 1006 p = dup_task_struct(current); 1007 if (!p) 1008 goto fork_out; 1009 1010 ftrace_graph_init_task(p); 1011 1012 rt_mutex_init_task(p); 1013 1014 #ifdef CONFIG_PROVE_LOCKING 1015 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1016 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1017 #endif 1018 retval = -EAGAIN; 1019 if (atomic_read(&p->real_cred->user->processes) >= 1020 task_rlimit(p, RLIMIT_NPROC)) { 1021 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1022 p->real_cred->user != INIT_USER) 1023 goto bad_fork_free; 1024 } 1025 1026 retval = copy_creds(p, clone_flags); 1027 if (retval < 0) 1028 goto bad_fork_free; 1029 1030 /* 1031 * If multiple threads are within copy_process(), then this check 1032 * triggers too late. This doesn't hurt, the check is only there 1033 * to stop root fork bombs. 1034 */ 1035 retval = -EAGAIN; 1036 if (nr_threads >= max_threads) 1037 goto bad_fork_cleanup_count; 1038 1039 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1040 goto bad_fork_cleanup_count; 1041 1042 p->did_exec = 0; 1043 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1044 copy_flags(clone_flags, p); 1045 INIT_LIST_HEAD(&p->children); 1046 INIT_LIST_HEAD(&p->sibling); 1047 rcu_copy_process(p); 1048 p->vfork_done = NULL; 1049 spin_lock_init(&p->alloc_lock); 1050 1051 init_sigpending(&p->pending); 1052 1053 p->utime = cputime_zero; 1054 p->stime = cputime_zero; 1055 p->gtime = cputime_zero; 1056 p->utimescaled = cputime_zero; 1057 p->stimescaled = cputime_zero; 1058 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1059 p->prev_utime = cputime_zero; 1060 p->prev_stime = cputime_zero; 1061 #endif 1062 #if defined(SPLIT_RSS_COUNTING) 1063 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1064 #endif 1065 1066 p->default_timer_slack_ns = current->timer_slack_ns; 1067 1068 task_io_accounting_init(&p->ioac); 1069 acct_clear_integrals(p); 1070 1071 posix_cpu_timers_init(p); 1072 1073 p->lock_depth = -1; /* -1 = no lock */ 1074 do_posix_clock_monotonic_gettime(&p->start_time); 1075 p->real_start_time = p->start_time; 1076 monotonic_to_bootbased(&p->real_start_time); 1077 p->io_context = NULL; 1078 p->audit_context = NULL; 1079 cgroup_fork(p); 1080 #ifdef CONFIG_NUMA 1081 p->mempolicy = mpol_dup(p->mempolicy); 1082 if (IS_ERR(p->mempolicy)) { 1083 retval = PTR_ERR(p->mempolicy); 1084 p->mempolicy = NULL; 1085 goto bad_fork_cleanup_cgroup; 1086 } 1087 mpol_fix_fork_child_flag(p); 1088 #endif 1089 #ifdef CONFIG_TRACE_IRQFLAGS 1090 p->irq_events = 0; 1091 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1092 p->hardirqs_enabled = 1; 1093 #else 1094 p->hardirqs_enabled = 0; 1095 #endif 1096 p->hardirq_enable_ip = 0; 1097 p->hardirq_enable_event = 0; 1098 p->hardirq_disable_ip = _THIS_IP_; 1099 p->hardirq_disable_event = 0; 1100 p->softirqs_enabled = 1; 1101 p->softirq_enable_ip = _THIS_IP_; 1102 p->softirq_enable_event = 0; 1103 p->softirq_disable_ip = 0; 1104 p->softirq_disable_event = 0; 1105 p->hardirq_context = 0; 1106 p->softirq_context = 0; 1107 #endif 1108 #ifdef CONFIG_LOCKDEP 1109 p->lockdep_depth = 0; /* no locks held yet */ 1110 p->curr_chain_key = 0; 1111 p->lockdep_recursion = 0; 1112 #endif 1113 1114 #ifdef CONFIG_DEBUG_MUTEXES 1115 p->blocked_on = NULL; /* not blocked yet */ 1116 #endif 1117 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1118 p->memcg_batch.do_batch = 0; 1119 p->memcg_batch.memcg = NULL; 1120 #endif 1121 1122 /* Perform scheduler related setup. Assign this task to a CPU. */ 1123 sched_fork(p, clone_flags); 1124 1125 retval = perf_event_init_task(p); 1126 if (retval) 1127 goto bad_fork_cleanup_policy; 1128 1129 if ((retval = audit_alloc(p))) 1130 goto bad_fork_cleanup_policy; 1131 /* copy all the process information */ 1132 if ((retval = copy_semundo(clone_flags, p))) 1133 goto bad_fork_cleanup_audit; 1134 if ((retval = copy_files(clone_flags, p))) 1135 goto bad_fork_cleanup_semundo; 1136 if ((retval = copy_fs(clone_flags, p))) 1137 goto bad_fork_cleanup_files; 1138 if ((retval = copy_sighand(clone_flags, p))) 1139 goto bad_fork_cleanup_fs; 1140 if ((retval = copy_signal(clone_flags, p))) 1141 goto bad_fork_cleanup_sighand; 1142 if ((retval = copy_mm(clone_flags, p))) 1143 goto bad_fork_cleanup_signal; 1144 if ((retval = copy_namespaces(clone_flags, p))) 1145 goto bad_fork_cleanup_mm; 1146 if ((retval = copy_io(clone_flags, p))) 1147 goto bad_fork_cleanup_namespaces; 1148 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1149 if (retval) 1150 goto bad_fork_cleanup_io; 1151 1152 if (pid != &init_struct_pid) { 1153 retval = -ENOMEM; 1154 pid = alloc_pid(p->nsproxy->pid_ns); 1155 if (!pid) 1156 goto bad_fork_cleanup_io; 1157 1158 if (clone_flags & CLONE_NEWPID) { 1159 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1160 if (retval < 0) 1161 goto bad_fork_free_pid; 1162 } 1163 } 1164 1165 p->pid = pid_nr(pid); 1166 p->tgid = p->pid; 1167 if (clone_flags & CLONE_THREAD) 1168 p->tgid = current->tgid; 1169 1170 if (current->nsproxy != p->nsproxy) { 1171 retval = ns_cgroup_clone(p, pid); 1172 if (retval) 1173 goto bad_fork_free_pid; 1174 } 1175 1176 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1177 /* 1178 * Clear TID on mm_release()? 1179 */ 1180 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1181 #ifdef CONFIG_FUTEX 1182 p->robust_list = NULL; 1183 #ifdef CONFIG_COMPAT 1184 p->compat_robust_list = NULL; 1185 #endif 1186 INIT_LIST_HEAD(&p->pi_state_list); 1187 p->pi_state_cache = NULL; 1188 #endif 1189 /* 1190 * sigaltstack should be cleared when sharing the same VM 1191 */ 1192 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1193 p->sas_ss_sp = p->sas_ss_size = 0; 1194 1195 /* 1196 * Syscall tracing and stepping should be turned off in the 1197 * child regardless of CLONE_PTRACE. 1198 */ 1199 user_disable_single_step(p); 1200 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1201 #ifdef TIF_SYSCALL_EMU 1202 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1203 #endif 1204 clear_all_latency_tracing(p); 1205 1206 /* ok, now we should be set up.. */ 1207 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1208 p->pdeath_signal = 0; 1209 p->exit_state = 0; 1210 1211 /* 1212 * Ok, make it visible to the rest of the system. 1213 * We dont wake it up yet. 1214 */ 1215 p->group_leader = p; 1216 INIT_LIST_HEAD(&p->thread_group); 1217 1218 /* Now that the task is set up, run cgroup callbacks if 1219 * necessary. We need to run them before the task is visible 1220 * on the tasklist. */ 1221 cgroup_fork_callbacks(p); 1222 cgroup_callbacks_done = 1; 1223 1224 /* Need tasklist lock for parent etc handling! */ 1225 write_lock_irq(&tasklist_lock); 1226 1227 /* CLONE_PARENT re-uses the old parent */ 1228 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1229 p->real_parent = current->real_parent; 1230 p->parent_exec_id = current->parent_exec_id; 1231 } else { 1232 p->real_parent = current; 1233 p->parent_exec_id = current->self_exec_id; 1234 } 1235 1236 spin_lock(¤t->sighand->siglock); 1237 1238 /* 1239 * Process group and session signals need to be delivered to just the 1240 * parent before the fork or both the parent and the child after the 1241 * fork. Restart if a signal comes in before we add the new process to 1242 * it's process group. 1243 * A fatal signal pending means that current will exit, so the new 1244 * thread can't slip out of an OOM kill (or normal SIGKILL). 1245 */ 1246 recalc_sigpending(); 1247 if (signal_pending(current)) { 1248 spin_unlock(¤t->sighand->siglock); 1249 write_unlock_irq(&tasklist_lock); 1250 retval = -ERESTARTNOINTR; 1251 goto bad_fork_free_pid; 1252 } 1253 1254 if (clone_flags & CLONE_THREAD) { 1255 current->signal->nr_threads++; 1256 atomic_inc(¤t->signal->live); 1257 atomic_inc(¤t->signal->sigcnt); 1258 p->group_leader = current->group_leader; 1259 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1260 } 1261 1262 if (likely(p->pid)) { 1263 tracehook_finish_clone(p, clone_flags, trace); 1264 1265 if (thread_group_leader(p)) { 1266 if (clone_flags & CLONE_NEWPID) 1267 p->nsproxy->pid_ns->child_reaper = p; 1268 1269 p->signal->leader_pid = pid; 1270 p->signal->tty = tty_kref_get(current->signal->tty); 1271 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1272 attach_pid(p, PIDTYPE_SID, task_session(current)); 1273 list_add_tail(&p->sibling, &p->real_parent->children); 1274 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1275 __get_cpu_var(process_counts)++; 1276 } 1277 attach_pid(p, PIDTYPE_PID, pid); 1278 nr_threads++; 1279 } 1280 1281 total_forks++; 1282 spin_unlock(¤t->sighand->siglock); 1283 write_unlock_irq(&tasklist_lock); 1284 proc_fork_connector(p); 1285 cgroup_post_fork(p); 1286 perf_event_fork(p); 1287 return p; 1288 1289 bad_fork_free_pid: 1290 if (pid != &init_struct_pid) 1291 free_pid(pid); 1292 bad_fork_cleanup_io: 1293 if (p->io_context) 1294 exit_io_context(p); 1295 bad_fork_cleanup_namespaces: 1296 exit_task_namespaces(p); 1297 bad_fork_cleanup_mm: 1298 if (p->mm) 1299 mmput(p->mm); 1300 bad_fork_cleanup_signal: 1301 if (!(clone_flags & CLONE_THREAD)) 1302 free_signal_struct(p->signal); 1303 bad_fork_cleanup_sighand: 1304 __cleanup_sighand(p->sighand); 1305 bad_fork_cleanup_fs: 1306 exit_fs(p); /* blocking */ 1307 bad_fork_cleanup_files: 1308 exit_files(p); /* blocking */ 1309 bad_fork_cleanup_semundo: 1310 exit_sem(p); 1311 bad_fork_cleanup_audit: 1312 audit_free(p); 1313 bad_fork_cleanup_policy: 1314 perf_event_free_task(p); 1315 #ifdef CONFIG_NUMA 1316 mpol_put(p->mempolicy); 1317 bad_fork_cleanup_cgroup: 1318 #endif 1319 cgroup_exit(p, cgroup_callbacks_done); 1320 delayacct_tsk_free(p); 1321 module_put(task_thread_info(p)->exec_domain->module); 1322 bad_fork_cleanup_count: 1323 atomic_dec(&p->cred->user->processes); 1324 exit_creds(p); 1325 bad_fork_free: 1326 free_task(p); 1327 fork_out: 1328 return ERR_PTR(retval); 1329 } 1330 1331 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1332 { 1333 memset(regs, 0, sizeof(struct pt_regs)); 1334 return regs; 1335 } 1336 1337 static inline void init_idle_pids(struct pid_link *links) 1338 { 1339 enum pid_type type; 1340 1341 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1342 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1343 links[type].pid = &init_struct_pid; 1344 } 1345 } 1346 1347 struct task_struct * __cpuinit fork_idle(int cpu) 1348 { 1349 struct task_struct *task; 1350 struct pt_regs regs; 1351 1352 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1353 &init_struct_pid, 0); 1354 if (!IS_ERR(task)) { 1355 init_idle_pids(task->pids); 1356 init_idle(task, cpu); 1357 } 1358 1359 return task; 1360 } 1361 1362 /* 1363 * Ok, this is the main fork-routine. 1364 * 1365 * It copies the process, and if successful kick-starts 1366 * it and waits for it to finish using the VM if required. 1367 */ 1368 long do_fork(unsigned long clone_flags, 1369 unsigned long stack_start, 1370 struct pt_regs *regs, 1371 unsigned long stack_size, 1372 int __user *parent_tidptr, 1373 int __user *child_tidptr) 1374 { 1375 struct task_struct *p; 1376 int trace = 0; 1377 long nr; 1378 1379 /* 1380 * Do some preliminary argument and permissions checking before we 1381 * actually start allocating stuff 1382 */ 1383 if (clone_flags & CLONE_NEWUSER) { 1384 if (clone_flags & CLONE_THREAD) 1385 return -EINVAL; 1386 /* hopefully this check will go away when userns support is 1387 * complete 1388 */ 1389 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1390 !capable(CAP_SETGID)) 1391 return -EPERM; 1392 } 1393 1394 /* 1395 * We hope to recycle these flags after 2.6.26 1396 */ 1397 if (unlikely(clone_flags & CLONE_STOPPED)) { 1398 static int __read_mostly count = 100; 1399 1400 if (count > 0 && printk_ratelimit()) { 1401 char comm[TASK_COMM_LEN]; 1402 1403 count--; 1404 printk(KERN_INFO "fork(): process `%s' used deprecated " 1405 "clone flags 0x%lx\n", 1406 get_task_comm(comm, current), 1407 clone_flags & CLONE_STOPPED); 1408 } 1409 } 1410 1411 /* 1412 * When called from kernel_thread, don't do user tracing stuff. 1413 */ 1414 if (likely(user_mode(regs))) 1415 trace = tracehook_prepare_clone(clone_flags); 1416 1417 p = copy_process(clone_flags, stack_start, regs, stack_size, 1418 child_tidptr, NULL, trace); 1419 /* 1420 * Do this prior waking up the new thread - the thread pointer 1421 * might get invalid after that point, if the thread exits quickly. 1422 */ 1423 if (!IS_ERR(p)) { 1424 struct completion vfork; 1425 1426 trace_sched_process_fork(current, p); 1427 1428 nr = task_pid_vnr(p); 1429 1430 if (clone_flags & CLONE_PARENT_SETTID) 1431 put_user(nr, parent_tidptr); 1432 1433 if (clone_flags & CLONE_VFORK) { 1434 p->vfork_done = &vfork; 1435 init_completion(&vfork); 1436 } 1437 1438 audit_finish_fork(p); 1439 tracehook_report_clone(regs, clone_flags, nr, p); 1440 1441 /* 1442 * We set PF_STARTING at creation in case tracing wants to 1443 * use this to distinguish a fully live task from one that 1444 * hasn't gotten to tracehook_report_clone() yet. Now we 1445 * clear it and set the child going. 1446 */ 1447 p->flags &= ~PF_STARTING; 1448 1449 if (unlikely(clone_flags & CLONE_STOPPED)) { 1450 /* 1451 * We'll start up with an immediate SIGSTOP. 1452 */ 1453 sigaddset(&p->pending.signal, SIGSTOP); 1454 set_tsk_thread_flag(p, TIF_SIGPENDING); 1455 __set_task_state(p, TASK_STOPPED); 1456 } else { 1457 wake_up_new_task(p, clone_flags); 1458 } 1459 1460 tracehook_report_clone_complete(trace, regs, 1461 clone_flags, nr, p); 1462 1463 if (clone_flags & CLONE_VFORK) { 1464 freezer_do_not_count(); 1465 wait_for_completion(&vfork); 1466 freezer_count(); 1467 tracehook_report_vfork_done(p, nr); 1468 } 1469 } else { 1470 nr = PTR_ERR(p); 1471 } 1472 return nr; 1473 } 1474 1475 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1476 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1477 #endif 1478 1479 static void sighand_ctor(void *data) 1480 { 1481 struct sighand_struct *sighand = data; 1482 1483 spin_lock_init(&sighand->siglock); 1484 init_waitqueue_head(&sighand->signalfd_wqh); 1485 } 1486 1487 void __init proc_caches_init(void) 1488 { 1489 sighand_cachep = kmem_cache_create("sighand_cache", 1490 sizeof(struct sighand_struct), 0, 1491 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1492 SLAB_NOTRACK, sighand_ctor); 1493 signal_cachep = kmem_cache_create("signal_cache", 1494 sizeof(struct signal_struct), 0, 1495 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1496 files_cachep = kmem_cache_create("files_cache", 1497 sizeof(struct files_struct), 0, 1498 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1499 fs_cachep = kmem_cache_create("fs_cache", 1500 sizeof(struct fs_struct), 0, 1501 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1502 mm_cachep = kmem_cache_create("mm_struct", 1503 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1504 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1505 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1506 mmap_init(); 1507 } 1508 1509 /* 1510 * Check constraints on flags passed to the unshare system call and 1511 * force unsharing of additional process context as appropriate. 1512 */ 1513 static void check_unshare_flags(unsigned long *flags_ptr) 1514 { 1515 /* 1516 * If unsharing a thread from a thread group, must also 1517 * unshare vm. 1518 */ 1519 if (*flags_ptr & CLONE_THREAD) 1520 *flags_ptr |= CLONE_VM; 1521 1522 /* 1523 * If unsharing vm, must also unshare signal handlers. 1524 */ 1525 if (*flags_ptr & CLONE_VM) 1526 *flags_ptr |= CLONE_SIGHAND; 1527 1528 /* 1529 * If unsharing namespace, must also unshare filesystem information. 1530 */ 1531 if (*flags_ptr & CLONE_NEWNS) 1532 *flags_ptr |= CLONE_FS; 1533 } 1534 1535 /* 1536 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1537 */ 1538 static int unshare_thread(unsigned long unshare_flags) 1539 { 1540 if (unshare_flags & CLONE_THREAD) 1541 return -EINVAL; 1542 1543 return 0; 1544 } 1545 1546 /* 1547 * Unshare the filesystem structure if it is being shared 1548 */ 1549 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1550 { 1551 struct fs_struct *fs = current->fs; 1552 1553 if (!(unshare_flags & CLONE_FS) || !fs) 1554 return 0; 1555 1556 /* don't need lock here; in the worst case we'll do useless copy */ 1557 if (fs->users == 1) 1558 return 0; 1559 1560 *new_fsp = copy_fs_struct(fs); 1561 if (!*new_fsp) 1562 return -ENOMEM; 1563 1564 return 0; 1565 } 1566 1567 /* 1568 * Unsharing of sighand is not supported yet 1569 */ 1570 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1571 { 1572 struct sighand_struct *sigh = current->sighand; 1573 1574 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1575 return -EINVAL; 1576 else 1577 return 0; 1578 } 1579 1580 /* 1581 * Unshare vm if it is being shared 1582 */ 1583 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1584 { 1585 struct mm_struct *mm = current->mm; 1586 1587 if ((unshare_flags & CLONE_VM) && 1588 (mm && atomic_read(&mm->mm_users) > 1)) { 1589 return -EINVAL; 1590 } 1591 1592 return 0; 1593 } 1594 1595 /* 1596 * Unshare file descriptor table if it is being shared 1597 */ 1598 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1599 { 1600 struct files_struct *fd = current->files; 1601 int error = 0; 1602 1603 if ((unshare_flags & CLONE_FILES) && 1604 (fd && atomic_read(&fd->count) > 1)) { 1605 *new_fdp = dup_fd(fd, &error); 1606 if (!*new_fdp) 1607 return error; 1608 } 1609 1610 return 0; 1611 } 1612 1613 /* 1614 * unshare allows a process to 'unshare' part of the process 1615 * context which was originally shared using clone. copy_* 1616 * functions used by do_fork() cannot be used here directly 1617 * because they modify an inactive task_struct that is being 1618 * constructed. Here we are modifying the current, active, 1619 * task_struct. 1620 */ 1621 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1622 { 1623 int err = 0; 1624 struct fs_struct *fs, *new_fs = NULL; 1625 struct sighand_struct *new_sigh = NULL; 1626 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1627 struct files_struct *fd, *new_fd = NULL; 1628 struct nsproxy *new_nsproxy = NULL; 1629 int do_sysvsem = 0; 1630 1631 check_unshare_flags(&unshare_flags); 1632 1633 /* Return -EINVAL for all unsupported flags */ 1634 err = -EINVAL; 1635 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1636 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1637 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1638 goto bad_unshare_out; 1639 1640 /* 1641 * CLONE_NEWIPC must also detach from the undolist: after switching 1642 * to a new ipc namespace, the semaphore arrays from the old 1643 * namespace are unreachable. 1644 */ 1645 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1646 do_sysvsem = 1; 1647 if ((err = unshare_thread(unshare_flags))) 1648 goto bad_unshare_out; 1649 if ((err = unshare_fs(unshare_flags, &new_fs))) 1650 goto bad_unshare_cleanup_thread; 1651 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1652 goto bad_unshare_cleanup_fs; 1653 if ((err = unshare_vm(unshare_flags, &new_mm))) 1654 goto bad_unshare_cleanup_sigh; 1655 if ((err = unshare_fd(unshare_flags, &new_fd))) 1656 goto bad_unshare_cleanup_vm; 1657 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1658 new_fs))) 1659 goto bad_unshare_cleanup_fd; 1660 1661 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1662 if (do_sysvsem) { 1663 /* 1664 * CLONE_SYSVSEM is equivalent to sys_exit(). 1665 */ 1666 exit_sem(current); 1667 } 1668 1669 if (new_nsproxy) { 1670 switch_task_namespaces(current, new_nsproxy); 1671 new_nsproxy = NULL; 1672 } 1673 1674 task_lock(current); 1675 1676 if (new_fs) { 1677 fs = current->fs; 1678 write_lock(&fs->lock); 1679 current->fs = new_fs; 1680 if (--fs->users) 1681 new_fs = NULL; 1682 else 1683 new_fs = fs; 1684 write_unlock(&fs->lock); 1685 } 1686 1687 if (new_mm) { 1688 mm = current->mm; 1689 active_mm = current->active_mm; 1690 current->mm = new_mm; 1691 current->active_mm = new_mm; 1692 activate_mm(active_mm, new_mm); 1693 new_mm = mm; 1694 } 1695 1696 if (new_fd) { 1697 fd = current->files; 1698 current->files = new_fd; 1699 new_fd = fd; 1700 } 1701 1702 task_unlock(current); 1703 } 1704 1705 if (new_nsproxy) 1706 put_nsproxy(new_nsproxy); 1707 1708 bad_unshare_cleanup_fd: 1709 if (new_fd) 1710 put_files_struct(new_fd); 1711 1712 bad_unshare_cleanup_vm: 1713 if (new_mm) 1714 mmput(new_mm); 1715 1716 bad_unshare_cleanup_sigh: 1717 if (new_sigh) 1718 if (atomic_dec_and_test(&new_sigh->count)) 1719 kmem_cache_free(sighand_cachep, new_sigh); 1720 1721 bad_unshare_cleanup_fs: 1722 if (new_fs) 1723 free_fs_struct(new_fs); 1724 1725 bad_unshare_cleanup_thread: 1726 bad_unshare_out: 1727 return err; 1728 } 1729 1730 /* 1731 * Helper to unshare the files of the current task. 1732 * We don't want to expose copy_files internals to 1733 * the exec layer of the kernel. 1734 */ 1735 1736 int unshare_files(struct files_struct **displaced) 1737 { 1738 struct task_struct *task = current; 1739 struct files_struct *copy = NULL; 1740 int error; 1741 1742 error = unshare_fd(CLONE_FILES, ©); 1743 if (error || !copy) { 1744 *displaced = NULL; 1745 return error; 1746 } 1747 *displaced = task->files; 1748 task_lock(task); 1749 task->files = copy; 1750 task_unlock(task); 1751 return 0; 1752 } 1753