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/acct.h> 53 #include <linux/tsacct_kern.h> 54 #include <linux/cn_proc.h> 55 #include <linux/freezer.h> 56 #include <linux/delayacct.h> 57 #include <linux/taskstats_kern.h> 58 #include <linux/random.h> 59 #include <linux/tty.h> 60 #include <linux/proc_fs.h> 61 #include <linux/blkdev.h> 62 #include <linux/fs_struct.h> 63 #include <linux/magic.h> 64 #include <linux/perf_event.h> 65 66 #include <asm/pgtable.h> 67 #include <asm/pgalloc.h> 68 #include <asm/uaccess.h> 69 #include <asm/mmu_context.h> 70 #include <asm/cacheflush.h> 71 #include <asm/tlbflush.h> 72 73 #include <trace/events/sched.h> 74 75 /* 76 * Protected counters by write_lock_irq(&tasklist_lock) 77 */ 78 unsigned long total_forks; /* Handle normal Linux uptimes. */ 79 int nr_threads; /* The idle threads do not count.. */ 80 81 int max_threads; /* tunable limit on nr_threads */ 82 83 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 84 85 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 86 87 int nr_processes(void) 88 { 89 int cpu; 90 int total = 0; 91 92 for_each_online_cpu(cpu) 93 total += per_cpu(process_counts, cpu); 94 95 return total; 96 } 97 98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 99 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 100 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 101 static struct kmem_cache *task_struct_cachep; 102 #endif 103 104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 106 { 107 #ifdef CONFIG_DEBUG_STACK_USAGE 108 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 109 #else 110 gfp_t mask = GFP_KERNEL; 111 #endif 112 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 113 } 114 115 static inline void free_thread_info(struct thread_info *ti) 116 { 117 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 118 } 119 #endif 120 121 /* SLAB cache for signal_struct structures (tsk->signal) */ 122 static struct kmem_cache *signal_cachep; 123 124 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 125 struct kmem_cache *sighand_cachep; 126 127 /* SLAB cache for files_struct structures (tsk->files) */ 128 struct kmem_cache *files_cachep; 129 130 /* SLAB cache for fs_struct structures (tsk->fs) */ 131 struct kmem_cache *fs_cachep; 132 133 /* SLAB cache for vm_area_struct structures */ 134 struct kmem_cache *vm_area_cachep; 135 136 /* SLAB cache for mm_struct structures (tsk->mm) */ 137 static struct kmem_cache *mm_cachep; 138 139 void free_task(struct task_struct *tsk) 140 { 141 prop_local_destroy_single(&tsk->dirties); 142 free_thread_info(tsk->stack); 143 rt_mutex_debug_task_free(tsk); 144 ftrace_graph_exit_task(tsk); 145 free_task_struct(tsk); 146 } 147 EXPORT_SYMBOL(free_task); 148 149 void __put_task_struct(struct task_struct *tsk) 150 { 151 WARN_ON(!tsk->exit_state); 152 WARN_ON(atomic_read(&tsk->usage)); 153 WARN_ON(tsk == current); 154 155 exit_creds(tsk); 156 delayacct_tsk_free(tsk); 157 158 if (!profile_handoff_task(tsk)) 159 free_task(tsk); 160 } 161 162 /* 163 * macro override instead of weak attribute alias, to workaround 164 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 165 */ 166 #ifndef arch_task_cache_init 167 #define arch_task_cache_init() 168 #endif 169 170 void __init fork_init(unsigned long mempages) 171 { 172 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 173 #ifndef ARCH_MIN_TASKALIGN 174 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 175 #endif 176 /* create a slab on which task_structs can be allocated */ 177 task_struct_cachep = 178 kmem_cache_create("task_struct", sizeof(struct task_struct), 179 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 180 #endif 181 182 /* do the arch specific task caches init */ 183 arch_task_cache_init(); 184 185 /* 186 * The default maximum number of threads is set to a safe 187 * value: the thread structures can take up at most half 188 * of memory. 189 */ 190 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 191 192 /* 193 * we need to allow at least 20 threads to boot a system 194 */ 195 if(max_threads < 20) 196 max_threads = 20; 197 198 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 199 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 200 init_task.signal->rlim[RLIMIT_SIGPENDING] = 201 init_task.signal->rlim[RLIMIT_NPROC]; 202 } 203 204 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 205 struct task_struct *src) 206 { 207 *dst = *src; 208 return 0; 209 } 210 211 static struct task_struct *dup_task_struct(struct task_struct *orig) 212 { 213 struct task_struct *tsk; 214 struct thread_info *ti; 215 unsigned long *stackend; 216 217 int err; 218 219 prepare_to_copy(orig); 220 221 tsk = alloc_task_struct(); 222 if (!tsk) 223 return NULL; 224 225 ti = alloc_thread_info(tsk); 226 if (!ti) { 227 free_task_struct(tsk); 228 return NULL; 229 } 230 231 err = arch_dup_task_struct(tsk, orig); 232 if (err) 233 goto out; 234 235 tsk->stack = ti; 236 237 err = prop_local_init_single(&tsk->dirties); 238 if (err) 239 goto out; 240 241 setup_thread_stack(tsk, orig); 242 stackend = end_of_stack(tsk); 243 *stackend = STACK_END_MAGIC; /* for overflow detection */ 244 245 #ifdef CONFIG_CC_STACKPROTECTOR 246 tsk->stack_canary = get_random_int(); 247 #endif 248 249 /* One for us, one for whoever does the "release_task()" (usually parent) */ 250 atomic_set(&tsk->usage,2); 251 atomic_set(&tsk->fs_excl, 0); 252 #ifdef CONFIG_BLK_DEV_IO_TRACE 253 tsk->btrace_seq = 0; 254 #endif 255 tsk->splice_pipe = NULL; 256 return tsk; 257 258 out: 259 free_thread_info(ti); 260 free_task_struct(tsk); 261 return NULL; 262 } 263 264 #ifdef CONFIG_MMU 265 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 266 { 267 struct vm_area_struct *mpnt, *tmp, **pprev; 268 struct rb_node **rb_link, *rb_parent; 269 int retval; 270 unsigned long charge; 271 struct mempolicy *pol; 272 273 down_write(&oldmm->mmap_sem); 274 flush_cache_dup_mm(oldmm); 275 /* 276 * Not linked in yet - no deadlock potential: 277 */ 278 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 279 280 mm->locked_vm = 0; 281 mm->mmap = NULL; 282 mm->mmap_cache = NULL; 283 mm->free_area_cache = oldmm->mmap_base; 284 mm->cached_hole_size = ~0UL; 285 mm->map_count = 0; 286 cpumask_clear(mm_cpumask(mm)); 287 mm->mm_rb = RB_ROOT; 288 rb_link = &mm->mm_rb.rb_node; 289 rb_parent = NULL; 290 pprev = &mm->mmap; 291 292 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 293 struct file *file; 294 295 if (mpnt->vm_flags & VM_DONTCOPY) { 296 long pages = vma_pages(mpnt); 297 mm->total_vm -= pages; 298 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 299 -pages); 300 continue; 301 } 302 charge = 0; 303 if (mpnt->vm_flags & VM_ACCOUNT) { 304 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 305 if (security_vm_enough_memory(len)) 306 goto fail_nomem; 307 charge = len; 308 } 309 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 310 if (!tmp) 311 goto fail_nomem; 312 *tmp = *mpnt; 313 pol = mpol_dup(vma_policy(mpnt)); 314 retval = PTR_ERR(pol); 315 if (IS_ERR(pol)) 316 goto fail_nomem_policy; 317 vma_set_policy(tmp, pol); 318 tmp->vm_flags &= ~VM_LOCKED; 319 tmp->vm_mm = mm; 320 tmp->vm_next = NULL; 321 anon_vma_link(tmp); 322 file = tmp->vm_file; 323 if (file) { 324 struct inode *inode = file->f_path.dentry->d_inode; 325 struct address_space *mapping = file->f_mapping; 326 327 get_file(file); 328 if (tmp->vm_flags & VM_DENYWRITE) 329 atomic_dec(&inode->i_writecount); 330 spin_lock(&mapping->i_mmap_lock); 331 if (tmp->vm_flags & VM_SHARED) 332 mapping->i_mmap_writable++; 333 tmp->vm_truncate_count = mpnt->vm_truncate_count; 334 flush_dcache_mmap_lock(mapping); 335 /* insert tmp into the share list, just after mpnt */ 336 vma_prio_tree_add(tmp, mpnt); 337 flush_dcache_mmap_unlock(mapping); 338 spin_unlock(&mapping->i_mmap_lock); 339 } 340 341 /* 342 * Clear hugetlb-related page reserves for children. This only 343 * affects MAP_PRIVATE mappings. Faults generated by the child 344 * are not guaranteed to succeed, even if read-only 345 */ 346 if (is_vm_hugetlb_page(tmp)) 347 reset_vma_resv_huge_pages(tmp); 348 349 /* 350 * Link in the new vma and copy the page table entries. 351 */ 352 *pprev = tmp; 353 pprev = &tmp->vm_next; 354 355 __vma_link_rb(mm, tmp, rb_link, rb_parent); 356 rb_link = &tmp->vm_rb.rb_right; 357 rb_parent = &tmp->vm_rb; 358 359 mm->map_count++; 360 retval = copy_page_range(mm, oldmm, mpnt); 361 362 if (tmp->vm_ops && tmp->vm_ops->open) 363 tmp->vm_ops->open(tmp); 364 365 if (retval) 366 goto out; 367 } 368 /* a new mm has just been created */ 369 arch_dup_mmap(oldmm, mm); 370 retval = 0; 371 out: 372 up_write(&mm->mmap_sem); 373 flush_tlb_mm(oldmm); 374 up_write(&oldmm->mmap_sem); 375 return retval; 376 fail_nomem_policy: 377 kmem_cache_free(vm_area_cachep, tmp); 378 fail_nomem: 379 retval = -ENOMEM; 380 vm_unacct_memory(charge); 381 goto out; 382 } 383 384 static inline int mm_alloc_pgd(struct mm_struct * mm) 385 { 386 mm->pgd = pgd_alloc(mm); 387 if (unlikely(!mm->pgd)) 388 return -ENOMEM; 389 return 0; 390 } 391 392 static inline void mm_free_pgd(struct mm_struct * mm) 393 { 394 pgd_free(mm, mm->pgd); 395 } 396 #else 397 #define dup_mmap(mm, oldmm) (0) 398 #define mm_alloc_pgd(mm) (0) 399 #define mm_free_pgd(mm) 400 #endif /* CONFIG_MMU */ 401 402 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 403 404 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 405 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 406 407 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 408 409 static int __init coredump_filter_setup(char *s) 410 { 411 default_dump_filter = 412 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 413 MMF_DUMP_FILTER_MASK; 414 return 1; 415 } 416 417 __setup("coredump_filter=", coredump_filter_setup); 418 419 #include <linux/init_task.h> 420 421 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 422 { 423 atomic_set(&mm->mm_users, 1); 424 atomic_set(&mm->mm_count, 1); 425 init_rwsem(&mm->mmap_sem); 426 INIT_LIST_HEAD(&mm->mmlist); 427 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter; 428 mm->core_state = NULL; 429 mm->nr_ptes = 0; 430 set_mm_counter(mm, file_rss, 0); 431 set_mm_counter(mm, anon_rss, 0); 432 spin_lock_init(&mm->page_table_lock); 433 spin_lock_init(&mm->ioctx_lock); 434 INIT_HLIST_HEAD(&mm->ioctx_list); 435 mm->free_area_cache = TASK_UNMAPPED_BASE; 436 mm->cached_hole_size = ~0UL; 437 mm_init_owner(mm, p); 438 439 if (likely(!mm_alloc_pgd(mm))) { 440 mm->def_flags = 0; 441 mmu_notifier_mm_init(mm); 442 return mm; 443 } 444 445 free_mm(mm); 446 return NULL; 447 } 448 449 /* 450 * Allocate and initialize an mm_struct. 451 */ 452 struct mm_struct * mm_alloc(void) 453 { 454 struct mm_struct * mm; 455 456 mm = allocate_mm(); 457 if (mm) { 458 memset(mm, 0, sizeof(*mm)); 459 mm = mm_init(mm, current); 460 } 461 return mm; 462 } 463 464 /* 465 * Called when the last reference to the mm 466 * is dropped: either by a lazy thread or by 467 * mmput. Free the page directory and the mm. 468 */ 469 void __mmdrop(struct mm_struct *mm) 470 { 471 BUG_ON(mm == &init_mm); 472 mm_free_pgd(mm); 473 destroy_context(mm); 474 mmu_notifier_mm_destroy(mm); 475 free_mm(mm); 476 } 477 EXPORT_SYMBOL_GPL(__mmdrop); 478 479 /* 480 * Decrement the use count and release all resources for an mm. 481 */ 482 void mmput(struct mm_struct *mm) 483 { 484 might_sleep(); 485 486 if (atomic_dec_and_test(&mm->mm_users)) { 487 exit_aio(mm); 488 exit_mmap(mm); 489 set_mm_exe_file(mm, NULL); 490 if (!list_empty(&mm->mmlist)) { 491 spin_lock(&mmlist_lock); 492 list_del(&mm->mmlist); 493 spin_unlock(&mmlist_lock); 494 } 495 put_swap_token(mm); 496 mmdrop(mm); 497 } 498 } 499 EXPORT_SYMBOL_GPL(mmput); 500 501 /** 502 * get_task_mm - acquire a reference to the task's mm 503 * 504 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 505 * this kernel workthread has transiently adopted a user mm with use_mm, 506 * to do its AIO) is not set and if so returns a reference to it, after 507 * bumping up the use count. User must release the mm via mmput() 508 * after use. Typically used by /proc and ptrace. 509 */ 510 struct mm_struct *get_task_mm(struct task_struct *task) 511 { 512 struct mm_struct *mm; 513 514 task_lock(task); 515 mm = task->mm; 516 if (mm) { 517 if (task->flags & PF_KTHREAD) 518 mm = NULL; 519 else 520 atomic_inc(&mm->mm_users); 521 } 522 task_unlock(task); 523 return mm; 524 } 525 EXPORT_SYMBOL_GPL(get_task_mm); 526 527 /* Please note the differences between mmput and mm_release. 528 * mmput is called whenever we stop holding onto a mm_struct, 529 * error success whatever. 530 * 531 * mm_release is called after a mm_struct has been removed 532 * from the current process. 533 * 534 * This difference is important for error handling, when we 535 * only half set up a mm_struct for a new process and need to restore 536 * the old one. Because we mmput the new mm_struct before 537 * restoring the old one. . . 538 * Eric Biederman 10 January 1998 539 */ 540 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 541 { 542 struct completion *vfork_done = tsk->vfork_done; 543 544 /* Get rid of any futexes when releasing the mm */ 545 #ifdef CONFIG_FUTEX 546 if (unlikely(tsk->robust_list)) 547 exit_robust_list(tsk); 548 #ifdef CONFIG_COMPAT 549 if (unlikely(tsk->compat_robust_list)) 550 compat_exit_robust_list(tsk); 551 #endif 552 #endif 553 554 /* Get rid of any cached register state */ 555 deactivate_mm(tsk, mm); 556 557 /* notify parent sleeping on vfork() */ 558 if (vfork_done) { 559 tsk->vfork_done = NULL; 560 complete(vfork_done); 561 } 562 563 /* 564 * If we're exiting normally, clear a user-space tid field if 565 * requested. We leave this alone when dying by signal, to leave 566 * the value intact in a core dump, and to save the unnecessary 567 * trouble otherwise. Userland only wants this done for a sys_exit. 568 */ 569 if (tsk->clear_child_tid) { 570 if (!(tsk->flags & PF_SIGNALED) && 571 atomic_read(&mm->mm_users) > 1) { 572 /* 573 * We don't check the error code - if userspace has 574 * not set up a proper pointer then tough luck. 575 */ 576 put_user(0, tsk->clear_child_tid); 577 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 578 1, NULL, NULL, 0); 579 } 580 tsk->clear_child_tid = NULL; 581 } 582 } 583 584 /* 585 * Allocate a new mm structure and copy contents from the 586 * mm structure of the passed in task structure. 587 */ 588 struct mm_struct *dup_mm(struct task_struct *tsk) 589 { 590 struct mm_struct *mm, *oldmm = current->mm; 591 int err; 592 593 if (!oldmm) 594 return NULL; 595 596 mm = allocate_mm(); 597 if (!mm) 598 goto fail_nomem; 599 600 memcpy(mm, oldmm, sizeof(*mm)); 601 602 /* Initializing for Swap token stuff */ 603 mm->token_priority = 0; 604 mm->last_interval = 0; 605 606 if (!mm_init(mm, tsk)) 607 goto fail_nomem; 608 609 if (init_new_context(tsk, mm)) 610 goto fail_nocontext; 611 612 dup_mm_exe_file(oldmm, mm); 613 614 err = dup_mmap(mm, oldmm); 615 if (err) 616 goto free_pt; 617 618 mm->hiwater_rss = get_mm_rss(mm); 619 mm->hiwater_vm = mm->total_vm; 620 621 return mm; 622 623 free_pt: 624 mmput(mm); 625 626 fail_nomem: 627 return NULL; 628 629 fail_nocontext: 630 /* 631 * If init_new_context() failed, we cannot use mmput() to free the mm 632 * because it calls destroy_context() 633 */ 634 mm_free_pgd(mm); 635 free_mm(mm); 636 return NULL; 637 } 638 639 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 640 { 641 struct mm_struct * mm, *oldmm; 642 int retval; 643 644 tsk->min_flt = tsk->maj_flt = 0; 645 tsk->nvcsw = tsk->nivcsw = 0; 646 #ifdef CONFIG_DETECT_HUNG_TASK 647 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 648 #endif 649 650 tsk->mm = NULL; 651 tsk->active_mm = NULL; 652 653 /* 654 * Are we cloning a kernel thread? 655 * 656 * We need to steal a active VM for that.. 657 */ 658 oldmm = current->mm; 659 if (!oldmm) 660 return 0; 661 662 if (clone_flags & CLONE_VM) { 663 atomic_inc(&oldmm->mm_users); 664 mm = oldmm; 665 goto good_mm; 666 } 667 668 retval = -ENOMEM; 669 mm = dup_mm(tsk); 670 if (!mm) 671 goto fail_nomem; 672 673 good_mm: 674 /* Initializing for Swap token stuff */ 675 mm->token_priority = 0; 676 mm->last_interval = 0; 677 678 tsk->mm = mm; 679 tsk->active_mm = mm; 680 return 0; 681 682 fail_nomem: 683 return retval; 684 } 685 686 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 687 { 688 struct fs_struct *fs = current->fs; 689 if (clone_flags & CLONE_FS) { 690 /* tsk->fs is already what we want */ 691 write_lock(&fs->lock); 692 if (fs->in_exec) { 693 write_unlock(&fs->lock); 694 return -EAGAIN; 695 } 696 fs->users++; 697 write_unlock(&fs->lock); 698 return 0; 699 } 700 tsk->fs = copy_fs_struct(fs); 701 if (!tsk->fs) 702 return -ENOMEM; 703 return 0; 704 } 705 706 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 707 { 708 struct files_struct *oldf, *newf; 709 int error = 0; 710 711 /* 712 * A background process may not have any files ... 713 */ 714 oldf = current->files; 715 if (!oldf) 716 goto out; 717 718 if (clone_flags & CLONE_FILES) { 719 atomic_inc(&oldf->count); 720 goto out; 721 } 722 723 newf = dup_fd(oldf, &error); 724 if (!newf) 725 goto out; 726 727 tsk->files = newf; 728 error = 0; 729 out: 730 return error; 731 } 732 733 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 734 { 735 #ifdef CONFIG_BLOCK 736 struct io_context *ioc = current->io_context; 737 738 if (!ioc) 739 return 0; 740 /* 741 * Share io context with parent, if CLONE_IO is set 742 */ 743 if (clone_flags & CLONE_IO) { 744 tsk->io_context = ioc_task_link(ioc); 745 if (unlikely(!tsk->io_context)) 746 return -ENOMEM; 747 } else if (ioprio_valid(ioc->ioprio)) { 748 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 749 if (unlikely(!tsk->io_context)) 750 return -ENOMEM; 751 752 tsk->io_context->ioprio = ioc->ioprio; 753 } 754 #endif 755 return 0; 756 } 757 758 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 759 { 760 struct sighand_struct *sig; 761 762 if (clone_flags & CLONE_SIGHAND) { 763 atomic_inc(¤t->sighand->count); 764 return 0; 765 } 766 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 767 rcu_assign_pointer(tsk->sighand, sig); 768 if (!sig) 769 return -ENOMEM; 770 atomic_set(&sig->count, 1); 771 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 772 return 0; 773 } 774 775 void __cleanup_sighand(struct sighand_struct *sighand) 776 { 777 if (atomic_dec_and_test(&sighand->count)) 778 kmem_cache_free(sighand_cachep, sighand); 779 } 780 781 782 /* 783 * Initialize POSIX timer handling for a thread group. 784 */ 785 static void posix_cpu_timers_init_group(struct signal_struct *sig) 786 { 787 /* Thread group counters. */ 788 thread_group_cputime_init(sig); 789 790 /* Expiration times and increments. */ 791 sig->it_virt_expires = cputime_zero; 792 sig->it_virt_incr = cputime_zero; 793 sig->it_prof_expires = cputime_zero; 794 sig->it_prof_incr = cputime_zero; 795 796 /* Cached expiration times. */ 797 sig->cputime_expires.prof_exp = cputime_zero; 798 sig->cputime_expires.virt_exp = cputime_zero; 799 sig->cputime_expires.sched_exp = 0; 800 801 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 802 sig->cputime_expires.prof_exp = 803 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 804 sig->cputimer.running = 1; 805 } 806 807 /* The timer lists. */ 808 INIT_LIST_HEAD(&sig->cpu_timers[0]); 809 INIT_LIST_HEAD(&sig->cpu_timers[1]); 810 INIT_LIST_HEAD(&sig->cpu_timers[2]); 811 } 812 813 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 814 { 815 struct signal_struct *sig; 816 817 if (clone_flags & CLONE_THREAD) 818 return 0; 819 820 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 821 tsk->signal = sig; 822 if (!sig) 823 return -ENOMEM; 824 825 atomic_set(&sig->count, 1); 826 atomic_set(&sig->live, 1); 827 init_waitqueue_head(&sig->wait_chldexit); 828 sig->flags = 0; 829 if (clone_flags & CLONE_NEWPID) 830 sig->flags |= SIGNAL_UNKILLABLE; 831 sig->group_exit_code = 0; 832 sig->group_exit_task = NULL; 833 sig->group_stop_count = 0; 834 sig->curr_target = tsk; 835 init_sigpending(&sig->shared_pending); 836 INIT_LIST_HEAD(&sig->posix_timers); 837 838 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 839 sig->it_real_incr.tv64 = 0; 840 sig->real_timer.function = it_real_fn; 841 842 sig->leader = 0; /* session leadership doesn't inherit */ 843 sig->tty_old_pgrp = NULL; 844 sig->tty = NULL; 845 846 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 847 sig->gtime = cputime_zero; 848 sig->cgtime = cputime_zero; 849 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 850 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 851 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 852 task_io_accounting_init(&sig->ioac); 853 sig->sum_sched_runtime = 0; 854 taskstats_tgid_init(sig); 855 856 task_lock(current->group_leader); 857 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 858 task_unlock(current->group_leader); 859 860 posix_cpu_timers_init_group(sig); 861 862 acct_init_pacct(&sig->pacct); 863 864 tty_audit_fork(sig); 865 866 return 0; 867 } 868 869 void __cleanup_signal(struct signal_struct *sig) 870 { 871 thread_group_cputime_free(sig); 872 tty_kref_put(sig->tty); 873 kmem_cache_free(signal_cachep, sig); 874 } 875 876 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 877 { 878 unsigned long new_flags = p->flags; 879 880 new_flags &= ~PF_SUPERPRIV; 881 new_flags |= PF_FORKNOEXEC; 882 new_flags |= PF_STARTING; 883 p->flags = new_flags; 884 clear_freeze_flag(p); 885 } 886 887 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 888 { 889 current->clear_child_tid = tidptr; 890 891 return task_pid_vnr(current); 892 } 893 894 static void rt_mutex_init_task(struct task_struct *p) 895 { 896 spin_lock_init(&p->pi_lock); 897 #ifdef CONFIG_RT_MUTEXES 898 plist_head_init(&p->pi_waiters, &p->pi_lock); 899 p->pi_blocked_on = NULL; 900 #endif 901 } 902 903 #ifdef CONFIG_MM_OWNER 904 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 905 { 906 mm->owner = p; 907 } 908 #endif /* CONFIG_MM_OWNER */ 909 910 /* 911 * Initialize POSIX timer handling for a single task. 912 */ 913 static void posix_cpu_timers_init(struct task_struct *tsk) 914 { 915 tsk->cputime_expires.prof_exp = cputime_zero; 916 tsk->cputime_expires.virt_exp = cputime_zero; 917 tsk->cputime_expires.sched_exp = 0; 918 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 919 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 920 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 921 } 922 923 /* 924 * This creates a new process as a copy of the old one, 925 * but does not actually start it yet. 926 * 927 * It copies the registers, and all the appropriate 928 * parts of the process environment (as per the clone 929 * flags). The actual kick-off is left to the caller. 930 */ 931 static struct task_struct *copy_process(unsigned long clone_flags, 932 unsigned long stack_start, 933 struct pt_regs *regs, 934 unsigned long stack_size, 935 int __user *child_tidptr, 936 struct pid *pid, 937 int trace) 938 { 939 int retval; 940 struct task_struct *p; 941 int cgroup_callbacks_done = 0; 942 943 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 944 return ERR_PTR(-EINVAL); 945 946 /* 947 * Thread groups must share signals as well, and detached threads 948 * can only be started up within the thread group. 949 */ 950 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 951 return ERR_PTR(-EINVAL); 952 953 /* 954 * Shared signal handlers imply shared VM. By way of the above, 955 * thread groups also imply shared VM. Blocking this case allows 956 * for various simplifications in other code. 957 */ 958 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 959 return ERR_PTR(-EINVAL); 960 961 retval = security_task_create(clone_flags); 962 if (retval) 963 goto fork_out; 964 965 retval = -ENOMEM; 966 p = dup_task_struct(current); 967 if (!p) 968 goto fork_out; 969 970 ftrace_graph_init_task(p); 971 972 rt_mutex_init_task(p); 973 974 #ifdef CONFIG_PROVE_LOCKING 975 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 976 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 977 #endif 978 retval = -EAGAIN; 979 if (atomic_read(&p->real_cred->user->processes) >= 980 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 981 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 982 p->real_cred->user != INIT_USER) 983 goto bad_fork_free; 984 } 985 986 retval = copy_creds(p, clone_flags); 987 if (retval < 0) 988 goto bad_fork_free; 989 990 /* 991 * If multiple threads are within copy_process(), then this check 992 * triggers too late. This doesn't hurt, the check is only there 993 * to stop root fork bombs. 994 */ 995 retval = -EAGAIN; 996 if (nr_threads >= max_threads) 997 goto bad_fork_cleanup_count; 998 999 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1000 goto bad_fork_cleanup_count; 1001 1002 if (p->binfmt && !try_module_get(p->binfmt->module)) 1003 goto bad_fork_cleanup_put_domain; 1004 1005 p->did_exec = 0; 1006 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1007 copy_flags(clone_flags, p); 1008 INIT_LIST_HEAD(&p->children); 1009 INIT_LIST_HEAD(&p->sibling); 1010 rcu_copy_process(p); 1011 p->vfork_done = NULL; 1012 spin_lock_init(&p->alloc_lock); 1013 1014 init_sigpending(&p->pending); 1015 1016 p->utime = cputime_zero; 1017 p->stime = cputime_zero; 1018 p->gtime = cputime_zero; 1019 p->utimescaled = cputime_zero; 1020 p->stimescaled = cputime_zero; 1021 p->prev_utime = cputime_zero; 1022 p->prev_stime = cputime_zero; 1023 1024 p->default_timer_slack_ns = current->timer_slack_ns; 1025 1026 task_io_accounting_init(&p->ioac); 1027 acct_clear_integrals(p); 1028 1029 posix_cpu_timers_init(p); 1030 1031 p->lock_depth = -1; /* -1 = no lock */ 1032 do_posix_clock_monotonic_gettime(&p->start_time); 1033 p->real_start_time = p->start_time; 1034 monotonic_to_bootbased(&p->real_start_time); 1035 p->io_context = NULL; 1036 p->audit_context = NULL; 1037 cgroup_fork(p); 1038 #ifdef CONFIG_NUMA 1039 p->mempolicy = mpol_dup(p->mempolicy); 1040 if (IS_ERR(p->mempolicy)) { 1041 retval = PTR_ERR(p->mempolicy); 1042 p->mempolicy = NULL; 1043 goto bad_fork_cleanup_cgroup; 1044 } 1045 mpol_fix_fork_child_flag(p); 1046 #endif 1047 #ifdef CONFIG_TRACE_IRQFLAGS 1048 p->irq_events = 0; 1049 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1050 p->hardirqs_enabled = 1; 1051 #else 1052 p->hardirqs_enabled = 0; 1053 #endif 1054 p->hardirq_enable_ip = 0; 1055 p->hardirq_enable_event = 0; 1056 p->hardirq_disable_ip = _THIS_IP_; 1057 p->hardirq_disable_event = 0; 1058 p->softirqs_enabled = 1; 1059 p->softirq_enable_ip = _THIS_IP_; 1060 p->softirq_enable_event = 0; 1061 p->softirq_disable_ip = 0; 1062 p->softirq_disable_event = 0; 1063 p->hardirq_context = 0; 1064 p->softirq_context = 0; 1065 #endif 1066 #ifdef CONFIG_LOCKDEP 1067 p->lockdep_depth = 0; /* no locks held yet */ 1068 p->curr_chain_key = 0; 1069 p->lockdep_recursion = 0; 1070 #endif 1071 1072 #ifdef CONFIG_DEBUG_MUTEXES 1073 p->blocked_on = NULL; /* not blocked yet */ 1074 #endif 1075 1076 p->bts = NULL; 1077 1078 /* Perform scheduler related setup. Assign this task to a CPU. */ 1079 sched_fork(p, clone_flags); 1080 1081 retval = perf_event_init_task(p); 1082 if (retval) 1083 goto bad_fork_cleanup_policy; 1084 1085 if ((retval = audit_alloc(p))) 1086 goto bad_fork_cleanup_policy; 1087 /* copy all the process information */ 1088 if ((retval = copy_semundo(clone_flags, p))) 1089 goto bad_fork_cleanup_audit; 1090 if ((retval = copy_files(clone_flags, p))) 1091 goto bad_fork_cleanup_semundo; 1092 if ((retval = copy_fs(clone_flags, p))) 1093 goto bad_fork_cleanup_files; 1094 if ((retval = copy_sighand(clone_flags, p))) 1095 goto bad_fork_cleanup_fs; 1096 if ((retval = copy_signal(clone_flags, p))) 1097 goto bad_fork_cleanup_sighand; 1098 if ((retval = copy_mm(clone_flags, p))) 1099 goto bad_fork_cleanup_signal; 1100 if ((retval = copy_namespaces(clone_flags, p))) 1101 goto bad_fork_cleanup_mm; 1102 if ((retval = copy_io(clone_flags, p))) 1103 goto bad_fork_cleanup_namespaces; 1104 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1105 if (retval) 1106 goto bad_fork_cleanup_io; 1107 1108 if (pid != &init_struct_pid) { 1109 retval = -ENOMEM; 1110 pid = alloc_pid(p->nsproxy->pid_ns); 1111 if (!pid) 1112 goto bad_fork_cleanup_io; 1113 1114 if (clone_flags & CLONE_NEWPID) { 1115 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1116 if (retval < 0) 1117 goto bad_fork_free_pid; 1118 } 1119 } 1120 1121 p->pid = pid_nr(pid); 1122 p->tgid = p->pid; 1123 if (clone_flags & CLONE_THREAD) 1124 p->tgid = current->tgid; 1125 1126 if (current->nsproxy != p->nsproxy) { 1127 retval = ns_cgroup_clone(p, pid); 1128 if (retval) 1129 goto bad_fork_free_pid; 1130 } 1131 1132 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1133 /* 1134 * Clear TID on mm_release()? 1135 */ 1136 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1137 #ifdef CONFIG_FUTEX 1138 p->robust_list = NULL; 1139 #ifdef CONFIG_COMPAT 1140 p->compat_robust_list = NULL; 1141 #endif 1142 INIT_LIST_HEAD(&p->pi_state_list); 1143 p->pi_state_cache = NULL; 1144 #endif 1145 /* 1146 * sigaltstack should be cleared when sharing the same VM 1147 */ 1148 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1149 p->sas_ss_sp = p->sas_ss_size = 0; 1150 1151 /* 1152 * Syscall tracing should be turned off in the child regardless 1153 * of CLONE_PTRACE. 1154 */ 1155 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1156 #ifdef TIF_SYSCALL_EMU 1157 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1158 #endif 1159 clear_all_latency_tracing(p); 1160 1161 /* ok, now we should be set up.. */ 1162 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1163 p->pdeath_signal = 0; 1164 p->exit_state = 0; 1165 1166 /* 1167 * Ok, make it visible to the rest of the system. 1168 * We dont wake it up yet. 1169 */ 1170 p->group_leader = p; 1171 INIT_LIST_HEAD(&p->thread_group); 1172 1173 /* Now that the task is set up, run cgroup callbacks if 1174 * necessary. We need to run them before the task is visible 1175 * on the tasklist. */ 1176 cgroup_fork_callbacks(p); 1177 cgroup_callbacks_done = 1; 1178 1179 /* Need tasklist lock for parent etc handling! */ 1180 write_lock_irq(&tasklist_lock); 1181 1182 /* 1183 * The task hasn't been attached yet, so its cpus_allowed mask will 1184 * not be changed, nor will its assigned CPU. 1185 * 1186 * The cpus_allowed mask of the parent may have changed after it was 1187 * copied first time - so re-copy it here, then check the child's CPU 1188 * to ensure it is on a valid CPU (and if not, just force it back to 1189 * parent's CPU). This avoids alot of nasty races. 1190 */ 1191 p->cpus_allowed = current->cpus_allowed; 1192 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1193 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1194 !cpu_online(task_cpu(p)))) 1195 set_task_cpu(p, smp_processor_id()); 1196 1197 /* CLONE_PARENT re-uses the old parent */ 1198 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1199 p->real_parent = current->real_parent; 1200 p->parent_exec_id = current->parent_exec_id; 1201 } else { 1202 p->real_parent = current; 1203 p->parent_exec_id = current->self_exec_id; 1204 } 1205 1206 spin_lock(¤t->sighand->siglock); 1207 1208 /* 1209 * Process group and session signals need to be delivered to just the 1210 * parent before the fork or both the parent and the child after the 1211 * fork. Restart if a signal comes in before we add the new process to 1212 * it's process group. 1213 * A fatal signal pending means that current will exit, so the new 1214 * thread can't slip out of an OOM kill (or normal SIGKILL). 1215 */ 1216 recalc_sigpending(); 1217 if (signal_pending(current)) { 1218 spin_unlock(¤t->sighand->siglock); 1219 write_unlock_irq(&tasklist_lock); 1220 retval = -ERESTARTNOINTR; 1221 goto bad_fork_free_pid; 1222 } 1223 1224 if (clone_flags & CLONE_THREAD) { 1225 atomic_inc(¤t->signal->count); 1226 atomic_inc(¤t->signal->live); 1227 p->group_leader = current->group_leader; 1228 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1229 } 1230 1231 if (likely(p->pid)) { 1232 list_add_tail(&p->sibling, &p->real_parent->children); 1233 tracehook_finish_clone(p, clone_flags, trace); 1234 1235 if (thread_group_leader(p)) { 1236 if (clone_flags & CLONE_NEWPID) 1237 p->nsproxy->pid_ns->child_reaper = p; 1238 1239 p->signal->leader_pid = pid; 1240 tty_kref_put(p->signal->tty); 1241 p->signal->tty = tty_kref_get(current->signal->tty); 1242 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1243 attach_pid(p, PIDTYPE_SID, task_session(current)); 1244 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1245 __get_cpu_var(process_counts)++; 1246 } 1247 attach_pid(p, PIDTYPE_PID, pid); 1248 nr_threads++; 1249 } 1250 1251 total_forks++; 1252 spin_unlock(¤t->sighand->siglock); 1253 write_unlock_irq(&tasklist_lock); 1254 proc_fork_connector(p); 1255 cgroup_post_fork(p); 1256 perf_event_fork(p); 1257 return p; 1258 1259 bad_fork_free_pid: 1260 if (pid != &init_struct_pid) 1261 free_pid(pid); 1262 bad_fork_cleanup_io: 1263 put_io_context(p->io_context); 1264 bad_fork_cleanup_namespaces: 1265 exit_task_namespaces(p); 1266 bad_fork_cleanup_mm: 1267 if (p->mm) 1268 mmput(p->mm); 1269 bad_fork_cleanup_signal: 1270 if (!(clone_flags & CLONE_THREAD)) 1271 __cleanup_signal(p->signal); 1272 bad_fork_cleanup_sighand: 1273 __cleanup_sighand(p->sighand); 1274 bad_fork_cleanup_fs: 1275 exit_fs(p); /* blocking */ 1276 bad_fork_cleanup_files: 1277 exit_files(p); /* blocking */ 1278 bad_fork_cleanup_semundo: 1279 exit_sem(p); 1280 bad_fork_cleanup_audit: 1281 audit_free(p); 1282 bad_fork_cleanup_policy: 1283 perf_event_free_task(p); 1284 #ifdef CONFIG_NUMA 1285 mpol_put(p->mempolicy); 1286 bad_fork_cleanup_cgroup: 1287 #endif 1288 cgroup_exit(p, cgroup_callbacks_done); 1289 delayacct_tsk_free(p); 1290 if (p->binfmt) 1291 module_put(p->binfmt->module); 1292 bad_fork_cleanup_put_domain: 1293 module_put(task_thread_info(p)->exec_domain->module); 1294 bad_fork_cleanup_count: 1295 atomic_dec(&p->cred->user->processes); 1296 exit_creds(p); 1297 bad_fork_free: 1298 free_task(p); 1299 fork_out: 1300 return ERR_PTR(retval); 1301 } 1302 1303 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1304 { 1305 memset(regs, 0, sizeof(struct pt_regs)); 1306 return regs; 1307 } 1308 1309 struct task_struct * __cpuinit fork_idle(int cpu) 1310 { 1311 struct task_struct *task; 1312 struct pt_regs regs; 1313 1314 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1315 &init_struct_pid, 0); 1316 if (!IS_ERR(task)) 1317 init_idle(task, cpu); 1318 1319 return task; 1320 } 1321 1322 /* 1323 * Ok, this is the main fork-routine. 1324 * 1325 * It copies the process, and if successful kick-starts 1326 * it and waits for it to finish using the VM if required. 1327 */ 1328 long do_fork(unsigned long clone_flags, 1329 unsigned long stack_start, 1330 struct pt_regs *regs, 1331 unsigned long stack_size, 1332 int __user *parent_tidptr, 1333 int __user *child_tidptr) 1334 { 1335 struct task_struct *p; 1336 int trace = 0; 1337 long nr; 1338 1339 /* 1340 * Do some preliminary argument and permissions checking before we 1341 * actually start allocating stuff 1342 */ 1343 if (clone_flags & CLONE_NEWUSER) { 1344 if (clone_flags & CLONE_THREAD) 1345 return -EINVAL; 1346 /* hopefully this check will go away when userns support is 1347 * complete 1348 */ 1349 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1350 !capable(CAP_SETGID)) 1351 return -EPERM; 1352 } 1353 1354 /* 1355 * We hope to recycle these flags after 2.6.26 1356 */ 1357 if (unlikely(clone_flags & CLONE_STOPPED)) { 1358 static int __read_mostly count = 100; 1359 1360 if (count > 0 && printk_ratelimit()) { 1361 char comm[TASK_COMM_LEN]; 1362 1363 count--; 1364 printk(KERN_INFO "fork(): process `%s' used deprecated " 1365 "clone flags 0x%lx\n", 1366 get_task_comm(comm, current), 1367 clone_flags & CLONE_STOPPED); 1368 } 1369 } 1370 1371 /* 1372 * When called from kernel_thread, don't do user tracing stuff. 1373 */ 1374 if (likely(user_mode(regs))) 1375 trace = tracehook_prepare_clone(clone_flags); 1376 1377 p = copy_process(clone_flags, stack_start, regs, stack_size, 1378 child_tidptr, NULL, trace); 1379 /* 1380 * Do this prior waking up the new thread - the thread pointer 1381 * might get invalid after that point, if the thread exits quickly. 1382 */ 1383 if (!IS_ERR(p)) { 1384 struct completion vfork; 1385 1386 trace_sched_process_fork(current, p); 1387 1388 nr = task_pid_vnr(p); 1389 1390 if (clone_flags & CLONE_PARENT_SETTID) 1391 put_user(nr, parent_tidptr); 1392 1393 if (clone_flags & CLONE_VFORK) { 1394 p->vfork_done = &vfork; 1395 init_completion(&vfork); 1396 } 1397 1398 audit_finish_fork(p); 1399 tracehook_report_clone(regs, clone_flags, nr, p); 1400 1401 /* 1402 * We set PF_STARTING at creation in case tracing wants to 1403 * use this to distinguish a fully live task from one that 1404 * hasn't gotten to tracehook_report_clone() yet. Now we 1405 * clear it and set the child going. 1406 */ 1407 p->flags &= ~PF_STARTING; 1408 1409 if (unlikely(clone_flags & CLONE_STOPPED)) { 1410 /* 1411 * We'll start up with an immediate SIGSTOP. 1412 */ 1413 sigaddset(&p->pending.signal, SIGSTOP); 1414 set_tsk_thread_flag(p, TIF_SIGPENDING); 1415 __set_task_state(p, TASK_STOPPED); 1416 } else { 1417 wake_up_new_task(p, clone_flags); 1418 } 1419 1420 tracehook_report_clone_complete(trace, regs, 1421 clone_flags, nr, p); 1422 1423 if (clone_flags & CLONE_VFORK) { 1424 freezer_do_not_count(); 1425 wait_for_completion(&vfork); 1426 freezer_count(); 1427 tracehook_report_vfork_done(p, nr); 1428 } 1429 } else { 1430 nr = PTR_ERR(p); 1431 } 1432 return nr; 1433 } 1434 1435 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1436 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1437 #endif 1438 1439 static void sighand_ctor(void *data) 1440 { 1441 struct sighand_struct *sighand = data; 1442 1443 spin_lock_init(&sighand->siglock); 1444 init_waitqueue_head(&sighand->signalfd_wqh); 1445 } 1446 1447 void __init proc_caches_init(void) 1448 { 1449 sighand_cachep = kmem_cache_create("sighand_cache", 1450 sizeof(struct sighand_struct), 0, 1451 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1452 SLAB_NOTRACK, sighand_ctor); 1453 signal_cachep = kmem_cache_create("signal_cache", 1454 sizeof(struct signal_struct), 0, 1455 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1456 files_cachep = kmem_cache_create("files_cache", 1457 sizeof(struct files_struct), 0, 1458 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1459 fs_cachep = kmem_cache_create("fs_cache", 1460 sizeof(struct fs_struct), 0, 1461 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1462 mm_cachep = kmem_cache_create("mm_struct", 1463 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1464 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1465 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1466 mmap_init(); 1467 } 1468 1469 /* 1470 * Check constraints on flags passed to the unshare system call and 1471 * force unsharing of additional process context as appropriate. 1472 */ 1473 static void check_unshare_flags(unsigned long *flags_ptr) 1474 { 1475 /* 1476 * If unsharing a thread from a thread group, must also 1477 * unshare vm. 1478 */ 1479 if (*flags_ptr & CLONE_THREAD) 1480 *flags_ptr |= CLONE_VM; 1481 1482 /* 1483 * If unsharing vm, must also unshare signal handlers. 1484 */ 1485 if (*flags_ptr & CLONE_VM) 1486 *flags_ptr |= CLONE_SIGHAND; 1487 1488 /* 1489 * If unsharing signal handlers and the task was created 1490 * using CLONE_THREAD, then must unshare the thread 1491 */ 1492 if ((*flags_ptr & CLONE_SIGHAND) && 1493 (atomic_read(¤t->signal->count) > 1)) 1494 *flags_ptr |= CLONE_THREAD; 1495 1496 /* 1497 * If unsharing namespace, must also unshare filesystem information. 1498 */ 1499 if (*flags_ptr & CLONE_NEWNS) 1500 *flags_ptr |= CLONE_FS; 1501 } 1502 1503 /* 1504 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1505 */ 1506 static int unshare_thread(unsigned long unshare_flags) 1507 { 1508 if (unshare_flags & CLONE_THREAD) 1509 return -EINVAL; 1510 1511 return 0; 1512 } 1513 1514 /* 1515 * Unshare the filesystem structure if it is being shared 1516 */ 1517 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1518 { 1519 struct fs_struct *fs = current->fs; 1520 1521 if (!(unshare_flags & CLONE_FS) || !fs) 1522 return 0; 1523 1524 /* don't need lock here; in the worst case we'll do useless copy */ 1525 if (fs->users == 1) 1526 return 0; 1527 1528 *new_fsp = copy_fs_struct(fs); 1529 if (!*new_fsp) 1530 return -ENOMEM; 1531 1532 return 0; 1533 } 1534 1535 /* 1536 * Unsharing of sighand is not supported yet 1537 */ 1538 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1539 { 1540 struct sighand_struct *sigh = current->sighand; 1541 1542 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1543 return -EINVAL; 1544 else 1545 return 0; 1546 } 1547 1548 /* 1549 * Unshare vm if it is being shared 1550 */ 1551 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1552 { 1553 struct mm_struct *mm = current->mm; 1554 1555 if ((unshare_flags & CLONE_VM) && 1556 (mm && atomic_read(&mm->mm_users) > 1)) { 1557 return -EINVAL; 1558 } 1559 1560 return 0; 1561 } 1562 1563 /* 1564 * Unshare file descriptor table if it is being shared 1565 */ 1566 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1567 { 1568 struct files_struct *fd = current->files; 1569 int error = 0; 1570 1571 if ((unshare_flags & CLONE_FILES) && 1572 (fd && atomic_read(&fd->count) > 1)) { 1573 *new_fdp = dup_fd(fd, &error); 1574 if (!*new_fdp) 1575 return error; 1576 } 1577 1578 return 0; 1579 } 1580 1581 /* 1582 * unshare allows a process to 'unshare' part of the process 1583 * context which was originally shared using clone. copy_* 1584 * functions used by do_fork() cannot be used here directly 1585 * because they modify an inactive task_struct that is being 1586 * constructed. Here we are modifying the current, active, 1587 * task_struct. 1588 */ 1589 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1590 { 1591 int err = 0; 1592 struct fs_struct *fs, *new_fs = NULL; 1593 struct sighand_struct *new_sigh = NULL; 1594 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1595 struct files_struct *fd, *new_fd = NULL; 1596 struct nsproxy *new_nsproxy = NULL; 1597 int do_sysvsem = 0; 1598 1599 check_unshare_flags(&unshare_flags); 1600 1601 /* Return -EINVAL for all unsupported flags */ 1602 err = -EINVAL; 1603 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1604 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1605 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1606 goto bad_unshare_out; 1607 1608 /* 1609 * CLONE_NEWIPC must also detach from the undolist: after switching 1610 * to a new ipc namespace, the semaphore arrays from the old 1611 * namespace are unreachable. 1612 */ 1613 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1614 do_sysvsem = 1; 1615 if ((err = unshare_thread(unshare_flags))) 1616 goto bad_unshare_out; 1617 if ((err = unshare_fs(unshare_flags, &new_fs))) 1618 goto bad_unshare_cleanup_thread; 1619 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1620 goto bad_unshare_cleanup_fs; 1621 if ((err = unshare_vm(unshare_flags, &new_mm))) 1622 goto bad_unshare_cleanup_sigh; 1623 if ((err = unshare_fd(unshare_flags, &new_fd))) 1624 goto bad_unshare_cleanup_vm; 1625 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1626 new_fs))) 1627 goto bad_unshare_cleanup_fd; 1628 1629 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1630 if (do_sysvsem) { 1631 /* 1632 * CLONE_SYSVSEM is equivalent to sys_exit(). 1633 */ 1634 exit_sem(current); 1635 } 1636 1637 if (new_nsproxy) { 1638 switch_task_namespaces(current, new_nsproxy); 1639 new_nsproxy = NULL; 1640 } 1641 1642 task_lock(current); 1643 1644 if (new_fs) { 1645 fs = current->fs; 1646 write_lock(&fs->lock); 1647 current->fs = new_fs; 1648 if (--fs->users) 1649 new_fs = NULL; 1650 else 1651 new_fs = fs; 1652 write_unlock(&fs->lock); 1653 } 1654 1655 if (new_mm) { 1656 mm = current->mm; 1657 active_mm = current->active_mm; 1658 current->mm = new_mm; 1659 current->active_mm = new_mm; 1660 activate_mm(active_mm, new_mm); 1661 new_mm = mm; 1662 } 1663 1664 if (new_fd) { 1665 fd = current->files; 1666 current->files = new_fd; 1667 new_fd = fd; 1668 } 1669 1670 task_unlock(current); 1671 } 1672 1673 if (new_nsproxy) 1674 put_nsproxy(new_nsproxy); 1675 1676 bad_unshare_cleanup_fd: 1677 if (new_fd) 1678 put_files_struct(new_fd); 1679 1680 bad_unshare_cleanup_vm: 1681 if (new_mm) 1682 mmput(new_mm); 1683 1684 bad_unshare_cleanup_sigh: 1685 if (new_sigh) 1686 if (atomic_dec_and_test(&new_sigh->count)) 1687 kmem_cache_free(sighand_cachep, new_sigh); 1688 1689 bad_unshare_cleanup_fs: 1690 if (new_fs) 1691 free_fs_struct(new_fs); 1692 1693 bad_unshare_cleanup_thread: 1694 bad_unshare_out: 1695 return err; 1696 } 1697 1698 /* 1699 * Helper to unshare the files of the current task. 1700 * We don't want to expose copy_files internals to 1701 * the exec layer of the kernel. 1702 */ 1703 1704 int unshare_files(struct files_struct **displaced) 1705 { 1706 struct task_struct *task = current; 1707 struct files_struct *copy = NULL; 1708 int error; 1709 1710 error = unshare_fd(CLONE_FILES, ©); 1711 if (error || !copy) { 1712 *displaced = NULL; 1713 return error; 1714 } 1715 *displaced = task->files; 1716 task_lock(task); 1717 task->files = copy; 1718 task_unlock(task); 1719 return 0; 1720 } 1721