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/mnt_namespace.h> 21 #include <linux/personality.h> 22 #include <linux/mempolicy.h> 23 #include <linux/sem.h> 24 #include <linux/file.h> 25 #include <linux/fdtable.h> 26 #include <linux/iocontext.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/mmu_notifier.h> 31 #include <linux/fs.h> 32 #include <linux/nsproxy.h> 33 #include <linux/capability.h> 34 #include <linux/cpu.h> 35 #include <linux/cgroup.h> 36 #include <linux/security.h> 37 #include <linux/hugetlb.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/tracehook.h> 42 #include <linux/futex.h> 43 #include <linux/compat.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/profile.h> 52 #include <linux/rmap.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 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 put_cred(tsk->real_cred); 156 put_cred(tsk->cred); 157 delayacct_tsk_free(tsk); 158 159 if (!profile_handoff_task(tsk)) 160 free_task(tsk); 161 } 162 163 /* 164 * macro override instead of weak attribute alias, to workaround 165 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 166 */ 167 #ifndef arch_task_cache_init 168 #define arch_task_cache_init() 169 #endif 170 171 void __init fork_init(unsigned long mempages) 172 { 173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 174 #ifndef ARCH_MIN_TASKALIGN 175 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 176 #endif 177 /* create a slab on which task_structs can be allocated */ 178 task_struct_cachep = 179 kmem_cache_create("task_struct", sizeof(struct task_struct), 180 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 181 #endif 182 183 /* do the arch specific task caches init */ 184 arch_task_cache_init(); 185 186 /* 187 * The default maximum number of threads is set to a safe 188 * value: the thread structures can take up at most half 189 * of memory. 190 */ 191 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 192 193 /* 194 * we need to allow at least 20 threads to boot a system 195 */ 196 if(max_threads < 20) 197 max_threads = 20; 198 199 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 200 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 201 init_task.signal->rlim[RLIMIT_SIGPENDING] = 202 init_task.signal->rlim[RLIMIT_NPROC]; 203 } 204 205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 206 struct task_struct *src) 207 { 208 *dst = *src; 209 return 0; 210 } 211 212 static struct task_struct *dup_task_struct(struct task_struct *orig) 213 { 214 struct task_struct *tsk; 215 struct thread_info *ti; 216 unsigned long *stackend; 217 218 int err; 219 220 prepare_to_copy(orig); 221 222 tsk = alloc_task_struct(); 223 if (!tsk) 224 return NULL; 225 226 ti = alloc_thread_info(tsk); 227 if (!ti) { 228 free_task_struct(tsk); 229 return NULL; 230 } 231 232 err = arch_dup_task_struct(tsk, orig); 233 if (err) 234 goto out; 235 236 tsk->stack = ti; 237 238 err = prop_local_init_single(&tsk->dirties); 239 if (err) 240 goto out; 241 242 setup_thread_stack(tsk, orig); 243 stackend = end_of_stack(tsk); 244 *stackend = STACK_END_MAGIC; /* for overflow detection */ 245 246 #ifdef CONFIG_CC_STACKPROTECTOR 247 tsk->stack_canary = get_random_int(); 248 #endif 249 250 /* One for us, one for whoever does the "release_task()" (usually parent) */ 251 atomic_set(&tsk->usage,2); 252 atomic_set(&tsk->fs_excl, 0); 253 #ifdef CONFIG_BLK_DEV_IO_TRACE 254 tsk->btrace_seq = 0; 255 #endif 256 tsk->splice_pipe = NULL; 257 return tsk; 258 259 out: 260 free_thread_info(ti); 261 free_task_struct(tsk); 262 return NULL; 263 } 264 265 #ifdef CONFIG_MMU 266 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 267 { 268 struct vm_area_struct *mpnt, *tmp, **pprev; 269 struct rb_node **rb_link, *rb_parent; 270 int retval; 271 unsigned long charge; 272 struct mempolicy *pol; 273 274 down_write(&oldmm->mmap_sem); 275 flush_cache_dup_mm(oldmm); 276 /* 277 * Not linked in yet - no deadlock potential: 278 */ 279 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 280 281 mm->locked_vm = 0; 282 mm->mmap = NULL; 283 mm->mmap_cache = NULL; 284 mm->free_area_cache = oldmm->mmap_base; 285 mm->cached_hole_size = ~0UL; 286 mm->map_count = 0; 287 cpumask_clear(mm_cpumask(mm)); 288 mm->mm_rb = RB_ROOT; 289 rb_link = &mm->mm_rb.rb_node; 290 rb_parent = NULL; 291 pprev = &mm->mmap; 292 293 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 294 struct file *file; 295 296 if (mpnt->vm_flags & VM_DONTCOPY) { 297 long pages = vma_pages(mpnt); 298 mm->total_vm -= pages; 299 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 300 -pages); 301 continue; 302 } 303 charge = 0; 304 if (mpnt->vm_flags & VM_ACCOUNT) { 305 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 306 if (security_vm_enough_memory(len)) 307 goto fail_nomem; 308 charge = len; 309 } 310 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 311 if (!tmp) 312 goto fail_nomem; 313 *tmp = *mpnt; 314 pol = mpol_dup(vma_policy(mpnt)); 315 retval = PTR_ERR(pol); 316 if (IS_ERR(pol)) 317 goto fail_nomem_policy; 318 vma_set_policy(tmp, pol); 319 tmp->vm_flags &= ~VM_LOCKED; 320 tmp->vm_mm = mm; 321 tmp->vm_next = NULL; 322 anon_vma_link(tmp); 323 file = tmp->vm_file; 324 if (file) { 325 struct inode *inode = file->f_path.dentry->d_inode; 326 struct address_space *mapping = file->f_mapping; 327 328 get_file(file); 329 if (tmp->vm_flags & VM_DENYWRITE) 330 atomic_dec(&inode->i_writecount); 331 spin_lock(&mapping->i_mmap_lock); 332 if (tmp->vm_flags & VM_SHARED) 333 mapping->i_mmap_writable++; 334 tmp->vm_truncate_count = mpnt->vm_truncate_count; 335 flush_dcache_mmap_lock(mapping); 336 /* insert tmp into the share list, just after mpnt */ 337 vma_prio_tree_add(tmp, mpnt); 338 flush_dcache_mmap_unlock(mapping); 339 spin_unlock(&mapping->i_mmap_lock); 340 } 341 342 /* 343 * Clear hugetlb-related page reserves for children. This only 344 * affects MAP_PRIVATE mappings. Faults generated by the child 345 * are not guaranteed to succeed, even if read-only 346 */ 347 if (is_vm_hugetlb_page(tmp)) 348 reset_vma_resv_huge_pages(tmp); 349 350 /* 351 * Link in the new vma and copy the page table entries. 352 */ 353 *pprev = tmp; 354 pprev = &tmp->vm_next; 355 356 __vma_link_rb(mm, tmp, rb_link, rb_parent); 357 rb_link = &tmp->vm_rb.rb_right; 358 rb_parent = &tmp->vm_rb; 359 360 mm->map_count++; 361 retval = copy_page_range(mm, oldmm, mpnt); 362 363 if (tmp->vm_ops && tmp->vm_ops->open) 364 tmp->vm_ops->open(tmp); 365 366 if (retval) 367 goto out; 368 } 369 /* a new mm has just been created */ 370 arch_dup_mmap(oldmm, mm); 371 retval = 0; 372 out: 373 up_write(&mm->mmap_sem); 374 flush_tlb_mm(oldmm); 375 up_write(&oldmm->mmap_sem); 376 return retval; 377 fail_nomem_policy: 378 kmem_cache_free(vm_area_cachep, tmp); 379 fail_nomem: 380 retval = -ENOMEM; 381 vm_unacct_memory(charge); 382 goto out; 383 } 384 385 static inline int mm_alloc_pgd(struct mm_struct * mm) 386 { 387 mm->pgd = pgd_alloc(mm); 388 if (unlikely(!mm->pgd)) 389 return -ENOMEM; 390 return 0; 391 } 392 393 static inline void mm_free_pgd(struct mm_struct * mm) 394 { 395 pgd_free(mm, mm->pgd); 396 } 397 #else 398 #define dup_mmap(mm, oldmm) (0) 399 #define mm_alloc_pgd(mm) (0) 400 #define mm_free_pgd(mm) 401 #endif /* CONFIG_MMU */ 402 403 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 404 405 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 406 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 407 408 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 409 410 static int __init coredump_filter_setup(char *s) 411 { 412 default_dump_filter = 413 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 414 MMF_DUMP_FILTER_MASK; 415 return 1; 416 } 417 418 __setup("coredump_filter=", coredump_filter_setup); 419 420 #include <linux/init_task.h> 421 422 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 423 { 424 atomic_set(&mm->mm_users, 1); 425 atomic_set(&mm->mm_count, 1); 426 init_rwsem(&mm->mmap_sem); 427 INIT_LIST_HEAD(&mm->mmlist); 428 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter; 429 mm->core_state = NULL; 430 mm->nr_ptes = 0; 431 set_mm_counter(mm, file_rss, 0); 432 set_mm_counter(mm, anon_rss, 0); 433 spin_lock_init(&mm->page_table_lock); 434 spin_lock_init(&mm->ioctx_lock); 435 INIT_HLIST_HEAD(&mm->ioctx_list); 436 mm->free_area_cache = TASK_UNMAPPED_BASE; 437 mm->cached_hole_size = ~0UL; 438 mm_init_owner(mm, p); 439 440 if (likely(!mm_alloc_pgd(mm))) { 441 mm->def_flags = 0; 442 mmu_notifier_mm_init(mm); 443 return mm; 444 } 445 446 free_mm(mm); 447 return NULL; 448 } 449 450 /* 451 * Allocate and initialize an mm_struct. 452 */ 453 struct mm_struct * mm_alloc(void) 454 { 455 struct mm_struct * mm; 456 457 mm = allocate_mm(); 458 if (mm) { 459 memset(mm, 0, sizeof(*mm)); 460 mm = mm_init(mm, current); 461 } 462 return mm; 463 } 464 465 /* 466 * Called when the last reference to the mm 467 * is dropped: either by a lazy thread or by 468 * mmput. Free the page directory and the mm. 469 */ 470 void __mmdrop(struct mm_struct *mm) 471 { 472 BUG_ON(mm == &init_mm); 473 mm_free_pgd(mm); 474 destroy_context(mm); 475 mmu_notifier_mm_destroy(mm); 476 free_mm(mm); 477 } 478 EXPORT_SYMBOL_GPL(__mmdrop); 479 480 /* 481 * Decrement the use count and release all resources for an mm. 482 */ 483 void mmput(struct mm_struct *mm) 484 { 485 might_sleep(); 486 487 if (atomic_dec_and_test(&mm->mm_users)) { 488 exit_aio(mm); 489 exit_mmap(mm); 490 set_mm_exe_file(mm, NULL); 491 if (!list_empty(&mm->mmlist)) { 492 spin_lock(&mmlist_lock); 493 list_del(&mm->mmlist); 494 spin_unlock(&mmlist_lock); 495 } 496 put_swap_token(mm); 497 mmdrop(mm); 498 } 499 } 500 EXPORT_SYMBOL_GPL(mmput); 501 502 /** 503 * get_task_mm - acquire a reference to the task's mm 504 * 505 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 506 * this kernel workthread has transiently adopted a user mm with use_mm, 507 * to do its AIO) is not set and if so returns a reference to it, after 508 * bumping up the use count. User must release the mm via mmput() 509 * after use. Typically used by /proc and ptrace. 510 */ 511 struct mm_struct *get_task_mm(struct task_struct *task) 512 { 513 struct mm_struct *mm; 514 515 task_lock(task); 516 mm = task->mm; 517 if (mm) { 518 if (task->flags & PF_KTHREAD) 519 mm = NULL; 520 else 521 atomic_inc(&mm->mm_users); 522 } 523 task_unlock(task); 524 return mm; 525 } 526 EXPORT_SYMBOL_GPL(get_task_mm); 527 528 /* Please note the differences between mmput and mm_release. 529 * mmput is called whenever we stop holding onto a mm_struct, 530 * error success whatever. 531 * 532 * mm_release is called after a mm_struct has been removed 533 * from the current process. 534 * 535 * This difference is important for error handling, when we 536 * only half set up a mm_struct for a new process and need to restore 537 * the old one. Because we mmput the new mm_struct before 538 * restoring the old one. . . 539 * Eric Biederman 10 January 1998 540 */ 541 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 542 { 543 struct completion *vfork_done = tsk->vfork_done; 544 545 /* Get rid of any futexes when releasing the mm */ 546 #ifdef CONFIG_FUTEX 547 if (unlikely(tsk->robust_list)) 548 exit_robust_list(tsk); 549 #ifdef CONFIG_COMPAT 550 if (unlikely(tsk->compat_robust_list)) 551 compat_exit_robust_list(tsk); 552 #endif 553 #endif 554 555 /* Get rid of any cached register state */ 556 deactivate_mm(tsk, mm); 557 558 /* notify parent sleeping on vfork() */ 559 if (vfork_done) { 560 tsk->vfork_done = NULL; 561 complete(vfork_done); 562 } 563 564 /* 565 * If we're exiting normally, clear a user-space tid field if 566 * requested. We leave this alone when dying by signal, to leave 567 * the value intact in a core dump, and to save the unnecessary 568 * trouble otherwise. Userland only wants this done for a sys_exit. 569 */ 570 if (tsk->clear_child_tid 571 && !(tsk->flags & PF_SIGNALED) 572 && atomic_read(&mm->mm_users) > 1) { 573 u32 __user * tidptr = tsk->clear_child_tid; 574 tsk->clear_child_tid = NULL; 575 576 /* 577 * We don't check the error code - if userspace has 578 * not set up a proper pointer then tough luck. 579 */ 580 put_user(0, tidptr); 581 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 582 } 583 } 584 585 /* 586 * Allocate a new mm structure and copy contents from the 587 * mm structure of the passed in task structure. 588 */ 589 struct mm_struct *dup_mm(struct task_struct *tsk) 590 { 591 struct mm_struct *mm, *oldmm = current->mm; 592 int err; 593 594 if (!oldmm) 595 return NULL; 596 597 mm = allocate_mm(); 598 if (!mm) 599 goto fail_nomem; 600 601 memcpy(mm, oldmm, sizeof(*mm)); 602 603 /* Initializing for Swap token stuff */ 604 mm->token_priority = 0; 605 mm->last_interval = 0; 606 607 if (!mm_init(mm, tsk)) 608 goto fail_nomem; 609 610 if (init_new_context(tsk, mm)) 611 goto fail_nocontext; 612 613 dup_mm_exe_file(oldmm, mm); 614 615 err = dup_mmap(mm, oldmm); 616 if (err) 617 goto free_pt; 618 619 mm->hiwater_rss = get_mm_rss(mm); 620 mm->hiwater_vm = mm->total_vm; 621 622 return mm; 623 624 free_pt: 625 mmput(mm); 626 627 fail_nomem: 628 return NULL; 629 630 fail_nocontext: 631 /* 632 * If init_new_context() failed, we cannot use mmput() to free the mm 633 * because it calls destroy_context() 634 */ 635 mm_free_pgd(mm); 636 free_mm(mm); 637 return NULL; 638 } 639 640 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 641 { 642 struct mm_struct * mm, *oldmm; 643 int retval; 644 645 tsk->min_flt = tsk->maj_flt = 0; 646 tsk->nvcsw = tsk->nivcsw = 0; 647 #ifdef CONFIG_DETECT_HUNG_TASK 648 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 649 #endif 650 651 tsk->mm = NULL; 652 tsk->active_mm = NULL; 653 654 /* 655 * Are we cloning a kernel thread? 656 * 657 * We need to steal a active VM for that.. 658 */ 659 oldmm = current->mm; 660 if (!oldmm) 661 return 0; 662 663 if (clone_flags & CLONE_VM) { 664 atomic_inc(&oldmm->mm_users); 665 mm = oldmm; 666 goto good_mm; 667 } 668 669 retval = -ENOMEM; 670 mm = dup_mm(tsk); 671 if (!mm) 672 goto fail_nomem; 673 674 good_mm: 675 /* Initializing for Swap token stuff */ 676 mm->token_priority = 0; 677 mm->last_interval = 0; 678 679 tsk->mm = mm; 680 tsk->active_mm = mm; 681 return 0; 682 683 fail_nomem: 684 return retval; 685 } 686 687 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 688 { 689 struct fs_struct *fs = current->fs; 690 if (clone_flags & CLONE_FS) { 691 /* tsk->fs is already what we want */ 692 write_lock(&fs->lock); 693 if (fs->in_exec) { 694 write_unlock(&fs->lock); 695 return -EAGAIN; 696 } 697 fs->users++; 698 write_unlock(&fs->lock); 699 return 0; 700 } 701 tsk->fs = copy_fs_struct(fs); 702 if (!tsk->fs) 703 return -ENOMEM; 704 return 0; 705 } 706 707 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 708 { 709 struct files_struct *oldf, *newf; 710 int error = 0; 711 712 /* 713 * A background process may not have any files ... 714 */ 715 oldf = current->files; 716 if (!oldf) 717 goto out; 718 719 if (clone_flags & CLONE_FILES) { 720 atomic_inc(&oldf->count); 721 goto out; 722 } 723 724 newf = dup_fd(oldf, &error); 725 if (!newf) 726 goto out; 727 728 tsk->files = newf; 729 error = 0; 730 out: 731 return error; 732 } 733 734 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 735 { 736 #ifdef CONFIG_BLOCK 737 struct io_context *ioc = current->io_context; 738 739 if (!ioc) 740 return 0; 741 /* 742 * Share io context with parent, if CLONE_IO is set 743 */ 744 if (clone_flags & CLONE_IO) { 745 tsk->io_context = ioc_task_link(ioc); 746 if (unlikely(!tsk->io_context)) 747 return -ENOMEM; 748 } else if (ioprio_valid(ioc->ioprio)) { 749 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 750 if (unlikely(!tsk->io_context)) 751 return -ENOMEM; 752 753 tsk->io_context->ioprio = ioc->ioprio; 754 } 755 #endif 756 return 0; 757 } 758 759 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 760 { 761 struct sighand_struct *sig; 762 763 if (clone_flags & CLONE_SIGHAND) { 764 atomic_inc(¤t->sighand->count); 765 return 0; 766 } 767 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 768 rcu_assign_pointer(tsk->sighand, sig); 769 if (!sig) 770 return -ENOMEM; 771 atomic_set(&sig->count, 1); 772 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 773 return 0; 774 } 775 776 void __cleanup_sighand(struct sighand_struct *sighand) 777 { 778 if (atomic_dec_and_test(&sighand->count)) 779 kmem_cache_free(sighand_cachep, sighand); 780 } 781 782 783 /* 784 * Initialize POSIX timer handling for a thread group. 785 */ 786 static void posix_cpu_timers_init_group(struct signal_struct *sig) 787 { 788 /* Thread group counters. */ 789 thread_group_cputime_init(sig); 790 791 /* Expiration times and increments. */ 792 sig->it_virt_expires = cputime_zero; 793 sig->it_virt_incr = cputime_zero; 794 sig->it_prof_expires = cputime_zero; 795 sig->it_prof_incr = cputime_zero; 796 797 /* Cached expiration times. */ 798 sig->cputime_expires.prof_exp = cputime_zero; 799 sig->cputime_expires.virt_exp = cputime_zero; 800 sig->cputime_expires.sched_exp = 0; 801 802 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 803 sig->cputime_expires.prof_exp = 804 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 805 sig->cputimer.running = 1; 806 } 807 808 /* The timer lists. */ 809 INIT_LIST_HEAD(&sig->cpu_timers[0]); 810 INIT_LIST_HEAD(&sig->cpu_timers[1]); 811 INIT_LIST_HEAD(&sig->cpu_timers[2]); 812 } 813 814 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 815 { 816 struct signal_struct *sig; 817 818 if (clone_flags & CLONE_THREAD) { 819 atomic_inc(¤t->signal->count); 820 atomic_inc(¤t->signal->live); 821 return 0; 822 } 823 824 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 825 tsk->signal = sig; 826 if (!sig) 827 return -ENOMEM; 828 829 atomic_set(&sig->count, 1); 830 atomic_set(&sig->live, 1); 831 init_waitqueue_head(&sig->wait_chldexit); 832 sig->flags = 0; 833 if (clone_flags & CLONE_NEWPID) 834 sig->flags |= SIGNAL_UNKILLABLE; 835 sig->group_exit_code = 0; 836 sig->group_exit_task = NULL; 837 sig->group_stop_count = 0; 838 sig->curr_target = tsk; 839 init_sigpending(&sig->shared_pending); 840 INIT_LIST_HEAD(&sig->posix_timers); 841 842 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 843 sig->it_real_incr.tv64 = 0; 844 sig->real_timer.function = it_real_fn; 845 846 sig->leader = 0; /* session leadership doesn't inherit */ 847 sig->tty_old_pgrp = NULL; 848 sig->tty = NULL; 849 850 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 851 sig->gtime = cputime_zero; 852 sig->cgtime = cputime_zero; 853 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 854 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 855 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 856 task_io_accounting_init(&sig->ioac); 857 sig->sum_sched_runtime = 0; 858 taskstats_tgid_init(sig); 859 860 task_lock(current->group_leader); 861 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 862 task_unlock(current->group_leader); 863 864 posix_cpu_timers_init_group(sig); 865 866 acct_init_pacct(&sig->pacct); 867 868 tty_audit_fork(sig); 869 870 return 0; 871 } 872 873 void __cleanup_signal(struct signal_struct *sig) 874 { 875 thread_group_cputime_free(sig); 876 tty_kref_put(sig->tty); 877 kmem_cache_free(signal_cachep, sig); 878 } 879 880 static void cleanup_signal(struct task_struct *tsk) 881 { 882 struct signal_struct *sig = tsk->signal; 883 884 atomic_dec(&sig->live); 885 886 if (atomic_dec_and_test(&sig->count)) 887 __cleanup_signal(sig); 888 } 889 890 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 891 { 892 unsigned long new_flags = p->flags; 893 894 new_flags &= ~PF_SUPERPRIV; 895 new_flags |= PF_FORKNOEXEC; 896 new_flags |= PF_STARTING; 897 p->flags = new_flags; 898 clear_freeze_flag(p); 899 } 900 901 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 902 { 903 current->clear_child_tid = tidptr; 904 905 return task_pid_vnr(current); 906 } 907 908 static void rt_mutex_init_task(struct task_struct *p) 909 { 910 spin_lock_init(&p->pi_lock); 911 #ifdef CONFIG_RT_MUTEXES 912 plist_head_init(&p->pi_waiters, &p->pi_lock); 913 p->pi_blocked_on = NULL; 914 #endif 915 } 916 917 #ifdef CONFIG_MM_OWNER 918 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 919 { 920 mm->owner = p; 921 } 922 #endif /* CONFIG_MM_OWNER */ 923 924 /* 925 * Initialize POSIX timer handling for a single task. 926 */ 927 static void posix_cpu_timers_init(struct task_struct *tsk) 928 { 929 tsk->cputime_expires.prof_exp = cputime_zero; 930 tsk->cputime_expires.virt_exp = cputime_zero; 931 tsk->cputime_expires.sched_exp = 0; 932 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 933 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 934 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 935 } 936 937 /* 938 * This creates a new process as a copy of the old one, 939 * but does not actually start it yet. 940 * 941 * It copies the registers, and all the appropriate 942 * parts of the process environment (as per the clone 943 * flags). The actual kick-off is left to the caller. 944 */ 945 static struct task_struct *copy_process(unsigned long clone_flags, 946 unsigned long stack_start, 947 struct pt_regs *regs, 948 unsigned long stack_size, 949 int __user *child_tidptr, 950 struct pid *pid, 951 int trace) 952 { 953 int retval; 954 struct task_struct *p; 955 int cgroup_callbacks_done = 0; 956 957 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 958 return ERR_PTR(-EINVAL); 959 960 /* 961 * Thread groups must share signals as well, and detached threads 962 * can only be started up within the thread group. 963 */ 964 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 965 return ERR_PTR(-EINVAL); 966 967 /* 968 * Shared signal handlers imply shared VM. By way of the above, 969 * thread groups also imply shared VM. Blocking this case allows 970 * for various simplifications in other code. 971 */ 972 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 973 return ERR_PTR(-EINVAL); 974 975 retval = security_task_create(clone_flags); 976 if (retval) 977 goto fork_out; 978 979 retval = -ENOMEM; 980 p = dup_task_struct(current); 981 if (!p) 982 goto fork_out; 983 984 rt_mutex_init_task(p); 985 986 #ifdef CONFIG_PROVE_LOCKING 987 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 988 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 989 #endif 990 retval = -EAGAIN; 991 if (atomic_read(&p->real_cred->user->processes) >= 992 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 993 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 994 p->real_cred->user != INIT_USER) 995 goto bad_fork_free; 996 } 997 998 retval = copy_creds(p, clone_flags); 999 if (retval < 0) 1000 goto bad_fork_free; 1001 1002 /* 1003 * If multiple threads are within copy_process(), then this check 1004 * triggers too late. This doesn't hurt, the check is only there 1005 * to stop root fork bombs. 1006 */ 1007 retval = -EAGAIN; 1008 if (nr_threads >= max_threads) 1009 goto bad_fork_cleanup_count; 1010 1011 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1012 goto bad_fork_cleanup_count; 1013 1014 if (p->binfmt && !try_module_get(p->binfmt->module)) 1015 goto bad_fork_cleanup_put_domain; 1016 1017 p->did_exec = 0; 1018 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1019 copy_flags(clone_flags, p); 1020 INIT_LIST_HEAD(&p->children); 1021 INIT_LIST_HEAD(&p->sibling); 1022 #ifdef CONFIG_PREEMPT_RCU 1023 p->rcu_read_lock_nesting = 0; 1024 p->rcu_flipctr_idx = 0; 1025 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1026 p->vfork_done = NULL; 1027 spin_lock_init(&p->alloc_lock); 1028 1029 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1030 init_sigpending(&p->pending); 1031 1032 p->utime = cputime_zero; 1033 p->stime = cputime_zero; 1034 p->gtime = cputime_zero; 1035 p->utimescaled = cputime_zero; 1036 p->stimescaled = cputime_zero; 1037 p->prev_utime = cputime_zero; 1038 p->prev_stime = cputime_zero; 1039 1040 p->default_timer_slack_ns = current->timer_slack_ns; 1041 1042 task_io_accounting_init(&p->ioac); 1043 acct_clear_integrals(p); 1044 1045 posix_cpu_timers_init(p); 1046 1047 p->lock_depth = -1; /* -1 = no lock */ 1048 do_posix_clock_monotonic_gettime(&p->start_time); 1049 p->real_start_time = p->start_time; 1050 monotonic_to_bootbased(&p->real_start_time); 1051 p->io_context = NULL; 1052 p->audit_context = NULL; 1053 cgroup_fork(p); 1054 #ifdef CONFIG_NUMA 1055 p->mempolicy = mpol_dup(p->mempolicy); 1056 if (IS_ERR(p->mempolicy)) { 1057 retval = PTR_ERR(p->mempolicy); 1058 p->mempolicy = NULL; 1059 goto bad_fork_cleanup_cgroup; 1060 } 1061 mpol_fix_fork_child_flag(p); 1062 #endif 1063 #ifdef CONFIG_TRACE_IRQFLAGS 1064 p->irq_events = 0; 1065 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1066 p->hardirqs_enabled = 1; 1067 #else 1068 p->hardirqs_enabled = 0; 1069 #endif 1070 p->hardirq_enable_ip = 0; 1071 p->hardirq_enable_event = 0; 1072 p->hardirq_disable_ip = _THIS_IP_; 1073 p->hardirq_disable_event = 0; 1074 p->softirqs_enabled = 1; 1075 p->softirq_enable_ip = _THIS_IP_; 1076 p->softirq_enable_event = 0; 1077 p->softirq_disable_ip = 0; 1078 p->softirq_disable_event = 0; 1079 p->hardirq_context = 0; 1080 p->softirq_context = 0; 1081 #endif 1082 #ifdef CONFIG_LOCKDEP 1083 p->lockdep_depth = 0; /* no locks held yet */ 1084 p->curr_chain_key = 0; 1085 p->lockdep_recursion = 0; 1086 #endif 1087 1088 #ifdef CONFIG_DEBUG_MUTEXES 1089 p->blocked_on = NULL; /* not blocked yet */ 1090 #endif 1091 1092 p->bts = NULL; 1093 1094 /* Perform scheduler related setup. Assign this task to a CPU. */ 1095 sched_fork(p, clone_flags); 1096 1097 if ((retval = audit_alloc(p))) 1098 goto bad_fork_cleanup_policy; 1099 /* copy all the process information */ 1100 if ((retval = copy_semundo(clone_flags, p))) 1101 goto bad_fork_cleanup_audit; 1102 if ((retval = copy_files(clone_flags, p))) 1103 goto bad_fork_cleanup_semundo; 1104 if ((retval = copy_fs(clone_flags, p))) 1105 goto bad_fork_cleanup_files; 1106 if ((retval = copy_sighand(clone_flags, p))) 1107 goto bad_fork_cleanup_fs; 1108 if ((retval = copy_signal(clone_flags, p))) 1109 goto bad_fork_cleanup_sighand; 1110 if ((retval = copy_mm(clone_flags, p))) 1111 goto bad_fork_cleanup_signal; 1112 if ((retval = copy_namespaces(clone_flags, p))) 1113 goto bad_fork_cleanup_mm; 1114 if ((retval = copy_io(clone_flags, p))) 1115 goto bad_fork_cleanup_namespaces; 1116 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1117 if (retval) 1118 goto bad_fork_cleanup_io; 1119 1120 if (pid != &init_struct_pid) { 1121 retval = -ENOMEM; 1122 pid = alloc_pid(p->nsproxy->pid_ns); 1123 if (!pid) 1124 goto bad_fork_cleanup_io; 1125 1126 if (clone_flags & CLONE_NEWPID) { 1127 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1128 if (retval < 0) 1129 goto bad_fork_free_pid; 1130 } 1131 } 1132 1133 ftrace_graph_init_task(p); 1134 1135 p->pid = pid_nr(pid); 1136 p->tgid = p->pid; 1137 if (clone_flags & CLONE_THREAD) 1138 p->tgid = current->tgid; 1139 1140 if (current->nsproxy != p->nsproxy) { 1141 retval = ns_cgroup_clone(p, pid); 1142 if (retval) 1143 goto bad_fork_free_graph; 1144 } 1145 1146 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1147 /* 1148 * Clear TID on mm_release()? 1149 */ 1150 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1151 #ifdef CONFIG_FUTEX 1152 p->robust_list = NULL; 1153 #ifdef CONFIG_COMPAT 1154 p->compat_robust_list = NULL; 1155 #endif 1156 INIT_LIST_HEAD(&p->pi_state_list); 1157 p->pi_state_cache = NULL; 1158 #endif 1159 /* 1160 * sigaltstack should be cleared when sharing the same VM 1161 */ 1162 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1163 p->sas_ss_sp = p->sas_ss_size = 0; 1164 1165 /* 1166 * Syscall tracing should be turned off in the child regardless 1167 * of CLONE_PTRACE. 1168 */ 1169 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1170 #ifdef TIF_SYSCALL_EMU 1171 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1172 #endif 1173 clear_all_latency_tracing(p); 1174 1175 /* ok, now we should be set up.. */ 1176 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1177 p->pdeath_signal = 0; 1178 p->exit_state = 0; 1179 1180 /* 1181 * Ok, make it visible to the rest of the system. 1182 * We dont wake it up yet. 1183 */ 1184 p->group_leader = p; 1185 INIT_LIST_HEAD(&p->thread_group); 1186 1187 /* Now that the task is set up, run cgroup callbacks if 1188 * necessary. We need to run them before the task is visible 1189 * on the tasklist. */ 1190 cgroup_fork_callbacks(p); 1191 cgroup_callbacks_done = 1; 1192 1193 /* Need tasklist lock for parent etc handling! */ 1194 write_lock_irq(&tasklist_lock); 1195 1196 /* 1197 * The task hasn't been attached yet, so its cpus_allowed mask will 1198 * not be changed, nor will its assigned CPU. 1199 * 1200 * The cpus_allowed mask of the parent may have changed after it was 1201 * copied first time - so re-copy it here, then check the child's CPU 1202 * to ensure it is on a valid CPU (and if not, just force it back to 1203 * parent's CPU). This avoids alot of nasty races. 1204 */ 1205 p->cpus_allowed = current->cpus_allowed; 1206 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1207 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1208 !cpu_online(task_cpu(p)))) 1209 set_task_cpu(p, smp_processor_id()); 1210 1211 /* CLONE_PARENT re-uses the old parent */ 1212 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1213 p->real_parent = current->real_parent; 1214 p->parent_exec_id = current->parent_exec_id; 1215 } else { 1216 p->real_parent = current; 1217 p->parent_exec_id = current->self_exec_id; 1218 } 1219 1220 spin_lock(¤t->sighand->siglock); 1221 1222 /* 1223 * Process group and session signals need to be delivered to just the 1224 * parent before the fork or both the parent and the child after the 1225 * fork. Restart if a signal comes in before we add the new process to 1226 * it's process group. 1227 * A fatal signal pending means that current will exit, so the new 1228 * thread can't slip out of an OOM kill (or normal SIGKILL). 1229 */ 1230 recalc_sigpending(); 1231 if (signal_pending(current)) { 1232 spin_unlock(¤t->sighand->siglock); 1233 write_unlock_irq(&tasklist_lock); 1234 retval = -ERESTARTNOINTR; 1235 goto bad_fork_free_graph; 1236 } 1237 1238 if (clone_flags & CLONE_THREAD) { 1239 p->group_leader = current->group_leader; 1240 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1241 } 1242 1243 if (likely(p->pid)) { 1244 list_add_tail(&p->sibling, &p->real_parent->children); 1245 tracehook_finish_clone(p, clone_flags, trace); 1246 1247 if (thread_group_leader(p)) { 1248 if (clone_flags & CLONE_NEWPID) 1249 p->nsproxy->pid_ns->child_reaper = p; 1250 1251 p->signal->leader_pid = pid; 1252 tty_kref_put(p->signal->tty); 1253 p->signal->tty = tty_kref_get(current->signal->tty); 1254 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1255 attach_pid(p, PIDTYPE_SID, task_session(current)); 1256 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1257 __get_cpu_var(process_counts)++; 1258 } 1259 attach_pid(p, PIDTYPE_PID, pid); 1260 nr_threads++; 1261 } 1262 1263 total_forks++; 1264 spin_unlock(¤t->sighand->siglock); 1265 write_unlock_irq(&tasklist_lock); 1266 proc_fork_connector(p); 1267 cgroup_post_fork(p); 1268 return p; 1269 1270 bad_fork_free_graph: 1271 ftrace_graph_exit_task(p); 1272 bad_fork_free_pid: 1273 if (pid != &init_struct_pid) 1274 free_pid(pid); 1275 bad_fork_cleanup_io: 1276 put_io_context(p->io_context); 1277 bad_fork_cleanup_namespaces: 1278 exit_task_namespaces(p); 1279 bad_fork_cleanup_mm: 1280 if (p->mm) 1281 mmput(p->mm); 1282 bad_fork_cleanup_signal: 1283 cleanup_signal(p); 1284 bad_fork_cleanup_sighand: 1285 __cleanup_sighand(p->sighand); 1286 bad_fork_cleanup_fs: 1287 exit_fs(p); /* blocking */ 1288 bad_fork_cleanup_files: 1289 exit_files(p); /* blocking */ 1290 bad_fork_cleanup_semundo: 1291 exit_sem(p); 1292 bad_fork_cleanup_audit: 1293 audit_free(p); 1294 bad_fork_cleanup_policy: 1295 #ifdef CONFIG_NUMA 1296 mpol_put(p->mempolicy); 1297 bad_fork_cleanup_cgroup: 1298 #endif 1299 cgroup_exit(p, cgroup_callbacks_done); 1300 delayacct_tsk_free(p); 1301 if (p->binfmt) 1302 module_put(p->binfmt->module); 1303 bad_fork_cleanup_put_domain: 1304 module_put(task_thread_info(p)->exec_domain->module); 1305 bad_fork_cleanup_count: 1306 atomic_dec(&p->cred->user->processes); 1307 put_cred(p->real_cred); 1308 put_cred(p->cred); 1309 bad_fork_free: 1310 free_task(p); 1311 fork_out: 1312 return ERR_PTR(retval); 1313 } 1314 1315 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1316 { 1317 memset(regs, 0, sizeof(struct pt_regs)); 1318 return regs; 1319 } 1320 1321 struct task_struct * __cpuinit fork_idle(int cpu) 1322 { 1323 struct task_struct *task; 1324 struct pt_regs regs; 1325 1326 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1327 &init_struct_pid, 0); 1328 if (!IS_ERR(task)) 1329 init_idle(task, cpu); 1330 1331 return task; 1332 } 1333 1334 /* 1335 * Ok, this is the main fork-routine. 1336 * 1337 * It copies the process, and if successful kick-starts 1338 * it and waits for it to finish using the VM if required. 1339 */ 1340 long do_fork(unsigned long clone_flags, 1341 unsigned long stack_start, 1342 struct pt_regs *regs, 1343 unsigned long stack_size, 1344 int __user *parent_tidptr, 1345 int __user *child_tidptr) 1346 { 1347 struct task_struct *p; 1348 int trace = 0; 1349 long nr; 1350 1351 /* 1352 * Do some preliminary argument and permissions checking before we 1353 * actually start allocating stuff 1354 */ 1355 if (clone_flags & CLONE_NEWUSER) { 1356 if (clone_flags & CLONE_THREAD) 1357 return -EINVAL; 1358 /* hopefully this check will go away when userns support is 1359 * complete 1360 */ 1361 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1362 !capable(CAP_SETGID)) 1363 return -EPERM; 1364 } 1365 1366 /* 1367 * We hope to recycle these flags after 2.6.26 1368 */ 1369 if (unlikely(clone_flags & CLONE_STOPPED)) { 1370 static int __read_mostly count = 100; 1371 1372 if (count > 0 && printk_ratelimit()) { 1373 char comm[TASK_COMM_LEN]; 1374 1375 count--; 1376 printk(KERN_INFO "fork(): process `%s' used deprecated " 1377 "clone flags 0x%lx\n", 1378 get_task_comm(comm, current), 1379 clone_flags & CLONE_STOPPED); 1380 } 1381 } 1382 1383 /* 1384 * When called from kernel_thread, don't do user tracing stuff. 1385 */ 1386 if (likely(user_mode(regs))) 1387 trace = tracehook_prepare_clone(clone_flags); 1388 1389 p = copy_process(clone_flags, stack_start, regs, stack_size, 1390 child_tidptr, NULL, trace); 1391 /* 1392 * Do this prior waking up the new thread - the thread pointer 1393 * might get invalid after that point, if the thread exits quickly. 1394 */ 1395 if (!IS_ERR(p)) { 1396 struct completion vfork; 1397 1398 trace_sched_process_fork(current, p); 1399 1400 nr = task_pid_vnr(p); 1401 1402 if (clone_flags & CLONE_PARENT_SETTID) 1403 put_user(nr, parent_tidptr); 1404 1405 if (clone_flags & CLONE_VFORK) { 1406 p->vfork_done = &vfork; 1407 init_completion(&vfork); 1408 } 1409 1410 audit_finish_fork(p); 1411 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1412 1413 /* 1414 * We set PF_STARTING at creation in case tracing wants to 1415 * use this to distinguish a fully live task from one that 1416 * hasn't gotten to tracehook_report_clone() yet. Now we 1417 * clear it and set the child going. 1418 */ 1419 p->flags &= ~PF_STARTING; 1420 1421 if (unlikely(clone_flags & CLONE_STOPPED)) { 1422 /* 1423 * We'll start up with an immediate SIGSTOP. 1424 */ 1425 sigaddset(&p->pending.signal, SIGSTOP); 1426 set_tsk_thread_flag(p, TIF_SIGPENDING); 1427 __set_task_state(p, TASK_STOPPED); 1428 } else { 1429 wake_up_new_task(p, clone_flags); 1430 } 1431 1432 tracehook_report_clone_complete(trace, regs, 1433 clone_flags, nr, p); 1434 1435 if (clone_flags & CLONE_VFORK) { 1436 freezer_do_not_count(); 1437 wait_for_completion(&vfork); 1438 freezer_count(); 1439 tracehook_report_vfork_done(p, nr); 1440 } 1441 } else { 1442 nr = PTR_ERR(p); 1443 } 1444 return nr; 1445 } 1446 1447 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1448 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1449 #endif 1450 1451 static void sighand_ctor(void *data) 1452 { 1453 struct sighand_struct *sighand = data; 1454 1455 spin_lock_init(&sighand->siglock); 1456 init_waitqueue_head(&sighand->signalfd_wqh); 1457 } 1458 1459 void __init proc_caches_init(void) 1460 { 1461 sighand_cachep = kmem_cache_create("sighand_cache", 1462 sizeof(struct sighand_struct), 0, 1463 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1464 sighand_ctor); 1465 signal_cachep = kmem_cache_create("signal_cache", 1466 sizeof(struct signal_struct), 0, 1467 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1468 files_cachep = kmem_cache_create("files_cache", 1469 sizeof(struct files_struct), 0, 1470 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1471 fs_cachep = kmem_cache_create("fs_cache", 1472 sizeof(struct fs_struct), 0, 1473 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1474 mm_cachep = kmem_cache_create("mm_struct", 1475 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1476 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1477 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1478 mmap_init(); 1479 } 1480 1481 /* 1482 * Check constraints on flags passed to the unshare system call and 1483 * force unsharing of additional process context as appropriate. 1484 */ 1485 static void check_unshare_flags(unsigned long *flags_ptr) 1486 { 1487 /* 1488 * If unsharing a thread from a thread group, must also 1489 * unshare vm. 1490 */ 1491 if (*flags_ptr & CLONE_THREAD) 1492 *flags_ptr |= CLONE_VM; 1493 1494 /* 1495 * If unsharing vm, must also unshare signal handlers. 1496 */ 1497 if (*flags_ptr & CLONE_VM) 1498 *flags_ptr |= CLONE_SIGHAND; 1499 1500 /* 1501 * If unsharing signal handlers and the task was created 1502 * using CLONE_THREAD, then must unshare the thread 1503 */ 1504 if ((*flags_ptr & CLONE_SIGHAND) && 1505 (atomic_read(¤t->signal->count) > 1)) 1506 *flags_ptr |= CLONE_THREAD; 1507 1508 /* 1509 * If unsharing namespace, must also unshare filesystem information. 1510 */ 1511 if (*flags_ptr & CLONE_NEWNS) 1512 *flags_ptr |= CLONE_FS; 1513 } 1514 1515 /* 1516 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1517 */ 1518 static int unshare_thread(unsigned long unshare_flags) 1519 { 1520 if (unshare_flags & CLONE_THREAD) 1521 return -EINVAL; 1522 1523 return 0; 1524 } 1525 1526 /* 1527 * Unshare the filesystem structure if it is being shared 1528 */ 1529 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1530 { 1531 struct fs_struct *fs = current->fs; 1532 1533 if (!(unshare_flags & CLONE_FS) || !fs) 1534 return 0; 1535 1536 /* don't need lock here; in the worst case we'll do useless copy */ 1537 if (fs->users == 1) 1538 return 0; 1539 1540 *new_fsp = copy_fs_struct(fs); 1541 if (!*new_fsp) 1542 return -ENOMEM; 1543 1544 return 0; 1545 } 1546 1547 /* 1548 * Unsharing of sighand is not supported yet 1549 */ 1550 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1551 { 1552 struct sighand_struct *sigh = current->sighand; 1553 1554 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1555 return -EINVAL; 1556 else 1557 return 0; 1558 } 1559 1560 /* 1561 * Unshare vm if it is being shared 1562 */ 1563 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1564 { 1565 struct mm_struct *mm = current->mm; 1566 1567 if ((unshare_flags & CLONE_VM) && 1568 (mm && atomic_read(&mm->mm_users) > 1)) { 1569 return -EINVAL; 1570 } 1571 1572 return 0; 1573 } 1574 1575 /* 1576 * Unshare file descriptor table if it is being shared 1577 */ 1578 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1579 { 1580 struct files_struct *fd = current->files; 1581 int error = 0; 1582 1583 if ((unshare_flags & CLONE_FILES) && 1584 (fd && atomic_read(&fd->count) > 1)) { 1585 *new_fdp = dup_fd(fd, &error); 1586 if (!*new_fdp) 1587 return error; 1588 } 1589 1590 return 0; 1591 } 1592 1593 /* 1594 * unshare allows a process to 'unshare' part of the process 1595 * context which was originally shared using clone. copy_* 1596 * functions used by do_fork() cannot be used here directly 1597 * because they modify an inactive task_struct that is being 1598 * constructed. Here we are modifying the current, active, 1599 * task_struct. 1600 */ 1601 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1602 { 1603 int err = 0; 1604 struct fs_struct *fs, *new_fs = NULL; 1605 struct sighand_struct *new_sigh = NULL; 1606 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1607 struct files_struct *fd, *new_fd = NULL; 1608 struct nsproxy *new_nsproxy = NULL; 1609 int do_sysvsem = 0; 1610 1611 check_unshare_flags(&unshare_flags); 1612 1613 /* Return -EINVAL for all unsupported flags */ 1614 err = -EINVAL; 1615 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1616 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1617 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1618 goto bad_unshare_out; 1619 1620 /* 1621 * CLONE_NEWIPC must also detach from the undolist: after switching 1622 * to a new ipc namespace, the semaphore arrays from the old 1623 * namespace are unreachable. 1624 */ 1625 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1626 do_sysvsem = 1; 1627 if ((err = unshare_thread(unshare_flags))) 1628 goto bad_unshare_out; 1629 if ((err = unshare_fs(unshare_flags, &new_fs))) 1630 goto bad_unshare_cleanup_thread; 1631 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1632 goto bad_unshare_cleanup_fs; 1633 if ((err = unshare_vm(unshare_flags, &new_mm))) 1634 goto bad_unshare_cleanup_sigh; 1635 if ((err = unshare_fd(unshare_flags, &new_fd))) 1636 goto bad_unshare_cleanup_vm; 1637 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1638 new_fs))) 1639 goto bad_unshare_cleanup_fd; 1640 1641 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1642 if (do_sysvsem) { 1643 /* 1644 * CLONE_SYSVSEM is equivalent to sys_exit(). 1645 */ 1646 exit_sem(current); 1647 } 1648 1649 if (new_nsproxy) { 1650 switch_task_namespaces(current, new_nsproxy); 1651 new_nsproxy = NULL; 1652 } 1653 1654 task_lock(current); 1655 1656 if (new_fs) { 1657 fs = current->fs; 1658 write_lock(&fs->lock); 1659 current->fs = new_fs; 1660 if (--fs->users) 1661 new_fs = NULL; 1662 else 1663 new_fs = fs; 1664 write_unlock(&fs->lock); 1665 } 1666 1667 if (new_mm) { 1668 mm = current->mm; 1669 active_mm = current->active_mm; 1670 current->mm = new_mm; 1671 current->active_mm = new_mm; 1672 activate_mm(active_mm, new_mm); 1673 new_mm = mm; 1674 } 1675 1676 if (new_fd) { 1677 fd = current->files; 1678 current->files = new_fd; 1679 new_fd = fd; 1680 } 1681 1682 task_unlock(current); 1683 } 1684 1685 if (new_nsproxy) 1686 put_nsproxy(new_nsproxy); 1687 1688 bad_unshare_cleanup_fd: 1689 if (new_fd) 1690 put_files_struct(new_fd); 1691 1692 bad_unshare_cleanup_vm: 1693 if (new_mm) 1694 mmput(new_mm); 1695 1696 bad_unshare_cleanup_sigh: 1697 if (new_sigh) 1698 if (atomic_dec_and_test(&new_sigh->count)) 1699 kmem_cache_free(sighand_cachep, new_sigh); 1700 1701 bad_unshare_cleanup_fs: 1702 if (new_fs) 1703 free_fs_struct(new_fs); 1704 1705 bad_unshare_cleanup_thread: 1706 bad_unshare_out: 1707 return err; 1708 } 1709 1710 /* 1711 * Helper to unshare the files of the current task. 1712 * We don't want to expose copy_files internals to 1713 * the exec layer of the kernel. 1714 */ 1715 1716 int unshare_files(struct files_struct **displaced) 1717 { 1718 struct task_struct *task = current; 1719 struct files_struct *copy = NULL; 1720 int error; 1721 1722 error = unshare_fd(CLONE_FILES, ©); 1723 if (error || !copy) { 1724 *displaced = NULL; 1725 return error; 1726 } 1727 *displaced = task->files; 1728 task_lock(task); 1729 task->files = copy; 1730 task_unlock(task); 1731 return 0; 1732 } 1733