1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/swap.h> 38 #include <linux/syscalls.h> 39 #include <linux/jiffies.h> 40 #include <linux/tracehook.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/ksm.h> 53 #include <linux/acct.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/freezer.h> 57 #include <linux/delayacct.h> 58 #include <linux/taskstats_kern.h> 59 #include <linux/random.h> 60 #include <linux/tty.h> 61 #include <linux/proc_fs.h> 62 #include <linux/blkdev.h> 63 #include <linux/fs_struct.h> 64 #include <linux/magic.h> 65 #include <linux/perf_event.h> 66 #include <linux/posix-timers.h> 67 #include <linux/user-return-notifier.h> 68 #include <linux/oom.h> 69 #include <linux/khugepaged.h> 70 71 #include <asm/pgtable.h> 72 #include <asm/pgalloc.h> 73 #include <asm/uaccess.h> 74 #include <asm/mmu_context.h> 75 #include <asm/cacheflush.h> 76 #include <asm/tlbflush.h> 77 78 #include <trace/events/sched.h> 79 80 /* 81 * Protected counters by write_lock_irq(&tasklist_lock) 82 */ 83 unsigned long total_forks; /* Handle normal Linux uptimes. */ 84 int nr_threads; /* The idle threads do not count.. */ 85 86 int max_threads; /* tunable limit on nr_threads */ 87 88 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 89 90 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 91 92 #ifdef CONFIG_PROVE_RCU 93 int lockdep_tasklist_lock_is_held(void) 94 { 95 return lockdep_is_held(&tasklist_lock); 96 } 97 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 98 #endif /* #ifdef CONFIG_PROVE_RCU */ 99 100 int nr_processes(void) 101 { 102 int cpu; 103 int total = 0; 104 105 for_each_possible_cpu(cpu) 106 total += per_cpu(process_counts, cpu); 107 108 return total; 109 } 110 111 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 112 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 113 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 114 static struct kmem_cache *task_struct_cachep; 115 #endif 116 117 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 118 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 119 { 120 #ifdef CONFIG_DEBUG_STACK_USAGE 121 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 122 #else 123 gfp_t mask = GFP_KERNEL; 124 #endif 125 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 126 } 127 128 static inline void free_thread_info(struct thread_info *ti) 129 { 130 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 131 } 132 #endif 133 134 /* SLAB cache for signal_struct structures (tsk->signal) */ 135 static struct kmem_cache *signal_cachep; 136 137 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 138 struct kmem_cache *sighand_cachep; 139 140 /* SLAB cache for files_struct structures (tsk->files) */ 141 struct kmem_cache *files_cachep; 142 143 /* SLAB cache for fs_struct structures (tsk->fs) */ 144 struct kmem_cache *fs_cachep; 145 146 /* SLAB cache for vm_area_struct structures */ 147 struct kmem_cache *vm_area_cachep; 148 149 /* SLAB cache for mm_struct structures (tsk->mm) */ 150 static struct kmem_cache *mm_cachep; 151 152 static void account_kernel_stack(struct thread_info *ti, int account) 153 { 154 struct zone *zone = page_zone(virt_to_page(ti)); 155 156 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 157 } 158 159 void free_task(struct task_struct *tsk) 160 { 161 prop_local_destroy_single(&tsk->dirties); 162 account_kernel_stack(tsk->stack, -1); 163 free_thread_info(tsk->stack); 164 rt_mutex_debug_task_free(tsk); 165 ftrace_graph_exit_task(tsk); 166 free_task_struct(tsk); 167 } 168 EXPORT_SYMBOL(free_task); 169 170 static inline void free_signal_struct(struct signal_struct *sig) 171 { 172 taskstats_tgid_free(sig); 173 sched_autogroup_exit(sig); 174 kmem_cache_free(signal_cachep, sig); 175 } 176 177 static inline void put_signal_struct(struct signal_struct *sig) 178 { 179 if (atomic_dec_and_test(&sig->sigcnt)) 180 free_signal_struct(sig); 181 } 182 183 void __put_task_struct(struct task_struct *tsk) 184 { 185 WARN_ON(!tsk->exit_state); 186 WARN_ON(atomic_read(&tsk->usage)); 187 WARN_ON(tsk == current); 188 189 exit_creds(tsk); 190 delayacct_tsk_free(tsk); 191 put_signal_struct(tsk->signal); 192 193 if (!profile_handoff_task(tsk)) 194 free_task(tsk); 195 } 196 EXPORT_SYMBOL_GPL(__put_task_struct); 197 198 /* 199 * macro override instead of weak attribute alias, to workaround 200 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 201 */ 202 #ifndef arch_task_cache_init 203 #define arch_task_cache_init() 204 #endif 205 206 void __init fork_init(unsigned long mempages) 207 { 208 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 209 #ifndef ARCH_MIN_TASKALIGN 210 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 211 #endif 212 /* create a slab on which task_structs can be allocated */ 213 task_struct_cachep = 214 kmem_cache_create("task_struct", sizeof(struct task_struct), 215 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 216 #endif 217 218 /* do the arch specific task caches init */ 219 arch_task_cache_init(); 220 221 /* 222 * The default maximum number of threads is set to a safe 223 * value: the thread structures can take up at most half 224 * of memory. 225 */ 226 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 227 228 /* 229 * we need to allow at least 20 threads to boot a system 230 */ 231 if(max_threads < 20) 232 max_threads = 20; 233 234 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 235 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 236 init_task.signal->rlim[RLIMIT_SIGPENDING] = 237 init_task.signal->rlim[RLIMIT_NPROC]; 238 } 239 240 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 241 struct task_struct *src) 242 { 243 *dst = *src; 244 return 0; 245 } 246 247 static struct task_struct *dup_task_struct(struct task_struct *orig) 248 { 249 struct task_struct *tsk; 250 struct thread_info *ti; 251 unsigned long *stackend; 252 253 int err; 254 255 prepare_to_copy(orig); 256 257 tsk = alloc_task_struct(); 258 if (!tsk) 259 return NULL; 260 261 ti = alloc_thread_info(tsk); 262 if (!ti) { 263 free_task_struct(tsk); 264 return NULL; 265 } 266 267 err = arch_dup_task_struct(tsk, orig); 268 if (err) 269 goto out; 270 271 tsk->stack = ti; 272 273 err = prop_local_init_single(&tsk->dirties); 274 if (err) 275 goto out; 276 277 setup_thread_stack(tsk, orig); 278 clear_user_return_notifier(tsk); 279 clear_tsk_need_resched(tsk); 280 stackend = end_of_stack(tsk); 281 *stackend = STACK_END_MAGIC; /* for overflow detection */ 282 283 #ifdef CONFIG_CC_STACKPROTECTOR 284 tsk->stack_canary = get_random_int(); 285 #endif 286 287 /* One for us, one for whoever does the "release_task()" (usually parent) */ 288 atomic_set(&tsk->usage,2); 289 atomic_set(&tsk->fs_excl, 0); 290 #ifdef CONFIG_BLK_DEV_IO_TRACE 291 tsk->btrace_seq = 0; 292 #endif 293 tsk->splice_pipe = NULL; 294 295 account_kernel_stack(ti, 1); 296 297 return tsk; 298 299 out: 300 free_thread_info(ti); 301 free_task_struct(tsk); 302 return NULL; 303 } 304 305 #ifdef CONFIG_MMU 306 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 307 { 308 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 309 struct rb_node **rb_link, *rb_parent; 310 int retval; 311 unsigned long charge; 312 struct mempolicy *pol; 313 314 down_write(&oldmm->mmap_sem); 315 flush_cache_dup_mm(oldmm); 316 /* 317 * Not linked in yet - no deadlock potential: 318 */ 319 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 320 321 mm->locked_vm = 0; 322 mm->mmap = NULL; 323 mm->mmap_cache = NULL; 324 mm->free_area_cache = oldmm->mmap_base; 325 mm->cached_hole_size = ~0UL; 326 mm->map_count = 0; 327 cpumask_clear(mm_cpumask(mm)); 328 mm->mm_rb = RB_ROOT; 329 rb_link = &mm->mm_rb.rb_node; 330 rb_parent = NULL; 331 pprev = &mm->mmap; 332 retval = ksm_fork(mm, oldmm); 333 if (retval) 334 goto out; 335 retval = khugepaged_fork(mm, oldmm); 336 if (retval) 337 goto out; 338 339 prev = NULL; 340 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 341 struct file *file; 342 343 if (mpnt->vm_flags & VM_DONTCOPY) { 344 long pages = vma_pages(mpnt); 345 mm->total_vm -= pages; 346 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 347 -pages); 348 continue; 349 } 350 charge = 0; 351 if (mpnt->vm_flags & VM_ACCOUNT) { 352 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 353 if (security_vm_enough_memory(len)) 354 goto fail_nomem; 355 charge = len; 356 } 357 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 358 if (!tmp) 359 goto fail_nomem; 360 *tmp = *mpnt; 361 INIT_LIST_HEAD(&tmp->anon_vma_chain); 362 pol = mpol_dup(vma_policy(mpnt)); 363 retval = PTR_ERR(pol); 364 if (IS_ERR(pol)) 365 goto fail_nomem_policy; 366 vma_set_policy(tmp, pol); 367 tmp->vm_mm = mm; 368 if (anon_vma_fork(tmp, mpnt)) 369 goto fail_nomem_anon_vma_fork; 370 tmp->vm_flags &= ~VM_LOCKED; 371 tmp->vm_next = tmp->vm_prev = NULL; 372 file = tmp->vm_file; 373 if (file) { 374 struct inode *inode = file->f_path.dentry->d_inode; 375 struct address_space *mapping = file->f_mapping; 376 377 get_file(file); 378 if (tmp->vm_flags & VM_DENYWRITE) 379 atomic_dec(&inode->i_writecount); 380 spin_lock(&mapping->i_mmap_lock); 381 if (tmp->vm_flags & VM_SHARED) 382 mapping->i_mmap_writable++; 383 tmp->vm_truncate_count = mpnt->vm_truncate_count; 384 flush_dcache_mmap_lock(mapping); 385 /* insert tmp into the share list, just after mpnt */ 386 vma_prio_tree_add(tmp, mpnt); 387 flush_dcache_mmap_unlock(mapping); 388 spin_unlock(&mapping->i_mmap_lock); 389 } 390 391 /* 392 * Clear hugetlb-related page reserves for children. This only 393 * affects MAP_PRIVATE mappings. Faults generated by the child 394 * are not guaranteed to succeed, even if read-only 395 */ 396 if (is_vm_hugetlb_page(tmp)) 397 reset_vma_resv_huge_pages(tmp); 398 399 /* 400 * Link in the new vma and copy the page table entries. 401 */ 402 *pprev = tmp; 403 pprev = &tmp->vm_next; 404 tmp->vm_prev = prev; 405 prev = tmp; 406 407 __vma_link_rb(mm, tmp, rb_link, rb_parent); 408 rb_link = &tmp->vm_rb.rb_right; 409 rb_parent = &tmp->vm_rb; 410 411 mm->map_count++; 412 retval = copy_page_range(mm, oldmm, mpnt); 413 414 if (tmp->vm_ops && tmp->vm_ops->open) 415 tmp->vm_ops->open(tmp); 416 417 if (retval) 418 goto out; 419 } 420 /* a new mm has just been created */ 421 arch_dup_mmap(oldmm, mm); 422 retval = 0; 423 out: 424 up_write(&mm->mmap_sem); 425 flush_tlb_mm(oldmm); 426 up_write(&oldmm->mmap_sem); 427 return retval; 428 fail_nomem_anon_vma_fork: 429 mpol_put(pol); 430 fail_nomem_policy: 431 kmem_cache_free(vm_area_cachep, tmp); 432 fail_nomem: 433 retval = -ENOMEM; 434 vm_unacct_memory(charge); 435 goto out; 436 } 437 438 static inline int mm_alloc_pgd(struct mm_struct * mm) 439 { 440 mm->pgd = pgd_alloc(mm); 441 if (unlikely(!mm->pgd)) 442 return -ENOMEM; 443 return 0; 444 } 445 446 static inline void mm_free_pgd(struct mm_struct * mm) 447 { 448 pgd_free(mm, mm->pgd); 449 } 450 #else 451 #define dup_mmap(mm, oldmm) (0) 452 #define mm_alloc_pgd(mm) (0) 453 #define mm_free_pgd(mm) 454 #endif /* CONFIG_MMU */ 455 456 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 457 458 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 459 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 460 461 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 462 463 static int __init coredump_filter_setup(char *s) 464 { 465 default_dump_filter = 466 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 467 MMF_DUMP_FILTER_MASK; 468 return 1; 469 } 470 471 __setup("coredump_filter=", coredump_filter_setup); 472 473 #include <linux/init_task.h> 474 475 static void mm_init_aio(struct mm_struct *mm) 476 { 477 #ifdef CONFIG_AIO 478 spin_lock_init(&mm->ioctx_lock); 479 INIT_HLIST_HEAD(&mm->ioctx_list); 480 #endif 481 } 482 483 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 484 { 485 atomic_set(&mm->mm_users, 1); 486 atomic_set(&mm->mm_count, 1); 487 init_rwsem(&mm->mmap_sem); 488 INIT_LIST_HEAD(&mm->mmlist); 489 mm->flags = (current->mm) ? 490 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 491 mm->core_state = NULL; 492 mm->nr_ptes = 0; 493 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 494 spin_lock_init(&mm->page_table_lock); 495 mm->free_area_cache = TASK_UNMAPPED_BASE; 496 mm->cached_hole_size = ~0UL; 497 mm_init_aio(mm); 498 mm_init_owner(mm, p); 499 atomic_set(&mm->oom_disable_count, 0); 500 501 if (likely(!mm_alloc_pgd(mm))) { 502 mm->def_flags = 0; 503 mmu_notifier_mm_init(mm); 504 return mm; 505 } 506 507 free_mm(mm); 508 return NULL; 509 } 510 511 /* 512 * Allocate and initialize an mm_struct. 513 */ 514 struct mm_struct * mm_alloc(void) 515 { 516 struct mm_struct * mm; 517 518 mm = allocate_mm(); 519 if (mm) { 520 memset(mm, 0, sizeof(*mm)); 521 mm = mm_init(mm, current); 522 } 523 return mm; 524 } 525 526 /* 527 * Called when the last reference to the mm 528 * is dropped: either by a lazy thread or by 529 * mmput. Free the page directory and the mm. 530 */ 531 void __mmdrop(struct mm_struct *mm) 532 { 533 BUG_ON(mm == &init_mm); 534 mm_free_pgd(mm); 535 destroy_context(mm); 536 mmu_notifier_mm_destroy(mm); 537 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 538 VM_BUG_ON(mm->pmd_huge_pte); 539 #endif 540 free_mm(mm); 541 } 542 EXPORT_SYMBOL_GPL(__mmdrop); 543 544 /* 545 * Decrement the use count and release all resources for an mm. 546 */ 547 void mmput(struct mm_struct *mm) 548 { 549 might_sleep(); 550 551 if (atomic_dec_and_test(&mm->mm_users)) { 552 exit_aio(mm); 553 ksm_exit(mm); 554 khugepaged_exit(mm); /* must run before exit_mmap */ 555 exit_mmap(mm); 556 set_mm_exe_file(mm, NULL); 557 if (!list_empty(&mm->mmlist)) { 558 spin_lock(&mmlist_lock); 559 list_del(&mm->mmlist); 560 spin_unlock(&mmlist_lock); 561 } 562 put_swap_token(mm); 563 if (mm->binfmt) 564 module_put(mm->binfmt->module); 565 mmdrop(mm); 566 } 567 } 568 EXPORT_SYMBOL_GPL(mmput); 569 570 /** 571 * get_task_mm - acquire a reference to the task's mm 572 * 573 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 574 * this kernel workthread has transiently adopted a user mm with use_mm, 575 * to do its AIO) is not set and if so returns a reference to it, after 576 * bumping up the use count. User must release the mm via mmput() 577 * after use. Typically used by /proc and ptrace. 578 */ 579 struct mm_struct *get_task_mm(struct task_struct *task) 580 { 581 struct mm_struct *mm; 582 583 task_lock(task); 584 mm = task->mm; 585 if (mm) { 586 if (task->flags & PF_KTHREAD) 587 mm = NULL; 588 else 589 atomic_inc(&mm->mm_users); 590 } 591 task_unlock(task); 592 return mm; 593 } 594 EXPORT_SYMBOL_GPL(get_task_mm); 595 596 /* Please note the differences between mmput and mm_release. 597 * mmput is called whenever we stop holding onto a mm_struct, 598 * error success whatever. 599 * 600 * mm_release is called after a mm_struct has been removed 601 * from the current process. 602 * 603 * This difference is important for error handling, when we 604 * only half set up a mm_struct for a new process and need to restore 605 * the old one. Because we mmput the new mm_struct before 606 * restoring the old one. . . 607 * Eric Biederman 10 January 1998 608 */ 609 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 610 { 611 struct completion *vfork_done = tsk->vfork_done; 612 613 /* Get rid of any futexes when releasing the mm */ 614 #ifdef CONFIG_FUTEX 615 if (unlikely(tsk->robust_list)) { 616 exit_robust_list(tsk); 617 tsk->robust_list = NULL; 618 } 619 #ifdef CONFIG_COMPAT 620 if (unlikely(tsk->compat_robust_list)) { 621 compat_exit_robust_list(tsk); 622 tsk->compat_robust_list = NULL; 623 } 624 #endif 625 if (unlikely(!list_empty(&tsk->pi_state_list))) 626 exit_pi_state_list(tsk); 627 #endif 628 629 /* Get rid of any cached register state */ 630 deactivate_mm(tsk, mm); 631 632 /* notify parent sleeping on vfork() */ 633 if (vfork_done) { 634 tsk->vfork_done = NULL; 635 complete(vfork_done); 636 } 637 638 /* 639 * If we're exiting normally, clear a user-space tid field if 640 * requested. We leave this alone when dying by signal, to leave 641 * the value intact in a core dump, and to save the unnecessary 642 * trouble otherwise. Userland only wants this done for a sys_exit. 643 */ 644 if (tsk->clear_child_tid) { 645 if (!(tsk->flags & PF_SIGNALED) && 646 atomic_read(&mm->mm_users) > 1) { 647 /* 648 * We don't check the error code - if userspace has 649 * not set up a proper pointer then tough luck. 650 */ 651 put_user(0, tsk->clear_child_tid); 652 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 653 1, NULL, NULL, 0); 654 } 655 tsk->clear_child_tid = NULL; 656 } 657 } 658 659 /* 660 * Allocate a new mm structure and copy contents from the 661 * mm structure of the passed in task structure. 662 */ 663 struct mm_struct *dup_mm(struct task_struct *tsk) 664 { 665 struct mm_struct *mm, *oldmm = current->mm; 666 int err; 667 668 if (!oldmm) 669 return NULL; 670 671 mm = allocate_mm(); 672 if (!mm) 673 goto fail_nomem; 674 675 memcpy(mm, oldmm, sizeof(*mm)); 676 677 /* Initializing for Swap token stuff */ 678 mm->token_priority = 0; 679 mm->last_interval = 0; 680 681 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 682 mm->pmd_huge_pte = NULL; 683 #endif 684 685 if (!mm_init(mm, tsk)) 686 goto fail_nomem; 687 688 if (init_new_context(tsk, mm)) 689 goto fail_nocontext; 690 691 dup_mm_exe_file(oldmm, mm); 692 693 err = dup_mmap(mm, oldmm); 694 if (err) 695 goto free_pt; 696 697 mm->hiwater_rss = get_mm_rss(mm); 698 mm->hiwater_vm = mm->total_vm; 699 700 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 701 goto free_pt; 702 703 return mm; 704 705 free_pt: 706 /* don't put binfmt in mmput, we haven't got module yet */ 707 mm->binfmt = NULL; 708 mmput(mm); 709 710 fail_nomem: 711 return NULL; 712 713 fail_nocontext: 714 /* 715 * If init_new_context() failed, we cannot use mmput() to free the mm 716 * because it calls destroy_context() 717 */ 718 mm_free_pgd(mm); 719 free_mm(mm); 720 return NULL; 721 } 722 723 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 724 { 725 struct mm_struct * mm, *oldmm; 726 int retval; 727 728 tsk->min_flt = tsk->maj_flt = 0; 729 tsk->nvcsw = tsk->nivcsw = 0; 730 #ifdef CONFIG_DETECT_HUNG_TASK 731 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 732 #endif 733 734 tsk->mm = NULL; 735 tsk->active_mm = NULL; 736 737 /* 738 * Are we cloning a kernel thread? 739 * 740 * We need to steal a active VM for that.. 741 */ 742 oldmm = current->mm; 743 if (!oldmm) 744 return 0; 745 746 if (clone_flags & CLONE_VM) { 747 atomic_inc(&oldmm->mm_users); 748 mm = oldmm; 749 goto good_mm; 750 } 751 752 retval = -ENOMEM; 753 mm = dup_mm(tsk); 754 if (!mm) 755 goto fail_nomem; 756 757 good_mm: 758 /* Initializing for Swap token stuff */ 759 mm->token_priority = 0; 760 mm->last_interval = 0; 761 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 762 atomic_inc(&mm->oom_disable_count); 763 764 tsk->mm = mm; 765 tsk->active_mm = mm; 766 return 0; 767 768 fail_nomem: 769 return retval; 770 } 771 772 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 773 { 774 struct fs_struct *fs = current->fs; 775 if (clone_flags & CLONE_FS) { 776 /* tsk->fs is already what we want */ 777 spin_lock(&fs->lock); 778 if (fs->in_exec) { 779 spin_unlock(&fs->lock); 780 return -EAGAIN; 781 } 782 fs->users++; 783 spin_unlock(&fs->lock); 784 return 0; 785 } 786 tsk->fs = copy_fs_struct(fs); 787 if (!tsk->fs) 788 return -ENOMEM; 789 return 0; 790 } 791 792 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 793 { 794 struct files_struct *oldf, *newf; 795 int error = 0; 796 797 /* 798 * A background process may not have any files ... 799 */ 800 oldf = current->files; 801 if (!oldf) 802 goto out; 803 804 if (clone_flags & CLONE_FILES) { 805 atomic_inc(&oldf->count); 806 goto out; 807 } 808 809 newf = dup_fd(oldf, &error); 810 if (!newf) 811 goto out; 812 813 tsk->files = newf; 814 error = 0; 815 out: 816 return error; 817 } 818 819 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 820 { 821 #ifdef CONFIG_BLOCK 822 struct io_context *ioc = current->io_context; 823 824 if (!ioc) 825 return 0; 826 /* 827 * Share io context with parent, if CLONE_IO is set 828 */ 829 if (clone_flags & CLONE_IO) { 830 tsk->io_context = ioc_task_link(ioc); 831 if (unlikely(!tsk->io_context)) 832 return -ENOMEM; 833 } else if (ioprio_valid(ioc->ioprio)) { 834 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 835 if (unlikely(!tsk->io_context)) 836 return -ENOMEM; 837 838 tsk->io_context->ioprio = ioc->ioprio; 839 } 840 #endif 841 return 0; 842 } 843 844 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 845 { 846 struct sighand_struct *sig; 847 848 if (clone_flags & CLONE_SIGHAND) { 849 atomic_inc(¤t->sighand->count); 850 return 0; 851 } 852 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 853 rcu_assign_pointer(tsk->sighand, sig); 854 if (!sig) 855 return -ENOMEM; 856 atomic_set(&sig->count, 1); 857 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 858 return 0; 859 } 860 861 void __cleanup_sighand(struct sighand_struct *sighand) 862 { 863 if (atomic_dec_and_test(&sighand->count)) 864 kmem_cache_free(sighand_cachep, sighand); 865 } 866 867 868 /* 869 * Initialize POSIX timer handling for a thread group. 870 */ 871 static void posix_cpu_timers_init_group(struct signal_struct *sig) 872 { 873 unsigned long cpu_limit; 874 875 /* Thread group counters. */ 876 thread_group_cputime_init(sig); 877 878 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 879 if (cpu_limit != RLIM_INFINITY) { 880 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 881 sig->cputimer.running = 1; 882 } 883 884 /* The timer lists. */ 885 INIT_LIST_HEAD(&sig->cpu_timers[0]); 886 INIT_LIST_HEAD(&sig->cpu_timers[1]); 887 INIT_LIST_HEAD(&sig->cpu_timers[2]); 888 } 889 890 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 891 { 892 struct signal_struct *sig; 893 894 if (clone_flags & CLONE_THREAD) 895 return 0; 896 897 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 898 tsk->signal = sig; 899 if (!sig) 900 return -ENOMEM; 901 902 sig->nr_threads = 1; 903 atomic_set(&sig->live, 1); 904 atomic_set(&sig->sigcnt, 1); 905 init_waitqueue_head(&sig->wait_chldexit); 906 if (clone_flags & CLONE_NEWPID) 907 sig->flags |= SIGNAL_UNKILLABLE; 908 sig->curr_target = tsk; 909 init_sigpending(&sig->shared_pending); 910 INIT_LIST_HEAD(&sig->posix_timers); 911 912 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 913 sig->real_timer.function = it_real_fn; 914 915 task_lock(current->group_leader); 916 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 917 task_unlock(current->group_leader); 918 919 posix_cpu_timers_init_group(sig); 920 921 tty_audit_fork(sig); 922 sched_autogroup_fork(sig); 923 924 sig->oom_adj = current->signal->oom_adj; 925 sig->oom_score_adj = current->signal->oom_score_adj; 926 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 927 928 mutex_init(&sig->cred_guard_mutex); 929 930 return 0; 931 } 932 933 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 934 { 935 unsigned long new_flags = p->flags; 936 937 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 938 new_flags |= PF_FORKNOEXEC; 939 new_flags |= PF_STARTING; 940 p->flags = new_flags; 941 clear_freeze_flag(p); 942 } 943 944 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 945 { 946 current->clear_child_tid = tidptr; 947 948 return task_pid_vnr(current); 949 } 950 951 static void rt_mutex_init_task(struct task_struct *p) 952 { 953 raw_spin_lock_init(&p->pi_lock); 954 #ifdef CONFIG_RT_MUTEXES 955 plist_head_init_raw(&p->pi_waiters, &p->pi_lock); 956 p->pi_blocked_on = NULL; 957 #endif 958 } 959 960 #ifdef CONFIG_MM_OWNER 961 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 962 { 963 mm->owner = p; 964 } 965 #endif /* CONFIG_MM_OWNER */ 966 967 /* 968 * Initialize POSIX timer handling for a single task. 969 */ 970 static void posix_cpu_timers_init(struct task_struct *tsk) 971 { 972 tsk->cputime_expires.prof_exp = cputime_zero; 973 tsk->cputime_expires.virt_exp = cputime_zero; 974 tsk->cputime_expires.sched_exp = 0; 975 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 976 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 977 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 978 } 979 980 /* 981 * This creates a new process as a copy of the old one, 982 * but does not actually start it yet. 983 * 984 * It copies the registers, and all the appropriate 985 * parts of the process environment (as per the clone 986 * flags). The actual kick-off is left to the caller. 987 */ 988 static struct task_struct *copy_process(unsigned long clone_flags, 989 unsigned long stack_start, 990 struct pt_regs *regs, 991 unsigned long stack_size, 992 int __user *child_tidptr, 993 struct pid *pid, 994 int trace) 995 { 996 int retval; 997 struct task_struct *p; 998 int cgroup_callbacks_done = 0; 999 1000 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1001 return ERR_PTR(-EINVAL); 1002 1003 /* 1004 * Thread groups must share signals as well, and detached threads 1005 * can only be started up within the thread group. 1006 */ 1007 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1008 return ERR_PTR(-EINVAL); 1009 1010 /* 1011 * Shared signal handlers imply shared VM. By way of the above, 1012 * thread groups also imply shared VM. Blocking this case allows 1013 * for various simplifications in other code. 1014 */ 1015 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1016 return ERR_PTR(-EINVAL); 1017 1018 /* 1019 * Siblings of global init remain as zombies on exit since they are 1020 * not reaped by their parent (swapper). To solve this and to avoid 1021 * multi-rooted process trees, prevent global and container-inits 1022 * from creating siblings. 1023 */ 1024 if ((clone_flags & CLONE_PARENT) && 1025 current->signal->flags & SIGNAL_UNKILLABLE) 1026 return ERR_PTR(-EINVAL); 1027 1028 retval = security_task_create(clone_flags); 1029 if (retval) 1030 goto fork_out; 1031 1032 retval = -ENOMEM; 1033 p = dup_task_struct(current); 1034 if (!p) 1035 goto fork_out; 1036 1037 ftrace_graph_init_task(p); 1038 1039 rt_mutex_init_task(p); 1040 1041 #ifdef CONFIG_PROVE_LOCKING 1042 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1043 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1044 #endif 1045 retval = -EAGAIN; 1046 if (atomic_read(&p->real_cred->user->processes) >= 1047 task_rlimit(p, RLIMIT_NPROC)) { 1048 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1049 p->real_cred->user != INIT_USER) 1050 goto bad_fork_free; 1051 } 1052 1053 retval = copy_creds(p, clone_flags); 1054 if (retval < 0) 1055 goto bad_fork_free; 1056 1057 /* 1058 * If multiple threads are within copy_process(), then this check 1059 * triggers too late. This doesn't hurt, the check is only there 1060 * to stop root fork bombs. 1061 */ 1062 retval = -EAGAIN; 1063 if (nr_threads >= max_threads) 1064 goto bad_fork_cleanup_count; 1065 1066 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1067 goto bad_fork_cleanup_count; 1068 1069 p->did_exec = 0; 1070 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1071 copy_flags(clone_flags, p); 1072 INIT_LIST_HEAD(&p->children); 1073 INIT_LIST_HEAD(&p->sibling); 1074 rcu_copy_process(p); 1075 p->vfork_done = NULL; 1076 spin_lock_init(&p->alloc_lock); 1077 1078 init_sigpending(&p->pending); 1079 1080 p->utime = cputime_zero; 1081 p->stime = cputime_zero; 1082 p->gtime = cputime_zero; 1083 p->utimescaled = cputime_zero; 1084 p->stimescaled = cputime_zero; 1085 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1086 p->prev_utime = cputime_zero; 1087 p->prev_stime = cputime_zero; 1088 #endif 1089 #if defined(SPLIT_RSS_COUNTING) 1090 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1091 #endif 1092 1093 p->default_timer_slack_ns = current->timer_slack_ns; 1094 1095 task_io_accounting_init(&p->ioac); 1096 acct_clear_integrals(p); 1097 1098 posix_cpu_timers_init(p); 1099 1100 p->lock_depth = -1; /* -1 = no lock */ 1101 do_posix_clock_monotonic_gettime(&p->start_time); 1102 p->real_start_time = p->start_time; 1103 monotonic_to_bootbased(&p->real_start_time); 1104 p->io_context = NULL; 1105 p->audit_context = NULL; 1106 cgroup_fork(p); 1107 #ifdef CONFIG_NUMA 1108 p->mempolicy = mpol_dup(p->mempolicy); 1109 if (IS_ERR(p->mempolicy)) { 1110 retval = PTR_ERR(p->mempolicy); 1111 p->mempolicy = NULL; 1112 goto bad_fork_cleanup_cgroup; 1113 } 1114 mpol_fix_fork_child_flag(p); 1115 #endif 1116 #ifdef CONFIG_TRACE_IRQFLAGS 1117 p->irq_events = 0; 1118 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1119 p->hardirqs_enabled = 1; 1120 #else 1121 p->hardirqs_enabled = 0; 1122 #endif 1123 p->hardirq_enable_ip = 0; 1124 p->hardirq_enable_event = 0; 1125 p->hardirq_disable_ip = _THIS_IP_; 1126 p->hardirq_disable_event = 0; 1127 p->softirqs_enabled = 1; 1128 p->softirq_enable_ip = _THIS_IP_; 1129 p->softirq_enable_event = 0; 1130 p->softirq_disable_ip = 0; 1131 p->softirq_disable_event = 0; 1132 p->hardirq_context = 0; 1133 p->softirq_context = 0; 1134 #endif 1135 #ifdef CONFIG_LOCKDEP 1136 p->lockdep_depth = 0; /* no locks held yet */ 1137 p->curr_chain_key = 0; 1138 p->lockdep_recursion = 0; 1139 #endif 1140 1141 #ifdef CONFIG_DEBUG_MUTEXES 1142 p->blocked_on = NULL; /* not blocked yet */ 1143 #endif 1144 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1145 p->memcg_batch.do_batch = 0; 1146 p->memcg_batch.memcg = NULL; 1147 #endif 1148 1149 /* Perform scheduler related setup. Assign this task to a CPU. */ 1150 sched_fork(p, clone_flags); 1151 1152 retval = perf_event_init_task(p); 1153 if (retval) 1154 goto bad_fork_cleanup_policy; 1155 1156 if ((retval = audit_alloc(p))) 1157 goto bad_fork_cleanup_policy; 1158 /* copy all the process information */ 1159 if ((retval = copy_semundo(clone_flags, p))) 1160 goto bad_fork_cleanup_audit; 1161 if ((retval = copy_files(clone_flags, p))) 1162 goto bad_fork_cleanup_semundo; 1163 if ((retval = copy_fs(clone_flags, p))) 1164 goto bad_fork_cleanup_files; 1165 if ((retval = copy_sighand(clone_flags, p))) 1166 goto bad_fork_cleanup_fs; 1167 if ((retval = copy_signal(clone_flags, p))) 1168 goto bad_fork_cleanup_sighand; 1169 if ((retval = copy_mm(clone_flags, p))) 1170 goto bad_fork_cleanup_signal; 1171 if ((retval = copy_namespaces(clone_flags, p))) 1172 goto bad_fork_cleanup_mm; 1173 if ((retval = copy_io(clone_flags, p))) 1174 goto bad_fork_cleanup_namespaces; 1175 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1176 if (retval) 1177 goto bad_fork_cleanup_io; 1178 1179 if (pid != &init_struct_pid) { 1180 retval = -ENOMEM; 1181 pid = alloc_pid(p->nsproxy->pid_ns); 1182 if (!pid) 1183 goto bad_fork_cleanup_io; 1184 1185 if (clone_flags & CLONE_NEWPID) { 1186 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1187 if (retval < 0) 1188 goto bad_fork_free_pid; 1189 } 1190 } 1191 1192 p->pid = pid_nr(pid); 1193 p->tgid = p->pid; 1194 if (clone_flags & CLONE_THREAD) 1195 p->tgid = current->tgid; 1196 1197 if (current->nsproxy != p->nsproxy) { 1198 retval = ns_cgroup_clone(p, pid); 1199 if (retval) 1200 goto bad_fork_free_pid; 1201 } 1202 1203 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1204 /* 1205 * Clear TID on mm_release()? 1206 */ 1207 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1208 #ifdef CONFIG_FUTEX 1209 p->robust_list = NULL; 1210 #ifdef CONFIG_COMPAT 1211 p->compat_robust_list = NULL; 1212 #endif 1213 INIT_LIST_HEAD(&p->pi_state_list); 1214 p->pi_state_cache = NULL; 1215 #endif 1216 /* 1217 * sigaltstack should be cleared when sharing the same VM 1218 */ 1219 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1220 p->sas_ss_sp = p->sas_ss_size = 0; 1221 1222 /* 1223 * Syscall tracing and stepping should be turned off in the 1224 * child regardless of CLONE_PTRACE. 1225 */ 1226 user_disable_single_step(p); 1227 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1228 #ifdef TIF_SYSCALL_EMU 1229 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1230 #endif 1231 clear_all_latency_tracing(p); 1232 1233 /* ok, now we should be set up.. */ 1234 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1235 p->pdeath_signal = 0; 1236 p->exit_state = 0; 1237 1238 /* 1239 * Ok, make it visible to the rest of the system. 1240 * We dont wake it up yet. 1241 */ 1242 p->group_leader = p; 1243 INIT_LIST_HEAD(&p->thread_group); 1244 1245 /* Now that the task is set up, run cgroup callbacks if 1246 * necessary. We need to run them before the task is visible 1247 * on the tasklist. */ 1248 cgroup_fork_callbacks(p); 1249 cgroup_callbacks_done = 1; 1250 1251 /* Need tasklist lock for parent etc handling! */ 1252 write_lock_irq(&tasklist_lock); 1253 1254 /* CLONE_PARENT re-uses the old parent */ 1255 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1256 p->real_parent = current->real_parent; 1257 p->parent_exec_id = current->parent_exec_id; 1258 } else { 1259 p->real_parent = current; 1260 p->parent_exec_id = current->self_exec_id; 1261 } 1262 1263 spin_lock(¤t->sighand->siglock); 1264 1265 /* 1266 * Process group and session signals need to be delivered to just the 1267 * parent before the fork or both the parent and the child after the 1268 * fork. Restart if a signal comes in before we add the new process to 1269 * it's process group. 1270 * A fatal signal pending means that current will exit, so the new 1271 * thread can't slip out of an OOM kill (or normal SIGKILL). 1272 */ 1273 recalc_sigpending(); 1274 if (signal_pending(current)) { 1275 spin_unlock(¤t->sighand->siglock); 1276 write_unlock_irq(&tasklist_lock); 1277 retval = -ERESTARTNOINTR; 1278 goto bad_fork_free_pid; 1279 } 1280 1281 if (clone_flags & CLONE_THREAD) { 1282 current->signal->nr_threads++; 1283 atomic_inc(¤t->signal->live); 1284 atomic_inc(¤t->signal->sigcnt); 1285 p->group_leader = current->group_leader; 1286 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1287 } 1288 1289 if (likely(p->pid)) { 1290 tracehook_finish_clone(p, clone_flags, trace); 1291 1292 if (thread_group_leader(p)) { 1293 if (clone_flags & CLONE_NEWPID) 1294 p->nsproxy->pid_ns->child_reaper = p; 1295 1296 p->signal->leader_pid = pid; 1297 p->signal->tty = tty_kref_get(current->signal->tty); 1298 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1299 attach_pid(p, PIDTYPE_SID, task_session(current)); 1300 list_add_tail(&p->sibling, &p->real_parent->children); 1301 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1302 __this_cpu_inc(process_counts); 1303 } 1304 attach_pid(p, PIDTYPE_PID, pid); 1305 nr_threads++; 1306 } 1307 1308 total_forks++; 1309 spin_unlock(¤t->sighand->siglock); 1310 write_unlock_irq(&tasklist_lock); 1311 proc_fork_connector(p); 1312 cgroup_post_fork(p); 1313 perf_event_fork(p); 1314 return p; 1315 1316 bad_fork_free_pid: 1317 if (pid != &init_struct_pid) 1318 free_pid(pid); 1319 bad_fork_cleanup_io: 1320 if (p->io_context) 1321 exit_io_context(p); 1322 bad_fork_cleanup_namespaces: 1323 exit_task_namespaces(p); 1324 bad_fork_cleanup_mm: 1325 if (p->mm) { 1326 task_lock(p); 1327 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) 1328 atomic_dec(&p->mm->oom_disable_count); 1329 task_unlock(p); 1330 mmput(p->mm); 1331 } 1332 bad_fork_cleanup_signal: 1333 if (!(clone_flags & CLONE_THREAD)) 1334 free_signal_struct(p->signal); 1335 bad_fork_cleanup_sighand: 1336 __cleanup_sighand(p->sighand); 1337 bad_fork_cleanup_fs: 1338 exit_fs(p); /* blocking */ 1339 bad_fork_cleanup_files: 1340 exit_files(p); /* blocking */ 1341 bad_fork_cleanup_semundo: 1342 exit_sem(p); 1343 bad_fork_cleanup_audit: 1344 audit_free(p); 1345 bad_fork_cleanup_policy: 1346 perf_event_free_task(p); 1347 #ifdef CONFIG_NUMA 1348 mpol_put(p->mempolicy); 1349 bad_fork_cleanup_cgroup: 1350 #endif 1351 cgroup_exit(p, cgroup_callbacks_done); 1352 delayacct_tsk_free(p); 1353 module_put(task_thread_info(p)->exec_domain->module); 1354 bad_fork_cleanup_count: 1355 atomic_dec(&p->cred->user->processes); 1356 exit_creds(p); 1357 bad_fork_free: 1358 free_task(p); 1359 fork_out: 1360 return ERR_PTR(retval); 1361 } 1362 1363 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1364 { 1365 memset(regs, 0, sizeof(struct pt_regs)); 1366 return regs; 1367 } 1368 1369 static inline void init_idle_pids(struct pid_link *links) 1370 { 1371 enum pid_type type; 1372 1373 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1374 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1375 links[type].pid = &init_struct_pid; 1376 } 1377 } 1378 1379 struct task_struct * __cpuinit fork_idle(int cpu) 1380 { 1381 struct task_struct *task; 1382 struct pt_regs regs; 1383 1384 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1385 &init_struct_pid, 0); 1386 if (!IS_ERR(task)) { 1387 init_idle_pids(task->pids); 1388 init_idle(task, cpu); 1389 } 1390 1391 return task; 1392 } 1393 1394 /* 1395 * Ok, this is the main fork-routine. 1396 * 1397 * It copies the process, and if successful kick-starts 1398 * it and waits for it to finish using the VM if required. 1399 */ 1400 long do_fork(unsigned long clone_flags, 1401 unsigned long stack_start, 1402 struct pt_regs *regs, 1403 unsigned long stack_size, 1404 int __user *parent_tidptr, 1405 int __user *child_tidptr) 1406 { 1407 struct task_struct *p; 1408 int trace = 0; 1409 long nr; 1410 1411 /* 1412 * Do some preliminary argument and permissions checking before we 1413 * actually start allocating stuff 1414 */ 1415 if (clone_flags & CLONE_NEWUSER) { 1416 if (clone_flags & CLONE_THREAD) 1417 return -EINVAL; 1418 /* hopefully this check will go away when userns support is 1419 * complete 1420 */ 1421 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1422 !capable(CAP_SETGID)) 1423 return -EPERM; 1424 } 1425 1426 /* 1427 * When called from kernel_thread, don't do user tracing stuff. 1428 */ 1429 if (likely(user_mode(regs))) 1430 trace = tracehook_prepare_clone(clone_flags); 1431 1432 p = copy_process(clone_flags, stack_start, regs, stack_size, 1433 child_tidptr, NULL, trace); 1434 /* 1435 * Do this prior waking up the new thread - the thread pointer 1436 * might get invalid after that point, if the thread exits quickly. 1437 */ 1438 if (!IS_ERR(p)) { 1439 struct completion vfork; 1440 1441 trace_sched_process_fork(current, p); 1442 1443 nr = task_pid_vnr(p); 1444 1445 if (clone_flags & CLONE_PARENT_SETTID) 1446 put_user(nr, parent_tidptr); 1447 1448 if (clone_flags & CLONE_VFORK) { 1449 p->vfork_done = &vfork; 1450 init_completion(&vfork); 1451 } 1452 1453 audit_finish_fork(p); 1454 tracehook_report_clone(regs, clone_flags, nr, p); 1455 1456 /* 1457 * We set PF_STARTING at creation in case tracing wants to 1458 * use this to distinguish a fully live task from one that 1459 * hasn't gotten to tracehook_report_clone() yet. Now we 1460 * clear it and set the child going. 1461 */ 1462 p->flags &= ~PF_STARTING; 1463 1464 wake_up_new_task(p, clone_flags); 1465 1466 tracehook_report_clone_complete(trace, regs, 1467 clone_flags, nr, p); 1468 1469 if (clone_flags & CLONE_VFORK) { 1470 freezer_do_not_count(); 1471 wait_for_completion(&vfork); 1472 freezer_count(); 1473 tracehook_report_vfork_done(p, nr); 1474 } 1475 } else { 1476 nr = PTR_ERR(p); 1477 } 1478 return nr; 1479 } 1480 1481 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1482 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1483 #endif 1484 1485 static void sighand_ctor(void *data) 1486 { 1487 struct sighand_struct *sighand = data; 1488 1489 spin_lock_init(&sighand->siglock); 1490 init_waitqueue_head(&sighand->signalfd_wqh); 1491 } 1492 1493 void __init proc_caches_init(void) 1494 { 1495 sighand_cachep = kmem_cache_create("sighand_cache", 1496 sizeof(struct sighand_struct), 0, 1497 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1498 SLAB_NOTRACK, sighand_ctor); 1499 signal_cachep = kmem_cache_create("signal_cache", 1500 sizeof(struct signal_struct), 0, 1501 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1502 files_cachep = kmem_cache_create("files_cache", 1503 sizeof(struct files_struct), 0, 1504 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1505 fs_cachep = kmem_cache_create("fs_cache", 1506 sizeof(struct fs_struct), 0, 1507 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1508 mm_cachep = kmem_cache_create("mm_struct", 1509 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1510 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1511 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1512 mmap_init(); 1513 } 1514 1515 /* 1516 * Check constraints on flags passed to the unshare system call and 1517 * force unsharing of additional process context as appropriate. 1518 */ 1519 static void check_unshare_flags(unsigned long *flags_ptr) 1520 { 1521 /* 1522 * If unsharing a thread from a thread group, must also 1523 * unshare vm. 1524 */ 1525 if (*flags_ptr & CLONE_THREAD) 1526 *flags_ptr |= CLONE_VM; 1527 1528 /* 1529 * If unsharing vm, must also unshare signal handlers. 1530 */ 1531 if (*flags_ptr & CLONE_VM) 1532 *flags_ptr |= CLONE_SIGHAND; 1533 1534 /* 1535 * If unsharing namespace, must also unshare filesystem information. 1536 */ 1537 if (*flags_ptr & CLONE_NEWNS) 1538 *flags_ptr |= CLONE_FS; 1539 } 1540 1541 /* 1542 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1543 */ 1544 static int unshare_thread(unsigned long unshare_flags) 1545 { 1546 if (unshare_flags & CLONE_THREAD) 1547 return -EINVAL; 1548 1549 return 0; 1550 } 1551 1552 /* 1553 * Unshare the filesystem structure if it is being shared 1554 */ 1555 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1556 { 1557 struct fs_struct *fs = current->fs; 1558 1559 if (!(unshare_flags & CLONE_FS) || !fs) 1560 return 0; 1561 1562 /* don't need lock here; in the worst case we'll do useless copy */ 1563 if (fs->users == 1) 1564 return 0; 1565 1566 *new_fsp = copy_fs_struct(fs); 1567 if (!*new_fsp) 1568 return -ENOMEM; 1569 1570 return 0; 1571 } 1572 1573 /* 1574 * Unsharing of sighand is not supported yet 1575 */ 1576 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1577 { 1578 struct sighand_struct *sigh = current->sighand; 1579 1580 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1581 return -EINVAL; 1582 else 1583 return 0; 1584 } 1585 1586 /* 1587 * Unshare vm if it is being shared 1588 */ 1589 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1590 { 1591 struct mm_struct *mm = current->mm; 1592 1593 if ((unshare_flags & CLONE_VM) && 1594 (mm && atomic_read(&mm->mm_users) > 1)) { 1595 return -EINVAL; 1596 } 1597 1598 return 0; 1599 } 1600 1601 /* 1602 * Unshare file descriptor table if it is being shared 1603 */ 1604 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1605 { 1606 struct files_struct *fd = current->files; 1607 int error = 0; 1608 1609 if ((unshare_flags & CLONE_FILES) && 1610 (fd && atomic_read(&fd->count) > 1)) { 1611 *new_fdp = dup_fd(fd, &error); 1612 if (!*new_fdp) 1613 return error; 1614 } 1615 1616 return 0; 1617 } 1618 1619 /* 1620 * unshare allows a process to 'unshare' part of the process 1621 * context which was originally shared using clone. copy_* 1622 * functions used by do_fork() cannot be used here directly 1623 * because they modify an inactive task_struct that is being 1624 * constructed. Here we are modifying the current, active, 1625 * task_struct. 1626 */ 1627 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1628 { 1629 int err = 0; 1630 struct fs_struct *fs, *new_fs = NULL; 1631 struct sighand_struct *new_sigh = NULL; 1632 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1633 struct files_struct *fd, *new_fd = NULL; 1634 struct nsproxy *new_nsproxy = NULL; 1635 int do_sysvsem = 0; 1636 1637 check_unshare_flags(&unshare_flags); 1638 1639 /* Return -EINVAL for all unsupported flags */ 1640 err = -EINVAL; 1641 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1642 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1643 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1644 goto bad_unshare_out; 1645 1646 /* 1647 * CLONE_NEWIPC must also detach from the undolist: after switching 1648 * to a new ipc namespace, the semaphore arrays from the old 1649 * namespace are unreachable. 1650 */ 1651 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1652 do_sysvsem = 1; 1653 if ((err = unshare_thread(unshare_flags))) 1654 goto bad_unshare_out; 1655 if ((err = unshare_fs(unshare_flags, &new_fs))) 1656 goto bad_unshare_cleanup_thread; 1657 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1658 goto bad_unshare_cleanup_fs; 1659 if ((err = unshare_vm(unshare_flags, &new_mm))) 1660 goto bad_unshare_cleanup_sigh; 1661 if ((err = unshare_fd(unshare_flags, &new_fd))) 1662 goto bad_unshare_cleanup_vm; 1663 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1664 new_fs))) 1665 goto bad_unshare_cleanup_fd; 1666 1667 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1668 if (do_sysvsem) { 1669 /* 1670 * CLONE_SYSVSEM is equivalent to sys_exit(). 1671 */ 1672 exit_sem(current); 1673 } 1674 1675 if (new_nsproxy) { 1676 switch_task_namespaces(current, new_nsproxy); 1677 new_nsproxy = NULL; 1678 } 1679 1680 task_lock(current); 1681 1682 if (new_fs) { 1683 fs = current->fs; 1684 spin_lock(&fs->lock); 1685 current->fs = new_fs; 1686 if (--fs->users) 1687 new_fs = NULL; 1688 else 1689 new_fs = fs; 1690 spin_unlock(&fs->lock); 1691 } 1692 1693 if (new_mm) { 1694 mm = current->mm; 1695 active_mm = current->active_mm; 1696 current->mm = new_mm; 1697 current->active_mm = new_mm; 1698 if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { 1699 atomic_dec(&mm->oom_disable_count); 1700 atomic_inc(&new_mm->oom_disable_count); 1701 } 1702 activate_mm(active_mm, new_mm); 1703 new_mm = mm; 1704 } 1705 1706 if (new_fd) { 1707 fd = current->files; 1708 current->files = new_fd; 1709 new_fd = fd; 1710 } 1711 1712 task_unlock(current); 1713 } 1714 1715 if (new_nsproxy) 1716 put_nsproxy(new_nsproxy); 1717 1718 bad_unshare_cleanup_fd: 1719 if (new_fd) 1720 put_files_struct(new_fd); 1721 1722 bad_unshare_cleanup_vm: 1723 if (new_mm) 1724 mmput(new_mm); 1725 1726 bad_unshare_cleanup_sigh: 1727 if (new_sigh) 1728 if (atomic_dec_and_test(&new_sigh->count)) 1729 kmem_cache_free(sighand_cachep, new_sigh); 1730 1731 bad_unshare_cleanup_fs: 1732 if (new_fs) 1733 free_fs_struct(new_fs); 1734 1735 bad_unshare_cleanup_thread: 1736 bad_unshare_out: 1737 return err; 1738 } 1739 1740 /* 1741 * Helper to unshare the files of the current task. 1742 * We don't want to expose copy_files internals to 1743 * the exec layer of the kernel. 1744 */ 1745 1746 int unshare_files(struct files_struct **displaced) 1747 { 1748 struct task_struct *task = current; 1749 struct files_struct *copy = NULL; 1750 int error; 1751 1752 error = unshare_fd(CLONE_FILES, ©); 1753 if (error || !copy) { 1754 *displaced = NULL; 1755 return error; 1756 } 1757 *displaced = task->files; 1758 task_lock(task); 1759 task->files = copy; 1760 task_unlock(task); 1761 return 0; 1762 } 1763