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