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/seccomp.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/kthread.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/proc_fs.h> 52 #include <linux/profile.h> 53 #include <linux/rmap.h> 54 #include <linux/ksm.h> 55 #include <linux/acct.h> 56 #include <linux/tsacct_kern.h> 57 #include <linux/cn_proc.h> 58 #include <linux/freezer.h> 59 #include <linux/delayacct.h> 60 #include <linux/taskstats_kern.h> 61 #include <linux/random.h> 62 #include <linux/tty.h> 63 #include <linux/blkdev.h> 64 #include <linux/fs_struct.h> 65 #include <linux/magic.h> 66 #include <linux/perf_event.h> 67 #include <linux/posix-timers.h> 68 #include <linux/user-return-notifier.h> 69 #include <linux/oom.h> 70 #include <linux/khugepaged.h> 71 #include <linux/signalfd.h> 72 #include <linux/uprobes.h> 73 74 #include <asm/pgtable.h> 75 #include <asm/pgalloc.h> 76 #include <asm/uaccess.h> 77 #include <asm/mmu_context.h> 78 #include <asm/cacheflush.h> 79 #include <asm/tlbflush.h> 80 81 #include <trace/events/sched.h> 82 83 #define CREATE_TRACE_POINTS 84 #include <trace/events/task.h> 85 86 /* 87 * Protected counters by write_lock_irq(&tasklist_lock) 88 */ 89 unsigned long total_forks; /* Handle normal Linux uptimes. */ 90 int nr_threads; /* The idle threads do not count.. */ 91 92 int max_threads; /* tunable limit on nr_threads */ 93 94 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 95 96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 97 98 #ifdef CONFIG_PROVE_RCU 99 int lockdep_tasklist_lock_is_held(void) 100 { 101 return lockdep_is_held(&tasklist_lock); 102 } 103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 104 #endif /* #ifdef CONFIG_PROVE_RCU */ 105 106 int nr_processes(void) 107 { 108 int cpu; 109 int total = 0; 110 111 for_each_possible_cpu(cpu) 112 total += per_cpu(process_counts, cpu); 113 114 return total; 115 } 116 117 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 118 static struct kmem_cache *task_struct_cachep; 119 120 static inline struct task_struct *alloc_task_struct_node(int node) 121 { 122 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 123 } 124 125 void __weak arch_release_task_struct(struct task_struct *tsk) { } 126 127 static inline void free_task_struct(struct task_struct *tsk) 128 { 129 arch_release_task_struct(tsk); 130 kmem_cache_free(task_struct_cachep, tsk); 131 } 132 #endif 133 134 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 135 void __weak arch_release_thread_info(struct thread_info *ti) { } 136 137 /* 138 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 139 * kmemcache based allocator. 140 */ 141 # if THREAD_SIZE >= PAGE_SIZE 142 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 143 int node) 144 { 145 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 146 THREAD_SIZE_ORDER); 147 148 return page ? page_address(page) : NULL; 149 } 150 151 static inline void free_thread_info(struct thread_info *ti) 152 { 153 arch_release_thread_info(ti); 154 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 155 } 156 # else 157 static struct kmem_cache *thread_info_cache; 158 159 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 160 int node) 161 { 162 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 163 } 164 165 static void free_thread_info(struct thread_info *ti) 166 { 167 arch_release_thread_info(ti); 168 kmem_cache_free(thread_info_cache, ti); 169 } 170 171 void thread_info_cache_init(void) 172 { 173 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 174 THREAD_SIZE, 0, NULL); 175 BUG_ON(thread_info_cache == NULL); 176 } 177 # endif 178 #endif 179 180 /* SLAB cache for signal_struct structures (tsk->signal) */ 181 static struct kmem_cache *signal_cachep; 182 183 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 184 struct kmem_cache *sighand_cachep; 185 186 /* SLAB cache for files_struct structures (tsk->files) */ 187 struct kmem_cache *files_cachep; 188 189 /* SLAB cache for fs_struct structures (tsk->fs) */ 190 struct kmem_cache *fs_cachep; 191 192 /* SLAB cache for vm_area_struct structures */ 193 struct kmem_cache *vm_area_cachep; 194 195 /* SLAB cache for mm_struct structures (tsk->mm) */ 196 static struct kmem_cache *mm_cachep; 197 198 static void account_kernel_stack(struct thread_info *ti, int account) 199 { 200 struct zone *zone = page_zone(virt_to_page(ti)); 201 202 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 203 } 204 205 void free_task(struct task_struct *tsk) 206 { 207 account_kernel_stack(tsk->stack, -1); 208 free_thread_info(tsk->stack); 209 rt_mutex_debug_task_free(tsk); 210 ftrace_graph_exit_task(tsk); 211 put_seccomp_filter(tsk); 212 free_task_struct(tsk); 213 } 214 EXPORT_SYMBOL(free_task); 215 216 static inline void free_signal_struct(struct signal_struct *sig) 217 { 218 taskstats_tgid_free(sig); 219 sched_autogroup_exit(sig); 220 kmem_cache_free(signal_cachep, sig); 221 } 222 223 static inline void put_signal_struct(struct signal_struct *sig) 224 { 225 if (atomic_dec_and_test(&sig->sigcnt)) 226 free_signal_struct(sig); 227 } 228 229 void __put_task_struct(struct task_struct *tsk) 230 { 231 WARN_ON(!tsk->exit_state); 232 WARN_ON(atomic_read(&tsk->usage)); 233 WARN_ON(tsk == current); 234 235 security_task_free(tsk); 236 exit_creds(tsk); 237 delayacct_tsk_free(tsk); 238 put_signal_struct(tsk->signal); 239 240 if (!profile_handoff_task(tsk)) 241 free_task(tsk); 242 } 243 EXPORT_SYMBOL_GPL(__put_task_struct); 244 245 void __init __weak arch_task_cache_init(void) { } 246 247 void __init fork_init(unsigned long mempages) 248 { 249 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 250 #ifndef ARCH_MIN_TASKALIGN 251 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 252 #endif 253 /* create a slab on which task_structs can be allocated */ 254 task_struct_cachep = 255 kmem_cache_create("task_struct", sizeof(struct task_struct), 256 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 257 #endif 258 259 /* do the arch specific task caches init */ 260 arch_task_cache_init(); 261 262 /* 263 * The default maximum number of threads is set to a safe 264 * value: the thread structures can take up at most half 265 * of memory. 266 */ 267 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 268 269 /* 270 * we need to allow at least 20 threads to boot a system 271 */ 272 if (max_threads < 20) 273 max_threads = 20; 274 275 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 276 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 277 init_task.signal->rlim[RLIMIT_SIGPENDING] = 278 init_task.signal->rlim[RLIMIT_NPROC]; 279 } 280 281 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 282 struct task_struct *src) 283 { 284 *dst = *src; 285 return 0; 286 } 287 288 static struct task_struct *dup_task_struct(struct task_struct *orig) 289 { 290 struct task_struct *tsk; 291 struct thread_info *ti; 292 unsigned long *stackend; 293 int node = tsk_fork_get_node(orig); 294 int err; 295 296 tsk = alloc_task_struct_node(node); 297 if (!tsk) 298 return NULL; 299 300 ti = alloc_thread_info_node(tsk, node); 301 if (!ti) { 302 free_task_struct(tsk); 303 return NULL; 304 } 305 306 err = arch_dup_task_struct(tsk, orig); 307 308 /* 309 * We defer looking at err, because we will need this setup 310 * for the clean up path to work correctly. 311 */ 312 tsk->stack = ti; 313 setup_thread_stack(tsk, orig); 314 315 if (err) 316 goto out; 317 318 clear_user_return_notifier(tsk); 319 clear_tsk_need_resched(tsk); 320 stackend = end_of_stack(tsk); 321 *stackend = STACK_END_MAGIC; /* for overflow detection */ 322 323 #ifdef CONFIG_CC_STACKPROTECTOR 324 tsk->stack_canary = get_random_int(); 325 #endif 326 327 /* 328 * One for us, one for whoever does the "release_task()" (usually 329 * parent) 330 */ 331 atomic_set(&tsk->usage, 2); 332 #ifdef CONFIG_BLK_DEV_IO_TRACE 333 tsk->btrace_seq = 0; 334 #endif 335 tsk->splice_pipe = NULL; 336 337 account_kernel_stack(ti, 1); 338 339 return tsk; 340 341 out: 342 free_thread_info(ti); 343 free_task_struct(tsk); 344 return NULL; 345 } 346 347 #ifdef CONFIG_MMU 348 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 349 { 350 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 351 struct rb_node **rb_link, *rb_parent; 352 int retval; 353 unsigned long charge; 354 struct mempolicy *pol; 355 356 down_write(&oldmm->mmap_sem); 357 flush_cache_dup_mm(oldmm); 358 /* 359 * Not linked in yet - no deadlock potential: 360 */ 361 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 362 363 mm->locked_vm = 0; 364 mm->mmap = NULL; 365 mm->mmap_cache = NULL; 366 mm->free_area_cache = oldmm->mmap_base; 367 mm->cached_hole_size = ~0UL; 368 mm->map_count = 0; 369 cpumask_clear(mm_cpumask(mm)); 370 mm->mm_rb = RB_ROOT; 371 rb_link = &mm->mm_rb.rb_node; 372 rb_parent = NULL; 373 pprev = &mm->mmap; 374 retval = ksm_fork(mm, oldmm); 375 if (retval) 376 goto out; 377 retval = khugepaged_fork(mm, oldmm); 378 if (retval) 379 goto out; 380 381 prev = NULL; 382 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 383 struct file *file; 384 385 if (mpnt->vm_flags & VM_DONTCOPY) { 386 long pages = vma_pages(mpnt); 387 mm->total_vm -= pages; 388 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 389 -pages); 390 continue; 391 } 392 charge = 0; 393 if (mpnt->vm_flags & VM_ACCOUNT) { 394 unsigned long len; 395 len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 396 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 397 goto fail_nomem; 398 charge = len; 399 } 400 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 401 if (!tmp) 402 goto fail_nomem; 403 *tmp = *mpnt; 404 INIT_LIST_HEAD(&tmp->anon_vma_chain); 405 pol = mpol_dup(vma_policy(mpnt)); 406 retval = PTR_ERR(pol); 407 if (IS_ERR(pol)) 408 goto fail_nomem_policy; 409 vma_set_policy(tmp, pol); 410 tmp->vm_mm = mm; 411 if (anon_vma_fork(tmp, mpnt)) 412 goto fail_nomem_anon_vma_fork; 413 tmp->vm_flags &= ~VM_LOCKED; 414 tmp->vm_next = tmp->vm_prev = NULL; 415 file = tmp->vm_file; 416 if (file) { 417 struct inode *inode = file->f_path.dentry->d_inode; 418 struct address_space *mapping = file->f_mapping; 419 420 get_file(file); 421 if (tmp->vm_flags & VM_DENYWRITE) 422 atomic_dec(&inode->i_writecount); 423 mutex_lock(&mapping->i_mmap_mutex); 424 if (tmp->vm_flags & VM_SHARED) 425 mapping->i_mmap_writable++; 426 flush_dcache_mmap_lock(mapping); 427 /* insert tmp into the share list, just after mpnt */ 428 vma_prio_tree_add(tmp, mpnt); 429 flush_dcache_mmap_unlock(mapping); 430 mutex_unlock(&mapping->i_mmap_mutex); 431 } 432 433 /* 434 * Clear hugetlb-related page reserves for children. This only 435 * affects MAP_PRIVATE mappings. Faults generated by the child 436 * are not guaranteed to succeed, even if read-only 437 */ 438 if (is_vm_hugetlb_page(tmp)) 439 reset_vma_resv_huge_pages(tmp); 440 441 /* 442 * Link in the new vma and copy the page table entries. 443 */ 444 *pprev = tmp; 445 pprev = &tmp->vm_next; 446 tmp->vm_prev = prev; 447 prev = tmp; 448 449 __vma_link_rb(mm, tmp, rb_link, rb_parent); 450 rb_link = &tmp->vm_rb.rb_right; 451 rb_parent = &tmp->vm_rb; 452 453 mm->map_count++; 454 retval = copy_page_range(mm, oldmm, mpnt); 455 456 if (tmp->vm_ops && tmp->vm_ops->open) 457 tmp->vm_ops->open(tmp); 458 459 if (retval) 460 goto out; 461 462 if (file && uprobe_mmap(tmp)) 463 goto out; 464 } 465 /* a new mm has just been created */ 466 arch_dup_mmap(oldmm, mm); 467 retval = 0; 468 out: 469 up_write(&mm->mmap_sem); 470 flush_tlb_mm(oldmm); 471 up_write(&oldmm->mmap_sem); 472 return retval; 473 fail_nomem_anon_vma_fork: 474 mpol_put(pol); 475 fail_nomem_policy: 476 kmem_cache_free(vm_area_cachep, tmp); 477 fail_nomem: 478 retval = -ENOMEM; 479 vm_unacct_memory(charge); 480 goto out; 481 } 482 483 static inline int mm_alloc_pgd(struct mm_struct *mm) 484 { 485 mm->pgd = pgd_alloc(mm); 486 if (unlikely(!mm->pgd)) 487 return -ENOMEM; 488 return 0; 489 } 490 491 static inline void mm_free_pgd(struct mm_struct *mm) 492 { 493 pgd_free(mm, mm->pgd); 494 } 495 #else 496 #define dup_mmap(mm, oldmm) (0) 497 #define mm_alloc_pgd(mm) (0) 498 #define mm_free_pgd(mm) 499 #endif /* CONFIG_MMU */ 500 501 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 502 503 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 504 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 505 506 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 507 508 static int __init coredump_filter_setup(char *s) 509 { 510 default_dump_filter = 511 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 512 MMF_DUMP_FILTER_MASK; 513 return 1; 514 } 515 516 __setup("coredump_filter=", coredump_filter_setup); 517 518 #include <linux/init_task.h> 519 520 static void mm_init_aio(struct mm_struct *mm) 521 { 522 #ifdef CONFIG_AIO 523 spin_lock_init(&mm->ioctx_lock); 524 INIT_HLIST_HEAD(&mm->ioctx_list); 525 #endif 526 } 527 528 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 529 { 530 atomic_set(&mm->mm_users, 1); 531 atomic_set(&mm->mm_count, 1); 532 init_rwsem(&mm->mmap_sem); 533 INIT_LIST_HEAD(&mm->mmlist); 534 mm->flags = (current->mm) ? 535 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 536 mm->core_state = NULL; 537 mm->nr_ptes = 0; 538 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 539 spin_lock_init(&mm->page_table_lock); 540 mm->free_area_cache = TASK_UNMAPPED_BASE; 541 mm->cached_hole_size = ~0UL; 542 mm_init_aio(mm); 543 mm_init_owner(mm, p); 544 545 if (likely(!mm_alloc_pgd(mm))) { 546 mm->def_flags = 0; 547 mmu_notifier_mm_init(mm); 548 return mm; 549 } 550 551 free_mm(mm); 552 return NULL; 553 } 554 555 static void check_mm(struct mm_struct *mm) 556 { 557 int i; 558 559 for (i = 0; i < NR_MM_COUNTERS; i++) { 560 long x = atomic_long_read(&mm->rss_stat.count[i]); 561 562 if (unlikely(x)) 563 printk(KERN_ALERT "BUG: Bad rss-counter state " 564 "mm:%p idx:%d val:%ld\n", mm, i, x); 565 } 566 567 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 568 VM_BUG_ON(mm->pmd_huge_pte); 569 #endif 570 } 571 572 /* 573 * Allocate and initialize an mm_struct. 574 */ 575 struct mm_struct *mm_alloc(void) 576 { 577 struct mm_struct *mm; 578 579 mm = allocate_mm(); 580 if (!mm) 581 return NULL; 582 583 memset(mm, 0, sizeof(*mm)); 584 mm_init_cpumask(mm); 585 return mm_init(mm, current); 586 } 587 588 /* 589 * Called when the last reference to the mm 590 * is dropped: either by a lazy thread or by 591 * mmput. Free the page directory and the mm. 592 */ 593 void __mmdrop(struct mm_struct *mm) 594 { 595 BUG_ON(mm == &init_mm); 596 mm_free_pgd(mm); 597 destroy_context(mm); 598 mmu_notifier_mm_destroy(mm); 599 check_mm(mm); 600 free_mm(mm); 601 } 602 EXPORT_SYMBOL_GPL(__mmdrop); 603 604 /* 605 * Decrement the use count and release all resources for an mm. 606 */ 607 void mmput(struct mm_struct *mm) 608 { 609 might_sleep(); 610 611 if (atomic_dec_and_test(&mm->mm_users)) { 612 uprobe_clear_state(mm); 613 exit_aio(mm); 614 ksm_exit(mm); 615 khugepaged_exit(mm); /* must run before exit_mmap */ 616 exit_mmap(mm); 617 set_mm_exe_file(mm, NULL); 618 if (!list_empty(&mm->mmlist)) { 619 spin_lock(&mmlist_lock); 620 list_del(&mm->mmlist); 621 spin_unlock(&mmlist_lock); 622 } 623 if (mm->binfmt) 624 module_put(mm->binfmt->module); 625 mmdrop(mm); 626 } 627 } 628 EXPORT_SYMBOL_GPL(mmput); 629 630 /* 631 * We added or removed a vma mapping the executable. The vmas are only mapped 632 * during exec and are not mapped with the mmap system call. 633 * Callers must hold down_write() on the mm's mmap_sem for these 634 */ 635 void added_exe_file_vma(struct mm_struct *mm) 636 { 637 mm->num_exe_file_vmas++; 638 } 639 640 void removed_exe_file_vma(struct mm_struct *mm) 641 { 642 mm->num_exe_file_vmas--; 643 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 644 fput(mm->exe_file); 645 mm->exe_file = NULL; 646 } 647 648 } 649 650 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 651 { 652 if (new_exe_file) 653 get_file(new_exe_file); 654 if (mm->exe_file) 655 fput(mm->exe_file); 656 mm->exe_file = new_exe_file; 657 mm->num_exe_file_vmas = 0; 658 } 659 660 struct file *get_mm_exe_file(struct mm_struct *mm) 661 { 662 struct file *exe_file; 663 664 /* We need mmap_sem to protect against races with removal of 665 * VM_EXECUTABLE vmas */ 666 down_read(&mm->mmap_sem); 667 exe_file = mm->exe_file; 668 if (exe_file) 669 get_file(exe_file); 670 up_read(&mm->mmap_sem); 671 return exe_file; 672 } 673 674 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 675 { 676 /* It's safe to write the exe_file pointer without exe_file_lock because 677 * this is called during fork when the task is not yet in /proc */ 678 newmm->exe_file = get_mm_exe_file(oldmm); 679 } 680 681 /** 682 * get_task_mm - acquire a reference to the task's mm 683 * 684 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 685 * this kernel workthread has transiently adopted a user mm with use_mm, 686 * to do its AIO) is not set and if so returns a reference to it, after 687 * bumping up the use count. User must release the mm via mmput() 688 * after use. Typically used by /proc and ptrace. 689 */ 690 struct mm_struct *get_task_mm(struct task_struct *task) 691 { 692 struct mm_struct *mm; 693 694 task_lock(task); 695 mm = task->mm; 696 if (mm) { 697 if (task->flags & PF_KTHREAD) 698 mm = NULL; 699 else 700 atomic_inc(&mm->mm_users); 701 } 702 task_unlock(task); 703 return mm; 704 } 705 EXPORT_SYMBOL_GPL(get_task_mm); 706 707 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 708 { 709 struct mm_struct *mm; 710 int err; 711 712 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 713 if (err) 714 return ERR_PTR(err); 715 716 mm = get_task_mm(task); 717 if (mm && mm != current->mm && 718 !ptrace_may_access(task, mode)) { 719 mmput(mm); 720 mm = ERR_PTR(-EACCES); 721 } 722 mutex_unlock(&task->signal->cred_guard_mutex); 723 724 return mm; 725 } 726 727 static void complete_vfork_done(struct task_struct *tsk) 728 { 729 struct completion *vfork; 730 731 task_lock(tsk); 732 vfork = tsk->vfork_done; 733 if (likely(vfork)) { 734 tsk->vfork_done = NULL; 735 complete(vfork); 736 } 737 task_unlock(tsk); 738 } 739 740 static int wait_for_vfork_done(struct task_struct *child, 741 struct completion *vfork) 742 { 743 int killed; 744 745 freezer_do_not_count(); 746 killed = wait_for_completion_killable(vfork); 747 freezer_count(); 748 749 if (killed) { 750 task_lock(child); 751 child->vfork_done = NULL; 752 task_unlock(child); 753 } 754 755 put_task_struct(child); 756 return killed; 757 } 758 759 /* Please note the differences between mmput and mm_release. 760 * mmput is called whenever we stop holding onto a mm_struct, 761 * error success whatever. 762 * 763 * mm_release is called after a mm_struct has been removed 764 * from the current process. 765 * 766 * This difference is important for error handling, when we 767 * only half set up a mm_struct for a new process and need to restore 768 * the old one. Because we mmput the new mm_struct before 769 * restoring the old one. . . 770 * Eric Biederman 10 January 1998 771 */ 772 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 773 { 774 /* Get rid of any futexes when releasing the mm */ 775 #ifdef CONFIG_FUTEX 776 if (unlikely(tsk->robust_list)) { 777 exit_robust_list(tsk); 778 tsk->robust_list = NULL; 779 } 780 #ifdef CONFIG_COMPAT 781 if (unlikely(tsk->compat_robust_list)) { 782 compat_exit_robust_list(tsk); 783 tsk->compat_robust_list = NULL; 784 } 785 #endif 786 if (unlikely(!list_empty(&tsk->pi_state_list))) 787 exit_pi_state_list(tsk); 788 #endif 789 790 uprobe_free_utask(tsk); 791 792 /* Get rid of any cached register state */ 793 deactivate_mm(tsk, mm); 794 795 /* 796 * If we're exiting normally, clear a user-space tid field if 797 * requested. We leave this alone when dying by signal, to leave 798 * the value intact in a core dump, and to save the unnecessary 799 * trouble, say, a killed vfork parent shouldn't touch this mm. 800 * Userland only wants this done for a sys_exit. 801 */ 802 if (tsk->clear_child_tid) { 803 if (!(tsk->flags & PF_SIGNALED) && 804 atomic_read(&mm->mm_users) > 1) { 805 /* 806 * We don't check the error code - if userspace has 807 * not set up a proper pointer then tough luck. 808 */ 809 put_user(0, tsk->clear_child_tid); 810 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 811 1, NULL, NULL, 0); 812 } 813 tsk->clear_child_tid = NULL; 814 } 815 816 /* 817 * All done, finally we can wake up parent and return this mm to him. 818 * Also kthread_stop() uses this completion for synchronization. 819 */ 820 if (tsk->vfork_done) 821 complete_vfork_done(tsk); 822 } 823 824 /* 825 * Allocate a new mm structure and copy contents from the 826 * mm structure of the passed in task structure. 827 */ 828 struct mm_struct *dup_mm(struct task_struct *tsk) 829 { 830 struct mm_struct *mm, *oldmm = current->mm; 831 int err; 832 833 if (!oldmm) 834 return NULL; 835 836 mm = allocate_mm(); 837 if (!mm) 838 goto fail_nomem; 839 840 memcpy(mm, oldmm, sizeof(*mm)); 841 mm_init_cpumask(mm); 842 843 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 844 mm->pmd_huge_pte = NULL; 845 #endif 846 uprobe_reset_state(mm); 847 848 if (!mm_init(mm, tsk)) 849 goto fail_nomem; 850 851 if (init_new_context(tsk, mm)) 852 goto fail_nocontext; 853 854 dup_mm_exe_file(oldmm, mm); 855 856 err = dup_mmap(mm, oldmm); 857 if (err) 858 goto free_pt; 859 860 mm->hiwater_rss = get_mm_rss(mm); 861 mm->hiwater_vm = mm->total_vm; 862 863 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 864 goto free_pt; 865 866 return mm; 867 868 free_pt: 869 /* don't put binfmt in mmput, we haven't got module yet */ 870 mm->binfmt = NULL; 871 mmput(mm); 872 873 fail_nomem: 874 return NULL; 875 876 fail_nocontext: 877 /* 878 * If init_new_context() failed, we cannot use mmput() to free the mm 879 * because it calls destroy_context() 880 */ 881 mm_free_pgd(mm); 882 free_mm(mm); 883 return NULL; 884 } 885 886 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 887 { 888 struct mm_struct *mm, *oldmm; 889 int retval; 890 891 tsk->min_flt = tsk->maj_flt = 0; 892 tsk->nvcsw = tsk->nivcsw = 0; 893 #ifdef CONFIG_DETECT_HUNG_TASK 894 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 895 #endif 896 897 tsk->mm = NULL; 898 tsk->active_mm = NULL; 899 900 /* 901 * Are we cloning a kernel thread? 902 * 903 * We need to steal a active VM for that.. 904 */ 905 oldmm = current->mm; 906 if (!oldmm) 907 return 0; 908 909 if (clone_flags & CLONE_VM) { 910 atomic_inc(&oldmm->mm_users); 911 mm = oldmm; 912 goto good_mm; 913 } 914 915 retval = -ENOMEM; 916 mm = dup_mm(tsk); 917 if (!mm) 918 goto fail_nomem; 919 920 good_mm: 921 tsk->mm = mm; 922 tsk->active_mm = mm; 923 return 0; 924 925 fail_nomem: 926 return retval; 927 } 928 929 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 930 { 931 struct fs_struct *fs = current->fs; 932 if (clone_flags & CLONE_FS) { 933 /* tsk->fs is already what we want */ 934 spin_lock(&fs->lock); 935 if (fs->in_exec) { 936 spin_unlock(&fs->lock); 937 return -EAGAIN; 938 } 939 fs->users++; 940 spin_unlock(&fs->lock); 941 return 0; 942 } 943 tsk->fs = copy_fs_struct(fs); 944 if (!tsk->fs) 945 return -ENOMEM; 946 return 0; 947 } 948 949 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 950 { 951 struct files_struct *oldf, *newf; 952 int error = 0; 953 954 /* 955 * A background process may not have any files ... 956 */ 957 oldf = current->files; 958 if (!oldf) 959 goto out; 960 961 if (clone_flags & CLONE_FILES) { 962 atomic_inc(&oldf->count); 963 goto out; 964 } 965 966 newf = dup_fd(oldf, &error); 967 if (!newf) 968 goto out; 969 970 tsk->files = newf; 971 error = 0; 972 out: 973 return error; 974 } 975 976 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 977 { 978 #ifdef CONFIG_BLOCK 979 struct io_context *ioc = current->io_context; 980 struct io_context *new_ioc; 981 982 if (!ioc) 983 return 0; 984 /* 985 * Share io context with parent, if CLONE_IO is set 986 */ 987 if (clone_flags & CLONE_IO) { 988 ioc_task_link(ioc); 989 tsk->io_context = ioc; 990 } else if (ioprio_valid(ioc->ioprio)) { 991 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 992 if (unlikely(!new_ioc)) 993 return -ENOMEM; 994 995 new_ioc->ioprio = ioc->ioprio; 996 put_io_context(new_ioc); 997 } 998 #endif 999 return 0; 1000 } 1001 1002 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1003 { 1004 struct sighand_struct *sig; 1005 1006 if (clone_flags & CLONE_SIGHAND) { 1007 atomic_inc(¤t->sighand->count); 1008 return 0; 1009 } 1010 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1011 rcu_assign_pointer(tsk->sighand, sig); 1012 if (!sig) 1013 return -ENOMEM; 1014 atomic_set(&sig->count, 1); 1015 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1016 return 0; 1017 } 1018 1019 void __cleanup_sighand(struct sighand_struct *sighand) 1020 { 1021 if (atomic_dec_and_test(&sighand->count)) { 1022 signalfd_cleanup(sighand); 1023 kmem_cache_free(sighand_cachep, sighand); 1024 } 1025 } 1026 1027 1028 /* 1029 * Initialize POSIX timer handling for a thread group. 1030 */ 1031 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1032 { 1033 unsigned long cpu_limit; 1034 1035 /* Thread group counters. */ 1036 thread_group_cputime_init(sig); 1037 1038 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1039 if (cpu_limit != RLIM_INFINITY) { 1040 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1041 sig->cputimer.running = 1; 1042 } 1043 1044 /* The timer lists. */ 1045 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1046 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1047 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1048 } 1049 1050 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1051 { 1052 struct signal_struct *sig; 1053 1054 if (clone_flags & CLONE_THREAD) 1055 return 0; 1056 1057 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1058 tsk->signal = sig; 1059 if (!sig) 1060 return -ENOMEM; 1061 1062 sig->nr_threads = 1; 1063 atomic_set(&sig->live, 1); 1064 atomic_set(&sig->sigcnt, 1); 1065 init_waitqueue_head(&sig->wait_chldexit); 1066 if (clone_flags & CLONE_NEWPID) 1067 sig->flags |= SIGNAL_UNKILLABLE; 1068 sig->curr_target = tsk; 1069 init_sigpending(&sig->shared_pending); 1070 INIT_LIST_HEAD(&sig->posix_timers); 1071 1072 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1073 sig->real_timer.function = it_real_fn; 1074 1075 task_lock(current->group_leader); 1076 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1077 task_unlock(current->group_leader); 1078 1079 posix_cpu_timers_init_group(sig); 1080 1081 tty_audit_fork(sig); 1082 sched_autogroup_fork(sig); 1083 1084 #ifdef CONFIG_CGROUPS 1085 init_rwsem(&sig->group_rwsem); 1086 #endif 1087 1088 sig->oom_adj = current->signal->oom_adj; 1089 sig->oom_score_adj = current->signal->oom_score_adj; 1090 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1091 1092 sig->has_child_subreaper = current->signal->has_child_subreaper || 1093 current->signal->is_child_subreaper; 1094 1095 mutex_init(&sig->cred_guard_mutex); 1096 1097 return 0; 1098 } 1099 1100 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1101 { 1102 unsigned long new_flags = p->flags; 1103 1104 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1105 new_flags |= PF_FORKNOEXEC; 1106 p->flags = new_flags; 1107 } 1108 1109 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1110 { 1111 current->clear_child_tid = tidptr; 1112 1113 return task_pid_vnr(current); 1114 } 1115 1116 static void rt_mutex_init_task(struct task_struct *p) 1117 { 1118 raw_spin_lock_init(&p->pi_lock); 1119 #ifdef CONFIG_RT_MUTEXES 1120 plist_head_init(&p->pi_waiters); 1121 p->pi_blocked_on = NULL; 1122 #endif 1123 } 1124 1125 #ifdef CONFIG_MM_OWNER 1126 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1127 { 1128 mm->owner = p; 1129 } 1130 #endif /* CONFIG_MM_OWNER */ 1131 1132 /* 1133 * Initialize POSIX timer handling for a single task. 1134 */ 1135 static void posix_cpu_timers_init(struct task_struct *tsk) 1136 { 1137 tsk->cputime_expires.prof_exp = 0; 1138 tsk->cputime_expires.virt_exp = 0; 1139 tsk->cputime_expires.sched_exp = 0; 1140 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1141 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1142 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1143 } 1144 1145 /* 1146 * This creates a new process as a copy of the old one, 1147 * but does not actually start it yet. 1148 * 1149 * It copies the registers, and all the appropriate 1150 * parts of the process environment (as per the clone 1151 * flags). The actual kick-off is left to the caller. 1152 */ 1153 static struct task_struct *copy_process(unsigned long clone_flags, 1154 unsigned long stack_start, 1155 struct pt_regs *regs, 1156 unsigned long stack_size, 1157 int __user *child_tidptr, 1158 struct pid *pid, 1159 int trace) 1160 { 1161 int retval; 1162 struct task_struct *p; 1163 int cgroup_callbacks_done = 0; 1164 1165 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1166 return ERR_PTR(-EINVAL); 1167 1168 /* 1169 * Thread groups must share signals as well, and detached threads 1170 * can only be started up within the thread group. 1171 */ 1172 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1173 return ERR_PTR(-EINVAL); 1174 1175 /* 1176 * Shared signal handlers imply shared VM. By way of the above, 1177 * thread groups also imply shared VM. Blocking this case allows 1178 * for various simplifications in other code. 1179 */ 1180 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1181 return ERR_PTR(-EINVAL); 1182 1183 /* 1184 * Siblings of global init remain as zombies on exit since they are 1185 * not reaped by their parent (swapper). To solve this and to avoid 1186 * multi-rooted process trees, prevent global and container-inits 1187 * from creating siblings. 1188 */ 1189 if ((clone_flags & CLONE_PARENT) && 1190 current->signal->flags & SIGNAL_UNKILLABLE) 1191 return ERR_PTR(-EINVAL); 1192 1193 retval = security_task_create(clone_flags); 1194 if (retval) 1195 goto fork_out; 1196 1197 retval = -ENOMEM; 1198 p = dup_task_struct(current); 1199 if (!p) 1200 goto fork_out; 1201 1202 ftrace_graph_init_task(p); 1203 get_seccomp_filter(p); 1204 1205 rt_mutex_init_task(p); 1206 1207 #ifdef CONFIG_PROVE_LOCKING 1208 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1209 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1210 #endif 1211 retval = -EAGAIN; 1212 if (atomic_read(&p->real_cred->user->processes) >= 1213 task_rlimit(p, RLIMIT_NPROC)) { 1214 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1215 p->real_cred->user != INIT_USER) 1216 goto bad_fork_free; 1217 } 1218 current->flags &= ~PF_NPROC_EXCEEDED; 1219 1220 retval = copy_creds(p, clone_flags); 1221 if (retval < 0) 1222 goto bad_fork_free; 1223 1224 /* 1225 * If multiple threads are within copy_process(), then this check 1226 * triggers too late. This doesn't hurt, the check is only there 1227 * to stop root fork bombs. 1228 */ 1229 retval = -EAGAIN; 1230 if (nr_threads >= max_threads) 1231 goto bad_fork_cleanup_count; 1232 1233 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1234 goto bad_fork_cleanup_count; 1235 1236 p->did_exec = 0; 1237 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1238 copy_flags(clone_flags, p); 1239 INIT_LIST_HEAD(&p->children); 1240 INIT_LIST_HEAD(&p->sibling); 1241 rcu_copy_process(p); 1242 p->vfork_done = NULL; 1243 spin_lock_init(&p->alloc_lock); 1244 1245 init_sigpending(&p->pending); 1246 1247 p->utime = p->stime = p->gtime = 0; 1248 p->utimescaled = p->stimescaled = 0; 1249 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1250 p->prev_utime = p->prev_stime = 0; 1251 #endif 1252 #if defined(SPLIT_RSS_COUNTING) 1253 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1254 #endif 1255 1256 p->default_timer_slack_ns = current->timer_slack_ns; 1257 1258 task_io_accounting_init(&p->ioac); 1259 acct_clear_integrals(p); 1260 1261 posix_cpu_timers_init(p); 1262 1263 do_posix_clock_monotonic_gettime(&p->start_time); 1264 p->real_start_time = p->start_time; 1265 monotonic_to_bootbased(&p->real_start_time); 1266 p->io_context = NULL; 1267 p->audit_context = NULL; 1268 if (clone_flags & CLONE_THREAD) 1269 threadgroup_change_begin(current); 1270 cgroup_fork(p); 1271 #ifdef CONFIG_NUMA 1272 p->mempolicy = mpol_dup(p->mempolicy); 1273 if (IS_ERR(p->mempolicy)) { 1274 retval = PTR_ERR(p->mempolicy); 1275 p->mempolicy = NULL; 1276 goto bad_fork_cleanup_cgroup; 1277 } 1278 mpol_fix_fork_child_flag(p); 1279 #endif 1280 #ifdef CONFIG_CPUSETS 1281 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1282 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1283 seqcount_init(&p->mems_allowed_seq); 1284 #endif 1285 #ifdef CONFIG_TRACE_IRQFLAGS 1286 p->irq_events = 0; 1287 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1288 p->hardirqs_enabled = 1; 1289 #else 1290 p->hardirqs_enabled = 0; 1291 #endif 1292 p->hardirq_enable_ip = 0; 1293 p->hardirq_enable_event = 0; 1294 p->hardirq_disable_ip = _THIS_IP_; 1295 p->hardirq_disable_event = 0; 1296 p->softirqs_enabled = 1; 1297 p->softirq_enable_ip = _THIS_IP_; 1298 p->softirq_enable_event = 0; 1299 p->softirq_disable_ip = 0; 1300 p->softirq_disable_event = 0; 1301 p->hardirq_context = 0; 1302 p->softirq_context = 0; 1303 #endif 1304 #ifdef CONFIG_LOCKDEP 1305 p->lockdep_depth = 0; /* no locks held yet */ 1306 p->curr_chain_key = 0; 1307 p->lockdep_recursion = 0; 1308 #endif 1309 1310 #ifdef CONFIG_DEBUG_MUTEXES 1311 p->blocked_on = NULL; /* not blocked yet */ 1312 #endif 1313 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1314 p->memcg_batch.do_batch = 0; 1315 p->memcg_batch.memcg = NULL; 1316 #endif 1317 1318 /* Perform scheduler related setup. Assign this task to a CPU. */ 1319 sched_fork(p); 1320 1321 retval = perf_event_init_task(p); 1322 if (retval) 1323 goto bad_fork_cleanup_policy; 1324 retval = audit_alloc(p); 1325 if (retval) 1326 goto bad_fork_cleanup_policy; 1327 /* copy all the process information */ 1328 retval = copy_semundo(clone_flags, p); 1329 if (retval) 1330 goto bad_fork_cleanup_audit; 1331 retval = copy_files(clone_flags, p); 1332 if (retval) 1333 goto bad_fork_cleanup_semundo; 1334 retval = copy_fs(clone_flags, p); 1335 if (retval) 1336 goto bad_fork_cleanup_files; 1337 retval = copy_sighand(clone_flags, p); 1338 if (retval) 1339 goto bad_fork_cleanup_fs; 1340 retval = copy_signal(clone_flags, p); 1341 if (retval) 1342 goto bad_fork_cleanup_sighand; 1343 retval = copy_mm(clone_flags, p); 1344 if (retval) 1345 goto bad_fork_cleanup_signal; 1346 retval = copy_namespaces(clone_flags, p); 1347 if (retval) 1348 goto bad_fork_cleanup_mm; 1349 retval = copy_io(clone_flags, p); 1350 if (retval) 1351 goto bad_fork_cleanup_namespaces; 1352 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1353 if (retval) 1354 goto bad_fork_cleanup_io; 1355 1356 if (pid != &init_struct_pid) { 1357 retval = -ENOMEM; 1358 pid = alloc_pid(p->nsproxy->pid_ns); 1359 if (!pid) 1360 goto bad_fork_cleanup_io; 1361 } 1362 1363 p->pid = pid_nr(pid); 1364 p->tgid = p->pid; 1365 if (clone_flags & CLONE_THREAD) 1366 p->tgid = current->tgid; 1367 1368 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1369 /* 1370 * Clear TID on mm_release()? 1371 */ 1372 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1373 #ifdef CONFIG_BLOCK 1374 p->plug = NULL; 1375 #endif 1376 #ifdef CONFIG_FUTEX 1377 p->robust_list = NULL; 1378 #ifdef CONFIG_COMPAT 1379 p->compat_robust_list = NULL; 1380 #endif 1381 INIT_LIST_HEAD(&p->pi_state_list); 1382 p->pi_state_cache = NULL; 1383 #endif 1384 uprobe_copy_process(p); 1385 /* 1386 * sigaltstack should be cleared when sharing the same VM 1387 */ 1388 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1389 p->sas_ss_sp = p->sas_ss_size = 0; 1390 1391 /* 1392 * Syscall tracing and stepping should be turned off in the 1393 * child regardless of CLONE_PTRACE. 1394 */ 1395 user_disable_single_step(p); 1396 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1397 #ifdef TIF_SYSCALL_EMU 1398 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1399 #endif 1400 clear_all_latency_tracing(p); 1401 1402 /* ok, now we should be set up.. */ 1403 if (clone_flags & CLONE_THREAD) 1404 p->exit_signal = -1; 1405 else if (clone_flags & CLONE_PARENT) 1406 p->exit_signal = current->group_leader->exit_signal; 1407 else 1408 p->exit_signal = (clone_flags & CSIGNAL); 1409 1410 p->pdeath_signal = 0; 1411 p->exit_state = 0; 1412 1413 p->nr_dirtied = 0; 1414 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1415 p->dirty_paused_when = 0; 1416 1417 /* 1418 * Ok, make it visible to the rest of the system. 1419 * We dont wake it up yet. 1420 */ 1421 p->group_leader = p; 1422 INIT_LIST_HEAD(&p->thread_group); 1423 INIT_HLIST_HEAD(&p->task_works); 1424 1425 /* Now that the task is set up, run cgroup callbacks if 1426 * necessary. We need to run them before the task is visible 1427 * on the tasklist. */ 1428 cgroup_fork_callbacks(p); 1429 cgroup_callbacks_done = 1; 1430 1431 /* Need tasklist lock for parent etc handling! */ 1432 write_lock_irq(&tasklist_lock); 1433 1434 /* CLONE_PARENT re-uses the old parent */ 1435 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1436 p->real_parent = current->real_parent; 1437 p->parent_exec_id = current->parent_exec_id; 1438 } else { 1439 p->real_parent = current; 1440 p->parent_exec_id = current->self_exec_id; 1441 } 1442 1443 spin_lock(¤t->sighand->siglock); 1444 1445 /* 1446 * Process group and session signals need to be delivered to just the 1447 * parent before the fork or both the parent and the child after the 1448 * fork. Restart if a signal comes in before we add the new process to 1449 * it's process group. 1450 * A fatal signal pending means that current will exit, so the new 1451 * thread can't slip out of an OOM kill (or normal SIGKILL). 1452 */ 1453 recalc_sigpending(); 1454 if (signal_pending(current)) { 1455 spin_unlock(¤t->sighand->siglock); 1456 write_unlock_irq(&tasklist_lock); 1457 retval = -ERESTARTNOINTR; 1458 goto bad_fork_free_pid; 1459 } 1460 1461 if (clone_flags & CLONE_THREAD) { 1462 current->signal->nr_threads++; 1463 atomic_inc(¤t->signal->live); 1464 atomic_inc(¤t->signal->sigcnt); 1465 p->group_leader = current->group_leader; 1466 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1467 } 1468 1469 if (likely(p->pid)) { 1470 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1471 1472 if (thread_group_leader(p)) { 1473 if (is_child_reaper(pid)) 1474 p->nsproxy->pid_ns->child_reaper = p; 1475 1476 p->signal->leader_pid = pid; 1477 p->signal->tty = tty_kref_get(current->signal->tty); 1478 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1479 attach_pid(p, PIDTYPE_SID, task_session(current)); 1480 list_add_tail(&p->sibling, &p->real_parent->children); 1481 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1482 __this_cpu_inc(process_counts); 1483 } 1484 attach_pid(p, PIDTYPE_PID, pid); 1485 nr_threads++; 1486 } 1487 1488 total_forks++; 1489 spin_unlock(¤t->sighand->siglock); 1490 write_unlock_irq(&tasklist_lock); 1491 proc_fork_connector(p); 1492 cgroup_post_fork(p); 1493 if (clone_flags & CLONE_THREAD) 1494 threadgroup_change_end(current); 1495 perf_event_fork(p); 1496 1497 trace_task_newtask(p, clone_flags); 1498 1499 return p; 1500 1501 bad_fork_free_pid: 1502 if (pid != &init_struct_pid) 1503 free_pid(pid); 1504 bad_fork_cleanup_io: 1505 if (p->io_context) 1506 exit_io_context(p); 1507 bad_fork_cleanup_namespaces: 1508 if (unlikely(clone_flags & CLONE_NEWPID)) 1509 pid_ns_release_proc(p->nsproxy->pid_ns); 1510 exit_task_namespaces(p); 1511 bad_fork_cleanup_mm: 1512 if (p->mm) 1513 mmput(p->mm); 1514 bad_fork_cleanup_signal: 1515 if (!(clone_flags & CLONE_THREAD)) 1516 free_signal_struct(p->signal); 1517 bad_fork_cleanup_sighand: 1518 __cleanup_sighand(p->sighand); 1519 bad_fork_cleanup_fs: 1520 exit_fs(p); /* blocking */ 1521 bad_fork_cleanup_files: 1522 exit_files(p); /* blocking */ 1523 bad_fork_cleanup_semundo: 1524 exit_sem(p); 1525 bad_fork_cleanup_audit: 1526 audit_free(p); 1527 bad_fork_cleanup_policy: 1528 perf_event_free_task(p); 1529 #ifdef CONFIG_NUMA 1530 mpol_put(p->mempolicy); 1531 bad_fork_cleanup_cgroup: 1532 #endif 1533 if (clone_flags & CLONE_THREAD) 1534 threadgroup_change_end(current); 1535 cgroup_exit(p, cgroup_callbacks_done); 1536 delayacct_tsk_free(p); 1537 module_put(task_thread_info(p)->exec_domain->module); 1538 bad_fork_cleanup_count: 1539 atomic_dec(&p->cred->user->processes); 1540 exit_creds(p); 1541 bad_fork_free: 1542 free_task(p); 1543 fork_out: 1544 return ERR_PTR(retval); 1545 } 1546 1547 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1548 { 1549 memset(regs, 0, sizeof(struct pt_regs)); 1550 return regs; 1551 } 1552 1553 static inline void init_idle_pids(struct pid_link *links) 1554 { 1555 enum pid_type type; 1556 1557 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1558 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1559 links[type].pid = &init_struct_pid; 1560 } 1561 } 1562 1563 struct task_struct * __cpuinit fork_idle(int cpu) 1564 { 1565 struct task_struct *task; 1566 struct pt_regs regs; 1567 1568 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1569 &init_struct_pid, 0); 1570 if (!IS_ERR(task)) { 1571 init_idle_pids(task->pids); 1572 init_idle(task, cpu); 1573 } 1574 1575 return task; 1576 } 1577 1578 /* 1579 * Ok, this is the main fork-routine. 1580 * 1581 * It copies the process, and if successful kick-starts 1582 * it and waits for it to finish using the VM if required. 1583 */ 1584 long do_fork(unsigned long clone_flags, 1585 unsigned long stack_start, 1586 struct pt_regs *regs, 1587 unsigned long stack_size, 1588 int __user *parent_tidptr, 1589 int __user *child_tidptr) 1590 { 1591 struct task_struct *p; 1592 int trace = 0; 1593 long nr; 1594 1595 /* 1596 * Do some preliminary argument and permissions checking before we 1597 * actually start allocating stuff 1598 */ 1599 if (clone_flags & CLONE_NEWUSER) { 1600 if (clone_flags & CLONE_THREAD) 1601 return -EINVAL; 1602 /* hopefully this check will go away when userns support is 1603 * complete 1604 */ 1605 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1606 !capable(CAP_SETGID)) 1607 return -EPERM; 1608 } 1609 1610 /* 1611 * Determine whether and which event to report to ptracer. When 1612 * called from kernel_thread or CLONE_UNTRACED is explicitly 1613 * requested, no event is reported; otherwise, report if the event 1614 * for the type of forking is enabled. 1615 */ 1616 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1617 if (clone_flags & CLONE_VFORK) 1618 trace = PTRACE_EVENT_VFORK; 1619 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1620 trace = PTRACE_EVENT_CLONE; 1621 else 1622 trace = PTRACE_EVENT_FORK; 1623 1624 if (likely(!ptrace_event_enabled(current, trace))) 1625 trace = 0; 1626 } 1627 1628 p = copy_process(clone_flags, stack_start, regs, stack_size, 1629 child_tidptr, NULL, trace); 1630 /* 1631 * Do this prior waking up the new thread - the thread pointer 1632 * might get invalid after that point, if the thread exits quickly. 1633 */ 1634 if (!IS_ERR(p)) { 1635 struct completion vfork; 1636 1637 trace_sched_process_fork(current, p); 1638 1639 nr = task_pid_vnr(p); 1640 1641 if (clone_flags & CLONE_PARENT_SETTID) 1642 put_user(nr, parent_tidptr); 1643 1644 if (clone_flags & CLONE_VFORK) { 1645 p->vfork_done = &vfork; 1646 init_completion(&vfork); 1647 get_task_struct(p); 1648 } 1649 1650 wake_up_new_task(p); 1651 1652 /* forking complete and child started to run, tell ptracer */ 1653 if (unlikely(trace)) 1654 ptrace_event(trace, nr); 1655 1656 if (clone_flags & CLONE_VFORK) { 1657 if (!wait_for_vfork_done(p, &vfork)) 1658 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1659 } 1660 } else { 1661 nr = PTR_ERR(p); 1662 } 1663 return nr; 1664 } 1665 1666 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1667 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1668 #endif 1669 1670 static void sighand_ctor(void *data) 1671 { 1672 struct sighand_struct *sighand = data; 1673 1674 spin_lock_init(&sighand->siglock); 1675 init_waitqueue_head(&sighand->signalfd_wqh); 1676 } 1677 1678 void __init proc_caches_init(void) 1679 { 1680 sighand_cachep = kmem_cache_create("sighand_cache", 1681 sizeof(struct sighand_struct), 0, 1682 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1683 SLAB_NOTRACK, sighand_ctor); 1684 signal_cachep = kmem_cache_create("signal_cache", 1685 sizeof(struct signal_struct), 0, 1686 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1687 files_cachep = kmem_cache_create("files_cache", 1688 sizeof(struct files_struct), 0, 1689 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1690 fs_cachep = kmem_cache_create("fs_cache", 1691 sizeof(struct fs_struct), 0, 1692 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1693 /* 1694 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1695 * whole struct cpumask for the OFFSTACK case. We could change 1696 * this to *only* allocate as much of it as required by the 1697 * maximum number of CPU's we can ever have. The cpumask_allocation 1698 * is at the end of the structure, exactly for that reason. 1699 */ 1700 mm_cachep = kmem_cache_create("mm_struct", 1701 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1702 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1703 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1704 mmap_init(); 1705 nsproxy_cache_init(); 1706 } 1707 1708 /* 1709 * Check constraints on flags passed to the unshare system call. 1710 */ 1711 static int check_unshare_flags(unsigned long unshare_flags) 1712 { 1713 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1714 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1715 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1716 return -EINVAL; 1717 /* 1718 * Not implemented, but pretend it works if there is nothing to 1719 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1720 * needs to unshare vm. 1721 */ 1722 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1723 /* FIXME: get_task_mm() increments ->mm_users */ 1724 if (atomic_read(¤t->mm->mm_users) > 1) 1725 return -EINVAL; 1726 } 1727 1728 return 0; 1729 } 1730 1731 /* 1732 * Unshare the filesystem structure if it is being shared 1733 */ 1734 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1735 { 1736 struct fs_struct *fs = current->fs; 1737 1738 if (!(unshare_flags & CLONE_FS) || !fs) 1739 return 0; 1740 1741 /* don't need lock here; in the worst case we'll do useless copy */ 1742 if (fs->users == 1) 1743 return 0; 1744 1745 *new_fsp = copy_fs_struct(fs); 1746 if (!*new_fsp) 1747 return -ENOMEM; 1748 1749 return 0; 1750 } 1751 1752 /* 1753 * Unshare file descriptor table if it is being shared 1754 */ 1755 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1756 { 1757 struct files_struct *fd = current->files; 1758 int error = 0; 1759 1760 if ((unshare_flags & CLONE_FILES) && 1761 (fd && atomic_read(&fd->count) > 1)) { 1762 *new_fdp = dup_fd(fd, &error); 1763 if (!*new_fdp) 1764 return error; 1765 } 1766 1767 return 0; 1768 } 1769 1770 /* 1771 * unshare allows a process to 'unshare' part of the process 1772 * context which was originally shared using clone. copy_* 1773 * functions used by do_fork() cannot be used here directly 1774 * because they modify an inactive task_struct that is being 1775 * constructed. Here we are modifying the current, active, 1776 * task_struct. 1777 */ 1778 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1779 { 1780 struct fs_struct *fs, *new_fs = NULL; 1781 struct files_struct *fd, *new_fd = NULL; 1782 struct nsproxy *new_nsproxy = NULL; 1783 int do_sysvsem = 0; 1784 int err; 1785 1786 err = check_unshare_flags(unshare_flags); 1787 if (err) 1788 goto bad_unshare_out; 1789 1790 /* 1791 * If unsharing namespace, must also unshare filesystem information. 1792 */ 1793 if (unshare_flags & CLONE_NEWNS) 1794 unshare_flags |= CLONE_FS; 1795 /* 1796 * CLONE_NEWIPC must also detach from the undolist: after switching 1797 * to a new ipc namespace, the semaphore arrays from the old 1798 * namespace are unreachable. 1799 */ 1800 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1801 do_sysvsem = 1; 1802 err = unshare_fs(unshare_flags, &new_fs); 1803 if (err) 1804 goto bad_unshare_out; 1805 err = unshare_fd(unshare_flags, &new_fd); 1806 if (err) 1807 goto bad_unshare_cleanup_fs; 1808 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1809 if (err) 1810 goto bad_unshare_cleanup_fd; 1811 1812 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1813 if (do_sysvsem) { 1814 /* 1815 * CLONE_SYSVSEM is equivalent to sys_exit(). 1816 */ 1817 exit_sem(current); 1818 } 1819 1820 if (new_nsproxy) { 1821 switch_task_namespaces(current, new_nsproxy); 1822 new_nsproxy = NULL; 1823 } 1824 1825 task_lock(current); 1826 1827 if (new_fs) { 1828 fs = current->fs; 1829 spin_lock(&fs->lock); 1830 current->fs = new_fs; 1831 if (--fs->users) 1832 new_fs = NULL; 1833 else 1834 new_fs = fs; 1835 spin_unlock(&fs->lock); 1836 } 1837 1838 if (new_fd) { 1839 fd = current->files; 1840 current->files = new_fd; 1841 new_fd = fd; 1842 } 1843 1844 task_unlock(current); 1845 } 1846 1847 if (new_nsproxy) 1848 put_nsproxy(new_nsproxy); 1849 1850 bad_unshare_cleanup_fd: 1851 if (new_fd) 1852 put_files_struct(new_fd); 1853 1854 bad_unshare_cleanup_fs: 1855 if (new_fs) 1856 free_fs_struct(new_fs); 1857 1858 bad_unshare_out: 1859 return err; 1860 } 1861 1862 /* 1863 * Helper to unshare the files of the current task. 1864 * We don't want to expose copy_files internals to 1865 * the exec layer of the kernel. 1866 */ 1867 1868 int unshare_files(struct files_struct **displaced) 1869 { 1870 struct task_struct *task = current; 1871 struct files_struct *copy = NULL; 1872 int error; 1873 1874 error = unshare_fd(CLONE_FILES, ©); 1875 if (error || !copy) { 1876 *displaced = NULL; 1877 return error; 1878 } 1879 *displaced = task->files; 1880 task_lock(task); 1881 task->files = copy; 1882 task_unlock(task); 1883 return 0; 1884 } 1885