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/futex.h> 41 #include <linux/compat.h> 42 #include <linux/kthread.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/blkdev.h> 62 #include <linux/fs_struct.h> 63 #include <linux/magic.h> 64 #include <linux/perf_event.h> 65 #include <linux/posix-timers.h> 66 #include <linux/user-return-notifier.h> 67 #include <linux/oom.h> 68 #include <linux/khugepaged.h> 69 70 #include <asm/pgtable.h> 71 #include <asm/pgalloc.h> 72 #include <asm/uaccess.h> 73 #include <asm/mmu_context.h> 74 #include <asm/cacheflush.h> 75 #include <asm/tlbflush.h> 76 77 #include <trace/events/sched.h> 78 79 /* 80 * Protected counters by write_lock_irq(&tasklist_lock) 81 */ 82 unsigned long total_forks; /* Handle normal Linux uptimes. */ 83 int nr_threads; /* The idle threads do not count.. */ 84 85 int max_threads; /* tunable limit on nr_threads */ 86 87 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 88 89 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 90 91 #ifdef CONFIG_PROVE_RCU 92 int lockdep_tasklist_lock_is_held(void) 93 { 94 return lockdep_is_held(&tasklist_lock); 95 } 96 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 97 #endif /* #ifdef CONFIG_PROVE_RCU */ 98 99 int nr_processes(void) 100 { 101 int cpu; 102 int total = 0; 103 104 for_each_possible_cpu(cpu) 105 total += per_cpu(process_counts, cpu); 106 107 return total; 108 } 109 110 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 111 # define alloc_task_struct_node(node) \ 112 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node) 113 # define free_task_struct(tsk) \ 114 kmem_cache_free(task_struct_cachep, (tsk)) 115 static struct kmem_cache *task_struct_cachep; 116 #endif 117 118 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 119 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 120 int node) 121 { 122 #ifdef CONFIG_DEBUG_STACK_USAGE 123 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 124 #else 125 gfp_t mask = GFP_KERNEL; 126 #endif 127 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER); 128 129 return page ? page_address(page) : NULL; 130 } 131 132 static inline void free_thread_info(struct thread_info *ti) 133 { 134 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 135 } 136 #endif 137 138 /* SLAB cache for signal_struct structures (tsk->signal) */ 139 static struct kmem_cache *signal_cachep; 140 141 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 142 struct kmem_cache *sighand_cachep; 143 144 /* SLAB cache for files_struct structures (tsk->files) */ 145 struct kmem_cache *files_cachep; 146 147 /* SLAB cache for fs_struct structures (tsk->fs) */ 148 struct kmem_cache *fs_cachep; 149 150 /* SLAB cache for vm_area_struct structures */ 151 struct kmem_cache *vm_area_cachep; 152 153 /* SLAB cache for mm_struct structures (tsk->mm) */ 154 static struct kmem_cache *mm_cachep; 155 156 static void account_kernel_stack(struct thread_info *ti, int account) 157 { 158 struct zone *zone = page_zone(virt_to_page(ti)); 159 160 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 161 } 162 163 void free_task(struct task_struct *tsk) 164 { 165 account_kernel_stack(tsk->stack, -1); 166 free_thread_info(tsk->stack); 167 rt_mutex_debug_task_free(tsk); 168 ftrace_graph_exit_task(tsk); 169 free_task_struct(tsk); 170 } 171 EXPORT_SYMBOL(free_task); 172 173 static inline void free_signal_struct(struct signal_struct *sig) 174 { 175 taskstats_tgid_free(sig); 176 sched_autogroup_exit(sig); 177 kmem_cache_free(signal_cachep, sig); 178 } 179 180 static inline void put_signal_struct(struct signal_struct *sig) 181 { 182 if (atomic_dec_and_test(&sig->sigcnt)) 183 free_signal_struct(sig); 184 } 185 186 void __put_task_struct(struct task_struct *tsk) 187 { 188 WARN_ON(!tsk->exit_state); 189 WARN_ON(atomic_read(&tsk->usage)); 190 WARN_ON(tsk == current); 191 192 exit_creds(tsk); 193 delayacct_tsk_free(tsk); 194 put_signal_struct(tsk->signal); 195 196 if (!profile_handoff_task(tsk)) 197 free_task(tsk); 198 } 199 EXPORT_SYMBOL_GPL(__put_task_struct); 200 201 /* 202 * macro override instead of weak attribute alias, to workaround 203 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 204 */ 205 #ifndef arch_task_cache_init 206 #define arch_task_cache_init() 207 #endif 208 209 void __init fork_init(unsigned long mempages) 210 { 211 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 212 #ifndef ARCH_MIN_TASKALIGN 213 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 214 #endif 215 /* create a slab on which task_structs can be allocated */ 216 task_struct_cachep = 217 kmem_cache_create("task_struct", sizeof(struct task_struct), 218 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 219 #endif 220 221 /* do the arch specific task caches init */ 222 arch_task_cache_init(); 223 224 /* 225 * The default maximum number of threads is set to a safe 226 * value: the thread structures can take up at most half 227 * of memory. 228 */ 229 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 230 231 /* 232 * we need to allow at least 20 threads to boot a system 233 */ 234 if (max_threads < 20) 235 max_threads = 20; 236 237 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 238 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 239 init_task.signal->rlim[RLIMIT_SIGPENDING] = 240 init_task.signal->rlim[RLIMIT_NPROC]; 241 } 242 243 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 244 struct task_struct *src) 245 { 246 *dst = *src; 247 return 0; 248 } 249 250 static struct task_struct *dup_task_struct(struct task_struct *orig) 251 { 252 struct task_struct *tsk; 253 struct thread_info *ti; 254 unsigned long *stackend; 255 int node = tsk_fork_get_node(orig); 256 int err; 257 258 prepare_to_copy(orig); 259 260 tsk = alloc_task_struct_node(node); 261 if (!tsk) 262 return NULL; 263 264 ti = alloc_thread_info_node(tsk, node); 265 if (!ti) { 266 free_task_struct(tsk); 267 return NULL; 268 } 269 270 err = arch_dup_task_struct(tsk, orig); 271 if (err) 272 goto out; 273 274 tsk->stack = ti; 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 /* 287 * One for us, one for whoever does the "release_task()" (usually 288 * parent) 289 */ 290 atomic_set(&tsk->usage, 2); 291 #ifdef CONFIG_BLK_DEV_IO_TRACE 292 tsk->btrace_seq = 0; 293 #endif 294 tsk->splice_pipe = NULL; 295 296 account_kernel_stack(ti, 1); 297 298 return tsk; 299 300 out: 301 free_thread_info(ti); 302 free_task_struct(tsk); 303 return NULL; 304 } 305 306 #ifdef CONFIG_MMU 307 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 308 { 309 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 310 struct rb_node **rb_link, *rb_parent; 311 int retval; 312 unsigned long charge; 313 struct mempolicy *pol; 314 315 down_write(&oldmm->mmap_sem); 316 flush_cache_dup_mm(oldmm); 317 /* 318 * Not linked in yet - no deadlock potential: 319 */ 320 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 321 322 mm->locked_vm = 0; 323 mm->mmap = NULL; 324 mm->mmap_cache = NULL; 325 mm->free_area_cache = oldmm->mmap_base; 326 mm->cached_hole_size = ~0UL; 327 mm->map_count = 0; 328 cpumask_clear(mm_cpumask(mm)); 329 mm->mm_rb = RB_ROOT; 330 rb_link = &mm->mm_rb.rb_node; 331 rb_parent = NULL; 332 pprev = &mm->mmap; 333 retval = ksm_fork(mm, oldmm); 334 if (retval) 335 goto out; 336 retval = khugepaged_fork(mm, oldmm); 337 if (retval) 338 goto out; 339 340 prev = NULL; 341 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 342 struct file *file; 343 344 if (mpnt->vm_flags & VM_DONTCOPY) { 345 long pages = vma_pages(mpnt); 346 mm->total_vm -= pages; 347 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 348 -pages); 349 continue; 350 } 351 charge = 0; 352 if (mpnt->vm_flags & VM_ACCOUNT) { 353 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 354 if (security_vm_enough_memory(len)) 355 goto fail_nomem; 356 charge = len; 357 } 358 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 359 if (!tmp) 360 goto fail_nomem; 361 *tmp = *mpnt; 362 INIT_LIST_HEAD(&tmp->anon_vma_chain); 363 pol = mpol_dup(vma_policy(mpnt)); 364 retval = PTR_ERR(pol); 365 if (IS_ERR(pol)) 366 goto fail_nomem_policy; 367 vma_set_policy(tmp, pol); 368 tmp->vm_mm = mm; 369 if (anon_vma_fork(tmp, mpnt)) 370 goto fail_nomem_anon_vma_fork; 371 tmp->vm_flags &= ~VM_LOCKED; 372 tmp->vm_next = tmp->vm_prev = NULL; 373 file = tmp->vm_file; 374 if (file) { 375 struct inode *inode = file->f_path.dentry->d_inode; 376 struct address_space *mapping = file->f_mapping; 377 378 get_file(file); 379 if (tmp->vm_flags & VM_DENYWRITE) 380 atomic_dec(&inode->i_writecount); 381 mutex_lock(&mapping->i_mmap_mutex); 382 if (tmp->vm_flags & VM_SHARED) 383 mapping->i_mmap_writable++; 384 flush_dcache_mmap_lock(mapping); 385 /* insert tmp into the share list, just after mpnt */ 386 vma_prio_tree_add(tmp, mpnt); 387 flush_dcache_mmap_unlock(mapping); 388 mutex_unlock(&mapping->i_mmap_mutex); 389 } 390 391 /* 392 * Clear hugetlb-related page reserves for children. This only 393 * affects MAP_PRIVATE mappings. Faults generated by the child 394 * are not guaranteed to succeed, even if read-only 395 */ 396 if (is_vm_hugetlb_page(tmp)) 397 reset_vma_resv_huge_pages(tmp); 398 399 /* 400 * Link in the new vma and copy the page table entries. 401 */ 402 *pprev = tmp; 403 pprev = &tmp->vm_next; 404 tmp->vm_prev = prev; 405 prev = tmp; 406 407 __vma_link_rb(mm, tmp, rb_link, rb_parent); 408 rb_link = &tmp->vm_rb.rb_right; 409 rb_parent = &tmp->vm_rb; 410 411 mm->map_count++; 412 retval = copy_page_range(mm, oldmm, mpnt); 413 414 if (tmp->vm_ops && tmp->vm_ops->open) 415 tmp->vm_ops->open(tmp); 416 417 if (retval) 418 goto out; 419 } 420 /* a new mm has just been created */ 421 arch_dup_mmap(oldmm, mm); 422 retval = 0; 423 out: 424 up_write(&mm->mmap_sem); 425 flush_tlb_mm(oldmm); 426 up_write(&oldmm->mmap_sem); 427 return retval; 428 fail_nomem_anon_vma_fork: 429 mpol_put(pol); 430 fail_nomem_policy: 431 kmem_cache_free(vm_area_cachep, tmp); 432 fail_nomem: 433 retval = -ENOMEM; 434 vm_unacct_memory(charge); 435 goto out; 436 } 437 438 static inline int mm_alloc_pgd(struct mm_struct *mm) 439 { 440 mm->pgd = pgd_alloc(mm); 441 if (unlikely(!mm->pgd)) 442 return -ENOMEM; 443 return 0; 444 } 445 446 static inline void mm_free_pgd(struct mm_struct *mm) 447 { 448 pgd_free(mm, mm->pgd); 449 } 450 #else 451 #define dup_mmap(mm, oldmm) (0) 452 #define mm_alloc_pgd(mm) (0) 453 #define mm_free_pgd(mm) 454 #endif /* CONFIG_MMU */ 455 456 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 457 458 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 459 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 460 461 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 462 463 static int __init coredump_filter_setup(char *s) 464 { 465 default_dump_filter = 466 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 467 MMF_DUMP_FILTER_MASK; 468 return 1; 469 } 470 471 __setup("coredump_filter=", coredump_filter_setup); 472 473 #include <linux/init_task.h> 474 475 static void mm_init_aio(struct mm_struct *mm) 476 { 477 #ifdef CONFIG_AIO 478 spin_lock_init(&mm->ioctx_lock); 479 INIT_HLIST_HEAD(&mm->ioctx_list); 480 #endif 481 } 482 483 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 484 { 485 atomic_set(&mm->mm_users, 1); 486 atomic_set(&mm->mm_count, 1); 487 init_rwsem(&mm->mmap_sem); 488 INIT_LIST_HEAD(&mm->mmlist); 489 mm->flags = (current->mm) ? 490 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 491 mm->core_state = NULL; 492 mm->nr_ptes = 0; 493 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 494 spin_lock_init(&mm->page_table_lock); 495 mm->free_area_cache = TASK_UNMAPPED_BASE; 496 mm->cached_hole_size = ~0UL; 497 mm_init_aio(mm); 498 mm_init_owner(mm, p); 499 500 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 return NULL; 520 521 memset(mm, 0, sizeof(*mm)); 522 mm_init_cpumask(mm); 523 return mm_init(mm, current); 524 } 525 526 /* 527 * Called when the last reference to the mm 528 * is dropped: either by a lazy thread or by 529 * mmput. Free the page directory and the mm. 530 */ 531 void __mmdrop(struct mm_struct *mm) 532 { 533 BUG_ON(mm == &init_mm); 534 mm_free_pgd(mm); 535 destroy_context(mm); 536 mmu_notifier_mm_destroy(mm); 537 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 538 VM_BUG_ON(mm->pmd_huge_pte); 539 #endif 540 free_mm(mm); 541 } 542 EXPORT_SYMBOL_GPL(__mmdrop); 543 544 /* 545 * Decrement the use count and release all resources for an mm. 546 */ 547 void mmput(struct mm_struct *mm) 548 { 549 might_sleep(); 550 551 if (atomic_dec_and_test(&mm->mm_users)) { 552 exit_aio(mm); 553 ksm_exit(mm); 554 khugepaged_exit(mm); /* must run before exit_mmap */ 555 exit_mmap(mm); 556 set_mm_exe_file(mm, NULL); 557 if (!list_empty(&mm->mmlist)) { 558 spin_lock(&mmlist_lock); 559 list_del(&mm->mmlist); 560 spin_unlock(&mmlist_lock); 561 } 562 put_swap_token(mm); 563 if (mm->binfmt) 564 module_put(mm->binfmt->module); 565 mmdrop(mm); 566 } 567 } 568 EXPORT_SYMBOL_GPL(mmput); 569 570 /* 571 * We added or removed a vma mapping the executable. The vmas are only mapped 572 * during exec and are not mapped with the mmap system call. 573 * Callers must hold down_write() on the mm's mmap_sem for these 574 */ 575 void added_exe_file_vma(struct mm_struct *mm) 576 { 577 mm->num_exe_file_vmas++; 578 } 579 580 void removed_exe_file_vma(struct mm_struct *mm) 581 { 582 mm->num_exe_file_vmas--; 583 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 584 fput(mm->exe_file); 585 mm->exe_file = NULL; 586 } 587 588 } 589 590 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 591 { 592 if (new_exe_file) 593 get_file(new_exe_file); 594 if (mm->exe_file) 595 fput(mm->exe_file); 596 mm->exe_file = new_exe_file; 597 mm->num_exe_file_vmas = 0; 598 } 599 600 struct file *get_mm_exe_file(struct mm_struct *mm) 601 { 602 struct file *exe_file; 603 604 /* We need mmap_sem to protect against races with removal of 605 * VM_EXECUTABLE vmas */ 606 down_read(&mm->mmap_sem); 607 exe_file = mm->exe_file; 608 if (exe_file) 609 get_file(exe_file); 610 up_read(&mm->mmap_sem); 611 return exe_file; 612 } 613 614 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 615 { 616 /* It's safe to write the exe_file pointer without exe_file_lock because 617 * this is called during fork when the task is not yet in /proc */ 618 newmm->exe_file = get_mm_exe_file(oldmm); 619 } 620 621 /** 622 * get_task_mm - acquire a reference to the task's mm 623 * 624 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 625 * this kernel workthread has transiently adopted a user mm with use_mm, 626 * to do its AIO) is not set and if so returns a reference to it, after 627 * bumping up the use count. User must release the mm via mmput() 628 * after use. Typically used by /proc and ptrace. 629 */ 630 struct mm_struct *get_task_mm(struct task_struct *task) 631 { 632 struct mm_struct *mm; 633 634 task_lock(task); 635 mm = task->mm; 636 if (mm) { 637 if (task->flags & PF_KTHREAD) 638 mm = NULL; 639 else 640 atomic_inc(&mm->mm_users); 641 } 642 task_unlock(task); 643 return mm; 644 } 645 EXPORT_SYMBOL_GPL(get_task_mm); 646 647 /* Please note the differences between mmput and mm_release. 648 * mmput is called whenever we stop holding onto a mm_struct, 649 * error success whatever. 650 * 651 * mm_release is called after a mm_struct has been removed 652 * from the current process. 653 * 654 * This difference is important for error handling, when we 655 * only half set up a mm_struct for a new process and need to restore 656 * the old one. Because we mmput the new mm_struct before 657 * restoring the old one. . . 658 * Eric Biederman 10 January 1998 659 */ 660 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 661 { 662 struct completion *vfork_done = tsk->vfork_done; 663 664 /* Get rid of any futexes when releasing the mm */ 665 #ifdef CONFIG_FUTEX 666 if (unlikely(tsk->robust_list)) { 667 exit_robust_list(tsk); 668 tsk->robust_list = NULL; 669 } 670 #ifdef CONFIG_COMPAT 671 if (unlikely(tsk->compat_robust_list)) { 672 compat_exit_robust_list(tsk); 673 tsk->compat_robust_list = NULL; 674 } 675 #endif 676 if (unlikely(!list_empty(&tsk->pi_state_list))) 677 exit_pi_state_list(tsk); 678 #endif 679 680 /* Get rid of any cached register state */ 681 deactivate_mm(tsk, mm); 682 683 /* notify parent sleeping on vfork() */ 684 if (vfork_done) { 685 tsk->vfork_done = NULL; 686 complete(vfork_done); 687 } 688 689 /* 690 * If we're exiting normally, clear a user-space tid field if 691 * requested. We leave this alone when dying by signal, to leave 692 * the value intact in a core dump, and to save the unnecessary 693 * trouble otherwise. Userland only wants this done for a sys_exit. 694 */ 695 if (tsk->clear_child_tid) { 696 if (!(tsk->flags & PF_SIGNALED) && 697 atomic_read(&mm->mm_users) > 1) { 698 /* 699 * We don't check the error code - if userspace has 700 * not set up a proper pointer then tough luck. 701 */ 702 put_user(0, tsk->clear_child_tid); 703 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 704 1, NULL, NULL, 0); 705 } 706 tsk->clear_child_tid = NULL; 707 } 708 } 709 710 /* 711 * Allocate a new mm structure and copy contents from the 712 * mm structure of the passed in task structure. 713 */ 714 struct mm_struct *dup_mm(struct task_struct *tsk) 715 { 716 struct mm_struct *mm, *oldmm = current->mm; 717 int err; 718 719 if (!oldmm) 720 return NULL; 721 722 mm = allocate_mm(); 723 if (!mm) 724 goto fail_nomem; 725 726 memcpy(mm, oldmm, sizeof(*mm)); 727 mm_init_cpumask(mm); 728 729 /* Initializing for Swap token stuff */ 730 mm->token_priority = 0; 731 mm->last_interval = 0; 732 733 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 734 mm->pmd_huge_pte = NULL; 735 #endif 736 737 if (!mm_init(mm, tsk)) 738 goto fail_nomem; 739 740 if (init_new_context(tsk, mm)) 741 goto fail_nocontext; 742 743 dup_mm_exe_file(oldmm, mm); 744 745 err = dup_mmap(mm, oldmm); 746 if (err) 747 goto free_pt; 748 749 mm->hiwater_rss = get_mm_rss(mm); 750 mm->hiwater_vm = mm->total_vm; 751 752 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 753 goto free_pt; 754 755 return mm; 756 757 free_pt: 758 /* don't put binfmt in mmput, we haven't got module yet */ 759 mm->binfmt = NULL; 760 mmput(mm); 761 762 fail_nomem: 763 return NULL; 764 765 fail_nocontext: 766 /* 767 * If init_new_context() failed, we cannot use mmput() to free the mm 768 * because it calls destroy_context() 769 */ 770 mm_free_pgd(mm); 771 free_mm(mm); 772 return NULL; 773 } 774 775 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 776 { 777 struct mm_struct *mm, *oldmm; 778 int retval; 779 780 tsk->min_flt = tsk->maj_flt = 0; 781 tsk->nvcsw = tsk->nivcsw = 0; 782 #ifdef CONFIG_DETECT_HUNG_TASK 783 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 784 #endif 785 786 tsk->mm = NULL; 787 tsk->active_mm = NULL; 788 789 /* 790 * Are we cloning a kernel thread? 791 * 792 * We need to steal a active VM for that.. 793 */ 794 oldmm = current->mm; 795 if (!oldmm) 796 return 0; 797 798 if (clone_flags & CLONE_VM) { 799 atomic_inc(&oldmm->mm_users); 800 mm = oldmm; 801 goto good_mm; 802 } 803 804 retval = -ENOMEM; 805 mm = dup_mm(tsk); 806 if (!mm) 807 goto fail_nomem; 808 809 good_mm: 810 /* Initializing for Swap token stuff */ 811 mm->token_priority = 0; 812 mm->last_interval = 0; 813 814 tsk->mm = mm; 815 tsk->active_mm = mm; 816 return 0; 817 818 fail_nomem: 819 return retval; 820 } 821 822 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 823 { 824 struct fs_struct *fs = current->fs; 825 if (clone_flags & CLONE_FS) { 826 /* tsk->fs is already what we want */ 827 spin_lock(&fs->lock); 828 if (fs->in_exec) { 829 spin_unlock(&fs->lock); 830 return -EAGAIN; 831 } 832 fs->users++; 833 spin_unlock(&fs->lock); 834 return 0; 835 } 836 tsk->fs = copy_fs_struct(fs); 837 if (!tsk->fs) 838 return -ENOMEM; 839 return 0; 840 } 841 842 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 843 { 844 struct files_struct *oldf, *newf; 845 int error = 0; 846 847 /* 848 * A background process may not have any files ... 849 */ 850 oldf = current->files; 851 if (!oldf) 852 goto out; 853 854 if (clone_flags & CLONE_FILES) { 855 atomic_inc(&oldf->count); 856 goto out; 857 } 858 859 newf = dup_fd(oldf, &error); 860 if (!newf) 861 goto out; 862 863 tsk->files = newf; 864 error = 0; 865 out: 866 return error; 867 } 868 869 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 870 { 871 #ifdef CONFIG_BLOCK 872 struct io_context *ioc = current->io_context; 873 struct io_context *new_ioc; 874 875 if (!ioc) 876 return 0; 877 /* 878 * Share io context with parent, if CLONE_IO is set 879 */ 880 if (clone_flags & CLONE_IO) { 881 tsk->io_context = ioc_task_link(ioc); 882 if (unlikely(!tsk->io_context)) 883 return -ENOMEM; 884 } else if (ioprio_valid(ioc->ioprio)) { 885 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 886 if (unlikely(!new_ioc)) 887 return -ENOMEM; 888 889 new_ioc->ioprio = ioc->ioprio; 890 put_io_context(new_ioc); 891 } 892 #endif 893 return 0; 894 } 895 896 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 897 { 898 struct sighand_struct *sig; 899 900 if (clone_flags & CLONE_SIGHAND) { 901 atomic_inc(¤t->sighand->count); 902 return 0; 903 } 904 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 905 rcu_assign_pointer(tsk->sighand, sig); 906 if (!sig) 907 return -ENOMEM; 908 atomic_set(&sig->count, 1); 909 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 910 return 0; 911 } 912 913 void __cleanup_sighand(struct sighand_struct *sighand) 914 { 915 if (atomic_dec_and_test(&sighand->count)) 916 kmem_cache_free(sighand_cachep, sighand); 917 } 918 919 920 /* 921 * Initialize POSIX timer handling for a thread group. 922 */ 923 static void posix_cpu_timers_init_group(struct signal_struct *sig) 924 { 925 unsigned long cpu_limit; 926 927 /* Thread group counters. */ 928 thread_group_cputime_init(sig); 929 930 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 931 if (cpu_limit != RLIM_INFINITY) { 932 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 933 sig->cputimer.running = 1; 934 } 935 936 /* The timer lists. */ 937 INIT_LIST_HEAD(&sig->cpu_timers[0]); 938 INIT_LIST_HEAD(&sig->cpu_timers[1]); 939 INIT_LIST_HEAD(&sig->cpu_timers[2]); 940 } 941 942 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 943 { 944 struct signal_struct *sig; 945 946 if (clone_flags & CLONE_THREAD) 947 return 0; 948 949 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 950 tsk->signal = sig; 951 if (!sig) 952 return -ENOMEM; 953 954 sig->nr_threads = 1; 955 atomic_set(&sig->live, 1); 956 atomic_set(&sig->sigcnt, 1); 957 init_waitqueue_head(&sig->wait_chldexit); 958 if (clone_flags & CLONE_NEWPID) 959 sig->flags |= SIGNAL_UNKILLABLE; 960 sig->curr_target = tsk; 961 init_sigpending(&sig->shared_pending); 962 INIT_LIST_HEAD(&sig->posix_timers); 963 964 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 965 sig->real_timer.function = it_real_fn; 966 967 task_lock(current->group_leader); 968 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 969 task_unlock(current->group_leader); 970 971 posix_cpu_timers_init_group(sig); 972 973 tty_audit_fork(sig); 974 sched_autogroup_fork(sig); 975 976 #ifdef CONFIG_CGROUPS 977 init_rwsem(&sig->threadgroup_fork_lock); 978 #endif 979 980 sig->oom_adj = current->signal->oom_adj; 981 sig->oom_score_adj = current->signal->oom_score_adj; 982 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 983 984 mutex_init(&sig->cred_guard_mutex); 985 986 return 0; 987 } 988 989 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 990 { 991 unsigned long new_flags = p->flags; 992 993 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 994 new_flags |= PF_FORKNOEXEC; 995 new_flags |= PF_STARTING; 996 p->flags = new_flags; 997 clear_freeze_flag(p); 998 } 999 1000 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1001 { 1002 current->clear_child_tid = tidptr; 1003 1004 return task_pid_vnr(current); 1005 } 1006 1007 static void rt_mutex_init_task(struct task_struct *p) 1008 { 1009 raw_spin_lock_init(&p->pi_lock); 1010 #ifdef CONFIG_RT_MUTEXES 1011 plist_head_init(&p->pi_waiters); 1012 p->pi_blocked_on = NULL; 1013 #endif 1014 } 1015 1016 #ifdef CONFIG_MM_OWNER 1017 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1018 { 1019 mm->owner = p; 1020 } 1021 #endif /* CONFIG_MM_OWNER */ 1022 1023 /* 1024 * Initialize POSIX timer handling for a single task. 1025 */ 1026 static void posix_cpu_timers_init(struct task_struct *tsk) 1027 { 1028 tsk->cputime_expires.prof_exp = cputime_zero; 1029 tsk->cputime_expires.virt_exp = cputime_zero; 1030 tsk->cputime_expires.sched_exp = 0; 1031 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1032 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1033 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1034 } 1035 1036 /* 1037 * This creates a new process as a copy of the old one, 1038 * but does not actually start it yet. 1039 * 1040 * It copies the registers, and all the appropriate 1041 * parts of the process environment (as per the clone 1042 * flags). The actual kick-off is left to the caller. 1043 */ 1044 static struct task_struct *copy_process(unsigned long clone_flags, 1045 unsigned long stack_start, 1046 struct pt_regs *regs, 1047 unsigned long stack_size, 1048 int __user *child_tidptr, 1049 struct pid *pid, 1050 int trace) 1051 { 1052 int retval; 1053 struct task_struct *p; 1054 int cgroup_callbacks_done = 0; 1055 1056 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1057 return ERR_PTR(-EINVAL); 1058 1059 /* 1060 * Thread groups must share signals as well, and detached threads 1061 * can only be started up within the thread group. 1062 */ 1063 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1064 return ERR_PTR(-EINVAL); 1065 1066 /* 1067 * Shared signal handlers imply shared VM. By way of the above, 1068 * thread groups also imply shared VM. Blocking this case allows 1069 * for various simplifications in other code. 1070 */ 1071 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1072 return ERR_PTR(-EINVAL); 1073 1074 /* 1075 * Siblings of global init remain as zombies on exit since they are 1076 * not reaped by their parent (swapper). To solve this and to avoid 1077 * multi-rooted process trees, prevent global and container-inits 1078 * from creating siblings. 1079 */ 1080 if ((clone_flags & CLONE_PARENT) && 1081 current->signal->flags & SIGNAL_UNKILLABLE) 1082 return ERR_PTR(-EINVAL); 1083 1084 retval = security_task_create(clone_flags); 1085 if (retval) 1086 goto fork_out; 1087 1088 retval = -ENOMEM; 1089 p = dup_task_struct(current); 1090 if (!p) 1091 goto fork_out; 1092 1093 ftrace_graph_init_task(p); 1094 1095 rt_mutex_init_task(p); 1096 1097 #ifdef CONFIG_PROVE_LOCKING 1098 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1099 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1100 #endif 1101 retval = -EAGAIN; 1102 if (atomic_read(&p->real_cred->user->processes) >= 1103 task_rlimit(p, RLIMIT_NPROC)) { 1104 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1105 p->real_cred->user != INIT_USER) 1106 goto bad_fork_free; 1107 } 1108 current->flags &= ~PF_NPROC_EXCEEDED; 1109 1110 retval = copy_creds(p, clone_flags); 1111 if (retval < 0) 1112 goto bad_fork_free; 1113 1114 /* 1115 * If multiple threads are within copy_process(), then this check 1116 * triggers too late. This doesn't hurt, the check is only there 1117 * to stop root fork bombs. 1118 */ 1119 retval = -EAGAIN; 1120 if (nr_threads >= max_threads) 1121 goto bad_fork_cleanup_count; 1122 1123 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1124 goto bad_fork_cleanup_count; 1125 1126 p->did_exec = 0; 1127 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1128 copy_flags(clone_flags, p); 1129 INIT_LIST_HEAD(&p->children); 1130 INIT_LIST_HEAD(&p->sibling); 1131 rcu_copy_process(p); 1132 p->vfork_done = NULL; 1133 spin_lock_init(&p->alloc_lock); 1134 1135 init_sigpending(&p->pending); 1136 1137 p->utime = cputime_zero; 1138 p->stime = cputime_zero; 1139 p->gtime = cputime_zero; 1140 p->utimescaled = cputime_zero; 1141 p->stimescaled = cputime_zero; 1142 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1143 p->prev_utime = cputime_zero; 1144 p->prev_stime = cputime_zero; 1145 #endif 1146 #if defined(SPLIT_RSS_COUNTING) 1147 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1148 #endif 1149 1150 p->default_timer_slack_ns = current->timer_slack_ns; 1151 1152 task_io_accounting_init(&p->ioac); 1153 acct_clear_integrals(p); 1154 1155 posix_cpu_timers_init(p); 1156 1157 do_posix_clock_monotonic_gettime(&p->start_time); 1158 p->real_start_time = p->start_time; 1159 monotonic_to_bootbased(&p->real_start_time); 1160 p->io_context = NULL; 1161 p->audit_context = NULL; 1162 if (clone_flags & CLONE_THREAD) 1163 threadgroup_fork_read_lock(current); 1164 cgroup_fork(p); 1165 #ifdef CONFIG_NUMA 1166 p->mempolicy = mpol_dup(p->mempolicy); 1167 if (IS_ERR(p->mempolicy)) { 1168 retval = PTR_ERR(p->mempolicy); 1169 p->mempolicy = NULL; 1170 goto bad_fork_cleanup_cgroup; 1171 } 1172 mpol_fix_fork_child_flag(p); 1173 #endif 1174 #ifdef CONFIG_CPUSETS 1175 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1176 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1177 #endif 1178 #ifdef CONFIG_TRACE_IRQFLAGS 1179 p->irq_events = 0; 1180 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1181 p->hardirqs_enabled = 1; 1182 #else 1183 p->hardirqs_enabled = 0; 1184 #endif 1185 p->hardirq_enable_ip = 0; 1186 p->hardirq_enable_event = 0; 1187 p->hardirq_disable_ip = _THIS_IP_; 1188 p->hardirq_disable_event = 0; 1189 p->softirqs_enabled = 1; 1190 p->softirq_enable_ip = _THIS_IP_; 1191 p->softirq_enable_event = 0; 1192 p->softirq_disable_ip = 0; 1193 p->softirq_disable_event = 0; 1194 p->hardirq_context = 0; 1195 p->softirq_context = 0; 1196 #endif 1197 #ifdef CONFIG_LOCKDEP 1198 p->lockdep_depth = 0; /* no locks held yet */ 1199 p->curr_chain_key = 0; 1200 p->lockdep_recursion = 0; 1201 #endif 1202 1203 #ifdef CONFIG_DEBUG_MUTEXES 1204 p->blocked_on = NULL; /* not blocked yet */ 1205 #endif 1206 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1207 p->memcg_batch.do_batch = 0; 1208 p->memcg_batch.memcg = NULL; 1209 #endif 1210 1211 /* Perform scheduler related setup. Assign this task to a CPU. */ 1212 sched_fork(p); 1213 1214 retval = perf_event_init_task(p); 1215 if (retval) 1216 goto bad_fork_cleanup_policy; 1217 retval = audit_alloc(p); 1218 if (retval) 1219 goto bad_fork_cleanup_policy; 1220 /* copy all the process information */ 1221 retval = copy_semundo(clone_flags, p); 1222 if (retval) 1223 goto bad_fork_cleanup_audit; 1224 retval = copy_files(clone_flags, p); 1225 if (retval) 1226 goto bad_fork_cleanup_semundo; 1227 retval = copy_fs(clone_flags, p); 1228 if (retval) 1229 goto bad_fork_cleanup_files; 1230 retval = copy_sighand(clone_flags, p); 1231 if (retval) 1232 goto bad_fork_cleanup_fs; 1233 retval = copy_signal(clone_flags, p); 1234 if (retval) 1235 goto bad_fork_cleanup_sighand; 1236 retval = copy_mm(clone_flags, p); 1237 if (retval) 1238 goto bad_fork_cleanup_signal; 1239 retval = copy_namespaces(clone_flags, p); 1240 if (retval) 1241 goto bad_fork_cleanup_mm; 1242 retval = copy_io(clone_flags, p); 1243 if (retval) 1244 goto bad_fork_cleanup_namespaces; 1245 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1246 if (retval) 1247 goto bad_fork_cleanup_io; 1248 1249 if (pid != &init_struct_pid) { 1250 retval = -ENOMEM; 1251 pid = alloc_pid(p->nsproxy->pid_ns); 1252 if (!pid) 1253 goto bad_fork_cleanup_io; 1254 } 1255 1256 p->pid = pid_nr(pid); 1257 p->tgid = p->pid; 1258 if (clone_flags & CLONE_THREAD) 1259 p->tgid = current->tgid; 1260 1261 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1262 /* 1263 * Clear TID on mm_release()? 1264 */ 1265 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1266 #ifdef CONFIG_BLOCK 1267 p->plug = NULL; 1268 #endif 1269 #ifdef CONFIG_FUTEX 1270 p->robust_list = NULL; 1271 #ifdef CONFIG_COMPAT 1272 p->compat_robust_list = NULL; 1273 #endif 1274 INIT_LIST_HEAD(&p->pi_state_list); 1275 p->pi_state_cache = NULL; 1276 #endif 1277 /* 1278 * sigaltstack should be cleared when sharing the same VM 1279 */ 1280 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1281 p->sas_ss_sp = p->sas_ss_size = 0; 1282 1283 /* 1284 * Syscall tracing and stepping should be turned off in the 1285 * child regardless of CLONE_PTRACE. 1286 */ 1287 user_disable_single_step(p); 1288 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1289 #ifdef TIF_SYSCALL_EMU 1290 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1291 #endif 1292 clear_all_latency_tracing(p); 1293 1294 /* ok, now we should be set up.. */ 1295 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1296 p->pdeath_signal = 0; 1297 p->exit_state = 0; 1298 1299 p->nr_dirtied = 0; 1300 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1301 1302 /* 1303 * Ok, make it visible to the rest of the system. 1304 * We dont wake it up yet. 1305 */ 1306 p->group_leader = p; 1307 INIT_LIST_HEAD(&p->thread_group); 1308 1309 /* Now that the task is set up, run cgroup callbacks if 1310 * necessary. We need to run them before the task is visible 1311 * on the tasklist. */ 1312 cgroup_fork_callbacks(p); 1313 cgroup_callbacks_done = 1; 1314 1315 /* Need tasklist lock for parent etc handling! */ 1316 write_lock_irq(&tasklist_lock); 1317 1318 /* CLONE_PARENT re-uses the old parent */ 1319 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1320 p->real_parent = current->real_parent; 1321 p->parent_exec_id = current->parent_exec_id; 1322 } else { 1323 p->real_parent = current; 1324 p->parent_exec_id = current->self_exec_id; 1325 } 1326 1327 spin_lock(¤t->sighand->siglock); 1328 1329 /* 1330 * Process group and session signals need to be delivered to just the 1331 * parent before the fork or both the parent and the child after the 1332 * fork. Restart if a signal comes in before we add the new process to 1333 * it's process group. 1334 * A fatal signal pending means that current will exit, so the new 1335 * thread can't slip out of an OOM kill (or normal SIGKILL). 1336 */ 1337 recalc_sigpending(); 1338 if (signal_pending(current)) { 1339 spin_unlock(¤t->sighand->siglock); 1340 write_unlock_irq(&tasklist_lock); 1341 retval = -ERESTARTNOINTR; 1342 goto bad_fork_free_pid; 1343 } 1344 1345 if (clone_flags & CLONE_THREAD) { 1346 current->signal->nr_threads++; 1347 atomic_inc(¤t->signal->live); 1348 atomic_inc(¤t->signal->sigcnt); 1349 p->group_leader = current->group_leader; 1350 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1351 } 1352 1353 if (likely(p->pid)) { 1354 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1355 1356 if (thread_group_leader(p)) { 1357 if (is_child_reaper(pid)) 1358 p->nsproxy->pid_ns->child_reaper = p; 1359 1360 p->signal->leader_pid = pid; 1361 p->signal->tty = tty_kref_get(current->signal->tty); 1362 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1363 attach_pid(p, PIDTYPE_SID, task_session(current)); 1364 list_add_tail(&p->sibling, &p->real_parent->children); 1365 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1366 __this_cpu_inc(process_counts); 1367 } 1368 attach_pid(p, PIDTYPE_PID, pid); 1369 nr_threads++; 1370 } 1371 1372 total_forks++; 1373 spin_unlock(¤t->sighand->siglock); 1374 write_unlock_irq(&tasklist_lock); 1375 proc_fork_connector(p); 1376 cgroup_post_fork(p); 1377 if (clone_flags & CLONE_THREAD) 1378 threadgroup_fork_read_unlock(current); 1379 perf_event_fork(p); 1380 return p; 1381 1382 bad_fork_free_pid: 1383 if (pid != &init_struct_pid) 1384 free_pid(pid); 1385 bad_fork_cleanup_io: 1386 if (p->io_context) 1387 exit_io_context(p); 1388 bad_fork_cleanup_namespaces: 1389 exit_task_namespaces(p); 1390 bad_fork_cleanup_mm: 1391 if (p->mm) 1392 mmput(p->mm); 1393 bad_fork_cleanup_signal: 1394 if (!(clone_flags & CLONE_THREAD)) 1395 free_signal_struct(p->signal); 1396 bad_fork_cleanup_sighand: 1397 __cleanup_sighand(p->sighand); 1398 bad_fork_cleanup_fs: 1399 exit_fs(p); /* blocking */ 1400 bad_fork_cleanup_files: 1401 exit_files(p); /* blocking */ 1402 bad_fork_cleanup_semundo: 1403 exit_sem(p); 1404 bad_fork_cleanup_audit: 1405 audit_free(p); 1406 bad_fork_cleanup_policy: 1407 perf_event_free_task(p); 1408 #ifdef CONFIG_NUMA 1409 mpol_put(p->mempolicy); 1410 bad_fork_cleanup_cgroup: 1411 #endif 1412 if (clone_flags & CLONE_THREAD) 1413 threadgroup_fork_read_unlock(current); 1414 cgroup_exit(p, cgroup_callbacks_done); 1415 delayacct_tsk_free(p); 1416 module_put(task_thread_info(p)->exec_domain->module); 1417 bad_fork_cleanup_count: 1418 atomic_dec(&p->cred->user->processes); 1419 exit_creds(p); 1420 bad_fork_free: 1421 free_task(p); 1422 fork_out: 1423 return ERR_PTR(retval); 1424 } 1425 1426 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1427 { 1428 memset(regs, 0, sizeof(struct pt_regs)); 1429 return regs; 1430 } 1431 1432 static inline void init_idle_pids(struct pid_link *links) 1433 { 1434 enum pid_type type; 1435 1436 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1437 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1438 links[type].pid = &init_struct_pid; 1439 } 1440 } 1441 1442 struct task_struct * __cpuinit fork_idle(int cpu) 1443 { 1444 struct task_struct *task; 1445 struct pt_regs regs; 1446 1447 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1448 &init_struct_pid, 0); 1449 if (!IS_ERR(task)) { 1450 init_idle_pids(task->pids); 1451 init_idle(task, cpu); 1452 } 1453 1454 return task; 1455 } 1456 1457 /* 1458 * Ok, this is the main fork-routine. 1459 * 1460 * It copies the process, and if successful kick-starts 1461 * it and waits for it to finish using the VM if required. 1462 */ 1463 long do_fork(unsigned long clone_flags, 1464 unsigned long stack_start, 1465 struct pt_regs *regs, 1466 unsigned long stack_size, 1467 int __user *parent_tidptr, 1468 int __user *child_tidptr) 1469 { 1470 struct task_struct *p; 1471 int trace = 0; 1472 long nr; 1473 1474 /* 1475 * Do some preliminary argument and permissions checking before we 1476 * actually start allocating stuff 1477 */ 1478 if (clone_flags & CLONE_NEWUSER) { 1479 if (clone_flags & CLONE_THREAD) 1480 return -EINVAL; 1481 /* hopefully this check will go away when userns support is 1482 * complete 1483 */ 1484 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1485 !capable(CAP_SETGID)) 1486 return -EPERM; 1487 } 1488 1489 /* 1490 * Determine whether and which event to report to ptracer. When 1491 * called from kernel_thread or CLONE_UNTRACED is explicitly 1492 * requested, no event is reported; otherwise, report if the event 1493 * for the type of forking is enabled. 1494 */ 1495 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1496 if (clone_flags & CLONE_VFORK) 1497 trace = PTRACE_EVENT_VFORK; 1498 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1499 trace = PTRACE_EVENT_CLONE; 1500 else 1501 trace = PTRACE_EVENT_FORK; 1502 1503 if (likely(!ptrace_event_enabled(current, trace))) 1504 trace = 0; 1505 } 1506 1507 p = copy_process(clone_flags, stack_start, regs, stack_size, 1508 child_tidptr, NULL, trace); 1509 /* 1510 * Do this prior waking up the new thread - the thread pointer 1511 * might get invalid after that point, if the thread exits quickly. 1512 */ 1513 if (!IS_ERR(p)) { 1514 struct completion vfork; 1515 1516 trace_sched_process_fork(current, p); 1517 1518 nr = task_pid_vnr(p); 1519 1520 if (clone_flags & CLONE_PARENT_SETTID) 1521 put_user(nr, parent_tidptr); 1522 1523 if (clone_flags & CLONE_VFORK) { 1524 p->vfork_done = &vfork; 1525 init_completion(&vfork); 1526 } 1527 1528 audit_finish_fork(p); 1529 1530 /* 1531 * We set PF_STARTING at creation in case tracing wants to 1532 * use this to distinguish a fully live task from one that 1533 * hasn't finished SIGSTOP raising yet. Now we clear it 1534 * and set the child going. 1535 */ 1536 p->flags &= ~PF_STARTING; 1537 1538 wake_up_new_task(p); 1539 1540 /* forking complete and child started to run, tell ptracer */ 1541 if (unlikely(trace)) 1542 ptrace_event(trace, nr); 1543 1544 if (clone_flags & CLONE_VFORK) { 1545 freezer_do_not_count(); 1546 wait_for_completion(&vfork); 1547 freezer_count(); 1548 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1549 } 1550 } else { 1551 nr = PTR_ERR(p); 1552 } 1553 return nr; 1554 } 1555 1556 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1557 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1558 #endif 1559 1560 static void sighand_ctor(void *data) 1561 { 1562 struct sighand_struct *sighand = data; 1563 1564 spin_lock_init(&sighand->siglock); 1565 init_waitqueue_head(&sighand->signalfd_wqh); 1566 } 1567 1568 void __init proc_caches_init(void) 1569 { 1570 sighand_cachep = kmem_cache_create("sighand_cache", 1571 sizeof(struct sighand_struct), 0, 1572 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1573 SLAB_NOTRACK, sighand_ctor); 1574 signal_cachep = kmem_cache_create("signal_cache", 1575 sizeof(struct signal_struct), 0, 1576 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1577 files_cachep = kmem_cache_create("files_cache", 1578 sizeof(struct files_struct), 0, 1579 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1580 fs_cachep = kmem_cache_create("fs_cache", 1581 sizeof(struct fs_struct), 0, 1582 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1583 /* 1584 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1585 * whole struct cpumask for the OFFSTACK case. We could change 1586 * this to *only* allocate as much of it as required by the 1587 * maximum number of CPU's we can ever have. The cpumask_allocation 1588 * is at the end of the structure, exactly for that reason. 1589 */ 1590 mm_cachep = kmem_cache_create("mm_struct", 1591 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1592 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1593 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1594 mmap_init(); 1595 nsproxy_cache_init(); 1596 } 1597 1598 /* 1599 * Check constraints on flags passed to the unshare system call. 1600 */ 1601 static int check_unshare_flags(unsigned long unshare_flags) 1602 { 1603 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1604 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1605 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1606 return -EINVAL; 1607 /* 1608 * Not implemented, but pretend it works if there is nothing to 1609 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1610 * needs to unshare vm. 1611 */ 1612 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1613 /* FIXME: get_task_mm() increments ->mm_users */ 1614 if (atomic_read(¤t->mm->mm_users) > 1) 1615 return -EINVAL; 1616 } 1617 1618 return 0; 1619 } 1620 1621 /* 1622 * Unshare the filesystem structure if it is being shared 1623 */ 1624 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1625 { 1626 struct fs_struct *fs = current->fs; 1627 1628 if (!(unshare_flags & CLONE_FS) || !fs) 1629 return 0; 1630 1631 /* don't need lock here; in the worst case we'll do useless copy */ 1632 if (fs->users == 1) 1633 return 0; 1634 1635 *new_fsp = copy_fs_struct(fs); 1636 if (!*new_fsp) 1637 return -ENOMEM; 1638 1639 return 0; 1640 } 1641 1642 /* 1643 * Unshare file descriptor table if it is being shared 1644 */ 1645 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1646 { 1647 struct files_struct *fd = current->files; 1648 int error = 0; 1649 1650 if ((unshare_flags & CLONE_FILES) && 1651 (fd && atomic_read(&fd->count) > 1)) { 1652 *new_fdp = dup_fd(fd, &error); 1653 if (!*new_fdp) 1654 return error; 1655 } 1656 1657 return 0; 1658 } 1659 1660 /* 1661 * unshare allows a process to 'unshare' part of the process 1662 * context which was originally shared using clone. copy_* 1663 * functions used by do_fork() cannot be used here directly 1664 * because they modify an inactive task_struct that is being 1665 * constructed. Here we are modifying the current, active, 1666 * task_struct. 1667 */ 1668 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1669 { 1670 struct fs_struct *fs, *new_fs = NULL; 1671 struct files_struct *fd, *new_fd = NULL; 1672 struct nsproxy *new_nsproxy = NULL; 1673 int do_sysvsem = 0; 1674 int err; 1675 1676 err = check_unshare_flags(unshare_flags); 1677 if (err) 1678 goto bad_unshare_out; 1679 1680 /* 1681 * If unsharing namespace, must also unshare filesystem information. 1682 */ 1683 if (unshare_flags & CLONE_NEWNS) 1684 unshare_flags |= CLONE_FS; 1685 /* 1686 * CLONE_NEWIPC must also detach from the undolist: after switching 1687 * to a new ipc namespace, the semaphore arrays from the old 1688 * namespace are unreachable. 1689 */ 1690 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1691 do_sysvsem = 1; 1692 err = unshare_fs(unshare_flags, &new_fs); 1693 if (err) 1694 goto bad_unshare_out; 1695 err = unshare_fd(unshare_flags, &new_fd); 1696 if (err) 1697 goto bad_unshare_cleanup_fs; 1698 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1699 if (err) 1700 goto bad_unshare_cleanup_fd; 1701 1702 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1703 if (do_sysvsem) { 1704 /* 1705 * CLONE_SYSVSEM is equivalent to sys_exit(). 1706 */ 1707 exit_sem(current); 1708 } 1709 1710 if (new_nsproxy) { 1711 switch_task_namespaces(current, new_nsproxy); 1712 new_nsproxy = NULL; 1713 } 1714 1715 task_lock(current); 1716 1717 if (new_fs) { 1718 fs = current->fs; 1719 spin_lock(&fs->lock); 1720 current->fs = new_fs; 1721 if (--fs->users) 1722 new_fs = NULL; 1723 else 1724 new_fs = fs; 1725 spin_unlock(&fs->lock); 1726 } 1727 1728 if (new_fd) { 1729 fd = current->files; 1730 current->files = new_fd; 1731 new_fd = fd; 1732 } 1733 1734 task_unlock(current); 1735 } 1736 1737 if (new_nsproxy) 1738 put_nsproxy(new_nsproxy); 1739 1740 bad_unshare_cleanup_fd: 1741 if (new_fd) 1742 put_files_struct(new_fd); 1743 1744 bad_unshare_cleanup_fs: 1745 if (new_fs) 1746 free_fs_struct(new_fs); 1747 1748 bad_unshare_out: 1749 return err; 1750 } 1751 1752 /* 1753 * Helper to unshare the files of the current task. 1754 * We don't want to expose copy_files internals to 1755 * the exec layer of the kernel. 1756 */ 1757 1758 int unshare_files(struct files_struct **displaced) 1759 { 1760 struct task_struct *task = current; 1761 struct files_struct *copy = NULL; 1762 int error; 1763 1764 error = unshare_fd(CLONE_FILES, ©); 1765 if (error || !copy) { 1766 *displaced = NULL; 1767 return error; 1768 } 1769 *displaced = task->files; 1770 task_lock(task); 1771 task->files = copy; 1772 task_unlock(task); 1773 return 0; 1774 } 1775