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 #define CREATE_TRACE_POINTS 80 #include <trace/events/task.h> 81 82 /* 83 * Protected counters by write_lock_irq(&tasklist_lock) 84 */ 85 unsigned long total_forks; /* Handle normal Linux uptimes. */ 86 int nr_threads; /* The idle threads do not count.. */ 87 88 int max_threads; /* tunable limit on nr_threads */ 89 90 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 91 92 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 93 94 #ifdef CONFIG_PROVE_RCU 95 int lockdep_tasklist_lock_is_held(void) 96 { 97 return lockdep_is_held(&tasklist_lock); 98 } 99 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 100 #endif /* #ifdef CONFIG_PROVE_RCU */ 101 102 int nr_processes(void) 103 { 104 int cpu; 105 int total = 0; 106 107 for_each_possible_cpu(cpu) 108 total += per_cpu(process_counts, cpu); 109 110 return total; 111 } 112 113 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 114 # define alloc_task_struct_node(node) \ 115 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node) 116 # define free_task_struct(tsk) \ 117 kmem_cache_free(task_struct_cachep, (tsk)) 118 static struct kmem_cache *task_struct_cachep; 119 #endif 120 121 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 122 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 123 int node) 124 { 125 #ifdef CONFIG_DEBUG_STACK_USAGE 126 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 127 #else 128 gfp_t mask = GFP_KERNEL; 129 #endif 130 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER); 131 132 return page ? page_address(page) : NULL; 133 } 134 135 static inline void free_thread_info(struct thread_info *ti) 136 { 137 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 138 } 139 #endif 140 141 /* SLAB cache for signal_struct structures (tsk->signal) */ 142 static struct kmem_cache *signal_cachep; 143 144 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 145 struct kmem_cache *sighand_cachep; 146 147 /* SLAB cache for files_struct structures (tsk->files) */ 148 struct kmem_cache *files_cachep; 149 150 /* SLAB cache for fs_struct structures (tsk->fs) */ 151 struct kmem_cache *fs_cachep; 152 153 /* SLAB cache for vm_area_struct structures */ 154 struct kmem_cache *vm_area_cachep; 155 156 /* SLAB cache for mm_struct structures (tsk->mm) */ 157 static struct kmem_cache *mm_cachep; 158 159 static void account_kernel_stack(struct thread_info *ti, int account) 160 { 161 struct zone *zone = page_zone(virt_to_page(ti)); 162 163 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 164 } 165 166 void free_task(struct task_struct *tsk) 167 { 168 account_kernel_stack(tsk->stack, -1); 169 free_thread_info(tsk->stack); 170 rt_mutex_debug_task_free(tsk); 171 ftrace_graph_exit_task(tsk); 172 free_task_struct(tsk); 173 } 174 EXPORT_SYMBOL(free_task); 175 176 static inline void free_signal_struct(struct signal_struct *sig) 177 { 178 taskstats_tgid_free(sig); 179 sched_autogroup_exit(sig); 180 kmem_cache_free(signal_cachep, sig); 181 } 182 183 static inline void put_signal_struct(struct signal_struct *sig) 184 { 185 if (atomic_dec_and_test(&sig->sigcnt)) 186 free_signal_struct(sig); 187 } 188 189 void __put_task_struct(struct task_struct *tsk) 190 { 191 WARN_ON(!tsk->exit_state); 192 WARN_ON(atomic_read(&tsk->usage)); 193 WARN_ON(tsk == current); 194 195 exit_creds(tsk); 196 delayacct_tsk_free(tsk); 197 put_signal_struct(tsk->signal); 198 199 if (!profile_handoff_task(tsk)) 200 free_task(tsk); 201 } 202 EXPORT_SYMBOL_GPL(__put_task_struct); 203 204 /* 205 * macro override instead of weak attribute alias, to workaround 206 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 207 */ 208 #ifndef arch_task_cache_init 209 #define arch_task_cache_init() 210 #endif 211 212 void __init fork_init(unsigned long mempages) 213 { 214 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 215 #ifndef ARCH_MIN_TASKALIGN 216 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 217 #endif 218 /* create a slab on which task_structs can be allocated */ 219 task_struct_cachep = 220 kmem_cache_create("task_struct", sizeof(struct task_struct), 221 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 222 #endif 223 224 /* do the arch specific task caches init */ 225 arch_task_cache_init(); 226 227 /* 228 * The default maximum number of threads is set to a safe 229 * value: the thread structures can take up at most half 230 * of memory. 231 */ 232 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 233 234 /* 235 * we need to allow at least 20 threads to boot a system 236 */ 237 if (max_threads < 20) 238 max_threads = 20; 239 240 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 241 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 242 init_task.signal->rlim[RLIMIT_SIGPENDING] = 243 init_task.signal->rlim[RLIMIT_NPROC]; 244 } 245 246 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 247 struct task_struct *src) 248 { 249 *dst = *src; 250 return 0; 251 } 252 253 static struct task_struct *dup_task_struct(struct task_struct *orig) 254 { 255 struct task_struct *tsk; 256 struct thread_info *ti; 257 unsigned long *stackend; 258 int node = tsk_fork_get_node(orig); 259 int err; 260 261 prepare_to_copy(orig); 262 263 tsk = alloc_task_struct_node(node); 264 if (!tsk) 265 return NULL; 266 267 ti = alloc_thread_info_node(tsk, node); 268 if (!ti) { 269 free_task_struct(tsk); 270 return NULL; 271 } 272 273 err = arch_dup_task_struct(tsk, orig); 274 if (err) 275 goto out; 276 277 tsk->stack = ti; 278 279 setup_thread_stack(tsk, orig); 280 clear_user_return_notifier(tsk); 281 clear_tsk_need_resched(tsk); 282 stackend = end_of_stack(tsk); 283 *stackend = STACK_END_MAGIC; /* for overflow detection */ 284 285 #ifdef CONFIG_CC_STACKPROTECTOR 286 tsk->stack_canary = get_random_int(); 287 #endif 288 289 /* 290 * One for us, one for whoever does the "release_task()" (usually 291 * parent) 292 */ 293 atomic_set(&tsk->usage, 2); 294 #ifdef CONFIG_BLK_DEV_IO_TRACE 295 tsk->btrace_seq = 0; 296 #endif 297 tsk->splice_pipe = NULL; 298 299 account_kernel_stack(ti, 1); 300 301 return tsk; 302 303 out: 304 free_thread_info(ti); 305 free_task_struct(tsk); 306 return NULL; 307 } 308 309 #ifdef CONFIG_MMU 310 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 311 { 312 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 313 struct rb_node **rb_link, *rb_parent; 314 int retval; 315 unsigned long charge; 316 struct mempolicy *pol; 317 318 down_write(&oldmm->mmap_sem); 319 flush_cache_dup_mm(oldmm); 320 /* 321 * Not linked in yet - no deadlock potential: 322 */ 323 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 324 325 mm->locked_vm = 0; 326 mm->mmap = NULL; 327 mm->mmap_cache = NULL; 328 mm->free_area_cache = oldmm->mmap_base; 329 mm->cached_hole_size = ~0UL; 330 mm->map_count = 0; 331 cpumask_clear(mm_cpumask(mm)); 332 mm->mm_rb = RB_ROOT; 333 rb_link = &mm->mm_rb.rb_node; 334 rb_parent = NULL; 335 pprev = &mm->mmap; 336 retval = ksm_fork(mm, oldmm); 337 if (retval) 338 goto out; 339 retval = khugepaged_fork(mm, oldmm); 340 if (retval) 341 goto out; 342 343 prev = NULL; 344 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 345 struct file *file; 346 347 if (mpnt->vm_flags & VM_DONTCOPY) { 348 long pages = vma_pages(mpnt); 349 mm->total_vm -= pages; 350 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 351 -pages); 352 continue; 353 } 354 charge = 0; 355 if (mpnt->vm_flags & VM_ACCOUNT) { 356 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 357 if (security_vm_enough_memory(len)) 358 goto fail_nomem; 359 charge = len; 360 } 361 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 362 if (!tmp) 363 goto fail_nomem; 364 *tmp = *mpnt; 365 INIT_LIST_HEAD(&tmp->anon_vma_chain); 366 pol = mpol_dup(vma_policy(mpnt)); 367 retval = PTR_ERR(pol); 368 if (IS_ERR(pol)) 369 goto fail_nomem_policy; 370 vma_set_policy(tmp, pol); 371 tmp->vm_mm = mm; 372 if (anon_vma_fork(tmp, mpnt)) 373 goto fail_nomem_anon_vma_fork; 374 tmp->vm_flags &= ~VM_LOCKED; 375 tmp->vm_next = tmp->vm_prev = NULL; 376 file = tmp->vm_file; 377 if (file) { 378 struct inode *inode = file->f_path.dentry->d_inode; 379 struct address_space *mapping = file->f_mapping; 380 381 get_file(file); 382 if (tmp->vm_flags & VM_DENYWRITE) 383 atomic_dec(&inode->i_writecount); 384 mutex_lock(&mapping->i_mmap_mutex); 385 if (tmp->vm_flags & VM_SHARED) 386 mapping->i_mmap_writable++; 387 flush_dcache_mmap_lock(mapping); 388 /* insert tmp into the share list, just after mpnt */ 389 vma_prio_tree_add(tmp, mpnt); 390 flush_dcache_mmap_unlock(mapping); 391 mutex_unlock(&mapping->i_mmap_mutex); 392 } 393 394 /* 395 * Clear hugetlb-related page reserves for children. This only 396 * affects MAP_PRIVATE mappings. Faults generated by the child 397 * are not guaranteed to succeed, even if read-only 398 */ 399 if (is_vm_hugetlb_page(tmp)) 400 reset_vma_resv_huge_pages(tmp); 401 402 /* 403 * Link in the new vma and copy the page table entries. 404 */ 405 *pprev = tmp; 406 pprev = &tmp->vm_next; 407 tmp->vm_prev = prev; 408 prev = tmp; 409 410 __vma_link_rb(mm, tmp, rb_link, rb_parent); 411 rb_link = &tmp->vm_rb.rb_right; 412 rb_parent = &tmp->vm_rb; 413 414 mm->map_count++; 415 retval = copy_page_range(mm, oldmm, mpnt); 416 417 if (tmp->vm_ops && tmp->vm_ops->open) 418 tmp->vm_ops->open(tmp); 419 420 if (retval) 421 goto out; 422 } 423 /* a new mm has just been created */ 424 arch_dup_mmap(oldmm, mm); 425 retval = 0; 426 out: 427 up_write(&mm->mmap_sem); 428 flush_tlb_mm(oldmm); 429 up_write(&oldmm->mmap_sem); 430 return retval; 431 fail_nomem_anon_vma_fork: 432 mpol_put(pol); 433 fail_nomem_policy: 434 kmem_cache_free(vm_area_cachep, tmp); 435 fail_nomem: 436 retval = -ENOMEM; 437 vm_unacct_memory(charge); 438 goto out; 439 } 440 441 static inline int mm_alloc_pgd(struct mm_struct *mm) 442 { 443 mm->pgd = pgd_alloc(mm); 444 if (unlikely(!mm->pgd)) 445 return -ENOMEM; 446 return 0; 447 } 448 449 static inline void mm_free_pgd(struct mm_struct *mm) 450 { 451 pgd_free(mm, mm->pgd); 452 } 453 #else 454 #define dup_mmap(mm, oldmm) (0) 455 #define mm_alloc_pgd(mm) (0) 456 #define mm_free_pgd(mm) 457 #endif /* CONFIG_MMU */ 458 459 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 460 461 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 462 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 463 464 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 465 466 static int __init coredump_filter_setup(char *s) 467 { 468 default_dump_filter = 469 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 470 MMF_DUMP_FILTER_MASK; 471 return 1; 472 } 473 474 __setup("coredump_filter=", coredump_filter_setup); 475 476 #include <linux/init_task.h> 477 478 static void mm_init_aio(struct mm_struct *mm) 479 { 480 #ifdef CONFIG_AIO 481 spin_lock_init(&mm->ioctx_lock); 482 INIT_HLIST_HEAD(&mm->ioctx_list); 483 #endif 484 } 485 486 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 487 { 488 atomic_set(&mm->mm_users, 1); 489 atomic_set(&mm->mm_count, 1); 490 init_rwsem(&mm->mmap_sem); 491 INIT_LIST_HEAD(&mm->mmlist); 492 mm->flags = (current->mm) ? 493 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 494 mm->core_state = NULL; 495 mm->nr_ptes = 0; 496 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 497 spin_lock_init(&mm->page_table_lock); 498 mm->free_area_cache = TASK_UNMAPPED_BASE; 499 mm->cached_hole_size = ~0UL; 500 mm_init_aio(mm); 501 mm_init_owner(mm, p); 502 503 if (likely(!mm_alloc_pgd(mm))) { 504 mm->def_flags = 0; 505 mmu_notifier_mm_init(mm); 506 return mm; 507 } 508 509 free_mm(mm); 510 return NULL; 511 } 512 513 /* 514 * Allocate and initialize an mm_struct. 515 */ 516 struct mm_struct *mm_alloc(void) 517 { 518 struct mm_struct *mm; 519 520 mm = allocate_mm(); 521 if (!mm) 522 return NULL; 523 524 memset(mm, 0, sizeof(*mm)); 525 mm_init_cpumask(mm); 526 return mm_init(mm, current); 527 } 528 529 /* 530 * Called when the last reference to the mm 531 * is dropped: either by a lazy thread or by 532 * mmput. Free the page directory and the mm. 533 */ 534 void __mmdrop(struct mm_struct *mm) 535 { 536 BUG_ON(mm == &init_mm); 537 mm_free_pgd(mm); 538 destroy_context(mm); 539 mmu_notifier_mm_destroy(mm); 540 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 541 VM_BUG_ON(mm->pmd_huge_pte); 542 #endif 543 free_mm(mm); 544 } 545 EXPORT_SYMBOL_GPL(__mmdrop); 546 547 /* 548 * Decrement the use count and release all resources for an mm. 549 */ 550 void mmput(struct mm_struct *mm) 551 { 552 might_sleep(); 553 554 if (atomic_dec_and_test(&mm->mm_users)) { 555 exit_aio(mm); 556 ksm_exit(mm); 557 khugepaged_exit(mm); /* must run before exit_mmap */ 558 exit_mmap(mm); 559 set_mm_exe_file(mm, NULL); 560 if (!list_empty(&mm->mmlist)) { 561 spin_lock(&mmlist_lock); 562 list_del(&mm->mmlist); 563 spin_unlock(&mmlist_lock); 564 } 565 put_swap_token(mm); 566 if (mm->binfmt) 567 module_put(mm->binfmt->module); 568 mmdrop(mm); 569 } 570 } 571 EXPORT_SYMBOL_GPL(mmput); 572 573 /* 574 * We added or removed a vma mapping the executable. The vmas are only mapped 575 * during exec and are not mapped with the mmap system call. 576 * Callers must hold down_write() on the mm's mmap_sem for these 577 */ 578 void added_exe_file_vma(struct mm_struct *mm) 579 { 580 mm->num_exe_file_vmas++; 581 } 582 583 void removed_exe_file_vma(struct mm_struct *mm) 584 { 585 mm->num_exe_file_vmas--; 586 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 587 fput(mm->exe_file); 588 mm->exe_file = NULL; 589 } 590 591 } 592 593 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 594 { 595 if (new_exe_file) 596 get_file(new_exe_file); 597 if (mm->exe_file) 598 fput(mm->exe_file); 599 mm->exe_file = new_exe_file; 600 mm->num_exe_file_vmas = 0; 601 } 602 603 struct file *get_mm_exe_file(struct mm_struct *mm) 604 { 605 struct file *exe_file; 606 607 /* We need mmap_sem to protect against races with removal of 608 * VM_EXECUTABLE vmas */ 609 down_read(&mm->mmap_sem); 610 exe_file = mm->exe_file; 611 if (exe_file) 612 get_file(exe_file); 613 up_read(&mm->mmap_sem); 614 return exe_file; 615 } 616 617 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 618 { 619 /* It's safe to write the exe_file pointer without exe_file_lock because 620 * this is called during fork when the task is not yet in /proc */ 621 newmm->exe_file = get_mm_exe_file(oldmm); 622 } 623 624 /** 625 * get_task_mm - acquire a reference to the task's mm 626 * 627 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 628 * this kernel workthread has transiently adopted a user mm with use_mm, 629 * to do its AIO) is not set and if so returns a reference to it, after 630 * bumping up the use count. User must release the mm via mmput() 631 * after use. Typically used by /proc and ptrace. 632 */ 633 struct mm_struct *get_task_mm(struct task_struct *task) 634 { 635 struct mm_struct *mm; 636 637 task_lock(task); 638 mm = task->mm; 639 if (mm) { 640 if (task->flags & PF_KTHREAD) 641 mm = NULL; 642 else 643 atomic_inc(&mm->mm_users); 644 } 645 task_unlock(task); 646 return mm; 647 } 648 EXPORT_SYMBOL_GPL(get_task_mm); 649 650 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 651 { 652 struct mm_struct *mm; 653 int err; 654 655 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 656 if (err) 657 return ERR_PTR(err); 658 659 mm = get_task_mm(task); 660 if (mm && mm != current->mm && 661 !ptrace_may_access(task, mode)) { 662 mmput(mm); 663 mm = ERR_PTR(-EACCES); 664 } 665 mutex_unlock(&task->signal->cred_guard_mutex); 666 667 return mm; 668 } 669 670 /* Please note the differences between mmput and mm_release. 671 * mmput is called whenever we stop holding onto a mm_struct, 672 * error success whatever. 673 * 674 * mm_release is called after a mm_struct has been removed 675 * from the current process. 676 * 677 * This difference is important for error handling, when we 678 * only half set up a mm_struct for a new process and need to restore 679 * the old one. Because we mmput the new mm_struct before 680 * restoring the old one. . . 681 * Eric Biederman 10 January 1998 682 */ 683 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 684 { 685 struct completion *vfork_done = tsk->vfork_done; 686 687 /* Get rid of any futexes when releasing the mm */ 688 #ifdef CONFIG_FUTEX 689 if (unlikely(tsk->robust_list)) { 690 exit_robust_list(tsk); 691 tsk->robust_list = NULL; 692 } 693 #ifdef CONFIG_COMPAT 694 if (unlikely(tsk->compat_robust_list)) { 695 compat_exit_robust_list(tsk); 696 tsk->compat_robust_list = NULL; 697 } 698 #endif 699 if (unlikely(!list_empty(&tsk->pi_state_list))) 700 exit_pi_state_list(tsk); 701 #endif 702 703 /* Get rid of any cached register state */ 704 deactivate_mm(tsk, mm); 705 706 /* notify parent sleeping on vfork() */ 707 if (vfork_done) { 708 tsk->vfork_done = NULL; 709 complete(vfork_done); 710 } 711 712 /* 713 * If we're exiting normally, clear a user-space tid field if 714 * requested. We leave this alone when dying by signal, to leave 715 * the value intact in a core dump, and to save the unnecessary 716 * trouble otherwise. Userland only wants this done for a sys_exit. 717 */ 718 if (tsk->clear_child_tid) { 719 if (!(tsk->flags & PF_SIGNALED) && 720 atomic_read(&mm->mm_users) > 1) { 721 /* 722 * We don't check the error code - if userspace has 723 * not set up a proper pointer then tough luck. 724 */ 725 put_user(0, tsk->clear_child_tid); 726 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 727 1, NULL, NULL, 0); 728 } 729 tsk->clear_child_tid = NULL; 730 } 731 } 732 733 /* 734 * Allocate a new mm structure and copy contents from the 735 * mm structure of the passed in task structure. 736 */ 737 struct mm_struct *dup_mm(struct task_struct *tsk) 738 { 739 struct mm_struct *mm, *oldmm = current->mm; 740 int err; 741 742 if (!oldmm) 743 return NULL; 744 745 mm = allocate_mm(); 746 if (!mm) 747 goto fail_nomem; 748 749 memcpy(mm, oldmm, sizeof(*mm)); 750 mm_init_cpumask(mm); 751 752 /* Initializing for Swap token stuff */ 753 mm->token_priority = 0; 754 mm->last_interval = 0; 755 756 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 757 mm->pmd_huge_pte = NULL; 758 #endif 759 760 if (!mm_init(mm, tsk)) 761 goto fail_nomem; 762 763 if (init_new_context(tsk, mm)) 764 goto fail_nocontext; 765 766 dup_mm_exe_file(oldmm, mm); 767 768 err = dup_mmap(mm, oldmm); 769 if (err) 770 goto free_pt; 771 772 mm->hiwater_rss = get_mm_rss(mm); 773 mm->hiwater_vm = mm->total_vm; 774 775 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 776 goto free_pt; 777 778 return mm; 779 780 free_pt: 781 /* don't put binfmt in mmput, we haven't got module yet */ 782 mm->binfmt = NULL; 783 mmput(mm); 784 785 fail_nomem: 786 return NULL; 787 788 fail_nocontext: 789 /* 790 * If init_new_context() failed, we cannot use mmput() to free the mm 791 * because it calls destroy_context() 792 */ 793 mm_free_pgd(mm); 794 free_mm(mm); 795 return NULL; 796 } 797 798 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 799 { 800 struct mm_struct *mm, *oldmm; 801 int retval; 802 803 tsk->min_flt = tsk->maj_flt = 0; 804 tsk->nvcsw = tsk->nivcsw = 0; 805 #ifdef CONFIG_DETECT_HUNG_TASK 806 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 807 #endif 808 809 tsk->mm = NULL; 810 tsk->active_mm = NULL; 811 812 /* 813 * Are we cloning a kernel thread? 814 * 815 * We need to steal a active VM for that.. 816 */ 817 oldmm = current->mm; 818 if (!oldmm) 819 return 0; 820 821 if (clone_flags & CLONE_VM) { 822 atomic_inc(&oldmm->mm_users); 823 mm = oldmm; 824 goto good_mm; 825 } 826 827 retval = -ENOMEM; 828 mm = dup_mm(tsk); 829 if (!mm) 830 goto fail_nomem; 831 832 good_mm: 833 /* Initializing for Swap token stuff */ 834 mm->token_priority = 0; 835 mm->last_interval = 0; 836 837 tsk->mm = mm; 838 tsk->active_mm = mm; 839 return 0; 840 841 fail_nomem: 842 return retval; 843 } 844 845 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 846 { 847 struct fs_struct *fs = current->fs; 848 if (clone_flags & CLONE_FS) { 849 /* tsk->fs is already what we want */ 850 spin_lock(&fs->lock); 851 if (fs->in_exec) { 852 spin_unlock(&fs->lock); 853 return -EAGAIN; 854 } 855 fs->users++; 856 spin_unlock(&fs->lock); 857 return 0; 858 } 859 tsk->fs = copy_fs_struct(fs); 860 if (!tsk->fs) 861 return -ENOMEM; 862 return 0; 863 } 864 865 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 866 { 867 struct files_struct *oldf, *newf; 868 int error = 0; 869 870 /* 871 * A background process may not have any files ... 872 */ 873 oldf = current->files; 874 if (!oldf) 875 goto out; 876 877 if (clone_flags & CLONE_FILES) { 878 atomic_inc(&oldf->count); 879 goto out; 880 } 881 882 newf = dup_fd(oldf, &error); 883 if (!newf) 884 goto out; 885 886 tsk->files = newf; 887 error = 0; 888 out: 889 return error; 890 } 891 892 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 893 { 894 #ifdef CONFIG_BLOCK 895 struct io_context *ioc = current->io_context; 896 struct io_context *new_ioc; 897 898 if (!ioc) 899 return 0; 900 /* 901 * Share io context with parent, if CLONE_IO is set 902 */ 903 if (clone_flags & CLONE_IO) { 904 tsk->io_context = ioc_task_link(ioc); 905 if (unlikely(!tsk->io_context)) 906 return -ENOMEM; 907 } else if (ioprio_valid(ioc->ioprio)) { 908 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 909 if (unlikely(!new_ioc)) 910 return -ENOMEM; 911 912 new_ioc->ioprio = ioc->ioprio; 913 put_io_context(new_ioc); 914 } 915 #endif 916 return 0; 917 } 918 919 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 920 { 921 struct sighand_struct *sig; 922 923 if (clone_flags & CLONE_SIGHAND) { 924 atomic_inc(¤t->sighand->count); 925 return 0; 926 } 927 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 928 rcu_assign_pointer(tsk->sighand, sig); 929 if (!sig) 930 return -ENOMEM; 931 atomic_set(&sig->count, 1); 932 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 933 return 0; 934 } 935 936 void __cleanup_sighand(struct sighand_struct *sighand) 937 { 938 if (atomic_dec_and_test(&sighand->count)) 939 kmem_cache_free(sighand_cachep, sighand); 940 } 941 942 943 /* 944 * Initialize POSIX timer handling for a thread group. 945 */ 946 static void posix_cpu_timers_init_group(struct signal_struct *sig) 947 { 948 unsigned long cpu_limit; 949 950 /* Thread group counters. */ 951 thread_group_cputime_init(sig); 952 953 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 954 if (cpu_limit != RLIM_INFINITY) { 955 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 956 sig->cputimer.running = 1; 957 } 958 959 /* The timer lists. */ 960 INIT_LIST_HEAD(&sig->cpu_timers[0]); 961 INIT_LIST_HEAD(&sig->cpu_timers[1]); 962 INIT_LIST_HEAD(&sig->cpu_timers[2]); 963 } 964 965 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 966 { 967 struct signal_struct *sig; 968 969 if (clone_flags & CLONE_THREAD) 970 return 0; 971 972 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 973 tsk->signal = sig; 974 if (!sig) 975 return -ENOMEM; 976 977 sig->nr_threads = 1; 978 atomic_set(&sig->live, 1); 979 atomic_set(&sig->sigcnt, 1); 980 init_waitqueue_head(&sig->wait_chldexit); 981 if (clone_flags & CLONE_NEWPID) 982 sig->flags |= SIGNAL_UNKILLABLE; 983 sig->curr_target = tsk; 984 init_sigpending(&sig->shared_pending); 985 INIT_LIST_HEAD(&sig->posix_timers); 986 987 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 988 sig->real_timer.function = it_real_fn; 989 990 task_lock(current->group_leader); 991 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 992 task_unlock(current->group_leader); 993 994 posix_cpu_timers_init_group(sig); 995 996 tty_audit_fork(sig); 997 sched_autogroup_fork(sig); 998 999 #ifdef CONFIG_CGROUPS 1000 init_rwsem(&sig->group_rwsem); 1001 #endif 1002 1003 sig->oom_adj = current->signal->oom_adj; 1004 sig->oom_score_adj = current->signal->oom_score_adj; 1005 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1006 1007 mutex_init(&sig->cred_guard_mutex); 1008 1009 return 0; 1010 } 1011 1012 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1013 { 1014 unsigned long new_flags = p->flags; 1015 1016 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1017 new_flags |= PF_FORKNOEXEC; 1018 new_flags |= PF_STARTING; 1019 p->flags = new_flags; 1020 } 1021 1022 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1023 { 1024 current->clear_child_tid = tidptr; 1025 1026 return task_pid_vnr(current); 1027 } 1028 1029 static void rt_mutex_init_task(struct task_struct *p) 1030 { 1031 raw_spin_lock_init(&p->pi_lock); 1032 #ifdef CONFIG_RT_MUTEXES 1033 plist_head_init(&p->pi_waiters); 1034 p->pi_blocked_on = NULL; 1035 #endif 1036 } 1037 1038 #ifdef CONFIG_MM_OWNER 1039 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1040 { 1041 mm->owner = p; 1042 } 1043 #endif /* CONFIG_MM_OWNER */ 1044 1045 /* 1046 * Initialize POSIX timer handling for a single task. 1047 */ 1048 static void posix_cpu_timers_init(struct task_struct *tsk) 1049 { 1050 tsk->cputime_expires.prof_exp = 0; 1051 tsk->cputime_expires.virt_exp = 0; 1052 tsk->cputime_expires.sched_exp = 0; 1053 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1054 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1055 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1056 } 1057 1058 /* 1059 * This creates a new process as a copy of the old one, 1060 * but does not actually start it yet. 1061 * 1062 * It copies the registers, and all the appropriate 1063 * parts of the process environment (as per the clone 1064 * flags). The actual kick-off is left to the caller. 1065 */ 1066 static struct task_struct *copy_process(unsigned long clone_flags, 1067 unsigned long stack_start, 1068 struct pt_regs *regs, 1069 unsigned long stack_size, 1070 int __user *child_tidptr, 1071 struct pid *pid, 1072 int trace) 1073 { 1074 int retval; 1075 struct task_struct *p; 1076 int cgroup_callbacks_done = 0; 1077 1078 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1079 return ERR_PTR(-EINVAL); 1080 1081 /* 1082 * Thread groups must share signals as well, and detached threads 1083 * can only be started up within the thread group. 1084 */ 1085 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1086 return ERR_PTR(-EINVAL); 1087 1088 /* 1089 * Shared signal handlers imply shared VM. By way of the above, 1090 * thread groups also imply shared VM. Blocking this case allows 1091 * for various simplifications in other code. 1092 */ 1093 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1094 return ERR_PTR(-EINVAL); 1095 1096 /* 1097 * Siblings of global init remain as zombies on exit since they are 1098 * not reaped by their parent (swapper). To solve this and to avoid 1099 * multi-rooted process trees, prevent global and container-inits 1100 * from creating siblings. 1101 */ 1102 if ((clone_flags & CLONE_PARENT) && 1103 current->signal->flags & SIGNAL_UNKILLABLE) 1104 return ERR_PTR(-EINVAL); 1105 1106 retval = security_task_create(clone_flags); 1107 if (retval) 1108 goto fork_out; 1109 1110 retval = -ENOMEM; 1111 p = dup_task_struct(current); 1112 if (!p) 1113 goto fork_out; 1114 1115 ftrace_graph_init_task(p); 1116 1117 rt_mutex_init_task(p); 1118 1119 #ifdef CONFIG_PROVE_LOCKING 1120 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1121 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1122 #endif 1123 retval = -EAGAIN; 1124 if (atomic_read(&p->real_cred->user->processes) >= 1125 task_rlimit(p, RLIMIT_NPROC)) { 1126 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1127 p->real_cred->user != INIT_USER) 1128 goto bad_fork_free; 1129 } 1130 current->flags &= ~PF_NPROC_EXCEEDED; 1131 1132 retval = copy_creds(p, clone_flags); 1133 if (retval < 0) 1134 goto bad_fork_free; 1135 1136 /* 1137 * If multiple threads are within copy_process(), then this check 1138 * triggers too late. This doesn't hurt, the check is only there 1139 * to stop root fork bombs. 1140 */ 1141 retval = -EAGAIN; 1142 if (nr_threads >= max_threads) 1143 goto bad_fork_cleanup_count; 1144 1145 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1146 goto bad_fork_cleanup_count; 1147 1148 p->did_exec = 0; 1149 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1150 copy_flags(clone_flags, p); 1151 INIT_LIST_HEAD(&p->children); 1152 INIT_LIST_HEAD(&p->sibling); 1153 rcu_copy_process(p); 1154 p->vfork_done = NULL; 1155 spin_lock_init(&p->alloc_lock); 1156 1157 init_sigpending(&p->pending); 1158 1159 p->utime = p->stime = p->gtime = 0; 1160 p->utimescaled = p->stimescaled = 0; 1161 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1162 p->prev_utime = p->prev_stime = 0; 1163 #endif 1164 #if defined(SPLIT_RSS_COUNTING) 1165 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1166 #endif 1167 1168 p->default_timer_slack_ns = current->timer_slack_ns; 1169 1170 task_io_accounting_init(&p->ioac); 1171 acct_clear_integrals(p); 1172 1173 posix_cpu_timers_init(p); 1174 1175 do_posix_clock_monotonic_gettime(&p->start_time); 1176 p->real_start_time = p->start_time; 1177 monotonic_to_bootbased(&p->real_start_time); 1178 p->io_context = NULL; 1179 p->audit_context = NULL; 1180 if (clone_flags & CLONE_THREAD) 1181 threadgroup_change_begin(current); 1182 cgroup_fork(p); 1183 #ifdef CONFIG_NUMA 1184 p->mempolicy = mpol_dup(p->mempolicy); 1185 if (IS_ERR(p->mempolicy)) { 1186 retval = PTR_ERR(p->mempolicy); 1187 p->mempolicy = NULL; 1188 goto bad_fork_cleanup_cgroup; 1189 } 1190 mpol_fix_fork_child_flag(p); 1191 #endif 1192 #ifdef CONFIG_CPUSETS 1193 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1194 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1195 #endif 1196 #ifdef CONFIG_TRACE_IRQFLAGS 1197 p->irq_events = 0; 1198 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1199 p->hardirqs_enabled = 1; 1200 #else 1201 p->hardirqs_enabled = 0; 1202 #endif 1203 p->hardirq_enable_ip = 0; 1204 p->hardirq_enable_event = 0; 1205 p->hardirq_disable_ip = _THIS_IP_; 1206 p->hardirq_disable_event = 0; 1207 p->softirqs_enabled = 1; 1208 p->softirq_enable_ip = _THIS_IP_; 1209 p->softirq_enable_event = 0; 1210 p->softirq_disable_ip = 0; 1211 p->softirq_disable_event = 0; 1212 p->hardirq_context = 0; 1213 p->softirq_context = 0; 1214 #endif 1215 #ifdef CONFIG_LOCKDEP 1216 p->lockdep_depth = 0; /* no locks held yet */ 1217 p->curr_chain_key = 0; 1218 p->lockdep_recursion = 0; 1219 #endif 1220 1221 #ifdef CONFIG_DEBUG_MUTEXES 1222 p->blocked_on = NULL; /* not blocked yet */ 1223 #endif 1224 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1225 p->memcg_batch.do_batch = 0; 1226 p->memcg_batch.memcg = NULL; 1227 #endif 1228 1229 /* Perform scheduler related setup. Assign this task to a CPU. */ 1230 sched_fork(p); 1231 1232 retval = perf_event_init_task(p); 1233 if (retval) 1234 goto bad_fork_cleanup_policy; 1235 retval = audit_alloc(p); 1236 if (retval) 1237 goto bad_fork_cleanup_policy; 1238 /* copy all the process information */ 1239 retval = copy_semundo(clone_flags, p); 1240 if (retval) 1241 goto bad_fork_cleanup_audit; 1242 retval = copy_files(clone_flags, p); 1243 if (retval) 1244 goto bad_fork_cleanup_semundo; 1245 retval = copy_fs(clone_flags, p); 1246 if (retval) 1247 goto bad_fork_cleanup_files; 1248 retval = copy_sighand(clone_flags, p); 1249 if (retval) 1250 goto bad_fork_cleanup_fs; 1251 retval = copy_signal(clone_flags, p); 1252 if (retval) 1253 goto bad_fork_cleanup_sighand; 1254 retval = copy_mm(clone_flags, p); 1255 if (retval) 1256 goto bad_fork_cleanup_signal; 1257 retval = copy_namespaces(clone_flags, p); 1258 if (retval) 1259 goto bad_fork_cleanup_mm; 1260 retval = copy_io(clone_flags, p); 1261 if (retval) 1262 goto bad_fork_cleanup_namespaces; 1263 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1264 if (retval) 1265 goto bad_fork_cleanup_io; 1266 1267 if (pid != &init_struct_pid) { 1268 retval = -ENOMEM; 1269 pid = alloc_pid(p->nsproxy->pid_ns); 1270 if (!pid) 1271 goto bad_fork_cleanup_io; 1272 } 1273 1274 p->pid = pid_nr(pid); 1275 p->tgid = p->pid; 1276 if (clone_flags & CLONE_THREAD) 1277 p->tgid = current->tgid; 1278 1279 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1280 /* 1281 * Clear TID on mm_release()? 1282 */ 1283 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1284 #ifdef CONFIG_BLOCK 1285 p->plug = NULL; 1286 #endif 1287 #ifdef CONFIG_FUTEX 1288 p->robust_list = NULL; 1289 #ifdef CONFIG_COMPAT 1290 p->compat_robust_list = NULL; 1291 #endif 1292 INIT_LIST_HEAD(&p->pi_state_list); 1293 p->pi_state_cache = NULL; 1294 #endif 1295 /* 1296 * sigaltstack should be cleared when sharing the same VM 1297 */ 1298 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1299 p->sas_ss_sp = p->sas_ss_size = 0; 1300 1301 /* 1302 * Syscall tracing and stepping should be turned off in the 1303 * child regardless of CLONE_PTRACE. 1304 */ 1305 user_disable_single_step(p); 1306 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1307 #ifdef TIF_SYSCALL_EMU 1308 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1309 #endif 1310 clear_all_latency_tracing(p); 1311 1312 /* ok, now we should be set up.. */ 1313 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1314 p->pdeath_signal = 0; 1315 p->exit_state = 0; 1316 1317 p->nr_dirtied = 0; 1318 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1319 p->dirty_paused_when = 0; 1320 1321 /* 1322 * Ok, make it visible to the rest of the system. 1323 * We dont wake it up yet. 1324 */ 1325 p->group_leader = p; 1326 INIT_LIST_HEAD(&p->thread_group); 1327 1328 /* Now that the task is set up, run cgroup callbacks if 1329 * necessary. We need to run them before the task is visible 1330 * on the tasklist. */ 1331 cgroup_fork_callbacks(p); 1332 cgroup_callbacks_done = 1; 1333 1334 /* Need tasklist lock for parent etc handling! */ 1335 write_lock_irq(&tasklist_lock); 1336 1337 /* CLONE_PARENT re-uses the old parent */ 1338 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1339 p->real_parent = current->real_parent; 1340 p->parent_exec_id = current->parent_exec_id; 1341 } else { 1342 p->real_parent = current; 1343 p->parent_exec_id = current->self_exec_id; 1344 } 1345 1346 spin_lock(¤t->sighand->siglock); 1347 1348 /* 1349 * Process group and session signals need to be delivered to just the 1350 * parent before the fork or both the parent and the child after the 1351 * fork. Restart if a signal comes in before we add the new process to 1352 * it's process group. 1353 * A fatal signal pending means that current will exit, so the new 1354 * thread can't slip out of an OOM kill (or normal SIGKILL). 1355 */ 1356 recalc_sigpending(); 1357 if (signal_pending(current)) { 1358 spin_unlock(¤t->sighand->siglock); 1359 write_unlock_irq(&tasklist_lock); 1360 retval = -ERESTARTNOINTR; 1361 goto bad_fork_free_pid; 1362 } 1363 1364 if (clone_flags & CLONE_THREAD) { 1365 current->signal->nr_threads++; 1366 atomic_inc(¤t->signal->live); 1367 atomic_inc(¤t->signal->sigcnt); 1368 p->group_leader = current->group_leader; 1369 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1370 } 1371 1372 if (likely(p->pid)) { 1373 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1374 1375 if (thread_group_leader(p)) { 1376 if (is_child_reaper(pid)) 1377 p->nsproxy->pid_ns->child_reaper = p; 1378 1379 p->signal->leader_pid = pid; 1380 p->signal->tty = tty_kref_get(current->signal->tty); 1381 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1382 attach_pid(p, PIDTYPE_SID, task_session(current)); 1383 list_add_tail(&p->sibling, &p->real_parent->children); 1384 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1385 __this_cpu_inc(process_counts); 1386 } 1387 attach_pid(p, PIDTYPE_PID, pid); 1388 nr_threads++; 1389 } 1390 1391 total_forks++; 1392 spin_unlock(¤t->sighand->siglock); 1393 write_unlock_irq(&tasklist_lock); 1394 proc_fork_connector(p); 1395 cgroup_post_fork(p); 1396 if (clone_flags & CLONE_THREAD) 1397 threadgroup_change_end(current); 1398 perf_event_fork(p); 1399 1400 trace_task_newtask(p, clone_flags); 1401 1402 return p; 1403 1404 bad_fork_free_pid: 1405 if (pid != &init_struct_pid) 1406 free_pid(pid); 1407 bad_fork_cleanup_io: 1408 if (p->io_context) 1409 exit_io_context(p); 1410 bad_fork_cleanup_namespaces: 1411 exit_task_namespaces(p); 1412 bad_fork_cleanup_mm: 1413 if (p->mm) 1414 mmput(p->mm); 1415 bad_fork_cleanup_signal: 1416 if (!(clone_flags & CLONE_THREAD)) 1417 free_signal_struct(p->signal); 1418 bad_fork_cleanup_sighand: 1419 __cleanup_sighand(p->sighand); 1420 bad_fork_cleanup_fs: 1421 exit_fs(p); /* blocking */ 1422 bad_fork_cleanup_files: 1423 exit_files(p); /* blocking */ 1424 bad_fork_cleanup_semundo: 1425 exit_sem(p); 1426 bad_fork_cleanup_audit: 1427 audit_free(p); 1428 bad_fork_cleanup_policy: 1429 perf_event_free_task(p); 1430 #ifdef CONFIG_NUMA 1431 mpol_put(p->mempolicy); 1432 bad_fork_cleanup_cgroup: 1433 #endif 1434 if (clone_flags & CLONE_THREAD) 1435 threadgroup_change_end(current); 1436 cgroup_exit(p, cgroup_callbacks_done); 1437 delayacct_tsk_free(p); 1438 module_put(task_thread_info(p)->exec_domain->module); 1439 bad_fork_cleanup_count: 1440 atomic_dec(&p->cred->user->processes); 1441 exit_creds(p); 1442 bad_fork_free: 1443 free_task(p); 1444 fork_out: 1445 return ERR_PTR(retval); 1446 } 1447 1448 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1449 { 1450 memset(regs, 0, sizeof(struct pt_regs)); 1451 return regs; 1452 } 1453 1454 static inline void init_idle_pids(struct pid_link *links) 1455 { 1456 enum pid_type type; 1457 1458 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1459 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1460 links[type].pid = &init_struct_pid; 1461 } 1462 } 1463 1464 struct task_struct * __cpuinit fork_idle(int cpu) 1465 { 1466 struct task_struct *task; 1467 struct pt_regs regs; 1468 1469 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1470 &init_struct_pid, 0); 1471 if (!IS_ERR(task)) { 1472 init_idle_pids(task->pids); 1473 init_idle(task, cpu); 1474 } 1475 1476 return task; 1477 } 1478 1479 /* 1480 * Ok, this is the main fork-routine. 1481 * 1482 * It copies the process, and if successful kick-starts 1483 * it and waits for it to finish using the VM if required. 1484 */ 1485 long do_fork(unsigned long clone_flags, 1486 unsigned long stack_start, 1487 struct pt_regs *regs, 1488 unsigned long stack_size, 1489 int __user *parent_tidptr, 1490 int __user *child_tidptr) 1491 { 1492 struct task_struct *p; 1493 int trace = 0; 1494 long nr; 1495 1496 /* 1497 * Do some preliminary argument and permissions checking before we 1498 * actually start allocating stuff 1499 */ 1500 if (clone_flags & CLONE_NEWUSER) { 1501 if (clone_flags & CLONE_THREAD) 1502 return -EINVAL; 1503 /* hopefully this check will go away when userns support is 1504 * complete 1505 */ 1506 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1507 !capable(CAP_SETGID)) 1508 return -EPERM; 1509 } 1510 1511 /* 1512 * Determine whether and which event to report to ptracer. When 1513 * called from kernel_thread or CLONE_UNTRACED is explicitly 1514 * requested, no event is reported; otherwise, report if the event 1515 * for the type of forking is enabled. 1516 */ 1517 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1518 if (clone_flags & CLONE_VFORK) 1519 trace = PTRACE_EVENT_VFORK; 1520 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1521 trace = PTRACE_EVENT_CLONE; 1522 else 1523 trace = PTRACE_EVENT_FORK; 1524 1525 if (likely(!ptrace_event_enabled(current, trace))) 1526 trace = 0; 1527 } 1528 1529 p = copy_process(clone_flags, stack_start, regs, stack_size, 1530 child_tidptr, NULL, trace); 1531 /* 1532 * Do this prior waking up the new thread - the thread pointer 1533 * might get invalid after that point, if the thread exits quickly. 1534 */ 1535 if (!IS_ERR(p)) { 1536 struct completion vfork; 1537 1538 trace_sched_process_fork(current, p); 1539 1540 nr = task_pid_vnr(p); 1541 1542 if (clone_flags & CLONE_PARENT_SETTID) 1543 put_user(nr, parent_tidptr); 1544 1545 if (clone_flags & CLONE_VFORK) { 1546 p->vfork_done = &vfork; 1547 init_completion(&vfork); 1548 } 1549 1550 /* 1551 * We set PF_STARTING at creation in case tracing wants to 1552 * use this to distinguish a fully live task from one that 1553 * hasn't finished SIGSTOP raising yet. Now we clear it 1554 * and set the child going. 1555 */ 1556 p->flags &= ~PF_STARTING; 1557 1558 wake_up_new_task(p); 1559 1560 /* forking complete and child started to run, tell ptracer */ 1561 if (unlikely(trace)) 1562 ptrace_event(trace, nr); 1563 1564 if (clone_flags & CLONE_VFORK) { 1565 freezer_do_not_count(); 1566 wait_for_completion(&vfork); 1567 freezer_count(); 1568 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1569 } 1570 } else { 1571 nr = PTR_ERR(p); 1572 } 1573 return nr; 1574 } 1575 1576 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1577 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1578 #endif 1579 1580 static void sighand_ctor(void *data) 1581 { 1582 struct sighand_struct *sighand = data; 1583 1584 spin_lock_init(&sighand->siglock); 1585 init_waitqueue_head(&sighand->signalfd_wqh); 1586 } 1587 1588 void __init proc_caches_init(void) 1589 { 1590 sighand_cachep = kmem_cache_create("sighand_cache", 1591 sizeof(struct sighand_struct), 0, 1592 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1593 SLAB_NOTRACK, sighand_ctor); 1594 signal_cachep = kmem_cache_create("signal_cache", 1595 sizeof(struct signal_struct), 0, 1596 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1597 files_cachep = kmem_cache_create("files_cache", 1598 sizeof(struct files_struct), 0, 1599 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1600 fs_cachep = kmem_cache_create("fs_cache", 1601 sizeof(struct fs_struct), 0, 1602 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1603 /* 1604 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1605 * whole struct cpumask for the OFFSTACK case. We could change 1606 * this to *only* allocate as much of it as required by the 1607 * maximum number of CPU's we can ever have. The cpumask_allocation 1608 * is at the end of the structure, exactly for that reason. 1609 */ 1610 mm_cachep = kmem_cache_create("mm_struct", 1611 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1612 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1613 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1614 mmap_init(); 1615 nsproxy_cache_init(); 1616 } 1617 1618 /* 1619 * Check constraints on flags passed to the unshare system call. 1620 */ 1621 static int check_unshare_flags(unsigned long unshare_flags) 1622 { 1623 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1624 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1625 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1626 return -EINVAL; 1627 /* 1628 * Not implemented, but pretend it works if there is nothing to 1629 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1630 * needs to unshare vm. 1631 */ 1632 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1633 /* FIXME: get_task_mm() increments ->mm_users */ 1634 if (atomic_read(¤t->mm->mm_users) > 1) 1635 return -EINVAL; 1636 } 1637 1638 return 0; 1639 } 1640 1641 /* 1642 * Unshare the filesystem structure if it is being shared 1643 */ 1644 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1645 { 1646 struct fs_struct *fs = current->fs; 1647 1648 if (!(unshare_flags & CLONE_FS) || !fs) 1649 return 0; 1650 1651 /* don't need lock here; in the worst case we'll do useless copy */ 1652 if (fs->users == 1) 1653 return 0; 1654 1655 *new_fsp = copy_fs_struct(fs); 1656 if (!*new_fsp) 1657 return -ENOMEM; 1658 1659 return 0; 1660 } 1661 1662 /* 1663 * Unshare file descriptor table if it is being shared 1664 */ 1665 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1666 { 1667 struct files_struct *fd = current->files; 1668 int error = 0; 1669 1670 if ((unshare_flags & CLONE_FILES) && 1671 (fd && atomic_read(&fd->count) > 1)) { 1672 *new_fdp = dup_fd(fd, &error); 1673 if (!*new_fdp) 1674 return error; 1675 } 1676 1677 return 0; 1678 } 1679 1680 /* 1681 * unshare allows a process to 'unshare' part of the process 1682 * context which was originally shared using clone. copy_* 1683 * functions used by do_fork() cannot be used here directly 1684 * because they modify an inactive task_struct that is being 1685 * constructed. Here we are modifying the current, active, 1686 * task_struct. 1687 */ 1688 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1689 { 1690 struct fs_struct *fs, *new_fs = NULL; 1691 struct files_struct *fd, *new_fd = NULL; 1692 struct nsproxy *new_nsproxy = NULL; 1693 int do_sysvsem = 0; 1694 int err; 1695 1696 err = check_unshare_flags(unshare_flags); 1697 if (err) 1698 goto bad_unshare_out; 1699 1700 /* 1701 * If unsharing namespace, must also unshare filesystem information. 1702 */ 1703 if (unshare_flags & CLONE_NEWNS) 1704 unshare_flags |= CLONE_FS; 1705 /* 1706 * CLONE_NEWIPC must also detach from the undolist: after switching 1707 * to a new ipc namespace, the semaphore arrays from the old 1708 * namespace are unreachable. 1709 */ 1710 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1711 do_sysvsem = 1; 1712 err = unshare_fs(unshare_flags, &new_fs); 1713 if (err) 1714 goto bad_unshare_out; 1715 err = unshare_fd(unshare_flags, &new_fd); 1716 if (err) 1717 goto bad_unshare_cleanup_fs; 1718 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1719 if (err) 1720 goto bad_unshare_cleanup_fd; 1721 1722 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1723 if (do_sysvsem) { 1724 /* 1725 * CLONE_SYSVSEM is equivalent to sys_exit(). 1726 */ 1727 exit_sem(current); 1728 } 1729 1730 if (new_nsproxy) { 1731 switch_task_namespaces(current, new_nsproxy); 1732 new_nsproxy = NULL; 1733 } 1734 1735 task_lock(current); 1736 1737 if (new_fs) { 1738 fs = current->fs; 1739 spin_lock(&fs->lock); 1740 current->fs = new_fs; 1741 if (--fs->users) 1742 new_fs = NULL; 1743 else 1744 new_fs = fs; 1745 spin_unlock(&fs->lock); 1746 } 1747 1748 if (new_fd) { 1749 fd = current->files; 1750 current->files = new_fd; 1751 new_fd = fd; 1752 } 1753 1754 task_unlock(current); 1755 } 1756 1757 if (new_nsproxy) 1758 put_nsproxy(new_nsproxy); 1759 1760 bad_unshare_cleanup_fd: 1761 if (new_fd) 1762 put_files_struct(new_fd); 1763 1764 bad_unshare_cleanup_fs: 1765 if (new_fs) 1766 free_fs_struct(new_fs); 1767 1768 bad_unshare_out: 1769 return err; 1770 } 1771 1772 /* 1773 * Helper to unshare the files of the current task. 1774 * We don't want to expose copy_files internals to 1775 * the exec layer of the kernel. 1776 */ 1777 1778 int unshare_files(struct files_struct **displaced) 1779 { 1780 struct task_struct *task = current; 1781 struct files_struct *copy = NULL; 1782 int error; 1783 1784 error = unshare_fd(CLONE_FILES, ©); 1785 if (error || !copy) { 1786 *displaced = NULL; 1787 return error; 1788 } 1789 *displaced = task->files; 1790 task_lock(task); 1791 task->files = copy; 1792 task_unlock(task); 1793 return 0; 1794 } 1795