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; 873 874 if (!ioc) 875 return 0; 876 /* 877 * Share io context with parent, if CLONE_IO is set 878 */ 879 if (clone_flags & CLONE_IO) { 880 tsk->io_context = ioc_task_link(ioc); 881 if (unlikely(!tsk->io_context)) 882 return -ENOMEM; 883 } else if (ioprio_valid(ioc->ioprio)) { 884 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 885 if (unlikely(!tsk->io_context)) 886 return -ENOMEM; 887 888 tsk->io_context->ioprio = ioc->ioprio; 889 } 890 #endif 891 return 0; 892 } 893 894 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 895 { 896 struct sighand_struct *sig; 897 898 if (clone_flags & CLONE_SIGHAND) { 899 atomic_inc(¤t->sighand->count); 900 return 0; 901 } 902 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 903 rcu_assign_pointer(tsk->sighand, sig); 904 if (!sig) 905 return -ENOMEM; 906 atomic_set(&sig->count, 1); 907 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 908 return 0; 909 } 910 911 void __cleanup_sighand(struct sighand_struct *sighand) 912 { 913 if (atomic_dec_and_test(&sighand->count)) 914 kmem_cache_free(sighand_cachep, sighand); 915 } 916 917 918 /* 919 * Initialize POSIX timer handling for a thread group. 920 */ 921 static void posix_cpu_timers_init_group(struct signal_struct *sig) 922 { 923 unsigned long cpu_limit; 924 925 /* Thread group counters. */ 926 thread_group_cputime_init(sig); 927 928 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 929 if (cpu_limit != RLIM_INFINITY) { 930 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 931 sig->cputimer.running = 1; 932 } 933 934 /* The timer lists. */ 935 INIT_LIST_HEAD(&sig->cpu_timers[0]); 936 INIT_LIST_HEAD(&sig->cpu_timers[1]); 937 INIT_LIST_HEAD(&sig->cpu_timers[2]); 938 } 939 940 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 941 { 942 struct signal_struct *sig; 943 944 if (clone_flags & CLONE_THREAD) 945 return 0; 946 947 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 948 tsk->signal = sig; 949 if (!sig) 950 return -ENOMEM; 951 952 sig->nr_threads = 1; 953 atomic_set(&sig->live, 1); 954 atomic_set(&sig->sigcnt, 1); 955 init_waitqueue_head(&sig->wait_chldexit); 956 if (clone_flags & CLONE_NEWPID) 957 sig->flags |= SIGNAL_UNKILLABLE; 958 sig->curr_target = tsk; 959 init_sigpending(&sig->shared_pending); 960 INIT_LIST_HEAD(&sig->posix_timers); 961 962 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 963 sig->real_timer.function = it_real_fn; 964 965 task_lock(current->group_leader); 966 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 967 task_unlock(current->group_leader); 968 969 posix_cpu_timers_init_group(sig); 970 971 tty_audit_fork(sig); 972 sched_autogroup_fork(sig); 973 974 #ifdef CONFIG_CGROUPS 975 init_rwsem(&sig->threadgroup_fork_lock); 976 #endif 977 978 sig->oom_adj = current->signal->oom_adj; 979 sig->oom_score_adj = current->signal->oom_score_adj; 980 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 981 982 mutex_init(&sig->cred_guard_mutex); 983 984 return 0; 985 } 986 987 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 988 { 989 unsigned long new_flags = p->flags; 990 991 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 992 new_flags |= PF_FORKNOEXEC; 993 new_flags |= PF_STARTING; 994 p->flags = new_flags; 995 clear_freeze_flag(p); 996 } 997 998 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 999 { 1000 current->clear_child_tid = tidptr; 1001 1002 return task_pid_vnr(current); 1003 } 1004 1005 static void rt_mutex_init_task(struct task_struct *p) 1006 { 1007 raw_spin_lock_init(&p->pi_lock); 1008 #ifdef CONFIG_RT_MUTEXES 1009 plist_head_init(&p->pi_waiters); 1010 p->pi_blocked_on = NULL; 1011 #endif 1012 } 1013 1014 #ifdef CONFIG_MM_OWNER 1015 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1016 { 1017 mm->owner = p; 1018 } 1019 #endif /* CONFIG_MM_OWNER */ 1020 1021 /* 1022 * Initialize POSIX timer handling for a single task. 1023 */ 1024 static void posix_cpu_timers_init(struct task_struct *tsk) 1025 { 1026 tsk->cputime_expires.prof_exp = cputime_zero; 1027 tsk->cputime_expires.virt_exp = cputime_zero; 1028 tsk->cputime_expires.sched_exp = 0; 1029 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1030 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1031 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1032 } 1033 1034 /* 1035 * This creates a new process as a copy of the old one, 1036 * but does not actually start it yet. 1037 * 1038 * It copies the registers, and all the appropriate 1039 * parts of the process environment (as per the clone 1040 * flags). The actual kick-off is left to the caller. 1041 */ 1042 static struct task_struct *copy_process(unsigned long clone_flags, 1043 unsigned long stack_start, 1044 struct pt_regs *regs, 1045 unsigned long stack_size, 1046 int __user *child_tidptr, 1047 struct pid *pid, 1048 int trace) 1049 { 1050 int retval; 1051 struct task_struct *p; 1052 int cgroup_callbacks_done = 0; 1053 1054 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1055 return ERR_PTR(-EINVAL); 1056 1057 /* 1058 * Thread groups must share signals as well, and detached threads 1059 * can only be started up within the thread group. 1060 */ 1061 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1062 return ERR_PTR(-EINVAL); 1063 1064 /* 1065 * Shared signal handlers imply shared VM. By way of the above, 1066 * thread groups also imply shared VM. Blocking this case allows 1067 * for various simplifications in other code. 1068 */ 1069 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1070 return ERR_PTR(-EINVAL); 1071 1072 /* 1073 * Siblings of global init remain as zombies on exit since they are 1074 * not reaped by their parent (swapper). To solve this and to avoid 1075 * multi-rooted process trees, prevent global and container-inits 1076 * from creating siblings. 1077 */ 1078 if ((clone_flags & CLONE_PARENT) && 1079 current->signal->flags & SIGNAL_UNKILLABLE) 1080 return ERR_PTR(-EINVAL); 1081 1082 retval = security_task_create(clone_flags); 1083 if (retval) 1084 goto fork_out; 1085 1086 retval = -ENOMEM; 1087 p = dup_task_struct(current); 1088 if (!p) 1089 goto fork_out; 1090 1091 ftrace_graph_init_task(p); 1092 1093 rt_mutex_init_task(p); 1094 1095 #ifdef CONFIG_PROVE_LOCKING 1096 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1097 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1098 #endif 1099 retval = -EAGAIN; 1100 if (atomic_read(&p->real_cred->user->processes) >= 1101 task_rlimit(p, RLIMIT_NPROC)) { 1102 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1103 p->real_cred->user != INIT_USER) 1104 goto bad_fork_free; 1105 } 1106 current->flags &= ~PF_NPROC_EXCEEDED; 1107 1108 retval = copy_creds(p, clone_flags); 1109 if (retval < 0) 1110 goto bad_fork_free; 1111 1112 /* 1113 * If multiple threads are within copy_process(), then this check 1114 * triggers too late. This doesn't hurt, the check is only there 1115 * to stop root fork bombs. 1116 */ 1117 retval = -EAGAIN; 1118 if (nr_threads >= max_threads) 1119 goto bad_fork_cleanup_count; 1120 1121 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1122 goto bad_fork_cleanup_count; 1123 1124 p->did_exec = 0; 1125 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1126 copy_flags(clone_flags, p); 1127 INIT_LIST_HEAD(&p->children); 1128 INIT_LIST_HEAD(&p->sibling); 1129 rcu_copy_process(p); 1130 p->vfork_done = NULL; 1131 spin_lock_init(&p->alloc_lock); 1132 1133 init_sigpending(&p->pending); 1134 1135 p->utime = cputime_zero; 1136 p->stime = cputime_zero; 1137 p->gtime = cputime_zero; 1138 p->utimescaled = cputime_zero; 1139 p->stimescaled = cputime_zero; 1140 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1141 p->prev_utime = cputime_zero; 1142 p->prev_stime = cputime_zero; 1143 #endif 1144 #if defined(SPLIT_RSS_COUNTING) 1145 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1146 #endif 1147 1148 p->default_timer_slack_ns = current->timer_slack_ns; 1149 1150 task_io_accounting_init(&p->ioac); 1151 acct_clear_integrals(p); 1152 1153 posix_cpu_timers_init(p); 1154 1155 do_posix_clock_monotonic_gettime(&p->start_time); 1156 p->real_start_time = p->start_time; 1157 monotonic_to_bootbased(&p->real_start_time); 1158 p->io_context = NULL; 1159 p->audit_context = NULL; 1160 if (clone_flags & CLONE_THREAD) 1161 threadgroup_fork_read_lock(current); 1162 cgroup_fork(p); 1163 #ifdef CONFIG_NUMA 1164 p->mempolicy = mpol_dup(p->mempolicy); 1165 if (IS_ERR(p->mempolicy)) { 1166 retval = PTR_ERR(p->mempolicy); 1167 p->mempolicy = NULL; 1168 goto bad_fork_cleanup_cgroup; 1169 } 1170 mpol_fix_fork_child_flag(p); 1171 #endif 1172 #ifdef CONFIG_CPUSETS 1173 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1174 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1175 #endif 1176 #ifdef CONFIG_TRACE_IRQFLAGS 1177 p->irq_events = 0; 1178 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1179 p->hardirqs_enabled = 1; 1180 #else 1181 p->hardirqs_enabled = 0; 1182 #endif 1183 p->hardirq_enable_ip = 0; 1184 p->hardirq_enable_event = 0; 1185 p->hardirq_disable_ip = _THIS_IP_; 1186 p->hardirq_disable_event = 0; 1187 p->softirqs_enabled = 1; 1188 p->softirq_enable_ip = _THIS_IP_; 1189 p->softirq_enable_event = 0; 1190 p->softirq_disable_ip = 0; 1191 p->softirq_disable_event = 0; 1192 p->hardirq_context = 0; 1193 p->softirq_context = 0; 1194 #endif 1195 #ifdef CONFIG_LOCKDEP 1196 p->lockdep_depth = 0; /* no locks held yet */ 1197 p->curr_chain_key = 0; 1198 p->lockdep_recursion = 0; 1199 #endif 1200 1201 #ifdef CONFIG_DEBUG_MUTEXES 1202 p->blocked_on = NULL; /* not blocked yet */ 1203 #endif 1204 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1205 p->memcg_batch.do_batch = 0; 1206 p->memcg_batch.memcg = NULL; 1207 #endif 1208 1209 /* Perform scheduler related setup. Assign this task to a CPU. */ 1210 sched_fork(p); 1211 1212 retval = perf_event_init_task(p); 1213 if (retval) 1214 goto bad_fork_cleanup_policy; 1215 retval = audit_alloc(p); 1216 if (retval) 1217 goto bad_fork_cleanup_policy; 1218 /* copy all the process information */ 1219 retval = copy_semundo(clone_flags, p); 1220 if (retval) 1221 goto bad_fork_cleanup_audit; 1222 retval = copy_files(clone_flags, p); 1223 if (retval) 1224 goto bad_fork_cleanup_semundo; 1225 retval = copy_fs(clone_flags, p); 1226 if (retval) 1227 goto bad_fork_cleanup_files; 1228 retval = copy_sighand(clone_flags, p); 1229 if (retval) 1230 goto bad_fork_cleanup_fs; 1231 retval = copy_signal(clone_flags, p); 1232 if (retval) 1233 goto bad_fork_cleanup_sighand; 1234 retval = copy_mm(clone_flags, p); 1235 if (retval) 1236 goto bad_fork_cleanup_signal; 1237 retval = copy_namespaces(clone_flags, p); 1238 if (retval) 1239 goto bad_fork_cleanup_mm; 1240 retval = copy_io(clone_flags, p); 1241 if (retval) 1242 goto bad_fork_cleanup_namespaces; 1243 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1244 if (retval) 1245 goto bad_fork_cleanup_io; 1246 1247 if (pid != &init_struct_pid) { 1248 retval = -ENOMEM; 1249 pid = alloc_pid(p->nsproxy->pid_ns); 1250 if (!pid) 1251 goto bad_fork_cleanup_io; 1252 } 1253 1254 p->pid = pid_nr(pid); 1255 p->tgid = p->pid; 1256 if (clone_flags & CLONE_THREAD) 1257 p->tgid = current->tgid; 1258 1259 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1260 /* 1261 * Clear TID on mm_release()? 1262 */ 1263 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1264 #ifdef CONFIG_BLOCK 1265 p->plug = NULL; 1266 #endif 1267 #ifdef CONFIG_FUTEX 1268 p->robust_list = NULL; 1269 #ifdef CONFIG_COMPAT 1270 p->compat_robust_list = NULL; 1271 #endif 1272 INIT_LIST_HEAD(&p->pi_state_list); 1273 p->pi_state_cache = NULL; 1274 #endif 1275 /* 1276 * sigaltstack should be cleared when sharing the same VM 1277 */ 1278 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1279 p->sas_ss_sp = p->sas_ss_size = 0; 1280 1281 /* 1282 * Syscall tracing and stepping should be turned off in the 1283 * child regardless of CLONE_PTRACE. 1284 */ 1285 user_disable_single_step(p); 1286 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1287 #ifdef TIF_SYSCALL_EMU 1288 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1289 #endif 1290 clear_all_latency_tracing(p); 1291 1292 /* ok, now we should be set up.. */ 1293 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1294 p->pdeath_signal = 0; 1295 p->exit_state = 0; 1296 1297 p->nr_dirtied = 0; 1298 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1299 1300 /* 1301 * Ok, make it visible to the rest of the system. 1302 * We dont wake it up yet. 1303 */ 1304 p->group_leader = p; 1305 INIT_LIST_HEAD(&p->thread_group); 1306 1307 /* Now that the task is set up, run cgroup callbacks if 1308 * necessary. We need to run them before the task is visible 1309 * on the tasklist. */ 1310 cgroup_fork_callbacks(p); 1311 cgroup_callbacks_done = 1; 1312 1313 /* Need tasklist lock for parent etc handling! */ 1314 write_lock_irq(&tasklist_lock); 1315 1316 /* CLONE_PARENT re-uses the old parent */ 1317 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1318 p->real_parent = current->real_parent; 1319 p->parent_exec_id = current->parent_exec_id; 1320 } else { 1321 p->real_parent = current; 1322 p->parent_exec_id = current->self_exec_id; 1323 } 1324 1325 spin_lock(¤t->sighand->siglock); 1326 1327 /* 1328 * Process group and session signals need to be delivered to just the 1329 * parent before the fork or both the parent and the child after the 1330 * fork. Restart if a signal comes in before we add the new process to 1331 * it's process group. 1332 * A fatal signal pending means that current will exit, so the new 1333 * thread can't slip out of an OOM kill (or normal SIGKILL). 1334 */ 1335 recalc_sigpending(); 1336 if (signal_pending(current)) { 1337 spin_unlock(¤t->sighand->siglock); 1338 write_unlock_irq(&tasklist_lock); 1339 retval = -ERESTARTNOINTR; 1340 goto bad_fork_free_pid; 1341 } 1342 1343 if (clone_flags & CLONE_THREAD) { 1344 current->signal->nr_threads++; 1345 atomic_inc(¤t->signal->live); 1346 atomic_inc(¤t->signal->sigcnt); 1347 p->group_leader = current->group_leader; 1348 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1349 } 1350 1351 if (likely(p->pid)) { 1352 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1353 1354 if (thread_group_leader(p)) { 1355 if (is_child_reaper(pid)) 1356 p->nsproxy->pid_ns->child_reaper = p; 1357 1358 p->signal->leader_pid = pid; 1359 p->signal->tty = tty_kref_get(current->signal->tty); 1360 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1361 attach_pid(p, PIDTYPE_SID, task_session(current)); 1362 list_add_tail(&p->sibling, &p->real_parent->children); 1363 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1364 __this_cpu_inc(process_counts); 1365 } 1366 attach_pid(p, PIDTYPE_PID, pid); 1367 nr_threads++; 1368 } 1369 1370 total_forks++; 1371 spin_unlock(¤t->sighand->siglock); 1372 write_unlock_irq(&tasklist_lock); 1373 proc_fork_connector(p); 1374 cgroup_post_fork(p); 1375 if (clone_flags & CLONE_THREAD) 1376 threadgroup_fork_read_unlock(current); 1377 perf_event_fork(p); 1378 return p; 1379 1380 bad_fork_free_pid: 1381 if (pid != &init_struct_pid) 1382 free_pid(pid); 1383 bad_fork_cleanup_io: 1384 if (p->io_context) 1385 exit_io_context(p); 1386 bad_fork_cleanup_namespaces: 1387 exit_task_namespaces(p); 1388 bad_fork_cleanup_mm: 1389 if (p->mm) 1390 mmput(p->mm); 1391 bad_fork_cleanup_signal: 1392 if (!(clone_flags & CLONE_THREAD)) 1393 free_signal_struct(p->signal); 1394 bad_fork_cleanup_sighand: 1395 __cleanup_sighand(p->sighand); 1396 bad_fork_cleanup_fs: 1397 exit_fs(p); /* blocking */ 1398 bad_fork_cleanup_files: 1399 exit_files(p); /* blocking */ 1400 bad_fork_cleanup_semundo: 1401 exit_sem(p); 1402 bad_fork_cleanup_audit: 1403 audit_free(p); 1404 bad_fork_cleanup_policy: 1405 perf_event_free_task(p); 1406 #ifdef CONFIG_NUMA 1407 mpol_put(p->mempolicy); 1408 bad_fork_cleanup_cgroup: 1409 #endif 1410 if (clone_flags & CLONE_THREAD) 1411 threadgroup_fork_read_unlock(current); 1412 cgroup_exit(p, cgroup_callbacks_done); 1413 delayacct_tsk_free(p); 1414 module_put(task_thread_info(p)->exec_domain->module); 1415 bad_fork_cleanup_count: 1416 atomic_dec(&p->cred->user->processes); 1417 exit_creds(p); 1418 bad_fork_free: 1419 free_task(p); 1420 fork_out: 1421 return ERR_PTR(retval); 1422 } 1423 1424 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1425 { 1426 memset(regs, 0, sizeof(struct pt_regs)); 1427 return regs; 1428 } 1429 1430 static inline void init_idle_pids(struct pid_link *links) 1431 { 1432 enum pid_type type; 1433 1434 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1435 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1436 links[type].pid = &init_struct_pid; 1437 } 1438 } 1439 1440 struct task_struct * __cpuinit fork_idle(int cpu) 1441 { 1442 struct task_struct *task; 1443 struct pt_regs regs; 1444 1445 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1446 &init_struct_pid, 0); 1447 if (!IS_ERR(task)) { 1448 init_idle_pids(task->pids); 1449 init_idle(task, cpu); 1450 } 1451 1452 return task; 1453 } 1454 1455 /* 1456 * Ok, this is the main fork-routine. 1457 * 1458 * It copies the process, and if successful kick-starts 1459 * it and waits for it to finish using the VM if required. 1460 */ 1461 long do_fork(unsigned long clone_flags, 1462 unsigned long stack_start, 1463 struct pt_regs *regs, 1464 unsigned long stack_size, 1465 int __user *parent_tidptr, 1466 int __user *child_tidptr) 1467 { 1468 struct task_struct *p; 1469 int trace = 0; 1470 long nr; 1471 1472 /* 1473 * Do some preliminary argument and permissions checking before we 1474 * actually start allocating stuff 1475 */ 1476 if (clone_flags & CLONE_NEWUSER) { 1477 if (clone_flags & CLONE_THREAD) 1478 return -EINVAL; 1479 /* hopefully this check will go away when userns support is 1480 * complete 1481 */ 1482 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1483 !capable(CAP_SETGID)) 1484 return -EPERM; 1485 } 1486 1487 /* 1488 * Determine whether and which event to report to ptracer. When 1489 * called from kernel_thread or CLONE_UNTRACED is explicitly 1490 * requested, no event is reported; otherwise, report if the event 1491 * for the type of forking is enabled. 1492 */ 1493 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1494 if (clone_flags & CLONE_VFORK) 1495 trace = PTRACE_EVENT_VFORK; 1496 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1497 trace = PTRACE_EVENT_CLONE; 1498 else 1499 trace = PTRACE_EVENT_FORK; 1500 1501 if (likely(!ptrace_event_enabled(current, trace))) 1502 trace = 0; 1503 } 1504 1505 p = copy_process(clone_flags, stack_start, regs, stack_size, 1506 child_tidptr, NULL, trace); 1507 /* 1508 * Do this prior waking up the new thread - the thread pointer 1509 * might get invalid after that point, if the thread exits quickly. 1510 */ 1511 if (!IS_ERR(p)) { 1512 struct completion vfork; 1513 1514 trace_sched_process_fork(current, p); 1515 1516 nr = task_pid_vnr(p); 1517 1518 if (clone_flags & CLONE_PARENT_SETTID) 1519 put_user(nr, parent_tidptr); 1520 1521 if (clone_flags & CLONE_VFORK) { 1522 p->vfork_done = &vfork; 1523 init_completion(&vfork); 1524 } 1525 1526 audit_finish_fork(p); 1527 1528 /* 1529 * We set PF_STARTING at creation in case tracing wants to 1530 * use this to distinguish a fully live task from one that 1531 * hasn't finished SIGSTOP raising yet. Now we clear it 1532 * and set the child going. 1533 */ 1534 p->flags &= ~PF_STARTING; 1535 1536 wake_up_new_task(p); 1537 1538 /* forking complete and child started to run, tell ptracer */ 1539 if (unlikely(trace)) 1540 ptrace_event(trace, nr); 1541 1542 if (clone_flags & CLONE_VFORK) { 1543 freezer_do_not_count(); 1544 wait_for_completion(&vfork); 1545 freezer_count(); 1546 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1547 } 1548 } else { 1549 nr = PTR_ERR(p); 1550 } 1551 return nr; 1552 } 1553 1554 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1555 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1556 #endif 1557 1558 static void sighand_ctor(void *data) 1559 { 1560 struct sighand_struct *sighand = data; 1561 1562 spin_lock_init(&sighand->siglock); 1563 init_waitqueue_head(&sighand->signalfd_wqh); 1564 } 1565 1566 void __init proc_caches_init(void) 1567 { 1568 sighand_cachep = kmem_cache_create("sighand_cache", 1569 sizeof(struct sighand_struct), 0, 1570 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1571 SLAB_NOTRACK, sighand_ctor); 1572 signal_cachep = kmem_cache_create("signal_cache", 1573 sizeof(struct signal_struct), 0, 1574 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1575 files_cachep = kmem_cache_create("files_cache", 1576 sizeof(struct files_struct), 0, 1577 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1578 fs_cachep = kmem_cache_create("fs_cache", 1579 sizeof(struct fs_struct), 0, 1580 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1581 /* 1582 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1583 * whole struct cpumask for the OFFSTACK case. We could change 1584 * this to *only* allocate as much of it as required by the 1585 * maximum number of CPU's we can ever have. The cpumask_allocation 1586 * is at the end of the structure, exactly for that reason. 1587 */ 1588 mm_cachep = kmem_cache_create("mm_struct", 1589 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1590 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1591 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1592 mmap_init(); 1593 nsproxy_cache_init(); 1594 } 1595 1596 /* 1597 * Check constraints on flags passed to the unshare system call. 1598 */ 1599 static int check_unshare_flags(unsigned long unshare_flags) 1600 { 1601 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1602 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1603 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1604 return -EINVAL; 1605 /* 1606 * Not implemented, but pretend it works if there is nothing to 1607 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1608 * needs to unshare vm. 1609 */ 1610 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1611 /* FIXME: get_task_mm() increments ->mm_users */ 1612 if (atomic_read(¤t->mm->mm_users) > 1) 1613 return -EINVAL; 1614 } 1615 1616 return 0; 1617 } 1618 1619 /* 1620 * Unshare the filesystem structure if it is being shared 1621 */ 1622 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1623 { 1624 struct fs_struct *fs = current->fs; 1625 1626 if (!(unshare_flags & CLONE_FS) || !fs) 1627 return 0; 1628 1629 /* don't need lock here; in the worst case we'll do useless copy */ 1630 if (fs->users == 1) 1631 return 0; 1632 1633 *new_fsp = copy_fs_struct(fs); 1634 if (!*new_fsp) 1635 return -ENOMEM; 1636 1637 return 0; 1638 } 1639 1640 /* 1641 * Unshare file descriptor table if it is being shared 1642 */ 1643 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1644 { 1645 struct files_struct *fd = current->files; 1646 int error = 0; 1647 1648 if ((unshare_flags & CLONE_FILES) && 1649 (fd && atomic_read(&fd->count) > 1)) { 1650 *new_fdp = dup_fd(fd, &error); 1651 if (!*new_fdp) 1652 return error; 1653 } 1654 1655 return 0; 1656 } 1657 1658 /* 1659 * unshare allows a process to 'unshare' part of the process 1660 * context which was originally shared using clone. copy_* 1661 * functions used by do_fork() cannot be used here directly 1662 * because they modify an inactive task_struct that is being 1663 * constructed. Here we are modifying the current, active, 1664 * task_struct. 1665 */ 1666 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1667 { 1668 struct fs_struct *fs, *new_fs = NULL; 1669 struct files_struct *fd, *new_fd = NULL; 1670 struct nsproxy *new_nsproxy = NULL; 1671 int do_sysvsem = 0; 1672 int err; 1673 1674 err = check_unshare_flags(unshare_flags); 1675 if (err) 1676 goto bad_unshare_out; 1677 1678 /* 1679 * If unsharing namespace, must also unshare filesystem information. 1680 */ 1681 if (unshare_flags & CLONE_NEWNS) 1682 unshare_flags |= CLONE_FS; 1683 /* 1684 * CLONE_NEWIPC must also detach from the undolist: after switching 1685 * to a new ipc namespace, the semaphore arrays from the old 1686 * namespace are unreachable. 1687 */ 1688 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1689 do_sysvsem = 1; 1690 err = unshare_fs(unshare_flags, &new_fs); 1691 if (err) 1692 goto bad_unshare_out; 1693 err = unshare_fd(unshare_flags, &new_fd); 1694 if (err) 1695 goto bad_unshare_cleanup_fs; 1696 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1697 if (err) 1698 goto bad_unshare_cleanup_fd; 1699 1700 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1701 if (do_sysvsem) { 1702 /* 1703 * CLONE_SYSVSEM is equivalent to sys_exit(). 1704 */ 1705 exit_sem(current); 1706 } 1707 1708 if (new_nsproxy) { 1709 switch_task_namespaces(current, new_nsproxy); 1710 new_nsproxy = NULL; 1711 } 1712 1713 task_lock(current); 1714 1715 if (new_fs) { 1716 fs = current->fs; 1717 spin_lock(&fs->lock); 1718 current->fs = new_fs; 1719 if (--fs->users) 1720 new_fs = NULL; 1721 else 1722 new_fs = fs; 1723 spin_unlock(&fs->lock); 1724 } 1725 1726 if (new_fd) { 1727 fd = current->files; 1728 current->files = new_fd; 1729 new_fd = fd; 1730 } 1731 1732 task_unlock(current); 1733 } 1734 1735 if (new_nsproxy) 1736 put_nsproxy(new_nsproxy); 1737 1738 bad_unshare_cleanup_fd: 1739 if (new_fd) 1740 put_files_struct(new_fd); 1741 1742 bad_unshare_cleanup_fs: 1743 if (new_fs) 1744 free_fs_struct(new_fs); 1745 1746 bad_unshare_out: 1747 return err; 1748 } 1749 1750 /* 1751 * Helper to unshare the files of the current task. 1752 * We don't want to expose copy_files internals to 1753 * the exec layer of the kernel. 1754 */ 1755 1756 int unshare_files(struct files_struct **displaced) 1757 { 1758 struct task_struct *task = current; 1759 struct files_struct *copy = NULL; 1760 int error; 1761 1762 error = unshare_fd(CLONE_FILES, ©); 1763 if (error || !copy) { 1764 *displaced = NULL; 1765 return error; 1766 } 1767 *displaced = task->files; 1768 task_lock(task); 1769 task->files = copy; 1770 task_unlock(task); 1771 return 0; 1772 } 1773