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