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/mm.h> 32 #include <linux/vmacache.h> 33 #include <linux/nsproxy.h> 34 #include <linux/capability.h> 35 #include <linux/cpu.h> 36 #include <linux/cgroup.h> 37 #include <linux/security.h> 38 #include <linux/hugetlb.h> 39 #include <linux/seccomp.h> 40 #include <linux/swap.h> 41 #include <linux/syscalls.h> 42 #include <linux/jiffies.h> 43 #include <linux/futex.h> 44 #include <linux/compat.h> 45 #include <linux/kthread.h> 46 #include <linux/task_io_accounting_ops.h> 47 #include <linux/rcupdate.h> 48 #include <linux/ptrace.h> 49 #include <linux/mount.h> 50 #include <linux/audit.h> 51 #include <linux/memcontrol.h> 52 #include <linux/ftrace.h> 53 #include <linux/proc_fs.h> 54 #include <linux/profile.h> 55 #include <linux/rmap.h> 56 #include <linux/ksm.h> 57 #include <linux/acct.h> 58 #include <linux/tsacct_kern.h> 59 #include <linux/cn_proc.h> 60 #include <linux/freezer.h> 61 #include <linux/delayacct.h> 62 #include <linux/taskstats_kern.h> 63 #include <linux/random.h> 64 #include <linux/tty.h> 65 #include <linux/blkdev.h> 66 #include <linux/fs_struct.h> 67 #include <linux/magic.h> 68 #include <linux/perf_event.h> 69 #include <linux/posix-timers.h> 70 #include <linux/user-return-notifier.h> 71 #include <linux/oom.h> 72 #include <linux/khugepaged.h> 73 #include <linux/signalfd.h> 74 #include <linux/uprobes.h> 75 #include <linux/aio.h> 76 #include <linux/compiler.h> 77 78 #include <asm/pgtable.h> 79 #include <asm/pgalloc.h> 80 #include <asm/uaccess.h> 81 #include <asm/mmu_context.h> 82 #include <asm/cacheflush.h> 83 #include <asm/tlbflush.h> 84 85 #include <trace/events/sched.h> 86 87 #define CREATE_TRACE_POINTS 88 #include <trace/events/task.h> 89 90 /* 91 * Protected counters by write_lock_irq(&tasklist_lock) 92 */ 93 unsigned long total_forks; /* Handle normal Linux uptimes. */ 94 int nr_threads; /* The idle threads do not count.. */ 95 96 int max_threads; /* tunable limit on nr_threads */ 97 98 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 99 100 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 101 102 #ifdef CONFIG_PROVE_RCU 103 int lockdep_tasklist_lock_is_held(void) 104 { 105 return lockdep_is_held(&tasklist_lock); 106 } 107 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 108 #endif /* #ifdef CONFIG_PROVE_RCU */ 109 110 int nr_processes(void) 111 { 112 int cpu; 113 int total = 0; 114 115 for_each_possible_cpu(cpu) 116 total += per_cpu(process_counts, cpu); 117 118 return total; 119 } 120 121 void __weak arch_release_task_struct(struct task_struct *tsk) 122 { 123 } 124 125 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 126 static struct kmem_cache *task_struct_cachep; 127 128 static inline struct task_struct *alloc_task_struct_node(int node) 129 { 130 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 131 } 132 133 static inline void free_task_struct(struct task_struct *tsk) 134 { 135 kmem_cache_free(task_struct_cachep, tsk); 136 } 137 #endif 138 139 void __weak arch_release_thread_info(struct thread_info *ti) 140 { 141 } 142 143 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 144 145 /* 146 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 147 * kmemcache based allocator. 148 */ 149 # if THREAD_SIZE >= PAGE_SIZE 150 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 151 int node) 152 { 153 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP, 154 THREAD_SIZE_ORDER); 155 156 return page ? page_address(page) : NULL; 157 } 158 159 static inline void free_thread_info(struct thread_info *ti) 160 { 161 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); 162 } 163 # else 164 static struct kmem_cache *thread_info_cache; 165 166 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 167 int node) 168 { 169 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 170 } 171 172 static void free_thread_info(struct thread_info *ti) 173 { 174 kmem_cache_free(thread_info_cache, ti); 175 } 176 177 void thread_info_cache_init(void) 178 { 179 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 180 THREAD_SIZE, 0, NULL); 181 BUG_ON(thread_info_cache == NULL); 182 } 183 # endif 184 #endif 185 186 /* SLAB cache for signal_struct structures (tsk->signal) */ 187 static struct kmem_cache *signal_cachep; 188 189 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 190 struct kmem_cache *sighand_cachep; 191 192 /* SLAB cache for files_struct structures (tsk->files) */ 193 struct kmem_cache *files_cachep; 194 195 /* SLAB cache for fs_struct structures (tsk->fs) */ 196 struct kmem_cache *fs_cachep; 197 198 /* SLAB cache for vm_area_struct structures */ 199 struct kmem_cache *vm_area_cachep; 200 201 /* SLAB cache for mm_struct structures (tsk->mm) */ 202 static struct kmem_cache *mm_cachep; 203 204 static void account_kernel_stack(struct thread_info *ti, int account) 205 { 206 struct zone *zone = page_zone(virt_to_page(ti)); 207 208 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 209 } 210 211 void free_task(struct task_struct *tsk) 212 { 213 account_kernel_stack(tsk->stack, -1); 214 arch_release_thread_info(tsk->stack); 215 free_thread_info(tsk->stack); 216 rt_mutex_debug_task_free(tsk); 217 ftrace_graph_exit_task(tsk); 218 put_seccomp_filter(tsk); 219 arch_release_task_struct(tsk); 220 free_task_struct(tsk); 221 } 222 EXPORT_SYMBOL(free_task); 223 224 static inline void free_signal_struct(struct signal_struct *sig) 225 { 226 taskstats_tgid_free(sig); 227 sched_autogroup_exit(sig); 228 kmem_cache_free(signal_cachep, sig); 229 } 230 231 static inline void put_signal_struct(struct signal_struct *sig) 232 { 233 if (atomic_dec_and_test(&sig->sigcnt)) 234 free_signal_struct(sig); 235 } 236 237 void __put_task_struct(struct task_struct *tsk) 238 { 239 WARN_ON(!tsk->exit_state); 240 WARN_ON(atomic_read(&tsk->usage)); 241 WARN_ON(tsk == current); 242 243 task_numa_free(tsk); 244 security_task_free(tsk); 245 exit_creds(tsk); 246 delayacct_tsk_free(tsk); 247 put_signal_struct(tsk->signal); 248 249 if (!profile_handoff_task(tsk)) 250 free_task(tsk); 251 } 252 EXPORT_SYMBOL_GPL(__put_task_struct); 253 254 void __init __weak arch_task_cache_init(void) { } 255 256 void __init fork_init(unsigned long mempages) 257 { 258 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 259 #ifndef ARCH_MIN_TASKALIGN 260 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 261 #endif 262 /* create a slab on which task_structs can be allocated */ 263 task_struct_cachep = 264 kmem_cache_create("task_struct", sizeof(struct task_struct), 265 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 266 #endif 267 268 /* do the arch specific task caches init */ 269 arch_task_cache_init(); 270 271 /* 272 * The default maximum number of threads is set to a safe 273 * value: the thread structures can take up at most half 274 * of memory. 275 */ 276 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 277 278 /* 279 * we need to allow at least 20 threads to boot a system 280 */ 281 if (max_threads < 20) 282 max_threads = 20; 283 284 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 285 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 286 init_task.signal->rlim[RLIMIT_SIGPENDING] = 287 init_task.signal->rlim[RLIMIT_NPROC]; 288 } 289 290 int __weak arch_dup_task_struct(struct task_struct *dst, 291 struct task_struct *src) 292 { 293 *dst = *src; 294 return 0; 295 } 296 297 void set_task_stack_end_magic(struct task_struct *tsk) 298 { 299 unsigned long *stackend; 300 301 stackend = end_of_stack(tsk); 302 *stackend = STACK_END_MAGIC; /* for overflow detection */ 303 } 304 305 static struct task_struct *dup_task_struct(struct task_struct *orig) 306 { 307 struct task_struct *tsk; 308 struct thread_info *ti; 309 int node = tsk_fork_get_node(orig); 310 int err; 311 312 tsk = alloc_task_struct_node(node); 313 if (!tsk) 314 return NULL; 315 316 ti = alloc_thread_info_node(tsk, node); 317 if (!ti) 318 goto free_tsk; 319 320 err = arch_dup_task_struct(tsk, orig); 321 if (err) 322 goto free_ti; 323 324 tsk->stack = ti; 325 #ifdef CONFIG_SECCOMP 326 /* 327 * We must handle setting up seccomp filters once we're under 328 * the sighand lock in case orig has changed between now and 329 * then. Until then, filter must be NULL to avoid messing up 330 * the usage counts on the error path calling free_task. 331 */ 332 tsk->seccomp.filter = NULL; 333 #endif 334 335 setup_thread_stack(tsk, orig); 336 clear_user_return_notifier(tsk); 337 clear_tsk_need_resched(tsk); 338 set_task_stack_end_magic(tsk); 339 340 #ifdef CONFIG_CC_STACKPROTECTOR 341 tsk->stack_canary = get_random_int(); 342 #endif 343 344 /* 345 * One for us, one for whoever does the "release_task()" (usually 346 * parent) 347 */ 348 atomic_set(&tsk->usage, 2); 349 #ifdef CONFIG_BLK_DEV_IO_TRACE 350 tsk->btrace_seq = 0; 351 #endif 352 tsk->splice_pipe = NULL; 353 tsk->task_frag.page = NULL; 354 355 account_kernel_stack(ti, 1); 356 357 return tsk; 358 359 free_ti: 360 free_thread_info(ti); 361 free_tsk: 362 free_task_struct(tsk); 363 return NULL; 364 } 365 366 #ifdef CONFIG_MMU 367 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 368 { 369 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 370 struct rb_node **rb_link, *rb_parent; 371 int retval; 372 unsigned long charge; 373 374 uprobe_start_dup_mmap(); 375 down_write(&oldmm->mmap_sem); 376 flush_cache_dup_mm(oldmm); 377 uprobe_dup_mmap(oldmm, mm); 378 /* 379 * Not linked in yet - no deadlock potential: 380 */ 381 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 382 383 mm->total_vm = oldmm->total_vm; 384 mm->shared_vm = oldmm->shared_vm; 385 mm->exec_vm = oldmm->exec_vm; 386 mm->stack_vm = oldmm->stack_vm; 387 388 rb_link = &mm->mm_rb.rb_node; 389 rb_parent = NULL; 390 pprev = &mm->mmap; 391 retval = ksm_fork(mm, oldmm); 392 if (retval) 393 goto out; 394 retval = khugepaged_fork(mm, oldmm); 395 if (retval) 396 goto out; 397 398 prev = NULL; 399 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 400 struct file *file; 401 402 if (mpnt->vm_flags & VM_DONTCOPY) { 403 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 404 -vma_pages(mpnt)); 405 continue; 406 } 407 charge = 0; 408 if (mpnt->vm_flags & VM_ACCOUNT) { 409 unsigned long len = vma_pages(mpnt); 410 411 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 412 goto fail_nomem; 413 charge = len; 414 } 415 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 416 if (!tmp) 417 goto fail_nomem; 418 *tmp = *mpnt; 419 INIT_LIST_HEAD(&tmp->anon_vma_chain); 420 retval = vma_dup_policy(mpnt, tmp); 421 if (retval) 422 goto fail_nomem_policy; 423 tmp->vm_mm = mm; 424 if (anon_vma_fork(tmp, mpnt)) 425 goto fail_nomem_anon_vma_fork; 426 tmp->vm_flags &= ~VM_LOCKED; 427 tmp->vm_next = tmp->vm_prev = NULL; 428 file = tmp->vm_file; 429 if (file) { 430 struct inode *inode = file_inode(file); 431 struct address_space *mapping = file->f_mapping; 432 433 get_file(file); 434 if (tmp->vm_flags & VM_DENYWRITE) 435 atomic_dec(&inode->i_writecount); 436 i_mmap_lock_write(mapping); 437 if (tmp->vm_flags & VM_SHARED) 438 atomic_inc(&mapping->i_mmap_writable); 439 flush_dcache_mmap_lock(mapping); 440 /* insert tmp into the share list, just after mpnt */ 441 vma_interval_tree_insert_after(tmp, mpnt, 442 &mapping->i_mmap); 443 flush_dcache_mmap_unlock(mapping); 444 i_mmap_unlock_write(mapping); 445 } 446 447 /* 448 * Clear hugetlb-related page reserves for children. This only 449 * affects MAP_PRIVATE mappings. Faults generated by the child 450 * are not guaranteed to succeed, even if read-only 451 */ 452 if (is_vm_hugetlb_page(tmp)) 453 reset_vma_resv_huge_pages(tmp); 454 455 /* 456 * Link in the new vma and copy the page table entries. 457 */ 458 *pprev = tmp; 459 pprev = &tmp->vm_next; 460 tmp->vm_prev = prev; 461 prev = tmp; 462 463 __vma_link_rb(mm, tmp, rb_link, rb_parent); 464 rb_link = &tmp->vm_rb.rb_right; 465 rb_parent = &tmp->vm_rb; 466 467 mm->map_count++; 468 retval = copy_page_range(mm, oldmm, mpnt); 469 470 if (tmp->vm_ops && tmp->vm_ops->open) 471 tmp->vm_ops->open(tmp); 472 473 if (retval) 474 goto out; 475 } 476 /* a new mm has just been created */ 477 arch_dup_mmap(oldmm, mm); 478 retval = 0; 479 out: 480 up_write(&mm->mmap_sem); 481 flush_tlb_mm(oldmm); 482 up_write(&oldmm->mmap_sem); 483 uprobe_end_dup_mmap(); 484 return retval; 485 fail_nomem_anon_vma_fork: 486 mpol_put(vma_policy(tmp)); 487 fail_nomem_policy: 488 kmem_cache_free(vm_area_cachep, tmp); 489 fail_nomem: 490 retval = -ENOMEM; 491 vm_unacct_memory(charge); 492 goto out; 493 } 494 495 static inline int mm_alloc_pgd(struct mm_struct *mm) 496 { 497 mm->pgd = pgd_alloc(mm); 498 if (unlikely(!mm->pgd)) 499 return -ENOMEM; 500 return 0; 501 } 502 503 static inline void mm_free_pgd(struct mm_struct *mm) 504 { 505 pgd_free(mm, mm->pgd); 506 } 507 #else 508 #define dup_mmap(mm, oldmm) (0) 509 #define mm_alloc_pgd(mm) (0) 510 #define mm_free_pgd(mm) 511 #endif /* CONFIG_MMU */ 512 513 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 514 515 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 516 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 517 518 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 519 520 static int __init coredump_filter_setup(char *s) 521 { 522 default_dump_filter = 523 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 524 MMF_DUMP_FILTER_MASK; 525 return 1; 526 } 527 528 __setup("coredump_filter=", coredump_filter_setup); 529 530 #include <linux/init_task.h> 531 532 static void mm_init_aio(struct mm_struct *mm) 533 { 534 #ifdef CONFIG_AIO 535 spin_lock_init(&mm->ioctx_lock); 536 mm->ioctx_table = NULL; 537 #endif 538 } 539 540 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 541 { 542 #ifdef CONFIG_MEMCG 543 mm->owner = p; 544 #endif 545 } 546 547 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 548 { 549 mm->mmap = NULL; 550 mm->mm_rb = RB_ROOT; 551 mm->vmacache_seqnum = 0; 552 atomic_set(&mm->mm_users, 1); 553 atomic_set(&mm->mm_count, 1); 554 init_rwsem(&mm->mmap_sem); 555 INIT_LIST_HEAD(&mm->mmlist); 556 mm->core_state = NULL; 557 atomic_long_set(&mm->nr_ptes, 0); 558 mm_nr_pmds_init(mm); 559 mm->map_count = 0; 560 mm->locked_vm = 0; 561 mm->pinned_vm = 0; 562 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 563 spin_lock_init(&mm->page_table_lock); 564 mm_init_cpumask(mm); 565 mm_init_aio(mm); 566 mm_init_owner(mm, p); 567 mmu_notifier_mm_init(mm); 568 clear_tlb_flush_pending(mm); 569 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 570 mm->pmd_huge_pte = NULL; 571 #endif 572 573 if (current->mm) { 574 mm->flags = current->mm->flags & MMF_INIT_MASK; 575 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 576 } else { 577 mm->flags = default_dump_filter; 578 mm->def_flags = 0; 579 } 580 581 if (mm_alloc_pgd(mm)) 582 goto fail_nopgd; 583 584 if (init_new_context(p, mm)) 585 goto fail_nocontext; 586 587 return mm; 588 589 fail_nocontext: 590 mm_free_pgd(mm); 591 fail_nopgd: 592 free_mm(mm); 593 return NULL; 594 } 595 596 static void check_mm(struct mm_struct *mm) 597 { 598 int i; 599 600 for (i = 0; i < NR_MM_COUNTERS; i++) { 601 long x = atomic_long_read(&mm->rss_stat.count[i]); 602 603 if (unlikely(x)) 604 printk(KERN_ALERT "BUG: Bad rss-counter state " 605 "mm:%p idx:%d val:%ld\n", mm, i, x); 606 } 607 608 if (atomic_long_read(&mm->nr_ptes)) 609 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 610 atomic_long_read(&mm->nr_ptes)); 611 if (mm_nr_pmds(mm)) 612 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 613 mm_nr_pmds(mm)); 614 615 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 616 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 617 #endif 618 } 619 620 /* 621 * Allocate and initialize an mm_struct. 622 */ 623 struct mm_struct *mm_alloc(void) 624 { 625 struct mm_struct *mm; 626 627 mm = allocate_mm(); 628 if (!mm) 629 return NULL; 630 631 memset(mm, 0, sizeof(*mm)); 632 return mm_init(mm, current); 633 } 634 635 /* 636 * Called when the last reference to the mm 637 * is dropped: either by a lazy thread or by 638 * mmput. Free the page directory and the mm. 639 */ 640 void __mmdrop(struct mm_struct *mm) 641 { 642 BUG_ON(mm == &init_mm); 643 mm_free_pgd(mm); 644 destroy_context(mm); 645 mmu_notifier_mm_destroy(mm); 646 check_mm(mm); 647 free_mm(mm); 648 } 649 EXPORT_SYMBOL_GPL(__mmdrop); 650 651 /* 652 * Decrement the use count and release all resources for an mm. 653 */ 654 void mmput(struct mm_struct *mm) 655 { 656 might_sleep(); 657 658 if (atomic_dec_and_test(&mm->mm_users)) { 659 uprobe_clear_state(mm); 660 exit_aio(mm); 661 ksm_exit(mm); 662 khugepaged_exit(mm); /* must run before exit_mmap */ 663 exit_mmap(mm); 664 set_mm_exe_file(mm, NULL); 665 if (!list_empty(&mm->mmlist)) { 666 spin_lock(&mmlist_lock); 667 list_del(&mm->mmlist); 668 spin_unlock(&mmlist_lock); 669 } 670 if (mm->binfmt) 671 module_put(mm->binfmt->module); 672 mmdrop(mm); 673 } 674 } 675 EXPORT_SYMBOL_GPL(mmput); 676 677 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 678 { 679 if (new_exe_file) 680 get_file(new_exe_file); 681 if (mm->exe_file) 682 fput(mm->exe_file); 683 mm->exe_file = new_exe_file; 684 } 685 686 struct file *get_mm_exe_file(struct mm_struct *mm) 687 { 688 struct file *exe_file; 689 690 /* We need mmap_sem to protect against races with removal of exe_file */ 691 down_read(&mm->mmap_sem); 692 exe_file = mm->exe_file; 693 if (exe_file) 694 get_file(exe_file); 695 up_read(&mm->mmap_sem); 696 return exe_file; 697 } 698 699 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 700 { 701 /* It's safe to write the exe_file pointer without exe_file_lock because 702 * this is called during fork when the task is not yet in /proc */ 703 newmm->exe_file = get_mm_exe_file(oldmm); 704 } 705 706 /** 707 * get_task_mm - acquire a reference to the task's mm 708 * 709 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 710 * this kernel workthread has transiently adopted a user mm with use_mm, 711 * to do its AIO) is not set and if so returns a reference to it, after 712 * bumping up the use count. User must release the mm via mmput() 713 * after use. Typically used by /proc and ptrace. 714 */ 715 struct mm_struct *get_task_mm(struct task_struct *task) 716 { 717 struct mm_struct *mm; 718 719 task_lock(task); 720 mm = task->mm; 721 if (mm) { 722 if (task->flags & PF_KTHREAD) 723 mm = NULL; 724 else 725 atomic_inc(&mm->mm_users); 726 } 727 task_unlock(task); 728 return mm; 729 } 730 EXPORT_SYMBOL_GPL(get_task_mm); 731 732 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 733 { 734 struct mm_struct *mm; 735 int err; 736 737 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 738 if (err) 739 return ERR_PTR(err); 740 741 mm = get_task_mm(task); 742 if (mm && mm != current->mm && 743 !ptrace_may_access(task, mode)) { 744 mmput(mm); 745 mm = ERR_PTR(-EACCES); 746 } 747 mutex_unlock(&task->signal->cred_guard_mutex); 748 749 return mm; 750 } 751 752 static void complete_vfork_done(struct task_struct *tsk) 753 { 754 struct completion *vfork; 755 756 task_lock(tsk); 757 vfork = tsk->vfork_done; 758 if (likely(vfork)) { 759 tsk->vfork_done = NULL; 760 complete(vfork); 761 } 762 task_unlock(tsk); 763 } 764 765 static int wait_for_vfork_done(struct task_struct *child, 766 struct completion *vfork) 767 { 768 int killed; 769 770 freezer_do_not_count(); 771 killed = wait_for_completion_killable(vfork); 772 freezer_count(); 773 774 if (killed) { 775 task_lock(child); 776 child->vfork_done = NULL; 777 task_unlock(child); 778 } 779 780 put_task_struct(child); 781 return killed; 782 } 783 784 /* Please note the differences between mmput and mm_release. 785 * mmput is called whenever we stop holding onto a mm_struct, 786 * error success whatever. 787 * 788 * mm_release is called after a mm_struct has been removed 789 * from the current process. 790 * 791 * This difference is important for error handling, when we 792 * only half set up a mm_struct for a new process and need to restore 793 * the old one. Because we mmput the new mm_struct before 794 * restoring the old one. . . 795 * Eric Biederman 10 January 1998 796 */ 797 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 798 { 799 /* Get rid of any futexes when releasing the mm */ 800 #ifdef CONFIG_FUTEX 801 if (unlikely(tsk->robust_list)) { 802 exit_robust_list(tsk); 803 tsk->robust_list = NULL; 804 } 805 #ifdef CONFIG_COMPAT 806 if (unlikely(tsk->compat_robust_list)) { 807 compat_exit_robust_list(tsk); 808 tsk->compat_robust_list = NULL; 809 } 810 #endif 811 if (unlikely(!list_empty(&tsk->pi_state_list))) 812 exit_pi_state_list(tsk); 813 #endif 814 815 uprobe_free_utask(tsk); 816 817 /* Get rid of any cached register state */ 818 deactivate_mm(tsk, mm); 819 820 /* 821 * If we're exiting normally, clear a user-space tid field if 822 * requested. We leave this alone when dying by signal, to leave 823 * the value intact in a core dump, and to save the unnecessary 824 * trouble, say, a killed vfork parent shouldn't touch this mm. 825 * Userland only wants this done for a sys_exit. 826 */ 827 if (tsk->clear_child_tid) { 828 if (!(tsk->flags & PF_SIGNALED) && 829 atomic_read(&mm->mm_users) > 1) { 830 /* 831 * We don't check the error code - if userspace has 832 * not set up a proper pointer then tough luck. 833 */ 834 put_user(0, tsk->clear_child_tid); 835 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 836 1, NULL, NULL, 0); 837 } 838 tsk->clear_child_tid = NULL; 839 } 840 841 /* 842 * All done, finally we can wake up parent and return this mm to him. 843 * Also kthread_stop() uses this completion for synchronization. 844 */ 845 if (tsk->vfork_done) 846 complete_vfork_done(tsk); 847 } 848 849 /* 850 * Allocate a new mm structure and copy contents from the 851 * mm structure of the passed in task structure. 852 */ 853 static struct mm_struct *dup_mm(struct task_struct *tsk) 854 { 855 struct mm_struct *mm, *oldmm = current->mm; 856 int err; 857 858 mm = allocate_mm(); 859 if (!mm) 860 goto fail_nomem; 861 862 memcpy(mm, oldmm, sizeof(*mm)); 863 864 if (!mm_init(mm, tsk)) 865 goto fail_nomem; 866 867 dup_mm_exe_file(oldmm, mm); 868 869 err = dup_mmap(mm, oldmm); 870 if (err) 871 goto free_pt; 872 873 mm->hiwater_rss = get_mm_rss(mm); 874 mm->hiwater_vm = mm->total_vm; 875 876 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 877 goto free_pt; 878 879 return mm; 880 881 free_pt: 882 /* don't put binfmt in mmput, we haven't got module yet */ 883 mm->binfmt = NULL; 884 mmput(mm); 885 886 fail_nomem: 887 return NULL; 888 } 889 890 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 891 { 892 struct mm_struct *mm, *oldmm; 893 int retval; 894 895 tsk->min_flt = tsk->maj_flt = 0; 896 tsk->nvcsw = tsk->nivcsw = 0; 897 #ifdef CONFIG_DETECT_HUNG_TASK 898 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 899 #endif 900 901 tsk->mm = NULL; 902 tsk->active_mm = NULL; 903 904 /* 905 * Are we cloning a kernel thread? 906 * 907 * We need to steal a active VM for that.. 908 */ 909 oldmm = current->mm; 910 if (!oldmm) 911 return 0; 912 913 /* initialize the new vmacache entries */ 914 vmacache_flush(tsk); 915 916 if (clone_flags & CLONE_VM) { 917 atomic_inc(&oldmm->mm_users); 918 mm = oldmm; 919 goto good_mm; 920 } 921 922 retval = -ENOMEM; 923 mm = dup_mm(tsk); 924 if (!mm) 925 goto fail_nomem; 926 927 good_mm: 928 tsk->mm = mm; 929 tsk->active_mm = mm; 930 return 0; 931 932 fail_nomem: 933 return retval; 934 } 935 936 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 937 { 938 struct fs_struct *fs = current->fs; 939 if (clone_flags & CLONE_FS) { 940 /* tsk->fs is already what we want */ 941 spin_lock(&fs->lock); 942 if (fs->in_exec) { 943 spin_unlock(&fs->lock); 944 return -EAGAIN; 945 } 946 fs->users++; 947 spin_unlock(&fs->lock); 948 return 0; 949 } 950 tsk->fs = copy_fs_struct(fs); 951 if (!tsk->fs) 952 return -ENOMEM; 953 return 0; 954 } 955 956 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 957 { 958 struct files_struct *oldf, *newf; 959 int error = 0; 960 961 /* 962 * A background process may not have any files ... 963 */ 964 oldf = current->files; 965 if (!oldf) 966 goto out; 967 968 if (clone_flags & CLONE_FILES) { 969 atomic_inc(&oldf->count); 970 goto out; 971 } 972 973 newf = dup_fd(oldf, &error); 974 if (!newf) 975 goto out; 976 977 tsk->files = newf; 978 error = 0; 979 out: 980 return error; 981 } 982 983 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 984 { 985 #ifdef CONFIG_BLOCK 986 struct io_context *ioc = current->io_context; 987 struct io_context *new_ioc; 988 989 if (!ioc) 990 return 0; 991 /* 992 * Share io context with parent, if CLONE_IO is set 993 */ 994 if (clone_flags & CLONE_IO) { 995 ioc_task_link(ioc); 996 tsk->io_context = ioc; 997 } else if (ioprio_valid(ioc->ioprio)) { 998 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 999 if (unlikely(!new_ioc)) 1000 return -ENOMEM; 1001 1002 new_ioc->ioprio = ioc->ioprio; 1003 put_io_context(new_ioc); 1004 } 1005 #endif 1006 return 0; 1007 } 1008 1009 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1010 { 1011 struct sighand_struct *sig; 1012 1013 if (clone_flags & CLONE_SIGHAND) { 1014 atomic_inc(¤t->sighand->count); 1015 return 0; 1016 } 1017 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1018 rcu_assign_pointer(tsk->sighand, sig); 1019 if (!sig) 1020 return -ENOMEM; 1021 atomic_set(&sig->count, 1); 1022 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1023 return 0; 1024 } 1025 1026 void __cleanup_sighand(struct sighand_struct *sighand) 1027 { 1028 if (atomic_dec_and_test(&sighand->count)) { 1029 signalfd_cleanup(sighand); 1030 /* 1031 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1032 * without an RCU grace period, see __lock_task_sighand(). 1033 */ 1034 kmem_cache_free(sighand_cachep, sighand); 1035 } 1036 } 1037 1038 /* 1039 * Initialize POSIX timer handling for a thread group. 1040 */ 1041 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1042 { 1043 unsigned long cpu_limit; 1044 1045 /* Thread group counters. */ 1046 thread_group_cputime_init(sig); 1047 1048 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1049 if (cpu_limit != RLIM_INFINITY) { 1050 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1051 sig->cputimer.running = 1; 1052 } 1053 1054 /* The timer lists. */ 1055 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1056 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1057 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1058 } 1059 1060 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1061 { 1062 struct signal_struct *sig; 1063 1064 if (clone_flags & CLONE_THREAD) 1065 return 0; 1066 1067 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1068 tsk->signal = sig; 1069 if (!sig) 1070 return -ENOMEM; 1071 1072 sig->nr_threads = 1; 1073 atomic_set(&sig->live, 1); 1074 atomic_set(&sig->sigcnt, 1); 1075 1076 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1077 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1078 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1079 1080 init_waitqueue_head(&sig->wait_chldexit); 1081 sig->curr_target = tsk; 1082 init_sigpending(&sig->shared_pending); 1083 INIT_LIST_HEAD(&sig->posix_timers); 1084 seqlock_init(&sig->stats_lock); 1085 1086 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1087 sig->real_timer.function = it_real_fn; 1088 1089 task_lock(current->group_leader); 1090 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1091 task_unlock(current->group_leader); 1092 1093 posix_cpu_timers_init_group(sig); 1094 1095 tty_audit_fork(sig); 1096 sched_autogroup_fork(sig); 1097 1098 #ifdef CONFIG_CGROUPS 1099 init_rwsem(&sig->group_rwsem); 1100 #endif 1101 1102 sig->oom_score_adj = current->signal->oom_score_adj; 1103 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1104 1105 sig->has_child_subreaper = current->signal->has_child_subreaper || 1106 current->signal->is_child_subreaper; 1107 1108 mutex_init(&sig->cred_guard_mutex); 1109 1110 return 0; 1111 } 1112 1113 static void copy_seccomp(struct task_struct *p) 1114 { 1115 #ifdef CONFIG_SECCOMP 1116 /* 1117 * Must be called with sighand->lock held, which is common to 1118 * all threads in the group. Holding cred_guard_mutex is not 1119 * needed because this new task is not yet running and cannot 1120 * be racing exec. 1121 */ 1122 assert_spin_locked(¤t->sighand->siglock); 1123 1124 /* Ref-count the new filter user, and assign it. */ 1125 get_seccomp_filter(current); 1126 p->seccomp = current->seccomp; 1127 1128 /* 1129 * Explicitly enable no_new_privs here in case it got set 1130 * between the task_struct being duplicated and holding the 1131 * sighand lock. The seccomp state and nnp must be in sync. 1132 */ 1133 if (task_no_new_privs(current)) 1134 task_set_no_new_privs(p); 1135 1136 /* 1137 * If the parent gained a seccomp mode after copying thread 1138 * flags and between before we held the sighand lock, we have 1139 * to manually enable the seccomp thread flag here. 1140 */ 1141 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1142 set_tsk_thread_flag(p, TIF_SECCOMP); 1143 #endif 1144 } 1145 1146 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1147 { 1148 current->clear_child_tid = tidptr; 1149 1150 return task_pid_vnr(current); 1151 } 1152 1153 static void rt_mutex_init_task(struct task_struct *p) 1154 { 1155 raw_spin_lock_init(&p->pi_lock); 1156 #ifdef CONFIG_RT_MUTEXES 1157 p->pi_waiters = RB_ROOT; 1158 p->pi_waiters_leftmost = NULL; 1159 p->pi_blocked_on = NULL; 1160 #endif 1161 } 1162 1163 /* 1164 * Initialize POSIX timer handling for a single task. 1165 */ 1166 static void posix_cpu_timers_init(struct task_struct *tsk) 1167 { 1168 tsk->cputime_expires.prof_exp = 0; 1169 tsk->cputime_expires.virt_exp = 0; 1170 tsk->cputime_expires.sched_exp = 0; 1171 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1172 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1173 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1174 } 1175 1176 static inline void 1177 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1178 { 1179 task->pids[type].pid = pid; 1180 } 1181 1182 /* 1183 * This creates a new process as a copy of the old one, 1184 * but does not actually start it yet. 1185 * 1186 * It copies the registers, and all the appropriate 1187 * parts of the process environment (as per the clone 1188 * flags). The actual kick-off is left to the caller. 1189 */ 1190 static struct task_struct *copy_process(unsigned long clone_flags, 1191 unsigned long stack_start, 1192 unsigned long stack_size, 1193 int __user *child_tidptr, 1194 struct pid *pid, 1195 int trace) 1196 { 1197 int retval; 1198 struct task_struct *p; 1199 1200 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1201 return ERR_PTR(-EINVAL); 1202 1203 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1204 return ERR_PTR(-EINVAL); 1205 1206 /* 1207 * Thread groups must share signals as well, and detached threads 1208 * can only be started up within the thread group. 1209 */ 1210 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1211 return ERR_PTR(-EINVAL); 1212 1213 /* 1214 * Shared signal handlers imply shared VM. By way of the above, 1215 * thread groups also imply shared VM. Blocking this case allows 1216 * for various simplifications in other code. 1217 */ 1218 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1219 return ERR_PTR(-EINVAL); 1220 1221 /* 1222 * Siblings of global init remain as zombies on exit since they are 1223 * not reaped by their parent (swapper). To solve this and to avoid 1224 * multi-rooted process trees, prevent global and container-inits 1225 * from creating siblings. 1226 */ 1227 if ((clone_flags & CLONE_PARENT) && 1228 current->signal->flags & SIGNAL_UNKILLABLE) 1229 return ERR_PTR(-EINVAL); 1230 1231 /* 1232 * If the new process will be in a different pid or user namespace 1233 * do not allow it to share a thread group or signal handlers or 1234 * parent with the forking task. 1235 */ 1236 if (clone_flags & CLONE_SIGHAND) { 1237 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1238 (task_active_pid_ns(current) != 1239 current->nsproxy->pid_ns_for_children)) 1240 return ERR_PTR(-EINVAL); 1241 } 1242 1243 retval = security_task_create(clone_flags); 1244 if (retval) 1245 goto fork_out; 1246 1247 retval = -ENOMEM; 1248 p = dup_task_struct(current); 1249 if (!p) 1250 goto fork_out; 1251 1252 ftrace_graph_init_task(p); 1253 1254 rt_mutex_init_task(p); 1255 1256 #ifdef CONFIG_PROVE_LOCKING 1257 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1258 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1259 #endif 1260 retval = -EAGAIN; 1261 if (atomic_read(&p->real_cred->user->processes) >= 1262 task_rlimit(p, RLIMIT_NPROC)) { 1263 if (p->real_cred->user != INIT_USER && 1264 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1265 goto bad_fork_free; 1266 } 1267 current->flags &= ~PF_NPROC_EXCEEDED; 1268 1269 retval = copy_creds(p, clone_flags); 1270 if (retval < 0) 1271 goto bad_fork_free; 1272 1273 /* 1274 * If multiple threads are within copy_process(), then this check 1275 * triggers too late. This doesn't hurt, the check is only there 1276 * to stop root fork bombs. 1277 */ 1278 retval = -EAGAIN; 1279 if (nr_threads >= max_threads) 1280 goto bad_fork_cleanup_count; 1281 1282 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1283 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1284 p->flags |= PF_FORKNOEXEC; 1285 INIT_LIST_HEAD(&p->children); 1286 INIT_LIST_HEAD(&p->sibling); 1287 rcu_copy_process(p); 1288 p->vfork_done = NULL; 1289 spin_lock_init(&p->alloc_lock); 1290 1291 init_sigpending(&p->pending); 1292 1293 p->utime = p->stime = p->gtime = 0; 1294 p->utimescaled = p->stimescaled = 0; 1295 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE 1296 p->prev_cputime.utime = p->prev_cputime.stime = 0; 1297 #endif 1298 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1299 seqlock_init(&p->vtime_seqlock); 1300 p->vtime_snap = 0; 1301 p->vtime_snap_whence = VTIME_SLEEPING; 1302 #endif 1303 1304 #if defined(SPLIT_RSS_COUNTING) 1305 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1306 #endif 1307 1308 p->default_timer_slack_ns = current->timer_slack_ns; 1309 1310 task_io_accounting_init(&p->ioac); 1311 acct_clear_integrals(p); 1312 1313 posix_cpu_timers_init(p); 1314 1315 p->start_time = ktime_get_ns(); 1316 p->real_start_time = ktime_get_boot_ns(); 1317 p->io_context = NULL; 1318 p->audit_context = NULL; 1319 if (clone_flags & CLONE_THREAD) 1320 threadgroup_change_begin(current); 1321 cgroup_fork(p); 1322 #ifdef CONFIG_NUMA 1323 p->mempolicy = mpol_dup(p->mempolicy); 1324 if (IS_ERR(p->mempolicy)) { 1325 retval = PTR_ERR(p->mempolicy); 1326 p->mempolicy = NULL; 1327 goto bad_fork_cleanup_threadgroup_lock; 1328 } 1329 #endif 1330 #ifdef CONFIG_CPUSETS 1331 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1332 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1333 seqcount_init(&p->mems_allowed_seq); 1334 #endif 1335 #ifdef CONFIG_TRACE_IRQFLAGS 1336 p->irq_events = 0; 1337 p->hardirqs_enabled = 0; 1338 p->hardirq_enable_ip = 0; 1339 p->hardirq_enable_event = 0; 1340 p->hardirq_disable_ip = _THIS_IP_; 1341 p->hardirq_disable_event = 0; 1342 p->softirqs_enabled = 1; 1343 p->softirq_enable_ip = _THIS_IP_; 1344 p->softirq_enable_event = 0; 1345 p->softirq_disable_ip = 0; 1346 p->softirq_disable_event = 0; 1347 p->hardirq_context = 0; 1348 p->softirq_context = 0; 1349 #endif 1350 #ifdef CONFIG_LOCKDEP 1351 p->lockdep_depth = 0; /* no locks held yet */ 1352 p->curr_chain_key = 0; 1353 p->lockdep_recursion = 0; 1354 #endif 1355 1356 #ifdef CONFIG_DEBUG_MUTEXES 1357 p->blocked_on = NULL; /* not blocked yet */ 1358 #endif 1359 #ifdef CONFIG_BCACHE 1360 p->sequential_io = 0; 1361 p->sequential_io_avg = 0; 1362 #endif 1363 1364 /* Perform scheduler related setup. Assign this task to a CPU. */ 1365 retval = sched_fork(clone_flags, p); 1366 if (retval) 1367 goto bad_fork_cleanup_policy; 1368 1369 retval = perf_event_init_task(p); 1370 if (retval) 1371 goto bad_fork_cleanup_policy; 1372 retval = audit_alloc(p); 1373 if (retval) 1374 goto bad_fork_cleanup_perf; 1375 /* copy all the process information */ 1376 shm_init_task(p); 1377 retval = copy_semundo(clone_flags, p); 1378 if (retval) 1379 goto bad_fork_cleanup_audit; 1380 retval = copy_files(clone_flags, p); 1381 if (retval) 1382 goto bad_fork_cleanup_semundo; 1383 retval = copy_fs(clone_flags, p); 1384 if (retval) 1385 goto bad_fork_cleanup_files; 1386 retval = copy_sighand(clone_flags, p); 1387 if (retval) 1388 goto bad_fork_cleanup_fs; 1389 retval = copy_signal(clone_flags, p); 1390 if (retval) 1391 goto bad_fork_cleanup_sighand; 1392 retval = copy_mm(clone_flags, p); 1393 if (retval) 1394 goto bad_fork_cleanup_signal; 1395 retval = copy_namespaces(clone_flags, p); 1396 if (retval) 1397 goto bad_fork_cleanup_mm; 1398 retval = copy_io(clone_flags, p); 1399 if (retval) 1400 goto bad_fork_cleanup_namespaces; 1401 retval = copy_thread(clone_flags, stack_start, stack_size, p); 1402 if (retval) 1403 goto bad_fork_cleanup_io; 1404 1405 if (pid != &init_struct_pid) { 1406 retval = -ENOMEM; 1407 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1408 if (!pid) 1409 goto bad_fork_cleanup_io; 1410 } 1411 1412 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1413 /* 1414 * Clear TID on mm_release()? 1415 */ 1416 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1417 #ifdef CONFIG_BLOCK 1418 p->plug = NULL; 1419 #endif 1420 #ifdef CONFIG_FUTEX 1421 p->robust_list = NULL; 1422 #ifdef CONFIG_COMPAT 1423 p->compat_robust_list = NULL; 1424 #endif 1425 INIT_LIST_HEAD(&p->pi_state_list); 1426 p->pi_state_cache = NULL; 1427 #endif 1428 /* 1429 * sigaltstack should be cleared when sharing the same VM 1430 */ 1431 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1432 p->sas_ss_sp = p->sas_ss_size = 0; 1433 1434 /* 1435 * Syscall tracing and stepping should be turned off in the 1436 * child regardless of CLONE_PTRACE. 1437 */ 1438 user_disable_single_step(p); 1439 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1440 #ifdef TIF_SYSCALL_EMU 1441 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1442 #endif 1443 clear_all_latency_tracing(p); 1444 1445 /* ok, now we should be set up.. */ 1446 p->pid = pid_nr(pid); 1447 if (clone_flags & CLONE_THREAD) { 1448 p->exit_signal = -1; 1449 p->group_leader = current->group_leader; 1450 p->tgid = current->tgid; 1451 } else { 1452 if (clone_flags & CLONE_PARENT) 1453 p->exit_signal = current->group_leader->exit_signal; 1454 else 1455 p->exit_signal = (clone_flags & CSIGNAL); 1456 p->group_leader = p; 1457 p->tgid = p->pid; 1458 } 1459 1460 p->nr_dirtied = 0; 1461 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1462 p->dirty_paused_when = 0; 1463 1464 p->pdeath_signal = 0; 1465 INIT_LIST_HEAD(&p->thread_group); 1466 p->task_works = NULL; 1467 1468 /* 1469 * Make it visible to the rest of the system, but dont wake it up yet. 1470 * Need tasklist lock for parent etc handling! 1471 */ 1472 write_lock_irq(&tasklist_lock); 1473 1474 /* CLONE_PARENT re-uses the old parent */ 1475 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1476 p->real_parent = current->real_parent; 1477 p->parent_exec_id = current->parent_exec_id; 1478 } else { 1479 p->real_parent = current; 1480 p->parent_exec_id = current->self_exec_id; 1481 } 1482 1483 spin_lock(¤t->sighand->siglock); 1484 1485 /* 1486 * Copy seccomp details explicitly here, in case they were changed 1487 * before holding sighand lock. 1488 */ 1489 copy_seccomp(p); 1490 1491 /* 1492 * Process group and session signals need to be delivered to just the 1493 * parent before the fork or both the parent and the child after the 1494 * fork. Restart if a signal comes in before we add the new process to 1495 * it's process group. 1496 * A fatal signal pending means that current will exit, so the new 1497 * thread can't slip out of an OOM kill (or normal SIGKILL). 1498 */ 1499 recalc_sigpending(); 1500 if (signal_pending(current)) { 1501 spin_unlock(¤t->sighand->siglock); 1502 write_unlock_irq(&tasklist_lock); 1503 retval = -ERESTARTNOINTR; 1504 goto bad_fork_free_pid; 1505 } 1506 1507 if (likely(p->pid)) { 1508 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1509 1510 init_task_pid(p, PIDTYPE_PID, pid); 1511 if (thread_group_leader(p)) { 1512 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1513 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1514 1515 if (is_child_reaper(pid)) { 1516 ns_of_pid(pid)->child_reaper = p; 1517 p->signal->flags |= SIGNAL_UNKILLABLE; 1518 } 1519 1520 p->signal->leader_pid = pid; 1521 p->signal->tty = tty_kref_get(current->signal->tty); 1522 list_add_tail(&p->sibling, &p->real_parent->children); 1523 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1524 attach_pid(p, PIDTYPE_PGID); 1525 attach_pid(p, PIDTYPE_SID); 1526 __this_cpu_inc(process_counts); 1527 } else { 1528 current->signal->nr_threads++; 1529 atomic_inc(¤t->signal->live); 1530 atomic_inc(¤t->signal->sigcnt); 1531 list_add_tail_rcu(&p->thread_group, 1532 &p->group_leader->thread_group); 1533 list_add_tail_rcu(&p->thread_node, 1534 &p->signal->thread_head); 1535 } 1536 attach_pid(p, PIDTYPE_PID); 1537 nr_threads++; 1538 } 1539 1540 total_forks++; 1541 spin_unlock(¤t->sighand->siglock); 1542 syscall_tracepoint_update(p); 1543 write_unlock_irq(&tasklist_lock); 1544 1545 proc_fork_connector(p); 1546 cgroup_post_fork(p); 1547 if (clone_flags & CLONE_THREAD) 1548 threadgroup_change_end(current); 1549 perf_event_fork(p); 1550 1551 trace_task_newtask(p, clone_flags); 1552 uprobe_copy_process(p, clone_flags); 1553 1554 return p; 1555 1556 bad_fork_free_pid: 1557 if (pid != &init_struct_pid) 1558 free_pid(pid); 1559 bad_fork_cleanup_io: 1560 if (p->io_context) 1561 exit_io_context(p); 1562 bad_fork_cleanup_namespaces: 1563 exit_task_namespaces(p); 1564 bad_fork_cleanup_mm: 1565 if (p->mm) 1566 mmput(p->mm); 1567 bad_fork_cleanup_signal: 1568 if (!(clone_flags & CLONE_THREAD)) 1569 free_signal_struct(p->signal); 1570 bad_fork_cleanup_sighand: 1571 __cleanup_sighand(p->sighand); 1572 bad_fork_cleanup_fs: 1573 exit_fs(p); /* blocking */ 1574 bad_fork_cleanup_files: 1575 exit_files(p); /* blocking */ 1576 bad_fork_cleanup_semundo: 1577 exit_sem(p); 1578 bad_fork_cleanup_audit: 1579 audit_free(p); 1580 bad_fork_cleanup_perf: 1581 perf_event_free_task(p); 1582 bad_fork_cleanup_policy: 1583 #ifdef CONFIG_NUMA 1584 mpol_put(p->mempolicy); 1585 bad_fork_cleanup_threadgroup_lock: 1586 #endif 1587 if (clone_flags & CLONE_THREAD) 1588 threadgroup_change_end(current); 1589 delayacct_tsk_free(p); 1590 bad_fork_cleanup_count: 1591 atomic_dec(&p->cred->user->processes); 1592 exit_creds(p); 1593 bad_fork_free: 1594 free_task(p); 1595 fork_out: 1596 return ERR_PTR(retval); 1597 } 1598 1599 static inline void init_idle_pids(struct pid_link *links) 1600 { 1601 enum pid_type type; 1602 1603 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1604 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1605 links[type].pid = &init_struct_pid; 1606 } 1607 } 1608 1609 struct task_struct *fork_idle(int cpu) 1610 { 1611 struct task_struct *task; 1612 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0); 1613 if (!IS_ERR(task)) { 1614 init_idle_pids(task->pids); 1615 init_idle(task, cpu); 1616 } 1617 1618 return task; 1619 } 1620 1621 /* 1622 * Ok, this is the main fork-routine. 1623 * 1624 * It copies the process, and if successful kick-starts 1625 * it and waits for it to finish using the VM if required. 1626 */ 1627 long do_fork(unsigned long clone_flags, 1628 unsigned long stack_start, 1629 unsigned long stack_size, 1630 int __user *parent_tidptr, 1631 int __user *child_tidptr) 1632 { 1633 struct task_struct *p; 1634 int trace = 0; 1635 long nr; 1636 1637 /* 1638 * Determine whether and which event to report to ptracer. When 1639 * called from kernel_thread or CLONE_UNTRACED is explicitly 1640 * requested, no event is reported; otherwise, report if the event 1641 * for the type of forking is enabled. 1642 */ 1643 if (!(clone_flags & CLONE_UNTRACED)) { 1644 if (clone_flags & CLONE_VFORK) 1645 trace = PTRACE_EVENT_VFORK; 1646 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1647 trace = PTRACE_EVENT_CLONE; 1648 else 1649 trace = PTRACE_EVENT_FORK; 1650 1651 if (likely(!ptrace_event_enabled(current, trace))) 1652 trace = 0; 1653 } 1654 1655 p = copy_process(clone_flags, stack_start, stack_size, 1656 child_tidptr, NULL, trace); 1657 /* 1658 * Do this prior waking up the new thread - the thread pointer 1659 * might get invalid after that point, if the thread exits quickly. 1660 */ 1661 if (!IS_ERR(p)) { 1662 struct completion vfork; 1663 struct pid *pid; 1664 1665 trace_sched_process_fork(current, p); 1666 1667 pid = get_task_pid(p, PIDTYPE_PID); 1668 nr = pid_vnr(pid); 1669 1670 if (clone_flags & CLONE_PARENT_SETTID) 1671 put_user(nr, parent_tidptr); 1672 1673 if (clone_flags & CLONE_VFORK) { 1674 p->vfork_done = &vfork; 1675 init_completion(&vfork); 1676 get_task_struct(p); 1677 } 1678 1679 wake_up_new_task(p); 1680 1681 /* forking complete and child started to run, tell ptracer */ 1682 if (unlikely(trace)) 1683 ptrace_event_pid(trace, pid); 1684 1685 if (clone_flags & CLONE_VFORK) { 1686 if (!wait_for_vfork_done(p, &vfork)) 1687 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1688 } 1689 1690 put_pid(pid); 1691 } else { 1692 nr = PTR_ERR(p); 1693 } 1694 return nr; 1695 } 1696 1697 /* 1698 * Create a kernel thread. 1699 */ 1700 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1701 { 1702 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1703 (unsigned long)arg, NULL, NULL); 1704 } 1705 1706 #ifdef __ARCH_WANT_SYS_FORK 1707 SYSCALL_DEFINE0(fork) 1708 { 1709 #ifdef CONFIG_MMU 1710 return do_fork(SIGCHLD, 0, 0, NULL, NULL); 1711 #else 1712 /* can not support in nommu mode */ 1713 return -EINVAL; 1714 #endif 1715 } 1716 #endif 1717 1718 #ifdef __ARCH_WANT_SYS_VFORK 1719 SYSCALL_DEFINE0(vfork) 1720 { 1721 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1722 0, NULL, NULL); 1723 } 1724 #endif 1725 1726 #ifdef __ARCH_WANT_SYS_CLONE 1727 #ifdef CONFIG_CLONE_BACKWARDS 1728 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1729 int __user *, parent_tidptr, 1730 int, tls_val, 1731 int __user *, child_tidptr) 1732 #elif defined(CONFIG_CLONE_BACKWARDS2) 1733 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1734 int __user *, parent_tidptr, 1735 int __user *, child_tidptr, 1736 int, tls_val) 1737 #elif defined(CONFIG_CLONE_BACKWARDS3) 1738 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1739 int, stack_size, 1740 int __user *, parent_tidptr, 1741 int __user *, child_tidptr, 1742 int, tls_val) 1743 #else 1744 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1745 int __user *, parent_tidptr, 1746 int __user *, child_tidptr, 1747 int, tls_val) 1748 #endif 1749 { 1750 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr); 1751 } 1752 #endif 1753 1754 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1755 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1756 #endif 1757 1758 static void sighand_ctor(void *data) 1759 { 1760 struct sighand_struct *sighand = data; 1761 1762 spin_lock_init(&sighand->siglock); 1763 init_waitqueue_head(&sighand->signalfd_wqh); 1764 } 1765 1766 void __init proc_caches_init(void) 1767 { 1768 sighand_cachep = kmem_cache_create("sighand_cache", 1769 sizeof(struct sighand_struct), 0, 1770 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1771 SLAB_NOTRACK, sighand_ctor); 1772 signal_cachep = kmem_cache_create("signal_cache", 1773 sizeof(struct signal_struct), 0, 1774 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1775 files_cachep = kmem_cache_create("files_cache", 1776 sizeof(struct files_struct), 0, 1777 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1778 fs_cachep = kmem_cache_create("fs_cache", 1779 sizeof(struct fs_struct), 0, 1780 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1781 /* 1782 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1783 * whole struct cpumask for the OFFSTACK case. We could change 1784 * this to *only* allocate as much of it as required by the 1785 * maximum number of CPU's we can ever have. The cpumask_allocation 1786 * is at the end of the structure, exactly for that reason. 1787 */ 1788 mm_cachep = kmem_cache_create("mm_struct", 1789 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1790 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1791 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1792 mmap_init(); 1793 nsproxy_cache_init(); 1794 } 1795 1796 /* 1797 * Check constraints on flags passed to the unshare system call. 1798 */ 1799 static int check_unshare_flags(unsigned long unshare_flags) 1800 { 1801 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1802 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1803 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1804 CLONE_NEWUSER|CLONE_NEWPID)) 1805 return -EINVAL; 1806 /* 1807 * Not implemented, but pretend it works if there is nothing to 1808 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1809 * needs to unshare vm. 1810 */ 1811 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1812 /* FIXME: get_task_mm() increments ->mm_users */ 1813 if (atomic_read(¤t->mm->mm_users) > 1) 1814 return -EINVAL; 1815 } 1816 1817 return 0; 1818 } 1819 1820 /* 1821 * Unshare the filesystem structure if it is being shared 1822 */ 1823 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1824 { 1825 struct fs_struct *fs = current->fs; 1826 1827 if (!(unshare_flags & CLONE_FS) || !fs) 1828 return 0; 1829 1830 /* don't need lock here; in the worst case we'll do useless copy */ 1831 if (fs->users == 1) 1832 return 0; 1833 1834 *new_fsp = copy_fs_struct(fs); 1835 if (!*new_fsp) 1836 return -ENOMEM; 1837 1838 return 0; 1839 } 1840 1841 /* 1842 * Unshare file descriptor table if it is being shared 1843 */ 1844 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1845 { 1846 struct files_struct *fd = current->files; 1847 int error = 0; 1848 1849 if ((unshare_flags & CLONE_FILES) && 1850 (fd && atomic_read(&fd->count) > 1)) { 1851 *new_fdp = dup_fd(fd, &error); 1852 if (!*new_fdp) 1853 return error; 1854 } 1855 1856 return 0; 1857 } 1858 1859 /* 1860 * unshare allows a process to 'unshare' part of the process 1861 * context which was originally shared using clone. copy_* 1862 * functions used by do_fork() cannot be used here directly 1863 * because they modify an inactive task_struct that is being 1864 * constructed. Here we are modifying the current, active, 1865 * task_struct. 1866 */ 1867 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1868 { 1869 struct fs_struct *fs, *new_fs = NULL; 1870 struct files_struct *fd, *new_fd = NULL; 1871 struct cred *new_cred = NULL; 1872 struct nsproxy *new_nsproxy = NULL; 1873 int do_sysvsem = 0; 1874 int err; 1875 1876 /* 1877 * If unsharing a user namespace must also unshare the thread. 1878 */ 1879 if (unshare_flags & CLONE_NEWUSER) 1880 unshare_flags |= CLONE_THREAD | CLONE_FS; 1881 /* 1882 * If unsharing a thread from a thread group, must also unshare vm. 1883 */ 1884 if (unshare_flags & CLONE_THREAD) 1885 unshare_flags |= CLONE_VM; 1886 /* 1887 * If unsharing vm, must also unshare signal handlers. 1888 */ 1889 if (unshare_flags & CLONE_VM) 1890 unshare_flags |= CLONE_SIGHAND; 1891 /* 1892 * If unsharing namespace, must also unshare filesystem information. 1893 */ 1894 if (unshare_flags & CLONE_NEWNS) 1895 unshare_flags |= CLONE_FS; 1896 1897 err = check_unshare_flags(unshare_flags); 1898 if (err) 1899 goto bad_unshare_out; 1900 /* 1901 * CLONE_NEWIPC must also detach from the undolist: after switching 1902 * to a new ipc namespace, the semaphore arrays from the old 1903 * namespace are unreachable. 1904 */ 1905 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1906 do_sysvsem = 1; 1907 err = unshare_fs(unshare_flags, &new_fs); 1908 if (err) 1909 goto bad_unshare_out; 1910 err = unshare_fd(unshare_flags, &new_fd); 1911 if (err) 1912 goto bad_unshare_cleanup_fs; 1913 err = unshare_userns(unshare_flags, &new_cred); 1914 if (err) 1915 goto bad_unshare_cleanup_fd; 1916 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1917 new_cred, new_fs); 1918 if (err) 1919 goto bad_unshare_cleanup_cred; 1920 1921 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 1922 if (do_sysvsem) { 1923 /* 1924 * CLONE_SYSVSEM is equivalent to sys_exit(). 1925 */ 1926 exit_sem(current); 1927 } 1928 if (unshare_flags & CLONE_NEWIPC) { 1929 /* Orphan segments in old ns (see sem above). */ 1930 exit_shm(current); 1931 shm_init_task(current); 1932 } 1933 1934 if (new_nsproxy) 1935 switch_task_namespaces(current, new_nsproxy); 1936 1937 task_lock(current); 1938 1939 if (new_fs) { 1940 fs = current->fs; 1941 spin_lock(&fs->lock); 1942 current->fs = new_fs; 1943 if (--fs->users) 1944 new_fs = NULL; 1945 else 1946 new_fs = fs; 1947 spin_unlock(&fs->lock); 1948 } 1949 1950 if (new_fd) { 1951 fd = current->files; 1952 current->files = new_fd; 1953 new_fd = fd; 1954 } 1955 1956 task_unlock(current); 1957 1958 if (new_cred) { 1959 /* Install the new user namespace */ 1960 commit_creds(new_cred); 1961 new_cred = NULL; 1962 } 1963 } 1964 1965 bad_unshare_cleanup_cred: 1966 if (new_cred) 1967 put_cred(new_cred); 1968 bad_unshare_cleanup_fd: 1969 if (new_fd) 1970 put_files_struct(new_fd); 1971 1972 bad_unshare_cleanup_fs: 1973 if (new_fs) 1974 free_fs_struct(new_fs); 1975 1976 bad_unshare_out: 1977 return err; 1978 } 1979 1980 /* 1981 * Helper to unshare the files of the current task. 1982 * We don't want to expose copy_files internals to 1983 * the exec layer of the kernel. 1984 */ 1985 1986 int unshare_files(struct files_struct **displaced) 1987 { 1988 struct task_struct *task = current; 1989 struct files_struct *copy = NULL; 1990 int error; 1991 1992 error = unshare_fd(CLONE_FILES, ©); 1993 if (error || !copy) { 1994 *displaced = NULL; 1995 return error; 1996 } 1997 *displaced = task->files; 1998 task_lock(task); 1999 task->files = copy; 2000 task_unlock(task); 2001 return 0; 2002 } 2003