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 #include <linux/sysctl.h> 78 #include <linux/kcov.h> 79 80 #include <asm/pgtable.h> 81 #include <asm/pgalloc.h> 82 #include <asm/uaccess.h> 83 #include <asm/mmu_context.h> 84 #include <asm/cacheflush.h> 85 #include <asm/tlbflush.h> 86 87 #include <trace/events/sched.h> 88 89 #define CREATE_TRACE_POINTS 90 #include <trace/events/task.h> 91 92 /* 93 * Minimum number of threads to boot the kernel 94 */ 95 #define MIN_THREADS 20 96 97 /* 98 * Maximum number of threads 99 */ 100 #define MAX_THREADS FUTEX_TID_MASK 101 102 /* 103 * Protected counters by write_lock_irq(&tasklist_lock) 104 */ 105 unsigned long total_forks; /* Handle normal Linux uptimes. */ 106 int nr_threads; /* The idle threads do not count.. */ 107 108 int max_threads; /* tunable limit on nr_threads */ 109 110 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 111 112 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 113 114 #ifdef CONFIG_PROVE_RCU 115 int lockdep_tasklist_lock_is_held(void) 116 { 117 return lockdep_is_held(&tasklist_lock); 118 } 119 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 120 #endif /* #ifdef CONFIG_PROVE_RCU */ 121 122 int nr_processes(void) 123 { 124 int cpu; 125 int total = 0; 126 127 for_each_possible_cpu(cpu) 128 total += per_cpu(process_counts, cpu); 129 130 return total; 131 } 132 133 void __weak arch_release_task_struct(struct task_struct *tsk) 134 { 135 } 136 137 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 138 static struct kmem_cache *task_struct_cachep; 139 140 static inline struct task_struct *alloc_task_struct_node(int node) 141 { 142 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 143 } 144 145 static inline void free_task_struct(struct task_struct *tsk) 146 { 147 kmem_cache_free(task_struct_cachep, tsk); 148 } 149 #endif 150 151 void __weak arch_release_thread_stack(unsigned long *stack) 152 { 153 } 154 155 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 156 157 /* 158 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 159 * kmemcache based allocator. 160 */ 161 # if THREAD_SIZE >= PAGE_SIZE 162 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 163 int node) 164 { 165 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 166 THREAD_SIZE_ORDER); 167 168 return page ? page_address(page) : NULL; 169 } 170 171 static inline void free_thread_stack(unsigned long *stack) 172 { 173 __free_pages(virt_to_page(stack), THREAD_SIZE_ORDER); 174 } 175 # else 176 static struct kmem_cache *thread_stack_cache; 177 178 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 179 int node) 180 { 181 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 182 } 183 184 static void free_thread_stack(unsigned long *stack) 185 { 186 kmem_cache_free(thread_stack_cache, stack); 187 } 188 189 void thread_stack_cache_init(void) 190 { 191 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 192 THREAD_SIZE, 0, NULL); 193 BUG_ON(thread_stack_cache == NULL); 194 } 195 # endif 196 #endif 197 198 /* SLAB cache for signal_struct structures (tsk->signal) */ 199 static struct kmem_cache *signal_cachep; 200 201 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 202 struct kmem_cache *sighand_cachep; 203 204 /* SLAB cache for files_struct structures (tsk->files) */ 205 struct kmem_cache *files_cachep; 206 207 /* SLAB cache for fs_struct structures (tsk->fs) */ 208 struct kmem_cache *fs_cachep; 209 210 /* SLAB cache for vm_area_struct structures */ 211 struct kmem_cache *vm_area_cachep; 212 213 /* SLAB cache for mm_struct structures (tsk->mm) */ 214 static struct kmem_cache *mm_cachep; 215 216 static void account_kernel_stack(unsigned long *stack, int account) 217 { 218 /* All stack pages are in the same zone and belong to the same memcg. */ 219 struct page *first_page = virt_to_page(stack); 220 221 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 222 THREAD_SIZE / 1024 * account); 223 224 memcg_kmem_update_page_stat( 225 first_page, MEMCG_KERNEL_STACK_KB, 226 account * (THREAD_SIZE / 1024)); 227 } 228 229 void free_task(struct task_struct *tsk) 230 { 231 account_kernel_stack(tsk->stack, -1); 232 arch_release_thread_stack(tsk->stack); 233 free_thread_stack(tsk->stack); 234 rt_mutex_debug_task_free(tsk); 235 ftrace_graph_exit_task(tsk); 236 put_seccomp_filter(tsk); 237 arch_release_task_struct(tsk); 238 free_task_struct(tsk); 239 } 240 EXPORT_SYMBOL(free_task); 241 242 static inline void free_signal_struct(struct signal_struct *sig) 243 { 244 taskstats_tgid_free(sig); 245 sched_autogroup_exit(sig); 246 kmem_cache_free(signal_cachep, sig); 247 } 248 249 static inline void put_signal_struct(struct signal_struct *sig) 250 { 251 if (atomic_dec_and_test(&sig->sigcnt)) 252 free_signal_struct(sig); 253 } 254 255 void __put_task_struct(struct task_struct *tsk) 256 { 257 WARN_ON(!tsk->exit_state); 258 WARN_ON(atomic_read(&tsk->usage)); 259 WARN_ON(tsk == current); 260 261 cgroup_free(tsk); 262 task_numa_free(tsk); 263 security_task_free(tsk); 264 exit_creds(tsk); 265 delayacct_tsk_free(tsk); 266 put_signal_struct(tsk->signal); 267 268 if (!profile_handoff_task(tsk)) 269 free_task(tsk); 270 } 271 EXPORT_SYMBOL_GPL(__put_task_struct); 272 273 void __init __weak arch_task_cache_init(void) { } 274 275 /* 276 * set_max_threads 277 */ 278 static void set_max_threads(unsigned int max_threads_suggested) 279 { 280 u64 threads; 281 282 /* 283 * The number of threads shall be limited such that the thread 284 * structures may only consume a small part of the available memory. 285 */ 286 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 287 threads = MAX_THREADS; 288 else 289 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 290 (u64) THREAD_SIZE * 8UL); 291 292 if (threads > max_threads_suggested) 293 threads = max_threads_suggested; 294 295 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 296 } 297 298 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 299 /* Initialized by the architecture: */ 300 int arch_task_struct_size __read_mostly; 301 #endif 302 303 void __init fork_init(void) 304 { 305 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 306 #ifndef ARCH_MIN_TASKALIGN 307 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 308 #endif 309 /* create a slab on which task_structs can be allocated */ 310 task_struct_cachep = kmem_cache_create("task_struct", 311 arch_task_struct_size, ARCH_MIN_TASKALIGN, 312 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 313 #endif 314 315 /* do the arch specific task caches init */ 316 arch_task_cache_init(); 317 318 set_max_threads(MAX_THREADS); 319 320 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 321 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 322 init_task.signal->rlim[RLIMIT_SIGPENDING] = 323 init_task.signal->rlim[RLIMIT_NPROC]; 324 } 325 326 int __weak arch_dup_task_struct(struct task_struct *dst, 327 struct task_struct *src) 328 { 329 *dst = *src; 330 return 0; 331 } 332 333 void set_task_stack_end_magic(struct task_struct *tsk) 334 { 335 unsigned long *stackend; 336 337 stackend = end_of_stack(tsk); 338 *stackend = STACK_END_MAGIC; /* for overflow detection */ 339 } 340 341 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 342 { 343 struct task_struct *tsk; 344 unsigned long *stack; 345 int err; 346 347 if (node == NUMA_NO_NODE) 348 node = tsk_fork_get_node(orig); 349 tsk = alloc_task_struct_node(node); 350 if (!tsk) 351 return NULL; 352 353 stack = alloc_thread_stack_node(tsk, node); 354 if (!stack) 355 goto free_tsk; 356 357 err = arch_dup_task_struct(tsk, orig); 358 if (err) 359 goto free_stack; 360 361 tsk->stack = stack; 362 #ifdef CONFIG_SECCOMP 363 /* 364 * We must handle setting up seccomp filters once we're under 365 * the sighand lock in case orig has changed between now and 366 * then. Until then, filter must be NULL to avoid messing up 367 * the usage counts on the error path calling free_task. 368 */ 369 tsk->seccomp.filter = NULL; 370 #endif 371 372 setup_thread_stack(tsk, orig); 373 clear_user_return_notifier(tsk); 374 clear_tsk_need_resched(tsk); 375 set_task_stack_end_magic(tsk); 376 377 #ifdef CONFIG_CC_STACKPROTECTOR 378 tsk->stack_canary = get_random_int(); 379 #endif 380 381 /* 382 * One for us, one for whoever does the "release_task()" (usually 383 * parent) 384 */ 385 atomic_set(&tsk->usage, 2); 386 #ifdef CONFIG_BLK_DEV_IO_TRACE 387 tsk->btrace_seq = 0; 388 #endif 389 tsk->splice_pipe = NULL; 390 tsk->task_frag.page = NULL; 391 tsk->wake_q.next = NULL; 392 393 account_kernel_stack(stack, 1); 394 395 kcov_task_init(tsk); 396 397 return tsk; 398 399 free_stack: 400 free_thread_stack(stack); 401 free_tsk: 402 free_task_struct(tsk); 403 return NULL; 404 } 405 406 #ifdef CONFIG_MMU 407 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 408 { 409 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 410 struct rb_node **rb_link, *rb_parent; 411 int retval; 412 unsigned long charge; 413 414 uprobe_start_dup_mmap(); 415 if (down_write_killable(&oldmm->mmap_sem)) { 416 retval = -EINTR; 417 goto fail_uprobe_end; 418 } 419 flush_cache_dup_mm(oldmm); 420 uprobe_dup_mmap(oldmm, mm); 421 /* 422 * Not linked in yet - no deadlock potential: 423 */ 424 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 425 426 /* No ordering required: file already has been exposed. */ 427 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 428 429 mm->total_vm = oldmm->total_vm; 430 mm->data_vm = oldmm->data_vm; 431 mm->exec_vm = oldmm->exec_vm; 432 mm->stack_vm = oldmm->stack_vm; 433 434 rb_link = &mm->mm_rb.rb_node; 435 rb_parent = NULL; 436 pprev = &mm->mmap; 437 retval = ksm_fork(mm, oldmm); 438 if (retval) 439 goto out; 440 retval = khugepaged_fork(mm, oldmm); 441 if (retval) 442 goto out; 443 444 prev = NULL; 445 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 446 struct file *file; 447 448 if (mpnt->vm_flags & VM_DONTCOPY) { 449 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 450 continue; 451 } 452 charge = 0; 453 if (mpnt->vm_flags & VM_ACCOUNT) { 454 unsigned long len = vma_pages(mpnt); 455 456 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 457 goto fail_nomem; 458 charge = len; 459 } 460 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 461 if (!tmp) 462 goto fail_nomem; 463 *tmp = *mpnt; 464 INIT_LIST_HEAD(&tmp->anon_vma_chain); 465 retval = vma_dup_policy(mpnt, tmp); 466 if (retval) 467 goto fail_nomem_policy; 468 tmp->vm_mm = mm; 469 if (anon_vma_fork(tmp, mpnt)) 470 goto fail_nomem_anon_vma_fork; 471 tmp->vm_flags &= 472 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP); 473 tmp->vm_next = tmp->vm_prev = NULL; 474 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 475 file = tmp->vm_file; 476 if (file) { 477 struct inode *inode = file_inode(file); 478 struct address_space *mapping = file->f_mapping; 479 480 get_file(file); 481 if (tmp->vm_flags & VM_DENYWRITE) 482 atomic_dec(&inode->i_writecount); 483 i_mmap_lock_write(mapping); 484 if (tmp->vm_flags & VM_SHARED) 485 atomic_inc(&mapping->i_mmap_writable); 486 flush_dcache_mmap_lock(mapping); 487 /* insert tmp into the share list, just after mpnt */ 488 vma_interval_tree_insert_after(tmp, mpnt, 489 &mapping->i_mmap); 490 flush_dcache_mmap_unlock(mapping); 491 i_mmap_unlock_write(mapping); 492 } 493 494 /* 495 * Clear hugetlb-related page reserves for children. This only 496 * affects MAP_PRIVATE mappings. Faults generated by the child 497 * are not guaranteed to succeed, even if read-only 498 */ 499 if (is_vm_hugetlb_page(tmp)) 500 reset_vma_resv_huge_pages(tmp); 501 502 /* 503 * Link in the new vma and copy the page table entries. 504 */ 505 *pprev = tmp; 506 pprev = &tmp->vm_next; 507 tmp->vm_prev = prev; 508 prev = tmp; 509 510 __vma_link_rb(mm, tmp, rb_link, rb_parent); 511 rb_link = &tmp->vm_rb.rb_right; 512 rb_parent = &tmp->vm_rb; 513 514 mm->map_count++; 515 retval = copy_page_range(mm, oldmm, mpnt); 516 517 if (tmp->vm_ops && tmp->vm_ops->open) 518 tmp->vm_ops->open(tmp); 519 520 if (retval) 521 goto out; 522 } 523 /* a new mm has just been created */ 524 arch_dup_mmap(oldmm, mm); 525 retval = 0; 526 out: 527 up_write(&mm->mmap_sem); 528 flush_tlb_mm(oldmm); 529 up_write(&oldmm->mmap_sem); 530 fail_uprobe_end: 531 uprobe_end_dup_mmap(); 532 return retval; 533 fail_nomem_anon_vma_fork: 534 mpol_put(vma_policy(tmp)); 535 fail_nomem_policy: 536 kmem_cache_free(vm_area_cachep, tmp); 537 fail_nomem: 538 retval = -ENOMEM; 539 vm_unacct_memory(charge); 540 goto out; 541 } 542 543 static inline int mm_alloc_pgd(struct mm_struct *mm) 544 { 545 mm->pgd = pgd_alloc(mm); 546 if (unlikely(!mm->pgd)) 547 return -ENOMEM; 548 return 0; 549 } 550 551 static inline void mm_free_pgd(struct mm_struct *mm) 552 { 553 pgd_free(mm, mm->pgd); 554 } 555 #else 556 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 557 { 558 down_write(&oldmm->mmap_sem); 559 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 560 up_write(&oldmm->mmap_sem); 561 return 0; 562 } 563 #define mm_alloc_pgd(mm) (0) 564 #define mm_free_pgd(mm) 565 #endif /* CONFIG_MMU */ 566 567 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 568 569 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 570 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 571 572 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 573 574 static int __init coredump_filter_setup(char *s) 575 { 576 default_dump_filter = 577 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 578 MMF_DUMP_FILTER_MASK; 579 return 1; 580 } 581 582 __setup("coredump_filter=", coredump_filter_setup); 583 584 #include <linux/init_task.h> 585 586 static void mm_init_aio(struct mm_struct *mm) 587 { 588 #ifdef CONFIG_AIO 589 spin_lock_init(&mm->ioctx_lock); 590 mm->ioctx_table = NULL; 591 #endif 592 } 593 594 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 595 { 596 #ifdef CONFIG_MEMCG 597 mm->owner = p; 598 #endif 599 } 600 601 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 602 { 603 mm->mmap = NULL; 604 mm->mm_rb = RB_ROOT; 605 mm->vmacache_seqnum = 0; 606 atomic_set(&mm->mm_users, 1); 607 atomic_set(&mm->mm_count, 1); 608 init_rwsem(&mm->mmap_sem); 609 INIT_LIST_HEAD(&mm->mmlist); 610 mm->core_state = NULL; 611 atomic_long_set(&mm->nr_ptes, 0); 612 mm_nr_pmds_init(mm); 613 mm->map_count = 0; 614 mm->locked_vm = 0; 615 mm->pinned_vm = 0; 616 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 617 spin_lock_init(&mm->page_table_lock); 618 mm_init_cpumask(mm); 619 mm_init_aio(mm); 620 mm_init_owner(mm, p); 621 mmu_notifier_mm_init(mm); 622 clear_tlb_flush_pending(mm); 623 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 624 mm->pmd_huge_pte = NULL; 625 #endif 626 627 if (current->mm) { 628 mm->flags = current->mm->flags & MMF_INIT_MASK; 629 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 630 } else { 631 mm->flags = default_dump_filter; 632 mm->def_flags = 0; 633 } 634 635 if (mm_alloc_pgd(mm)) 636 goto fail_nopgd; 637 638 if (init_new_context(p, mm)) 639 goto fail_nocontext; 640 641 return mm; 642 643 fail_nocontext: 644 mm_free_pgd(mm); 645 fail_nopgd: 646 free_mm(mm); 647 return NULL; 648 } 649 650 static void check_mm(struct mm_struct *mm) 651 { 652 int i; 653 654 for (i = 0; i < NR_MM_COUNTERS; i++) { 655 long x = atomic_long_read(&mm->rss_stat.count[i]); 656 657 if (unlikely(x)) 658 printk(KERN_ALERT "BUG: Bad rss-counter state " 659 "mm:%p idx:%d val:%ld\n", mm, i, x); 660 } 661 662 if (atomic_long_read(&mm->nr_ptes)) 663 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 664 atomic_long_read(&mm->nr_ptes)); 665 if (mm_nr_pmds(mm)) 666 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 667 mm_nr_pmds(mm)); 668 669 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 670 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 671 #endif 672 } 673 674 /* 675 * Allocate and initialize an mm_struct. 676 */ 677 struct mm_struct *mm_alloc(void) 678 { 679 struct mm_struct *mm; 680 681 mm = allocate_mm(); 682 if (!mm) 683 return NULL; 684 685 memset(mm, 0, sizeof(*mm)); 686 return mm_init(mm, current); 687 } 688 689 /* 690 * Called when the last reference to the mm 691 * is dropped: either by a lazy thread or by 692 * mmput. Free the page directory and the mm. 693 */ 694 void __mmdrop(struct mm_struct *mm) 695 { 696 BUG_ON(mm == &init_mm); 697 mm_free_pgd(mm); 698 destroy_context(mm); 699 mmu_notifier_mm_destroy(mm); 700 check_mm(mm); 701 free_mm(mm); 702 } 703 EXPORT_SYMBOL_GPL(__mmdrop); 704 705 static inline void __mmput(struct mm_struct *mm) 706 { 707 VM_BUG_ON(atomic_read(&mm->mm_users)); 708 709 uprobe_clear_state(mm); 710 exit_aio(mm); 711 ksm_exit(mm); 712 khugepaged_exit(mm); /* must run before exit_mmap */ 713 exit_mmap(mm); 714 set_mm_exe_file(mm, NULL); 715 if (!list_empty(&mm->mmlist)) { 716 spin_lock(&mmlist_lock); 717 list_del(&mm->mmlist); 718 spin_unlock(&mmlist_lock); 719 } 720 if (mm->binfmt) 721 module_put(mm->binfmt->module); 722 mmdrop(mm); 723 } 724 725 /* 726 * Decrement the use count and release all resources for an mm. 727 */ 728 void mmput(struct mm_struct *mm) 729 { 730 might_sleep(); 731 732 if (atomic_dec_and_test(&mm->mm_users)) 733 __mmput(mm); 734 } 735 EXPORT_SYMBOL_GPL(mmput); 736 737 #ifdef CONFIG_MMU 738 static void mmput_async_fn(struct work_struct *work) 739 { 740 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 741 __mmput(mm); 742 } 743 744 void mmput_async(struct mm_struct *mm) 745 { 746 if (atomic_dec_and_test(&mm->mm_users)) { 747 INIT_WORK(&mm->async_put_work, mmput_async_fn); 748 schedule_work(&mm->async_put_work); 749 } 750 } 751 #endif 752 753 /** 754 * set_mm_exe_file - change a reference to the mm's executable file 755 * 756 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 757 * 758 * Main users are mmput() and sys_execve(). Callers prevent concurrent 759 * invocations: in mmput() nobody alive left, in execve task is single 760 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 761 * mm->exe_file, but does so without using set_mm_exe_file() in order 762 * to do avoid the need for any locks. 763 */ 764 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 765 { 766 struct file *old_exe_file; 767 768 /* 769 * It is safe to dereference the exe_file without RCU as 770 * this function is only called if nobody else can access 771 * this mm -- see comment above for justification. 772 */ 773 old_exe_file = rcu_dereference_raw(mm->exe_file); 774 775 if (new_exe_file) 776 get_file(new_exe_file); 777 rcu_assign_pointer(mm->exe_file, new_exe_file); 778 if (old_exe_file) 779 fput(old_exe_file); 780 } 781 782 /** 783 * get_mm_exe_file - acquire a reference to the mm's executable file 784 * 785 * Returns %NULL if mm has no associated executable file. 786 * User must release file via fput(). 787 */ 788 struct file *get_mm_exe_file(struct mm_struct *mm) 789 { 790 struct file *exe_file; 791 792 rcu_read_lock(); 793 exe_file = rcu_dereference(mm->exe_file); 794 if (exe_file && !get_file_rcu(exe_file)) 795 exe_file = NULL; 796 rcu_read_unlock(); 797 return exe_file; 798 } 799 EXPORT_SYMBOL(get_mm_exe_file); 800 801 /** 802 * get_task_exe_file - acquire a reference to the task's executable file 803 * 804 * Returns %NULL if task's mm (if any) has no associated executable file or 805 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 806 * User must release file via fput(). 807 */ 808 struct file *get_task_exe_file(struct task_struct *task) 809 { 810 struct file *exe_file = NULL; 811 struct mm_struct *mm; 812 813 task_lock(task); 814 mm = task->mm; 815 if (mm) { 816 if (!(task->flags & PF_KTHREAD)) 817 exe_file = get_mm_exe_file(mm); 818 } 819 task_unlock(task); 820 return exe_file; 821 } 822 EXPORT_SYMBOL(get_task_exe_file); 823 824 /** 825 * get_task_mm - acquire a reference to the task's mm 826 * 827 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 828 * this kernel workthread has transiently adopted a user mm with use_mm, 829 * to do its AIO) is not set and if so returns a reference to it, after 830 * bumping up the use count. User must release the mm via mmput() 831 * after use. Typically used by /proc and ptrace. 832 */ 833 struct mm_struct *get_task_mm(struct task_struct *task) 834 { 835 struct mm_struct *mm; 836 837 task_lock(task); 838 mm = task->mm; 839 if (mm) { 840 if (task->flags & PF_KTHREAD) 841 mm = NULL; 842 else 843 atomic_inc(&mm->mm_users); 844 } 845 task_unlock(task); 846 return mm; 847 } 848 EXPORT_SYMBOL_GPL(get_task_mm); 849 850 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 851 { 852 struct mm_struct *mm; 853 int err; 854 855 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 856 if (err) 857 return ERR_PTR(err); 858 859 mm = get_task_mm(task); 860 if (mm && mm != current->mm && 861 !ptrace_may_access(task, mode)) { 862 mmput(mm); 863 mm = ERR_PTR(-EACCES); 864 } 865 mutex_unlock(&task->signal->cred_guard_mutex); 866 867 return mm; 868 } 869 870 static void complete_vfork_done(struct task_struct *tsk) 871 { 872 struct completion *vfork; 873 874 task_lock(tsk); 875 vfork = tsk->vfork_done; 876 if (likely(vfork)) { 877 tsk->vfork_done = NULL; 878 complete(vfork); 879 } 880 task_unlock(tsk); 881 } 882 883 static int wait_for_vfork_done(struct task_struct *child, 884 struct completion *vfork) 885 { 886 int killed; 887 888 freezer_do_not_count(); 889 killed = wait_for_completion_killable(vfork); 890 freezer_count(); 891 892 if (killed) { 893 task_lock(child); 894 child->vfork_done = NULL; 895 task_unlock(child); 896 } 897 898 put_task_struct(child); 899 return killed; 900 } 901 902 /* Please note the differences between mmput and mm_release. 903 * mmput is called whenever we stop holding onto a mm_struct, 904 * error success whatever. 905 * 906 * mm_release is called after a mm_struct has been removed 907 * from the current process. 908 * 909 * This difference is important for error handling, when we 910 * only half set up a mm_struct for a new process and need to restore 911 * the old one. Because we mmput the new mm_struct before 912 * restoring the old one. . . 913 * Eric Biederman 10 January 1998 914 */ 915 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 916 { 917 /* Get rid of any futexes when releasing the mm */ 918 #ifdef CONFIG_FUTEX 919 if (unlikely(tsk->robust_list)) { 920 exit_robust_list(tsk); 921 tsk->robust_list = NULL; 922 } 923 #ifdef CONFIG_COMPAT 924 if (unlikely(tsk->compat_robust_list)) { 925 compat_exit_robust_list(tsk); 926 tsk->compat_robust_list = NULL; 927 } 928 #endif 929 if (unlikely(!list_empty(&tsk->pi_state_list))) 930 exit_pi_state_list(tsk); 931 #endif 932 933 uprobe_free_utask(tsk); 934 935 /* Get rid of any cached register state */ 936 deactivate_mm(tsk, mm); 937 938 /* 939 * Signal userspace if we're not exiting with a core dump 940 * because we want to leave the value intact for debugging 941 * purposes. 942 */ 943 if (tsk->clear_child_tid) { 944 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 945 atomic_read(&mm->mm_users) > 1) { 946 /* 947 * We don't check the error code - if userspace has 948 * not set up a proper pointer then tough luck. 949 */ 950 put_user(0, tsk->clear_child_tid); 951 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 952 1, NULL, NULL, 0); 953 } 954 tsk->clear_child_tid = NULL; 955 } 956 957 /* 958 * All done, finally we can wake up parent and return this mm to him. 959 * Also kthread_stop() uses this completion for synchronization. 960 */ 961 if (tsk->vfork_done) 962 complete_vfork_done(tsk); 963 } 964 965 /* 966 * Allocate a new mm structure and copy contents from the 967 * mm structure of the passed in task structure. 968 */ 969 static struct mm_struct *dup_mm(struct task_struct *tsk) 970 { 971 struct mm_struct *mm, *oldmm = current->mm; 972 int err; 973 974 mm = allocate_mm(); 975 if (!mm) 976 goto fail_nomem; 977 978 memcpy(mm, oldmm, sizeof(*mm)); 979 980 if (!mm_init(mm, tsk)) 981 goto fail_nomem; 982 983 err = dup_mmap(mm, oldmm); 984 if (err) 985 goto free_pt; 986 987 mm->hiwater_rss = get_mm_rss(mm); 988 mm->hiwater_vm = mm->total_vm; 989 990 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 991 goto free_pt; 992 993 return mm; 994 995 free_pt: 996 /* don't put binfmt in mmput, we haven't got module yet */ 997 mm->binfmt = NULL; 998 mmput(mm); 999 1000 fail_nomem: 1001 return NULL; 1002 } 1003 1004 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1005 { 1006 struct mm_struct *mm, *oldmm; 1007 int retval; 1008 1009 tsk->min_flt = tsk->maj_flt = 0; 1010 tsk->nvcsw = tsk->nivcsw = 0; 1011 #ifdef CONFIG_DETECT_HUNG_TASK 1012 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1013 #endif 1014 1015 tsk->mm = NULL; 1016 tsk->active_mm = NULL; 1017 1018 /* 1019 * Are we cloning a kernel thread? 1020 * 1021 * We need to steal a active VM for that.. 1022 */ 1023 oldmm = current->mm; 1024 if (!oldmm) 1025 return 0; 1026 1027 /* initialize the new vmacache entries */ 1028 vmacache_flush(tsk); 1029 1030 if (clone_flags & CLONE_VM) { 1031 atomic_inc(&oldmm->mm_users); 1032 mm = oldmm; 1033 goto good_mm; 1034 } 1035 1036 retval = -ENOMEM; 1037 mm = dup_mm(tsk); 1038 if (!mm) 1039 goto fail_nomem; 1040 1041 good_mm: 1042 tsk->mm = mm; 1043 tsk->active_mm = mm; 1044 return 0; 1045 1046 fail_nomem: 1047 return retval; 1048 } 1049 1050 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1051 { 1052 struct fs_struct *fs = current->fs; 1053 if (clone_flags & CLONE_FS) { 1054 /* tsk->fs is already what we want */ 1055 spin_lock(&fs->lock); 1056 if (fs->in_exec) { 1057 spin_unlock(&fs->lock); 1058 return -EAGAIN; 1059 } 1060 fs->users++; 1061 spin_unlock(&fs->lock); 1062 return 0; 1063 } 1064 tsk->fs = copy_fs_struct(fs); 1065 if (!tsk->fs) 1066 return -ENOMEM; 1067 return 0; 1068 } 1069 1070 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1071 { 1072 struct files_struct *oldf, *newf; 1073 int error = 0; 1074 1075 /* 1076 * A background process may not have any files ... 1077 */ 1078 oldf = current->files; 1079 if (!oldf) 1080 goto out; 1081 1082 if (clone_flags & CLONE_FILES) { 1083 atomic_inc(&oldf->count); 1084 goto out; 1085 } 1086 1087 newf = dup_fd(oldf, &error); 1088 if (!newf) 1089 goto out; 1090 1091 tsk->files = newf; 1092 error = 0; 1093 out: 1094 return error; 1095 } 1096 1097 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1098 { 1099 #ifdef CONFIG_BLOCK 1100 struct io_context *ioc = current->io_context; 1101 struct io_context *new_ioc; 1102 1103 if (!ioc) 1104 return 0; 1105 /* 1106 * Share io context with parent, if CLONE_IO is set 1107 */ 1108 if (clone_flags & CLONE_IO) { 1109 ioc_task_link(ioc); 1110 tsk->io_context = ioc; 1111 } else if (ioprio_valid(ioc->ioprio)) { 1112 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1113 if (unlikely(!new_ioc)) 1114 return -ENOMEM; 1115 1116 new_ioc->ioprio = ioc->ioprio; 1117 put_io_context(new_ioc); 1118 } 1119 #endif 1120 return 0; 1121 } 1122 1123 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1124 { 1125 struct sighand_struct *sig; 1126 1127 if (clone_flags & CLONE_SIGHAND) { 1128 atomic_inc(¤t->sighand->count); 1129 return 0; 1130 } 1131 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1132 rcu_assign_pointer(tsk->sighand, sig); 1133 if (!sig) 1134 return -ENOMEM; 1135 1136 atomic_set(&sig->count, 1); 1137 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1138 return 0; 1139 } 1140 1141 void __cleanup_sighand(struct sighand_struct *sighand) 1142 { 1143 if (atomic_dec_and_test(&sighand->count)) { 1144 signalfd_cleanup(sighand); 1145 /* 1146 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1147 * without an RCU grace period, see __lock_task_sighand(). 1148 */ 1149 kmem_cache_free(sighand_cachep, sighand); 1150 } 1151 } 1152 1153 /* 1154 * Initialize POSIX timer handling for a thread group. 1155 */ 1156 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1157 { 1158 unsigned long cpu_limit; 1159 1160 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1161 if (cpu_limit != RLIM_INFINITY) { 1162 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1163 sig->cputimer.running = true; 1164 } 1165 1166 /* The timer lists. */ 1167 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1168 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1169 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1170 } 1171 1172 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1173 { 1174 struct signal_struct *sig; 1175 1176 if (clone_flags & CLONE_THREAD) 1177 return 0; 1178 1179 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1180 tsk->signal = sig; 1181 if (!sig) 1182 return -ENOMEM; 1183 1184 sig->nr_threads = 1; 1185 atomic_set(&sig->live, 1); 1186 atomic_set(&sig->sigcnt, 1); 1187 1188 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1189 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1190 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1191 1192 init_waitqueue_head(&sig->wait_chldexit); 1193 sig->curr_target = tsk; 1194 init_sigpending(&sig->shared_pending); 1195 INIT_LIST_HEAD(&sig->posix_timers); 1196 seqlock_init(&sig->stats_lock); 1197 prev_cputime_init(&sig->prev_cputime); 1198 1199 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1200 sig->real_timer.function = it_real_fn; 1201 1202 task_lock(current->group_leader); 1203 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1204 task_unlock(current->group_leader); 1205 1206 posix_cpu_timers_init_group(sig); 1207 1208 tty_audit_fork(sig); 1209 sched_autogroup_fork(sig); 1210 1211 sig->oom_score_adj = current->signal->oom_score_adj; 1212 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1213 1214 sig->has_child_subreaper = current->signal->has_child_subreaper || 1215 current->signal->is_child_subreaper; 1216 1217 mutex_init(&sig->cred_guard_mutex); 1218 1219 return 0; 1220 } 1221 1222 static void copy_seccomp(struct task_struct *p) 1223 { 1224 #ifdef CONFIG_SECCOMP 1225 /* 1226 * Must be called with sighand->lock held, which is common to 1227 * all threads in the group. Holding cred_guard_mutex is not 1228 * needed because this new task is not yet running and cannot 1229 * be racing exec. 1230 */ 1231 assert_spin_locked(¤t->sighand->siglock); 1232 1233 /* Ref-count the new filter user, and assign it. */ 1234 get_seccomp_filter(current); 1235 p->seccomp = current->seccomp; 1236 1237 /* 1238 * Explicitly enable no_new_privs here in case it got set 1239 * between the task_struct being duplicated and holding the 1240 * sighand lock. The seccomp state and nnp must be in sync. 1241 */ 1242 if (task_no_new_privs(current)) 1243 task_set_no_new_privs(p); 1244 1245 /* 1246 * If the parent gained a seccomp mode after copying thread 1247 * flags and between before we held the sighand lock, we have 1248 * to manually enable the seccomp thread flag here. 1249 */ 1250 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1251 set_tsk_thread_flag(p, TIF_SECCOMP); 1252 #endif 1253 } 1254 1255 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1256 { 1257 current->clear_child_tid = tidptr; 1258 1259 return task_pid_vnr(current); 1260 } 1261 1262 static void rt_mutex_init_task(struct task_struct *p) 1263 { 1264 raw_spin_lock_init(&p->pi_lock); 1265 #ifdef CONFIG_RT_MUTEXES 1266 p->pi_waiters = RB_ROOT; 1267 p->pi_waiters_leftmost = NULL; 1268 p->pi_blocked_on = NULL; 1269 #endif 1270 } 1271 1272 /* 1273 * Initialize POSIX timer handling for a single task. 1274 */ 1275 static void posix_cpu_timers_init(struct task_struct *tsk) 1276 { 1277 tsk->cputime_expires.prof_exp = 0; 1278 tsk->cputime_expires.virt_exp = 0; 1279 tsk->cputime_expires.sched_exp = 0; 1280 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1281 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1282 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1283 } 1284 1285 static inline void 1286 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1287 { 1288 task->pids[type].pid = pid; 1289 } 1290 1291 /* 1292 * This creates a new process as a copy of the old one, 1293 * but does not actually start it yet. 1294 * 1295 * It copies the registers, and all the appropriate 1296 * parts of the process environment (as per the clone 1297 * flags). The actual kick-off is left to the caller. 1298 */ 1299 static struct task_struct *copy_process(unsigned long clone_flags, 1300 unsigned long stack_start, 1301 unsigned long stack_size, 1302 int __user *child_tidptr, 1303 struct pid *pid, 1304 int trace, 1305 unsigned long tls, 1306 int node) 1307 { 1308 int retval; 1309 struct task_struct *p; 1310 1311 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1312 return ERR_PTR(-EINVAL); 1313 1314 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1315 return ERR_PTR(-EINVAL); 1316 1317 /* 1318 * Thread groups must share signals as well, and detached threads 1319 * can only be started up within the thread group. 1320 */ 1321 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1322 return ERR_PTR(-EINVAL); 1323 1324 /* 1325 * Shared signal handlers imply shared VM. By way of the above, 1326 * thread groups also imply shared VM. Blocking this case allows 1327 * for various simplifications in other code. 1328 */ 1329 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1330 return ERR_PTR(-EINVAL); 1331 1332 /* 1333 * Siblings of global init remain as zombies on exit since they are 1334 * not reaped by their parent (swapper). To solve this and to avoid 1335 * multi-rooted process trees, prevent global and container-inits 1336 * from creating siblings. 1337 */ 1338 if ((clone_flags & CLONE_PARENT) && 1339 current->signal->flags & SIGNAL_UNKILLABLE) 1340 return ERR_PTR(-EINVAL); 1341 1342 /* 1343 * If the new process will be in a different pid or user namespace 1344 * do not allow it to share a thread group with the forking task. 1345 */ 1346 if (clone_flags & CLONE_THREAD) { 1347 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1348 (task_active_pid_ns(current) != 1349 current->nsproxy->pid_ns_for_children)) 1350 return ERR_PTR(-EINVAL); 1351 } 1352 1353 retval = security_task_create(clone_flags); 1354 if (retval) 1355 goto fork_out; 1356 1357 retval = -ENOMEM; 1358 p = dup_task_struct(current, node); 1359 if (!p) 1360 goto fork_out; 1361 1362 ftrace_graph_init_task(p); 1363 1364 rt_mutex_init_task(p); 1365 1366 #ifdef CONFIG_PROVE_LOCKING 1367 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1368 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1369 #endif 1370 retval = -EAGAIN; 1371 if (atomic_read(&p->real_cred->user->processes) >= 1372 task_rlimit(p, RLIMIT_NPROC)) { 1373 if (p->real_cred->user != INIT_USER && 1374 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1375 goto bad_fork_free; 1376 } 1377 current->flags &= ~PF_NPROC_EXCEEDED; 1378 1379 retval = copy_creds(p, clone_flags); 1380 if (retval < 0) 1381 goto bad_fork_free; 1382 1383 /* 1384 * If multiple threads are within copy_process(), then this check 1385 * triggers too late. This doesn't hurt, the check is only there 1386 * to stop root fork bombs. 1387 */ 1388 retval = -EAGAIN; 1389 if (nr_threads >= max_threads) 1390 goto bad_fork_cleanup_count; 1391 1392 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1393 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1394 p->flags |= PF_FORKNOEXEC; 1395 INIT_LIST_HEAD(&p->children); 1396 INIT_LIST_HEAD(&p->sibling); 1397 rcu_copy_process(p); 1398 p->vfork_done = NULL; 1399 spin_lock_init(&p->alloc_lock); 1400 1401 init_sigpending(&p->pending); 1402 1403 p->utime = p->stime = p->gtime = 0; 1404 p->utimescaled = p->stimescaled = 0; 1405 prev_cputime_init(&p->prev_cputime); 1406 1407 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1408 seqcount_init(&p->vtime_seqcount); 1409 p->vtime_snap = 0; 1410 p->vtime_snap_whence = VTIME_INACTIVE; 1411 #endif 1412 1413 #if defined(SPLIT_RSS_COUNTING) 1414 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1415 #endif 1416 1417 p->default_timer_slack_ns = current->timer_slack_ns; 1418 1419 task_io_accounting_init(&p->ioac); 1420 acct_clear_integrals(p); 1421 1422 posix_cpu_timers_init(p); 1423 1424 p->start_time = ktime_get_ns(); 1425 p->real_start_time = ktime_get_boot_ns(); 1426 p->io_context = NULL; 1427 p->audit_context = NULL; 1428 cgroup_fork(p); 1429 #ifdef CONFIG_NUMA 1430 p->mempolicy = mpol_dup(p->mempolicy); 1431 if (IS_ERR(p->mempolicy)) { 1432 retval = PTR_ERR(p->mempolicy); 1433 p->mempolicy = NULL; 1434 goto bad_fork_cleanup_threadgroup_lock; 1435 } 1436 #endif 1437 #ifdef CONFIG_CPUSETS 1438 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1439 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1440 seqcount_init(&p->mems_allowed_seq); 1441 #endif 1442 #ifdef CONFIG_TRACE_IRQFLAGS 1443 p->irq_events = 0; 1444 p->hardirqs_enabled = 0; 1445 p->hardirq_enable_ip = 0; 1446 p->hardirq_enable_event = 0; 1447 p->hardirq_disable_ip = _THIS_IP_; 1448 p->hardirq_disable_event = 0; 1449 p->softirqs_enabled = 1; 1450 p->softirq_enable_ip = _THIS_IP_; 1451 p->softirq_enable_event = 0; 1452 p->softirq_disable_ip = 0; 1453 p->softirq_disable_event = 0; 1454 p->hardirq_context = 0; 1455 p->softirq_context = 0; 1456 #endif 1457 1458 p->pagefault_disabled = 0; 1459 1460 #ifdef CONFIG_LOCKDEP 1461 p->lockdep_depth = 0; /* no locks held yet */ 1462 p->curr_chain_key = 0; 1463 p->lockdep_recursion = 0; 1464 #endif 1465 1466 #ifdef CONFIG_DEBUG_MUTEXES 1467 p->blocked_on = NULL; /* not blocked yet */ 1468 #endif 1469 #ifdef CONFIG_BCACHE 1470 p->sequential_io = 0; 1471 p->sequential_io_avg = 0; 1472 #endif 1473 1474 /* Perform scheduler related setup. Assign this task to a CPU. */ 1475 retval = sched_fork(clone_flags, p); 1476 if (retval) 1477 goto bad_fork_cleanup_policy; 1478 1479 retval = perf_event_init_task(p); 1480 if (retval) 1481 goto bad_fork_cleanup_policy; 1482 retval = audit_alloc(p); 1483 if (retval) 1484 goto bad_fork_cleanup_perf; 1485 /* copy all the process information */ 1486 shm_init_task(p); 1487 retval = copy_semundo(clone_flags, p); 1488 if (retval) 1489 goto bad_fork_cleanup_audit; 1490 retval = copy_files(clone_flags, p); 1491 if (retval) 1492 goto bad_fork_cleanup_semundo; 1493 retval = copy_fs(clone_flags, p); 1494 if (retval) 1495 goto bad_fork_cleanup_files; 1496 retval = copy_sighand(clone_flags, p); 1497 if (retval) 1498 goto bad_fork_cleanup_fs; 1499 retval = copy_signal(clone_flags, p); 1500 if (retval) 1501 goto bad_fork_cleanup_sighand; 1502 retval = copy_mm(clone_flags, p); 1503 if (retval) 1504 goto bad_fork_cleanup_signal; 1505 retval = copy_namespaces(clone_flags, p); 1506 if (retval) 1507 goto bad_fork_cleanup_mm; 1508 retval = copy_io(clone_flags, p); 1509 if (retval) 1510 goto bad_fork_cleanup_namespaces; 1511 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1512 if (retval) 1513 goto bad_fork_cleanup_io; 1514 1515 if (pid != &init_struct_pid) { 1516 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1517 if (IS_ERR(pid)) { 1518 retval = PTR_ERR(pid); 1519 goto bad_fork_cleanup_thread; 1520 } 1521 } 1522 1523 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1524 /* 1525 * Clear TID on mm_release()? 1526 */ 1527 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1528 #ifdef CONFIG_BLOCK 1529 p->plug = NULL; 1530 #endif 1531 #ifdef CONFIG_FUTEX 1532 p->robust_list = NULL; 1533 #ifdef CONFIG_COMPAT 1534 p->compat_robust_list = NULL; 1535 #endif 1536 INIT_LIST_HEAD(&p->pi_state_list); 1537 p->pi_state_cache = NULL; 1538 #endif 1539 /* 1540 * sigaltstack should be cleared when sharing the same VM 1541 */ 1542 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1543 sas_ss_reset(p); 1544 1545 /* 1546 * Syscall tracing and stepping should be turned off in the 1547 * child regardless of CLONE_PTRACE. 1548 */ 1549 user_disable_single_step(p); 1550 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1551 #ifdef TIF_SYSCALL_EMU 1552 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1553 #endif 1554 clear_all_latency_tracing(p); 1555 1556 /* ok, now we should be set up.. */ 1557 p->pid = pid_nr(pid); 1558 if (clone_flags & CLONE_THREAD) { 1559 p->exit_signal = -1; 1560 p->group_leader = current->group_leader; 1561 p->tgid = current->tgid; 1562 } else { 1563 if (clone_flags & CLONE_PARENT) 1564 p->exit_signal = current->group_leader->exit_signal; 1565 else 1566 p->exit_signal = (clone_flags & CSIGNAL); 1567 p->group_leader = p; 1568 p->tgid = p->pid; 1569 } 1570 1571 p->nr_dirtied = 0; 1572 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1573 p->dirty_paused_when = 0; 1574 1575 p->pdeath_signal = 0; 1576 INIT_LIST_HEAD(&p->thread_group); 1577 p->task_works = NULL; 1578 1579 threadgroup_change_begin(current); 1580 /* 1581 * Ensure that the cgroup subsystem policies allow the new process to be 1582 * forked. It should be noted the the new process's css_set can be changed 1583 * between here and cgroup_post_fork() if an organisation operation is in 1584 * progress. 1585 */ 1586 retval = cgroup_can_fork(p); 1587 if (retval) 1588 goto bad_fork_free_pid; 1589 1590 /* 1591 * Make it visible to the rest of the system, but dont wake it up yet. 1592 * Need tasklist lock for parent etc handling! 1593 */ 1594 write_lock_irq(&tasklist_lock); 1595 1596 /* CLONE_PARENT re-uses the old parent */ 1597 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1598 p->real_parent = current->real_parent; 1599 p->parent_exec_id = current->parent_exec_id; 1600 } else { 1601 p->real_parent = current; 1602 p->parent_exec_id = current->self_exec_id; 1603 } 1604 1605 spin_lock(¤t->sighand->siglock); 1606 1607 /* 1608 * Copy seccomp details explicitly here, in case they were changed 1609 * before holding sighand lock. 1610 */ 1611 copy_seccomp(p); 1612 1613 /* 1614 * Process group and session signals need to be delivered to just the 1615 * parent before the fork or both the parent and the child after the 1616 * fork. Restart if a signal comes in before we add the new process to 1617 * it's process group. 1618 * A fatal signal pending means that current will exit, so the new 1619 * thread can't slip out of an OOM kill (or normal SIGKILL). 1620 */ 1621 recalc_sigpending(); 1622 if (signal_pending(current)) { 1623 spin_unlock(¤t->sighand->siglock); 1624 write_unlock_irq(&tasklist_lock); 1625 retval = -ERESTARTNOINTR; 1626 goto bad_fork_cancel_cgroup; 1627 } 1628 1629 if (likely(p->pid)) { 1630 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1631 1632 init_task_pid(p, PIDTYPE_PID, pid); 1633 if (thread_group_leader(p)) { 1634 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1635 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1636 1637 if (is_child_reaper(pid)) { 1638 ns_of_pid(pid)->child_reaper = p; 1639 p->signal->flags |= SIGNAL_UNKILLABLE; 1640 } 1641 1642 p->signal->leader_pid = pid; 1643 p->signal->tty = tty_kref_get(current->signal->tty); 1644 list_add_tail(&p->sibling, &p->real_parent->children); 1645 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1646 attach_pid(p, PIDTYPE_PGID); 1647 attach_pid(p, PIDTYPE_SID); 1648 __this_cpu_inc(process_counts); 1649 } else { 1650 current->signal->nr_threads++; 1651 atomic_inc(¤t->signal->live); 1652 atomic_inc(¤t->signal->sigcnt); 1653 list_add_tail_rcu(&p->thread_group, 1654 &p->group_leader->thread_group); 1655 list_add_tail_rcu(&p->thread_node, 1656 &p->signal->thread_head); 1657 } 1658 attach_pid(p, PIDTYPE_PID); 1659 nr_threads++; 1660 } 1661 1662 total_forks++; 1663 spin_unlock(¤t->sighand->siglock); 1664 syscall_tracepoint_update(p); 1665 write_unlock_irq(&tasklist_lock); 1666 1667 proc_fork_connector(p); 1668 cgroup_post_fork(p); 1669 threadgroup_change_end(current); 1670 perf_event_fork(p); 1671 1672 trace_task_newtask(p, clone_flags); 1673 uprobe_copy_process(p, clone_flags); 1674 1675 return p; 1676 1677 bad_fork_cancel_cgroup: 1678 cgroup_cancel_fork(p); 1679 bad_fork_free_pid: 1680 threadgroup_change_end(current); 1681 if (pid != &init_struct_pid) 1682 free_pid(pid); 1683 bad_fork_cleanup_thread: 1684 exit_thread(p); 1685 bad_fork_cleanup_io: 1686 if (p->io_context) 1687 exit_io_context(p); 1688 bad_fork_cleanup_namespaces: 1689 exit_task_namespaces(p); 1690 bad_fork_cleanup_mm: 1691 if (p->mm) 1692 mmput(p->mm); 1693 bad_fork_cleanup_signal: 1694 if (!(clone_flags & CLONE_THREAD)) 1695 free_signal_struct(p->signal); 1696 bad_fork_cleanup_sighand: 1697 __cleanup_sighand(p->sighand); 1698 bad_fork_cleanup_fs: 1699 exit_fs(p); /* blocking */ 1700 bad_fork_cleanup_files: 1701 exit_files(p); /* blocking */ 1702 bad_fork_cleanup_semundo: 1703 exit_sem(p); 1704 bad_fork_cleanup_audit: 1705 audit_free(p); 1706 bad_fork_cleanup_perf: 1707 perf_event_free_task(p); 1708 bad_fork_cleanup_policy: 1709 #ifdef CONFIG_NUMA 1710 mpol_put(p->mempolicy); 1711 bad_fork_cleanup_threadgroup_lock: 1712 #endif 1713 delayacct_tsk_free(p); 1714 bad_fork_cleanup_count: 1715 atomic_dec(&p->cred->user->processes); 1716 exit_creds(p); 1717 bad_fork_free: 1718 free_task(p); 1719 fork_out: 1720 return ERR_PTR(retval); 1721 } 1722 1723 static inline void init_idle_pids(struct pid_link *links) 1724 { 1725 enum pid_type type; 1726 1727 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1728 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1729 links[type].pid = &init_struct_pid; 1730 } 1731 } 1732 1733 struct task_struct *fork_idle(int cpu) 1734 { 1735 struct task_struct *task; 1736 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1737 cpu_to_node(cpu)); 1738 if (!IS_ERR(task)) { 1739 init_idle_pids(task->pids); 1740 init_idle(task, cpu); 1741 } 1742 1743 return task; 1744 } 1745 1746 /* 1747 * Ok, this is the main fork-routine. 1748 * 1749 * It copies the process, and if successful kick-starts 1750 * it and waits for it to finish using the VM if required. 1751 */ 1752 long _do_fork(unsigned long clone_flags, 1753 unsigned long stack_start, 1754 unsigned long stack_size, 1755 int __user *parent_tidptr, 1756 int __user *child_tidptr, 1757 unsigned long tls) 1758 { 1759 struct task_struct *p; 1760 int trace = 0; 1761 long nr; 1762 1763 /* 1764 * Determine whether and which event to report to ptracer. When 1765 * called from kernel_thread or CLONE_UNTRACED is explicitly 1766 * requested, no event is reported; otherwise, report if the event 1767 * for the type of forking is enabled. 1768 */ 1769 if (!(clone_flags & CLONE_UNTRACED)) { 1770 if (clone_flags & CLONE_VFORK) 1771 trace = PTRACE_EVENT_VFORK; 1772 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1773 trace = PTRACE_EVENT_CLONE; 1774 else 1775 trace = PTRACE_EVENT_FORK; 1776 1777 if (likely(!ptrace_event_enabled(current, trace))) 1778 trace = 0; 1779 } 1780 1781 p = copy_process(clone_flags, stack_start, stack_size, 1782 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 1783 /* 1784 * Do this prior waking up the new thread - the thread pointer 1785 * might get invalid after that point, if the thread exits quickly. 1786 */ 1787 if (!IS_ERR(p)) { 1788 struct completion vfork; 1789 struct pid *pid; 1790 1791 trace_sched_process_fork(current, p); 1792 1793 pid = get_task_pid(p, PIDTYPE_PID); 1794 nr = pid_vnr(pid); 1795 1796 if (clone_flags & CLONE_PARENT_SETTID) 1797 put_user(nr, parent_tidptr); 1798 1799 if (clone_flags & CLONE_VFORK) { 1800 p->vfork_done = &vfork; 1801 init_completion(&vfork); 1802 get_task_struct(p); 1803 } 1804 1805 wake_up_new_task(p); 1806 1807 /* forking complete and child started to run, tell ptracer */ 1808 if (unlikely(trace)) 1809 ptrace_event_pid(trace, pid); 1810 1811 if (clone_flags & CLONE_VFORK) { 1812 if (!wait_for_vfork_done(p, &vfork)) 1813 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1814 } 1815 1816 put_pid(pid); 1817 } else { 1818 nr = PTR_ERR(p); 1819 } 1820 return nr; 1821 } 1822 1823 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 1824 /* For compatibility with architectures that call do_fork directly rather than 1825 * using the syscall entry points below. */ 1826 long do_fork(unsigned long clone_flags, 1827 unsigned long stack_start, 1828 unsigned long stack_size, 1829 int __user *parent_tidptr, 1830 int __user *child_tidptr) 1831 { 1832 return _do_fork(clone_flags, stack_start, stack_size, 1833 parent_tidptr, child_tidptr, 0); 1834 } 1835 #endif 1836 1837 /* 1838 * Create a kernel thread. 1839 */ 1840 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1841 { 1842 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1843 (unsigned long)arg, NULL, NULL, 0); 1844 } 1845 1846 #ifdef __ARCH_WANT_SYS_FORK 1847 SYSCALL_DEFINE0(fork) 1848 { 1849 #ifdef CONFIG_MMU 1850 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 1851 #else 1852 /* can not support in nommu mode */ 1853 return -EINVAL; 1854 #endif 1855 } 1856 #endif 1857 1858 #ifdef __ARCH_WANT_SYS_VFORK 1859 SYSCALL_DEFINE0(vfork) 1860 { 1861 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1862 0, NULL, NULL, 0); 1863 } 1864 #endif 1865 1866 #ifdef __ARCH_WANT_SYS_CLONE 1867 #ifdef CONFIG_CLONE_BACKWARDS 1868 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1869 int __user *, parent_tidptr, 1870 unsigned long, tls, 1871 int __user *, child_tidptr) 1872 #elif defined(CONFIG_CLONE_BACKWARDS2) 1873 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 1874 int __user *, parent_tidptr, 1875 int __user *, child_tidptr, 1876 unsigned long, tls) 1877 #elif defined(CONFIG_CLONE_BACKWARDS3) 1878 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 1879 int, stack_size, 1880 int __user *, parent_tidptr, 1881 int __user *, child_tidptr, 1882 unsigned long, tls) 1883 #else 1884 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 1885 int __user *, parent_tidptr, 1886 int __user *, child_tidptr, 1887 unsigned long, tls) 1888 #endif 1889 { 1890 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 1891 } 1892 #endif 1893 1894 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1895 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1896 #endif 1897 1898 static void sighand_ctor(void *data) 1899 { 1900 struct sighand_struct *sighand = data; 1901 1902 spin_lock_init(&sighand->siglock); 1903 init_waitqueue_head(&sighand->signalfd_wqh); 1904 } 1905 1906 void __init proc_caches_init(void) 1907 { 1908 sighand_cachep = kmem_cache_create("sighand_cache", 1909 sizeof(struct sighand_struct), 0, 1910 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1911 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 1912 signal_cachep = kmem_cache_create("signal_cache", 1913 sizeof(struct signal_struct), 0, 1914 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 1915 NULL); 1916 files_cachep = kmem_cache_create("files_cache", 1917 sizeof(struct files_struct), 0, 1918 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 1919 NULL); 1920 fs_cachep = kmem_cache_create("fs_cache", 1921 sizeof(struct fs_struct), 0, 1922 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 1923 NULL); 1924 /* 1925 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1926 * whole struct cpumask for the OFFSTACK case. We could change 1927 * this to *only* allocate as much of it as required by the 1928 * maximum number of CPU's we can ever have. The cpumask_allocation 1929 * is at the end of the structure, exactly for that reason. 1930 */ 1931 mm_cachep = kmem_cache_create("mm_struct", 1932 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1933 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 1934 NULL); 1935 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 1936 mmap_init(); 1937 nsproxy_cache_init(); 1938 } 1939 1940 /* 1941 * Check constraints on flags passed to the unshare system call. 1942 */ 1943 static int check_unshare_flags(unsigned long unshare_flags) 1944 { 1945 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1946 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1947 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 1948 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 1949 return -EINVAL; 1950 /* 1951 * Not implemented, but pretend it works if there is nothing 1952 * to unshare. Note that unsharing the address space or the 1953 * signal handlers also need to unshare the signal queues (aka 1954 * CLONE_THREAD). 1955 */ 1956 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1957 if (!thread_group_empty(current)) 1958 return -EINVAL; 1959 } 1960 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 1961 if (atomic_read(¤t->sighand->count) > 1) 1962 return -EINVAL; 1963 } 1964 if (unshare_flags & CLONE_VM) { 1965 if (!current_is_single_threaded()) 1966 return -EINVAL; 1967 } 1968 1969 return 0; 1970 } 1971 1972 /* 1973 * Unshare the filesystem structure if it is being shared 1974 */ 1975 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1976 { 1977 struct fs_struct *fs = current->fs; 1978 1979 if (!(unshare_flags & CLONE_FS) || !fs) 1980 return 0; 1981 1982 /* don't need lock here; in the worst case we'll do useless copy */ 1983 if (fs->users == 1) 1984 return 0; 1985 1986 *new_fsp = copy_fs_struct(fs); 1987 if (!*new_fsp) 1988 return -ENOMEM; 1989 1990 return 0; 1991 } 1992 1993 /* 1994 * Unshare file descriptor table if it is being shared 1995 */ 1996 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1997 { 1998 struct files_struct *fd = current->files; 1999 int error = 0; 2000 2001 if ((unshare_flags & CLONE_FILES) && 2002 (fd && atomic_read(&fd->count) > 1)) { 2003 *new_fdp = dup_fd(fd, &error); 2004 if (!*new_fdp) 2005 return error; 2006 } 2007 2008 return 0; 2009 } 2010 2011 /* 2012 * unshare allows a process to 'unshare' part of the process 2013 * context which was originally shared using clone. copy_* 2014 * functions used by do_fork() cannot be used here directly 2015 * because they modify an inactive task_struct that is being 2016 * constructed. Here we are modifying the current, active, 2017 * task_struct. 2018 */ 2019 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2020 { 2021 struct fs_struct *fs, *new_fs = NULL; 2022 struct files_struct *fd, *new_fd = NULL; 2023 struct cred *new_cred = NULL; 2024 struct nsproxy *new_nsproxy = NULL; 2025 int do_sysvsem = 0; 2026 int err; 2027 2028 /* 2029 * If unsharing a user namespace must also unshare the thread group 2030 * and unshare the filesystem root and working directories. 2031 */ 2032 if (unshare_flags & CLONE_NEWUSER) 2033 unshare_flags |= CLONE_THREAD | CLONE_FS; 2034 /* 2035 * If unsharing vm, must also unshare signal handlers. 2036 */ 2037 if (unshare_flags & CLONE_VM) 2038 unshare_flags |= CLONE_SIGHAND; 2039 /* 2040 * If unsharing a signal handlers, must also unshare the signal queues. 2041 */ 2042 if (unshare_flags & CLONE_SIGHAND) 2043 unshare_flags |= CLONE_THREAD; 2044 /* 2045 * If unsharing namespace, must also unshare filesystem information. 2046 */ 2047 if (unshare_flags & CLONE_NEWNS) 2048 unshare_flags |= CLONE_FS; 2049 2050 err = check_unshare_flags(unshare_flags); 2051 if (err) 2052 goto bad_unshare_out; 2053 /* 2054 * CLONE_NEWIPC must also detach from the undolist: after switching 2055 * to a new ipc namespace, the semaphore arrays from the old 2056 * namespace are unreachable. 2057 */ 2058 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2059 do_sysvsem = 1; 2060 err = unshare_fs(unshare_flags, &new_fs); 2061 if (err) 2062 goto bad_unshare_out; 2063 err = unshare_fd(unshare_flags, &new_fd); 2064 if (err) 2065 goto bad_unshare_cleanup_fs; 2066 err = unshare_userns(unshare_flags, &new_cred); 2067 if (err) 2068 goto bad_unshare_cleanup_fd; 2069 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2070 new_cred, new_fs); 2071 if (err) 2072 goto bad_unshare_cleanup_cred; 2073 2074 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2075 if (do_sysvsem) { 2076 /* 2077 * CLONE_SYSVSEM is equivalent to sys_exit(). 2078 */ 2079 exit_sem(current); 2080 } 2081 if (unshare_flags & CLONE_NEWIPC) { 2082 /* Orphan segments in old ns (see sem above). */ 2083 exit_shm(current); 2084 shm_init_task(current); 2085 } 2086 2087 if (new_nsproxy) 2088 switch_task_namespaces(current, new_nsproxy); 2089 2090 task_lock(current); 2091 2092 if (new_fs) { 2093 fs = current->fs; 2094 spin_lock(&fs->lock); 2095 current->fs = new_fs; 2096 if (--fs->users) 2097 new_fs = NULL; 2098 else 2099 new_fs = fs; 2100 spin_unlock(&fs->lock); 2101 } 2102 2103 if (new_fd) { 2104 fd = current->files; 2105 current->files = new_fd; 2106 new_fd = fd; 2107 } 2108 2109 task_unlock(current); 2110 2111 if (new_cred) { 2112 /* Install the new user namespace */ 2113 commit_creds(new_cred); 2114 new_cred = NULL; 2115 } 2116 } 2117 2118 bad_unshare_cleanup_cred: 2119 if (new_cred) 2120 put_cred(new_cred); 2121 bad_unshare_cleanup_fd: 2122 if (new_fd) 2123 put_files_struct(new_fd); 2124 2125 bad_unshare_cleanup_fs: 2126 if (new_fs) 2127 free_fs_struct(new_fs); 2128 2129 bad_unshare_out: 2130 return err; 2131 } 2132 2133 /* 2134 * Helper to unshare the files of the current task. 2135 * We don't want to expose copy_files internals to 2136 * the exec layer of the kernel. 2137 */ 2138 2139 int unshare_files(struct files_struct **displaced) 2140 { 2141 struct task_struct *task = current; 2142 struct files_struct *copy = NULL; 2143 int error; 2144 2145 error = unshare_fd(CLONE_FILES, ©); 2146 if (error || !copy) { 2147 *displaced = NULL; 2148 return error; 2149 } 2150 *displaced = task->files; 2151 task_lock(task); 2152 task->files = copy; 2153 task_unlock(task); 2154 return 0; 2155 } 2156 2157 int sysctl_max_threads(struct ctl_table *table, int write, 2158 void __user *buffer, size_t *lenp, loff_t *ppos) 2159 { 2160 struct ctl_table t; 2161 int ret; 2162 int threads = max_threads; 2163 int min = MIN_THREADS; 2164 int max = MAX_THREADS; 2165 2166 t = *table; 2167 t.data = &threads; 2168 t.extra1 = &min; 2169 t.extra2 = &max; 2170 2171 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2172 if (ret || !write) 2173 return ret; 2174 2175 set_max_threads(threads); 2176 2177 return 0; 2178 } 2179