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