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