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