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