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