1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/mm.h> 32 #include <linux/vmacache.h> 33 #include <linux/nsproxy.h> 34 #include <linux/capability.h> 35 #include <linux/cpu.h> 36 #include <linux/cgroup.h> 37 #include <linux/security.h> 38 #include <linux/hugetlb.h> 39 #include <linux/seccomp.h> 40 #include <linux/swap.h> 41 #include <linux/syscalls.h> 42 #include <linux/jiffies.h> 43 #include <linux/futex.h> 44 #include <linux/compat.h> 45 #include <linux/kthread.h> 46 #include <linux/task_io_accounting_ops.h> 47 #include <linux/rcupdate.h> 48 #include <linux/ptrace.h> 49 #include <linux/mount.h> 50 #include <linux/audit.h> 51 #include <linux/memcontrol.h> 52 #include <linux/ftrace.h> 53 #include <linux/proc_fs.h> 54 #include <linux/profile.h> 55 #include <linux/rmap.h> 56 #include <linux/ksm.h> 57 #include <linux/acct.h> 58 #include <linux/tsacct_kern.h> 59 #include <linux/cn_proc.h> 60 #include <linux/freezer.h> 61 #include <linux/delayacct.h> 62 #include <linux/taskstats_kern.h> 63 #include <linux/random.h> 64 #include <linux/tty.h> 65 #include <linux/blkdev.h> 66 #include <linux/fs_struct.h> 67 #include <linux/magic.h> 68 #include <linux/perf_event.h> 69 #include <linux/posix-timers.h> 70 #include <linux/user-return-notifier.h> 71 #include <linux/oom.h> 72 #include <linux/khugepaged.h> 73 #include <linux/signalfd.h> 74 #include <linux/uprobes.h> 75 #include <linux/aio.h> 76 #include <linux/compiler.h> 77 #include <linux/sysctl.h> 78 #include <linux/kcov.h> 79 80 #include <asm/pgtable.h> 81 #include <asm/pgalloc.h> 82 #include <asm/uaccess.h> 83 #include <asm/mmu_context.h> 84 #include <asm/cacheflush.h> 85 #include <asm/tlbflush.h> 86 87 #include <trace/events/sched.h> 88 89 #define CREATE_TRACE_POINTS 90 #include <trace/events/task.h> 91 92 /* 93 * Minimum number of threads to boot the kernel 94 */ 95 #define MIN_THREADS 20 96 97 /* 98 * Maximum number of threads 99 */ 100 #define MAX_THREADS FUTEX_TID_MASK 101 102 /* 103 * Protected counters by write_lock_irq(&tasklist_lock) 104 */ 105 unsigned long total_forks; /* Handle normal Linux uptimes. */ 106 int nr_threads; /* The idle threads do not count.. */ 107 108 int max_threads; /* tunable limit on nr_threads */ 109 110 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 111 112 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 113 114 #ifdef CONFIG_PROVE_RCU 115 int lockdep_tasklist_lock_is_held(void) 116 { 117 return lockdep_is_held(&tasklist_lock); 118 } 119 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 120 #endif /* #ifdef CONFIG_PROVE_RCU */ 121 122 int nr_processes(void) 123 { 124 int cpu; 125 int total = 0; 126 127 for_each_possible_cpu(cpu) 128 total += per_cpu(process_counts, cpu); 129 130 return total; 131 } 132 133 void __weak arch_release_task_struct(struct task_struct *tsk) 134 { 135 } 136 137 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 138 static struct kmem_cache *task_struct_cachep; 139 140 static inline struct task_struct *alloc_task_struct_node(int node) 141 { 142 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 143 } 144 145 static inline void free_task_struct(struct task_struct *tsk) 146 { 147 kmem_cache_free(task_struct_cachep, tsk); 148 } 149 #endif 150 151 void __weak arch_release_thread_stack(unsigned long *stack) 152 { 153 } 154 155 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 156 157 /* 158 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 159 * kmemcache based allocator. 160 */ 161 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 162 163 #ifdef CONFIG_VMAP_STACK 164 /* 165 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 166 * flush. Try to minimize the number of calls by caching stacks. 167 */ 168 #define NR_CACHED_STACKS 2 169 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 170 #endif 171 172 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 173 { 174 #ifdef CONFIG_VMAP_STACK 175 void *stack; 176 int i; 177 178 local_irq_disable(); 179 for (i = 0; i < NR_CACHED_STACKS; i++) { 180 struct vm_struct *s = this_cpu_read(cached_stacks[i]); 181 182 if (!s) 183 continue; 184 this_cpu_write(cached_stacks[i], NULL); 185 186 tsk->stack_vm_area = s; 187 local_irq_enable(); 188 return s->addr; 189 } 190 local_irq_enable(); 191 192 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, 193 VMALLOC_START, VMALLOC_END, 194 THREADINFO_GFP | __GFP_HIGHMEM, 195 PAGE_KERNEL, 196 0, node, __builtin_return_address(0)); 197 198 /* 199 * We can't call find_vm_area() in interrupt context, and 200 * free_thread_stack() can be called in interrupt context, 201 * so cache the vm_struct. 202 */ 203 if (stack) 204 tsk->stack_vm_area = find_vm_area(stack); 205 return stack; 206 #else 207 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 208 THREAD_SIZE_ORDER); 209 210 return page ? page_address(page) : NULL; 211 #endif 212 } 213 214 static inline void free_thread_stack(struct task_struct *tsk) 215 { 216 #ifdef CONFIG_VMAP_STACK 217 if (task_stack_vm_area(tsk)) { 218 unsigned long flags; 219 int i; 220 221 local_irq_save(flags); 222 for (i = 0; i < NR_CACHED_STACKS; i++) { 223 if (this_cpu_read(cached_stacks[i])) 224 continue; 225 226 this_cpu_write(cached_stacks[i], tsk->stack_vm_area); 227 local_irq_restore(flags); 228 return; 229 } 230 local_irq_restore(flags); 231 232 vfree(tsk->stack); 233 return; 234 } 235 #endif 236 237 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 238 } 239 # else 240 static struct kmem_cache *thread_stack_cache; 241 242 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 243 int node) 244 { 245 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 246 } 247 248 static void free_thread_stack(struct task_struct *tsk) 249 { 250 kmem_cache_free(thread_stack_cache, tsk->stack); 251 } 252 253 void thread_stack_cache_init(void) 254 { 255 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 256 THREAD_SIZE, 0, NULL); 257 BUG_ON(thread_stack_cache == NULL); 258 } 259 # endif 260 #endif 261 262 /* SLAB cache for signal_struct structures (tsk->signal) */ 263 static struct kmem_cache *signal_cachep; 264 265 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 266 struct kmem_cache *sighand_cachep; 267 268 /* SLAB cache for files_struct structures (tsk->files) */ 269 struct kmem_cache *files_cachep; 270 271 /* SLAB cache for fs_struct structures (tsk->fs) */ 272 struct kmem_cache *fs_cachep; 273 274 /* SLAB cache for vm_area_struct structures */ 275 struct kmem_cache *vm_area_cachep; 276 277 /* SLAB cache for mm_struct structures (tsk->mm) */ 278 static struct kmem_cache *mm_cachep; 279 280 static void account_kernel_stack(struct task_struct *tsk, int account) 281 { 282 void *stack = task_stack_page(tsk); 283 struct vm_struct *vm = task_stack_vm_area(tsk); 284 285 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 286 287 if (vm) { 288 int i; 289 290 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 291 292 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 293 mod_zone_page_state(page_zone(vm->pages[i]), 294 NR_KERNEL_STACK_KB, 295 PAGE_SIZE / 1024 * account); 296 } 297 298 /* All stack pages belong to the same memcg. */ 299 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB, 300 account * (THREAD_SIZE / 1024)); 301 } else { 302 /* 303 * All stack pages are in the same zone and belong to the 304 * same memcg. 305 */ 306 struct page *first_page = virt_to_page(stack); 307 308 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 309 THREAD_SIZE / 1024 * account); 310 311 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB, 312 account * (THREAD_SIZE / 1024)); 313 } 314 } 315 316 static void release_task_stack(struct task_struct *tsk) 317 { 318 account_kernel_stack(tsk, -1); 319 arch_release_thread_stack(tsk->stack); 320 free_thread_stack(tsk); 321 tsk->stack = NULL; 322 #ifdef CONFIG_VMAP_STACK 323 tsk->stack_vm_area = NULL; 324 #endif 325 } 326 327 #ifdef CONFIG_THREAD_INFO_IN_TASK 328 void put_task_stack(struct task_struct *tsk) 329 { 330 if (atomic_dec_and_test(&tsk->stack_refcount)) 331 release_task_stack(tsk); 332 } 333 #endif 334 335 void free_task(struct task_struct *tsk) 336 { 337 #ifndef CONFIG_THREAD_INFO_IN_TASK 338 /* 339 * The task is finally done with both the stack and thread_info, 340 * so free both. 341 */ 342 release_task_stack(tsk); 343 #else 344 /* 345 * If the task had a separate stack allocation, it should be gone 346 * by now. 347 */ 348 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 349 #endif 350 rt_mutex_debug_task_free(tsk); 351 ftrace_graph_exit_task(tsk); 352 put_seccomp_filter(tsk); 353 arch_release_task_struct(tsk); 354 free_task_struct(tsk); 355 } 356 EXPORT_SYMBOL(free_task); 357 358 static inline void free_signal_struct(struct signal_struct *sig) 359 { 360 taskstats_tgid_free(sig); 361 sched_autogroup_exit(sig); 362 kmem_cache_free(signal_cachep, sig); 363 } 364 365 static inline void put_signal_struct(struct signal_struct *sig) 366 { 367 if (atomic_dec_and_test(&sig->sigcnt)) 368 free_signal_struct(sig); 369 } 370 371 void __put_task_struct(struct task_struct *tsk) 372 { 373 WARN_ON(!tsk->exit_state); 374 WARN_ON(atomic_read(&tsk->usage)); 375 WARN_ON(tsk == current); 376 377 cgroup_free(tsk); 378 task_numa_free(tsk); 379 security_task_free(tsk); 380 exit_creds(tsk); 381 delayacct_tsk_free(tsk); 382 put_signal_struct(tsk->signal); 383 384 if (!profile_handoff_task(tsk)) 385 free_task(tsk); 386 } 387 EXPORT_SYMBOL_GPL(__put_task_struct); 388 389 void __init __weak arch_task_cache_init(void) { } 390 391 /* 392 * set_max_threads 393 */ 394 static void set_max_threads(unsigned int max_threads_suggested) 395 { 396 u64 threads; 397 398 /* 399 * The number of threads shall be limited such that the thread 400 * structures may only consume a small part of the available memory. 401 */ 402 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 403 threads = MAX_THREADS; 404 else 405 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 406 (u64) THREAD_SIZE * 8UL); 407 408 if (threads > max_threads_suggested) 409 threads = max_threads_suggested; 410 411 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 412 } 413 414 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 415 /* Initialized by the architecture: */ 416 int arch_task_struct_size __read_mostly; 417 #endif 418 419 void __init fork_init(void) 420 { 421 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 422 #ifndef ARCH_MIN_TASKALIGN 423 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 424 #endif 425 /* create a slab on which task_structs can be allocated */ 426 task_struct_cachep = kmem_cache_create("task_struct", 427 arch_task_struct_size, ARCH_MIN_TASKALIGN, 428 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 429 #endif 430 431 /* do the arch specific task caches init */ 432 arch_task_cache_init(); 433 434 set_max_threads(MAX_THREADS); 435 436 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 437 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 438 init_task.signal->rlim[RLIMIT_SIGPENDING] = 439 init_task.signal->rlim[RLIMIT_NPROC]; 440 } 441 442 int __weak arch_dup_task_struct(struct task_struct *dst, 443 struct task_struct *src) 444 { 445 *dst = *src; 446 return 0; 447 } 448 449 void set_task_stack_end_magic(struct task_struct *tsk) 450 { 451 unsigned long *stackend; 452 453 stackend = end_of_stack(tsk); 454 *stackend = STACK_END_MAGIC; /* for overflow detection */ 455 } 456 457 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 458 { 459 struct task_struct *tsk; 460 unsigned long *stack; 461 struct vm_struct *stack_vm_area; 462 int err; 463 464 if (node == NUMA_NO_NODE) 465 node = tsk_fork_get_node(orig); 466 tsk = alloc_task_struct_node(node); 467 if (!tsk) 468 return NULL; 469 470 stack = alloc_thread_stack_node(tsk, node); 471 if (!stack) 472 goto free_tsk; 473 474 stack_vm_area = task_stack_vm_area(tsk); 475 476 err = arch_dup_task_struct(tsk, orig); 477 478 /* 479 * arch_dup_task_struct() clobbers the stack-related fields. Make 480 * sure they're properly initialized before using any stack-related 481 * functions again. 482 */ 483 tsk->stack = stack; 484 #ifdef CONFIG_VMAP_STACK 485 tsk->stack_vm_area = stack_vm_area; 486 #endif 487 #ifdef CONFIG_THREAD_INFO_IN_TASK 488 atomic_set(&tsk->stack_refcount, 1); 489 #endif 490 491 if (err) 492 goto free_stack; 493 494 #ifdef CONFIG_SECCOMP 495 /* 496 * We must handle setting up seccomp filters once we're under 497 * the sighand lock in case orig has changed between now and 498 * then. Until then, filter must be NULL to avoid messing up 499 * the usage counts on the error path calling free_task. 500 */ 501 tsk->seccomp.filter = NULL; 502 #endif 503 504 setup_thread_stack(tsk, orig); 505 clear_user_return_notifier(tsk); 506 clear_tsk_need_resched(tsk); 507 set_task_stack_end_magic(tsk); 508 509 #ifdef CONFIG_CC_STACKPROTECTOR 510 tsk->stack_canary = get_random_int(); 511 #endif 512 513 /* 514 * One for us, one for whoever does the "release_task()" (usually 515 * parent) 516 */ 517 atomic_set(&tsk->usage, 2); 518 #ifdef CONFIG_BLK_DEV_IO_TRACE 519 tsk->btrace_seq = 0; 520 #endif 521 tsk->splice_pipe = NULL; 522 tsk->task_frag.page = NULL; 523 tsk->wake_q.next = NULL; 524 525 account_kernel_stack(tsk, 1); 526 527 kcov_task_init(tsk); 528 529 return tsk; 530 531 free_stack: 532 free_thread_stack(tsk); 533 free_tsk: 534 free_task_struct(tsk); 535 return NULL; 536 } 537 538 #ifdef CONFIG_MMU 539 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 540 { 541 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 542 struct rb_node **rb_link, *rb_parent; 543 int retval; 544 unsigned long charge; 545 546 uprobe_start_dup_mmap(); 547 if (down_write_killable(&oldmm->mmap_sem)) { 548 retval = -EINTR; 549 goto fail_uprobe_end; 550 } 551 flush_cache_dup_mm(oldmm); 552 uprobe_dup_mmap(oldmm, mm); 553 /* 554 * Not linked in yet - no deadlock potential: 555 */ 556 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 557 558 /* No ordering required: file already has been exposed. */ 559 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 560 561 mm->total_vm = oldmm->total_vm; 562 mm->data_vm = oldmm->data_vm; 563 mm->exec_vm = oldmm->exec_vm; 564 mm->stack_vm = oldmm->stack_vm; 565 566 rb_link = &mm->mm_rb.rb_node; 567 rb_parent = NULL; 568 pprev = &mm->mmap; 569 retval = ksm_fork(mm, oldmm); 570 if (retval) 571 goto out; 572 retval = khugepaged_fork(mm, oldmm); 573 if (retval) 574 goto out; 575 576 prev = NULL; 577 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 578 struct file *file; 579 580 if (mpnt->vm_flags & VM_DONTCOPY) { 581 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 582 continue; 583 } 584 charge = 0; 585 if (mpnt->vm_flags & VM_ACCOUNT) { 586 unsigned long len = vma_pages(mpnt); 587 588 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 589 goto fail_nomem; 590 charge = len; 591 } 592 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 593 if (!tmp) 594 goto fail_nomem; 595 *tmp = *mpnt; 596 INIT_LIST_HEAD(&tmp->anon_vma_chain); 597 retval = vma_dup_policy(mpnt, tmp); 598 if (retval) 599 goto fail_nomem_policy; 600 tmp->vm_mm = mm; 601 if (anon_vma_fork(tmp, mpnt)) 602 goto fail_nomem_anon_vma_fork; 603 tmp->vm_flags &= 604 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP); 605 tmp->vm_next = tmp->vm_prev = NULL; 606 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 607 file = tmp->vm_file; 608 if (file) { 609 struct inode *inode = file_inode(file); 610 struct address_space *mapping = file->f_mapping; 611 612 get_file(file); 613 if (tmp->vm_flags & VM_DENYWRITE) 614 atomic_dec(&inode->i_writecount); 615 i_mmap_lock_write(mapping); 616 if (tmp->vm_flags & VM_SHARED) 617 atomic_inc(&mapping->i_mmap_writable); 618 flush_dcache_mmap_lock(mapping); 619 /* insert tmp into the share list, just after mpnt */ 620 vma_interval_tree_insert_after(tmp, mpnt, 621 &mapping->i_mmap); 622 flush_dcache_mmap_unlock(mapping); 623 i_mmap_unlock_write(mapping); 624 } 625 626 /* 627 * Clear hugetlb-related page reserves for children. This only 628 * affects MAP_PRIVATE mappings. Faults generated by the child 629 * are not guaranteed to succeed, even if read-only 630 */ 631 if (is_vm_hugetlb_page(tmp)) 632 reset_vma_resv_huge_pages(tmp); 633 634 /* 635 * Link in the new vma and copy the page table entries. 636 */ 637 *pprev = tmp; 638 pprev = &tmp->vm_next; 639 tmp->vm_prev = prev; 640 prev = tmp; 641 642 __vma_link_rb(mm, tmp, rb_link, rb_parent); 643 rb_link = &tmp->vm_rb.rb_right; 644 rb_parent = &tmp->vm_rb; 645 646 mm->map_count++; 647 retval = copy_page_range(mm, oldmm, mpnt); 648 649 if (tmp->vm_ops && tmp->vm_ops->open) 650 tmp->vm_ops->open(tmp); 651 652 if (retval) 653 goto out; 654 } 655 /* a new mm has just been created */ 656 arch_dup_mmap(oldmm, mm); 657 retval = 0; 658 out: 659 up_write(&mm->mmap_sem); 660 flush_tlb_mm(oldmm); 661 up_write(&oldmm->mmap_sem); 662 fail_uprobe_end: 663 uprobe_end_dup_mmap(); 664 return retval; 665 fail_nomem_anon_vma_fork: 666 mpol_put(vma_policy(tmp)); 667 fail_nomem_policy: 668 kmem_cache_free(vm_area_cachep, tmp); 669 fail_nomem: 670 retval = -ENOMEM; 671 vm_unacct_memory(charge); 672 goto out; 673 } 674 675 static inline int mm_alloc_pgd(struct mm_struct *mm) 676 { 677 mm->pgd = pgd_alloc(mm); 678 if (unlikely(!mm->pgd)) 679 return -ENOMEM; 680 return 0; 681 } 682 683 static inline void mm_free_pgd(struct mm_struct *mm) 684 { 685 pgd_free(mm, mm->pgd); 686 } 687 #else 688 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 689 { 690 down_write(&oldmm->mmap_sem); 691 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 692 up_write(&oldmm->mmap_sem); 693 return 0; 694 } 695 #define mm_alloc_pgd(mm) (0) 696 #define mm_free_pgd(mm) 697 #endif /* CONFIG_MMU */ 698 699 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 700 701 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 702 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 703 704 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 705 706 static int __init coredump_filter_setup(char *s) 707 { 708 default_dump_filter = 709 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 710 MMF_DUMP_FILTER_MASK; 711 return 1; 712 } 713 714 __setup("coredump_filter=", coredump_filter_setup); 715 716 #include <linux/init_task.h> 717 718 static void mm_init_aio(struct mm_struct *mm) 719 { 720 #ifdef CONFIG_AIO 721 spin_lock_init(&mm->ioctx_lock); 722 mm->ioctx_table = NULL; 723 #endif 724 } 725 726 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 727 { 728 #ifdef CONFIG_MEMCG 729 mm->owner = p; 730 #endif 731 } 732 733 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 734 { 735 mm->mmap = NULL; 736 mm->mm_rb = RB_ROOT; 737 mm->vmacache_seqnum = 0; 738 atomic_set(&mm->mm_users, 1); 739 atomic_set(&mm->mm_count, 1); 740 init_rwsem(&mm->mmap_sem); 741 INIT_LIST_HEAD(&mm->mmlist); 742 mm->core_state = NULL; 743 atomic_long_set(&mm->nr_ptes, 0); 744 mm_nr_pmds_init(mm); 745 mm->map_count = 0; 746 mm->locked_vm = 0; 747 mm->pinned_vm = 0; 748 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 749 spin_lock_init(&mm->page_table_lock); 750 mm_init_cpumask(mm); 751 mm_init_aio(mm); 752 mm_init_owner(mm, p); 753 mmu_notifier_mm_init(mm); 754 clear_tlb_flush_pending(mm); 755 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 756 mm->pmd_huge_pte = NULL; 757 #endif 758 759 if (current->mm) { 760 mm->flags = current->mm->flags & MMF_INIT_MASK; 761 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 762 } else { 763 mm->flags = default_dump_filter; 764 mm->def_flags = 0; 765 } 766 767 if (mm_alloc_pgd(mm)) 768 goto fail_nopgd; 769 770 if (init_new_context(p, mm)) 771 goto fail_nocontext; 772 773 return mm; 774 775 fail_nocontext: 776 mm_free_pgd(mm); 777 fail_nopgd: 778 free_mm(mm); 779 return NULL; 780 } 781 782 static void check_mm(struct mm_struct *mm) 783 { 784 int i; 785 786 for (i = 0; i < NR_MM_COUNTERS; i++) { 787 long x = atomic_long_read(&mm->rss_stat.count[i]); 788 789 if (unlikely(x)) 790 printk(KERN_ALERT "BUG: Bad rss-counter state " 791 "mm:%p idx:%d val:%ld\n", mm, i, x); 792 } 793 794 if (atomic_long_read(&mm->nr_ptes)) 795 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 796 atomic_long_read(&mm->nr_ptes)); 797 if (mm_nr_pmds(mm)) 798 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 799 mm_nr_pmds(mm)); 800 801 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 802 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 803 #endif 804 } 805 806 /* 807 * Allocate and initialize an mm_struct. 808 */ 809 struct mm_struct *mm_alloc(void) 810 { 811 struct mm_struct *mm; 812 813 mm = allocate_mm(); 814 if (!mm) 815 return NULL; 816 817 memset(mm, 0, sizeof(*mm)); 818 return mm_init(mm, current); 819 } 820 821 /* 822 * Called when the last reference to the mm 823 * is dropped: either by a lazy thread or by 824 * mmput. Free the page directory and the mm. 825 */ 826 void __mmdrop(struct mm_struct *mm) 827 { 828 BUG_ON(mm == &init_mm); 829 mm_free_pgd(mm); 830 destroy_context(mm); 831 mmu_notifier_mm_destroy(mm); 832 check_mm(mm); 833 free_mm(mm); 834 } 835 EXPORT_SYMBOL_GPL(__mmdrop); 836 837 static inline void __mmput(struct mm_struct *mm) 838 { 839 VM_BUG_ON(atomic_read(&mm->mm_users)); 840 841 uprobe_clear_state(mm); 842 exit_aio(mm); 843 ksm_exit(mm); 844 khugepaged_exit(mm); /* must run before exit_mmap */ 845 exit_mmap(mm); 846 set_mm_exe_file(mm, NULL); 847 if (!list_empty(&mm->mmlist)) { 848 spin_lock(&mmlist_lock); 849 list_del(&mm->mmlist); 850 spin_unlock(&mmlist_lock); 851 } 852 if (mm->binfmt) 853 module_put(mm->binfmt->module); 854 mmdrop(mm); 855 } 856 857 /* 858 * Decrement the use count and release all resources for an mm. 859 */ 860 void mmput(struct mm_struct *mm) 861 { 862 might_sleep(); 863 864 if (atomic_dec_and_test(&mm->mm_users)) 865 __mmput(mm); 866 } 867 EXPORT_SYMBOL_GPL(mmput); 868 869 #ifdef CONFIG_MMU 870 static void mmput_async_fn(struct work_struct *work) 871 { 872 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 873 __mmput(mm); 874 } 875 876 void mmput_async(struct mm_struct *mm) 877 { 878 if (atomic_dec_and_test(&mm->mm_users)) { 879 INIT_WORK(&mm->async_put_work, mmput_async_fn); 880 schedule_work(&mm->async_put_work); 881 } 882 } 883 #endif 884 885 /** 886 * set_mm_exe_file - change a reference to the mm's executable file 887 * 888 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 889 * 890 * Main users are mmput() and sys_execve(). Callers prevent concurrent 891 * invocations: in mmput() nobody alive left, in execve task is single 892 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 893 * mm->exe_file, but does so without using set_mm_exe_file() in order 894 * to do avoid the need for any locks. 895 */ 896 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 897 { 898 struct file *old_exe_file; 899 900 /* 901 * It is safe to dereference the exe_file without RCU as 902 * this function is only called if nobody else can access 903 * this mm -- see comment above for justification. 904 */ 905 old_exe_file = rcu_dereference_raw(mm->exe_file); 906 907 if (new_exe_file) 908 get_file(new_exe_file); 909 rcu_assign_pointer(mm->exe_file, new_exe_file); 910 if (old_exe_file) 911 fput(old_exe_file); 912 } 913 914 /** 915 * get_mm_exe_file - acquire a reference to the mm's executable file 916 * 917 * Returns %NULL if mm has no associated executable file. 918 * User must release file via fput(). 919 */ 920 struct file *get_mm_exe_file(struct mm_struct *mm) 921 { 922 struct file *exe_file; 923 924 rcu_read_lock(); 925 exe_file = rcu_dereference(mm->exe_file); 926 if (exe_file && !get_file_rcu(exe_file)) 927 exe_file = NULL; 928 rcu_read_unlock(); 929 return exe_file; 930 } 931 EXPORT_SYMBOL(get_mm_exe_file); 932 933 /** 934 * get_task_exe_file - acquire a reference to the task's executable file 935 * 936 * Returns %NULL if task's mm (if any) has no associated executable file or 937 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 938 * User must release file via fput(). 939 */ 940 struct file *get_task_exe_file(struct task_struct *task) 941 { 942 struct file *exe_file = NULL; 943 struct mm_struct *mm; 944 945 task_lock(task); 946 mm = task->mm; 947 if (mm) { 948 if (!(task->flags & PF_KTHREAD)) 949 exe_file = get_mm_exe_file(mm); 950 } 951 task_unlock(task); 952 return exe_file; 953 } 954 EXPORT_SYMBOL(get_task_exe_file); 955 956 /** 957 * get_task_mm - acquire a reference to the task's mm 958 * 959 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 960 * this kernel workthread has transiently adopted a user mm with use_mm, 961 * to do its AIO) is not set and if so returns a reference to it, after 962 * bumping up the use count. User must release the mm via mmput() 963 * after use. Typically used by /proc and ptrace. 964 */ 965 struct mm_struct *get_task_mm(struct task_struct *task) 966 { 967 struct mm_struct *mm; 968 969 task_lock(task); 970 mm = task->mm; 971 if (mm) { 972 if (task->flags & PF_KTHREAD) 973 mm = NULL; 974 else 975 atomic_inc(&mm->mm_users); 976 } 977 task_unlock(task); 978 return mm; 979 } 980 EXPORT_SYMBOL_GPL(get_task_mm); 981 982 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 983 { 984 struct mm_struct *mm; 985 int err; 986 987 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 988 if (err) 989 return ERR_PTR(err); 990 991 mm = get_task_mm(task); 992 if (mm && mm != current->mm && 993 !ptrace_may_access(task, mode)) { 994 mmput(mm); 995 mm = ERR_PTR(-EACCES); 996 } 997 mutex_unlock(&task->signal->cred_guard_mutex); 998 999 return mm; 1000 } 1001 1002 static void complete_vfork_done(struct task_struct *tsk) 1003 { 1004 struct completion *vfork; 1005 1006 task_lock(tsk); 1007 vfork = tsk->vfork_done; 1008 if (likely(vfork)) { 1009 tsk->vfork_done = NULL; 1010 complete(vfork); 1011 } 1012 task_unlock(tsk); 1013 } 1014 1015 static int wait_for_vfork_done(struct task_struct *child, 1016 struct completion *vfork) 1017 { 1018 int killed; 1019 1020 freezer_do_not_count(); 1021 killed = wait_for_completion_killable(vfork); 1022 freezer_count(); 1023 1024 if (killed) { 1025 task_lock(child); 1026 child->vfork_done = NULL; 1027 task_unlock(child); 1028 } 1029 1030 put_task_struct(child); 1031 return killed; 1032 } 1033 1034 /* Please note the differences between mmput and mm_release. 1035 * mmput is called whenever we stop holding onto a mm_struct, 1036 * error success whatever. 1037 * 1038 * mm_release is called after a mm_struct has been removed 1039 * from the current process. 1040 * 1041 * This difference is important for error handling, when we 1042 * only half set up a mm_struct for a new process and need to restore 1043 * the old one. Because we mmput the new mm_struct before 1044 * restoring the old one. . . 1045 * Eric Biederman 10 January 1998 1046 */ 1047 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1048 { 1049 /* Get rid of any futexes when releasing the mm */ 1050 #ifdef CONFIG_FUTEX 1051 if (unlikely(tsk->robust_list)) { 1052 exit_robust_list(tsk); 1053 tsk->robust_list = NULL; 1054 } 1055 #ifdef CONFIG_COMPAT 1056 if (unlikely(tsk->compat_robust_list)) { 1057 compat_exit_robust_list(tsk); 1058 tsk->compat_robust_list = NULL; 1059 } 1060 #endif 1061 if (unlikely(!list_empty(&tsk->pi_state_list))) 1062 exit_pi_state_list(tsk); 1063 #endif 1064 1065 uprobe_free_utask(tsk); 1066 1067 /* Get rid of any cached register state */ 1068 deactivate_mm(tsk, mm); 1069 1070 /* 1071 * Signal userspace if we're not exiting with a core dump 1072 * because we want to leave the value intact for debugging 1073 * purposes. 1074 */ 1075 if (tsk->clear_child_tid) { 1076 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1077 atomic_read(&mm->mm_users) > 1) { 1078 /* 1079 * We don't check the error code - if userspace has 1080 * not set up a proper pointer then tough luck. 1081 */ 1082 put_user(0, tsk->clear_child_tid); 1083 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1084 1, NULL, NULL, 0); 1085 } 1086 tsk->clear_child_tid = NULL; 1087 } 1088 1089 /* 1090 * All done, finally we can wake up parent and return this mm to him. 1091 * Also kthread_stop() uses this completion for synchronization. 1092 */ 1093 if (tsk->vfork_done) 1094 complete_vfork_done(tsk); 1095 } 1096 1097 /* 1098 * Allocate a new mm structure and copy contents from the 1099 * mm structure of the passed in task structure. 1100 */ 1101 static struct mm_struct *dup_mm(struct task_struct *tsk) 1102 { 1103 struct mm_struct *mm, *oldmm = current->mm; 1104 int err; 1105 1106 mm = allocate_mm(); 1107 if (!mm) 1108 goto fail_nomem; 1109 1110 memcpy(mm, oldmm, sizeof(*mm)); 1111 1112 if (!mm_init(mm, tsk)) 1113 goto fail_nomem; 1114 1115 err = dup_mmap(mm, oldmm); 1116 if (err) 1117 goto free_pt; 1118 1119 mm->hiwater_rss = get_mm_rss(mm); 1120 mm->hiwater_vm = mm->total_vm; 1121 1122 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1123 goto free_pt; 1124 1125 return mm; 1126 1127 free_pt: 1128 /* don't put binfmt in mmput, we haven't got module yet */ 1129 mm->binfmt = NULL; 1130 mmput(mm); 1131 1132 fail_nomem: 1133 return NULL; 1134 } 1135 1136 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1137 { 1138 struct mm_struct *mm, *oldmm; 1139 int retval; 1140 1141 tsk->min_flt = tsk->maj_flt = 0; 1142 tsk->nvcsw = tsk->nivcsw = 0; 1143 #ifdef CONFIG_DETECT_HUNG_TASK 1144 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1145 #endif 1146 1147 tsk->mm = NULL; 1148 tsk->active_mm = NULL; 1149 1150 /* 1151 * Are we cloning a kernel thread? 1152 * 1153 * We need to steal a active VM for that.. 1154 */ 1155 oldmm = current->mm; 1156 if (!oldmm) 1157 return 0; 1158 1159 /* initialize the new vmacache entries */ 1160 vmacache_flush(tsk); 1161 1162 if (clone_flags & CLONE_VM) { 1163 atomic_inc(&oldmm->mm_users); 1164 mm = oldmm; 1165 goto good_mm; 1166 } 1167 1168 retval = -ENOMEM; 1169 mm = dup_mm(tsk); 1170 if (!mm) 1171 goto fail_nomem; 1172 1173 good_mm: 1174 tsk->mm = mm; 1175 tsk->active_mm = mm; 1176 return 0; 1177 1178 fail_nomem: 1179 return retval; 1180 } 1181 1182 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1183 { 1184 struct fs_struct *fs = current->fs; 1185 if (clone_flags & CLONE_FS) { 1186 /* tsk->fs is already what we want */ 1187 spin_lock(&fs->lock); 1188 if (fs->in_exec) { 1189 spin_unlock(&fs->lock); 1190 return -EAGAIN; 1191 } 1192 fs->users++; 1193 spin_unlock(&fs->lock); 1194 return 0; 1195 } 1196 tsk->fs = copy_fs_struct(fs); 1197 if (!tsk->fs) 1198 return -ENOMEM; 1199 return 0; 1200 } 1201 1202 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1203 { 1204 struct files_struct *oldf, *newf; 1205 int error = 0; 1206 1207 /* 1208 * A background process may not have any files ... 1209 */ 1210 oldf = current->files; 1211 if (!oldf) 1212 goto out; 1213 1214 if (clone_flags & CLONE_FILES) { 1215 atomic_inc(&oldf->count); 1216 goto out; 1217 } 1218 1219 newf = dup_fd(oldf, &error); 1220 if (!newf) 1221 goto out; 1222 1223 tsk->files = newf; 1224 error = 0; 1225 out: 1226 return error; 1227 } 1228 1229 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1230 { 1231 #ifdef CONFIG_BLOCK 1232 struct io_context *ioc = current->io_context; 1233 struct io_context *new_ioc; 1234 1235 if (!ioc) 1236 return 0; 1237 /* 1238 * Share io context with parent, if CLONE_IO is set 1239 */ 1240 if (clone_flags & CLONE_IO) { 1241 ioc_task_link(ioc); 1242 tsk->io_context = ioc; 1243 } else if (ioprio_valid(ioc->ioprio)) { 1244 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1245 if (unlikely(!new_ioc)) 1246 return -ENOMEM; 1247 1248 new_ioc->ioprio = ioc->ioprio; 1249 put_io_context(new_ioc); 1250 } 1251 #endif 1252 return 0; 1253 } 1254 1255 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1256 { 1257 struct sighand_struct *sig; 1258 1259 if (clone_flags & CLONE_SIGHAND) { 1260 atomic_inc(¤t->sighand->count); 1261 return 0; 1262 } 1263 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1264 rcu_assign_pointer(tsk->sighand, sig); 1265 if (!sig) 1266 return -ENOMEM; 1267 1268 atomic_set(&sig->count, 1); 1269 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1270 return 0; 1271 } 1272 1273 void __cleanup_sighand(struct sighand_struct *sighand) 1274 { 1275 if (atomic_dec_and_test(&sighand->count)) { 1276 signalfd_cleanup(sighand); 1277 /* 1278 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1279 * without an RCU grace period, see __lock_task_sighand(). 1280 */ 1281 kmem_cache_free(sighand_cachep, sighand); 1282 } 1283 } 1284 1285 /* 1286 * Initialize POSIX timer handling for a thread group. 1287 */ 1288 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1289 { 1290 unsigned long cpu_limit; 1291 1292 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1293 if (cpu_limit != RLIM_INFINITY) { 1294 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1295 sig->cputimer.running = true; 1296 } 1297 1298 /* The timer lists. */ 1299 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1300 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1301 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1302 } 1303 1304 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1305 { 1306 struct signal_struct *sig; 1307 1308 if (clone_flags & CLONE_THREAD) 1309 return 0; 1310 1311 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1312 tsk->signal = sig; 1313 if (!sig) 1314 return -ENOMEM; 1315 1316 sig->nr_threads = 1; 1317 atomic_set(&sig->live, 1); 1318 atomic_set(&sig->sigcnt, 1); 1319 1320 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1321 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1322 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1323 1324 init_waitqueue_head(&sig->wait_chldexit); 1325 sig->curr_target = tsk; 1326 init_sigpending(&sig->shared_pending); 1327 INIT_LIST_HEAD(&sig->posix_timers); 1328 seqlock_init(&sig->stats_lock); 1329 prev_cputime_init(&sig->prev_cputime); 1330 1331 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1332 sig->real_timer.function = it_real_fn; 1333 1334 task_lock(current->group_leader); 1335 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1336 task_unlock(current->group_leader); 1337 1338 posix_cpu_timers_init_group(sig); 1339 1340 tty_audit_fork(sig); 1341 sched_autogroup_fork(sig); 1342 1343 sig->oom_score_adj = current->signal->oom_score_adj; 1344 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1345 1346 sig->has_child_subreaper = current->signal->has_child_subreaper || 1347 current->signal->is_child_subreaper; 1348 1349 mutex_init(&sig->cred_guard_mutex); 1350 1351 return 0; 1352 } 1353 1354 static void copy_seccomp(struct task_struct *p) 1355 { 1356 #ifdef CONFIG_SECCOMP 1357 /* 1358 * Must be called with sighand->lock held, which is common to 1359 * all threads in the group. Holding cred_guard_mutex is not 1360 * needed because this new task is not yet running and cannot 1361 * be racing exec. 1362 */ 1363 assert_spin_locked(¤t->sighand->siglock); 1364 1365 /* Ref-count the new filter user, and assign it. */ 1366 get_seccomp_filter(current); 1367 p->seccomp = current->seccomp; 1368 1369 /* 1370 * Explicitly enable no_new_privs here in case it got set 1371 * between the task_struct being duplicated and holding the 1372 * sighand lock. The seccomp state and nnp must be in sync. 1373 */ 1374 if (task_no_new_privs(current)) 1375 task_set_no_new_privs(p); 1376 1377 /* 1378 * If the parent gained a seccomp mode after copying thread 1379 * flags and between before we held the sighand lock, we have 1380 * to manually enable the seccomp thread flag here. 1381 */ 1382 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1383 set_tsk_thread_flag(p, TIF_SECCOMP); 1384 #endif 1385 } 1386 1387 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1388 { 1389 current->clear_child_tid = tidptr; 1390 1391 return task_pid_vnr(current); 1392 } 1393 1394 static void rt_mutex_init_task(struct task_struct *p) 1395 { 1396 raw_spin_lock_init(&p->pi_lock); 1397 #ifdef CONFIG_RT_MUTEXES 1398 p->pi_waiters = RB_ROOT; 1399 p->pi_waiters_leftmost = NULL; 1400 p->pi_blocked_on = NULL; 1401 #endif 1402 } 1403 1404 /* 1405 * Initialize POSIX timer handling for a single task. 1406 */ 1407 static void posix_cpu_timers_init(struct task_struct *tsk) 1408 { 1409 tsk->cputime_expires.prof_exp = 0; 1410 tsk->cputime_expires.virt_exp = 0; 1411 tsk->cputime_expires.sched_exp = 0; 1412 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1413 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1414 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1415 } 1416 1417 static inline void 1418 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1419 { 1420 task->pids[type].pid = pid; 1421 } 1422 1423 /* 1424 * This creates a new process as a copy of the old one, 1425 * but does not actually start it yet. 1426 * 1427 * It copies the registers, and all the appropriate 1428 * parts of the process environment (as per the clone 1429 * flags). The actual kick-off is left to the caller. 1430 */ 1431 static struct task_struct *copy_process(unsigned long clone_flags, 1432 unsigned long stack_start, 1433 unsigned long stack_size, 1434 int __user *child_tidptr, 1435 struct pid *pid, 1436 int trace, 1437 unsigned long tls, 1438 int node) 1439 { 1440 int retval; 1441 struct task_struct *p; 1442 1443 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1444 return ERR_PTR(-EINVAL); 1445 1446 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1447 return ERR_PTR(-EINVAL); 1448 1449 /* 1450 * Thread groups must share signals as well, and detached threads 1451 * can only be started up within the thread group. 1452 */ 1453 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1454 return ERR_PTR(-EINVAL); 1455 1456 /* 1457 * Shared signal handlers imply shared VM. By way of the above, 1458 * thread groups also imply shared VM. Blocking this case allows 1459 * for various simplifications in other code. 1460 */ 1461 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1462 return ERR_PTR(-EINVAL); 1463 1464 /* 1465 * Siblings of global init remain as zombies on exit since they are 1466 * not reaped by their parent (swapper). To solve this and to avoid 1467 * multi-rooted process trees, prevent global and container-inits 1468 * from creating siblings. 1469 */ 1470 if ((clone_flags & CLONE_PARENT) && 1471 current->signal->flags & SIGNAL_UNKILLABLE) 1472 return ERR_PTR(-EINVAL); 1473 1474 /* 1475 * If the new process will be in a different pid or user namespace 1476 * do not allow it to share a thread group with the forking task. 1477 */ 1478 if (clone_flags & CLONE_THREAD) { 1479 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1480 (task_active_pid_ns(current) != 1481 current->nsproxy->pid_ns_for_children)) 1482 return ERR_PTR(-EINVAL); 1483 } 1484 1485 retval = security_task_create(clone_flags); 1486 if (retval) 1487 goto fork_out; 1488 1489 retval = -ENOMEM; 1490 p = dup_task_struct(current, node); 1491 if (!p) 1492 goto fork_out; 1493 1494 ftrace_graph_init_task(p); 1495 1496 rt_mutex_init_task(p); 1497 1498 #ifdef CONFIG_PROVE_LOCKING 1499 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1500 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1501 #endif 1502 retval = -EAGAIN; 1503 if (atomic_read(&p->real_cred->user->processes) >= 1504 task_rlimit(p, RLIMIT_NPROC)) { 1505 if (p->real_cred->user != INIT_USER && 1506 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1507 goto bad_fork_free; 1508 } 1509 current->flags &= ~PF_NPROC_EXCEEDED; 1510 1511 retval = copy_creds(p, clone_flags); 1512 if (retval < 0) 1513 goto bad_fork_free; 1514 1515 /* 1516 * If multiple threads are within copy_process(), then this check 1517 * triggers too late. This doesn't hurt, the check is only there 1518 * to stop root fork bombs. 1519 */ 1520 retval = -EAGAIN; 1521 if (nr_threads >= max_threads) 1522 goto bad_fork_cleanup_count; 1523 1524 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1525 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1526 p->flags |= PF_FORKNOEXEC; 1527 INIT_LIST_HEAD(&p->children); 1528 INIT_LIST_HEAD(&p->sibling); 1529 rcu_copy_process(p); 1530 p->vfork_done = NULL; 1531 spin_lock_init(&p->alloc_lock); 1532 1533 init_sigpending(&p->pending); 1534 1535 p->utime = p->stime = p->gtime = 0; 1536 p->utimescaled = p->stimescaled = 0; 1537 prev_cputime_init(&p->prev_cputime); 1538 1539 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1540 seqcount_init(&p->vtime_seqcount); 1541 p->vtime_snap = 0; 1542 p->vtime_snap_whence = VTIME_INACTIVE; 1543 #endif 1544 1545 #if defined(SPLIT_RSS_COUNTING) 1546 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1547 #endif 1548 1549 p->default_timer_slack_ns = current->timer_slack_ns; 1550 1551 task_io_accounting_init(&p->ioac); 1552 acct_clear_integrals(p); 1553 1554 posix_cpu_timers_init(p); 1555 1556 p->start_time = ktime_get_ns(); 1557 p->real_start_time = ktime_get_boot_ns(); 1558 p->io_context = NULL; 1559 p->audit_context = NULL; 1560 cgroup_fork(p); 1561 #ifdef CONFIG_NUMA 1562 p->mempolicy = mpol_dup(p->mempolicy); 1563 if (IS_ERR(p->mempolicy)) { 1564 retval = PTR_ERR(p->mempolicy); 1565 p->mempolicy = NULL; 1566 goto bad_fork_cleanup_threadgroup_lock; 1567 } 1568 #endif 1569 #ifdef CONFIG_CPUSETS 1570 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1571 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1572 seqcount_init(&p->mems_allowed_seq); 1573 #endif 1574 #ifdef CONFIG_TRACE_IRQFLAGS 1575 p->irq_events = 0; 1576 p->hardirqs_enabled = 0; 1577 p->hardirq_enable_ip = 0; 1578 p->hardirq_enable_event = 0; 1579 p->hardirq_disable_ip = _THIS_IP_; 1580 p->hardirq_disable_event = 0; 1581 p->softirqs_enabled = 1; 1582 p->softirq_enable_ip = _THIS_IP_; 1583 p->softirq_enable_event = 0; 1584 p->softirq_disable_ip = 0; 1585 p->softirq_disable_event = 0; 1586 p->hardirq_context = 0; 1587 p->softirq_context = 0; 1588 #endif 1589 1590 p->pagefault_disabled = 0; 1591 1592 #ifdef CONFIG_LOCKDEP 1593 p->lockdep_depth = 0; /* no locks held yet */ 1594 p->curr_chain_key = 0; 1595 p->lockdep_recursion = 0; 1596 #endif 1597 1598 #ifdef CONFIG_DEBUG_MUTEXES 1599 p->blocked_on = NULL; /* not blocked yet */ 1600 #endif 1601 #ifdef CONFIG_BCACHE 1602 p->sequential_io = 0; 1603 p->sequential_io_avg = 0; 1604 #endif 1605 1606 /* Perform scheduler related setup. Assign this task to a CPU. */ 1607 retval = sched_fork(clone_flags, p); 1608 if (retval) 1609 goto bad_fork_cleanup_policy; 1610 1611 retval = perf_event_init_task(p); 1612 if (retval) 1613 goto bad_fork_cleanup_policy; 1614 retval = audit_alloc(p); 1615 if (retval) 1616 goto bad_fork_cleanup_perf; 1617 /* copy all the process information */ 1618 shm_init_task(p); 1619 retval = copy_semundo(clone_flags, p); 1620 if (retval) 1621 goto bad_fork_cleanup_audit; 1622 retval = copy_files(clone_flags, p); 1623 if (retval) 1624 goto bad_fork_cleanup_semundo; 1625 retval = copy_fs(clone_flags, p); 1626 if (retval) 1627 goto bad_fork_cleanup_files; 1628 retval = copy_sighand(clone_flags, p); 1629 if (retval) 1630 goto bad_fork_cleanup_fs; 1631 retval = copy_signal(clone_flags, p); 1632 if (retval) 1633 goto bad_fork_cleanup_sighand; 1634 retval = copy_mm(clone_flags, p); 1635 if (retval) 1636 goto bad_fork_cleanup_signal; 1637 retval = copy_namespaces(clone_flags, p); 1638 if (retval) 1639 goto bad_fork_cleanup_mm; 1640 retval = copy_io(clone_flags, p); 1641 if (retval) 1642 goto bad_fork_cleanup_namespaces; 1643 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1644 if (retval) 1645 goto bad_fork_cleanup_io; 1646 1647 if (pid != &init_struct_pid) { 1648 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1649 if (IS_ERR(pid)) { 1650 retval = PTR_ERR(pid); 1651 goto bad_fork_cleanup_thread; 1652 } 1653 } 1654 1655 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1656 /* 1657 * Clear TID on mm_release()? 1658 */ 1659 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1660 #ifdef CONFIG_BLOCK 1661 p->plug = NULL; 1662 #endif 1663 #ifdef CONFIG_FUTEX 1664 p->robust_list = NULL; 1665 #ifdef CONFIG_COMPAT 1666 p->compat_robust_list = NULL; 1667 #endif 1668 INIT_LIST_HEAD(&p->pi_state_list); 1669 p->pi_state_cache = NULL; 1670 #endif 1671 /* 1672 * sigaltstack should be cleared when sharing the same VM 1673 */ 1674 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1675 sas_ss_reset(p); 1676 1677 /* 1678 * Syscall tracing and stepping should be turned off in the 1679 * child regardless of CLONE_PTRACE. 1680 */ 1681 user_disable_single_step(p); 1682 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1683 #ifdef TIF_SYSCALL_EMU 1684 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1685 #endif 1686 clear_all_latency_tracing(p); 1687 1688 /* ok, now we should be set up.. */ 1689 p->pid = pid_nr(pid); 1690 if (clone_flags & CLONE_THREAD) { 1691 p->exit_signal = -1; 1692 p->group_leader = current->group_leader; 1693 p->tgid = current->tgid; 1694 } else { 1695 if (clone_flags & CLONE_PARENT) 1696 p->exit_signal = current->group_leader->exit_signal; 1697 else 1698 p->exit_signal = (clone_flags & CSIGNAL); 1699 p->group_leader = p; 1700 p->tgid = p->pid; 1701 } 1702 1703 p->nr_dirtied = 0; 1704 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1705 p->dirty_paused_when = 0; 1706 1707 p->pdeath_signal = 0; 1708 INIT_LIST_HEAD(&p->thread_group); 1709 p->task_works = NULL; 1710 1711 threadgroup_change_begin(current); 1712 /* 1713 * Ensure that the cgroup subsystem policies allow the new process to be 1714 * forked. It should be noted the the new process's css_set can be changed 1715 * between here and cgroup_post_fork() if an organisation operation is in 1716 * progress. 1717 */ 1718 retval = cgroup_can_fork(p); 1719 if (retval) 1720 goto bad_fork_free_pid; 1721 1722 /* 1723 * Make it visible to the rest of the system, but dont wake it up yet. 1724 * Need tasklist lock for parent etc handling! 1725 */ 1726 write_lock_irq(&tasklist_lock); 1727 1728 /* CLONE_PARENT re-uses the old parent */ 1729 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1730 p->real_parent = current->real_parent; 1731 p->parent_exec_id = current->parent_exec_id; 1732 } else { 1733 p->real_parent = current; 1734 p->parent_exec_id = current->self_exec_id; 1735 } 1736 1737 spin_lock(¤t->sighand->siglock); 1738 1739 /* 1740 * Copy seccomp details explicitly here, in case they were changed 1741 * before holding sighand lock. 1742 */ 1743 copy_seccomp(p); 1744 1745 /* 1746 * Process group and session signals need to be delivered to just the 1747 * parent before the fork or both the parent and the child after the 1748 * fork. Restart if a signal comes in before we add the new process to 1749 * it's process group. 1750 * A fatal signal pending means that current will exit, so the new 1751 * thread can't slip out of an OOM kill (or normal SIGKILL). 1752 */ 1753 recalc_sigpending(); 1754 if (signal_pending(current)) { 1755 spin_unlock(¤t->sighand->siglock); 1756 write_unlock_irq(&tasklist_lock); 1757 retval = -ERESTARTNOINTR; 1758 goto bad_fork_cancel_cgroup; 1759 } 1760 1761 if (likely(p->pid)) { 1762 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1763 1764 init_task_pid(p, PIDTYPE_PID, pid); 1765 if (thread_group_leader(p)) { 1766 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1767 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1768 1769 if (is_child_reaper(pid)) { 1770 ns_of_pid(pid)->child_reaper = p; 1771 p->signal->flags |= SIGNAL_UNKILLABLE; 1772 } 1773 1774 p->signal->leader_pid = pid; 1775 p->signal->tty = tty_kref_get(current->signal->tty); 1776 list_add_tail(&p->sibling, &p->real_parent->children); 1777 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1778 attach_pid(p, PIDTYPE_PGID); 1779 attach_pid(p, PIDTYPE_SID); 1780 __this_cpu_inc(process_counts); 1781 } else { 1782 current->signal->nr_threads++; 1783 atomic_inc(¤t->signal->live); 1784 atomic_inc(¤t->signal->sigcnt); 1785 list_add_tail_rcu(&p->thread_group, 1786 &p->group_leader->thread_group); 1787 list_add_tail_rcu(&p->thread_node, 1788 &p->signal->thread_head); 1789 } 1790 attach_pid(p, PIDTYPE_PID); 1791 nr_threads++; 1792 } 1793 1794 total_forks++; 1795 spin_unlock(¤t->sighand->siglock); 1796 syscall_tracepoint_update(p); 1797 write_unlock_irq(&tasklist_lock); 1798 1799 proc_fork_connector(p); 1800 cgroup_post_fork(p); 1801 threadgroup_change_end(current); 1802 perf_event_fork(p); 1803 1804 trace_task_newtask(p, clone_flags); 1805 uprobe_copy_process(p, clone_flags); 1806 1807 return p; 1808 1809 bad_fork_cancel_cgroup: 1810 cgroup_cancel_fork(p); 1811 bad_fork_free_pid: 1812 threadgroup_change_end(current); 1813 if (pid != &init_struct_pid) 1814 free_pid(pid); 1815 bad_fork_cleanup_thread: 1816 exit_thread(p); 1817 bad_fork_cleanup_io: 1818 if (p->io_context) 1819 exit_io_context(p); 1820 bad_fork_cleanup_namespaces: 1821 exit_task_namespaces(p); 1822 bad_fork_cleanup_mm: 1823 if (p->mm) 1824 mmput(p->mm); 1825 bad_fork_cleanup_signal: 1826 if (!(clone_flags & CLONE_THREAD)) 1827 free_signal_struct(p->signal); 1828 bad_fork_cleanup_sighand: 1829 __cleanup_sighand(p->sighand); 1830 bad_fork_cleanup_fs: 1831 exit_fs(p); /* blocking */ 1832 bad_fork_cleanup_files: 1833 exit_files(p); /* blocking */ 1834 bad_fork_cleanup_semundo: 1835 exit_sem(p); 1836 bad_fork_cleanup_audit: 1837 audit_free(p); 1838 bad_fork_cleanup_perf: 1839 perf_event_free_task(p); 1840 bad_fork_cleanup_policy: 1841 #ifdef CONFIG_NUMA 1842 mpol_put(p->mempolicy); 1843 bad_fork_cleanup_threadgroup_lock: 1844 #endif 1845 delayacct_tsk_free(p); 1846 bad_fork_cleanup_count: 1847 atomic_dec(&p->cred->user->processes); 1848 exit_creds(p); 1849 bad_fork_free: 1850 put_task_stack(p); 1851 free_task(p); 1852 fork_out: 1853 return ERR_PTR(retval); 1854 } 1855 1856 static inline void init_idle_pids(struct pid_link *links) 1857 { 1858 enum pid_type type; 1859 1860 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1861 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1862 links[type].pid = &init_struct_pid; 1863 } 1864 } 1865 1866 struct task_struct *fork_idle(int cpu) 1867 { 1868 struct task_struct *task; 1869 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1870 cpu_to_node(cpu)); 1871 if (!IS_ERR(task)) { 1872 init_idle_pids(task->pids); 1873 init_idle(task, cpu); 1874 } 1875 1876 return task; 1877 } 1878 1879 /* 1880 * Ok, this is the main fork-routine. 1881 * 1882 * It copies the process, and if successful kick-starts 1883 * it and waits for it to finish using the VM if required. 1884 */ 1885 long _do_fork(unsigned long clone_flags, 1886 unsigned long stack_start, 1887 unsigned long stack_size, 1888 int __user *parent_tidptr, 1889 int __user *child_tidptr, 1890 unsigned long tls) 1891 { 1892 struct task_struct *p; 1893 int trace = 0; 1894 long nr; 1895 1896 /* 1897 * Determine whether and which event to report to ptracer. When 1898 * called from kernel_thread or CLONE_UNTRACED is explicitly 1899 * requested, no event is reported; otherwise, report if the event 1900 * for the type of forking is enabled. 1901 */ 1902 if (!(clone_flags & CLONE_UNTRACED)) { 1903 if (clone_flags & CLONE_VFORK) 1904 trace = PTRACE_EVENT_VFORK; 1905 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1906 trace = PTRACE_EVENT_CLONE; 1907 else 1908 trace = PTRACE_EVENT_FORK; 1909 1910 if (likely(!ptrace_event_enabled(current, trace))) 1911 trace = 0; 1912 } 1913 1914 p = copy_process(clone_flags, stack_start, stack_size, 1915 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 1916 /* 1917 * Do this prior waking up the new thread - the thread pointer 1918 * might get invalid after that point, if the thread exits quickly. 1919 */ 1920 if (!IS_ERR(p)) { 1921 struct completion vfork; 1922 struct pid *pid; 1923 1924 trace_sched_process_fork(current, p); 1925 1926 pid = get_task_pid(p, PIDTYPE_PID); 1927 nr = pid_vnr(pid); 1928 1929 if (clone_flags & CLONE_PARENT_SETTID) 1930 put_user(nr, parent_tidptr); 1931 1932 if (clone_flags & CLONE_VFORK) { 1933 p->vfork_done = &vfork; 1934 init_completion(&vfork); 1935 get_task_struct(p); 1936 } 1937 1938 wake_up_new_task(p); 1939 1940 /* forking complete and child started to run, tell ptracer */ 1941 if (unlikely(trace)) 1942 ptrace_event_pid(trace, pid); 1943 1944 if (clone_flags & CLONE_VFORK) { 1945 if (!wait_for_vfork_done(p, &vfork)) 1946 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1947 } 1948 1949 put_pid(pid); 1950 } else { 1951 nr = PTR_ERR(p); 1952 } 1953 return nr; 1954 } 1955 1956 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 1957 /* For compatibility with architectures that call do_fork directly rather than 1958 * using the syscall entry points below. */ 1959 long do_fork(unsigned long clone_flags, 1960 unsigned long stack_start, 1961 unsigned long stack_size, 1962 int __user *parent_tidptr, 1963 int __user *child_tidptr) 1964 { 1965 return _do_fork(clone_flags, stack_start, stack_size, 1966 parent_tidptr, child_tidptr, 0); 1967 } 1968 #endif 1969 1970 /* 1971 * Create a kernel thread. 1972 */ 1973 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1974 { 1975 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1976 (unsigned long)arg, NULL, NULL, 0); 1977 } 1978 1979 #ifdef __ARCH_WANT_SYS_FORK 1980 SYSCALL_DEFINE0(fork) 1981 { 1982 #ifdef CONFIG_MMU 1983 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 1984 #else 1985 /* can not support in nommu mode */ 1986 return -EINVAL; 1987 #endif 1988 } 1989 #endif 1990 1991 #ifdef __ARCH_WANT_SYS_VFORK 1992 SYSCALL_DEFINE0(vfork) 1993 { 1994 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 1995 0, NULL, NULL, 0); 1996 } 1997 #endif 1998 1999 #ifdef __ARCH_WANT_SYS_CLONE 2000 #ifdef CONFIG_CLONE_BACKWARDS 2001 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2002 int __user *, parent_tidptr, 2003 unsigned long, tls, 2004 int __user *, child_tidptr) 2005 #elif defined(CONFIG_CLONE_BACKWARDS2) 2006 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2007 int __user *, parent_tidptr, 2008 int __user *, child_tidptr, 2009 unsigned long, tls) 2010 #elif defined(CONFIG_CLONE_BACKWARDS3) 2011 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2012 int, stack_size, 2013 int __user *, parent_tidptr, 2014 int __user *, child_tidptr, 2015 unsigned long, tls) 2016 #else 2017 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2018 int __user *, parent_tidptr, 2019 int __user *, child_tidptr, 2020 unsigned long, tls) 2021 #endif 2022 { 2023 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2024 } 2025 #endif 2026 2027 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2028 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2029 #endif 2030 2031 static void sighand_ctor(void *data) 2032 { 2033 struct sighand_struct *sighand = data; 2034 2035 spin_lock_init(&sighand->siglock); 2036 init_waitqueue_head(&sighand->signalfd_wqh); 2037 } 2038 2039 void __init proc_caches_init(void) 2040 { 2041 sighand_cachep = kmem_cache_create("sighand_cache", 2042 sizeof(struct sighand_struct), 0, 2043 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 2044 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2045 signal_cachep = kmem_cache_create("signal_cache", 2046 sizeof(struct signal_struct), 0, 2047 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2048 NULL); 2049 files_cachep = kmem_cache_create("files_cache", 2050 sizeof(struct files_struct), 0, 2051 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2052 NULL); 2053 fs_cachep = kmem_cache_create("fs_cache", 2054 sizeof(struct fs_struct), 0, 2055 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2056 NULL); 2057 /* 2058 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2059 * whole struct cpumask for the OFFSTACK case. We could change 2060 * this to *only* allocate as much of it as required by the 2061 * maximum number of CPU's we can ever have. The cpumask_allocation 2062 * is at the end of the structure, exactly for that reason. 2063 */ 2064 mm_cachep = kmem_cache_create("mm_struct", 2065 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2066 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2067 NULL); 2068 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2069 mmap_init(); 2070 nsproxy_cache_init(); 2071 } 2072 2073 /* 2074 * Check constraints on flags passed to the unshare system call. 2075 */ 2076 static int check_unshare_flags(unsigned long unshare_flags) 2077 { 2078 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2079 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2080 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2081 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2082 return -EINVAL; 2083 /* 2084 * Not implemented, but pretend it works if there is nothing 2085 * to unshare. Note that unsharing the address space or the 2086 * signal handlers also need to unshare the signal queues (aka 2087 * CLONE_THREAD). 2088 */ 2089 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2090 if (!thread_group_empty(current)) 2091 return -EINVAL; 2092 } 2093 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2094 if (atomic_read(¤t->sighand->count) > 1) 2095 return -EINVAL; 2096 } 2097 if (unshare_flags & CLONE_VM) { 2098 if (!current_is_single_threaded()) 2099 return -EINVAL; 2100 } 2101 2102 return 0; 2103 } 2104 2105 /* 2106 * Unshare the filesystem structure if it is being shared 2107 */ 2108 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2109 { 2110 struct fs_struct *fs = current->fs; 2111 2112 if (!(unshare_flags & CLONE_FS) || !fs) 2113 return 0; 2114 2115 /* don't need lock here; in the worst case we'll do useless copy */ 2116 if (fs->users == 1) 2117 return 0; 2118 2119 *new_fsp = copy_fs_struct(fs); 2120 if (!*new_fsp) 2121 return -ENOMEM; 2122 2123 return 0; 2124 } 2125 2126 /* 2127 * Unshare file descriptor table if it is being shared 2128 */ 2129 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2130 { 2131 struct files_struct *fd = current->files; 2132 int error = 0; 2133 2134 if ((unshare_flags & CLONE_FILES) && 2135 (fd && atomic_read(&fd->count) > 1)) { 2136 *new_fdp = dup_fd(fd, &error); 2137 if (!*new_fdp) 2138 return error; 2139 } 2140 2141 return 0; 2142 } 2143 2144 /* 2145 * unshare allows a process to 'unshare' part of the process 2146 * context which was originally shared using clone. copy_* 2147 * functions used by do_fork() cannot be used here directly 2148 * because they modify an inactive task_struct that is being 2149 * constructed. Here we are modifying the current, active, 2150 * task_struct. 2151 */ 2152 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2153 { 2154 struct fs_struct *fs, *new_fs = NULL; 2155 struct files_struct *fd, *new_fd = NULL; 2156 struct cred *new_cred = NULL; 2157 struct nsproxy *new_nsproxy = NULL; 2158 int do_sysvsem = 0; 2159 int err; 2160 2161 /* 2162 * If unsharing a user namespace must also unshare the thread group 2163 * and unshare the filesystem root and working directories. 2164 */ 2165 if (unshare_flags & CLONE_NEWUSER) 2166 unshare_flags |= CLONE_THREAD | CLONE_FS; 2167 /* 2168 * If unsharing vm, must also unshare signal handlers. 2169 */ 2170 if (unshare_flags & CLONE_VM) 2171 unshare_flags |= CLONE_SIGHAND; 2172 /* 2173 * If unsharing a signal handlers, must also unshare the signal queues. 2174 */ 2175 if (unshare_flags & CLONE_SIGHAND) 2176 unshare_flags |= CLONE_THREAD; 2177 /* 2178 * If unsharing namespace, must also unshare filesystem information. 2179 */ 2180 if (unshare_flags & CLONE_NEWNS) 2181 unshare_flags |= CLONE_FS; 2182 2183 err = check_unshare_flags(unshare_flags); 2184 if (err) 2185 goto bad_unshare_out; 2186 /* 2187 * CLONE_NEWIPC must also detach from the undolist: after switching 2188 * to a new ipc namespace, the semaphore arrays from the old 2189 * namespace are unreachable. 2190 */ 2191 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2192 do_sysvsem = 1; 2193 err = unshare_fs(unshare_flags, &new_fs); 2194 if (err) 2195 goto bad_unshare_out; 2196 err = unshare_fd(unshare_flags, &new_fd); 2197 if (err) 2198 goto bad_unshare_cleanup_fs; 2199 err = unshare_userns(unshare_flags, &new_cred); 2200 if (err) 2201 goto bad_unshare_cleanup_fd; 2202 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2203 new_cred, new_fs); 2204 if (err) 2205 goto bad_unshare_cleanup_cred; 2206 2207 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2208 if (do_sysvsem) { 2209 /* 2210 * CLONE_SYSVSEM is equivalent to sys_exit(). 2211 */ 2212 exit_sem(current); 2213 } 2214 if (unshare_flags & CLONE_NEWIPC) { 2215 /* Orphan segments in old ns (see sem above). */ 2216 exit_shm(current); 2217 shm_init_task(current); 2218 } 2219 2220 if (new_nsproxy) 2221 switch_task_namespaces(current, new_nsproxy); 2222 2223 task_lock(current); 2224 2225 if (new_fs) { 2226 fs = current->fs; 2227 spin_lock(&fs->lock); 2228 current->fs = new_fs; 2229 if (--fs->users) 2230 new_fs = NULL; 2231 else 2232 new_fs = fs; 2233 spin_unlock(&fs->lock); 2234 } 2235 2236 if (new_fd) { 2237 fd = current->files; 2238 current->files = new_fd; 2239 new_fd = fd; 2240 } 2241 2242 task_unlock(current); 2243 2244 if (new_cred) { 2245 /* Install the new user namespace */ 2246 commit_creds(new_cred); 2247 new_cred = NULL; 2248 } 2249 } 2250 2251 bad_unshare_cleanup_cred: 2252 if (new_cred) 2253 put_cred(new_cred); 2254 bad_unshare_cleanup_fd: 2255 if (new_fd) 2256 put_files_struct(new_fd); 2257 2258 bad_unshare_cleanup_fs: 2259 if (new_fs) 2260 free_fs_struct(new_fs); 2261 2262 bad_unshare_out: 2263 return err; 2264 } 2265 2266 /* 2267 * Helper to unshare the files of the current task. 2268 * We don't want to expose copy_files internals to 2269 * the exec layer of the kernel. 2270 */ 2271 2272 int unshare_files(struct files_struct **displaced) 2273 { 2274 struct task_struct *task = current; 2275 struct files_struct *copy = NULL; 2276 int error; 2277 2278 error = unshare_fd(CLONE_FILES, ©); 2279 if (error || !copy) { 2280 *displaced = NULL; 2281 return error; 2282 } 2283 *displaced = task->files; 2284 task_lock(task); 2285 task->files = copy; 2286 task_unlock(task); 2287 return 0; 2288 } 2289 2290 int sysctl_max_threads(struct ctl_table *table, int write, 2291 void __user *buffer, size_t *lenp, loff_t *ppos) 2292 { 2293 struct ctl_table t; 2294 int ret; 2295 int threads = max_threads; 2296 int min = MIN_THREADS; 2297 int max = MAX_THREADS; 2298 2299 t = *table; 2300 t.data = &threads; 2301 t.extra1 = &min; 2302 t.extra2 = &max; 2303 2304 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2305 if (ret || !write) 2306 return ret; 2307 2308 set_max_threads(threads); 2309 2310 return 0; 2311 } 2312