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 /* 363 * __mmdrop is not safe to call from softirq context on x86 due to 364 * pgd_dtor so postpone it to the async context 365 */ 366 if (sig->oom_mm) 367 mmdrop_async(sig->oom_mm); 368 kmem_cache_free(signal_cachep, sig); 369 } 370 371 static inline void put_signal_struct(struct signal_struct *sig) 372 { 373 if (atomic_dec_and_test(&sig->sigcnt)) 374 free_signal_struct(sig); 375 } 376 377 void __put_task_struct(struct task_struct *tsk) 378 { 379 WARN_ON(!tsk->exit_state); 380 WARN_ON(atomic_read(&tsk->usage)); 381 WARN_ON(tsk == current); 382 383 cgroup_free(tsk); 384 task_numa_free(tsk); 385 security_task_free(tsk); 386 exit_creds(tsk); 387 delayacct_tsk_free(tsk); 388 put_signal_struct(tsk->signal); 389 390 if (!profile_handoff_task(tsk)) 391 free_task(tsk); 392 } 393 EXPORT_SYMBOL_GPL(__put_task_struct); 394 395 void __init __weak arch_task_cache_init(void) { } 396 397 /* 398 * set_max_threads 399 */ 400 static void set_max_threads(unsigned int max_threads_suggested) 401 { 402 u64 threads; 403 404 /* 405 * The number of threads shall be limited such that the thread 406 * structures may only consume a small part of the available memory. 407 */ 408 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 409 threads = MAX_THREADS; 410 else 411 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 412 (u64) THREAD_SIZE * 8UL); 413 414 if (threads > max_threads_suggested) 415 threads = max_threads_suggested; 416 417 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 418 } 419 420 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 421 /* Initialized by the architecture: */ 422 int arch_task_struct_size __read_mostly; 423 #endif 424 425 void __init fork_init(void) 426 { 427 int i; 428 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 429 #ifndef ARCH_MIN_TASKALIGN 430 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 431 #endif 432 /* create a slab on which task_structs can be allocated */ 433 task_struct_cachep = kmem_cache_create("task_struct", 434 arch_task_struct_size, ARCH_MIN_TASKALIGN, 435 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 436 #endif 437 438 /* do the arch specific task caches init */ 439 arch_task_cache_init(); 440 441 set_max_threads(MAX_THREADS); 442 443 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 444 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 445 init_task.signal->rlim[RLIMIT_SIGPENDING] = 446 init_task.signal->rlim[RLIMIT_NPROC]; 447 448 for (i = 0; i < UCOUNT_COUNTS; i++) { 449 init_user_ns.ucount_max[i] = max_threads/2; 450 } 451 } 452 453 int __weak arch_dup_task_struct(struct task_struct *dst, 454 struct task_struct *src) 455 { 456 *dst = *src; 457 return 0; 458 } 459 460 void set_task_stack_end_magic(struct task_struct *tsk) 461 { 462 unsigned long *stackend; 463 464 stackend = end_of_stack(tsk); 465 *stackend = STACK_END_MAGIC; /* for overflow detection */ 466 } 467 468 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 469 { 470 struct task_struct *tsk; 471 unsigned long *stack; 472 struct vm_struct *stack_vm_area; 473 int err; 474 475 if (node == NUMA_NO_NODE) 476 node = tsk_fork_get_node(orig); 477 tsk = alloc_task_struct_node(node); 478 if (!tsk) 479 return NULL; 480 481 stack = alloc_thread_stack_node(tsk, node); 482 if (!stack) 483 goto free_tsk; 484 485 stack_vm_area = task_stack_vm_area(tsk); 486 487 err = arch_dup_task_struct(tsk, orig); 488 489 /* 490 * arch_dup_task_struct() clobbers the stack-related fields. Make 491 * sure they're properly initialized before using any stack-related 492 * functions again. 493 */ 494 tsk->stack = stack; 495 #ifdef CONFIG_VMAP_STACK 496 tsk->stack_vm_area = stack_vm_area; 497 #endif 498 #ifdef CONFIG_THREAD_INFO_IN_TASK 499 atomic_set(&tsk->stack_refcount, 1); 500 #endif 501 502 if (err) 503 goto free_stack; 504 505 #ifdef CONFIG_SECCOMP 506 /* 507 * We must handle setting up seccomp filters once we're under 508 * the sighand lock in case orig has changed between now and 509 * then. Until then, filter must be NULL to avoid messing up 510 * the usage counts on the error path calling free_task. 511 */ 512 tsk->seccomp.filter = NULL; 513 #endif 514 515 setup_thread_stack(tsk, orig); 516 clear_user_return_notifier(tsk); 517 clear_tsk_need_resched(tsk); 518 set_task_stack_end_magic(tsk); 519 520 #ifdef CONFIG_CC_STACKPROTECTOR 521 tsk->stack_canary = get_random_int(); 522 #endif 523 524 /* 525 * One for us, one for whoever does the "release_task()" (usually 526 * parent) 527 */ 528 atomic_set(&tsk->usage, 2); 529 #ifdef CONFIG_BLK_DEV_IO_TRACE 530 tsk->btrace_seq = 0; 531 #endif 532 tsk->splice_pipe = NULL; 533 tsk->task_frag.page = NULL; 534 tsk->wake_q.next = NULL; 535 536 account_kernel_stack(tsk, 1); 537 538 kcov_task_init(tsk); 539 540 return tsk; 541 542 free_stack: 543 free_thread_stack(tsk); 544 free_tsk: 545 free_task_struct(tsk); 546 return NULL; 547 } 548 549 #ifdef CONFIG_MMU 550 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 551 { 552 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 553 struct rb_node **rb_link, *rb_parent; 554 int retval; 555 unsigned long charge; 556 557 uprobe_start_dup_mmap(); 558 if (down_write_killable(&oldmm->mmap_sem)) { 559 retval = -EINTR; 560 goto fail_uprobe_end; 561 } 562 flush_cache_dup_mm(oldmm); 563 uprobe_dup_mmap(oldmm, mm); 564 /* 565 * Not linked in yet - no deadlock potential: 566 */ 567 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 568 569 /* No ordering required: file already has been exposed. */ 570 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 571 572 mm->total_vm = oldmm->total_vm; 573 mm->data_vm = oldmm->data_vm; 574 mm->exec_vm = oldmm->exec_vm; 575 mm->stack_vm = oldmm->stack_vm; 576 577 rb_link = &mm->mm_rb.rb_node; 578 rb_parent = NULL; 579 pprev = &mm->mmap; 580 retval = ksm_fork(mm, oldmm); 581 if (retval) 582 goto out; 583 retval = khugepaged_fork(mm, oldmm); 584 if (retval) 585 goto out; 586 587 prev = NULL; 588 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 589 struct file *file; 590 591 if (mpnt->vm_flags & VM_DONTCOPY) { 592 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 593 continue; 594 } 595 charge = 0; 596 if (mpnt->vm_flags & VM_ACCOUNT) { 597 unsigned long len = vma_pages(mpnt); 598 599 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 600 goto fail_nomem; 601 charge = len; 602 } 603 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 604 if (!tmp) 605 goto fail_nomem; 606 *tmp = *mpnt; 607 INIT_LIST_HEAD(&tmp->anon_vma_chain); 608 retval = vma_dup_policy(mpnt, tmp); 609 if (retval) 610 goto fail_nomem_policy; 611 tmp->vm_mm = mm; 612 if (anon_vma_fork(tmp, mpnt)) 613 goto fail_nomem_anon_vma_fork; 614 tmp->vm_flags &= 615 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP); 616 tmp->vm_next = tmp->vm_prev = NULL; 617 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 618 file = tmp->vm_file; 619 if (file) { 620 struct inode *inode = file_inode(file); 621 struct address_space *mapping = file->f_mapping; 622 623 get_file(file); 624 if (tmp->vm_flags & VM_DENYWRITE) 625 atomic_dec(&inode->i_writecount); 626 i_mmap_lock_write(mapping); 627 if (tmp->vm_flags & VM_SHARED) 628 atomic_inc(&mapping->i_mmap_writable); 629 flush_dcache_mmap_lock(mapping); 630 /* insert tmp into the share list, just after mpnt */ 631 vma_interval_tree_insert_after(tmp, mpnt, 632 &mapping->i_mmap); 633 flush_dcache_mmap_unlock(mapping); 634 i_mmap_unlock_write(mapping); 635 } 636 637 /* 638 * Clear hugetlb-related page reserves for children. This only 639 * affects MAP_PRIVATE mappings. Faults generated by the child 640 * are not guaranteed to succeed, even if read-only 641 */ 642 if (is_vm_hugetlb_page(tmp)) 643 reset_vma_resv_huge_pages(tmp); 644 645 /* 646 * Link in the new vma and copy the page table entries. 647 */ 648 *pprev = tmp; 649 pprev = &tmp->vm_next; 650 tmp->vm_prev = prev; 651 prev = tmp; 652 653 __vma_link_rb(mm, tmp, rb_link, rb_parent); 654 rb_link = &tmp->vm_rb.rb_right; 655 rb_parent = &tmp->vm_rb; 656 657 mm->map_count++; 658 retval = copy_page_range(mm, oldmm, mpnt); 659 660 if (tmp->vm_ops && tmp->vm_ops->open) 661 tmp->vm_ops->open(tmp); 662 663 if (retval) 664 goto out; 665 } 666 /* a new mm has just been created */ 667 arch_dup_mmap(oldmm, mm); 668 retval = 0; 669 out: 670 up_write(&mm->mmap_sem); 671 flush_tlb_mm(oldmm); 672 up_write(&oldmm->mmap_sem); 673 fail_uprobe_end: 674 uprobe_end_dup_mmap(); 675 return retval; 676 fail_nomem_anon_vma_fork: 677 mpol_put(vma_policy(tmp)); 678 fail_nomem_policy: 679 kmem_cache_free(vm_area_cachep, tmp); 680 fail_nomem: 681 retval = -ENOMEM; 682 vm_unacct_memory(charge); 683 goto out; 684 } 685 686 static inline int mm_alloc_pgd(struct mm_struct *mm) 687 { 688 mm->pgd = pgd_alloc(mm); 689 if (unlikely(!mm->pgd)) 690 return -ENOMEM; 691 return 0; 692 } 693 694 static inline void mm_free_pgd(struct mm_struct *mm) 695 { 696 pgd_free(mm, mm->pgd); 697 } 698 #else 699 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 700 { 701 down_write(&oldmm->mmap_sem); 702 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 703 up_write(&oldmm->mmap_sem); 704 return 0; 705 } 706 #define mm_alloc_pgd(mm) (0) 707 #define mm_free_pgd(mm) 708 #endif /* CONFIG_MMU */ 709 710 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 711 712 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 713 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 714 715 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 716 717 static int __init coredump_filter_setup(char *s) 718 { 719 default_dump_filter = 720 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 721 MMF_DUMP_FILTER_MASK; 722 return 1; 723 } 724 725 __setup("coredump_filter=", coredump_filter_setup); 726 727 #include <linux/init_task.h> 728 729 static void mm_init_aio(struct mm_struct *mm) 730 { 731 #ifdef CONFIG_AIO 732 spin_lock_init(&mm->ioctx_lock); 733 mm->ioctx_table = NULL; 734 #endif 735 } 736 737 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 738 { 739 #ifdef CONFIG_MEMCG 740 mm->owner = p; 741 #endif 742 } 743 744 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 745 { 746 mm->mmap = NULL; 747 mm->mm_rb = RB_ROOT; 748 mm->vmacache_seqnum = 0; 749 atomic_set(&mm->mm_users, 1); 750 atomic_set(&mm->mm_count, 1); 751 init_rwsem(&mm->mmap_sem); 752 INIT_LIST_HEAD(&mm->mmlist); 753 mm->core_state = NULL; 754 atomic_long_set(&mm->nr_ptes, 0); 755 mm_nr_pmds_init(mm); 756 mm->map_count = 0; 757 mm->locked_vm = 0; 758 mm->pinned_vm = 0; 759 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 760 spin_lock_init(&mm->page_table_lock); 761 mm_init_cpumask(mm); 762 mm_init_aio(mm); 763 mm_init_owner(mm, p); 764 mmu_notifier_mm_init(mm); 765 clear_tlb_flush_pending(mm); 766 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 767 mm->pmd_huge_pte = NULL; 768 #endif 769 770 if (current->mm) { 771 mm->flags = current->mm->flags & MMF_INIT_MASK; 772 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 773 } else { 774 mm->flags = default_dump_filter; 775 mm->def_flags = 0; 776 } 777 778 if (mm_alloc_pgd(mm)) 779 goto fail_nopgd; 780 781 if (init_new_context(p, mm)) 782 goto fail_nocontext; 783 784 return mm; 785 786 fail_nocontext: 787 mm_free_pgd(mm); 788 fail_nopgd: 789 free_mm(mm); 790 return NULL; 791 } 792 793 static void check_mm(struct mm_struct *mm) 794 { 795 int i; 796 797 for (i = 0; i < NR_MM_COUNTERS; i++) { 798 long x = atomic_long_read(&mm->rss_stat.count[i]); 799 800 if (unlikely(x)) 801 printk(KERN_ALERT "BUG: Bad rss-counter state " 802 "mm:%p idx:%d val:%ld\n", mm, i, x); 803 } 804 805 if (atomic_long_read(&mm->nr_ptes)) 806 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 807 atomic_long_read(&mm->nr_ptes)); 808 if (mm_nr_pmds(mm)) 809 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 810 mm_nr_pmds(mm)); 811 812 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 813 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 814 #endif 815 } 816 817 /* 818 * Allocate and initialize an mm_struct. 819 */ 820 struct mm_struct *mm_alloc(void) 821 { 822 struct mm_struct *mm; 823 824 mm = allocate_mm(); 825 if (!mm) 826 return NULL; 827 828 memset(mm, 0, sizeof(*mm)); 829 return mm_init(mm, current); 830 } 831 832 /* 833 * Called when the last reference to the mm 834 * is dropped: either by a lazy thread or by 835 * mmput. Free the page directory and the mm. 836 */ 837 void __mmdrop(struct mm_struct *mm) 838 { 839 BUG_ON(mm == &init_mm); 840 mm_free_pgd(mm); 841 destroy_context(mm); 842 mmu_notifier_mm_destroy(mm); 843 check_mm(mm); 844 free_mm(mm); 845 } 846 EXPORT_SYMBOL_GPL(__mmdrop); 847 848 static inline void __mmput(struct mm_struct *mm) 849 { 850 VM_BUG_ON(atomic_read(&mm->mm_users)); 851 852 uprobe_clear_state(mm); 853 exit_aio(mm); 854 ksm_exit(mm); 855 khugepaged_exit(mm); /* must run before exit_mmap */ 856 exit_mmap(mm); 857 mm_put_huge_zero_page(mm); 858 set_mm_exe_file(mm, NULL); 859 if (!list_empty(&mm->mmlist)) { 860 spin_lock(&mmlist_lock); 861 list_del(&mm->mmlist); 862 spin_unlock(&mmlist_lock); 863 } 864 if (mm->binfmt) 865 module_put(mm->binfmt->module); 866 set_bit(MMF_OOM_SKIP, &mm->flags); 867 mmdrop(mm); 868 } 869 870 /* 871 * Decrement the use count and release all resources for an mm. 872 */ 873 void mmput(struct mm_struct *mm) 874 { 875 might_sleep(); 876 877 if (atomic_dec_and_test(&mm->mm_users)) 878 __mmput(mm); 879 } 880 EXPORT_SYMBOL_GPL(mmput); 881 882 #ifdef CONFIG_MMU 883 static void mmput_async_fn(struct work_struct *work) 884 { 885 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 886 __mmput(mm); 887 } 888 889 void mmput_async(struct mm_struct *mm) 890 { 891 if (atomic_dec_and_test(&mm->mm_users)) { 892 INIT_WORK(&mm->async_put_work, mmput_async_fn); 893 schedule_work(&mm->async_put_work); 894 } 895 } 896 #endif 897 898 /** 899 * set_mm_exe_file - change a reference to the mm's executable file 900 * 901 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 902 * 903 * Main users are mmput() and sys_execve(). Callers prevent concurrent 904 * invocations: in mmput() nobody alive left, in execve task is single 905 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 906 * mm->exe_file, but does so without using set_mm_exe_file() in order 907 * to do avoid the need for any locks. 908 */ 909 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 910 { 911 struct file *old_exe_file; 912 913 /* 914 * It is safe to dereference the exe_file without RCU as 915 * this function is only called if nobody else can access 916 * this mm -- see comment above for justification. 917 */ 918 old_exe_file = rcu_dereference_raw(mm->exe_file); 919 920 if (new_exe_file) 921 get_file(new_exe_file); 922 rcu_assign_pointer(mm->exe_file, new_exe_file); 923 if (old_exe_file) 924 fput(old_exe_file); 925 } 926 927 /** 928 * get_mm_exe_file - acquire a reference to the mm's executable file 929 * 930 * Returns %NULL if mm has no associated executable file. 931 * User must release file via fput(). 932 */ 933 struct file *get_mm_exe_file(struct mm_struct *mm) 934 { 935 struct file *exe_file; 936 937 rcu_read_lock(); 938 exe_file = rcu_dereference(mm->exe_file); 939 if (exe_file && !get_file_rcu(exe_file)) 940 exe_file = NULL; 941 rcu_read_unlock(); 942 return exe_file; 943 } 944 EXPORT_SYMBOL(get_mm_exe_file); 945 946 /** 947 * get_task_exe_file - acquire a reference to the task's executable file 948 * 949 * Returns %NULL if task's mm (if any) has no associated executable file or 950 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 951 * User must release file via fput(). 952 */ 953 struct file *get_task_exe_file(struct task_struct *task) 954 { 955 struct file *exe_file = NULL; 956 struct mm_struct *mm; 957 958 task_lock(task); 959 mm = task->mm; 960 if (mm) { 961 if (!(task->flags & PF_KTHREAD)) 962 exe_file = get_mm_exe_file(mm); 963 } 964 task_unlock(task); 965 return exe_file; 966 } 967 EXPORT_SYMBOL(get_task_exe_file); 968 969 /** 970 * get_task_mm - acquire a reference to the task's mm 971 * 972 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 973 * this kernel workthread has transiently adopted a user mm with use_mm, 974 * to do its AIO) is not set and if so returns a reference to it, after 975 * bumping up the use count. User must release the mm via mmput() 976 * after use. Typically used by /proc and ptrace. 977 */ 978 struct mm_struct *get_task_mm(struct task_struct *task) 979 { 980 struct mm_struct *mm; 981 982 task_lock(task); 983 mm = task->mm; 984 if (mm) { 985 if (task->flags & PF_KTHREAD) 986 mm = NULL; 987 else 988 atomic_inc(&mm->mm_users); 989 } 990 task_unlock(task); 991 return mm; 992 } 993 EXPORT_SYMBOL_GPL(get_task_mm); 994 995 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 996 { 997 struct mm_struct *mm; 998 int err; 999 1000 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1001 if (err) 1002 return ERR_PTR(err); 1003 1004 mm = get_task_mm(task); 1005 if (mm && mm != current->mm && 1006 !ptrace_may_access(task, mode)) { 1007 mmput(mm); 1008 mm = ERR_PTR(-EACCES); 1009 } 1010 mutex_unlock(&task->signal->cred_guard_mutex); 1011 1012 return mm; 1013 } 1014 1015 static void complete_vfork_done(struct task_struct *tsk) 1016 { 1017 struct completion *vfork; 1018 1019 task_lock(tsk); 1020 vfork = tsk->vfork_done; 1021 if (likely(vfork)) { 1022 tsk->vfork_done = NULL; 1023 complete(vfork); 1024 } 1025 task_unlock(tsk); 1026 } 1027 1028 static int wait_for_vfork_done(struct task_struct *child, 1029 struct completion *vfork) 1030 { 1031 int killed; 1032 1033 freezer_do_not_count(); 1034 killed = wait_for_completion_killable(vfork); 1035 freezer_count(); 1036 1037 if (killed) { 1038 task_lock(child); 1039 child->vfork_done = NULL; 1040 task_unlock(child); 1041 } 1042 1043 put_task_struct(child); 1044 return killed; 1045 } 1046 1047 /* Please note the differences between mmput and mm_release. 1048 * mmput is called whenever we stop holding onto a mm_struct, 1049 * error success whatever. 1050 * 1051 * mm_release is called after a mm_struct has been removed 1052 * from the current process. 1053 * 1054 * This difference is important for error handling, when we 1055 * only half set up a mm_struct for a new process and need to restore 1056 * the old one. Because we mmput the new mm_struct before 1057 * restoring the old one. . . 1058 * Eric Biederman 10 January 1998 1059 */ 1060 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1061 { 1062 /* Get rid of any futexes when releasing the mm */ 1063 #ifdef CONFIG_FUTEX 1064 if (unlikely(tsk->robust_list)) { 1065 exit_robust_list(tsk); 1066 tsk->robust_list = NULL; 1067 } 1068 #ifdef CONFIG_COMPAT 1069 if (unlikely(tsk->compat_robust_list)) { 1070 compat_exit_robust_list(tsk); 1071 tsk->compat_robust_list = NULL; 1072 } 1073 #endif 1074 if (unlikely(!list_empty(&tsk->pi_state_list))) 1075 exit_pi_state_list(tsk); 1076 #endif 1077 1078 uprobe_free_utask(tsk); 1079 1080 /* Get rid of any cached register state */ 1081 deactivate_mm(tsk, mm); 1082 1083 /* 1084 * Signal userspace if we're not exiting with a core dump 1085 * because we want to leave the value intact for debugging 1086 * purposes. 1087 */ 1088 if (tsk->clear_child_tid) { 1089 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1090 atomic_read(&mm->mm_users) > 1) { 1091 /* 1092 * We don't check the error code - if userspace has 1093 * not set up a proper pointer then tough luck. 1094 */ 1095 put_user(0, tsk->clear_child_tid); 1096 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1097 1, NULL, NULL, 0); 1098 } 1099 tsk->clear_child_tid = NULL; 1100 } 1101 1102 /* 1103 * All done, finally we can wake up parent and return this mm to him. 1104 * Also kthread_stop() uses this completion for synchronization. 1105 */ 1106 if (tsk->vfork_done) 1107 complete_vfork_done(tsk); 1108 } 1109 1110 /* 1111 * Allocate a new mm structure and copy contents from the 1112 * mm structure of the passed in task structure. 1113 */ 1114 static struct mm_struct *dup_mm(struct task_struct *tsk) 1115 { 1116 struct mm_struct *mm, *oldmm = current->mm; 1117 int err; 1118 1119 mm = allocate_mm(); 1120 if (!mm) 1121 goto fail_nomem; 1122 1123 memcpy(mm, oldmm, sizeof(*mm)); 1124 1125 if (!mm_init(mm, tsk)) 1126 goto fail_nomem; 1127 1128 err = dup_mmap(mm, oldmm); 1129 if (err) 1130 goto free_pt; 1131 1132 mm->hiwater_rss = get_mm_rss(mm); 1133 mm->hiwater_vm = mm->total_vm; 1134 1135 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1136 goto free_pt; 1137 1138 return mm; 1139 1140 free_pt: 1141 /* don't put binfmt in mmput, we haven't got module yet */ 1142 mm->binfmt = NULL; 1143 mmput(mm); 1144 1145 fail_nomem: 1146 return NULL; 1147 } 1148 1149 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1150 { 1151 struct mm_struct *mm, *oldmm; 1152 int retval; 1153 1154 tsk->min_flt = tsk->maj_flt = 0; 1155 tsk->nvcsw = tsk->nivcsw = 0; 1156 #ifdef CONFIG_DETECT_HUNG_TASK 1157 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1158 #endif 1159 1160 tsk->mm = NULL; 1161 tsk->active_mm = NULL; 1162 1163 /* 1164 * Are we cloning a kernel thread? 1165 * 1166 * We need to steal a active VM for that.. 1167 */ 1168 oldmm = current->mm; 1169 if (!oldmm) 1170 return 0; 1171 1172 /* initialize the new vmacache entries */ 1173 vmacache_flush(tsk); 1174 1175 if (clone_flags & CLONE_VM) { 1176 atomic_inc(&oldmm->mm_users); 1177 mm = oldmm; 1178 goto good_mm; 1179 } 1180 1181 retval = -ENOMEM; 1182 mm = dup_mm(tsk); 1183 if (!mm) 1184 goto fail_nomem; 1185 1186 good_mm: 1187 tsk->mm = mm; 1188 tsk->active_mm = mm; 1189 return 0; 1190 1191 fail_nomem: 1192 return retval; 1193 } 1194 1195 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1196 { 1197 struct fs_struct *fs = current->fs; 1198 if (clone_flags & CLONE_FS) { 1199 /* tsk->fs is already what we want */ 1200 spin_lock(&fs->lock); 1201 if (fs->in_exec) { 1202 spin_unlock(&fs->lock); 1203 return -EAGAIN; 1204 } 1205 fs->users++; 1206 spin_unlock(&fs->lock); 1207 return 0; 1208 } 1209 tsk->fs = copy_fs_struct(fs); 1210 if (!tsk->fs) 1211 return -ENOMEM; 1212 return 0; 1213 } 1214 1215 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1216 { 1217 struct files_struct *oldf, *newf; 1218 int error = 0; 1219 1220 /* 1221 * A background process may not have any files ... 1222 */ 1223 oldf = current->files; 1224 if (!oldf) 1225 goto out; 1226 1227 if (clone_flags & CLONE_FILES) { 1228 atomic_inc(&oldf->count); 1229 goto out; 1230 } 1231 1232 newf = dup_fd(oldf, &error); 1233 if (!newf) 1234 goto out; 1235 1236 tsk->files = newf; 1237 error = 0; 1238 out: 1239 return error; 1240 } 1241 1242 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1243 { 1244 #ifdef CONFIG_BLOCK 1245 struct io_context *ioc = current->io_context; 1246 struct io_context *new_ioc; 1247 1248 if (!ioc) 1249 return 0; 1250 /* 1251 * Share io context with parent, if CLONE_IO is set 1252 */ 1253 if (clone_flags & CLONE_IO) { 1254 ioc_task_link(ioc); 1255 tsk->io_context = ioc; 1256 } else if (ioprio_valid(ioc->ioprio)) { 1257 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1258 if (unlikely(!new_ioc)) 1259 return -ENOMEM; 1260 1261 new_ioc->ioprio = ioc->ioprio; 1262 put_io_context(new_ioc); 1263 } 1264 #endif 1265 return 0; 1266 } 1267 1268 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1269 { 1270 struct sighand_struct *sig; 1271 1272 if (clone_flags & CLONE_SIGHAND) { 1273 atomic_inc(¤t->sighand->count); 1274 return 0; 1275 } 1276 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1277 rcu_assign_pointer(tsk->sighand, sig); 1278 if (!sig) 1279 return -ENOMEM; 1280 1281 atomic_set(&sig->count, 1); 1282 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1283 return 0; 1284 } 1285 1286 void __cleanup_sighand(struct sighand_struct *sighand) 1287 { 1288 if (atomic_dec_and_test(&sighand->count)) { 1289 signalfd_cleanup(sighand); 1290 /* 1291 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1292 * without an RCU grace period, see __lock_task_sighand(). 1293 */ 1294 kmem_cache_free(sighand_cachep, sighand); 1295 } 1296 } 1297 1298 /* 1299 * Initialize POSIX timer handling for a thread group. 1300 */ 1301 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1302 { 1303 unsigned long cpu_limit; 1304 1305 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1306 if (cpu_limit != RLIM_INFINITY) { 1307 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1308 sig->cputimer.running = true; 1309 } 1310 1311 /* The timer lists. */ 1312 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1313 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1314 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1315 } 1316 1317 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1318 { 1319 struct signal_struct *sig; 1320 1321 if (clone_flags & CLONE_THREAD) 1322 return 0; 1323 1324 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1325 tsk->signal = sig; 1326 if (!sig) 1327 return -ENOMEM; 1328 1329 sig->nr_threads = 1; 1330 atomic_set(&sig->live, 1); 1331 atomic_set(&sig->sigcnt, 1); 1332 1333 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1334 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1335 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1336 1337 init_waitqueue_head(&sig->wait_chldexit); 1338 sig->curr_target = tsk; 1339 init_sigpending(&sig->shared_pending); 1340 INIT_LIST_HEAD(&sig->posix_timers); 1341 seqlock_init(&sig->stats_lock); 1342 prev_cputime_init(&sig->prev_cputime); 1343 1344 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1345 sig->real_timer.function = it_real_fn; 1346 1347 task_lock(current->group_leader); 1348 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1349 task_unlock(current->group_leader); 1350 1351 posix_cpu_timers_init_group(sig); 1352 1353 tty_audit_fork(sig); 1354 sched_autogroup_fork(sig); 1355 1356 sig->oom_score_adj = current->signal->oom_score_adj; 1357 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1358 1359 sig->has_child_subreaper = current->signal->has_child_subreaper || 1360 current->signal->is_child_subreaper; 1361 1362 mutex_init(&sig->cred_guard_mutex); 1363 1364 return 0; 1365 } 1366 1367 static void copy_seccomp(struct task_struct *p) 1368 { 1369 #ifdef CONFIG_SECCOMP 1370 /* 1371 * Must be called with sighand->lock held, which is common to 1372 * all threads in the group. Holding cred_guard_mutex is not 1373 * needed because this new task is not yet running and cannot 1374 * be racing exec. 1375 */ 1376 assert_spin_locked(¤t->sighand->siglock); 1377 1378 /* Ref-count the new filter user, and assign it. */ 1379 get_seccomp_filter(current); 1380 p->seccomp = current->seccomp; 1381 1382 /* 1383 * Explicitly enable no_new_privs here in case it got set 1384 * between the task_struct being duplicated and holding the 1385 * sighand lock. The seccomp state and nnp must be in sync. 1386 */ 1387 if (task_no_new_privs(current)) 1388 task_set_no_new_privs(p); 1389 1390 /* 1391 * If the parent gained a seccomp mode after copying thread 1392 * flags and between before we held the sighand lock, we have 1393 * to manually enable the seccomp thread flag here. 1394 */ 1395 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1396 set_tsk_thread_flag(p, TIF_SECCOMP); 1397 #endif 1398 } 1399 1400 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1401 { 1402 current->clear_child_tid = tidptr; 1403 1404 return task_pid_vnr(current); 1405 } 1406 1407 static void rt_mutex_init_task(struct task_struct *p) 1408 { 1409 raw_spin_lock_init(&p->pi_lock); 1410 #ifdef CONFIG_RT_MUTEXES 1411 p->pi_waiters = RB_ROOT; 1412 p->pi_waiters_leftmost = NULL; 1413 p->pi_blocked_on = NULL; 1414 #endif 1415 } 1416 1417 /* 1418 * Initialize POSIX timer handling for a single task. 1419 */ 1420 static void posix_cpu_timers_init(struct task_struct *tsk) 1421 { 1422 tsk->cputime_expires.prof_exp = 0; 1423 tsk->cputime_expires.virt_exp = 0; 1424 tsk->cputime_expires.sched_exp = 0; 1425 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1426 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1427 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1428 } 1429 1430 static inline void 1431 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1432 { 1433 task->pids[type].pid = pid; 1434 } 1435 1436 /* 1437 * This creates a new process as a copy of the old one, 1438 * but does not actually start it yet. 1439 * 1440 * It copies the registers, and all the appropriate 1441 * parts of the process environment (as per the clone 1442 * flags). The actual kick-off is left to the caller. 1443 */ 1444 static struct task_struct *copy_process(unsigned long clone_flags, 1445 unsigned long stack_start, 1446 unsigned long stack_size, 1447 int __user *child_tidptr, 1448 struct pid *pid, 1449 int trace, 1450 unsigned long tls, 1451 int node) 1452 { 1453 int retval; 1454 struct task_struct *p; 1455 1456 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1457 return ERR_PTR(-EINVAL); 1458 1459 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1460 return ERR_PTR(-EINVAL); 1461 1462 /* 1463 * Thread groups must share signals as well, and detached threads 1464 * can only be started up within the thread group. 1465 */ 1466 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1467 return ERR_PTR(-EINVAL); 1468 1469 /* 1470 * Shared signal handlers imply shared VM. By way of the above, 1471 * thread groups also imply shared VM. Blocking this case allows 1472 * for various simplifications in other code. 1473 */ 1474 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1475 return ERR_PTR(-EINVAL); 1476 1477 /* 1478 * Siblings of global init remain as zombies on exit since they are 1479 * not reaped by their parent (swapper). To solve this and to avoid 1480 * multi-rooted process trees, prevent global and container-inits 1481 * from creating siblings. 1482 */ 1483 if ((clone_flags & CLONE_PARENT) && 1484 current->signal->flags & SIGNAL_UNKILLABLE) 1485 return ERR_PTR(-EINVAL); 1486 1487 /* 1488 * If the new process will be in a different pid or user namespace 1489 * do not allow it to share a thread group with the forking task. 1490 */ 1491 if (clone_flags & CLONE_THREAD) { 1492 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1493 (task_active_pid_ns(current) != 1494 current->nsproxy->pid_ns_for_children)) 1495 return ERR_PTR(-EINVAL); 1496 } 1497 1498 retval = security_task_create(clone_flags); 1499 if (retval) 1500 goto fork_out; 1501 1502 retval = -ENOMEM; 1503 p = dup_task_struct(current, node); 1504 if (!p) 1505 goto fork_out; 1506 1507 ftrace_graph_init_task(p); 1508 1509 rt_mutex_init_task(p); 1510 1511 #ifdef CONFIG_PROVE_LOCKING 1512 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1513 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1514 #endif 1515 retval = -EAGAIN; 1516 if (atomic_read(&p->real_cred->user->processes) >= 1517 task_rlimit(p, RLIMIT_NPROC)) { 1518 if (p->real_cred->user != INIT_USER && 1519 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1520 goto bad_fork_free; 1521 } 1522 current->flags &= ~PF_NPROC_EXCEEDED; 1523 1524 retval = copy_creds(p, clone_flags); 1525 if (retval < 0) 1526 goto bad_fork_free; 1527 1528 /* 1529 * If multiple threads are within copy_process(), then this check 1530 * triggers too late. This doesn't hurt, the check is only there 1531 * to stop root fork bombs. 1532 */ 1533 retval = -EAGAIN; 1534 if (nr_threads >= max_threads) 1535 goto bad_fork_cleanup_count; 1536 1537 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1538 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1539 p->flags |= PF_FORKNOEXEC; 1540 INIT_LIST_HEAD(&p->children); 1541 INIT_LIST_HEAD(&p->sibling); 1542 rcu_copy_process(p); 1543 p->vfork_done = NULL; 1544 spin_lock_init(&p->alloc_lock); 1545 1546 init_sigpending(&p->pending); 1547 1548 p->utime = p->stime = p->gtime = 0; 1549 p->utimescaled = p->stimescaled = 0; 1550 prev_cputime_init(&p->prev_cputime); 1551 1552 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1553 seqcount_init(&p->vtime_seqcount); 1554 p->vtime_snap = 0; 1555 p->vtime_snap_whence = VTIME_INACTIVE; 1556 #endif 1557 1558 #if defined(SPLIT_RSS_COUNTING) 1559 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1560 #endif 1561 1562 p->default_timer_slack_ns = current->timer_slack_ns; 1563 1564 task_io_accounting_init(&p->ioac); 1565 acct_clear_integrals(p); 1566 1567 posix_cpu_timers_init(p); 1568 1569 p->start_time = ktime_get_ns(); 1570 p->real_start_time = ktime_get_boot_ns(); 1571 p->io_context = NULL; 1572 p->audit_context = NULL; 1573 cgroup_fork(p); 1574 #ifdef CONFIG_NUMA 1575 p->mempolicy = mpol_dup(p->mempolicy); 1576 if (IS_ERR(p->mempolicy)) { 1577 retval = PTR_ERR(p->mempolicy); 1578 p->mempolicy = NULL; 1579 goto bad_fork_cleanup_threadgroup_lock; 1580 } 1581 #endif 1582 #ifdef CONFIG_CPUSETS 1583 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1584 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1585 seqcount_init(&p->mems_allowed_seq); 1586 #endif 1587 #ifdef CONFIG_TRACE_IRQFLAGS 1588 p->irq_events = 0; 1589 p->hardirqs_enabled = 0; 1590 p->hardirq_enable_ip = 0; 1591 p->hardirq_enable_event = 0; 1592 p->hardirq_disable_ip = _THIS_IP_; 1593 p->hardirq_disable_event = 0; 1594 p->softirqs_enabled = 1; 1595 p->softirq_enable_ip = _THIS_IP_; 1596 p->softirq_enable_event = 0; 1597 p->softirq_disable_ip = 0; 1598 p->softirq_disable_event = 0; 1599 p->hardirq_context = 0; 1600 p->softirq_context = 0; 1601 #endif 1602 1603 p->pagefault_disabled = 0; 1604 1605 #ifdef CONFIG_LOCKDEP 1606 p->lockdep_depth = 0; /* no locks held yet */ 1607 p->curr_chain_key = 0; 1608 p->lockdep_recursion = 0; 1609 #endif 1610 1611 #ifdef CONFIG_DEBUG_MUTEXES 1612 p->blocked_on = NULL; /* not blocked yet */ 1613 #endif 1614 #ifdef CONFIG_BCACHE 1615 p->sequential_io = 0; 1616 p->sequential_io_avg = 0; 1617 #endif 1618 1619 /* Perform scheduler related setup. Assign this task to a CPU. */ 1620 retval = sched_fork(clone_flags, p); 1621 if (retval) 1622 goto bad_fork_cleanup_policy; 1623 1624 retval = perf_event_init_task(p); 1625 if (retval) 1626 goto bad_fork_cleanup_policy; 1627 retval = audit_alloc(p); 1628 if (retval) 1629 goto bad_fork_cleanup_perf; 1630 /* copy all the process information */ 1631 shm_init_task(p); 1632 retval = copy_semundo(clone_flags, p); 1633 if (retval) 1634 goto bad_fork_cleanup_audit; 1635 retval = copy_files(clone_flags, p); 1636 if (retval) 1637 goto bad_fork_cleanup_semundo; 1638 retval = copy_fs(clone_flags, p); 1639 if (retval) 1640 goto bad_fork_cleanup_files; 1641 retval = copy_sighand(clone_flags, p); 1642 if (retval) 1643 goto bad_fork_cleanup_fs; 1644 retval = copy_signal(clone_flags, p); 1645 if (retval) 1646 goto bad_fork_cleanup_sighand; 1647 retval = copy_mm(clone_flags, p); 1648 if (retval) 1649 goto bad_fork_cleanup_signal; 1650 retval = copy_namespaces(clone_flags, p); 1651 if (retval) 1652 goto bad_fork_cleanup_mm; 1653 retval = copy_io(clone_flags, p); 1654 if (retval) 1655 goto bad_fork_cleanup_namespaces; 1656 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1657 if (retval) 1658 goto bad_fork_cleanup_io; 1659 1660 if (pid != &init_struct_pid) { 1661 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1662 if (IS_ERR(pid)) { 1663 retval = PTR_ERR(pid); 1664 goto bad_fork_cleanup_thread; 1665 } 1666 } 1667 1668 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1669 /* 1670 * Clear TID on mm_release()? 1671 */ 1672 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1673 #ifdef CONFIG_BLOCK 1674 p->plug = NULL; 1675 #endif 1676 #ifdef CONFIG_FUTEX 1677 p->robust_list = NULL; 1678 #ifdef CONFIG_COMPAT 1679 p->compat_robust_list = NULL; 1680 #endif 1681 INIT_LIST_HEAD(&p->pi_state_list); 1682 p->pi_state_cache = NULL; 1683 #endif 1684 /* 1685 * sigaltstack should be cleared when sharing the same VM 1686 */ 1687 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1688 sas_ss_reset(p); 1689 1690 /* 1691 * Syscall tracing and stepping should be turned off in the 1692 * child regardless of CLONE_PTRACE. 1693 */ 1694 user_disable_single_step(p); 1695 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1696 #ifdef TIF_SYSCALL_EMU 1697 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1698 #endif 1699 clear_all_latency_tracing(p); 1700 1701 /* ok, now we should be set up.. */ 1702 p->pid = pid_nr(pid); 1703 if (clone_flags & CLONE_THREAD) { 1704 p->exit_signal = -1; 1705 p->group_leader = current->group_leader; 1706 p->tgid = current->tgid; 1707 } else { 1708 if (clone_flags & CLONE_PARENT) 1709 p->exit_signal = current->group_leader->exit_signal; 1710 else 1711 p->exit_signal = (clone_flags & CSIGNAL); 1712 p->group_leader = p; 1713 p->tgid = p->pid; 1714 } 1715 1716 p->nr_dirtied = 0; 1717 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1718 p->dirty_paused_when = 0; 1719 1720 p->pdeath_signal = 0; 1721 INIT_LIST_HEAD(&p->thread_group); 1722 p->task_works = NULL; 1723 1724 threadgroup_change_begin(current); 1725 /* 1726 * Ensure that the cgroup subsystem policies allow the new process to be 1727 * forked. It should be noted the the new process's css_set can be changed 1728 * between here and cgroup_post_fork() if an organisation operation is in 1729 * progress. 1730 */ 1731 retval = cgroup_can_fork(p); 1732 if (retval) 1733 goto bad_fork_free_pid; 1734 1735 /* 1736 * Make it visible to the rest of the system, but dont wake it up yet. 1737 * Need tasklist lock for parent etc handling! 1738 */ 1739 write_lock_irq(&tasklist_lock); 1740 1741 /* CLONE_PARENT re-uses the old parent */ 1742 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1743 p->real_parent = current->real_parent; 1744 p->parent_exec_id = current->parent_exec_id; 1745 } else { 1746 p->real_parent = current; 1747 p->parent_exec_id = current->self_exec_id; 1748 } 1749 1750 spin_lock(¤t->sighand->siglock); 1751 1752 /* 1753 * Copy seccomp details explicitly here, in case they were changed 1754 * before holding sighand lock. 1755 */ 1756 copy_seccomp(p); 1757 1758 /* 1759 * Process group and session signals need to be delivered to just the 1760 * parent before the fork or both the parent and the child after the 1761 * fork. Restart if a signal comes in before we add the new process to 1762 * it's process group. 1763 * A fatal signal pending means that current will exit, so the new 1764 * thread can't slip out of an OOM kill (or normal SIGKILL). 1765 */ 1766 recalc_sigpending(); 1767 if (signal_pending(current)) { 1768 spin_unlock(¤t->sighand->siglock); 1769 write_unlock_irq(&tasklist_lock); 1770 retval = -ERESTARTNOINTR; 1771 goto bad_fork_cancel_cgroup; 1772 } 1773 1774 if (likely(p->pid)) { 1775 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1776 1777 init_task_pid(p, PIDTYPE_PID, pid); 1778 if (thread_group_leader(p)) { 1779 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1780 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1781 1782 if (is_child_reaper(pid)) { 1783 ns_of_pid(pid)->child_reaper = p; 1784 p->signal->flags |= SIGNAL_UNKILLABLE; 1785 } 1786 1787 p->signal->leader_pid = pid; 1788 p->signal->tty = tty_kref_get(current->signal->tty); 1789 list_add_tail(&p->sibling, &p->real_parent->children); 1790 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1791 attach_pid(p, PIDTYPE_PGID); 1792 attach_pid(p, PIDTYPE_SID); 1793 __this_cpu_inc(process_counts); 1794 } else { 1795 current->signal->nr_threads++; 1796 atomic_inc(¤t->signal->live); 1797 atomic_inc(¤t->signal->sigcnt); 1798 list_add_tail_rcu(&p->thread_group, 1799 &p->group_leader->thread_group); 1800 list_add_tail_rcu(&p->thread_node, 1801 &p->signal->thread_head); 1802 } 1803 attach_pid(p, PIDTYPE_PID); 1804 nr_threads++; 1805 } 1806 1807 total_forks++; 1808 spin_unlock(¤t->sighand->siglock); 1809 syscall_tracepoint_update(p); 1810 write_unlock_irq(&tasklist_lock); 1811 1812 proc_fork_connector(p); 1813 cgroup_post_fork(p); 1814 threadgroup_change_end(current); 1815 perf_event_fork(p); 1816 1817 trace_task_newtask(p, clone_flags); 1818 uprobe_copy_process(p, clone_flags); 1819 1820 return p; 1821 1822 bad_fork_cancel_cgroup: 1823 cgroup_cancel_fork(p); 1824 bad_fork_free_pid: 1825 threadgroup_change_end(current); 1826 if (pid != &init_struct_pid) 1827 free_pid(pid); 1828 bad_fork_cleanup_thread: 1829 exit_thread(p); 1830 bad_fork_cleanup_io: 1831 if (p->io_context) 1832 exit_io_context(p); 1833 bad_fork_cleanup_namespaces: 1834 exit_task_namespaces(p); 1835 bad_fork_cleanup_mm: 1836 if (p->mm) 1837 mmput(p->mm); 1838 bad_fork_cleanup_signal: 1839 if (!(clone_flags & CLONE_THREAD)) 1840 free_signal_struct(p->signal); 1841 bad_fork_cleanup_sighand: 1842 __cleanup_sighand(p->sighand); 1843 bad_fork_cleanup_fs: 1844 exit_fs(p); /* blocking */ 1845 bad_fork_cleanup_files: 1846 exit_files(p); /* blocking */ 1847 bad_fork_cleanup_semundo: 1848 exit_sem(p); 1849 bad_fork_cleanup_audit: 1850 audit_free(p); 1851 bad_fork_cleanup_perf: 1852 perf_event_free_task(p); 1853 bad_fork_cleanup_policy: 1854 #ifdef CONFIG_NUMA 1855 mpol_put(p->mempolicy); 1856 bad_fork_cleanup_threadgroup_lock: 1857 #endif 1858 delayacct_tsk_free(p); 1859 bad_fork_cleanup_count: 1860 atomic_dec(&p->cred->user->processes); 1861 exit_creds(p); 1862 bad_fork_free: 1863 put_task_stack(p); 1864 free_task(p); 1865 fork_out: 1866 return ERR_PTR(retval); 1867 } 1868 1869 static inline void init_idle_pids(struct pid_link *links) 1870 { 1871 enum pid_type type; 1872 1873 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1874 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1875 links[type].pid = &init_struct_pid; 1876 } 1877 } 1878 1879 struct task_struct *fork_idle(int cpu) 1880 { 1881 struct task_struct *task; 1882 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1883 cpu_to_node(cpu)); 1884 if (!IS_ERR(task)) { 1885 init_idle_pids(task->pids); 1886 init_idle(task, cpu); 1887 } 1888 1889 return task; 1890 } 1891 1892 /* 1893 * Ok, this is the main fork-routine. 1894 * 1895 * It copies the process, and if successful kick-starts 1896 * it and waits for it to finish using the VM if required. 1897 */ 1898 long _do_fork(unsigned long clone_flags, 1899 unsigned long stack_start, 1900 unsigned long stack_size, 1901 int __user *parent_tidptr, 1902 int __user *child_tidptr, 1903 unsigned long tls) 1904 { 1905 struct task_struct *p; 1906 int trace = 0; 1907 long nr; 1908 1909 /* 1910 * Determine whether and which event to report to ptracer. When 1911 * called from kernel_thread or CLONE_UNTRACED is explicitly 1912 * requested, no event is reported; otherwise, report if the event 1913 * for the type of forking is enabled. 1914 */ 1915 if (!(clone_flags & CLONE_UNTRACED)) { 1916 if (clone_flags & CLONE_VFORK) 1917 trace = PTRACE_EVENT_VFORK; 1918 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1919 trace = PTRACE_EVENT_CLONE; 1920 else 1921 trace = PTRACE_EVENT_FORK; 1922 1923 if (likely(!ptrace_event_enabled(current, trace))) 1924 trace = 0; 1925 } 1926 1927 p = copy_process(clone_flags, stack_start, stack_size, 1928 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 1929 /* 1930 * Do this prior waking up the new thread - the thread pointer 1931 * might get invalid after that point, if the thread exits quickly. 1932 */ 1933 if (!IS_ERR(p)) { 1934 struct completion vfork; 1935 struct pid *pid; 1936 1937 trace_sched_process_fork(current, p); 1938 1939 pid = get_task_pid(p, PIDTYPE_PID); 1940 nr = pid_vnr(pid); 1941 1942 if (clone_flags & CLONE_PARENT_SETTID) 1943 put_user(nr, parent_tidptr); 1944 1945 if (clone_flags & CLONE_VFORK) { 1946 p->vfork_done = &vfork; 1947 init_completion(&vfork); 1948 get_task_struct(p); 1949 } 1950 1951 wake_up_new_task(p); 1952 1953 /* forking complete and child started to run, tell ptracer */ 1954 if (unlikely(trace)) 1955 ptrace_event_pid(trace, pid); 1956 1957 if (clone_flags & CLONE_VFORK) { 1958 if (!wait_for_vfork_done(p, &vfork)) 1959 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 1960 } 1961 1962 put_pid(pid); 1963 } else { 1964 nr = PTR_ERR(p); 1965 } 1966 return nr; 1967 } 1968 1969 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 1970 /* For compatibility with architectures that call do_fork directly rather than 1971 * using the syscall entry points below. */ 1972 long do_fork(unsigned long clone_flags, 1973 unsigned long stack_start, 1974 unsigned long stack_size, 1975 int __user *parent_tidptr, 1976 int __user *child_tidptr) 1977 { 1978 return _do_fork(clone_flags, stack_start, stack_size, 1979 parent_tidptr, child_tidptr, 0); 1980 } 1981 #endif 1982 1983 /* 1984 * Create a kernel thread. 1985 */ 1986 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 1987 { 1988 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 1989 (unsigned long)arg, NULL, NULL, 0); 1990 } 1991 1992 #ifdef __ARCH_WANT_SYS_FORK 1993 SYSCALL_DEFINE0(fork) 1994 { 1995 #ifdef CONFIG_MMU 1996 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 1997 #else 1998 /* can not support in nommu mode */ 1999 return -EINVAL; 2000 #endif 2001 } 2002 #endif 2003 2004 #ifdef __ARCH_WANT_SYS_VFORK 2005 SYSCALL_DEFINE0(vfork) 2006 { 2007 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2008 0, NULL, NULL, 0); 2009 } 2010 #endif 2011 2012 #ifdef __ARCH_WANT_SYS_CLONE 2013 #ifdef CONFIG_CLONE_BACKWARDS 2014 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2015 int __user *, parent_tidptr, 2016 unsigned long, tls, 2017 int __user *, child_tidptr) 2018 #elif defined(CONFIG_CLONE_BACKWARDS2) 2019 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2020 int __user *, parent_tidptr, 2021 int __user *, child_tidptr, 2022 unsigned long, tls) 2023 #elif defined(CONFIG_CLONE_BACKWARDS3) 2024 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2025 int, stack_size, 2026 int __user *, parent_tidptr, 2027 int __user *, child_tidptr, 2028 unsigned long, tls) 2029 #else 2030 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2031 int __user *, parent_tidptr, 2032 int __user *, child_tidptr, 2033 unsigned long, tls) 2034 #endif 2035 { 2036 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2037 } 2038 #endif 2039 2040 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2041 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2042 #endif 2043 2044 static void sighand_ctor(void *data) 2045 { 2046 struct sighand_struct *sighand = data; 2047 2048 spin_lock_init(&sighand->siglock); 2049 init_waitqueue_head(&sighand->signalfd_wqh); 2050 } 2051 2052 void __init proc_caches_init(void) 2053 { 2054 sighand_cachep = kmem_cache_create("sighand_cache", 2055 sizeof(struct sighand_struct), 0, 2056 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 2057 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2058 signal_cachep = kmem_cache_create("signal_cache", 2059 sizeof(struct signal_struct), 0, 2060 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2061 NULL); 2062 files_cachep = kmem_cache_create("files_cache", 2063 sizeof(struct files_struct), 0, 2064 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2065 NULL); 2066 fs_cachep = kmem_cache_create("fs_cache", 2067 sizeof(struct fs_struct), 0, 2068 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2069 NULL); 2070 /* 2071 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2072 * whole struct cpumask for the OFFSTACK case. We could change 2073 * this to *only* allocate as much of it as required by the 2074 * maximum number of CPU's we can ever have. The cpumask_allocation 2075 * is at the end of the structure, exactly for that reason. 2076 */ 2077 mm_cachep = kmem_cache_create("mm_struct", 2078 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2079 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2080 NULL); 2081 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2082 mmap_init(); 2083 nsproxy_cache_init(); 2084 } 2085 2086 /* 2087 * Check constraints on flags passed to the unshare system call. 2088 */ 2089 static int check_unshare_flags(unsigned long unshare_flags) 2090 { 2091 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2092 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2093 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2094 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2095 return -EINVAL; 2096 /* 2097 * Not implemented, but pretend it works if there is nothing 2098 * to unshare. Note that unsharing the address space or the 2099 * signal handlers also need to unshare the signal queues (aka 2100 * CLONE_THREAD). 2101 */ 2102 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2103 if (!thread_group_empty(current)) 2104 return -EINVAL; 2105 } 2106 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2107 if (atomic_read(¤t->sighand->count) > 1) 2108 return -EINVAL; 2109 } 2110 if (unshare_flags & CLONE_VM) { 2111 if (!current_is_single_threaded()) 2112 return -EINVAL; 2113 } 2114 2115 return 0; 2116 } 2117 2118 /* 2119 * Unshare the filesystem structure if it is being shared 2120 */ 2121 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2122 { 2123 struct fs_struct *fs = current->fs; 2124 2125 if (!(unshare_flags & CLONE_FS) || !fs) 2126 return 0; 2127 2128 /* don't need lock here; in the worst case we'll do useless copy */ 2129 if (fs->users == 1) 2130 return 0; 2131 2132 *new_fsp = copy_fs_struct(fs); 2133 if (!*new_fsp) 2134 return -ENOMEM; 2135 2136 return 0; 2137 } 2138 2139 /* 2140 * Unshare file descriptor table if it is being shared 2141 */ 2142 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2143 { 2144 struct files_struct *fd = current->files; 2145 int error = 0; 2146 2147 if ((unshare_flags & CLONE_FILES) && 2148 (fd && atomic_read(&fd->count) > 1)) { 2149 *new_fdp = dup_fd(fd, &error); 2150 if (!*new_fdp) 2151 return error; 2152 } 2153 2154 return 0; 2155 } 2156 2157 /* 2158 * unshare allows a process to 'unshare' part of the process 2159 * context which was originally shared using clone. copy_* 2160 * functions used by do_fork() cannot be used here directly 2161 * because they modify an inactive task_struct that is being 2162 * constructed. Here we are modifying the current, active, 2163 * task_struct. 2164 */ 2165 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2166 { 2167 struct fs_struct *fs, *new_fs = NULL; 2168 struct files_struct *fd, *new_fd = NULL; 2169 struct cred *new_cred = NULL; 2170 struct nsproxy *new_nsproxy = NULL; 2171 int do_sysvsem = 0; 2172 int err; 2173 2174 /* 2175 * If unsharing a user namespace must also unshare the thread group 2176 * and unshare the filesystem root and working directories. 2177 */ 2178 if (unshare_flags & CLONE_NEWUSER) 2179 unshare_flags |= CLONE_THREAD | CLONE_FS; 2180 /* 2181 * If unsharing vm, must also unshare signal handlers. 2182 */ 2183 if (unshare_flags & CLONE_VM) 2184 unshare_flags |= CLONE_SIGHAND; 2185 /* 2186 * If unsharing a signal handlers, must also unshare the signal queues. 2187 */ 2188 if (unshare_flags & CLONE_SIGHAND) 2189 unshare_flags |= CLONE_THREAD; 2190 /* 2191 * If unsharing namespace, must also unshare filesystem information. 2192 */ 2193 if (unshare_flags & CLONE_NEWNS) 2194 unshare_flags |= CLONE_FS; 2195 2196 err = check_unshare_flags(unshare_flags); 2197 if (err) 2198 goto bad_unshare_out; 2199 /* 2200 * CLONE_NEWIPC must also detach from the undolist: after switching 2201 * to a new ipc namespace, the semaphore arrays from the old 2202 * namespace are unreachable. 2203 */ 2204 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2205 do_sysvsem = 1; 2206 err = unshare_fs(unshare_flags, &new_fs); 2207 if (err) 2208 goto bad_unshare_out; 2209 err = unshare_fd(unshare_flags, &new_fd); 2210 if (err) 2211 goto bad_unshare_cleanup_fs; 2212 err = unshare_userns(unshare_flags, &new_cred); 2213 if (err) 2214 goto bad_unshare_cleanup_fd; 2215 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2216 new_cred, new_fs); 2217 if (err) 2218 goto bad_unshare_cleanup_cred; 2219 2220 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2221 if (do_sysvsem) { 2222 /* 2223 * CLONE_SYSVSEM is equivalent to sys_exit(). 2224 */ 2225 exit_sem(current); 2226 } 2227 if (unshare_flags & CLONE_NEWIPC) { 2228 /* Orphan segments in old ns (see sem above). */ 2229 exit_shm(current); 2230 shm_init_task(current); 2231 } 2232 2233 if (new_nsproxy) 2234 switch_task_namespaces(current, new_nsproxy); 2235 2236 task_lock(current); 2237 2238 if (new_fs) { 2239 fs = current->fs; 2240 spin_lock(&fs->lock); 2241 current->fs = new_fs; 2242 if (--fs->users) 2243 new_fs = NULL; 2244 else 2245 new_fs = fs; 2246 spin_unlock(&fs->lock); 2247 } 2248 2249 if (new_fd) { 2250 fd = current->files; 2251 current->files = new_fd; 2252 new_fd = fd; 2253 } 2254 2255 task_unlock(current); 2256 2257 if (new_cred) { 2258 /* Install the new user namespace */ 2259 commit_creds(new_cred); 2260 new_cred = NULL; 2261 } 2262 } 2263 2264 bad_unshare_cleanup_cred: 2265 if (new_cred) 2266 put_cred(new_cred); 2267 bad_unshare_cleanup_fd: 2268 if (new_fd) 2269 put_files_struct(new_fd); 2270 2271 bad_unshare_cleanup_fs: 2272 if (new_fs) 2273 free_fs_struct(new_fs); 2274 2275 bad_unshare_out: 2276 return err; 2277 } 2278 2279 /* 2280 * Helper to unshare the files of the current task. 2281 * We don't want to expose copy_files internals to 2282 * the exec layer of the kernel. 2283 */ 2284 2285 int unshare_files(struct files_struct **displaced) 2286 { 2287 struct task_struct *task = current; 2288 struct files_struct *copy = NULL; 2289 int error; 2290 2291 error = unshare_fd(CLONE_FILES, ©); 2292 if (error || !copy) { 2293 *displaced = NULL; 2294 return error; 2295 } 2296 *displaced = task->files; 2297 task_lock(task); 2298 task->files = copy; 2299 task_unlock(task); 2300 return 0; 2301 } 2302 2303 int sysctl_max_threads(struct ctl_table *table, int write, 2304 void __user *buffer, size_t *lenp, loff_t *ppos) 2305 { 2306 struct ctl_table t; 2307 int ret; 2308 int threads = max_threads; 2309 int min = MIN_THREADS; 2310 int max = MAX_THREADS; 2311 2312 t = *table; 2313 t.data = &threads; 2314 t.extra1 = &min; 2315 t.extra2 = &max; 2316 2317 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2318 if (ret || !write) 2319 return ret; 2320 2321 set_max_threads(threads); 2322 2323 return 0; 2324 } 2325