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/sched/autogroup.h> 16 #include <linux/sched/mm.h> 17 #include <linux/sched/coredump.h> 18 #include <linux/sched/user.h> 19 #include <linux/sched/numa_balancing.h> 20 #include <linux/sched/stat.h> 21 #include <linux/sched/task.h> 22 #include <linux/sched/task_stack.h> 23 #include <linux/sched/cputime.h> 24 #include <linux/rtmutex.h> 25 #include <linux/init.h> 26 #include <linux/unistd.h> 27 #include <linux/module.h> 28 #include <linux/vmalloc.h> 29 #include <linux/completion.h> 30 #include <linux/personality.h> 31 #include <linux/mempolicy.h> 32 #include <linux/sem.h> 33 #include <linux/file.h> 34 #include <linux/fdtable.h> 35 #include <linux/iocontext.h> 36 #include <linux/key.h> 37 #include <linux/binfmts.h> 38 #include <linux/mman.h> 39 #include <linux/mmu_notifier.h> 40 #include <linux/fs.h> 41 #include <linux/mm.h> 42 #include <linux/vmacache.h> 43 #include <linux/nsproxy.h> 44 #include <linux/capability.h> 45 #include <linux/cpu.h> 46 #include <linux/cgroup.h> 47 #include <linux/security.h> 48 #include <linux/hugetlb.h> 49 #include <linux/seccomp.h> 50 #include <linux/swap.h> 51 #include <linux/syscalls.h> 52 #include <linux/jiffies.h> 53 #include <linux/futex.h> 54 #include <linux/compat.h> 55 #include <linux/kthread.h> 56 #include <linux/task_io_accounting_ops.h> 57 #include <linux/rcupdate.h> 58 #include <linux/ptrace.h> 59 #include <linux/mount.h> 60 #include <linux/audit.h> 61 #include <linux/memcontrol.h> 62 #include <linux/ftrace.h> 63 #include <linux/proc_fs.h> 64 #include <linux/profile.h> 65 #include <linux/rmap.h> 66 #include <linux/ksm.h> 67 #include <linux/acct.h> 68 #include <linux/userfaultfd_k.h> 69 #include <linux/tsacct_kern.h> 70 #include <linux/cn_proc.h> 71 #include <linux/freezer.h> 72 #include <linux/delayacct.h> 73 #include <linux/taskstats_kern.h> 74 #include <linux/random.h> 75 #include <linux/tty.h> 76 #include <linux/blkdev.h> 77 #include <linux/fs_struct.h> 78 #include <linux/magic.h> 79 #include <linux/perf_event.h> 80 #include <linux/posix-timers.h> 81 #include <linux/user-return-notifier.h> 82 #include <linux/oom.h> 83 #include <linux/khugepaged.h> 84 #include <linux/signalfd.h> 85 #include <linux/uprobes.h> 86 #include <linux/aio.h> 87 #include <linux/compiler.h> 88 #include <linux/sysctl.h> 89 #include <linux/kcov.h> 90 #include <linux/livepatch.h> 91 92 #include <asm/pgtable.h> 93 #include <asm/pgalloc.h> 94 #include <linux/uaccess.h> 95 #include <asm/mmu_context.h> 96 #include <asm/cacheflush.h> 97 #include <asm/tlbflush.h> 98 99 #include <trace/events/sched.h> 100 101 #define CREATE_TRACE_POINTS 102 #include <trace/events/task.h> 103 104 /* 105 * Minimum number of threads to boot the kernel 106 */ 107 #define MIN_THREADS 20 108 109 /* 110 * Maximum number of threads 111 */ 112 #define MAX_THREADS FUTEX_TID_MASK 113 114 /* 115 * Protected counters by write_lock_irq(&tasklist_lock) 116 */ 117 unsigned long total_forks; /* Handle normal Linux uptimes. */ 118 int nr_threads; /* The idle threads do not count.. */ 119 120 int max_threads; /* tunable limit on nr_threads */ 121 122 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 123 124 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 125 126 #ifdef CONFIG_PROVE_RCU 127 int lockdep_tasklist_lock_is_held(void) 128 { 129 return lockdep_is_held(&tasklist_lock); 130 } 131 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 132 #endif /* #ifdef CONFIG_PROVE_RCU */ 133 134 int nr_processes(void) 135 { 136 int cpu; 137 int total = 0; 138 139 for_each_possible_cpu(cpu) 140 total += per_cpu(process_counts, cpu); 141 142 return total; 143 } 144 145 void __weak arch_release_task_struct(struct task_struct *tsk) 146 { 147 } 148 149 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 150 static struct kmem_cache *task_struct_cachep; 151 152 static inline struct task_struct *alloc_task_struct_node(int node) 153 { 154 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 155 } 156 157 static inline void free_task_struct(struct task_struct *tsk) 158 { 159 kmem_cache_free(task_struct_cachep, tsk); 160 } 161 #endif 162 163 void __weak arch_release_thread_stack(unsigned long *stack) 164 { 165 } 166 167 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 168 169 /* 170 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 171 * kmemcache based allocator. 172 */ 173 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 174 175 #ifdef CONFIG_VMAP_STACK 176 /* 177 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 178 * flush. Try to minimize the number of calls by caching stacks. 179 */ 180 #define NR_CACHED_STACKS 2 181 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 182 183 static int free_vm_stack_cache(unsigned int cpu) 184 { 185 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 186 int i; 187 188 for (i = 0; i < NR_CACHED_STACKS; i++) { 189 struct vm_struct *vm_stack = cached_vm_stacks[i]; 190 191 if (!vm_stack) 192 continue; 193 194 vfree(vm_stack->addr); 195 cached_vm_stacks[i] = NULL; 196 } 197 198 return 0; 199 } 200 #endif 201 202 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 203 { 204 #ifdef CONFIG_VMAP_STACK 205 void *stack; 206 int i; 207 208 for (i = 0; i < NR_CACHED_STACKS; i++) { 209 struct vm_struct *s; 210 211 s = this_cpu_xchg(cached_stacks[i], NULL); 212 213 if (!s) 214 continue; 215 216 tsk->stack_vm_area = s; 217 return s->addr; 218 } 219 220 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, 221 VMALLOC_START, VMALLOC_END, 222 THREADINFO_GFP, 223 PAGE_KERNEL, 224 0, node, __builtin_return_address(0)); 225 226 /* 227 * We can't call find_vm_area() in interrupt context, and 228 * free_thread_stack() can be called in interrupt context, 229 * so cache the vm_struct. 230 */ 231 if (stack) 232 tsk->stack_vm_area = find_vm_area(stack); 233 return stack; 234 #else 235 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 236 THREAD_SIZE_ORDER); 237 238 return page ? page_address(page) : NULL; 239 #endif 240 } 241 242 static inline void free_thread_stack(struct task_struct *tsk) 243 { 244 #ifdef CONFIG_VMAP_STACK 245 if (task_stack_vm_area(tsk)) { 246 int i; 247 248 for (i = 0; i < NR_CACHED_STACKS; i++) { 249 if (this_cpu_cmpxchg(cached_stacks[i], 250 NULL, tsk->stack_vm_area) != NULL) 251 continue; 252 253 return; 254 } 255 256 vfree_atomic(tsk->stack); 257 return; 258 } 259 #endif 260 261 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 262 } 263 # else 264 static struct kmem_cache *thread_stack_cache; 265 266 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 267 int node) 268 { 269 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 270 } 271 272 static void free_thread_stack(struct task_struct *tsk) 273 { 274 kmem_cache_free(thread_stack_cache, tsk->stack); 275 } 276 277 void thread_stack_cache_init(void) 278 { 279 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 280 THREAD_SIZE, 0, NULL); 281 BUG_ON(thread_stack_cache == NULL); 282 } 283 # endif 284 #endif 285 286 /* SLAB cache for signal_struct structures (tsk->signal) */ 287 static struct kmem_cache *signal_cachep; 288 289 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 290 struct kmem_cache *sighand_cachep; 291 292 /* SLAB cache for files_struct structures (tsk->files) */ 293 struct kmem_cache *files_cachep; 294 295 /* SLAB cache for fs_struct structures (tsk->fs) */ 296 struct kmem_cache *fs_cachep; 297 298 /* SLAB cache for vm_area_struct structures */ 299 struct kmem_cache *vm_area_cachep; 300 301 /* SLAB cache for mm_struct structures (tsk->mm) */ 302 static struct kmem_cache *mm_cachep; 303 304 static void account_kernel_stack(struct task_struct *tsk, int account) 305 { 306 void *stack = task_stack_page(tsk); 307 struct vm_struct *vm = task_stack_vm_area(tsk); 308 309 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 310 311 if (vm) { 312 int i; 313 314 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 315 316 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 317 mod_zone_page_state(page_zone(vm->pages[i]), 318 NR_KERNEL_STACK_KB, 319 PAGE_SIZE / 1024 * account); 320 } 321 322 /* All stack pages belong to the same memcg. */ 323 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB, 324 account * (THREAD_SIZE / 1024)); 325 } else { 326 /* 327 * All stack pages are in the same zone and belong to the 328 * same memcg. 329 */ 330 struct page *first_page = virt_to_page(stack); 331 332 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 333 THREAD_SIZE / 1024 * account); 334 335 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, 336 account * (THREAD_SIZE / 1024)); 337 } 338 } 339 340 static void release_task_stack(struct task_struct *tsk) 341 { 342 if (WARN_ON(tsk->state != TASK_DEAD)) 343 return; /* Better to leak the stack than to free prematurely */ 344 345 account_kernel_stack(tsk, -1); 346 arch_release_thread_stack(tsk->stack); 347 free_thread_stack(tsk); 348 tsk->stack = NULL; 349 #ifdef CONFIG_VMAP_STACK 350 tsk->stack_vm_area = NULL; 351 #endif 352 } 353 354 #ifdef CONFIG_THREAD_INFO_IN_TASK 355 void put_task_stack(struct task_struct *tsk) 356 { 357 if (atomic_dec_and_test(&tsk->stack_refcount)) 358 release_task_stack(tsk); 359 } 360 #endif 361 362 void free_task(struct task_struct *tsk) 363 { 364 #ifndef CONFIG_THREAD_INFO_IN_TASK 365 /* 366 * The task is finally done with both the stack and thread_info, 367 * so free both. 368 */ 369 release_task_stack(tsk); 370 #else 371 /* 372 * If the task had a separate stack allocation, it should be gone 373 * by now. 374 */ 375 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 376 #endif 377 rt_mutex_debug_task_free(tsk); 378 ftrace_graph_exit_task(tsk); 379 put_seccomp_filter(tsk); 380 arch_release_task_struct(tsk); 381 if (tsk->flags & PF_KTHREAD) 382 free_kthread_struct(tsk); 383 free_task_struct(tsk); 384 } 385 EXPORT_SYMBOL(free_task); 386 387 static inline void free_signal_struct(struct signal_struct *sig) 388 { 389 taskstats_tgid_free(sig); 390 sched_autogroup_exit(sig); 391 /* 392 * __mmdrop is not safe to call from softirq context on x86 due to 393 * pgd_dtor so postpone it to the async context 394 */ 395 if (sig->oom_mm) 396 mmdrop_async(sig->oom_mm); 397 kmem_cache_free(signal_cachep, sig); 398 } 399 400 static inline void put_signal_struct(struct signal_struct *sig) 401 { 402 if (atomic_dec_and_test(&sig->sigcnt)) 403 free_signal_struct(sig); 404 } 405 406 void __put_task_struct(struct task_struct *tsk) 407 { 408 WARN_ON(!tsk->exit_state); 409 WARN_ON(atomic_read(&tsk->usage)); 410 WARN_ON(tsk == current); 411 412 cgroup_free(tsk); 413 task_numa_free(tsk); 414 security_task_free(tsk); 415 exit_creds(tsk); 416 delayacct_tsk_free(tsk); 417 put_signal_struct(tsk->signal); 418 419 if (!profile_handoff_task(tsk)) 420 free_task(tsk); 421 } 422 EXPORT_SYMBOL_GPL(__put_task_struct); 423 424 void __init __weak arch_task_cache_init(void) { } 425 426 /* 427 * set_max_threads 428 */ 429 static void set_max_threads(unsigned int max_threads_suggested) 430 { 431 u64 threads; 432 433 /* 434 * The number of threads shall be limited such that the thread 435 * structures may only consume a small part of the available memory. 436 */ 437 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 438 threads = MAX_THREADS; 439 else 440 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 441 (u64) THREAD_SIZE * 8UL); 442 443 if (threads > max_threads_suggested) 444 threads = max_threads_suggested; 445 446 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 447 } 448 449 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 450 /* Initialized by the architecture: */ 451 int arch_task_struct_size __read_mostly; 452 #endif 453 454 void __init fork_init(void) 455 { 456 int i; 457 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 458 #ifndef ARCH_MIN_TASKALIGN 459 #define ARCH_MIN_TASKALIGN 0 460 #endif 461 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 462 463 /* create a slab on which task_structs can be allocated */ 464 task_struct_cachep = kmem_cache_create("task_struct", 465 arch_task_struct_size, align, 466 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 467 #endif 468 469 /* do the arch specific task caches init */ 470 arch_task_cache_init(); 471 472 set_max_threads(MAX_THREADS); 473 474 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 475 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 476 init_task.signal->rlim[RLIMIT_SIGPENDING] = 477 init_task.signal->rlim[RLIMIT_NPROC]; 478 479 for (i = 0; i < UCOUNT_COUNTS; i++) { 480 init_user_ns.ucount_max[i] = max_threads/2; 481 } 482 483 #ifdef CONFIG_VMAP_STACK 484 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 485 NULL, free_vm_stack_cache); 486 #endif 487 } 488 489 int __weak arch_dup_task_struct(struct task_struct *dst, 490 struct task_struct *src) 491 { 492 *dst = *src; 493 return 0; 494 } 495 496 void set_task_stack_end_magic(struct task_struct *tsk) 497 { 498 unsigned long *stackend; 499 500 stackend = end_of_stack(tsk); 501 *stackend = STACK_END_MAGIC; /* for overflow detection */ 502 } 503 504 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 505 { 506 struct task_struct *tsk; 507 unsigned long *stack; 508 struct vm_struct *stack_vm_area; 509 int err; 510 511 if (node == NUMA_NO_NODE) 512 node = tsk_fork_get_node(orig); 513 tsk = alloc_task_struct_node(node); 514 if (!tsk) 515 return NULL; 516 517 stack = alloc_thread_stack_node(tsk, node); 518 if (!stack) 519 goto free_tsk; 520 521 stack_vm_area = task_stack_vm_area(tsk); 522 523 err = arch_dup_task_struct(tsk, orig); 524 525 /* 526 * arch_dup_task_struct() clobbers the stack-related fields. Make 527 * sure they're properly initialized before using any stack-related 528 * functions again. 529 */ 530 tsk->stack = stack; 531 #ifdef CONFIG_VMAP_STACK 532 tsk->stack_vm_area = stack_vm_area; 533 #endif 534 #ifdef CONFIG_THREAD_INFO_IN_TASK 535 atomic_set(&tsk->stack_refcount, 1); 536 #endif 537 538 if (err) 539 goto free_stack; 540 541 #ifdef CONFIG_SECCOMP 542 /* 543 * We must handle setting up seccomp filters once we're under 544 * the sighand lock in case orig has changed between now and 545 * then. Until then, filter must be NULL to avoid messing up 546 * the usage counts on the error path calling free_task. 547 */ 548 tsk->seccomp.filter = NULL; 549 #endif 550 551 setup_thread_stack(tsk, orig); 552 clear_user_return_notifier(tsk); 553 clear_tsk_need_resched(tsk); 554 set_task_stack_end_magic(tsk); 555 556 #ifdef CONFIG_CC_STACKPROTECTOR 557 tsk->stack_canary = get_random_canary(); 558 #endif 559 560 /* 561 * One for us, one for whoever does the "release_task()" (usually 562 * parent) 563 */ 564 atomic_set(&tsk->usage, 2); 565 #ifdef CONFIG_BLK_DEV_IO_TRACE 566 tsk->btrace_seq = 0; 567 #endif 568 tsk->splice_pipe = NULL; 569 tsk->task_frag.page = NULL; 570 tsk->wake_q.next = NULL; 571 572 account_kernel_stack(tsk, 1); 573 574 kcov_task_init(tsk); 575 576 #ifdef CONFIG_FAULT_INJECTION 577 tsk->fail_nth = 0; 578 #endif 579 580 return tsk; 581 582 free_stack: 583 free_thread_stack(tsk); 584 free_tsk: 585 free_task_struct(tsk); 586 return NULL; 587 } 588 589 #ifdef CONFIG_MMU 590 static __latent_entropy int dup_mmap(struct mm_struct *mm, 591 struct mm_struct *oldmm) 592 { 593 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 594 struct rb_node **rb_link, *rb_parent; 595 int retval; 596 unsigned long charge; 597 LIST_HEAD(uf); 598 599 uprobe_start_dup_mmap(); 600 if (down_write_killable(&oldmm->mmap_sem)) { 601 retval = -EINTR; 602 goto fail_uprobe_end; 603 } 604 flush_cache_dup_mm(oldmm); 605 uprobe_dup_mmap(oldmm, mm); 606 /* 607 * Not linked in yet - no deadlock potential: 608 */ 609 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 610 611 /* No ordering required: file already has been exposed. */ 612 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 613 614 mm->total_vm = oldmm->total_vm; 615 mm->data_vm = oldmm->data_vm; 616 mm->exec_vm = oldmm->exec_vm; 617 mm->stack_vm = oldmm->stack_vm; 618 619 rb_link = &mm->mm_rb.rb_node; 620 rb_parent = NULL; 621 pprev = &mm->mmap; 622 retval = ksm_fork(mm, oldmm); 623 if (retval) 624 goto out; 625 retval = khugepaged_fork(mm, oldmm); 626 if (retval) 627 goto out; 628 629 prev = NULL; 630 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 631 struct file *file; 632 633 if (mpnt->vm_flags & VM_DONTCOPY) { 634 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 635 continue; 636 } 637 charge = 0; 638 if (mpnt->vm_flags & VM_ACCOUNT) { 639 unsigned long len = vma_pages(mpnt); 640 641 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 642 goto fail_nomem; 643 charge = len; 644 } 645 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 646 if (!tmp) 647 goto fail_nomem; 648 *tmp = *mpnt; 649 INIT_LIST_HEAD(&tmp->anon_vma_chain); 650 retval = vma_dup_policy(mpnt, tmp); 651 if (retval) 652 goto fail_nomem_policy; 653 tmp->vm_mm = mm; 654 retval = dup_userfaultfd(tmp, &uf); 655 if (retval) 656 goto fail_nomem_anon_vma_fork; 657 if (anon_vma_fork(tmp, mpnt)) 658 goto fail_nomem_anon_vma_fork; 659 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 660 tmp->vm_next = tmp->vm_prev = NULL; 661 file = tmp->vm_file; 662 if (file) { 663 struct inode *inode = file_inode(file); 664 struct address_space *mapping = file->f_mapping; 665 666 get_file(file); 667 if (tmp->vm_flags & VM_DENYWRITE) 668 atomic_dec(&inode->i_writecount); 669 i_mmap_lock_write(mapping); 670 if (tmp->vm_flags & VM_SHARED) 671 atomic_inc(&mapping->i_mmap_writable); 672 flush_dcache_mmap_lock(mapping); 673 /* insert tmp into the share list, just after mpnt */ 674 vma_interval_tree_insert_after(tmp, mpnt, 675 &mapping->i_mmap); 676 flush_dcache_mmap_unlock(mapping); 677 i_mmap_unlock_write(mapping); 678 } 679 680 /* 681 * Clear hugetlb-related page reserves for children. This only 682 * affects MAP_PRIVATE mappings. Faults generated by the child 683 * are not guaranteed to succeed, even if read-only 684 */ 685 if (is_vm_hugetlb_page(tmp)) 686 reset_vma_resv_huge_pages(tmp); 687 688 /* 689 * Link in the new vma and copy the page table entries. 690 */ 691 *pprev = tmp; 692 pprev = &tmp->vm_next; 693 tmp->vm_prev = prev; 694 prev = tmp; 695 696 __vma_link_rb(mm, tmp, rb_link, rb_parent); 697 rb_link = &tmp->vm_rb.rb_right; 698 rb_parent = &tmp->vm_rb; 699 700 mm->map_count++; 701 retval = copy_page_range(mm, oldmm, mpnt); 702 703 if (tmp->vm_ops && tmp->vm_ops->open) 704 tmp->vm_ops->open(tmp); 705 706 if (retval) 707 goto out; 708 } 709 /* a new mm has just been created */ 710 arch_dup_mmap(oldmm, mm); 711 retval = 0; 712 out: 713 up_write(&mm->mmap_sem); 714 flush_tlb_mm(oldmm); 715 up_write(&oldmm->mmap_sem); 716 dup_userfaultfd_complete(&uf); 717 fail_uprobe_end: 718 uprobe_end_dup_mmap(); 719 return retval; 720 fail_nomem_anon_vma_fork: 721 mpol_put(vma_policy(tmp)); 722 fail_nomem_policy: 723 kmem_cache_free(vm_area_cachep, tmp); 724 fail_nomem: 725 retval = -ENOMEM; 726 vm_unacct_memory(charge); 727 goto out; 728 } 729 730 static inline int mm_alloc_pgd(struct mm_struct *mm) 731 { 732 mm->pgd = pgd_alloc(mm); 733 if (unlikely(!mm->pgd)) 734 return -ENOMEM; 735 return 0; 736 } 737 738 static inline void mm_free_pgd(struct mm_struct *mm) 739 { 740 pgd_free(mm, mm->pgd); 741 } 742 #else 743 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 744 { 745 down_write(&oldmm->mmap_sem); 746 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 747 up_write(&oldmm->mmap_sem); 748 return 0; 749 } 750 #define mm_alloc_pgd(mm) (0) 751 #define mm_free_pgd(mm) 752 #endif /* CONFIG_MMU */ 753 754 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 755 756 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 757 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 758 759 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 760 761 static int __init coredump_filter_setup(char *s) 762 { 763 default_dump_filter = 764 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 765 MMF_DUMP_FILTER_MASK; 766 return 1; 767 } 768 769 __setup("coredump_filter=", coredump_filter_setup); 770 771 #include <linux/init_task.h> 772 773 static void mm_init_aio(struct mm_struct *mm) 774 { 775 #ifdef CONFIG_AIO 776 spin_lock_init(&mm->ioctx_lock); 777 mm->ioctx_table = NULL; 778 #endif 779 } 780 781 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 782 { 783 #ifdef CONFIG_MEMCG 784 mm->owner = p; 785 #endif 786 } 787 788 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 789 struct user_namespace *user_ns) 790 { 791 mm->mmap = NULL; 792 mm->mm_rb = RB_ROOT; 793 mm->vmacache_seqnum = 0; 794 atomic_set(&mm->mm_users, 1); 795 atomic_set(&mm->mm_count, 1); 796 init_rwsem(&mm->mmap_sem); 797 INIT_LIST_HEAD(&mm->mmlist); 798 mm->core_state = NULL; 799 atomic_long_set(&mm->nr_ptes, 0); 800 mm_nr_pmds_init(mm); 801 mm->map_count = 0; 802 mm->locked_vm = 0; 803 mm->pinned_vm = 0; 804 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 805 spin_lock_init(&mm->page_table_lock); 806 mm_init_cpumask(mm); 807 mm_init_aio(mm); 808 mm_init_owner(mm, p); 809 RCU_INIT_POINTER(mm->exe_file, NULL); 810 mmu_notifier_mm_init(mm); 811 init_tlb_flush_pending(mm); 812 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 813 mm->pmd_huge_pte = NULL; 814 #endif 815 816 if (current->mm) { 817 mm->flags = current->mm->flags & MMF_INIT_MASK; 818 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 819 } else { 820 mm->flags = default_dump_filter; 821 mm->def_flags = 0; 822 } 823 824 if (mm_alloc_pgd(mm)) 825 goto fail_nopgd; 826 827 if (init_new_context(p, mm)) 828 goto fail_nocontext; 829 830 mm->user_ns = get_user_ns(user_ns); 831 return mm; 832 833 fail_nocontext: 834 mm_free_pgd(mm); 835 fail_nopgd: 836 free_mm(mm); 837 return NULL; 838 } 839 840 static void check_mm(struct mm_struct *mm) 841 { 842 int i; 843 844 for (i = 0; i < NR_MM_COUNTERS; i++) { 845 long x = atomic_long_read(&mm->rss_stat.count[i]); 846 847 if (unlikely(x)) 848 printk(KERN_ALERT "BUG: Bad rss-counter state " 849 "mm:%p idx:%d val:%ld\n", mm, i, x); 850 } 851 852 if (atomic_long_read(&mm->nr_ptes)) 853 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 854 atomic_long_read(&mm->nr_ptes)); 855 if (mm_nr_pmds(mm)) 856 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 857 mm_nr_pmds(mm)); 858 859 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 860 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 861 #endif 862 } 863 864 /* 865 * Allocate and initialize an mm_struct. 866 */ 867 struct mm_struct *mm_alloc(void) 868 { 869 struct mm_struct *mm; 870 871 mm = allocate_mm(); 872 if (!mm) 873 return NULL; 874 875 memset(mm, 0, sizeof(*mm)); 876 return mm_init(mm, current, current_user_ns()); 877 } 878 879 /* 880 * Called when the last reference to the mm 881 * is dropped: either by a lazy thread or by 882 * mmput. Free the page directory and the mm. 883 */ 884 void __mmdrop(struct mm_struct *mm) 885 { 886 BUG_ON(mm == &init_mm); 887 mm_free_pgd(mm); 888 destroy_context(mm); 889 mmu_notifier_mm_destroy(mm); 890 check_mm(mm); 891 put_user_ns(mm->user_ns); 892 free_mm(mm); 893 } 894 EXPORT_SYMBOL_GPL(__mmdrop); 895 896 static inline void __mmput(struct mm_struct *mm) 897 { 898 VM_BUG_ON(atomic_read(&mm->mm_users)); 899 900 uprobe_clear_state(mm); 901 exit_aio(mm); 902 ksm_exit(mm); 903 khugepaged_exit(mm); /* must run before exit_mmap */ 904 exit_mmap(mm); 905 mm_put_huge_zero_page(mm); 906 set_mm_exe_file(mm, NULL); 907 if (!list_empty(&mm->mmlist)) { 908 spin_lock(&mmlist_lock); 909 list_del(&mm->mmlist); 910 spin_unlock(&mmlist_lock); 911 } 912 if (mm->binfmt) 913 module_put(mm->binfmt->module); 914 set_bit(MMF_OOM_SKIP, &mm->flags); 915 mmdrop(mm); 916 } 917 918 /* 919 * Decrement the use count and release all resources for an mm. 920 */ 921 void mmput(struct mm_struct *mm) 922 { 923 might_sleep(); 924 925 if (atomic_dec_and_test(&mm->mm_users)) 926 __mmput(mm); 927 } 928 EXPORT_SYMBOL_GPL(mmput); 929 930 #ifdef CONFIG_MMU 931 static void mmput_async_fn(struct work_struct *work) 932 { 933 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 934 __mmput(mm); 935 } 936 937 void mmput_async(struct mm_struct *mm) 938 { 939 if (atomic_dec_and_test(&mm->mm_users)) { 940 INIT_WORK(&mm->async_put_work, mmput_async_fn); 941 schedule_work(&mm->async_put_work); 942 } 943 } 944 #endif 945 946 /** 947 * set_mm_exe_file - change a reference to the mm's executable file 948 * 949 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 950 * 951 * Main users are mmput() and sys_execve(). Callers prevent concurrent 952 * invocations: in mmput() nobody alive left, in execve task is single 953 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 954 * mm->exe_file, but does so without using set_mm_exe_file() in order 955 * to do avoid the need for any locks. 956 */ 957 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 958 { 959 struct file *old_exe_file; 960 961 /* 962 * It is safe to dereference the exe_file without RCU as 963 * this function is only called if nobody else can access 964 * this mm -- see comment above for justification. 965 */ 966 old_exe_file = rcu_dereference_raw(mm->exe_file); 967 968 if (new_exe_file) 969 get_file(new_exe_file); 970 rcu_assign_pointer(mm->exe_file, new_exe_file); 971 if (old_exe_file) 972 fput(old_exe_file); 973 } 974 975 /** 976 * get_mm_exe_file - acquire a reference to the mm's executable file 977 * 978 * Returns %NULL if mm has no associated executable file. 979 * User must release file via fput(). 980 */ 981 struct file *get_mm_exe_file(struct mm_struct *mm) 982 { 983 struct file *exe_file; 984 985 rcu_read_lock(); 986 exe_file = rcu_dereference(mm->exe_file); 987 if (exe_file && !get_file_rcu(exe_file)) 988 exe_file = NULL; 989 rcu_read_unlock(); 990 return exe_file; 991 } 992 EXPORT_SYMBOL(get_mm_exe_file); 993 994 /** 995 * get_task_exe_file - acquire a reference to the task's executable file 996 * 997 * Returns %NULL if task's mm (if any) has no associated executable file or 998 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 999 * User must release file via fput(). 1000 */ 1001 struct file *get_task_exe_file(struct task_struct *task) 1002 { 1003 struct file *exe_file = NULL; 1004 struct mm_struct *mm; 1005 1006 task_lock(task); 1007 mm = task->mm; 1008 if (mm) { 1009 if (!(task->flags & PF_KTHREAD)) 1010 exe_file = get_mm_exe_file(mm); 1011 } 1012 task_unlock(task); 1013 return exe_file; 1014 } 1015 EXPORT_SYMBOL(get_task_exe_file); 1016 1017 /** 1018 * get_task_mm - acquire a reference to the task's mm 1019 * 1020 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1021 * this kernel workthread has transiently adopted a user mm with use_mm, 1022 * to do its AIO) is not set and if so returns a reference to it, after 1023 * bumping up the use count. User must release the mm via mmput() 1024 * after use. Typically used by /proc and ptrace. 1025 */ 1026 struct mm_struct *get_task_mm(struct task_struct *task) 1027 { 1028 struct mm_struct *mm; 1029 1030 task_lock(task); 1031 mm = task->mm; 1032 if (mm) { 1033 if (task->flags & PF_KTHREAD) 1034 mm = NULL; 1035 else 1036 mmget(mm); 1037 } 1038 task_unlock(task); 1039 return mm; 1040 } 1041 EXPORT_SYMBOL_GPL(get_task_mm); 1042 1043 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1044 { 1045 struct mm_struct *mm; 1046 int err; 1047 1048 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1049 if (err) 1050 return ERR_PTR(err); 1051 1052 mm = get_task_mm(task); 1053 if (mm && mm != current->mm && 1054 !ptrace_may_access(task, mode)) { 1055 mmput(mm); 1056 mm = ERR_PTR(-EACCES); 1057 } 1058 mutex_unlock(&task->signal->cred_guard_mutex); 1059 1060 return mm; 1061 } 1062 1063 static void complete_vfork_done(struct task_struct *tsk) 1064 { 1065 struct completion *vfork; 1066 1067 task_lock(tsk); 1068 vfork = tsk->vfork_done; 1069 if (likely(vfork)) { 1070 tsk->vfork_done = NULL; 1071 complete(vfork); 1072 } 1073 task_unlock(tsk); 1074 } 1075 1076 static int wait_for_vfork_done(struct task_struct *child, 1077 struct completion *vfork) 1078 { 1079 int killed; 1080 1081 freezer_do_not_count(); 1082 killed = wait_for_completion_killable(vfork); 1083 freezer_count(); 1084 1085 if (killed) { 1086 task_lock(child); 1087 child->vfork_done = NULL; 1088 task_unlock(child); 1089 } 1090 1091 put_task_struct(child); 1092 return killed; 1093 } 1094 1095 /* Please note the differences between mmput and mm_release. 1096 * mmput is called whenever we stop holding onto a mm_struct, 1097 * error success whatever. 1098 * 1099 * mm_release is called after a mm_struct has been removed 1100 * from the current process. 1101 * 1102 * This difference is important for error handling, when we 1103 * only half set up a mm_struct for a new process and need to restore 1104 * the old one. Because we mmput the new mm_struct before 1105 * restoring the old one. . . 1106 * Eric Biederman 10 January 1998 1107 */ 1108 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1109 { 1110 /* Get rid of any futexes when releasing the mm */ 1111 #ifdef CONFIG_FUTEX 1112 if (unlikely(tsk->robust_list)) { 1113 exit_robust_list(tsk); 1114 tsk->robust_list = NULL; 1115 } 1116 #ifdef CONFIG_COMPAT 1117 if (unlikely(tsk->compat_robust_list)) { 1118 compat_exit_robust_list(tsk); 1119 tsk->compat_robust_list = NULL; 1120 } 1121 #endif 1122 if (unlikely(!list_empty(&tsk->pi_state_list))) 1123 exit_pi_state_list(tsk); 1124 #endif 1125 1126 uprobe_free_utask(tsk); 1127 1128 /* Get rid of any cached register state */ 1129 deactivate_mm(tsk, mm); 1130 1131 /* 1132 * Signal userspace if we're not exiting with a core dump 1133 * because we want to leave the value intact for debugging 1134 * purposes. 1135 */ 1136 if (tsk->clear_child_tid) { 1137 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1138 atomic_read(&mm->mm_users) > 1) { 1139 /* 1140 * We don't check the error code - if userspace has 1141 * not set up a proper pointer then tough luck. 1142 */ 1143 put_user(0, tsk->clear_child_tid); 1144 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1145 1, NULL, NULL, 0); 1146 } 1147 tsk->clear_child_tid = NULL; 1148 } 1149 1150 /* 1151 * All done, finally we can wake up parent and return this mm to him. 1152 * Also kthread_stop() uses this completion for synchronization. 1153 */ 1154 if (tsk->vfork_done) 1155 complete_vfork_done(tsk); 1156 } 1157 1158 /* 1159 * Allocate a new mm structure and copy contents from the 1160 * mm structure of the passed in task structure. 1161 */ 1162 static struct mm_struct *dup_mm(struct task_struct *tsk) 1163 { 1164 struct mm_struct *mm, *oldmm = current->mm; 1165 int err; 1166 1167 mm = allocate_mm(); 1168 if (!mm) 1169 goto fail_nomem; 1170 1171 memcpy(mm, oldmm, sizeof(*mm)); 1172 1173 if (!mm_init(mm, tsk, mm->user_ns)) 1174 goto fail_nomem; 1175 1176 err = dup_mmap(mm, oldmm); 1177 if (err) 1178 goto free_pt; 1179 1180 mm->hiwater_rss = get_mm_rss(mm); 1181 mm->hiwater_vm = mm->total_vm; 1182 1183 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1184 goto free_pt; 1185 1186 return mm; 1187 1188 free_pt: 1189 /* don't put binfmt in mmput, we haven't got module yet */ 1190 mm->binfmt = NULL; 1191 mmput(mm); 1192 1193 fail_nomem: 1194 return NULL; 1195 } 1196 1197 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1198 { 1199 struct mm_struct *mm, *oldmm; 1200 int retval; 1201 1202 tsk->min_flt = tsk->maj_flt = 0; 1203 tsk->nvcsw = tsk->nivcsw = 0; 1204 #ifdef CONFIG_DETECT_HUNG_TASK 1205 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1206 #endif 1207 1208 tsk->mm = NULL; 1209 tsk->active_mm = NULL; 1210 1211 /* 1212 * Are we cloning a kernel thread? 1213 * 1214 * We need to steal a active VM for that.. 1215 */ 1216 oldmm = current->mm; 1217 if (!oldmm) 1218 return 0; 1219 1220 /* initialize the new vmacache entries */ 1221 vmacache_flush(tsk); 1222 1223 if (clone_flags & CLONE_VM) { 1224 mmget(oldmm); 1225 mm = oldmm; 1226 goto good_mm; 1227 } 1228 1229 retval = -ENOMEM; 1230 mm = dup_mm(tsk); 1231 if (!mm) 1232 goto fail_nomem; 1233 1234 good_mm: 1235 tsk->mm = mm; 1236 tsk->active_mm = mm; 1237 return 0; 1238 1239 fail_nomem: 1240 return retval; 1241 } 1242 1243 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1244 { 1245 struct fs_struct *fs = current->fs; 1246 if (clone_flags & CLONE_FS) { 1247 /* tsk->fs is already what we want */ 1248 spin_lock(&fs->lock); 1249 if (fs->in_exec) { 1250 spin_unlock(&fs->lock); 1251 return -EAGAIN; 1252 } 1253 fs->users++; 1254 spin_unlock(&fs->lock); 1255 return 0; 1256 } 1257 tsk->fs = copy_fs_struct(fs); 1258 if (!tsk->fs) 1259 return -ENOMEM; 1260 return 0; 1261 } 1262 1263 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1264 { 1265 struct files_struct *oldf, *newf; 1266 int error = 0; 1267 1268 /* 1269 * A background process may not have any files ... 1270 */ 1271 oldf = current->files; 1272 if (!oldf) 1273 goto out; 1274 1275 if (clone_flags & CLONE_FILES) { 1276 atomic_inc(&oldf->count); 1277 goto out; 1278 } 1279 1280 newf = dup_fd(oldf, &error); 1281 if (!newf) 1282 goto out; 1283 1284 tsk->files = newf; 1285 error = 0; 1286 out: 1287 return error; 1288 } 1289 1290 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1291 { 1292 #ifdef CONFIG_BLOCK 1293 struct io_context *ioc = current->io_context; 1294 struct io_context *new_ioc; 1295 1296 if (!ioc) 1297 return 0; 1298 /* 1299 * Share io context with parent, if CLONE_IO is set 1300 */ 1301 if (clone_flags & CLONE_IO) { 1302 ioc_task_link(ioc); 1303 tsk->io_context = ioc; 1304 } else if (ioprio_valid(ioc->ioprio)) { 1305 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1306 if (unlikely(!new_ioc)) 1307 return -ENOMEM; 1308 1309 new_ioc->ioprio = ioc->ioprio; 1310 put_io_context(new_ioc); 1311 } 1312 #endif 1313 return 0; 1314 } 1315 1316 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1317 { 1318 struct sighand_struct *sig; 1319 1320 if (clone_flags & CLONE_SIGHAND) { 1321 atomic_inc(¤t->sighand->count); 1322 return 0; 1323 } 1324 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1325 rcu_assign_pointer(tsk->sighand, sig); 1326 if (!sig) 1327 return -ENOMEM; 1328 1329 atomic_set(&sig->count, 1); 1330 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1331 return 0; 1332 } 1333 1334 void __cleanup_sighand(struct sighand_struct *sighand) 1335 { 1336 if (atomic_dec_and_test(&sighand->count)) { 1337 signalfd_cleanup(sighand); 1338 /* 1339 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1340 * without an RCU grace period, see __lock_task_sighand(). 1341 */ 1342 kmem_cache_free(sighand_cachep, sighand); 1343 } 1344 } 1345 1346 #ifdef CONFIG_POSIX_TIMERS 1347 /* 1348 * Initialize POSIX timer handling for a thread group. 1349 */ 1350 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1351 { 1352 unsigned long cpu_limit; 1353 1354 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1355 if (cpu_limit != RLIM_INFINITY) { 1356 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1357 sig->cputimer.running = true; 1358 } 1359 1360 /* The timer lists. */ 1361 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1362 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1363 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1364 } 1365 #else 1366 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1367 #endif 1368 1369 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1370 { 1371 struct signal_struct *sig; 1372 1373 if (clone_flags & CLONE_THREAD) 1374 return 0; 1375 1376 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1377 tsk->signal = sig; 1378 if (!sig) 1379 return -ENOMEM; 1380 1381 sig->nr_threads = 1; 1382 atomic_set(&sig->live, 1); 1383 atomic_set(&sig->sigcnt, 1); 1384 1385 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1386 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1387 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1388 1389 init_waitqueue_head(&sig->wait_chldexit); 1390 sig->curr_target = tsk; 1391 init_sigpending(&sig->shared_pending); 1392 seqlock_init(&sig->stats_lock); 1393 prev_cputime_init(&sig->prev_cputime); 1394 1395 #ifdef CONFIG_POSIX_TIMERS 1396 INIT_LIST_HEAD(&sig->posix_timers); 1397 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1398 sig->real_timer.function = it_real_fn; 1399 #endif 1400 1401 task_lock(current->group_leader); 1402 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1403 task_unlock(current->group_leader); 1404 1405 posix_cpu_timers_init_group(sig); 1406 1407 tty_audit_fork(sig); 1408 sched_autogroup_fork(sig); 1409 1410 sig->oom_score_adj = current->signal->oom_score_adj; 1411 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1412 1413 mutex_init(&sig->cred_guard_mutex); 1414 1415 return 0; 1416 } 1417 1418 static void copy_seccomp(struct task_struct *p) 1419 { 1420 #ifdef CONFIG_SECCOMP 1421 /* 1422 * Must be called with sighand->lock held, which is common to 1423 * all threads in the group. Holding cred_guard_mutex is not 1424 * needed because this new task is not yet running and cannot 1425 * be racing exec. 1426 */ 1427 assert_spin_locked(¤t->sighand->siglock); 1428 1429 /* Ref-count the new filter user, and assign it. */ 1430 get_seccomp_filter(current); 1431 p->seccomp = current->seccomp; 1432 1433 /* 1434 * Explicitly enable no_new_privs here in case it got set 1435 * between the task_struct being duplicated and holding the 1436 * sighand lock. The seccomp state and nnp must be in sync. 1437 */ 1438 if (task_no_new_privs(current)) 1439 task_set_no_new_privs(p); 1440 1441 /* 1442 * If the parent gained a seccomp mode after copying thread 1443 * flags and between before we held the sighand lock, we have 1444 * to manually enable the seccomp thread flag here. 1445 */ 1446 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1447 set_tsk_thread_flag(p, TIF_SECCOMP); 1448 #endif 1449 } 1450 1451 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1452 { 1453 current->clear_child_tid = tidptr; 1454 1455 return task_pid_vnr(current); 1456 } 1457 1458 static void rt_mutex_init_task(struct task_struct *p) 1459 { 1460 raw_spin_lock_init(&p->pi_lock); 1461 #ifdef CONFIG_RT_MUTEXES 1462 p->pi_waiters = RB_ROOT; 1463 p->pi_waiters_leftmost = NULL; 1464 p->pi_top_task = NULL; 1465 p->pi_blocked_on = NULL; 1466 #endif 1467 } 1468 1469 #ifdef CONFIG_POSIX_TIMERS 1470 /* 1471 * Initialize POSIX timer handling for a single task. 1472 */ 1473 static void posix_cpu_timers_init(struct task_struct *tsk) 1474 { 1475 tsk->cputime_expires.prof_exp = 0; 1476 tsk->cputime_expires.virt_exp = 0; 1477 tsk->cputime_expires.sched_exp = 0; 1478 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1479 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1480 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1481 } 1482 #else 1483 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1484 #endif 1485 1486 static inline void 1487 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1488 { 1489 task->pids[type].pid = pid; 1490 } 1491 1492 static inline void rcu_copy_process(struct task_struct *p) 1493 { 1494 #ifdef CONFIG_PREEMPT_RCU 1495 p->rcu_read_lock_nesting = 0; 1496 p->rcu_read_unlock_special.s = 0; 1497 p->rcu_blocked_node = NULL; 1498 INIT_LIST_HEAD(&p->rcu_node_entry); 1499 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1500 #ifdef CONFIG_TASKS_RCU 1501 p->rcu_tasks_holdout = false; 1502 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1503 p->rcu_tasks_idle_cpu = -1; 1504 #endif /* #ifdef CONFIG_TASKS_RCU */ 1505 } 1506 1507 /* 1508 * This creates a new process as a copy of the old one, 1509 * but does not actually start it yet. 1510 * 1511 * It copies the registers, and all the appropriate 1512 * parts of the process environment (as per the clone 1513 * flags). The actual kick-off is left to the caller. 1514 */ 1515 static __latent_entropy struct task_struct *copy_process( 1516 unsigned long clone_flags, 1517 unsigned long stack_start, 1518 unsigned long stack_size, 1519 int __user *child_tidptr, 1520 struct pid *pid, 1521 int trace, 1522 unsigned long tls, 1523 int node) 1524 { 1525 int retval; 1526 struct task_struct *p; 1527 1528 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1529 return ERR_PTR(-EINVAL); 1530 1531 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1532 return ERR_PTR(-EINVAL); 1533 1534 /* 1535 * Thread groups must share signals as well, and detached threads 1536 * can only be started up within the thread group. 1537 */ 1538 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1539 return ERR_PTR(-EINVAL); 1540 1541 /* 1542 * Shared signal handlers imply shared VM. By way of the above, 1543 * thread groups also imply shared VM. Blocking this case allows 1544 * for various simplifications in other code. 1545 */ 1546 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1547 return ERR_PTR(-EINVAL); 1548 1549 /* 1550 * Siblings of global init remain as zombies on exit since they are 1551 * not reaped by their parent (swapper). To solve this and to avoid 1552 * multi-rooted process trees, prevent global and container-inits 1553 * from creating siblings. 1554 */ 1555 if ((clone_flags & CLONE_PARENT) && 1556 current->signal->flags & SIGNAL_UNKILLABLE) 1557 return ERR_PTR(-EINVAL); 1558 1559 /* 1560 * If the new process will be in a different pid or user namespace 1561 * do not allow it to share a thread group with the forking task. 1562 */ 1563 if (clone_flags & CLONE_THREAD) { 1564 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1565 (task_active_pid_ns(current) != 1566 current->nsproxy->pid_ns_for_children)) 1567 return ERR_PTR(-EINVAL); 1568 } 1569 1570 retval = security_task_create(clone_flags); 1571 if (retval) 1572 goto fork_out; 1573 1574 retval = -ENOMEM; 1575 p = dup_task_struct(current, node); 1576 if (!p) 1577 goto fork_out; 1578 1579 /* 1580 * This _must_ happen before we call free_task(), i.e. before we jump 1581 * to any of the bad_fork_* labels. This is to avoid freeing 1582 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1583 * kernel threads (PF_KTHREAD). 1584 */ 1585 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1586 /* 1587 * Clear TID on mm_release()? 1588 */ 1589 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1590 1591 ftrace_graph_init_task(p); 1592 1593 rt_mutex_init_task(p); 1594 1595 #ifdef CONFIG_PROVE_LOCKING 1596 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1597 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1598 #endif 1599 retval = -EAGAIN; 1600 if (atomic_read(&p->real_cred->user->processes) >= 1601 task_rlimit(p, RLIMIT_NPROC)) { 1602 if (p->real_cred->user != INIT_USER && 1603 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1604 goto bad_fork_free; 1605 } 1606 current->flags &= ~PF_NPROC_EXCEEDED; 1607 1608 retval = copy_creds(p, clone_flags); 1609 if (retval < 0) 1610 goto bad_fork_free; 1611 1612 /* 1613 * If multiple threads are within copy_process(), then this check 1614 * triggers too late. This doesn't hurt, the check is only there 1615 * to stop root fork bombs. 1616 */ 1617 retval = -EAGAIN; 1618 if (nr_threads >= max_threads) 1619 goto bad_fork_cleanup_count; 1620 1621 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1622 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1623 p->flags |= PF_FORKNOEXEC; 1624 INIT_LIST_HEAD(&p->children); 1625 INIT_LIST_HEAD(&p->sibling); 1626 rcu_copy_process(p); 1627 p->vfork_done = NULL; 1628 spin_lock_init(&p->alloc_lock); 1629 1630 init_sigpending(&p->pending); 1631 1632 p->utime = p->stime = p->gtime = 0; 1633 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1634 p->utimescaled = p->stimescaled = 0; 1635 #endif 1636 prev_cputime_init(&p->prev_cputime); 1637 1638 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1639 seqcount_init(&p->vtime.seqcount); 1640 p->vtime.starttime = 0; 1641 p->vtime.state = VTIME_INACTIVE; 1642 #endif 1643 1644 #if defined(SPLIT_RSS_COUNTING) 1645 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1646 #endif 1647 1648 p->default_timer_slack_ns = current->timer_slack_ns; 1649 1650 task_io_accounting_init(&p->ioac); 1651 acct_clear_integrals(p); 1652 1653 posix_cpu_timers_init(p); 1654 1655 p->start_time = ktime_get_ns(); 1656 p->real_start_time = ktime_get_boot_ns(); 1657 p->io_context = NULL; 1658 p->audit_context = NULL; 1659 cgroup_fork(p); 1660 #ifdef CONFIG_NUMA 1661 p->mempolicy = mpol_dup(p->mempolicy); 1662 if (IS_ERR(p->mempolicy)) { 1663 retval = PTR_ERR(p->mempolicy); 1664 p->mempolicy = NULL; 1665 goto bad_fork_cleanup_threadgroup_lock; 1666 } 1667 #endif 1668 #ifdef CONFIG_CPUSETS 1669 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1670 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1671 seqcount_init(&p->mems_allowed_seq); 1672 #endif 1673 #ifdef CONFIG_TRACE_IRQFLAGS 1674 p->irq_events = 0; 1675 p->hardirqs_enabled = 0; 1676 p->hardirq_enable_ip = 0; 1677 p->hardirq_enable_event = 0; 1678 p->hardirq_disable_ip = _THIS_IP_; 1679 p->hardirq_disable_event = 0; 1680 p->softirqs_enabled = 1; 1681 p->softirq_enable_ip = _THIS_IP_; 1682 p->softirq_enable_event = 0; 1683 p->softirq_disable_ip = 0; 1684 p->softirq_disable_event = 0; 1685 p->hardirq_context = 0; 1686 p->softirq_context = 0; 1687 #endif 1688 1689 p->pagefault_disabled = 0; 1690 1691 #ifdef CONFIG_LOCKDEP 1692 p->lockdep_depth = 0; /* no locks held yet */ 1693 p->curr_chain_key = 0; 1694 p->lockdep_recursion = 0; 1695 #endif 1696 1697 #ifdef CONFIG_DEBUG_MUTEXES 1698 p->blocked_on = NULL; /* not blocked yet */ 1699 #endif 1700 #ifdef CONFIG_BCACHE 1701 p->sequential_io = 0; 1702 p->sequential_io_avg = 0; 1703 #endif 1704 1705 /* Perform scheduler related setup. Assign this task to a CPU. */ 1706 retval = sched_fork(clone_flags, p); 1707 if (retval) 1708 goto bad_fork_cleanup_policy; 1709 1710 retval = perf_event_init_task(p); 1711 if (retval) 1712 goto bad_fork_cleanup_policy; 1713 retval = audit_alloc(p); 1714 if (retval) 1715 goto bad_fork_cleanup_perf; 1716 /* copy all the process information */ 1717 shm_init_task(p); 1718 retval = security_task_alloc(p, clone_flags); 1719 if (retval) 1720 goto bad_fork_cleanup_audit; 1721 retval = copy_semundo(clone_flags, p); 1722 if (retval) 1723 goto bad_fork_cleanup_security; 1724 retval = copy_files(clone_flags, p); 1725 if (retval) 1726 goto bad_fork_cleanup_semundo; 1727 retval = copy_fs(clone_flags, p); 1728 if (retval) 1729 goto bad_fork_cleanup_files; 1730 retval = copy_sighand(clone_flags, p); 1731 if (retval) 1732 goto bad_fork_cleanup_fs; 1733 retval = copy_signal(clone_flags, p); 1734 if (retval) 1735 goto bad_fork_cleanup_sighand; 1736 retval = copy_mm(clone_flags, p); 1737 if (retval) 1738 goto bad_fork_cleanup_signal; 1739 retval = copy_namespaces(clone_flags, p); 1740 if (retval) 1741 goto bad_fork_cleanup_mm; 1742 retval = copy_io(clone_flags, p); 1743 if (retval) 1744 goto bad_fork_cleanup_namespaces; 1745 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1746 if (retval) 1747 goto bad_fork_cleanup_io; 1748 1749 if (pid != &init_struct_pid) { 1750 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1751 if (IS_ERR(pid)) { 1752 retval = PTR_ERR(pid); 1753 goto bad_fork_cleanup_thread; 1754 } 1755 } 1756 1757 #ifdef CONFIG_BLOCK 1758 p->plug = NULL; 1759 #endif 1760 #ifdef CONFIG_FUTEX 1761 p->robust_list = NULL; 1762 #ifdef CONFIG_COMPAT 1763 p->compat_robust_list = NULL; 1764 #endif 1765 INIT_LIST_HEAD(&p->pi_state_list); 1766 p->pi_state_cache = NULL; 1767 #endif 1768 /* 1769 * sigaltstack should be cleared when sharing the same VM 1770 */ 1771 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1772 sas_ss_reset(p); 1773 1774 /* 1775 * Syscall tracing and stepping should be turned off in the 1776 * child regardless of CLONE_PTRACE. 1777 */ 1778 user_disable_single_step(p); 1779 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1780 #ifdef TIF_SYSCALL_EMU 1781 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1782 #endif 1783 clear_all_latency_tracing(p); 1784 1785 /* ok, now we should be set up.. */ 1786 p->pid = pid_nr(pid); 1787 if (clone_flags & CLONE_THREAD) { 1788 p->exit_signal = -1; 1789 p->group_leader = current->group_leader; 1790 p->tgid = current->tgid; 1791 } else { 1792 if (clone_flags & CLONE_PARENT) 1793 p->exit_signal = current->group_leader->exit_signal; 1794 else 1795 p->exit_signal = (clone_flags & CSIGNAL); 1796 p->group_leader = p; 1797 p->tgid = p->pid; 1798 } 1799 1800 p->nr_dirtied = 0; 1801 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1802 p->dirty_paused_when = 0; 1803 1804 p->pdeath_signal = 0; 1805 INIT_LIST_HEAD(&p->thread_group); 1806 p->task_works = NULL; 1807 1808 cgroup_threadgroup_change_begin(current); 1809 /* 1810 * Ensure that the cgroup subsystem policies allow the new process to be 1811 * forked. It should be noted the the new process's css_set can be changed 1812 * between here and cgroup_post_fork() if an organisation operation is in 1813 * progress. 1814 */ 1815 retval = cgroup_can_fork(p); 1816 if (retval) 1817 goto bad_fork_free_pid; 1818 1819 /* 1820 * Make it visible to the rest of the system, but dont wake it up yet. 1821 * Need tasklist lock for parent etc handling! 1822 */ 1823 write_lock_irq(&tasklist_lock); 1824 1825 /* CLONE_PARENT re-uses the old parent */ 1826 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1827 p->real_parent = current->real_parent; 1828 p->parent_exec_id = current->parent_exec_id; 1829 } else { 1830 p->real_parent = current; 1831 p->parent_exec_id = current->self_exec_id; 1832 } 1833 1834 klp_copy_process(p); 1835 1836 spin_lock(¤t->sighand->siglock); 1837 1838 /* 1839 * Copy seccomp details explicitly here, in case they were changed 1840 * before holding sighand lock. 1841 */ 1842 copy_seccomp(p); 1843 1844 /* 1845 * Process group and session signals need to be delivered to just the 1846 * parent before the fork or both the parent and the child after the 1847 * fork. Restart if a signal comes in before we add the new process to 1848 * it's process group. 1849 * A fatal signal pending means that current will exit, so the new 1850 * thread can't slip out of an OOM kill (or normal SIGKILL). 1851 */ 1852 recalc_sigpending(); 1853 if (signal_pending(current)) { 1854 retval = -ERESTARTNOINTR; 1855 goto bad_fork_cancel_cgroup; 1856 } 1857 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) { 1858 retval = -ENOMEM; 1859 goto bad_fork_cancel_cgroup; 1860 } 1861 1862 if (likely(p->pid)) { 1863 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1864 1865 init_task_pid(p, PIDTYPE_PID, pid); 1866 if (thread_group_leader(p)) { 1867 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1868 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1869 1870 if (is_child_reaper(pid)) { 1871 ns_of_pid(pid)->child_reaper = p; 1872 p->signal->flags |= SIGNAL_UNKILLABLE; 1873 } 1874 1875 p->signal->leader_pid = pid; 1876 p->signal->tty = tty_kref_get(current->signal->tty); 1877 /* 1878 * Inherit has_child_subreaper flag under the same 1879 * tasklist_lock with adding child to the process tree 1880 * for propagate_has_child_subreaper optimization. 1881 */ 1882 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1883 p->real_parent->signal->is_child_subreaper; 1884 list_add_tail(&p->sibling, &p->real_parent->children); 1885 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1886 attach_pid(p, PIDTYPE_PGID); 1887 attach_pid(p, PIDTYPE_SID); 1888 __this_cpu_inc(process_counts); 1889 } else { 1890 current->signal->nr_threads++; 1891 atomic_inc(¤t->signal->live); 1892 atomic_inc(¤t->signal->sigcnt); 1893 list_add_tail_rcu(&p->thread_group, 1894 &p->group_leader->thread_group); 1895 list_add_tail_rcu(&p->thread_node, 1896 &p->signal->thread_head); 1897 } 1898 attach_pid(p, PIDTYPE_PID); 1899 nr_threads++; 1900 } 1901 1902 total_forks++; 1903 spin_unlock(¤t->sighand->siglock); 1904 syscall_tracepoint_update(p); 1905 write_unlock_irq(&tasklist_lock); 1906 1907 proc_fork_connector(p); 1908 cgroup_post_fork(p); 1909 cgroup_threadgroup_change_end(current); 1910 perf_event_fork(p); 1911 1912 trace_task_newtask(p, clone_flags); 1913 uprobe_copy_process(p, clone_flags); 1914 1915 return p; 1916 1917 bad_fork_cancel_cgroup: 1918 spin_unlock(¤t->sighand->siglock); 1919 write_unlock_irq(&tasklist_lock); 1920 cgroup_cancel_fork(p); 1921 bad_fork_free_pid: 1922 cgroup_threadgroup_change_end(current); 1923 if (pid != &init_struct_pid) 1924 free_pid(pid); 1925 bad_fork_cleanup_thread: 1926 exit_thread(p); 1927 bad_fork_cleanup_io: 1928 if (p->io_context) 1929 exit_io_context(p); 1930 bad_fork_cleanup_namespaces: 1931 exit_task_namespaces(p); 1932 bad_fork_cleanup_mm: 1933 if (p->mm) 1934 mmput(p->mm); 1935 bad_fork_cleanup_signal: 1936 if (!(clone_flags & CLONE_THREAD)) 1937 free_signal_struct(p->signal); 1938 bad_fork_cleanup_sighand: 1939 __cleanup_sighand(p->sighand); 1940 bad_fork_cleanup_fs: 1941 exit_fs(p); /* blocking */ 1942 bad_fork_cleanup_files: 1943 exit_files(p); /* blocking */ 1944 bad_fork_cleanup_semundo: 1945 exit_sem(p); 1946 bad_fork_cleanup_security: 1947 security_task_free(p); 1948 bad_fork_cleanup_audit: 1949 audit_free(p); 1950 bad_fork_cleanup_perf: 1951 perf_event_free_task(p); 1952 bad_fork_cleanup_policy: 1953 #ifdef CONFIG_NUMA 1954 mpol_put(p->mempolicy); 1955 bad_fork_cleanup_threadgroup_lock: 1956 #endif 1957 delayacct_tsk_free(p); 1958 bad_fork_cleanup_count: 1959 atomic_dec(&p->cred->user->processes); 1960 exit_creds(p); 1961 bad_fork_free: 1962 p->state = TASK_DEAD; 1963 put_task_stack(p); 1964 free_task(p); 1965 fork_out: 1966 return ERR_PTR(retval); 1967 } 1968 1969 static inline void init_idle_pids(struct pid_link *links) 1970 { 1971 enum pid_type type; 1972 1973 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1974 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1975 links[type].pid = &init_struct_pid; 1976 } 1977 } 1978 1979 struct task_struct *fork_idle(int cpu) 1980 { 1981 struct task_struct *task; 1982 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1983 cpu_to_node(cpu)); 1984 if (!IS_ERR(task)) { 1985 init_idle_pids(task->pids); 1986 init_idle(task, cpu); 1987 } 1988 1989 return task; 1990 } 1991 1992 /* 1993 * Ok, this is the main fork-routine. 1994 * 1995 * It copies the process, and if successful kick-starts 1996 * it and waits for it to finish using the VM if required. 1997 */ 1998 long _do_fork(unsigned long clone_flags, 1999 unsigned long stack_start, 2000 unsigned long stack_size, 2001 int __user *parent_tidptr, 2002 int __user *child_tidptr, 2003 unsigned long tls) 2004 { 2005 struct task_struct *p; 2006 int trace = 0; 2007 long nr; 2008 2009 /* 2010 * Determine whether and which event to report to ptracer. When 2011 * called from kernel_thread or CLONE_UNTRACED is explicitly 2012 * requested, no event is reported; otherwise, report if the event 2013 * for the type of forking is enabled. 2014 */ 2015 if (!(clone_flags & CLONE_UNTRACED)) { 2016 if (clone_flags & CLONE_VFORK) 2017 trace = PTRACE_EVENT_VFORK; 2018 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2019 trace = PTRACE_EVENT_CLONE; 2020 else 2021 trace = PTRACE_EVENT_FORK; 2022 2023 if (likely(!ptrace_event_enabled(current, trace))) 2024 trace = 0; 2025 } 2026 2027 p = copy_process(clone_flags, stack_start, stack_size, 2028 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2029 add_latent_entropy(); 2030 /* 2031 * Do this prior waking up the new thread - the thread pointer 2032 * might get invalid after that point, if the thread exits quickly. 2033 */ 2034 if (!IS_ERR(p)) { 2035 struct completion vfork; 2036 struct pid *pid; 2037 2038 trace_sched_process_fork(current, p); 2039 2040 pid = get_task_pid(p, PIDTYPE_PID); 2041 nr = pid_vnr(pid); 2042 2043 if (clone_flags & CLONE_PARENT_SETTID) 2044 put_user(nr, parent_tidptr); 2045 2046 if (clone_flags & CLONE_VFORK) { 2047 p->vfork_done = &vfork; 2048 init_completion(&vfork); 2049 get_task_struct(p); 2050 } 2051 2052 wake_up_new_task(p); 2053 2054 /* forking complete and child started to run, tell ptracer */ 2055 if (unlikely(trace)) 2056 ptrace_event_pid(trace, pid); 2057 2058 if (clone_flags & CLONE_VFORK) { 2059 if (!wait_for_vfork_done(p, &vfork)) 2060 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2061 } 2062 2063 put_pid(pid); 2064 } else { 2065 nr = PTR_ERR(p); 2066 } 2067 return nr; 2068 } 2069 2070 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2071 /* For compatibility with architectures that call do_fork directly rather than 2072 * using the syscall entry points below. */ 2073 long do_fork(unsigned long clone_flags, 2074 unsigned long stack_start, 2075 unsigned long stack_size, 2076 int __user *parent_tidptr, 2077 int __user *child_tidptr) 2078 { 2079 return _do_fork(clone_flags, stack_start, stack_size, 2080 parent_tidptr, child_tidptr, 0); 2081 } 2082 #endif 2083 2084 /* 2085 * Create a kernel thread. 2086 */ 2087 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2088 { 2089 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2090 (unsigned long)arg, NULL, NULL, 0); 2091 } 2092 2093 #ifdef __ARCH_WANT_SYS_FORK 2094 SYSCALL_DEFINE0(fork) 2095 { 2096 #ifdef CONFIG_MMU 2097 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2098 #else 2099 /* can not support in nommu mode */ 2100 return -EINVAL; 2101 #endif 2102 } 2103 #endif 2104 2105 #ifdef __ARCH_WANT_SYS_VFORK 2106 SYSCALL_DEFINE0(vfork) 2107 { 2108 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2109 0, NULL, NULL, 0); 2110 } 2111 #endif 2112 2113 #ifdef __ARCH_WANT_SYS_CLONE 2114 #ifdef CONFIG_CLONE_BACKWARDS 2115 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2116 int __user *, parent_tidptr, 2117 unsigned long, tls, 2118 int __user *, child_tidptr) 2119 #elif defined(CONFIG_CLONE_BACKWARDS2) 2120 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2121 int __user *, parent_tidptr, 2122 int __user *, child_tidptr, 2123 unsigned long, tls) 2124 #elif defined(CONFIG_CLONE_BACKWARDS3) 2125 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2126 int, stack_size, 2127 int __user *, parent_tidptr, 2128 int __user *, child_tidptr, 2129 unsigned long, tls) 2130 #else 2131 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2132 int __user *, parent_tidptr, 2133 int __user *, child_tidptr, 2134 unsigned long, tls) 2135 #endif 2136 { 2137 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2138 } 2139 #endif 2140 2141 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2142 { 2143 struct task_struct *leader, *parent, *child; 2144 int res; 2145 2146 read_lock(&tasklist_lock); 2147 leader = top = top->group_leader; 2148 down: 2149 for_each_thread(leader, parent) { 2150 list_for_each_entry(child, &parent->children, sibling) { 2151 res = visitor(child, data); 2152 if (res) { 2153 if (res < 0) 2154 goto out; 2155 leader = child; 2156 goto down; 2157 } 2158 up: 2159 ; 2160 } 2161 } 2162 2163 if (leader != top) { 2164 child = leader; 2165 parent = child->real_parent; 2166 leader = parent->group_leader; 2167 goto up; 2168 } 2169 out: 2170 read_unlock(&tasklist_lock); 2171 } 2172 2173 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2174 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2175 #endif 2176 2177 static void sighand_ctor(void *data) 2178 { 2179 struct sighand_struct *sighand = data; 2180 2181 spin_lock_init(&sighand->siglock); 2182 init_waitqueue_head(&sighand->signalfd_wqh); 2183 } 2184 2185 void __init proc_caches_init(void) 2186 { 2187 sighand_cachep = kmem_cache_create("sighand_cache", 2188 sizeof(struct sighand_struct), 0, 2189 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2190 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2191 signal_cachep = kmem_cache_create("signal_cache", 2192 sizeof(struct signal_struct), 0, 2193 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2194 NULL); 2195 files_cachep = kmem_cache_create("files_cache", 2196 sizeof(struct files_struct), 0, 2197 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2198 NULL); 2199 fs_cachep = kmem_cache_create("fs_cache", 2200 sizeof(struct fs_struct), 0, 2201 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2202 NULL); 2203 /* 2204 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2205 * whole struct cpumask for the OFFSTACK case. We could change 2206 * this to *only* allocate as much of it as required by the 2207 * maximum number of CPU's we can ever have. The cpumask_allocation 2208 * is at the end of the structure, exactly for that reason. 2209 */ 2210 mm_cachep = kmem_cache_create("mm_struct", 2211 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2212 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2213 NULL); 2214 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2215 mmap_init(); 2216 nsproxy_cache_init(); 2217 } 2218 2219 /* 2220 * Check constraints on flags passed to the unshare system call. 2221 */ 2222 static int check_unshare_flags(unsigned long unshare_flags) 2223 { 2224 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2225 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2226 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2227 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2228 return -EINVAL; 2229 /* 2230 * Not implemented, but pretend it works if there is nothing 2231 * to unshare. Note that unsharing the address space or the 2232 * signal handlers also need to unshare the signal queues (aka 2233 * CLONE_THREAD). 2234 */ 2235 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2236 if (!thread_group_empty(current)) 2237 return -EINVAL; 2238 } 2239 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2240 if (atomic_read(¤t->sighand->count) > 1) 2241 return -EINVAL; 2242 } 2243 if (unshare_flags & CLONE_VM) { 2244 if (!current_is_single_threaded()) 2245 return -EINVAL; 2246 } 2247 2248 return 0; 2249 } 2250 2251 /* 2252 * Unshare the filesystem structure if it is being shared 2253 */ 2254 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2255 { 2256 struct fs_struct *fs = current->fs; 2257 2258 if (!(unshare_flags & CLONE_FS) || !fs) 2259 return 0; 2260 2261 /* don't need lock here; in the worst case we'll do useless copy */ 2262 if (fs->users == 1) 2263 return 0; 2264 2265 *new_fsp = copy_fs_struct(fs); 2266 if (!*new_fsp) 2267 return -ENOMEM; 2268 2269 return 0; 2270 } 2271 2272 /* 2273 * Unshare file descriptor table if it is being shared 2274 */ 2275 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2276 { 2277 struct files_struct *fd = current->files; 2278 int error = 0; 2279 2280 if ((unshare_flags & CLONE_FILES) && 2281 (fd && atomic_read(&fd->count) > 1)) { 2282 *new_fdp = dup_fd(fd, &error); 2283 if (!*new_fdp) 2284 return error; 2285 } 2286 2287 return 0; 2288 } 2289 2290 /* 2291 * unshare allows a process to 'unshare' part of the process 2292 * context which was originally shared using clone. copy_* 2293 * functions used by do_fork() cannot be used here directly 2294 * because they modify an inactive task_struct that is being 2295 * constructed. Here we are modifying the current, active, 2296 * task_struct. 2297 */ 2298 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2299 { 2300 struct fs_struct *fs, *new_fs = NULL; 2301 struct files_struct *fd, *new_fd = NULL; 2302 struct cred *new_cred = NULL; 2303 struct nsproxy *new_nsproxy = NULL; 2304 int do_sysvsem = 0; 2305 int err; 2306 2307 /* 2308 * If unsharing a user namespace must also unshare the thread group 2309 * and unshare the filesystem root and working directories. 2310 */ 2311 if (unshare_flags & CLONE_NEWUSER) 2312 unshare_flags |= CLONE_THREAD | CLONE_FS; 2313 /* 2314 * If unsharing vm, must also unshare signal handlers. 2315 */ 2316 if (unshare_flags & CLONE_VM) 2317 unshare_flags |= CLONE_SIGHAND; 2318 /* 2319 * If unsharing a signal handlers, must also unshare the signal queues. 2320 */ 2321 if (unshare_flags & CLONE_SIGHAND) 2322 unshare_flags |= CLONE_THREAD; 2323 /* 2324 * If unsharing namespace, must also unshare filesystem information. 2325 */ 2326 if (unshare_flags & CLONE_NEWNS) 2327 unshare_flags |= CLONE_FS; 2328 2329 err = check_unshare_flags(unshare_flags); 2330 if (err) 2331 goto bad_unshare_out; 2332 /* 2333 * CLONE_NEWIPC must also detach from the undolist: after switching 2334 * to a new ipc namespace, the semaphore arrays from the old 2335 * namespace are unreachable. 2336 */ 2337 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2338 do_sysvsem = 1; 2339 err = unshare_fs(unshare_flags, &new_fs); 2340 if (err) 2341 goto bad_unshare_out; 2342 err = unshare_fd(unshare_flags, &new_fd); 2343 if (err) 2344 goto bad_unshare_cleanup_fs; 2345 err = unshare_userns(unshare_flags, &new_cred); 2346 if (err) 2347 goto bad_unshare_cleanup_fd; 2348 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2349 new_cred, new_fs); 2350 if (err) 2351 goto bad_unshare_cleanup_cred; 2352 2353 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2354 if (do_sysvsem) { 2355 /* 2356 * CLONE_SYSVSEM is equivalent to sys_exit(). 2357 */ 2358 exit_sem(current); 2359 } 2360 if (unshare_flags & CLONE_NEWIPC) { 2361 /* Orphan segments in old ns (see sem above). */ 2362 exit_shm(current); 2363 shm_init_task(current); 2364 } 2365 2366 if (new_nsproxy) 2367 switch_task_namespaces(current, new_nsproxy); 2368 2369 task_lock(current); 2370 2371 if (new_fs) { 2372 fs = current->fs; 2373 spin_lock(&fs->lock); 2374 current->fs = new_fs; 2375 if (--fs->users) 2376 new_fs = NULL; 2377 else 2378 new_fs = fs; 2379 spin_unlock(&fs->lock); 2380 } 2381 2382 if (new_fd) { 2383 fd = current->files; 2384 current->files = new_fd; 2385 new_fd = fd; 2386 } 2387 2388 task_unlock(current); 2389 2390 if (new_cred) { 2391 /* Install the new user namespace */ 2392 commit_creds(new_cred); 2393 new_cred = NULL; 2394 } 2395 } 2396 2397 perf_event_namespaces(current); 2398 2399 bad_unshare_cleanup_cred: 2400 if (new_cred) 2401 put_cred(new_cred); 2402 bad_unshare_cleanup_fd: 2403 if (new_fd) 2404 put_files_struct(new_fd); 2405 2406 bad_unshare_cleanup_fs: 2407 if (new_fs) 2408 free_fs_struct(new_fs); 2409 2410 bad_unshare_out: 2411 return err; 2412 } 2413 2414 /* 2415 * Helper to unshare the files of the current task. 2416 * We don't want to expose copy_files internals to 2417 * the exec layer of the kernel. 2418 */ 2419 2420 int unshare_files(struct files_struct **displaced) 2421 { 2422 struct task_struct *task = current; 2423 struct files_struct *copy = NULL; 2424 int error; 2425 2426 error = unshare_fd(CLONE_FILES, ©); 2427 if (error || !copy) { 2428 *displaced = NULL; 2429 return error; 2430 } 2431 *displaced = task->files; 2432 task_lock(task); 2433 task->files = copy; 2434 task_unlock(task); 2435 return 0; 2436 } 2437 2438 int sysctl_max_threads(struct ctl_table *table, int write, 2439 void __user *buffer, size_t *lenp, loff_t *ppos) 2440 { 2441 struct ctl_table t; 2442 int ret; 2443 int threads = max_threads; 2444 int min = MIN_THREADS; 2445 int max = MAX_THREADS; 2446 2447 t = *table; 2448 t.data = &threads; 2449 t.extra1 = &min; 2450 t.extra2 = &max; 2451 2452 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2453 if (ret || !write) 2454 return ret; 2455 2456 set_max_threads(threads); 2457 2458 return 0; 2459 } 2460