개념 설명 전체 · v6.6 / kernel/fork.c
1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/kernel/fork.c 4 * 5 * Copyright (C) 1991, 1992 Linus Torvalds 6 */ 7 8 /* 9 * 'fork.c' contains the help-routines for the 'fork' system call 10 * (see also entry.S and others). 11 * Fork is rather simple, once you get the hang of it, but the memory 12 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 13 */ 14 15 #include <linux/anon_inodes.h> 16 #include <linux/slab.h> 17 #include <linux/sched/autogroup.h> 18 #include <linux/sched/mm.h> 19 #include <linux/sched/coredump.h> 20 #include <linux/sched/user.h> 21 #include <linux/sched/numa_balancing.h> 22 #include <linux/sched/stat.h> 23 #include <linux/sched/task.h> 24 #include <linux/sched/task_stack.h> 25 #include <linux/sched/cputime.h> 26 #include <linux/seq_file.h> 27 #include <linux/rtmutex.h> 28 #include <linux/init.h> 29 #include <linux/unistd.h> 30 #include <linux/module.h> 31 #include <linux/vmalloc.h> 32 #include <linux/completion.h> 33 #include <linux/personality.h> 34 #include <linux/mempolicy.h> 35 #include <linux/sem.h> 36 #include <linux/file.h> 37 #include <linux/fdtable.h> 38 #include <linux/iocontext.h> 39 #include <linux/key.h> 40 #include <linux/kmsan.h> 41 #include <linux/binfmts.h> 42 #include <linux/mman.h> 43 #include <linux/mmu_notifier.h> 44 #include <linux/fs.h> 45 #include <linux/mm.h> 46 #include <linux/mm_inline.h> 47 #include <linux/nsproxy.h> 48 #include <linux/capability.h> 49 #include <linux/cpu.h> 50 #include <linux/cgroup.h> 51 #include <linux/security.h> 52 #include <linux/hugetlb.h> 53 #include <linux/seccomp.h> 54 #include <linux/swap.h> 55 #include <linux/syscalls.h> 56 #include <linux/jiffies.h> 57 #include <linux/futex.h> 58 #include <linux/compat.h> 59 #include <linux/kthread.h> 60 #include <linux/task_io_accounting_ops.h> 61 #include <linux/rcupdate.h> 62 #include <linux/ptrace.h> 63 #include <linux/mount.h> 64 #include <linux/audit.h> 65 #include <linux/memcontrol.h> 66 #include <linux/ftrace.h> 67 #include <linux/proc_fs.h> 68 #include <linux/profile.h> 69 #include <linux/rmap.h> 70 #include <linux/ksm.h> 71 #include <linux/acct.h> 72 #include <linux/userfaultfd_k.h> 73 #include <linux/tsacct_kern.h> 74 #include <linux/cn_proc.h> 75 #include <linux/freezer.h> 76 #include <linux/delayacct.h> 77 #include <linux/taskstats_kern.h> 78 #include <linux/tty.h> 79 #include <linux/fs_struct.h> 80 #include <linux/magic.h> 81 #include <linux/perf_event.h> 82 #include <linux/posix-timers.h> 83 #include <linux/user-return-notifier.h> 84 #include <linux/oom.h> 85 #include <linux/khugepaged.h> 86 #include <linux/signalfd.h> 87 #include <linux/uprobes.h> 88 #include <linux/aio.h> 89 #include <linux/compiler.h> 90 #include <linux/sysctl.h> 91 #include <linux/kcov.h> 92 #include <linux/livepatch.h> 93 #include <linux/thread_info.h> 94 #include <linux/stackleak.h> 95 #include <linux/kasan.h> 96 #include <linux/scs.h> 97 #include <linux/io_uring.h> 98 #include <linux/bpf.h> 99 #include <linux/stackprotector.h> 100 #include <linux/user_events.h> 101 #include <linux/iommu.h> 102 103 #include <asm/pgalloc.h> 104 #include <linux/uaccess.h> 105 #include <asm/mmu_context.h> 106 #include <asm/cacheflush.h> 107 #include <asm/tlbflush.h> 108 109 #include <trace/events/sched.h> 110 111 #define CREATE_TRACE_POINTS 112 #include <trace/events/task.h> 113 114 /* 115 * Minimum number of threads to boot the kernel 116 */ 117 #define MIN_THREADS 20 118 119 /* 120 * Maximum number of threads 121 */ 122 #define MAX_THREADS FUTEX_TID_MASK 123 124 /* 125 * Protected counters by write_lock_irq(&tasklist_lock) 126 */ 127 unsigned long total_forks; /* Handle normal Linux uptimes. */ 128 int nr_threads; /* The idle threads do not count.. */ 129 130 static int max_threads; /* tunable limit on nr_threads */ 131 132 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x) 133 134 static const char * const resident_page_types[] = { 135 NAMED_ARRAY_INDEX(MM_FILEPAGES), 136 NAMED_ARRAY_INDEX(MM_ANONPAGES), 137 NAMED_ARRAY_INDEX(MM_SWAPENTS), 138 NAMED_ARRAY_INDEX(MM_SHMEMPAGES), 139 }; 140 141 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 142 143 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 144 145 #ifdef CONFIG_PROVE_RCU 146 int lockdep_tasklist_lock_is_held(void) 147 { 148 return lockdep_is_held(&tasklist_lock); 149 } 150 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 151 #endif /* #ifdef CONFIG_PROVE_RCU */ 152 153 int nr_processes(void) 154 { 155 int cpu; 156 int total = 0; 157 158 for_each_possible_cpu(cpu) 159 total += per_cpu(process_counts, cpu); 160 161 return total; 162 } 163 164 void __weak arch_release_task_struct(struct task_struct *tsk) 165 { 166 } 167 168 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 169 static struct kmem_cache *task_struct_cachep; 170 171 static inline struct task_struct *alloc_task_struct_node(int node) 172 { 173 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 174 } 175 176 static inline void free_task_struct(struct task_struct *tsk) 177 { 178 kmem_cache_free(task_struct_cachep, tsk); 179 } 180 #endif 181 182 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 183 184 /* 185 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 186 * kmemcache based allocator. 187 */ 188 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 189 190 # ifdef CONFIG_VMAP_STACK 191 /* 192 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 193 * flush. Try to minimize the number of calls by caching stacks. 194 */ 195 #define NR_CACHED_STACKS 2 196 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 197 198 struct vm_stack { 199 struct rcu_head rcu; 200 struct vm_struct *stack_vm_area; 201 }; 202 203 static bool try_release_thread_stack_to_cache(struct vm_struct *vm) 204 { 205 unsigned int i; 206 207 for (i = 0; i < NR_CACHED_STACKS; i++) { 208 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL) 209 continue; 210 return true; 211 } 212 return false; 213 } 214 215 static void thread_stack_free_rcu(struct rcu_head *rh) 216 { 217 struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu); 218 219 if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area)) 220 return; 221 222 vfree(vm_stack); 223 } 224 225 static void thread_stack_delayed_free(struct task_struct *tsk) 226 { 227 struct vm_stack *vm_stack = tsk->stack; 228 229 vm_stack->stack_vm_area = tsk->stack_vm_area; 230 call_rcu(&vm_stack->rcu, thread_stack_free_rcu); 231 } 232 233 static int free_vm_stack_cache(unsigned int cpu) 234 { 235 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 236 int i; 237 238 for (i = 0; i < NR_CACHED_STACKS; i++) { 239 struct vm_struct *vm_stack = cached_vm_stacks[i]; 240 241 if (!vm_stack) 242 continue; 243 244 vfree(vm_stack->addr); 245 cached_vm_stacks[i] = NULL; 246 } 247 248 return 0; 249 } 250 251 static int memcg_charge_kernel_stack(struct vm_struct *vm) 252 { 253 int i; 254 int ret; 255 int nr_charged = 0; 256 257 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 258 259 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 260 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0); 261 if (ret) 262 goto err; 263 nr_charged++; 264 } 265 return 0; 266 err: 267 for (i = 0; i < nr_charged; i++) 268 memcg_kmem_uncharge_page(vm->pages[i], 0); 269 return ret; 270 } 271 272 static int alloc_thread_stack_node(struct task_struct *tsk, int node) 273 { 274 struct vm_struct *vm; 275 void *stack; 276 int i; 277 278 for (i = 0; i < NR_CACHED_STACKS; i++) { 279 struct vm_struct *s; 280 281 s = this_cpu_xchg(cached_stacks[i], NULL); 282 283 if (!s) 284 continue; 285 286 /* Reset stack metadata. */ 287 kasan_unpoison_range(s->addr, THREAD_SIZE); 288 289 stack = kasan_reset_tag(s->addr); 290 291 /* Clear stale pointers from reused stack. */ 292 memset(stack, 0, THREAD_SIZE); 293 294 if (memcg_charge_kernel_stack(s)) { 295 vfree(s->addr); 296 return -ENOMEM; 297 } 298 299 tsk->stack_vm_area = s; 300 tsk->stack = stack; 301 return 0; 302 } 303 304 /* 305 * Allocated stacks are cached and later reused by new threads, 306 * so memcg accounting is performed manually on assigning/releasing 307 * stacks to tasks. Drop __GFP_ACCOUNT. 308 */ 309 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, 310 VMALLOC_START, VMALLOC_END, 311 THREADINFO_GFP & ~__GFP_ACCOUNT, 312 PAGE_KERNEL, 313 0, node, __builtin_return_address(0)); 314 if (!stack) 315 return -ENOMEM; 316 317 vm = find_vm_area(stack); 318 if (memcg_charge_kernel_stack(vm)) { 319 vfree(stack); 320 return -ENOMEM; 321 } 322 /* 323 * We can't call find_vm_area() in interrupt context, and 324 * free_thread_stack() can be called in interrupt context, 325 * so cache the vm_struct. 326 */ 327 tsk->stack_vm_area = vm; 328 stack = kasan_reset_tag(stack); 329 tsk->stack = stack; 330 return 0; 331 } 332 333 static void free_thread_stack(struct task_struct *tsk) 334 { 335 if (!try_release_thread_stack_to_cache(tsk->stack_vm_area)) 336 thread_stack_delayed_free(tsk); 337 338 tsk->stack = NULL; 339 tsk->stack_vm_area = NULL; 340 } 341 342 # else /* !CONFIG_VMAP_STACK */ 343 344 static void thread_stack_free_rcu(struct rcu_head *rh) 345 { 346 __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER); 347 } 348 349 static void thread_stack_delayed_free(struct task_struct *tsk) 350 { 351 struct rcu_head *rh = tsk->stack; 352 353 call_rcu(rh, thread_stack_free_rcu); 354 } 355 356 static int alloc_thread_stack_node(struct task_struct *tsk, int node) 357 { 358 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 359 THREAD_SIZE_ORDER); 360 361 if (likely(page)) { 362 tsk->stack = kasan_reset_tag(page_address(page)); 363 return 0; 364 } 365 return -ENOMEM; 366 } 367 368 static void free_thread_stack(struct task_struct *tsk) 369 { 370 thread_stack_delayed_free(tsk); 371 tsk->stack = NULL; 372 } 373 374 # endif /* CONFIG_VMAP_STACK */ 375 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */ 376 377 static struct kmem_cache *thread_stack_cache; 378 379 static void thread_stack_free_rcu(struct rcu_head *rh) 380 { 381 kmem_cache_free(thread_stack_cache, rh); 382 } 383 384 static void thread_stack_delayed_free(struct task_struct *tsk) 385 { 386 struct rcu_head *rh = tsk->stack; 387 388 call_rcu(rh, thread_stack_free_rcu); 389 } 390 391 static int alloc_thread_stack_node(struct task_struct *tsk, int node) 392 { 393 unsigned long *stack; 394 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 395 stack = kasan_reset_tag(stack); 396 tsk->stack = stack; 397 return stack ? 0 : -ENOMEM; 398 } 399 400 static void free_thread_stack(struct task_struct *tsk) 401 { 402 thread_stack_delayed_free(tsk); 403 tsk->stack = NULL; 404 } 405 406 void thread_stack_cache_init(void) 407 { 408 thread_stack_cache = kmem_cache_create_usercopy("thread_stack", 409 THREAD_SIZE, THREAD_SIZE, 0, 0, 410 THREAD_SIZE, NULL); 411 BUG_ON(thread_stack_cache == NULL); 412 } 413 414 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */ 415 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */ 416 417 static int alloc_thread_stack_node(struct task_struct *tsk, int node) 418 { 419 unsigned long *stack; 420 421 stack = arch_alloc_thread_stack_node(tsk, node); 422 tsk->stack = stack; 423 return stack ? 0 : -ENOMEM; 424 } 425 426 static void free_thread_stack(struct task_struct *tsk) 427 { 428 arch_free_thread_stack(tsk); 429 tsk->stack = NULL; 430 } 431 432 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */ 433 434 /* SLAB cache for signal_struct structures (tsk->signal) */ 435 static struct kmem_cache *signal_cachep; 436 437 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 438 struct kmem_cache *sighand_cachep; 439 440 /* SLAB cache for files_struct structures (tsk->files) */ 441 struct kmem_cache *files_cachep; 442 443 /* SLAB cache for fs_struct structures (tsk->fs) */ 444 struct kmem_cache *fs_cachep; 445 446 /* SLAB cache for vm_area_struct structures */ 447 static struct kmem_cache *vm_area_cachep; 448 449 /* SLAB cache for mm_struct structures (tsk->mm) */ 450 static struct kmem_cache *mm_cachep; 451 452 #ifdef CONFIG_PER_VMA_LOCK 453 454 /* SLAB cache for vm_area_struct.lock */ 455 static struct kmem_cache *vma_lock_cachep; 456 457 static bool vma_lock_alloc(struct vm_area_struct *vma) 458 { 459 vma->vm_lock = kmem_cache_alloc(vma_lock_cachep, GFP_KERNEL); 460 if (!vma->vm_lock) 461 return false; 462 463 init_rwsem(&vma->vm_lock->lock); 464 vma->vm_lock_seq = -1; 465 466 return true; 467 } 468 469 static inline void vma_lock_free(struct vm_area_struct *vma) 470 { 471 kmem_cache_free(vma_lock_cachep, vma->vm_lock); 472 } 473 474 #else /* CONFIG_PER_VMA_LOCK */ 475 476 static inline bool vma_lock_alloc(struct vm_area_struct *vma) { return true; } 477 static inline void vma_lock_free(struct vm_area_struct *vma) {} 478 479 #endif /* CONFIG_PER_VMA_LOCK */ 480 481 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm) 482 { 483 struct vm_area_struct *vma; 484 485 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 486 if (!vma) 487 return NULL; 488 489 vma_init(vma, mm); 490 if (!vma_lock_alloc(vma)) { 491 kmem_cache_free(vm_area_cachep, vma); 492 return NULL; 493 } 494 495 return vma; 496 } 497 498 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) 499 { 500 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 501 502 if (!new) 503 return NULL; 504 505 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags); 506 ASSERT_EXCLUSIVE_WRITER(orig->vm_file); 507 /* 508 * orig->shared.rb may be modified concurrently, but the clone 509 * will be reinitialized. 510 */ 511 data_race(memcpy(new, orig, sizeof(*new))); 512 if (!vma_lock_alloc(new)) { 513 kmem_cache_free(vm_area_cachep, new); 514 return NULL; 515 } 516 INIT_LIST_HEAD(&new->anon_vma_chain); 517 vma_numab_state_init(new); 518 dup_anon_vma_name(orig, new); 519 520 return new; 521 } 522 523 void __vm_area_free(struct vm_area_struct *vma) 524 { 525 vma_numab_state_free(vma); 526 free_anon_vma_name(vma); 527 vma_lock_free(vma); 528 kmem_cache_free(vm_area_cachep, vma); 529 } 530 531 #ifdef CONFIG_PER_VMA_LOCK 532 static void vm_area_free_rcu_cb(struct rcu_head *head) 533 { 534 struct vm_area_struct *vma = container_of(head, struct vm_area_struct, 535 vm_rcu); 536 537 /* The vma should not be locked while being destroyed. */ 538 VM_BUG_ON_VMA(rwsem_is_locked(&vma->vm_lock->lock), vma); 539 __vm_area_free(vma); 540 } 541 #endif 542 543 void vm_area_free(struct vm_area_struct *vma) 544 { 545 #ifdef CONFIG_PER_VMA_LOCK 546 call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb); 547 #else 548 __vm_area_free(vma); 549 #endif 550 } 551 552 static void account_kernel_stack(struct task_struct *tsk, int account) 553 { 554 if (IS_ENABLED(CONFIG_VMAP_STACK)) { 555 struct vm_struct *vm = task_stack_vm_area(tsk); 556 int i; 557 558 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) 559 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB, 560 account * (PAGE_SIZE / 1024)); 561 } else { 562 void *stack = task_stack_page(tsk); 563 564 /* All stack pages are in the same node. */ 565 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB, 566 account * (THREAD_SIZE / 1024)); 567 } 568 } 569 570 void exit_task_stack_account(struct task_struct *tsk) 571 { 572 account_kernel_stack(tsk, -1); 573 574 if (IS_ENABLED(CONFIG_VMAP_STACK)) { 575 struct vm_struct *vm; 576 int i; 577 578 vm = task_stack_vm_area(tsk); 579 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) 580 memcg_kmem_uncharge_page(vm->pages[i], 0); 581 } 582 } 583 584 static void release_task_stack(struct task_struct *tsk) 585 { 586 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD)) 587 return; /* Better to leak the stack than to free prematurely */ 588 589 free_thread_stack(tsk); 590 } 591 592 #ifdef CONFIG_THREAD_INFO_IN_TASK 593 void put_task_stack(struct task_struct *tsk) 594 { 595 if (refcount_dec_and_test(&tsk->stack_refcount)) 596 release_task_stack(tsk); 597 } 598 #endif 599 600 void free_task(struct task_struct *tsk) 601 { 602 #ifdef CONFIG_SECCOMP 603 WARN_ON_ONCE(tsk->seccomp.filter); 604 #endif 605 release_user_cpus_ptr(tsk); 606 scs_release(tsk); 607 608 #ifndef CONFIG_THREAD_INFO_IN_TASK 609 /* 610 * The task is finally done with both the stack and thread_info, 611 * so free both. 612 */ 613 release_task_stack(tsk); 614 #else 615 /* 616 * If the task had a separate stack allocation, it should be gone 617 * by now. 618 */ 619 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0); 620 #endif 621 rt_mutex_debug_task_free(tsk); 622 ftrace_graph_exit_task(tsk); 623 arch_release_task_struct(tsk); 624 if (tsk->flags & PF_KTHREAD) 625 free_kthread_struct(tsk); 626 bpf_task_storage_free(tsk); 627 free_task_struct(tsk); 628 } 629 EXPORT_SYMBOL(free_task); 630 631 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm) 632 { 633 struct file *exe_file; 634 635 exe_file = get_mm_exe_file(oldmm); 636 RCU_INIT_POINTER(mm->exe_file, exe_file); 637 /* 638 * We depend on the oldmm having properly denied write access to the 639 * exe_file already. 640 */ 641 if (exe_file && deny_write_access(exe_file)) 642 pr_warn_once("deny_write_access() failed in %s\n", __func__); 643 } 644 645 #ifdef CONFIG_MMU 646 static __latent_entropy int dup_mmap(struct mm_struct *mm, 647 struct mm_struct *oldmm) 648 { 649 struct vm_area_struct *mpnt, *tmp; 650 int retval; 651 unsigned long charge = 0; 652 LIST_HEAD(uf); 653 VMA_ITERATOR(old_vmi, oldmm, 0); 654 VMA_ITERATOR(vmi, mm, 0); 655 656 uprobe_start_dup_mmap(); 657 if (mmap_write_lock_killable(oldmm)) { 658 retval = -EINTR; 659 goto fail_uprobe_end; 660 } 661 flush_cache_dup_mm(oldmm); 662 uprobe_dup_mmap(oldmm, mm); 663 /* 664 * Not linked in yet - no deadlock potential: 665 */ 666 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); 667 668 /* No ordering required: file already has been exposed. */ 669 dup_mm_exe_file(mm, oldmm); 670 671 mm->total_vm = oldmm->total_vm; 672 mm->data_vm = oldmm->data_vm; 673 mm->exec_vm = oldmm->exec_vm; 674 mm->stack_vm = oldmm->stack_vm; 675 676 retval = ksm_fork(mm, oldmm); 677 if (retval) 678 goto out; 679 khugepaged_fork(mm, oldmm); 680 681 retval = vma_iter_bulk_alloc(&vmi, oldmm->map_count); 682 if (retval) 683 goto out; 684 685 mt_clear_in_rcu(vmi.mas.tree); 686 for_each_vma(old_vmi, mpnt) { 687 struct file *file; 688 689 vma_start_write(mpnt); 690 if (mpnt->vm_flags & VM_DONTCOPY) { 691 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 692 continue; 693 } 694 charge = 0; 695 /* 696 * Don't duplicate many vmas if we've been oom-killed (for 697 * example) 698 */ 699 if (fatal_signal_pending(current)) { 700 retval = -EINTR; 701 goto loop_out; 702 } 703 if (mpnt->vm_flags & VM_ACCOUNT) { 704 unsigned long len = vma_pages(mpnt); 705 706 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 707 goto fail_nomem; 708 charge = len; 709 } 710 tmp = vm_area_dup(mpnt); 711 if (!tmp) 712 goto fail_nomem; 713 retval = vma_dup_policy(mpnt, tmp); 714 if (retval) 715 goto fail_nomem_policy; 716 tmp->vm_mm = mm; 717 retval = dup_userfaultfd(tmp, &uf); 718 if (retval) 719 goto fail_nomem_anon_vma_fork; 720 if (tmp->vm_flags & VM_WIPEONFORK) { 721 /* 722 * VM_WIPEONFORK gets a clean slate in the child. 723 * Don't prepare anon_vma until fault since we don't 724 * copy page for current vma. 725 */ 726 tmp->anon_vma = NULL; 727 } else if (anon_vma_fork(tmp, mpnt)) 728 goto fail_nomem_anon_vma_fork; 729 vm_flags_clear(tmp, VM_LOCKED_MASK); 730 file = tmp->vm_file; 731 if (file) { 732 struct address_space *mapping = file->f_mapping; 733 734 get_file(file); 735 i_mmap_lock_write(mapping); 736 if (tmp->vm_flags & VM_SHARED) 737 mapping_allow_writable(mapping); 738 flush_dcache_mmap_lock(mapping); 739 /* insert tmp into the share list, just after mpnt */ 740 vma_interval_tree_insert_after(tmp, mpnt, 741 &mapping->i_mmap); 742 flush_dcache_mmap_unlock(mapping); 743 i_mmap_unlock_write(mapping); 744 } 745 746 /* 747 * Copy/update hugetlb private vma information. 748 */ 749 if (is_vm_hugetlb_page(tmp)) 750 hugetlb_dup_vma_private(tmp); 751 752 /* Link the vma into the MT */ 753 if (vma_iter_bulk_store(&vmi, tmp)) 754 goto fail_nomem_vmi_store; 755 756 mm->map_count++; 757 if (!(tmp->vm_flags & VM_WIPEONFORK)) 758 retval = copy_page_range(tmp, mpnt); 759 760 if (tmp->vm_ops && tmp->vm_ops->open) 761 tmp->vm_ops->open(tmp); 762 763 if (retval) 764 goto loop_out; 765 } 766 /* a new mm has just been created */ 767 retval = arch_dup_mmap(oldmm, mm); 768 loop_out: 769 vma_iter_free(&vmi); 770 if (!retval) 771 mt_set_in_rcu(vmi.mas.tree); 772 out: 773 mmap_write_unlock(mm); 774 flush_tlb_mm(oldmm); 775 mmap_write_unlock(oldmm); 776 dup_userfaultfd_complete(&uf); 777 fail_uprobe_end: 778 uprobe_end_dup_mmap(); 779 return retval; 780 781 fail_nomem_vmi_store: 782 unlink_anon_vmas(tmp); 783 fail_nomem_anon_vma_fork: 784 mpol_put(vma_policy(tmp)); 785 fail_nomem_policy: 786 vm_area_free(tmp); 787 fail_nomem: 788 retval = -ENOMEM; 789 vm_unacct_memory(charge); 790 goto loop_out; 791 } 792 793 static inline int mm_alloc_pgd(struct mm_struct *mm) 794 { 795 mm->pgd = pgd_alloc(mm); 796 if (unlikely(!mm->pgd)) 797 return -ENOMEM; 798 return 0; 799 } 800 801 static inline void mm_free_pgd(struct mm_struct *mm) 802 { 803 pgd_free(mm, mm->pgd); 804 } 805 #else 806 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 807 { 808 mmap_write_lock(oldmm); 809 dup_mm_exe_file(mm, oldmm); 810 mmap_write_unlock(oldmm); 811 return 0; 812 } 813 #define mm_alloc_pgd(mm) (0) 814 #define mm_free_pgd(mm) 815 #endif /* CONFIG_MMU */ 816 817 static void check_mm(struct mm_struct *mm) 818 { 819 int i; 820 821 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS, 822 "Please make sure 'struct resident_page_types[]' is updated as well"); 823 824 for (i = 0; i < NR_MM_COUNTERS; i++) { 825 long x = percpu_counter_sum(&mm->rss_stat[i]); 826 827 if (unlikely(x)) 828 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", 829 mm, resident_page_types[i], x); 830 } 831 832 if (mm_pgtables_bytes(mm)) 833 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", 834 mm_pgtables_bytes(mm)); 835 836 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 837 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 838 #endif 839 } 840 841 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 842 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 843 844 static void do_check_lazy_tlb(void *arg) 845 { 846 struct mm_struct *mm = arg; 847 848 WARN_ON_ONCE(current->active_mm == mm); 849 } 850 851 static void do_shoot_lazy_tlb(void *arg) 852 { 853 struct mm_struct *mm = arg; 854 855 if (current->active_mm == mm) { 856 WARN_ON_ONCE(current->mm); 857 current->active_mm = &init_mm; 858 switch_mm(mm, &init_mm, current); 859 } 860 } 861 862 static void cleanup_lazy_tlbs(struct mm_struct *mm) 863 { 864 if (!IS_ENABLED(CONFIG_MMU_LAZY_TLB_SHOOTDOWN)) { 865 /* 866 * In this case, lazy tlb mms are refounted and would not reach 867 * __mmdrop until all CPUs have switched away and mmdrop()ed. 868 */ 869 return; 870 } 871 872 /* 873 * Lazy mm shootdown does not refcount "lazy tlb mm" usage, rather it 874 * requires lazy mm users to switch to another mm when the refcount 875 * drops to zero, before the mm is freed. This requires IPIs here to 876 * switch kernel threads to init_mm. 877 * 878 * archs that use IPIs to flush TLBs can piggy-back that lazy tlb mm 879 * switch with the final userspace teardown TLB flush which leaves the 880 * mm lazy on this CPU but no others, reducing the need for additional 881 * IPIs here. There are cases where a final IPI is still required here, 882 * such as the final mmdrop being performed on a different CPU than the 883 * one exiting, or kernel threads using the mm when userspace exits. 884 * 885 * IPI overheads have not found to be expensive, but they could be 886 * reduced in a number of possible ways, for example (roughly 887 * increasing order of complexity): 888 * - The last lazy reference created by exit_mm() could instead switch 889 * to init_mm, however it's probable this will run on the same CPU 890 * immediately afterwards, so this may not reduce IPIs much. 891 * - A batch of mms requiring IPIs could be gathered and freed at once. 892 * - CPUs store active_mm where it can be remotely checked without a 893 * lock, to filter out false-positives in the cpumask. 894 * - After mm_users or mm_count reaches zero, switching away from the 895 * mm could clear mm_cpumask to reduce some IPIs, perhaps together 896 * with some batching or delaying of the final IPIs. 897 * - A delayed freeing and RCU-like quiescing sequence based on mm 898 * switching to avoid IPIs completely. 899 */ 900 on_each_cpu_mask(mm_cpumask(mm), do_shoot_lazy_tlb, (void *)mm, 1); 901 if (IS_ENABLED(CONFIG_DEBUG_VM_SHOOT_LAZIES)) 902 on_each_cpu(do_check_lazy_tlb, (void *)mm, 1); 903 } 904 905 /* 906 * Called when the last reference to the mm 907 * is dropped: either by a lazy thread or by 908 * mmput. Free the page directory and the mm. 909 */ 910 void __mmdrop(struct mm_struct *mm) 911 { 912 BUG_ON(mm == &init_mm); 913 WARN_ON_ONCE(mm == current->mm); 914 915 /* Ensure no CPUs are using this as their lazy tlb mm */ 916 cleanup_lazy_tlbs(mm); 917 918 WARN_ON_ONCE(mm == current->active_mm); 919 mm_free_pgd(mm); 920 destroy_context(mm); 921 mmu_notifier_subscriptions_destroy(mm); 922 check_mm(mm); 923 put_user_ns(mm->user_ns); 924 mm_pasid_drop(mm); 925 mm_destroy_cid(mm); 926 percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS); 927 928 free_mm(mm); 929 } 930 EXPORT_SYMBOL_GPL(__mmdrop); 931 932 static void mmdrop_async_fn(struct work_struct *work) 933 { 934 struct mm_struct *mm; 935 936 mm = container_of(work, struct mm_struct, async_put_work); 937 __mmdrop(mm); 938 } 939 940 static void mmdrop_async(struct mm_struct *mm) 941 { 942 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 943 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 944 schedule_work(&mm->async_put_work); 945 } 946 } 947 948 static inline void free_signal_struct(struct signal_struct *sig) 949 { 950 taskstats_tgid_free(sig); 951 sched_autogroup_exit(sig); 952 /* 953 * __mmdrop is not safe to call from softirq context on x86 due to 954 * pgd_dtor so postpone it to the async context 955 */ 956 if (sig->oom_mm) 957 mmdrop_async(sig->oom_mm); 958 kmem_cache_free(signal_cachep, sig); 959 } 960 961 static inline void put_signal_struct(struct signal_struct *sig) 962 { 963 if (refcount_dec_and_test(&sig->sigcnt)) 964 free_signal_struct(sig); 965 } 966 967 void __put_task_struct(struct task_struct *tsk) 968 { 969 WARN_ON(!tsk->exit_state); 970 WARN_ON(refcount_read(&tsk->usage)); 971 WARN_ON(tsk == current); 972 973 io_uring_free(tsk); 974 cgroup_free(tsk); 975 task_numa_free(tsk, true); 976 security_task_free(tsk); 977 exit_creds(tsk); 978 delayacct_tsk_free(tsk); 979 put_signal_struct(tsk->signal); 980 sched_core_free(tsk); 981 free_task(tsk); 982 } 983 EXPORT_SYMBOL_GPL(__put_task_struct); 984 985 void __put_task_struct_rcu_cb(struct rcu_head *rhp) 986 { 987 struct task_struct *task = container_of(rhp, struct task_struct, rcu); 988 989 __put_task_struct(task); 990 } 991 EXPORT_SYMBOL_GPL(__put_task_struct_rcu_cb); 992 993 void __init __weak arch_task_cache_init(void) { } 994 995 /* 996 * set_max_threads 997 */ 998 static void set_max_threads(unsigned int max_threads_suggested) 999 { 1000 u64 threads; 1001 unsigned long nr_pages = totalram_pages(); 1002 1003 /* 1004 * The number of threads shall be limited such that the thread 1005 * structures may only consume a small part of the available memory. 1006 */ 1007 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64) 1008 threads = MAX_THREADS; 1009 else 1010 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE, 1011 (u64) THREAD_SIZE * 8UL); 1012 1013 if (threads > max_threads_suggested) 1014 threads = max_threads_suggested; 1015 1016 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 1017 } 1018 1019 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 1020 /* Initialized by the architecture: */ 1021 int arch_task_struct_size __read_mostly; 1022 #endif 1023 1024 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 1025 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 1026 { 1027 /* Fetch thread_struct whitelist for the architecture. */ 1028 arch_thread_struct_whitelist(offset, size); 1029 1030 /* 1031 * Handle zero-sized whitelist or empty thread_struct, otherwise 1032 * adjust offset to position of thread_struct in task_struct. 1033 */ 1034 if (unlikely(*size == 0)) 1035 *offset = 0; 1036 else 1037 *offset += offsetof(struct task_struct, thread); 1038 } 1039 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */ 1040 1041 void __init fork_init(void) 1042 { 1043 int i; 1044 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 1045 #ifndef ARCH_MIN_TASKALIGN 1046 #define ARCH_MIN_TASKALIGN 0 1047 #endif 1048 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 1049 unsigned long useroffset, usersize; 1050 1051 /* create a slab on which task_structs can be allocated */ 1052 task_struct_whitelist(&useroffset, &usersize); 1053 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 1054 arch_task_struct_size, align, 1055 SLAB_PANIC|SLAB_ACCOUNT, 1056 useroffset, usersize, NULL); 1057 #endif 1058 1059 /* do the arch specific task caches init */ 1060 arch_task_cache_init(); 1061 1062 set_max_threads(MAX_THREADS); 1063 1064 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 1065 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 1066 init_task.signal->rlim[RLIMIT_SIGPENDING] = 1067 init_task.signal->rlim[RLIMIT_NPROC]; 1068 1069 for (i = 0; i < UCOUNT_COUNTS; i++) 1070 init_user_ns.ucount_max[i] = max_threads/2; 1071 1072 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY); 1073 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY); 1074 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY); 1075 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY); 1076 1077 #ifdef CONFIG_VMAP_STACK 1078 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 1079 NULL, free_vm_stack_cache); 1080 #endif 1081 1082 scs_init(); 1083 1084 lockdep_init_task(&init_task); 1085 uprobes_init(); 1086 } 1087 1088 int __weak arch_dup_task_struct(struct task_struct *dst, 1089 struct task_struct *src) 1090 { 1091 *dst = *src; 1092 return 0; 1093 } 1094 1095 void set_task_stack_end_magic(struct task_struct *tsk) 1096 { 1097 unsigned long *stackend; 1098 1099 stackend = end_of_stack(tsk); 1100 *stackend = STACK_END_MAGIC; /* for overflow detection */ 1101 } 1102 1103 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 1104 { 1105 struct task_struct *tsk; 1106 int err; 1107 1108 if (node == NUMA_NO_NODE) 1109 node = tsk_fork_get_node(orig); 1110 tsk = alloc_task_struct_node(node); 1111 if (!tsk) 1112 return NULL; 1113 1114 err = arch_dup_task_struct(tsk, orig); 1115 if (err) 1116 goto free_tsk; 1117 1118 err = alloc_thread_stack_node(tsk, node); 1119 if (err) 1120 goto free_tsk; 1121 1122 #ifdef CONFIG_THREAD_INFO_IN_TASK 1123 refcount_set(&tsk->stack_refcount, 1); 1124 #endif 1125 account_kernel_stack(tsk, 1); 1126 1127 err = scs_prepare(tsk, node); 1128 if (err) 1129 goto free_stack; 1130 1131 #ifdef CONFIG_SECCOMP 1132 /* 1133 * We must handle setting up seccomp filters once we're under 1134 * the sighand lock in case orig has changed between now and 1135 * then. Until then, filter must be NULL to avoid messing up 1136 * the usage counts on the error path calling free_task. 1137 */ 1138 tsk->seccomp.filter = NULL; 1139 #endif 1140 1141 setup_thread_stack(tsk, orig); 1142 clear_user_return_notifier(tsk); 1143 clear_tsk_need_resched(tsk); 1144 set_task_stack_end_magic(tsk); 1145 clear_syscall_work_syscall_user_dispatch(tsk); 1146 1147 #ifdef CONFIG_STACKPROTECTOR 1148 tsk->stack_canary = get_random_canary(); 1149 #endif 1150 if (orig->cpus_ptr == &orig->cpus_mask) 1151 tsk->cpus_ptr = &tsk->cpus_mask; 1152 dup_user_cpus_ptr(tsk, orig, node); 1153 1154 /* 1155 * One for the user space visible state that goes away when reaped. 1156 * One for the scheduler. 1157 */ 1158 refcount_set(&tsk->rcu_users, 2); 1159 /* One for the rcu users */ 1160 refcount_set(&tsk->usage, 1); 1161 #ifdef CONFIG_BLK_DEV_IO_TRACE 1162 tsk->btrace_seq = 0; 1163 #endif 1164 tsk->splice_pipe = NULL; 1165 tsk->task_frag.page = NULL; 1166 tsk->wake_q.next = NULL; 1167 tsk->worker_private = NULL; 1168 1169 kcov_task_init(tsk); 1170 kmsan_task_create(tsk); 1171 kmap_local_fork(tsk); 1172 1173 #ifdef CONFIG_FAULT_INJECTION 1174 tsk->fail_nth = 0; 1175 #endif 1176 1177 #ifdef CONFIG_BLK_CGROUP 1178 tsk->throttle_disk = NULL; 1179 tsk->use_memdelay = 0; 1180 #endif 1181 1182 #ifdef CONFIG_IOMMU_SVA 1183 tsk->pasid_activated = 0; 1184 #endif 1185 1186 #ifdef CONFIG_MEMCG 1187 tsk->active_memcg = NULL; 1188 #endif 1189 1190 #ifdef CONFIG_CPU_SUP_INTEL 1191 tsk->reported_split_lock = 0; 1192 #endif 1193 1194 #ifdef CONFIG_SCHED_MM_CID 1195 tsk->mm_cid = -1; 1196 tsk->last_mm_cid = -1; 1197 tsk->mm_cid_active = 0; 1198 tsk->migrate_from_cpu = -1; 1199 #endif 1200 return tsk; 1201 1202 free_stack: 1203 exit_task_stack_account(tsk); 1204 free_thread_stack(tsk); 1205 free_tsk: 1206 free_task_struct(tsk); 1207 return NULL; 1208 } 1209 1210 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 1211 1212 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 1213 1214 static int __init coredump_filter_setup(char *s) 1215 { 1216 default_dump_filter = 1217 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 1218 MMF_DUMP_FILTER_MASK; 1219 return 1; 1220 } 1221 1222 __setup("coredump_filter=", coredump_filter_setup); 1223 1224 #include <linux/init_task.h> 1225 1226 static void mm_init_aio(struct mm_struct *mm) 1227 { 1228 #ifdef CONFIG_AIO 1229 spin_lock_init(&mm->ioctx_lock); 1230 mm->ioctx_table = NULL; 1231 #endif 1232 } 1233 1234 static __always_inline void mm_clear_owner(struct mm_struct *mm, 1235 struct task_struct *p) 1236 { 1237 #ifdef CONFIG_MEMCG 1238 if (mm->owner == p) 1239 WRITE_ONCE(mm->owner, NULL); 1240 #endif 1241 } 1242 1243 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1244 { 1245 #ifdef CONFIG_MEMCG 1246 mm->owner = p; 1247 #endif 1248 } 1249 1250 static void mm_init_uprobes_state(struct mm_struct *mm) 1251 { 1252 #ifdef CONFIG_UPROBES 1253 mm->uprobes_state.xol_area = NULL; 1254 #endif 1255 } 1256 1257 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 1258 struct user_namespace *user_ns) 1259 { 1260 mt_init_flags(&mm->mm_mt, MM_MT_FLAGS); 1261 mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock); 1262 atomic_set(&mm->mm_users, 1); 1263 atomic_set(&mm->mm_count, 1); 1264 seqcount_init(&mm->write_protect_seq); 1265 mmap_init_lock(mm); 1266 INIT_LIST_HEAD(&mm->mmlist); 1267 #ifdef CONFIG_PER_VMA_LOCK 1268 mm->mm_lock_seq = 0; 1269 #endif 1270 mm_pgtables_bytes_init(mm); 1271 mm->map_count = 0; 1272 mm->locked_vm = 0; 1273 atomic64_set(&mm->pinned_vm, 0); 1274 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 1275 spin_lock_init(&mm->page_table_lock); 1276 spin_lock_init(&mm->arg_lock); 1277 mm_init_cpumask(mm); 1278 mm_init_aio(mm); 1279 mm_init_owner(mm, p); 1280 mm_pasid_init(mm); 1281 RCU_INIT_POINTER(mm->exe_file, NULL); 1282 mmu_notifier_subscriptions_init(mm); 1283 init_tlb_flush_pending(mm); 1284 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 1285 mm->pmd_huge_pte = NULL; 1286 #endif 1287 mm_init_uprobes_state(mm); 1288 hugetlb_count_init(mm); 1289 1290 if (current->mm) { 1291 mm->flags = current->mm->flags & MMF_INIT_MASK; 1292 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 1293 } else { 1294 mm->flags = default_dump_filter; 1295 mm->def_flags = 0; 1296 } 1297 1298 if (mm_alloc_pgd(mm)) 1299 goto fail_nopgd; 1300 1301 if (init_new_context(p, mm)) 1302 goto fail_nocontext; 1303 1304 if (mm_alloc_cid(mm)) 1305 goto fail_cid; 1306 1307 if (percpu_counter_init_many(mm->rss_stat, 0, GFP_KERNEL_ACCOUNT, 1308 NR_MM_COUNTERS)) 1309 goto fail_pcpu; 1310 1311 mm->user_ns = get_user_ns(user_ns); 1312 lru_gen_init_mm(mm); 1313 return mm; 1314 1315 fail_pcpu: 1316 mm_destroy_cid(mm); 1317 fail_cid: 1318 destroy_context(mm); 1319 fail_nocontext: 1320 mm_free_pgd(mm); 1321 fail_nopgd: 1322 free_mm(mm); 1323 return NULL; 1324 } 1325 1326 /* 1327 * Allocate and initialize an mm_struct. 1328 */ 1329 struct mm_struct *mm_alloc(void) 1330 { 1331 struct mm_struct *mm; 1332 1333 mm = allocate_mm(); 1334 if (!mm) 1335 return NULL; 1336 1337 memset(mm, 0, sizeof(*mm)); 1338 return mm_init(mm, current, current_user_ns()); 1339 } 1340 1341 static inline void __mmput(struct mm_struct *mm) 1342 { 1343 VM_BUG_ON(atomic_read(&mm->mm_users)); 1344 1345 uprobe_clear_state(mm); 1346 exit_aio(mm); 1347 ksm_exit(mm); 1348 khugepaged_exit(mm); /* must run before exit_mmap */ 1349 exit_mmap(mm); 1350 mm_put_huge_zero_page(mm); 1351 set_mm_exe_file(mm, NULL); 1352 if (!list_empty(&mm->mmlist)) { 1353 spin_lock(&mmlist_lock); 1354 list_del(&mm->mmlist); 1355 spin_unlock(&mmlist_lock); 1356 } 1357 if (mm->binfmt) 1358 module_put(mm->binfmt->module); 1359 lru_gen_del_mm(mm); 1360 mmdrop(mm); 1361 } 1362 1363 /* 1364 * Decrement the use count and release all resources for an mm. 1365 */ 1366 void mmput(struct mm_struct *mm) 1367 { 1368 might_sleep(); 1369 1370 if (atomic_dec_and_test(&mm->mm_users)) 1371 __mmput(mm); 1372 } 1373 EXPORT_SYMBOL_GPL(mmput); 1374 1375 #ifdef CONFIG_MMU 1376 static void mmput_async_fn(struct work_struct *work) 1377 { 1378 struct mm_struct *mm = container_of(work, struct mm_struct, 1379 async_put_work); 1380 1381 __mmput(mm); 1382 } 1383 1384 void mmput_async(struct mm_struct *mm) 1385 { 1386 if (atomic_dec_and_test(&mm->mm_users)) { 1387 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1388 schedule_work(&mm->async_put_work); 1389 } 1390 } 1391 EXPORT_SYMBOL_GPL(mmput_async); 1392 #endif 1393 1394 /** 1395 * set_mm_exe_file - change a reference to the mm's executable file 1396 * 1397 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1398 * 1399 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1400 * invocations: in mmput() nobody alive left, in execve it happens before 1401 * the new mm is made visible to anyone. 1402 * 1403 * Can only fail if new_exe_file != NULL. 1404 */ 1405 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1406 { 1407 struct file *old_exe_file; 1408 1409 /* 1410 * It is safe to dereference the exe_file without RCU as 1411 * this function is only called if nobody else can access 1412 * this mm -- see comment above for justification. 1413 */ 1414 old_exe_file = rcu_dereference_raw(mm->exe_file); 1415 1416 if (new_exe_file) { 1417 /* 1418 * We expect the caller (i.e., sys_execve) to already denied 1419 * write access, so this is unlikely to fail. 1420 */ 1421 if (unlikely(deny_write_access(new_exe_file))) 1422 return -EACCES; 1423 get_file(new_exe_file); 1424 } 1425 rcu_assign_pointer(mm->exe_file, new_exe_file); 1426 if (old_exe_file) { 1427 allow_write_access(old_exe_file); 1428 fput(old_exe_file); 1429 } 1430 return 0; 1431 } 1432 1433 /** 1434 * replace_mm_exe_file - replace a reference to the mm's executable file 1435 * 1436 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1437 * 1438 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE). 1439 */ 1440 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1441 { 1442 struct vm_area_struct *vma; 1443 struct file *old_exe_file; 1444 int ret = 0; 1445 1446 /* Forbid mm->exe_file change if old file still mapped. */ 1447 old_exe_file = get_mm_exe_file(mm); 1448 if (old_exe_file) { 1449 VMA_ITERATOR(vmi, mm, 0); 1450 mmap_read_lock(mm); 1451 for_each_vma(vmi, vma) { 1452 if (!vma->vm_file) 1453 continue; 1454 if (path_equal(&vma->vm_file->f_path, 1455 &old_exe_file->f_path)) { 1456 ret = -EBUSY; 1457 break; 1458 } 1459 } 1460 mmap_read_unlock(mm); 1461 fput(old_exe_file); 1462 if (ret) 1463 return ret; 1464 } 1465 1466 ret = deny_write_access(new_exe_file); 1467 if (ret) 1468 return -EACCES; 1469 get_file(new_exe_file); 1470 1471 /* set the new file */ 1472 mmap_write_lock(mm); 1473 old_exe_file = rcu_dereference_raw(mm->exe_file); 1474 rcu_assign_pointer(mm->exe_file, new_exe_file); 1475 mmap_write_unlock(mm); 1476 1477 if (old_exe_file) { 1478 allow_write_access(old_exe_file); 1479 fput(old_exe_file); 1480 } 1481 return 0; 1482 } 1483 1484 /** 1485 * get_mm_exe_file - acquire a reference to the mm's executable file 1486 * 1487 * Returns %NULL if mm has no associated executable file. 1488 * User must release file via fput(). 1489 */ 1490 struct file *get_mm_exe_file(struct mm_struct *mm) 1491 { 1492 struct file *exe_file; 1493 1494 rcu_read_lock(); 1495 exe_file = rcu_dereference(mm->exe_file); 1496 if (exe_file && !get_file_rcu(exe_file)) 1497 exe_file = NULL; 1498 rcu_read_unlock(); 1499 return exe_file; 1500 } 1501 1502 /** 1503 * get_task_exe_file - acquire a reference to the task's executable file 1504 * 1505 * Returns %NULL if task's mm (if any) has no associated executable file or 1506 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1507 * User must release file via fput(). 1508 */ 1509 struct file *get_task_exe_file(struct task_struct *task) 1510 { 1511 struct file *exe_file = NULL; 1512 struct mm_struct *mm; 1513 1514 task_lock(task); 1515 mm = task->mm; 1516 if (mm) { 1517 if (!(task->flags & PF_KTHREAD)) 1518 exe_file = get_mm_exe_file(mm); 1519 } 1520 task_unlock(task); 1521 return exe_file; 1522 } 1523 1524 /** 1525 * get_task_mm - acquire a reference to the task's mm 1526 * 1527 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1528 * this kernel workthread has transiently adopted a user mm with use_mm, 1529 * to do its AIO) is not set and if so returns a reference to it, after 1530 * bumping up the use count. User must release the mm via mmput() 1531 * after use. Typically used by /proc and ptrace. 1532 */ 1533 struct mm_struct *get_task_mm(struct task_struct *task) 1534 { 1535 struct mm_struct *mm; 1536 1537 task_lock(task); 1538 mm = task->mm; 1539 if (mm) { 1540 if (task->flags & PF_KTHREAD) 1541 mm = NULL; 1542 else 1543 mmget(mm); 1544 } 1545 task_unlock(task); 1546 return mm; 1547 } 1548 EXPORT_SYMBOL_GPL(get_task_mm); 1549 1550 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1551 { 1552 struct mm_struct *mm; 1553 int err; 1554 1555 err = down_read_killable(&task->signal->exec_update_lock); 1556 if (err) 1557 return ERR_PTR(err); 1558 1559 mm = get_task_mm(task); 1560 if (mm && mm != current->mm && 1561 !ptrace_may_access(task, mode)) { 1562 mmput(mm); 1563 mm = ERR_PTR(-EACCES); 1564 } 1565 up_read(&task->signal->exec_update_lock); 1566 1567 return mm; 1568 } 1569 1570 static void complete_vfork_done(struct task_struct *tsk) 1571 { 1572 struct completion *vfork; 1573 1574 task_lock(tsk); 1575 vfork = tsk->vfork_done; 1576 if (likely(vfork)) { 1577 tsk->vfork_done = NULL; 1578 complete(vfork); 1579 } 1580 task_unlock(tsk); 1581 } 1582 1583 static int wait_for_vfork_done(struct task_struct *child, 1584 struct completion *vfork) 1585 { 1586 unsigned int state = TASK_UNINTERRUPTIBLE|TASK_KILLABLE|TASK_FREEZABLE; 1587 int killed; 1588 1589 cgroup_enter_frozen(); 1590 killed = wait_for_completion_state(vfork, state); 1591 cgroup_leave_frozen(false); 1592 1593 if (killed) { 1594 task_lock(child); 1595 child->vfork_done = NULL; 1596 task_unlock(child); 1597 } 1598 1599 put_task_struct(child); 1600 return killed; 1601 } 1602 1603 /* Please note the differences between mmput and mm_release. 1604 * mmput is called whenever we stop holding onto a mm_struct, 1605 * error success whatever. 1606 * 1607 * mm_release is called after a mm_struct has been removed 1608 * from the current process. 1609 * 1610 * This difference is important for error handling, when we 1611 * only half set up a mm_struct for a new process and need to restore 1612 * the old one. Because we mmput the new mm_struct before 1613 * restoring the old one. . . 1614 * Eric Biederman 10 January 1998 1615 */ 1616 static void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1617 { 1618 uprobe_free_utask(tsk); 1619 1620 /* Get rid of any cached register state */ 1621 deactivate_mm(tsk, mm); 1622 1623 /* 1624 * Signal userspace if we're not exiting with a core dump 1625 * because we want to leave the value intact for debugging 1626 * purposes. 1627 */ 1628 if (tsk->clear_child_tid) { 1629 if (atomic_read(&mm->mm_users) > 1) { 1630 /* 1631 * We don't check the error code - if userspace has 1632 * not set up a proper pointer then tough luck. 1633 */ 1634 put_user(0, tsk->clear_child_tid); 1635 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1636 1, NULL, NULL, 0, 0); 1637 } 1638 tsk->clear_child_tid = NULL; 1639 } 1640 1641 /* 1642 * All done, finally we can wake up parent and return this mm to him. 1643 * Also kthread_stop() uses this completion for synchronization. 1644 */ 1645 if (tsk->vfork_done) 1646 complete_vfork_done(tsk); 1647 } 1648 1649 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1650 { 1651 futex_exit_release(tsk); 1652 mm_release(tsk, mm); 1653 } 1654 1655 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1656 { 1657 futex_exec_release(tsk); 1658 mm_release(tsk, mm); 1659 } 1660 1661 /** 1662 * dup_mm() - duplicates an existing mm structure 1663 * @tsk: the task_struct with which the new mm will be associated. 1664 * @oldmm: the mm to duplicate. 1665 * 1666 * Allocates a new mm structure and duplicates the provided @oldmm structure 1667 * content into it. 1668 * 1669 * Return: the duplicated mm or NULL on failure. 1670 */ 1671 static struct mm_struct *dup_mm(struct task_struct *tsk, 1672 struct mm_struct *oldmm) 1673 { 1674 struct mm_struct *mm; 1675 int err; 1676 1677 mm = allocate_mm(); 1678 if (!mm) 1679 goto fail_nomem; 1680 1681 memcpy(mm, oldmm, sizeof(*mm)); 1682 1683 if (!mm_init(mm, tsk, mm->user_ns)) 1684 goto fail_nomem; 1685 1686 err = dup_mmap(mm, oldmm); 1687 if (err) 1688 goto free_pt; 1689 1690 mm->hiwater_rss = get_mm_rss(mm); 1691 mm->hiwater_vm = mm->total_vm; 1692 1693 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1694 goto free_pt; 1695 1696 return mm; 1697 1698 free_pt: 1699 /* don't put binfmt in mmput, we haven't got module yet */ 1700 mm->binfmt = NULL; 1701 mm_init_owner(mm, NULL); 1702 mmput(mm); 1703 1704 fail_nomem: 1705 return NULL; 1706 } 1707 1708 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1709 { 1710 struct mm_struct *mm, *oldmm; 1711 1712 tsk->min_flt = tsk->maj_flt = 0; 1713 tsk->nvcsw = tsk->nivcsw = 0; 1714 #ifdef CONFIG_DETECT_HUNG_TASK 1715 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1716 tsk->last_switch_time = 0; 1717 #endif 1718 1719 tsk->mm = NULL; 1720 tsk->active_mm = NULL; 1721 1722 /* 1723 * Are we cloning a kernel thread? 1724 * 1725 * We need to steal a active VM for that.. 1726 */ 1727 oldmm = current->mm; 1728 if (!oldmm) 1729 return 0; 1730 1731 if (clone_flags & CLONE_VM) { 1732 mmget(oldmm); 1733 mm = oldmm; 1734 } else { 1735 mm = dup_mm(tsk, current->mm); 1736 if (!mm) 1737 return -ENOMEM; 1738 } 1739 1740 tsk->mm = mm; 1741 tsk->active_mm = mm; 1742 sched_mm_cid_fork(tsk); 1743 return 0; 1744 } 1745 1746 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1747 { 1748 struct fs_struct *fs = current->fs; 1749 if (clone_flags & CLONE_FS) { 1750 /* tsk->fs is already what we want */ 1751 spin_lock(&fs->lock); 1752 if (fs->in_exec) { 1753 spin_unlock(&fs->lock); 1754 return -EAGAIN; 1755 } 1756 fs->users++; 1757 spin_unlock(&fs->lock); 1758 return 0; 1759 } 1760 tsk->fs = copy_fs_struct(fs); 1761 if (!tsk->fs) 1762 return -ENOMEM; 1763 return 0; 1764 } 1765 1766 static int copy_files(unsigned long clone_flags, struct task_struct *tsk, 1767 int no_files) 1768 { 1769 struct files_struct *oldf, *newf; 1770 int error = 0; 1771 1772 /* 1773 * A background process may not have any files ... 1774 */ 1775 oldf = current->files; 1776 if (!oldf) 1777 goto out; 1778 1779 if (no_files) { 1780 tsk->files = NULL; 1781 goto out; 1782 } 1783 1784 if (clone_flags & CLONE_FILES) { 1785 atomic_inc(&oldf->count); 1786 goto out; 1787 } 1788 1789 newf = dup_fd(oldf, NR_OPEN_MAX, &error); 1790 if (!newf) 1791 goto out; 1792 1793 tsk->files = newf; 1794 error = 0; 1795 out: 1796 return error; 1797 } 1798 1799 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1800 { 1801 struct sighand_struct *sig; 1802 1803 if (clone_flags & CLONE_SIGHAND) { 1804 refcount_inc(¤t->sighand->count); 1805 return 0; 1806 } 1807 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1808 RCU_INIT_POINTER(tsk->sighand, sig); 1809 if (!sig) 1810 return -ENOMEM; 1811 1812 refcount_set(&sig->count, 1); 1813 spin_lock_irq(¤t->sighand->siglock); 1814 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1815 spin_unlock_irq(¤t->sighand->siglock); 1816 1817 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */ 1818 if (clone_flags & CLONE_CLEAR_SIGHAND) 1819 flush_signal_handlers(tsk, 0); 1820 1821 return 0; 1822 } 1823 1824 void __cleanup_sighand(struct sighand_struct *sighand) 1825 { 1826 if (refcount_dec_and_test(&sighand->count)) { 1827 signalfd_cleanup(sighand); 1828 /* 1829 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1830 * without an RCU grace period, see __lock_task_sighand(). 1831 */ 1832 kmem_cache_free(sighand_cachep, sighand); 1833 } 1834 } 1835 1836 /* 1837 * Initialize POSIX timer handling for a thread group. 1838 */ 1839 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1840 { 1841 struct posix_cputimers *pct = &sig->posix_cputimers; 1842 unsigned long cpu_limit; 1843 1844 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1845 posix_cputimers_group_init(pct, cpu_limit); 1846 } 1847 1848 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1849 { 1850 struct signal_struct *sig; 1851 1852 if (clone_flags & CLONE_THREAD) 1853 return 0; 1854 1855 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1856 tsk->signal = sig; 1857 if (!sig) 1858 return -ENOMEM; 1859 1860 sig->nr_threads = 1; 1861 sig->quick_threads = 1; 1862 atomic_set(&sig->live, 1); 1863 refcount_set(&sig->sigcnt, 1); 1864 1865 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1866 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1867 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1868 1869 init_waitqueue_head(&sig->wait_chldexit); 1870 sig->curr_target = tsk; 1871 init_sigpending(&sig->shared_pending); 1872 INIT_HLIST_HEAD(&sig->multiprocess); 1873 seqlock_init(&sig->stats_lock); 1874 prev_cputime_init(&sig->prev_cputime); 1875 1876 #ifdef CONFIG_POSIX_TIMERS 1877 INIT_LIST_HEAD(&sig->posix_timers); 1878 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1879 sig->real_timer.function = it_real_fn; 1880 #endif 1881 1882 task_lock(current->group_leader); 1883 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1884 task_unlock(current->group_leader); 1885 1886 posix_cpu_timers_init_group(sig); 1887 1888 tty_audit_fork(sig); 1889 sched_autogroup_fork(sig); 1890 1891 sig->oom_score_adj = current->signal->oom_score_adj; 1892 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1893 1894 mutex_init(&sig->cred_guard_mutex); 1895 init_rwsem(&sig->exec_update_lock); 1896 1897 return 0; 1898 } 1899 1900 static void copy_seccomp(struct task_struct *p) 1901 { 1902 #ifdef CONFIG_SECCOMP 1903 /* 1904 * Must be called with sighand->lock held, which is common to 1905 * all threads in the group. Holding cred_guard_mutex is not 1906 * needed because this new task is not yet running and cannot 1907 * be racing exec. 1908 */ 1909 assert_spin_locked(¤t->sighand->siglock); 1910 1911 /* Ref-count the new filter user, and assign it. */ 1912 get_seccomp_filter(current); 1913 p->seccomp = current->seccomp; 1914 1915 /* 1916 * Explicitly enable no_new_privs here in case it got set 1917 * between the task_struct being duplicated and holding the 1918 * sighand lock. The seccomp state and nnp must be in sync. 1919 */ 1920 if (task_no_new_privs(current)) 1921 task_set_no_new_privs(p); 1922 1923 /* 1924 * If the parent gained a seccomp mode after copying thread 1925 * flags and between before we held the sighand lock, we have 1926 * to manually enable the seccomp thread flag here. 1927 */ 1928 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1929 set_task_syscall_work(p, SECCOMP); 1930 #endif 1931 } 1932 1933 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1934 { 1935 current->clear_child_tid = tidptr; 1936 1937 return task_pid_vnr(current); 1938 } 1939 1940 static void rt_mutex_init_task(struct task_struct *p) 1941 { 1942 raw_spin_lock_init(&p->pi_lock); 1943 #ifdef CONFIG_RT_MUTEXES 1944 p->pi_waiters = RB_ROOT_CACHED; 1945 p->pi_top_task = NULL; 1946 p->pi_blocked_on = NULL; 1947 #endif 1948 } 1949 1950 static inline void init_task_pid_links(struct task_struct *task) 1951 { 1952 enum pid_type type; 1953 1954 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) 1955 INIT_HLIST_NODE(&task->pid_links[type]); 1956 } 1957 1958 static inline void 1959 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1960 { 1961 if (type == PIDTYPE_PID) 1962 task->thread_pid = pid; 1963 else 1964 task->signal->pids[type] = pid; 1965 } 1966 1967 static inline void rcu_copy_process(struct task_struct *p) 1968 { 1969 #ifdef CONFIG_PREEMPT_RCU 1970 p->rcu_read_lock_nesting = 0; 1971 p->rcu_read_unlock_special.s = 0; 1972 p->rcu_blocked_node = NULL; 1973 INIT_LIST_HEAD(&p->rcu_node_entry); 1974 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1975 #ifdef CONFIG_TASKS_RCU 1976 p->rcu_tasks_holdout = false; 1977 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1978 p->rcu_tasks_idle_cpu = -1; 1979 #endif /* #ifdef CONFIG_TASKS_RCU */ 1980 #ifdef CONFIG_TASKS_TRACE_RCU 1981 p->trc_reader_nesting = 0; 1982 p->trc_reader_special.s = 0; 1983 INIT_LIST_HEAD(&p->trc_holdout_list); 1984 INIT_LIST_HEAD(&p->trc_blkd_node); 1985 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ 1986 } 1987 1988 struct pid *pidfd_pid(const struct file *file) 1989 { 1990 if (file->f_op == &pidfd_fops) 1991 return file->private_data; 1992 1993 return ERR_PTR(-EBADF); 1994 } 1995 1996 static int pidfd_release(struct inode *inode, struct file *file) 1997 { 1998 struct pid *pid = file->private_data; 1999 2000 file->private_data = NULL; 2001 put_pid(pid); 2002 return 0; 2003 } 2004 2005 #ifdef CONFIG_PROC_FS 2006 /** 2007 * pidfd_show_fdinfo - print information about a pidfd 2008 * @m: proc fdinfo file 2009 * @f: file referencing a pidfd 2010 * 2011 * Pid: 2012 * This function will print the pid that a given pidfd refers to in the 2013 * pid namespace of the procfs instance. 2014 * If the pid namespace of the process is not a descendant of the pid 2015 * namespace of the procfs instance 0 will be shown as its pid. This is 2016 * similar to calling getppid() on a process whose parent is outside of 2017 * its pid namespace. 2018 * 2019 * NSpid: 2020 * If pid namespaces are supported then this function will also print 2021 * the pid of a given pidfd refers to for all descendant pid namespaces 2022 * starting from the current pid namespace of the instance, i.e. the 2023 * Pid field and the first entry in the NSpid field will be identical. 2024 * If the pid namespace of the process is not a descendant of the pid 2025 * namespace of the procfs instance 0 will be shown as its first NSpid 2026 * entry and no others will be shown. 2027 * Note that this differs from the Pid and NSpid fields in 2028 * /proc/<pid>/status where Pid and NSpid are always shown relative to 2029 * the pid namespace of the procfs instance. The difference becomes 2030 * obvious when sending around a pidfd between pid namespaces from a 2031 * different branch of the tree, i.e. where no ancestral relation is 2032 * present between the pid namespaces: 2033 * - create two new pid namespaces ns1 and ns2 in the initial pid 2034 * namespace (also take care to create new mount namespaces in the 2035 * new pid namespace and mount procfs) 2036 * - create a process with a pidfd in ns1 2037 * - send pidfd from ns1 to ns2 2038 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid 2039 * have exactly one entry, which is 0 2040 */ 2041 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) 2042 { 2043 struct pid *pid = f->private_data; 2044 struct pid_namespace *ns; 2045 pid_t nr = -1; 2046 2047 if (likely(pid_has_task(pid, PIDTYPE_PID))) { 2048 ns = proc_pid_ns(file_inode(m->file)->i_sb); 2049 nr = pid_nr_ns(pid, ns); 2050 } 2051 2052 seq_put_decimal_ll(m, "Pid:\t", nr); 2053 2054 #ifdef CONFIG_PID_NS 2055 seq_put_decimal_ll(m, "\nNSpid:\t", nr); 2056 if (nr > 0) { 2057 int i; 2058 2059 /* If nr is non-zero it means that 'pid' is valid and that 2060 * ns, i.e. the pid namespace associated with the procfs 2061 * instance, is in the pid namespace hierarchy of pid. 2062 * Start at one below the already printed level. 2063 */ 2064 for (i = ns->level + 1; i <= pid->level; i++) 2065 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr); 2066 } 2067 #endif 2068 seq_putc(m, '\n'); 2069 } 2070 #endif 2071 2072 /* 2073 * Poll support for process exit notification. 2074 */ 2075 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) 2076 { 2077 struct pid *pid = file->private_data; 2078 __poll_t poll_flags = 0; 2079 2080 poll_wait(file, &pid->wait_pidfd, pts); 2081 2082 /* 2083 * Inform pollers only when the whole thread group exits. 2084 * If the thread group leader exits before all other threads in the 2085 * group, then poll(2) should block, similar to the wait(2) family. 2086 */ 2087 if (thread_group_exited(pid)) 2088 poll_flags = EPOLLIN | EPOLLRDNORM; 2089 2090 return poll_flags; 2091 } 2092 2093 const struct file_operations pidfd_fops = { 2094 .release = pidfd_release, 2095 .poll = pidfd_poll, 2096 #ifdef CONFIG_PROC_FS 2097 .show_fdinfo = pidfd_show_fdinfo, 2098 #endif 2099 }; 2100 2101 /** 2102 * __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd 2103 * @pid: the struct pid for which to create a pidfd 2104 * @flags: flags of the new @pidfd 2105 * @pidfd: the pidfd to return 2106 * 2107 * Allocate a new file that stashes @pid and reserve a new pidfd number in the 2108 * caller's file descriptor table. The pidfd is reserved but not installed yet. 2109 2110 * The helper doesn't perform checks on @pid which makes it useful for pidfds 2111 * created via CLONE_PIDFD where @pid has no task attached when the pidfd and 2112 * pidfd file are prepared. 2113 * 2114 * If this function returns successfully the caller is responsible to either 2115 * call fd_install() passing the returned pidfd and pidfd file as arguments in 2116 * order to install the pidfd into its file descriptor table or they must use 2117 * put_unused_fd() and fput() on the returned pidfd and pidfd file 2118 * respectively. 2119 * 2120 * This function is useful when a pidfd must already be reserved but there 2121 * might still be points of failure afterwards and the caller wants to ensure 2122 * that no pidfd is leaked into its file descriptor table. 2123 * 2124 * Return: On success, a reserved pidfd is returned from the function and a new 2125 * pidfd file is returned in the last argument to the function. On 2126 * error, a negative error code is returned from the function and the 2127 * last argument remains unchanged. 2128 */ 2129 static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret) 2130 { 2131 int pidfd; 2132 struct file *pidfd_file; 2133 2134 if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC)) 2135 return -EINVAL; 2136 2137 pidfd = get_unused_fd_flags(O_RDWR | O_CLOEXEC); 2138 if (pidfd < 0) 2139 return pidfd; 2140 2141 pidfd_file = anon_inode_getfile("[pidfd]", &pidfd_fops, pid, 2142 flags | O_RDWR | O_CLOEXEC); 2143 if (IS_ERR(pidfd_file)) { 2144 put_unused_fd(pidfd); 2145 return PTR_ERR(pidfd_file); 2146 } 2147 get_pid(pid); /* held by pidfd_file now */ 2148 *ret = pidfd_file; 2149 return pidfd; 2150 } 2151 2152 /** 2153 * pidfd_prepare - allocate a new pidfd_file and reserve a pidfd 2154 * @pid: the struct pid for which to create a pidfd 2155 * @flags: flags of the new @pidfd 2156 * @pidfd: the pidfd to return 2157 * 2158 * Allocate a new file that stashes @pid and reserve a new pidfd number in the 2159 * caller's file descriptor table. The pidfd is reserved but not installed yet. 2160 * 2161 * The helper verifies that @pid is used as a thread group leader. 2162 * 2163 * If this function returns successfully the caller is responsible to either 2164 * call fd_install() passing the returned pidfd and pidfd file as arguments in 2165 * order to install the pidfd into its file descriptor table or they must use 2166 * put_unused_fd() and fput() on the returned pidfd and pidfd file 2167 * respectively. 2168 * 2169 * This function is useful when a pidfd must already be reserved but there 2170 * might still be points of failure afterwards and the caller wants to ensure 2171 * that no pidfd is leaked into its file descriptor table. 2172 * 2173 * Return: On success, a reserved pidfd is returned from the function and a new 2174 * pidfd file is returned in the last argument to the function. On 2175 * error, a negative error code is returned from the function and the 2176 * last argument remains unchanged. 2177 */ 2178 int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret) 2179 { 2180 if (!pid || !pid_has_task(pid, PIDTYPE_TGID)) 2181 return -EINVAL; 2182 2183 return __pidfd_prepare(pid, flags, ret); 2184 } 2185 2186 static void __delayed_free_task(struct rcu_head *rhp) 2187 { 2188 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 2189 2190 free_task(tsk); 2191 } 2192 2193 static __always_inline void delayed_free_task(struct task_struct *tsk) 2194 { 2195 if (IS_ENABLED(CONFIG_MEMCG)) 2196 call_rcu(&tsk->rcu, __delayed_free_task); 2197 else 2198 free_task(tsk); 2199 } 2200 2201 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk) 2202 { 2203 /* Skip if kernel thread */ 2204 if (!tsk->mm) 2205 return; 2206 2207 /* Skip if spawning a thread or using vfork */ 2208 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM) 2209 return; 2210 2211 /* We need to synchronize with __set_oom_adj */ 2212 mutex_lock(&oom_adj_mutex); 2213 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags); 2214 /* Update the values in case they were changed after copy_signal */ 2215 tsk->signal->oom_score_adj = current->signal->oom_score_adj; 2216 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min; 2217 mutex_unlock(&oom_adj_mutex); 2218 } 2219 2220 #ifdef CONFIG_RV 2221 static void rv_task_fork(struct task_struct *p) 2222 { 2223 int i; 2224 2225 for (i = 0; i < RV_PER_TASK_MONITORS; i++) 2226 p->rv[i].da_mon.monitoring = false; 2227 } 2228 #else 2229 #define rv_task_fork(p) do {} while (0) 2230 #endif 2231 2232 /* 2233 * This creates a new process as a copy of the old one, 2234 * but does not actually start it yet. 2235 * 2236 * It copies the registers, and all the appropriate 2237 * parts of the process environment (as per the clone 2238 * flags). The actual kick-off is left to the caller. 2239 */ 2240 __latent_entropy struct task_struct *copy_process( 2241 struct pid *pid, 2242 int trace, 2243 int node, 2244 struct kernel_clone_args *args) 2245 { 2246 int pidfd = -1, retval; 2247 struct task_struct *p; 2248 struct multiprocess_signals delayed; 2249 struct file *pidfile = NULL; 2250 const u64 clone_flags = args->flags; 2251 struct nsproxy *nsp = current->nsproxy; 2252 2253 /* 2254 * Don't allow sharing the root directory with processes in a different 2255 * namespace 2256 */ 2257 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 2258 return ERR_PTR(-EINVAL); 2259 2260 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 2261 return ERR_PTR(-EINVAL); 2262 2263 /* 2264 * Thread groups must share signals as well, and detached threads 2265 * can only be started up within the thread group. 2266 */ 2267 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 2268 return ERR_PTR(-EINVAL); 2269 2270 /* 2271 * Shared signal handlers imply shared VM. By way of the above, 2272 * thread groups also imply shared VM. Blocking this case allows 2273 * for various simplifications in other code. 2274 */ 2275 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 2276 return ERR_PTR(-EINVAL); 2277 2278 /* 2279 * Siblings of global init remain as zombies on exit since they are 2280 * not reaped by their parent (swapper). To solve this and to avoid 2281 * multi-rooted process trees, prevent global and container-inits 2282 * from creating siblings. 2283 */ 2284 if ((clone_flags & CLONE_PARENT) && 2285 current->signal->flags & SIGNAL_UNKILLABLE) 2286 return ERR_PTR(-EINVAL); 2287 2288 /* 2289 * If the new process will be in a different pid or user namespace 2290 * do not allow it to share a thread group with the forking task. 2291 */ 2292 if (clone_flags & CLONE_THREAD) { 2293 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 2294 (task_active_pid_ns(current) != nsp->pid_ns_for_children)) 2295 return ERR_PTR(-EINVAL); 2296 } 2297 2298 if (clone_flags & CLONE_PIDFD) { 2299 /* 2300 * - CLONE_DETACHED is blocked so that we can potentially 2301 * reuse it later for CLONE_PIDFD. 2302 * - CLONE_THREAD is blocked until someone really needs it. 2303 */ 2304 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD)) 2305 return ERR_PTR(-EINVAL); 2306 } 2307 2308 /* 2309 * Force any signals received before this point to be delivered 2310 * before the fork happens. Collect up signals sent to multiple 2311 * processes that happen during the fork and delay them so that 2312 * they appear to happen after the fork. 2313 */ 2314 sigemptyset(&delayed.signal); 2315 INIT_HLIST_NODE(&delayed.node); 2316 2317 spin_lock_irq(¤t->sighand->siglock); 2318 if (!(clone_flags & CLONE_THREAD)) 2319 hlist_add_head(&delayed.node, ¤t->signal->multiprocess); 2320 recalc_sigpending(); 2321 spin_unlock_irq(¤t->sighand->siglock); 2322 retval = -ERESTARTNOINTR; 2323 if (task_sigpending(current)) 2324 goto fork_out; 2325 2326 retval = -ENOMEM; 2327 p = dup_task_struct(current, node); 2328 if (!p) 2329 goto fork_out; 2330 p->flags &= ~PF_KTHREAD; 2331 if (args->kthread) 2332 p->flags |= PF_KTHREAD; 2333 if (args->user_worker) { 2334 /* 2335 * Mark us a user worker, and block any signal that isn't 2336 * fatal or STOP 2337 */ 2338 p->flags |= PF_USER_WORKER; 2339 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP)); 2340 } 2341 if (args->io_thread) 2342 p->flags |= PF_IO_WORKER; 2343 2344 if (args->name) 2345 strscpy_pad(p->comm, args->name, sizeof(p->comm)); 2346 2347 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL; 2348 /* 2349 * Clear TID on mm_release()? 2350 */ 2351 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL; 2352 2353 ftrace_graph_init_task(p); 2354 2355 rt_mutex_init_task(p); 2356 2357 lockdep_assert_irqs_enabled(); 2358 #ifdef CONFIG_PROVE_LOCKING 2359 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 2360 #endif 2361 retval = copy_creds(p, clone_flags); 2362 if (retval < 0) 2363 goto bad_fork_free; 2364 2365 retval = -EAGAIN; 2366 if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) { 2367 if (p->real_cred->user != INIT_USER && 2368 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 2369 goto bad_fork_cleanup_count; 2370 } 2371 current->flags &= ~PF_NPROC_EXCEEDED; 2372 2373 /* 2374 * If multiple threads are within copy_process(), then this check 2375 * triggers too late. This doesn't hurt, the check is only there 2376 * to stop root fork bombs. 2377 */ 2378 retval = -EAGAIN; 2379 if (data_race(nr_threads >= max_threads)) 2380 goto bad_fork_cleanup_count; 2381 2382 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 2383 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY); 2384 p->flags |= PF_FORKNOEXEC; 2385 INIT_LIST_HEAD(&p->children); 2386 INIT_LIST_HEAD(&p->sibling); 2387 rcu_copy_process(p); 2388 p->vfork_done = NULL; 2389 spin_lock_init(&p->alloc_lock); 2390 2391 init_sigpending(&p->pending); 2392 2393 p->utime = p->stime = p->gtime = 0; 2394 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 2395 p->utimescaled = p->stimescaled = 0; 2396 #endif 2397 prev_cputime_init(&p->prev_cputime); 2398 2399 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 2400 seqcount_init(&p->vtime.seqcount); 2401 p->vtime.starttime = 0; 2402 p->vtime.state = VTIME_INACTIVE; 2403 #endif 2404 2405 #ifdef CONFIG_IO_URING 2406 p->io_uring = NULL; 2407 #endif 2408 2409 #if defined(SPLIT_RSS_COUNTING) 2410 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 2411 #endif 2412 2413 p->default_timer_slack_ns = current->timer_slack_ns; 2414 2415 #ifdef CONFIG_PSI 2416 p->psi_flags = 0; 2417 #endif 2418 2419 task_io_accounting_init(&p->ioac); 2420 acct_clear_integrals(p); 2421 2422 posix_cputimers_init(&p->posix_cputimers); 2423 2424 p->io_context = NULL; 2425 audit_set_context(p, NULL); 2426 cgroup_fork(p); 2427 if (args->kthread) { 2428 if (!set_kthread_struct(p)) 2429 goto bad_fork_cleanup_delayacct; 2430 } 2431 #ifdef CONFIG_NUMA 2432 p->mempolicy = mpol_dup(p->mempolicy); 2433 if (IS_ERR(p->mempolicy)) { 2434 retval = PTR_ERR(p->mempolicy); 2435 p->mempolicy = NULL; 2436 goto bad_fork_cleanup_delayacct; 2437 } 2438 #endif 2439 #ifdef CONFIG_CPUSETS 2440 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 2441 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 2442 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock); 2443 #endif 2444 #ifdef CONFIG_TRACE_IRQFLAGS 2445 memset(&p->irqtrace, 0, sizeof(p->irqtrace)); 2446 p->irqtrace.hardirq_disable_ip = _THIS_IP_; 2447 p->irqtrace.softirq_enable_ip = _THIS_IP_; 2448 p->softirqs_enabled = 1; 2449 p->softirq_context = 0; 2450 #endif 2451 2452 p->pagefault_disabled = 0; 2453 2454 #ifdef CONFIG_LOCKDEP 2455 lockdep_init_task(p); 2456 #endif 2457 2458 #ifdef CONFIG_DEBUG_MUTEXES 2459 p->blocked_on = NULL; /* not blocked yet */ 2460 #endif 2461 #ifdef CONFIG_BCACHE 2462 p->sequential_io = 0; 2463 p->sequential_io_avg = 0; 2464 #endif 2465 #ifdef CONFIG_BPF_SYSCALL 2466 RCU_INIT_POINTER(p->bpf_storage, NULL); 2467 p->bpf_ctx = NULL; 2468 #endif 2469 2470 /* Perform scheduler related setup. Assign this task to a CPU. */ 2471 retval = sched_fork(clone_flags, p); 2472 if (retval) 2473 goto bad_fork_cleanup_policy; 2474 2475 retval = perf_event_init_task(p, clone_flags); 2476 if (retval) 2477 goto bad_fork_cleanup_policy; 2478 retval = audit_alloc(p); 2479 if (retval) 2480 goto bad_fork_cleanup_perf; 2481 /* copy all the process information */ 2482 shm_init_task(p); 2483 retval = security_task_alloc(p, clone_flags); 2484 if (retval) 2485 goto bad_fork_cleanup_audit; 2486 retval = copy_semundo(clone_flags, p); 2487 if (retval) 2488 goto bad_fork_cleanup_security; 2489 retval = copy_files(clone_flags, p, args->no_files); 2490 if (retval) 2491 goto bad_fork_cleanup_semundo; 2492 retval = copy_fs(clone_flags, p); 2493 if (retval) 2494 goto bad_fork_cleanup_files; 2495 retval = copy_sighand(clone_flags, p); 2496 if (retval) 2497 goto bad_fork_cleanup_fs; 2498 retval = copy_signal(clone_flags, p); 2499 if (retval) 2500 goto bad_fork_cleanup_sighand; 2501 retval = copy_mm(clone_flags, p); 2502 if (retval) 2503 goto bad_fork_cleanup_signal; 2504 retval = copy_namespaces(clone_flags, p); 2505 if (retval) 2506 goto bad_fork_cleanup_mm; 2507 retval = copy_io(clone_flags, p); 2508 if (retval) 2509 goto bad_fork_cleanup_namespaces; 2510 retval = copy_thread(p, args); 2511 if (retval) 2512 goto bad_fork_cleanup_io; 2513 2514 stackleak_task_init(p); 2515 2516 if (pid != &init_struct_pid) { 2517 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid, 2518 args->set_tid_size); 2519 if (IS_ERR(pid)) { 2520 retval = PTR_ERR(pid); 2521 goto bad_fork_cleanup_thread; 2522 } 2523 } 2524 2525 /* 2526 * This has to happen after we've potentially unshared the file 2527 * descriptor table (so that the pidfd doesn't leak into the child 2528 * if the fd table isn't shared). 2529 */ 2530 if (clone_flags & CLONE_PIDFD) { 2531 /* Note that no task has been attached to @pid yet. */ 2532 retval = __pidfd_prepare(pid, O_RDWR | O_CLOEXEC, &pidfile); 2533 if (retval < 0) 2534 goto bad_fork_free_pid; 2535 pidfd = retval; 2536 2537 retval = put_user(pidfd, args->pidfd); 2538 if (retval) 2539 goto bad_fork_put_pidfd; 2540 } 2541 2542 #ifdef CONFIG_BLOCK 2543 p->plug = NULL; 2544 #endif 2545 futex_init_task(p); 2546 2547 /* 2548 * sigaltstack should be cleared when sharing the same VM 2549 */ 2550 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 2551 sas_ss_reset(p); 2552 2553 /* 2554 * Syscall tracing and stepping should be turned off in the 2555 * child regardless of CLONE_PTRACE. 2556 */ 2557 user_disable_single_step(p); 2558 clear_task_syscall_work(p, SYSCALL_TRACE); 2559 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU) 2560 clear_task_syscall_work(p, SYSCALL_EMU); 2561 #endif 2562 clear_tsk_latency_tracing(p); 2563 2564 /* ok, now we should be set up.. */ 2565 p->pid = pid_nr(pid); 2566 if (clone_flags & CLONE_THREAD) { 2567 p->group_leader = current->group_leader; 2568 p->tgid = current->tgid; 2569 } else { 2570 p->group_leader = p; 2571 p->tgid = p->pid; 2572 } 2573 2574 p->nr_dirtied = 0; 2575 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 2576 p->dirty_paused_when = 0; 2577 2578 p->pdeath_signal = 0; 2579 INIT_LIST_HEAD(&p->thread_group); 2580 p->task_works = NULL; 2581 clear_posix_cputimers_work(p); 2582 2583 #ifdef CONFIG_KRETPROBES 2584 p->kretprobe_instances.first = NULL; 2585 #endif 2586 #ifdef CONFIG_RETHOOK 2587 p->rethooks.first = NULL; 2588 #endif 2589 2590 /* 2591 * Ensure that the cgroup subsystem policies allow the new process to be 2592 * forked. It should be noted that the new process's css_set can be changed 2593 * between here and cgroup_post_fork() if an organisation operation is in 2594 * progress. 2595 */ 2596 retval = cgroup_can_fork(p, args); 2597 if (retval) 2598 goto bad_fork_put_pidfd; 2599 2600 /* 2601 * Now that the cgroups are pinned, re-clone the parent cgroup and put 2602 * the new task on the correct runqueue. All this *before* the task 2603 * becomes visible. 2604 * 2605 * This isn't part of ->can_fork() because while the re-cloning is 2606 * cgroup specific, it unconditionally needs to place the task on a 2607 * runqueue. 2608 */ 2609 sched_cgroup_fork(p, args); 2610 2611 /* 2612 * From this point on we must avoid any synchronous user-space 2613 * communication until we take the tasklist-lock. In particular, we do 2614 * not want user-space to be able to predict the process start-time by 2615 * stalling fork(2) after we recorded the start_time but before it is 2616 * visible to the system. 2617 */ 2618 2619 p->start_time = ktime_get_ns(); 2620 p->start_boottime = ktime_get_boottime_ns(); 2621 2622 /* 2623 * Make it visible to the rest of the system, but dont wake it up yet. 2624 * Need tasklist lock for parent etc handling! 2625 */ 2626 write_lock_irq(&tasklist_lock); 2627 2628 /* CLONE_PARENT re-uses the old parent */ 2629 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 2630 p->real_parent = current->real_parent; 2631 p->parent_exec_id = current->parent_exec_id; 2632 if (clone_flags & CLONE_THREAD) 2633 p->exit_signal = -1; 2634 else 2635 p->exit_signal = current->group_leader->exit_signal; 2636 } else { 2637 p->real_parent = current; 2638 p->parent_exec_id = current->self_exec_id; 2639 p->exit_signal = args->exit_signal; 2640 } 2641 2642 klp_copy_process(p); 2643 2644 sched_core_fork(p); 2645 2646 spin_lock(¤t->sighand->siglock); 2647 2648 rv_task_fork(p); 2649 2650 rseq_fork(p, clone_flags); 2651 2652 /* Don't start children in a dying pid namespace */ 2653 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 2654 retval = -ENOMEM; 2655 goto bad_fork_cancel_cgroup; 2656 } 2657 2658 /* Let kill terminate clone/fork in the middle */ 2659 if (fatal_signal_pending(current)) { 2660 retval = -EINTR; 2661 goto bad_fork_cancel_cgroup; 2662 } 2663 2664 /* No more failure paths after this point. */ 2665 2666 /* 2667 * Copy seccomp details explicitly here, in case they were changed 2668 * before holding sighand lock. 2669 */ 2670 copy_seccomp(p); 2671 2672 init_task_pid_links(p); 2673 if (likely(p->pid)) { 2674 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 2675 2676 init_task_pid(p, PIDTYPE_PID, pid); 2677 if (thread_group_leader(p)) { 2678 init_task_pid(p, PIDTYPE_TGID, pid); 2679 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 2680 init_task_pid(p, PIDTYPE_SID, task_session(current)); 2681 2682 if (is_child_reaper(pid)) { 2683 ns_of_pid(pid)->child_reaper = p; 2684 p->signal->flags |= SIGNAL_UNKILLABLE; 2685 } 2686 p->signal->shared_pending.signal = delayed.signal; 2687 p->signal->tty = tty_kref_get(current->signal->tty); 2688 /* 2689 * Inherit has_child_subreaper flag under the same 2690 * tasklist_lock with adding child to the process tree 2691 * for propagate_has_child_subreaper optimization. 2692 */ 2693 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 2694 p->real_parent->signal->is_child_subreaper; 2695 list_add_tail(&p->sibling, &p->real_parent->children); 2696 list_add_tail_rcu(&p->tasks, &init_task.tasks); 2697 attach_pid(p, PIDTYPE_TGID); 2698 attach_pid(p, PIDTYPE_PGID); 2699 attach_pid(p, PIDTYPE_SID); 2700 __this_cpu_inc(process_counts); 2701 } else { 2702 current->signal->nr_threads++; 2703 current->signal->quick_threads++; 2704 atomic_inc(¤t->signal->live); 2705 refcount_inc(¤t->signal->sigcnt); 2706 task_join_group_stop(p); 2707 list_add_tail_rcu(&p->thread_group, 2708 &p->group_leader->thread_group); 2709 list_add_tail_rcu(&p->thread_node, 2710 &p->signal->thread_head); 2711 } 2712 attach_pid(p, PIDTYPE_PID); 2713 nr_threads++; 2714 } 2715 total_forks++; 2716 hlist_del_init(&delayed.node); 2717 spin_unlock(¤t->sighand->siglock); 2718 syscall_tracepoint_update(p); 2719 write_unlock_irq(&tasklist_lock); 2720 2721 if (pidfile) 2722 fd_install(pidfd, pidfile); 2723 2724 proc_fork_connector(p); 2725 sched_post_fork(p); 2726 cgroup_post_fork(p, args); 2727 perf_event_fork(p); 2728 2729 trace_task_newtask(p, clone_flags); 2730 uprobe_copy_process(p, clone_flags); 2731 user_events_fork(p, clone_flags); 2732 2733 copy_oom_score_adj(clone_flags, p); 2734 2735 return p; 2736 2737 bad_fork_cancel_cgroup: 2738 sched_core_free(p); 2739 spin_unlock(¤t->sighand->siglock); 2740 write_unlock_irq(&tasklist_lock); 2741 cgroup_cancel_fork(p, args); 2742 bad_fork_put_pidfd: 2743 if (clone_flags & CLONE_PIDFD) { 2744 fput(pidfile); 2745 put_unused_fd(pidfd); 2746 } 2747 bad_fork_free_pid: 2748 if (pid != &init_struct_pid) 2749 free_pid(pid); 2750 bad_fork_cleanup_thread: 2751 exit_thread(p); 2752 bad_fork_cleanup_io: 2753 if (p->io_context) 2754 exit_io_context(p); 2755 bad_fork_cleanup_namespaces: 2756 exit_task_namespaces(p); 2757 bad_fork_cleanup_mm: 2758 if (p->mm) { 2759 mm_clear_owner(p->mm, p); 2760 mmput(p->mm); 2761 } 2762 bad_fork_cleanup_signal: 2763 if (!(clone_flags & CLONE_THREAD)) 2764 free_signal_struct(p->signal); 2765 bad_fork_cleanup_sighand: 2766 __cleanup_sighand(p->sighand); 2767 bad_fork_cleanup_fs: 2768 exit_fs(p); /* blocking */ 2769 bad_fork_cleanup_files: 2770 exit_files(p); /* blocking */ 2771 bad_fork_cleanup_semundo: 2772 exit_sem(p); 2773 bad_fork_cleanup_security: 2774 security_task_free(p); 2775 bad_fork_cleanup_audit: 2776 audit_free(p); 2777 bad_fork_cleanup_perf: 2778 perf_event_free_task(p); 2779 bad_fork_cleanup_policy: 2780 lockdep_free_task(p); 2781 #ifdef CONFIG_NUMA 2782 mpol_put(p->mempolicy); 2783 #endif 2784 bad_fork_cleanup_delayacct: 2785 delayacct_tsk_free(p); 2786 bad_fork_cleanup_count: 2787 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); 2788 exit_creds(p); 2789 bad_fork_free: 2790 WRITE_ONCE(p->__state, TASK_DEAD); 2791 exit_task_stack_account(p); 2792 put_task_stack(p); 2793 delayed_free_task(p); 2794 fork_out: 2795 spin_lock_irq(¤t->sighand->siglock); 2796 hlist_del_init(&delayed.node); 2797 spin_unlock_irq(¤t->sighand->siglock); 2798 return ERR_PTR(retval); 2799 } 2800 2801 static inline void init_idle_pids(struct task_struct *idle) 2802 { 2803 enum pid_type type; 2804 2805 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2806 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */ 2807 init_task_pid(idle, type, &init_struct_pid); 2808 } 2809 } 2810 2811 static int idle_dummy(void *dummy) 2812 { 2813 /* This function is never called */ 2814 return 0; 2815 } 2816 2817 struct task_struct * __init fork_idle(int cpu) 2818 { 2819 struct task_struct *task; 2820 struct kernel_clone_args args = { 2821 .flags = CLONE_VM, 2822 .fn = &idle_dummy, 2823 .fn_arg = NULL, 2824 .kthread = 1, 2825 .idle = 1, 2826 }; 2827 2828 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args); 2829 if (!IS_ERR(task)) { 2830 init_idle_pids(task); 2831 init_idle(task, cpu); 2832 } 2833 2834 return task; 2835 } 2836 2837 /* 2838 * This is like kernel_clone(), but shaved down and tailored to just 2839 * creating io_uring workers. It returns a created task, or an error pointer. 2840 * The returned task is inactive, and the caller must fire it up through 2841 * wake_up_new_task(p). All signals are blocked in the created task. 2842 */ 2843 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node) 2844 { 2845 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD| 2846 CLONE_IO; 2847 struct kernel_clone_args args = { 2848 .flags = ((lower_32_bits(flags) | CLONE_VM | 2849 CLONE_UNTRACED) & ~CSIGNAL), 2850 .exit_signal = (lower_32_bits(flags) & CSIGNAL), 2851 .fn = fn, 2852 .fn_arg = arg, 2853 .io_thread = 1, 2854 .user_worker = 1, 2855 }; 2856 2857 return copy_process(NULL, 0, node, &args); 2858 } 2859 2860 /* 2861 * Ok, this is the main fork-routine. 2862 * 2863 * It copies the process, and if successful kick-starts 2864 * it and waits for it to finish using the VM if required. 2865 * 2866 * args->exit_signal is expected to be checked for sanity by the caller. 2867 */ 2868 pid_t kernel_clone(struct kernel_clone_args *args) 2869 { 2870 u64 clone_flags = args->flags; 2871 struct completion vfork; 2872 struct pid *pid; 2873 struct task_struct *p; 2874 int trace = 0; 2875 pid_t nr; 2876 2877 /* 2878 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument 2879 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are 2880 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate 2881 * field in struct clone_args and it still doesn't make sense to have 2882 * them both point at the same memory location. Performing this check 2883 * here has the advantage that we don't need to have a separate helper 2884 * to check for legacy clone(). 2885 */ 2886 if ((args->flags & CLONE_PIDFD) && 2887 (args->flags & CLONE_PARENT_SETTID) && 2888 (args->pidfd == args->parent_tid)) 2889 return -EINVAL; 2890 2891 /* 2892 * Determine whether and which event to report to ptracer. When 2893 * called from kernel_thread or CLONE_UNTRACED is explicitly 2894 * requested, no event is reported; otherwise, report if the event 2895 * for the type of forking is enabled. 2896 */ 2897 if (!(clone_flags & CLONE_UNTRACED)) { 2898 if (clone_flags & CLONE_VFORK) 2899 trace = PTRACE_EVENT_VFORK; 2900 else if (args->exit_signal != SIGCHLD) 2901 trace = PTRACE_EVENT_CLONE; 2902 else 2903 trace = PTRACE_EVENT_FORK; 2904 2905 if (likely(!ptrace_event_enabled(current, trace))) 2906 trace = 0; 2907 } 2908 2909 p = copy_process(NULL, trace, NUMA_NO_NODE, args); 2910 add_latent_entropy(); 2911 2912 if (IS_ERR(p)) 2913 return PTR_ERR(p); 2914 2915 /* 2916 * Do this prior waking up the new thread - the thread pointer 2917 * might get invalid after that point, if the thread exits quickly. 2918 */ 2919 trace_sched_process_fork(current, p); 2920 2921 pid = get_task_pid(p, PIDTYPE_PID); 2922 nr = pid_vnr(pid); 2923 2924 if (clone_flags & CLONE_PARENT_SETTID) 2925 put_user(nr, args->parent_tid); 2926 2927 if (clone_flags & CLONE_VFORK) { 2928 p->vfork_done = &vfork; 2929 init_completion(&vfork); 2930 get_task_struct(p); 2931 } 2932 2933 if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) { 2934 /* lock the task to synchronize with memcg migration */ 2935 task_lock(p); 2936 lru_gen_add_mm(p->mm); 2937 task_unlock(p); 2938 } 2939 2940 wake_up_new_task(p); 2941 2942 /* forking complete and child started to run, tell ptracer */ 2943 if (unlikely(trace)) 2944 ptrace_event_pid(trace, pid); 2945 2946 if (clone_flags & CLONE_VFORK) { 2947 if (!wait_for_vfork_done(p, &vfork)) 2948 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2949 } 2950 2951 put_pid(pid); 2952 return nr; 2953 } 2954 2955 /* 2956 * Create a kernel thread. 2957 */ 2958 pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name, 2959 unsigned long flags) 2960 { 2961 struct kernel_clone_args args = { 2962 .flags = ((lower_32_bits(flags) | CLONE_VM | 2963 CLONE_UNTRACED) & ~CSIGNAL), 2964 .exit_signal = (lower_32_bits(flags) & CSIGNAL), 2965 .fn = fn, 2966 .fn_arg = arg, 2967 .name = name, 2968 .kthread = 1, 2969 }; 2970 2971 return kernel_clone(&args); 2972 } 2973 2974 /* 2975 * Create a user mode thread. 2976 */ 2977 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags) 2978 { 2979 struct kernel_clone_args args = { 2980 .flags = ((lower_32_bits(flags) | CLONE_VM | 2981 CLONE_UNTRACED) & ~CSIGNAL), 2982 .exit_signal = (lower_32_bits(flags) & CSIGNAL), 2983 .fn = fn, 2984 .fn_arg = arg, 2985 }; 2986 2987 return kernel_clone(&args); 2988 } 2989 2990 #ifdef __ARCH_WANT_SYS_FORK 2991 SYSCALL_DEFINE0(fork) 2992 { 2993 #ifdef CONFIG_MMU 2994 struct kernel_clone_args args = { 2995 .exit_signal = SIGCHLD, 2996 }; 2997 2998 return kernel_clone(&args); 2999 #else 3000 /* can not support in nommu mode */ 3001 return -EINVAL; 3002 #endif 3003 } 3004 #endif 3005 3006 #ifdef __ARCH_WANT_SYS_VFORK 3007 SYSCALL_DEFINE0(vfork) 3008 { 3009 struct kernel_clone_args args = { 3010 .flags = CLONE_VFORK | CLONE_VM, 3011 .exit_signal = SIGCHLD, 3012 }; 3013 3014 return kernel_clone(&args); 3015 } 3016 #endif 3017 3018 #ifdef __ARCH_WANT_SYS_CLONE 3019 #ifdef CONFIG_CLONE_BACKWARDS 3020 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 3021 int __user *, parent_tidptr, 3022 unsigned long, tls, 3023 int __user *, child_tidptr) 3024 #elif defined(CONFIG_CLONE_BACKWARDS2) 3025 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 3026 int __user *, parent_tidptr, 3027 int __user *, child_tidptr, 3028 unsigned long, tls) 3029 #elif defined(CONFIG_CLONE_BACKWARDS3) 3030 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 3031 int, stack_size, 3032 int __user *, parent_tidptr, 3033 int __user *, child_tidptr, 3034 unsigned long, tls) 3035 #else 3036 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 3037 int __user *, parent_tidptr, 3038 int __user *, child_tidptr, 3039 unsigned long, tls) 3040 #endif 3041 { 3042 struct kernel_clone_args args = { 3043 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL), 3044 .pidfd = parent_tidptr, 3045 .child_tid = child_tidptr, 3046 .parent_tid = parent_tidptr, 3047 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL), 3048 .stack = newsp, 3049 .tls = tls, 3050 }; 3051 3052 return kernel_clone(&args); 3053 } 3054 #endif 3055 3056 #ifdef __ARCH_WANT_SYS_CLONE3 3057 3058 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, 3059 struct clone_args __user *uargs, 3060 size_t usize) 3061 { 3062 int err; 3063 struct clone_args args; 3064 pid_t *kset_tid = kargs->set_tid; 3065 3066 BUILD_BUG_ON(offsetofend(struct clone_args, tls) != 3067 CLONE_ARGS_SIZE_VER0); 3068 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) != 3069 CLONE_ARGS_SIZE_VER1); 3070 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) != 3071 CLONE_ARGS_SIZE_VER2); 3072 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2); 3073 3074 if (unlikely(usize > PAGE_SIZE)) 3075 return -E2BIG; 3076 if (unlikely(usize < CLONE_ARGS_SIZE_VER0)) 3077 return -EINVAL; 3078 3079 err = copy_struct_from_user(&args, sizeof(args), uargs, usize); 3080 if (err) 3081 return err; 3082 3083 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL)) 3084 return -EINVAL; 3085 3086 if (unlikely(!args.set_tid && args.set_tid_size > 0)) 3087 return -EINVAL; 3088 3089 if (unlikely(args.set_tid && args.set_tid_size == 0)) 3090 return -EINVAL; 3091 3092 /* 3093 * Verify that higher 32bits of exit_signal are unset and that 3094 * it is a valid signal 3095 */ 3096 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) || 3097 !valid_signal(args.exit_signal))) 3098 return -EINVAL; 3099 3100 if ((args.flags & CLONE_INTO_CGROUP) && 3101 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2)) 3102 return -EINVAL; 3103 3104 *kargs = (struct kernel_clone_args){ 3105 .flags = args.flags, 3106 .pidfd = u64_to_user_ptr(args.pidfd), 3107 .child_tid = u64_to_user_ptr(args.child_tid), 3108 .parent_tid = u64_to_user_ptr(args.parent_tid), 3109 .exit_signal = args.exit_signal, 3110 .stack = args.stack, 3111 .stack_size = args.stack_size, 3112 .tls = args.tls, 3113 .set_tid_size = args.set_tid_size, 3114 .cgroup = args.cgroup, 3115 }; 3116 3117 if (args.set_tid && 3118 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid), 3119 (kargs->set_tid_size * sizeof(pid_t)))) 3120 return -EFAULT; 3121 3122 kargs->set_tid = kset_tid; 3123 3124 return 0; 3125 } 3126 3127 /** 3128 * clone3_stack_valid - check and prepare stack 3129 * @kargs: kernel clone args 3130 * 3131 * Verify that the stack arguments userspace gave us are sane. 3132 * In addition, set the stack direction for userspace since it's easy for us to 3133 * determine. 3134 */ 3135 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs) 3136 { 3137 if (kargs->stack == 0) { 3138 if (kargs->stack_size > 0) 3139 return false; 3140 } else { 3141 if (kargs->stack_size == 0) 3142 return false; 3143 3144 if (!access_ok((void __user *)kargs->stack, kargs->stack_size)) 3145 return false; 3146 3147 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64) 3148 kargs->stack += kargs->stack_size; 3149 #endif 3150 } 3151 3152 return true; 3153 } 3154 3155 static bool clone3_args_valid(struct kernel_clone_args *kargs) 3156 { 3157 /* Verify that no unknown flags are passed along. */ 3158 if (kargs->flags & 3159 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP)) 3160 return false; 3161 3162 /* 3163 * - make the CLONE_DETACHED bit reusable for clone3 3164 * - make the CSIGNAL bits reusable for clone3 3165 */ 3166 if (kargs->flags & (CLONE_DETACHED | (CSIGNAL & (~CLONE_NEWTIME)))) 3167 return false; 3168 3169 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) == 3170 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) 3171 return false; 3172 3173 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) && 3174 kargs->exit_signal) 3175 return false; 3176 3177 if (!clone3_stack_valid(kargs)) 3178 return false; 3179 3180 return true; 3181 } 3182 3183 /** 3184 * clone3 - create a new process with specific properties 3185 * @uargs: argument structure 3186 * @size: size of @uargs 3187 * 3188 * clone3() is the extensible successor to clone()/clone2(). 3189 * It takes a struct as argument that is versioned by its size. 3190 * 3191 * Return: On success, a positive PID for the child process. 3192 * On error, a negative errno number. 3193 */ 3194 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size) 3195 { 3196 int err; 3197 3198 struct kernel_clone_args kargs; 3199 pid_t set_tid[MAX_PID_NS_LEVEL]; 3200 3201 kargs.set_tid = set_tid; 3202 3203 err = copy_clone_args_from_user(&kargs, uargs, size); 3204 if (err) 3205 return err; 3206 3207 if (!clone3_args_valid(&kargs)) 3208 return -EINVAL; 3209 3210 return kernel_clone(&kargs); 3211 } 3212 #endif 3213 3214 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 3215 { 3216 struct task_struct *leader, *parent, *child; 3217 int res; 3218 3219 read_lock(&tasklist_lock); 3220 leader = top = top->group_leader; 3221 down: 3222 for_each_thread(leader, parent) { 3223 list_for_each_entry(child, &parent->children, sibling) { 3224 res = visitor(child, data); 3225 if (res) { 3226 if (res < 0) 3227 goto out; 3228 leader = child; 3229 goto down; 3230 } 3231 up: 3232 ; 3233 } 3234 } 3235 3236 if (leader != top) { 3237 child = leader; 3238 parent = child->real_parent; 3239 leader = parent->group_leader; 3240 goto up; 3241 } 3242 out: 3243 read_unlock(&tasklist_lock); 3244 } 3245 3246 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 3247 #define ARCH_MIN_MMSTRUCT_ALIGN 0 3248 #endif 3249 3250 static void sighand_ctor(void *data) 3251 { 3252 struct sighand_struct *sighand = data; 3253 3254 spin_lock_init(&sighand->siglock); 3255 init_waitqueue_head(&sighand->signalfd_wqh); 3256 } 3257 3258 void __init mm_cache_init(void) 3259 { 3260 unsigned int mm_size; 3261 3262 /* 3263 * The mm_cpumask is located at the end of mm_struct, and is 3264 * dynamically sized based on the maximum CPU number this system 3265 * can have, taking hotplug into account (nr_cpu_ids). 3266 */ 3267 mm_size = sizeof(struct mm_struct) + cpumask_size() + mm_cid_size(); 3268 3269 mm_cachep = kmem_cache_create_usercopy("mm_struct", 3270 mm_size, ARCH_MIN_MMSTRUCT_ALIGN, 3271 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 3272 offsetof(struct mm_struct, saved_auxv), 3273 sizeof_field(struct mm_struct, saved_auxv), 3274 NULL); 3275 } 3276 3277 void __init proc_caches_init(void) 3278 { 3279 sighand_cachep = kmem_cache_create("sighand_cache", 3280 sizeof(struct sighand_struct), 0, 3281 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 3282 SLAB_ACCOUNT, sighand_ctor); 3283 signal_cachep = kmem_cache_create("signal_cache", 3284 sizeof(struct signal_struct), 0, 3285 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 3286 NULL); 3287 files_cachep = kmem_cache_create("files_cache", 3288 sizeof(struct files_struct), 0, 3289 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 3290 NULL); 3291 fs_cachep = kmem_cache_create("fs_cache", 3292 sizeof(struct fs_struct), 0, 3293 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 3294 NULL); 3295 3296 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 3297 #ifdef CONFIG_PER_VMA_LOCK 3298 vma_lock_cachep = KMEM_CACHE(vma_lock, SLAB_PANIC|SLAB_ACCOUNT); 3299 #endif 3300 mmap_init(); 3301 nsproxy_cache_init(); 3302 } 3303 3304 /* 3305 * Check constraints on flags passed to the unshare system call. 3306 */ 3307 static int check_unshare_flags(unsigned long unshare_flags) 3308 { 3309 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 3310 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 3311 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 3312 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP| 3313 CLONE_NEWTIME)) 3314 return -EINVAL; 3315 /* 3316 * Not implemented, but pretend it works if there is nothing 3317 * to unshare. Note that unsharing the address space or the 3318 * signal handlers also need to unshare the signal queues (aka 3319 * CLONE_THREAD). 3320 */ 3321 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 3322 if (!thread_group_empty(current)) 3323 return -EINVAL; 3324 } 3325 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 3326 if (refcount_read(¤t->sighand->count) > 1) 3327 return -EINVAL; 3328 } 3329 if (unshare_flags & CLONE_VM) { 3330 if (!current_is_single_threaded()) 3331 return -EINVAL; 3332 } 3333 3334 return 0; 3335 } 3336 3337 /* 3338 * Unshare the filesystem structure if it is being shared 3339 */ 3340 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 3341 { 3342 struct fs_struct *fs = current->fs; 3343 3344 if (!(unshare_flags & CLONE_FS) || !fs) 3345 return 0; 3346 3347 /* don't need lock here; in the worst case we'll do useless copy */ 3348 if (fs->users == 1) 3349 return 0; 3350 3351 *new_fsp = copy_fs_struct(fs); 3352 if (!*new_fsp) 3353 return -ENOMEM; 3354 3355 return 0; 3356 } 3357 3358 /* 3359 * Unshare file descriptor table if it is being shared 3360 */ 3361 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 3362 struct files_struct **new_fdp) 3363 { 3364 struct files_struct *fd = current->files; 3365 int error = 0; 3366 3367 if ((unshare_flags & CLONE_FILES) && 3368 (fd && atomic_read(&fd->count) > 1)) { 3369 *new_fdp = dup_fd(fd, max_fds, &error); 3370 if (!*new_fdp) 3371 return error; 3372 } 3373 3374 return 0; 3375 } 3376 3377 /* 3378 * unshare allows a process to 'unshare' part of the process 3379 * context which was originally shared using clone. copy_* 3380 * functions used by kernel_clone() cannot be used here directly 3381 * because they modify an inactive task_struct that is being 3382 * constructed. Here we are modifying the current, active, 3383 * task_struct. 3384 */ 3385 int ksys_unshare(unsigned long unshare_flags) 3386 { 3387 struct fs_struct *fs, *new_fs = NULL; 3388 struct files_struct *new_fd = NULL; 3389 struct cred *new_cred = NULL; 3390 struct nsproxy *new_nsproxy = NULL; 3391 int do_sysvsem = 0; 3392 int err; 3393 3394 /* 3395 * If unsharing a user namespace must also unshare the thread group 3396 * and unshare the filesystem root and working directories. 3397 */ 3398 if (unshare_flags & CLONE_NEWUSER) 3399 unshare_flags |= CLONE_THREAD | CLONE_FS; 3400 /* 3401 * If unsharing vm, must also unshare signal handlers. 3402 */ 3403 if (unshare_flags & CLONE_VM) 3404 unshare_flags |= CLONE_SIGHAND; 3405 /* 3406 * If unsharing a signal handlers, must also unshare the signal queues. 3407 */ 3408 if (unshare_flags & CLONE_SIGHAND) 3409 unshare_flags |= CLONE_THREAD; 3410 /* 3411 * If unsharing namespace, must also unshare filesystem information. 3412 */ 3413 if (unshare_flags & CLONE_NEWNS) 3414 unshare_flags |= CLONE_FS; 3415 3416 err = check_unshare_flags(unshare_flags); 3417 if (err) 3418 goto bad_unshare_out; 3419 /* 3420 * CLONE_NEWIPC must also detach from the undolist: after switching 3421 * to a new ipc namespace, the semaphore arrays from the old 3422 * namespace are unreachable. 3423 */ 3424 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 3425 do_sysvsem = 1; 3426 err = unshare_fs(unshare_flags, &new_fs); 3427 if (err) 3428 goto bad_unshare_out; 3429 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd); 3430 if (err) 3431 goto bad_unshare_cleanup_fs; 3432 err = unshare_userns(unshare_flags, &new_cred); 3433 if (err) 3434 goto bad_unshare_cleanup_fd; 3435 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 3436 new_cred, new_fs); 3437 if (err) 3438 goto bad_unshare_cleanup_cred; 3439 3440 if (new_cred) { 3441 err = set_cred_ucounts(new_cred); 3442 if (err) 3443 goto bad_unshare_cleanup_cred; 3444 } 3445 3446 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 3447 if (do_sysvsem) { 3448 /* 3449 * CLONE_SYSVSEM is equivalent to sys_exit(). 3450 */ 3451 exit_sem(current); 3452 } 3453 if (unshare_flags & CLONE_NEWIPC) { 3454 /* Orphan segments in old ns (see sem above). */ 3455 exit_shm(current); 3456 shm_init_task(current); 3457 } 3458 3459 if (new_nsproxy) 3460 switch_task_namespaces(current, new_nsproxy); 3461 3462 task_lock(current); 3463 3464 if (new_fs) { 3465 fs = current->fs; 3466 spin_lock(&fs->lock); 3467 current->fs = new_fs; 3468 if (--fs->users) 3469 new_fs = NULL; 3470 else 3471 new_fs = fs; 3472 spin_unlock(&fs->lock); 3473 } 3474 3475 if (new_fd) 3476 swap(current->files, new_fd); 3477 3478 task_unlock(current); 3479 3480 if (new_cred) { 3481 /* Install the new user namespace */ 3482 commit_creds(new_cred); 3483 new_cred = NULL; 3484 } 3485 } 3486 3487 perf_event_namespaces(current); 3488 3489 bad_unshare_cleanup_cred: 3490 if (new_cred) 3491 put_cred(new_cred); 3492 bad_unshare_cleanup_fd: 3493 if (new_fd) 3494 put_files_struct(new_fd); 3495 3496 bad_unshare_cleanup_fs: 3497 if (new_fs) 3498 free_fs_struct(new_fs); 3499 3500 bad_unshare_out: 3501 return err; 3502 } 3503 3504 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 3505 { 3506 return ksys_unshare(unshare_flags); 3507 } 3508 3509 /* 3510 * Helper to unshare the files of the current task. 3511 * We don't want to expose copy_files internals to 3512 * the exec layer of the kernel. 3513 */ 3514 3515 int unshare_files(void) 3516 { 3517 struct task_struct *task = current; 3518 struct files_struct *old, *copy = NULL; 3519 int error; 3520 3521 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©); 3522 if (error || !copy) 3523 return error; 3524 3525 old = task->files; 3526 task_lock(task); 3527 task->files = copy; 3528 task_unlock(task); 3529 put_files_struct(old); 3530 return 0; 3531 } 3532 3533 int sysctl_max_threads(struct ctl_table *table, int write, 3534 void *buffer, size_t *lenp, loff_t *ppos) 3535 { 3536 struct ctl_table t; 3537 int ret; 3538 int threads = max_threads; 3539 int min = 1; 3540 int max = MAX_THREADS; 3541 3542 t = *table; 3543 t.data = &threads; 3544 t.extra1 = &min; 3545 t.extra2 = &max; 3546 3547 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 3548 if (ret || !write) 3549 return ret; 3550 3551 max_threads = threads; 3552 3553 return 0; 3554 }