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