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 = 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 mod_memcg_page_state(vm->pages[i], 281 MEMCG_KERNEL_STACK_KB, 282 -(int)(PAGE_SIZE / 1024)); 283 284 memcg_kmem_uncharge_page(vm->pages[i], 0); 285 } 286 287 for (i = 0; i < NR_CACHED_STACKS; i++) { 288 if (this_cpu_cmpxchg(cached_stacks[i], 289 NULL, tsk->stack_vm_area) != NULL) 290 continue; 291 292 return; 293 } 294 295 vfree_atomic(tsk->stack); 296 return; 297 } 298 #endif 299 300 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 301 } 302 # else 303 static struct kmem_cache *thread_stack_cache; 304 305 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 306 int node) 307 { 308 unsigned long *stack; 309 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 310 tsk->stack = stack; 311 return stack; 312 } 313 314 static void free_thread_stack(struct task_struct *tsk) 315 { 316 kmem_cache_free(thread_stack_cache, tsk->stack); 317 } 318 319 void thread_stack_cache_init(void) 320 { 321 thread_stack_cache = kmem_cache_create_usercopy("thread_stack", 322 THREAD_SIZE, THREAD_SIZE, 0, 0, 323 THREAD_SIZE, NULL); 324 BUG_ON(thread_stack_cache == NULL); 325 } 326 # endif 327 #endif 328 329 /* SLAB cache for signal_struct structures (tsk->signal) */ 330 static struct kmem_cache *signal_cachep; 331 332 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 333 struct kmem_cache *sighand_cachep; 334 335 /* SLAB cache for files_struct structures (tsk->files) */ 336 struct kmem_cache *files_cachep; 337 338 /* SLAB cache for fs_struct structures (tsk->fs) */ 339 struct kmem_cache *fs_cachep; 340 341 /* SLAB cache for vm_area_struct structures */ 342 static struct kmem_cache *vm_area_cachep; 343 344 /* SLAB cache for mm_struct structures (tsk->mm) */ 345 static struct kmem_cache *mm_cachep; 346 347 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm) 348 { 349 struct vm_area_struct *vma; 350 351 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 352 if (vma) 353 vma_init(vma, mm); 354 return vma; 355 } 356 357 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) 358 { 359 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 360 361 if (new) { 362 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags); 363 ASSERT_EXCLUSIVE_WRITER(orig->vm_file); 364 /* 365 * orig->shared.rb may be modified concurrently, but the clone 366 * will be reinitialized. 367 */ 368 *new = data_race(*orig); 369 INIT_LIST_HEAD(&new->anon_vma_chain); 370 new->vm_next = new->vm_prev = NULL; 371 } 372 return new; 373 } 374 375 void vm_area_free(struct vm_area_struct *vma) 376 { 377 kmem_cache_free(vm_area_cachep, vma); 378 } 379 380 static void account_kernel_stack(struct task_struct *tsk, int account) 381 { 382 void *stack = task_stack_page(tsk); 383 struct vm_struct *vm = task_stack_vm_area(tsk); 384 385 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 386 387 if (vm) { 388 int i; 389 390 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 391 392 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 393 mod_zone_page_state(page_zone(vm->pages[i]), 394 NR_KERNEL_STACK_KB, 395 PAGE_SIZE / 1024 * account); 396 } 397 } else { 398 /* 399 * All stack pages are in the same zone and belong to the 400 * same memcg. 401 */ 402 struct page *first_page = virt_to_page(stack); 403 404 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 405 THREAD_SIZE / 1024 * account); 406 407 mod_memcg_obj_state(stack, MEMCG_KERNEL_STACK_KB, 408 account * (THREAD_SIZE / 1024)); 409 } 410 } 411 412 static int memcg_charge_kernel_stack(struct task_struct *tsk) 413 { 414 #ifdef CONFIG_VMAP_STACK 415 struct vm_struct *vm = task_stack_vm_area(tsk); 416 int ret; 417 418 if (vm) { 419 int i; 420 421 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 422 /* 423 * If memcg_kmem_charge_page() fails, page->mem_cgroup 424 * pointer is NULL, and both memcg_kmem_uncharge_page() 425 * and mod_memcg_page_state() in free_thread_stack() 426 * will ignore this page. So it's safe. 427 */ 428 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 429 0); 430 if (ret) 431 return ret; 432 433 mod_memcg_page_state(vm->pages[i], 434 MEMCG_KERNEL_STACK_KB, 435 PAGE_SIZE / 1024); 436 } 437 } 438 #endif 439 return 0; 440 } 441 442 static void release_task_stack(struct task_struct *tsk) 443 { 444 if (WARN_ON(tsk->state != TASK_DEAD)) 445 return; /* Better to leak the stack than to free prematurely */ 446 447 account_kernel_stack(tsk, -1); 448 free_thread_stack(tsk); 449 tsk->stack = NULL; 450 #ifdef CONFIG_VMAP_STACK 451 tsk->stack_vm_area = NULL; 452 #endif 453 } 454 455 #ifdef CONFIG_THREAD_INFO_IN_TASK 456 void put_task_stack(struct task_struct *tsk) 457 { 458 if (refcount_dec_and_test(&tsk->stack_refcount)) 459 release_task_stack(tsk); 460 } 461 #endif 462 463 void free_task(struct task_struct *tsk) 464 { 465 scs_release(tsk); 466 467 #ifndef CONFIG_THREAD_INFO_IN_TASK 468 /* 469 * The task is finally done with both the stack and thread_info, 470 * so free both. 471 */ 472 release_task_stack(tsk); 473 #else 474 /* 475 * If the task had a separate stack allocation, it should be gone 476 * by now. 477 */ 478 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0); 479 #endif 480 rt_mutex_debug_task_free(tsk); 481 ftrace_graph_exit_task(tsk); 482 arch_release_task_struct(tsk); 483 if (tsk->flags & PF_KTHREAD) 484 free_kthread_struct(tsk); 485 free_task_struct(tsk); 486 } 487 EXPORT_SYMBOL(free_task); 488 489 #ifdef CONFIG_MMU 490 static __latent_entropy int dup_mmap(struct mm_struct *mm, 491 struct mm_struct *oldmm) 492 { 493 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 494 struct rb_node **rb_link, *rb_parent; 495 int retval; 496 unsigned long charge; 497 LIST_HEAD(uf); 498 499 uprobe_start_dup_mmap(); 500 if (mmap_write_lock_killable(oldmm)) { 501 retval = -EINTR; 502 goto fail_uprobe_end; 503 } 504 flush_cache_dup_mm(oldmm); 505 uprobe_dup_mmap(oldmm, mm); 506 /* 507 * Not linked in yet - no deadlock potential: 508 */ 509 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); 510 511 /* No ordering required: file already has been exposed. */ 512 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 513 514 mm->total_vm = oldmm->total_vm; 515 mm->data_vm = oldmm->data_vm; 516 mm->exec_vm = oldmm->exec_vm; 517 mm->stack_vm = oldmm->stack_vm; 518 519 rb_link = &mm->mm_rb.rb_node; 520 rb_parent = NULL; 521 pprev = &mm->mmap; 522 retval = ksm_fork(mm, oldmm); 523 if (retval) 524 goto out; 525 retval = khugepaged_fork(mm, oldmm); 526 if (retval) 527 goto out; 528 529 prev = NULL; 530 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 531 struct file *file; 532 533 if (mpnt->vm_flags & VM_DONTCOPY) { 534 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 535 continue; 536 } 537 charge = 0; 538 /* 539 * Don't duplicate many vmas if we've been oom-killed (for 540 * example) 541 */ 542 if (fatal_signal_pending(current)) { 543 retval = -EINTR; 544 goto out; 545 } 546 if (mpnt->vm_flags & VM_ACCOUNT) { 547 unsigned long len = vma_pages(mpnt); 548 549 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 550 goto fail_nomem; 551 charge = len; 552 } 553 tmp = vm_area_dup(mpnt); 554 if (!tmp) 555 goto fail_nomem; 556 retval = vma_dup_policy(mpnt, tmp); 557 if (retval) 558 goto fail_nomem_policy; 559 tmp->vm_mm = mm; 560 retval = dup_userfaultfd(tmp, &uf); 561 if (retval) 562 goto fail_nomem_anon_vma_fork; 563 if (tmp->vm_flags & VM_WIPEONFORK) { 564 /* 565 * VM_WIPEONFORK gets a clean slate in the child. 566 * Don't prepare anon_vma until fault since we don't 567 * copy page for current vma. 568 */ 569 tmp->anon_vma = NULL; 570 } else if (anon_vma_fork(tmp, mpnt)) 571 goto fail_nomem_anon_vma_fork; 572 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 573 file = tmp->vm_file; 574 if (file) { 575 struct inode *inode = file_inode(file); 576 struct address_space *mapping = file->f_mapping; 577 578 get_file(file); 579 if (tmp->vm_flags & VM_DENYWRITE) 580 atomic_dec(&inode->i_writecount); 581 i_mmap_lock_write(mapping); 582 if (tmp->vm_flags & VM_SHARED) 583 atomic_inc(&mapping->i_mmap_writable); 584 flush_dcache_mmap_lock(mapping); 585 /* insert tmp into the share list, just after mpnt */ 586 vma_interval_tree_insert_after(tmp, mpnt, 587 &mapping->i_mmap); 588 flush_dcache_mmap_unlock(mapping); 589 i_mmap_unlock_write(mapping); 590 } 591 592 /* 593 * Clear hugetlb-related page reserves for children. This only 594 * affects MAP_PRIVATE mappings. Faults generated by the child 595 * are not guaranteed to succeed, even if read-only 596 */ 597 if (is_vm_hugetlb_page(tmp)) 598 reset_vma_resv_huge_pages(tmp); 599 600 /* 601 * Link in the new vma and copy the page table entries. 602 */ 603 *pprev = tmp; 604 pprev = &tmp->vm_next; 605 tmp->vm_prev = prev; 606 prev = tmp; 607 608 __vma_link_rb(mm, tmp, rb_link, rb_parent); 609 rb_link = &tmp->vm_rb.rb_right; 610 rb_parent = &tmp->vm_rb; 611 612 mm->map_count++; 613 if (!(tmp->vm_flags & VM_WIPEONFORK)) 614 retval = copy_page_range(mm, oldmm, mpnt); 615 616 if (tmp->vm_ops && tmp->vm_ops->open) 617 tmp->vm_ops->open(tmp); 618 619 if (retval) 620 goto out; 621 } 622 /* a new mm has just been created */ 623 retval = arch_dup_mmap(oldmm, mm); 624 out: 625 mmap_write_unlock(mm); 626 flush_tlb_mm(oldmm); 627 mmap_write_unlock(oldmm); 628 dup_userfaultfd_complete(&uf); 629 fail_uprobe_end: 630 uprobe_end_dup_mmap(); 631 return retval; 632 fail_nomem_anon_vma_fork: 633 mpol_put(vma_policy(tmp)); 634 fail_nomem_policy: 635 vm_area_free(tmp); 636 fail_nomem: 637 retval = -ENOMEM; 638 vm_unacct_memory(charge); 639 goto out; 640 } 641 642 static inline int mm_alloc_pgd(struct mm_struct *mm) 643 { 644 mm->pgd = pgd_alloc(mm); 645 if (unlikely(!mm->pgd)) 646 return -ENOMEM; 647 return 0; 648 } 649 650 static inline void mm_free_pgd(struct mm_struct *mm) 651 { 652 pgd_free(mm, mm->pgd); 653 } 654 #else 655 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 656 { 657 mmap_write_lock(oldmm); 658 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 659 mmap_write_unlock(oldmm); 660 return 0; 661 } 662 #define mm_alloc_pgd(mm) (0) 663 #define mm_free_pgd(mm) 664 #endif /* CONFIG_MMU */ 665 666 static void check_mm(struct mm_struct *mm) 667 { 668 int i; 669 670 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS, 671 "Please make sure 'struct resident_page_types[]' is updated as well"); 672 673 for (i = 0; i < NR_MM_COUNTERS; i++) { 674 long x = atomic_long_read(&mm->rss_stat.count[i]); 675 676 if (unlikely(x)) 677 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", 678 mm, resident_page_types[i], x); 679 } 680 681 if (mm_pgtables_bytes(mm)) 682 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", 683 mm_pgtables_bytes(mm)); 684 685 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 686 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 687 #endif 688 } 689 690 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 691 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 692 693 /* 694 * Called when the last reference to the mm 695 * is dropped: either by a lazy thread or by 696 * mmput. Free the page directory and the mm. 697 */ 698 void __mmdrop(struct mm_struct *mm) 699 { 700 BUG_ON(mm == &init_mm); 701 WARN_ON_ONCE(mm == current->mm); 702 WARN_ON_ONCE(mm == current->active_mm); 703 mm_free_pgd(mm); 704 destroy_context(mm); 705 mmu_notifier_subscriptions_destroy(mm); 706 check_mm(mm); 707 put_user_ns(mm->user_ns); 708 free_mm(mm); 709 } 710 EXPORT_SYMBOL_GPL(__mmdrop); 711 712 static void mmdrop_async_fn(struct work_struct *work) 713 { 714 struct mm_struct *mm; 715 716 mm = container_of(work, struct mm_struct, async_put_work); 717 __mmdrop(mm); 718 } 719 720 static void mmdrop_async(struct mm_struct *mm) 721 { 722 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 723 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 724 schedule_work(&mm->async_put_work); 725 } 726 } 727 728 static inline void free_signal_struct(struct signal_struct *sig) 729 { 730 taskstats_tgid_free(sig); 731 sched_autogroup_exit(sig); 732 /* 733 * __mmdrop is not safe to call from softirq context on x86 due to 734 * pgd_dtor so postpone it to the async context 735 */ 736 if (sig->oom_mm) 737 mmdrop_async(sig->oom_mm); 738 kmem_cache_free(signal_cachep, sig); 739 } 740 741 static inline void put_signal_struct(struct signal_struct *sig) 742 { 743 if (refcount_dec_and_test(&sig->sigcnt)) 744 free_signal_struct(sig); 745 } 746 747 void __put_task_struct(struct task_struct *tsk) 748 { 749 WARN_ON(!tsk->exit_state); 750 WARN_ON(refcount_read(&tsk->usage)); 751 WARN_ON(tsk == current); 752 753 cgroup_free(tsk); 754 task_numa_free(tsk, true); 755 security_task_free(tsk); 756 exit_creds(tsk); 757 delayacct_tsk_free(tsk); 758 put_signal_struct(tsk->signal); 759 760 if (!profile_handoff_task(tsk)) 761 free_task(tsk); 762 } 763 EXPORT_SYMBOL_GPL(__put_task_struct); 764 765 void __init __weak arch_task_cache_init(void) { } 766 767 /* 768 * set_max_threads 769 */ 770 static void set_max_threads(unsigned int max_threads_suggested) 771 { 772 u64 threads; 773 unsigned long nr_pages = totalram_pages(); 774 775 /* 776 * The number of threads shall be limited such that the thread 777 * structures may only consume a small part of the available memory. 778 */ 779 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64) 780 threads = MAX_THREADS; 781 else 782 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE, 783 (u64) THREAD_SIZE * 8UL); 784 785 if (threads > max_threads_suggested) 786 threads = max_threads_suggested; 787 788 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 789 } 790 791 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 792 /* Initialized by the architecture: */ 793 int arch_task_struct_size __read_mostly; 794 #endif 795 796 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 797 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 798 { 799 /* Fetch thread_struct whitelist for the architecture. */ 800 arch_thread_struct_whitelist(offset, size); 801 802 /* 803 * Handle zero-sized whitelist or empty thread_struct, otherwise 804 * adjust offset to position of thread_struct in task_struct. 805 */ 806 if (unlikely(*size == 0)) 807 *offset = 0; 808 else 809 *offset += offsetof(struct task_struct, thread); 810 } 811 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */ 812 813 void __init fork_init(void) 814 { 815 int i; 816 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 817 #ifndef ARCH_MIN_TASKALIGN 818 #define ARCH_MIN_TASKALIGN 0 819 #endif 820 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 821 unsigned long useroffset, usersize; 822 823 /* create a slab on which task_structs can be allocated */ 824 task_struct_whitelist(&useroffset, &usersize); 825 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 826 arch_task_struct_size, align, 827 SLAB_PANIC|SLAB_ACCOUNT, 828 useroffset, usersize, NULL); 829 #endif 830 831 /* do the arch specific task caches init */ 832 arch_task_cache_init(); 833 834 set_max_threads(MAX_THREADS); 835 836 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 837 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 838 init_task.signal->rlim[RLIMIT_SIGPENDING] = 839 init_task.signal->rlim[RLIMIT_NPROC]; 840 841 for (i = 0; i < UCOUNT_COUNTS; i++) { 842 init_user_ns.ucount_max[i] = max_threads/2; 843 } 844 845 #ifdef CONFIG_VMAP_STACK 846 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 847 NULL, free_vm_stack_cache); 848 #endif 849 850 scs_init(); 851 852 lockdep_init_task(&init_task); 853 uprobes_init(); 854 } 855 856 int __weak arch_dup_task_struct(struct task_struct *dst, 857 struct task_struct *src) 858 { 859 *dst = *src; 860 return 0; 861 } 862 863 void set_task_stack_end_magic(struct task_struct *tsk) 864 { 865 unsigned long *stackend; 866 867 stackend = end_of_stack(tsk); 868 *stackend = STACK_END_MAGIC; /* for overflow detection */ 869 } 870 871 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 872 { 873 struct task_struct *tsk; 874 unsigned long *stack; 875 struct vm_struct *stack_vm_area __maybe_unused; 876 int err; 877 878 if (node == NUMA_NO_NODE) 879 node = tsk_fork_get_node(orig); 880 tsk = alloc_task_struct_node(node); 881 if (!tsk) 882 return NULL; 883 884 stack = alloc_thread_stack_node(tsk, node); 885 if (!stack) 886 goto free_tsk; 887 888 if (memcg_charge_kernel_stack(tsk)) 889 goto free_stack; 890 891 stack_vm_area = task_stack_vm_area(tsk); 892 893 err = arch_dup_task_struct(tsk, orig); 894 895 /* 896 * arch_dup_task_struct() clobbers the stack-related fields. Make 897 * sure they're properly initialized before using any stack-related 898 * functions again. 899 */ 900 tsk->stack = stack; 901 #ifdef CONFIG_VMAP_STACK 902 tsk->stack_vm_area = stack_vm_area; 903 #endif 904 #ifdef CONFIG_THREAD_INFO_IN_TASK 905 refcount_set(&tsk->stack_refcount, 1); 906 #endif 907 908 if (err) 909 goto free_stack; 910 911 err = scs_prepare(tsk, node); 912 if (err) 913 goto free_stack; 914 915 #ifdef CONFIG_SECCOMP 916 /* 917 * We must handle setting up seccomp filters once we're under 918 * the sighand lock in case orig has changed between now and 919 * then. Until then, filter must be NULL to avoid messing up 920 * the usage counts on the error path calling free_task. 921 */ 922 tsk->seccomp.filter = NULL; 923 #endif 924 925 setup_thread_stack(tsk, orig); 926 clear_user_return_notifier(tsk); 927 clear_tsk_need_resched(tsk); 928 set_task_stack_end_magic(tsk); 929 930 #ifdef CONFIG_STACKPROTECTOR 931 tsk->stack_canary = get_random_canary(); 932 #endif 933 if (orig->cpus_ptr == &orig->cpus_mask) 934 tsk->cpus_ptr = &tsk->cpus_mask; 935 936 /* 937 * One for the user space visible state that goes away when reaped. 938 * One for the scheduler. 939 */ 940 refcount_set(&tsk->rcu_users, 2); 941 /* One for the rcu users */ 942 refcount_set(&tsk->usage, 1); 943 #ifdef CONFIG_BLK_DEV_IO_TRACE 944 tsk->btrace_seq = 0; 945 #endif 946 tsk->splice_pipe = NULL; 947 tsk->task_frag.page = NULL; 948 tsk->wake_q.next = NULL; 949 950 account_kernel_stack(tsk, 1); 951 952 kcov_task_init(tsk); 953 954 #ifdef CONFIG_FAULT_INJECTION 955 tsk->fail_nth = 0; 956 #endif 957 958 #ifdef CONFIG_BLK_CGROUP 959 tsk->throttle_queue = NULL; 960 tsk->use_memdelay = 0; 961 #endif 962 963 #ifdef CONFIG_MEMCG 964 tsk->active_memcg = NULL; 965 #endif 966 return tsk; 967 968 free_stack: 969 free_thread_stack(tsk); 970 free_tsk: 971 free_task_struct(tsk); 972 return NULL; 973 } 974 975 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 976 977 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 978 979 static int __init coredump_filter_setup(char *s) 980 { 981 default_dump_filter = 982 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 983 MMF_DUMP_FILTER_MASK; 984 return 1; 985 } 986 987 __setup("coredump_filter=", coredump_filter_setup); 988 989 #include <linux/init_task.h> 990 991 static void mm_init_aio(struct mm_struct *mm) 992 { 993 #ifdef CONFIG_AIO 994 spin_lock_init(&mm->ioctx_lock); 995 mm->ioctx_table = NULL; 996 #endif 997 } 998 999 static __always_inline void mm_clear_owner(struct mm_struct *mm, 1000 struct task_struct *p) 1001 { 1002 #ifdef CONFIG_MEMCG 1003 if (mm->owner == p) 1004 WRITE_ONCE(mm->owner, NULL); 1005 #endif 1006 } 1007 1008 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1009 { 1010 #ifdef CONFIG_MEMCG 1011 mm->owner = p; 1012 #endif 1013 } 1014 1015 static void mm_init_uprobes_state(struct mm_struct *mm) 1016 { 1017 #ifdef CONFIG_UPROBES 1018 mm->uprobes_state.xol_area = NULL; 1019 #endif 1020 } 1021 1022 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 1023 struct user_namespace *user_ns) 1024 { 1025 mm->mmap = NULL; 1026 mm->mm_rb = RB_ROOT; 1027 mm->vmacache_seqnum = 0; 1028 atomic_set(&mm->mm_users, 1); 1029 atomic_set(&mm->mm_count, 1); 1030 mmap_init_lock(mm); 1031 INIT_LIST_HEAD(&mm->mmlist); 1032 mm->core_state = NULL; 1033 mm_pgtables_bytes_init(mm); 1034 mm->map_count = 0; 1035 mm->locked_vm = 0; 1036 atomic64_set(&mm->pinned_vm, 0); 1037 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 1038 spin_lock_init(&mm->page_table_lock); 1039 spin_lock_init(&mm->arg_lock); 1040 mm_init_cpumask(mm); 1041 mm_init_aio(mm); 1042 mm_init_owner(mm, p); 1043 RCU_INIT_POINTER(mm->exe_file, NULL); 1044 mmu_notifier_subscriptions_init(mm); 1045 init_tlb_flush_pending(mm); 1046 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 1047 mm->pmd_huge_pte = NULL; 1048 #endif 1049 mm_init_uprobes_state(mm); 1050 1051 if (current->mm) { 1052 mm->flags = current->mm->flags & MMF_INIT_MASK; 1053 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 1054 } else { 1055 mm->flags = default_dump_filter; 1056 mm->def_flags = 0; 1057 } 1058 1059 if (mm_alloc_pgd(mm)) 1060 goto fail_nopgd; 1061 1062 if (init_new_context(p, mm)) 1063 goto fail_nocontext; 1064 1065 mm->user_ns = get_user_ns(user_ns); 1066 return mm; 1067 1068 fail_nocontext: 1069 mm_free_pgd(mm); 1070 fail_nopgd: 1071 free_mm(mm); 1072 return NULL; 1073 } 1074 1075 /* 1076 * Allocate and initialize an mm_struct. 1077 */ 1078 struct mm_struct *mm_alloc(void) 1079 { 1080 struct mm_struct *mm; 1081 1082 mm = allocate_mm(); 1083 if (!mm) 1084 return NULL; 1085 1086 memset(mm, 0, sizeof(*mm)); 1087 return mm_init(mm, current, current_user_ns()); 1088 } 1089 1090 static inline void __mmput(struct mm_struct *mm) 1091 { 1092 VM_BUG_ON(atomic_read(&mm->mm_users)); 1093 1094 uprobe_clear_state(mm); 1095 exit_aio(mm); 1096 ksm_exit(mm); 1097 khugepaged_exit(mm); /* must run before exit_mmap */ 1098 exit_mmap(mm); 1099 mm_put_huge_zero_page(mm); 1100 set_mm_exe_file(mm, NULL); 1101 if (!list_empty(&mm->mmlist)) { 1102 spin_lock(&mmlist_lock); 1103 list_del(&mm->mmlist); 1104 spin_unlock(&mmlist_lock); 1105 } 1106 if (mm->binfmt) 1107 module_put(mm->binfmt->module); 1108 mmdrop(mm); 1109 } 1110 1111 /* 1112 * Decrement the use count and release all resources for an mm. 1113 */ 1114 void mmput(struct mm_struct *mm) 1115 { 1116 might_sleep(); 1117 1118 if (atomic_dec_and_test(&mm->mm_users)) 1119 __mmput(mm); 1120 } 1121 EXPORT_SYMBOL_GPL(mmput); 1122 1123 #ifdef CONFIG_MMU 1124 static void mmput_async_fn(struct work_struct *work) 1125 { 1126 struct mm_struct *mm = container_of(work, struct mm_struct, 1127 async_put_work); 1128 1129 __mmput(mm); 1130 } 1131 1132 void mmput_async(struct mm_struct *mm) 1133 { 1134 if (atomic_dec_and_test(&mm->mm_users)) { 1135 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1136 schedule_work(&mm->async_put_work); 1137 } 1138 } 1139 #endif 1140 1141 /** 1142 * set_mm_exe_file - change a reference to the mm's executable file 1143 * 1144 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1145 * 1146 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1147 * invocations: in mmput() nobody alive left, in execve task is single 1148 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1149 * mm->exe_file, but does so without using set_mm_exe_file() in order 1150 * to do avoid the need for any locks. 1151 */ 1152 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1153 { 1154 struct file *old_exe_file; 1155 1156 /* 1157 * It is safe to dereference the exe_file without RCU as 1158 * this function is only called if nobody else can access 1159 * this mm -- see comment above for justification. 1160 */ 1161 old_exe_file = rcu_dereference_raw(mm->exe_file); 1162 1163 if (new_exe_file) 1164 get_file(new_exe_file); 1165 rcu_assign_pointer(mm->exe_file, new_exe_file); 1166 if (old_exe_file) 1167 fput(old_exe_file); 1168 } 1169 1170 /** 1171 * get_mm_exe_file - acquire a reference to the mm's executable file 1172 * 1173 * Returns %NULL if mm has no associated executable file. 1174 * User must release file via fput(). 1175 */ 1176 struct file *get_mm_exe_file(struct mm_struct *mm) 1177 { 1178 struct file *exe_file; 1179 1180 rcu_read_lock(); 1181 exe_file = rcu_dereference(mm->exe_file); 1182 if (exe_file && !get_file_rcu(exe_file)) 1183 exe_file = NULL; 1184 rcu_read_unlock(); 1185 return exe_file; 1186 } 1187 EXPORT_SYMBOL(get_mm_exe_file); 1188 1189 /** 1190 * get_task_exe_file - acquire a reference to the task's executable file 1191 * 1192 * Returns %NULL if task's mm (if any) has no associated executable file or 1193 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1194 * User must release file via fput(). 1195 */ 1196 struct file *get_task_exe_file(struct task_struct *task) 1197 { 1198 struct file *exe_file = NULL; 1199 struct mm_struct *mm; 1200 1201 task_lock(task); 1202 mm = task->mm; 1203 if (mm) { 1204 if (!(task->flags & PF_KTHREAD)) 1205 exe_file = get_mm_exe_file(mm); 1206 } 1207 task_unlock(task); 1208 return exe_file; 1209 } 1210 EXPORT_SYMBOL(get_task_exe_file); 1211 1212 /** 1213 * get_task_mm - acquire a reference to the task's mm 1214 * 1215 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1216 * this kernel workthread has transiently adopted a user mm with use_mm, 1217 * to do its AIO) is not set and if so returns a reference to it, after 1218 * bumping up the use count. User must release the mm via mmput() 1219 * after use. Typically used by /proc and ptrace. 1220 */ 1221 struct mm_struct *get_task_mm(struct task_struct *task) 1222 { 1223 struct mm_struct *mm; 1224 1225 task_lock(task); 1226 mm = task->mm; 1227 if (mm) { 1228 if (task->flags & PF_KTHREAD) 1229 mm = NULL; 1230 else 1231 mmget(mm); 1232 } 1233 task_unlock(task); 1234 return mm; 1235 } 1236 EXPORT_SYMBOL_GPL(get_task_mm); 1237 1238 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1239 { 1240 struct mm_struct *mm; 1241 int err; 1242 1243 err = mutex_lock_killable(&task->signal->exec_update_mutex); 1244 if (err) 1245 return ERR_PTR(err); 1246 1247 mm = get_task_mm(task); 1248 if (mm && mm != current->mm && 1249 !ptrace_may_access(task, mode)) { 1250 mmput(mm); 1251 mm = ERR_PTR(-EACCES); 1252 } 1253 mutex_unlock(&task->signal->exec_update_mutex); 1254 1255 return mm; 1256 } 1257 1258 static void complete_vfork_done(struct task_struct *tsk) 1259 { 1260 struct completion *vfork; 1261 1262 task_lock(tsk); 1263 vfork = tsk->vfork_done; 1264 if (likely(vfork)) { 1265 tsk->vfork_done = NULL; 1266 complete(vfork); 1267 } 1268 task_unlock(tsk); 1269 } 1270 1271 static int wait_for_vfork_done(struct task_struct *child, 1272 struct completion *vfork) 1273 { 1274 int killed; 1275 1276 freezer_do_not_count(); 1277 cgroup_enter_frozen(); 1278 killed = wait_for_completion_killable(vfork); 1279 cgroup_leave_frozen(false); 1280 freezer_count(); 1281 1282 if (killed) { 1283 task_lock(child); 1284 child->vfork_done = NULL; 1285 task_unlock(child); 1286 } 1287 1288 put_task_struct(child); 1289 return killed; 1290 } 1291 1292 /* Please note the differences between mmput and mm_release. 1293 * mmput is called whenever we stop holding onto a mm_struct, 1294 * error success whatever. 1295 * 1296 * mm_release is called after a mm_struct has been removed 1297 * from the current process. 1298 * 1299 * This difference is important for error handling, when we 1300 * only half set up a mm_struct for a new process and need to restore 1301 * the old one. Because we mmput the new mm_struct before 1302 * restoring the old one. . . 1303 * Eric Biederman 10 January 1998 1304 */ 1305 static void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1306 { 1307 uprobe_free_utask(tsk); 1308 1309 /* Get rid of any cached register state */ 1310 deactivate_mm(tsk, mm); 1311 1312 /* 1313 * Signal userspace if we're not exiting with a core dump 1314 * because we want to leave the value intact for debugging 1315 * purposes. 1316 */ 1317 if (tsk->clear_child_tid) { 1318 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1319 atomic_read(&mm->mm_users) > 1) { 1320 /* 1321 * We don't check the error code - if userspace has 1322 * not set up a proper pointer then tough luck. 1323 */ 1324 put_user(0, tsk->clear_child_tid); 1325 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1326 1, NULL, NULL, 0, 0); 1327 } 1328 tsk->clear_child_tid = NULL; 1329 } 1330 1331 /* 1332 * All done, finally we can wake up parent and return this mm to him. 1333 * Also kthread_stop() uses this completion for synchronization. 1334 */ 1335 if (tsk->vfork_done) 1336 complete_vfork_done(tsk); 1337 } 1338 1339 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1340 { 1341 futex_exit_release(tsk); 1342 mm_release(tsk, mm); 1343 } 1344 1345 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1346 { 1347 futex_exec_release(tsk); 1348 mm_release(tsk, mm); 1349 } 1350 1351 /** 1352 * dup_mm() - duplicates an existing mm structure 1353 * @tsk: the task_struct with which the new mm will be associated. 1354 * @oldmm: the mm to duplicate. 1355 * 1356 * Allocates a new mm structure and duplicates the provided @oldmm structure 1357 * content into it. 1358 * 1359 * Return: the duplicated mm or NULL on failure. 1360 */ 1361 static struct mm_struct *dup_mm(struct task_struct *tsk, 1362 struct mm_struct *oldmm) 1363 { 1364 struct mm_struct *mm; 1365 int err; 1366 1367 mm = allocate_mm(); 1368 if (!mm) 1369 goto fail_nomem; 1370 1371 memcpy(mm, oldmm, sizeof(*mm)); 1372 1373 if (!mm_init(mm, tsk, mm->user_ns)) 1374 goto fail_nomem; 1375 1376 err = dup_mmap(mm, oldmm); 1377 if (err) 1378 goto free_pt; 1379 1380 mm->hiwater_rss = get_mm_rss(mm); 1381 mm->hiwater_vm = mm->total_vm; 1382 1383 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1384 goto free_pt; 1385 1386 return mm; 1387 1388 free_pt: 1389 /* don't put binfmt in mmput, we haven't got module yet */ 1390 mm->binfmt = NULL; 1391 mm_init_owner(mm, NULL); 1392 mmput(mm); 1393 1394 fail_nomem: 1395 return NULL; 1396 } 1397 1398 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1399 { 1400 struct mm_struct *mm, *oldmm; 1401 int retval; 1402 1403 tsk->min_flt = tsk->maj_flt = 0; 1404 tsk->nvcsw = tsk->nivcsw = 0; 1405 #ifdef CONFIG_DETECT_HUNG_TASK 1406 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1407 tsk->last_switch_time = 0; 1408 #endif 1409 1410 tsk->mm = NULL; 1411 tsk->active_mm = NULL; 1412 1413 /* 1414 * Are we cloning a kernel thread? 1415 * 1416 * We need to steal a active VM for that.. 1417 */ 1418 oldmm = current->mm; 1419 if (!oldmm) 1420 return 0; 1421 1422 /* initialize the new vmacache entries */ 1423 vmacache_flush(tsk); 1424 1425 if (clone_flags & CLONE_VM) { 1426 mmget(oldmm); 1427 mm = oldmm; 1428 goto good_mm; 1429 } 1430 1431 retval = -ENOMEM; 1432 mm = dup_mm(tsk, current->mm); 1433 if (!mm) 1434 goto fail_nomem; 1435 1436 good_mm: 1437 tsk->mm = mm; 1438 tsk->active_mm = mm; 1439 return 0; 1440 1441 fail_nomem: 1442 return retval; 1443 } 1444 1445 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1446 { 1447 struct fs_struct *fs = current->fs; 1448 if (clone_flags & CLONE_FS) { 1449 /* tsk->fs is already what we want */ 1450 spin_lock(&fs->lock); 1451 if (fs->in_exec) { 1452 spin_unlock(&fs->lock); 1453 return -EAGAIN; 1454 } 1455 fs->users++; 1456 spin_unlock(&fs->lock); 1457 return 0; 1458 } 1459 tsk->fs = copy_fs_struct(fs); 1460 if (!tsk->fs) 1461 return -ENOMEM; 1462 return 0; 1463 } 1464 1465 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1466 { 1467 struct files_struct *oldf, *newf; 1468 int error = 0; 1469 1470 /* 1471 * A background process may not have any files ... 1472 */ 1473 oldf = current->files; 1474 if (!oldf) 1475 goto out; 1476 1477 if (clone_flags & CLONE_FILES) { 1478 atomic_inc(&oldf->count); 1479 goto out; 1480 } 1481 1482 newf = dup_fd(oldf, NR_OPEN_MAX, &error); 1483 if (!newf) 1484 goto out; 1485 1486 tsk->files = newf; 1487 error = 0; 1488 out: 1489 return error; 1490 } 1491 1492 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1493 { 1494 #ifdef CONFIG_BLOCK 1495 struct io_context *ioc = current->io_context; 1496 struct io_context *new_ioc; 1497 1498 if (!ioc) 1499 return 0; 1500 /* 1501 * Share io context with parent, if CLONE_IO is set 1502 */ 1503 if (clone_flags & CLONE_IO) { 1504 ioc_task_link(ioc); 1505 tsk->io_context = ioc; 1506 } else if (ioprio_valid(ioc->ioprio)) { 1507 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1508 if (unlikely(!new_ioc)) 1509 return -ENOMEM; 1510 1511 new_ioc->ioprio = ioc->ioprio; 1512 put_io_context(new_ioc); 1513 } 1514 #endif 1515 return 0; 1516 } 1517 1518 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1519 { 1520 struct sighand_struct *sig; 1521 1522 if (clone_flags & CLONE_SIGHAND) { 1523 refcount_inc(¤t->sighand->count); 1524 return 0; 1525 } 1526 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1527 RCU_INIT_POINTER(tsk->sighand, sig); 1528 if (!sig) 1529 return -ENOMEM; 1530 1531 refcount_set(&sig->count, 1); 1532 spin_lock_irq(¤t->sighand->siglock); 1533 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1534 spin_unlock_irq(¤t->sighand->siglock); 1535 1536 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */ 1537 if (clone_flags & CLONE_CLEAR_SIGHAND) 1538 flush_signal_handlers(tsk, 0); 1539 1540 return 0; 1541 } 1542 1543 void __cleanup_sighand(struct sighand_struct *sighand) 1544 { 1545 if (refcount_dec_and_test(&sighand->count)) { 1546 signalfd_cleanup(sighand); 1547 /* 1548 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1549 * without an RCU grace period, see __lock_task_sighand(). 1550 */ 1551 kmem_cache_free(sighand_cachep, sighand); 1552 } 1553 } 1554 1555 /* 1556 * Initialize POSIX timer handling for a thread group. 1557 */ 1558 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1559 { 1560 struct posix_cputimers *pct = &sig->posix_cputimers; 1561 unsigned long cpu_limit; 1562 1563 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1564 posix_cputimers_group_init(pct, cpu_limit); 1565 } 1566 1567 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1568 { 1569 struct signal_struct *sig; 1570 1571 if (clone_flags & CLONE_THREAD) 1572 return 0; 1573 1574 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1575 tsk->signal = sig; 1576 if (!sig) 1577 return -ENOMEM; 1578 1579 sig->nr_threads = 1; 1580 atomic_set(&sig->live, 1); 1581 refcount_set(&sig->sigcnt, 1); 1582 1583 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1584 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1585 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1586 1587 init_waitqueue_head(&sig->wait_chldexit); 1588 sig->curr_target = tsk; 1589 init_sigpending(&sig->shared_pending); 1590 INIT_HLIST_HEAD(&sig->multiprocess); 1591 seqlock_init(&sig->stats_lock); 1592 prev_cputime_init(&sig->prev_cputime); 1593 1594 #ifdef CONFIG_POSIX_TIMERS 1595 INIT_LIST_HEAD(&sig->posix_timers); 1596 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1597 sig->real_timer.function = it_real_fn; 1598 #endif 1599 1600 task_lock(current->group_leader); 1601 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1602 task_unlock(current->group_leader); 1603 1604 posix_cpu_timers_init_group(sig); 1605 1606 tty_audit_fork(sig); 1607 sched_autogroup_fork(sig); 1608 1609 sig->oom_score_adj = current->signal->oom_score_adj; 1610 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1611 1612 mutex_init(&sig->cred_guard_mutex); 1613 mutex_init(&sig->exec_update_mutex); 1614 1615 return 0; 1616 } 1617 1618 static void copy_seccomp(struct task_struct *p) 1619 { 1620 #ifdef CONFIG_SECCOMP 1621 /* 1622 * Must be called with sighand->lock held, which is common to 1623 * all threads in the group. Holding cred_guard_mutex is not 1624 * needed because this new task is not yet running and cannot 1625 * be racing exec. 1626 */ 1627 assert_spin_locked(¤t->sighand->siglock); 1628 1629 /* Ref-count the new filter user, and assign it. */ 1630 get_seccomp_filter(current); 1631 p->seccomp = current->seccomp; 1632 1633 /* 1634 * Explicitly enable no_new_privs here in case it got set 1635 * between the task_struct being duplicated and holding the 1636 * sighand lock. The seccomp state and nnp must be in sync. 1637 */ 1638 if (task_no_new_privs(current)) 1639 task_set_no_new_privs(p); 1640 1641 /* 1642 * If the parent gained a seccomp mode after copying thread 1643 * flags and between before we held the sighand lock, we have 1644 * to manually enable the seccomp thread flag here. 1645 */ 1646 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1647 set_tsk_thread_flag(p, TIF_SECCOMP); 1648 #endif 1649 } 1650 1651 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1652 { 1653 current->clear_child_tid = tidptr; 1654 1655 return task_pid_vnr(current); 1656 } 1657 1658 static void rt_mutex_init_task(struct task_struct *p) 1659 { 1660 raw_spin_lock_init(&p->pi_lock); 1661 #ifdef CONFIG_RT_MUTEXES 1662 p->pi_waiters = RB_ROOT_CACHED; 1663 p->pi_top_task = NULL; 1664 p->pi_blocked_on = NULL; 1665 #endif 1666 } 1667 1668 static inline void init_task_pid_links(struct task_struct *task) 1669 { 1670 enum pid_type type; 1671 1672 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1673 INIT_HLIST_NODE(&task->pid_links[type]); 1674 } 1675 } 1676 1677 static inline void 1678 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1679 { 1680 if (type == PIDTYPE_PID) 1681 task->thread_pid = pid; 1682 else 1683 task->signal->pids[type] = pid; 1684 } 1685 1686 static inline void rcu_copy_process(struct task_struct *p) 1687 { 1688 #ifdef CONFIG_PREEMPT_RCU 1689 p->rcu_read_lock_nesting = 0; 1690 p->rcu_read_unlock_special.s = 0; 1691 p->rcu_blocked_node = NULL; 1692 INIT_LIST_HEAD(&p->rcu_node_entry); 1693 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1694 #ifdef CONFIG_TASKS_RCU 1695 p->rcu_tasks_holdout = false; 1696 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1697 p->rcu_tasks_idle_cpu = -1; 1698 #endif /* #ifdef CONFIG_TASKS_RCU */ 1699 #ifdef CONFIG_TASKS_TRACE_RCU 1700 p->trc_reader_nesting = 0; 1701 p->trc_reader_special.s = 0; 1702 INIT_LIST_HEAD(&p->trc_holdout_list); 1703 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ 1704 } 1705 1706 struct pid *pidfd_pid(const struct file *file) 1707 { 1708 if (file->f_op == &pidfd_fops) 1709 return file->private_data; 1710 1711 return ERR_PTR(-EBADF); 1712 } 1713 1714 static int pidfd_release(struct inode *inode, struct file *file) 1715 { 1716 struct pid *pid = file->private_data; 1717 1718 file->private_data = NULL; 1719 put_pid(pid); 1720 return 0; 1721 } 1722 1723 #ifdef CONFIG_PROC_FS 1724 /** 1725 * pidfd_show_fdinfo - print information about a pidfd 1726 * @m: proc fdinfo file 1727 * @f: file referencing a pidfd 1728 * 1729 * Pid: 1730 * This function will print the pid that a given pidfd refers to in the 1731 * pid namespace of the procfs instance. 1732 * If the pid namespace of the process is not a descendant of the pid 1733 * namespace of the procfs instance 0 will be shown as its pid. This is 1734 * similar to calling getppid() on a process whose parent is outside of 1735 * its pid namespace. 1736 * 1737 * NSpid: 1738 * If pid namespaces are supported then this function will also print 1739 * the pid of a given pidfd refers to for all descendant pid namespaces 1740 * starting from the current pid namespace of the instance, i.e. the 1741 * Pid field and the first entry in the NSpid field will be identical. 1742 * If the pid namespace of the process is not a descendant of the pid 1743 * namespace of the procfs instance 0 will be shown as its first NSpid 1744 * entry and no others will be shown. 1745 * Note that this differs from the Pid and NSpid fields in 1746 * /proc/<pid>/status where Pid and NSpid are always shown relative to 1747 * the pid namespace of the procfs instance. The difference becomes 1748 * obvious when sending around a pidfd between pid namespaces from a 1749 * different branch of the tree, i.e. where no ancestoral relation is 1750 * present between the pid namespaces: 1751 * - create two new pid namespaces ns1 and ns2 in the initial pid 1752 * namespace (also take care to create new mount namespaces in the 1753 * new pid namespace and mount procfs) 1754 * - create a process with a pidfd in ns1 1755 * - send pidfd from ns1 to ns2 1756 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid 1757 * have exactly one entry, which is 0 1758 */ 1759 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) 1760 { 1761 struct pid *pid = f->private_data; 1762 struct pid_namespace *ns; 1763 pid_t nr = -1; 1764 1765 if (likely(pid_has_task(pid, PIDTYPE_PID))) { 1766 ns = proc_pid_ns(file_inode(m->file)->i_sb); 1767 nr = pid_nr_ns(pid, ns); 1768 } 1769 1770 seq_put_decimal_ll(m, "Pid:\t", nr); 1771 1772 #ifdef CONFIG_PID_NS 1773 seq_put_decimal_ll(m, "\nNSpid:\t", nr); 1774 if (nr > 0) { 1775 int i; 1776 1777 /* If nr is non-zero it means that 'pid' is valid and that 1778 * ns, i.e. the pid namespace associated with the procfs 1779 * instance, is in the pid namespace hierarchy of pid. 1780 * Start at one below the already printed level. 1781 */ 1782 for (i = ns->level + 1; i <= pid->level; i++) 1783 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr); 1784 } 1785 #endif 1786 seq_putc(m, '\n'); 1787 } 1788 #endif 1789 1790 /* 1791 * Poll support for process exit notification. 1792 */ 1793 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) 1794 { 1795 struct pid *pid = file->private_data; 1796 __poll_t poll_flags = 0; 1797 1798 poll_wait(file, &pid->wait_pidfd, pts); 1799 1800 /* 1801 * Inform pollers only when the whole thread group exits. 1802 * If the thread group leader exits before all other threads in the 1803 * group, then poll(2) should block, similar to the wait(2) family. 1804 */ 1805 if (thread_group_exited(pid)) 1806 poll_flags = EPOLLIN | EPOLLRDNORM; 1807 1808 return poll_flags; 1809 } 1810 1811 const struct file_operations pidfd_fops = { 1812 .release = pidfd_release, 1813 .poll = pidfd_poll, 1814 #ifdef CONFIG_PROC_FS 1815 .show_fdinfo = pidfd_show_fdinfo, 1816 #endif 1817 }; 1818 1819 static void __delayed_free_task(struct rcu_head *rhp) 1820 { 1821 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 1822 1823 free_task(tsk); 1824 } 1825 1826 static __always_inline void delayed_free_task(struct task_struct *tsk) 1827 { 1828 if (IS_ENABLED(CONFIG_MEMCG)) 1829 call_rcu(&tsk->rcu, __delayed_free_task); 1830 else 1831 free_task(tsk); 1832 } 1833 1834 /* 1835 * This creates a new process as a copy of the old one, 1836 * but does not actually start it yet. 1837 * 1838 * It copies the registers, and all the appropriate 1839 * parts of the process environment (as per the clone 1840 * flags). The actual kick-off is left to the caller. 1841 */ 1842 static __latent_entropy struct task_struct *copy_process( 1843 struct pid *pid, 1844 int trace, 1845 int node, 1846 struct kernel_clone_args *args) 1847 { 1848 int pidfd = -1, retval; 1849 struct task_struct *p; 1850 struct multiprocess_signals delayed; 1851 struct file *pidfile = NULL; 1852 u64 clone_flags = args->flags; 1853 struct nsproxy *nsp = current->nsproxy; 1854 1855 /* 1856 * Don't allow sharing the root directory with processes in a different 1857 * namespace 1858 */ 1859 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1860 return ERR_PTR(-EINVAL); 1861 1862 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1863 return ERR_PTR(-EINVAL); 1864 1865 /* 1866 * Thread groups must share signals as well, and detached threads 1867 * can only be started up within the thread group. 1868 */ 1869 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1870 return ERR_PTR(-EINVAL); 1871 1872 /* 1873 * Shared signal handlers imply shared VM. By way of the above, 1874 * thread groups also imply shared VM. Blocking this case allows 1875 * for various simplifications in other code. 1876 */ 1877 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1878 return ERR_PTR(-EINVAL); 1879 1880 /* 1881 * Siblings of global init remain as zombies on exit since they are 1882 * not reaped by their parent (swapper). To solve this and to avoid 1883 * multi-rooted process trees, prevent global and container-inits 1884 * from creating siblings. 1885 */ 1886 if ((clone_flags & CLONE_PARENT) && 1887 current->signal->flags & SIGNAL_UNKILLABLE) 1888 return ERR_PTR(-EINVAL); 1889 1890 /* 1891 * If the new process will be in a different pid or user namespace 1892 * do not allow it to share a thread group with the forking task. 1893 */ 1894 if (clone_flags & CLONE_THREAD) { 1895 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1896 (task_active_pid_ns(current) != nsp->pid_ns_for_children)) 1897 return ERR_PTR(-EINVAL); 1898 } 1899 1900 /* 1901 * If the new process will be in a different time namespace 1902 * do not allow it to share VM or a thread group with the forking task. 1903 */ 1904 if (clone_flags & (CLONE_THREAD | CLONE_VM)) { 1905 if (nsp->time_ns != nsp->time_ns_for_children) 1906 return ERR_PTR(-EINVAL); 1907 } 1908 1909 if (clone_flags & CLONE_PIDFD) { 1910 /* 1911 * - CLONE_DETACHED is blocked so that we can potentially 1912 * reuse it later for CLONE_PIDFD. 1913 * - CLONE_THREAD is blocked until someone really needs it. 1914 */ 1915 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD)) 1916 return ERR_PTR(-EINVAL); 1917 } 1918 1919 /* 1920 * Force any signals received before this point to be delivered 1921 * before the fork happens. Collect up signals sent to multiple 1922 * processes that happen during the fork and delay them so that 1923 * they appear to happen after the fork. 1924 */ 1925 sigemptyset(&delayed.signal); 1926 INIT_HLIST_NODE(&delayed.node); 1927 1928 spin_lock_irq(¤t->sighand->siglock); 1929 if (!(clone_flags & CLONE_THREAD)) 1930 hlist_add_head(&delayed.node, ¤t->signal->multiprocess); 1931 recalc_sigpending(); 1932 spin_unlock_irq(¤t->sighand->siglock); 1933 retval = -ERESTARTNOINTR; 1934 if (signal_pending(current)) 1935 goto fork_out; 1936 1937 retval = -ENOMEM; 1938 p = dup_task_struct(current, node); 1939 if (!p) 1940 goto fork_out; 1941 1942 /* 1943 * This _must_ happen before we call free_task(), i.e. before we jump 1944 * to any of the bad_fork_* labels. This is to avoid freeing 1945 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1946 * kernel threads (PF_KTHREAD). 1947 */ 1948 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL; 1949 /* 1950 * Clear TID on mm_release()? 1951 */ 1952 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL; 1953 1954 ftrace_graph_init_task(p); 1955 1956 rt_mutex_init_task(p); 1957 1958 lockdep_assert_irqs_enabled(); 1959 #ifdef CONFIG_PROVE_LOCKING 1960 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1961 #endif 1962 retval = -EAGAIN; 1963 if (atomic_read(&p->real_cred->user->processes) >= 1964 task_rlimit(p, RLIMIT_NPROC)) { 1965 if (p->real_cred->user != INIT_USER && 1966 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1967 goto bad_fork_free; 1968 } 1969 current->flags &= ~PF_NPROC_EXCEEDED; 1970 1971 retval = copy_creds(p, clone_flags); 1972 if (retval < 0) 1973 goto bad_fork_free; 1974 1975 /* 1976 * If multiple threads are within copy_process(), then this check 1977 * triggers too late. This doesn't hurt, the check is only there 1978 * to stop root fork bombs. 1979 */ 1980 retval = -EAGAIN; 1981 if (data_race(nr_threads >= max_threads)) 1982 goto bad_fork_cleanup_count; 1983 1984 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1985 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1986 p->flags |= PF_FORKNOEXEC; 1987 INIT_LIST_HEAD(&p->children); 1988 INIT_LIST_HEAD(&p->sibling); 1989 rcu_copy_process(p); 1990 p->vfork_done = NULL; 1991 spin_lock_init(&p->alloc_lock); 1992 1993 init_sigpending(&p->pending); 1994 1995 p->utime = p->stime = p->gtime = 0; 1996 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1997 p->utimescaled = p->stimescaled = 0; 1998 #endif 1999 prev_cputime_init(&p->prev_cputime); 2000 2001 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 2002 seqcount_init(&p->vtime.seqcount); 2003 p->vtime.starttime = 0; 2004 p->vtime.state = VTIME_INACTIVE; 2005 #endif 2006 2007 #if defined(SPLIT_RSS_COUNTING) 2008 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 2009 #endif 2010 2011 p->default_timer_slack_ns = current->timer_slack_ns; 2012 2013 #ifdef CONFIG_PSI 2014 p->psi_flags = 0; 2015 #endif 2016 2017 task_io_accounting_init(&p->ioac); 2018 acct_clear_integrals(p); 2019 2020 posix_cputimers_init(&p->posix_cputimers); 2021 2022 p->io_context = NULL; 2023 audit_set_context(p, NULL); 2024 cgroup_fork(p); 2025 #ifdef CONFIG_NUMA 2026 p->mempolicy = mpol_dup(p->mempolicy); 2027 if (IS_ERR(p->mempolicy)) { 2028 retval = PTR_ERR(p->mempolicy); 2029 p->mempolicy = NULL; 2030 goto bad_fork_cleanup_threadgroup_lock; 2031 } 2032 #endif 2033 #ifdef CONFIG_CPUSETS 2034 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 2035 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 2036 seqcount_init(&p->mems_allowed_seq); 2037 #endif 2038 #ifdef CONFIG_TRACE_IRQFLAGS 2039 memset(&p->irqtrace, 0, sizeof(p->irqtrace)); 2040 p->irqtrace.hardirq_disable_ip = _THIS_IP_; 2041 p->irqtrace.softirq_enable_ip = _THIS_IP_; 2042 p->softirqs_enabled = 1; 2043 p->softirq_context = 0; 2044 #endif 2045 2046 p->pagefault_disabled = 0; 2047 2048 #ifdef CONFIG_LOCKDEP 2049 lockdep_init_task(p); 2050 #endif 2051 2052 #ifdef CONFIG_DEBUG_MUTEXES 2053 p->blocked_on = NULL; /* not blocked yet */ 2054 #endif 2055 #ifdef CONFIG_BCACHE 2056 p->sequential_io = 0; 2057 p->sequential_io_avg = 0; 2058 #endif 2059 2060 /* Perform scheduler related setup. Assign this task to a CPU. */ 2061 retval = sched_fork(clone_flags, p); 2062 if (retval) 2063 goto bad_fork_cleanup_policy; 2064 2065 retval = perf_event_init_task(p); 2066 if (retval) 2067 goto bad_fork_cleanup_policy; 2068 retval = audit_alloc(p); 2069 if (retval) 2070 goto bad_fork_cleanup_perf; 2071 /* copy all the process information */ 2072 shm_init_task(p); 2073 retval = security_task_alloc(p, clone_flags); 2074 if (retval) 2075 goto bad_fork_cleanup_audit; 2076 retval = copy_semundo(clone_flags, p); 2077 if (retval) 2078 goto bad_fork_cleanup_security; 2079 retval = copy_files(clone_flags, p); 2080 if (retval) 2081 goto bad_fork_cleanup_semundo; 2082 retval = copy_fs(clone_flags, p); 2083 if (retval) 2084 goto bad_fork_cleanup_files; 2085 retval = copy_sighand(clone_flags, p); 2086 if (retval) 2087 goto bad_fork_cleanup_fs; 2088 retval = copy_signal(clone_flags, p); 2089 if (retval) 2090 goto bad_fork_cleanup_sighand; 2091 retval = copy_mm(clone_flags, p); 2092 if (retval) 2093 goto bad_fork_cleanup_signal; 2094 retval = copy_namespaces(clone_flags, p); 2095 if (retval) 2096 goto bad_fork_cleanup_mm; 2097 retval = copy_io(clone_flags, p); 2098 if (retval) 2099 goto bad_fork_cleanup_namespaces; 2100 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls); 2101 if (retval) 2102 goto bad_fork_cleanup_io; 2103 2104 stackleak_task_init(p); 2105 2106 if (pid != &init_struct_pid) { 2107 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid, 2108 args->set_tid_size); 2109 if (IS_ERR(pid)) { 2110 retval = PTR_ERR(pid); 2111 goto bad_fork_cleanup_thread; 2112 } 2113 } 2114 2115 /* 2116 * This has to happen after we've potentially unshared the file 2117 * descriptor table (so that the pidfd doesn't leak into the child 2118 * if the fd table isn't shared). 2119 */ 2120 if (clone_flags & CLONE_PIDFD) { 2121 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC); 2122 if (retval < 0) 2123 goto bad_fork_free_pid; 2124 2125 pidfd = retval; 2126 2127 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid, 2128 O_RDWR | O_CLOEXEC); 2129 if (IS_ERR(pidfile)) { 2130 put_unused_fd(pidfd); 2131 retval = PTR_ERR(pidfile); 2132 goto bad_fork_free_pid; 2133 } 2134 get_pid(pid); /* held by pidfile now */ 2135 2136 retval = put_user(pidfd, args->pidfd); 2137 if (retval) 2138 goto bad_fork_put_pidfd; 2139 } 2140 2141 #ifdef CONFIG_BLOCK 2142 p->plug = NULL; 2143 #endif 2144 futex_init_task(p); 2145 2146 /* 2147 * sigaltstack should be cleared when sharing the same VM 2148 */ 2149 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 2150 sas_ss_reset(p); 2151 2152 /* 2153 * Syscall tracing and stepping should be turned off in the 2154 * child regardless of CLONE_PTRACE. 2155 */ 2156 user_disable_single_step(p); 2157 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 2158 #ifdef TIF_SYSCALL_EMU 2159 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 2160 #endif 2161 clear_tsk_latency_tracing(p); 2162 2163 /* ok, now we should be set up.. */ 2164 p->pid = pid_nr(pid); 2165 if (clone_flags & CLONE_THREAD) { 2166 p->exit_signal = -1; 2167 p->group_leader = current->group_leader; 2168 p->tgid = current->tgid; 2169 } else { 2170 if (clone_flags & CLONE_PARENT) 2171 p->exit_signal = current->group_leader->exit_signal; 2172 else 2173 p->exit_signal = args->exit_signal; 2174 p->group_leader = p; 2175 p->tgid = p->pid; 2176 } 2177 2178 p->nr_dirtied = 0; 2179 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 2180 p->dirty_paused_when = 0; 2181 2182 p->pdeath_signal = 0; 2183 INIT_LIST_HEAD(&p->thread_group); 2184 p->task_works = NULL; 2185 2186 /* 2187 * Ensure that the cgroup subsystem policies allow the new process to be 2188 * forked. It should be noted the the new process's css_set can be changed 2189 * between here and cgroup_post_fork() if an organisation operation is in 2190 * progress. 2191 */ 2192 retval = cgroup_can_fork(p, args); 2193 if (retval) 2194 goto bad_fork_put_pidfd; 2195 2196 /* 2197 * From this point on we must avoid any synchronous user-space 2198 * communication until we take the tasklist-lock. In particular, we do 2199 * not want user-space to be able to predict the process start-time by 2200 * stalling fork(2) after we recorded the start_time but before it is 2201 * visible to the system. 2202 */ 2203 2204 p->start_time = ktime_get_ns(); 2205 p->start_boottime = ktime_get_boottime_ns(); 2206 2207 /* 2208 * Make it visible to the rest of the system, but dont wake it up yet. 2209 * Need tasklist lock for parent etc handling! 2210 */ 2211 write_lock_irq(&tasklist_lock); 2212 2213 /* CLONE_PARENT re-uses the old parent */ 2214 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 2215 p->real_parent = current->real_parent; 2216 p->parent_exec_id = current->parent_exec_id; 2217 } else { 2218 p->real_parent = current; 2219 p->parent_exec_id = current->self_exec_id; 2220 } 2221 2222 klp_copy_process(p); 2223 2224 spin_lock(¤t->sighand->siglock); 2225 2226 /* 2227 * Copy seccomp details explicitly here, in case they were changed 2228 * before holding sighand lock. 2229 */ 2230 copy_seccomp(p); 2231 2232 rseq_fork(p, clone_flags); 2233 2234 /* Don't start children in a dying pid namespace */ 2235 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 2236 retval = -ENOMEM; 2237 goto bad_fork_cancel_cgroup; 2238 } 2239 2240 /* Let kill terminate clone/fork in the middle */ 2241 if (fatal_signal_pending(current)) { 2242 retval = -EINTR; 2243 goto bad_fork_cancel_cgroup; 2244 } 2245 2246 /* past the last point of failure */ 2247 if (pidfile) 2248 fd_install(pidfd, pidfile); 2249 2250 init_task_pid_links(p); 2251 if (likely(p->pid)) { 2252 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 2253 2254 init_task_pid(p, PIDTYPE_PID, pid); 2255 if (thread_group_leader(p)) { 2256 init_task_pid(p, PIDTYPE_TGID, pid); 2257 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 2258 init_task_pid(p, PIDTYPE_SID, task_session(current)); 2259 2260 if (is_child_reaper(pid)) { 2261 ns_of_pid(pid)->child_reaper = p; 2262 p->signal->flags |= SIGNAL_UNKILLABLE; 2263 } 2264 p->signal->shared_pending.signal = delayed.signal; 2265 p->signal->tty = tty_kref_get(current->signal->tty); 2266 /* 2267 * Inherit has_child_subreaper flag under the same 2268 * tasklist_lock with adding child to the process tree 2269 * for propagate_has_child_subreaper optimization. 2270 */ 2271 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 2272 p->real_parent->signal->is_child_subreaper; 2273 list_add_tail(&p->sibling, &p->real_parent->children); 2274 list_add_tail_rcu(&p->tasks, &init_task.tasks); 2275 attach_pid(p, PIDTYPE_TGID); 2276 attach_pid(p, PIDTYPE_PGID); 2277 attach_pid(p, PIDTYPE_SID); 2278 __this_cpu_inc(process_counts); 2279 } else { 2280 current->signal->nr_threads++; 2281 atomic_inc(¤t->signal->live); 2282 refcount_inc(¤t->signal->sigcnt); 2283 task_join_group_stop(p); 2284 list_add_tail_rcu(&p->thread_group, 2285 &p->group_leader->thread_group); 2286 list_add_tail_rcu(&p->thread_node, 2287 &p->signal->thread_head); 2288 } 2289 attach_pid(p, PIDTYPE_PID); 2290 nr_threads++; 2291 } 2292 total_forks++; 2293 hlist_del_init(&delayed.node); 2294 spin_unlock(¤t->sighand->siglock); 2295 syscall_tracepoint_update(p); 2296 write_unlock_irq(&tasklist_lock); 2297 2298 proc_fork_connector(p); 2299 sched_post_fork(p); 2300 cgroup_post_fork(p, args); 2301 perf_event_fork(p); 2302 2303 trace_task_newtask(p, clone_flags); 2304 uprobe_copy_process(p, clone_flags); 2305 2306 return p; 2307 2308 bad_fork_cancel_cgroup: 2309 spin_unlock(¤t->sighand->siglock); 2310 write_unlock_irq(&tasklist_lock); 2311 cgroup_cancel_fork(p, args); 2312 bad_fork_put_pidfd: 2313 if (clone_flags & CLONE_PIDFD) { 2314 fput(pidfile); 2315 put_unused_fd(pidfd); 2316 } 2317 bad_fork_free_pid: 2318 if (pid != &init_struct_pid) 2319 free_pid(pid); 2320 bad_fork_cleanup_thread: 2321 exit_thread(p); 2322 bad_fork_cleanup_io: 2323 if (p->io_context) 2324 exit_io_context(p); 2325 bad_fork_cleanup_namespaces: 2326 exit_task_namespaces(p); 2327 bad_fork_cleanup_mm: 2328 if (p->mm) { 2329 mm_clear_owner(p->mm, p); 2330 mmput(p->mm); 2331 } 2332 bad_fork_cleanup_signal: 2333 if (!(clone_flags & CLONE_THREAD)) 2334 free_signal_struct(p->signal); 2335 bad_fork_cleanup_sighand: 2336 __cleanup_sighand(p->sighand); 2337 bad_fork_cleanup_fs: 2338 exit_fs(p); /* blocking */ 2339 bad_fork_cleanup_files: 2340 exit_files(p); /* blocking */ 2341 bad_fork_cleanup_semundo: 2342 exit_sem(p); 2343 bad_fork_cleanup_security: 2344 security_task_free(p); 2345 bad_fork_cleanup_audit: 2346 audit_free(p); 2347 bad_fork_cleanup_perf: 2348 perf_event_free_task(p); 2349 bad_fork_cleanup_policy: 2350 lockdep_free_task(p); 2351 #ifdef CONFIG_NUMA 2352 mpol_put(p->mempolicy); 2353 bad_fork_cleanup_threadgroup_lock: 2354 #endif 2355 delayacct_tsk_free(p); 2356 bad_fork_cleanup_count: 2357 atomic_dec(&p->cred->user->processes); 2358 exit_creds(p); 2359 bad_fork_free: 2360 p->state = TASK_DEAD; 2361 put_task_stack(p); 2362 delayed_free_task(p); 2363 fork_out: 2364 spin_lock_irq(¤t->sighand->siglock); 2365 hlist_del_init(&delayed.node); 2366 spin_unlock_irq(¤t->sighand->siglock); 2367 return ERR_PTR(retval); 2368 } 2369 2370 static inline void init_idle_pids(struct task_struct *idle) 2371 { 2372 enum pid_type type; 2373 2374 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2375 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */ 2376 init_task_pid(idle, type, &init_struct_pid); 2377 } 2378 } 2379 2380 struct task_struct *fork_idle(int cpu) 2381 { 2382 struct task_struct *task; 2383 struct kernel_clone_args args = { 2384 .flags = CLONE_VM, 2385 }; 2386 2387 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args); 2388 if (!IS_ERR(task)) { 2389 init_idle_pids(task); 2390 init_idle(task, cpu); 2391 } 2392 2393 return task; 2394 } 2395 2396 struct mm_struct *copy_init_mm(void) 2397 { 2398 return dup_mm(NULL, &init_mm); 2399 } 2400 2401 /* 2402 * Ok, this is the main fork-routine. 2403 * 2404 * It copies the process, and if successful kick-starts 2405 * it and waits for it to finish using the VM if required. 2406 * 2407 * args->exit_signal is expected to be checked for sanity by the caller. 2408 */ 2409 long _do_fork(struct kernel_clone_args *args) 2410 { 2411 u64 clone_flags = args->flags; 2412 struct completion vfork; 2413 struct pid *pid; 2414 struct task_struct *p; 2415 int trace = 0; 2416 long nr; 2417 2418 /* 2419 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument 2420 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are 2421 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate 2422 * field in struct clone_args and it still doesn't make sense to have 2423 * them both point at the same memory location. Performing this check 2424 * here has the advantage that we don't need to have a separate helper 2425 * to check for legacy clone(). 2426 */ 2427 if ((args->flags & CLONE_PIDFD) && 2428 (args->flags & CLONE_PARENT_SETTID) && 2429 (args->pidfd == args->parent_tid)) 2430 return -EINVAL; 2431 2432 /* 2433 * Determine whether and which event to report to ptracer. When 2434 * called from kernel_thread or CLONE_UNTRACED is explicitly 2435 * requested, no event is reported; otherwise, report if the event 2436 * for the type of forking is enabled. 2437 */ 2438 if (!(clone_flags & CLONE_UNTRACED)) { 2439 if (clone_flags & CLONE_VFORK) 2440 trace = PTRACE_EVENT_VFORK; 2441 else if (args->exit_signal != SIGCHLD) 2442 trace = PTRACE_EVENT_CLONE; 2443 else 2444 trace = PTRACE_EVENT_FORK; 2445 2446 if (likely(!ptrace_event_enabled(current, trace))) 2447 trace = 0; 2448 } 2449 2450 p = copy_process(NULL, trace, NUMA_NO_NODE, args); 2451 add_latent_entropy(); 2452 2453 if (IS_ERR(p)) 2454 return PTR_ERR(p); 2455 2456 /* 2457 * Do this prior waking up the new thread - the thread pointer 2458 * might get invalid after that point, if the thread exits quickly. 2459 */ 2460 trace_sched_process_fork(current, p); 2461 2462 pid = get_task_pid(p, PIDTYPE_PID); 2463 nr = pid_vnr(pid); 2464 2465 if (clone_flags & CLONE_PARENT_SETTID) 2466 put_user(nr, args->parent_tid); 2467 2468 if (clone_flags & CLONE_VFORK) { 2469 p->vfork_done = &vfork; 2470 init_completion(&vfork); 2471 get_task_struct(p); 2472 } 2473 2474 wake_up_new_task(p); 2475 2476 /* forking complete and child started to run, tell ptracer */ 2477 if (unlikely(trace)) 2478 ptrace_event_pid(trace, pid); 2479 2480 if (clone_flags & CLONE_VFORK) { 2481 if (!wait_for_vfork_done(p, &vfork)) 2482 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2483 } 2484 2485 put_pid(pid); 2486 return nr; 2487 } 2488 2489 /* 2490 * Create a kernel thread. 2491 */ 2492 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2493 { 2494 struct kernel_clone_args args = { 2495 .flags = ((lower_32_bits(flags) | CLONE_VM | 2496 CLONE_UNTRACED) & ~CSIGNAL), 2497 .exit_signal = (lower_32_bits(flags) & CSIGNAL), 2498 .stack = (unsigned long)fn, 2499 .stack_size = (unsigned long)arg, 2500 }; 2501 2502 return _do_fork(&args); 2503 } 2504 2505 #ifdef __ARCH_WANT_SYS_FORK 2506 SYSCALL_DEFINE0(fork) 2507 { 2508 #ifdef CONFIG_MMU 2509 struct kernel_clone_args args = { 2510 .exit_signal = SIGCHLD, 2511 }; 2512 2513 return _do_fork(&args); 2514 #else 2515 /* can not support in nommu mode */ 2516 return -EINVAL; 2517 #endif 2518 } 2519 #endif 2520 2521 #ifdef __ARCH_WANT_SYS_VFORK 2522 SYSCALL_DEFINE0(vfork) 2523 { 2524 struct kernel_clone_args args = { 2525 .flags = CLONE_VFORK | CLONE_VM, 2526 .exit_signal = SIGCHLD, 2527 }; 2528 2529 return _do_fork(&args); 2530 } 2531 #endif 2532 2533 #ifdef __ARCH_WANT_SYS_CLONE 2534 #ifdef CONFIG_CLONE_BACKWARDS 2535 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2536 int __user *, parent_tidptr, 2537 unsigned long, tls, 2538 int __user *, child_tidptr) 2539 #elif defined(CONFIG_CLONE_BACKWARDS2) 2540 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2541 int __user *, parent_tidptr, 2542 int __user *, child_tidptr, 2543 unsigned long, tls) 2544 #elif defined(CONFIG_CLONE_BACKWARDS3) 2545 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2546 int, stack_size, 2547 int __user *, parent_tidptr, 2548 int __user *, child_tidptr, 2549 unsigned long, tls) 2550 #else 2551 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2552 int __user *, parent_tidptr, 2553 int __user *, child_tidptr, 2554 unsigned long, tls) 2555 #endif 2556 { 2557 struct kernel_clone_args args = { 2558 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL), 2559 .pidfd = parent_tidptr, 2560 .child_tid = child_tidptr, 2561 .parent_tid = parent_tidptr, 2562 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL), 2563 .stack = newsp, 2564 .tls = tls, 2565 }; 2566 2567 return _do_fork(&args); 2568 } 2569 #endif 2570 2571 #ifdef __ARCH_WANT_SYS_CLONE3 2572 2573 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, 2574 struct clone_args __user *uargs, 2575 size_t usize) 2576 { 2577 int err; 2578 struct clone_args args; 2579 pid_t *kset_tid = kargs->set_tid; 2580 2581 BUILD_BUG_ON(offsetofend(struct clone_args, tls) != 2582 CLONE_ARGS_SIZE_VER0); 2583 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) != 2584 CLONE_ARGS_SIZE_VER1); 2585 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) != 2586 CLONE_ARGS_SIZE_VER2); 2587 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2); 2588 2589 if (unlikely(usize > PAGE_SIZE)) 2590 return -E2BIG; 2591 if (unlikely(usize < CLONE_ARGS_SIZE_VER0)) 2592 return -EINVAL; 2593 2594 err = copy_struct_from_user(&args, sizeof(args), uargs, usize); 2595 if (err) 2596 return err; 2597 2598 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL)) 2599 return -EINVAL; 2600 2601 if (unlikely(!args.set_tid && args.set_tid_size > 0)) 2602 return -EINVAL; 2603 2604 if (unlikely(args.set_tid && args.set_tid_size == 0)) 2605 return -EINVAL; 2606 2607 /* 2608 * Verify that higher 32bits of exit_signal are unset and that 2609 * it is a valid signal 2610 */ 2611 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) || 2612 !valid_signal(args.exit_signal))) 2613 return -EINVAL; 2614 2615 if ((args.flags & CLONE_INTO_CGROUP) && 2616 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2)) 2617 return -EINVAL; 2618 2619 *kargs = (struct kernel_clone_args){ 2620 .flags = args.flags, 2621 .pidfd = u64_to_user_ptr(args.pidfd), 2622 .child_tid = u64_to_user_ptr(args.child_tid), 2623 .parent_tid = u64_to_user_ptr(args.parent_tid), 2624 .exit_signal = args.exit_signal, 2625 .stack = args.stack, 2626 .stack_size = args.stack_size, 2627 .tls = args.tls, 2628 .set_tid_size = args.set_tid_size, 2629 .cgroup = args.cgroup, 2630 }; 2631 2632 if (args.set_tid && 2633 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid), 2634 (kargs->set_tid_size * sizeof(pid_t)))) 2635 return -EFAULT; 2636 2637 kargs->set_tid = kset_tid; 2638 2639 return 0; 2640 } 2641 2642 /** 2643 * clone3_stack_valid - check and prepare stack 2644 * @kargs: kernel clone args 2645 * 2646 * Verify that the stack arguments userspace gave us are sane. 2647 * In addition, set the stack direction for userspace since it's easy for us to 2648 * determine. 2649 */ 2650 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs) 2651 { 2652 if (kargs->stack == 0) { 2653 if (kargs->stack_size > 0) 2654 return false; 2655 } else { 2656 if (kargs->stack_size == 0) 2657 return false; 2658 2659 if (!access_ok((void __user *)kargs->stack, kargs->stack_size)) 2660 return false; 2661 2662 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64) 2663 kargs->stack += kargs->stack_size; 2664 #endif 2665 } 2666 2667 return true; 2668 } 2669 2670 static bool clone3_args_valid(struct kernel_clone_args *kargs) 2671 { 2672 /* Verify that no unknown flags are passed along. */ 2673 if (kargs->flags & 2674 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP)) 2675 return false; 2676 2677 /* 2678 * - make the CLONE_DETACHED bit reuseable for clone3 2679 * - make the CSIGNAL bits reuseable for clone3 2680 */ 2681 if (kargs->flags & (CLONE_DETACHED | CSIGNAL)) 2682 return false; 2683 2684 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) == 2685 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) 2686 return false; 2687 2688 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) && 2689 kargs->exit_signal) 2690 return false; 2691 2692 if (!clone3_stack_valid(kargs)) 2693 return false; 2694 2695 return true; 2696 } 2697 2698 /** 2699 * clone3 - create a new process with specific properties 2700 * @uargs: argument structure 2701 * @size: size of @uargs 2702 * 2703 * clone3() is the extensible successor to clone()/clone2(). 2704 * It takes a struct as argument that is versioned by its size. 2705 * 2706 * Return: On success, a positive PID for the child process. 2707 * On error, a negative errno number. 2708 */ 2709 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size) 2710 { 2711 int err; 2712 2713 struct kernel_clone_args kargs; 2714 pid_t set_tid[MAX_PID_NS_LEVEL]; 2715 2716 kargs.set_tid = set_tid; 2717 2718 err = copy_clone_args_from_user(&kargs, uargs, size); 2719 if (err) 2720 return err; 2721 2722 if (!clone3_args_valid(&kargs)) 2723 return -EINVAL; 2724 2725 return _do_fork(&kargs); 2726 } 2727 #endif 2728 2729 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2730 { 2731 struct task_struct *leader, *parent, *child; 2732 int res; 2733 2734 read_lock(&tasklist_lock); 2735 leader = top = top->group_leader; 2736 down: 2737 for_each_thread(leader, parent) { 2738 list_for_each_entry(child, &parent->children, sibling) { 2739 res = visitor(child, data); 2740 if (res) { 2741 if (res < 0) 2742 goto out; 2743 leader = child; 2744 goto down; 2745 } 2746 up: 2747 ; 2748 } 2749 } 2750 2751 if (leader != top) { 2752 child = leader; 2753 parent = child->real_parent; 2754 leader = parent->group_leader; 2755 goto up; 2756 } 2757 out: 2758 read_unlock(&tasklist_lock); 2759 } 2760 2761 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2762 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2763 #endif 2764 2765 static void sighand_ctor(void *data) 2766 { 2767 struct sighand_struct *sighand = data; 2768 2769 spin_lock_init(&sighand->siglock); 2770 init_waitqueue_head(&sighand->signalfd_wqh); 2771 } 2772 2773 void __init proc_caches_init(void) 2774 { 2775 unsigned int mm_size; 2776 2777 sighand_cachep = kmem_cache_create("sighand_cache", 2778 sizeof(struct sighand_struct), 0, 2779 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2780 SLAB_ACCOUNT, sighand_ctor); 2781 signal_cachep = kmem_cache_create("signal_cache", 2782 sizeof(struct signal_struct), 0, 2783 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2784 NULL); 2785 files_cachep = kmem_cache_create("files_cache", 2786 sizeof(struct files_struct), 0, 2787 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2788 NULL); 2789 fs_cachep = kmem_cache_create("fs_cache", 2790 sizeof(struct fs_struct), 0, 2791 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2792 NULL); 2793 2794 /* 2795 * The mm_cpumask is located at the end of mm_struct, and is 2796 * dynamically sized based on the maximum CPU number this system 2797 * can have, taking hotplug into account (nr_cpu_ids). 2798 */ 2799 mm_size = sizeof(struct mm_struct) + cpumask_size(); 2800 2801 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2802 mm_size, ARCH_MIN_MMSTRUCT_ALIGN, 2803 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2804 offsetof(struct mm_struct, saved_auxv), 2805 sizeof_field(struct mm_struct, saved_auxv), 2806 NULL); 2807 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2808 mmap_init(); 2809 nsproxy_cache_init(); 2810 } 2811 2812 /* 2813 * Check constraints on flags passed to the unshare system call. 2814 */ 2815 static int check_unshare_flags(unsigned long unshare_flags) 2816 { 2817 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2818 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2819 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2820 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP| 2821 CLONE_NEWTIME)) 2822 return -EINVAL; 2823 /* 2824 * Not implemented, but pretend it works if there is nothing 2825 * to unshare. Note that unsharing the address space or the 2826 * signal handlers also need to unshare the signal queues (aka 2827 * CLONE_THREAD). 2828 */ 2829 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2830 if (!thread_group_empty(current)) 2831 return -EINVAL; 2832 } 2833 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2834 if (refcount_read(¤t->sighand->count) > 1) 2835 return -EINVAL; 2836 } 2837 if (unshare_flags & CLONE_VM) { 2838 if (!current_is_single_threaded()) 2839 return -EINVAL; 2840 } 2841 2842 return 0; 2843 } 2844 2845 /* 2846 * Unshare the filesystem structure if it is being shared 2847 */ 2848 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2849 { 2850 struct fs_struct *fs = current->fs; 2851 2852 if (!(unshare_flags & CLONE_FS) || !fs) 2853 return 0; 2854 2855 /* don't need lock here; in the worst case we'll do useless copy */ 2856 if (fs->users == 1) 2857 return 0; 2858 2859 *new_fsp = copy_fs_struct(fs); 2860 if (!*new_fsp) 2861 return -ENOMEM; 2862 2863 return 0; 2864 } 2865 2866 /* 2867 * Unshare file descriptor table if it is being shared 2868 */ 2869 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 2870 struct files_struct **new_fdp) 2871 { 2872 struct files_struct *fd = current->files; 2873 int error = 0; 2874 2875 if ((unshare_flags & CLONE_FILES) && 2876 (fd && atomic_read(&fd->count) > 1)) { 2877 *new_fdp = dup_fd(fd, max_fds, &error); 2878 if (!*new_fdp) 2879 return error; 2880 } 2881 2882 return 0; 2883 } 2884 2885 /* 2886 * unshare allows a process to 'unshare' part of the process 2887 * context which was originally shared using clone. copy_* 2888 * functions used by _do_fork() cannot be used here directly 2889 * because they modify an inactive task_struct that is being 2890 * constructed. Here we are modifying the current, active, 2891 * task_struct. 2892 */ 2893 int ksys_unshare(unsigned long unshare_flags) 2894 { 2895 struct fs_struct *fs, *new_fs = NULL; 2896 struct files_struct *fd, *new_fd = NULL; 2897 struct cred *new_cred = NULL; 2898 struct nsproxy *new_nsproxy = NULL; 2899 int do_sysvsem = 0; 2900 int err; 2901 2902 /* 2903 * If unsharing a user namespace must also unshare the thread group 2904 * and unshare the filesystem root and working directories. 2905 */ 2906 if (unshare_flags & CLONE_NEWUSER) 2907 unshare_flags |= CLONE_THREAD | CLONE_FS; 2908 /* 2909 * If unsharing vm, must also unshare signal handlers. 2910 */ 2911 if (unshare_flags & CLONE_VM) 2912 unshare_flags |= CLONE_SIGHAND; 2913 /* 2914 * If unsharing a signal handlers, must also unshare the signal queues. 2915 */ 2916 if (unshare_flags & CLONE_SIGHAND) 2917 unshare_flags |= CLONE_THREAD; 2918 /* 2919 * If unsharing namespace, must also unshare filesystem information. 2920 */ 2921 if (unshare_flags & CLONE_NEWNS) 2922 unshare_flags |= CLONE_FS; 2923 2924 err = check_unshare_flags(unshare_flags); 2925 if (err) 2926 goto bad_unshare_out; 2927 /* 2928 * CLONE_NEWIPC must also detach from the undolist: after switching 2929 * to a new ipc namespace, the semaphore arrays from the old 2930 * namespace are unreachable. 2931 */ 2932 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2933 do_sysvsem = 1; 2934 err = unshare_fs(unshare_flags, &new_fs); 2935 if (err) 2936 goto bad_unshare_out; 2937 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd); 2938 if (err) 2939 goto bad_unshare_cleanup_fs; 2940 err = unshare_userns(unshare_flags, &new_cred); 2941 if (err) 2942 goto bad_unshare_cleanup_fd; 2943 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2944 new_cred, new_fs); 2945 if (err) 2946 goto bad_unshare_cleanup_cred; 2947 2948 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2949 if (do_sysvsem) { 2950 /* 2951 * CLONE_SYSVSEM is equivalent to sys_exit(). 2952 */ 2953 exit_sem(current); 2954 } 2955 if (unshare_flags & CLONE_NEWIPC) { 2956 /* Orphan segments in old ns (see sem above). */ 2957 exit_shm(current); 2958 shm_init_task(current); 2959 } 2960 2961 if (new_nsproxy) 2962 switch_task_namespaces(current, new_nsproxy); 2963 2964 task_lock(current); 2965 2966 if (new_fs) { 2967 fs = current->fs; 2968 spin_lock(&fs->lock); 2969 current->fs = new_fs; 2970 if (--fs->users) 2971 new_fs = NULL; 2972 else 2973 new_fs = fs; 2974 spin_unlock(&fs->lock); 2975 } 2976 2977 if (new_fd) { 2978 fd = current->files; 2979 current->files = new_fd; 2980 new_fd = fd; 2981 } 2982 2983 task_unlock(current); 2984 2985 if (new_cred) { 2986 /* Install the new user namespace */ 2987 commit_creds(new_cred); 2988 new_cred = NULL; 2989 } 2990 } 2991 2992 perf_event_namespaces(current); 2993 2994 bad_unshare_cleanup_cred: 2995 if (new_cred) 2996 put_cred(new_cred); 2997 bad_unshare_cleanup_fd: 2998 if (new_fd) 2999 put_files_struct(new_fd); 3000 3001 bad_unshare_cleanup_fs: 3002 if (new_fs) 3003 free_fs_struct(new_fs); 3004 3005 bad_unshare_out: 3006 return err; 3007 } 3008 3009 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 3010 { 3011 return ksys_unshare(unshare_flags); 3012 } 3013 3014 /* 3015 * Helper to unshare the files of the current task. 3016 * We don't want to expose copy_files internals to 3017 * the exec layer of the kernel. 3018 */ 3019 3020 int unshare_files(struct files_struct **displaced) 3021 { 3022 struct task_struct *task = current; 3023 struct files_struct *copy = NULL; 3024 int error; 3025 3026 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©); 3027 if (error || !copy) { 3028 *displaced = NULL; 3029 return error; 3030 } 3031 *displaced = task->files; 3032 task_lock(task); 3033 task->files = copy; 3034 task_unlock(task); 3035 return 0; 3036 } 3037 3038 int sysctl_max_threads(struct ctl_table *table, int write, 3039 void __user *buffer, size_t *lenp, loff_t *ppos) 3040 { 3041 struct ctl_table t; 3042 int ret; 3043 int threads = max_threads; 3044 int min = 1; 3045 int max = MAX_THREADS; 3046 3047 t = *table; 3048 t.data = &threads; 3049 t.extra1 = &min; 3050 t.extra2 = &max; 3051 3052 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 3053 if (ret || !write) 3054 return ret; 3055 3056 max_threads = threads; 3057 3058 return 0; 3059 } 3060