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