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 97 #include <asm/pgtable.h> 98 #include <asm/pgalloc.h> 99 #include <linux/uaccess.h> 100 #include <asm/mmu_context.h> 101 #include <asm/cacheflush.h> 102 #include <asm/tlbflush.h> 103 104 #include <trace/events/sched.h> 105 106 #define CREATE_TRACE_POINTS 107 #include <trace/events/task.h> 108 109 /* 110 * Minimum number of threads to boot the kernel 111 */ 112 #define MIN_THREADS 20 113 114 /* 115 * Maximum number of threads 116 */ 117 #define MAX_THREADS FUTEX_TID_MASK 118 119 /* 120 * Protected counters by write_lock_irq(&tasklist_lock) 121 */ 122 unsigned long total_forks; /* Handle normal Linux uptimes. */ 123 int nr_threads; /* The idle threads do not count.. */ 124 125 static int max_threads; /* tunable limit on nr_threads */ 126 127 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x) 128 129 static const char * const resident_page_types[] = { 130 NAMED_ARRAY_INDEX(MM_FILEPAGES), 131 NAMED_ARRAY_INDEX(MM_ANONPAGES), 132 NAMED_ARRAY_INDEX(MM_SWAPENTS), 133 NAMED_ARRAY_INDEX(MM_SHMEMPAGES), 134 }; 135 136 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 137 138 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 139 140 #ifdef CONFIG_PROVE_RCU 141 int lockdep_tasklist_lock_is_held(void) 142 { 143 return lockdep_is_held(&tasklist_lock); 144 } 145 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 146 #endif /* #ifdef CONFIG_PROVE_RCU */ 147 148 int nr_processes(void) 149 { 150 int cpu; 151 int total = 0; 152 153 for_each_possible_cpu(cpu) 154 total += per_cpu(process_counts, cpu); 155 156 return total; 157 } 158 159 void __weak arch_release_task_struct(struct task_struct *tsk) 160 { 161 } 162 163 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 164 static struct kmem_cache *task_struct_cachep; 165 166 static inline struct task_struct *alloc_task_struct_node(int node) 167 { 168 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 169 } 170 171 static inline void free_task_struct(struct task_struct *tsk) 172 { 173 kmem_cache_free(task_struct_cachep, tsk); 174 } 175 #endif 176 177 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 178 179 /* 180 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 181 * kmemcache based allocator. 182 */ 183 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 184 185 #ifdef CONFIG_VMAP_STACK 186 /* 187 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 188 * flush. Try to minimize the number of calls by caching stacks. 189 */ 190 #define NR_CACHED_STACKS 2 191 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 192 193 static int free_vm_stack_cache(unsigned int cpu) 194 { 195 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 196 int i; 197 198 for (i = 0; i < NR_CACHED_STACKS; i++) { 199 struct vm_struct *vm_stack = cached_vm_stacks[i]; 200 201 if (!vm_stack) 202 continue; 203 204 vfree(vm_stack->addr); 205 cached_vm_stacks[i] = NULL; 206 } 207 208 return 0; 209 } 210 #endif 211 212 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 213 { 214 #ifdef CONFIG_VMAP_STACK 215 void *stack; 216 int i; 217 218 for (i = 0; i < NR_CACHED_STACKS; i++) { 219 struct vm_struct *s; 220 221 s = this_cpu_xchg(cached_stacks[i], NULL); 222 223 if (!s) 224 continue; 225 226 /* Clear stale pointers from reused stack. */ 227 memset(s->addr, 0, THREAD_SIZE); 228 229 tsk->stack_vm_area = s; 230 tsk->stack = s->addr; 231 return s->addr; 232 } 233 234 /* 235 * Allocated stacks are cached and later reused by new threads, 236 * so memcg accounting is performed manually on assigning/releasing 237 * stacks to tasks. Drop __GFP_ACCOUNT. 238 */ 239 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, 240 VMALLOC_START, VMALLOC_END, 241 THREADINFO_GFP & ~__GFP_ACCOUNT, 242 PAGE_KERNEL, 243 0, node, __builtin_return_address(0)); 244 245 /* 246 * We can't call find_vm_area() in interrupt context, and 247 * free_thread_stack() can be called in interrupt context, 248 * so cache the vm_struct. 249 */ 250 if (stack) { 251 tsk->stack_vm_area = find_vm_area(stack); 252 tsk->stack = stack; 253 } 254 return stack; 255 #else 256 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 257 THREAD_SIZE_ORDER); 258 259 if (likely(page)) { 260 tsk->stack = page_address(page); 261 return tsk->stack; 262 } 263 return NULL; 264 #endif 265 } 266 267 static inline void free_thread_stack(struct task_struct *tsk) 268 { 269 #ifdef CONFIG_VMAP_STACK 270 struct vm_struct *vm = task_stack_vm_area(tsk); 271 272 if (vm) { 273 int i; 274 275 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 276 mod_memcg_page_state(vm->pages[i], 277 MEMCG_KERNEL_STACK_KB, 278 -(int)(PAGE_SIZE / 1024)); 279 280 memcg_kmem_uncharge(vm->pages[i], 0); 281 } 282 283 for (i = 0; i < NR_CACHED_STACKS; i++) { 284 if (this_cpu_cmpxchg(cached_stacks[i], 285 NULL, tsk->stack_vm_area) != NULL) 286 continue; 287 288 return; 289 } 290 291 vfree_atomic(tsk->stack); 292 return; 293 } 294 #endif 295 296 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 297 } 298 # else 299 static struct kmem_cache *thread_stack_cache; 300 301 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 302 int node) 303 { 304 unsigned long *stack; 305 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 306 tsk->stack = stack; 307 return stack; 308 } 309 310 static void free_thread_stack(struct task_struct *tsk) 311 { 312 kmem_cache_free(thread_stack_cache, tsk->stack); 313 } 314 315 void thread_stack_cache_init(void) 316 { 317 thread_stack_cache = kmem_cache_create_usercopy("thread_stack", 318 THREAD_SIZE, THREAD_SIZE, 0, 0, 319 THREAD_SIZE, NULL); 320 BUG_ON(thread_stack_cache == NULL); 321 } 322 # endif 323 #endif 324 325 /* SLAB cache for signal_struct structures (tsk->signal) */ 326 static struct kmem_cache *signal_cachep; 327 328 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 329 struct kmem_cache *sighand_cachep; 330 331 /* SLAB cache for files_struct structures (tsk->files) */ 332 struct kmem_cache *files_cachep; 333 334 /* SLAB cache for fs_struct structures (tsk->fs) */ 335 struct kmem_cache *fs_cachep; 336 337 /* SLAB cache for vm_area_struct structures */ 338 static struct kmem_cache *vm_area_cachep; 339 340 /* SLAB cache for mm_struct structures (tsk->mm) */ 341 static struct kmem_cache *mm_cachep; 342 343 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm) 344 { 345 struct vm_area_struct *vma; 346 347 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 348 if (vma) 349 vma_init(vma, mm); 350 return vma; 351 } 352 353 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) 354 { 355 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 356 357 if (new) { 358 *new = *orig; 359 INIT_LIST_HEAD(&new->anon_vma_chain); 360 } 361 return new; 362 } 363 364 void vm_area_free(struct vm_area_struct *vma) 365 { 366 kmem_cache_free(vm_area_cachep, vma); 367 } 368 369 static void account_kernel_stack(struct task_struct *tsk, int account) 370 { 371 void *stack = task_stack_page(tsk); 372 struct vm_struct *vm = task_stack_vm_area(tsk); 373 374 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 375 376 if (vm) { 377 int i; 378 379 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 380 381 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 382 mod_zone_page_state(page_zone(vm->pages[i]), 383 NR_KERNEL_STACK_KB, 384 PAGE_SIZE / 1024 * account); 385 } 386 } else { 387 /* 388 * All stack pages are in the same zone and belong to the 389 * same memcg. 390 */ 391 struct page *first_page = virt_to_page(stack); 392 393 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 394 THREAD_SIZE / 1024 * account); 395 396 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, 397 account * (THREAD_SIZE / 1024)); 398 } 399 } 400 401 static int memcg_charge_kernel_stack(struct task_struct *tsk) 402 { 403 #ifdef CONFIG_VMAP_STACK 404 struct vm_struct *vm = task_stack_vm_area(tsk); 405 int ret; 406 407 if (vm) { 408 int i; 409 410 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 411 /* 412 * If memcg_kmem_charge() fails, page->mem_cgroup 413 * pointer is NULL, and both memcg_kmem_uncharge() 414 * and mod_memcg_page_state() in free_thread_stack() 415 * will ignore this page. So it's safe. 416 */ 417 ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0); 418 if (ret) 419 return ret; 420 421 mod_memcg_page_state(vm->pages[i], 422 MEMCG_KERNEL_STACK_KB, 423 PAGE_SIZE / 1024); 424 } 425 } 426 #endif 427 return 0; 428 } 429 430 static void release_task_stack(struct task_struct *tsk) 431 { 432 if (WARN_ON(tsk->state != TASK_DEAD)) 433 return; /* Better to leak the stack than to free prematurely */ 434 435 account_kernel_stack(tsk, -1); 436 free_thread_stack(tsk); 437 tsk->stack = NULL; 438 #ifdef CONFIG_VMAP_STACK 439 tsk->stack_vm_area = NULL; 440 #endif 441 } 442 443 #ifdef CONFIG_THREAD_INFO_IN_TASK 444 void put_task_stack(struct task_struct *tsk) 445 { 446 if (refcount_dec_and_test(&tsk->stack_refcount)) 447 release_task_stack(tsk); 448 } 449 #endif 450 451 void free_task(struct task_struct *tsk) 452 { 453 #ifndef CONFIG_THREAD_INFO_IN_TASK 454 /* 455 * The task is finally done with both the stack and thread_info, 456 * so free both. 457 */ 458 release_task_stack(tsk); 459 #else 460 /* 461 * If the task had a separate stack allocation, it should be gone 462 * by now. 463 */ 464 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0); 465 #endif 466 rt_mutex_debug_task_free(tsk); 467 ftrace_graph_exit_task(tsk); 468 put_seccomp_filter(tsk); 469 arch_release_task_struct(tsk); 470 if (tsk->flags & PF_KTHREAD) 471 free_kthread_struct(tsk); 472 free_task_struct(tsk); 473 } 474 EXPORT_SYMBOL(free_task); 475 476 #ifdef CONFIG_MMU 477 static __latent_entropy int dup_mmap(struct mm_struct *mm, 478 struct mm_struct *oldmm) 479 { 480 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 481 struct rb_node **rb_link, *rb_parent; 482 int retval; 483 unsigned long charge; 484 LIST_HEAD(uf); 485 486 uprobe_start_dup_mmap(); 487 if (down_write_killable(&oldmm->mmap_sem)) { 488 retval = -EINTR; 489 goto fail_uprobe_end; 490 } 491 flush_cache_dup_mm(oldmm); 492 uprobe_dup_mmap(oldmm, mm); 493 /* 494 * Not linked in yet - no deadlock potential: 495 */ 496 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 497 498 /* No ordering required: file already has been exposed. */ 499 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 500 501 mm->total_vm = oldmm->total_vm; 502 mm->data_vm = oldmm->data_vm; 503 mm->exec_vm = oldmm->exec_vm; 504 mm->stack_vm = oldmm->stack_vm; 505 506 rb_link = &mm->mm_rb.rb_node; 507 rb_parent = NULL; 508 pprev = &mm->mmap; 509 retval = ksm_fork(mm, oldmm); 510 if (retval) 511 goto out; 512 retval = khugepaged_fork(mm, oldmm); 513 if (retval) 514 goto out; 515 516 prev = NULL; 517 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 518 struct file *file; 519 520 if (mpnt->vm_flags & VM_DONTCOPY) { 521 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 522 continue; 523 } 524 charge = 0; 525 /* 526 * Don't duplicate many vmas if we've been oom-killed (for 527 * example) 528 */ 529 if (fatal_signal_pending(current)) { 530 retval = -EINTR; 531 goto out; 532 } 533 if (mpnt->vm_flags & VM_ACCOUNT) { 534 unsigned long len = vma_pages(mpnt); 535 536 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 537 goto fail_nomem; 538 charge = len; 539 } 540 tmp = vm_area_dup(mpnt); 541 if (!tmp) 542 goto fail_nomem; 543 retval = vma_dup_policy(mpnt, tmp); 544 if (retval) 545 goto fail_nomem_policy; 546 tmp->vm_mm = mm; 547 retval = dup_userfaultfd(tmp, &uf); 548 if (retval) 549 goto fail_nomem_anon_vma_fork; 550 if (tmp->vm_flags & VM_WIPEONFORK) { 551 /* VM_WIPEONFORK gets a clean slate in the child. */ 552 tmp->anon_vma = NULL; 553 if (anon_vma_prepare(tmp)) 554 goto fail_nomem_anon_vma_fork; 555 } else if (anon_vma_fork(tmp, mpnt)) 556 goto fail_nomem_anon_vma_fork; 557 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 558 tmp->vm_next = tmp->vm_prev = NULL; 559 file = tmp->vm_file; 560 if (file) { 561 struct inode *inode = file_inode(file); 562 struct address_space *mapping = file->f_mapping; 563 564 get_file(file); 565 if (tmp->vm_flags & VM_DENYWRITE) 566 atomic_dec(&inode->i_writecount); 567 i_mmap_lock_write(mapping); 568 if (tmp->vm_flags & VM_SHARED) 569 atomic_inc(&mapping->i_mmap_writable); 570 flush_dcache_mmap_lock(mapping); 571 /* insert tmp into the share list, just after mpnt */ 572 vma_interval_tree_insert_after(tmp, mpnt, 573 &mapping->i_mmap); 574 flush_dcache_mmap_unlock(mapping); 575 i_mmap_unlock_write(mapping); 576 } 577 578 /* 579 * Clear hugetlb-related page reserves for children. This only 580 * affects MAP_PRIVATE mappings. Faults generated by the child 581 * are not guaranteed to succeed, even if read-only 582 */ 583 if (is_vm_hugetlb_page(tmp)) 584 reset_vma_resv_huge_pages(tmp); 585 586 /* 587 * Link in the new vma and copy the page table entries. 588 */ 589 *pprev = tmp; 590 pprev = &tmp->vm_next; 591 tmp->vm_prev = prev; 592 prev = tmp; 593 594 __vma_link_rb(mm, tmp, rb_link, rb_parent); 595 rb_link = &tmp->vm_rb.rb_right; 596 rb_parent = &tmp->vm_rb; 597 598 mm->map_count++; 599 if (!(tmp->vm_flags & VM_WIPEONFORK)) 600 retval = copy_page_range(mm, oldmm, mpnt); 601 602 if (tmp->vm_ops && tmp->vm_ops->open) 603 tmp->vm_ops->open(tmp); 604 605 if (retval) 606 goto out; 607 } 608 /* a new mm has just been created */ 609 retval = arch_dup_mmap(oldmm, mm); 610 out: 611 up_write(&mm->mmap_sem); 612 flush_tlb_mm(oldmm); 613 up_write(&oldmm->mmap_sem); 614 dup_userfaultfd_complete(&uf); 615 fail_uprobe_end: 616 uprobe_end_dup_mmap(); 617 return retval; 618 fail_nomem_anon_vma_fork: 619 mpol_put(vma_policy(tmp)); 620 fail_nomem_policy: 621 vm_area_free(tmp); 622 fail_nomem: 623 retval = -ENOMEM; 624 vm_unacct_memory(charge); 625 goto out; 626 } 627 628 static inline int mm_alloc_pgd(struct mm_struct *mm) 629 { 630 mm->pgd = pgd_alloc(mm); 631 if (unlikely(!mm->pgd)) 632 return -ENOMEM; 633 return 0; 634 } 635 636 static inline void mm_free_pgd(struct mm_struct *mm) 637 { 638 pgd_free(mm, mm->pgd); 639 } 640 #else 641 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 642 { 643 down_write(&oldmm->mmap_sem); 644 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 645 up_write(&oldmm->mmap_sem); 646 return 0; 647 } 648 #define mm_alloc_pgd(mm) (0) 649 #define mm_free_pgd(mm) 650 #endif /* CONFIG_MMU */ 651 652 static void check_mm(struct mm_struct *mm) 653 { 654 int i; 655 656 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS, 657 "Please make sure 'struct resident_page_types[]' is updated as well"); 658 659 for (i = 0; i < NR_MM_COUNTERS; i++) { 660 long x = atomic_long_read(&mm->rss_stat.count[i]); 661 662 if (unlikely(x)) 663 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", 664 mm, resident_page_types[i], x); 665 } 666 667 if (mm_pgtables_bytes(mm)) 668 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", 669 mm_pgtables_bytes(mm)); 670 671 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 672 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 673 #endif 674 } 675 676 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 677 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 678 679 /* 680 * Called when the last reference to the mm 681 * is dropped: either by a lazy thread or by 682 * mmput. Free the page directory and the mm. 683 */ 684 void __mmdrop(struct mm_struct *mm) 685 { 686 BUG_ON(mm == &init_mm); 687 WARN_ON_ONCE(mm == current->mm); 688 WARN_ON_ONCE(mm == current->active_mm); 689 mm_free_pgd(mm); 690 destroy_context(mm); 691 mmu_notifier_mm_destroy(mm); 692 check_mm(mm); 693 put_user_ns(mm->user_ns); 694 free_mm(mm); 695 } 696 EXPORT_SYMBOL_GPL(__mmdrop); 697 698 static void mmdrop_async_fn(struct work_struct *work) 699 { 700 struct mm_struct *mm; 701 702 mm = container_of(work, struct mm_struct, async_put_work); 703 __mmdrop(mm); 704 } 705 706 static void mmdrop_async(struct mm_struct *mm) 707 { 708 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 709 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 710 schedule_work(&mm->async_put_work); 711 } 712 } 713 714 static inline void free_signal_struct(struct signal_struct *sig) 715 { 716 taskstats_tgid_free(sig); 717 sched_autogroup_exit(sig); 718 /* 719 * __mmdrop is not safe to call from softirq context on x86 due to 720 * pgd_dtor so postpone it to the async context 721 */ 722 if (sig->oom_mm) 723 mmdrop_async(sig->oom_mm); 724 kmem_cache_free(signal_cachep, sig); 725 } 726 727 static inline void put_signal_struct(struct signal_struct *sig) 728 { 729 if (refcount_dec_and_test(&sig->sigcnt)) 730 free_signal_struct(sig); 731 } 732 733 void __put_task_struct(struct task_struct *tsk) 734 { 735 WARN_ON(!tsk->exit_state); 736 WARN_ON(refcount_read(&tsk->usage)); 737 WARN_ON(tsk == current); 738 739 cgroup_free(tsk); 740 task_numa_free(tsk, true); 741 security_task_free(tsk); 742 exit_creds(tsk); 743 delayacct_tsk_free(tsk); 744 put_signal_struct(tsk->signal); 745 746 if (!profile_handoff_task(tsk)) 747 free_task(tsk); 748 } 749 EXPORT_SYMBOL_GPL(__put_task_struct); 750 751 void __init __weak arch_task_cache_init(void) { } 752 753 /* 754 * set_max_threads 755 */ 756 static void set_max_threads(unsigned int max_threads_suggested) 757 { 758 u64 threads; 759 unsigned long nr_pages = totalram_pages(); 760 761 /* 762 * The number of threads shall be limited such that the thread 763 * structures may only consume a small part of the available memory. 764 */ 765 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64) 766 threads = MAX_THREADS; 767 else 768 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE, 769 (u64) THREAD_SIZE * 8UL); 770 771 if (threads > max_threads_suggested) 772 threads = max_threads_suggested; 773 774 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 775 } 776 777 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 778 /* Initialized by the architecture: */ 779 int arch_task_struct_size __read_mostly; 780 #endif 781 782 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 783 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 784 { 785 /* Fetch thread_struct whitelist for the architecture. */ 786 arch_thread_struct_whitelist(offset, size); 787 788 /* 789 * Handle zero-sized whitelist or empty thread_struct, otherwise 790 * adjust offset to position of thread_struct in task_struct. 791 */ 792 if (unlikely(*size == 0)) 793 *offset = 0; 794 else 795 *offset += offsetof(struct task_struct, thread); 796 } 797 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */ 798 799 void __init fork_init(void) 800 { 801 int i; 802 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 803 #ifndef ARCH_MIN_TASKALIGN 804 #define ARCH_MIN_TASKALIGN 0 805 #endif 806 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 807 unsigned long useroffset, usersize; 808 809 /* create a slab on which task_structs can be allocated */ 810 task_struct_whitelist(&useroffset, &usersize); 811 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 812 arch_task_struct_size, align, 813 SLAB_PANIC|SLAB_ACCOUNT, 814 useroffset, usersize, NULL); 815 #endif 816 817 /* do the arch specific task caches init */ 818 arch_task_cache_init(); 819 820 set_max_threads(MAX_THREADS); 821 822 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 823 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 824 init_task.signal->rlim[RLIMIT_SIGPENDING] = 825 init_task.signal->rlim[RLIMIT_NPROC]; 826 827 for (i = 0; i < UCOUNT_COUNTS; i++) { 828 init_user_ns.ucount_max[i] = max_threads/2; 829 } 830 831 #ifdef CONFIG_VMAP_STACK 832 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 833 NULL, free_vm_stack_cache); 834 #endif 835 836 lockdep_init_task(&init_task); 837 uprobes_init(); 838 } 839 840 int __weak arch_dup_task_struct(struct task_struct *dst, 841 struct task_struct *src) 842 { 843 *dst = *src; 844 return 0; 845 } 846 847 void set_task_stack_end_magic(struct task_struct *tsk) 848 { 849 unsigned long *stackend; 850 851 stackend = end_of_stack(tsk); 852 *stackend = STACK_END_MAGIC; /* for overflow detection */ 853 } 854 855 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 856 { 857 struct task_struct *tsk; 858 unsigned long *stack; 859 struct vm_struct *stack_vm_area __maybe_unused; 860 int err; 861 862 if (node == NUMA_NO_NODE) 863 node = tsk_fork_get_node(orig); 864 tsk = alloc_task_struct_node(node); 865 if (!tsk) 866 return NULL; 867 868 stack = alloc_thread_stack_node(tsk, node); 869 if (!stack) 870 goto free_tsk; 871 872 if (memcg_charge_kernel_stack(tsk)) 873 goto free_stack; 874 875 stack_vm_area = task_stack_vm_area(tsk); 876 877 err = arch_dup_task_struct(tsk, orig); 878 879 /* 880 * arch_dup_task_struct() clobbers the stack-related fields. Make 881 * sure they're properly initialized before using any stack-related 882 * functions again. 883 */ 884 tsk->stack = stack; 885 #ifdef CONFIG_VMAP_STACK 886 tsk->stack_vm_area = stack_vm_area; 887 #endif 888 #ifdef CONFIG_THREAD_INFO_IN_TASK 889 refcount_set(&tsk->stack_refcount, 1); 890 #endif 891 892 if (err) 893 goto free_stack; 894 895 #ifdef CONFIG_SECCOMP 896 /* 897 * We must handle setting up seccomp filters once we're under 898 * the sighand lock in case orig has changed between now and 899 * then. Until then, filter must be NULL to avoid messing up 900 * the usage counts on the error path calling free_task. 901 */ 902 tsk->seccomp.filter = NULL; 903 #endif 904 905 setup_thread_stack(tsk, orig); 906 clear_user_return_notifier(tsk); 907 clear_tsk_need_resched(tsk); 908 set_task_stack_end_magic(tsk); 909 910 #ifdef CONFIG_STACKPROTECTOR 911 tsk->stack_canary = get_random_canary(); 912 #endif 913 if (orig->cpus_ptr == &orig->cpus_mask) 914 tsk->cpus_ptr = &tsk->cpus_mask; 915 916 /* 917 * One for the user space visible state that goes away when reaped. 918 * One for the scheduler. 919 */ 920 refcount_set(&tsk->rcu_users, 2); 921 /* One for the rcu users */ 922 refcount_set(&tsk->usage, 1); 923 #ifdef CONFIG_BLK_DEV_IO_TRACE 924 tsk->btrace_seq = 0; 925 #endif 926 tsk->splice_pipe = NULL; 927 tsk->task_frag.page = NULL; 928 tsk->wake_q.next = NULL; 929 930 account_kernel_stack(tsk, 1); 931 932 kcov_task_init(tsk); 933 934 #ifdef CONFIG_FAULT_INJECTION 935 tsk->fail_nth = 0; 936 #endif 937 938 #ifdef CONFIG_BLK_CGROUP 939 tsk->throttle_queue = NULL; 940 tsk->use_memdelay = 0; 941 #endif 942 943 #ifdef CONFIG_MEMCG 944 tsk->active_memcg = NULL; 945 #endif 946 return tsk; 947 948 free_stack: 949 free_thread_stack(tsk); 950 free_tsk: 951 free_task_struct(tsk); 952 return NULL; 953 } 954 955 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 956 957 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 958 959 static int __init coredump_filter_setup(char *s) 960 { 961 default_dump_filter = 962 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 963 MMF_DUMP_FILTER_MASK; 964 return 1; 965 } 966 967 __setup("coredump_filter=", coredump_filter_setup); 968 969 #include <linux/init_task.h> 970 971 static void mm_init_aio(struct mm_struct *mm) 972 { 973 #ifdef CONFIG_AIO 974 spin_lock_init(&mm->ioctx_lock); 975 mm->ioctx_table = NULL; 976 #endif 977 } 978 979 static __always_inline void mm_clear_owner(struct mm_struct *mm, 980 struct task_struct *p) 981 { 982 #ifdef CONFIG_MEMCG 983 if (mm->owner == p) 984 WRITE_ONCE(mm->owner, NULL); 985 #endif 986 } 987 988 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 989 { 990 #ifdef CONFIG_MEMCG 991 mm->owner = p; 992 #endif 993 } 994 995 static void mm_init_uprobes_state(struct mm_struct *mm) 996 { 997 #ifdef CONFIG_UPROBES 998 mm->uprobes_state.xol_area = NULL; 999 #endif 1000 } 1001 1002 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 1003 struct user_namespace *user_ns) 1004 { 1005 mm->mmap = NULL; 1006 mm->mm_rb = RB_ROOT; 1007 mm->vmacache_seqnum = 0; 1008 atomic_set(&mm->mm_users, 1); 1009 atomic_set(&mm->mm_count, 1); 1010 init_rwsem(&mm->mmap_sem); 1011 INIT_LIST_HEAD(&mm->mmlist); 1012 mm->core_state = NULL; 1013 mm_pgtables_bytes_init(mm); 1014 mm->map_count = 0; 1015 mm->locked_vm = 0; 1016 atomic64_set(&mm->pinned_vm, 0); 1017 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 1018 spin_lock_init(&mm->page_table_lock); 1019 spin_lock_init(&mm->arg_lock); 1020 mm_init_cpumask(mm); 1021 mm_init_aio(mm); 1022 mm_init_owner(mm, p); 1023 RCU_INIT_POINTER(mm->exe_file, NULL); 1024 mmu_notifier_mm_init(mm); 1025 init_tlb_flush_pending(mm); 1026 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 1027 mm->pmd_huge_pte = NULL; 1028 #endif 1029 mm_init_uprobes_state(mm); 1030 1031 if (current->mm) { 1032 mm->flags = current->mm->flags & MMF_INIT_MASK; 1033 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 1034 } else { 1035 mm->flags = default_dump_filter; 1036 mm->def_flags = 0; 1037 } 1038 1039 if (mm_alloc_pgd(mm)) 1040 goto fail_nopgd; 1041 1042 if (init_new_context(p, mm)) 1043 goto fail_nocontext; 1044 1045 mm->user_ns = get_user_ns(user_ns); 1046 return mm; 1047 1048 fail_nocontext: 1049 mm_free_pgd(mm); 1050 fail_nopgd: 1051 free_mm(mm); 1052 return NULL; 1053 } 1054 1055 /* 1056 * Allocate and initialize an mm_struct. 1057 */ 1058 struct mm_struct *mm_alloc(void) 1059 { 1060 struct mm_struct *mm; 1061 1062 mm = allocate_mm(); 1063 if (!mm) 1064 return NULL; 1065 1066 memset(mm, 0, sizeof(*mm)); 1067 return mm_init(mm, current, current_user_ns()); 1068 } 1069 1070 static inline void __mmput(struct mm_struct *mm) 1071 { 1072 VM_BUG_ON(atomic_read(&mm->mm_users)); 1073 1074 uprobe_clear_state(mm); 1075 exit_aio(mm); 1076 ksm_exit(mm); 1077 khugepaged_exit(mm); /* must run before exit_mmap */ 1078 exit_mmap(mm); 1079 mm_put_huge_zero_page(mm); 1080 set_mm_exe_file(mm, NULL); 1081 if (!list_empty(&mm->mmlist)) { 1082 spin_lock(&mmlist_lock); 1083 list_del(&mm->mmlist); 1084 spin_unlock(&mmlist_lock); 1085 } 1086 if (mm->binfmt) 1087 module_put(mm->binfmt->module); 1088 mmdrop(mm); 1089 } 1090 1091 /* 1092 * Decrement the use count and release all resources for an mm. 1093 */ 1094 void mmput(struct mm_struct *mm) 1095 { 1096 might_sleep(); 1097 1098 if (atomic_dec_and_test(&mm->mm_users)) 1099 __mmput(mm); 1100 } 1101 EXPORT_SYMBOL_GPL(mmput); 1102 1103 #ifdef CONFIG_MMU 1104 static void mmput_async_fn(struct work_struct *work) 1105 { 1106 struct mm_struct *mm = container_of(work, struct mm_struct, 1107 async_put_work); 1108 1109 __mmput(mm); 1110 } 1111 1112 void mmput_async(struct mm_struct *mm) 1113 { 1114 if (atomic_dec_and_test(&mm->mm_users)) { 1115 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1116 schedule_work(&mm->async_put_work); 1117 } 1118 } 1119 #endif 1120 1121 /** 1122 * set_mm_exe_file - change a reference to the mm's executable file 1123 * 1124 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1125 * 1126 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1127 * invocations: in mmput() nobody alive left, in execve task is single 1128 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1129 * mm->exe_file, but does so without using set_mm_exe_file() in order 1130 * to do avoid the need for any locks. 1131 */ 1132 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1133 { 1134 struct file *old_exe_file; 1135 1136 /* 1137 * It is safe to dereference the exe_file without RCU as 1138 * this function is only called if nobody else can access 1139 * this mm -- see comment above for justification. 1140 */ 1141 old_exe_file = rcu_dereference_raw(mm->exe_file); 1142 1143 if (new_exe_file) 1144 get_file(new_exe_file); 1145 rcu_assign_pointer(mm->exe_file, new_exe_file); 1146 if (old_exe_file) 1147 fput(old_exe_file); 1148 } 1149 1150 /** 1151 * get_mm_exe_file - acquire a reference to the mm's executable file 1152 * 1153 * Returns %NULL if mm has no associated executable file. 1154 * User must release file via fput(). 1155 */ 1156 struct file *get_mm_exe_file(struct mm_struct *mm) 1157 { 1158 struct file *exe_file; 1159 1160 rcu_read_lock(); 1161 exe_file = rcu_dereference(mm->exe_file); 1162 if (exe_file && !get_file_rcu(exe_file)) 1163 exe_file = NULL; 1164 rcu_read_unlock(); 1165 return exe_file; 1166 } 1167 EXPORT_SYMBOL(get_mm_exe_file); 1168 1169 /** 1170 * get_task_exe_file - acquire a reference to the task's executable file 1171 * 1172 * Returns %NULL if task's mm (if any) has no associated executable file or 1173 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1174 * User must release file via fput(). 1175 */ 1176 struct file *get_task_exe_file(struct task_struct *task) 1177 { 1178 struct file *exe_file = NULL; 1179 struct mm_struct *mm; 1180 1181 task_lock(task); 1182 mm = task->mm; 1183 if (mm) { 1184 if (!(task->flags & PF_KTHREAD)) 1185 exe_file = get_mm_exe_file(mm); 1186 } 1187 task_unlock(task); 1188 return exe_file; 1189 } 1190 EXPORT_SYMBOL(get_task_exe_file); 1191 1192 /** 1193 * get_task_mm - acquire a reference to the task's mm 1194 * 1195 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1196 * this kernel workthread has transiently adopted a user mm with use_mm, 1197 * to do its AIO) is not set and if so returns a reference to it, after 1198 * bumping up the use count. User must release the mm via mmput() 1199 * after use. Typically used by /proc and ptrace. 1200 */ 1201 struct mm_struct *get_task_mm(struct task_struct *task) 1202 { 1203 struct mm_struct *mm; 1204 1205 task_lock(task); 1206 mm = task->mm; 1207 if (mm) { 1208 if (task->flags & PF_KTHREAD) 1209 mm = NULL; 1210 else 1211 mmget(mm); 1212 } 1213 task_unlock(task); 1214 return mm; 1215 } 1216 EXPORT_SYMBOL_GPL(get_task_mm); 1217 1218 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1219 { 1220 struct mm_struct *mm; 1221 int err; 1222 1223 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1224 if (err) 1225 return ERR_PTR(err); 1226 1227 mm = get_task_mm(task); 1228 if (mm && mm != current->mm && 1229 !ptrace_may_access(task, mode)) { 1230 mmput(mm); 1231 mm = ERR_PTR(-EACCES); 1232 } 1233 mutex_unlock(&task->signal->cred_guard_mutex); 1234 1235 return mm; 1236 } 1237 1238 static void complete_vfork_done(struct task_struct *tsk) 1239 { 1240 struct completion *vfork; 1241 1242 task_lock(tsk); 1243 vfork = tsk->vfork_done; 1244 if (likely(vfork)) { 1245 tsk->vfork_done = NULL; 1246 complete(vfork); 1247 } 1248 task_unlock(tsk); 1249 } 1250 1251 static int wait_for_vfork_done(struct task_struct *child, 1252 struct completion *vfork) 1253 { 1254 int killed; 1255 1256 freezer_do_not_count(); 1257 cgroup_enter_frozen(); 1258 killed = wait_for_completion_killable(vfork); 1259 cgroup_leave_frozen(false); 1260 freezer_count(); 1261 1262 if (killed) { 1263 task_lock(child); 1264 child->vfork_done = NULL; 1265 task_unlock(child); 1266 } 1267 1268 put_task_struct(child); 1269 return killed; 1270 } 1271 1272 /* Please note the differences between mmput and mm_release. 1273 * mmput is called whenever we stop holding onto a mm_struct, 1274 * error success whatever. 1275 * 1276 * mm_release is called after a mm_struct has been removed 1277 * from the current process. 1278 * 1279 * This difference is important for error handling, when we 1280 * only half set up a mm_struct for a new process and need to restore 1281 * the old one. Because we mmput the new mm_struct before 1282 * restoring the old one. . . 1283 * Eric Biederman 10 January 1998 1284 */ 1285 static void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1286 { 1287 uprobe_free_utask(tsk); 1288 1289 /* Get rid of any cached register state */ 1290 deactivate_mm(tsk, mm); 1291 1292 /* 1293 * Signal userspace if we're not exiting with a core dump 1294 * because we want to leave the value intact for debugging 1295 * purposes. 1296 */ 1297 if (tsk->clear_child_tid) { 1298 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1299 atomic_read(&mm->mm_users) > 1) { 1300 /* 1301 * We don't check the error code - if userspace has 1302 * not set up a proper pointer then tough luck. 1303 */ 1304 put_user(0, tsk->clear_child_tid); 1305 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1306 1, NULL, NULL, 0, 0); 1307 } 1308 tsk->clear_child_tid = NULL; 1309 } 1310 1311 /* 1312 * All done, finally we can wake up parent and return this mm to him. 1313 * Also kthread_stop() uses this completion for synchronization. 1314 */ 1315 if (tsk->vfork_done) 1316 complete_vfork_done(tsk); 1317 } 1318 1319 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1320 { 1321 futex_exit_release(tsk); 1322 mm_release(tsk, mm); 1323 } 1324 1325 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm) 1326 { 1327 futex_exec_release(tsk); 1328 mm_release(tsk, mm); 1329 } 1330 1331 /** 1332 * dup_mm() - duplicates an existing mm structure 1333 * @tsk: the task_struct with which the new mm will be associated. 1334 * @oldmm: the mm to duplicate. 1335 * 1336 * Allocates a new mm structure and duplicates the provided @oldmm structure 1337 * content into it. 1338 * 1339 * Return: the duplicated mm or NULL on failure. 1340 */ 1341 static struct mm_struct *dup_mm(struct task_struct *tsk, 1342 struct mm_struct *oldmm) 1343 { 1344 struct mm_struct *mm; 1345 int err; 1346 1347 mm = allocate_mm(); 1348 if (!mm) 1349 goto fail_nomem; 1350 1351 memcpy(mm, oldmm, sizeof(*mm)); 1352 1353 if (!mm_init(mm, tsk, mm->user_ns)) 1354 goto fail_nomem; 1355 1356 err = dup_mmap(mm, oldmm); 1357 if (err) 1358 goto free_pt; 1359 1360 mm->hiwater_rss = get_mm_rss(mm); 1361 mm->hiwater_vm = mm->total_vm; 1362 1363 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1364 goto free_pt; 1365 1366 return mm; 1367 1368 free_pt: 1369 /* don't put binfmt in mmput, we haven't got module yet */ 1370 mm->binfmt = NULL; 1371 mm_init_owner(mm, NULL); 1372 mmput(mm); 1373 1374 fail_nomem: 1375 return NULL; 1376 } 1377 1378 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1379 { 1380 struct mm_struct *mm, *oldmm; 1381 int retval; 1382 1383 tsk->min_flt = tsk->maj_flt = 0; 1384 tsk->nvcsw = tsk->nivcsw = 0; 1385 #ifdef CONFIG_DETECT_HUNG_TASK 1386 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1387 tsk->last_switch_time = 0; 1388 #endif 1389 1390 tsk->mm = NULL; 1391 tsk->active_mm = NULL; 1392 1393 /* 1394 * Are we cloning a kernel thread? 1395 * 1396 * We need to steal a active VM for that.. 1397 */ 1398 oldmm = current->mm; 1399 if (!oldmm) 1400 return 0; 1401 1402 /* initialize the new vmacache entries */ 1403 vmacache_flush(tsk); 1404 1405 if (clone_flags & CLONE_VM) { 1406 mmget(oldmm); 1407 mm = oldmm; 1408 goto good_mm; 1409 } 1410 1411 retval = -ENOMEM; 1412 mm = dup_mm(tsk, current->mm); 1413 if (!mm) 1414 goto fail_nomem; 1415 1416 good_mm: 1417 tsk->mm = mm; 1418 tsk->active_mm = mm; 1419 return 0; 1420 1421 fail_nomem: 1422 return retval; 1423 } 1424 1425 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1426 { 1427 struct fs_struct *fs = current->fs; 1428 if (clone_flags & CLONE_FS) { 1429 /* tsk->fs is already what we want */ 1430 spin_lock(&fs->lock); 1431 if (fs->in_exec) { 1432 spin_unlock(&fs->lock); 1433 return -EAGAIN; 1434 } 1435 fs->users++; 1436 spin_unlock(&fs->lock); 1437 return 0; 1438 } 1439 tsk->fs = copy_fs_struct(fs); 1440 if (!tsk->fs) 1441 return -ENOMEM; 1442 return 0; 1443 } 1444 1445 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1446 { 1447 struct files_struct *oldf, *newf; 1448 int error = 0; 1449 1450 /* 1451 * A background process may not have any files ... 1452 */ 1453 oldf = current->files; 1454 if (!oldf) 1455 goto out; 1456 1457 if (clone_flags & CLONE_FILES) { 1458 atomic_inc(&oldf->count); 1459 goto out; 1460 } 1461 1462 newf = dup_fd(oldf, &error); 1463 if (!newf) 1464 goto out; 1465 1466 tsk->files = newf; 1467 error = 0; 1468 out: 1469 return error; 1470 } 1471 1472 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1473 { 1474 #ifdef CONFIG_BLOCK 1475 struct io_context *ioc = current->io_context; 1476 struct io_context *new_ioc; 1477 1478 if (!ioc) 1479 return 0; 1480 /* 1481 * Share io context with parent, if CLONE_IO is set 1482 */ 1483 if (clone_flags & CLONE_IO) { 1484 ioc_task_link(ioc); 1485 tsk->io_context = ioc; 1486 } else if (ioprio_valid(ioc->ioprio)) { 1487 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1488 if (unlikely(!new_ioc)) 1489 return -ENOMEM; 1490 1491 new_ioc->ioprio = ioc->ioprio; 1492 put_io_context(new_ioc); 1493 } 1494 #endif 1495 return 0; 1496 } 1497 1498 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1499 { 1500 struct sighand_struct *sig; 1501 1502 if (clone_flags & CLONE_SIGHAND) { 1503 refcount_inc(¤t->sighand->count); 1504 return 0; 1505 } 1506 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1507 rcu_assign_pointer(tsk->sighand, sig); 1508 if (!sig) 1509 return -ENOMEM; 1510 1511 refcount_set(&sig->count, 1); 1512 spin_lock_irq(¤t->sighand->siglock); 1513 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1514 spin_unlock_irq(¤t->sighand->siglock); 1515 1516 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */ 1517 if (clone_flags & CLONE_CLEAR_SIGHAND) 1518 flush_signal_handlers(tsk, 0); 1519 1520 return 0; 1521 } 1522 1523 void __cleanup_sighand(struct sighand_struct *sighand) 1524 { 1525 if (refcount_dec_and_test(&sighand->count)) { 1526 signalfd_cleanup(sighand); 1527 /* 1528 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1529 * without an RCU grace period, see __lock_task_sighand(). 1530 */ 1531 kmem_cache_free(sighand_cachep, sighand); 1532 } 1533 } 1534 1535 /* 1536 * Initialize POSIX timer handling for a thread group. 1537 */ 1538 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1539 { 1540 struct posix_cputimers *pct = &sig->posix_cputimers; 1541 unsigned long cpu_limit; 1542 1543 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1544 posix_cputimers_group_init(pct, cpu_limit); 1545 } 1546 1547 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1548 { 1549 struct signal_struct *sig; 1550 1551 if (clone_flags & CLONE_THREAD) 1552 return 0; 1553 1554 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1555 tsk->signal = sig; 1556 if (!sig) 1557 return -ENOMEM; 1558 1559 sig->nr_threads = 1; 1560 atomic_set(&sig->live, 1); 1561 refcount_set(&sig->sigcnt, 1); 1562 1563 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1564 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1565 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1566 1567 init_waitqueue_head(&sig->wait_chldexit); 1568 sig->curr_target = tsk; 1569 init_sigpending(&sig->shared_pending); 1570 INIT_HLIST_HEAD(&sig->multiprocess); 1571 seqlock_init(&sig->stats_lock); 1572 prev_cputime_init(&sig->prev_cputime); 1573 1574 #ifdef CONFIG_POSIX_TIMERS 1575 INIT_LIST_HEAD(&sig->posix_timers); 1576 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1577 sig->real_timer.function = it_real_fn; 1578 #endif 1579 1580 task_lock(current->group_leader); 1581 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1582 task_unlock(current->group_leader); 1583 1584 posix_cpu_timers_init_group(sig); 1585 1586 tty_audit_fork(sig); 1587 sched_autogroup_fork(sig); 1588 1589 sig->oom_score_adj = current->signal->oom_score_adj; 1590 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1591 1592 mutex_init(&sig->cred_guard_mutex); 1593 1594 return 0; 1595 } 1596 1597 static void copy_seccomp(struct task_struct *p) 1598 { 1599 #ifdef CONFIG_SECCOMP 1600 /* 1601 * Must be called with sighand->lock held, which is common to 1602 * all threads in the group. Holding cred_guard_mutex is not 1603 * needed because this new task is not yet running and cannot 1604 * be racing exec. 1605 */ 1606 assert_spin_locked(¤t->sighand->siglock); 1607 1608 /* Ref-count the new filter user, and assign it. */ 1609 get_seccomp_filter(current); 1610 p->seccomp = current->seccomp; 1611 1612 /* 1613 * Explicitly enable no_new_privs here in case it got set 1614 * between the task_struct being duplicated and holding the 1615 * sighand lock. The seccomp state and nnp must be in sync. 1616 */ 1617 if (task_no_new_privs(current)) 1618 task_set_no_new_privs(p); 1619 1620 /* 1621 * If the parent gained a seccomp mode after copying thread 1622 * flags and between before we held the sighand lock, we have 1623 * to manually enable the seccomp thread flag here. 1624 */ 1625 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1626 set_tsk_thread_flag(p, TIF_SECCOMP); 1627 #endif 1628 } 1629 1630 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1631 { 1632 current->clear_child_tid = tidptr; 1633 1634 return task_pid_vnr(current); 1635 } 1636 1637 static void rt_mutex_init_task(struct task_struct *p) 1638 { 1639 raw_spin_lock_init(&p->pi_lock); 1640 #ifdef CONFIG_RT_MUTEXES 1641 p->pi_waiters = RB_ROOT_CACHED; 1642 p->pi_top_task = NULL; 1643 p->pi_blocked_on = NULL; 1644 #endif 1645 } 1646 1647 static inline void init_task_pid_links(struct task_struct *task) 1648 { 1649 enum pid_type type; 1650 1651 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1652 INIT_HLIST_NODE(&task->pid_links[type]); 1653 } 1654 } 1655 1656 static inline void 1657 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1658 { 1659 if (type == PIDTYPE_PID) 1660 task->thread_pid = pid; 1661 else 1662 task->signal->pids[type] = pid; 1663 } 1664 1665 static inline void rcu_copy_process(struct task_struct *p) 1666 { 1667 #ifdef CONFIG_PREEMPT_RCU 1668 p->rcu_read_lock_nesting = 0; 1669 p->rcu_read_unlock_special.s = 0; 1670 p->rcu_blocked_node = NULL; 1671 INIT_LIST_HEAD(&p->rcu_node_entry); 1672 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1673 #ifdef CONFIG_TASKS_RCU 1674 p->rcu_tasks_holdout = false; 1675 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1676 p->rcu_tasks_idle_cpu = -1; 1677 #endif /* #ifdef CONFIG_TASKS_RCU */ 1678 } 1679 1680 struct pid *pidfd_pid(const struct file *file) 1681 { 1682 if (file->f_op == &pidfd_fops) 1683 return file->private_data; 1684 1685 return ERR_PTR(-EBADF); 1686 } 1687 1688 static int pidfd_release(struct inode *inode, struct file *file) 1689 { 1690 struct pid *pid = file->private_data; 1691 1692 file->private_data = NULL; 1693 put_pid(pid); 1694 return 0; 1695 } 1696 1697 #ifdef CONFIG_PROC_FS 1698 /** 1699 * pidfd_show_fdinfo - print information about a pidfd 1700 * @m: proc fdinfo file 1701 * @f: file referencing a pidfd 1702 * 1703 * Pid: 1704 * This function will print the pid that a given pidfd refers to in the 1705 * pid namespace of the procfs instance. 1706 * If the pid namespace of the process is not a descendant of the pid 1707 * namespace of the procfs instance 0 will be shown as its pid. This is 1708 * similar to calling getppid() on a process whose parent is outside of 1709 * its pid namespace. 1710 * 1711 * NSpid: 1712 * If pid namespaces are supported then this function will also print 1713 * the pid of a given pidfd refers to for all descendant pid namespaces 1714 * starting from the current pid namespace of the instance, i.e. the 1715 * Pid field and the first entry in the NSpid field will be identical. 1716 * If the pid namespace of the process is not a descendant of the pid 1717 * namespace of the procfs instance 0 will be shown as its first NSpid 1718 * entry and no others will be shown. 1719 * Note that this differs from the Pid and NSpid fields in 1720 * /proc/<pid>/status where Pid and NSpid are always shown relative to 1721 * the pid namespace of the procfs instance. The difference becomes 1722 * obvious when sending around a pidfd between pid namespaces from a 1723 * different branch of the tree, i.e. where no ancestoral relation is 1724 * present between the pid namespaces: 1725 * - create two new pid namespaces ns1 and ns2 in the initial pid 1726 * namespace (also take care to create new mount namespaces in the 1727 * new pid namespace and mount procfs) 1728 * - create a process with a pidfd in ns1 1729 * - send pidfd from ns1 to ns2 1730 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid 1731 * have exactly one entry, which is 0 1732 */ 1733 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) 1734 { 1735 struct pid *pid = f->private_data; 1736 struct pid_namespace *ns; 1737 pid_t nr = -1; 1738 1739 if (likely(pid_has_task(pid, PIDTYPE_PID))) { 1740 ns = proc_pid_ns(file_inode(m->file)); 1741 nr = pid_nr_ns(pid, ns); 1742 } 1743 1744 seq_put_decimal_ll(m, "Pid:\t", nr); 1745 1746 #ifdef CONFIG_PID_NS 1747 seq_put_decimal_ll(m, "\nNSpid:\t", nr); 1748 if (nr > 0) { 1749 int i; 1750 1751 /* If nr is non-zero it means that 'pid' is valid and that 1752 * ns, i.e. the pid namespace associated with the procfs 1753 * instance, is in the pid namespace hierarchy of pid. 1754 * Start at one below the already printed level. 1755 */ 1756 for (i = ns->level + 1; i <= pid->level; i++) 1757 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr); 1758 } 1759 #endif 1760 seq_putc(m, '\n'); 1761 } 1762 #endif 1763 1764 /* 1765 * Poll support for process exit notification. 1766 */ 1767 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) 1768 { 1769 struct task_struct *task; 1770 struct pid *pid = file->private_data; 1771 __poll_t poll_flags = 0; 1772 1773 poll_wait(file, &pid->wait_pidfd, pts); 1774 1775 rcu_read_lock(); 1776 task = pid_task(pid, PIDTYPE_PID); 1777 /* 1778 * Inform pollers only when the whole thread group exits. 1779 * If the thread group leader exits before all other threads in the 1780 * group, then poll(2) should block, similar to the wait(2) family. 1781 */ 1782 if (!task || (task->exit_state && thread_group_empty(task))) 1783 poll_flags = EPOLLIN | EPOLLRDNORM; 1784 rcu_read_unlock(); 1785 1786 return poll_flags; 1787 } 1788 1789 const struct file_operations pidfd_fops = { 1790 .release = pidfd_release, 1791 .poll = pidfd_poll, 1792 #ifdef CONFIG_PROC_FS 1793 .show_fdinfo = pidfd_show_fdinfo, 1794 #endif 1795 }; 1796 1797 static void __delayed_free_task(struct rcu_head *rhp) 1798 { 1799 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 1800 1801 free_task(tsk); 1802 } 1803 1804 static __always_inline void delayed_free_task(struct task_struct *tsk) 1805 { 1806 if (IS_ENABLED(CONFIG_MEMCG)) 1807 call_rcu(&tsk->rcu, __delayed_free_task); 1808 else 1809 free_task(tsk); 1810 } 1811 1812 /* 1813 * This creates a new process as a copy of the old one, 1814 * but does not actually start it yet. 1815 * 1816 * It copies the registers, and all the appropriate 1817 * parts of the process environment (as per the clone 1818 * flags). The actual kick-off is left to the caller. 1819 */ 1820 static __latent_entropy struct task_struct *copy_process( 1821 struct pid *pid, 1822 int trace, 1823 int node, 1824 struct kernel_clone_args *args) 1825 { 1826 int pidfd = -1, retval; 1827 struct task_struct *p; 1828 struct multiprocess_signals delayed; 1829 struct file *pidfile = NULL; 1830 u64 clone_flags = args->flags; 1831 1832 /* 1833 * Don't allow sharing the root directory with processes in a different 1834 * namespace 1835 */ 1836 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1837 return ERR_PTR(-EINVAL); 1838 1839 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1840 return ERR_PTR(-EINVAL); 1841 1842 /* 1843 * Thread groups must share signals as well, and detached threads 1844 * can only be started up within the thread group. 1845 */ 1846 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1847 return ERR_PTR(-EINVAL); 1848 1849 /* 1850 * Shared signal handlers imply shared VM. By way of the above, 1851 * thread groups also imply shared VM. Blocking this case allows 1852 * for various simplifications in other code. 1853 */ 1854 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1855 return ERR_PTR(-EINVAL); 1856 1857 /* 1858 * Siblings of global init remain as zombies on exit since they are 1859 * not reaped by their parent (swapper). To solve this and to avoid 1860 * multi-rooted process trees, prevent global and container-inits 1861 * from creating siblings. 1862 */ 1863 if ((clone_flags & CLONE_PARENT) && 1864 current->signal->flags & SIGNAL_UNKILLABLE) 1865 return ERR_PTR(-EINVAL); 1866 1867 /* 1868 * If the new process will be in a different pid or user namespace 1869 * do not allow it to share a thread group with the forking task. 1870 */ 1871 if (clone_flags & CLONE_THREAD) { 1872 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1873 (task_active_pid_ns(current) != 1874 current->nsproxy->pid_ns_for_children)) 1875 return ERR_PTR(-EINVAL); 1876 } 1877 1878 if (clone_flags & CLONE_PIDFD) { 1879 /* 1880 * - CLONE_DETACHED is blocked so that we can potentially 1881 * reuse it later for CLONE_PIDFD. 1882 * - CLONE_THREAD is blocked until someone really needs it. 1883 */ 1884 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD)) 1885 return ERR_PTR(-EINVAL); 1886 } 1887 1888 /* 1889 * Force any signals received before this point to be delivered 1890 * before the fork happens. Collect up signals sent to multiple 1891 * processes that happen during the fork and delay them so that 1892 * they appear to happen after the fork. 1893 */ 1894 sigemptyset(&delayed.signal); 1895 INIT_HLIST_NODE(&delayed.node); 1896 1897 spin_lock_irq(¤t->sighand->siglock); 1898 if (!(clone_flags & CLONE_THREAD)) 1899 hlist_add_head(&delayed.node, ¤t->signal->multiprocess); 1900 recalc_sigpending(); 1901 spin_unlock_irq(¤t->sighand->siglock); 1902 retval = -ERESTARTNOINTR; 1903 if (signal_pending(current)) 1904 goto fork_out; 1905 1906 retval = -ENOMEM; 1907 p = dup_task_struct(current, node); 1908 if (!p) 1909 goto fork_out; 1910 1911 /* 1912 * This _must_ happen before we call free_task(), i.e. before we jump 1913 * to any of the bad_fork_* labels. This is to avoid freeing 1914 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1915 * kernel threads (PF_KTHREAD). 1916 */ 1917 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL; 1918 /* 1919 * Clear TID on mm_release()? 1920 */ 1921 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL; 1922 1923 ftrace_graph_init_task(p); 1924 1925 rt_mutex_init_task(p); 1926 1927 #ifdef CONFIG_PROVE_LOCKING 1928 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1929 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1930 #endif 1931 retval = -EAGAIN; 1932 if (atomic_read(&p->real_cred->user->processes) >= 1933 task_rlimit(p, RLIMIT_NPROC)) { 1934 if (p->real_cred->user != INIT_USER && 1935 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1936 goto bad_fork_free; 1937 } 1938 current->flags &= ~PF_NPROC_EXCEEDED; 1939 1940 retval = copy_creds(p, clone_flags); 1941 if (retval < 0) 1942 goto bad_fork_free; 1943 1944 /* 1945 * If multiple threads are within copy_process(), then this check 1946 * triggers too late. This doesn't hurt, the check is only there 1947 * to stop root fork bombs. 1948 */ 1949 retval = -EAGAIN; 1950 if (nr_threads >= max_threads) 1951 goto bad_fork_cleanup_count; 1952 1953 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1954 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1955 p->flags |= PF_FORKNOEXEC; 1956 INIT_LIST_HEAD(&p->children); 1957 INIT_LIST_HEAD(&p->sibling); 1958 rcu_copy_process(p); 1959 p->vfork_done = NULL; 1960 spin_lock_init(&p->alloc_lock); 1961 1962 init_sigpending(&p->pending); 1963 1964 p->utime = p->stime = p->gtime = 0; 1965 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1966 p->utimescaled = p->stimescaled = 0; 1967 #endif 1968 prev_cputime_init(&p->prev_cputime); 1969 1970 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1971 seqcount_init(&p->vtime.seqcount); 1972 p->vtime.starttime = 0; 1973 p->vtime.state = VTIME_INACTIVE; 1974 #endif 1975 1976 #if defined(SPLIT_RSS_COUNTING) 1977 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1978 #endif 1979 1980 p->default_timer_slack_ns = current->timer_slack_ns; 1981 1982 #ifdef CONFIG_PSI 1983 p->psi_flags = 0; 1984 #endif 1985 1986 task_io_accounting_init(&p->ioac); 1987 acct_clear_integrals(p); 1988 1989 posix_cputimers_init(&p->posix_cputimers); 1990 1991 p->io_context = NULL; 1992 audit_set_context(p, NULL); 1993 cgroup_fork(p); 1994 #ifdef CONFIG_NUMA 1995 p->mempolicy = mpol_dup(p->mempolicy); 1996 if (IS_ERR(p->mempolicy)) { 1997 retval = PTR_ERR(p->mempolicy); 1998 p->mempolicy = NULL; 1999 goto bad_fork_cleanup_threadgroup_lock; 2000 } 2001 #endif 2002 #ifdef CONFIG_CPUSETS 2003 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 2004 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 2005 seqcount_init(&p->mems_allowed_seq); 2006 #endif 2007 #ifdef CONFIG_TRACE_IRQFLAGS 2008 p->irq_events = 0; 2009 p->hardirqs_enabled = 0; 2010 p->hardirq_enable_ip = 0; 2011 p->hardirq_enable_event = 0; 2012 p->hardirq_disable_ip = _THIS_IP_; 2013 p->hardirq_disable_event = 0; 2014 p->softirqs_enabled = 1; 2015 p->softirq_enable_ip = _THIS_IP_; 2016 p->softirq_enable_event = 0; 2017 p->softirq_disable_ip = 0; 2018 p->softirq_disable_event = 0; 2019 p->hardirq_context = 0; 2020 p->softirq_context = 0; 2021 #endif 2022 2023 p->pagefault_disabled = 0; 2024 2025 #ifdef CONFIG_LOCKDEP 2026 lockdep_init_task(p); 2027 #endif 2028 2029 #ifdef CONFIG_DEBUG_MUTEXES 2030 p->blocked_on = NULL; /* not blocked yet */ 2031 #endif 2032 #ifdef CONFIG_BCACHE 2033 p->sequential_io = 0; 2034 p->sequential_io_avg = 0; 2035 #endif 2036 2037 /* Perform scheduler related setup. Assign this task to a CPU. */ 2038 retval = sched_fork(clone_flags, p); 2039 if (retval) 2040 goto bad_fork_cleanup_policy; 2041 2042 retval = perf_event_init_task(p); 2043 if (retval) 2044 goto bad_fork_cleanup_policy; 2045 retval = audit_alloc(p); 2046 if (retval) 2047 goto bad_fork_cleanup_perf; 2048 /* copy all the process information */ 2049 shm_init_task(p); 2050 retval = security_task_alloc(p, clone_flags); 2051 if (retval) 2052 goto bad_fork_cleanup_audit; 2053 retval = copy_semundo(clone_flags, p); 2054 if (retval) 2055 goto bad_fork_cleanup_security; 2056 retval = copy_files(clone_flags, p); 2057 if (retval) 2058 goto bad_fork_cleanup_semundo; 2059 retval = copy_fs(clone_flags, p); 2060 if (retval) 2061 goto bad_fork_cleanup_files; 2062 retval = copy_sighand(clone_flags, p); 2063 if (retval) 2064 goto bad_fork_cleanup_fs; 2065 retval = copy_signal(clone_flags, p); 2066 if (retval) 2067 goto bad_fork_cleanup_sighand; 2068 retval = copy_mm(clone_flags, p); 2069 if (retval) 2070 goto bad_fork_cleanup_signal; 2071 retval = copy_namespaces(clone_flags, p); 2072 if (retval) 2073 goto bad_fork_cleanup_mm; 2074 retval = copy_io(clone_flags, p); 2075 if (retval) 2076 goto bad_fork_cleanup_namespaces; 2077 retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p, 2078 args->tls); 2079 if (retval) 2080 goto bad_fork_cleanup_io; 2081 2082 stackleak_task_init(p); 2083 2084 if (pid != &init_struct_pid) { 2085 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid, 2086 args->set_tid_size); 2087 if (IS_ERR(pid)) { 2088 retval = PTR_ERR(pid); 2089 goto bad_fork_cleanup_thread; 2090 } 2091 } 2092 2093 /* 2094 * This has to happen after we've potentially unshared the file 2095 * descriptor table (so that the pidfd doesn't leak into the child 2096 * if the fd table isn't shared). 2097 */ 2098 if (clone_flags & CLONE_PIDFD) { 2099 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC); 2100 if (retval < 0) 2101 goto bad_fork_free_pid; 2102 2103 pidfd = retval; 2104 2105 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid, 2106 O_RDWR | O_CLOEXEC); 2107 if (IS_ERR(pidfile)) { 2108 put_unused_fd(pidfd); 2109 retval = PTR_ERR(pidfile); 2110 goto bad_fork_free_pid; 2111 } 2112 get_pid(pid); /* held by pidfile now */ 2113 2114 retval = put_user(pidfd, args->pidfd); 2115 if (retval) 2116 goto bad_fork_put_pidfd; 2117 } 2118 2119 #ifdef CONFIG_BLOCK 2120 p->plug = NULL; 2121 #endif 2122 futex_init_task(p); 2123 2124 /* 2125 * sigaltstack should be cleared when sharing the same VM 2126 */ 2127 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 2128 sas_ss_reset(p); 2129 2130 /* 2131 * Syscall tracing and stepping should be turned off in the 2132 * child regardless of CLONE_PTRACE. 2133 */ 2134 user_disable_single_step(p); 2135 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 2136 #ifdef TIF_SYSCALL_EMU 2137 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 2138 #endif 2139 clear_tsk_latency_tracing(p); 2140 2141 /* ok, now we should be set up.. */ 2142 p->pid = pid_nr(pid); 2143 if (clone_flags & CLONE_THREAD) { 2144 p->exit_signal = -1; 2145 p->group_leader = current->group_leader; 2146 p->tgid = current->tgid; 2147 } else { 2148 if (clone_flags & CLONE_PARENT) 2149 p->exit_signal = current->group_leader->exit_signal; 2150 else 2151 p->exit_signal = args->exit_signal; 2152 p->group_leader = p; 2153 p->tgid = p->pid; 2154 } 2155 2156 p->nr_dirtied = 0; 2157 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 2158 p->dirty_paused_when = 0; 2159 2160 p->pdeath_signal = 0; 2161 INIT_LIST_HEAD(&p->thread_group); 2162 p->task_works = NULL; 2163 2164 cgroup_threadgroup_change_begin(current); 2165 /* 2166 * Ensure that the cgroup subsystem policies allow the new process to be 2167 * forked. It should be noted the the new process's css_set can be changed 2168 * between here and cgroup_post_fork() if an organisation operation is in 2169 * progress. 2170 */ 2171 retval = cgroup_can_fork(p); 2172 if (retval) 2173 goto bad_fork_cgroup_threadgroup_change_end; 2174 2175 /* 2176 * From this point on we must avoid any synchronous user-space 2177 * communication until we take the tasklist-lock. In particular, we do 2178 * not want user-space to be able to predict the process start-time by 2179 * stalling fork(2) after we recorded the start_time but before it is 2180 * visible to the system. 2181 */ 2182 2183 p->start_time = ktime_get_ns(); 2184 p->real_start_time = ktime_get_boottime_ns(); 2185 2186 /* 2187 * Make it visible to the rest of the system, but dont wake it up yet. 2188 * Need tasklist lock for parent etc handling! 2189 */ 2190 write_lock_irq(&tasklist_lock); 2191 2192 /* CLONE_PARENT re-uses the old parent */ 2193 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 2194 p->real_parent = current->real_parent; 2195 p->parent_exec_id = current->parent_exec_id; 2196 } else { 2197 p->real_parent = current; 2198 p->parent_exec_id = current->self_exec_id; 2199 } 2200 2201 klp_copy_process(p); 2202 2203 spin_lock(¤t->sighand->siglock); 2204 2205 /* 2206 * Copy seccomp details explicitly here, in case they were changed 2207 * before holding sighand lock. 2208 */ 2209 copy_seccomp(p); 2210 2211 rseq_fork(p, clone_flags); 2212 2213 /* Don't start children in a dying pid namespace */ 2214 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 2215 retval = -ENOMEM; 2216 goto bad_fork_cancel_cgroup; 2217 } 2218 2219 /* Let kill terminate clone/fork in the middle */ 2220 if (fatal_signal_pending(current)) { 2221 retval = -EINTR; 2222 goto bad_fork_cancel_cgroup; 2223 } 2224 2225 /* past the last point of failure */ 2226 if (pidfile) 2227 fd_install(pidfd, pidfile); 2228 2229 init_task_pid_links(p); 2230 if (likely(p->pid)) { 2231 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 2232 2233 init_task_pid(p, PIDTYPE_PID, pid); 2234 if (thread_group_leader(p)) { 2235 init_task_pid(p, PIDTYPE_TGID, pid); 2236 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 2237 init_task_pid(p, PIDTYPE_SID, task_session(current)); 2238 2239 if (is_child_reaper(pid)) { 2240 ns_of_pid(pid)->child_reaper = p; 2241 p->signal->flags |= SIGNAL_UNKILLABLE; 2242 } 2243 p->signal->shared_pending.signal = delayed.signal; 2244 p->signal->tty = tty_kref_get(current->signal->tty); 2245 /* 2246 * Inherit has_child_subreaper flag under the same 2247 * tasklist_lock with adding child to the process tree 2248 * for propagate_has_child_subreaper optimization. 2249 */ 2250 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 2251 p->real_parent->signal->is_child_subreaper; 2252 list_add_tail(&p->sibling, &p->real_parent->children); 2253 list_add_tail_rcu(&p->tasks, &init_task.tasks); 2254 attach_pid(p, PIDTYPE_TGID); 2255 attach_pid(p, PIDTYPE_PGID); 2256 attach_pid(p, PIDTYPE_SID); 2257 __this_cpu_inc(process_counts); 2258 } else { 2259 current->signal->nr_threads++; 2260 atomic_inc(¤t->signal->live); 2261 refcount_inc(¤t->signal->sigcnt); 2262 task_join_group_stop(p); 2263 list_add_tail_rcu(&p->thread_group, 2264 &p->group_leader->thread_group); 2265 list_add_tail_rcu(&p->thread_node, 2266 &p->signal->thread_head); 2267 } 2268 attach_pid(p, PIDTYPE_PID); 2269 nr_threads++; 2270 } 2271 total_forks++; 2272 hlist_del_init(&delayed.node); 2273 spin_unlock(¤t->sighand->siglock); 2274 syscall_tracepoint_update(p); 2275 write_unlock_irq(&tasklist_lock); 2276 2277 proc_fork_connector(p); 2278 cgroup_post_fork(p); 2279 cgroup_threadgroup_change_end(current); 2280 perf_event_fork(p); 2281 2282 trace_task_newtask(p, clone_flags); 2283 uprobe_copy_process(p, clone_flags); 2284 2285 return p; 2286 2287 bad_fork_cancel_cgroup: 2288 spin_unlock(¤t->sighand->siglock); 2289 write_unlock_irq(&tasklist_lock); 2290 cgroup_cancel_fork(p); 2291 bad_fork_cgroup_threadgroup_change_end: 2292 cgroup_threadgroup_change_end(current); 2293 bad_fork_put_pidfd: 2294 if (clone_flags & CLONE_PIDFD) { 2295 fput(pidfile); 2296 put_unused_fd(pidfd); 2297 } 2298 bad_fork_free_pid: 2299 if (pid != &init_struct_pid) 2300 free_pid(pid); 2301 bad_fork_cleanup_thread: 2302 exit_thread(p); 2303 bad_fork_cleanup_io: 2304 if (p->io_context) 2305 exit_io_context(p); 2306 bad_fork_cleanup_namespaces: 2307 exit_task_namespaces(p); 2308 bad_fork_cleanup_mm: 2309 if (p->mm) { 2310 mm_clear_owner(p->mm, p); 2311 mmput(p->mm); 2312 } 2313 bad_fork_cleanup_signal: 2314 if (!(clone_flags & CLONE_THREAD)) 2315 free_signal_struct(p->signal); 2316 bad_fork_cleanup_sighand: 2317 __cleanup_sighand(p->sighand); 2318 bad_fork_cleanup_fs: 2319 exit_fs(p); /* blocking */ 2320 bad_fork_cleanup_files: 2321 exit_files(p); /* blocking */ 2322 bad_fork_cleanup_semundo: 2323 exit_sem(p); 2324 bad_fork_cleanup_security: 2325 security_task_free(p); 2326 bad_fork_cleanup_audit: 2327 audit_free(p); 2328 bad_fork_cleanup_perf: 2329 perf_event_free_task(p); 2330 bad_fork_cleanup_policy: 2331 lockdep_free_task(p); 2332 #ifdef CONFIG_NUMA 2333 mpol_put(p->mempolicy); 2334 bad_fork_cleanup_threadgroup_lock: 2335 #endif 2336 delayacct_tsk_free(p); 2337 bad_fork_cleanup_count: 2338 atomic_dec(&p->cred->user->processes); 2339 exit_creds(p); 2340 bad_fork_free: 2341 p->state = TASK_DEAD; 2342 put_task_stack(p); 2343 delayed_free_task(p); 2344 fork_out: 2345 spin_lock_irq(¤t->sighand->siglock); 2346 hlist_del_init(&delayed.node); 2347 spin_unlock_irq(¤t->sighand->siglock); 2348 return ERR_PTR(retval); 2349 } 2350 2351 static inline void init_idle_pids(struct task_struct *idle) 2352 { 2353 enum pid_type type; 2354 2355 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2356 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */ 2357 init_task_pid(idle, type, &init_struct_pid); 2358 } 2359 } 2360 2361 struct task_struct *fork_idle(int cpu) 2362 { 2363 struct task_struct *task; 2364 struct kernel_clone_args args = { 2365 .flags = CLONE_VM, 2366 }; 2367 2368 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args); 2369 if (!IS_ERR(task)) { 2370 init_idle_pids(task); 2371 init_idle(task, cpu); 2372 } 2373 2374 return task; 2375 } 2376 2377 struct mm_struct *copy_init_mm(void) 2378 { 2379 return dup_mm(NULL, &init_mm); 2380 } 2381 2382 /* 2383 * Ok, this is the main fork-routine. 2384 * 2385 * It copies the process, and if successful kick-starts 2386 * it and waits for it to finish using the VM if required. 2387 * 2388 * args->exit_signal is expected to be checked for sanity by the caller. 2389 */ 2390 long _do_fork(struct kernel_clone_args *args) 2391 { 2392 u64 clone_flags = args->flags; 2393 struct completion vfork; 2394 struct pid *pid; 2395 struct task_struct *p; 2396 int trace = 0; 2397 long nr; 2398 2399 /* 2400 * Determine whether and which event to report to ptracer. When 2401 * called from kernel_thread or CLONE_UNTRACED is explicitly 2402 * requested, no event is reported; otherwise, report if the event 2403 * for the type of forking is enabled. 2404 */ 2405 if (!(clone_flags & CLONE_UNTRACED)) { 2406 if (clone_flags & CLONE_VFORK) 2407 trace = PTRACE_EVENT_VFORK; 2408 else if (args->exit_signal != SIGCHLD) 2409 trace = PTRACE_EVENT_CLONE; 2410 else 2411 trace = PTRACE_EVENT_FORK; 2412 2413 if (likely(!ptrace_event_enabled(current, trace))) 2414 trace = 0; 2415 } 2416 2417 p = copy_process(NULL, trace, NUMA_NO_NODE, args); 2418 add_latent_entropy(); 2419 2420 if (IS_ERR(p)) 2421 return PTR_ERR(p); 2422 2423 /* 2424 * Do this prior waking up the new thread - the thread pointer 2425 * might get invalid after that point, if the thread exits quickly. 2426 */ 2427 trace_sched_process_fork(current, p); 2428 2429 pid = get_task_pid(p, PIDTYPE_PID); 2430 nr = pid_vnr(pid); 2431 2432 if (clone_flags & CLONE_PARENT_SETTID) 2433 put_user(nr, args->parent_tid); 2434 2435 if (clone_flags & CLONE_VFORK) { 2436 p->vfork_done = &vfork; 2437 init_completion(&vfork); 2438 get_task_struct(p); 2439 } 2440 2441 wake_up_new_task(p); 2442 2443 /* forking complete and child started to run, tell ptracer */ 2444 if (unlikely(trace)) 2445 ptrace_event_pid(trace, pid); 2446 2447 if (clone_flags & CLONE_VFORK) { 2448 if (!wait_for_vfork_done(p, &vfork)) 2449 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2450 } 2451 2452 put_pid(pid); 2453 return nr; 2454 } 2455 2456 bool legacy_clone_args_valid(const struct kernel_clone_args *kargs) 2457 { 2458 /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */ 2459 if ((kargs->flags & CLONE_PIDFD) && 2460 (kargs->flags & CLONE_PARENT_SETTID)) 2461 return false; 2462 2463 return true; 2464 } 2465 2466 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2467 /* For compatibility with architectures that call do_fork directly rather than 2468 * using the syscall entry points below. */ 2469 long do_fork(unsigned long clone_flags, 2470 unsigned long stack_start, 2471 unsigned long stack_size, 2472 int __user *parent_tidptr, 2473 int __user *child_tidptr) 2474 { 2475 struct kernel_clone_args args = { 2476 .flags = (clone_flags & ~CSIGNAL), 2477 .pidfd = parent_tidptr, 2478 .child_tid = child_tidptr, 2479 .parent_tid = parent_tidptr, 2480 .exit_signal = (clone_flags & CSIGNAL), 2481 .stack = stack_start, 2482 .stack_size = stack_size, 2483 }; 2484 2485 if (!legacy_clone_args_valid(&args)) 2486 return -EINVAL; 2487 2488 return _do_fork(&args); 2489 } 2490 #endif 2491 2492 /* 2493 * Create a kernel thread. 2494 */ 2495 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2496 { 2497 struct kernel_clone_args args = { 2498 .flags = ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL), 2499 .exit_signal = (flags & CSIGNAL), 2500 .stack = (unsigned long)fn, 2501 .stack_size = (unsigned long)arg, 2502 }; 2503 2504 return _do_fork(&args); 2505 } 2506 2507 #ifdef __ARCH_WANT_SYS_FORK 2508 SYSCALL_DEFINE0(fork) 2509 { 2510 #ifdef CONFIG_MMU 2511 struct kernel_clone_args args = { 2512 .exit_signal = SIGCHLD, 2513 }; 2514 2515 return _do_fork(&args); 2516 #else 2517 /* can not support in nommu mode */ 2518 return -EINVAL; 2519 #endif 2520 } 2521 #endif 2522 2523 #ifdef __ARCH_WANT_SYS_VFORK 2524 SYSCALL_DEFINE0(vfork) 2525 { 2526 struct kernel_clone_args args = { 2527 .flags = CLONE_VFORK | CLONE_VM, 2528 .exit_signal = SIGCHLD, 2529 }; 2530 2531 return _do_fork(&args); 2532 } 2533 #endif 2534 2535 #ifdef __ARCH_WANT_SYS_CLONE 2536 #ifdef CONFIG_CLONE_BACKWARDS 2537 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2538 int __user *, parent_tidptr, 2539 unsigned long, tls, 2540 int __user *, child_tidptr) 2541 #elif defined(CONFIG_CLONE_BACKWARDS2) 2542 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2543 int __user *, parent_tidptr, 2544 int __user *, child_tidptr, 2545 unsigned long, tls) 2546 #elif defined(CONFIG_CLONE_BACKWARDS3) 2547 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2548 int, stack_size, 2549 int __user *, parent_tidptr, 2550 int __user *, child_tidptr, 2551 unsigned long, tls) 2552 #else 2553 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2554 int __user *, parent_tidptr, 2555 int __user *, child_tidptr, 2556 unsigned long, tls) 2557 #endif 2558 { 2559 struct kernel_clone_args args = { 2560 .flags = (clone_flags & ~CSIGNAL), 2561 .pidfd = parent_tidptr, 2562 .child_tid = child_tidptr, 2563 .parent_tid = parent_tidptr, 2564 .exit_signal = (clone_flags & CSIGNAL), 2565 .stack = newsp, 2566 .tls = tls, 2567 }; 2568 2569 if (!legacy_clone_args_valid(&args)) 2570 return -EINVAL; 2571 2572 return _do_fork(&args); 2573 } 2574 #endif 2575 2576 #ifdef __ARCH_WANT_SYS_CLONE3 2577 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, 2578 struct clone_args __user *uargs, 2579 size_t usize) 2580 { 2581 int err; 2582 struct clone_args args; 2583 pid_t *kset_tid = kargs->set_tid; 2584 2585 if (unlikely(usize > PAGE_SIZE)) 2586 return -E2BIG; 2587 if (unlikely(usize < CLONE_ARGS_SIZE_VER0)) 2588 return -EINVAL; 2589 2590 err = copy_struct_from_user(&args, sizeof(args), uargs, usize); 2591 if (err) 2592 return err; 2593 2594 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL)) 2595 return -EINVAL; 2596 2597 if (unlikely(!args.set_tid && args.set_tid_size > 0)) 2598 return -EINVAL; 2599 2600 if (unlikely(args.set_tid && args.set_tid_size == 0)) 2601 return -EINVAL; 2602 2603 /* 2604 * Verify that higher 32bits of exit_signal are unset and that 2605 * it is a valid signal 2606 */ 2607 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) || 2608 !valid_signal(args.exit_signal))) 2609 return -EINVAL; 2610 2611 *kargs = (struct kernel_clone_args){ 2612 .flags = args.flags, 2613 .pidfd = u64_to_user_ptr(args.pidfd), 2614 .child_tid = u64_to_user_ptr(args.child_tid), 2615 .parent_tid = u64_to_user_ptr(args.parent_tid), 2616 .exit_signal = args.exit_signal, 2617 .stack = args.stack, 2618 .stack_size = args.stack_size, 2619 .tls = args.tls, 2620 .set_tid_size = args.set_tid_size, 2621 }; 2622 2623 if (args.set_tid && 2624 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid), 2625 (kargs->set_tid_size * sizeof(pid_t)))) 2626 return -EFAULT; 2627 2628 kargs->set_tid = kset_tid; 2629 2630 return 0; 2631 } 2632 2633 /** 2634 * clone3_stack_valid - check and prepare stack 2635 * @kargs: kernel clone args 2636 * 2637 * Verify that the stack arguments userspace gave us are sane. 2638 * In addition, set the stack direction for userspace since it's easy for us to 2639 * determine. 2640 */ 2641 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs) 2642 { 2643 if (kargs->stack == 0) { 2644 if (kargs->stack_size > 0) 2645 return false; 2646 } else { 2647 if (kargs->stack_size == 0) 2648 return false; 2649 2650 if (!access_ok((void __user *)kargs->stack, kargs->stack_size)) 2651 return false; 2652 2653 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64) 2654 kargs->stack += kargs->stack_size; 2655 #endif 2656 } 2657 2658 return true; 2659 } 2660 2661 static bool clone3_args_valid(struct kernel_clone_args *kargs) 2662 { 2663 /* Verify that no unknown flags are passed along. */ 2664 if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND)) 2665 return false; 2666 2667 /* 2668 * - make the CLONE_DETACHED bit reuseable for clone3 2669 * - make the CSIGNAL bits reuseable for clone3 2670 */ 2671 if (kargs->flags & (CLONE_DETACHED | CSIGNAL)) 2672 return false; 2673 2674 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) == 2675 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) 2676 return false; 2677 2678 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) && 2679 kargs->exit_signal) 2680 return false; 2681 2682 if (!clone3_stack_valid(kargs)) 2683 return false; 2684 2685 return true; 2686 } 2687 2688 /** 2689 * clone3 - create a new process with specific properties 2690 * @uargs: argument structure 2691 * @size: size of @uargs 2692 * 2693 * clone3() is the extensible successor to clone()/clone2(). 2694 * It takes a struct as argument that is versioned by its size. 2695 * 2696 * Return: On success, a positive PID for the child process. 2697 * On error, a negative errno number. 2698 */ 2699 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size) 2700 { 2701 int err; 2702 2703 struct kernel_clone_args kargs; 2704 pid_t set_tid[MAX_PID_NS_LEVEL]; 2705 2706 kargs.set_tid = set_tid; 2707 2708 err = copy_clone_args_from_user(&kargs, uargs, size); 2709 if (err) 2710 return err; 2711 2712 if (!clone3_args_valid(&kargs)) 2713 return -EINVAL; 2714 2715 return _do_fork(&kargs); 2716 } 2717 #endif 2718 2719 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2720 { 2721 struct task_struct *leader, *parent, *child; 2722 int res; 2723 2724 read_lock(&tasklist_lock); 2725 leader = top = top->group_leader; 2726 down: 2727 for_each_thread(leader, parent) { 2728 list_for_each_entry(child, &parent->children, sibling) { 2729 res = visitor(child, data); 2730 if (res) { 2731 if (res < 0) 2732 goto out; 2733 leader = child; 2734 goto down; 2735 } 2736 up: 2737 ; 2738 } 2739 } 2740 2741 if (leader != top) { 2742 child = leader; 2743 parent = child->real_parent; 2744 leader = parent->group_leader; 2745 goto up; 2746 } 2747 out: 2748 read_unlock(&tasklist_lock); 2749 } 2750 2751 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2752 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2753 #endif 2754 2755 static void sighand_ctor(void *data) 2756 { 2757 struct sighand_struct *sighand = data; 2758 2759 spin_lock_init(&sighand->siglock); 2760 init_waitqueue_head(&sighand->signalfd_wqh); 2761 } 2762 2763 void __init proc_caches_init(void) 2764 { 2765 unsigned int mm_size; 2766 2767 sighand_cachep = kmem_cache_create("sighand_cache", 2768 sizeof(struct sighand_struct), 0, 2769 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2770 SLAB_ACCOUNT, sighand_ctor); 2771 signal_cachep = kmem_cache_create("signal_cache", 2772 sizeof(struct signal_struct), 0, 2773 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2774 NULL); 2775 files_cachep = kmem_cache_create("files_cache", 2776 sizeof(struct files_struct), 0, 2777 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2778 NULL); 2779 fs_cachep = kmem_cache_create("fs_cache", 2780 sizeof(struct fs_struct), 0, 2781 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2782 NULL); 2783 2784 /* 2785 * The mm_cpumask is located at the end of mm_struct, and is 2786 * dynamically sized based on the maximum CPU number this system 2787 * can have, taking hotplug into account (nr_cpu_ids). 2788 */ 2789 mm_size = sizeof(struct mm_struct) + cpumask_size(); 2790 2791 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2792 mm_size, ARCH_MIN_MMSTRUCT_ALIGN, 2793 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2794 offsetof(struct mm_struct, saved_auxv), 2795 sizeof_field(struct mm_struct, saved_auxv), 2796 NULL); 2797 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2798 mmap_init(); 2799 nsproxy_cache_init(); 2800 } 2801 2802 /* 2803 * Check constraints on flags passed to the unshare system call. 2804 */ 2805 static int check_unshare_flags(unsigned long unshare_flags) 2806 { 2807 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2808 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2809 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2810 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2811 return -EINVAL; 2812 /* 2813 * Not implemented, but pretend it works if there is nothing 2814 * to unshare. Note that unsharing the address space or the 2815 * signal handlers also need to unshare the signal queues (aka 2816 * CLONE_THREAD). 2817 */ 2818 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2819 if (!thread_group_empty(current)) 2820 return -EINVAL; 2821 } 2822 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2823 if (refcount_read(¤t->sighand->count) > 1) 2824 return -EINVAL; 2825 } 2826 if (unshare_flags & CLONE_VM) { 2827 if (!current_is_single_threaded()) 2828 return -EINVAL; 2829 } 2830 2831 return 0; 2832 } 2833 2834 /* 2835 * Unshare the filesystem structure if it is being shared 2836 */ 2837 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2838 { 2839 struct fs_struct *fs = current->fs; 2840 2841 if (!(unshare_flags & CLONE_FS) || !fs) 2842 return 0; 2843 2844 /* don't need lock here; in the worst case we'll do useless copy */ 2845 if (fs->users == 1) 2846 return 0; 2847 2848 *new_fsp = copy_fs_struct(fs); 2849 if (!*new_fsp) 2850 return -ENOMEM; 2851 2852 return 0; 2853 } 2854 2855 /* 2856 * Unshare file descriptor table if it is being shared 2857 */ 2858 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2859 { 2860 struct files_struct *fd = current->files; 2861 int error = 0; 2862 2863 if ((unshare_flags & CLONE_FILES) && 2864 (fd && atomic_read(&fd->count) > 1)) { 2865 *new_fdp = dup_fd(fd, &error); 2866 if (!*new_fdp) 2867 return error; 2868 } 2869 2870 return 0; 2871 } 2872 2873 /* 2874 * unshare allows a process to 'unshare' part of the process 2875 * context which was originally shared using clone. copy_* 2876 * functions used by do_fork() cannot be used here directly 2877 * because they modify an inactive task_struct that is being 2878 * constructed. Here we are modifying the current, active, 2879 * task_struct. 2880 */ 2881 int ksys_unshare(unsigned long unshare_flags) 2882 { 2883 struct fs_struct *fs, *new_fs = NULL; 2884 struct files_struct *fd, *new_fd = NULL; 2885 struct cred *new_cred = NULL; 2886 struct nsproxy *new_nsproxy = NULL; 2887 int do_sysvsem = 0; 2888 int err; 2889 2890 /* 2891 * If unsharing a user namespace must also unshare the thread group 2892 * and unshare the filesystem root and working directories. 2893 */ 2894 if (unshare_flags & CLONE_NEWUSER) 2895 unshare_flags |= CLONE_THREAD | CLONE_FS; 2896 /* 2897 * If unsharing vm, must also unshare signal handlers. 2898 */ 2899 if (unshare_flags & CLONE_VM) 2900 unshare_flags |= CLONE_SIGHAND; 2901 /* 2902 * If unsharing a signal handlers, must also unshare the signal queues. 2903 */ 2904 if (unshare_flags & CLONE_SIGHAND) 2905 unshare_flags |= CLONE_THREAD; 2906 /* 2907 * If unsharing namespace, must also unshare filesystem information. 2908 */ 2909 if (unshare_flags & CLONE_NEWNS) 2910 unshare_flags |= CLONE_FS; 2911 2912 err = check_unshare_flags(unshare_flags); 2913 if (err) 2914 goto bad_unshare_out; 2915 /* 2916 * CLONE_NEWIPC must also detach from the undolist: after switching 2917 * to a new ipc namespace, the semaphore arrays from the old 2918 * namespace are unreachable. 2919 */ 2920 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2921 do_sysvsem = 1; 2922 err = unshare_fs(unshare_flags, &new_fs); 2923 if (err) 2924 goto bad_unshare_out; 2925 err = unshare_fd(unshare_flags, &new_fd); 2926 if (err) 2927 goto bad_unshare_cleanup_fs; 2928 err = unshare_userns(unshare_flags, &new_cred); 2929 if (err) 2930 goto bad_unshare_cleanup_fd; 2931 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2932 new_cred, new_fs); 2933 if (err) 2934 goto bad_unshare_cleanup_cred; 2935 2936 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2937 if (do_sysvsem) { 2938 /* 2939 * CLONE_SYSVSEM is equivalent to sys_exit(). 2940 */ 2941 exit_sem(current); 2942 } 2943 if (unshare_flags & CLONE_NEWIPC) { 2944 /* Orphan segments in old ns (see sem above). */ 2945 exit_shm(current); 2946 shm_init_task(current); 2947 } 2948 2949 if (new_nsproxy) 2950 switch_task_namespaces(current, new_nsproxy); 2951 2952 task_lock(current); 2953 2954 if (new_fs) { 2955 fs = current->fs; 2956 spin_lock(&fs->lock); 2957 current->fs = new_fs; 2958 if (--fs->users) 2959 new_fs = NULL; 2960 else 2961 new_fs = fs; 2962 spin_unlock(&fs->lock); 2963 } 2964 2965 if (new_fd) { 2966 fd = current->files; 2967 current->files = new_fd; 2968 new_fd = fd; 2969 } 2970 2971 task_unlock(current); 2972 2973 if (new_cred) { 2974 /* Install the new user namespace */ 2975 commit_creds(new_cred); 2976 new_cred = NULL; 2977 } 2978 } 2979 2980 perf_event_namespaces(current); 2981 2982 bad_unshare_cleanup_cred: 2983 if (new_cred) 2984 put_cred(new_cred); 2985 bad_unshare_cleanup_fd: 2986 if (new_fd) 2987 put_files_struct(new_fd); 2988 2989 bad_unshare_cleanup_fs: 2990 if (new_fs) 2991 free_fs_struct(new_fs); 2992 2993 bad_unshare_out: 2994 return err; 2995 } 2996 2997 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2998 { 2999 return ksys_unshare(unshare_flags); 3000 } 3001 3002 /* 3003 * Helper to unshare the files of the current task. 3004 * We don't want to expose copy_files internals to 3005 * the exec layer of the kernel. 3006 */ 3007 3008 int unshare_files(struct files_struct **displaced) 3009 { 3010 struct task_struct *task = current; 3011 struct files_struct *copy = NULL; 3012 int error; 3013 3014 error = unshare_fd(CLONE_FILES, ©); 3015 if (error || !copy) { 3016 *displaced = NULL; 3017 return error; 3018 } 3019 *displaced = task->files; 3020 task_lock(task); 3021 task->files = copy; 3022 task_unlock(task); 3023 return 0; 3024 } 3025 3026 int sysctl_max_threads(struct ctl_table *table, int write, 3027 void __user *buffer, size_t *lenp, loff_t *ppos) 3028 { 3029 struct ctl_table t; 3030 int ret; 3031 int threads = max_threads; 3032 int min = 1; 3033 int max = MAX_THREADS; 3034 3035 t = *table; 3036 t.data = &threads; 3037 t.extra1 = &min; 3038 t.extra2 = &max; 3039 3040 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 3041 if (ret || !write) 3042 return ret; 3043 3044 max_threads = threads; 3045 3046 return 0; 3047 } 3048