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