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