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