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