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