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