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 INIT_HLIST_HEAD(&sig->multiprocess); 1491 seqlock_init(&sig->stats_lock); 1492 prev_cputime_init(&sig->prev_cputime); 1493 1494 #ifdef CONFIG_POSIX_TIMERS 1495 INIT_LIST_HEAD(&sig->posix_timers); 1496 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1497 sig->real_timer.function = it_real_fn; 1498 #endif 1499 1500 task_lock(current->group_leader); 1501 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1502 task_unlock(current->group_leader); 1503 1504 posix_cpu_timers_init_group(sig); 1505 1506 tty_audit_fork(sig); 1507 sched_autogroup_fork(sig); 1508 1509 sig->oom_score_adj = current->signal->oom_score_adj; 1510 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1511 1512 mutex_init(&sig->cred_guard_mutex); 1513 1514 return 0; 1515 } 1516 1517 static void copy_seccomp(struct task_struct *p) 1518 { 1519 #ifdef CONFIG_SECCOMP 1520 /* 1521 * Must be called with sighand->lock held, which is common to 1522 * all threads in the group. Holding cred_guard_mutex is not 1523 * needed because this new task is not yet running and cannot 1524 * be racing exec. 1525 */ 1526 assert_spin_locked(¤t->sighand->siglock); 1527 1528 /* Ref-count the new filter user, and assign it. */ 1529 get_seccomp_filter(current); 1530 p->seccomp = current->seccomp; 1531 1532 /* 1533 * Explicitly enable no_new_privs here in case it got set 1534 * between the task_struct being duplicated and holding the 1535 * sighand lock. The seccomp state and nnp must be in sync. 1536 */ 1537 if (task_no_new_privs(current)) 1538 task_set_no_new_privs(p); 1539 1540 /* 1541 * If the parent gained a seccomp mode after copying thread 1542 * flags and between before we held the sighand lock, we have 1543 * to manually enable the seccomp thread flag here. 1544 */ 1545 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1546 set_tsk_thread_flag(p, TIF_SECCOMP); 1547 #endif 1548 } 1549 1550 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1551 { 1552 current->clear_child_tid = tidptr; 1553 1554 return task_pid_vnr(current); 1555 } 1556 1557 static void rt_mutex_init_task(struct task_struct *p) 1558 { 1559 raw_spin_lock_init(&p->pi_lock); 1560 #ifdef CONFIG_RT_MUTEXES 1561 p->pi_waiters = RB_ROOT_CACHED; 1562 p->pi_top_task = NULL; 1563 p->pi_blocked_on = NULL; 1564 #endif 1565 } 1566 1567 #ifdef CONFIG_POSIX_TIMERS 1568 /* 1569 * Initialize POSIX timer handling for a single task. 1570 */ 1571 static void posix_cpu_timers_init(struct task_struct *tsk) 1572 { 1573 tsk->cputime_expires.prof_exp = 0; 1574 tsk->cputime_expires.virt_exp = 0; 1575 tsk->cputime_expires.sched_exp = 0; 1576 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1577 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1578 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1579 } 1580 #else 1581 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1582 #endif 1583 1584 static inline void init_task_pid_links(struct task_struct *task) 1585 { 1586 enum pid_type type; 1587 1588 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1589 INIT_HLIST_NODE(&task->pid_links[type]); 1590 } 1591 } 1592 1593 static inline void 1594 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1595 { 1596 if (type == PIDTYPE_PID) 1597 task->thread_pid = pid; 1598 else 1599 task->signal->pids[type] = pid; 1600 } 1601 1602 static inline void rcu_copy_process(struct task_struct *p) 1603 { 1604 #ifdef CONFIG_PREEMPT_RCU 1605 p->rcu_read_lock_nesting = 0; 1606 p->rcu_read_unlock_special.s = 0; 1607 p->rcu_blocked_node = NULL; 1608 INIT_LIST_HEAD(&p->rcu_node_entry); 1609 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1610 #ifdef CONFIG_TASKS_RCU 1611 p->rcu_tasks_holdout = false; 1612 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1613 p->rcu_tasks_idle_cpu = -1; 1614 #endif /* #ifdef CONFIG_TASKS_RCU */ 1615 } 1616 1617 /* 1618 * This creates a new process as a copy of the old one, 1619 * but does not actually start it yet. 1620 * 1621 * It copies the registers, and all the appropriate 1622 * parts of the process environment (as per the clone 1623 * flags). The actual kick-off is left to the caller. 1624 */ 1625 static __latent_entropy struct task_struct *copy_process( 1626 unsigned long clone_flags, 1627 unsigned long stack_start, 1628 unsigned long stack_size, 1629 int __user *child_tidptr, 1630 struct pid *pid, 1631 int trace, 1632 unsigned long tls, 1633 int node) 1634 { 1635 int retval; 1636 struct task_struct *p; 1637 struct multiprocess_signals delayed; 1638 1639 /* 1640 * Don't allow sharing the root directory with processes in a different 1641 * namespace 1642 */ 1643 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1644 return ERR_PTR(-EINVAL); 1645 1646 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1647 return ERR_PTR(-EINVAL); 1648 1649 /* 1650 * Thread groups must share signals as well, and detached threads 1651 * can only be started up within the thread group. 1652 */ 1653 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1654 return ERR_PTR(-EINVAL); 1655 1656 /* 1657 * Shared signal handlers imply shared VM. By way of the above, 1658 * thread groups also imply shared VM. Blocking this case allows 1659 * for various simplifications in other code. 1660 */ 1661 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1662 return ERR_PTR(-EINVAL); 1663 1664 /* 1665 * Siblings of global init remain as zombies on exit since they are 1666 * not reaped by their parent (swapper). To solve this and to avoid 1667 * multi-rooted process trees, prevent global and container-inits 1668 * from creating siblings. 1669 */ 1670 if ((clone_flags & CLONE_PARENT) && 1671 current->signal->flags & SIGNAL_UNKILLABLE) 1672 return ERR_PTR(-EINVAL); 1673 1674 /* 1675 * If the new process will be in a different pid or user namespace 1676 * do not allow it to share a thread group with the forking task. 1677 */ 1678 if (clone_flags & CLONE_THREAD) { 1679 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1680 (task_active_pid_ns(current) != 1681 current->nsproxy->pid_ns_for_children)) 1682 return ERR_PTR(-EINVAL); 1683 } 1684 1685 /* 1686 * Force any signals received before this point to be delivered 1687 * before the fork happens. Collect up signals sent to multiple 1688 * processes that happen during the fork and delay them so that 1689 * they appear to happen after the fork. 1690 */ 1691 sigemptyset(&delayed.signal); 1692 INIT_HLIST_NODE(&delayed.node); 1693 1694 spin_lock_irq(¤t->sighand->siglock); 1695 if (!(clone_flags & CLONE_THREAD)) 1696 hlist_add_head(&delayed.node, ¤t->signal->multiprocess); 1697 recalc_sigpending(); 1698 spin_unlock_irq(¤t->sighand->siglock); 1699 retval = -ERESTARTNOINTR; 1700 if (signal_pending(current)) 1701 goto fork_out; 1702 1703 retval = -ENOMEM; 1704 p = dup_task_struct(current, node); 1705 if (!p) 1706 goto fork_out; 1707 1708 /* 1709 * This _must_ happen before we call free_task(), i.e. before we jump 1710 * to any of the bad_fork_* labels. This is to avoid freeing 1711 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1712 * kernel threads (PF_KTHREAD). 1713 */ 1714 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1715 /* 1716 * Clear TID on mm_release()? 1717 */ 1718 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1719 1720 ftrace_graph_init_task(p); 1721 1722 rt_mutex_init_task(p); 1723 1724 #ifdef CONFIG_PROVE_LOCKING 1725 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1726 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1727 #endif 1728 retval = -EAGAIN; 1729 if (atomic_read(&p->real_cred->user->processes) >= 1730 task_rlimit(p, RLIMIT_NPROC)) { 1731 if (p->real_cred->user != INIT_USER && 1732 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1733 goto bad_fork_free; 1734 } 1735 current->flags &= ~PF_NPROC_EXCEEDED; 1736 1737 retval = copy_creds(p, clone_flags); 1738 if (retval < 0) 1739 goto bad_fork_free; 1740 1741 /* 1742 * If multiple threads are within copy_process(), then this check 1743 * triggers too late. This doesn't hurt, the check is only there 1744 * to stop root fork bombs. 1745 */ 1746 retval = -EAGAIN; 1747 if (nr_threads >= max_threads) 1748 goto bad_fork_cleanup_count; 1749 1750 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1751 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1752 p->flags |= PF_FORKNOEXEC; 1753 INIT_LIST_HEAD(&p->children); 1754 INIT_LIST_HEAD(&p->sibling); 1755 rcu_copy_process(p); 1756 p->vfork_done = NULL; 1757 spin_lock_init(&p->alloc_lock); 1758 1759 init_sigpending(&p->pending); 1760 1761 p->utime = p->stime = p->gtime = 0; 1762 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1763 p->utimescaled = p->stimescaled = 0; 1764 #endif 1765 prev_cputime_init(&p->prev_cputime); 1766 1767 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1768 seqcount_init(&p->vtime.seqcount); 1769 p->vtime.starttime = 0; 1770 p->vtime.state = VTIME_INACTIVE; 1771 #endif 1772 1773 #if defined(SPLIT_RSS_COUNTING) 1774 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1775 #endif 1776 1777 p->default_timer_slack_ns = current->timer_slack_ns; 1778 1779 task_io_accounting_init(&p->ioac); 1780 acct_clear_integrals(p); 1781 1782 posix_cpu_timers_init(p); 1783 1784 p->start_time = ktime_get_ns(); 1785 p->real_start_time = ktime_get_boot_ns(); 1786 p->io_context = NULL; 1787 audit_set_context(p, NULL); 1788 cgroup_fork(p); 1789 #ifdef CONFIG_NUMA 1790 p->mempolicy = mpol_dup(p->mempolicy); 1791 if (IS_ERR(p->mempolicy)) { 1792 retval = PTR_ERR(p->mempolicy); 1793 p->mempolicy = NULL; 1794 goto bad_fork_cleanup_threadgroup_lock; 1795 } 1796 #endif 1797 #ifdef CONFIG_CPUSETS 1798 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1799 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1800 seqcount_init(&p->mems_allowed_seq); 1801 #endif 1802 #ifdef CONFIG_TRACE_IRQFLAGS 1803 p->irq_events = 0; 1804 p->hardirqs_enabled = 0; 1805 p->hardirq_enable_ip = 0; 1806 p->hardirq_enable_event = 0; 1807 p->hardirq_disable_ip = _THIS_IP_; 1808 p->hardirq_disable_event = 0; 1809 p->softirqs_enabled = 1; 1810 p->softirq_enable_ip = _THIS_IP_; 1811 p->softirq_enable_event = 0; 1812 p->softirq_disable_ip = 0; 1813 p->softirq_disable_event = 0; 1814 p->hardirq_context = 0; 1815 p->softirq_context = 0; 1816 #endif 1817 1818 p->pagefault_disabled = 0; 1819 1820 #ifdef CONFIG_LOCKDEP 1821 p->lockdep_depth = 0; /* no locks held yet */ 1822 p->curr_chain_key = 0; 1823 p->lockdep_recursion = 0; 1824 lockdep_init_task(p); 1825 #endif 1826 1827 #ifdef CONFIG_DEBUG_MUTEXES 1828 p->blocked_on = NULL; /* not blocked yet */ 1829 #endif 1830 #ifdef CONFIG_BCACHE 1831 p->sequential_io = 0; 1832 p->sequential_io_avg = 0; 1833 #endif 1834 1835 /* Perform scheduler related setup. Assign this task to a CPU. */ 1836 retval = sched_fork(clone_flags, p); 1837 if (retval) 1838 goto bad_fork_cleanup_policy; 1839 1840 retval = perf_event_init_task(p); 1841 if (retval) 1842 goto bad_fork_cleanup_policy; 1843 retval = audit_alloc(p); 1844 if (retval) 1845 goto bad_fork_cleanup_perf; 1846 /* copy all the process information */ 1847 shm_init_task(p); 1848 retval = security_task_alloc(p, clone_flags); 1849 if (retval) 1850 goto bad_fork_cleanup_audit; 1851 retval = copy_semundo(clone_flags, p); 1852 if (retval) 1853 goto bad_fork_cleanup_security; 1854 retval = copy_files(clone_flags, p); 1855 if (retval) 1856 goto bad_fork_cleanup_semundo; 1857 retval = copy_fs(clone_flags, p); 1858 if (retval) 1859 goto bad_fork_cleanup_files; 1860 retval = copy_sighand(clone_flags, p); 1861 if (retval) 1862 goto bad_fork_cleanup_fs; 1863 retval = copy_signal(clone_flags, p); 1864 if (retval) 1865 goto bad_fork_cleanup_sighand; 1866 retval = copy_mm(clone_flags, p); 1867 if (retval) 1868 goto bad_fork_cleanup_signal; 1869 retval = copy_namespaces(clone_flags, p); 1870 if (retval) 1871 goto bad_fork_cleanup_mm; 1872 retval = copy_io(clone_flags, p); 1873 if (retval) 1874 goto bad_fork_cleanup_namespaces; 1875 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1876 if (retval) 1877 goto bad_fork_cleanup_io; 1878 1879 if (pid != &init_struct_pid) { 1880 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1881 if (IS_ERR(pid)) { 1882 retval = PTR_ERR(pid); 1883 goto bad_fork_cleanup_thread; 1884 } 1885 } 1886 1887 #ifdef CONFIG_BLOCK 1888 p->plug = NULL; 1889 #endif 1890 #ifdef CONFIG_FUTEX 1891 p->robust_list = NULL; 1892 #ifdef CONFIG_COMPAT 1893 p->compat_robust_list = NULL; 1894 #endif 1895 INIT_LIST_HEAD(&p->pi_state_list); 1896 p->pi_state_cache = NULL; 1897 #endif 1898 /* 1899 * sigaltstack should be cleared when sharing the same VM 1900 */ 1901 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1902 sas_ss_reset(p); 1903 1904 /* 1905 * Syscall tracing and stepping should be turned off in the 1906 * child regardless of CLONE_PTRACE. 1907 */ 1908 user_disable_single_step(p); 1909 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1910 #ifdef TIF_SYSCALL_EMU 1911 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1912 #endif 1913 clear_all_latency_tracing(p); 1914 1915 /* ok, now we should be set up.. */ 1916 p->pid = pid_nr(pid); 1917 if (clone_flags & CLONE_THREAD) { 1918 p->exit_signal = -1; 1919 p->group_leader = current->group_leader; 1920 p->tgid = current->tgid; 1921 } else { 1922 if (clone_flags & CLONE_PARENT) 1923 p->exit_signal = current->group_leader->exit_signal; 1924 else 1925 p->exit_signal = (clone_flags & CSIGNAL); 1926 p->group_leader = p; 1927 p->tgid = p->pid; 1928 } 1929 1930 p->nr_dirtied = 0; 1931 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1932 p->dirty_paused_when = 0; 1933 1934 p->pdeath_signal = 0; 1935 INIT_LIST_HEAD(&p->thread_group); 1936 p->task_works = NULL; 1937 1938 cgroup_threadgroup_change_begin(current); 1939 /* 1940 * Ensure that the cgroup subsystem policies allow the new process to be 1941 * forked. It should be noted the the new process's css_set can be changed 1942 * between here and cgroup_post_fork() if an organisation operation is in 1943 * progress. 1944 */ 1945 retval = cgroup_can_fork(p); 1946 if (retval) 1947 goto bad_fork_free_pid; 1948 1949 /* 1950 * Make it visible to the rest of the system, but dont wake it up yet. 1951 * Need tasklist lock for parent etc handling! 1952 */ 1953 write_lock_irq(&tasklist_lock); 1954 1955 /* CLONE_PARENT re-uses the old parent */ 1956 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1957 p->real_parent = current->real_parent; 1958 p->parent_exec_id = current->parent_exec_id; 1959 } else { 1960 p->real_parent = current; 1961 p->parent_exec_id = current->self_exec_id; 1962 } 1963 1964 klp_copy_process(p); 1965 1966 spin_lock(¤t->sighand->siglock); 1967 1968 /* 1969 * Copy seccomp details explicitly here, in case they were changed 1970 * before holding sighand lock. 1971 */ 1972 copy_seccomp(p); 1973 1974 rseq_fork(p, clone_flags); 1975 1976 /* Don't start children in a dying pid namespace */ 1977 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 1978 retval = -ENOMEM; 1979 goto bad_fork_cancel_cgroup; 1980 } 1981 1982 /* Let kill terminate clone/fork in the middle */ 1983 if (fatal_signal_pending(current)) { 1984 retval = -EINTR; 1985 goto bad_fork_cancel_cgroup; 1986 } 1987 1988 1989 init_task_pid_links(p); 1990 if (likely(p->pid)) { 1991 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1992 1993 init_task_pid(p, PIDTYPE_PID, pid); 1994 if (thread_group_leader(p)) { 1995 init_task_pid(p, PIDTYPE_TGID, pid); 1996 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1997 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1998 1999 if (is_child_reaper(pid)) { 2000 ns_of_pid(pid)->child_reaper = p; 2001 p->signal->flags |= SIGNAL_UNKILLABLE; 2002 } 2003 p->signal->shared_pending.signal = delayed.signal; 2004 p->signal->tty = tty_kref_get(current->signal->tty); 2005 /* 2006 * Inherit has_child_subreaper flag under the same 2007 * tasklist_lock with adding child to the process tree 2008 * for propagate_has_child_subreaper optimization. 2009 */ 2010 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 2011 p->real_parent->signal->is_child_subreaper; 2012 list_add_tail(&p->sibling, &p->real_parent->children); 2013 list_add_tail_rcu(&p->tasks, &init_task.tasks); 2014 attach_pid(p, PIDTYPE_TGID); 2015 attach_pid(p, PIDTYPE_PGID); 2016 attach_pid(p, PIDTYPE_SID); 2017 __this_cpu_inc(process_counts); 2018 } else { 2019 current->signal->nr_threads++; 2020 atomic_inc(¤t->signal->live); 2021 atomic_inc(¤t->signal->sigcnt); 2022 task_join_group_stop(p); 2023 list_add_tail_rcu(&p->thread_group, 2024 &p->group_leader->thread_group); 2025 list_add_tail_rcu(&p->thread_node, 2026 &p->signal->thread_head); 2027 } 2028 attach_pid(p, PIDTYPE_PID); 2029 nr_threads++; 2030 } 2031 total_forks++; 2032 hlist_del_init(&delayed.node); 2033 spin_unlock(¤t->sighand->siglock); 2034 syscall_tracepoint_update(p); 2035 write_unlock_irq(&tasklist_lock); 2036 2037 proc_fork_connector(p); 2038 cgroup_post_fork(p); 2039 cgroup_threadgroup_change_end(current); 2040 perf_event_fork(p); 2041 2042 trace_task_newtask(p, clone_flags); 2043 uprobe_copy_process(p, clone_flags); 2044 2045 return p; 2046 2047 bad_fork_cancel_cgroup: 2048 spin_unlock(¤t->sighand->siglock); 2049 write_unlock_irq(&tasklist_lock); 2050 cgroup_cancel_fork(p); 2051 bad_fork_free_pid: 2052 cgroup_threadgroup_change_end(current); 2053 if (pid != &init_struct_pid) 2054 free_pid(pid); 2055 bad_fork_cleanup_thread: 2056 exit_thread(p); 2057 bad_fork_cleanup_io: 2058 if (p->io_context) 2059 exit_io_context(p); 2060 bad_fork_cleanup_namespaces: 2061 exit_task_namespaces(p); 2062 bad_fork_cleanup_mm: 2063 if (p->mm) 2064 mmput(p->mm); 2065 bad_fork_cleanup_signal: 2066 if (!(clone_flags & CLONE_THREAD)) 2067 free_signal_struct(p->signal); 2068 bad_fork_cleanup_sighand: 2069 __cleanup_sighand(p->sighand); 2070 bad_fork_cleanup_fs: 2071 exit_fs(p); /* blocking */ 2072 bad_fork_cleanup_files: 2073 exit_files(p); /* blocking */ 2074 bad_fork_cleanup_semundo: 2075 exit_sem(p); 2076 bad_fork_cleanup_security: 2077 security_task_free(p); 2078 bad_fork_cleanup_audit: 2079 audit_free(p); 2080 bad_fork_cleanup_perf: 2081 perf_event_free_task(p); 2082 bad_fork_cleanup_policy: 2083 lockdep_free_task(p); 2084 #ifdef CONFIG_NUMA 2085 mpol_put(p->mempolicy); 2086 bad_fork_cleanup_threadgroup_lock: 2087 #endif 2088 delayacct_tsk_free(p); 2089 bad_fork_cleanup_count: 2090 atomic_dec(&p->cred->user->processes); 2091 exit_creds(p); 2092 bad_fork_free: 2093 p->state = TASK_DEAD; 2094 put_task_stack(p); 2095 free_task(p); 2096 fork_out: 2097 spin_lock_irq(¤t->sighand->siglock); 2098 hlist_del_init(&delayed.node); 2099 spin_unlock_irq(¤t->sighand->siglock); 2100 return ERR_PTR(retval); 2101 } 2102 2103 static inline void init_idle_pids(struct task_struct *idle) 2104 { 2105 enum pid_type type; 2106 2107 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2108 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */ 2109 init_task_pid(idle, type, &init_struct_pid); 2110 } 2111 } 2112 2113 struct task_struct *fork_idle(int cpu) 2114 { 2115 struct task_struct *task; 2116 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2117 cpu_to_node(cpu)); 2118 if (!IS_ERR(task)) { 2119 init_idle_pids(task); 2120 init_idle(task, cpu); 2121 } 2122 2123 return task; 2124 } 2125 2126 /* 2127 * Ok, this is the main fork-routine. 2128 * 2129 * It copies the process, and if successful kick-starts 2130 * it and waits for it to finish using the VM if required. 2131 */ 2132 long _do_fork(unsigned long clone_flags, 2133 unsigned long stack_start, 2134 unsigned long stack_size, 2135 int __user *parent_tidptr, 2136 int __user *child_tidptr, 2137 unsigned long tls) 2138 { 2139 struct completion vfork; 2140 struct pid *pid; 2141 struct task_struct *p; 2142 int trace = 0; 2143 long nr; 2144 2145 /* 2146 * Determine whether and which event to report to ptracer. When 2147 * called from kernel_thread or CLONE_UNTRACED is explicitly 2148 * requested, no event is reported; otherwise, report if the event 2149 * for the type of forking is enabled. 2150 */ 2151 if (!(clone_flags & CLONE_UNTRACED)) { 2152 if (clone_flags & CLONE_VFORK) 2153 trace = PTRACE_EVENT_VFORK; 2154 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2155 trace = PTRACE_EVENT_CLONE; 2156 else 2157 trace = PTRACE_EVENT_FORK; 2158 2159 if (likely(!ptrace_event_enabled(current, trace))) 2160 trace = 0; 2161 } 2162 2163 p = copy_process(clone_flags, stack_start, stack_size, 2164 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2165 add_latent_entropy(); 2166 2167 if (IS_ERR(p)) 2168 return PTR_ERR(p); 2169 2170 /* 2171 * Do this prior waking up the new thread - the thread pointer 2172 * might get invalid after that point, if the thread exits quickly. 2173 */ 2174 trace_sched_process_fork(current, p); 2175 2176 pid = get_task_pid(p, PIDTYPE_PID); 2177 nr = pid_vnr(pid); 2178 2179 if (clone_flags & CLONE_PARENT_SETTID) 2180 put_user(nr, parent_tidptr); 2181 2182 if (clone_flags & CLONE_VFORK) { 2183 p->vfork_done = &vfork; 2184 init_completion(&vfork); 2185 get_task_struct(p); 2186 } 2187 2188 wake_up_new_task(p); 2189 2190 /* forking complete and child started to run, tell ptracer */ 2191 if (unlikely(trace)) 2192 ptrace_event_pid(trace, pid); 2193 2194 if (clone_flags & CLONE_VFORK) { 2195 if (!wait_for_vfork_done(p, &vfork)) 2196 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2197 } 2198 2199 put_pid(pid); 2200 return nr; 2201 } 2202 2203 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2204 /* For compatibility with architectures that call do_fork directly rather than 2205 * using the syscall entry points below. */ 2206 long do_fork(unsigned long clone_flags, 2207 unsigned long stack_start, 2208 unsigned long stack_size, 2209 int __user *parent_tidptr, 2210 int __user *child_tidptr) 2211 { 2212 return _do_fork(clone_flags, stack_start, stack_size, 2213 parent_tidptr, child_tidptr, 0); 2214 } 2215 #endif 2216 2217 /* 2218 * Create a kernel thread. 2219 */ 2220 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2221 { 2222 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2223 (unsigned long)arg, NULL, NULL, 0); 2224 } 2225 2226 #ifdef __ARCH_WANT_SYS_FORK 2227 SYSCALL_DEFINE0(fork) 2228 { 2229 #ifdef CONFIG_MMU 2230 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2231 #else 2232 /* can not support in nommu mode */ 2233 return -EINVAL; 2234 #endif 2235 } 2236 #endif 2237 2238 #ifdef __ARCH_WANT_SYS_VFORK 2239 SYSCALL_DEFINE0(vfork) 2240 { 2241 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2242 0, NULL, NULL, 0); 2243 } 2244 #endif 2245 2246 #ifdef __ARCH_WANT_SYS_CLONE 2247 #ifdef CONFIG_CLONE_BACKWARDS 2248 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2249 int __user *, parent_tidptr, 2250 unsigned long, tls, 2251 int __user *, child_tidptr) 2252 #elif defined(CONFIG_CLONE_BACKWARDS2) 2253 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2254 int __user *, parent_tidptr, 2255 int __user *, child_tidptr, 2256 unsigned long, tls) 2257 #elif defined(CONFIG_CLONE_BACKWARDS3) 2258 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2259 int, stack_size, 2260 int __user *, parent_tidptr, 2261 int __user *, child_tidptr, 2262 unsigned long, tls) 2263 #else 2264 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2265 int __user *, parent_tidptr, 2266 int __user *, child_tidptr, 2267 unsigned long, tls) 2268 #endif 2269 { 2270 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2271 } 2272 #endif 2273 2274 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2275 { 2276 struct task_struct *leader, *parent, *child; 2277 int res; 2278 2279 read_lock(&tasklist_lock); 2280 leader = top = top->group_leader; 2281 down: 2282 for_each_thread(leader, parent) { 2283 list_for_each_entry(child, &parent->children, sibling) { 2284 res = visitor(child, data); 2285 if (res) { 2286 if (res < 0) 2287 goto out; 2288 leader = child; 2289 goto down; 2290 } 2291 up: 2292 ; 2293 } 2294 } 2295 2296 if (leader != top) { 2297 child = leader; 2298 parent = child->real_parent; 2299 leader = parent->group_leader; 2300 goto up; 2301 } 2302 out: 2303 read_unlock(&tasklist_lock); 2304 } 2305 2306 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2307 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2308 #endif 2309 2310 static void sighand_ctor(void *data) 2311 { 2312 struct sighand_struct *sighand = data; 2313 2314 spin_lock_init(&sighand->siglock); 2315 init_waitqueue_head(&sighand->signalfd_wqh); 2316 } 2317 2318 void __init proc_caches_init(void) 2319 { 2320 unsigned int mm_size; 2321 2322 sighand_cachep = kmem_cache_create("sighand_cache", 2323 sizeof(struct sighand_struct), 0, 2324 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2325 SLAB_ACCOUNT, sighand_ctor); 2326 signal_cachep = kmem_cache_create("signal_cache", 2327 sizeof(struct signal_struct), 0, 2328 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2329 NULL); 2330 files_cachep = kmem_cache_create("files_cache", 2331 sizeof(struct files_struct), 0, 2332 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2333 NULL); 2334 fs_cachep = kmem_cache_create("fs_cache", 2335 sizeof(struct fs_struct), 0, 2336 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2337 NULL); 2338 2339 /* 2340 * The mm_cpumask is located at the end of mm_struct, and is 2341 * dynamically sized based on the maximum CPU number this system 2342 * can have, taking hotplug into account (nr_cpu_ids). 2343 */ 2344 mm_size = sizeof(struct mm_struct) + cpumask_size(); 2345 2346 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2347 mm_size, ARCH_MIN_MMSTRUCT_ALIGN, 2348 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2349 offsetof(struct mm_struct, saved_auxv), 2350 sizeof_field(struct mm_struct, saved_auxv), 2351 NULL); 2352 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2353 mmap_init(); 2354 nsproxy_cache_init(); 2355 } 2356 2357 /* 2358 * Check constraints on flags passed to the unshare system call. 2359 */ 2360 static int check_unshare_flags(unsigned long unshare_flags) 2361 { 2362 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2363 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2364 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2365 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2366 return -EINVAL; 2367 /* 2368 * Not implemented, but pretend it works if there is nothing 2369 * to unshare. Note that unsharing the address space or the 2370 * signal handlers also need to unshare the signal queues (aka 2371 * CLONE_THREAD). 2372 */ 2373 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2374 if (!thread_group_empty(current)) 2375 return -EINVAL; 2376 } 2377 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2378 if (atomic_read(¤t->sighand->count) > 1) 2379 return -EINVAL; 2380 } 2381 if (unshare_flags & CLONE_VM) { 2382 if (!current_is_single_threaded()) 2383 return -EINVAL; 2384 } 2385 2386 return 0; 2387 } 2388 2389 /* 2390 * Unshare the filesystem structure if it is being shared 2391 */ 2392 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2393 { 2394 struct fs_struct *fs = current->fs; 2395 2396 if (!(unshare_flags & CLONE_FS) || !fs) 2397 return 0; 2398 2399 /* don't need lock here; in the worst case we'll do useless copy */ 2400 if (fs->users == 1) 2401 return 0; 2402 2403 *new_fsp = copy_fs_struct(fs); 2404 if (!*new_fsp) 2405 return -ENOMEM; 2406 2407 return 0; 2408 } 2409 2410 /* 2411 * Unshare file descriptor table if it is being shared 2412 */ 2413 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2414 { 2415 struct files_struct *fd = current->files; 2416 int error = 0; 2417 2418 if ((unshare_flags & CLONE_FILES) && 2419 (fd && atomic_read(&fd->count) > 1)) { 2420 *new_fdp = dup_fd(fd, &error); 2421 if (!*new_fdp) 2422 return error; 2423 } 2424 2425 return 0; 2426 } 2427 2428 /* 2429 * unshare allows a process to 'unshare' part of the process 2430 * context which was originally shared using clone. copy_* 2431 * functions used by do_fork() cannot be used here directly 2432 * because they modify an inactive task_struct that is being 2433 * constructed. Here we are modifying the current, active, 2434 * task_struct. 2435 */ 2436 int ksys_unshare(unsigned long unshare_flags) 2437 { 2438 struct fs_struct *fs, *new_fs = NULL; 2439 struct files_struct *fd, *new_fd = NULL; 2440 struct cred *new_cred = NULL; 2441 struct nsproxy *new_nsproxy = NULL; 2442 int do_sysvsem = 0; 2443 int err; 2444 2445 /* 2446 * If unsharing a user namespace must also unshare the thread group 2447 * and unshare the filesystem root and working directories. 2448 */ 2449 if (unshare_flags & CLONE_NEWUSER) 2450 unshare_flags |= CLONE_THREAD | CLONE_FS; 2451 /* 2452 * If unsharing vm, must also unshare signal handlers. 2453 */ 2454 if (unshare_flags & CLONE_VM) 2455 unshare_flags |= CLONE_SIGHAND; 2456 /* 2457 * If unsharing a signal handlers, must also unshare the signal queues. 2458 */ 2459 if (unshare_flags & CLONE_SIGHAND) 2460 unshare_flags |= CLONE_THREAD; 2461 /* 2462 * If unsharing namespace, must also unshare filesystem information. 2463 */ 2464 if (unshare_flags & CLONE_NEWNS) 2465 unshare_flags |= CLONE_FS; 2466 2467 err = check_unshare_flags(unshare_flags); 2468 if (err) 2469 goto bad_unshare_out; 2470 /* 2471 * CLONE_NEWIPC must also detach from the undolist: after switching 2472 * to a new ipc namespace, the semaphore arrays from the old 2473 * namespace are unreachable. 2474 */ 2475 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2476 do_sysvsem = 1; 2477 err = unshare_fs(unshare_flags, &new_fs); 2478 if (err) 2479 goto bad_unshare_out; 2480 err = unshare_fd(unshare_flags, &new_fd); 2481 if (err) 2482 goto bad_unshare_cleanup_fs; 2483 err = unshare_userns(unshare_flags, &new_cred); 2484 if (err) 2485 goto bad_unshare_cleanup_fd; 2486 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2487 new_cred, new_fs); 2488 if (err) 2489 goto bad_unshare_cleanup_cred; 2490 2491 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2492 if (do_sysvsem) { 2493 /* 2494 * CLONE_SYSVSEM is equivalent to sys_exit(). 2495 */ 2496 exit_sem(current); 2497 } 2498 if (unshare_flags & CLONE_NEWIPC) { 2499 /* Orphan segments in old ns (see sem above). */ 2500 exit_shm(current); 2501 shm_init_task(current); 2502 } 2503 2504 if (new_nsproxy) 2505 switch_task_namespaces(current, new_nsproxy); 2506 2507 task_lock(current); 2508 2509 if (new_fs) { 2510 fs = current->fs; 2511 spin_lock(&fs->lock); 2512 current->fs = new_fs; 2513 if (--fs->users) 2514 new_fs = NULL; 2515 else 2516 new_fs = fs; 2517 spin_unlock(&fs->lock); 2518 } 2519 2520 if (new_fd) { 2521 fd = current->files; 2522 current->files = new_fd; 2523 new_fd = fd; 2524 } 2525 2526 task_unlock(current); 2527 2528 if (new_cred) { 2529 /* Install the new user namespace */ 2530 commit_creds(new_cred); 2531 new_cred = NULL; 2532 } 2533 } 2534 2535 perf_event_namespaces(current); 2536 2537 bad_unshare_cleanup_cred: 2538 if (new_cred) 2539 put_cred(new_cred); 2540 bad_unshare_cleanup_fd: 2541 if (new_fd) 2542 put_files_struct(new_fd); 2543 2544 bad_unshare_cleanup_fs: 2545 if (new_fs) 2546 free_fs_struct(new_fs); 2547 2548 bad_unshare_out: 2549 return err; 2550 } 2551 2552 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2553 { 2554 return ksys_unshare(unshare_flags); 2555 } 2556 2557 /* 2558 * Helper to unshare the files of the current task. 2559 * We don't want to expose copy_files internals to 2560 * the exec layer of the kernel. 2561 */ 2562 2563 int unshare_files(struct files_struct **displaced) 2564 { 2565 struct task_struct *task = current; 2566 struct files_struct *copy = NULL; 2567 int error; 2568 2569 error = unshare_fd(CLONE_FILES, ©); 2570 if (error || !copy) { 2571 *displaced = NULL; 2572 return error; 2573 } 2574 *displaced = task->files; 2575 task_lock(task); 2576 task->files = copy; 2577 task_unlock(task); 2578 return 0; 2579 } 2580 2581 int sysctl_max_threads(struct ctl_table *table, int write, 2582 void __user *buffer, size_t *lenp, loff_t *ppos) 2583 { 2584 struct ctl_table t; 2585 int ret; 2586 int threads = max_threads; 2587 int min = MIN_THREADS; 2588 int max = MAX_THREADS; 2589 2590 t = *table; 2591 t.data = &threads; 2592 t.extra1 = &min; 2593 t.extra2 = &max; 2594 2595 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2596 if (ret || !write) 2597 return ret; 2598 2599 set_max_threads(threads); 2600 2601 return 0; 2602 } 2603