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 return tsk; 870 871 free_stack: 872 free_thread_stack(tsk); 873 free_tsk: 874 free_task_struct(tsk); 875 return NULL; 876 } 877 878 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 879 880 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 881 882 static int __init coredump_filter_setup(char *s) 883 { 884 default_dump_filter = 885 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 886 MMF_DUMP_FILTER_MASK; 887 return 1; 888 } 889 890 __setup("coredump_filter=", coredump_filter_setup); 891 892 #include <linux/init_task.h> 893 894 static void mm_init_aio(struct mm_struct *mm) 895 { 896 #ifdef CONFIG_AIO 897 spin_lock_init(&mm->ioctx_lock); 898 mm->ioctx_table = NULL; 899 #endif 900 } 901 902 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 903 { 904 #ifdef CONFIG_MEMCG 905 mm->owner = p; 906 #endif 907 } 908 909 static void mm_init_uprobes_state(struct mm_struct *mm) 910 { 911 #ifdef CONFIG_UPROBES 912 mm->uprobes_state.xol_area = NULL; 913 #endif 914 } 915 916 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 917 struct user_namespace *user_ns) 918 { 919 mm->mmap = NULL; 920 mm->mm_rb = RB_ROOT; 921 mm->vmacache_seqnum = 0; 922 atomic_set(&mm->mm_users, 1); 923 atomic_set(&mm->mm_count, 1); 924 init_rwsem(&mm->mmap_sem); 925 INIT_LIST_HEAD(&mm->mmlist); 926 mm->core_state = NULL; 927 mm_pgtables_bytes_init(mm); 928 mm->map_count = 0; 929 mm->locked_vm = 0; 930 mm->pinned_vm = 0; 931 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 932 spin_lock_init(&mm->page_table_lock); 933 spin_lock_init(&mm->arg_lock); 934 mm_init_cpumask(mm); 935 mm_init_aio(mm); 936 mm_init_owner(mm, p); 937 RCU_INIT_POINTER(mm->exe_file, NULL); 938 mmu_notifier_mm_init(mm); 939 hmm_mm_init(mm); 940 init_tlb_flush_pending(mm); 941 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 942 mm->pmd_huge_pte = NULL; 943 #endif 944 mm_init_uprobes_state(mm); 945 946 if (current->mm) { 947 mm->flags = current->mm->flags & MMF_INIT_MASK; 948 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 949 } else { 950 mm->flags = default_dump_filter; 951 mm->def_flags = 0; 952 } 953 954 if (mm_alloc_pgd(mm)) 955 goto fail_nopgd; 956 957 if (init_new_context(p, mm)) 958 goto fail_nocontext; 959 960 mm->user_ns = get_user_ns(user_ns); 961 return mm; 962 963 fail_nocontext: 964 mm_free_pgd(mm); 965 fail_nopgd: 966 free_mm(mm); 967 return NULL; 968 } 969 970 /* 971 * Allocate and initialize an mm_struct. 972 */ 973 struct mm_struct *mm_alloc(void) 974 { 975 struct mm_struct *mm; 976 977 mm = allocate_mm(); 978 if (!mm) 979 return NULL; 980 981 memset(mm, 0, sizeof(*mm)); 982 return mm_init(mm, current, current_user_ns()); 983 } 984 985 static inline void __mmput(struct mm_struct *mm) 986 { 987 VM_BUG_ON(atomic_read(&mm->mm_users)); 988 989 uprobe_clear_state(mm); 990 exit_aio(mm); 991 ksm_exit(mm); 992 khugepaged_exit(mm); /* must run before exit_mmap */ 993 exit_mmap(mm); 994 mm_put_huge_zero_page(mm); 995 set_mm_exe_file(mm, NULL); 996 if (!list_empty(&mm->mmlist)) { 997 spin_lock(&mmlist_lock); 998 list_del(&mm->mmlist); 999 spin_unlock(&mmlist_lock); 1000 } 1001 if (mm->binfmt) 1002 module_put(mm->binfmt->module); 1003 mmdrop(mm); 1004 } 1005 1006 /* 1007 * Decrement the use count and release all resources for an mm. 1008 */ 1009 void mmput(struct mm_struct *mm) 1010 { 1011 might_sleep(); 1012 1013 if (atomic_dec_and_test(&mm->mm_users)) 1014 __mmput(mm); 1015 } 1016 EXPORT_SYMBOL_GPL(mmput); 1017 1018 #ifdef CONFIG_MMU 1019 static void mmput_async_fn(struct work_struct *work) 1020 { 1021 struct mm_struct *mm = container_of(work, struct mm_struct, 1022 async_put_work); 1023 1024 __mmput(mm); 1025 } 1026 1027 void mmput_async(struct mm_struct *mm) 1028 { 1029 if (atomic_dec_and_test(&mm->mm_users)) { 1030 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1031 schedule_work(&mm->async_put_work); 1032 } 1033 } 1034 #endif 1035 1036 /** 1037 * set_mm_exe_file - change a reference to the mm's executable file 1038 * 1039 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1040 * 1041 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1042 * invocations: in mmput() nobody alive left, in execve task is single 1043 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1044 * mm->exe_file, but does so without using set_mm_exe_file() in order 1045 * to do avoid the need for any locks. 1046 */ 1047 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1048 { 1049 struct file *old_exe_file; 1050 1051 /* 1052 * It is safe to dereference the exe_file without RCU as 1053 * this function is only called if nobody else can access 1054 * this mm -- see comment above for justification. 1055 */ 1056 old_exe_file = rcu_dereference_raw(mm->exe_file); 1057 1058 if (new_exe_file) 1059 get_file(new_exe_file); 1060 rcu_assign_pointer(mm->exe_file, new_exe_file); 1061 if (old_exe_file) 1062 fput(old_exe_file); 1063 } 1064 1065 /** 1066 * get_mm_exe_file - acquire a reference to the mm's executable file 1067 * 1068 * Returns %NULL if mm has no associated executable file. 1069 * User must release file via fput(). 1070 */ 1071 struct file *get_mm_exe_file(struct mm_struct *mm) 1072 { 1073 struct file *exe_file; 1074 1075 rcu_read_lock(); 1076 exe_file = rcu_dereference(mm->exe_file); 1077 if (exe_file && !get_file_rcu(exe_file)) 1078 exe_file = NULL; 1079 rcu_read_unlock(); 1080 return exe_file; 1081 } 1082 EXPORT_SYMBOL(get_mm_exe_file); 1083 1084 /** 1085 * get_task_exe_file - acquire a reference to the task's executable file 1086 * 1087 * Returns %NULL if task's mm (if any) has no associated executable file or 1088 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1089 * User must release file via fput(). 1090 */ 1091 struct file *get_task_exe_file(struct task_struct *task) 1092 { 1093 struct file *exe_file = NULL; 1094 struct mm_struct *mm; 1095 1096 task_lock(task); 1097 mm = task->mm; 1098 if (mm) { 1099 if (!(task->flags & PF_KTHREAD)) 1100 exe_file = get_mm_exe_file(mm); 1101 } 1102 task_unlock(task); 1103 return exe_file; 1104 } 1105 EXPORT_SYMBOL(get_task_exe_file); 1106 1107 /** 1108 * get_task_mm - acquire a reference to the task's mm 1109 * 1110 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1111 * this kernel workthread has transiently adopted a user mm with use_mm, 1112 * to do its AIO) is not set and if so returns a reference to it, after 1113 * bumping up the use count. User must release the mm via mmput() 1114 * after use. Typically used by /proc and ptrace. 1115 */ 1116 struct mm_struct *get_task_mm(struct task_struct *task) 1117 { 1118 struct mm_struct *mm; 1119 1120 task_lock(task); 1121 mm = task->mm; 1122 if (mm) { 1123 if (task->flags & PF_KTHREAD) 1124 mm = NULL; 1125 else 1126 mmget(mm); 1127 } 1128 task_unlock(task); 1129 return mm; 1130 } 1131 EXPORT_SYMBOL_GPL(get_task_mm); 1132 1133 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1134 { 1135 struct mm_struct *mm; 1136 int err; 1137 1138 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1139 if (err) 1140 return ERR_PTR(err); 1141 1142 mm = get_task_mm(task); 1143 if (mm && mm != current->mm && 1144 !ptrace_may_access(task, mode)) { 1145 mmput(mm); 1146 mm = ERR_PTR(-EACCES); 1147 } 1148 mutex_unlock(&task->signal->cred_guard_mutex); 1149 1150 return mm; 1151 } 1152 1153 static void complete_vfork_done(struct task_struct *tsk) 1154 { 1155 struct completion *vfork; 1156 1157 task_lock(tsk); 1158 vfork = tsk->vfork_done; 1159 if (likely(vfork)) { 1160 tsk->vfork_done = NULL; 1161 complete(vfork); 1162 } 1163 task_unlock(tsk); 1164 } 1165 1166 static int wait_for_vfork_done(struct task_struct *child, 1167 struct completion *vfork) 1168 { 1169 int killed; 1170 1171 freezer_do_not_count(); 1172 killed = wait_for_completion_killable(vfork); 1173 freezer_count(); 1174 1175 if (killed) { 1176 task_lock(child); 1177 child->vfork_done = NULL; 1178 task_unlock(child); 1179 } 1180 1181 put_task_struct(child); 1182 return killed; 1183 } 1184 1185 /* Please note the differences between mmput and mm_release. 1186 * mmput is called whenever we stop holding onto a mm_struct, 1187 * error success whatever. 1188 * 1189 * mm_release is called after a mm_struct has been removed 1190 * from the current process. 1191 * 1192 * This difference is important for error handling, when we 1193 * only half set up a mm_struct for a new process and need to restore 1194 * the old one. Because we mmput the new mm_struct before 1195 * restoring the old one. . . 1196 * Eric Biederman 10 January 1998 1197 */ 1198 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1199 { 1200 /* Get rid of any futexes when releasing the mm */ 1201 #ifdef CONFIG_FUTEX 1202 if (unlikely(tsk->robust_list)) { 1203 exit_robust_list(tsk); 1204 tsk->robust_list = NULL; 1205 } 1206 #ifdef CONFIG_COMPAT 1207 if (unlikely(tsk->compat_robust_list)) { 1208 compat_exit_robust_list(tsk); 1209 tsk->compat_robust_list = NULL; 1210 } 1211 #endif 1212 if (unlikely(!list_empty(&tsk->pi_state_list))) 1213 exit_pi_state_list(tsk); 1214 #endif 1215 1216 uprobe_free_utask(tsk); 1217 1218 /* Get rid of any cached register state */ 1219 deactivate_mm(tsk, mm); 1220 1221 /* 1222 * Signal userspace if we're not exiting with a core dump 1223 * because we want to leave the value intact for debugging 1224 * purposes. 1225 */ 1226 if (tsk->clear_child_tid) { 1227 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1228 atomic_read(&mm->mm_users) > 1) { 1229 /* 1230 * We don't check the error code - if userspace has 1231 * not set up a proper pointer then tough luck. 1232 */ 1233 put_user(0, tsk->clear_child_tid); 1234 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1235 1, NULL, NULL, 0, 0); 1236 } 1237 tsk->clear_child_tid = NULL; 1238 } 1239 1240 /* 1241 * All done, finally we can wake up parent and return this mm to him. 1242 * Also kthread_stop() uses this completion for synchronization. 1243 */ 1244 if (tsk->vfork_done) 1245 complete_vfork_done(tsk); 1246 } 1247 1248 /* 1249 * Allocate a new mm structure and copy contents from the 1250 * mm structure of the passed in task structure. 1251 */ 1252 static struct mm_struct *dup_mm(struct task_struct *tsk) 1253 { 1254 struct mm_struct *mm, *oldmm = current->mm; 1255 int err; 1256 1257 mm = allocate_mm(); 1258 if (!mm) 1259 goto fail_nomem; 1260 1261 memcpy(mm, oldmm, sizeof(*mm)); 1262 1263 if (!mm_init(mm, tsk, mm->user_ns)) 1264 goto fail_nomem; 1265 1266 err = dup_mmap(mm, oldmm); 1267 if (err) 1268 goto free_pt; 1269 1270 mm->hiwater_rss = get_mm_rss(mm); 1271 mm->hiwater_vm = mm->total_vm; 1272 1273 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1274 goto free_pt; 1275 1276 return mm; 1277 1278 free_pt: 1279 /* don't put binfmt in mmput, we haven't got module yet */ 1280 mm->binfmt = NULL; 1281 mmput(mm); 1282 1283 fail_nomem: 1284 return NULL; 1285 } 1286 1287 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1288 { 1289 struct mm_struct *mm, *oldmm; 1290 int retval; 1291 1292 tsk->min_flt = tsk->maj_flt = 0; 1293 tsk->nvcsw = tsk->nivcsw = 0; 1294 #ifdef CONFIG_DETECT_HUNG_TASK 1295 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1296 #endif 1297 1298 tsk->mm = NULL; 1299 tsk->active_mm = NULL; 1300 1301 /* 1302 * Are we cloning a kernel thread? 1303 * 1304 * We need to steal a active VM for that.. 1305 */ 1306 oldmm = current->mm; 1307 if (!oldmm) 1308 return 0; 1309 1310 /* initialize the new vmacache entries */ 1311 vmacache_flush(tsk); 1312 1313 if (clone_flags & CLONE_VM) { 1314 mmget(oldmm); 1315 mm = oldmm; 1316 goto good_mm; 1317 } 1318 1319 retval = -ENOMEM; 1320 mm = dup_mm(tsk); 1321 if (!mm) 1322 goto fail_nomem; 1323 1324 good_mm: 1325 tsk->mm = mm; 1326 tsk->active_mm = mm; 1327 return 0; 1328 1329 fail_nomem: 1330 return retval; 1331 } 1332 1333 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1334 { 1335 struct fs_struct *fs = current->fs; 1336 if (clone_flags & CLONE_FS) { 1337 /* tsk->fs is already what we want */ 1338 spin_lock(&fs->lock); 1339 if (fs->in_exec) { 1340 spin_unlock(&fs->lock); 1341 return -EAGAIN; 1342 } 1343 fs->users++; 1344 spin_unlock(&fs->lock); 1345 return 0; 1346 } 1347 tsk->fs = copy_fs_struct(fs); 1348 if (!tsk->fs) 1349 return -ENOMEM; 1350 return 0; 1351 } 1352 1353 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1354 { 1355 struct files_struct *oldf, *newf; 1356 int error = 0; 1357 1358 /* 1359 * A background process may not have any files ... 1360 */ 1361 oldf = current->files; 1362 if (!oldf) 1363 goto out; 1364 1365 if (clone_flags & CLONE_FILES) { 1366 atomic_inc(&oldf->count); 1367 goto out; 1368 } 1369 1370 newf = dup_fd(oldf, &error); 1371 if (!newf) 1372 goto out; 1373 1374 tsk->files = newf; 1375 error = 0; 1376 out: 1377 return error; 1378 } 1379 1380 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1381 { 1382 #ifdef CONFIG_BLOCK 1383 struct io_context *ioc = current->io_context; 1384 struct io_context *new_ioc; 1385 1386 if (!ioc) 1387 return 0; 1388 /* 1389 * Share io context with parent, if CLONE_IO is set 1390 */ 1391 if (clone_flags & CLONE_IO) { 1392 ioc_task_link(ioc); 1393 tsk->io_context = ioc; 1394 } else if (ioprio_valid(ioc->ioprio)) { 1395 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1396 if (unlikely(!new_ioc)) 1397 return -ENOMEM; 1398 1399 new_ioc->ioprio = ioc->ioprio; 1400 put_io_context(new_ioc); 1401 } 1402 #endif 1403 return 0; 1404 } 1405 1406 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1407 { 1408 struct sighand_struct *sig; 1409 1410 if (clone_flags & CLONE_SIGHAND) { 1411 atomic_inc(¤t->sighand->count); 1412 return 0; 1413 } 1414 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1415 rcu_assign_pointer(tsk->sighand, sig); 1416 if (!sig) 1417 return -ENOMEM; 1418 1419 atomic_set(&sig->count, 1); 1420 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1421 return 0; 1422 } 1423 1424 void __cleanup_sighand(struct sighand_struct *sighand) 1425 { 1426 if (atomic_dec_and_test(&sighand->count)) { 1427 signalfd_cleanup(sighand); 1428 /* 1429 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1430 * without an RCU grace period, see __lock_task_sighand(). 1431 */ 1432 kmem_cache_free(sighand_cachep, sighand); 1433 } 1434 } 1435 1436 #ifdef CONFIG_POSIX_TIMERS 1437 /* 1438 * Initialize POSIX timer handling for a thread group. 1439 */ 1440 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1441 { 1442 unsigned long cpu_limit; 1443 1444 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1445 if (cpu_limit != RLIM_INFINITY) { 1446 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1447 sig->cputimer.running = true; 1448 } 1449 1450 /* The timer lists. */ 1451 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1452 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1453 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1454 } 1455 #else 1456 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1457 #endif 1458 1459 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1460 { 1461 struct signal_struct *sig; 1462 1463 if (clone_flags & CLONE_THREAD) 1464 return 0; 1465 1466 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1467 tsk->signal = sig; 1468 if (!sig) 1469 return -ENOMEM; 1470 1471 sig->nr_threads = 1; 1472 atomic_set(&sig->live, 1); 1473 atomic_set(&sig->sigcnt, 1); 1474 1475 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1476 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1477 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1478 1479 init_waitqueue_head(&sig->wait_chldexit); 1480 sig->curr_target = tsk; 1481 init_sigpending(&sig->shared_pending); 1482 seqlock_init(&sig->stats_lock); 1483 prev_cputime_init(&sig->prev_cputime); 1484 1485 #ifdef CONFIG_POSIX_TIMERS 1486 INIT_LIST_HEAD(&sig->posix_timers); 1487 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1488 sig->real_timer.function = it_real_fn; 1489 #endif 1490 1491 task_lock(current->group_leader); 1492 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1493 task_unlock(current->group_leader); 1494 1495 posix_cpu_timers_init_group(sig); 1496 1497 tty_audit_fork(sig); 1498 sched_autogroup_fork(sig); 1499 1500 sig->oom_score_adj = current->signal->oom_score_adj; 1501 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1502 1503 mutex_init(&sig->cred_guard_mutex); 1504 1505 return 0; 1506 } 1507 1508 static void copy_seccomp(struct task_struct *p) 1509 { 1510 #ifdef CONFIG_SECCOMP 1511 /* 1512 * Must be called with sighand->lock held, which is common to 1513 * all threads in the group. Holding cred_guard_mutex is not 1514 * needed because this new task is not yet running and cannot 1515 * be racing exec. 1516 */ 1517 assert_spin_locked(¤t->sighand->siglock); 1518 1519 /* Ref-count the new filter user, and assign it. */ 1520 get_seccomp_filter(current); 1521 p->seccomp = current->seccomp; 1522 1523 /* 1524 * Explicitly enable no_new_privs here in case it got set 1525 * between the task_struct being duplicated and holding the 1526 * sighand lock. The seccomp state and nnp must be in sync. 1527 */ 1528 if (task_no_new_privs(current)) 1529 task_set_no_new_privs(p); 1530 1531 /* 1532 * If the parent gained a seccomp mode after copying thread 1533 * flags and between before we held the sighand lock, we have 1534 * to manually enable the seccomp thread flag here. 1535 */ 1536 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1537 set_tsk_thread_flag(p, TIF_SECCOMP); 1538 #endif 1539 } 1540 1541 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1542 { 1543 current->clear_child_tid = tidptr; 1544 1545 return task_pid_vnr(current); 1546 } 1547 1548 static void rt_mutex_init_task(struct task_struct *p) 1549 { 1550 raw_spin_lock_init(&p->pi_lock); 1551 #ifdef CONFIG_RT_MUTEXES 1552 p->pi_waiters = RB_ROOT_CACHED; 1553 p->pi_top_task = NULL; 1554 p->pi_blocked_on = NULL; 1555 #endif 1556 } 1557 1558 #ifdef CONFIG_POSIX_TIMERS 1559 /* 1560 * Initialize POSIX timer handling for a single task. 1561 */ 1562 static void posix_cpu_timers_init(struct task_struct *tsk) 1563 { 1564 tsk->cputime_expires.prof_exp = 0; 1565 tsk->cputime_expires.virt_exp = 0; 1566 tsk->cputime_expires.sched_exp = 0; 1567 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1568 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1569 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1570 } 1571 #else 1572 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1573 #endif 1574 1575 static inline void 1576 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1577 { 1578 task->pids[type].pid = pid; 1579 } 1580 1581 static inline void rcu_copy_process(struct task_struct *p) 1582 { 1583 #ifdef CONFIG_PREEMPT_RCU 1584 p->rcu_read_lock_nesting = 0; 1585 p->rcu_read_unlock_special.s = 0; 1586 p->rcu_blocked_node = NULL; 1587 INIT_LIST_HEAD(&p->rcu_node_entry); 1588 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1589 #ifdef CONFIG_TASKS_RCU 1590 p->rcu_tasks_holdout = false; 1591 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1592 p->rcu_tasks_idle_cpu = -1; 1593 #endif /* #ifdef CONFIG_TASKS_RCU */ 1594 } 1595 1596 /* 1597 * This creates a new process as a copy of the old one, 1598 * but does not actually start it yet. 1599 * 1600 * It copies the registers, and all the appropriate 1601 * parts of the process environment (as per the clone 1602 * flags). The actual kick-off is left to the caller. 1603 */ 1604 static __latent_entropy struct task_struct *copy_process( 1605 unsigned long clone_flags, 1606 unsigned long stack_start, 1607 unsigned long stack_size, 1608 int __user *child_tidptr, 1609 struct pid *pid, 1610 int trace, 1611 unsigned long tls, 1612 int node) 1613 { 1614 int retval; 1615 struct task_struct *p; 1616 1617 /* 1618 * Don't allow sharing the root directory with processes in a different 1619 * namespace 1620 */ 1621 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1622 return ERR_PTR(-EINVAL); 1623 1624 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1625 return ERR_PTR(-EINVAL); 1626 1627 /* 1628 * Thread groups must share signals as well, and detached threads 1629 * can only be started up within the thread group. 1630 */ 1631 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1632 return ERR_PTR(-EINVAL); 1633 1634 /* 1635 * Shared signal handlers imply shared VM. By way of the above, 1636 * thread groups also imply shared VM. Blocking this case allows 1637 * for various simplifications in other code. 1638 */ 1639 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1640 return ERR_PTR(-EINVAL); 1641 1642 /* 1643 * Siblings of global init remain as zombies on exit since they are 1644 * not reaped by their parent (swapper). To solve this and to avoid 1645 * multi-rooted process trees, prevent global and container-inits 1646 * from creating siblings. 1647 */ 1648 if ((clone_flags & CLONE_PARENT) && 1649 current->signal->flags & SIGNAL_UNKILLABLE) 1650 return ERR_PTR(-EINVAL); 1651 1652 /* 1653 * If the new process will be in a different pid or user namespace 1654 * do not allow it to share a thread group with the forking task. 1655 */ 1656 if (clone_flags & CLONE_THREAD) { 1657 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1658 (task_active_pid_ns(current) != 1659 current->nsproxy->pid_ns_for_children)) 1660 return ERR_PTR(-EINVAL); 1661 } 1662 1663 retval = -ENOMEM; 1664 p = dup_task_struct(current, node); 1665 if (!p) 1666 goto fork_out; 1667 1668 /* 1669 * This _must_ happen before we call free_task(), i.e. before we jump 1670 * to any of the bad_fork_* labels. This is to avoid freeing 1671 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1672 * kernel threads (PF_KTHREAD). 1673 */ 1674 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1675 /* 1676 * Clear TID on mm_release()? 1677 */ 1678 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1679 1680 ftrace_graph_init_task(p); 1681 1682 rt_mutex_init_task(p); 1683 1684 #ifdef CONFIG_PROVE_LOCKING 1685 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1686 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1687 #endif 1688 retval = -EAGAIN; 1689 if (atomic_read(&p->real_cred->user->processes) >= 1690 task_rlimit(p, RLIMIT_NPROC)) { 1691 if (p->real_cred->user != INIT_USER && 1692 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1693 goto bad_fork_free; 1694 } 1695 current->flags &= ~PF_NPROC_EXCEEDED; 1696 1697 retval = copy_creds(p, clone_flags); 1698 if (retval < 0) 1699 goto bad_fork_free; 1700 1701 /* 1702 * If multiple threads are within copy_process(), then this check 1703 * triggers too late. This doesn't hurt, the check is only there 1704 * to stop root fork bombs. 1705 */ 1706 retval = -EAGAIN; 1707 if (nr_threads >= max_threads) 1708 goto bad_fork_cleanup_count; 1709 1710 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1711 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1712 p->flags |= PF_FORKNOEXEC; 1713 INIT_LIST_HEAD(&p->children); 1714 INIT_LIST_HEAD(&p->sibling); 1715 rcu_copy_process(p); 1716 p->vfork_done = NULL; 1717 spin_lock_init(&p->alloc_lock); 1718 1719 init_sigpending(&p->pending); 1720 1721 p->utime = p->stime = p->gtime = 0; 1722 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1723 p->utimescaled = p->stimescaled = 0; 1724 #endif 1725 prev_cputime_init(&p->prev_cputime); 1726 1727 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1728 seqcount_init(&p->vtime.seqcount); 1729 p->vtime.starttime = 0; 1730 p->vtime.state = VTIME_INACTIVE; 1731 #endif 1732 1733 #if defined(SPLIT_RSS_COUNTING) 1734 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1735 #endif 1736 1737 p->default_timer_slack_ns = current->timer_slack_ns; 1738 1739 task_io_accounting_init(&p->ioac); 1740 acct_clear_integrals(p); 1741 1742 posix_cpu_timers_init(p); 1743 1744 p->start_time = ktime_get_ns(); 1745 p->real_start_time = ktime_get_boot_ns(); 1746 p->io_context = NULL; 1747 audit_set_context(p, NULL); 1748 cgroup_fork(p); 1749 #ifdef CONFIG_NUMA 1750 p->mempolicy = mpol_dup(p->mempolicy); 1751 if (IS_ERR(p->mempolicy)) { 1752 retval = PTR_ERR(p->mempolicy); 1753 p->mempolicy = NULL; 1754 goto bad_fork_cleanup_threadgroup_lock; 1755 } 1756 #endif 1757 #ifdef CONFIG_CPUSETS 1758 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1759 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1760 seqcount_init(&p->mems_allowed_seq); 1761 #endif 1762 #ifdef CONFIG_TRACE_IRQFLAGS 1763 p->irq_events = 0; 1764 p->hardirqs_enabled = 0; 1765 p->hardirq_enable_ip = 0; 1766 p->hardirq_enable_event = 0; 1767 p->hardirq_disable_ip = _THIS_IP_; 1768 p->hardirq_disable_event = 0; 1769 p->softirqs_enabled = 1; 1770 p->softirq_enable_ip = _THIS_IP_; 1771 p->softirq_enable_event = 0; 1772 p->softirq_disable_ip = 0; 1773 p->softirq_disable_event = 0; 1774 p->hardirq_context = 0; 1775 p->softirq_context = 0; 1776 #endif 1777 1778 p->pagefault_disabled = 0; 1779 1780 #ifdef CONFIG_LOCKDEP 1781 p->lockdep_depth = 0; /* no locks held yet */ 1782 p->curr_chain_key = 0; 1783 p->lockdep_recursion = 0; 1784 lockdep_init_task(p); 1785 #endif 1786 1787 #ifdef CONFIG_DEBUG_MUTEXES 1788 p->blocked_on = NULL; /* not blocked yet */ 1789 #endif 1790 #ifdef CONFIG_BCACHE 1791 p->sequential_io = 0; 1792 p->sequential_io_avg = 0; 1793 #endif 1794 1795 /* Perform scheduler related setup. Assign this task to a CPU. */ 1796 retval = sched_fork(clone_flags, p); 1797 if (retval) 1798 goto bad_fork_cleanup_policy; 1799 1800 retval = perf_event_init_task(p); 1801 if (retval) 1802 goto bad_fork_cleanup_policy; 1803 retval = audit_alloc(p); 1804 if (retval) 1805 goto bad_fork_cleanup_perf; 1806 /* copy all the process information */ 1807 shm_init_task(p); 1808 retval = security_task_alloc(p, clone_flags); 1809 if (retval) 1810 goto bad_fork_cleanup_audit; 1811 retval = copy_semundo(clone_flags, p); 1812 if (retval) 1813 goto bad_fork_cleanup_security; 1814 retval = copy_files(clone_flags, p); 1815 if (retval) 1816 goto bad_fork_cleanup_semundo; 1817 retval = copy_fs(clone_flags, p); 1818 if (retval) 1819 goto bad_fork_cleanup_files; 1820 retval = copy_sighand(clone_flags, p); 1821 if (retval) 1822 goto bad_fork_cleanup_fs; 1823 retval = copy_signal(clone_flags, p); 1824 if (retval) 1825 goto bad_fork_cleanup_sighand; 1826 retval = copy_mm(clone_flags, p); 1827 if (retval) 1828 goto bad_fork_cleanup_signal; 1829 retval = copy_namespaces(clone_flags, p); 1830 if (retval) 1831 goto bad_fork_cleanup_mm; 1832 retval = copy_io(clone_flags, p); 1833 if (retval) 1834 goto bad_fork_cleanup_namespaces; 1835 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1836 if (retval) 1837 goto bad_fork_cleanup_io; 1838 1839 if (pid != &init_struct_pid) { 1840 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1841 if (IS_ERR(pid)) { 1842 retval = PTR_ERR(pid); 1843 goto bad_fork_cleanup_thread; 1844 } 1845 } 1846 1847 #ifdef CONFIG_BLOCK 1848 p->plug = NULL; 1849 #endif 1850 #ifdef CONFIG_FUTEX 1851 p->robust_list = NULL; 1852 #ifdef CONFIG_COMPAT 1853 p->compat_robust_list = NULL; 1854 #endif 1855 INIT_LIST_HEAD(&p->pi_state_list); 1856 p->pi_state_cache = NULL; 1857 #endif 1858 /* 1859 * sigaltstack should be cleared when sharing the same VM 1860 */ 1861 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1862 sas_ss_reset(p); 1863 1864 /* 1865 * Syscall tracing and stepping should be turned off in the 1866 * child regardless of CLONE_PTRACE. 1867 */ 1868 user_disable_single_step(p); 1869 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1870 #ifdef TIF_SYSCALL_EMU 1871 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1872 #endif 1873 clear_all_latency_tracing(p); 1874 1875 /* ok, now we should be set up.. */ 1876 p->pid = pid_nr(pid); 1877 if (clone_flags & CLONE_THREAD) { 1878 p->exit_signal = -1; 1879 p->group_leader = current->group_leader; 1880 p->tgid = current->tgid; 1881 } else { 1882 if (clone_flags & CLONE_PARENT) 1883 p->exit_signal = current->group_leader->exit_signal; 1884 else 1885 p->exit_signal = (clone_flags & CSIGNAL); 1886 p->group_leader = p; 1887 p->tgid = p->pid; 1888 } 1889 1890 p->nr_dirtied = 0; 1891 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1892 p->dirty_paused_when = 0; 1893 1894 p->pdeath_signal = 0; 1895 INIT_LIST_HEAD(&p->thread_group); 1896 p->task_works = NULL; 1897 1898 cgroup_threadgroup_change_begin(current); 1899 /* 1900 * Ensure that the cgroup subsystem policies allow the new process to be 1901 * forked. It should be noted the the new process's css_set can be changed 1902 * between here and cgroup_post_fork() if an organisation operation is in 1903 * progress. 1904 */ 1905 retval = cgroup_can_fork(p); 1906 if (retval) 1907 goto bad_fork_free_pid; 1908 1909 /* 1910 * Make it visible to the rest of the system, but dont wake it up yet. 1911 * Need tasklist lock for parent etc handling! 1912 */ 1913 write_lock_irq(&tasklist_lock); 1914 1915 /* CLONE_PARENT re-uses the old parent */ 1916 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1917 p->real_parent = current->real_parent; 1918 p->parent_exec_id = current->parent_exec_id; 1919 } else { 1920 p->real_parent = current; 1921 p->parent_exec_id = current->self_exec_id; 1922 } 1923 1924 klp_copy_process(p); 1925 1926 spin_lock(¤t->sighand->siglock); 1927 1928 /* 1929 * Copy seccomp details explicitly here, in case they were changed 1930 * before holding sighand lock. 1931 */ 1932 copy_seccomp(p); 1933 1934 rseq_fork(p, clone_flags); 1935 1936 /* 1937 * Process group and session signals need to be delivered to just the 1938 * parent before the fork or both the parent and the child after the 1939 * fork. Restart if a signal comes in before we add the new process to 1940 * it's process group. 1941 * A fatal signal pending means that current will exit, so the new 1942 * thread can't slip out of an OOM kill (or normal SIGKILL). 1943 */ 1944 recalc_sigpending(); 1945 if (signal_pending(current)) { 1946 retval = -ERESTARTNOINTR; 1947 goto bad_fork_cancel_cgroup; 1948 } 1949 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 1950 retval = -ENOMEM; 1951 goto bad_fork_cancel_cgroup; 1952 } 1953 1954 if (likely(p->pid)) { 1955 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1956 1957 init_task_pid(p, PIDTYPE_PID, pid); 1958 if (thread_group_leader(p)) { 1959 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1960 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1961 1962 if (is_child_reaper(pid)) { 1963 ns_of_pid(pid)->child_reaper = p; 1964 p->signal->flags |= SIGNAL_UNKILLABLE; 1965 } 1966 1967 p->signal->leader_pid = pid; 1968 p->signal->tty = tty_kref_get(current->signal->tty); 1969 /* 1970 * Inherit has_child_subreaper flag under the same 1971 * tasklist_lock with adding child to the process tree 1972 * for propagate_has_child_subreaper optimization. 1973 */ 1974 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1975 p->real_parent->signal->is_child_subreaper; 1976 list_add_tail(&p->sibling, &p->real_parent->children); 1977 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1978 attach_pid(p, PIDTYPE_PGID); 1979 attach_pid(p, PIDTYPE_SID); 1980 __this_cpu_inc(process_counts); 1981 } else { 1982 current->signal->nr_threads++; 1983 atomic_inc(¤t->signal->live); 1984 atomic_inc(¤t->signal->sigcnt); 1985 list_add_tail_rcu(&p->thread_group, 1986 &p->group_leader->thread_group); 1987 list_add_tail_rcu(&p->thread_node, 1988 &p->signal->thread_head); 1989 } 1990 attach_pid(p, PIDTYPE_PID); 1991 nr_threads++; 1992 } 1993 1994 total_forks++; 1995 spin_unlock(¤t->sighand->siglock); 1996 syscall_tracepoint_update(p); 1997 write_unlock_irq(&tasklist_lock); 1998 1999 proc_fork_connector(p); 2000 cgroup_post_fork(p); 2001 cgroup_threadgroup_change_end(current); 2002 perf_event_fork(p); 2003 2004 trace_task_newtask(p, clone_flags); 2005 uprobe_copy_process(p, clone_flags); 2006 2007 return p; 2008 2009 bad_fork_cancel_cgroup: 2010 spin_unlock(¤t->sighand->siglock); 2011 write_unlock_irq(&tasklist_lock); 2012 cgroup_cancel_fork(p); 2013 bad_fork_free_pid: 2014 cgroup_threadgroup_change_end(current); 2015 if (pid != &init_struct_pid) 2016 free_pid(pid); 2017 bad_fork_cleanup_thread: 2018 exit_thread(p); 2019 bad_fork_cleanup_io: 2020 if (p->io_context) 2021 exit_io_context(p); 2022 bad_fork_cleanup_namespaces: 2023 exit_task_namespaces(p); 2024 bad_fork_cleanup_mm: 2025 if (p->mm) 2026 mmput(p->mm); 2027 bad_fork_cleanup_signal: 2028 if (!(clone_flags & CLONE_THREAD)) 2029 free_signal_struct(p->signal); 2030 bad_fork_cleanup_sighand: 2031 __cleanup_sighand(p->sighand); 2032 bad_fork_cleanup_fs: 2033 exit_fs(p); /* blocking */ 2034 bad_fork_cleanup_files: 2035 exit_files(p); /* blocking */ 2036 bad_fork_cleanup_semundo: 2037 exit_sem(p); 2038 bad_fork_cleanup_security: 2039 security_task_free(p); 2040 bad_fork_cleanup_audit: 2041 audit_free(p); 2042 bad_fork_cleanup_perf: 2043 perf_event_free_task(p); 2044 bad_fork_cleanup_policy: 2045 lockdep_free_task(p); 2046 #ifdef CONFIG_NUMA 2047 mpol_put(p->mempolicy); 2048 bad_fork_cleanup_threadgroup_lock: 2049 #endif 2050 delayacct_tsk_free(p); 2051 bad_fork_cleanup_count: 2052 atomic_dec(&p->cred->user->processes); 2053 exit_creds(p); 2054 bad_fork_free: 2055 p->state = TASK_DEAD; 2056 put_task_stack(p); 2057 free_task(p); 2058 fork_out: 2059 return ERR_PTR(retval); 2060 } 2061 2062 static inline void init_idle_pids(struct pid_link *links) 2063 { 2064 enum pid_type type; 2065 2066 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2067 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 2068 links[type].pid = &init_struct_pid; 2069 } 2070 } 2071 2072 struct task_struct *fork_idle(int cpu) 2073 { 2074 struct task_struct *task; 2075 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2076 cpu_to_node(cpu)); 2077 if (!IS_ERR(task)) { 2078 init_idle_pids(task->pids); 2079 init_idle(task, cpu); 2080 } 2081 2082 return task; 2083 } 2084 2085 /* 2086 * Ok, this is the main fork-routine. 2087 * 2088 * It copies the process, and if successful kick-starts 2089 * it and waits for it to finish using the VM if required. 2090 */ 2091 long _do_fork(unsigned long clone_flags, 2092 unsigned long stack_start, 2093 unsigned long stack_size, 2094 int __user *parent_tidptr, 2095 int __user *child_tidptr, 2096 unsigned long tls) 2097 { 2098 struct completion vfork; 2099 struct pid *pid; 2100 struct task_struct *p; 2101 int trace = 0; 2102 long nr; 2103 2104 /* 2105 * Determine whether and which event to report to ptracer. When 2106 * called from kernel_thread or CLONE_UNTRACED is explicitly 2107 * requested, no event is reported; otherwise, report if the event 2108 * for the type of forking is enabled. 2109 */ 2110 if (!(clone_flags & CLONE_UNTRACED)) { 2111 if (clone_flags & CLONE_VFORK) 2112 trace = PTRACE_EVENT_VFORK; 2113 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2114 trace = PTRACE_EVENT_CLONE; 2115 else 2116 trace = PTRACE_EVENT_FORK; 2117 2118 if (likely(!ptrace_event_enabled(current, trace))) 2119 trace = 0; 2120 } 2121 2122 p = copy_process(clone_flags, stack_start, stack_size, 2123 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2124 add_latent_entropy(); 2125 2126 if (IS_ERR(p)) 2127 return PTR_ERR(p); 2128 2129 /* 2130 * Do this prior waking up the new thread - the thread pointer 2131 * might get invalid after that point, if the thread exits quickly. 2132 */ 2133 trace_sched_process_fork(current, p); 2134 2135 pid = get_task_pid(p, PIDTYPE_PID); 2136 nr = pid_vnr(pid); 2137 2138 if (clone_flags & CLONE_PARENT_SETTID) 2139 put_user(nr, parent_tidptr); 2140 2141 if (clone_flags & CLONE_VFORK) { 2142 p->vfork_done = &vfork; 2143 init_completion(&vfork); 2144 get_task_struct(p); 2145 } 2146 2147 wake_up_new_task(p); 2148 2149 /* forking complete and child started to run, tell ptracer */ 2150 if (unlikely(trace)) 2151 ptrace_event_pid(trace, pid); 2152 2153 if (clone_flags & CLONE_VFORK) { 2154 if (!wait_for_vfork_done(p, &vfork)) 2155 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2156 } 2157 2158 put_pid(pid); 2159 return nr; 2160 } 2161 2162 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2163 /* For compatibility with architectures that call do_fork directly rather than 2164 * using the syscall entry points below. */ 2165 long do_fork(unsigned long clone_flags, 2166 unsigned long stack_start, 2167 unsigned long stack_size, 2168 int __user *parent_tidptr, 2169 int __user *child_tidptr) 2170 { 2171 return _do_fork(clone_flags, stack_start, stack_size, 2172 parent_tidptr, child_tidptr, 0); 2173 } 2174 #endif 2175 2176 /* 2177 * Create a kernel thread. 2178 */ 2179 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2180 { 2181 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2182 (unsigned long)arg, NULL, NULL, 0); 2183 } 2184 2185 #ifdef __ARCH_WANT_SYS_FORK 2186 SYSCALL_DEFINE0(fork) 2187 { 2188 #ifdef CONFIG_MMU 2189 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2190 #else 2191 /* can not support in nommu mode */ 2192 return -EINVAL; 2193 #endif 2194 } 2195 #endif 2196 2197 #ifdef __ARCH_WANT_SYS_VFORK 2198 SYSCALL_DEFINE0(vfork) 2199 { 2200 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2201 0, NULL, NULL, 0); 2202 } 2203 #endif 2204 2205 #ifdef __ARCH_WANT_SYS_CLONE 2206 #ifdef CONFIG_CLONE_BACKWARDS 2207 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2208 int __user *, parent_tidptr, 2209 unsigned long, tls, 2210 int __user *, child_tidptr) 2211 #elif defined(CONFIG_CLONE_BACKWARDS2) 2212 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2213 int __user *, parent_tidptr, 2214 int __user *, child_tidptr, 2215 unsigned long, tls) 2216 #elif defined(CONFIG_CLONE_BACKWARDS3) 2217 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2218 int, stack_size, 2219 int __user *, parent_tidptr, 2220 int __user *, child_tidptr, 2221 unsigned long, tls) 2222 #else 2223 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2224 int __user *, parent_tidptr, 2225 int __user *, child_tidptr, 2226 unsigned long, tls) 2227 #endif 2228 { 2229 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2230 } 2231 #endif 2232 2233 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2234 { 2235 struct task_struct *leader, *parent, *child; 2236 int res; 2237 2238 read_lock(&tasklist_lock); 2239 leader = top = top->group_leader; 2240 down: 2241 for_each_thread(leader, parent) { 2242 list_for_each_entry(child, &parent->children, sibling) { 2243 res = visitor(child, data); 2244 if (res) { 2245 if (res < 0) 2246 goto out; 2247 leader = child; 2248 goto down; 2249 } 2250 up: 2251 ; 2252 } 2253 } 2254 2255 if (leader != top) { 2256 child = leader; 2257 parent = child->real_parent; 2258 leader = parent->group_leader; 2259 goto up; 2260 } 2261 out: 2262 read_unlock(&tasklist_lock); 2263 } 2264 2265 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2266 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2267 #endif 2268 2269 static void sighand_ctor(void *data) 2270 { 2271 struct sighand_struct *sighand = data; 2272 2273 spin_lock_init(&sighand->siglock); 2274 init_waitqueue_head(&sighand->signalfd_wqh); 2275 } 2276 2277 void __init proc_caches_init(void) 2278 { 2279 sighand_cachep = kmem_cache_create("sighand_cache", 2280 sizeof(struct sighand_struct), 0, 2281 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2282 SLAB_ACCOUNT, sighand_ctor); 2283 signal_cachep = kmem_cache_create("signal_cache", 2284 sizeof(struct signal_struct), 0, 2285 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2286 NULL); 2287 files_cachep = kmem_cache_create("files_cache", 2288 sizeof(struct files_struct), 0, 2289 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2290 NULL); 2291 fs_cachep = kmem_cache_create("fs_cache", 2292 sizeof(struct fs_struct), 0, 2293 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2294 NULL); 2295 /* 2296 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2297 * whole struct cpumask for the OFFSTACK case. We could change 2298 * this to *only* allocate as much of it as required by the 2299 * maximum number of CPU's we can ever have. The cpumask_allocation 2300 * is at the end of the structure, exactly for that reason. 2301 */ 2302 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2303 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2304 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2305 offsetof(struct mm_struct, saved_auxv), 2306 sizeof_field(struct mm_struct, saved_auxv), 2307 NULL); 2308 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2309 mmap_init(); 2310 nsproxy_cache_init(); 2311 } 2312 2313 /* 2314 * Check constraints on flags passed to the unshare system call. 2315 */ 2316 static int check_unshare_flags(unsigned long unshare_flags) 2317 { 2318 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2319 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2320 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2321 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2322 return -EINVAL; 2323 /* 2324 * Not implemented, but pretend it works if there is nothing 2325 * to unshare. Note that unsharing the address space or the 2326 * signal handlers also need to unshare the signal queues (aka 2327 * CLONE_THREAD). 2328 */ 2329 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2330 if (!thread_group_empty(current)) 2331 return -EINVAL; 2332 } 2333 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2334 if (atomic_read(¤t->sighand->count) > 1) 2335 return -EINVAL; 2336 } 2337 if (unshare_flags & CLONE_VM) { 2338 if (!current_is_single_threaded()) 2339 return -EINVAL; 2340 } 2341 2342 return 0; 2343 } 2344 2345 /* 2346 * Unshare the filesystem structure if it is being shared 2347 */ 2348 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2349 { 2350 struct fs_struct *fs = current->fs; 2351 2352 if (!(unshare_flags & CLONE_FS) || !fs) 2353 return 0; 2354 2355 /* don't need lock here; in the worst case we'll do useless copy */ 2356 if (fs->users == 1) 2357 return 0; 2358 2359 *new_fsp = copy_fs_struct(fs); 2360 if (!*new_fsp) 2361 return -ENOMEM; 2362 2363 return 0; 2364 } 2365 2366 /* 2367 * Unshare file descriptor table if it is being shared 2368 */ 2369 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2370 { 2371 struct files_struct *fd = current->files; 2372 int error = 0; 2373 2374 if ((unshare_flags & CLONE_FILES) && 2375 (fd && atomic_read(&fd->count) > 1)) { 2376 *new_fdp = dup_fd(fd, &error); 2377 if (!*new_fdp) 2378 return error; 2379 } 2380 2381 return 0; 2382 } 2383 2384 /* 2385 * unshare allows a process to 'unshare' part of the process 2386 * context which was originally shared using clone. copy_* 2387 * functions used by do_fork() cannot be used here directly 2388 * because they modify an inactive task_struct that is being 2389 * constructed. Here we are modifying the current, active, 2390 * task_struct. 2391 */ 2392 int ksys_unshare(unsigned long unshare_flags) 2393 { 2394 struct fs_struct *fs, *new_fs = NULL; 2395 struct files_struct *fd, *new_fd = NULL; 2396 struct cred *new_cred = NULL; 2397 struct nsproxy *new_nsproxy = NULL; 2398 int do_sysvsem = 0; 2399 int err; 2400 2401 /* 2402 * If unsharing a user namespace must also unshare the thread group 2403 * and unshare the filesystem root and working directories. 2404 */ 2405 if (unshare_flags & CLONE_NEWUSER) 2406 unshare_flags |= CLONE_THREAD | CLONE_FS; 2407 /* 2408 * If unsharing vm, must also unshare signal handlers. 2409 */ 2410 if (unshare_flags & CLONE_VM) 2411 unshare_flags |= CLONE_SIGHAND; 2412 /* 2413 * If unsharing a signal handlers, must also unshare the signal queues. 2414 */ 2415 if (unshare_flags & CLONE_SIGHAND) 2416 unshare_flags |= CLONE_THREAD; 2417 /* 2418 * If unsharing namespace, must also unshare filesystem information. 2419 */ 2420 if (unshare_flags & CLONE_NEWNS) 2421 unshare_flags |= CLONE_FS; 2422 2423 err = check_unshare_flags(unshare_flags); 2424 if (err) 2425 goto bad_unshare_out; 2426 /* 2427 * CLONE_NEWIPC must also detach from the undolist: after switching 2428 * to a new ipc namespace, the semaphore arrays from the old 2429 * namespace are unreachable. 2430 */ 2431 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2432 do_sysvsem = 1; 2433 err = unshare_fs(unshare_flags, &new_fs); 2434 if (err) 2435 goto bad_unshare_out; 2436 err = unshare_fd(unshare_flags, &new_fd); 2437 if (err) 2438 goto bad_unshare_cleanup_fs; 2439 err = unshare_userns(unshare_flags, &new_cred); 2440 if (err) 2441 goto bad_unshare_cleanup_fd; 2442 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2443 new_cred, new_fs); 2444 if (err) 2445 goto bad_unshare_cleanup_cred; 2446 2447 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2448 if (do_sysvsem) { 2449 /* 2450 * CLONE_SYSVSEM is equivalent to sys_exit(). 2451 */ 2452 exit_sem(current); 2453 } 2454 if (unshare_flags & CLONE_NEWIPC) { 2455 /* Orphan segments in old ns (see sem above). */ 2456 exit_shm(current); 2457 shm_init_task(current); 2458 } 2459 2460 if (new_nsproxy) 2461 switch_task_namespaces(current, new_nsproxy); 2462 2463 task_lock(current); 2464 2465 if (new_fs) { 2466 fs = current->fs; 2467 spin_lock(&fs->lock); 2468 current->fs = new_fs; 2469 if (--fs->users) 2470 new_fs = NULL; 2471 else 2472 new_fs = fs; 2473 spin_unlock(&fs->lock); 2474 } 2475 2476 if (new_fd) { 2477 fd = current->files; 2478 current->files = new_fd; 2479 new_fd = fd; 2480 } 2481 2482 task_unlock(current); 2483 2484 if (new_cred) { 2485 /* Install the new user namespace */ 2486 commit_creds(new_cred); 2487 new_cred = NULL; 2488 } 2489 } 2490 2491 perf_event_namespaces(current); 2492 2493 bad_unshare_cleanup_cred: 2494 if (new_cred) 2495 put_cred(new_cred); 2496 bad_unshare_cleanup_fd: 2497 if (new_fd) 2498 put_files_struct(new_fd); 2499 2500 bad_unshare_cleanup_fs: 2501 if (new_fs) 2502 free_fs_struct(new_fs); 2503 2504 bad_unshare_out: 2505 return err; 2506 } 2507 2508 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2509 { 2510 return ksys_unshare(unshare_flags); 2511 } 2512 2513 /* 2514 * Helper to unshare the files of the current task. 2515 * We don't want to expose copy_files internals to 2516 * the exec layer of the kernel. 2517 */ 2518 2519 int unshare_files(struct files_struct **displaced) 2520 { 2521 struct task_struct *task = current; 2522 struct files_struct *copy = NULL; 2523 int error; 2524 2525 error = unshare_fd(CLONE_FILES, ©); 2526 if (error || !copy) { 2527 *displaced = NULL; 2528 return error; 2529 } 2530 *displaced = task->files; 2531 task_lock(task); 2532 task->files = copy; 2533 task_unlock(task); 2534 return 0; 2535 } 2536 2537 int sysctl_max_threads(struct ctl_table *table, int write, 2538 void __user *buffer, size_t *lenp, loff_t *ppos) 2539 { 2540 struct ctl_table t; 2541 int ret; 2542 int threads = max_threads; 2543 int min = MIN_THREADS; 2544 int max = MAX_THREADS; 2545 2546 t = *table; 2547 t.data = &threads; 2548 t.extra1 = &min; 2549 t.extra2 = &max; 2550 2551 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2552 if (ret || !write) 2553 return ret; 2554 2555 set_max_threads(threads); 2556 2557 return 0; 2558 } 2559