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/fs.h> 41 #include <linux/mm.h> 42 #include <linux/vmacache.h> 43 #include <linux/nsproxy.h> 44 #include <linux/capability.h> 45 #include <linux/cpu.h> 46 #include <linux/cgroup.h> 47 #include <linux/security.h> 48 #include <linux/hugetlb.h> 49 #include <linux/seccomp.h> 50 #include <linux/swap.h> 51 #include <linux/syscalls.h> 52 #include <linux/jiffies.h> 53 #include <linux/futex.h> 54 #include <linux/compat.h> 55 #include <linux/kthread.h> 56 #include <linux/task_io_accounting_ops.h> 57 #include <linux/rcupdate.h> 58 #include <linux/ptrace.h> 59 #include <linux/mount.h> 60 #include <linux/audit.h> 61 #include <linux/memcontrol.h> 62 #include <linux/ftrace.h> 63 #include <linux/proc_fs.h> 64 #include <linux/profile.h> 65 #include <linux/rmap.h> 66 #include <linux/ksm.h> 67 #include <linux/acct.h> 68 #include <linux/userfaultfd_k.h> 69 #include <linux/tsacct_kern.h> 70 #include <linux/cn_proc.h> 71 #include <linux/freezer.h> 72 #include <linux/delayacct.h> 73 #include <linux/taskstats_kern.h> 74 #include <linux/random.h> 75 #include <linux/tty.h> 76 #include <linux/blkdev.h> 77 #include <linux/fs_struct.h> 78 #include <linux/magic.h> 79 #include <linux/perf_event.h> 80 #include <linux/posix-timers.h> 81 #include <linux/user-return-notifier.h> 82 #include <linux/oom.h> 83 #include <linux/khugepaged.h> 84 #include <linux/signalfd.h> 85 #include <linux/uprobes.h> 86 #include <linux/aio.h> 87 #include <linux/compiler.h> 88 #include <linux/sysctl.h> 89 #include <linux/kcov.h> 90 #include <linux/livepatch.h> 91 92 #include <asm/pgtable.h> 93 #include <asm/pgalloc.h> 94 #include <linux/uaccess.h> 95 #include <asm/mmu_context.h> 96 #include <asm/cacheflush.h> 97 #include <asm/tlbflush.h> 98 99 #include <trace/events/sched.h> 100 101 #define CREATE_TRACE_POINTS 102 #include <trace/events/task.h> 103 104 /* 105 * Minimum number of threads to boot the kernel 106 */ 107 #define MIN_THREADS 20 108 109 /* 110 * Maximum number of threads 111 */ 112 #define MAX_THREADS FUTEX_TID_MASK 113 114 /* 115 * Protected counters by write_lock_irq(&tasklist_lock) 116 */ 117 unsigned long total_forks; /* Handle normal Linux uptimes. */ 118 int nr_threads; /* The idle threads do not count.. */ 119 120 int max_threads; /* tunable limit on nr_threads */ 121 122 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 123 124 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 125 126 #ifdef CONFIG_PROVE_RCU 127 int lockdep_tasklist_lock_is_held(void) 128 { 129 return lockdep_is_held(&tasklist_lock); 130 } 131 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 132 #endif /* #ifdef CONFIG_PROVE_RCU */ 133 134 int nr_processes(void) 135 { 136 int cpu; 137 int total = 0; 138 139 for_each_possible_cpu(cpu) 140 total += per_cpu(process_counts, cpu); 141 142 return total; 143 } 144 145 void __weak arch_release_task_struct(struct task_struct *tsk) 146 { 147 } 148 149 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 150 static struct kmem_cache *task_struct_cachep; 151 152 static inline struct task_struct *alloc_task_struct_node(int node) 153 { 154 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 155 } 156 157 static inline void free_task_struct(struct task_struct *tsk) 158 { 159 kmem_cache_free(task_struct_cachep, tsk); 160 } 161 #endif 162 163 void __weak arch_release_thread_stack(unsigned long *stack) 164 { 165 } 166 167 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 168 169 /* 170 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 171 * kmemcache based allocator. 172 */ 173 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 174 175 #ifdef CONFIG_VMAP_STACK 176 /* 177 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 178 * flush. Try to minimize the number of calls by caching stacks. 179 */ 180 #define NR_CACHED_STACKS 2 181 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 182 183 static int free_vm_stack_cache(unsigned int cpu) 184 { 185 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 186 int i; 187 188 for (i = 0; i < NR_CACHED_STACKS; i++) { 189 struct vm_struct *vm_stack = cached_vm_stacks[i]; 190 191 if (!vm_stack) 192 continue; 193 194 vfree(vm_stack->addr); 195 cached_vm_stacks[i] = NULL; 196 } 197 198 return 0; 199 } 200 #endif 201 202 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 203 { 204 #ifdef CONFIG_VMAP_STACK 205 void *stack; 206 int i; 207 208 for (i = 0; i < NR_CACHED_STACKS; i++) { 209 struct vm_struct *s; 210 211 s = this_cpu_xchg(cached_stacks[i], NULL); 212 213 if (!s) 214 continue; 215 216 tsk->stack_vm_area = s; 217 return s->addr; 218 } 219 220 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, 221 VMALLOC_START, VMALLOC_END, 222 THREADINFO_GFP, 223 PAGE_KERNEL, 224 0, node, __builtin_return_address(0)); 225 226 /* 227 * We can't call find_vm_area() in interrupt context, and 228 * free_thread_stack() can be called in interrupt context, 229 * so cache the vm_struct. 230 */ 231 if (stack) 232 tsk->stack_vm_area = find_vm_area(stack); 233 return stack; 234 #else 235 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 236 THREAD_SIZE_ORDER); 237 238 return page ? page_address(page) : NULL; 239 #endif 240 } 241 242 static inline void free_thread_stack(struct task_struct *tsk) 243 { 244 #ifdef CONFIG_VMAP_STACK 245 if (task_stack_vm_area(tsk)) { 246 int i; 247 248 for (i = 0; i < NR_CACHED_STACKS; i++) { 249 if (this_cpu_cmpxchg(cached_stacks[i], 250 NULL, tsk->stack_vm_area) != NULL) 251 continue; 252 253 return; 254 } 255 256 vfree_atomic(tsk->stack); 257 return; 258 } 259 #endif 260 261 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 262 } 263 # else 264 static struct kmem_cache *thread_stack_cache; 265 266 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 267 int node) 268 { 269 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 270 } 271 272 static void free_thread_stack(struct task_struct *tsk) 273 { 274 kmem_cache_free(thread_stack_cache, tsk->stack); 275 } 276 277 void thread_stack_cache_init(void) 278 { 279 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 280 THREAD_SIZE, 0, NULL); 281 BUG_ON(thread_stack_cache == NULL); 282 } 283 # endif 284 #endif 285 286 /* SLAB cache for signal_struct structures (tsk->signal) */ 287 static struct kmem_cache *signal_cachep; 288 289 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 290 struct kmem_cache *sighand_cachep; 291 292 /* SLAB cache for files_struct structures (tsk->files) */ 293 struct kmem_cache *files_cachep; 294 295 /* SLAB cache for fs_struct structures (tsk->fs) */ 296 struct kmem_cache *fs_cachep; 297 298 /* SLAB cache for vm_area_struct structures */ 299 struct kmem_cache *vm_area_cachep; 300 301 /* SLAB cache for mm_struct structures (tsk->mm) */ 302 static struct kmem_cache *mm_cachep; 303 304 static void account_kernel_stack(struct task_struct *tsk, int account) 305 { 306 void *stack = task_stack_page(tsk); 307 struct vm_struct *vm = task_stack_vm_area(tsk); 308 309 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 310 311 if (vm) { 312 int i; 313 314 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 315 316 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 317 mod_zone_page_state(page_zone(vm->pages[i]), 318 NR_KERNEL_STACK_KB, 319 PAGE_SIZE / 1024 * account); 320 } 321 322 /* All stack pages belong to the same memcg. */ 323 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB, 324 account * (THREAD_SIZE / 1024)); 325 } else { 326 /* 327 * All stack pages are in the same zone and belong to the 328 * same memcg. 329 */ 330 struct page *first_page = virt_to_page(stack); 331 332 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 333 THREAD_SIZE / 1024 * account); 334 335 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, 336 account * (THREAD_SIZE / 1024)); 337 } 338 } 339 340 static void release_task_stack(struct task_struct *tsk) 341 { 342 if (WARN_ON(tsk->state != TASK_DEAD)) 343 return; /* Better to leak the stack than to free prematurely */ 344 345 account_kernel_stack(tsk, -1); 346 arch_release_thread_stack(tsk->stack); 347 free_thread_stack(tsk); 348 tsk->stack = NULL; 349 #ifdef CONFIG_VMAP_STACK 350 tsk->stack_vm_area = NULL; 351 #endif 352 } 353 354 #ifdef CONFIG_THREAD_INFO_IN_TASK 355 void put_task_stack(struct task_struct *tsk) 356 { 357 if (atomic_dec_and_test(&tsk->stack_refcount)) 358 release_task_stack(tsk); 359 } 360 #endif 361 362 void free_task(struct task_struct *tsk) 363 { 364 #ifndef CONFIG_THREAD_INFO_IN_TASK 365 /* 366 * The task is finally done with both the stack and thread_info, 367 * so free both. 368 */ 369 release_task_stack(tsk); 370 #else 371 /* 372 * If the task had a separate stack allocation, it should be gone 373 * by now. 374 */ 375 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 376 #endif 377 rt_mutex_debug_task_free(tsk); 378 ftrace_graph_exit_task(tsk); 379 put_seccomp_filter(tsk); 380 arch_release_task_struct(tsk); 381 if (tsk->flags & PF_KTHREAD) 382 free_kthread_struct(tsk); 383 free_task_struct(tsk); 384 } 385 EXPORT_SYMBOL(free_task); 386 387 static inline void free_signal_struct(struct signal_struct *sig) 388 { 389 taskstats_tgid_free(sig); 390 sched_autogroup_exit(sig); 391 /* 392 * __mmdrop is not safe to call from softirq context on x86 due to 393 * pgd_dtor so postpone it to the async context 394 */ 395 if (sig->oom_mm) 396 mmdrop_async(sig->oom_mm); 397 kmem_cache_free(signal_cachep, sig); 398 } 399 400 static inline void put_signal_struct(struct signal_struct *sig) 401 { 402 if (atomic_dec_and_test(&sig->sigcnt)) 403 free_signal_struct(sig); 404 } 405 406 void __put_task_struct(struct task_struct *tsk) 407 { 408 WARN_ON(!tsk->exit_state); 409 WARN_ON(atomic_read(&tsk->usage)); 410 WARN_ON(tsk == current); 411 412 cgroup_free(tsk); 413 task_numa_free(tsk); 414 security_task_free(tsk); 415 exit_creds(tsk); 416 delayacct_tsk_free(tsk); 417 put_signal_struct(tsk->signal); 418 419 if (!profile_handoff_task(tsk)) 420 free_task(tsk); 421 } 422 EXPORT_SYMBOL_GPL(__put_task_struct); 423 424 void __init __weak arch_task_cache_init(void) { } 425 426 /* 427 * set_max_threads 428 */ 429 static void set_max_threads(unsigned int max_threads_suggested) 430 { 431 u64 threads; 432 433 /* 434 * The number of threads shall be limited such that the thread 435 * structures may only consume a small part of the available memory. 436 */ 437 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 438 threads = MAX_THREADS; 439 else 440 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 441 (u64) THREAD_SIZE * 8UL); 442 443 if (threads > max_threads_suggested) 444 threads = max_threads_suggested; 445 446 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 447 } 448 449 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 450 /* Initialized by the architecture: */ 451 int arch_task_struct_size __read_mostly; 452 #endif 453 454 void __init fork_init(void) 455 { 456 int i; 457 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 458 #ifndef ARCH_MIN_TASKALIGN 459 #define ARCH_MIN_TASKALIGN 0 460 #endif 461 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 462 463 /* create a slab on which task_structs can be allocated */ 464 task_struct_cachep = kmem_cache_create("task_struct", 465 arch_task_struct_size, align, 466 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 467 #endif 468 469 /* do the arch specific task caches init */ 470 arch_task_cache_init(); 471 472 set_max_threads(MAX_THREADS); 473 474 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 475 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 476 init_task.signal->rlim[RLIMIT_SIGPENDING] = 477 init_task.signal->rlim[RLIMIT_NPROC]; 478 479 for (i = 0; i < UCOUNT_COUNTS; i++) { 480 init_user_ns.ucount_max[i] = max_threads/2; 481 } 482 483 #ifdef CONFIG_VMAP_STACK 484 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 485 NULL, free_vm_stack_cache); 486 #endif 487 } 488 489 int __weak arch_dup_task_struct(struct task_struct *dst, 490 struct task_struct *src) 491 { 492 *dst = *src; 493 return 0; 494 } 495 496 void set_task_stack_end_magic(struct task_struct *tsk) 497 { 498 unsigned long *stackend; 499 500 stackend = end_of_stack(tsk); 501 *stackend = STACK_END_MAGIC; /* for overflow detection */ 502 } 503 504 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 505 { 506 struct task_struct *tsk; 507 unsigned long *stack; 508 struct vm_struct *stack_vm_area; 509 int err; 510 511 if (node == NUMA_NO_NODE) 512 node = tsk_fork_get_node(orig); 513 tsk = alloc_task_struct_node(node); 514 if (!tsk) 515 return NULL; 516 517 stack = alloc_thread_stack_node(tsk, node); 518 if (!stack) 519 goto free_tsk; 520 521 stack_vm_area = task_stack_vm_area(tsk); 522 523 err = arch_dup_task_struct(tsk, orig); 524 525 /* 526 * arch_dup_task_struct() clobbers the stack-related fields. Make 527 * sure they're properly initialized before using any stack-related 528 * functions again. 529 */ 530 tsk->stack = stack; 531 #ifdef CONFIG_VMAP_STACK 532 tsk->stack_vm_area = stack_vm_area; 533 #endif 534 #ifdef CONFIG_THREAD_INFO_IN_TASK 535 atomic_set(&tsk->stack_refcount, 1); 536 #endif 537 538 if (err) 539 goto free_stack; 540 541 #ifdef CONFIG_SECCOMP 542 /* 543 * We must handle setting up seccomp filters once we're under 544 * the sighand lock in case orig has changed between now and 545 * then. Until then, filter must be NULL to avoid messing up 546 * the usage counts on the error path calling free_task. 547 */ 548 tsk->seccomp.filter = NULL; 549 #endif 550 551 setup_thread_stack(tsk, orig); 552 clear_user_return_notifier(tsk); 553 clear_tsk_need_resched(tsk); 554 set_task_stack_end_magic(tsk); 555 556 #ifdef CONFIG_CC_STACKPROTECTOR 557 tsk->stack_canary = get_random_canary(); 558 #endif 559 560 /* 561 * One for us, one for whoever does the "release_task()" (usually 562 * parent) 563 */ 564 atomic_set(&tsk->usage, 2); 565 #ifdef CONFIG_BLK_DEV_IO_TRACE 566 tsk->btrace_seq = 0; 567 #endif 568 tsk->splice_pipe = NULL; 569 tsk->task_frag.page = NULL; 570 tsk->wake_q.next = NULL; 571 572 account_kernel_stack(tsk, 1); 573 574 kcov_task_init(tsk); 575 576 #ifdef CONFIG_FAULT_INJECTION 577 tsk->fail_nth = 0; 578 #endif 579 580 return tsk; 581 582 free_stack: 583 free_thread_stack(tsk); 584 free_tsk: 585 free_task_struct(tsk); 586 return NULL; 587 } 588 589 #ifdef CONFIG_MMU 590 static __latent_entropy int dup_mmap(struct mm_struct *mm, 591 struct mm_struct *oldmm) 592 { 593 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 594 struct rb_node **rb_link, *rb_parent; 595 int retval; 596 unsigned long charge; 597 LIST_HEAD(uf); 598 599 uprobe_start_dup_mmap(); 600 if (down_write_killable(&oldmm->mmap_sem)) { 601 retval = -EINTR; 602 goto fail_uprobe_end; 603 } 604 flush_cache_dup_mm(oldmm); 605 uprobe_dup_mmap(oldmm, mm); 606 /* 607 * Not linked in yet - no deadlock potential: 608 */ 609 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 610 611 /* No ordering required: file already has been exposed. */ 612 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 613 614 mm->total_vm = oldmm->total_vm; 615 mm->data_vm = oldmm->data_vm; 616 mm->exec_vm = oldmm->exec_vm; 617 mm->stack_vm = oldmm->stack_vm; 618 619 rb_link = &mm->mm_rb.rb_node; 620 rb_parent = NULL; 621 pprev = &mm->mmap; 622 retval = ksm_fork(mm, oldmm); 623 if (retval) 624 goto out; 625 retval = khugepaged_fork(mm, oldmm); 626 if (retval) 627 goto out; 628 629 prev = NULL; 630 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 631 struct file *file; 632 633 if (mpnt->vm_flags & VM_DONTCOPY) { 634 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 635 continue; 636 } 637 charge = 0; 638 if (mpnt->vm_flags & VM_ACCOUNT) { 639 unsigned long len = vma_pages(mpnt); 640 641 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 642 goto fail_nomem; 643 charge = len; 644 } 645 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 646 if (!tmp) 647 goto fail_nomem; 648 *tmp = *mpnt; 649 INIT_LIST_HEAD(&tmp->anon_vma_chain); 650 retval = vma_dup_policy(mpnt, tmp); 651 if (retval) 652 goto fail_nomem_policy; 653 tmp->vm_mm = mm; 654 retval = dup_userfaultfd(tmp, &uf); 655 if (retval) 656 goto fail_nomem_anon_vma_fork; 657 if (anon_vma_fork(tmp, mpnt)) 658 goto fail_nomem_anon_vma_fork; 659 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 660 tmp->vm_next = tmp->vm_prev = NULL; 661 file = tmp->vm_file; 662 if (file) { 663 struct inode *inode = file_inode(file); 664 struct address_space *mapping = file->f_mapping; 665 666 get_file(file); 667 if (tmp->vm_flags & VM_DENYWRITE) 668 atomic_dec(&inode->i_writecount); 669 i_mmap_lock_write(mapping); 670 if (tmp->vm_flags & VM_SHARED) 671 atomic_inc(&mapping->i_mmap_writable); 672 flush_dcache_mmap_lock(mapping); 673 /* insert tmp into the share list, just after mpnt */ 674 vma_interval_tree_insert_after(tmp, mpnt, 675 &mapping->i_mmap); 676 flush_dcache_mmap_unlock(mapping); 677 i_mmap_unlock_write(mapping); 678 } 679 680 /* 681 * Clear hugetlb-related page reserves for children. This only 682 * affects MAP_PRIVATE mappings. Faults generated by the child 683 * are not guaranteed to succeed, even if read-only 684 */ 685 if (is_vm_hugetlb_page(tmp)) 686 reset_vma_resv_huge_pages(tmp); 687 688 /* 689 * Link in the new vma and copy the page table entries. 690 */ 691 *pprev = tmp; 692 pprev = &tmp->vm_next; 693 tmp->vm_prev = prev; 694 prev = tmp; 695 696 __vma_link_rb(mm, tmp, rb_link, rb_parent); 697 rb_link = &tmp->vm_rb.rb_right; 698 rb_parent = &tmp->vm_rb; 699 700 mm->map_count++; 701 retval = copy_page_range(mm, oldmm, mpnt); 702 703 if (tmp->vm_ops && tmp->vm_ops->open) 704 tmp->vm_ops->open(tmp); 705 706 if (retval) 707 goto out; 708 } 709 /* a new mm has just been created */ 710 arch_dup_mmap(oldmm, mm); 711 retval = 0; 712 out: 713 up_write(&mm->mmap_sem); 714 flush_tlb_mm(oldmm); 715 up_write(&oldmm->mmap_sem); 716 dup_userfaultfd_complete(&uf); 717 fail_uprobe_end: 718 uprobe_end_dup_mmap(); 719 return retval; 720 fail_nomem_anon_vma_fork: 721 mpol_put(vma_policy(tmp)); 722 fail_nomem_policy: 723 kmem_cache_free(vm_area_cachep, tmp); 724 fail_nomem: 725 retval = -ENOMEM; 726 vm_unacct_memory(charge); 727 goto out; 728 } 729 730 static inline int mm_alloc_pgd(struct mm_struct *mm) 731 { 732 mm->pgd = pgd_alloc(mm); 733 if (unlikely(!mm->pgd)) 734 return -ENOMEM; 735 return 0; 736 } 737 738 static inline void mm_free_pgd(struct mm_struct *mm) 739 { 740 pgd_free(mm, mm->pgd); 741 } 742 #else 743 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 744 { 745 down_write(&oldmm->mmap_sem); 746 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 747 up_write(&oldmm->mmap_sem); 748 return 0; 749 } 750 #define mm_alloc_pgd(mm) (0) 751 #define mm_free_pgd(mm) 752 #endif /* CONFIG_MMU */ 753 754 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 755 756 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 757 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 758 759 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 760 761 static int __init coredump_filter_setup(char *s) 762 { 763 default_dump_filter = 764 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 765 MMF_DUMP_FILTER_MASK; 766 return 1; 767 } 768 769 __setup("coredump_filter=", coredump_filter_setup); 770 771 #include <linux/init_task.h> 772 773 static void mm_init_aio(struct mm_struct *mm) 774 { 775 #ifdef CONFIG_AIO 776 spin_lock_init(&mm->ioctx_lock); 777 mm->ioctx_table = NULL; 778 #endif 779 } 780 781 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 782 { 783 #ifdef CONFIG_MEMCG 784 mm->owner = p; 785 #endif 786 } 787 788 static void mm_init_uprobes_state(struct mm_struct *mm) 789 { 790 #ifdef CONFIG_UPROBES 791 mm->uprobes_state.xol_area = NULL; 792 #endif 793 } 794 795 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 796 struct user_namespace *user_ns) 797 { 798 mm->mmap = NULL; 799 mm->mm_rb = RB_ROOT; 800 mm->vmacache_seqnum = 0; 801 atomic_set(&mm->mm_users, 1); 802 atomic_set(&mm->mm_count, 1); 803 init_rwsem(&mm->mmap_sem); 804 INIT_LIST_HEAD(&mm->mmlist); 805 mm->core_state = NULL; 806 atomic_long_set(&mm->nr_ptes, 0); 807 mm_nr_pmds_init(mm); 808 mm->map_count = 0; 809 mm->locked_vm = 0; 810 mm->pinned_vm = 0; 811 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 812 spin_lock_init(&mm->page_table_lock); 813 mm_init_cpumask(mm); 814 mm_init_aio(mm); 815 mm_init_owner(mm, p); 816 RCU_INIT_POINTER(mm->exe_file, NULL); 817 mmu_notifier_mm_init(mm); 818 init_tlb_flush_pending(mm); 819 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 820 mm->pmd_huge_pte = NULL; 821 #endif 822 mm_init_uprobes_state(mm); 823 824 if (current->mm) { 825 mm->flags = current->mm->flags & MMF_INIT_MASK; 826 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 827 } else { 828 mm->flags = default_dump_filter; 829 mm->def_flags = 0; 830 } 831 832 if (mm_alloc_pgd(mm)) 833 goto fail_nopgd; 834 835 if (init_new_context(p, mm)) 836 goto fail_nocontext; 837 838 mm->user_ns = get_user_ns(user_ns); 839 return mm; 840 841 fail_nocontext: 842 mm_free_pgd(mm); 843 fail_nopgd: 844 free_mm(mm); 845 return NULL; 846 } 847 848 static void check_mm(struct mm_struct *mm) 849 { 850 int i; 851 852 for (i = 0; i < NR_MM_COUNTERS; i++) { 853 long x = atomic_long_read(&mm->rss_stat.count[i]); 854 855 if (unlikely(x)) 856 printk(KERN_ALERT "BUG: Bad rss-counter state " 857 "mm:%p idx:%d val:%ld\n", mm, i, x); 858 } 859 860 if (atomic_long_read(&mm->nr_ptes)) 861 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 862 atomic_long_read(&mm->nr_ptes)); 863 if (mm_nr_pmds(mm)) 864 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 865 mm_nr_pmds(mm)); 866 867 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 868 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 869 #endif 870 } 871 872 /* 873 * Allocate and initialize an mm_struct. 874 */ 875 struct mm_struct *mm_alloc(void) 876 { 877 struct mm_struct *mm; 878 879 mm = allocate_mm(); 880 if (!mm) 881 return NULL; 882 883 memset(mm, 0, sizeof(*mm)); 884 return mm_init(mm, current, current_user_ns()); 885 } 886 887 /* 888 * Called when the last reference to the mm 889 * is dropped: either by a lazy thread or by 890 * mmput. Free the page directory and the mm. 891 */ 892 void __mmdrop(struct mm_struct *mm) 893 { 894 BUG_ON(mm == &init_mm); 895 mm_free_pgd(mm); 896 destroy_context(mm); 897 mmu_notifier_mm_destroy(mm); 898 check_mm(mm); 899 put_user_ns(mm->user_ns); 900 free_mm(mm); 901 } 902 EXPORT_SYMBOL_GPL(__mmdrop); 903 904 static inline void __mmput(struct mm_struct *mm) 905 { 906 VM_BUG_ON(atomic_read(&mm->mm_users)); 907 908 uprobe_clear_state(mm); 909 exit_aio(mm); 910 ksm_exit(mm); 911 khugepaged_exit(mm); /* must run before exit_mmap */ 912 exit_mmap(mm); 913 mm_put_huge_zero_page(mm); 914 set_mm_exe_file(mm, NULL); 915 if (!list_empty(&mm->mmlist)) { 916 spin_lock(&mmlist_lock); 917 list_del(&mm->mmlist); 918 spin_unlock(&mmlist_lock); 919 } 920 if (mm->binfmt) 921 module_put(mm->binfmt->module); 922 set_bit(MMF_OOM_SKIP, &mm->flags); 923 mmdrop(mm); 924 } 925 926 /* 927 * Decrement the use count and release all resources for an mm. 928 */ 929 void mmput(struct mm_struct *mm) 930 { 931 might_sleep(); 932 933 if (atomic_dec_and_test(&mm->mm_users)) 934 __mmput(mm); 935 } 936 EXPORT_SYMBOL_GPL(mmput); 937 938 #ifdef CONFIG_MMU 939 static void mmput_async_fn(struct work_struct *work) 940 { 941 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 942 __mmput(mm); 943 } 944 945 void mmput_async(struct mm_struct *mm) 946 { 947 if (atomic_dec_and_test(&mm->mm_users)) { 948 INIT_WORK(&mm->async_put_work, mmput_async_fn); 949 schedule_work(&mm->async_put_work); 950 } 951 } 952 #endif 953 954 /** 955 * set_mm_exe_file - change a reference to the mm's executable file 956 * 957 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 958 * 959 * Main users are mmput() and sys_execve(). Callers prevent concurrent 960 * invocations: in mmput() nobody alive left, in execve task is single 961 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 962 * mm->exe_file, but does so without using set_mm_exe_file() in order 963 * to do avoid the need for any locks. 964 */ 965 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 966 { 967 struct file *old_exe_file; 968 969 /* 970 * It is safe to dereference the exe_file without RCU as 971 * this function is only called if nobody else can access 972 * this mm -- see comment above for justification. 973 */ 974 old_exe_file = rcu_dereference_raw(mm->exe_file); 975 976 if (new_exe_file) 977 get_file(new_exe_file); 978 rcu_assign_pointer(mm->exe_file, new_exe_file); 979 if (old_exe_file) 980 fput(old_exe_file); 981 } 982 983 /** 984 * get_mm_exe_file - acquire a reference to the mm's executable file 985 * 986 * Returns %NULL if mm has no associated executable file. 987 * User must release file via fput(). 988 */ 989 struct file *get_mm_exe_file(struct mm_struct *mm) 990 { 991 struct file *exe_file; 992 993 rcu_read_lock(); 994 exe_file = rcu_dereference(mm->exe_file); 995 if (exe_file && !get_file_rcu(exe_file)) 996 exe_file = NULL; 997 rcu_read_unlock(); 998 return exe_file; 999 } 1000 EXPORT_SYMBOL(get_mm_exe_file); 1001 1002 /** 1003 * get_task_exe_file - acquire a reference to the task's executable file 1004 * 1005 * Returns %NULL if task's mm (if any) has no associated executable file or 1006 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1007 * User must release file via fput(). 1008 */ 1009 struct file *get_task_exe_file(struct task_struct *task) 1010 { 1011 struct file *exe_file = NULL; 1012 struct mm_struct *mm; 1013 1014 task_lock(task); 1015 mm = task->mm; 1016 if (mm) { 1017 if (!(task->flags & PF_KTHREAD)) 1018 exe_file = get_mm_exe_file(mm); 1019 } 1020 task_unlock(task); 1021 return exe_file; 1022 } 1023 EXPORT_SYMBOL(get_task_exe_file); 1024 1025 /** 1026 * get_task_mm - acquire a reference to the task's mm 1027 * 1028 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1029 * this kernel workthread has transiently adopted a user mm with use_mm, 1030 * to do its AIO) is not set and if so returns a reference to it, after 1031 * bumping up the use count. User must release the mm via mmput() 1032 * after use. Typically used by /proc and ptrace. 1033 */ 1034 struct mm_struct *get_task_mm(struct task_struct *task) 1035 { 1036 struct mm_struct *mm; 1037 1038 task_lock(task); 1039 mm = task->mm; 1040 if (mm) { 1041 if (task->flags & PF_KTHREAD) 1042 mm = NULL; 1043 else 1044 mmget(mm); 1045 } 1046 task_unlock(task); 1047 return mm; 1048 } 1049 EXPORT_SYMBOL_GPL(get_task_mm); 1050 1051 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1052 { 1053 struct mm_struct *mm; 1054 int err; 1055 1056 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1057 if (err) 1058 return ERR_PTR(err); 1059 1060 mm = get_task_mm(task); 1061 if (mm && mm != current->mm && 1062 !ptrace_may_access(task, mode)) { 1063 mmput(mm); 1064 mm = ERR_PTR(-EACCES); 1065 } 1066 mutex_unlock(&task->signal->cred_guard_mutex); 1067 1068 return mm; 1069 } 1070 1071 static void complete_vfork_done(struct task_struct *tsk) 1072 { 1073 struct completion *vfork; 1074 1075 task_lock(tsk); 1076 vfork = tsk->vfork_done; 1077 if (likely(vfork)) { 1078 tsk->vfork_done = NULL; 1079 complete(vfork); 1080 } 1081 task_unlock(tsk); 1082 } 1083 1084 static int wait_for_vfork_done(struct task_struct *child, 1085 struct completion *vfork) 1086 { 1087 int killed; 1088 1089 freezer_do_not_count(); 1090 killed = wait_for_completion_killable(vfork); 1091 freezer_count(); 1092 1093 if (killed) { 1094 task_lock(child); 1095 child->vfork_done = NULL; 1096 task_unlock(child); 1097 } 1098 1099 put_task_struct(child); 1100 return killed; 1101 } 1102 1103 /* Please note the differences between mmput and mm_release. 1104 * mmput is called whenever we stop holding onto a mm_struct, 1105 * error success whatever. 1106 * 1107 * mm_release is called after a mm_struct has been removed 1108 * from the current process. 1109 * 1110 * This difference is important for error handling, when we 1111 * only half set up a mm_struct for a new process and need to restore 1112 * the old one. Because we mmput the new mm_struct before 1113 * restoring the old one. . . 1114 * Eric Biederman 10 January 1998 1115 */ 1116 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1117 { 1118 /* Get rid of any futexes when releasing the mm */ 1119 #ifdef CONFIG_FUTEX 1120 if (unlikely(tsk->robust_list)) { 1121 exit_robust_list(tsk); 1122 tsk->robust_list = NULL; 1123 } 1124 #ifdef CONFIG_COMPAT 1125 if (unlikely(tsk->compat_robust_list)) { 1126 compat_exit_robust_list(tsk); 1127 tsk->compat_robust_list = NULL; 1128 } 1129 #endif 1130 if (unlikely(!list_empty(&tsk->pi_state_list))) 1131 exit_pi_state_list(tsk); 1132 #endif 1133 1134 uprobe_free_utask(tsk); 1135 1136 /* Get rid of any cached register state */ 1137 deactivate_mm(tsk, mm); 1138 1139 /* 1140 * Signal userspace if we're not exiting with a core dump 1141 * because we want to leave the value intact for debugging 1142 * purposes. 1143 */ 1144 if (tsk->clear_child_tid) { 1145 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1146 atomic_read(&mm->mm_users) > 1) { 1147 /* 1148 * We don't check the error code - if userspace has 1149 * not set up a proper pointer then tough luck. 1150 */ 1151 put_user(0, tsk->clear_child_tid); 1152 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1153 1, NULL, NULL, 0); 1154 } 1155 tsk->clear_child_tid = NULL; 1156 } 1157 1158 /* 1159 * All done, finally we can wake up parent and return this mm to him. 1160 * Also kthread_stop() uses this completion for synchronization. 1161 */ 1162 if (tsk->vfork_done) 1163 complete_vfork_done(tsk); 1164 } 1165 1166 /* 1167 * Allocate a new mm structure and copy contents from the 1168 * mm structure of the passed in task structure. 1169 */ 1170 static struct mm_struct *dup_mm(struct task_struct *tsk) 1171 { 1172 struct mm_struct *mm, *oldmm = current->mm; 1173 int err; 1174 1175 mm = allocate_mm(); 1176 if (!mm) 1177 goto fail_nomem; 1178 1179 memcpy(mm, oldmm, sizeof(*mm)); 1180 1181 if (!mm_init(mm, tsk, mm->user_ns)) 1182 goto fail_nomem; 1183 1184 err = dup_mmap(mm, oldmm); 1185 if (err) 1186 goto free_pt; 1187 1188 mm->hiwater_rss = get_mm_rss(mm); 1189 mm->hiwater_vm = mm->total_vm; 1190 1191 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1192 goto free_pt; 1193 1194 return mm; 1195 1196 free_pt: 1197 /* don't put binfmt in mmput, we haven't got module yet */ 1198 mm->binfmt = NULL; 1199 mmput(mm); 1200 1201 fail_nomem: 1202 return NULL; 1203 } 1204 1205 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1206 { 1207 struct mm_struct *mm, *oldmm; 1208 int retval; 1209 1210 tsk->min_flt = tsk->maj_flt = 0; 1211 tsk->nvcsw = tsk->nivcsw = 0; 1212 #ifdef CONFIG_DETECT_HUNG_TASK 1213 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1214 #endif 1215 1216 tsk->mm = NULL; 1217 tsk->active_mm = NULL; 1218 1219 /* 1220 * Are we cloning a kernel thread? 1221 * 1222 * We need to steal a active VM for that.. 1223 */ 1224 oldmm = current->mm; 1225 if (!oldmm) 1226 return 0; 1227 1228 /* initialize the new vmacache entries */ 1229 vmacache_flush(tsk); 1230 1231 if (clone_flags & CLONE_VM) { 1232 mmget(oldmm); 1233 mm = oldmm; 1234 goto good_mm; 1235 } 1236 1237 retval = -ENOMEM; 1238 mm = dup_mm(tsk); 1239 if (!mm) 1240 goto fail_nomem; 1241 1242 good_mm: 1243 tsk->mm = mm; 1244 tsk->active_mm = mm; 1245 return 0; 1246 1247 fail_nomem: 1248 return retval; 1249 } 1250 1251 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1252 { 1253 struct fs_struct *fs = current->fs; 1254 if (clone_flags & CLONE_FS) { 1255 /* tsk->fs is already what we want */ 1256 spin_lock(&fs->lock); 1257 if (fs->in_exec) { 1258 spin_unlock(&fs->lock); 1259 return -EAGAIN; 1260 } 1261 fs->users++; 1262 spin_unlock(&fs->lock); 1263 return 0; 1264 } 1265 tsk->fs = copy_fs_struct(fs); 1266 if (!tsk->fs) 1267 return -ENOMEM; 1268 return 0; 1269 } 1270 1271 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1272 { 1273 struct files_struct *oldf, *newf; 1274 int error = 0; 1275 1276 /* 1277 * A background process may not have any files ... 1278 */ 1279 oldf = current->files; 1280 if (!oldf) 1281 goto out; 1282 1283 if (clone_flags & CLONE_FILES) { 1284 atomic_inc(&oldf->count); 1285 goto out; 1286 } 1287 1288 newf = dup_fd(oldf, &error); 1289 if (!newf) 1290 goto out; 1291 1292 tsk->files = newf; 1293 error = 0; 1294 out: 1295 return error; 1296 } 1297 1298 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1299 { 1300 #ifdef CONFIG_BLOCK 1301 struct io_context *ioc = current->io_context; 1302 struct io_context *new_ioc; 1303 1304 if (!ioc) 1305 return 0; 1306 /* 1307 * Share io context with parent, if CLONE_IO is set 1308 */ 1309 if (clone_flags & CLONE_IO) { 1310 ioc_task_link(ioc); 1311 tsk->io_context = ioc; 1312 } else if (ioprio_valid(ioc->ioprio)) { 1313 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1314 if (unlikely(!new_ioc)) 1315 return -ENOMEM; 1316 1317 new_ioc->ioprio = ioc->ioprio; 1318 put_io_context(new_ioc); 1319 } 1320 #endif 1321 return 0; 1322 } 1323 1324 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1325 { 1326 struct sighand_struct *sig; 1327 1328 if (clone_flags & CLONE_SIGHAND) { 1329 atomic_inc(¤t->sighand->count); 1330 return 0; 1331 } 1332 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1333 rcu_assign_pointer(tsk->sighand, sig); 1334 if (!sig) 1335 return -ENOMEM; 1336 1337 atomic_set(&sig->count, 1); 1338 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1339 return 0; 1340 } 1341 1342 void __cleanup_sighand(struct sighand_struct *sighand) 1343 { 1344 if (atomic_dec_and_test(&sighand->count)) { 1345 signalfd_cleanup(sighand); 1346 /* 1347 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1348 * without an RCU grace period, see __lock_task_sighand(). 1349 */ 1350 kmem_cache_free(sighand_cachep, sighand); 1351 } 1352 } 1353 1354 #ifdef CONFIG_POSIX_TIMERS 1355 /* 1356 * Initialize POSIX timer handling for a thread group. 1357 */ 1358 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1359 { 1360 unsigned long cpu_limit; 1361 1362 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1363 if (cpu_limit != RLIM_INFINITY) { 1364 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1365 sig->cputimer.running = true; 1366 } 1367 1368 /* The timer lists. */ 1369 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1370 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1371 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1372 } 1373 #else 1374 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1375 #endif 1376 1377 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1378 { 1379 struct signal_struct *sig; 1380 1381 if (clone_flags & CLONE_THREAD) 1382 return 0; 1383 1384 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1385 tsk->signal = sig; 1386 if (!sig) 1387 return -ENOMEM; 1388 1389 sig->nr_threads = 1; 1390 atomic_set(&sig->live, 1); 1391 atomic_set(&sig->sigcnt, 1); 1392 1393 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1394 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1395 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1396 1397 init_waitqueue_head(&sig->wait_chldexit); 1398 sig->curr_target = tsk; 1399 init_sigpending(&sig->shared_pending); 1400 seqlock_init(&sig->stats_lock); 1401 prev_cputime_init(&sig->prev_cputime); 1402 1403 #ifdef CONFIG_POSIX_TIMERS 1404 INIT_LIST_HEAD(&sig->posix_timers); 1405 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1406 sig->real_timer.function = it_real_fn; 1407 #endif 1408 1409 task_lock(current->group_leader); 1410 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1411 task_unlock(current->group_leader); 1412 1413 posix_cpu_timers_init_group(sig); 1414 1415 tty_audit_fork(sig); 1416 sched_autogroup_fork(sig); 1417 1418 sig->oom_score_adj = current->signal->oom_score_adj; 1419 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1420 1421 mutex_init(&sig->cred_guard_mutex); 1422 1423 return 0; 1424 } 1425 1426 static void copy_seccomp(struct task_struct *p) 1427 { 1428 #ifdef CONFIG_SECCOMP 1429 /* 1430 * Must be called with sighand->lock held, which is common to 1431 * all threads in the group. Holding cred_guard_mutex is not 1432 * needed because this new task is not yet running and cannot 1433 * be racing exec. 1434 */ 1435 assert_spin_locked(¤t->sighand->siglock); 1436 1437 /* Ref-count the new filter user, and assign it. */ 1438 get_seccomp_filter(current); 1439 p->seccomp = current->seccomp; 1440 1441 /* 1442 * Explicitly enable no_new_privs here in case it got set 1443 * between the task_struct being duplicated and holding the 1444 * sighand lock. The seccomp state and nnp must be in sync. 1445 */ 1446 if (task_no_new_privs(current)) 1447 task_set_no_new_privs(p); 1448 1449 /* 1450 * If the parent gained a seccomp mode after copying thread 1451 * flags and between before we held the sighand lock, we have 1452 * to manually enable the seccomp thread flag here. 1453 */ 1454 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1455 set_tsk_thread_flag(p, TIF_SECCOMP); 1456 #endif 1457 } 1458 1459 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1460 { 1461 current->clear_child_tid = tidptr; 1462 1463 return task_pid_vnr(current); 1464 } 1465 1466 static void rt_mutex_init_task(struct task_struct *p) 1467 { 1468 raw_spin_lock_init(&p->pi_lock); 1469 #ifdef CONFIG_RT_MUTEXES 1470 p->pi_waiters = RB_ROOT; 1471 p->pi_waiters_leftmost = NULL; 1472 p->pi_top_task = NULL; 1473 p->pi_blocked_on = NULL; 1474 #endif 1475 } 1476 1477 #ifdef CONFIG_POSIX_TIMERS 1478 /* 1479 * Initialize POSIX timer handling for a single task. 1480 */ 1481 static void posix_cpu_timers_init(struct task_struct *tsk) 1482 { 1483 tsk->cputime_expires.prof_exp = 0; 1484 tsk->cputime_expires.virt_exp = 0; 1485 tsk->cputime_expires.sched_exp = 0; 1486 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1487 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1488 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1489 } 1490 #else 1491 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1492 #endif 1493 1494 static inline void 1495 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1496 { 1497 task->pids[type].pid = pid; 1498 } 1499 1500 static inline void rcu_copy_process(struct task_struct *p) 1501 { 1502 #ifdef CONFIG_PREEMPT_RCU 1503 p->rcu_read_lock_nesting = 0; 1504 p->rcu_read_unlock_special.s = 0; 1505 p->rcu_blocked_node = NULL; 1506 INIT_LIST_HEAD(&p->rcu_node_entry); 1507 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1508 #ifdef CONFIG_TASKS_RCU 1509 p->rcu_tasks_holdout = false; 1510 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1511 p->rcu_tasks_idle_cpu = -1; 1512 #endif /* #ifdef CONFIG_TASKS_RCU */ 1513 } 1514 1515 /* 1516 * This creates a new process as a copy of the old one, 1517 * but does not actually start it yet. 1518 * 1519 * It copies the registers, and all the appropriate 1520 * parts of the process environment (as per the clone 1521 * flags). The actual kick-off is left to the caller. 1522 */ 1523 static __latent_entropy struct task_struct *copy_process( 1524 unsigned long clone_flags, 1525 unsigned long stack_start, 1526 unsigned long stack_size, 1527 int __user *child_tidptr, 1528 struct pid *pid, 1529 int trace, 1530 unsigned long tls, 1531 int node) 1532 { 1533 int retval; 1534 struct task_struct *p; 1535 1536 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1537 return ERR_PTR(-EINVAL); 1538 1539 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1540 return ERR_PTR(-EINVAL); 1541 1542 /* 1543 * Thread groups must share signals as well, and detached threads 1544 * can only be started up within the thread group. 1545 */ 1546 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1547 return ERR_PTR(-EINVAL); 1548 1549 /* 1550 * Shared signal handlers imply shared VM. By way of the above, 1551 * thread groups also imply shared VM. Blocking this case allows 1552 * for various simplifications in other code. 1553 */ 1554 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1555 return ERR_PTR(-EINVAL); 1556 1557 /* 1558 * Siblings of global init remain as zombies on exit since they are 1559 * not reaped by their parent (swapper). To solve this and to avoid 1560 * multi-rooted process trees, prevent global and container-inits 1561 * from creating siblings. 1562 */ 1563 if ((clone_flags & CLONE_PARENT) && 1564 current->signal->flags & SIGNAL_UNKILLABLE) 1565 return ERR_PTR(-EINVAL); 1566 1567 /* 1568 * If the new process will be in a different pid or user namespace 1569 * do not allow it to share a thread group with the forking task. 1570 */ 1571 if (clone_flags & CLONE_THREAD) { 1572 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1573 (task_active_pid_ns(current) != 1574 current->nsproxy->pid_ns_for_children)) 1575 return ERR_PTR(-EINVAL); 1576 } 1577 1578 retval = security_task_create(clone_flags); 1579 if (retval) 1580 goto fork_out; 1581 1582 retval = -ENOMEM; 1583 p = dup_task_struct(current, node); 1584 if (!p) 1585 goto fork_out; 1586 1587 /* 1588 * This _must_ happen before we call free_task(), i.e. before we jump 1589 * to any of the bad_fork_* labels. This is to avoid freeing 1590 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1591 * kernel threads (PF_KTHREAD). 1592 */ 1593 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1594 /* 1595 * Clear TID on mm_release()? 1596 */ 1597 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1598 1599 ftrace_graph_init_task(p); 1600 1601 rt_mutex_init_task(p); 1602 1603 #ifdef CONFIG_PROVE_LOCKING 1604 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1605 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1606 #endif 1607 retval = -EAGAIN; 1608 if (atomic_read(&p->real_cred->user->processes) >= 1609 task_rlimit(p, RLIMIT_NPROC)) { 1610 if (p->real_cred->user != INIT_USER && 1611 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1612 goto bad_fork_free; 1613 } 1614 current->flags &= ~PF_NPROC_EXCEEDED; 1615 1616 retval = copy_creds(p, clone_flags); 1617 if (retval < 0) 1618 goto bad_fork_free; 1619 1620 /* 1621 * If multiple threads are within copy_process(), then this check 1622 * triggers too late. This doesn't hurt, the check is only there 1623 * to stop root fork bombs. 1624 */ 1625 retval = -EAGAIN; 1626 if (nr_threads >= max_threads) 1627 goto bad_fork_cleanup_count; 1628 1629 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1630 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1631 p->flags |= PF_FORKNOEXEC; 1632 INIT_LIST_HEAD(&p->children); 1633 INIT_LIST_HEAD(&p->sibling); 1634 rcu_copy_process(p); 1635 p->vfork_done = NULL; 1636 spin_lock_init(&p->alloc_lock); 1637 1638 init_sigpending(&p->pending); 1639 1640 p->utime = p->stime = p->gtime = 0; 1641 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1642 p->utimescaled = p->stimescaled = 0; 1643 #endif 1644 prev_cputime_init(&p->prev_cputime); 1645 1646 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1647 seqcount_init(&p->vtime.seqcount); 1648 p->vtime.starttime = 0; 1649 p->vtime.state = VTIME_INACTIVE; 1650 #endif 1651 1652 #if defined(SPLIT_RSS_COUNTING) 1653 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1654 #endif 1655 1656 p->default_timer_slack_ns = current->timer_slack_ns; 1657 1658 task_io_accounting_init(&p->ioac); 1659 acct_clear_integrals(p); 1660 1661 posix_cpu_timers_init(p); 1662 1663 p->start_time = ktime_get_ns(); 1664 p->real_start_time = ktime_get_boot_ns(); 1665 p->io_context = NULL; 1666 p->audit_context = NULL; 1667 cgroup_fork(p); 1668 #ifdef CONFIG_NUMA 1669 p->mempolicy = mpol_dup(p->mempolicy); 1670 if (IS_ERR(p->mempolicy)) { 1671 retval = PTR_ERR(p->mempolicy); 1672 p->mempolicy = NULL; 1673 goto bad_fork_cleanup_threadgroup_lock; 1674 } 1675 #endif 1676 #ifdef CONFIG_CPUSETS 1677 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1678 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1679 seqcount_init(&p->mems_allowed_seq); 1680 #endif 1681 #ifdef CONFIG_TRACE_IRQFLAGS 1682 p->irq_events = 0; 1683 p->hardirqs_enabled = 0; 1684 p->hardirq_enable_ip = 0; 1685 p->hardirq_enable_event = 0; 1686 p->hardirq_disable_ip = _THIS_IP_; 1687 p->hardirq_disable_event = 0; 1688 p->softirqs_enabled = 1; 1689 p->softirq_enable_ip = _THIS_IP_; 1690 p->softirq_enable_event = 0; 1691 p->softirq_disable_ip = 0; 1692 p->softirq_disable_event = 0; 1693 p->hardirq_context = 0; 1694 p->softirq_context = 0; 1695 #endif 1696 1697 p->pagefault_disabled = 0; 1698 1699 #ifdef CONFIG_LOCKDEP 1700 p->lockdep_depth = 0; /* no locks held yet */ 1701 p->curr_chain_key = 0; 1702 p->lockdep_recursion = 0; 1703 #endif 1704 1705 #ifdef CONFIG_DEBUG_MUTEXES 1706 p->blocked_on = NULL; /* not blocked yet */ 1707 #endif 1708 #ifdef CONFIG_BCACHE 1709 p->sequential_io = 0; 1710 p->sequential_io_avg = 0; 1711 #endif 1712 1713 /* Perform scheduler related setup. Assign this task to a CPU. */ 1714 retval = sched_fork(clone_flags, p); 1715 if (retval) 1716 goto bad_fork_cleanup_policy; 1717 1718 retval = perf_event_init_task(p); 1719 if (retval) 1720 goto bad_fork_cleanup_policy; 1721 retval = audit_alloc(p); 1722 if (retval) 1723 goto bad_fork_cleanup_perf; 1724 /* copy all the process information */ 1725 shm_init_task(p); 1726 retval = security_task_alloc(p, clone_flags); 1727 if (retval) 1728 goto bad_fork_cleanup_audit; 1729 retval = copy_semundo(clone_flags, p); 1730 if (retval) 1731 goto bad_fork_cleanup_security; 1732 retval = copy_files(clone_flags, p); 1733 if (retval) 1734 goto bad_fork_cleanup_semundo; 1735 retval = copy_fs(clone_flags, p); 1736 if (retval) 1737 goto bad_fork_cleanup_files; 1738 retval = copy_sighand(clone_flags, p); 1739 if (retval) 1740 goto bad_fork_cleanup_fs; 1741 retval = copy_signal(clone_flags, p); 1742 if (retval) 1743 goto bad_fork_cleanup_sighand; 1744 retval = copy_mm(clone_flags, p); 1745 if (retval) 1746 goto bad_fork_cleanup_signal; 1747 retval = copy_namespaces(clone_flags, p); 1748 if (retval) 1749 goto bad_fork_cleanup_mm; 1750 retval = copy_io(clone_flags, p); 1751 if (retval) 1752 goto bad_fork_cleanup_namespaces; 1753 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1754 if (retval) 1755 goto bad_fork_cleanup_io; 1756 1757 if (pid != &init_struct_pid) { 1758 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1759 if (IS_ERR(pid)) { 1760 retval = PTR_ERR(pid); 1761 goto bad_fork_cleanup_thread; 1762 } 1763 } 1764 1765 #ifdef CONFIG_BLOCK 1766 p->plug = NULL; 1767 #endif 1768 #ifdef CONFIG_FUTEX 1769 p->robust_list = NULL; 1770 #ifdef CONFIG_COMPAT 1771 p->compat_robust_list = NULL; 1772 #endif 1773 INIT_LIST_HEAD(&p->pi_state_list); 1774 p->pi_state_cache = NULL; 1775 #endif 1776 /* 1777 * sigaltstack should be cleared when sharing the same VM 1778 */ 1779 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1780 sas_ss_reset(p); 1781 1782 /* 1783 * Syscall tracing and stepping should be turned off in the 1784 * child regardless of CLONE_PTRACE. 1785 */ 1786 user_disable_single_step(p); 1787 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1788 #ifdef TIF_SYSCALL_EMU 1789 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1790 #endif 1791 clear_all_latency_tracing(p); 1792 1793 /* ok, now we should be set up.. */ 1794 p->pid = pid_nr(pid); 1795 if (clone_flags & CLONE_THREAD) { 1796 p->exit_signal = -1; 1797 p->group_leader = current->group_leader; 1798 p->tgid = current->tgid; 1799 } else { 1800 if (clone_flags & CLONE_PARENT) 1801 p->exit_signal = current->group_leader->exit_signal; 1802 else 1803 p->exit_signal = (clone_flags & CSIGNAL); 1804 p->group_leader = p; 1805 p->tgid = p->pid; 1806 } 1807 1808 p->nr_dirtied = 0; 1809 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1810 p->dirty_paused_when = 0; 1811 1812 p->pdeath_signal = 0; 1813 INIT_LIST_HEAD(&p->thread_group); 1814 p->task_works = NULL; 1815 1816 cgroup_threadgroup_change_begin(current); 1817 /* 1818 * Ensure that the cgroup subsystem policies allow the new process to be 1819 * forked. It should be noted the the new process's css_set can be changed 1820 * between here and cgroup_post_fork() if an organisation operation is in 1821 * progress. 1822 */ 1823 retval = cgroup_can_fork(p); 1824 if (retval) 1825 goto bad_fork_free_pid; 1826 1827 /* 1828 * Make it visible to the rest of the system, but dont wake it up yet. 1829 * Need tasklist lock for parent etc handling! 1830 */ 1831 write_lock_irq(&tasklist_lock); 1832 1833 /* CLONE_PARENT re-uses the old parent */ 1834 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1835 p->real_parent = current->real_parent; 1836 p->parent_exec_id = current->parent_exec_id; 1837 } else { 1838 p->real_parent = current; 1839 p->parent_exec_id = current->self_exec_id; 1840 } 1841 1842 klp_copy_process(p); 1843 1844 spin_lock(¤t->sighand->siglock); 1845 1846 /* 1847 * Copy seccomp details explicitly here, in case they were changed 1848 * before holding sighand lock. 1849 */ 1850 copy_seccomp(p); 1851 1852 /* 1853 * Process group and session signals need to be delivered to just the 1854 * parent before the fork or both the parent and the child after the 1855 * fork. Restart if a signal comes in before we add the new process to 1856 * it's process group. 1857 * A fatal signal pending means that current will exit, so the new 1858 * thread can't slip out of an OOM kill (or normal SIGKILL). 1859 */ 1860 recalc_sigpending(); 1861 if (signal_pending(current)) { 1862 retval = -ERESTARTNOINTR; 1863 goto bad_fork_cancel_cgroup; 1864 } 1865 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) { 1866 retval = -ENOMEM; 1867 goto bad_fork_cancel_cgroup; 1868 } 1869 1870 if (likely(p->pid)) { 1871 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1872 1873 init_task_pid(p, PIDTYPE_PID, pid); 1874 if (thread_group_leader(p)) { 1875 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1876 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1877 1878 if (is_child_reaper(pid)) { 1879 ns_of_pid(pid)->child_reaper = p; 1880 p->signal->flags |= SIGNAL_UNKILLABLE; 1881 } 1882 1883 p->signal->leader_pid = pid; 1884 p->signal->tty = tty_kref_get(current->signal->tty); 1885 /* 1886 * Inherit has_child_subreaper flag under the same 1887 * tasklist_lock with adding child to the process tree 1888 * for propagate_has_child_subreaper optimization. 1889 */ 1890 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1891 p->real_parent->signal->is_child_subreaper; 1892 list_add_tail(&p->sibling, &p->real_parent->children); 1893 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1894 attach_pid(p, PIDTYPE_PGID); 1895 attach_pid(p, PIDTYPE_SID); 1896 __this_cpu_inc(process_counts); 1897 } else { 1898 current->signal->nr_threads++; 1899 atomic_inc(¤t->signal->live); 1900 atomic_inc(¤t->signal->sigcnt); 1901 list_add_tail_rcu(&p->thread_group, 1902 &p->group_leader->thread_group); 1903 list_add_tail_rcu(&p->thread_node, 1904 &p->signal->thread_head); 1905 } 1906 attach_pid(p, PIDTYPE_PID); 1907 nr_threads++; 1908 } 1909 1910 total_forks++; 1911 spin_unlock(¤t->sighand->siglock); 1912 syscall_tracepoint_update(p); 1913 write_unlock_irq(&tasklist_lock); 1914 1915 proc_fork_connector(p); 1916 cgroup_post_fork(p); 1917 cgroup_threadgroup_change_end(current); 1918 perf_event_fork(p); 1919 1920 trace_task_newtask(p, clone_flags); 1921 uprobe_copy_process(p, clone_flags); 1922 1923 return p; 1924 1925 bad_fork_cancel_cgroup: 1926 spin_unlock(¤t->sighand->siglock); 1927 write_unlock_irq(&tasklist_lock); 1928 cgroup_cancel_fork(p); 1929 bad_fork_free_pid: 1930 cgroup_threadgroup_change_end(current); 1931 if (pid != &init_struct_pid) 1932 free_pid(pid); 1933 bad_fork_cleanup_thread: 1934 exit_thread(p); 1935 bad_fork_cleanup_io: 1936 if (p->io_context) 1937 exit_io_context(p); 1938 bad_fork_cleanup_namespaces: 1939 exit_task_namespaces(p); 1940 bad_fork_cleanup_mm: 1941 if (p->mm) 1942 mmput(p->mm); 1943 bad_fork_cleanup_signal: 1944 if (!(clone_flags & CLONE_THREAD)) 1945 free_signal_struct(p->signal); 1946 bad_fork_cleanup_sighand: 1947 __cleanup_sighand(p->sighand); 1948 bad_fork_cleanup_fs: 1949 exit_fs(p); /* blocking */ 1950 bad_fork_cleanup_files: 1951 exit_files(p); /* blocking */ 1952 bad_fork_cleanup_semundo: 1953 exit_sem(p); 1954 bad_fork_cleanup_security: 1955 security_task_free(p); 1956 bad_fork_cleanup_audit: 1957 audit_free(p); 1958 bad_fork_cleanup_perf: 1959 perf_event_free_task(p); 1960 bad_fork_cleanup_policy: 1961 #ifdef CONFIG_NUMA 1962 mpol_put(p->mempolicy); 1963 bad_fork_cleanup_threadgroup_lock: 1964 #endif 1965 delayacct_tsk_free(p); 1966 bad_fork_cleanup_count: 1967 atomic_dec(&p->cred->user->processes); 1968 exit_creds(p); 1969 bad_fork_free: 1970 p->state = TASK_DEAD; 1971 put_task_stack(p); 1972 free_task(p); 1973 fork_out: 1974 return ERR_PTR(retval); 1975 } 1976 1977 static inline void init_idle_pids(struct pid_link *links) 1978 { 1979 enum pid_type type; 1980 1981 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1982 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1983 links[type].pid = &init_struct_pid; 1984 } 1985 } 1986 1987 struct task_struct *fork_idle(int cpu) 1988 { 1989 struct task_struct *task; 1990 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1991 cpu_to_node(cpu)); 1992 if (!IS_ERR(task)) { 1993 init_idle_pids(task->pids); 1994 init_idle(task, cpu); 1995 } 1996 1997 return task; 1998 } 1999 2000 /* 2001 * Ok, this is the main fork-routine. 2002 * 2003 * It copies the process, and if successful kick-starts 2004 * it and waits for it to finish using the VM if required. 2005 */ 2006 long _do_fork(unsigned long clone_flags, 2007 unsigned long stack_start, 2008 unsigned long stack_size, 2009 int __user *parent_tidptr, 2010 int __user *child_tidptr, 2011 unsigned long tls) 2012 { 2013 struct task_struct *p; 2014 int trace = 0; 2015 long nr; 2016 2017 /* 2018 * Determine whether and which event to report to ptracer. When 2019 * called from kernel_thread or CLONE_UNTRACED is explicitly 2020 * requested, no event is reported; otherwise, report if the event 2021 * for the type of forking is enabled. 2022 */ 2023 if (!(clone_flags & CLONE_UNTRACED)) { 2024 if (clone_flags & CLONE_VFORK) 2025 trace = PTRACE_EVENT_VFORK; 2026 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2027 trace = PTRACE_EVENT_CLONE; 2028 else 2029 trace = PTRACE_EVENT_FORK; 2030 2031 if (likely(!ptrace_event_enabled(current, trace))) 2032 trace = 0; 2033 } 2034 2035 p = copy_process(clone_flags, stack_start, stack_size, 2036 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2037 add_latent_entropy(); 2038 /* 2039 * Do this prior waking up the new thread - the thread pointer 2040 * might get invalid after that point, if the thread exits quickly. 2041 */ 2042 if (!IS_ERR(p)) { 2043 struct completion vfork; 2044 struct pid *pid; 2045 2046 trace_sched_process_fork(current, p); 2047 2048 pid = get_task_pid(p, PIDTYPE_PID); 2049 nr = pid_vnr(pid); 2050 2051 if (clone_flags & CLONE_PARENT_SETTID) 2052 put_user(nr, parent_tidptr); 2053 2054 if (clone_flags & CLONE_VFORK) { 2055 p->vfork_done = &vfork; 2056 init_completion(&vfork); 2057 get_task_struct(p); 2058 } 2059 2060 wake_up_new_task(p); 2061 2062 /* forking complete and child started to run, tell ptracer */ 2063 if (unlikely(trace)) 2064 ptrace_event_pid(trace, pid); 2065 2066 if (clone_flags & CLONE_VFORK) { 2067 if (!wait_for_vfork_done(p, &vfork)) 2068 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2069 } 2070 2071 put_pid(pid); 2072 } else { 2073 nr = PTR_ERR(p); 2074 } 2075 return nr; 2076 } 2077 2078 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2079 /* For compatibility with architectures that call do_fork directly rather than 2080 * using the syscall entry points below. */ 2081 long do_fork(unsigned long clone_flags, 2082 unsigned long stack_start, 2083 unsigned long stack_size, 2084 int __user *parent_tidptr, 2085 int __user *child_tidptr) 2086 { 2087 return _do_fork(clone_flags, stack_start, stack_size, 2088 parent_tidptr, child_tidptr, 0); 2089 } 2090 #endif 2091 2092 /* 2093 * Create a kernel thread. 2094 */ 2095 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2096 { 2097 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2098 (unsigned long)arg, NULL, NULL, 0); 2099 } 2100 2101 #ifdef __ARCH_WANT_SYS_FORK 2102 SYSCALL_DEFINE0(fork) 2103 { 2104 #ifdef CONFIG_MMU 2105 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2106 #else 2107 /* can not support in nommu mode */ 2108 return -EINVAL; 2109 #endif 2110 } 2111 #endif 2112 2113 #ifdef __ARCH_WANT_SYS_VFORK 2114 SYSCALL_DEFINE0(vfork) 2115 { 2116 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2117 0, NULL, NULL, 0); 2118 } 2119 #endif 2120 2121 #ifdef __ARCH_WANT_SYS_CLONE 2122 #ifdef CONFIG_CLONE_BACKWARDS 2123 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2124 int __user *, parent_tidptr, 2125 unsigned long, tls, 2126 int __user *, child_tidptr) 2127 #elif defined(CONFIG_CLONE_BACKWARDS2) 2128 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2129 int __user *, parent_tidptr, 2130 int __user *, child_tidptr, 2131 unsigned long, tls) 2132 #elif defined(CONFIG_CLONE_BACKWARDS3) 2133 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2134 int, stack_size, 2135 int __user *, parent_tidptr, 2136 int __user *, child_tidptr, 2137 unsigned long, tls) 2138 #else 2139 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2140 int __user *, parent_tidptr, 2141 int __user *, child_tidptr, 2142 unsigned long, tls) 2143 #endif 2144 { 2145 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2146 } 2147 #endif 2148 2149 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2150 { 2151 struct task_struct *leader, *parent, *child; 2152 int res; 2153 2154 read_lock(&tasklist_lock); 2155 leader = top = top->group_leader; 2156 down: 2157 for_each_thread(leader, parent) { 2158 list_for_each_entry(child, &parent->children, sibling) { 2159 res = visitor(child, data); 2160 if (res) { 2161 if (res < 0) 2162 goto out; 2163 leader = child; 2164 goto down; 2165 } 2166 up: 2167 ; 2168 } 2169 } 2170 2171 if (leader != top) { 2172 child = leader; 2173 parent = child->real_parent; 2174 leader = parent->group_leader; 2175 goto up; 2176 } 2177 out: 2178 read_unlock(&tasklist_lock); 2179 } 2180 2181 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2182 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2183 #endif 2184 2185 static void sighand_ctor(void *data) 2186 { 2187 struct sighand_struct *sighand = data; 2188 2189 spin_lock_init(&sighand->siglock); 2190 init_waitqueue_head(&sighand->signalfd_wqh); 2191 } 2192 2193 void __init proc_caches_init(void) 2194 { 2195 sighand_cachep = kmem_cache_create("sighand_cache", 2196 sizeof(struct sighand_struct), 0, 2197 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2198 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2199 signal_cachep = kmem_cache_create("signal_cache", 2200 sizeof(struct signal_struct), 0, 2201 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2202 NULL); 2203 files_cachep = kmem_cache_create("files_cache", 2204 sizeof(struct files_struct), 0, 2205 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2206 NULL); 2207 fs_cachep = kmem_cache_create("fs_cache", 2208 sizeof(struct fs_struct), 0, 2209 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2210 NULL); 2211 /* 2212 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2213 * whole struct cpumask for the OFFSTACK case. We could change 2214 * this to *only* allocate as much of it as required by the 2215 * maximum number of CPU's we can ever have. The cpumask_allocation 2216 * is at the end of the structure, exactly for that reason. 2217 */ 2218 mm_cachep = kmem_cache_create("mm_struct", 2219 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2220 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2221 NULL); 2222 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2223 mmap_init(); 2224 nsproxy_cache_init(); 2225 } 2226 2227 /* 2228 * Check constraints on flags passed to the unshare system call. 2229 */ 2230 static int check_unshare_flags(unsigned long unshare_flags) 2231 { 2232 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2233 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2234 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2235 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2236 return -EINVAL; 2237 /* 2238 * Not implemented, but pretend it works if there is nothing 2239 * to unshare. Note that unsharing the address space or the 2240 * signal handlers also need to unshare the signal queues (aka 2241 * CLONE_THREAD). 2242 */ 2243 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2244 if (!thread_group_empty(current)) 2245 return -EINVAL; 2246 } 2247 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2248 if (atomic_read(¤t->sighand->count) > 1) 2249 return -EINVAL; 2250 } 2251 if (unshare_flags & CLONE_VM) { 2252 if (!current_is_single_threaded()) 2253 return -EINVAL; 2254 } 2255 2256 return 0; 2257 } 2258 2259 /* 2260 * Unshare the filesystem structure if it is being shared 2261 */ 2262 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2263 { 2264 struct fs_struct *fs = current->fs; 2265 2266 if (!(unshare_flags & CLONE_FS) || !fs) 2267 return 0; 2268 2269 /* don't need lock here; in the worst case we'll do useless copy */ 2270 if (fs->users == 1) 2271 return 0; 2272 2273 *new_fsp = copy_fs_struct(fs); 2274 if (!*new_fsp) 2275 return -ENOMEM; 2276 2277 return 0; 2278 } 2279 2280 /* 2281 * Unshare file descriptor table if it is being shared 2282 */ 2283 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2284 { 2285 struct files_struct *fd = current->files; 2286 int error = 0; 2287 2288 if ((unshare_flags & CLONE_FILES) && 2289 (fd && atomic_read(&fd->count) > 1)) { 2290 *new_fdp = dup_fd(fd, &error); 2291 if (!*new_fdp) 2292 return error; 2293 } 2294 2295 return 0; 2296 } 2297 2298 /* 2299 * unshare allows a process to 'unshare' part of the process 2300 * context which was originally shared using clone. copy_* 2301 * functions used by do_fork() cannot be used here directly 2302 * because they modify an inactive task_struct that is being 2303 * constructed. Here we are modifying the current, active, 2304 * task_struct. 2305 */ 2306 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2307 { 2308 struct fs_struct *fs, *new_fs = NULL; 2309 struct files_struct *fd, *new_fd = NULL; 2310 struct cred *new_cred = NULL; 2311 struct nsproxy *new_nsproxy = NULL; 2312 int do_sysvsem = 0; 2313 int err; 2314 2315 /* 2316 * If unsharing a user namespace must also unshare the thread group 2317 * and unshare the filesystem root and working directories. 2318 */ 2319 if (unshare_flags & CLONE_NEWUSER) 2320 unshare_flags |= CLONE_THREAD | CLONE_FS; 2321 /* 2322 * If unsharing vm, must also unshare signal handlers. 2323 */ 2324 if (unshare_flags & CLONE_VM) 2325 unshare_flags |= CLONE_SIGHAND; 2326 /* 2327 * If unsharing a signal handlers, must also unshare the signal queues. 2328 */ 2329 if (unshare_flags & CLONE_SIGHAND) 2330 unshare_flags |= CLONE_THREAD; 2331 /* 2332 * If unsharing namespace, must also unshare filesystem information. 2333 */ 2334 if (unshare_flags & CLONE_NEWNS) 2335 unshare_flags |= CLONE_FS; 2336 2337 err = check_unshare_flags(unshare_flags); 2338 if (err) 2339 goto bad_unshare_out; 2340 /* 2341 * CLONE_NEWIPC must also detach from the undolist: after switching 2342 * to a new ipc namespace, the semaphore arrays from the old 2343 * namespace are unreachable. 2344 */ 2345 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2346 do_sysvsem = 1; 2347 err = unshare_fs(unshare_flags, &new_fs); 2348 if (err) 2349 goto bad_unshare_out; 2350 err = unshare_fd(unshare_flags, &new_fd); 2351 if (err) 2352 goto bad_unshare_cleanup_fs; 2353 err = unshare_userns(unshare_flags, &new_cred); 2354 if (err) 2355 goto bad_unshare_cleanup_fd; 2356 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2357 new_cred, new_fs); 2358 if (err) 2359 goto bad_unshare_cleanup_cred; 2360 2361 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2362 if (do_sysvsem) { 2363 /* 2364 * CLONE_SYSVSEM is equivalent to sys_exit(). 2365 */ 2366 exit_sem(current); 2367 } 2368 if (unshare_flags & CLONE_NEWIPC) { 2369 /* Orphan segments in old ns (see sem above). */ 2370 exit_shm(current); 2371 shm_init_task(current); 2372 } 2373 2374 if (new_nsproxy) 2375 switch_task_namespaces(current, new_nsproxy); 2376 2377 task_lock(current); 2378 2379 if (new_fs) { 2380 fs = current->fs; 2381 spin_lock(&fs->lock); 2382 current->fs = new_fs; 2383 if (--fs->users) 2384 new_fs = NULL; 2385 else 2386 new_fs = fs; 2387 spin_unlock(&fs->lock); 2388 } 2389 2390 if (new_fd) { 2391 fd = current->files; 2392 current->files = new_fd; 2393 new_fd = fd; 2394 } 2395 2396 task_unlock(current); 2397 2398 if (new_cred) { 2399 /* Install the new user namespace */ 2400 commit_creds(new_cred); 2401 new_cred = NULL; 2402 } 2403 } 2404 2405 perf_event_namespaces(current); 2406 2407 bad_unshare_cleanup_cred: 2408 if (new_cred) 2409 put_cred(new_cred); 2410 bad_unshare_cleanup_fd: 2411 if (new_fd) 2412 put_files_struct(new_fd); 2413 2414 bad_unshare_cleanup_fs: 2415 if (new_fs) 2416 free_fs_struct(new_fs); 2417 2418 bad_unshare_out: 2419 return err; 2420 } 2421 2422 /* 2423 * Helper to unshare the files of the current task. 2424 * We don't want to expose copy_files internals to 2425 * the exec layer of the kernel. 2426 */ 2427 2428 int unshare_files(struct files_struct **displaced) 2429 { 2430 struct task_struct *task = current; 2431 struct files_struct *copy = NULL; 2432 int error; 2433 2434 error = unshare_fd(CLONE_FILES, ©); 2435 if (error || !copy) { 2436 *displaced = NULL; 2437 return error; 2438 } 2439 *displaced = task->files; 2440 task_lock(task); 2441 task->files = copy; 2442 task_unlock(task); 2443 return 0; 2444 } 2445 2446 int sysctl_max_threads(struct ctl_table *table, int write, 2447 void __user *buffer, size_t *lenp, loff_t *ppos) 2448 { 2449 struct ctl_table t; 2450 int ret; 2451 int threads = max_threads; 2452 int min = MIN_THREADS; 2453 int max = MAX_THREADS; 2454 2455 t = *table; 2456 t.data = &threads; 2457 t.extra1 = &min; 2458 t.extra2 = &max; 2459 2460 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2461 if (ret || !write) 2462 return ret; 2463 2464 set_max_threads(threads); 2465 2466 return 0; 2467 } 2468