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