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 struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 789 struct user_namespace *user_ns) 790 { 791 mm->mmap = NULL; 792 mm->mm_rb = RB_ROOT; 793 mm->vmacache_seqnum = 0; 794 atomic_set(&mm->mm_users, 1); 795 atomic_set(&mm->mm_count, 1); 796 init_rwsem(&mm->mmap_sem); 797 INIT_LIST_HEAD(&mm->mmlist); 798 mm->core_state = NULL; 799 atomic_long_set(&mm->nr_ptes, 0); 800 mm_nr_pmds_init(mm); 801 mm->map_count = 0; 802 mm->locked_vm = 0; 803 mm->pinned_vm = 0; 804 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 805 spin_lock_init(&mm->page_table_lock); 806 mm_init_cpumask(mm); 807 mm_init_aio(mm); 808 mm_init_owner(mm, p); 809 mmu_notifier_mm_init(mm); 810 clear_tlb_flush_pending(mm); 811 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 812 mm->pmd_huge_pte = NULL; 813 #endif 814 815 if (current->mm) { 816 mm->flags = current->mm->flags & MMF_INIT_MASK; 817 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 818 } else { 819 mm->flags = default_dump_filter; 820 mm->def_flags = 0; 821 } 822 823 if (mm_alloc_pgd(mm)) 824 goto fail_nopgd; 825 826 if (init_new_context(p, mm)) 827 goto fail_nocontext; 828 829 mm->user_ns = get_user_ns(user_ns); 830 return mm; 831 832 fail_nocontext: 833 mm_free_pgd(mm); 834 fail_nopgd: 835 free_mm(mm); 836 return NULL; 837 } 838 839 static void check_mm(struct mm_struct *mm) 840 { 841 int i; 842 843 for (i = 0; i < NR_MM_COUNTERS; i++) { 844 long x = atomic_long_read(&mm->rss_stat.count[i]); 845 846 if (unlikely(x)) 847 printk(KERN_ALERT "BUG: Bad rss-counter state " 848 "mm:%p idx:%d val:%ld\n", mm, i, x); 849 } 850 851 if (atomic_long_read(&mm->nr_ptes)) 852 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 853 atomic_long_read(&mm->nr_ptes)); 854 if (mm_nr_pmds(mm)) 855 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 856 mm_nr_pmds(mm)); 857 858 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 859 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 860 #endif 861 } 862 863 /* 864 * Allocate and initialize an mm_struct. 865 */ 866 struct mm_struct *mm_alloc(void) 867 { 868 struct mm_struct *mm; 869 870 mm = allocate_mm(); 871 if (!mm) 872 return NULL; 873 874 memset(mm, 0, sizeof(*mm)); 875 return mm_init(mm, current, current_user_ns()); 876 } 877 878 /* 879 * Called when the last reference to the mm 880 * is dropped: either by a lazy thread or by 881 * mmput. Free the page directory and the mm. 882 */ 883 void __mmdrop(struct mm_struct *mm) 884 { 885 BUG_ON(mm == &init_mm); 886 mm_free_pgd(mm); 887 destroy_context(mm); 888 mmu_notifier_mm_destroy(mm); 889 check_mm(mm); 890 put_user_ns(mm->user_ns); 891 free_mm(mm); 892 } 893 EXPORT_SYMBOL_GPL(__mmdrop); 894 895 static inline void __mmput(struct mm_struct *mm) 896 { 897 VM_BUG_ON(atomic_read(&mm->mm_users)); 898 899 uprobe_clear_state(mm); 900 exit_aio(mm); 901 ksm_exit(mm); 902 khugepaged_exit(mm); /* must run before exit_mmap */ 903 exit_mmap(mm); 904 mm_put_huge_zero_page(mm); 905 set_mm_exe_file(mm, NULL); 906 if (!list_empty(&mm->mmlist)) { 907 spin_lock(&mmlist_lock); 908 list_del(&mm->mmlist); 909 spin_unlock(&mmlist_lock); 910 } 911 if (mm->binfmt) 912 module_put(mm->binfmt->module); 913 set_bit(MMF_OOM_SKIP, &mm->flags); 914 mmdrop(mm); 915 } 916 917 /* 918 * Decrement the use count and release all resources for an mm. 919 */ 920 void mmput(struct mm_struct *mm) 921 { 922 might_sleep(); 923 924 if (atomic_dec_and_test(&mm->mm_users)) 925 __mmput(mm); 926 } 927 EXPORT_SYMBOL_GPL(mmput); 928 929 #ifdef CONFIG_MMU 930 static void mmput_async_fn(struct work_struct *work) 931 { 932 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 933 __mmput(mm); 934 } 935 936 void mmput_async(struct mm_struct *mm) 937 { 938 if (atomic_dec_and_test(&mm->mm_users)) { 939 INIT_WORK(&mm->async_put_work, mmput_async_fn); 940 schedule_work(&mm->async_put_work); 941 } 942 } 943 #endif 944 945 /** 946 * set_mm_exe_file - change a reference to the mm's executable file 947 * 948 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 949 * 950 * Main users are mmput() and sys_execve(). Callers prevent concurrent 951 * invocations: in mmput() nobody alive left, in execve task is single 952 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 953 * mm->exe_file, but does so without using set_mm_exe_file() in order 954 * to do avoid the need for any locks. 955 */ 956 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 957 { 958 struct file *old_exe_file; 959 960 /* 961 * It is safe to dereference the exe_file without RCU as 962 * this function is only called if nobody else can access 963 * this mm -- see comment above for justification. 964 */ 965 old_exe_file = rcu_dereference_raw(mm->exe_file); 966 967 if (new_exe_file) 968 get_file(new_exe_file); 969 rcu_assign_pointer(mm->exe_file, new_exe_file); 970 if (old_exe_file) 971 fput(old_exe_file); 972 } 973 974 /** 975 * get_mm_exe_file - acquire a reference to the mm's executable file 976 * 977 * Returns %NULL if mm has no associated executable file. 978 * User must release file via fput(). 979 */ 980 struct file *get_mm_exe_file(struct mm_struct *mm) 981 { 982 struct file *exe_file; 983 984 rcu_read_lock(); 985 exe_file = rcu_dereference(mm->exe_file); 986 if (exe_file && !get_file_rcu(exe_file)) 987 exe_file = NULL; 988 rcu_read_unlock(); 989 return exe_file; 990 } 991 EXPORT_SYMBOL(get_mm_exe_file); 992 993 /** 994 * get_task_exe_file - acquire a reference to the task's executable file 995 * 996 * Returns %NULL if task's mm (if any) has no associated executable file or 997 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 998 * User must release file via fput(). 999 */ 1000 struct file *get_task_exe_file(struct task_struct *task) 1001 { 1002 struct file *exe_file = NULL; 1003 struct mm_struct *mm; 1004 1005 task_lock(task); 1006 mm = task->mm; 1007 if (mm) { 1008 if (!(task->flags & PF_KTHREAD)) 1009 exe_file = get_mm_exe_file(mm); 1010 } 1011 task_unlock(task); 1012 return exe_file; 1013 } 1014 EXPORT_SYMBOL(get_task_exe_file); 1015 1016 /** 1017 * get_task_mm - acquire a reference to the task's mm 1018 * 1019 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1020 * this kernel workthread has transiently adopted a user mm with use_mm, 1021 * to do its AIO) is not set and if so returns a reference to it, after 1022 * bumping up the use count. User must release the mm via mmput() 1023 * after use. Typically used by /proc and ptrace. 1024 */ 1025 struct mm_struct *get_task_mm(struct task_struct *task) 1026 { 1027 struct mm_struct *mm; 1028 1029 task_lock(task); 1030 mm = task->mm; 1031 if (mm) { 1032 if (task->flags & PF_KTHREAD) 1033 mm = NULL; 1034 else 1035 mmget(mm); 1036 } 1037 task_unlock(task); 1038 return mm; 1039 } 1040 EXPORT_SYMBOL_GPL(get_task_mm); 1041 1042 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1043 { 1044 struct mm_struct *mm; 1045 int err; 1046 1047 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1048 if (err) 1049 return ERR_PTR(err); 1050 1051 mm = get_task_mm(task); 1052 if (mm && mm != current->mm && 1053 !ptrace_may_access(task, mode)) { 1054 mmput(mm); 1055 mm = ERR_PTR(-EACCES); 1056 } 1057 mutex_unlock(&task->signal->cred_guard_mutex); 1058 1059 return mm; 1060 } 1061 1062 static void complete_vfork_done(struct task_struct *tsk) 1063 { 1064 struct completion *vfork; 1065 1066 task_lock(tsk); 1067 vfork = tsk->vfork_done; 1068 if (likely(vfork)) { 1069 tsk->vfork_done = NULL; 1070 complete(vfork); 1071 } 1072 task_unlock(tsk); 1073 } 1074 1075 static int wait_for_vfork_done(struct task_struct *child, 1076 struct completion *vfork) 1077 { 1078 int killed; 1079 1080 freezer_do_not_count(); 1081 killed = wait_for_completion_killable(vfork); 1082 freezer_count(); 1083 1084 if (killed) { 1085 task_lock(child); 1086 child->vfork_done = NULL; 1087 task_unlock(child); 1088 } 1089 1090 put_task_struct(child); 1091 return killed; 1092 } 1093 1094 /* Please note the differences between mmput and mm_release. 1095 * mmput is called whenever we stop holding onto a mm_struct, 1096 * error success whatever. 1097 * 1098 * mm_release is called after a mm_struct has been removed 1099 * from the current process. 1100 * 1101 * This difference is important for error handling, when we 1102 * only half set up a mm_struct for a new process and need to restore 1103 * the old one. Because we mmput the new mm_struct before 1104 * restoring the old one. . . 1105 * Eric Biederman 10 January 1998 1106 */ 1107 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1108 { 1109 /* Get rid of any futexes when releasing the mm */ 1110 #ifdef CONFIG_FUTEX 1111 if (unlikely(tsk->robust_list)) { 1112 exit_robust_list(tsk); 1113 tsk->robust_list = NULL; 1114 } 1115 #ifdef CONFIG_COMPAT 1116 if (unlikely(tsk->compat_robust_list)) { 1117 compat_exit_robust_list(tsk); 1118 tsk->compat_robust_list = NULL; 1119 } 1120 #endif 1121 if (unlikely(!list_empty(&tsk->pi_state_list))) 1122 exit_pi_state_list(tsk); 1123 #endif 1124 1125 uprobe_free_utask(tsk); 1126 1127 /* Get rid of any cached register state */ 1128 deactivate_mm(tsk, mm); 1129 1130 /* 1131 * Signal userspace if we're not exiting with a core dump 1132 * because we want to leave the value intact for debugging 1133 * purposes. 1134 */ 1135 if (tsk->clear_child_tid) { 1136 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1137 atomic_read(&mm->mm_users) > 1) { 1138 /* 1139 * We don't check the error code - if userspace has 1140 * not set up a proper pointer then tough luck. 1141 */ 1142 put_user(0, tsk->clear_child_tid); 1143 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1144 1, NULL, NULL, 0); 1145 } 1146 tsk->clear_child_tid = NULL; 1147 } 1148 1149 /* 1150 * All done, finally we can wake up parent and return this mm to him. 1151 * Also kthread_stop() uses this completion for synchronization. 1152 */ 1153 if (tsk->vfork_done) 1154 complete_vfork_done(tsk); 1155 } 1156 1157 /* 1158 * Allocate a new mm structure and copy contents from the 1159 * mm structure of the passed in task structure. 1160 */ 1161 static struct mm_struct *dup_mm(struct task_struct *tsk) 1162 { 1163 struct mm_struct *mm, *oldmm = current->mm; 1164 int err; 1165 1166 mm = allocate_mm(); 1167 if (!mm) 1168 goto fail_nomem; 1169 1170 memcpy(mm, oldmm, sizeof(*mm)); 1171 1172 if (!mm_init(mm, tsk, mm->user_ns)) 1173 goto fail_nomem; 1174 1175 err = dup_mmap(mm, oldmm); 1176 if (err) 1177 goto free_pt; 1178 1179 mm->hiwater_rss = get_mm_rss(mm); 1180 mm->hiwater_vm = mm->total_vm; 1181 1182 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1183 goto free_pt; 1184 1185 return mm; 1186 1187 free_pt: 1188 /* don't put binfmt in mmput, we haven't got module yet */ 1189 mm->binfmt = NULL; 1190 mmput(mm); 1191 1192 fail_nomem: 1193 return NULL; 1194 } 1195 1196 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1197 { 1198 struct mm_struct *mm, *oldmm; 1199 int retval; 1200 1201 tsk->min_flt = tsk->maj_flt = 0; 1202 tsk->nvcsw = tsk->nivcsw = 0; 1203 #ifdef CONFIG_DETECT_HUNG_TASK 1204 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1205 #endif 1206 1207 tsk->mm = NULL; 1208 tsk->active_mm = NULL; 1209 1210 /* 1211 * Are we cloning a kernel thread? 1212 * 1213 * We need to steal a active VM for that.. 1214 */ 1215 oldmm = current->mm; 1216 if (!oldmm) 1217 return 0; 1218 1219 /* initialize the new vmacache entries */ 1220 vmacache_flush(tsk); 1221 1222 if (clone_flags & CLONE_VM) { 1223 mmget(oldmm); 1224 mm = oldmm; 1225 goto good_mm; 1226 } 1227 1228 retval = -ENOMEM; 1229 mm = dup_mm(tsk); 1230 if (!mm) 1231 goto fail_nomem; 1232 1233 good_mm: 1234 tsk->mm = mm; 1235 tsk->active_mm = mm; 1236 return 0; 1237 1238 fail_nomem: 1239 return retval; 1240 } 1241 1242 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1243 { 1244 struct fs_struct *fs = current->fs; 1245 if (clone_flags & CLONE_FS) { 1246 /* tsk->fs is already what we want */ 1247 spin_lock(&fs->lock); 1248 if (fs->in_exec) { 1249 spin_unlock(&fs->lock); 1250 return -EAGAIN; 1251 } 1252 fs->users++; 1253 spin_unlock(&fs->lock); 1254 return 0; 1255 } 1256 tsk->fs = copy_fs_struct(fs); 1257 if (!tsk->fs) 1258 return -ENOMEM; 1259 return 0; 1260 } 1261 1262 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1263 { 1264 struct files_struct *oldf, *newf; 1265 int error = 0; 1266 1267 /* 1268 * A background process may not have any files ... 1269 */ 1270 oldf = current->files; 1271 if (!oldf) 1272 goto out; 1273 1274 if (clone_flags & CLONE_FILES) { 1275 atomic_inc(&oldf->count); 1276 goto out; 1277 } 1278 1279 newf = dup_fd(oldf, &error); 1280 if (!newf) 1281 goto out; 1282 1283 tsk->files = newf; 1284 error = 0; 1285 out: 1286 return error; 1287 } 1288 1289 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1290 { 1291 #ifdef CONFIG_BLOCK 1292 struct io_context *ioc = current->io_context; 1293 struct io_context *new_ioc; 1294 1295 if (!ioc) 1296 return 0; 1297 /* 1298 * Share io context with parent, if CLONE_IO is set 1299 */ 1300 if (clone_flags & CLONE_IO) { 1301 ioc_task_link(ioc); 1302 tsk->io_context = ioc; 1303 } else if (ioprio_valid(ioc->ioprio)) { 1304 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1305 if (unlikely(!new_ioc)) 1306 return -ENOMEM; 1307 1308 new_ioc->ioprio = ioc->ioprio; 1309 put_io_context(new_ioc); 1310 } 1311 #endif 1312 return 0; 1313 } 1314 1315 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1316 { 1317 struct sighand_struct *sig; 1318 1319 if (clone_flags & CLONE_SIGHAND) { 1320 atomic_inc(¤t->sighand->count); 1321 return 0; 1322 } 1323 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1324 rcu_assign_pointer(tsk->sighand, sig); 1325 if (!sig) 1326 return -ENOMEM; 1327 1328 atomic_set(&sig->count, 1); 1329 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1330 return 0; 1331 } 1332 1333 void __cleanup_sighand(struct sighand_struct *sighand) 1334 { 1335 if (atomic_dec_and_test(&sighand->count)) { 1336 signalfd_cleanup(sighand); 1337 /* 1338 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1339 * without an RCU grace period, see __lock_task_sighand(). 1340 */ 1341 kmem_cache_free(sighand_cachep, sighand); 1342 } 1343 } 1344 1345 #ifdef CONFIG_POSIX_TIMERS 1346 /* 1347 * Initialize POSIX timer handling for a thread group. 1348 */ 1349 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1350 { 1351 unsigned long cpu_limit; 1352 1353 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1354 if (cpu_limit != RLIM_INFINITY) { 1355 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1356 sig->cputimer.running = true; 1357 } 1358 1359 /* The timer lists. */ 1360 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1361 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1362 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1363 } 1364 #else 1365 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1366 #endif 1367 1368 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1369 { 1370 struct signal_struct *sig; 1371 1372 if (clone_flags & CLONE_THREAD) 1373 return 0; 1374 1375 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1376 tsk->signal = sig; 1377 if (!sig) 1378 return -ENOMEM; 1379 1380 sig->nr_threads = 1; 1381 atomic_set(&sig->live, 1); 1382 atomic_set(&sig->sigcnt, 1); 1383 1384 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1385 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1386 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1387 1388 init_waitqueue_head(&sig->wait_chldexit); 1389 sig->curr_target = tsk; 1390 init_sigpending(&sig->shared_pending); 1391 seqlock_init(&sig->stats_lock); 1392 prev_cputime_init(&sig->prev_cputime); 1393 1394 #ifdef CONFIG_POSIX_TIMERS 1395 INIT_LIST_HEAD(&sig->posix_timers); 1396 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1397 sig->real_timer.function = it_real_fn; 1398 #endif 1399 1400 task_lock(current->group_leader); 1401 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1402 task_unlock(current->group_leader); 1403 1404 posix_cpu_timers_init_group(sig); 1405 1406 tty_audit_fork(sig); 1407 sched_autogroup_fork(sig); 1408 1409 sig->oom_score_adj = current->signal->oom_score_adj; 1410 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1411 1412 mutex_init(&sig->cred_guard_mutex); 1413 1414 return 0; 1415 } 1416 1417 static void copy_seccomp(struct task_struct *p) 1418 { 1419 #ifdef CONFIG_SECCOMP 1420 /* 1421 * Must be called with sighand->lock held, which is common to 1422 * all threads in the group. Holding cred_guard_mutex is not 1423 * needed because this new task is not yet running and cannot 1424 * be racing exec. 1425 */ 1426 assert_spin_locked(¤t->sighand->siglock); 1427 1428 /* Ref-count the new filter user, and assign it. */ 1429 get_seccomp_filter(current); 1430 p->seccomp = current->seccomp; 1431 1432 /* 1433 * Explicitly enable no_new_privs here in case it got set 1434 * between the task_struct being duplicated and holding the 1435 * sighand lock. The seccomp state and nnp must be in sync. 1436 */ 1437 if (task_no_new_privs(current)) 1438 task_set_no_new_privs(p); 1439 1440 /* 1441 * If the parent gained a seccomp mode after copying thread 1442 * flags and between before we held the sighand lock, we have 1443 * to manually enable the seccomp thread flag here. 1444 */ 1445 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1446 set_tsk_thread_flag(p, TIF_SECCOMP); 1447 #endif 1448 } 1449 1450 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1451 { 1452 current->clear_child_tid = tidptr; 1453 1454 return task_pid_vnr(current); 1455 } 1456 1457 static void rt_mutex_init_task(struct task_struct *p) 1458 { 1459 raw_spin_lock_init(&p->pi_lock); 1460 #ifdef CONFIG_RT_MUTEXES 1461 p->pi_waiters = RB_ROOT; 1462 p->pi_waiters_leftmost = NULL; 1463 p->pi_top_task = NULL; 1464 p->pi_blocked_on = NULL; 1465 #endif 1466 } 1467 1468 #ifdef CONFIG_POSIX_TIMERS 1469 /* 1470 * Initialize POSIX timer handling for a single task. 1471 */ 1472 static void posix_cpu_timers_init(struct task_struct *tsk) 1473 { 1474 tsk->cputime_expires.prof_exp = 0; 1475 tsk->cputime_expires.virt_exp = 0; 1476 tsk->cputime_expires.sched_exp = 0; 1477 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1478 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1479 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1480 } 1481 #else 1482 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1483 #endif 1484 1485 static inline void 1486 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1487 { 1488 task->pids[type].pid = pid; 1489 } 1490 1491 static inline void rcu_copy_process(struct task_struct *p) 1492 { 1493 #ifdef CONFIG_PREEMPT_RCU 1494 p->rcu_read_lock_nesting = 0; 1495 p->rcu_read_unlock_special.s = 0; 1496 p->rcu_blocked_node = NULL; 1497 INIT_LIST_HEAD(&p->rcu_node_entry); 1498 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1499 #ifdef CONFIG_TASKS_RCU 1500 p->rcu_tasks_holdout = false; 1501 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1502 p->rcu_tasks_idle_cpu = -1; 1503 #endif /* #ifdef CONFIG_TASKS_RCU */ 1504 } 1505 1506 /* 1507 * This creates a new process as a copy of the old one, 1508 * but does not actually start it yet. 1509 * 1510 * It copies the registers, and all the appropriate 1511 * parts of the process environment (as per the clone 1512 * flags). The actual kick-off is left to the caller. 1513 */ 1514 static __latent_entropy struct task_struct *copy_process( 1515 unsigned long clone_flags, 1516 unsigned long stack_start, 1517 unsigned long stack_size, 1518 int __user *child_tidptr, 1519 struct pid *pid, 1520 int trace, 1521 unsigned long tls, 1522 int node) 1523 { 1524 int retval; 1525 struct task_struct *p; 1526 1527 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1528 return ERR_PTR(-EINVAL); 1529 1530 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1531 return ERR_PTR(-EINVAL); 1532 1533 /* 1534 * Thread groups must share signals as well, and detached threads 1535 * can only be started up within the thread group. 1536 */ 1537 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1538 return ERR_PTR(-EINVAL); 1539 1540 /* 1541 * Shared signal handlers imply shared VM. By way of the above, 1542 * thread groups also imply shared VM. Blocking this case allows 1543 * for various simplifications in other code. 1544 */ 1545 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1546 return ERR_PTR(-EINVAL); 1547 1548 /* 1549 * Siblings of global init remain as zombies on exit since they are 1550 * not reaped by their parent (swapper). To solve this and to avoid 1551 * multi-rooted process trees, prevent global and container-inits 1552 * from creating siblings. 1553 */ 1554 if ((clone_flags & CLONE_PARENT) && 1555 current->signal->flags & SIGNAL_UNKILLABLE) 1556 return ERR_PTR(-EINVAL); 1557 1558 /* 1559 * If the new process will be in a different pid or user namespace 1560 * do not allow it to share a thread group with the forking task. 1561 */ 1562 if (clone_flags & CLONE_THREAD) { 1563 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1564 (task_active_pid_ns(current) != 1565 current->nsproxy->pid_ns_for_children)) 1566 return ERR_PTR(-EINVAL); 1567 } 1568 1569 retval = -ENOMEM; 1570 p = dup_task_struct(current, node); 1571 if (!p) 1572 goto fork_out; 1573 1574 /* 1575 * This _must_ happen before we call free_task(), i.e. before we jump 1576 * to any of the bad_fork_* labels. This is to avoid freeing 1577 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1578 * kernel threads (PF_KTHREAD). 1579 */ 1580 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1581 /* 1582 * Clear TID on mm_release()? 1583 */ 1584 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1585 1586 ftrace_graph_init_task(p); 1587 1588 rt_mutex_init_task(p); 1589 1590 #ifdef CONFIG_PROVE_LOCKING 1591 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1592 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1593 #endif 1594 retval = -EAGAIN; 1595 if (atomic_read(&p->real_cred->user->processes) >= 1596 task_rlimit(p, RLIMIT_NPROC)) { 1597 if (p->real_cred->user != INIT_USER && 1598 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1599 goto bad_fork_free; 1600 } 1601 current->flags &= ~PF_NPROC_EXCEEDED; 1602 1603 retval = copy_creds(p, clone_flags); 1604 if (retval < 0) 1605 goto bad_fork_free; 1606 1607 /* 1608 * If multiple threads are within copy_process(), then this check 1609 * triggers too late. This doesn't hurt, the check is only there 1610 * to stop root fork bombs. 1611 */ 1612 retval = -EAGAIN; 1613 if (nr_threads >= max_threads) 1614 goto bad_fork_cleanup_count; 1615 1616 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1617 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1618 p->flags |= PF_FORKNOEXEC; 1619 INIT_LIST_HEAD(&p->children); 1620 INIT_LIST_HEAD(&p->sibling); 1621 rcu_copy_process(p); 1622 p->vfork_done = NULL; 1623 spin_lock_init(&p->alloc_lock); 1624 1625 init_sigpending(&p->pending); 1626 1627 p->utime = p->stime = p->gtime = 0; 1628 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1629 p->utimescaled = p->stimescaled = 0; 1630 #endif 1631 prev_cputime_init(&p->prev_cputime); 1632 1633 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1634 seqcount_init(&p->vtime.seqcount); 1635 p->vtime.starttime = 0; 1636 p->vtime.state = VTIME_INACTIVE; 1637 #endif 1638 1639 #if defined(SPLIT_RSS_COUNTING) 1640 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1641 #endif 1642 1643 p->default_timer_slack_ns = current->timer_slack_ns; 1644 1645 task_io_accounting_init(&p->ioac); 1646 acct_clear_integrals(p); 1647 1648 posix_cpu_timers_init(p); 1649 1650 p->start_time = ktime_get_ns(); 1651 p->real_start_time = ktime_get_boot_ns(); 1652 p->io_context = NULL; 1653 p->audit_context = NULL; 1654 cgroup_fork(p); 1655 #ifdef CONFIG_NUMA 1656 p->mempolicy = mpol_dup(p->mempolicy); 1657 if (IS_ERR(p->mempolicy)) { 1658 retval = PTR_ERR(p->mempolicy); 1659 p->mempolicy = NULL; 1660 goto bad_fork_cleanup_threadgroup_lock; 1661 } 1662 #endif 1663 #ifdef CONFIG_CPUSETS 1664 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1665 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1666 seqcount_init(&p->mems_allowed_seq); 1667 #endif 1668 #ifdef CONFIG_TRACE_IRQFLAGS 1669 p->irq_events = 0; 1670 p->hardirqs_enabled = 0; 1671 p->hardirq_enable_ip = 0; 1672 p->hardirq_enable_event = 0; 1673 p->hardirq_disable_ip = _THIS_IP_; 1674 p->hardirq_disable_event = 0; 1675 p->softirqs_enabled = 1; 1676 p->softirq_enable_ip = _THIS_IP_; 1677 p->softirq_enable_event = 0; 1678 p->softirq_disable_ip = 0; 1679 p->softirq_disable_event = 0; 1680 p->hardirq_context = 0; 1681 p->softirq_context = 0; 1682 #endif 1683 1684 p->pagefault_disabled = 0; 1685 1686 #ifdef CONFIG_LOCKDEP 1687 p->lockdep_depth = 0; /* no locks held yet */ 1688 p->curr_chain_key = 0; 1689 p->lockdep_recursion = 0; 1690 #endif 1691 1692 #ifdef CONFIG_DEBUG_MUTEXES 1693 p->blocked_on = NULL; /* not blocked yet */ 1694 #endif 1695 #ifdef CONFIG_BCACHE 1696 p->sequential_io = 0; 1697 p->sequential_io_avg = 0; 1698 #endif 1699 1700 /* Perform scheduler related setup. Assign this task to a CPU. */ 1701 retval = sched_fork(clone_flags, p); 1702 if (retval) 1703 goto bad_fork_cleanup_policy; 1704 1705 retval = perf_event_init_task(p); 1706 if (retval) 1707 goto bad_fork_cleanup_policy; 1708 retval = audit_alloc(p); 1709 if (retval) 1710 goto bad_fork_cleanup_perf; 1711 /* copy all the process information */ 1712 shm_init_task(p); 1713 retval = security_task_alloc(p, clone_flags); 1714 if (retval) 1715 goto bad_fork_cleanup_audit; 1716 retval = copy_semundo(clone_flags, p); 1717 if (retval) 1718 goto bad_fork_cleanup_security; 1719 retval = copy_files(clone_flags, p); 1720 if (retval) 1721 goto bad_fork_cleanup_semundo; 1722 retval = copy_fs(clone_flags, p); 1723 if (retval) 1724 goto bad_fork_cleanup_files; 1725 retval = copy_sighand(clone_flags, p); 1726 if (retval) 1727 goto bad_fork_cleanup_fs; 1728 retval = copy_signal(clone_flags, p); 1729 if (retval) 1730 goto bad_fork_cleanup_sighand; 1731 retval = copy_mm(clone_flags, p); 1732 if (retval) 1733 goto bad_fork_cleanup_signal; 1734 retval = copy_namespaces(clone_flags, p); 1735 if (retval) 1736 goto bad_fork_cleanup_mm; 1737 retval = copy_io(clone_flags, p); 1738 if (retval) 1739 goto bad_fork_cleanup_namespaces; 1740 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1741 if (retval) 1742 goto bad_fork_cleanup_io; 1743 1744 if (pid != &init_struct_pid) { 1745 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1746 if (IS_ERR(pid)) { 1747 retval = PTR_ERR(pid); 1748 goto bad_fork_cleanup_thread; 1749 } 1750 } 1751 1752 #ifdef CONFIG_BLOCK 1753 p->plug = NULL; 1754 #endif 1755 #ifdef CONFIG_FUTEX 1756 p->robust_list = NULL; 1757 #ifdef CONFIG_COMPAT 1758 p->compat_robust_list = NULL; 1759 #endif 1760 INIT_LIST_HEAD(&p->pi_state_list); 1761 p->pi_state_cache = NULL; 1762 #endif 1763 /* 1764 * sigaltstack should be cleared when sharing the same VM 1765 */ 1766 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1767 sas_ss_reset(p); 1768 1769 /* 1770 * Syscall tracing and stepping should be turned off in the 1771 * child regardless of CLONE_PTRACE. 1772 */ 1773 user_disable_single_step(p); 1774 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1775 #ifdef TIF_SYSCALL_EMU 1776 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1777 #endif 1778 clear_all_latency_tracing(p); 1779 1780 /* ok, now we should be set up.. */ 1781 p->pid = pid_nr(pid); 1782 if (clone_flags & CLONE_THREAD) { 1783 p->exit_signal = -1; 1784 p->group_leader = current->group_leader; 1785 p->tgid = current->tgid; 1786 } else { 1787 if (clone_flags & CLONE_PARENT) 1788 p->exit_signal = current->group_leader->exit_signal; 1789 else 1790 p->exit_signal = (clone_flags & CSIGNAL); 1791 p->group_leader = p; 1792 p->tgid = p->pid; 1793 } 1794 1795 p->nr_dirtied = 0; 1796 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1797 p->dirty_paused_when = 0; 1798 1799 p->pdeath_signal = 0; 1800 INIT_LIST_HEAD(&p->thread_group); 1801 p->task_works = NULL; 1802 1803 cgroup_threadgroup_change_begin(current); 1804 /* 1805 * Ensure that the cgroup subsystem policies allow the new process to be 1806 * forked. It should be noted the the new process's css_set can be changed 1807 * between here and cgroup_post_fork() if an organisation operation is in 1808 * progress. 1809 */ 1810 retval = cgroup_can_fork(p); 1811 if (retval) 1812 goto bad_fork_free_pid; 1813 1814 /* 1815 * Make it visible to the rest of the system, but dont wake it up yet. 1816 * Need tasklist lock for parent etc handling! 1817 */ 1818 write_lock_irq(&tasklist_lock); 1819 1820 /* CLONE_PARENT re-uses the old parent */ 1821 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1822 p->real_parent = current->real_parent; 1823 p->parent_exec_id = current->parent_exec_id; 1824 } else { 1825 p->real_parent = current; 1826 p->parent_exec_id = current->self_exec_id; 1827 } 1828 1829 klp_copy_process(p); 1830 1831 spin_lock(¤t->sighand->siglock); 1832 1833 /* 1834 * Copy seccomp details explicitly here, in case they were changed 1835 * before holding sighand lock. 1836 */ 1837 copy_seccomp(p); 1838 1839 /* 1840 * Process group and session signals need to be delivered to just the 1841 * parent before the fork or both the parent and the child after the 1842 * fork. Restart if a signal comes in before we add the new process to 1843 * it's process group. 1844 * A fatal signal pending means that current will exit, so the new 1845 * thread can't slip out of an OOM kill (or normal SIGKILL). 1846 */ 1847 recalc_sigpending(); 1848 if (signal_pending(current)) { 1849 retval = -ERESTARTNOINTR; 1850 goto bad_fork_cancel_cgroup; 1851 } 1852 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) { 1853 retval = -ENOMEM; 1854 goto bad_fork_cancel_cgroup; 1855 } 1856 1857 if (likely(p->pid)) { 1858 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1859 1860 init_task_pid(p, PIDTYPE_PID, pid); 1861 if (thread_group_leader(p)) { 1862 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1863 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1864 1865 if (is_child_reaper(pid)) { 1866 ns_of_pid(pid)->child_reaper = p; 1867 p->signal->flags |= SIGNAL_UNKILLABLE; 1868 } 1869 1870 p->signal->leader_pid = pid; 1871 p->signal->tty = tty_kref_get(current->signal->tty); 1872 /* 1873 * Inherit has_child_subreaper flag under the same 1874 * tasklist_lock with adding child to the process tree 1875 * for propagate_has_child_subreaper optimization. 1876 */ 1877 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1878 p->real_parent->signal->is_child_subreaper; 1879 list_add_tail(&p->sibling, &p->real_parent->children); 1880 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1881 attach_pid(p, PIDTYPE_PGID); 1882 attach_pid(p, PIDTYPE_SID); 1883 __this_cpu_inc(process_counts); 1884 } else { 1885 current->signal->nr_threads++; 1886 atomic_inc(¤t->signal->live); 1887 atomic_inc(¤t->signal->sigcnt); 1888 list_add_tail_rcu(&p->thread_group, 1889 &p->group_leader->thread_group); 1890 list_add_tail_rcu(&p->thread_node, 1891 &p->signal->thread_head); 1892 } 1893 attach_pid(p, PIDTYPE_PID); 1894 nr_threads++; 1895 } 1896 1897 total_forks++; 1898 spin_unlock(¤t->sighand->siglock); 1899 syscall_tracepoint_update(p); 1900 write_unlock_irq(&tasklist_lock); 1901 1902 proc_fork_connector(p); 1903 cgroup_post_fork(p); 1904 cgroup_threadgroup_change_end(current); 1905 perf_event_fork(p); 1906 1907 trace_task_newtask(p, clone_flags); 1908 uprobe_copy_process(p, clone_flags); 1909 1910 return p; 1911 1912 bad_fork_cancel_cgroup: 1913 spin_unlock(¤t->sighand->siglock); 1914 write_unlock_irq(&tasklist_lock); 1915 cgroup_cancel_fork(p); 1916 bad_fork_free_pid: 1917 cgroup_threadgroup_change_end(current); 1918 if (pid != &init_struct_pid) 1919 free_pid(pid); 1920 bad_fork_cleanup_thread: 1921 exit_thread(p); 1922 bad_fork_cleanup_io: 1923 if (p->io_context) 1924 exit_io_context(p); 1925 bad_fork_cleanup_namespaces: 1926 exit_task_namespaces(p); 1927 bad_fork_cleanup_mm: 1928 if (p->mm) 1929 mmput(p->mm); 1930 bad_fork_cleanup_signal: 1931 if (!(clone_flags & CLONE_THREAD)) 1932 free_signal_struct(p->signal); 1933 bad_fork_cleanup_sighand: 1934 __cleanup_sighand(p->sighand); 1935 bad_fork_cleanup_fs: 1936 exit_fs(p); /* blocking */ 1937 bad_fork_cleanup_files: 1938 exit_files(p); /* blocking */ 1939 bad_fork_cleanup_semundo: 1940 exit_sem(p); 1941 bad_fork_cleanup_security: 1942 security_task_free(p); 1943 bad_fork_cleanup_audit: 1944 audit_free(p); 1945 bad_fork_cleanup_perf: 1946 perf_event_free_task(p); 1947 bad_fork_cleanup_policy: 1948 #ifdef CONFIG_NUMA 1949 mpol_put(p->mempolicy); 1950 bad_fork_cleanup_threadgroup_lock: 1951 #endif 1952 delayacct_tsk_free(p); 1953 bad_fork_cleanup_count: 1954 atomic_dec(&p->cred->user->processes); 1955 exit_creds(p); 1956 bad_fork_free: 1957 p->state = TASK_DEAD; 1958 put_task_stack(p); 1959 free_task(p); 1960 fork_out: 1961 return ERR_PTR(retval); 1962 } 1963 1964 static inline void init_idle_pids(struct pid_link *links) 1965 { 1966 enum pid_type type; 1967 1968 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1969 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1970 links[type].pid = &init_struct_pid; 1971 } 1972 } 1973 1974 struct task_struct *fork_idle(int cpu) 1975 { 1976 struct task_struct *task; 1977 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1978 cpu_to_node(cpu)); 1979 if (!IS_ERR(task)) { 1980 init_idle_pids(task->pids); 1981 init_idle(task, cpu); 1982 } 1983 1984 return task; 1985 } 1986 1987 /* 1988 * Ok, this is the main fork-routine. 1989 * 1990 * It copies the process, and if successful kick-starts 1991 * it and waits for it to finish using the VM if required. 1992 */ 1993 long _do_fork(unsigned long clone_flags, 1994 unsigned long stack_start, 1995 unsigned long stack_size, 1996 int __user *parent_tidptr, 1997 int __user *child_tidptr, 1998 unsigned long tls) 1999 { 2000 struct task_struct *p; 2001 int trace = 0; 2002 long nr; 2003 2004 /* 2005 * Determine whether and which event to report to ptracer. When 2006 * called from kernel_thread or CLONE_UNTRACED is explicitly 2007 * requested, no event is reported; otherwise, report if the event 2008 * for the type of forking is enabled. 2009 */ 2010 if (!(clone_flags & CLONE_UNTRACED)) { 2011 if (clone_flags & CLONE_VFORK) 2012 trace = PTRACE_EVENT_VFORK; 2013 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2014 trace = PTRACE_EVENT_CLONE; 2015 else 2016 trace = PTRACE_EVENT_FORK; 2017 2018 if (likely(!ptrace_event_enabled(current, trace))) 2019 trace = 0; 2020 } 2021 2022 p = copy_process(clone_flags, stack_start, stack_size, 2023 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2024 add_latent_entropy(); 2025 /* 2026 * Do this prior waking up the new thread - the thread pointer 2027 * might get invalid after that point, if the thread exits quickly. 2028 */ 2029 if (!IS_ERR(p)) { 2030 struct completion vfork; 2031 struct pid *pid; 2032 2033 trace_sched_process_fork(current, p); 2034 2035 pid = get_task_pid(p, PIDTYPE_PID); 2036 nr = pid_vnr(pid); 2037 2038 if (clone_flags & CLONE_PARENT_SETTID) 2039 put_user(nr, parent_tidptr); 2040 2041 if (clone_flags & CLONE_VFORK) { 2042 p->vfork_done = &vfork; 2043 init_completion(&vfork); 2044 get_task_struct(p); 2045 } 2046 2047 wake_up_new_task(p); 2048 2049 /* forking complete and child started to run, tell ptracer */ 2050 if (unlikely(trace)) 2051 ptrace_event_pid(trace, pid); 2052 2053 if (clone_flags & CLONE_VFORK) { 2054 if (!wait_for_vfork_done(p, &vfork)) 2055 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2056 } 2057 2058 put_pid(pid); 2059 } else { 2060 nr = PTR_ERR(p); 2061 } 2062 return nr; 2063 } 2064 2065 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2066 /* For compatibility with architectures that call do_fork directly rather than 2067 * using the syscall entry points below. */ 2068 long do_fork(unsigned long clone_flags, 2069 unsigned long stack_start, 2070 unsigned long stack_size, 2071 int __user *parent_tidptr, 2072 int __user *child_tidptr) 2073 { 2074 return _do_fork(clone_flags, stack_start, stack_size, 2075 parent_tidptr, child_tidptr, 0); 2076 } 2077 #endif 2078 2079 /* 2080 * Create a kernel thread. 2081 */ 2082 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2083 { 2084 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2085 (unsigned long)arg, NULL, NULL, 0); 2086 } 2087 2088 #ifdef __ARCH_WANT_SYS_FORK 2089 SYSCALL_DEFINE0(fork) 2090 { 2091 #ifdef CONFIG_MMU 2092 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2093 #else 2094 /* can not support in nommu mode */ 2095 return -EINVAL; 2096 #endif 2097 } 2098 #endif 2099 2100 #ifdef __ARCH_WANT_SYS_VFORK 2101 SYSCALL_DEFINE0(vfork) 2102 { 2103 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2104 0, NULL, NULL, 0); 2105 } 2106 #endif 2107 2108 #ifdef __ARCH_WANT_SYS_CLONE 2109 #ifdef CONFIG_CLONE_BACKWARDS 2110 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2111 int __user *, parent_tidptr, 2112 unsigned long, tls, 2113 int __user *, child_tidptr) 2114 #elif defined(CONFIG_CLONE_BACKWARDS2) 2115 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2116 int __user *, parent_tidptr, 2117 int __user *, child_tidptr, 2118 unsigned long, tls) 2119 #elif defined(CONFIG_CLONE_BACKWARDS3) 2120 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2121 int, stack_size, 2122 int __user *, parent_tidptr, 2123 int __user *, child_tidptr, 2124 unsigned long, tls) 2125 #else 2126 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2127 int __user *, parent_tidptr, 2128 int __user *, child_tidptr, 2129 unsigned long, tls) 2130 #endif 2131 { 2132 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2133 } 2134 #endif 2135 2136 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2137 { 2138 struct task_struct *leader, *parent, *child; 2139 int res; 2140 2141 read_lock(&tasklist_lock); 2142 leader = top = top->group_leader; 2143 down: 2144 for_each_thread(leader, parent) { 2145 list_for_each_entry(child, &parent->children, sibling) { 2146 res = visitor(child, data); 2147 if (res) { 2148 if (res < 0) 2149 goto out; 2150 leader = child; 2151 goto down; 2152 } 2153 up: 2154 ; 2155 } 2156 } 2157 2158 if (leader != top) { 2159 child = leader; 2160 parent = child->real_parent; 2161 leader = parent->group_leader; 2162 goto up; 2163 } 2164 out: 2165 read_unlock(&tasklist_lock); 2166 } 2167 2168 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2169 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2170 #endif 2171 2172 static void sighand_ctor(void *data) 2173 { 2174 struct sighand_struct *sighand = data; 2175 2176 spin_lock_init(&sighand->siglock); 2177 init_waitqueue_head(&sighand->signalfd_wqh); 2178 } 2179 2180 void __init proc_caches_init(void) 2181 { 2182 sighand_cachep = kmem_cache_create("sighand_cache", 2183 sizeof(struct sighand_struct), 0, 2184 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2185 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2186 signal_cachep = kmem_cache_create("signal_cache", 2187 sizeof(struct signal_struct), 0, 2188 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2189 NULL); 2190 files_cachep = kmem_cache_create("files_cache", 2191 sizeof(struct files_struct), 0, 2192 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2193 NULL); 2194 fs_cachep = kmem_cache_create("fs_cache", 2195 sizeof(struct fs_struct), 0, 2196 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2197 NULL); 2198 /* 2199 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2200 * whole struct cpumask for the OFFSTACK case. We could change 2201 * this to *only* allocate as much of it as required by the 2202 * maximum number of CPU's we can ever have. The cpumask_allocation 2203 * is at the end of the structure, exactly for that reason. 2204 */ 2205 mm_cachep = kmem_cache_create("mm_struct", 2206 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2207 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2208 NULL); 2209 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2210 mmap_init(); 2211 nsproxy_cache_init(); 2212 } 2213 2214 /* 2215 * Check constraints on flags passed to the unshare system call. 2216 */ 2217 static int check_unshare_flags(unsigned long unshare_flags) 2218 { 2219 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2220 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2221 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2222 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2223 return -EINVAL; 2224 /* 2225 * Not implemented, but pretend it works if there is nothing 2226 * to unshare. Note that unsharing the address space or the 2227 * signal handlers also need to unshare the signal queues (aka 2228 * CLONE_THREAD). 2229 */ 2230 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2231 if (!thread_group_empty(current)) 2232 return -EINVAL; 2233 } 2234 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2235 if (atomic_read(¤t->sighand->count) > 1) 2236 return -EINVAL; 2237 } 2238 if (unshare_flags & CLONE_VM) { 2239 if (!current_is_single_threaded()) 2240 return -EINVAL; 2241 } 2242 2243 return 0; 2244 } 2245 2246 /* 2247 * Unshare the filesystem structure if it is being shared 2248 */ 2249 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2250 { 2251 struct fs_struct *fs = current->fs; 2252 2253 if (!(unshare_flags & CLONE_FS) || !fs) 2254 return 0; 2255 2256 /* don't need lock here; in the worst case we'll do useless copy */ 2257 if (fs->users == 1) 2258 return 0; 2259 2260 *new_fsp = copy_fs_struct(fs); 2261 if (!*new_fsp) 2262 return -ENOMEM; 2263 2264 return 0; 2265 } 2266 2267 /* 2268 * Unshare file descriptor table if it is being shared 2269 */ 2270 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2271 { 2272 struct files_struct *fd = current->files; 2273 int error = 0; 2274 2275 if ((unshare_flags & CLONE_FILES) && 2276 (fd && atomic_read(&fd->count) > 1)) { 2277 *new_fdp = dup_fd(fd, &error); 2278 if (!*new_fdp) 2279 return error; 2280 } 2281 2282 return 0; 2283 } 2284 2285 /* 2286 * unshare allows a process to 'unshare' part of the process 2287 * context which was originally shared using clone. copy_* 2288 * functions used by do_fork() cannot be used here directly 2289 * because they modify an inactive task_struct that is being 2290 * constructed. Here we are modifying the current, active, 2291 * task_struct. 2292 */ 2293 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2294 { 2295 struct fs_struct *fs, *new_fs = NULL; 2296 struct files_struct *fd, *new_fd = NULL; 2297 struct cred *new_cred = NULL; 2298 struct nsproxy *new_nsproxy = NULL; 2299 int do_sysvsem = 0; 2300 int err; 2301 2302 /* 2303 * If unsharing a user namespace must also unshare the thread group 2304 * and unshare the filesystem root and working directories. 2305 */ 2306 if (unshare_flags & CLONE_NEWUSER) 2307 unshare_flags |= CLONE_THREAD | CLONE_FS; 2308 /* 2309 * If unsharing vm, must also unshare signal handlers. 2310 */ 2311 if (unshare_flags & CLONE_VM) 2312 unshare_flags |= CLONE_SIGHAND; 2313 /* 2314 * If unsharing a signal handlers, must also unshare the signal queues. 2315 */ 2316 if (unshare_flags & CLONE_SIGHAND) 2317 unshare_flags |= CLONE_THREAD; 2318 /* 2319 * If unsharing namespace, must also unshare filesystem information. 2320 */ 2321 if (unshare_flags & CLONE_NEWNS) 2322 unshare_flags |= CLONE_FS; 2323 2324 err = check_unshare_flags(unshare_flags); 2325 if (err) 2326 goto bad_unshare_out; 2327 /* 2328 * CLONE_NEWIPC must also detach from the undolist: after switching 2329 * to a new ipc namespace, the semaphore arrays from the old 2330 * namespace are unreachable. 2331 */ 2332 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2333 do_sysvsem = 1; 2334 err = unshare_fs(unshare_flags, &new_fs); 2335 if (err) 2336 goto bad_unshare_out; 2337 err = unshare_fd(unshare_flags, &new_fd); 2338 if (err) 2339 goto bad_unshare_cleanup_fs; 2340 err = unshare_userns(unshare_flags, &new_cred); 2341 if (err) 2342 goto bad_unshare_cleanup_fd; 2343 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2344 new_cred, new_fs); 2345 if (err) 2346 goto bad_unshare_cleanup_cred; 2347 2348 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2349 if (do_sysvsem) { 2350 /* 2351 * CLONE_SYSVSEM is equivalent to sys_exit(). 2352 */ 2353 exit_sem(current); 2354 } 2355 if (unshare_flags & CLONE_NEWIPC) { 2356 /* Orphan segments in old ns (see sem above). */ 2357 exit_shm(current); 2358 shm_init_task(current); 2359 } 2360 2361 if (new_nsproxy) 2362 switch_task_namespaces(current, new_nsproxy); 2363 2364 task_lock(current); 2365 2366 if (new_fs) { 2367 fs = current->fs; 2368 spin_lock(&fs->lock); 2369 current->fs = new_fs; 2370 if (--fs->users) 2371 new_fs = NULL; 2372 else 2373 new_fs = fs; 2374 spin_unlock(&fs->lock); 2375 } 2376 2377 if (new_fd) { 2378 fd = current->files; 2379 current->files = new_fd; 2380 new_fd = fd; 2381 } 2382 2383 task_unlock(current); 2384 2385 if (new_cred) { 2386 /* Install the new user namespace */ 2387 commit_creds(new_cred); 2388 new_cred = NULL; 2389 } 2390 } 2391 2392 perf_event_namespaces(current); 2393 2394 bad_unshare_cleanup_cred: 2395 if (new_cred) 2396 put_cred(new_cred); 2397 bad_unshare_cleanup_fd: 2398 if (new_fd) 2399 put_files_struct(new_fd); 2400 2401 bad_unshare_cleanup_fs: 2402 if (new_fs) 2403 free_fs_struct(new_fs); 2404 2405 bad_unshare_out: 2406 return err; 2407 } 2408 2409 /* 2410 * Helper to unshare the files of the current task. 2411 * We don't want to expose copy_files internals to 2412 * the exec layer of the kernel. 2413 */ 2414 2415 int unshare_files(struct files_struct **displaced) 2416 { 2417 struct task_struct *task = current; 2418 struct files_struct *copy = NULL; 2419 int error; 2420 2421 error = unshare_fd(CLONE_FILES, ©); 2422 if (error || !copy) { 2423 *displaced = NULL; 2424 return error; 2425 } 2426 *displaced = task->files; 2427 task_lock(task); 2428 task->files = copy; 2429 task_unlock(task); 2430 return 0; 2431 } 2432 2433 int sysctl_max_threads(struct ctl_table *table, int write, 2434 void __user *buffer, size_t *lenp, loff_t *ppos) 2435 { 2436 struct ctl_table t; 2437 int ret; 2438 int threads = max_threads; 2439 int min = MIN_THREADS; 2440 int max = MAX_THREADS; 2441 2442 t = *table; 2443 t.data = &threads; 2444 t.extra1 = &min; 2445 t.extra2 = &max; 2446 2447 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2448 if (ret || !write) 2449 return ret; 2450 2451 set_max_threads(threads); 2452 2453 return 0; 2454 } 2455