1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/sched/autogroup.h> 16 #include <linux/sched/mm.h> 17 #include <linux/sched/coredump.h> 18 #include <linux/sched/user.h> 19 #include <linux/sched/numa_balancing.h> 20 #include <linux/sched/stat.h> 21 #include <linux/sched/task.h> 22 #include <linux/sched/task_stack.h> 23 #include <linux/sched/cputime.h> 24 #include <linux/rtmutex.h> 25 #include <linux/init.h> 26 #include <linux/unistd.h> 27 #include <linux/module.h> 28 #include <linux/vmalloc.h> 29 #include <linux/completion.h> 30 #include <linux/personality.h> 31 #include <linux/mempolicy.h> 32 #include <linux/sem.h> 33 #include <linux/file.h> 34 #include <linux/fdtable.h> 35 #include <linux/iocontext.h> 36 #include <linux/key.h> 37 #include <linux/binfmts.h> 38 #include <linux/mman.h> 39 #include <linux/mmu_notifier.h> 40 #include <linux/hmm.h> 41 #include <linux/fs.h> 42 #include <linux/mm.h> 43 #include <linux/vmacache.h> 44 #include <linux/nsproxy.h> 45 #include <linux/capability.h> 46 #include <linux/cpu.h> 47 #include <linux/cgroup.h> 48 #include <linux/security.h> 49 #include <linux/hugetlb.h> 50 #include <linux/seccomp.h> 51 #include <linux/swap.h> 52 #include <linux/syscalls.h> 53 #include <linux/jiffies.h> 54 #include <linux/futex.h> 55 #include <linux/compat.h> 56 #include <linux/kthread.h> 57 #include <linux/task_io_accounting_ops.h> 58 #include <linux/rcupdate.h> 59 #include <linux/ptrace.h> 60 #include <linux/mount.h> 61 #include <linux/audit.h> 62 #include <linux/memcontrol.h> 63 #include <linux/ftrace.h> 64 #include <linux/proc_fs.h> 65 #include <linux/profile.h> 66 #include <linux/rmap.h> 67 #include <linux/ksm.h> 68 #include <linux/acct.h> 69 #include <linux/userfaultfd_k.h> 70 #include <linux/tsacct_kern.h> 71 #include <linux/cn_proc.h> 72 #include <linux/freezer.h> 73 #include <linux/delayacct.h> 74 #include <linux/taskstats_kern.h> 75 #include <linux/random.h> 76 #include <linux/tty.h> 77 #include <linux/blkdev.h> 78 #include <linux/fs_struct.h> 79 #include <linux/magic.h> 80 #include <linux/perf_event.h> 81 #include <linux/posix-timers.h> 82 #include <linux/user-return-notifier.h> 83 #include <linux/oom.h> 84 #include <linux/khugepaged.h> 85 #include <linux/signalfd.h> 86 #include <linux/uprobes.h> 87 #include <linux/aio.h> 88 #include <linux/compiler.h> 89 #include <linux/sysctl.h> 90 #include <linux/kcov.h> 91 #include <linux/livepatch.h> 92 #include <linux/thread_info.h> 93 94 #include <asm/pgtable.h> 95 #include <asm/pgalloc.h> 96 #include <linux/uaccess.h> 97 #include <asm/mmu_context.h> 98 #include <asm/cacheflush.h> 99 #include <asm/tlbflush.h> 100 101 #include <trace/events/sched.h> 102 103 #define CREATE_TRACE_POINTS 104 #include <trace/events/task.h> 105 106 /* 107 * Minimum number of threads to boot the kernel 108 */ 109 #define MIN_THREADS 20 110 111 /* 112 * Maximum number of threads 113 */ 114 #define MAX_THREADS FUTEX_TID_MASK 115 116 /* 117 * Protected counters by write_lock_irq(&tasklist_lock) 118 */ 119 unsigned long total_forks; /* Handle normal Linux uptimes. */ 120 int nr_threads; /* The idle threads do not count.. */ 121 122 int max_threads; /* tunable limit on nr_threads */ 123 124 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 125 126 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 127 128 #ifdef CONFIG_PROVE_RCU 129 int lockdep_tasklist_lock_is_held(void) 130 { 131 return lockdep_is_held(&tasklist_lock); 132 } 133 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 134 #endif /* #ifdef CONFIG_PROVE_RCU */ 135 136 int nr_processes(void) 137 { 138 int cpu; 139 int total = 0; 140 141 for_each_possible_cpu(cpu) 142 total += per_cpu(process_counts, cpu); 143 144 return total; 145 } 146 147 void __weak arch_release_task_struct(struct task_struct *tsk) 148 { 149 } 150 151 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 152 static struct kmem_cache *task_struct_cachep; 153 154 static inline struct task_struct *alloc_task_struct_node(int node) 155 { 156 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 157 } 158 159 static inline void free_task_struct(struct task_struct *tsk) 160 { 161 kmem_cache_free(task_struct_cachep, tsk); 162 } 163 #endif 164 165 void __weak arch_release_thread_stack(unsigned long *stack) 166 { 167 } 168 169 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 170 171 /* 172 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 173 * kmemcache based allocator. 174 */ 175 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 176 177 #ifdef CONFIG_VMAP_STACK 178 /* 179 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 180 * flush. Try to minimize the number of calls by caching stacks. 181 */ 182 #define NR_CACHED_STACKS 2 183 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 184 185 static int free_vm_stack_cache(unsigned int cpu) 186 { 187 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 188 int i; 189 190 for (i = 0; i < NR_CACHED_STACKS; i++) { 191 struct vm_struct *vm_stack = cached_vm_stacks[i]; 192 193 if (!vm_stack) 194 continue; 195 196 vfree(vm_stack->addr); 197 cached_vm_stacks[i] = NULL; 198 } 199 200 return 0; 201 } 202 #endif 203 204 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 205 { 206 #ifdef CONFIG_VMAP_STACK 207 void *stack; 208 int i; 209 210 for (i = 0; i < NR_CACHED_STACKS; i++) { 211 struct vm_struct *s; 212 213 s = this_cpu_xchg(cached_stacks[i], NULL); 214 215 if (!s) 216 continue; 217 218 #ifdef CONFIG_DEBUG_KMEMLEAK 219 /* Clear stale pointers from reused stack. */ 220 memset(s->addr, 0, THREAD_SIZE); 221 #endif 222 tsk->stack_vm_area = s; 223 return s->addr; 224 } 225 226 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, 227 VMALLOC_START, VMALLOC_END, 228 THREADINFO_GFP, 229 PAGE_KERNEL, 230 0, node, __builtin_return_address(0)); 231 232 /* 233 * We can't call find_vm_area() in interrupt context, and 234 * free_thread_stack() can be called in interrupt context, 235 * so cache the vm_struct. 236 */ 237 if (stack) 238 tsk->stack_vm_area = find_vm_area(stack); 239 return stack; 240 #else 241 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 242 THREAD_SIZE_ORDER); 243 244 return page ? page_address(page) : NULL; 245 #endif 246 } 247 248 static inline void free_thread_stack(struct task_struct *tsk) 249 { 250 #ifdef CONFIG_VMAP_STACK 251 if (task_stack_vm_area(tsk)) { 252 int i; 253 254 for (i = 0; i < NR_CACHED_STACKS; i++) { 255 if (this_cpu_cmpxchg(cached_stacks[i], 256 NULL, tsk->stack_vm_area) != NULL) 257 continue; 258 259 return; 260 } 261 262 vfree_atomic(tsk->stack); 263 return; 264 } 265 #endif 266 267 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 268 } 269 # else 270 static struct kmem_cache *thread_stack_cache; 271 272 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 273 int node) 274 { 275 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 276 } 277 278 static void free_thread_stack(struct task_struct *tsk) 279 { 280 kmem_cache_free(thread_stack_cache, tsk->stack); 281 } 282 283 void thread_stack_cache_init(void) 284 { 285 thread_stack_cache = kmem_cache_create("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 mod_memcg_page_state(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 mod_memcg_page_state(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 lockdep_init_task(&init_task); 495 } 496 497 int __weak arch_dup_task_struct(struct task_struct *dst, 498 struct task_struct *src) 499 { 500 *dst = *src; 501 return 0; 502 } 503 504 void set_task_stack_end_magic(struct task_struct *tsk) 505 { 506 unsigned long *stackend; 507 508 stackend = end_of_stack(tsk); 509 *stackend = STACK_END_MAGIC; /* for overflow detection */ 510 } 511 512 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 513 { 514 struct task_struct *tsk; 515 unsigned long *stack; 516 struct vm_struct *stack_vm_area; 517 int err; 518 519 if (node == NUMA_NO_NODE) 520 node = tsk_fork_get_node(orig); 521 tsk = alloc_task_struct_node(node); 522 if (!tsk) 523 return NULL; 524 525 stack = alloc_thread_stack_node(tsk, node); 526 if (!stack) 527 goto free_tsk; 528 529 stack_vm_area = task_stack_vm_area(tsk); 530 531 err = arch_dup_task_struct(tsk, orig); 532 533 /* 534 * arch_dup_task_struct() clobbers the stack-related fields. Make 535 * sure they're properly initialized before using any stack-related 536 * functions again. 537 */ 538 tsk->stack = stack; 539 #ifdef CONFIG_VMAP_STACK 540 tsk->stack_vm_area = stack_vm_area; 541 #endif 542 #ifdef CONFIG_THREAD_INFO_IN_TASK 543 atomic_set(&tsk->stack_refcount, 1); 544 #endif 545 546 if (err) 547 goto free_stack; 548 549 #ifdef CONFIG_SECCOMP 550 /* 551 * We must handle setting up seccomp filters once we're under 552 * the sighand lock in case orig has changed between now and 553 * then. Until then, filter must be NULL to avoid messing up 554 * the usage counts on the error path calling free_task. 555 */ 556 tsk->seccomp.filter = NULL; 557 #endif 558 559 setup_thread_stack(tsk, orig); 560 clear_user_return_notifier(tsk); 561 clear_tsk_need_resched(tsk); 562 set_task_stack_end_magic(tsk); 563 564 #ifdef CONFIG_CC_STACKPROTECTOR 565 tsk->stack_canary = get_random_canary(); 566 #endif 567 568 /* 569 * One for us, one for whoever does the "release_task()" (usually 570 * parent) 571 */ 572 atomic_set(&tsk->usage, 2); 573 #ifdef CONFIG_BLK_DEV_IO_TRACE 574 tsk->btrace_seq = 0; 575 #endif 576 tsk->splice_pipe = NULL; 577 tsk->task_frag.page = NULL; 578 tsk->wake_q.next = NULL; 579 580 account_kernel_stack(tsk, 1); 581 582 kcov_task_init(tsk); 583 584 #ifdef CONFIG_FAULT_INJECTION 585 tsk->fail_nth = 0; 586 #endif 587 588 return tsk; 589 590 free_stack: 591 free_thread_stack(tsk); 592 free_tsk: 593 free_task_struct(tsk); 594 return NULL; 595 } 596 597 #ifdef CONFIG_MMU 598 static __latent_entropy int dup_mmap(struct mm_struct *mm, 599 struct mm_struct *oldmm) 600 { 601 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 602 struct rb_node **rb_link, *rb_parent; 603 int retval; 604 unsigned long charge; 605 LIST_HEAD(uf); 606 607 uprobe_start_dup_mmap(); 608 if (down_write_killable(&oldmm->mmap_sem)) { 609 retval = -EINTR; 610 goto fail_uprobe_end; 611 } 612 flush_cache_dup_mm(oldmm); 613 uprobe_dup_mmap(oldmm, mm); 614 /* 615 * Not linked in yet - no deadlock potential: 616 */ 617 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 618 619 /* No ordering required: file already has been exposed. */ 620 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 621 622 mm->total_vm = oldmm->total_vm; 623 mm->data_vm = oldmm->data_vm; 624 mm->exec_vm = oldmm->exec_vm; 625 mm->stack_vm = oldmm->stack_vm; 626 627 rb_link = &mm->mm_rb.rb_node; 628 rb_parent = NULL; 629 pprev = &mm->mmap; 630 retval = ksm_fork(mm, oldmm); 631 if (retval) 632 goto out; 633 retval = khugepaged_fork(mm, oldmm); 634 if (retval) 635 goto out; 636 637 prev = NULL; 638 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 639 struct file *file; 640 641 if (mpnt->vm_flags & VM_DONTCOPY) { 642 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 643 continue; 644 } 645 charge = 0; 646 if (mpnt->vm_flags & VM_ACCOUNT) { 647 unsigned long len = vma_pages(mpnt); 648 649 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 650 goto fail_nomem; 651 charge = len; 652 } 653 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 654 if (!tmp) 655 goto fail_nomem; 656 *tmp = *mpnt; 657 INIT_LIST_HEAD(&tmp->anon_vma_chain); 658 retval = vma_dup_policy(mpnt, tmp); 659 if (retval) 660 goto fail_nomem_policy; 661 tmp->vm_mm = mm; 662 retval = dup_userfaultfd(tmp, &uf); 663 if (retval) 664 goto fail_nomem_anon_vma_fork; 665 if (tmp->vm_flags & VM_WIPEONFORK) { 666 /* VM_WIPEONFORK gets a clean slate in the child. */ 667 tmp->anon_vma = NULL; 668 if (anon_vma_prepare(tmp)) 669 goto fail_nomem_anon_vma_fork; 670 } else if (anon_vma_fork(tmp, mpnt)) 671 goto fail_nomem_anon_vma_fork; 672 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 673 tmp->vm_next = tmp->vm_prev = NULL; 674 file = tmp->vm_file; 675 if (file) { 676 struct inode *inode = file_inode(file); 677 struct address_space *mapping = file->f_mapping; 678 679 get_file(file); 680 if (tmp->vm_flags & VM_DENYWRITE) 681 atomic_dec(&inode->i_writecount); 682 i_mmap_lock_write(mapping); 683 if (tmp->vm_flags & VM_SHARED) 684 atomic_inc(&mapping->i_mmap_writable); 685 flush_dcache_mmap_lock(mapping); 686 /* insert tmp into the share list, just after mpnt */ 687 vma_interval_tree_insert_after(tmp, mpnt, 688 &mapping->i_mmap); 689 flush_dcache_mmap_unlock(mapping); 690 i_mmap_unlock_write(mapping); 691 } 692 693 /* 694 * Clear hugetlb-related page reserves for children. This only 695 * affects MAP_PRIVATE mappings. Faults generated by the child 696 * are not guaranteed to succeed, even if read-only 697 */ 698 if (is_vm_hugetlb_page(tmp)) 699 reset_vma_resv_huge_pages(tmp); 700 701 /* 702 * Link in the new vma and copy the page table entries. 703 */ 704 *pprev = tmp; 705 pprev = &tmp->vm_next; 706 tmp->vm_prev = prev; 707 prev = tmp; 708 709 __vma_link_rb(mm, tmp, rb_link, rb_parent); 710 rb_link = &tmp->vm_rb.rb_right; 711 rb_parent = &tmp->vm_rb; 712 713 mm->map_count++; 714 if (!(tmp->vm_flags & VM_WIPEONFORK)) 715 retval = copy_page_range(mm, oldmm, mpnt); 716 717 if (tmp->vm_ops && tmp->vm_ops->open) 718 tmp->vm_ops->open(tmp); 719 720 if (retval) 721 goto out; 722 } 723 /* a new mm has just been created */ 724 arch_dup_mmap(oldmm, mm); 725 retval = 0; 726 out: 727 up_write(&mm->mmap_sem); 728 flush_tlb_mm(oldmm); 729 up_write(&oldmm->mmap_sem); 730 dup_userfaultfd_complete(&uf); 731 fail_uprobe_end: 732 uprobe_end_dup_mmap(); 733 return retval; 734 fail_nomem_anon_vma_fork: 735 mpol_put(vma_policy(tmp)); 736 fail_nomem_policy: 737 kmem_cache_free(vm_area_cachep, tmp); 738 fail_nomem: 739 retval = -ENOMEM; 740 vm_unacct_memory(charge); 741 goto out; 742 } 743 744 static inline int mm_alloc_pgd(struct mm_struct *mm) 745 { 746 mm->pgd = pgd_alloc(mm); 747 if (unlikely(!mm->pgd)) 748 return -ENOMEM; 749 return 0; 750 } 751 752 static inline void mm_free_pgd(struct mm_struct *mm) 753 { 754 pgd_free(mm, mm->pgd); 755 } 756 #else 757 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 758 { 759 down_write(&oldmm->mmap_sem); 760 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 761 up_write(&oldmm->mmap_sem); 762 return 0; 763 } 764 #define mm_alloc_pgd(mm) (0) 765 #define mm_free_pgd(mm) 766 #endif /* CONFIG_MMU */ 767 768 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 769 770 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 771 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 772 773 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 774 775 static int __init coredump_filter_setup(char *s) 776 { 777 default_dump_filter = 778 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 779 MMF_DUMP_FILTER_MASK; 780 return 1; 781 } 782 783 __setup("coredump_filter=", coredump_filter_setup); 784 785 #include <linux/init_task.h> 786 787 static void mm_init_aio(struct mm_struct *mm) 788 { 789 #ifdef CONFIG_AIO 790 spin_lock_init(&mm->ioctx_lock); 791 mm->ioctx_table = NULL; 792 #endif 793 } 794 795 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 796 { 797 #ifdef CONFIG_MEMCG 798 mm->owner = p; 799 #endif 800 } 801 802 static void mm_init_uprobes_state(struct mm_struct *mm) 803 { 804 #ifdef CONFIG_UPROBES 805 mm->uprobes_state.xol_area = NULL; 806 #endif 807 } 808 809 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 810 struct user_namespace *user_ns) 811 { 812 mm->mmap = NULL; 813 mm->mm_rb = RB_ROOT; 814 mm->vmacache_seqnum = 0; 815 atomic_set(&mm->mm_users, 1); 816 atomic_set(&mm->mm_count, 1); 817 init_rwsem(&mm->mmap_sem); 818 INIT_LIST_HEAD(&mm->mmlist); 819 mm->core_state = NULL; 820 atomic_long_set(&mm->nr_ptes, 0); 821 mm_nr_pmds_init(mm); 822 mm->map_count = 0; 823 mm->locked_vm = 0; 824 mm->pinned_vm = 0; 825 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 826 spin_lock_init(&mm->page_table_lock); 827 mm_init_cpumask(mm); 828 mm_init_aio(mm); 829 mm_init_owner(mm, p); 830 RCU_INIT_POINTER(mm->exe_file, NULL); 831 mmu_notifier_mm_init(mm); 832 hmm_mm_init(mm); 833 init_tlb_flush_pending(mm); 834 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 835 mm->pmd_huge_pte = NULL; 836 #endif 837 mm_init_uprobes_state(mm); 838 839 if (current->mm) { 840 mm->flags = current->mm->flags & MMF_INIT_MASK; 841 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 842 } else { 843 mm->flags = default_dump_filter; 844 mm->def_flags = 0; 845 } 846 847 if (mm_alloc_pgd(mm)) 848 goto fail_nopgd; 849 850 if (init_new_context(p, mm)) 851 goto fail_nocontext; 852 853 mm->user_ns = get_user_ns(user_ns); 854 return mm; 855 856 fail_nocontext: 857 mm_free_pgd(mm); 858 fail_nopgd: 859 free_mm(mm); 860 return NULL; 861 } 862 863 static void check_mm(struct mm_struct *mm) 864 { 865 int i; 866 867 for (i = 0; i < NR_MM_COUNTERS; i++) { 868 long x = atomic_long_read(&mm->rss_stat.count[i]); 869 870 if (unlikely(x)) 871 printk(KERN_ALERT "BUG: Bad rss-counter state " 872 "mm:%p idx:%d val:%ld\n", mm, i, x); 873 } 874 875 if (atomic_long_read(&mm->nr_ptes)) 876 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 877 atomic_long_read(&mm->nr_ptes)); 878 if (mm_nr_pmds(mm)) 879 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 880 mm_nr_pmds(mm)); 881 882 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 883 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 884 #endif 885 } 886 887 /* 888 * Allocate and initialize an mm_struct. 889 */ 890 struct mm_struct *mm_alloc(void) 891 { 892 struct mm_struct *mm; 893 894 mm = allocate_mm(); 895 if (!mm) 896 return NULL; 897 898 memset(mm, 0, sizeof(*mm)); 899 return mm_init(mm, current, current_user_ns()); 900 } 901 902 /* 903 * Called when the last reference to the mm 904 * is dropped: either by a lazy thread or by 905 * mmput. Free the page directory and the mm. 906 */ 907 void __mmdrop(struct mm_struct *mm) 908 { 909 BUG_ON(mm == &init_mm); 910 mm_free_pgd(mm); 911 destroy_context(mm); 912 hmm_mm_destroy(mm); 913 mmu_notifier_mm_destroy(mm); 914 check_mm(mm); 915 put_user_ns(mm->user_ns); 916 free_mm(mm); 917 } 918 EXPORT_SYMBOL_GPL(__mmdrop); 919 920 static inline void __mmput(struct mm_struct *mm) 921 { 922 VM_BUG_ON(atomic_read(&mm->mm_users)); 923 924 uprobe_clear_state(mm); 925 exit_aio(mm); 926 ksm_exit(mm); 927 khugepaged_exit(mm); /* must run before exit_mmap */ 928 exit_mmap(mm); 929 mm_put_huge_zero_page(mm); 930 set_mm_exe_file(mm, NULL); 931 if (!list_empty(&mm->mmlist)) { 932 spin_lock(&mmlist_lock); 933 list_del(&mm->mmlist); 934 spin_unlock(&mmlist_lock); 935 } 936 if (mm->binfmt) 937 module_put(mm->binfmt->module); 938 mmdrop(mm); 939 } 940 941 /* 942 * Decrement the use count and release all resources for an mm. 943 */ 944 void mmput(struct mm_struct *mm) 945 { 946 might_sleep(); 947 948 if (atomic_dec_and_test(&mm->mm_users)) 949 __mmput(mm); 950 } 951 EXPORT_SYMBOL_GPL(mmput); 952 953 #ifdef CONFIG_MMU 954 static void mmput_async_fn(struct work_struct *work) 955 { 956 struct mm_struct *mm = container_of(work, struct mm_struct, 957 async_put_work); 958 959 __mmput(mm); 960 } 961 962 void mmput_async(struct mm_struct *mm) 963 { 964 if (atomic_dec_and_test(&mm->mm_users)) { 965 INIT_WORK(&mm->async_put_work, mmput_async_fn); 966 schedule_work(&mm->async_put_work); 967 } 968 } 969 #endif 970 971 /** 972 * set_mm_exe_file - change a reference to the mm's executable file 973 * 974 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 975 * 976 * Main users are mmput() and sys_execve(). Callers prevent concurrent 977 * invocations: in mmput() nobody alive left, in execve task is single 978 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 979 * mm->exe_file, but does so without using set_mm_exe_file() in order 980 * to do avoid the need for any locks. 981 */ 982 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 983 { 984 struct file *old_exe_file; 985 986 /* 987 * It is safe to dereference the exe_file without RCU as 988 * this function is only called if nobody else can access 989 * this mm -- see comment above for justification. 990 */ 991 old_exe_file = rcu_dereference_raw(mm->exe_file); 992 993 if (new_exe_file) 994 get_file(new_exe_file); 995 rcu_assign_pointer(mm->exe_file, new_exe_file); 996 if (old_exe_file) 997 fput(old_exe_file); 998 } 999 1000 /** 1001 * get_mm_exe_file - acquire a reference to the mm's executable file 1002 * 1003 * Returns %NULL if mm has no associated executable file. 1004 * User must release file via fput(). 1005 */ 1006 struct file *get_mm_exe_file(struct mm_struct *mm) 1007 { 1008 struct file *exe_file; 1009 1010 rcu_read_lock(); 1011 exe_file = rcu_dereference(mm->exe_file); 1012 if (exe_file && !get_file_rcu(exe_file)) 1013 exe_file = NULL; 1014 rcu_read_unlock(); 1015 return exe_file; 1016 } 1017 EXPORT_SYMBOL(get_mm_exe_file); 1018 1019 /** 1020 * get_task_exe_file - acquire a reference to the task's executable file 1021 * 1022 * Returns %NULL if task's mm (if any) has no associated executable file or 1023 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1024 * User must release file via fput(). 1025 */ 1026 struct file *get_task_exe_file(struct task_struct *task) 1027 { 1028 struct file *exe_file = NULL; 1029 struct mm_struct *mm; 1030 1031 task_lock(task); 1032 mm = task->mm; 1033 if (mm) { 1034 if (!(task->flags & PF_KTHREAD)) 1035 exe_file = get_mm_exe_file(mm); 1036 } 1037 task_unlock(task); 1038 return exe_file; 1039 } 1040 EXPORT_SYMBOL(get_task_exe_file); 1041 1042 /** 1043 * get_task_mm - acquire a reference to the task's mm 1044 * 1045 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1046 * this kernel workthread has transiently adopted a user mm with use_mm, 1047 * to do its AIO) is not set and if so returns a reference to it, after 1048 * bumping up the use count. User must release the mm via mmput() 1049 * after use. Typically used by /proc and ptrace. 1050 */ 1051 struct mm_struct *get_task_mm(struct task_struct *task) 1052 { 1053 struct mm_struct *mm; 1054 1055 task_lock(task); 1056 mm = task->mm; 1057 if (mm) { 1058 if (task->flags & PF_KTHREAD) 1059 mm = NULL; 1060 else 1061 mmget(mm); 1062 } 1063 task_unlock(task); 1064 return mm; 1065 } 1066 EXPORT_SYMBOL_GPL(get_task_mm); 1067 1068 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1069 { 1070 struct mm_struct *mm; 1071 int err; 1072 1073 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1074 if (err) 1075 return ERR_PTR(err); 1076 1077 mm = get_task_mm(task); 1078 if (mm && mm != current->mm && 1079 !ptrace_may_access(task, mode)) { 1080 mmput(mm); 1081 mm = ERR_PTR(-EACCES); 1082 } 1083 mutex_unlock(&task->signal->cred_guard_mutex); 1084 1085 return mm; 1086 } 1087 1088 static void complete_vfork_done(struct task_struct *tsk) 1089 { 1090 struct completion *vfork; 1091 1092 task_lock(tsk); 1093 vfork = tsk->vfork_done; 1094 if (likely(vfork)) { 1095 tsk->vfork_done = NULL; 1096 complete(vfork); 1097 } 1098 task_unlock(tsk); 1099 } 1100 1101 static int wait_for_vfork_done(struct task_struct *child, 1102 struct completion *vfork) 1103 { 1104 int killed; 1105 1106 freezer_do_not_count(); 1107 killed = wait_for_completion_killable(vfork); 1108 freezer_count(); 1109 1110 if (killed) { 1111 task_lock(child); 1112 child->vfork_done = NULL; 1113 task_unlock(child); 1114 } 1115 1116 put_task_struct(child); 1117 return killed; 1118 } 1119 1120 /* Please note the differences between mmput and mm_release. 1121 * mmput is called whenever we stop holding onto a mm_struct, 1122 * error success whatever. 1123 * 1124 * mm_release is called after a mm_struct has been removed 1125 * from the current process. 1126 * 1127 * This difference is important for error handling, when we 1128 * only half set up a mm_struct for a new process and need to restore 1129 * the old one. Because we mmput the new mm_struct before 1130 * restoring the old one. . . 1131 * Eric Biederman 10 January 1998 1132 */ 1133 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1134 { 1135 /* Get rid of any futexes when releasing the mm */ 1136 #ifdef CONFIG_FUTEX 1137 if (unlikely(tsk->robust_list)) { 1138 exit_robust_list(tsk); 1139 tsk->robust_list = NULL; 1140 } 1141 #ifdef CONFIG_COMPAT 1142 if (unlikely(tsk->compat_robust_list)) { 1143 compat_exit_robust_list(tsk); 1144 tsk->compat_robust_list = NULL; 1145 } 1146 #endif 1147 if (unlikely(!list_empty(&tsk->pi_state_list))) 1148 exit_pi_state_list(tsk); 1149 #endif 1150 1151 uprobe_free_utask(tsk); 1152 1153 /* Get rid of any cached register state */ 1154 deactivate_mm(tsk, mm); 1155 1156 /* 1157 * Signal userspace if we're not exiting with a core dump 1158 * because we want to leave the value intact for debugging 1159 * purposes. 1160 */ 1161 if (tsk->clear_child_tid) { 1162 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1163 atomic_read(&mm->mm_users) > 1) { 1164 /* 1165 * We don't check the error code - if userspace has 1166 * not set up a proper pointer then tough luck. 1167 */ 1168 put_user(0, tsk->clear_child_tid); 1169 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1170 1, NULL, NULL, 0); 1171 } 1172 tsk->clear_child_tid = NULL; 1173 } 1174 1175 /* 1176 * All done, finally we can wake up parent and return this mm to him. 1177 * Also kthread_stop() uses this completion for synchronization. 1178 */ 1179 if (tsk->vfork_done) 1180 complete_vfork_done(tsk); 1181 } 1182 1183 /* 1184 * Allocate a new mm structure and copy contents from the 1185 * mm structure of the passed in task structure. 1186 */ 1187 static struct mm_struct *dup_mm(struct task_struct *tsk) 1188 { 1189 struct mm_struct *mm, *oldmm = current->mm; 1190 int err; 1191 1192 mm = allocate_mm(); 1193 if (!mm) 1194 goto fail_nomem; 1195 1196 memcpy(mm, oldmm, sizeof(*mm)); 1197 1198 if (!mm_init(mm, tsk, mm->user_ns)) 1199 goto fail_nomem; 1200 1201 err = dup_mmap(mm, oldmm); 1202 if (err) 1203 goto free_pt; 1204 1205 mm->hiwater_rss = get_mm_rss(mm); 1206 mm->hiwater_vm = mm->total_vm; 1207 1208 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1209 goto free_pt; 1210 1211 return mm; 1212 1213 free_pt: 1214 /* don't put binfmt in mmput, we haven't got module yet */ 1215 mm->binfmt = NULL; 1216 mmput(mm); 1217 1218 fail_nomem: 1219 return NULL; 1220 } 1221 1222 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1223 { 1224 struct mm_struct *mm, *oldmm; 1225 int retval; 1226 1227 tsk->min_flt = tsk->maj_flt = 0; 1228 tsk->nvcsw = tsk->nivcsw = 0; 1229 #ifdef CONFIG_DETECT_HUNG_TASK 1230 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1231 #endif 1232 1233 tsk->mm = NULL; 1234 tsk->active_mm = NULL; 1235 1236 /* 1237 * Are we cloning a kernel thread? 1238 * 1239 * We need to steal a active VM for that.. 1240 */ 1241 oldmm = current->mm; 1242 if (!oldmm) 1243 return 0; 1244 1245 /* initialize the new vmacache entries */ 1246 vmacache_flush(tsk); 1247 1248 if (clone_flags & CLONE_VM) { 1249 mmget(oldmm); 1250 mm = oldmm; 1251 goto good_mm; 1252 } 1253 1254 retval = -ENOMEM; 1255 mm = dup_mm(tsk); 1256 if (!mm) 1257 goto fail_nomem; 1258 1259 good_mm: 1260 tsk->mm = mm; 1261 tsk->active_mm = mm; 1262 return 0; 1263 1264 fail_nomem: 1265 return retval; 1266 } 1267 1268 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1269 { 1270 struct fs_struct *fs = current->fs; 1271 if (clone_flags & CLONE_FS) { 1272 /* tsk->fs is already what we want */ 1273 spin_lock(&fs->lock); 1274 if (fs->in_exec) { 1275 spin_unlock(&fs->lock); 1276 return -EAGAIN; 1277 } 1278 fs->users++; 1279 spin_unlock(&fs->lock); 1280 return 0; 1281 } 1282 tsk->fs = copy_fs_struct(fs); 1283 if (!tsk->fs) 1284 return -ENOMEM; 1285 return 0; 1286 } 1287 1288 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1289 { 1290 struct files_struct *oldf, *newf; 1291 int error = 0; 1292 1293 /* 1294 * A background process may not have any files ... 1295 */ 1296 oldf = current->files; 1297 if (!oldf) 1298 goto out; 1299 1300 if (clone_flags & CLONE_FILES) { 1301 atomic_inc(&oldf->count); 1302 goto out; 1303 } 1304 1305 newf = dup_fd(oldf, &error); 1306 if (!newf) 1307 goto out; 1308 1309 tsk->files = newf; 1310 error = 0; 1311 out: 1312 return error; 1313 } 1314 1315 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1316 { 1317 #ifdef CONFIG_BLOCK 1318 struct io_context *ioc = current->io_context; 1319 struct io_context *new_ioc; 1320 1321 if (!ioc) 1322 return 0; 1323 /* 1324 * Share io context with parent, if CLONE_IO is set 1325 */ 1326 if (clone_flags & CLONE_IO) { 1327 ioc_task_link(ioc); 1328 tsk->io_context = ioc; 1329 } else if (ioprio_valid(ioc->ioprio)) { 1330 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1331 if (unlikely(!new_ioc)) 1332 return -ENOMEM; 1333 1334 new_ioc->ioprio = ioc->ioprio; 1335 put_io_context(new_ioc); 1336 } 1337 #endif 1338 return 0; 1339 } 1340 1341 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1342 { 1343 struct sighand_struct *sig; 1344 1345 if (clone_flags & CLONE_SIGHAND) { 1346 atomic_inc(¤t->sighand->count); 1347 return 0; 1348 } 1349 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1350 rcu_assign_pointer(tsk->sighand, sig); 1351 if (!sig) 1352 return -ENOMEM; 1353 1354 atomic_set(&sig->count, 1); 1355 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1356 return 0; 1357 } 1358 1359 void __cleanup_sighand(struct sighand_struct *sighand) 1360 { 1361 if (atomic_dec_and_test(&sighand->count)) { 1362 signalfd_cleanup(sighand); 1363 /* 1364 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1365 * without an RCU grace period, see __lock_task_sighand(). 1366 */ 1367 kmem_cache_free(sighand_cachep, sighand); 1368 } 1369 } 1370 1371 #ifdef CONFIG_POSIX_TIMERS 1372 /* 1373 * Initialize POSIX timer handling for a thread group. 1374 */ 1375 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1376 { 1377 unsigned long cpu_limit; 1378 1379 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1380 if (cpu_limit != RLIM_INFINITY) { 1381 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1382 sig->cputimer.running = true; 1383 } 1384 1385 /* The timer lists. */ 1386 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1387 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1388 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1389 } 1390 #else 1391 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1392 #endif 1393 1394 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1395 { 1396 struct signal_struct *sig; 1397 1398 if (clone_flags & CLONE_THREAD) 1399 return 0; 1400 1401 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1402 tsk->signal = sig; 1403 if (!sig) 1404 return -ENOMEM; 1405 1406 sig->nr_threads = 1; 1407 atomic_set(&sig->live, 1); 1408 atomic_set(&sig->sigcnt, 1); 1409 1410 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1411 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1412 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1413 1414 init_waitqueue_head(&sig->wait_chldexit); 1415 sig->curr_target = tsk; 1416 init_sigpending(&sig->shared_pending); 1417 seqlock_init(&sig->stats_lock); 1418 prev_cputime_init(&sig->prev_cputime); 1419 1420 #ifdef CONFIG_POSIX_TIMERS 1421 INIT_LIST_HEAD(&sig->posix_timers); 1422 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1423 sig->real_timer.function = it_real_fn; 1424 #endif 1425 1426 task_lock(current->group_leader); 1427 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1428 task_unlock(current->group_leader); 1429 1430 posix_cpu_timers_init_group(sig); 1431 1432 tty_audit_fork(sig); 1433 sched_autogroup_fork(sig); 1434 1435 sig->oom_score_adj = current->signal->oom_score_adj; 1436 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1437 1438 mutex_init(&sig->cred_guard_mutex); 1439 1440 return 0; 1441 } 1442 1443 static void copy_seccomp(struct task_struct *p) 1444 { 1445 #ifdef CONFIG_SECCOMP 1446 /* 1447 * Must be called with sighand->lock held, which is common to 1448 * all threads in the group. Holding cred_guard_mutex is not 1449 * needed because this new task is not yet running and cannot 1450 * be racing exec. 1451 */ 1452 assert_spin_locked(¤t->sighand->siglock); 1453 1454 /* Ref-count the new filter user, and assign it. */ 1455 get_seccomp_filter(current); 1456 p->seccomp = current->seccomp; 1457 1458 /* 1459 * Explicitly enable no_new_privs here in case it got set 1460 * between the task_struct being duplicated and holding the 1461 * sighand lock. The seccomp state and nnp must be in sync. 1462 */ 1463 if (task_no_new_privs(current)) 1464 task_set_no_new_privs(p); 1465 1466 /* 1467 * If the parent gained a seccomp mode after copying thread 1468 * flags and between before we held the sighand lock, we have 1469 * to manually enable the seccomp thread flag here. 1470 */ 1471 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1472 set_tsk_thread_flag(p, TIF_SECCOMP); 1473 #endif 1474 } 1475 1476 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1477 { 1478 current->clear_child_tid = tidptr; 1479 1480 return task_pid_vnr(current); 1481 } 1482 1483 static void rt_mutex_init_task(struct task_struct *p) 1484 { 1485 raw_spin_lock_init(&p->pi_lock); 1486 #ifdef CONFIG_RT_MUTEXES 1487 p->pi_waiters = RB_ROOT_CACHED; 1488 p->pi_top_task = NULL; 1489 p->pi_blocked_on = NULL; 1490 #endif 1491 } 1492 1493 #ifdef CONFIG_POSIX_TIMERS 1494 /* 1495 * Initialize POSIX timer handling for a single task. 1496 */ 1497 static void posix_cpu_timers_init(struct task_struct *tsk) 1498 { 1499 tsk->cputime_expires.prof_exp = 0; 1500 tsk->cputime_expires.virt_exp = 0; 1501 tsk->cputime_expires.sched_exp = 0; 1502 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1503 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1504 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1505 } 1506 #else 1507 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1508 #endif 1509 1510 static inline void 1511 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1512 { 1513 task->pids[type].pid = pid; 1514 } 1515 1516 static inline void rcu_copy_process(struct task_struct *p) 1517 { 1518 #ifdef CONFIG_PREEMPT_RCU 1519 p->rcu_read_lock_nesting = 0; 1520 p->rcu_read_unlock_special.s = 0; 1521 p->rcu_blocked_node = NULL; 1522 INIT_LIST_HEAD(&p->rcu_node_entry); 1523 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1524 #ifdef CONFIG_TASKS_RCU 1525 p->rcu_tasks_holdout = false; 1526 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1527 p->rcu_tasks_idle_cpu = -1; 1528 #endif /* #ifdef CONFIG_TASKS_RCU */ 1529 } 1530 1531 /* 1532 * This creates a new process as a copy of the old one, 1533 * but does not actually start it yet. 1534 * 1535 * It copies the registers, and all the appropriate 1536 * parts of the process environment (as per the clone 1537 * flags). The actual kick-off is left to the caller. 1538 */ 1539 static __latent_entropy struct task_struct *copy_process( 1540 unsigned long clone_flags, 1541 unsigned long stack_start, 1542 unsigned long stack_size, 1543 int __user *child_tidptr, 1544 struct pid *pid, 1545 int trace, 1546 unsigned long tls, 1547 int node) 1548 { 1549 int retval; 1550 struct task_struct *p; 1551 1552 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1553 return ERR_PTR(-EINVAL); 1554 1555 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1556 return ERR_PTR(-EINVAL); 1557 1558 /* 1559 * Thread groups must share signals as well, and detached threads 1560 * can only be started up within the thread group. 1561 */ 1562 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1563 return ERR_PTR(-EINVAL); 1564 1565 /* 1566 * Shared signal handlers imply shared VM. By way of the above, 1567 * thread groups also imply shared VM. Blocking this case allows 1568 * for various simplifications in other code. 1569 */ 1570 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1571 return ERR_PTR(-EINVAL); 1572 1573 /* 1574 * Siblings of global init remain as zombies on exit since they are 1575 * not reaped by their parent (swapper). To solve this and to avoid 1576 * multi-rooted process trees, prevent global and container-inits 1577 * from creating siblings. 1578 */ 1579 if ((clone_flags & CLONE_PARENT) && 1580 current->signal->flags & SIGNAL_UNKILLABLE) 1581 return ERR_PTR(-EINVAL); 1582 1583 /* 1584 * If the new process will be in a different pid or user namespace 1585 * do not allow it to share a thread group with the forking task. 1586 */ 1587 if (clone_flags & CLONE_THREAD) { 1588 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1589 (task_active_pid_ns(current) != 1590 current->nsproxy->pid_ns_for_children)) 1591 return ERR_PTR(-EINVAL); 1592 } 1593 1594 retval = -ENOMEM; 1595 p = dup_task_struct(current, node); 1596 if (!p) 1597 goto fork_out; 1598 1599 /* 1600 * This _must_ happen before we call free_task(), i.e. before we jump 1601 * to any of the bad_fork_* labels. This is to avoid freeing 1602 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1603 * kernel threads (PF_KTHREAD). 1604 */ 1605 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1606 /* 1607 * Clear TID on mm_release()? 1608 */ 1609 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1610 1611 ftrace_graph_init_task(p); 1612 1613 rt_mutex_init_task(p); 1614 1615 #ifdef CONFIG_PROVE_LOCKING 1616 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1617 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1618 #endif 1619 retval = -EAGAIN; 1620 if (atomic_read(&p->real_cred->user->processes) >= 1621 task_rlimit(p, RLIMIT_NPROC)) { 1622 if (p->real_cred->user != INIT_USER && 1623 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1624 goto bad_fork_free; 1625 } 1626 current->flags &= ~PF_NPROC_EXCEEDED; 1627 1628 retval = copy_creds(p, clone_flags); 1629 if (retval < 0) 1630 goto bad_fork_free; 1631 1632 /* 1633 * If multiple threads are within copy_process(), then this check 1634 * triggers too late. This doesn't hurt, the check is only there 1635 * to stop root fork bombs. 1636 */ 1637 retval = -EAGAIN; 1638 if (nr_threads >= max_threads) 1639 goto bad_fork_cleanup_count; 1640 1641 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1642 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1643 p->flags |= PF_FORKNOEXEC; 1644 INIT_LIST_HEAD(&p->children); 1645 INIT_LIST_HEAD(&p->sibling); 1646 rcu_copy_process(p); 1647 p->vfork_done = NULL; 1648 spin_lock_init(&p->alloc_lock); 1649 1650 init_sigpending(&p->pending); 1651 1652 p->utime = p->stime = p->gtime = 0; 1653 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1654 p->utimescaled = p->stimescaled = 0; 1655 #endif 1656 prev_cputime_init(&p->prev_cputime); 1657 1658 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1659 seqcount_init(&p->vtime.seqcount); 1660 p->vtime.starttime = 0; 1661 p->vtime.state = VTIME_INACTIVE; 1662 #endif 1663 1664 #if defined(SPLIT_RSS_COUNTING) 1665 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1666 #endif 1667 1668 p->default_timer_slack_ns = current->timer_slack_ns; 1669 1670 task_io_accounting_init(&p->ioac); 1671 acct_clear_integrals(p); 1672 1673 posix_cpu_timers_init(p); 1674 1675 p->start_time = ktime_get_ns(); 1676 p->real_start_time = ktime_get_boot_ns(); 1677 p->io_context = NULL; 1678 p->audit_context = NULL; 1679 cgroup_fork(p); 1680 #ifdef CONFIG_NUMA 1681 p->mempolicy = mpol_dup(p->mempolicy); 1682 if (IS_ERR(p->mempolicy)) { 1683 retval = PTR_ERR(p->mempolicy); 1684 p->mempolicy = NULL; 1685 goto bad_fork_cleanup_threadgroup_lock; 1686 } 1687 #endif 1688 #ifdef CONFIG_CPUSETS 1689 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1690 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1691 seqcount_init(&p->mems_allowed_seq); 1692 #endif 1693 #ifdef CONFIG_TRACE_IRQFLAGS 1694 p->irq_events = 0; 1695 p->hardirqs_enabled = 0; 1696 p->hardirq_enable_ip = 0; 1697 p->hardirq_enable_event = 0; 1698 p->hardirq_disable_ip = _THIS_IP_; 1699 p->hardirq_disable_event = 0; 1700 p->softirqs_enabled = 1; 1701 p->softirq_enable_ip = _THIS_IP_; 1702 p->softirq_enable_event = 0; 1703 p->softirq_disable_ip = 0; 1704 p->softirq_disable_event = 0; 1705 p->hardirq_context = 0; 1706 p->softirq_context = 0; 1707 #endif 1708 1709 p->pagefault_disabled = 0; 1710 1711 #ifdef CONFIG_LOCKDEP 1712 p->lockdep_depth = 0; /* no locks held yet */ 1713 p->curr_chain_key = 0; 1714 p->lockdep_recursion = 0; 1715 lockdep_init_task(p); 1716 #endif 1717 1718 #ifdef CONFIG_DEBUG_MUTEXES 1719 p->blocked_on = NULL; /* not blocked yet */ 1720 #endif 1721 #ifdef CONFIG_BCACHE 1722 p->sequential_io = 0; 1723 p->sequential_io_avg = 0; 1724 #endif 1725 1726 /* Perform scheduler related setup. Assign this task to a CPU. */ 1727 retval = sched_fork(clone_flags, p); 1728 if (retval) 1729 goto bad_fork_cleanup_policy; 1730 1731 retval = perf_event_init_task(p); 1732 if (retval) 1733 goto bad_fork_cleanup_policy; 1734 retval = audit_alloc(p); 1735 if (retval) 1736 goto bad_fork_cleanup_perf; 1737 /* copy all the process information */ 1738 shm_init_task(p); 1739 retval = security_task_alloc(p, clone_flags); 1740 if (retval) 1741 goto bad_fork_cleanup_audit; 1742 retval = copy_semundo(clone_flags, p); 1743 if (retval) 1744 goto bad_fork_cleanup_security; 1745 retval = copy_files(clone_flags, p); 1746 if (retval) 1747 goto bad_fork_cleanup_semundo; 1748 retval = copy_fs(clone_flags, p); 1749 if (retval) 1750 goto bad_fork_cleanup_files; 1751 retval = copy_sighand(clone_flags, p); 1752 if (retval) 1753 goto bad_fork_cleanup_fs; 1754 retval = copy_signal(clone_flags, p); 1755 if (retval) 1756 goto bad_fork_cleanup_sighand; 1757 retval = copy_mm(clone_flags, p); 1758 if (retval) 1759 goto bad_fork_cleanup_signal; 1760 retval = copy_namespaces(clone_flags, p); 1761 if (retval) 1762 goto bad_fork_cleanup_mm; 1763 retval = copy_io(clone_flags, p); 1764 if (retval) 1765 goto bad_fork_cleanup_namespaces; 1766 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1767 if (retval) 1768 goto bad_fork_cleanup_io; 1769 1770 if (pid != &init_struct_pid) { 1771 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1772 if (IS_ERR(pid)) { 1773 retval = PTR_ERR(pid); 1774 goto bad_fork_cleanup_thread; 1775 } 1776 } 1777 1778 #ifdef CONFIG_BLOCK 1779 p->plug = NULL; 1780 #endif 1781 #ifdef CONFIG_FUTEX 1782 p->robust_list = NULL; 1783 #ifdef CONFIG_COMPAT 1784 p->compat_robust_list = NULL; 1785 #endif 1786 INIT_LIST_HEAD(&p->pi_state_list); 1787 p->pi_state_cache = NULL; 1788 #endif 1789 /* 1790 * sigaltstack should be cleared when sharing the same VM 1791 */ 1792 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1793 sas_ss_reset(p); 1794 1795 /* 1796 * Syscall tracing and stepping should be turned off in the 1797 * child regardless of CLONE_PTRACE. 1798 */ 1799 user_disable_single_step(p); 1800 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1801 #ifdef TIF_SYSCALL_EMU 1802 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1803 #endif 1804 clear_all_latency_tracing(p); 1805 1806 /* ok, now we should be set up.. */ 1807 p->pid = pid_nr(pid); 1808 if (clone_flags & CLONE_THREAD) { 1809 p->exit_signal = -1; 1810 p->group_leader = current->group_leader; 1811 p->tgid = current->tgid; 1812 } else { 1813 if (clone_flags & CLONE_PARENT) 1814 p->exit_signal = current->group_leader->exit_signal; 1815 else 1816 p->exit_signal = (clone_flags & CSIGNAL); 1817 p->group_leader = p; 1818 p->tgid = p->pid; 1819 } 1820 1821 p->nr_dirtied = 0; 1822 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1823 p->dirty_paused_when = 0; 1824 1825 p->pdeath_signal = 0; 1826 INIT_LIST_HEAD(&p->thread_group); 1827 p->task_works = NULL; 1828 1829 cgroup_threadgroup_change_begin(current); 1830 /* 1831 * Ensure that the cgroup subsystem policies allow the new process to be 1832 * forked. It should be noted the the new process's css_set can be changed 1833 * between here and cgroup_post_fork() if an organisation operation is in 1834 * progress. 1835 */ 1836 retval = cgroup_can_fork(p); 1837 if (retval) 1838 goto bad_fork_free_pid; 1839 1840 /* 1841 * Make it visible to the rest of the system, but dont wake it up yet. 1842 * Need tasklist lock for parent etc handling! 1843 */ 1844 write_lock_irq(&tasklist_lock); 1845 1846 /* CLONE_PARENT re-uses the old parent */ 1847 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1848 p->real_parent = current->real_parent; 1849 p->parent_exec_id = current->parent_exec_id; 1850 } else { 1851 p->real_parent = current; 1852 p->parent_exec_id = current->self_exec_id; 1853 } 1854 1855 klp_copy_process(p); 1856 1857 spin_lock(¤t->sighand->siglock); 1858 1859 /* 1860 * Copy seccomp details explicitly here, in case they were changed 1861 * before holding sighand lock. 1862 */ 1863 copy_seccomp(p); 1864 1865 /* 1866 * Process group and session signals need to be delivered to just the 1867 * parent before the fork or both the parent and the child after the 1868 * fork. Restart if a signal comes in before we add the new process to 1869 * it's process group. 1870 * A fatal signal pending means that current will exit, so the new 1871 * thread can't slip out of an OOM kill (or normal SIGKILL). 1872 */ 1873 recalc_sigpending(); 1874 if (signal_pending(current)) { 1875 retval = -ERESTARTNOINTR; 1876 goto bad_fork_cancel_cgroup; 1877 } 1878 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) { 1879 retval = -ENOMEM; 1880 goto bad_fork_cancel_cgroup; 1881 } 1882 1883 if (likely(p->pid)) { 1884 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1885 1886 init_task_pid(p, PIDTYPE_PID, pid); 1887 if (thread_group_leader(p)) { 1888 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1889 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1890 1891 if (is_child_reaper(pid)) { 1892 ns_of_pid(pid)->child_reaper = p; 1893 p->signal->flags |= SIGNAL_UNKILLABLE; 1894 } 1895 1896 p->signal->leader_pid = pid; 1897 p->signal->tty = tty_kref_get(current->signal->tty); 1898 /* 1899 * Inherit has_child_subreaper flag under the same 1900 * tasklist_lock with adding child to the process tree 1901 * for propagate_has_child_subreaper optimization. 1902 */ 1903 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1904 p->real_parent->signal->is_child_subreaper; 1905 list_add_tail(&p->sibling, &p->real_parent->children); 1906 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1907 attach_pid(p, PIDTYPE_PGID); 1908 attach_pid(p, PIDTYPE_SID); 1909 __this_cpu_inc(process_counts); 1910 } else { 1911 current->signal->nr_threads++; 1912 atomic_inc(¤t->signal->live); 1913 atomic_inc(¤t->signal->sigcnt); 1914 list_add_tail_rcu(&p->thread_group, 1915 &p->group_leader->thread_group); 1916 list_add_tail_rcu(&p->thread_node, 1917 &p->signal->thread_head); 1918 } 1919 attach_pid(p, PIDTYPE_PID); 1920 nr_threads++; 1921 } 1922 1923 total_forks++; 1924 spin_unlock(¤t->sighand->siglock); 1925 syscall_tracepoint_update(p); 1926 write_unlock_irq(&tasklist_lock); 1927 1928 proc_fork_connector(p); 1929 cgroup_post_fork(p); 1930 cgroup_threadgroup_change_end(current); 1931 perf_event_fork(p); 1932 1933 trace_task_newtask(p, clone_flags); 1934 uprobe_copy_process(p, clone_flags); 1935 1936 return p; 1937 1938 bad_fork_cancel_cgroup: 1939 spin_unlock(¤t->sighand->siglock); 1940 write_unlock_irq(&tasklist_lock); 1941 cgroup_cancel_fork(p); 1942 bad_fork_free_pid: 1943 cgroup_threadgroup_change_end(current); 1944 if (pid != &init_struct_pid) 1945 free_pid(pid); 1946 bad_fork_cleanup_thread: 1947 exit_thread(p); 1948 bad_fork_cleanup_io: 1949 if (p->io_context) 1950 exit_io_context(p); 1951 bad_fork_cleanup_namespaces: 1952 exit_task_namespaces(p); 1953 bad_fork_cleanup_mm: 1954 if (p->mm) 1955 mmput(p->mm); 1956 bad_fork_cleanup_signal: 1957 if (!(clone_flags & CLONE_THREAD)) 1958 free_signal_struct(p->signal); 1959 bad_fork_cleanup_sighand: 1960 __cleanup_sighand(p->sighand); 1961 bad_fork_cleanup_fs: 1962 exit_fs(p); /* blocking */ 1963 bad_fork_cleanup_files: 1964 exit_files(p); /* blocking */ 1965 bad_fork_cleanup_semundo: 1966 exit_sem(p); 1967 bad_fork_cleanup_security: 1968 security_task_free(p); 1969 bad_fork_cleanup_audit: 1970 audit_free(p); 1971 bad_fork_cleanup_perf: 1972 perf_event_free_task(p); 1973 bad_fork_cleanup_policy: 1974 lockdep_free_task(p); 1975 #ifdef CONFIG_NUMA 1976 mpol_put(p->mempolicy); 1977 bad_fork_cleanup_threadgroup_lock: 1978 #endif 1979 delayacct_tsk_free(p); 1980 bad_fork_cleanup_count: 1981 atomic_dec(&p->cred->user->processes); 1982 exit_creds(p); 1983 bad_fork_free: 1984 p->state = TASK_DEAD; 1985 put_task_stack(p); 1986 free_task(p); 1987 fork_out: 1988 return ERR_PTR(retval); 1989 } 1990 1991 static inline void init_idle_pids(struct pid_link *links) 1992 { 1993 enum pid_type type; 1994 1995 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1996 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1997 links[type].pid = &init_struct_pid; 1998 } 1999 } 2000 2001 struct task_struct *fork_idle(int cpu) 2002 { 2003 struct task_struct *task; 2004 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2005 cpu_to_node(cpu)); 2006 if (!IS_ERR(task)) { 2007 init_idle_pids(task->pids); 2008 init_idle(task, cpu); 2009 } 2010 2011 return task; 2012 } 2013 2014 /* 2015 * Ok, this is the main fork-routine. 2016 * 2017 * It copies the process, and if successful kick-starts 2018 * it and waits for it to finish using the VM if required. 2019 */ 2020 long _do_fork(unsigned long clone_flags, 2021 unsigned long stack_start, 2022 unsigned long stack_size, 2023 int __user *parent_tidptr, 2024 int __user *child_tidptr, 2025 unsigned long tls) 2026 { 2027 struct task_struct *p; 2028 int trace = 0; 2029 long nr; 2030 2031 /* 2032 * Determine whether and which event to report to ptracer. When 2033 * called from kernel_thread or CLONE_UNTRACED is explicitly 2034 * requested, no event is reported; otherwise, report if the event 2035 * for the type of forking is enabled. 2036 */ 2037 if (!(clone_flags & CLONE_UNTRACED)) { 2038 if (clone_flags & CLONE_VFORK) 2039 trace = PTRACE_EVENT_VFORK; 2040 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2041 trace = PTRACE_EVENT_CLONE; 2042 else 2043 trace = PTRACE_EVENT_FORK; 2044 2045 if (likely(!ptrace_event_enabled(current, trace))) 2046 trace = 0; 2047 } 2048 2049 p = copy_process(clone_flags, stack_start, stack_size, 2050 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2051 add_latent_entropy(); 2052 /* 2053 * Do this prior waking up the new thread - the thread pointer 2054 * might get invalid after that point, if the thread exits quickly. 2055 */ 2056 if (!IS_ERR(p)) { 2057 struct completion vfork; 2058 struct pid *pid; 2059 2060 trace_sched_process_fork(current, p); 2061 2062 pid = get_task_pid(p, PIDTYPE_PID); 2063 nr = pid_vnr(pid); 2064 2065 if (clone_flags & CLONE_PARENT_SETTID) 2066 put_user(nr, parent_tidptr); 2067 2068 if (clone_flags & CLONE_VFORK) { 2069 p->vfork_done = &vfork; 2070 init_completion(&vfork); 2071 get_task_struct(p); 2072 } 2073 2074 wake_up_new_task(p); 2075 2076 /* forking complete and child started to run, tell ptracer */ 2077 if (unlikely(trace)) 2078 ptrace_event_pid(trace, pid); 2079 2080 if (clone_flags & CLONE_VFORK) { 2081 if (!wait_for_vfork_done(p, &vfork)) 2082 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2083 } 2084 2085 put_pid(pid); 2086 } else { 2087 nr = PTR_ERR(p); 2088 } 2089 return nr; 2090 } 2091 2092 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2093 /* For compatibility with architectures that call do_fork directly rather than 2094 * using the syscall entry points below. */ 2095 long do_fork(unsigned long clone_flags, 2096 unsigned long stack_start, 2097 unsigned long stack_size, 2098 int __user *parent_tidptr, 2099 int __user *child_tidptr) 2100 { 2101 return _do_fork(clone_flags, stack_start, stack_size, 2102 parent_tidptr, child_tidptr, 0); 2103 } 2104 #endif 2105 2106 /* 2107 * Create a kernel thread. 2108 */ 2109 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2110 { 2111 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2112 (unsigned long)arg, NULL, NULL, 0); 2113 } 2114 2115 #ifdef __ARCH_WANT_SYS_FORK 2116 SYSCALL_DEFINE0(fork) 2117 { 2118 #ifdef CONFIG_MMU 2119 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2120 #else 2121 /* can not support in nommu mode */ 2122 return -EINVAL; 2123 #endif 2124 } 2125 #endif 2126 2127 #ifdef __ARCH_WANT_SYS_VFORK 2128 SYSCALL_DEFINE0(vfork) 2129 { 2130 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2131 0, NULL, NULL, 0); 2132 } 2133 #endif 2134 2135 #ifdef __ARCH_WANT_SYS_CLONE 2136 #ifdef CONFIG_CLONE_BACKWARDS 2137 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2138 int __user *, parent_tidptr, 2139 unsigned long, tls, 2140 int __user *, child_tidptr) 2141 #elif defined(CONFIG_CLONE_BACKWARDS2) 2142 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2143 int __user *, parent_tidptr, 2144 int __user *, child_tidptr, 2145 unsigned long, tls) 2146 #elif defined(CONFIG_CLONE_BACKWARDS3) 2147 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2148 int, stack_size, 2149 int __user *, parent_tidptr, 2150 int __user *, child_tidptr, 2151 unsigned long, tls) 2152 #else 2153 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2154 int __user *, parent_tidptr, 2155 int __user *, child_tidptr, 2156 unsigned long, tls) 2157 #endif 2158 { 2159 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2160 } 2161 #endif 2162 2163 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2164 { 2165 struct task_struct *leader, *parent, *child; 2166 int res; 2167 2168 read_lock(&tasklist_lock); 2169 leader = top = top->group_leader; 2170 down: 2171 for_each_thread(leader, parent) { 2172 list_for_each_entry(child, &parent->children, sibling) { 2173 res = visitor(child, data); 2174 if (res) { 2175 if (res < 0) 2176 goto out; 2177 leader = child; 2178 goto down; 2179 } 2180 up: 2181 ; 2182 } 2183 } 2184 2185 if (leader != top) { 2186 child = leader; 2187 parent = child->real_parent; 2188 leader = parent->group_leader; 2189 goto up; 2190 } 2191 out: 2192 read_unlock(&tasklist_lock); 2193 } 2194 2195 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2196 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2197 #endif 2198 2199 static void sighand_ctor(void *data) 2200 { 2201 struct sighand_struct *sighand = data; 2202 2203 spin_lock_init(&sighand->siglock); 2204 init_waitqueue_head(&sighand->signalfd_wqh); 2205 } 2206 2207 void __init proc_caches_init(void) 2208 { 2209 sighand_cachep = kmem_cache_create("sighand_cache", 2210 sizeof(struct sighand_struct), 0, 2211 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2212 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2213 signal_cachep = kmem_cache_create("signal_cache", 2214 sizeof(struct signal_struct), 0, 2215 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2216 NULL); 2217 files_cachep = kmem_cache_create("files_cache", 2218 sizeof(struct files_struct), 0, 2219 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2220 NULL); 2221 fs_cachep = kmem_cache_create("fs_cache", 2222 sizeof(struct fs_struct), 0, 2223 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2224 NULL); 2225 /* 2226 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2227 * whole struct cpumask for the OFFSTACK case. We could change 2228 * this to *only* allocate as much of it as required by the 2229 * maximum number of CPU's we can ever have. The cpumask_allocation 2230 * is at the end of the structure, exactly for that reason. 2231 */ 2232 mm_cachep = kmem_cache_create("mm_struct", 2233 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2234 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2235 NULL); 2236 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2237 mmap_init(); 2238 nsproxy_cache_init(); 2239 } 2240 2241 /* 2242 * Check constraints on flags passed to the unshare system call. 2243 */ 2244 static int check_unshare_flags(unsigned long unshare_flags) 2245 { 2246 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2247 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2248 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2249 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2250 return -EINVAL; 2251 /* 2252 * Not implemented, but pretend it works if there is nothing 2253 * to unshare. Note that unsharing the address space or the 2254 * signal handlers also need to unshare the signal queues (aka 2255 * CLONE_THREAD). 2256 */ 2257 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2258 if (!thread_group_empty(current)) 2259 return -EINVAL; 2260 } 2261 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2262 if (atomic_read(¤t->sighand->count) > 1) 2263 return -EINVAL; 2264 } 2265 if (unshare_flags & CLONE_VM) { 2266 if (!current_is_single_threaded()) 2267 return -EINVAL; 2268 } 2269 2270 return 0; 2271 } 2272 2273 /* 2274 * Unshare the filesystem structure if it is being shared 2275 */ 2276 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2277 { 2278 struct fs_struct *fs = current->fs; 2279 2280 if (!(unshare_flags & CLONE_FS) || !fs) 2281 return 0; 2282 2283 /* don't need lock here; in the worst case we'll do useless copy */ 2284 if (fs->users == 1) 2285 return 0; 2286 2287 *new_fsp = copy_fs_struct(fs); 2288 if (!*new_fsp) 2289 return -ENOMEM; 2290 2291 return 0; 2292 } 2293 2294 /* 2295 * Unshare file descriptor table if it is being shared 2296 */ 2297 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2298 { 2299 struct files_struct *fd = current->files; 2300 int error = 0; 2301 2302 if ((unshare_flags & CLONE_FILES) && 2303 (fd && atomic_read(&fd->count) > 1)) { 2304 *new_fdp = dup_fd(fd, &error); 2305 if (!*new_fdp) 2306 return error; 2307 } 2308 2309 return 0; 2310 } 2311 2312 /* 2313 * unshare allows a process to 'unshare' part of the process 2314 * context which was originally shared using clone. copy_* 2315 * functions used by do_fork() cannot be used here directly 2316 * because they modify an inactive task_struct that is being 2317 * constructed. Here we are modifying the current, active, 2318 * task_struct. 2319 */ 2320 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2321 { 2322 struct fs_struct *fs, *new_fs = NULL; 2323 struct files_struct *fd, *new_fd = NULL; 2324 struct cred *new_cred = NULL; 2325 struct nsproxy *new_nsproxy = NULL; 2326 int do_sysvsem = 0; 2327 int err; 2328 2329 /* 2330 * If unsharing a user namespace must also unshare the thread group 2331 * and unshare the filesystem root and working directories. 2332 */ 2333 if (unshare_flags & CLONE_NEWUSER) 2334 unshare_flags |= CLONE_THREAD | CLONE_FS; 2335 /* 2336 * If unsharing vm, must also unshare signal handlers. 2337 */ 2338 if (unshare_flags & CLONE_VM) 2339 unshare_flags |= CLONE_SIGHAND; 2340 /* 2341 * If unsharing a signal handlers, must also unshare the signal queues. 2342 */ 2343 if (unshare_flags & CLONE_SIGHAND) 2344 unshare_flags |= CLONE_THREAD; 2345 /* 2346 * If unsharing namespace, must also unshare filesystem information. 2347 */ 2348 if (unshare_flags & CLONE_NEWNS) 2349 unshare_flags |= CLONE_FS; 2350 2351 err = check_unshare_flags(unshare_flags); 2352 if (err) 2353 goto bad_unshare_out; 2354 /* 2355 * CLONE_NEWIPC must also detach from the undolist: after switching 2356 * to a new ipc namespace, the semaphore arrays from the old 2357 * namespace are unreachable. 2358 */ 2359 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2360 do_sysvsem = 1; 2361 err = unshare_fs(unshare_flags, &new_fs); 2362 if (err) 2363 goto bad_unshare_out; 2364 err = unshare_fd(unshare_flags, &new_fd); 2365 if (err) 2366 goto bad_unshare_cleanup_fs; 2367 err = unshare_userns(unshare_flags, &new_cred); 2368 if (err) 2369 goto bad_unshare_cleanup_fd; 2370 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2371 new_cred, new_fs); 2372 if (err) 2373 goto bad_unshare_cleanup_cred; 2374 2375 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2376 if (do_sysvsem) { 2377 /* 2378 * CLONE_SYSVSEM is equivalent to sys_exit(). 2379 */ 2380 exit_sem(current); 2381 } 2382 if (unshare_flags & CLONE_NEWIPC) { 2383 /* Orphan segments in old ns (see sem above). */ 2384 exit_shm(current); 2385 shm_init_task(current); 2386 } 2387 2388 if (new_nsproxy) 2389 switch_task_namespaces(current, new_nsproxy); 2390 2391 task_lock(current); 2392 2393 if (new_fs) { 2394 fs = current->fs; 2395 spin_lock(&fs->lock); 2396 current->fs = new_fs; 2397 if (--fs->users) 2398 new_fs = NULL; 2399 else 2400 new_fs = fs; 2401 spin_unlock(&fs->lock); 2402 } 2403 2404 if (new_fd) { 2405 fd = current->files; 2406 current->files = new_fd; 2407 new_fd = fd; 2408 } 2409 2410 task_unlock(current); 2411 2412 if (new_cred) { 2413 /* Install the new user namespace */ 2414 commit_creds(new_cred); 2415 new_cred = NULL; 2416 } 2417 } 2418 2419 perf_event_namespaces(current); 2420 2421 bad_unshare_cleanup_cred: 2422 if (new_cred) 2423 put_cred(new_cred); 2424 bad_unshare_cleanup_fd: 2425 if (new_fd) 2426 put_files_struct(new_fd); 2427 2428 bad_unshare_cleanup_fs: 2429 if (new_fs) 2430 free_fs_struct(new_fs); 2431 2432 bad_unshare_out: 2433 return err; 2434 } 2435 2436 /* 2437 * Helper to unshare the files of the current task. 2438 * We don't want to expose copy_files internals to 2439 * the exec layer of the kernel. 2440 */ 2441 2442 int unshare_files(struct files_struct **displaced) 2443 { 2444 struct task_struct *task = current; 2445 struct files_struct *copy = NULL; 2446 int error; 2447 2448 error = unshare_fd(CLONE_FILES, ©); 2449 if (error || !copy) { 2450 *displaced = NULL; 2451 return error; 2452 } 2453 *displaced = task->files; 2454 task_lock(task); 2455 task->files = copy; 2456 task_unlock(task); 2457 return 0; 2458 } 2459 2460 int sysctl_max_threads(struct ctl_table *table, int write, 2461 void __user *buffer, size_t *lenp, loff_t *ppos) 2462 { 2463 struct ctl_table t; 2464 int ret; 2465 int threads = max_threads; 2466 int min = MIN_THREADS; 2467 int max = MAX_THREADS; 2468 2469 t = *table; 2470 t.data = &threads; 2471 t.extra1 = &min; 2472 t.extra2 = &max; 2473 2474 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2475 if (ret || !write) 2476 return ret; 2477 2478 set_max_threads(threads); 2479 2480 return 0; 2481 } 2482