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