1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/sched/autogroup.h> 16 #include <linux/sched/mm.h> 17 #include <linux/sched/coredump.h> 18 #include <linux/sched/user.h> 19 #include <linux/sched/numa_balancing.h> 20 #include <linux/sched/stat.h> 21 #include <linux/sched/task.h> 22 #include <linux/sched/task_stack.h> 23 #include <linux/sched/cputime.h> 24 #include <linux/rtmutex.h> 25 #include <linux/init.h> 26 #include <linux/unistd.h> 27 #include <linux/module.h> 28 #include <linux/vmalloc.h> 29 #include <linux/completion.h> 30 #include <linux/personality.h> 31 #include <linux/mempolicy.h> 32 #include <linux/sem.h> 33 #include <linux/file.h> 34 #include <linux/fdtable.h> 35 #include <linux/iocontext.h> 36 #include <linux/key.h> 37 #include <linux/binfmts.h> 38 #include <linux/mman.h> 39 #include <linux/mmu_notifier.h> 40 #include <linux/fs.h> 41 #include <linux/mm.h> 42 #include <linux/vmacache.h> 43 #include <linux/nsproxy.h> 44 #include <linux/capability.h> 45 #include <linux/cpu.h> 46 #include <linux/cgroup.h> 47 #include <linux/security.h> 48 #include <linux/hugetlb.h> 49 #include <linux/seccomp.h> 50 #include <linux/swap.h> 51 #include <linux/syscalls.h> 52 #include <linux/jiffies.h> 53 #include <linux/futex.h> 54 #include <linux/compat.h> 55 #include <linux/kthread.h> 56 #include <linux/task_io_accounting_ops.h> 57 #include <linux/rcupdate.h> 58 #include <linux/ptrace.h> 59 #include <linux/mount.h> 60 #include <linux/audit.h> 61 #include <linux/memcontrol.h> 62 #include <linux/ftrace.h> 63 #include <linux/proc_fs.h> 64 #include <linux/profile.h> 65 #include <linux/rmap.h> 66 #include <linux/ksm.h> 67 #include <linux/acct.h> 68 #include <linux/userfaultfd_k.h> 69 #include <linux/tsacct_kern.h> 70 #include <linux/cn_proc.h> 71 #include <linux/freezer.h> 72 #include <linux/delayacct.h> 73 #include <linux/taskstats_kern.h> 74 #include <linux/random.h> 75 #include <linux/tty.h> 76 #include <linux/blkdev.h> 77 #include <linux/fs_struct.h> 78 #include <linux/magic.h> 79 #include <linux/perf_event.h> 80 #include <linux/posix-timers.h> 81 #include <linux/user-return-notifier.h> 82 #include <linux/oom.h> 83 #include <linux/khugepaged.h> 84 #include <linux/signalfd.h> 85 #include <linux/uprobes.h> 86 #include <linux/aio.h> 87 #include <linux/compiler.h> 88 #include <linux/sysctl.h> 89 #include <linux/kcov.h> 90 #include <linux/livepatch.h> 91 92 #include <asm/pgtable.h> 93 #include <asm/pgalloc.h> 94 #include <linux/uaccess.h> 95 #include <asm/mmu_context.h> 96 #include <asm/cacheflush.h> 97 #include <asm/tlbflush.h> 98 99 #include <trace/events/sched.h> 100 101 #define CREATE_TRACE_POINTS 102 #include <trace/events/task.h> 103 104 /* 105 * Minimum number of threads to boot the kernel 106 */ 107 #define MIN_THREADS 20 108 109 /* 110 * Maximum number of threads 111 */ 112 #define MAX_THREADS FUTEX_TID_MASK 113 114 /* 115 * Protected counters by write_lock_irq(&tasklist_lock) 116 */ 117 unsigned long total_forks; /* Handle normal Linux uptimes. */ 118 int nr_threads; /* The idle threads do not count.. */ 119 120 int max_threads; /* tunable limit on nr_threads */ 121 122 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 123 124 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 125 126 #ifdef CONFIG_PROVE_RCU 127 int lockdep_tasklist_lock_is_held(void) 128 { 129 return lockdep_is_held(&tasklist_lock); 130 } 131 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 132 #endif /* #ifdef CONFIG_PROVE_RCU */ 133 134 int nr_processes(void) 135 { 136 int cpu; 137 int total = 0; 138 139 for_each_possible_cpu(cpu) 140 total += per_cpu(process_counts, cpu); 141 142 return total; 143 } 144 145 void __weak arch_release_task_struct(struct task_struct *tsk) 146 { 147 } 148 149 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 150 static struct kmem_cache *task_struct_cachep; 151 152 static inline struct task_struct *alloc_task_struct_node(int node) 153 { 154 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 155 } 156 157 static inline void free_task_struct(struct task_struct *tsk) 158 { 159 kmem_cache_free(task_struct_cachep, tsk); 160 } 161 #endif 162 163 void __weak arch_release_thread_stack(unsigned long *stack) 164 { 165 } 166 167 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 168 169 /* 170 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 171 * kmemcache based allocator. 172 */ 173 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 174 175 #ifdef CONFIG_VMAP_STACK 176 /* 177 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 178 * flush. Try to minimize the number of calls by caching stacks. 179 */ 180 #define NR_CACHED_STACKS 2 181 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 182 #endif 183 184 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 185 { 186 #ifdef CONFIG_VMAP_STACK 187 void *stack; 188 int i; 189 190 local_irq_disable(); 191 for (i = 0; i < NR_CACHED_STACKS; i++) { 192 struct vm_struct *s = this_cpu_read(cached_stacks[i]); 193 194 if (!s) 195 continue; 196 this_cpu_write(cached_stacks[i], NULL); 197 198 tsk->stack_vm_area = s; 199 local_irq_enable(); 200 return s->addr; 201 } 202 local_irq_enable(); 203 204 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, 205 VMALLOC_START, VMALLOC_END, 206 THREADINFO_GFP | __GFP_HIGHMEM, 207 PAGE_KERNEL, 208 0, node, __builtin_return_address(0)); 209 210 /* 211 * We can't call find_vm_area() in interrupt context, and 212 * free_thread_stack() can be called in interrupt context, 213 * so cache the vm_struct. 214 */ 215 if (stack) 216 tsk->stack_vm_area = find_vm_area(stack); 217 return stack; 218 #else 219 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 220 THREAD_SIZE_ORDER); 221 222 return page ? page_address(page) : NULL; 223 #endif 224 } 225 226 static inline void free_thread_stack(struct task_struct *tsk) 227 { 228 #ifdef CONFIG_VMAP_STACK 229 if (task_stack_vm_area(tsk)) { 230 unsigned long flags; 231 int i; 232 233 local_irq_save(flags); 234 for (i = 0; i < NR_CACHED_STACKS; i++) { 235 if (this_cpu_read(cached_stacks[i])) 236 continue; 237 238 this_cpu_write(cached_stacks[i], tsk->stack_vm_area); 239 local_irq_restore(flags); 240 return; 241 } 242 local_irq_restore(flags); 243 244 vfree_atomic(tsk->stack); 245 return; 246 } 247 #endif 248 249 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 250 } 251 # else 252 static struct kmem_cache *thread_stack_cache; 253 254 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 255 int node) 256 { 257 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 258 } 259 260 static void free_thread_stack(struct task_struct *tsk) 261 { 262 kmem_cache_free(thread_stack_cache, tsk->stack); 263 } 264 265 void thread_stack_cache_init(void) 266 { 267 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 268 THREAD_SIZE, 0, NULL); 269 BUG_ON(thread_stack_cache == NULL); 270 } 271 # endif 272 #endif 273 274 /* SLAB cache for signal_struct structures (tsk->signal) */ 275 static struct kmem_cache *signal_cachep; 276 277 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 278 struct kmem_cache *sighand_cachep; 279 280 /* SLAB cache for files_struct structures (tsk->files) */ 281 struct kmem_cache *files_cachep; 282 283 /* SLAB cache for fs_struct structures (tsk->fs) */ 284 struct kmem_cache *fs_cachep; 285 286 /* SLAB cache for vm_area_struct structures */ 287 struct kmem_cache *vm_area_cachep; 288 289 /* SLAB cache for mm_struct structures (tsk->mm) */ 290 static struct kmem_cache *mm_cachep; 291 292 static void account_kernel_stack(struct task_struct *tsk, int account) 293 { 294 void *stack = task_stack_page(tsk); 295 struct vm_struct *vm = task_stack_vm_area(tsk); 296 297 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 298 299 if (vm) { 300 int i; 301 302 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 303 304 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 305 mod_zone_page_state(page_zone(vm->pages[i]), 306 NR_KERNEL_STACK_KB, 307 PAGE_SIZE / 1024 * account); 308 } 309 310 /* All stack pages belong to the same memcg. */ 311 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB, 312 account * (THREAD_SIZE / 1024)); 313 } else { 314 /* 315 * All stack pages are in the same zone and belong to the 316 * same memcg. 317 */ 318 struct page *first_page = virt_to_page(stack); 319 320 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 321 THREAD_SIZE / 1024 * account); 322 323 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB, 324 account * (THREAD_SIZE / 1024)); 325 } 326 } 327 328 static void release_task_stack(struct task_struct *tsk) 329 { 330 if (WARN_ON(tsk->state != TASK_DEAD)) 331 return; /* Better to leak the stack than to free prematurely */ 332 333 account_kernel_stack(tsk, -1); 334 arch_release_thread_stack(tsk->stack); 335 free_thread_stack(tsk); 336 tsk->stack = NULL; 337 #ifdef CONFIG_VMAP_STACK 338 tsk->stack_vm_area = NULL; 339 #endif 340 } 341 342 #ifdef CONFIG_THREAD_INFO_IN_TASK 343 void put_task_stack(struct task_struct *tsk) 344 { 345 if (atomic_dec_and_test(&tsk->stack_refcount)) 346 release_task_stack(tsk); 347 } 348 #endif 349 350 void free_task(struct task_struct *tsk) 351 { 352 #ifndef CONFIG_THREAD_INFO_IN_TASK 353 /* 354 * The task is finally done with both the stack and thread_info, 355 * so free both. 356 */ 357 release_task_stack(tsk); 358 #else 359 /* 360 * If the task had a separate stack allocation, it should be gone 361 * by now. 362 */ 363 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 364 #endif 365 rt_mutex_debug_task_free(tsk); 366 ftrace_graph_exit_task(tsk); 367 put_seccomp_filter(tsk); 368 arch_release_task_struct(tsk); 369 if (tsk->flags & PF_KTHREAD) 370 free_kthread_struct(tsk); 371 free_task_struct(tsk); 372 } 373 EXPORT_SYMBOL(free_task); 374 375 static inline void free_signal_struct(struct signal_struct *sig) 376 { 377 taskstats_tgid_free(sig); 378 sched_autogroup_exit(sig); 379 /* 380 * __mmdrop is not safe to call from softirq context on x86 due to 381 * pgd_dtor so postpone it to the async context 382 */ 383 if (sig->oom_mm) 384 mmdrop_async(sig->oom_mm); 385 kmem_cache_free(signal_cachep, sig); 386 } 387 388 static inline void put_signal_struct(struct signal_struct *sig) 389 { 390 if (atomic_dec_and_test(&sig->sigcnt)) 391 free_signal_struct(sig); 392 } 393 394 void __put_task_struct(struct task_struct *tsk) 395 { 396 WARN_ON(!tsk->exit_state); 397 WARN_ON(atomic_read(&tsk->usage)); 398 WARN_ON(tsk == current); 399 400 cgroup_free(tsk); 401 task_numa_free(tsk); 402 security_task_free(tsk); 403 exit_creds(tsk); 404 delayacct_tsk_free(tsk); 405 put_signal_struct(tsk->signal); 406 407 if (!profile_handoff_task(tsk)) 408 free_task(tsk); 409 } 410 EXPORT_SYMBOL_GPL(__put_task_struct); 411 412 void __init __weak arch_task_cache_init(void) { } 413 414 /* 415 * set_max_threads 416 */ 417 static void set_max_threads(unsigned int max_threads_suggested) 418 { 419 u64 threads; 420 421 /* 422 * The number of threads shall be limited such that the thread 423 * structures may only consume a small part of the available memory. 424 */ 425 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 426 threads = MAX_THREADS; 427 else 428 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 429 (u64) THREAD_SIZE * 8UL); 430 431 if (threads > max_threads_suggested) 432 threads = max_threads_suggested; 433 434 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 435 } 436 437 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 438 /* Initialized by the architecture: */ 439 int arch_task_struct_size __read_mostly; 440 #endif 441 442 void __init fork_init(void) 443 { 444 int i; 445 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 446 #ifndef ARCH_MIN_TASKALIGN 447 #define ARCH_MIN_TASKALIGN 0 448 #endif 449 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 450 451 /* create a slab on which task_structs can be allocated */ 452 task_struct_cachep = kmem_cache_create("task_struct", 453 arch_task_struct_size, align, 454 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 455 #endif 456 457 /* do the arch specific task caches init */ 458 arch_task_cache_init(); 459 460 set_max_threads(MAX_THREADS); 461 462 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 463 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 464 init_task.signal->rlim[RLIMIT_SIGPENDING] = 465 init_task.signal->rlim[RLIMIT_NPROC]; 466 467 for (i = 0; i < UCOUNT_COUNTS; i++) { 468 init_user_ns.ucount_max[i] = max_threads/2; 469 } 470 } 471 472 int __weak arch_dup_task_struct(struct task_struct *dst, 473 struct task_struct *src) 474 { 475 *dst = *src; 476 return 0; 477 } 478 479 void set_task_stack_end_magic(struct task_struct *tsk) 480 { 481 unsigned long *stackend; 482 483 stackend = end_of_stack(tsk); 484 *stackend = STACK_END_MAGIC; /* for overflow detection */ 485 } 486 487 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 488 { 489 struct task_struct *tsk; 490 unsigned long *stack; 491 struct vm_struct *stack_vm_area; 492 int err; 493 494 if (node == NUMA_NO_NODE) 495 node = tsk_fork_get_node(orig); 496 tsk = alloc_task_struct_node(node); 497 if (!tsk) 498 return NULL; 499 500 stack = alloc_thread_stack_node(tsk, node); 501 if (!stack) 502 goto free_tsk; 503 504 stack_vm_area = task_stack_vm_area(tsk); 505 506 err = arch_dup_task_struct(tsk, orig); 507 508 /* 509 * arch_dup_task_struct() clobbers the stack-related fields. Make 510 * sure they're properly initialized before using any stack-related 511 * functions again. 512 */ 513 tsk->stack = stack; 514 #ifdef CONFIG_VMAP_STACK 515 tsk->stack_vm_area = stack_vm_area; 516 #endif 517 #ifdef CONFIG_THREAD_INFO_IN_TASK 518 atomic_set(&tsk->stack_refcount, 1); 519 #endif 520 521 if (err) 522 goto free_stack; 523 524 #ifdef CONFIG_SECCOMP 525 /* 526 * We must handle setting up seccomp filters once we're under 527 * the sighand lock in case orig has changed between now and 528 * then. Until then, filter must be NULL to avoid messing up 529 * the usage counts on the error path calling free_task. 530 */ 531 tsk->seccomp.filter = NULL; 532 #endif 533 534 setup_thread_stack(tsk, orig); 535 clear_user_return_notifier(tsk); 536 clear_tsk_need_resched(tsk); 537 set_task_stack_end_magic(tsk); 538 539 #ifdef CONFIG_CC_STACKPROTECTOR 540 tsk->stack_canary = get_random_int(); 541 #endif 542 543 /* 544 * One for us, one for whoever does the "release_task()" (usually 545 * parent) 546 */ 547 atomic_set(&tsk->usage, 2); 548 #ifdef CONFIG_BLK_DEV_IO_TRACE 549 tsk->btrace_seq = 0; 550 #endif 551 tsk->splice_pipe = NULL; 552 tsk->task_frag.page = NULL; 553 tsk->wake_q.next = NULL; 554 555 account_kernel_stack(tsk, 1); 556 557 kcov_task_init(tsk); 558 559 return tsk; 560 561 free_stack: 562 free_thread_stack(tsk); 563 free_tsk: 564 free_task_struct(tsk); 565 return NULL; 566 } 567 568 #ifdef CONFIG_MMU 569 static __latent_entropy int dup_mmap(struct mm_struct *mm, 570 struct mm_struct *oldmm) 571 { 572 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 573 struct rb_node **rb_link, *rb_parent; 574 int retval; 575 unsigned long charge; 576 LIST_HEAD(uf); 577 578 uprobe_start_dup_mmap(); 579 if (down_write_killable(&oldmm->mmap_sem)) { 580 retval = -EINTR; 581 goto fail_uprobe_end; 582 } 583 flush_cache_dup_mm(oldmm); 584 uprobe_dup_mmap(oldmm, mm); 585 /* 586 * Not linked in yet - no deadlock potential: 587 */ 588 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 589 590 /* No ordering required: file already has been exposed. */ 591 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 592 593 mm->total_vm = oldmm->total_vm; 594 mm->data_vm = oldmm->data_vm; 595 mm->exec_vm = oldmm->exec_vm; 596 mm->stack_vm = oldmm->stack_vm; 597 598 rb_link = &mm->mm_rb.rb_node; 599 rb_parent = NULL; 600 pprev = &mm->mmap; 601 retval = ksm_fork(mm, oldmm); 602 if (retval) 603 goto out; 604 retval = khugepaged_fork(mm, oldmm); 605 if (retval) 606 goto out; 607 608 prev = NULL; 609 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 610 struct file *file; 611 612 if (mpnt->vm_flags & VM_DONTCOPY) { 613 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 614 continue; 615 } 616 charge = 0; 617 if (mpnt->vm_flags & VM_ACCOUNT) { 618 unsigned long len = vma_pages(mpnt); 619 620 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 621 goto fail_nomem; 622 charge = len; 623 } 624 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 625 if (!tmp) 626 goto fail_nomem; 627 *tmp = *mpnt; 628 INIT_LIST_HEAD(&tmp->anon_vma_chain); 629 retval = vma_dup_policy(mpnt, tmp); 630 if (retval) 631 goto fail_nomem_policy; 632 tmp->vm_mm = mm; 633 retval = dup_userfaultfd(tmp, &uf); 634 if (retval) 635 goto fail_nomem_anon_vma_fork; 636 if (anon_vma_fork(tmp, mpnt)) 637 goto fail_nomem_anon_vma_fork; 638 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 639 tmp->vm_next = tmp->vm_prev = NULL; 640 file = tmp->vm_file; 641 if (file) { 642 struct inode *inode = file_inode(file); 643 struct address_space *mapping = file->f_mapping; 644 645 get_file(file); 646 if (tmp->vm_flags & VM_DENYWRITE) 647 atomic_dec(&inode->i_writecount); 648 i_mmap_lock_write(mapping); 649 if (tmp->vm_flags & VM_SHARED) 650 atomic_inc(&mapping->i_mmap_writable); 651 flush_dcache_mmap_lock(mapping); 652 /* insert tmp into the share list, just after mpnt */ 653 vma_interval_tree_insert_after(tmp, mpnt, 654 &mapping->i_mmap); 655 flush_dcache_mmap_unlock(mapping); 656 i_mmap_unlock_write(mapping); 657 } 658 659 /* 660 * Clear hugetlb-related page reserves for children. This only 661 * affects MAP_PRIVATE mappings. Faults generated by the child 662 * are not guaranteed to succeed, even if read-only 663 */ 664 if (is_vm_hugetlb_page(tmp)) 665 reset_vma_resv_huge_pages(tmp); 666 667 /* 668 * Link in the new vma and copy the page table entries. 669 */ 670 *pprev = tmp; 671 pprev = &tmp->vm_next; 672 tmp->vm_prev = prev; 673 prev = tmp; 674 675 __vma_link_rb(mm, tmp, rb_link, rb_parent); 676 rb_link = &tmp->vm_rb.rb_right; 677 rb_parent = &tmp->vm_rb; 678 679 mm->map_count++; 680 retval = copy_page_range(mm, oldmm, mpnt); 681 682 if (tmp->vm_ops && tmp->vm_ops->open) 683 tmp->vm_ops->open(tmp); 684 685 if (retval) 686 goto out; 687 } 688 /* a new mm has just been created */ 689 arch_dup_mmap(oldmm, mm); 690 retval = 0; 691 out: 692 up_write(&mm->mmap_sem); 693 flush_tlb_mm(oldmm); 694 up_write(&oldmm->mmap_sem); 695 dup_userfaultfd_complete(&uf); 696 fail_uprobe_end: 697 uprobe_end_dup_mmap(); 698 return retval; 699 fail_nomem_anon_vma_fork: 700 mpol_put(vma_policy(tmp)); 701 fail_nomem_policy: 702 kmem_cache_free(vm_area_cachep, tmp); 703 fail_nomem: 704 retval = -ENOMEM; 705 vm_unacct_memory(charge); 706 goto out; 707 } 708 709 static inline int mm_alloc_pgd(struct mm_struct *mm) 710 { 711 mm->pgd = pgd_alloc(mm); 712 if (unlikely(!mm->pgd)) 713 return -ENOMEM; 714 return 0; 715 } 716 717 static inline void mm_free_pgd(struct mm_struct *mm) 718 { 719 pgd_free(mm, mm->pgd); 720 } 721 #else 722 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 723 { 724 down_write(&oldmm->mmap_sem); 725 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 726 up_write(&oldmm->mmap_sem); 727 return 0; 728 } 729 #define mm_alloc_pgd(mm) (0) 730 #define mm_free_pgd(mm) 731 #endif /* CONFIG_MMU */ 732 733 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 734 735 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 736 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 737 738 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 739 740 static int __init coredump_filter_setup(char *s) 741 { 742 default_dump_filter = 743 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 744 MMF_DUMP_FILTER_MASK; 745 return 1; 746 } 747 748 __setup("coredump_filter=", coredump_filter_setup); 749 750 #include <linux/init_task.h> 751 752 static void mm_init_aio(struct mm_struct *mm) 753 { 754 #ifdef CONFIG_AIO 755 spin_lock_init(&mm->ioctx_lock); 756 mm->ioctx_table = NULL; 757 #endif 758 } 759 760 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 761 { 762 #ifdef CONFIG_MEMCG 763 mm->owner = p; 764 #endif 765 } 766 767 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 768 struct user_namespace *user_ns) 769 { 770 mm->mmap = NULL; 771 mm->mm_rb = RB_ROOT; 772 mm->vmacache_seqnum = 0; 773 atomic_set(&mm->mm_users, 1); 774 atomic_set(&mm->mm_count, 1); 775 init_rwsem(&mm->mmap_sem); 776 INIT_LIST_HEAD(&mm->mmlist); 777 mm->core_state = NULL; 778 atomic_long_set(&mm->nr_ptes, 0); 779 mm_nr_pmds_init(mm); 780 mm->map_count = 0; 781 mm->locked_vm = 0; 782 mm->pinned_vm = 0; 783 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 784 spin_lock_init(&mm->page_table_lock); 785 mm_init_cpumask(mm); 786 mm_init_aio(mm); 787 mm_init_owner(mm, p); 788 mmu_notifier_mm_init(mm); 789 clear_tlb_flush_pending(mm); 790 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 791 mm->pmd_huge_pte = NULL; 792 #endif 793 794 if (current->mm) { 795 mm->flags = current->mm->flags & MMF_INIT_MASK; 796 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 797 } else { 798 mm->flags = default_dump_filter; 799 mm->def_flags = 0; 800 } 801 802 if (mm_alloc_pgd(mm)) 803 goto fail_nopgd; 804 805 if (init_new_context(p, mm)) 806 goto fail_nocontext; 807 808 mm->user_ns = get_user_ns(user_ns); 809 return mm; 810 811 fail_nocontext: 812 mm_free_pgd(mm); 813 fail_nopgd: 814 free_mm(mm); 815 return NULL; 816 } 817 818 static void check_mm(struct mm_struct *mm) 819 { 820 int i; 821 822 for (i = 0; i < NR_MM_COUNTERS; i++) { 823 long x = atomic_long_read(&mm->rss_stat.count[i]); 824 825 if (unlikely(x)) 826 printk(KERN_ALERT "BUG: Bad rss-counter state " 827 "mm:%p idx:%d val:%ld\n", mm, i, x); 828 } 829 830 if (atomic_long_read(&mm->nr_ptes)) 831 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 832 atomic_long_read(&mm->nr_ptes)); 833 if (mm_nr_pmds(mm)) 834 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 835 mm_nr_pmds(mm)); 836 837 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 838 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 839 #endif 840 } 841 842 /* 843 * Allocate and initialize an mm_struct. 844 */ 845 struct mm_struct *mm_alloc(void) 846 { 847 struct mm_struct *mm; 848 849 mm = allocate_mm(); 850 if (!mm) 851 return NULL; 852 853 memset(mm, 0, sizeof(*mm)); 854 return mm_init(mm, current, current_user_ns()); 855 } 856 857 /* 858 * Called when the last reference to the mm 859 * is dropped: either by a lazy thread or by 860 * mmput. Free the page directory and the mm. 861 */ 862 void __mmdrop(struct mm_struct *mm) 863 { 864 BUG_ON(mm == &init_mm); 865 mm_free_pgd(mm); 866 destroy_context(mm); 867 mmu_notifier_mm_destroy(mm); 868 check_mm(mm); 869 put_user_ns(mm->user_ns); 870 free_mm(mm); 871 } 872 EXPORT_SYMBOL_GPL(__mmdrop); 873 874 static inline void __mmput(struct mm_struct *mm) 875 { 876 VM_BUG_ON(atomic_read(&mm->mm_users)); 877 878 uprobe_clear_state(mm); 879 exit_aio(mm); 880 ksm_exit(mm); 881 khugepaged_exit(mm); /* must run before exit_mmap */ 882 exit_mmap(mm); 883 mm_put_huge_zero_page(mm); 884 set_mm_exe_file(mm, NULL); 885 if (!list_empty(&mm->mmlist)) { 886 spin_lock(&mmlist_lock); 887 list_del(&mm->mmlist); 888 spin_unlock(&mmlist_lock); 889 } 890 if (mm->binfmt) 891 module_put(mm->binfmt->module); 892 set_bit(MMF_OOM_SKIP, &mm->flags); 893 mmdrop(mm); 894 } 895 896 /* 897 * Decrement the use count and release all resources for an mm. 898 */ 899 void mmput(struct mm_struct *mm) 900 { 901 might_sleep(); 902 903 if (atomic_dec_and_test(&mm->mm_users)) 904 __mmput(mm); 905 } 906 EXPORT_SYMBOL_GPL(mmput); 907 908 #ifdef CONFIG_MMU 909 static void mmput_async_fn(struct work_struct *work) 910 { 911 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 912 __mmput(mm); 913 } 914 915 void mmput_async(struct mm_struct *mm) 916 { 917 if (atomic_dec_and_test(&mm->mm_users)) { 918 INIT_WORK(&mm->async_put_work, mmput_async_fn); 919 schedule_work(&mm->async_put_work); 920 } 921 } 922 #endif 923 924 /** 925 * set_mm_exe_file - change a reference to the mm's executable file 926 * 927 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 928 * 929 * Main users are mmput() and sys_execve(). Callers prevent concurrent 930 * invocations: in mmput() nobody alive left, in execve task is single 931 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 932 * mm->exe_file, but does so without using set_mm_exe_file() in order 933 * to do avoid the need for any locks. 934 */ 935 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 936 { 937 struct file *old_exe_file; 938 939 /* 940 * It is safe to dereference the exe_file without RCU as 941 * this function is only called if nobody else can access 942 * this mm -- see comment above for justification. 943 */ 944 old_exe_file = rcu_dereference_raw(mm->exe_file); 945 946 if (new_exe_file) 947 get_file(new_exe_file); 948 rcu_assign_pointer(mm->exe_file, new_exe_file); 949 if (old_exe_file) 950 fput(old_exe_file); 951 } 952 953 /** 954 * get_mm_exe_file - acquire a reference to the mm's executable file 955 * 956 * Returns %NULL if mm has no associated executable file. 957 * User must release file via fput(). 958 */ 959 struct file *get_mm_exe_file(struct mm_struct *mm) 960 { 961 struct file *exe_file; 962 963 rcu_read_lock(); 964 exe_file = rcu_dereference(mm->exe_file); 965 if (exe_file && !get_file_rcu(exe_file)) 966 exe_file = NULL; 967 rcu_read_unlock(); 968 return exe_file; 969 } 970 EXPORT_SYMBOL(get_mm_exe_file); 971 972 /** 973 * get_task_exe_file - acquire a reference to the task's executable file 974 * 975 * Returns %NULL if task's mm (if any) has no associated executable file or 976 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 977 * User must release file via fput(). 978 */ 979 struct file *get_task_exe_file(struct task_struct *task) 980 { 981 struct file *exe_file = NULL; 982 struct mm_struct *mm; 983 984 task_lock(task); 985 mm = task->mm; 986 if (mm) { 987 if (!(task->flags & PF_KTHREAD)) 988 exe_file = get_mm_exe_file(mm); 989 } 990 task_unlock(task); 991 return exe_file; 992 } 993 EXPORT_SYMBOL(get_task_exe_file); 994 995 /** 996 * get_task_mm - acquire a reference to the task's mm 997 * 998 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 999 * this kernel workthread has transiently adopted a user mm with use_mm, 1000 * to do its AIO) is not set and if so returns a reference to it, after 1001 * bumping up the use count. User must release the mm via mmput() 1002 * after use. Typically used by /proc and ptrace. 1003 */ 1004 struct mm_struct *get_task_mm(struct task_struct *task) 1005 { 1006 struct mm_struct *mm; 1007 1008 task_lock(task); 1009 mm = task->mm; 1010 if (mm) { 1011 if (task->flags & PF_KTHREAD) 1012 mm = NULL; 1013 else 1014 mmget(mm); 1015 } 1016 task_unlock(task); 1017 return mm; 1018 } 1019 EXPORT_SYMBOL_GPL(get_task_mm); 1020 1021 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1022 { 1023 struct mm_struct *mm; 1024 int err; 1025 1026 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1027 if (err) 1028 return ERR_PTR(err); 1029 1030 mm = get_task_mm(task); 1031 if (mm && mm != current->mm && 1032 !ptrace_may_access(task, mode)) { 1033 mmput(mm); 1034 mm = ERR_PTR(-EACCES); 1035 } 1036 mutex_unlock(&task->signal->cred_guard_mutex); 1037 1038 return mm; 1039 } 1040 1041 static void complete_vfork_done(struct task_struct *tsk) 1042 { 1043 struct completion *vfork; 1044 1045 task_lock(tsk); 1046 vfork = tsk->vfork_done; 1047 if (likely(vfork)) { 1048 tsk->vfork_done = NULL; 1049 complete(vfork); 1050 } 1051 task_unlock(tsk); 1052 } 1053 1054 static int wait_for_vfork_done(struct task_struct *child, 1055 struct completion *vfork) 1056 { 1057 int killed; 1058 1059 freezer_do_not_count(); 1060 killed = wait_for_completion_killable(vfork); 1061 freezer_count(); 1062 1063 if (killed) { 1064 task_lock(child); 1065 child->vfork_done = NULL; 1066 task_unlock(child); 1067 } 1068 1069 put_task_struct(child); 1070 return killed; 1071 } 1072 1073 /* Please note the differences between mmput and mm_release. 1074 * mmput is called whenever we stop holding onto a mm_struct, 1075 * error success whatever. 1076 * 1077 * mm_release is called after a mm_struct has been removed 1078 * from the current process. 1079 * 1080 * This difference is important for error handling, when we 1081 * only half set up a mm_struct for a new process and need to restore 1082 * the old one. Because we mmput the new mm_struct before 1083 * restoring the old one. . . 1084 * Eric Biederman 10 January 1998 1085 */ 1086 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1087 { 1088 /* Get rid of any futexes when releasing the mm */ 1089 #ifdef CONFIG_FUTEX 1090 if (unlikely(tsk->robust_list)) { 1091 exit_robust_list(tsk); 1092 tsk->robust_list = NULL; 1093 } 1094 #ifdef CONFIG_COMPAT 1095 if (unlikely(tsk->compat_robust_list)) { 1096 compat_exit_robust_list(tsk); 1097 tsk->compat_robust_list = NULL; 1098 } 1099 #endif 1100 if (unlikely(!list_empty(&tsk->pi_state_list))) 1101 exit_pi_state_list(tsk); 1102 #endif 1103 1104 uprobe_free_utask(tsk); 1105 1106 /* Get rid of any cached register state */ 1107 deactivate_mm(tsk, mm); 1108 1109 /* 1110 * Signal userspace if we're not exiting with a core dump 1111 * because we want to leave the value intact for debugging 1112 * purposes. 1113 */ 1114 if (tsk->clear_child_tid) { 1115 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1116 atomic_read(&mm->mm_users) > 1) { 1117 /* 1118 * We don't check the error code - if userspace has 1119 * not set up a proper pointer then tough luck. 1120 */ 1121 put_user(0, tsk->clear_child_tid); 1122 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1123 1, NULL, NULL, 0); 1124 } 1125 tsk->clear_child_tid = NULL; 1126 } 1127 1128 /* 1129 * All done, finally we can wake up parent and return this mm to him. 1130 * Also kthread_stop() uses this completion for synchronization. 1131 */ 1132 if (tsk->vfork_done) 1133 complete_vfork_done(tsk); 1134 } 1135 1136 /* 1137 * Allocate a new mm structure and copy contents from the 1138 * mm structure of the passed in task structure. 1139 */ 1140 static struct mm_struct *dup_mm(struct task_struct *tsk) 1141 { 1142 struct mm_struct *mm, *oldmm = current->mm; 1143 int err; 1144 1145 mm = allocate_mm(); 1146 if (!mm) 1147 goto fail_nomem; 1148 1149 memcpy(mm, oldmm, sizeof(*mm)); 1150 1151 if (!mm_init(mm, tsk, mm->user_ns)) 1152 goto fail_nomem; 1153 1154 err = dup_mmap(mm, oldmm); 1155 if (err) 1156 goto free_pt; 1157 1158 mm->hiwater_rss = get_mm_rss(mm); 1159 mm->hiwater_vm = mm->total_vm; 1160 1161 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1162 goto free_pt; 1163 1164 return mm; 1165 1166 free_pt: 1167 /* don't put binfmt in mmput, we haven't got module yet */ 1168 mm->binfmt = NULL; 1169 mmput(mm); 1170 1171 fail_nomem: 1172 return NULL; 1173 } 1174 1175 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1176 { 1177 struct mm_struct *mm, *oldmm; 1178 int retval; 1179 1180 tsk->min_flt = tsk->maj_flt = 0; 1181 tsk->nvcsw = tsk->nivcsw = 0; 1182 #ifdef CONFIG_DETECT_HUNG_TASK 1183 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1184 #endif 1185 1186 tsk->mm = NULL; 1187 tsk->active_mm = NULL; 1188 1189 /* 1190 * Are we cloning a kernel thread? 1191 * 1192 * We need to steal a active VM for that.. 1193 */ 1194 oldmm = current->mm; 1195 if (!oldmm) 1196 return 0; 1197 1198 /* initialize the new vmacache entries */ 1199 vmacache_flush(tsk); 1200 1201 if (clone_flags & CLONE_VM) { 1202 mmget(oldmm); 1203 mm = oldmm; 1204 goto good_mm; 1205 } 1206 1207 retval = -ENOMEM; 1208 mm = dup_mm(tsk); 1209 if (!mm) 1210 goto fail_nomem; 1211 1212 good_mm: 1213 tsk->mm = mm; 1214 tsk->active_mm = mm; 1215 return 0; 1216 1217 fail_nomem: 1218 return retval; 1219 } 1220 1221 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1222 { 1223 struct fs_struct *fs = current->fs; 1224 if (clone_flags & CLONE_FS) { 1225 /* tsk->fs is already what we want */ 1226 spin_lock(&fs->lock); 1227 if (fs->in_exec) { 1228 spin_unlock(&fs->lock); 1229 return -EAGAIN; 1230 } 1231 fs->users++; 1232 spin_unlock(&fs->lock); 1233 return 0; 1234 } 1235 tsk->fs = copy_fs_struct(fs); 1236 if (!tsk->fs) 1237 return -ENOMEM; 1238 return 0; 1239 } 1240 1241 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1242 { 1243 struct files_struct *oldf, *newf; 1244 int error = 0; 1245 1246 /* 1247 * A background process may not have any files ... 1248 */ 1249 oldf = current->files; 1250 if (!oldf) 1251 goto out; 1252 1253 if (clone_flags & CLONE_FILES) { 1254 atomic_inc(&oldf->count); 1255 goto out; 1256 } 1257 1258 newf = dup_fd(oldf, &error); 1259 if (!newf) 1260 goto out; 1261 1262 tsk->files = newf; 1263 error = 0; 1264 out: 1265 return error; 1266 } 1267 1268 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1269 { 1270 #ifdef CONFIG_BLOCK 1271 struct io_context *ioc = current->io_context; 1272 struct io_context *new_ioc; 1273 1274 if (!ioc) 1275 return 0; 1276 /* 1277 * Share io context with parent, if CLONE_IO is set 1278 */ 1279 if (clone_flags & CLONE_IO) { 1280 ioc_task_link(ioc); 1281 tsk->io_context = ioc; 1282 } else if (ioprio_valid(ioc->ioprio)) { 1283 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1284 if (unlikely(!new_ioc)) 1285 return -ENOMEM; 1286 1287 new_ioc->ioprio = ioc->ioprio; 1288 put_io_context(new_ioc); 1289 } 1290 #endif 1291 return 0; 1292 } 1293 1294 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1295 { 1296 struct sighand_struct *sig; 1297 1298 if (clone_flags & CLONE_SIGHAND) { 1299 atomic_inc(¤t->sighand->count); 1300 return 0; 1301 } 1302 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1303 rcu_assign_pointer(tsk->sighand, sig); 1304 if (!sig) 1305 return -ENOMEM; 1306 1307 atomic_set(&sig->count, 1); 1308 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1309 return 0; 1310 } 1311 1312 void __cleanup_sighand(struct sighand_struct *sighand) 1313 { 1314 if (atomic_dec_and_test(&sighand->count)) { 1315 signalfd_cleanup(sighand); 1316 /* 1317 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1318 * without an RCU grace period, see __lock_task_sighand(). 1319 */ 1320 kmem_cache_free(sighand_cachep, sighand); 1321 } 1322 } 1323 1324 #ifdef CONFIG_POSIX_TIMERS 1325 /* 1326 * Initialize POSIX timer handling for a thread group. 1327 */ 1328 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1329 { 1330 unsigned long cpu_limit; 1331 1332 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1333 if (cpu_limit != RLIM_INFINITY) { 1334 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1335 sig->cputimer.running = true; 1336 } 1337 1338 /* The timer lists. */ 1339 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1340 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1341 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1342 } 1343 #else 1344 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1345 #endif 1346 1347 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1348 { 1349 struct signal_struct *sig; 1350 1351 if (clone_flags & CLONE_THREAD) 1352 return 0; 1353 1354 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1355 tsk->signal = sig; 1356 if (!sig) 1357 return -ENOMEM; 1358 1359 sig->nr_threads = 1; 1360 atomic_set(&sig->live, 1); 1361 atomic_set(&sig->sigcnt, 1); 1362 1363 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1364 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1365 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1366 1367 init_waitqueue_head(&sig->wait_chldexit); 1368 sig->curr_target = tsk; 1369 init_sigpending(&sig->shared_pending); 1370 seqlock_init(&sig->stats_lock); 1371 prev_cputime_init(&sig->prev_cputime); 1372 1373 #ifdef CONFIG_POSIX_TIMERS 1374 INIT_LIST_HEAD(&sig->posix_timers); 1375 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1376 sig->real_timer.function = it_real_fn; 1377 #endif 1378 1379 task_lock(current->group_leader); 1380 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1381 task_unlock(current->group_leader); 1382 1383 posix_cpu_timers_init_group(sig); 1384 1385 tty_audit_fork(sig); 1386 sched_autogroup_fork(sig); 1387 1388 sig->oom_score_adj = current->signal->oom_score_adj; 1389 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1390 1391 mutex_init(&sig->cred_guard_mutex); 1392 1393 return 0; 1394 } 1395 1396 static void copy_seccomp(struct task_struct *p) 1397 { 1398 #ifdef CONFIG_SECCOMP 1399 /* 1400 * Must be called with sighand->lock held, which is common to 1401 * all threads in the group. Holding cred_guard_mutex is not 1402 * needed because this new task is not yet running and cannot 1403 * be racing exec. 1404 */ 1405 assert_spin_locked(¤t->sighand->siglock); 1406 1407 /* Ref-count the new filter user, and assign it. */ 1408 get_seccomp_filter(current); 1409 p->seccomp = current->seccomp; 1410 1411 /* 1412 * Explicitly enable no_new_privs here in case it got set 1413 * between the task_struct being duplicated and holding the 1414 * sighand lock. The seccomp state and nnp must be in sync. 1415 */ 1416 if (task_no_new_privs(current)) 1417 task_set_no_new_privs(p); 1418 1419 /* 1420 * If the parent gained a seccomp mode after copying thread 1421 * flags and between before we held the sighand lock, we have 1422 * to manually enable the seccomp thread flag here. 1423 */ 1424 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1425 set_tsk_thread_flag(p, TIF_SECCOMP); 1426 #endif 1427 } 1428 1429 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1430 { 1431 current->clear_child_tid = tidptr; 1432 1433 return task_pid_vnr(current); 1434 } 1435 1436 static void rt_mutex_init_task(struct task_struct *p) 1437 { 1438 raw_spin_lock_init(&p->pi_lock); 1439 #ifdef CONFIG_RT_MUTEXES 1440 p->pi_waiters = RB_ROOT; 1441 p->pi_waiters_leftmost = NULL; 1442 p->pi_blocked_on = NULL; 1443 #endif 1444 } 1445 1446 #ifdef CONFIG_POSIX_TIMERS 1447 /* 1448 * Initialize POSIX timer handling for a single task. 1449 */ 1450 static void posix_cpu_timers_init(struct task_struct *tsk) 1451 { 1452 tsk->cputime_expires.prof_exp = 0; 1453 tsk->cputime_expires.virt_exp = 0; 1454 tsk->cputime_expires.sched_exp = 0; 1455 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1456 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1457 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1458 } 1459 #else 1460 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1461 #endif 1462 1463 static inline void 1464 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1465 { 1466 task->pids[type].pid = pid; 1467 } 1468 1469 static inline void rcu_copy_process(struct task_struct *p) 1470 { 1471 #ifdef CONFIG_PREEMPT_RCU 1472 p->rcu_read_lock_nesting = 0; 1473 p->rcu_read_unlock_special.s = 0; 1474 p->rcu_blocked_node = NULL; 1475 INIT_LIST_HEAD(&p->rcu_node_entry); 1476 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1477 #ifdef CONFIG_TASKS_RCU 1478 p->rcu_tasks_holdout = false; 1479 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1480 p->rcu_tasks_idle_cpu = -1; 1481 #endif /* #ifdef CONFIG_TASKS_RCU */ 1482 } 1483 1484 /* 1485 * This creates a new process as a copy of the old one, 1486 * but does not actually start it yet. 1487 * 1488 * It copies the registers, and all the appropriate 1489 * parts of the process environment (as per the clone 1490 * flags). The actual kick-off is left to the caller. 1491 */ 1492 static __latent_entropy struct task_struct *copy_process( 1493 unsigned long clone_flags, 1494 unsigned long stack_start, 1495 unsigned long stack_size, 1496 int __user *child_tidptr, 1497 struct pid *pid, 1498 int trace, 1499 unsigned long tls, 1500 int node) 1501 { 1502 int retval; 1503 struct task_struct *p; 1504 1505 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1506 return ERR_PTR(-EINVAL); 1507 1508 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1509 return ERR_PTR(-EINVAL); 1510 1511 /* 1512 * Thread groups must share signals as well, and detached threads 1513 * can only be started up within the thread group. 1514 */ 1515 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1516 return ERR_PTR(-EINVAL); 1517 1518 /* 1519 * Shared signal handlers imply shared VM. By way of the above, 1520 * thread groups also imply shared VM. Blocking this case allows 1521 * for various simplifications in other code. 1522 */ 1523 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1524 return ERR_PTR(-EINVAL); 1525 1526 /* 1527 * Siblings of global init remain as zombies on exit since they are 1528 * not reaped by their parent (swapper). To solve this and to avoid 1529 * multi-rooted process trees, prevent global and container-inits 1530 * from creating siblings. 1531 */ 1532 if ((clone_flags & CLONE_PARENT) && 1533 current->signal->flags & SIGNAL_UNKILLABLE) 1534 return ERR_PTR(-EINVAL); 1535 1536 /* 1537 * If the new process will be in a different pid or user namespace 1538 * do not allow it to share a thread group with the forking task. 1539 */ 1540 if (clone_flags & CLONE_THREAD) { 1541 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1542 (task_active_pid_ns(current) != 1543 current->nsproxy->pid_ns_for_children)) 1544 return ERR_PTR(-EINVAL); 1545 } 1546 1547 retval = security_task_create(clone_flags); 1548 if (retval) 1549 goto fork_out; 1550 1551 retval = -ENOMEM; 1552 p = dup_task_struct(current, node); 1553 if (!p) 1554 goto fork_out; 1555 1556 ftrace_graph_init_task(p); 1557 1558 rt_mutex_init_task(p); 1559 1560 #ifdef CONFIG_PROVE_LOCKING 1561 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1562 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1563 #endif 1564 retval = -EAGAIN; 1565 if (atomic_read(&p->real_cred->user->processes) >= 1566 task_rlimit(p, RLIMIT_NPROC)) { 1567 if (p->real_cred->user != INIT_USER && 1568 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1569 goto bad_fork_free; 1570 } 1571 current->flags &= ~PF_NPROC_EXCEEDED; 1572 1573 retval = copy_creds(p, clone_flags); 1574 if (retval < 0) 1575 goto bad_fork_free; 1576 1577 /* 1578 * If multiple threads are within copy_process(), then this check 1579 * triggers too late. This doesn't hurt, the check is only there 1580 * to stop root fork bombs. 1581 */ 1582 retval = -EAGAIN; 1583 if (nr_threads >= max_threads) 1584 goto bad_fork_cleanup_count; 1585 1586 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1587 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1588 p->flags |= PF_FORKNOEXEC; 1589 INIT_LIST_HEAD(&p->children); 1590 INIT_LIST_HEAD(&p->sibling); 1591 rcu_copy_process(p); 1592 p->vfork_done = NULL; 1593 spin_lock_init(&p->alloc_lock); 1594 1595 init_sigpending(&p->pending); 1596 1597 p->utime = p->stime = p->gtime = 0; 1598 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1599 p->utimescaled = p->stimescaled = 0; 1600 #endif 1601 prev_cputime_init(&p->prev_cputime); 1602 1603 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1604 seqcount_init(&p->vtime_seqcount); 1605 p->vtime_snap = 0; 1606 p->vtime_snap_whence = VTIME_INACTIVE; 1607 #endif 1608 1609 #if defined(SPLIT_RSS_COUNTING) 1610 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1611 #endif 1612 1613 p->default_timer_slack_ns = current->timer_slack_ns; 1614 1615 task_io_accounting_init(&p->ioac); 1616 acct_clear_integrals(p); 1617 1618 posix_cpu_timers_init(p); 1619 1620 p->start_time = ktime_get_ns(); 1621 p->real_start_time = ktime_get_boot_ns(); 1622 p->io_context = NULL; 1623 p->audit_context = NULL; 1624 cgroup_fork(p); 1625 #ifdef CONFIG_NUMA 1626 p->mempolicy = mpol_dup(p->mempolicy); 1627 if (IS_ERR(p->mempolicy)) { 1628 retval = PTR_ERR(p->mempolicy); 1629 p->mempolicy = NULL; 1630 goto bad_fork_cleanup_threadgroup_lock; 1631 } 1632 #endif 1633 #ifdef CONFIG_CPUSETS 1634 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1635 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1636 seqcount_init(&p->mems_allowed_seq); 1637 #endif 1638 #ifdef CONFIG_TRACE_IRQFLAGS 1639 p->irq_events = 0; 1640 p->hardirqs_enabled = 0; 1641 p->hardirq_enable_ip = 0; 1642 p->hardirq_enable_event = 0; 1643 p->hardirq_disable_ip = _THIS_IP_; 1644 p->hardirq_disable_event = 0; 1645 p->softirqs_enabled = 1; 1646 p->softirq_enable_ip = _THIS_IP_; 1647 p->softirq_enable_event = 0; 1648 p->softirq_disable_ip = 0; 1649 p->softirq_disable_event = 0; 1650 p->hardirq_context = 0; 1651 p->softirq_context = 0; 1652 #endif 1653 1654 p->pagefault_disabled = 0; 1655 1656 #ifdef CONFIG_LOCKDEP 1657 p->lockdep_depth = 0; /* no locks held yet */ 1658 p->curr_chain_key = 0; 1659 p->lockdep_recursion = 0; 1660 #endif 1661 1662 #ifdef CONFIG_DEBUG_MUTEXES 1663 p->blocked_on = NULL; /* not blocked yet */ 1664 #endif 1665 #ifdef CONFIG_BCACHE 1666 p->sequential_io = 0; 1667 p->sequential_io_avg = 0; 1668 #endif 1669 1670 /* Perform scheduler related setup. Assign this task to a CPU. */ 1671 retval = sched_fork(clone_flags, p); 1672 if (retval) 1673 goto bad_fork_cleanup_policy; 1674 1675 retval = perf_event_init_task(p); 1676 if (retval) 1677 goto bad_fork_cleanup_policy; 1678 retval = audit_alloc(p); 1679 if (retval) 1680 goto bad_fork_cleanup_perf; 1681 /* copy all the process information */ 1682 shm_init_task(p); 1683 retval = copy_semundo(clone_flags, p); 1684 if (retval) 1685 goto bad_fork_cleanup_audit; 1686 retval = copy_files(clone_flags, p); 1687 if (retval) 1688 goto bad_fork_cleanup_semundo; 1689 retval = copy_fs(clone_flags, p); 1690 if (retval) 1691 goto bad_fork_cleanup_files; 1692 retval = copy_sighand(clone_flags, p); 1693 if (retval) 1694 goto bad_fork_cleanup_fs; 1695 retval = copy_signal(clone_flags, p); 1696 if (retval) 1697 goto bad_fork_cleanup_sighand; 1698 retval = copy_mm(clone_flags, p); 1699 if (retval) 1700 goto bad_fork_cleanup_signal; 1701 retval = copy_namespaces(clone_flags, p); 1702 if (retval) 1703 goto bad_fork_cleanup_mm; 1704 retval = copy_io(clone_flags, p); 1705 if (retval) 1706 goto bad_fork_cleanup_namespaces; 1707 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1708 if (retval) 1709 goto bad_fork_cleanup_io; 1710 1711 if (pid != &init_struct_pid) { 1712 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1713 if (IS_ERR(pid)) { 1714 retval = PTR_ERR(pid); 1715 goto bad_fork_cleanup_thread; 1716 } 1717 } 1718 1719 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1720 /* 1721 * Clear TID on mm_release()? 1722 */ 1723 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1724 #ifdef CONFIG_BLOCK 1725 p->plug = NULL; 1726 #endif 1727 #ifdef CONFIG_FUTEX 1728 p->robust_list = NULL; 1729 #ifdef CONFIG_COMPAT 1730 p->compat_robust_list = NULL; 1731 #endif 1732 INIT_LIST_HEAD(&p->pi_state_list); 1733 p->pi_state_cache = NULL; 1734 #endif 1735 /* 1736 * sigaltstack should be cleared when sharing the same VM 1737 */ 1738 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1739 sas_ss_reset(p); 1740 1741 /* 1742 * Syscall tracing and stepping should be turned off in the 1743 * child regardless of CLONE_PTRACE. 1744 */ 1745 user_disable_single_step(p); 1746 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1747 #ifdef TIF_SYSCALL_EMU 1748 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1749 #endif 1750 clear_all_latency_tracing(p); 1751 1752 /* ok, now we should be set up.. */ 1753 p->pid = pid_nr(pid); 1754 if (clone_flags & CLONE_THREAD) { 1755 p->exit_signal = -1; 1756 p->group_leader = current->group_leader; 1757 p->tgid = current->tgid; 1758 } else { 1759 if (clone_flags & CLONE_PARENT) 1760 p->exit_signal = current->group_leader->exit_signal; 1761 else 1762 p->exit_signal = (clone_flags & CSIGNAL); 1763 p->group_leader = p; 1764 p->tgid = p->pid; 1765 } 1766 1767 p->nr_dirtied = 0; 1768 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1769 p->dirty_paused_when = 0; 1770 1771 p->pdeath_signal = 0; 1772 INIT_LIST_HEAD(&p->thread_group); 1773 p->task_works = NULL; 1774 1775 cgroup_threadgroup_change_begin(current); 1776 /* 1777 * Ensure that the cgroup subsystem policies allow the new process to be 1778 * forked. It should be noted the the new process's css_set can be changed 1779 * between here and cgroup_post_fork() if an organisation operation is in 1780 * progress. 1781 */ 1782 retval = cgroup_can_fork(p); 1783 if (retval) 1784 goto bad_fork_free_pid; 1785 1786 /* 1787 * Make it visible to the rest of the system, but dont wake it up yet. 1788 * Need tasklist lock for parent etc handling! 1789 */ 1790 write_lock_irq(&tasklist_lock); 1791 1792 /* CLONE_PARENT re-uses the old parent */ 1793 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1794 p->real_parent = current->real_parent; 1795 p->parent_exec_id = current->parent_exec_id; 1796 } else { 1797 p->real_parent = current; 1798 p->parent_exec_id = current->self_exec_id; 1799 } 1800 1801 klp_copy_process(p); 1802 1803 spin_lock(¤t->sighand->siglock); 1804 1805 /* 1806 * Copy seccomp details explicitly here, in case they were changed 1807 * before holding sighand lock. 1808 */ 1809 copy_seccomp(p); 1810 1811 /* 1812 * Process group and session signals need to be delivered to just the 1813 * parent before the fork or both the parent and the child after the 1814 * fork. Restart if a signal comes in before we add the new process to 1815 * it's process group. 1816 * A fatal signal pending means that current will exit, so the new 1817 * thread can't slip out of an OOM kill (or normal SIGKILL). 1818 */ 1819 recalc_sigpending(); 1820 if (signal_pending(current)) { 1821 spin_unlock(¤t->sighand->siglock); 1822 write_unlock_irq(&tasklist_lock); 1823 retval = -ERESTARTNOINTR; 1824 goto bad_fork_cancel_cgroup; 1825 } 1826 1827 if (likely(p->pid)) { 1828 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1829 1830 init_task_pid(p, PIDTYPE_PID, pid); 1831 if (thread_group_leader(p)) { 1832 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1833 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1834 1835 if (is_child_reaper(pid)) { 1836 ns_of_pid(pid)->child_reaper = p; 1837 p->signal->flags |= SIGNAL_UNKILLABLE; 1838 } 1839 1840 p->signal->leader_pid = pid; 1841 p->signal->tty = tty_kref_get(current->signal->tty); 1842 /* 1843 * Inherit has_child_subreaper flag under the same 1844 * tasklist_lock with adding child to the process tree 1845 * for propagate_has_child_subreaper optimization. 1846 */ 1847 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1848 p->real_parent->signal->is_child_subreaper; 1849 list_add_tail(&p->sibling, &p->real_parent->children); 1850 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1851 attach_pid(p, PIDTYPE_PGID); 1852 attach_pid(p, PIDTYPE_SID); 1853 __this_cpu_inc(process_counts); 1854 } else { 1855 current->signal->nr_threads++; 1856 atomic_inc(¤t->signal->live); 1857 atomic_inc(¤t->signal->sigcnt); 1858 list_add_tail_rcu(&p->thread_group, 1859 &p->group_leader->thread_group); 1860 list_add_tail_rcu(&p->thread_node, 1861 &p->signal->thread_head); 1862 } 1863 attach_pid(p, PIDTYPE_PID); 1864 nr_threads++; 1865 } 1866 1867 total_forks++; 1868 spin_unlock(¤t->sighand->siglock); 1869 syscall_tracepoint_update(p); 1870 write_unlock_irq(&tasklist_lock); 1871 1872 proc_fork_connector(p); 1873 cgroup_post_fork(p); 1874 cgroup_threadgroup_change_end(current); 1875 perf_event_fork(p); 1876 1877 trace_task_newtask(p, clone_flags); 1878 uprobe_copy_process(p, clone_flags); 1879 1880 return p; 1881 1882 bad_fork_cancel_cgroup: 1883 cgroup_cancel_fork(p); 1884 bad_fork_free_pid: 1885 cgroup_threadgroup_change_end(current); 1886 if (pid != &init_struct_pid) 1887 free_pid(pid); 1888 bad_fork_cleanup_thread: 1889 exit_thread(p); 1890 bad_fork_cleanup_io: 1891 if (p->io_context) 1892 exit_io_context(p); 1893 bad_fork_cleanup_namespaces: 1894 exit_task_namespaces(p); 1895 bad_fork_cleanup_mm: 1896 if (p->mm) 1897 mmput(p->mm); 1898 bad_fork_cleanup_signal: 1899 if (!(clone_flags & CLONE_THREAD)) 1900 free_signal_struct(p->signal); 1901 bad_fork_cleanup_sighand: 1902 __cleanup_sighand(p->sighand); 1903 bad_fork_cleanup_fs: 1904 exit_fs(p); /* blocking */ 1905 bad_fork_cleanup_files: 1906 exit_files(p); /* blocking */ 1907 bad_fork_cleanup_semundo: 1908 exit_sem(p); 1909 bad_fork_cleanup_audit: 1910 audit_free(p); 1911 bad_fork_cleanup_perf: 1912 perf_event_free_task(p); 1913 bad_fork_cleanup_policy: 1914 #ifdef CONFIG_NUMA 1915 mpol_put(p->mempolicy); 1916 bad_fork_cleanup_threadgroup_lock: 1917 #endif 1918 delayacct_tsk_free(p); 1919 bad_fork_cleanup_count: 1920 atomic_dec(&p->cred->user->processes); 1921 exit_creds(p); 1922 bad_fork_free: 1923 p->state = TASK_DEAD; 1924 put_task_stack(p); 1925 free_task(p); 1926 fork_out: 1927 return ERR_PTR(retval); 1928 } 1929 1930 static inline void init_idle_pids(struct pid_link *links) 1931 { 1932 enum pid_type type; 1933 1934 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1935 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1936 links[type].pid = &init_struct_pid; 1937 } 1938 } 1939 1940 struct task_struct *fork_idle(int cpu) 1941 { 1942 struct task_struct *task; 1943 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1944 cpu_to_node(cpu)); 1945 if (!IS_ERR(task)) { 1946 init_idle_pids(task->pids); 1947 init_idle(task, cpu); 1948 } 1949 1950 return task; 1951 } 1952 1953 /* 1954 * Ok, this is the main fork-routine. 1955 * 1956 * It copies the process, and if successful kick-starts 1957 * it and waits for it to finish using the VM if required. 1958 */ 1959 long _do_fork(unsigned long clone_flags, 1960 unsigned long stack_start, 1961 unsigned long stack_size, 1962 int __user *parent_tidptr, 1963 int __user *child_tidptr, 1964 unsigned long tls) 1965 { 1966 struct task_struct *p; 1967 int trace = 0; 1968 long nr; 1969 1970 /* 1971 * Determine whether and which event to report to ptracer. When 1972 * called from kernel_thread or CLONE_UNTRACED is explicitly 1973 * requested, no event is reported; otherwise, report if the event 1974 * for the type of forking is enabled. 1975 */ 1976 if (!(clone_flags & CLONE_UNTRACED)) { 1977 if (clone_flags & CLONE_VFORK) 1978 trace = PTRACE_EVENT_VFORK; 1979 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1980 trace = PTRACE_EVENT_CLONE; 1981 else 1982 trace = PTRACE_EVENT_FORK; 1983 1984 if (likely(!ptrace_event_enabled(current, trace))) 1985 trace = 0; 1986 } 1987 1988 p = copy_process(clone_flags, stack_start, stack_size, 1989 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 1990 add_latent_entropy(); 1991 /* 1992 * Do this prior waking up the new thread - the thread pointer 1993 * might get invalid after that point, if the thread exits quickly. 1994 */ 1995 if (!IS_ERR(p)) { 1996 struct completion vfork; 1997 struct pid *pid; 1998 1999 trace_sched_process_fork(current, p); 2000 2001 pid = get_task_pid(p, PIDTYPE_PID); 2002 nr = pid_vnr(pid); 2003 2004 if (clone_flags & CLONE_PARENT_SETTID) 2005 put_user(nr, parent_tidptr); 2006 2007 if (clone_flags & CLONE_VFORK) { 2008 p->vfork_done = &vfork; 2009 init_completion(&vfork); 2010 get_task_struct(p); 2011 } 2012 2013 wake_up_new_task(p); 2014 2015 /* forking complete and child started to run, tell ptracer */ 2016 if (unlikely(trace)) 2017 ptrace_event_pid(trace, pid); 2018 2019 if (clone_flags & CLONE_VFORK) { 2020 if (!wait_for_vfork_done(p, &vfork)) 2021 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2022 } 2023 2024 put_pid(pid); 2025 } else { 2026 nr = PTR_ERR(p); 2027 } 2028 return nr; 2029 } 2030 2031 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2032 /* For compatibility with architectures that call do_fork directly rather than 2033 * using the syscall entry points below. */ 2034 long do_fork(unsigned long clone_flags, 2035 unsigned long stack_start, 2036 unsigned long stack_size, 2037 int __user *parent_tidptr, 2038 int __user *child_tidptr) 2039 { 2040 return _do_fork(clone_flags, stack_start, stack_size, 2041 parent_tidptr, child_tidptr, 0); 2042 } 2043 #endif 2044 2045 /* 2046 * Create a kernel thread. 2047 */ 2048 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2049 { 2050 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2051 (unsigned long)arg, NULL, NULL, 0); 2052 } 2053 2054 #ifdef __ARCH_WANT_SYS_FORK 2055 SYSCALL_DEFINE0(fork) 2056 { 2057 #ifdef CONFIG_MMU 2058 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2059 #else 2060 /* can not support in nommu mode */ 2061 return -EINVAL; 2062 #endif 2063 } 2064 #endif 2065 2066 #ifdef __ARCH_WANT_SYS_VFORK 2067 SYSCALL_DEFINE0(vfork) 2068 { 2069 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2070 0, NULL, NULL, 0); 2071 } 2072 #endif 2073 2074 #ifdef __ARCH_WANT_SYS_CLONE 2075 #ifdef CONFIG_CLONE_BACKWARDS 2076 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2077 int __user *, parent_tidptr, 2078 unsigned long, tls, 2079 int __user *, child_tidptr) 2080 #elif defined(CONFIG_CLONE_BACKWARDS2) 2081 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2082 int __user *, parent_tidptr, 2083 int __user *, child_tidptr, 2084 unsigned long, tls) 2085 #elif defined(CONFIG_CLONE_BACKWARDS3) 2086 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2087 int, stack_size, 2088 int __user *, parent_tidptr, 2089 int __user *, child_tidptr, 2090 unsigned long, tls) 2091 #else 2092 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2093 int __user *, parent_tidptr, 2094 int __user *, child_tidptr, 2095 unsigned long, tls) 2096 #endif 2097 { 2098 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2099 } 2100 #endif 2101 2102 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2103 { 2104 struct task_struct *leader, *parent, *child; 2105 int res; 2106 2107 read_lock(&tasklist_lock); 2108 leader = top = top->group_leader; 2109 down: 2110 for_each_thread(leader, parent) { 2111 list_for_each_entry(child, &parent->children, sibling) { 2112 res = visitor(child, data); 2113 if (res) { 2114 if (res < 0) 2115 goto out; 2116 leader = child; 2117 goto down; 2118 } 2119 up: 2120 ; 2121 } 2122 } 2123 2124 if (leader != top) { 2125 child = leader; 2126 parent = child->real_parent; 2127 leader = parent->group_leader; 2128 goto up; 2129 } 2130 out: 2131 read_unlock(&tasklist_lock); 2132 } 2133 2134 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2135 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2136 #endif 2137 2138 static void sighand_ctor(void *data) 2139 { 2140 struct sighand_struct *sighand = data; 2141 2142 spin_lock_init(&sighand->siglock); 2143 init_waitqueue_head(&sighand->signalfd_wqh); 2144 } 2145 2146 void __init proc_caches_init(void) 2147 { 2148 sighand_cachep = kmem_cache_create("sighand_cache", 2149 sizeof(struct sighand_struct), 0, 2150 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 2151 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2152 signal_cachep = kmem_cache_create("signal_cache", 2153 sizeof(struct signal_struct), 0, 2154 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2155 NULL); 2156 files_cachep = kmem_cache_create("files_cache", 2157 sizeof(struct files_struct), 0, 2158 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2159 NULL); 2160 fs_cachep = kmem_cache_create("fs_cache", 2161 sizeof(struct fs_struct), 0, 2162 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2163 NULL); 2164 /* 2165 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2166 * whole struct cpumask for the OFFSTACK case. We could change 2167 * this to *only* allocate as much of it as required by the 2168 * maximum number of CPU's we can ever have. The cpumask_allocation 2169 * is at the end of the structure, exactly for that reason. 2170 */ 2171 mm_cachep = kmem_cache_create("mm_struct", 2172 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2173 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2174 NULL); 2175 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2176 mmap_init(); 2177 nsproxy_cache_init(); 2178 } 2179 2180 /* 2181 * Check constraints on flags passed to the unshare system call. 2182 */ 2183 static int check_unshare_flags(unsigned long unshare_flags) 2184 { 2185 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2186 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2187 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2188 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2189 return -EINVAL; 2190 /* 2191 * Not implemented, but pretend it works if there is nothing 2192 * to unshare. Note that unsharing the address space or the 2193 * signal handlers also need to unshare the signal queues (aka 2194 * CLONE_THREAD). 2195 */ 2196 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2197 if (!thread_group_empty(current)) 2198 return -EINVAL; 2199 } 2200 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2201 if (atomic_read(¤t->sighand->count) > 1) 2202 return -EINVAL; 2203 } 2204 if (unshare_flags & CLONE_VM) { 2205 if (!current_is_single_threaded()) 2206 return -EINVAL; 2207 } 2208 2209 return 0; 2210 } 2211 2212 /* 2213 * Unshare the filesystem structure if it is being shared 2214 */ 2215 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2216 { 2217 struct fs_struct *fs = current->fs; 2218 2219 if (!(unshare_flags & CLONE_FS) || !fs) 2220 return 0; 2221 2222 /* don't need lock here; in the worst case we'll do useless copy */ 2223 if (fs->users == 1) 2224 return 0; 2225 2226 *new_fsp = copy_fs_struct(fs); 2227 if (!*new_fsp) 2228 return -ENOMEM; 2229 2230 return 0; 2231 } 2232 2233 /* 2234 * Unshare file descriptor table if it is being shared 2235 */ 2236 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2237 { 2238 struct files_struct *fd = current->files; 2239 int error = 0; 2240 2241 if ((unshare_flags & CLONE_FILES) && 2242 (fd && atomic_read(&fd->count) > 1)) { 2243 *new_fdp = dup_fd(fd, &error); 2244 if (!*new_fdp) 2245 return error; 2246 } 2247 2248 return 0; 2249 } 2250 2251 /* 2252 * unshare allows a process to 'unshare' part of the process 2253 * context which was originally shared using clone. copy_* 2254 * functions used by do_fork() cannot be used here directly 2255 * because they modify an inactive task_struct that is being 2256 * constructed. Here we are modifying the current, active, 2257 * task_struct. 2258 */ 2259 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2260 { 2261 struct fs_struct *fs, *new_fs = NULL; 2262 struct files_struct *fd, *new_fd = NULL; 2263 struct cred *new_cred = NULL; 2264 struct nsproxy *new_nsproxy = NULL; 2265 int do_sysvsem = 0; 2266 int err; 2267 2268 /* 2269 * If unsharing a user namespace must also unshare the thread group 2270 * and unshare the filesystem root and working directories. 2271 */ 2272 if (unshare_flags & CLONE_NEWUSER) 2273 unshare_flags |= CLONE_THREAD | CLONE_FS; 2274 /* 2275 * If unsharing vm, must also unshare signal handlers. 2276 */ 2277 if (unshare_flags & CLONE_VM) 2278 unshare_flags |= CLONE_SIGHAND; 2279 /* 2280 * If unsharing a signal handlers, must also unshare the signal queues. 2281 */ 2282 if (unshare_flags & CLONE_SIGHAND) 2283 unshare_flags |= CLONE_THREAD; 2284 /* 2285 * If unsharing namespace, must also unshare filesystem information. 2286 */ 2287 if (unshare_flags & CLONE_NEWNS) 2288 unshare_flags |= CLONE_FS; 2289 2290 err = check_unshare_flags(unshare_flags); 2291 if (err) 2292 goto bad_unshare_out; 2293 /* 2294 * CLONE_NEWIPC must also detach from the undolist: after switching 2295 * to a new ipc namespace, the semaphore arrays from the old 2296 * namespace are unreachable. 2297 */ 2298 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2299 do_sysvsem = 1; 2300 err = unshare_fs(unshare_flags, &new_fs); 2301 if (err) 2302 goto bad_unshare_out; 2303 err = unshare_fd(unshare_flags, &new_fd); 2304 if (err) 2305 goto bad_unshare_cleanup_fs; 2306 err = unshare_userns(unshare_flags, &new_cred); 2307 if (err) 2308 goto bad_unshare_cleanup_fd; 2309 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2310 new_cred, new_fs); 2311 if (err) 2312 goto bad_unshare_cleanup_cred; 2313 2314 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2315 if (do_sysvsem) { 2316 /* 2317 * CLONE_SYSVSEM is equivalent to sys_exit(). 2318 */ 2319 exit_sem(current); 2320 } 2321 if (unshare_flags & CLONE_NEWIPC) { 2322 /* Orphan segments in old ns (see sem above). */ 2323 exit_shm(current); 2324 shm_init_task(current); 2325 } 2326 2327 if (new_nsproxy) 2328 switch_task_namespaces(current, new_nsproxy); 2329 2330 task_lock(current); 2331 2332 if (new_fs) { 2333 fs = current->fs; 2334 spin_lock(&fs->lock); 2335 current->fs = new_fs; 2336 if (--fs->users) 2337 new_fs = NULL; 2338 else 2339 new_fs = fs; 2340 spin_unlock(&fs->lock); 2341 } 2342 2343 if (new_fd) { 2344 fd = current->files; 2345 current->files = new_fd; 2346 new_fd = fd; 2347 } 2348 2349 task_unlock(current); 2350 2351 if (new_cred) { 2352 /* Install the new user namespace */ 2353 commit_creds(new_cred); 2354 new_cred = NULL; 2355 } 2356 } 2357 2358 bad_unshare_cleanup_cred: 2359 if (new_cred) 2360 put_cred(new_cred); 2361 bad_unshare_cleanup_fd: 2362 if (new_fd) 2363 put_files_struct(new_fd); 2364 2365 bad_unshare_cleanup_fs: 2366 if (new_fs) 2367 free_fs_struct(new_fs); 2368 2369 bad_unshare_out: 2370 return err; 2371 } 2372 2373 /* 2374 * Helper to unshare the files of the current task. 2375 * We don't want to expose copy_files internals to 2376 * the exec layer of the kernel. 2377 */ 2378 2379 int unshare_files(struct files_struct **displaced) 2380 { 2381 struct task_struct *task = current; 2382 struct files_struct *copy = NULL; 2383 int error; 2384 2385 error = unshare_fd(CLONE_FILES, ©); 2386 if (error || !copy) { 2387 *displaced = NULL; 2388 return error; 2389 } 2390 *displaced = task->files; 2391 task_lock(task); 2392 task->files = copy; 2393 task_unlock(task); 2394 return 0; 2395 } 2396 2397 int sysctl_max_threads(struct ctl_table *table, int write, 2398 void __user *buffer, size_t *lenp, loff_t *ppos) 2399 { 2400 struct ctl_table t; 2401 int ret; 2402 int threads = max_threads; 2403 int min = MIN_THREADS; 2404 int max = MAX_THREADS; 2405 2406 t = *table; 2407 t.data = &threads; 2408 t.extra1 = &min; 2409 t.extra2 = &max; 2410 2411 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2412 if (ret || !write) 2413 return ret; 2414 2415 set_max_threads(threads); 2416 2417 return 0; 2418 } 2419