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