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