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