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