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