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/sched/autogroup.h> 16 #include <linux/sched/mm.h> 17 #include <linux/sched/coredump.h> 18 #include <linux/sched/user.h> 19 #include <linux/sched/numa_balancing.h> 20 #include <linux/rtmutex.h> 21 #include <linux/init.h> 22 #include <linux/unistd.h> 23 #include <linux/module.h> 24 #include <linux/vmalloc.h> 25 #include <linux/completion.h> 26 #include <linux/personality.h> 27 #include <linux/mempolicy.h> 28 #include <linux/sem.h> 29 #include <linux/file.h> 30 #include <linux/fdtable.h> 31 #include <linux/iocontext.h> 32 #include <linux/key.h> 33 #include <linux/binfmts.h> 34 #include <linux/mman.h> 35 #include <linux/mmu_notifier.h> 36 #include <linux/fs.h> 37 #include <linux/mm.h> 38 #include <linux/vmacache.h> 39 #include <linux/nsproxy.h> 40 #include <linux/capability.h> 41 #include <linux/cpu.h> 42 #include <linux/cgroup.h> 43 #include <linux/security.h> 44 #include <linux/hugetlb.h> 45 #include <linux/seccomp.h> 46 #include <linux/swap.h> 47 #include <linux/syscalls.h> 48 #include <linux/jiffies.h> 49 #include <linux/futex.h> 50 #include <linux/compat.h> 51 #include <linux/kthread.h> 52 #include <linux/task_io_accounting_ops.h> 53 #include <linux/rcupdate.h> 54 #include <linux/ptrace.h> 55 #include <linux/mount.h> 56 #include <linux/audit.h> 57 #include <linux/memcontrol.h> 58 #include <linux/ftrace.h> 59 #include <linux/proc_fs.h> 60 #include <linux/profile.h> 61 #include <linux/rmap.h> 62 #include <linux/ksm.h> 63 #include <linux/acct.h> 64 #include <linux/userfaultfd_k.h> 65 #include <linux/tsacct_kern.h> 66 #include <linux/cn_proc.h> 67 #include <linux/freezer.h> 68 #include <linux/delayacct.h> 69 #include <linux/taskstats_kern.h> 70 #include <linux/random.h> 71 #include <linux/tty.h> 72 #include <linux/blkdev.h> 73 #include <linux/fs_struct.h> 74 #include <linux/magic.h> 75 #include <linux/perf_event.h> 76 #include <linux/posix-timers.h> 77 #include <linux/user-return-notifier.h> 78 #include <linux/oom.h> 79 #include <linux/khugepaged.h> 80 #include <linux/signalfd.h> 81 #include <linux/uprobes.h> 82 #include <linux/aio.h> 83 #include <linux/compiler.h> 84 #include <linux/sysctl.h> 85 #include <linux/kcov.h> 86 87 #include <asm/pgtable.h> 88 #include <asm/pgalloc.h> 89 #include <linux/uaccess.h> 90 #include <asm/mmu_context.h> 91 #include <asm/cacheflush.h> 92 #include <asm/tlbflush.h> 93 94 #include <trace/events/sched.h> 95 96 #define CREATE_TRACE_POINTS 97 #include <trace/events/task.h> 98 99 /* 100 * Minimum number of threads to boot the kernel 101 */ 102 #define MIN_THREADS 20 103 104 /* 105 * Maximum number of threads 106 */ 107 #define MAX_THREADS FUTEX_TID_MASK 108 109 /* 110 * Protected counters by write_lock_irq(&tasklist_lock) 111 */ 112 unsigned long total_forks; /* Handle normal Linux uptimes. */ 113 int nr_threads; /* The idle threads do not count.. */ 114 115 int max_threads; /* tunable limit on nr_threads */ 116 117 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 118 119 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 120 121 #ifdef CONFIG_PROVE_RCU 122 int lockdep_tasklist_lock_is_held(void) 123 { 124 return lockdep_is_held(&tasklist_lock); 125 } 126 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 127 #endif /* #ifdef CONFIG_PROVE_RCU */ 128 129 int nr_processes(void) 130 { 131 int cpu; 132 int total = 0; 133 134 for_each_possible_cpu(cpu) 135 total += per_cpu(process_counts, cpu); 136 137 return total; 138 } 139 140 void __weak arch_release_task_struct(struct task_struct *tsk) 141 { 142 } 143 144 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 145 static struct kmem_cache *task_struct_cachep; 146 147 static inline struct task_struct *alloc_task_struct_node(int node) 148 { 149 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 150 } 151 152 static inline void free_task_struct(struct task_struct *tsk) 153 { 154 kmem_cache_free(task_struct_cachep, tsk); 155 } 156 #endif 157 158 void __weak arch_release_thread_stack(unsigned long *stack) 159 { 160 } 161 162 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 163 164 /* 165 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 166 * kmemcache based allocator. 167 */ 168 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 169 170 #ifdef CONFIG_VMAP_STACK 171 /* 172 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 173 * flush. Try to minimize the number of calls by caching stacks. 174 */ 175 #define NR_CACHED_STACKS 2 176 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 177 #endif 178 179 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 180 { 181 #ifdef CONFIG_VMAP_STACK 182 void *stack; 183 int i; 184 185 local_irq_disable(); 186 for (i = 0; i < NR_CACHED_STACKS; i++) { 187 struct vm_struct *s = this_cpu_read(cached_stacks[i]); 188 189 if (!s) 190 continue; 191 this_cpu_write(cached_stacks[i], NULL); 192 193 tsk->stack_vm_area = s; 194 local_irq_enable(); 195 return s->addr; 196 } 197 local_irq_enable(); 198 199 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, 200 VMALLOC_START, VMALLOC_END, 201 THREADINFO_GFP | __GFP_HIGHMEM, 202 PAGE_KERNEL, 203 0, node, __builtin_return_address(0)); 204 205 /* 206 * We can't call find_vm_area() in interrupt context, and 207 * free_thread_stack() can be called in interrupt context, 208 * so cache the vm_struct. 209 */ 210 if (stack) 211 tsk->stack_vm_area = find_vm_area(stack); 212 return stack; 213 #else 214 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 215 THREAD_SIZE_ORDER); 216 217 return page ? page_address(page) : NULL; 218 #endif 219 } 220 221 static inline void free_thread_stack(struct task_struct *tsk) 222 { 223 #ifdef CONFIG_VMAP_STACK 224 if (task_stack_vm_area(tsk)) { 225 unsigned long flags; 226 int i; 227 228 local_irq_save(flags); 229 for (i = 0; i < NR_CACHED_STACKS; i++) { 230 if (this_cpu_read(cached_stacks[i])) 231 continue; 232 233 this_cpu_write(cached_stacks[i], tsk->stack_vm_area); 234 local_irq_restore(flags); 235 return; 236 } 237 local_irq_restore(flags); 238 239 vfree_atomic(tsk->stack); 240 return; 241 } 242 #endif 243 244 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 245 } 246 # else 247 static struct kmem_cache *thread_stack_cache; 248 249 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 250 int node) 251 { 252 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 253 } 254 255 static void free_thread_stack(struct task_struct *tsk) 256 { 257 kmem_cache_free(thread_stack_cache, tsk->stack); 258 } 259 260 void thread_stack_cache_init(void) 261 { 262 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, 263 THREAD_SIZE, 0, NULL); 264 BUG_ON(thread_stack_cache == NULL); 265 } 266 # endif 267 #endif 268 269 /* SLAB cache for signal_struct structures (tsk->signal) */ 270 static struct kmem_cache *signal_cachep; 271 272 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 273 struct kmem_cache *sighand_cachep; 274 275 /* SLAB cache for files_struct structures (tsk->files) */ 276 struct kmem_cache *files_cachep; 277 278 /* SLAB cache for fs_struct structures (tsk->fs) */ 279 struct kmem_cache *fs_cachep; 280 281 /* SLAB cache for vm_area_struct structures */ 282 struct kmem_cache *vm_area_cachep; 283 284 /* SLAB cache for mm_struct structures (tsk->mm) */ 285 static struct kmem_cache *mm_cachep; 286 287 static void account_kernel_stack(struct task_struct *tsk, int account) 288 { 289 void *stack = task_stack_page(tsk); 290 struct vm_struct *vm = task_stack_vm_area(tsk); 291 292 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 293 294 if (vm) { 295 int i; 296 297 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 298 299 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 300 mod_zone_page_state(page_zone(vm->pages[i]), 301 NR_KERNEL_STACK_KB, 302 PAGE_SIZE / 1024 * account); 303 } 304 305 /* All stack pages belong to the same memcg. */ 306 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB, 307 account * (THREAD_SIZE / 1024)); 308 } else { 309 /* 310 * All stack pages are in the same zone and belong to the 311 * same memcg. 312 */ 313 struct page *first_page = virt_to_page(stack); 314 315 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 316 THREAD_SIZE / 1024 * account); 317 318 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB, 319 account * (THREAD_SIZE / 1024)); 320 } 321 } 322 323 static void release_task_stack(struct task_struct *tsk) 324 { 325 if (WARN_ON(tsk->state != TASK_DEAD)) 326 return; /* Better to leak the stack than to free prematurely */ 327 328 account_kernel_stack(tsk, -1); 329 arch_release_thread_stack(tsk->stack); 330 free_thread_stack(tsk); 331 tsk->stack = NULL; 332 #ifdef CONFIG_VMAP_STACK 333 tsk->stack_vm_area = NULL; 334 #endif 335 } 336 337 #ifdef CONFIG_THREAD_INFO_IN_TASK 338 void put_task_stack(struct task_struct *tsk) 339 { 340 if (atomic_dec_and_test(&tsk->stack_refcount)) 341 release_task_stack(tsk); 342 } 343 #endif 344 345 void free_task(struct task_struct *tsk) 346 { 347 #ifndef CONFIG_THREAD_INFO_IN_TASK 348 /* 349 * The task is finally done with both the stack and thread_info, 350 * so free both. 351 */ 352 release_task_stack(tsk); 353 #else 354 /* 355 * If the task had a separate stack allocation, it should be gone 356 * by now. 357 */ 358 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 359 #endif 360 rt_mutex_debug_task_free(tsk); 361 ftrace_graph_exit_task(tsk); 362 put_seccomp_filter(tsk); 363 arch_release_task_struct(tsk); 364 if (tsk->flags & PF_KTHREAD) 365 free_kthread_struct(tsk); 366 free_task_struct(tsk); 367 } 368 EXPORT_SYMBOL(free_task); 369 370 static inline void free_signal_struct(struct signal_struct *sig) 371 { 372 taskstats_tgid_free(sig); 373 sched_autogroup_exit(sig); 374 /* 375 * __mmdrop is not safe to call from softirq context on x86 due to 376 * pgd_dtor so postpone it to the async context 377 */ 378 if (sig->oom_mm) 379 mmdrop_async(sig->oom_mm); 380 kmem_cache_free(signal_cachep, sig); 381 } 382 383 static inline void put_signal_struct(struct signal_struct *sig) 384 { 385 if (atomic_dec_and_test(&sig->sigcnt)) 386 free_signal_struct(sig); 387 } 388 389 void __put_task_struct(struct task_struct *tsk) 390 { 391 WARN_ON(!tsk->exit_state); 392 WARN_ON(atomic_read(&tsk->usage)); 393 WARN_ON(tsk == current); 394 395 cgroup_free(tsk); 396 task_numa_free(tsk); 397 security_task_free(tsk); 398 exit_creds(tsk); 399 delayacct_tsk_free(tsk); 400 put_signal_struct(tsk->signal); 401 402 if (!profile_handoff_task(tsk)) 403 free_task(tsk); 404 } 405 EXPORT_SYMBOL_GPL(__put_task_struct); 406 407 void __init __weak arch_task_cache_init(void) { } 408 409 /* 410 * set_max_threads 411 */ 412 static void set_max_threads(unsigned int max_threads_suggested) 413 { 414 u64 threads; 415 416 /* 417 * The number of threads shall be limited such that the thread 418 * structures may only consume a small part of the available memory. 419 */ 420 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 421 threads = MAX_THREADS; 422 else 423 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 424 (u64) THREAD_SIZE * 8UL); 425 426 if (threads > max_threads_suggested) 427 threads = max_threads_suggested; 428 429 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 430 } 431 432 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 433 /* Initialized by the architecture: */ 434 int arch_task_struct_size __read_mostly; 435 #endif 436 437 void __init fork_init(void) 438 { 439 int i; 440 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 441 #ifndef ARCH_MIN_TASKALIGN 442 #define ARCH_MIN_TASKALIGN 0 443 #endif 444 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 445 446 /* create a slab on which task_structs can be allocated */ 447 task_struct_cachep = kmem_cache_create("task_struct", 448 arch_task_struct_size, align, 449 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL); 450 #endif 451 452 /* do the arch specific task caches init */ 453 arch_task_cache_init(); 454 455 set_max_threads(MAX_THREADS); 456 457 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 458 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 459 init_task.signal->rlim[RLIMIT_SIGPENDING] = 460 init_task.signal->rlim[RLIMIT_NPROC]; 461 462 for (i = 0; i < UCOUNT_COUNTS; i++) { 463 init_user_ns.ucount_max[i] = max_threads/2; 464 } 465 } 466 467 int __weak arch_dup_task_struct(struct task_struct *dst, 468 struct task_struct *src) 469 { 470 *dst = *src; 471 return 0; 472 } 473 474 void set_task_stack_end_magic(struct task_struct *tsk) 475 { 476 unsigned long *stackend; 477 478 stackend = end_of_stack(tsk); 479 *stackend = STACK_END_MAGIC; /* for overflow detection */ 480 } 481 482 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 483 { 484 struct task_struct *tsk; 485 unsigned long *stack; 486 struct vm_struct *stack_vm_area; 487 int err; 488 489 if (node == NUMA_NO_NODE) 490 node = tsk_fork_get_node(orig); 491 tsk = alloc_task_struct_node(node); 492 if (!tsk) 493 return NULL; 494 495 stack = alloc_thread_stack_node(tsk, node); 496 if (!stack) 497 goto free_tsk; 498 499 stack_vm_area = task_stack_vm_area(tsk); 500 501 err = arch_dup_task_struct(tsk, orig); 502 503 /* 504 * arch_dup_task_struct() clobbers the stack-related fields. Make 505 * sure they're properly initialized before using any stack-related 506 * functions again. 507 */ 508 tsk->stack = stack; 509 #ifdef CONFIG_VMAP_STACK 510 tsk->stack_vm_area = stack_vm_area; 511 #endif 512 #ifdef CONFIG_THREAD_INFO_IN_TASK 513 atomic_set(&tsk->stack_refcount, 1); 514 #endif 515 516 if (err) 517 goto free_stack; 518 519 #ifdef CONFIG_SECCOMP 520 /* 521 * We must handle setting up seccomp filters once we're under 522 * the sighand lock in case orig has changed between now and 523 * then. Until then, filter must be NULL to avoid messing up 524 * the usage counts on the error path calling free_task. 525 */ 526 tsk->seccomp.filter = NULL; 527 #endif 528 529 setup_thread_stack(tsk, orig); 530 clear_user_return_notifier(tsk); 531 clear_tsk_need_resched(tsk); 532 set_task_stack_end_magic(tsk); 533 534 #ifdef CONFIG_CC_STACKPROTECTOR 535 tsk->stack_canary = get_random_int(); 536 #endif 537 538 /* 539 * One for us, one for whoever does the "release_task()" (usually 540 * parent) 541 */ 542 atomic_set(&tsk->usage, 2); 543 #ifdef CONFIG_BLK_DEV_IO_TRACE 544 tsk->btrace_seq = 0; 545 #endif 546 tsk->splice_pipe = NULL; 547 tsk->task_frag.page = NULL; 548 tsk->wake_q.next = NULL; 549 550 account_kernel_stack(tsk, 1); 551 552 kcov_task_init(tsk); 553 554 return tsk; 555 556 free_stack: 557 free_thread_stack(tsk); 558 free_tsk: 559 free_task_struct(tsk); 560 return NULL; 561 } 562 563 #ifdef CONFIG_MMU 564 static __latent_entropy int dup_mmap(struct mm_struct *mm, 565 struct mm_struct *oldmm) 566 { 567 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 568 struct rb_node **rb_link, *rb_parent; 569 int retval; 570 unsigned long charge; 571 LIST_HEAD(uf); 572 573 uprobe_start_dup_mmap(); 574 if (down_write_killable(&oldmm->mmap_sem)) { 575 retval = -EINTR; 576 goto fail_uprobe_end; 577 } 578 flush_cache_dup_mm(oldmm); 579 uprobe_dup_mmap(oldmm, mm); 580 /* 581 * Not linked in yet - no deadlock potential: 582 */ 583 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 584 585 /* No ordering required: file already has been exposed. */ 586 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 587 588 mm->total_vm = oldmm->total_vm; 589 mm->data_vm = oldmm->data_vm; 590 mm->exec_vm = oldmm->exec_vm; 591 mm->stack_vm = oldmm->stack_vm; 592 593 rb_link = &mm->mm_rb.rb_node; 594 rb_parent = NULL; 595 pprev = &mm->mmap; 596 retval = ksm_fork(mm, oldmm); 597 if (retval) 598 goto out; 599 retval = khugepaged_fork(mm, oldmm); 600 if (retval) 601 goto out; 602 603 prev = NULL; 604 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 605 struct file *file; 606 607 if (mpnt->vm_flags & VM_DONTCOPY) { 608 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 609 continue; 610 } 611 charge = 0; 612 if (mpnt->vm_flags & VM_ACCOUNT) { 613 unsigned long len = vma_pages(mpnt); 614 615 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 616 goto fail_nomem; 617 charge = len; 618 } 619 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 620 if (!tmp) 621 goto fail_nomem; 622 *tmp = *mpnt; 623 INIT_LIST_HEAD(&tmp->anon_vma_chain); 624 retval = vma_dup_policy(mpnt, tmp); 625 if (retval) 626 goto fail_nomem_policy; 627 tmp->vm_mm = mm; 628 retval = dup_userfaultfd(tmp, &uf); 629 if (retval) 630 goto fail_nomem_anon_vma_fork; 631 if (anon_vma_fork(tmp, mpnt)) 632 goto fail_nomem_anon_vma_fork; 633 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 634 tmp->vm_next = tmp->vm_prev = NULL; 635 file = tmp->vm_file; 636 if (file) { 637 struct inode *inode = file_inode(file); 638 struct address_space *mapping = file->f_mapping; 639 640 get_file(file); 641 if (tmp->vm_flags & VM_DENYWRITE) 642 atomic_dec(&inode->i_writecount); 643 i_mmap_lock_write(mapping); 644 if (tmp->vm_flags & VM_SHARED) 645 atomic_inc(&mapping->i_mmap_writable); 646 flush_dcache_mmap_lock(mapping); 647 /* insert tmp into the share list, just after mpnt */ 648 vma_interval_tree_insert_after(tmp, mpnt, 649 &mapping->i_mmap); 650 flush_dcache_mmap_unlock(mapping); 651 i_mmap_unlock_write(mapping); 652 } 653 654 /* 655 * Clear hugetlb-related page reserves for children. This only 656 * affects MAP_PRIVATE mappings. Faults generated by the child 657 * are not guaranteed to succeed, even if read-only 658 */ 659 if (is_vm_hugetlb_page(tmp)) 660 reset_vma_resv_huge_pages(tmp); 661 662 /* 663 * Link in the new vma and copy the page table entries. 664 */ 665 *pprev = tmp; 666 pprev = &tmp->vm_next; 667 tmp->vm_prev = prev; 668 prev = tmp; 669 670 __vma_link_rb(mm, tmp, rb_link, rb_parent); 671 rb_link = &tmp->vm_rb.rb_right; 672 rb_parent = &tmp->vm_rb; 673 674 mm->map_count++; 675 retval = copy_page_range(mm, oldmm, mpnt); 676 677 if (tmp->vm_ops && tmp->vm_ops->open) 678 tmp->vm_ops->open(tmp); 679 680 if (retval) 681 goto out; 682 } 683 /* a new mm has just been created */ 684 arch_dup_mmap(oldmm, mm); 685 retval = 0; 686 out: 687 up_write(&mm->mmap_sem); 688 flush_tlb_mm(oldmm); 689 up_write(&oldmm->mmap_sem); 690 dup_userfaultfd_complete(&uf); 691 fail_uprobe_end: 692 uprobe_end_dup_mmap(); 693 return retval; 694 fail_nomem_anon_vma_fork: 695 mpol_put(vma_policy(tmp)); 696 fail_nomem_policy: 697 kmem_cache_free(vm_area_cachep, tmp); 698 fail_nomem: 699 retval = -ENOMEM; 700 vm_unacct_memory(charge); 701 goto out; 702 } 703 704 static inline int mm_alloc_pgd(struct mm_struct *mm) 705 { 706 mm->pgd = pgd_alloc(mm); 707 if (unlikely(!mm->pgd)) 708 return -ENOMEM; 709 return 0; 710 } 711 712 static inline void mm_free_pgd(struct mm_struct *mm) 713 { 714 pgd_free(mm, mm->pgd); 715 } 716 #else 717 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 718 { 719 down_write(&oldmm->mmap_sem); 720 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 721 up_write(&oldmm->mmap_sem); 722 return 0; 723 } 724 #define mm_alloc_pgd(mm) (0) 725 #define mm_free_pgd(mm) 726 #endif /* CONFIG_MMU */ 727 728 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 729 730 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 731 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 732 733 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 734 735 static int __init coredump_filter_setup(char *s) 736 { 737 default_dump_filter = 738 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 739 MMF_DUMP_FILTER_MASK; 740 return 1; 741 } 742 743 __setup("coredump_filter=", coredump_filter_setup); 744 745 #include <linux/init_task.h> 746 747 static void mm_init_aio(struct mm_struct *mm) 748 { 749 #ifdef CONFIG_AIO 750 spin_lock_init(&mm->ioctx_lock); 751 mm->ioctx_table = NULL; 752 #endif 753 } 754 755 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 756 { 757 #ifdef CONFIG_MEMCG 758 mm->owner = p; 759 #endif 760 } 761 762 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 763 struct user_namespace *user_ns) 764 { 765 mm->mmap = NULL; 766 mm->mm_rb = RB_ROOT; 767 mm->vmacache_seqnum = 0; 768 atomic_set(&mm->mm_users, 1); 769 atomic_set(&mm->mm_count, 1); 770 init_rwsem(&mm->mmap_sem); 771 INIT_LIST_HEAD(&mm->mmlist); 772 mm->core_state = NULL; 773 atomic_long_set(&mm->nr_ptes, 0); 774 mm_nr_pmds_init(mm); 775 mm->map_count = 0; 776 mm->locked_vm = 0; 777 mm->pinned_vm = 0; 778 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 779 spin_lock_init(&mm->page_table_lock); 780 mm_init_cpumask(mm); 781 mm_init_aio(mm); 782 mm_init_owner(mm, p); 783 mmu_notifier_mm_init(mm); 784 clear_tlb_flush_pending(mm); 785 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 786 mm->pmd_huge_pte = NULL; 787 #endif 788 789 if (current->mm) { 790 mm->flags = current->mm->flags & MMF_INIT_MASK; 791 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 792 } else { 793 mm->flags = default_dump_filter; 794 mm->def_flags = 0; 795 } 796 797 if (mm_alloc_pgd(mm)) 798 goto fail_nopgd; 799 800 if (init_new_context(p, mm)) 801 goto fail_nocontext; 802 803 mm->user_ns = get_user_ns(user_ns); 804 return mm; 805 806 fail_nocontext: 807 mm_free_pgd(mm); 808 fail_nopgd: 809 free_mm(mm); 810 return NULL; 811 } 812 813 static void check_mm(struct mm_struct *mm) 814 { 815 int i; 816 817 for (i = 0; i < NR_MM_COUNTERS; i++) { 818 long x = atomic_long_read(&mm->rss_stat.count[i]); 819 820 if (unlikely(x)) 821 printk(KERN_ALERT "BUG: Bad rss-counter state " 822 "mm:%p idx:%d val:%ld\n", mm, i, x); 823 } 824 825 if (atomic_long_read(&mm->nr_ptes)) 826 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n", 827 atomic_long_read(&mm->nr_ptes)); 828 if (mm_nr_pmds(mm)) 829 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n", 830 mm_nr_pmds(mm)); 831 832 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 833 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 834 #endif 835 } 836 837 /* 838 * Allocate and initialize an mm_struct. 839 */ 840 struct mm_struct *mm_alloc(void) 841 { 842 struct mm_struct *mm; 843 844 mm = allocate_mm(); 845 if (!mm) 846 return NULL; 847 848 memset(mm, 0, sizeof(*mm)); 849 return mm_init(mm, current, current_user_ns()); 850 } 851 852 /* 853 * Called when the last reference to the mm 854 * is dropped: either by a lazy thread or by 855 * mmput. Free the page directory and the mm. 856 */ 857 void __mmdrop(struct mm_struct *mm) 858 { 859 BUG_ON(mm == &init_mm); 860 mm_free_pgd(mm); 861 destroy_context(mm); 862 mmu_notifier_mm_destroy(mm); 863 check_mm(mm); 864 put_user_ns(mm->user_ns); 865 free_mm(mm); 866 } 867 EXPORT_SYMBOL_GPL(__mmdrop); 868 869 static inline void __mmput(struct mm_struct *mm) 870 { 871 VM_BUG_ON(atomic_read(&mm->mm_users)); 872 873 uprobe_clear_state(mm); 874 exit_aio(mm); 875 ksm_exit(mm); 876 khugepaged_exit(mm); /* must run before exit_mmap */ 877 exit_mmap(mm); 878 mm_put_huge_zero_page(mm); 879 set_mm_exe_file(mm, NULL); 880 if (!list_empty(&mm->mmlist)) { 881 spin_lock(&mmlist_lock); 882 list_del(&mm->mmlist); 883 spin_unlock(&mmlist_lock); 884 } 885 if (mm->binfmt) 886 module_put(mm->binfmt->module); 887 set_bit(MMF_OOM_SKIP, &mm->flags); 888 mmdrop(mm); 889 } 890 891 /* 892 * Decrement the use count and release all resources for an mm. 893 */ 894 void mmput(struct mm_struct *mm) 895 { 896 might_sleep(); 897 898 if (atomic_dec_and_test(&mm->mm_users)) 899 __mmput(mm); 900 } 901 EXPORT_SYMBOL_GPL(mmput); 902 903 #ifdef CONFIG_MMU 904 static void mmput_async_fn(struct work_struct *work) 905 { 906 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work); 907 __mmput(mm); 908 } 909 910 void mmput_async(struct mm_struct *mm) 911 { 912 if (atomic_dec_and_test(&mm->mm_users)) { 913 INIT_WORK(&mm->async_put_work, mmput_async_fn); 914 schedule_work(&mm->async_put_work); 915 } 916 } 917 #endif 918 919 /** 920 * set_mm_exe_file - change a reference to the mm's executable file 921 * 922 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 923 * 924 * Main users are mmput() and sys_execve(). Callers prevent concurrent 925 * invocations: in mmput() nobody alive left, in execve task is single 926 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 927 * mm->exe_file, but does so without using set_mm_exe_file() in order 928 * to do avoid the need for any locks. 929 */ 930 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 931 { 932 struct file *old_exe_file; 933 934 /* 935 * It is safe to dereference the exe_file without RCU as 936 * this function is only called if nobody else can access 937 * this mm -- see comment above for justification. 938 */ 939 old_exe_file = rcu_dereference_raw(mm->exe_file); 940 941 if (new_exe_file) 942 get_file(new_exe_file); 943 rcu_assign_pointer(mm->exe_file, new_exe_file); 944 if (old_exe_file) 945 fput(old_exe_file); 946 } 947 948 /** 949 * get_mm_exe_file - acquire a reference to the mm's executable file 950 * 951 * Returns %NULL if mm has no associated executable file. 952 * User must release file via fput(). 953 */ 954 struct file *get_mm_exe_file(struct mm_struct *mm) 955 { 956 struct file *exe_file; 957 958 rcu_read_lock(); 959 exe_file = rcu_dereference(mm->exe_file); 960 if (exe_file && !get_file_rcu(exe_file)) 961 exe_file = NULL; 962 rcu_read_unlock(); 963 return exe_file; 964 } 965 EXPORT_SYMBOL(get_mm_exe_file); 966 967 /** 968 * get_task_exe_file - acquire a reference to the task's executable file 969 * 970 * Returns %NULL if task's mm (if any) has no associated executable file or 971 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 972 * User must release file via fput(). 973 */ 974 struct file *get_task_exe_file(struct task_struct *task) 975 { 976 struct file *exe_file = NULL; 977 struct mm_struct *mm; 978 979 task_lock(task); 980 mm = task->mm; 981 if (mm) { 982 if (!(task->flags & PF_KTHREAD)) 983 exe_file = get_mm_exe_file(mm); 984 } 985 task_unlock(task); 986 return exe_file; 987 } 988 EXPORT_SYMBOL(get_task_exe_file); 989 990 /** 991 * get_task_mm - acquire a reference to the task's mm 992 * 993 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 994 * this kernel workthread has transiently adopted a user mm with use_mm, 995 * to do its AIO) is not set and if so returns a reference to it, after 996 * bumping up the use count. User must release the mm via mmput() 997 * after use. Typically used by /proc and ptrace. 998 */ 999 struct mm_struct *get_task_mm(struct task_struct *task) 1000 { 1001 struct mm_struct *mm; 1002 1003 task_lock(task); 1004 mm = task->mm; 1005 if (mm) { 1006 if (task->flags & PF_KTHREAD) 1007 mm = NULL; 1008 else 1009 mmget(mm); 1010 } 1011 task_unlock(task); 1012 return mm; 1013 } 1014 EXPORT_SYMBOL_GPL(get_task_mm); 1015 1016 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1017 { 1018 struct mm_struct *mm; 1019 int err; 1020 1021 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1022 if (err) 1023 return ERR_PTR(err); 1024 1025 mm = get_task_mm(task); 1026 if (mm && mm != current->mm && 1027 !ptrace_may_access(task, mode)) { 1028 mmput(mm); 1029 mm = ERR_PTR(-EACCES); 1030 } 1031 mutex_unlock(&task->signal->cred_guard_mutex); 1032 1033 return mm; 1034 } 1035 1036 static void complete_vfork_done(struct task_struct *tsk) 1037 { 1038 struct completion *vfork; 1039 1040 task_lock(tsk); 1041 vfork = tsk->vfork_done; 1042 if (likely(vfork)) { 1043 tsk->vfork_done = NULL; 1044 complete(vfork); 1045 } 1046 task_unlock(tsk); 1047 } 1048 1049 static int wait_for_vfork_done(struct task_struct *child, 1050 struct completion *vfork) 1051 { 1052 int killed; 1053 1054 freezer_do_not_count(); 1055 killed = wait_for_completion_killable(vfork); 1056 freezer_count(); 1057 1058 if (killed) { 1059 task_lock(child); 1060 child->vfork_done = NULL; 1061 task_unlock(child); 1062 } 1063 1064 put_task_struct(child); 1065 return killed; 1066 } 1067 1068 /* Please note the differences between mmput and mm_release. 1069 * mmput is called whenever we stop holding onto a mm_struct, 1070 * error success whatever. 1071 * 1072 * mm_release is called after a mm_struct has been removed 1073 * from the current process. 1074 * 1075 * This difference is important for error handling, when we 1076 * only half set up a mm_struct for a new process and need to restore 1077 * the old one. Because we mmput the new mm_struct before 1078 * restoring the old one. . . 1079 * Eric Biederman 10 January 1998 1080 */ 1081 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1082 { 1083 /* Get rid of any futexes when releasing the mm */ 1084 #ifdef CONFIG_FUTEX 1085 if (unlikely(tsk->robust_list)) { 1086 exit_robust_list(tsk); 1087 tsk->robust_list = NULL; 1088 } 1089 #ifdef CONFIG_COMPAT 1090 if (unlikely(tsk->compat_robust_list)) { 1091 compat_exit_robust_list(tsk); 1092 tsk->compat_robust_list = NULL; 1093 } 1094 #endif 1095 if (unlikely(!list_empty(&tsk->pi_state_list))) 1096 exit_pi_state_list(tsk); 1097 #endif 1098 1099 uprobe_free_utask(tsk); 1100 1101 /* Get rid of any cached register state */ 1102 deactivate_mm(tsk, mm); 1103 1104 /* 1105 * Signal userspace if we're not exiting with a core dump 1106 * because we want to leave the value intact for debugging 1107 * purposes. 1108 */ 1109 if (tsk->clear_child_tid) { 1110 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1111 atomic_read(&mm->mm_users) > 1) { 1112 /* 1113 * We don't check the error code - if userspace has 1114 * not set up a proper pointer then tough luck. 1115 */ 1116 put_user(0, tsk->clear_child_tid); 1117 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1118 1, NULL, NULL, 0); 1119 } 1120 tsk->clear_child_tid = NULL; 1121 } 1122 1123 /* 1124 * All done, finally we can wake up parent and return this mm to him. 1125 * Also kthread_stop() uses this completion for synchronization. 1126 */ 1127 if (tsk->vfork_done) 1128 complete_vfork_done(tsk); 1129 } 1130 1131 /* 1132 * Allocate a new mm structure and copy contents from the 1133 * mm structure of the passed in task structure. 1134 */ 1135 static struct mm_struct *dup_mm(struct task_struct *tsk) 1136 { 1137 struct mm_struct *mm, *oldmm = current->mm; 1138 int err; 1139 1140 mm = allocate_mm(); 1141 if (!mm) 1142 goto fail_nomem; 1143 1144 memcpy(mm, oldmm, sizeof(*mm)); 1145 1146 if (!mm_init(mm, tsk, mm->user_ns)) 1147 goto fail_nomem; 1148 1149 err = dup_mmap(mm, oldmm); 1150 if (err) 1151 goto free_pt; 1152 1153 mm->hiwater_rss = get_mm_rss(mm); 1154 mm->hiwater_vm = mm->total_vm; 1155 1156 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1157 goto free_pt; 1158 1159 return mm; 1160 1161 free_pt: 1162 /* don't put binfmt in mmput, we haven't got module yet */ 1163 mm->binfmt = NULL; 1164 mmput(mm); 1165 1166 fail_nomem: 1167 return NULL; 1168 } 1169 1170 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1171 { 1172 struct mm_struct *mm, *oldmm; 1173 int retval; 1174 1175 tsk->min_flt = tsk->maj_flt = 0; 1176 tsk->nvcsw = tsk->nivcsw = 0; 1177 #ifdef CONFIG_DETECT_HUNG_TASK 1178 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1179 #endif 1180 1181 tsk->mm = NULL; 1182 tsk->active_mm = NULL; 1183 1184 /* 1185 * Are we cloning a kernel thread? 1186 * 1187 * We need to steal a active VM for that.. 1188 */ 1189 oldmm = current->mm; 1190 if (!oldmm) 1191 return 0; 1192 1193 /* initialize the new vmacache entries */ 1194 vmacache_flush(tsk); 1195 1196 if (clone_flags & CLONE_VM) { 1197 mmget(oldmm); 1198 mm = oldmm; 1199 goto good_mm; 1200 } 1201 1202 retval = -ENOMEM; 1203 mm = dup_mm(tsk); 1204 if (!mm) 1205 goto fail_nomem; 1206 1207 good_mm: 1208 tsk->mm = mm; 1209 tsk->active_mm = mm; 1210 return 0; 1211 1212 fail_nomem: 1213 return retval; 1214 } 1215 1216 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1217 { 1218 struct fs_struct *fs = current->fs; 1219 if (clone_flags & CLONE_FS) { 1220 /* tsk->fs is already what we want */ 1221 spin_lock(&fs->lock); 1222 if (fs->in_exec) { 1223 spin_unlock(&fs->lock); 1224 return -EAGAIN; 1225 } 1226 fs->users++; 1227 spin_unlock(&fs->lock); 1228 return 0; 1229 } 1230 tsk->fs = copy_fs_struct(fs); 1231 if (!tsk->fs) 1232 return -ENOMEM; 1233 return 0; 1234 } 1235 1236 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1237 { 1238 struct files_struct *oldf, *newf; 1239 int error = 0; 1240 1241 /* 1242 * A background process may not have any files ... 1243 */ 1244 oldf = current->files; 1245 if (!oldf) 1246 goto out; 1247 1248 if (clone_flags & CLONE_FILES) { 1249 atomic_inc(&oldf->count); 1250 goto out; 1251 } 1252 1253 newf = dup_fd(oldf, &error); 1254 if (!newf) 1255 goto out; 1256 1257 tsk->files = newf; 1258 error = 0; 1259 out: 1260 return error; 1261 } 1262 1263 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1264 { 1265 #ifdef CONFIG_BLOCK 1266 struct io_context *ioc = current->io_context; 1267 struct io_context *new_ioc; 1268 1269 if (!ioc) 1270 return 0; 1271 /* 1272 * Share io context with parent, if CLONE_IO is set 1273 */ 1274 if (clone_flags & CLONE_IO) { 1275 ioc_task_link(ioc); 1276 tsk->io_context = ioc; 1277 } else if (ioprio_valid(ioc->ioprio)) { 1278 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1279 if (unlikely(!new_ioc)) 1280 return -ENOMEM; 1281 1282 new_ioc->ioprio = ioc->ioprio; 1283 put_io_context(new_ioc); 1284 } 1285 #endif 1286 return 0; 1287 } 1288 1289 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1290 { 1291 struct sighand_struct *sig; 1292 1293 if (clone_flags & CLONE_SIGHAND) { 1294 atomic_inc(¤t->sighand->count); 1295 return 0; 1296 } 1297 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1298 rcu_assign_pointer(tsk->sighand, sig); 1299 if (!sig) 1300 return -ENOMEM; 1301 1302 atomic_set(&sig->count, 1); 1303 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1304 return 0; 1305 } 1306 1307 void __cleanup_sighand(struct sighand_struct *sighand) 1308 { 1309 if (atomic_dec_and_test(&sighand->count)) { 1310 signalfd_cleanup(sighand); 1311 /* 1312 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it 1313 * without an RCU grace period, see __lock_task_sighand(). 1314 */ 1315 kmem_cache_free(sighand_cachep, sighand); 1316 } 1317 } 1318 1319 #ifdef CONFIG_POSIX_TIMERS 1320 /* 1321 * Initialize POSIX timer handling for a thread group. 1322 */ 1323 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1324 { 1325 unsigned long cpu_limit; 1326 1327 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1328 if (cpu_limit != RLIM_INFINITY) { 1329 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1330 sig->cputimer.running = true; 1331 } 1332 1333 /* The timer lists. */ 1334 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1335 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1336 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1337 } 1338 #else 1339 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1340 #endif 1341 1342 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1343 { 1344 struct signal_struct *sig; 1345 1346 if (clone_flags & CLONE_THREAD) 1347 return 0; 1348 1349 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1350 tsk->signal = sig; 1351 if (!sig) 1352 return -ENOMEM; 1353 1354 sig->nr_threads = 1; 1355 atomic_set(&sig->live, 1); 1356 atomic_set(&sig->sigcnt, 1); 1357 1358 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1359 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1360 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1361 1362 init_waitqueue_head(&sig->wait_chldexit); 1363 sig->curr_target = tsk; 1364 init_sigpending(&sig->shared_pending); 1365 seqlock_init(&sig->stats_lock); 1366 prev_cputime_init(&sig->prev_cputime); 1367 1368 #ifdef CONFIG_POSIX_TIMERS 1369 INIT_LIST_HEAD(&sig->posix_timers); 1370 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1371 sig->real_timer.function = it_real_fn; 1372 #endif 1373 1374 task_lock(current->group_leader); 1375 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1376 task_unlock(current->group_leader); 1377 1378 posix_cpu_timers_init_group(sig); 1379 1380 tty_audit_fork(sig); 1381 sched_autogroup_fork(sig); 1382 1383 sig->oom_score_adj = current->signal->oom_score_adj; 1384 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1385 1386 mutex_init(&sig->cred_guard_mutex); 1387 1388 return 0; 1389 } 1390 1391 static void copy_seccomp(struct task_struct *p) 1392 { 1393 #ifdef CONFIG_SECCOMP 1394 /* 1395 * Must be called with sighand->lock held, which is common to 1396 * all threads in the group. Holding cred_guard_mutex is not 1397 * needed because this new task is not yet running and cannot 1398 * be racing exec. 1399 */ 1400 assert_spin_locked(¤t->sighand->siglock); 1401 1402 /* Ref-count the new filter user, and assign it. */ 1403 get_seccomp_filter(current); 1404 p->seccomp = current->seccomp; 1405 1406 /* 1407 * Explicitly enable no_new_privs here in case it got set 1408 * between the task_struct being duplicated and holding the 1409 * sighand lock. The seccomp state and nnp must be in sync. 1410 */ 1411 if (task_no_new_privs(current)) 1412 task_set_no_new_privs(p); 1413 1414 /* 1415 * If the parent gained a seccomp mode after copying thread 1416 * flags and between before we held the sighand lock, we have 1417 * to manually enable the seccomp thread flag here. 1418 */ 1419 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1420 set_tsk_thread_flag(p, TIF_SECCOMP); 1421 #endif 1422 } 1423 1424 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1425 { 1426 current->clear_child_tid = tidptr; 1427 1428 return task_pid_vnr(current); 1429 } 1430 1431 static void rt_mutex_init_task(struct task_struct *p) 1432 { 1433 raw_spin_lock_init(&p->pi_lock); 1434 #ifdef CONFIG_RT_MUTEXES 1435 p->pi_waiters = RB_ROOT; 1436 p->pi_waiters_leftmost = NULL; 1437 p->pi_blocked_on = NULL; 1438 #endif 1439 } 1440 1441 #ifdef CONFIG_POSIX_TIMERS 1442 /* 1443 * Initialize POSIX timer handling for a single task. 1444 */ 1445 static void posix_cpu_timers_init(struct task_struct *tsk) 1446 { 1447 tsk->cputime_expires.prof_exp = 0; 1448 tsk->cputime_expires.virt_exp = 0; 1449 tsk->cputime_expires.sched_exp = 0; 1450 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1451 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1452 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1453 } 1454 #else 1455 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1456 #endif 1457 1458 static inline void 1459 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1460 { 1461 task->pids[type].pid = pid; 1462 } 1463 1464 /* 1465 * This creates a new process as a copy of the old one, 1466 * but does not actually start it yet. 1467 * 1468 * It copies the registers, and all the appropriate 1469 * parts of the process environment (as per the clone 1470 * flags). The actual kick-off is left to the caller. 1471 */ 1472 static __latent_entropy struct task_struct *copy_process( 1473 unsigned long clone_flags, 1474 unsigned long stack_start, 1475 unsigned long stack_size, 1476 int __user *child_tidptr, 1477 struct pid *pid, 1478 int trace, 1479 unsigned long tls, 1480 int node) 1481 { 1482 int retval; 1483 struct task_struct *p; 1484 1485 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1486 return ERR_PTR(-EINVAL); 1487 1488 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1489 return ERR_PTR(-EINVAL); 1490 1491 /* 1492 * Thread groups must share signals as well, and detached threads 1493 * can only be started up within the thread group. 1494 */ 1495 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1496 return ERR_PTR(-EINVAL); 1497 1498 /* 1499 * Shared signal handlers imply shared VM. By way of the above, 1500 * thread groups also imply shared VM. Blocking this case allows 1501 * for various simplifications in other code. 1502 */ 1503 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1504 return ERR_PTR(-EINVAL); 1505 1506 /* 1507 * Siblings of global init remain as zombies on exit since they are 1508 * not reaped by their parent (swapper). To solve this and to avoid 1509 * multi-rooted process trees, prevent global and container-inits 1510 * from creating siblings. 1511 */ 1512 if ((clone_flags & CLONE_PARENT) && 1513 current->signal->flags & SIGNAL_UNKILLABLE) 1514 return ERR_PTR(-EINVAL); 1515 1516 /* 1517 * If the new process will be in a different pid or user namespace 1518 * do not allow it to share a thread group with the forking task. 1519 */ 1520 if (clone_flags & CLONE_THREAD) { 1521 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1522 (task_active_pid_ns(current) != 1523 current->nsproxy->pid_ns_for_children)) 1524 return ERR_PTR(-EINVAL); 1525 } 1526 1527 retval = security_task_create(clone_flags); 1528 if (retval) 1529 goto fork_out; 1530 1531 retval = -ENOMEM; 1532 p = dup_task_struct(current, node); 1533 if (!p) 1534 goto fork_out; 1535 1536 ftrace_graph_init_task(p); 1537 1538 rt_mutex_init_task(p); 1539 1540 #ifdef CONFIG_PROVE_LOCKING 1541 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1542 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1543 #endif 1544 retval = -EAGAIN; 1545 if (atomic_read(&p->real_cred->user->processes) >= 1546 task_rlimit(p, RLIMIT_NPROC)) { 1547 if (p->real_cred->user != INIT_USER && 1548 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1549 goto bad_fork_free; 1550 } 1551 current->flags &= ~PF_NPROC_EXCEEDED; 1552 1553 retval = copy_creds(p, clone_flags); 1554 if (retval < 0) 1555 goto bad_fork_free; 1556 1557 /* 1558 * If multiple threads are within copy_process(), then this check 1559 * triggers too late. This doesn't hurt, the check is only there 1560 * to stop root fork bombs. 1561 */ 1562 retval = -EAGAIN; 1563 if (nr_threads >= max_threads) 1564 goto bad_fork_cleanup_count; 1565 1566 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1567 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1568 p->flags |= PF_FORKNOEXEC; 1569 INIT_LIST_HEAD(&p->children); 1570 INIT_LIST_HEAD(&p->sibling); 1571 rcu_copy_process(p); 1572 p->vfork_done = NULL; 1573 spin_lock_init(&p->alloc_lock); 1574 1575 init_sigpending(&p->pending); 1576 1577 p->utime = p->stime = p->gtime = 0; 1578 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1579 p->utimescaled = p->stimescaled = 0; 1580 #endif 1581 prev_cputime_init(&p->prev_cputime); 1582 1583 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1584 seqcount_init(&p->vtime_seqcount); 1585 p->vtime_snap = 0; 1586 p->vtime_snap_whence = VTIME_INACTIVE; 1587 #endif 1588 1589 #if defined(SPLIT_RSS_COUNTING) 1590 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1591 #endif 1592 1593 p->default_timer_slack_ns = current->timer_slack_ns; 1594 1595 task_io_accounting_init(&p->ioac); 1596 acct_clear_integrals(p); 1597 1598 posix_cpu_timers_init(p); 1599 1600 p->start_time = ktime_get_ns(); 1601 p->real_start_time = ktime_get_boot_ns(); 1602 p->io_context = NULL; 1603 p->audit_context = NULL; 1604 cgroup_fork(p); 1605 #ifdef CONFIG_NUMA 1606 p->mempolicy = mpol_dup(p->mempolicy); 1607 if (IS_ERR(p->mempolicy)) { 1608 retval = PTR_ERR(p->mempolicy); 1609 p->mempolicy = NULL; 1610 goto bad_fork_cleanup_threadgroup_lock; 1611 } 1612 #endif 1613 #ifdef CONFIG_CPUSETS 1614 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1615 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1616 seqcount_init(&p->mems_allowed_seq); 1617 #endif 1618 #ifdef CONFIG_TRACE_IRQFLAGS 1619 p->irq_events = 0; 1620 p->hardirqs_enabled = 0; 1621 p->hardirq_enable_ip = 0; 1622 p->hardirq_enable_event = 0; 1623 p->hardirq_disable_ip = _THIS_IP_; 1624 p->hardirq_disable_event = 0; 1625 p->softirqs_enabled = 1; 1626 p->softirq_enable_ip = _THIS_IP_; 1627 p->softirq_enable_event = 0; 1628 p->softirq_disable_ip = 0; 1629 p->softirq_disable_event = 0; 1630 p->hardirq_context = 0; 1631 p->softirq_context = 0; 1632 #endif 1633 1634 p->pagefault_disabled = 0; 1635 1636 #ifdef CONFIG_LOCKDEP 1637 p->lockdep_depth = 0; /* no locks held yet */ 1638 p->curr_chain_key = 0; 1639 p->lockdep_recursion = 0; 1640 #endif 1641 1642 #ifdef CONFIG_DEBUG_MUTEXES 1643 p->blocked_on = NULL; /* not blocked yet */ 1644 #endif 1645 #ifdef CONFIG_BCACHE 1646 p->sequential_io = 0; 1647 p->sequential_io_avg = 0; 1648 #endif 1649 1650 /* Perform scheduler related setup. Assign this task to a CPU. */ 1651 retval = sched_fork(clone_flags, p); 1652 if (retval) 1653 goto bad_fork_cleanup_policy; 1654 1655 retval = perf_event_init_task(p); 1656 if (retval) 1657 goto bad_fork_cleanup_policy; 1658 retval = audit_alloc(p); 1659 if (retval) 1660 goto bad_fork_cleanup_perf; 1661 /* copy all the process information */ 1662 shm_init_task(p); 1663 retval = copy_semundo(clone_flags, p); 1664 if (retval) 1665 goto bad_fork_cleanup_audit; 1666 retval = copy_files(clone_flags, p); 1667 if (retval) 1668 goto bad_fork_cleanup_semundo; 1669 retval = copy_fs(clone_flags, p); 1670 if (retval) 1671 goto bad_fork_cleanup_files; 1672 retval = copy_sighand(clone_flags, p); 1673 if (retval) 1674 goto bad_fork_cleanup_fs; 1675 retval = copy_signal(clone_flags, p); 1676 if (retval) 1677 goto bad_fork_cleanup_sighand; 1678 retval = copy_mm(clone_flags, p); 1679 if (retval) 1680 goto bad_fork_cleanup_signal; 1681 retval = copy_namespaces(clone_flags, p); 1682 if (retval) 1683 goto bad_fork_cleanup_mm; 1684 retval = copy_io(clone_flags, p); 1685 if (retval) 1686 goto bad_fork_cleanup_namespaces; 1687 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1688 if (retval) 1689 goto bad_fork_cleanup_io; 1690 1691 if (pid != &init_struct_pid) { 1692 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1693 if (IS_ERR(pid)) { 1694 retval = PTR_ERR(pid); 1695 goto bad_fork_cleanup_thread; 1696 } 1697 } 1698 1699 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1700 /* 1701 * Clear TID on mm_release()? 1702 */ 1703 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1704 #ifdef CONFIG_BLOCK 1705 p->plug = NULL; 1706 #endif 1707 #ifdef CONFIG_FUTEX 1708 p->robust_list = NULL; 1709 #ifdef CONFIG_COMPAT 1710 p->compat_robust_list = NULL; 1711 #endif 1712 INIT_LIST_HEAD(&p->pi_state_list); 1713 p->pi_state_cache = NULL; 1714 #endif 1715 /* 1716 * sigaltstack should be cleared when sharing the same VM 1717 */ 1718 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1719 sas_ss_reset(p); 1720 1721 /* 1722 * Syscall tracing and stepping should be turned off in the 1723 * child regardless of CLONE_PTRACE. 1724 */ 1725 user_disable_single_step(p); 1726 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1727 #ifdef TIF_SYSCALL_EMU 1728 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1729 #endif 1730 clear_all_latency_tracing(p); 1731 1732 /* ok, now we should be set up.. */ 1733 p->pid = pid_nr(pid); 1734 if (clone_flags & CLONE_THREAD) { 1735 p->exit_signal = -1; 1736 p->group_leader = current->group_leader; 1737 p->tgid = current->tgid; 1738 } else { 1739 if (clone_flags & CLONE_PARENT) 1740 p->exit_signal = current->group_leader->exit_signal; 1741 else 1742 p->exit_signal = (clone_flags & CSIGNAL); 1743 p->group_leader = p; 1744 p->tgid = p->pid; 1745 } 1746 1747 p->nr_dirtied = 0; 1748 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1749 p->dirty_paused_when = 0; 1750 1751 p->pdeath_signal = 0; 1752 INIT_LIST_HEAD(&p->thread_group); 1753 p->task_works = NULL; 1754 1755 cgroup_threadgroup_change_begin(current); 1756 /* 1757 * Ensure that the cgroup subsystem policies allow the new process to be 1758 * forked. It should be noted the the new process's css_set can be changed 1759 * between here and cgroup_post_fork() if an organisation operation is in 1760 * progress. 1761 */ 1762 retval = cgroup_can_fork(p); 1763 if (retval) 1764 goto bad_fork_free_pid; 1765 1766 /* 1767 * Make it visible to the rest of the system, but dont wake it up yet. 1768 * Need tasklist lock for parent etc handling! 1769 */ 1770 write_lock_irq(&tasklist_lock); 1771 1772 /* CLONE_PARENT re-uses the old parent */ 1773 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1774 p->real_parent = current->real_parent; 1775 p->parent_exec_id = current->parent_exec_id; 1776 } else { 1777 p->real_parent = current; 1778 p->parent_exec_id = current->self_exec_id; 1779 } 1780 1781 spin_lock(¤t->sighand->siglock); 1782 1783 /* 1784 * Copy seccomp details explicitly here, in case they were changed 1785 * before holding sighand lock. 1786 */ 1787 copy_seccomp(p); 1788 1789 /* 1790 * Process group and session signals need to be delivered to just the 1791 * parent before the fork or both the parent and the child after the 1792 * fork. Restart if a signal comes in before we add the new process to 1793 * it's process group. 1794 * A fatal signal pending means that current will exit, so the new 1795 * thread can't slip out of an OOM kill (or normal SIGKILL). 1796 */ 1797 recalc_sigpending(); 1798 if (signal_pending(current)) { 1799 spin_unlock(¤t->sighand->siglock); 1800 write_unlock_irq(&tasklist_lock); 1801 retval = -ERESTARTNOINTR; 1802 goto bad_fork_cancel_cgroup; 1803 } 1804 1805 if (likely(p->pid)) { 1806 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1807 1808 init_task_pid(p, PIDTYPE_PID, pid); 1809 if (thread_group_leader(p)) { 1810 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1811 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1812 1813 if (is_child_reaper(pid)) { 1814 ns_of_pid(pid)->child_reaper = p; 1815 p->signal->flags |= SIGNAL_UNKILLABLE; 1816 } 1817 1818 p->signal->leader_pid = pid; 1819 p->signal->tty = tty_kref_get(current->signal->tty); 1820 /* 1821 * Inherit has_child_subreaper flag under the same 1822 * tasklist_lock with adding child to the process tree 1823 * for propagate_has_child_subreaper optimization. 1824 */ 1825 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1826 p->real_parent->signal->is_child_subreaper; 1827 list_add_tail(&p->sibling, &p->real_parent->children); 1828 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1829 attach_pid(p, PIDTYPE_PGID); 1830 attach_pid(p, PIDTYPE_SID); 1831 __this_cpu_inc(process_counts); 1832 } else { 1833 current->signal->nr_threads++; 1834 atomic_inc(¤t->signal->live); 1835 atomic_inc(¤t->signal->sigcnt); 1836 list_add_tail_rcu(&p->thread_group, 1837 &p->group_leader->thread_group); 1838 list_add_tail_rcu(&p->thread_node, 1839 &p->signal->thread_head); 1840 } 1841 attach_pid(p, PIDTYPE_PID); 1842 nr_threads++; 1843 } 1844 1845 total_forks++; 1846 spin_unlock(¤t->sighand->siglock); 1847 syscall_tracepoint_update(p); 1848 write_unlock_irq(&tasklist_lock); 1849 1850 proc_fork_connector(p); 1851 cgroup_post_fork(p); 1852 cgroup_threadgroup_change_end(current); 1853 perf_event_fork(p); 1854 1855 trace_task_newtask(p, clone_flags); 1856 uprobe_copy_process(p, clone_flags); 1857 1858 return p; 1859 1860 bad_fork_cancel_cgroup: 1861 cgroup_cancel_fork(p); 1862 bad_fork_free_pid: 1863 cgroup_threadgroup_change_end(current); 1864 if (pid != &init_struct_pid) 1865 free_pid(pid); 1866 bad_fork_cleanup_thread: 1867 exit_thread(p); 1868 bad_fork_cleanup_io: 1869 if (p->io_context) 1870 exit_io_context(p); 1871 bad_fork_cleanup_namespaces: 1872 exit_task_namespaces(p); 1873 bad_fork_cleanup_mm: 1874 if (p->mm) 1875 mmput(p->mm); 1876 bad_fork_cleanup_signal: 1877 if (!(clone_flags & CLONE_THREAD)) 1878 free_signal_struct(p->signal); 1879 bad_fork_cleanup_sighand: 1880 __cleanup_sighand(p->sighand); 1881 bad_fork_cleanup_fs: 1882 exit_fs(p); /* blocking */ 1883 bad_fork_cleanup_files: 1884 exit_files(p); /* blocking */ 1885 bad_fork_cleanup_semundo: 1886 exit_sem(p); 1887 bad_fork_cleanup_audit: 1888 audit_free(p); 1889 bad_fork_cleanup_perf: 1890 perf_event_free_task(p); 1891 bad_fork_cleanup_policy: 1892 #ifdef CONFIG_NUMA 1893 mpol_put(p->mempolicy); 1894 bad_fork_cleanup_threadgroup_lock: 1895 #endif 1896 delayacct_tsk_free(p); 1897 bad_fork_cleanup_count: 1898 atomic_dec(&p->cred->user->processes); 1899 exit_creds(p); 1900 bad_fork_free: 1901 p->state = TASK_DEAD; 1902 put_task_stack(p); 1903 free_task(p); 1904 fork_out: 1905 return ERR_PTR(retval); 1906 } 1907 1908 static inline void init_idle_pids(struct pid_link *links) 1909 { 1910 enum pid_type type; 1911 1912 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1913 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1914 links[type].pid = &init_struct_pid; 1915 } 1916 } 1917 1918 struct task_struct *fork_idle(int cpu) 1919 { 1920 struct task_struct *task; 1921 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 1922 cpu_to_node(cpu)); 1923 if (!IS_ERR(task)) { 1924 init_idle_pids(task->pids); 1925 init_idle(task, cpu); 1926 } 1927 1928 return task; 1929 } 1930 1931 /* 1932 * Ok, this is the main fork-routine. 1933 * 1934 * It copies the process, and if successful kick-starts 1935 * it and waits for it to finish using the VM if required. 1936 */ 1937 long _do_fork(unsigned long clone_flags, 1938 unsigned long stack_start, 1939 unsigned long stack_size, 1940 int __user *parent_tidptr, 1941 int __user *child_tidptr, 1942 unsigned long tls) 1943 { 1944 struct task_struct *p; 1945 int trace = 0; 1946 long nr; 1947 1948 /* 1949 * Determine whether and which event to report to ptracer. When 1950 * called from kernel_thread or CLONE_UNTRACED is explicitly 1951 * requested, no event is reported; otherwise, report if the event 1952 * for the type of forking is enabled. 1953 */ 1954 if (!(clone_flags & CLONE_UNTRACED)) { 1955 if (clone_flags & CLONE_VFORK) 1956 trace = PTRACE_EVENT_VFORK; 1957 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1958 trace = PTRACE_EVENT_CLONE; 1959 else 1960 trace = PTRACE_EVENT_FORK; 1961 1962 if (likely(!ptrace_event_enabled(current, trace))) 1963 trace = 0; 1964 } 1965 1966 p = copy_process(clone_flags, stack_start, stack_size, 1967 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 1968 add_latent_entropy(); 1969 /* 1970 * Do this prior waking up the new thread - the thread pointer 1971 * might get invalid after that point, if the thread exits quickly. 1972 */ 1973 if (!IS_ERR(p)) { 1974 struct completion vfork; 1975 struct pid *pid; 1976 1977 trace_sched_process_fork(current, p); 1978 1979 pid = get_task_pid(p, PIDTYPE_PID); 1980 nr = pid_vnr(pid); 1981 1982 if (clone_flags & CLONE_PARENT_SETTID) 1983 put_user(nr, parent_tidptr); 1984 1985 if (clone_flags & CLONE_VFORK) { 1986 p->vfork_done = &vfork; 1987 init_completion(&vfork); 1988 get_task_struct(p); 1989 } 1990 1991 wake_up_new_task(p); 1992 1993 /* forking complete and child started to run, tell ptracer */ 1994 if (unlikely(trace)) 1995 ptrace_event_pid(trace, pid); 1996 1997 if (clone_flags & CLONE_VFORK) { 1998 if (!wait_for_vfork_done(p, &vfork)) 1999 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2000 } 2001 2002 put_pid(pid); 2003 } else { 2004 nr = PTR_ERR(p); 2005 } 2006 return nr; 2007 } 2008 2009 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2010 /* For compatibility with architectures that call do_fork directly rather than 2011 * using the syscall entry points below. */ 2012 long do_fork(unsigned long clone_flags, 2013 unsigned long stack_start, 2014 unsigned long stack_size, 2015 int __user *parent_tidptr, 2016 int __user *child_tidptr) 2017 { 2018 return _do_fork(clone_flags, stack_start, stack_size, 2019 parent_tidptr, child_tidptr, 0); 2020 } 2021 #endif 2022 2023 /* 2024 * Create a kernel thread. 2025 */ 2026 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2027 { 2028 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2029 (unsigned long)arg, NULL, NULL, 0); 2030 } 2031 2032 #ifdef __ARCH_WANT_SYS_FORK 2033 SYSCALL_DEFINE0(fork) 2034 { 2035 #ifdef CONFIG_MMU 2036 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2037 #else 2038 /* can not support in nommu mode */ 2039 return -EINVAL; 2040 #endif 2041 } 2042 #endif 2043 2044 #ifdef __ARCH_WANT_SYS_VFORK 2045 SYSCALL_DEFINE0(vfork) 2046 { 2047 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2048 0, NULL, NULL, 0); 2049 } 2050 #endif 2051 2052 #ifdef __ARCH_WANT_SYS_CLONE 2053 #ifdef CONFIG_CLONE_BACKWARDS 2054 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2055 int __user *, parent_tidptr, 2056 unsigned long, tls, 2057 int __user *, child_tidptr) 2058 #elif defined(CONFIG_CLONE_BACKWARDS2) 2059 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2060 int __user *, parent_tidptr, 2061 int __user *, child_tidptr, 2062 unsigned long, tls) 2063 #elif defined(CONFIG_CLONE_BACKWARDS3) 2064 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2065 int, stack_size, 2066 int __user *, parent_tidptr, 2067 int __user *, child_tidptr, 2068 unsigned long, tls) 2069 #else 2070 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2071 int __user *, parent_tidptr, 2072 int __user *, child_tidptr, 2073 unsigned long, tls) 2074 #endif 2075 { 2076 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2077 } 2078 #endif 2079 2080 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2081 { 2082 struct task_struct *leader, *parent, *child; 2083 int res; 2084 2085 read_lock(&tasklist_lock); 2086 leader = top = top->group_leader; 2087 down: 2088 for_each_thread(leader, parent) { 2089 list_for_each_entry(child, &parent->children, sibling) { 2090 res = visitor(child, data); 2091 if (res) { 2092 if (res < 0) 2093 goto out; 2094 leader = child; 2095 goto down; 2096 } 2097 up: 2098 ; 2099 } 2100 } 2101 2102 if (leader != top) { 2103 child = leader; 2104 parent = child->real_parent; 2105 leader = parent->group_leader; 2106 goto up; 2107 } 2108 out: 2109 read_unlock(&tasklist_lock); 2110 } 2111 2112 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2113 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2114 #endif 2115 2116 static void sighand_ctor(void *data) 2117 { 2118 struct sighand_struct *sighand = data; 2119 2120 spin_lock_init(&sighand->siglock); 2121 init_waitqueue_head(&sighand->signalfd_wqh); 2122 } 2123 2124 void __init proc_caches_init(void) 2125 { 2126 sighand_cachep = kmem_cache_create("sighand_cache", 2127 sizeof(struct sighand_struct), 0, 2128 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 2129 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor); 2130 signal_cachep = kmem_cache_create("signal_cache", 2131 sizeof(struct signal_struct), 0, 2132 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2133 NULL); 2134 files_cachep = kmem_cache_create("files_cache", 2135 sizeof(struct files_struct), 0, 2136 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2137 NULL); 2138 fs_cachep = kmem_cache_create("fs_cache", 2139 sizeof(struct fs_struct), 0, 2140 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2141 NULL); 2142 /* 2143 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2144 * whole struct cpumask for the OFFSTACK case. We could change 2145 * this to *only* allocate as much of it as required by the 2146 * maximum number of CPU's we can ever have. The cpumask_allocation 2147 * is at the end of the structure, exactly for that reason. 2148 */ 2149 mm_cachep = kmem_cache_create("mm_struct", 2150 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2151 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, 2152 NULL); 2153 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2154 mmap_init(); 2155 nsproxy_cache_init(); 2156 } 2157 2158 /* 2159 * Check constraints on flags passed to the unshare system call. 2160 */ 2161 static int check_unshare_flags(unsigned long unshare_flags) 2162 { 2163 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2164 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2165 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2166 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2167 return -EINVAL; 2168 /* 2169 * Not implemented, but pretend it works if there is nothing 2170 * to unshare. Note that unsharing the address space or the 2171 * signal handlers also need to unshare the signal queues (aka 2172 * CLONE_THREAD). 2173 */ 2174 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2175 if (!thread_group_empty(current)) 2176 return -EINVAL; 2177 } 2178 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2179 if (atomic_read(¤t->sighand->count) > 1) 2180 return -EINVAL; 2181 } 2182 if (unshare_flags & CLONE_VM) { 2183 if (!current_is_single_threaded()) 2184 return -EINVAL; 2185 } 2186 2187 return 0; 2188 } 2189 2190 /* 2191 * Unshare the filesystem structure if it is being shared 2192 */ 2193 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2194 { 2195 struct fs_struct *fs = current->fs; 2196 2197 if (!(unshare_flags & CLONE_FS) || !fs) 2198 return 0; 2199 2200 /* don't need lock here; in the worst case we'll do useless copy */ 2201 if (fs->users == 1) 2202 return 0; 2203 2204 *new_fsp = copy_fs_struct(fs); 2205 if (!*new_fsp) 2206 return -ENOMEM; 2207 2208 return 0; 2209 } 2210 2211 /* 2212 * Unshare file descriptor table if it is being shared 2213 */ 2214 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2215 { 2216 struct files_struct *fd = current->files; 2217 int error = 0; 2218 2219 if ((unshare_flags & CLONE_FILES) && 2220 (fd && atomic_read(&fd->count) > 1)) { 2221 *new_fdp = dup_fd(fd, &error); 2222 if (!*new_fdp) 2223 return error; 2224 } 2225 2226 return 0; 2227 } 2228 2229 /* 2230 * unshare allows a process to 'unshare' part of the process 2231 * context which was originally shared using clone. copy_* 2232 * functions used by do_fork() cannot be used here directly 2233 * because they modify an inactive task_struct that is being 2234 * constructed. Here we are modifying the current, active, 2235 * task_struct. 2236 */ 2237 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2238 { 2239 struct fs_struct *fs, *new_fs = NULL; 2240 struct files_struct *fd, *new_fd = NULL; 2241 struct cred *new_cred = NULL; 2242 struct nsproxy *new_nsproxy = NULL; 2243 int do_sysvsem = 0; 2244 int err; 2245 2246 /* 2247 * If unsharing a user namespace must also unshare the thread group 2248 * and unshare the filesystem root and working directories. 2249 */ 2250 if (unshare_flags & CLONE_NEWUSER) 2251 unshare_flags |= CLONE_THREAD | CLONE_FS; 2252 /* 2253 * If unsharing vm, must also unshare signal handlers. 2254 */ 2255 if (unshare_flags & CLONE_VM) 2256 unshare_flags |= CLONE_SIGHAND; 2257 /* 2258 * If unsharing a signal handlers, must also unshare the signal queues. 2259 */ 2260 if (unshare_flags & CLONE_SIGHAND) 2261 unshare_flags |= CLONE_THREAD; 2262 /* 2263 * If unsharing namespace, must also unshare filesystem information. 2264 */ 2265 if (unshare_flags & CLONE_NEWNS) 2266 unshare_flags |= CLONE_FS; 2267 2268 err = check_unshare_flags(unshare_flags); 2269 if (err) 2270 goto bad_unshare_out; 2271 /* 2272 * CLONE_NEWIPC must also detach from the undolist: after switching 2273 * to a new ipc namespace, the semaphore arrays from the old 2274 * namespace are unreachable. 2275 */ 2276 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2277 do_sysvsem = 1; 2278 err = unshare_fs(unshare_flags, &new_fs); 2279 if (err) 2280 goto bad_unshare_out; 2281 err = unshare_fd(unshare_flags, &new_fd); 2282 if (err) 2283 goto bad_unshare_cleanup_fs; 2284 err = unshare_userns(unshare_flags, &new_cred); 2285 if (err) 2286 goto bad_unshare_cleanup_fd; 2287 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2288 new_cred, new_fs); 2289 if (err) 2290 goto bad_unshare_cleanup_cred; 2291 2292 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2293 if (do_sysvsem) { 2294 /* 2295 * CLONE_SYSVSEM is equivalent to sys_exit(). 2296 */ 2297 exit_sem(current); 2298 } 2299 if (unshare_flags & CLONE_NEWIPC) { 2300 /* Orphan segments in old ns (see sem above). */ 2301 exit_shm(current); 2302 shm_init_task(current); 2303 } 2304 2305 if (new_nsproxy) 2306 switch_task_namespaces(current, new_nsproxy); 2307 2308 task_lock(current); 2309 2310 if (new_fs) { 2311 fs = current->fs; 2312 spin_lock(&fs->lock); 2313 current->fs = new_fs; 2314 if (--fs->users) 2315 new_fs = NULL; 2316 else 2317 new_fs = fs; 2318 spin_unlock(&fs->lock); 2319 } 2320 2321 if (new_fd) { 2322 fd = current->files; 2323 current->files = new_fd; 2324 new_fd = fd; 2325 } 2326 2327 task_unlock(current); 2328 2329 if (new_cred) { 2330 /* Install the new user namespace */ 2331 commit_creds(new_cred); 2332 new_cred = NULL; 2333 } 2334 } 2335 2336 bad_unshare_cleanup_cred: 2337 if (new_cred) 2338 put_cred(new_cred); 2339 bad_unshare_cleanup_fd: 2340 if (new_fd) 2341 put_files_struct(new_fd); 2342 2343 bad_unshare_cleanup_fs: 2344 if (new_fs) 2345 free_fs_struct(new_fs); 2346 2347 bad_unshare_out: 2348 return err; 2349 } 2350 2351 /* 2352 * Helper to unshare the files of the current task. 2353 * We don't want to expose copy_files internals to 2354 * the exec layer of the kernel. 2355 */ 2356 2357 int unshare_files(struct files_struct **displaced) 2358 { 2359 struct task_struct *task = current; 2360 struct files_struct *copy = NULL; 2361 int error; 2362 2363 error = unshare_fd(CLONE_FILES, ©); 2364 if (error || !copy) { 2365 *displaced = NULL; 2366 return error; 2367 } 2368 *displaced = task->files; 2369 task_lock(task); 2370 task->files = copy; 2371 task_unlock(task); 2372 return 0; 2373 } 2374 2375 int sysctl_max_threads(struct ctl_table *table, int write, 2376 void __user *buffer, size_t *lenp, loff_t *ppos) 2377 { 2378 struct ctl_table t; 2379 int ret; 2380 int threads = max_threads; 2381 int min = MIN_THREADS; 2382 int max = MAX_THREADS; 2383 2384 t = *table; 2385 t.data = &threads; 2386 t.extra1 = &min; 2387 t.extra2 = &max; 2388 2389 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2390 if (ret || !write) 2391 return ret; 2392 2393 set_max_threads(threads); 2394 2395 return 0; 2396 } 2397