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