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/sched/stat.h> 21 #include <linux/sched/task.h> 22 #include <linux/sched/task_stack.h> 23 #include <linux/sched/cputime.h> 24 #include <linux/rtmutex.h> 25 #include <linux/init.h> 26 #include <linux/unistd.h> 27 #include <linux/module.h> 28 #include <linux/vmalloc.h> 29 #include <linux/completion.h> 30 #include <linux/personality.h> 31 #include <linux/mempolicy.h> 32 #include <linux/sem.h> 33 #include <linux/file.h> 34 #include <linux/fdtable.h> 35 #include <linux/iocontext.h> 36 #include <linux/key.h> 37 #include <linux/binfmts.h> 38 #include <linux/mman.h> 39 #include <linux/mmu_notifier.h> 40 #include <linux/hmm.h> 41 #include <linux/fs.h> 42 #include <linux/mm.h> 43 #include <linux/vmacache.h> 44 #include <linux/nsproxy.h> 45 #include <linux/capability.h> 46 #include <linux/cpu.h> 47 #include <linux/cgroup.h> 48 #include <linux/security.h> 49 #include <linux/hugetlb.h> 50 #include <linux/seccomp.h> 51 #include <linux/swap.h> 52 #include <linux/syscalls.h> 53 #include <linux/jiffies.h> 54 #include <linux/futex.h> 55 #include <linux/compat.h> 56 #include <linux/kthread.h> 57 #include <linux/task_io_accounting_ops.h> 58 #include <linux/rcupdate.h> 59 #include <linux/ptrace.h> 60 #include <linux/mount.h> 61 #include <linux/audit.h> 62 #include <linux/memcontrol.h> 63 #include <linux/ftrace.h> 64 #include <linux/proc_fs.h> 65 #include <linux/profile.h> 66 #include <linux/rmap.h> 67 #include <linux/ksm.h> 68 #include <linux/acct.h> 69 #include <linux/userfaultfd_k.h> 70 #include <linux/tsacct_kern.h> 71 #include <linux/cn_proc.h> 72 #include <linux/freezer.h> 73 #include <linux/delayacct.h> 74 #include <linux/taskstats_kern.h> 75 #include <linux/random.h> 76 #include <linux/tty.h> 77 #include <linux/blkdev.h> 78 #include <linux/fs_struct.h> 79 #include <linux/magic.h> 80 #include <linux/sched/mm.h> 81 #include <linux/perf_event.h> 82 #include <linux/posix-timers.h> 83 #include <linux/user-return-notifier.h> 84 #include <linux/oom.h> 85 #include <linux/khugepaged.h> 86 #include <linux/signalfd.h> 87 #include <linux/uprobes.h> 88 #include <linux/aio.h> 89 #include <linux/compiler.h> 90 #include <linux/sysctl.h> 91 #include <linux/kcov.h> 92 #include <linux/livepatch.h> 93 #include <linux/thread_info.h> 94 95 #include <asm/pgtable.h> 96 #include <asm/pgalloc.h> 97 #include <linux/uaccess.h> 98 #include <asm/mmu_context.h> 99 #include <asm/cacheflush.h> 100 #include <asm/tlbflush.h> 101 102 #include <trace/events/sched.h> 103 104 #define CREATE_TRACE_POINTS 105 #include <trace/events/task.h> 106 107 /* 108 * Minimum number of threads to boot the kernel 109 */ 110 #define MIN_THREADS 20 111 112 /* 113 * Maximum number of threads 114 */ 115 #define MAX_THREADS FUTEX_TID_MASK 116 117 /* 118 * Protected counters by write_lock_irq(&tasklist_lock) 119 */ 120 unsigned long total_forks; /* Handle normal Linux uptimes. */ 121 int nr_threads; /* The idle threads do not count.. */ 122 123 int max_threads; /* tunable limit on nr_threads */ 124 125 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 126 127 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 128 129 #ifdef CONFIG_PROVE_RCU 130 int lockdep_tasklist_lock_is_held(void) 131 { 132 return lockdep_is_held(&tasklist_lock); 133 } 134 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 135 #endif /* #ifdef CONFIG_PROVE_RCU */ 136 137 int nr_processes(void) 138 { 139 int cpu; 140 int total = 0; 141 142 for_each_possible_cpu(cpu) 143 total += per_cpu(process_counts, cpu); 144 145 return total; 146 } 147 148 void __weak arch_release_task_struct(struct task_struct *tsk) 149 { 150 } 151 152 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 153 static struct kmem_cache *task_struct_cachep; 154 155 static inline struct task_struct *alloc_task_struct_node(int node) 156 { 157 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 158 } 159 160 static inline void free_task_struct(struct task_struct *tsk) 161 { 162 kmem_cache_free(task_struct_cachep, tsk); 163 } 164 #endif 165 166 void __weak arch_release_thread_stack(unsigned long *stack) 167 { 168 } 169 170 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR 171 172 /* 173 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 174 * kmemcache based allocator. 175 */ 176 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) 177 178 #ifdef CONFIG_VMAP_STACK 179 /* 180 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB 181 * flush. Try to minimize the number of calls by caching stacks. 182 */ 183 #define NR_CACHED_STACKS 2 184 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); 185 186 static int free_vm_stack_cache(unsigned int cpu) 187 { 188 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu); 189 int i; 190 191 for (i = 0; i < NR_CACHED_STACKS; i++) { 192 struct vm_struct *vm_stack = cached_vm_stacks[i]; 193 194 if (!vm_stack) 195 continue; 196 197 vfree(vm_stack->addr); 198 cached_vm_stacks[i] = NULL; 199 } 200 201 return 0; 202 } 203 #endif 204 205 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 206 { 207 #ifdef CONFIG_VMAP_STACK 208 void *stack; 209 int i; 210 211 for (i = 0; i < NR_CACHED_STACKS; i++) { 212 struct vm_struct *s; 213 214 s = this_cpu_xchg(cached_stacks[i], NULL); 215 216 if (!s) 217 continue; 218 219 /* Clear stale pointers from reused stack. */ 220 memset(s->addr, 0, THREAD_SIZE); 221 222 tsk->stack_vm_area = s; 223 return s->addr; 224 } 225 226 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, 227 VMALLOC_START, VMALLOC_END, 228 THREADINFO_GFP, 229 PAGE_KERNEL, 230 0, node, __builtin_return_address(0)); 231 232 /* 233 * We can't call find_vm_area() in interrupt context, and 234 * free_thread_stack() can be called in interrupt context, 235 * so cache the vm_struct. 236 */ 237 if (stack) 238 tsk->stack_vm_area = find_vm_area(stack); 239 return stack; 240 #else 241 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 242 THREAD_SIZE_ORDER); 243 244 return page ? page_address(page) : NULL; 245 #endif 246 } 247 248 static inline void free_thread_stack(struct task_struct *tsk) 249 { 250 #ifdef CONFIG_VMAP_STACK 251 if (task_stack_vm_area(tsk)) { 252 int i; 253 254 for (i = 0; i < NR_CACHED_STACKS; i++) { 255 if (this_cpu_cmpxchg(cached_stacks[i], 256 NULL, tsk->stack_vm_area) != NULL) 257 continue; 258 259 return; 260 } 261 262 vfree_atomic(tsk->stack); 263 return; 264 } 265 #endif 266 267 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); 268 } 269 # else 270 static struct kmem_cache *thread_stack_cache; 271 272 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, 273 int node) 274 { 275 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); 276 } 277 278 static void free_thread_stack(struct task_struct *tsk) 279 { 280 kmem_cache_free(thread_stack_cache, tsk->stack); 281 } 282 283 void thread_stack_cache_init(void) 284 { 285 thread_stack_cache = kmem_cache_create_usercopy("thread_stack", 286 THREAD_SIZE, THREAD_SIZE, 0, 0, 287 THREAD_SIZE, NULL); 288 BUG_ON(thread_stack_cache == NULL); 289 } 290 # endif 291 #endif 292 293 /* SLAB cache for signal_struct structures (tsk->signal) */ 294 static struct kmem_cache *signal_cachep; 295 296 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 297 struct kmem_cache *sighand_cachep; 298 299 /* SLAB cache for files_struct structures (tsk->files) */ 300 struct kmem_cache *files_cachep; 301 302 /* SLAB cache for fs_struct structures (tsk->fs) */ 303 struct kmem_cache *fs_cachep; 304 305 /* SLAB cache for vm_area_struct structures */ 306 struct kmem_cache *vm_area_cachep; 307 308 /* SLAB cache for mm_struct structures (tsk->mm) */ 309 static struct kmem_cache *mm_cachep; 310 311 static void account_kernel_stack(struct task_struct *tsk, int account) 312 { 313 void *stack = task_stack_page(tsk); 314 struct vm_struct *vm = task_stack_vm_area(tsk); 315 316 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0); 317 318 if (vm) { 319 int i; 320 321 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE); 322 323 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { 324 mod_zone_page_state(page_zone(vm->pages[i]), 325 NR_KERNEL_STACK_KB, 326 PAGE_SIZE / 1024 * account); 327 } 328 329 /* All stack pages belong to the same memcg. */ 330 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB, 331 account * (THREAD_SIZE / 1024)); 332 } else { 333 /* 334 * All stack pages are in the same zone and belong to the 335 * same memcg. 336 */ 337 struct page *first_page = virt_to_page(stack); 338 339 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, 340 THREAD_SIZE / 1024 * account); 341 342 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, 343 account * (THREAD_SIZE / 1024)); 344 } 345 } 346 347 static void release_task_stack(struct task_struct *tsk) 348 { 349 if (WARN_ON(tsk->state != TASK_DEAD)) 350 return; /* Better to leak the stack than to free prematurely */ 351 352 account_kernel_stack(tsk, -1); 353 arch_release_thread_stack(tsk->stack); 354 free_thread_stack(tsk); 355 tsk->stack = NULL; 356 #ifdef CONFIG_VMAP_STACK 357 tsk->stack_vm_area = NULL; 358 #endif 359 } 360 361 #ifdef CONFIG_THREAD_INFO_IN_TASK 362 void put_task_stack(struct task_struct *tsk) 363 { 364 if (atomic_dec_and_test(&tsk->stack_refcount)) 365 release_task_stack(tsk); 366 } 367 #endif 368 369 void free_task(struct task_struct *tsk) 370 { 371 #ifndef CONFIG_THREAD_INFO_IN_TASK 372 /* 373 * The task is finally done with both the stack and thread_info, 374 * so free both. 375 */ 376 release_task_stack(tsk); 377 #else 378 /* 379 * If the task had a separate stack allocation, it should be gone 380 * by now. 381 */ 382 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0); 383 #endif 384 rt_mutex_debug_task_free(tsk); 385 ftrace_graph_exit_task(tsk); 386 put_seccomp_filter(tsk); 387 arch_release_task_struct(tsk); 388 if (tsk->flags & PF_KTHREAD) 389 free_kthread_struct(tsk); 390 free_task_struct(tsk); 391 } 392 EXPORT_SYMBOL(free_task); 393 394 #ifdef CONFIG_MMU 395 static __latent_entropy int dup_mmap(struct mm_struct *mm, 396 struct mm_struct *oldmm) 397 { 398 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 399 struct rb_node **rb_link, *rb_parent; 400 int retval; 401 unsigned long charge; 402 LIST_HEAD(uf); 403 404 uprobe_start_dup_mmap(); 405 if (down_write_killable(&oldmm->mmap_sem)) { 406 retval = -EINTR; 407 goto fail_uprobe_end; 408 } 409 flush_cache_dup_mm(oldmm); 410 uprobe_dup_mmap(oldmm, mm); 411 /* 412 * Not linked in yet - no deadlock potential: 413 */ 414 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 415 416 /* No ordering required: file already has been exposed. */ 417 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 418 419 mm->total_vm = oldmm->total_vm; 420 mm->data_vm = oldmm->data_vm; 421 mm->exec_vm = oldmm->exec_vm; 422 mm->stack_vm = oldmm->stack_vm; 423 424 rb_link = &mm->mm_rb.rb_node; 425 rb_parent = NULL; 426 pprev = &mm->mmap; 427 retval = ksm_fork(mm, oldmm); 428 if (retval) 429 goto out; 430 retval = khugepaged_fork(mm, oldmm); 431 if (retval) 432 goto out; 433 434 prev = NULL; 435 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 436 struct file *file; 437 438 if (mpnt->vm_flags & VM_DONTCOPY) { 439 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 440 continue; 441 } 442 charge = 0; 443 /* 444 * Don't duplicate many vmas if we've been oom-killed (for 445 * example) 446 */ 447 if (fatal_signal_pending(current)) { 448 retval = -EINTR; 449 goto out; 450 } 451 if (mpnt->vm_flags & VM_ACCOUNT) { 452 unsigned long len = vma_pages(mpnt); 453 454 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 455 goto fail_nomem; 456 charge = len; 457 } 458 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 459 if (!tmp) 460 goto fail_nomem; 461 *tmp = *mpnt; 462 INIT_LIST_HEAD(&tmp->anon_vma_chain); 463 retval = vma_dup_policy(mpnt, tmp); 464 if (retval) 465 goto fail_nomem_policy; 466 tmp->vm_mm = mm; 467 retval = dup_userfaultfd(tmp, &uf); 468 if (retval) 469 goto fail_nomem_anon_vma_fork; 470 if (tmp->vm_flags & VM_WIPEONFORK) { 471 /* VM_WIPEONFORK gets a clean slate in the child. */ 472 tmp->anon_vma = NULL; 473 if (anon_vma_prepare(tmp)) 474 goto fail_nomem_anon_vma_fork; 475 } else if (anon_vma_fork(tmp, mpnt)) 476 goto fail_nomem_anon_vma_fork; 477 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); 478 tmp->vm_next = tmp->vm_prev = NULL; 479 file = tmp->vm_file; 480 if (file) { 481 struct inode *inode = file_inode(file); 482 struct address_space *mapping = file->f_mapping; 483 484 get_file(file); 485 if (tmp->vm_flags & VM_DENYWRITE) 486 atomic_dec(&inode->i_writecount); 487 i_mmap_lock_write(mapping); 488 if (tmp->vm_flags & VM_SHARED) 489 atomic_inc(&mapping->i_mmap_writable); 490 flush_dcache_mmap_lock(mapping); 491 /* insert tmp into the share list, just after mpnt */ 492 vma_interval_tree_insert_after(tmp, mpnt, 493 &mapping->i_mmap); 494 flush_dcache_mmap_unlock(mapping); 495 i_mmap_unlock_write(mapping); 496 } 497 498 /* 499 * Clear hugetlb-related page reserves for children. This only 500 * affects MAP_PRIVATE mappings. Faults generated by the child 501 * are not guaranteed to succeed, even if read-only 502 */ 503 if (is_vm_hugetlb_page(tmp)) 504 reset_vma_resv_huge_pages(tmp); 505 506 /* 507 * Link in the new vma and copy the page table entries. 508 */ 509 *pprev = tmp; 510 pprev = &tmp->vm_next; 511 tmp->vm_prev = prev; 512 prev = tmp; 513 514 __vma_link_rb(mm, tmp, rb_link, rb_parent); 515 rb_link = &tmp->vm_rb.rb_right; 516 rb_parent = &tmp->vm_rb; 517 518 mm->map_count++; 519 if (!(tmp->vm_flags & VM_WIPEONFORK)) 520 retval = copy_page_range(mm, oldmm, mpnt); 521 522 if (tmp->vm_ops && tmp->vm_ops->open) 523 tmp->vm_ops->open(tmp); 524 525 if (retval) 526 goto out; 527 } 528 /* a new mm has just been created */ 529 arch_dup_mmap(oldmm, mm); 530 retval = 0; 531 out: 532 up_write(&mm->mmap_sem); 533 flush_tlb_mm(oldmm); 534 up_write(&oldmm->mmap_sem); 535 dup_userfaultfd_complete(&uf); 536 fail_uprobe_end: 537 uprobe_end_dup_mmap(); 538 return retval; 539 fail_nomem_anon_vma_fork: 540 mpol_put(vma_policy(tmp)); 541 fail_nomem_policy: 542 kmem_cache_free(vm_area_cachep, tmp); 543 fail_nomem: 544 retval = -ENOMEM; 545 vm_unacct_memory(charge); 546 goto out; 547 } 548 549 static inline int mm_alloc_pgd(struct mm_struct *mm) 550 { 551 mm->pgd = pgd_alloc(mm); 552 if (unlikely(!mm->pgd)) 553 return -ENOMEM; 554 return 0; 555 } 556 557 static inline void mm_free_pgd(struct mm_struct *mm) 558 { 559 pgd_free(mm, mm->pgd); 560 } 561 #else 562 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 563 { 564 down_write(&oldmm->mmap_sem); 565 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm)); 566 up_write(&oldmm->mmap_sem); 567 return 0; 568 } 569 #define mm_alloc_pgd(mm) (0) 570 #define mm_free_pgd(mm) 571 #endif /* CONFIG_MMU */ 572 573 static void check_mm(struct mm_struct *mm) 574 { 575 int i; 576 577 for (i = 0; i < NR_MM_COUNTERS; i++) { 578 long x = atomic_long_read(&mm->rss_stat.count[i]); 579 580 if (unlikely(x)) 581 printk(KERN_ALERT "BUG: Bad rss-counter state " 582 "mm:%p idx:%d val:%ld\n", mm, i, x); 583 } 584 585 if (mm_pgtables_bytes(mm)) 586 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", 587 mm_pgtables_bytes(mm)); 588 589 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 590 VM_BUG_ON_MM(mm->pmd_huge_pte, mm); 591 #endif 592 } 593 594 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 595 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 596 597 /* 598 * Called when the last reference to the mm 599 * is dropped: either by a lazy thread or by 600 * mmput. Free the page directory and the mm. 601 */ 602 void __mmdrop(struct mm_struct *mm) 603 { 604 BUG_ON(mm == &init_mm); 605 WARN_ON_ONCE(mm == current->mm); 606 WARN_ON_ONCE(mm == current->active_mm); 607 mm_free_pgd(mm); 608 destroy_context(mm); 609 hmm_mm_destroy(mm); 610 mmu_notifier_mm_destroy(mm); 611 check_mm(mm); 612 put_user_ns(mm->user_ns); 613 free_mm(mm); 614 } 615 EXPORT_SYMBOL_GPL(__mmdrop); 616 617 static void mmdrop_async_fn(struct work_struct *work) 618 { 619 struct mm_struct *mm; 620 621 mm = container_of(work, struct mm_struct, async_put_work); 622 __mmdrop(mm); 623 } 624 625 static void mmdrop_async(struct mm_struct *mm) 626 { 627 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 628 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 629 schedule_work(&mm->async_put_work); 630 } 631 } 632 633 static inline void free_signal_struct(struct signal_struct *sig) 634 { 635 taskstats_tgid_free(sig); 636 sched_autogroup_exit(sig); 637 /* 638 * __mmdrop is not safe to call from softirq context on x86 due to 639 * pgd_dtor so postpone it to the async context 640 */ 641 if (sig->oom_mm) 642 mmdrop_async(sig->oom_mm); 643 kmem_cache_free(signal_cachep, sig); 644 } 645 646 static inline void put_signal_struct(struct signal_struct *sig) 647 { 648 if (atomic_dec_and_test(&sig->sigcnt)) 649 free_signal_struct(sig); 650 } 651 652 void __put_task_struct(struct task_struct *tsk) 653 { 654 WARN_ON(!tsk->exit_state); 655 WARN_ON(atomic_read(&tsk->usage)); 656 WARN_ON(tsk == current); 657 658 cgroup_free(tsk); 659 task_numa_free(tsk); 660 security_task_free(tsk); 661 exit_creds(tsk); 662 delayacct_tsk_free(tsk); 663 put_signal_struct(tsk->signal); 664 665 if (!profile_handoff_task(tsk)) 666 free_task(tsk); 667 } 668 EXPORT_SYMBOL_GPL(__put_task_struct); 669 670 void __init __weak arch_task_cache_init(void) { } 671 672 /* 673 * set_max_threads 674 */ 675 static void set_max_threads(unsigned int max_threads_suggested) 676 { 677 u64 threads; 678 679 /* 680 * The number of threads shall be limited such that the thread 681 * structures may only consume a small part of the available memory. 682 */ 683 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 684 threads = MAX_THREADS; 685 else 686 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 687 (u64) THREAD_SIZE * 8UL); 688 689 if (threads > max_threads_suggested) 690 threads = max_threads_suggested; 691 692 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 693 } 694 695 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 696 /* Initialized by the architecture: */ 697 int arch_task_struct_size __read_mostly; 698 #endif 699 700 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 701 { 702 /* Fetch thread_struct whitelist for the architecture. */ 703 arch_thread_struct_whitelist(offset, size); 704 705 /* 706 * Handle zero-sized whitelist or empty thread_struct, otherwise 707 * adjust offset to position of thread_struct in task_struct. 708 */ 709 if (unlikely(*size == 0)) 710 *offset = 0; 711 else 712 *offset += offsetof(struct task_struct, thread); 713 } 714 715 void __init fork_init(void) 716 { 717 int i; 718 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 719 #ifndef ARCH_MIN_TASKALIGN 720 #define ARCH_MIN_TASKALIGN 0 721 #endif 722 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 723 unsigned long useroffset, usersize; 724 725 /* create a slab on which task_structs can be allocated */ 726 task_struct_whitelist(&useroffset, &usersize); 727 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 728 arch_task_struct_size, align, 729 SLAB_PANIC|SLAB_ACCOUNT, 730 useroffset, usersize, NULL); 731 #endif 732 733 /* do the arch specific task caches init */ 734 arch_task_cache_init(); 735 736 set_max_threads(MAX_THREADS); 737 738 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 739 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 740 init_task.signal->rlim[RLIMIT_SIGPENDING] = 741 init_task.signal->rlim[RLIMIT_NPROC]; 742 743 for (i = 0; i < UCOUNT_COUNTS; i++) { 744 init_user_ns.ucount_max[i] = max_threads/2; 745 } 746 747 #ifdef CONFIG_VMAP_STACK 748 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 749 NULL, free_vm_stack_cache); 750 #endif 751 752 lockdep_init_task(&init_task); 753 } 754 755 int __weak arch_dup_task_struct(struct task_struct *dst, 756 struct task_struct *src) 757 { 758 *dst = *src; 759 return 0; 760 } 761 762 void set_task_stack_end_magic(struct task_struct *tsk) 763 { 764 unsigned long *stackend; 765 766 stackend = end_of_stack(tsk); 767 *stackend = STACK_END_MAGIC; /* for overflow detection */ 768 } 769 770 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 771 { 772 struct task_struct *tsk; 773 unsigned long *stack; 774 struct vm_struct *stack_vm_area; 775 int err; 776 777 if (node == NUMA_NO_NODE) 778 node = tsk_fork_get_node(orig); 779 tsk = alloc_task_struct_node(node); 780 if (!tsk) 781 return NULL; 782 783 stack = alloc_thread_stack_node(tsk, node); 784 if (!stack) 785 goto free_tsk; 786 787 stack_vm_area = task_stack_vm_area(tsk); 788 789 err = arch_dup_task_struct(tsk, orig); 790 791 /* 792 * arch_dup_task_struct() clobbers the stack-related fields. Make 793 * sure they're properly initialized before using any stack-related 794 * functions again. 795 */ 796 tsk->stack = stack; 797 #ifdef CONFIG_VMAP_STACK 798 tsk->stack_vm_area = stack_vm_area; 799 #endif 800 #ifdef CONFIG_THREAD_INFO_IN_TASK 801 atomic_set(&tsk->stack_refcount, 1); 802 #endif 803 804 if (err) 805 goto free_stack; 806 807 #ifdef CONFIG_SECCOMP 808 /* 809 * We must handle setting up seccomp filters once we're under 810 * the sighand lock in case orig has changed between now and 811 * then. Until then, filter must be NULL to avoid messing up 812 * the usage counts on the error path calling free_task. 813 */ 814 tsk->seccomp.filter = NULL; 815 #endif 816 817 setup_thread_stack(tsk, orig); 818 clear_user_return_notifier(tsk); 819 clear_tsk_need_resched(tsk); 820 set_task_stack_end_magic(tsk); 821 822 #ifdef CONFIG_STACKPROTECTOR 823 tsk->stack_canary = get_random_canary(); 824 #endif 825 826 /* 827 * One for us, one for whoever does the "release_task()" (usually 828 * parent) 829 */ 830 atomic_set(&tsk->usage, 2); 831 #ifdef CONFIG_BLK_DEV_IO_TRACE 832 tsk->btrace_seq = 0; 833 #endif 834 tsk->splice_pipe = NULL; 835 tsk->task_frag.page = NULL; 836 tsk->wake_q.next = NULL; 837 838 account_kernel_stack(tsk, 1); 839 840 kcov_task_init(tsk); 841 842 #ifdef CONFIG_FAULT_INJECTION 843 tsk->fail_nth = 0; 844 #endif 845 846 return tsk; 847 848 free_stack: 849 free_thread_stack(tsk); 850 free_tsk: 851 free_task_struct(tsk); 852 return NULL; 853 } 854 855 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 856 857 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 858 859 static int __init coredump_filter_setup(char *s) 860 { 861 default_dump_filter = 862 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 863 MMF_DUMP_FILTER_MASK; 864 return 1; 865 } 866 867 __setup("coredump_filter=", coredump_filter_setup); 868 869 #include <linux/init_task.h> 870 871 static void mm_init_aio(struct mm_struct *mm) 872 { 873 #ifdef CONFIG_AIO 874 spin_lock_init(&mm->ioctx_lock); 875 mm->ioctx_table = NULL; 876 #endif 877 } 878 879 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 880 { 881 #ifdef CONFIG_MEMCG 882 mm->owner = p; 883 #endif 884 } 885 886 static void mm_init_uprobes_state(struct mm_struct *mm) 887 { 888 #ifdef CONFIG_UPROBES 889 mm->uprobes_state.xol_area = NULL; 890 #endif 891 } 892 893 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 894 struct user_namespace *user_ns) 895 { 896 mm->mmap = NULL; 897 mm->mm_rb = RB_ROOT; 898 mm->vmacache_seqnum = 0; 899 atomic_set(&mm->mm_users, 1); 900 atomic_set(&mm->mm_count, 1); 901 init_rwsem(&mm->mmap_sem); 902 INIT_LIST_HEAD(&mm->mmlist); 903 mm->core_state = NULL; 904 mm_pgtables_bytes_init(mm); 905 mm->map_count = 0; 906 mm->locked_vm = 0; 907 mm->pinned_vm = 0; 908 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 909 spin_lock_init(&mm->page_table_lock); 910 spin_lock_init(&mm->arg_lock); 911 mm_init_cpumask(mm); 912 mm_init_aio(mm); 913 mm_init_owner(mm, p); 914 RCU_INIT_POINTER(mm->exe_file, NULL); 915 mmu_notifier_mm_init(mm); 916 hmm_mm_init(mm); 917 init_tlb_flush_pending(mm); 918 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 919 mm->pmd_huge_pte = NULL; 920 #endif 921 mm_init_uprobes_state(mm); 922 923 if (current->mm) { 924 mm->flags = current->mm->flags & MMF_INIT_MASK; 925 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 926 } else { 927 mm->flags = default_dump_filter; 928 mm->def_flags = 0; 929 } 930 931 if (mm_alloc_pgd(mm)) 932 goto fail_nopgd; 933 934 if (init_new_context(p, mm)) 935 goto fail_nocontext; 936 937 mm->user_ns = get_user_ns(user_ns); 938 return mm; 939 940 fail_nocontext: 941 mm_free_pgd(mm); 942 fail_nopgd: 943 free_mm(mm); 944 return NULL; 945 } 946 947 /* 948 * Allocate and initialize an mm_struct. 949 */ 950 struct mm_struct *mm_alloc(void) 951 { 952 struct mm_struct *mm; 953 954 mm = allocate_mm(); 955 if (!mm) 956 return NULL; 957 958 memset(mm, 0, sizeof(*mm)); 959 return mm_init(mm, current, current_user_ns()); 960 } 961 962 static inline void __mmput(struct mm_struct *mm) 963 { 964 VM_BUG_ON(atomic_read(&mm->mm_users)); 965 966 uprobe_clear_state(mm); 967 exit_aio(mm); 968 ksm_exit(mm); 969 khugepaged_exit(mm); /* must run before exit_mmap */ 970 exit_mmap(mm); 971 mm_put_huge_zero_page(mm); 972 set_mm_exe_file(mm, NULL); 973 if (!list_empty(&mm->mmlist)) { 974 spin_lock(&mmlist_lock); 975 list_del(&mm->mmlist); 976 spin_unlock(&mmlist_lock); 977 } 978 if (mm->binfmt) 979 module_put(mm->binfmt->module); 980 mmdrop(mm); 981 } 982 983 /* 984 * Decrement the use count and release all resources for an mm. 985 */ 986 void mmput(struct mm_struct *mm) 987 { 988 might_sleep(); 989 990 if (atomic_dec_and_test(&mm->mm_users)) 991 __mmput(mm); 992 } 993 EXPORT_SYMBOL_GPL(mmput); 994 995 #ifdef CONFIG_MMU 996 static void mmput_async_fn(struct work_struct *work) 997 { 998 struct mm_struct *mm = container_of(work, struct mm_struct, 999 async_put_work); 1000 1001 __mmput(mm); 1002 } 1003 1004 void mmput_async(struct mm_struct *mm) 1005 { 1006 if (atomic_dec_and_test(&mm->mm_users)) { 1007 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1008 schedule_work(&mm->async_put_work); 1009 } 1010 } 1011 #endif 1012 1013 /** 1014 * set_mm_exe_file - change a reference to the mm's executable file 1015 * 1016 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1017 * 1018 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1019 * invocations: in mmput() nobody alive left, in execve task is single 1020 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1021 * mm->exe_file, but does so without using set_mm_exe_file() in order 1022 * to do avoid the need for any locks. 1023 */ 1024 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1025 { 1026 struct file *old_exe_file; 1027 1028 /* 1029 * It is safe to dereference the exe_file without RCU as 1030 * this function is only called if nobody else can access 1031 * this mm -- see comment above for justification. 1032 */ 1033 old_exe_file = rcu_dereference_raw(mm->exe_file); 1034 1035 if (new_exe_file) 1036 get_file(new_exe_file); 1037 rcu_assign_pointer(mm->exe_file, new_exe_file); 1038 if (old_exe_file) 1039 fput(old_exe_file); 1040 } 1041 1042 /** 1043 * get_mm_exe_file - acquire a reference to the mm's executable file 1044 * 1045 * Returns %NULL if mm has no associated executable file. 1046 * User must release file via fput(). 1047 */ 1048 struct file *get_mm_exe_file(struct mm_struct *mm) 1049 { 1050 struct file *exe_file; 1051 1052 rcu_read_lock(); 1053 exe_file = rcu_dereference(mm->exe_file); 1054 if (exe_file && !get_file_rcu(exe_file)) 1055 exe_file = NULL; 1056 rcu_read_unlock(); 1057 return exe_file; 1058 } 1059 EXPORT_SYMBOL(get_mm_exe_file); 1060 1061 /** 1062 * get_task_exe_file - acquire a reference to the task's executable file 1063 * 1064 * Returns %NULL if task's mm (if any) has no associated executable file or 1065 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1066 * User must release file via fput(). 1067 */ 1068 struct file *get_task_exe_file(struct task_struct *task) 1069 { 1070 struct file *exe_file = NULL; 1071 struct mm_struct *mm; 1072 1073 task_lock(task); 1074 mm = task->mm; 1075 if (mm) { 1076 if (!(task->flags & PF_KTHREAD)) 1077 exe_file = get_mm_exe_file(mm); 1078 } 1079 task_unlock(task); 1080 return exe_file; 1081 } 1082 EXPORT_SYMBOL(get_task_exe_file); 1083 1084 /** 1085 * get_task_mm - acquire a reference to the task's mm 1086 * 1087 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1088 * this kernel workthread has transiently adopted a user mm with use_mm, 1089 * to do its AIO) is not set and if so returns a reference to it, after 1090 * bumping up the use count. User must release the mm via mmput() 1091 * after use. Typically used by /proc and ptrace. 1092 */ 1093 struct mm_struct *get_task_mm(struct task_struct *task) 1094 { 1095 struct mm_struct *mm; 1096 1097 task_lock(task); 1098 mm = task->mm; 1099 if (mm) { 1100 if (task->flags & PF_KTHREAD) 1101 mm = NULL; 1102 else 1103 mmget(mm); 1104 } 1105 task_unlock(task); 1106 return mm; 1107 } 1108 EXPORT_SYMBOL_GPL(get_task_mm); 1109 1110 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1111 { 1112 struct mm_struct *mm; 1113 int err; 1114 1115 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1116 if (err) 1117 return ERR_PTR(err); 1118 1119 mm = get_task_mm(task); 1120 if (mm && mm != current->mm && 1121 !ptrace_may_access(task, mode)) { 1122 mmput(mm); 1123 mm = ERR_PTR(-EACCES); 1124 } 1125 mutex_unlock(&task->signal->cred_guard_mutex); 1126 1127 return mm; 1128 } 1129 1130 static void complete_vfork_done(struct task_struct *tsk) 1131 { 1132 struct completion *vfork; 1133 1134 task_lock(tsk); 1135 vfork = tsk->vfork_done; 1136 if (likely(vfork)) { 1137 tsk->vfork_done = NULL; 1138 complete(vfork); 1139 } 1140 task_unlock(tsk); 1141 } 1142 1143 static int wait_for_vfork_done(struct task_struct *child, 1144 struct completion *vfork) 1145 { 1146 int killed; 1147 1148 freezer_do_not_count(); 1149 killed = wait_for_completion_killable(vfork); 1150 freezer_count(); 1151 1152 if (killed) { 1153 task_lock(child); 1154 child->vfork_done = NULL; 1155 task_unlock(child); 1156 } 1157 1158 put_task_struct(child); 1159 return killed; 1160 } 1161 1162 /* Please note the differences between mmput and mm_release. 1163 * mmput is called whenever we stop holding onto a mm_struct, 1164 * error success whatever. 1165 * 1166 * mm_release is called after a mm_struct has been removed 1167 * from the current process. 1168 * 1169 * This difference is important for error handling, when we 1170 * only half set up a mm_struct for a new process and need to restore 1171 * the old one. Because we mmput the new mm_struct before 1172 * restoring the old one. . . 1173 * Eric Biederman 10 January 1998 1174 */ 1175 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1176 { 1177 /* Get rid of any futexes when releasing the mm */ 1178 #ifdef CONFIG_FUTEX 1179 if (unlikely(tsk->robust_list)) { 1180 exit_robust_list(tsk); 1181 tsk->robust_list = NULL; 1182 } 1183 #ifdef CONFIG_COMPAT 1184 if (unlikely(tsk->compat_robust_list)) { 1185 compat_exit_robust_list(tsk); 1186 tsk->compat_robust_list = NULL; 1187 } 1188 #endif 1189 if (unlikely(!list_empty(&tsk->pi_state_list))) 1190 exit_pi_state_list(tsk); 1191 #endif 1192 1193 uprobe_free_utask(tsk); 1194 1195 /* Get rid of any cached register state */ 1196 deactivate_mm(tsk, mm); 1197 1198 /* 1199 * Signal userspace if we're not exiting with a core dump 1200 * because we want to leave the value intact for debugging 1201 * purposes. 1202 */ 1203 if (tsk->clear_child_tid) { 1204 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1205 atomic_read(&mm->mm_users) > 1) { 1206 /* 1207 * We don't check the error code - if userspace has 1208 * not set up a proper pointer then tough luck. 1209 */ 1210 put_user(0, tsk->clear_child_tid); 1211 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1212 1, NULL, NULL, 0, 0); 1213 } 1214 tsk->clear_child_tid = NULL; 1215 } 1216 1217 /* 1218 * All done, finally we can wake up parent and return this mm to him. 1219 * Also kthread_stop() uses this completion for synchronization. 1220 */ 1221 if (tsk->vfork_done) 1222 complete_vfork_done(tsk); 1223 } 1224 1225 /* 1226 * Allocate a new mm structure and copy contents from the 1227 * mm structure of the passed in task structure. 1228 */ 1229 static struct mm_struct *dup_mm(struct task_struct *tsk) 1230 { 1231 struct mm_struct *mm, *oldmm = current->mm; 1232 int err; 1233 1234 mm = allocate_mm(); 1235 if (!mm) 1236 goto fail_nomem; 1237 1238 memcpy(mm, oldmm, sizeof(*mm)); 1239 1240 if (!mm_init(mm, tsk, mm->user_ns)) 1241 goto fail_nomem; 1242 1243 err = dup_mmap(mm, oldmm); 1244 if (err) 1245 goto free_pt; 1246 1247 mm->hiwater_rss = get_mm_rss(mm); 1248 mm->hiwater_vm = mm->total_vm; 1249 1250 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1251 goto free_pt; 1252 1253 return mm; 1254 1255 free_pt: 1256 /* don't put binfmt in mmput, we haven't got module yet */ 1257 mm->binfmt = NULL; 1258 mmput(mm); 1259 1260 fail_nomem: 1261 return NULL; 1262 } 1263 1264 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1265 { 1266 struct mm_struct *mm, *oldmm; 1267 int retval; 1268 1269 tsk->min_flt = tsk->maj_flt = 0; 1270 tsk->nvcsw = tsk->nivcsw = 0; 1271 #ifdef CONFIG_DETECT_HUNG_TASK 1272 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1273 #endif 1274 1275 tsk->mm = NULL; 1276 tsk->active_mm = NULL; 1277 1278 /* 1279 * Are we cloning a kernel thread? 1280 * 1281 * We need to steal a active VM for that.. 1282 */ 1283 oldmm = current->mm; 1284 if (!oldmm) 1285 return 0; 1286 1287 /* initialize the new vmacache entries */ 1288 vmacache_flush(tsk); 1289 1290 if (clone_flags & CLONE_VM) { 1291 mmget(oldmm); 1292 mm = oldmm; 1293 goto good_mm; 1294 } 1295 1296 retval = -ENOMEM; 1297 mm = dup_mm(tsk); 1298 if (!mm) 1299 goto fail_nomem; 1300 1301 good_mm: 1302 tsk->mm = mm; 1303 tsk->active_mm = mm; 1304 return 0; 1305 1306 fail_nomem: 1307 return retval; 1308 } 1309 1310 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1311 { 1312 struct fs_struct *fs = current->fs; 1313 if (clone_flags & CLONE_FS) { 1314 /* tsk->fs is already what we want */ 1315 spin_lock(&fs->lock); 1316 if (fs->in_exec) { 1317 spin_unlock(&fs->lock); 1318 return -EAGAIN; 1319 } 1320 fs->users++; 1321 spin_unlock(&fs->lock); 1322 return 0; 1323 } 1324 tsk->fs = copy_fs_struct(fs); 1325 if (!tsk->fs) 1326 return -ENOMEM; 1327 return 0; 1328 } 1329 1330 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1331 { 1332 struct files_struct *oldf, *newf; 1333 int error = 0; 1334 1335 /* 1336 * A background process may not have any files ... 1337 */ 1338 oldf = current->files; 1339 if (!oldf) 1340 goto out; 1341 1342 if (clone_flags & CLONE_FILES) { 1343 atomic_inc(&oldf->count); 1344 goto out; 1345 } 1346 1347 newf = dup_fd(oldf, &error); 1348 if (!newf) 1349 goto out; 1350 1351 tsk->files = newf; 1352 error = 0; 1353 out: 1354 return error; 1355 } 1356 1357 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1358 { 1359 #ifdef CONFIG_BLOCK 1360 struct io_context *ioc = current->io_context; 1361 struct io_context *new_ioc; 1362 1363 if (!ioc) 1364 return 0; 1365 /* 1366 * Share io context with parent, if CLONE_IO is set 1367 */ 1368 if (clone_flags & CLONE_IO) { 1369 ioc_task_link(ioc); 1370 tsk->io_context = ioc; 1371 } else if (ioprio_valid(ioc->ioprio)) { 1372 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1373 if (unlikely(!new_ioc)) 1374 return -ENOMEM; 1375 1376 new_ioc->ioprio = ioc->ioprio; 1377 put_io_context(new_ioc); 1378 } 1379 #endif 1380 return 0; 1381 } 1382 1383 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1384 { 1385 struct sighand_struct *sig; 1386 1387 if (clone_flags & CLONE_SIGHAND) { 1388 atomic_inc(¤t->sighand->count); 1389 return 0; 1390 } 1391 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1392 rcu_assign_pointer(tsk->sighand, sig); 1393 if (!sig) 1394 return -ENOMEM; 1395 1396 atomic_set(&sig->count, 1); 1397 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1398 return 0; 1399 } 1400 1401 void __cleanup_sighand(struct sighand_struct *sighand) 1402 { 1403 if (atomic_dec_and_test(&sighand->count)) { 1404 signalfd_cleanup(sighand); 1405 /* 1406 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1407 * without an RCU grace period, see __lock_task_sighand(). 1408 */ 1409 kmem_cache_free(sighand_cachep, sighand); 1410 } 1411 } 1412 1413 #ifdef CONFIG_POSIX_TIMERS 1414 /* 1415 * Initialize POSIX timer handling for a thread group. 1416 */ 1417 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1418 { 1419 unsigned long cpu_limit; 1420 1421 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1422 if (cpu_limit != RLIM_INFINITY) { 1423 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1424 sig->cputimer.running = true; 1425 } 1426 1427 /* The timer lists. */ 1428 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1429 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1430 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1431 } 1432 #else 1433 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1434 #endif 1435 1436 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1437 { 1438 struct signal_struct *sig; 1439 1440 if (clone_flags & CLONE_THREAD) 1441 return 0; 1442 1443 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1444 tsk->signal = sig; 1445 if (!sig) 1446 return -ENOMEM; 1447 1448 sig->nr_threads = 1; 1449 atomic_set(&sig->live, 1); 1450 atomic_set(&sig->sigcnt, 1); 1451 1452 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1453 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1454 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1455 1456 init_waitqueue_head(&sig->wait_chldexit); 1457 sig->curr_target = tsk; 1458 init_sigpending(&sig->shared_pending); 1459 seqlock_init(&sig->stats_lock); 1460 prev_cputime_init(&sig->prev_cputime); 1461 1462 #ifdef CONFIG_POSIX_TIMERS 1463 INIT_LIST_HEAD(&sig->posix_timers); 1464 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1465 sig->real_timer.function = it_real_fn; 1466 #endif 1467 1468 task_lock(current->group_leader); 1469 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1470 task_unlock(current->group_leader); 1471 1472 posix_cpu_timers_init_group(sig); 1473 1474 tty_audit_fork(sig); 1475 sched_autogroup_fork(sig); 1476 1477 sig->oom_score_adj = current->signal->oom_score_adj; 1478 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1479 1480 mutex_init(&sig->cred_guard_mutex); 1481 1482 return 0; 1483 } 1484 1485 static void copy_seccomp(struct task_struct *p) 1486 { 1487 #ifdef CONFIG_SECCOMP 1488 /* 1489 * Must be called with sighand->lock held, which is common to 1490 * all threads in the group. Holding cred_guard_mutex is not 1491 * needed because this new task is not yet running and cannot 1492 * be racing exec. 1493 */ 1494 assert_spin_locked(¤t->sighand->siglock); 1495 1496 /* Ref-count the new filter user, and assign it. */ 1497 get_seccomp_filter(current); 1498 p->seccomp = current->seccomp; 1499 1500 /* 1501 * Explicitly enable no_new_privs here in case it got set 1502 * between the task_struct being duplicated and holding the 1503 * sighand lock. The seccomp state and nnp must be in sync. 1504 */ 1505 if (task_no_new_privs(current)) 1506 task_set_no_new_privs(p); 1507 1508 /* 1509 * If the parent gained a seccomp mode after copying thread 1510 * flags and between before we held the sighand lock, we have 1511 * to manually enable the seccomp thread flag here. 1512 */ 1513 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1514 set_tsk_thread_flag(p, TIF_SECCOMP); 1515 #endif 1516 } 1517 1518 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1519 { 1520 current->clear_child_tid = tidptr; 1521 1522 return task_pid_vnr(current); 1523 } 1524 1525 static void rt_mutex_init_task(struct task_struct *p) 1526 { 1527 raw_spin_lock_init(&p->pi_lock); 1528 #ifdef CONFIG_RT_MUTEXES 1529 p->pi_waiters = RB_ROOT_CACHED; 1530 p->pi_top_task = NULL; 1531 p->pi_blocked_on = NULL; 1532 #endif 1533 } 1534 1535 #ifdef CONFIG_POSIX_TIMERS 1536 /* 1537 * Initialize POSIX timer handling for a single task. 1538 */ 1539 static void posix_cpu_timers_init(struct task_struct *tsk) 1540 { 1541 tsk->cputime_expires.prof_exp = 0; 1542 tsk->cputime_expires.virt_exp = 0; 1543 tsk->cputime_expires.sched_exp = 0; 1544 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1545 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1546 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1547 } 1548 #else 1549 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1550 #endif 1551 1552 static inline void 1553 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1554 { 1555 task->pids[type].pid = pid; 1556 } 1557 1558 static inline void rcu_copy_process(struct task_struct *p) 1559 { 1560 #ifdef CONFIG_PREEMPT_RCU 1561 p->rcu_read_lock_nesting = 0; 1562 p->rcu_read_unlock_special.s = 0; 1563 p->rcu_blocked_node = NULL; 1564 INIT_LIST_HEAD(&p->rcu_node_entry); 1565 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1566 #ifdef CONFIG_TASKS_RCU 1567 p->rcu_tasks_holdout = false; 1568 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1569 p->rcu_tasks_idle_cpu = -1; 1570 #endif /* #ifdef CONFIG_TASKS_RCU */ 1571 } 1572 1573 /* 1574 * This creates a new process as a copy of the old one, 1575 * but does not actually start it yet. 1576 * 1577 * It copies the registers, and all the appropriate 1578 * parts of the process environment (as per the clone 1579 * flags). The actual kick-off is left to the caller. 1580 */ 1581 static __latent_entropy struct task_struct *copy_process( 1582 unsigned long clone_flags, 1583 unsigned long stack_start, 1584 unsigned long stack_size, 1585 int __user *child_tidptr, 1586 struct pid *pid, 1587 int trace, 1588 unsigned long tls, 1589 int node) 1590 { 1591 int retval; 1592 struct task_struct *p; 1593 1594 /* 1595 * Don't allow sharing the root directory with processes in a different 1596 * namespace 1597 */ 1598 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1599 return ERR_PTR(-EINVAL); 1600 1601 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1602 return ERR_PTR(-EINVAL); 1603 1604 /* 1605 * Thread groups must share signals as well, and detached threads 1606 * can only be started up within the thread group. 1607 */ 1608 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1609 return ERR_PTR(-EINVAL); 1610 1611 /* 1612 * Shared signal handlers imply shared VM. By way of the above, 1613 * thread groups also imply shared VM. Blocking this case allows 1614 * for various simplifications in other code. 1615 */ 1616 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1617 return ERR_PTR(-EINVAL); 1618 1619 /* 1620 * Siblings of global init remain as zombies on exit since they are 1621 * not reaped by their parent (swapper). To solve this and to avoid 1622 * multi-rooted process trees, prevent global and container-inits 1623 * from creating siblings. 1624 */ 1625 if ((clone_flags & CLONE_PARENT) && 1626 current->signal->flags & SIGNAL_UNKILLABLE) 1627 return ERR_PTR(-EINVAL); 1628 1629 /* 1630 * If the new process will be in a different pid or user namespace 1631 * do not allow it to share a thread group with the forking task. 1632 */ 1633 if (clone_flags & CLONE_THREAD) { 1634 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1635 (task_active_pid_ns(current) != 1636 current->nsproxy->pid_ns_for_children)) 1637 return ERR_PTR(-EINVAL); 1638 } 1639 1640 retval = -ENOMEM; 1641 p = dup_task_struct(current, node); 1642 if (!p) 1643 goto fork_out; 1644 1645 /* 1646 * This _must_ happen before we call free_task(), i.e. before we jump 1647 * to any of the bad_fork_* labels. This is to avoid freeing 1648 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1649 * kernel threads (PF_KTHREAD). 1650 */ 1651 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1652 /* 1653 * Clear TID on mm_release()? 1654 */ 1655 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1656 1657 ftrace_graph_init_task(p); 1658 1659 rt_mutex_init_task(p); 1660 1661 #ifdef CONFIG_PROVE_LOCKING 1662 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1663 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1664 #endif 1665 retval = -EAGAIN; 1666 if (atomic_read(&p->real_cred->user->processes) >= 1667 task_rlimit(p, RLIMIT_NPROC)) { 1668 if (p->real_cred->user != INIT_USER && 1669 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1670 goto bad_fork_free; 1671 } 1672 current->flags &= ~PF_NPROC_EXCEEDED; 1673 1674 retval = copy_creds(p, clone_flags); 1675 if (retval < 0) 1676 goto bad_fork_free; 1677 1678 /* 1679 * If multiple threads are within copy_process(), then this check 1680 * triggers too late. This doesn't hurt, the check is only there 1681 * to stop root fork bombs. 1682 */ 1683 retval = -EAGAIN; 1684 if (nr_threads >= max_threads) 1685 goto bad_fork_cleanup_count; 1686 1687 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1688 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1689 p->flags |= PF_FORKNOEXEC; 1690 INIT_LIST_HEAD(&p->children); 1691 INIT_LIST_HEAD(&p->sibling); 1692 rcu_copy_process(p); 1693 p->vfork_done = NULL; 1694 spin_lock_init(&p->alloc_lock); 1695 1696 init_sigpending(&p->pending); 1697 1698 p->utime = p->stime = p->gtime = 0; 1699 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1700 p->utimescaled = p->stimescaled = 0; 1701 #endif 1702 prev_cputime_init(&p->prev_cputime); 1703 1704 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1705 seqcount_init(&p->vtime.seqcount); 1706 p->vtime.starttime = 0; 1707 p->vtime.state = VTIME_INACTIVE; 1708 #endif 1709 1710 #if defined(SPLIT_RSS_COUNTING) 1711 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1712 #endif 1713 1714 p->default_timer_slack_ns = current->timer_slack_ns; 1715 1716 task_io_accounting_init(&p->ioac); 1717 acct_clear_integrals(p); 1718 1719 posix_cpu_timers_init(p); 1720 1721 p->start_time = ktime_get_ns(); 1722 p->real_start_time = ktime_get_boot_ns(); 1723 p->io_context = NULL; 1724 audit_set_context(p, NULL); 1725 cgroup_fork(p); 1726 #ifdef CONFIG_NUMA 1727 p->mempolicy = mpol_dup(p->mempolicy); 1728 if (IS_ERR(p->mempolicy)) { 1729 retval = PTR_ERR(p->mempolicy); 1730 p->mempolicy = NULL; 1731 goto bad_fork_cleanup_threadgroup_lock; 1732 } 1733 #endif 1734 #ifdef CONFIG_CPUSETS 1735 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1736 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1737 seqcount_init(&p->mems_allowed_seq); 1738 #endif 1739 #ifdef CONFIG_TRACE_IRQFLAGS 1740 p->irq_events = 0; 1741 p->hardirqs_enabled = 0; 1742 p->hardirq_enable_ip = 0; 1743 p->hardirq_enable_event = 0; 1744 p->hardirq_disable_ip = _THIS_IP_; 1745 p->hardirq_disable_event = 0; 1746 p->softirqs_enabled = 1; 1747 p->softirq_enable_ip = _THIS_IP_; 1748 p->softirq_enable_event = 0; 1749 p->softirq_disable_ip = 0; 1750 p->softirq_disable_event = 0; 1751 p->hardirq_context = 0; 1752 p->softirq_context = 0; 1753 #endif 1754 1755 p->pagefault_disabled = 0; 1756 1757 #ifdef CONFIG_LOCKDEP 1758 p->lockdep_depth = 0; /* no locks held yet */ 1759 p->curr_chain_key = 0; 1760 p->lockdep_recursion = 0; 1761 lockdep_init_task(p); 1762 #endif 1763 1764 #ifdef CONFIG_DEBUG_MUTEXES 1765 p->blocked_on = NULL; /* not blocked yet */ 1766 #endif 1767 #ifdef CONFIG_BCACHE 1768 p->sequential_io = 0; 1769 p->sequential_io_avg = 0; 1770 #endif 1771 1772 /* Perform scheduler related setup. Assign this task to a CPU. */ 1773 retval = sched_fork(clone_flags, p); 1774 if (retval) 1775 goto bad_fork_cleanup_policy; 1776 1777 retval = perf_event_init_task(p); 1778 if (retval) 1779 goto bad_fork_cleanup_policy; 1780 retval = audit_alloc(p); 1781 if (retval) 1782 goto bad_fork_cleanup_perf; 1783 /* copy all the process information */ 1784 shm_init_task(p); 1785 retval = security_task_alloc(p, clone_flags); 1786 if (retval) 1787 goto bad_fork_cleanup_audit; 1788 retval = copy_semundo(clone_flags, p); 1789 if (retval) 1790 goto bad_fork_cleanup_security; 1791 retval = copy_files(clone_flags, p); 1792 if (retval) 1793 goto bad_fork_cleanup_semundo; 1794 retval = copy_fs(clone_flags, p); 1795 if (retval) 1796 goto bad_fork_cleanup_files; 1797 retval = copy_sighand(clone_flags, p); 1798 if (retval) 1799 goto bad_fork_cleanup_fs; 1800 retval = copy_signal(clone_flags, p); 1801 if (retval) 1802 goto bad_fork_cleanup_sighand; 1803 retval = copy_mm(clone_flags, p); 1804 if (retval) 1805 goto bad_fork_cleanup_signal; 1806 retval = copy_namespaces(clone_flags, p); 1807 if (retval) 1808 goto bad_fork_cleanup_mm; 1809 retval = copy_io(clone_flags, p); 1810 if (retval) 1811 goto bad_fork_cleanup_namespaces; 1812 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1813 if (retval) 1814 goto bad_fork_cleanup_io; 1815 1816 if (pid != &init_struct_pid) { 1817 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1818 if (IS_ERR(pid)) { 1819 retval = PTR_ERR(pid); 1820 goto bad_fork_cleanup_thread; 1821 } 1822 } 1823 1824 #ifdef CONFIG_BLOCK 1825 p->plug = NULL; 1826 #endif 1827 #ifdef CONFIG_FUTEX 1828 p->robust_list = NULL; 1829 #ifdef CONFIG_COMPAT 1830 p->compat_robust_list = NULL; 1831 #endif 1832 INIT_LIST_HEAD(&p->pi_state_list); 1833 p->pi_state_cache = NULL; 1834 #endif 1835 /* 1836 * sigaltstack should be cleared when sharing the same VM 1837 */ 1838 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1839 sas_ss_reset(p); 1840 1841 /* 1842 * Syscall tracing and stepping should be turned off in the 1843 * child regardless of CLONE_PTRACE. 1844 */ 1845 user_disable_single_step(p); 1846 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1847 #ifdef TIF_SYSCALL_EMU 1848 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1849 #endif 1850 clear_all_latency_tracing(p); 1851 1852 /* ok, now we should be set up.. */ 1853 p->pid = pid_nr(pid); 1854 if (clone_flags & CLONE_THREAD) { 1855 p->exit_signal = -1; 1856 p->group_leader = current->group_leader; 1857 p->tgid = current->tgid; 1858 } else { 1859 if (clone_flags & CLONE_PARENT) 1860 p->exit_signal = current->group_leader->exit_signal; 1861 else 1862 p->exit_signal = (clone_flags & CSIGNAL); 1863 p->group_leader = p; 1864 p->tgid = p->pid; 1865 } 1866 1867 p->nr_dirtied = 0; 1868 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1869 p->dirty_paused_when = 0; 1870 1871 p->pdeath_signal = 0; 1872 INIT_LIST_HEAD(&p->thread_group); 1873 p->task_works = NULL; 1874 1875 cgroup_threadgroup_change_begin(current); 1876 /* 1877 * Ensure that the cgroup subsystem policies allow the new process to be 1878 * forked. It should be noted the the new process's css_set can be changed 1879 * between here and cgroup_post_fork() if an organisation operation is in 1880 * progress. 1881 */ 1882 retval = cgroup_can_fork(p); 1883 if (retval) 1884 goto bad_fork_free_pid; 1885 1886 /* 1887 * Make it visible to the rest of the system, but dont wake it up yet. 1888 * Need tasklist lock for parent etc handling! 1889 */ 1890 write_lock_irq(&tasklist_lock); 1891 1892 /* CLONE_PARENT re-uses the old parent */ 1893 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1894 p->real_parent = current->real_parent; 1895 p->parent_exec_id = current->parent_exec_id; 1896 } else { 1897 p->real_parent = current; 1898 p->parent_exec_id = current->self_exec_id; 1899 } 1900 1901 klp_copy_process(p); 1902 1903 spin_lock(¤t->sighand->siglock); 1904 1905 /* 1906 * Copy seccomp details explicitly here, in case they were changed 1907 * before holding sighand lock. 1908 */ 1909 copy_seccomp(p); 1910 1911 rseq_fork(p, clone_flags); 1912 1913 /* 1914 * Process group and session signals need to be delivered to just the 1915 * parent before the fork or both the parent and the child after the 1916 * fork. Restart if a signal comes in before we add the new process to 1917 * it's process group. 1918 * A fatal signal pending means that current will exit, so the new 1919 * thread can't slip out of an OOM kill (or normal SIGKILL). 1920 */ 1921 recalc_sigpending(); 1922 if (signal_pending(current)) { 1923 retval = -ERESTARTNOINTR; 1924 goto bad_fork_cancel_cgroup; 1925 } 1926 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 1927 retval = -ENOMEM; 1928 goto bad_fork_cancel_cgroup; 1929 } 1930 1931 if (likely(p->pid)) { 1932 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1933 1934 init_task_pid(p, PIDTYPE_PID, pid); 1935 if (thread_group_leader(p)) { 1936 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1937 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1938 1939 if (is_child_reaper(pid)) { 1940 ns_of_pid(pid)->child_reaper = p; 1941 p->signal->flags |= SIGNAL_UNKILLABLE; 1942 } 1943 1944 p->signal->leader_pid = pid; 1945 p->signal->tty = tty_kref_get(current->signal->tty); 1946 /* 1947 * Inherit has_child_subreaper flag under the same 1948 * tasklist_lock with adding child to the process tree 1949 * for propagate_has_child_subreaper optimization. 1950 */ 1951 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1952 p->real_parent->signal->is_child_subreaper; 1953 list_add_tail(&p->sibling, &p->real_parent->children); 1954 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1955 attach_pid(p, PIDTYPE_PGID); 1956 attach_pid(p, PIDTYPE_SID); 1957 __this_cpu_inc(process_counts); 1958 } else { 1959 current->signal->nr_threads++; 1960 atomic_inc(¤t->signal->live); 1961 atomic_inc(¤t->signal->sigcnt); 1962 list_add_tail_rcu(&p->thread_group, 1963 &p->group_leader->thread_group); 1964 list_add_tail_rcu(&p->thread_node, 1965 &p->signal->thread_head); 1966 } 1967 attach_pid(p, PIDTYPE_PID); 1968 nr_threads++; 1969 } 1970 1971 total_forks++; 1972 spin_unlock(¤t->sighand->siglock); 1973 syscall_tracepoint_update(p); 1974 write_unlock_irq(&tasklist_lock); 1975 1976 proc_fork_connector(p); 1977 cgroup_post_fork(p); 1978 cgroup_threadgroup_change_end(current); 1979 perf_event_fork(p); 1980 1981 trace_task_newtask(p, clone_flags); 1982 uprobe_copy_process(p, clone_flags); 1983 1984 return p; 1985 1986 bad_fork_cancel_cgroup: 1987 spin_unlock(¤t->sighand->siglock); 1988 write_unlock_irq(&tasklist_lock); 1989 cgroup_cancel_fork(p); 1990 bad_fork_free_pid: 1991 cgroup_threadgroup_change_end(current); 1992 if (pid != &init_struct_pid) 1993 free_pid(pid); 1994 bad_fork_cleanup_thread: 1995 exit_thread(p); 1996 bad_fork_cleanup_io: 1997 if (p->io_context) 1998 exit_io_context(p); 1999 bad_fork_cleanup_namespaces: 2000 exit_task_namespaces(p); 2001 bad_fork_cleanup_mm: 2002 if (p->mm) 2003 mmput(p->mm); 2004 bad_fork_cleanup_signal: 2005 if (!(clone_flags & CLONE_THREAD)) 2006 free_signal_struct(p->signal); 2007 bad_fork_cleanup_sighand: 2008 __cleanup_sighand(p->sighand); 2009 bad_fork_cleanup_fs: 2010 exit_fs(p); /* blocking */ 2011 bad_fork_cleanup_files: 2012 exit_files(p); /* blocking */ 2013 bad_fork_cleanup_semundo: 2014 exit_sem(p); 2015 bad_fork_cleanup_security: 2016 security_task_free(p); 2017 bad_fork_cleanup_audit: 2018 audit_free(p); 2019 bad_fork_cleanup_perf: 2020 perf_event_free_task(p); 2021 bad_fork_cleanup_policy: 2022 lockdep_free_task(p); 2023 #ifdef CONFIG_NUMA 2024 mpol_put(p->mempolicy); 2025 bad_fork_cleanup_threadgroup_lock: 2026 #endif 2027 delayacct_tsk_free(p); 2028 bad_fork_cleanup_count: 2029 atomic_dec(&p->cred->user->processes); 2030 exit_creds(p); 2031 bad_fork_free: 2032 p->state = TASK_DEAD; 2033 put_task_stack(p); 2034 free_task(p); 2035 fork_out: 2036 return ERR_PTR(retval); 2037 } 2038 2039 static inline void init_idle_pids(struct pid_link *links) 2040 { 2041 enum pid_type type; 2042 2043 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2044 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 2045 links[type].pid = &init_struct_pid; 2046 } 2047 } 2048 2049 struct task_struct *fork_idle(int cpu) 2050 { 2051 struct task_struct *task; 2052 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2053 cpu_to_node(cpu)); 2054 if (!IS_ERR(task)) { 2055 init_idle_pids(task->pids); 2056 init_idle(task, cpu); 2057 } 2058 2059 return task; 2060 } 2061 2062 /* 2063 * Ok, this is the main fork-routine. 2064 * 2065 * It copies the process, and if successful kick-starts 2066 * it and waits for it to finish using the VM if required. 2067 */ 2068 long _do_fork(unsigned long clone_flags, 2069 unsigned long stack_start, 2070 unsigned long stack_size, 2071 int __user *parent_tidptr, 2072 int __user *child_tidptr, 2073 unsigned long tls) 2074 { 2075 struct completion vfork; 2076 struct pid *pid; 2077 struct task_struct *p; 2078 int trace = 0; 2079 long nr; 2080 2081 /* 2082 * Determine whether and which event to report to ptracer. When 2083 * called from kernel_thread or CLONE_UNTRACED is explicitly 2084 * requested, no event is reported; otherwise, report if the event 2085 * for the type of forking is enabled. 2086 */ 2087 if (!(clone_flags & CLONE_UNTRACED)) { 2088 if (clone_flags & CLONE_VFORK) 2089 trace = PTRACE_EVENT_VFORK; 2090 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2091 trace = PTRACE_EVENT_CLONE; 2092 else 2093 trace = PTRACE_EVENT_FORK; 2094 2095 if (likely(!ptrace_event_enabled(current, trace))) 2096 trace = 0; 2097 } 2098 2099 p = copy_process(clone_flags, stack_start, stack_size, 2100 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2101 add_latent_entropy(); 2102 2103 if (IS_ERR(p)) 2104 return PTR_ERR(p); 2105 2106 /* 2107 * Do this prior waking up the new thread - the thread pointer 2108 * might get invalid after that point, if the thread exits quickly. 2109 */ 2110 trace_sched_process_fork(current, p); 2111 2112 pid = get_task_pid(p, PIDTYPE_PID); 2113 nr = pid_vnr(pid); 2114 2115 if (clone_flags & CLONE_PARENT_SETTID) 2116 put_user(nr, parent_tidptr); 2117 2118 if (clone_flags & CLONE_VFORK) { 2119 p->vfork_done = &vfork; 2120 init_completion(&vfork); 2121 get_task_struct(p); 2122 } 2123 2124 wake_up_new_task(p); 2125 2126 /* forking complete and child started to run, tell ptracer */ 2127 if (unlikely(trace)) 2128 ptrace_event_pid(trace, pid); 2129 2130 if (clone_flags & CLONE_VFORK) { 2131 if (!wait_for_vfork_done(p, &vfork)) 2132 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2133 } 2134 2135 put_pid(pid); 2136 return nr; 2137 } 2138 2139 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2140 /* For compatibility with architectures that call do_fork directly rather than 2141 * using the syscall entry points below. */ 2142 long do_fork(unsigned long clone_flags, 2143 unsigned long stack_start, 2144 unsigned long stack_size, 2145 int __user *parent_tidptr, 2146 int __user *child_tidptr) 2147 { 2148 return _do_fork(clone_flags, stack_start, stack_size, 2149 parent_tidptr, child_tidptr, 0); 2150 } 2151 #endif 2152 2153 /* 2154 * Create a kernel thread. 2155 */ 2156 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2157 { 2158 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2159 (unsigned long)arg, NULL, NULL, 0); 2160 } 2161 2162 #ifdef __ARCH_WANT_SYS_FORK 2163 SYSCALL_DEFINE0(fork) 2164 { 2165 #ifdef CONFIG_MMU 2166 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2167 #else 2168 /* can not support in nommu mode */ 2169 return -EINVAL; 2170 #endif 2171 } 2172 #endif 2173 2174 #ifdef __ARCH_WANT_SYS_VFORK 2175 SYSCALL_DEFINE0(vfork) 2176 { 2177 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2178 0, NULL, NULL, 0); 2179 } 2180 #endif 2181 2182 #ifdef __ARCH_WANT_SYS_CLONE 2183 #ifdef CONFIG_CLONE_BACKWARDS 2184 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2185 int __user *, parent_tidptr, 2186 unsigned long, tls, 2187 int __user *, child_tidptr) 2188 #elif defined(CONFIG_CLONE_BACKWARDS2) 2189 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2190 int __user *, parent_tidptr, 2191 int __user *, child_tidptr, 2192 unsigned long, tls) 2193 #elif defined(CONFIG_CLONE_BACKWARDS3) 2194 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2195 int, stack_size, 2196 int __user *, parent_tidptr, 2197 int __user *, child_tidptr, 2198 unsigned long, tls) 2199 #else 2200 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2201 int __user *, parent_tidptr, 2202 int __user *, child_tidptr, 2203 unsigned long, tls) 2204 #endif 2205 { 2206 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2207 } 2208 #endif 2209 2210 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2211 { 2212 struct task_struct *leader, *parent, *child; 2213 int res; 2214 2215 read_lock(&tasklist_lock); 2216 leader = top = top->group_leader; 2217 down: 2218 for_each_thread(leader, parent) { 2219 list_for_each_entry(child, &parent->children, sibling) { 2220 res = visitor(child, data); 2221 if (res) { 2222 if (res < 0) 2223 goto out; 2224 leader = child; 2225 goto down; 2226 } 2227 up: 2228 ; 2229 } 2230 } 2231 2232 if (leader != top) { 2233 child = leader; 2234 parent = child->real_parent; 2235 leader = parent->group_leader; 2236 goto up; 2237 } 2238 out: 2239 read_unlock(&tasklist_lock); 2240 } 2241 2242 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2243 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2244 #endif 2245 2246 static void sighand_ctor(void *data) 2247 { 2248 struct sighand_struct *sighand = data; 2249 2250 spin_lock_init(&sighand->siglock); 2251 init_waitqueue_head(&sighand->signalfd_wqh); 2252 } 2253 2254 void __init proc_caches_init(void) 2255 { 2256 sighand_cachep = kmem_cache_create("sighand_cache", 2257 sizeof(struct sighand_struct), 0, 2258 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2259 SLAB_ACCOUNT, sighand_ctor); 2260 signal_cachep = kmem_cache_create("signal_cache", 2261 sizeof(struct signal_struct), 0, 2262 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2263 NULL); 2264 files_cachep = kmem_cache_create("files_cache", 2265 sizeof(struct files_struct), 0, 2266 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2267 NULL); 2268 fs_cachep = kmem_cache_create("fs_cache", 2269 sizeof(struct fs_struct), 0, 2270 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2271 NULL); 2272 /* 2273 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2274 * whole struct cpumask for the OFFSTACK case. We could change 2275 * this to *only* allocate as much of it as required by the 2276 * maximum number of CPU's we can ever have. The cpumask_allocation 2277 * is at the end of the structure, exactly for that reason. 2278 */ 2279 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2280 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2281 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2282 offsetof(struct mm_struct, saved_auxv), 2283 sizeof_field(struct mm_struct, saved_auxv), 2284 NULL); 2285 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2286 mmap_init(); 2287 nsproxy_cache_init(); 2288 } 2289 2290 /* 2291 * Check constraints on flags passed to the unshare system call. 2292 */ 2293 static int check_unshare_flags(unsigned long unshare_flags) 2294 { 2295 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2296 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2297 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2298 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2299 return -EINVAL; 2300 /* 2301 * Not implemented, but pretend it works if there is nothing 2302 * to unshare. Note that unsharing the address space or the 2303 * signal handlers also need to unshare the signal queues (aka 2304 * CLONE_THREAD). 2305 */ 2306 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2307 if (!thread_group_empty(current)) 2308 return -EINVAL; 2309 } 2310 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2311 if (atomic_read(¤t->sighand->count) > 1) 2312 return -EINVAL; 2313 } 2314 if (unshare_flags & CLONE_VM) { 2315 if (!current_is_single_threaded()) 2316 return -EINVAL; 2317 } 2318 2319 return 0; 2320 } 2321 2322 /* 2323 * Unshare the filesystem structure if it is being shared 2324 */ 2325 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2326 { 2327 struct fs_struct *fs = current->fs; 2328 2329 if (!(unshare_flags & CLONE_FS) || !fs) 2330 return 0; 2331 2332 /* don't need lock here; in the worst case we'll do useless copy */ 2333 if (fs->users == 1) 2334 return 0; 2335 2336 *new_fsp = copy_fs_struct(fs); 2337 if (!*new_fsp) 2338 return -ENOMEM; 2339 2340 return 0; 2341 } 2342 2343 /* 2344 * Unshare file descriptor table if it is being shared 2345 */ 2346 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2347 { 2348 struct files_struct *fd = current->files; 2349 int error = 0; 2350 2351 if ((unshare_flags & CLONE_FILES) && 2352 (fd && atomic_read(&fd->count) > 1)) { 2353 *new_fdp = dup_fd(fd, &error); 2354 if (!*new_fdp) 2355 return error; 2356 } 2357 2358 return 0; 2359 } 2360 2361 /* 2362 * unshare allows a process to 'unshare' part of the process 2363 * context which was originally shared using clone. copy_* 2364 * functions used by do_fork() cannot be used here directly 2365 * because they modify an inactive task_struct that is being 2366 * constructed. Here we are modifying the current, active, 2367 * task_struct. 2368 */ 2369 int ksys_unshare(unsigned long unshare_flags) 2370 { 2371 struct fs_struct *fs, *new_fs = NULL; 2372 struct files_struct *fd, *new_fd = NULL; 2373 struct cred *new_cred = NULL; 2374 struct nsproxy *new_nsproxy = NULL; 2375 int do_sysvsem = 0; 2376 int err; 2377 2378 /* 2379 * If unsharing a user namespace must also unshare the thread group 2380 * and unshare the filesystem root and working directories. 2381 */ 2382 if (unshare_flags & CLONE_NEWUSER) 2383 unshare_flags |= CLONE_THREAD | CLONE_FS; 2384 /* 2385 * If unsharing vm, must also unshare signal handlers. 2386 */ 2387 if (unshare_flags & CLONE_VM) 2388 unshare_flags |= CLONE_SIGHAND; 2389 /* 2390 * If unsharing a signal handlers, must also unshare the signal queues. 2391 */ 2392 if (unshare_flags & CLONE_SIGHAND) 2393 unshare_flags |= CLONE_THREAD; 2394 /* 2395 * If unsharing namespace, must also unshare filesystem information. 2396 */ 2397 if (unshare_flags & CLONE_NEWNS) 2398 unshare_flags |= CLONE_FS; 2399 2400 err = check_unshare_flags(unshare_flags); 2401 if (err) 2402 goto bad_unshare_out; 2403 /* 2404 * CLONE_NEWIPC must also detach from the undolist: after switching 2405 * to a new ipc namespace, the semaphore arrays from the old 2406 * namespace are unreachable. 2407 */ 2408 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2409 do_sysvsem = 1; 2410 err = unshare_fs(unshare_flags, &new_fs); 2411 if (err) 2412 goto bad_unshare_out; 2413 err = unshare_fd(unshare_flags, &new_fd); 2414 if (err) 2415 goto bad_unshare_cleanup_fs; 2416 err = unshare_userns(unshare_flags, &new_cred); 2417 if (err) 2418 goto bad_unshare_cleanup_fd; 2419 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2420 new_cred, new_fs); 2421 if (err) 2422 goto bad_unshare_cleanup_cred; 2423 2424 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2425 if (do_sysvsem) { 2426 /* 2427 * CLONE_SYSVSEM is equivalent to sys_exit(). 2428 */ 2429 exit_sem(current); 2430 } 2431 if (unshare_flags & CLONE_NEWIPC) { 2432 /* Orphan segments in old ns (see sem above). */ 2433 exit_shm(current); 2434 shm_init_task(current); 2435 } 2436 2437 if (new_nsproxy) 2438 switch_task_namespaces(current, new_nsproxy); 2439 2440 task_lock(current); 2441 2442 if (new_fs) { 2443 fs = current->fs; 2444 spin_lock(&fs->lock); 2445 current->fs = new_fs; 2446 if (--fs->users) 2447 new_fs = NULL; 2448 else 2449 new_fs = fs; 2450 spin_unlock(&fs->lock); 2451 } 2452 2453 if (new_fd) { 2454 fd = current->files; 2455 current->files = new_fd; 2456 new_fd = fd; 2457 } 2458 2459 task_unlock(current); 2460 2461 if (new_cred) { 2462 /* Install the new user namespace */ 2463 commit_creds(new_cred); 2464 new_cred = NULL; 2465 } 2466 } 2467 2468 perf_event_namespaces(current); 2469 2470 bad_unshare_cleanup_cred: 2471 if (new_cred) 2472 put_cred(new_cred); 2473 bad_unshare_cleanup_fd: 2474 if (new_fd) 2475 put_files_struct(new_fd); 2476 2477 bad_unshare_cleanup_fs: 2478 if (new_fs) 2479 free_fs_struct(new_fs); 2480 2481 bad_unshare_out: 2482 return err; 2483 } 2484 2485 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2486 { 2487 return ksys_unshare(unshare_flags); 2488 } 2489 2490 /* 2491 * Helper to unshare the files of the current task. 2492 * We don't want to expose copy_files internals to 2493 * the exec layer of the kernel. 2494 */ 2495 2496 int unshare_files(struct files_struct **displaced) 2497 { 2498 struct task_struct *task = current; 2499 struct files_struct *copy = NULL; 2500 int error; 2501 2502 error = unshare_fd(CLONE_FILES, ©); 2503 if (error || !copy) { 2504 *displaced = NULL; 2505 return error; 2506 } 2507 *displaced = task->files; 2508 task_lock(task); 2509 task->files = copy; 2510 task_unlock(task); 2511 return 0; 2512 } 2513 2514 int sysctl_max_threads(struct ctl_table *table, int write, 2515 void __user *buffer, size_t *lenp, loff_t *ppos) 2516 { 2517 struct ctl_table t; 2518 int ret; 2519 int threads = max_threads; 2520 int min = MIN_THREADS; 2521 int max = MAX_THREADS; 2522 2523 t = *table; 2524 t.data = &threads; 2525 t.extra1 = &min; 2526 t.extra2 = &max; 2527 2528 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2529 if (ret || !write) 2530 return ret; 2531 2532 set_max_threads(threads); 2533 2534 return 0; 2535 } 2536