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