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