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 /* 610 * The implicit full barrier implied by atomic_dec_and_test() is 611 * required by the membarrier system call before returning to 612 * user-space, after storing to rq->curr. 613 */ 614 if (unlikely(atomic_dec_and_test(&mm->mm_count))) 615 __mmdrop(mm); 616 } 617 EXPORT_SYMBOL_GPL(mmdrop); 618 619 static void mmdrop_async_fn(struct work_struct *work) 620 { 621 struct mm_struct *mm; 622 623 mm = container_of(work, struct mm_struct, async_put_work); 624 __mmdrop(mm); 625 } 626 627 static void mmdrop_async(struct mm_struct *mm) 628 { 629 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 630 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 631 schedule_work(&mm->async_put_work); 632 } 633 } 634 635 static inline void free_signal_struct(struct signal_struct *sig) 636 { 637 taskstats_tgid_free(sig); 638 sched_autogroup_exit(sig); 639 /* 640 * __mmdrop is not safe to call from softirq context on x86 due to 641 * pgd_dtor so postpone it to the async context 642 */ 643 if (sig->oom_mm) 644 mmdrop_async(sig->oom_mm); 645 kmem_cache_free(signal_cachep, sig); 646 } 647 648 static inline void put_signal_struct(struct signal_struct *sig) 649 { 650 if (atomic_dec_and_test(&sig->sigcnt)) 651 free_signal_struct(sig); 652 } 653 654 void __put_task_struct(struct task_struct *tsk) 655 { 656 WARN_ON(!tsk->exit_state); 657 WARN_ON(atomic_read(&tsk->usage)); 658 WARN_ON(tsk == current); 659 660 cgroup_free(tsk); 661 task_numa_free(tsk); 662 security_task_free(tsk); 663 exit_creds(tsk); 664 delayacct_tsk_free(tsk); 665 put_signal_struct(tsk->signal); 666 667 if (!profile_handoff_task(tsk)) 668 free_task(tsk); 669 } 670 EXPORT_SYMBOL_GPL(__put_task_struct); 671 672 void __init __weak arch_task_cache_init(void) { } 673 674 /* 675 * set_max_threads 676 */ 677 static void set_max_threads(unsigned int max_threads_suggested) 678 { 679 u64 threads; 680 681 /* 682 * The number of threads shall be limited such that the thread 683 * structures may only consume a small part of the available memory. 684 */ 685 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 686 threads = MAX_THREADS; 687 else 688 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 689 (u64) THREAD_SIZE * 8UL); 690 691 if (threads > max_threads_suggested) 692 threads = max_threads_suggested; 693 694 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 695 } 696 697 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 698 /* Initialized by the architecture: */ 699 int arch_task_struct_size __read_mostly; 700 #endif 701 702 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 703 { 704 /* Fetch thread_struct whitelist for the architecture. */ 705 arch_thread_struct_whitelist(offset, size); 706 707 /* 708 * Handle zero-sized whitelist or empty thread_struct, otherwise 709 * adjust offset to position of thread_struct in task_struct. 710 */ 711 if (unlikely(*size == 0)) 712 *offset = 0; 713 else 714 *offset += offsetof(struct task_struct, thread); 715 } 716 717 void __init fork_init(void) 718 { 719 int i; 720 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 721 #ifndef ARCH_MIN_TASKALIGN 722 #define ARCH_MIN_TASKALIGN 0 723 #endif 724 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 725 unsigned long useroffset, usersize; 726 727 /* create a slab on which task_structs can be allocated */ 728 task_struct_whitelist(&useroffset, &usersize); 729 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 730 arch_task_struct_size, align, 731 SLAB_PANIC|SLAB_ACCOUNT, 732 useroffset, usersize, NULL); 733 #endif 734 735 /* do the arch specific task caches init */ 736 arch_task_cache_init(); 737 738 set_max_threads(MAX_THREADS); 739 740 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 741 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 742 init_task.signal->rlim[RLIMIT_SIGPENDING] = 743 init_task.signal->rlim[RLIMIT_NPROC]; 744 745 for (i = 0; i < UCOUNT_COUNTS; i++) { 746 init_user_ns.ucount_max[i] = max_threads/2; 747 } 748 749 #ifdef CONFIG_VMAP_STACK 750 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 751 NULL, free_vm_stack_cache); 752 #endif 753 754 lockdep_init_task(&init_task); 755 } 756 757 int __weak arch_dup_task_struct(struct task_struct *dst, 758 struct task_struct *src) 759 { 760 *dst = *src; 761 return 0; 762 } 763 764 void set_task_stack_end_magic(struct task_struct *tsk) 765 { 766 unsigned long *stackend; 767 768 stackend = end_of_stack(tsk); 769 *stackend = STACK_END_MAGIC; /* for overflow detection */ 770 } 771 772 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 773 { 774 struct task_struct *tsk; 775 unsigned long *stack; 776 struct vm_struct *stack_vm_area; 777 int err; 778 779 if (node == NUMA_NO_NODE) 780 node = tsk_fork_get_node(orig); 781 tsk = alloc_task_struct_node(node); 782 if (!tsk) 783 return NULL; 784 785 stack = alloc_thread_stack_node(tsk, node); 786 if (!stack) 787 goto free_tsk; 788 789 stack_vm_area = task_stack_vm_area(tsk); 790 791 err = arch_dup_task_struct(tsk, orig); 792 793 /* 794 * arch_dup_task_struct() clobbers the stack-related fields. Make 795 * sure they're properly initialized before using any stack-related 796 * functions again. 797 */ 798 tsk->stack = stack; 799 #ifdef CONFIG_VMAP_STACK 800 tsk->stack_vm_area = stack_vm_area; 801 #endif 802 #ifdef CONFIG_THREAD_INFO_IN_TASK 803 atomic_set(&tsk->stack_refcount, 1); 804 #endif 805 806 if (err) 807 goto free_stack; 808 809 #ifdef CONFIG_SECCOMP 810 /* 811 * We must handle setting up seccomp filters once we're under 812 * the sighand lock in case orig has changed between now and 813 * then. Until then, filter must be NULL to avoid messing up 814 * the usage counts on the error path calling free_task. 815 */ 816 tsk->seccomp.filter = NULL; 817 #endif 818 819 setup_thread_stack(tsk, orig); 820 clear_user_return_notifier(tsk); 821 clear_tsk_need_resched(tsk); 822 set_task_stack_end_magic(tsk); 823 824 #ifdef CONFIG_CC_STACKPROTECTOR 825 tsk->stack_canary = get_random_canary(); 826 #endif 827 828 /* 829 * One for us, one for whoever does the "release_task()" (usually 830 * parent) 831 */ 832 atomic_set(&tsk->usage, 2); 833 #ifdef CONFIG_BLK_DEV_IO_TRACE 834 tsk->btrace_seq = 0; 835 #endif 836 tsk->splice_pipe = NULL; 837 tsk->task_frag.page = NULL; 838 tsk->wake_q.next = NULL; 839 840 account_kernel_stack(tsk, 1); 841 842 kcov_task_init(tsk); 843 844 #ifdef CONFIG_FAULT_INJECTION 845 tsk->fail_nth = 0; 846 #endif 847 848 return tsk; 849 850 free_stack: 851 free_thread_stack(tsk); 852 free_tsk: 853 free_task_struct(tsk); 854 return NULL; 855 } 856 857 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 858 859 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 860 861 static int __init coredump_filter_setup(char *s) 862 { 863 default_dump_filter = 864 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 865 MMF_DUMP_FILTER_MASK; 866 return 1; 867 } 868 869 __setup("coredump_filter=", coredump_filter_setup); 870 871 #include <linux/init_task.h> 872 873 static void mm_init_aio(struct mm_struct *mm) 874 { 875 #ifdef CONFIG_AIO 876 spin_lock_init(&mm->ioctx_lock); 877 mm->ioctx_table = NULL; 878 #endif 879 } 880 881 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 882 { 883 #ifdef CONFIG_MEMCG 884 mm->owner = p; 885 #endif 886 } 887 888 static void mm_init_uprobes_state(struct mm_struct *mm) 889 { 890 #ifdef CONFIG_UPROBES 891 mm->uprobes_state.xol_area = NULL; 892 #endif 893 } 894 895 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 896 struct user_namespace *user_ns) 897 { 898 mm->mmap = NULL; 899 mm->mm_rb = RB_ROOT; 900 mm->vmacache_seqnum = 0; 901 atomic_set(&mm->mm_users, 1); 902 atomic_set(&mm->mm_count, 1); 903 init_rwsem(&mm->mmap_sem); 904 INIT_LIST_HEAD(&mm->mmlist); 905 mm->core_state = NULL; 906 mm_pgtables_bytes_init(mm); 907 mm->map_count = 0; 908 mm->locked_vm = 0; 909 mm->pinned_vm = 0; 910 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 911 spin_lock_init(&mm->page_table_lock); 912 mm_init_cpumask(mm); 913 mm_init_aio(mm); 914 mm_init_owner(mm, p); 915 RCU_INIT_POINTER(mm->exe_file, NULL); 916 mmu_notifier_mm_init(mm); 917 hmm_mm_init(mm); 918 init_tlb_flush_pending(mm); 919 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 920 mm->pmd_huge_pte = NULL; 921 #endif 922 mm_init_uprobes_state(mm); 923 924 if (current->mm) { 925 mm->flags = current->mm->flags & MMF_INIT_MASK; 926 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 927 } else { 928 mm->flags = default_dump_filter; 929 mm->def_flags = 0; 930 } 931 932 if (mm_alloc_pgd(mm)) 933 goto fail_nopgd; 934 935 if (init_new_context(p, mm)) 936 goto fail_nocontext; 937 938 mm->user_ns = get_user_ns(user_ns); 939 return mm; 940 941 fail_nocontext: 942 mm_free_pgd(mm); 943 fail_nopgd: 944 free_mm(mm); 945 return NULL; 946 } 947 948 /* 949 * Allocate and initialize an mm_struct. 950 */ 951 struct mm_struct *mm_alloc(void) 952 { 953 struct mm_struct *mm; 954 955 mm = allocate_mm(); 956 if (!mm) 957 return NULL; 958 959 memset(mm, 0, sizeof(*mm)); 960 return mm_init(mm, current, current_user_ns()); 961 } 962 963 static inline void __mmput(struct mm_struct *mm) 964 { 965 VM_BUG_ON(atomic_read(&mm->mm_users)); 966 967 uprobe_clear_state(mm); 968 exit_aio(mm); 969 ksm_exit(mm); 970 khugepaged_exit(mm); /* must run before exit_mmap */ 971 exit_mmap(mm); 972 mm_put_huge_zero_page(mm); 973 set_mm_exe_file(mm, NULL); 974 if (!list_empty(&mm->mmlist)) { 975 spin_lock(&mmlist_lock); 976 list_del(&mm->mmlist); 977 spin_unlock(&mmlist_lock); 978 } 979 if (mm->binfmt) 980 module_put(mm->binfmt->module); 981 mmdrop(mm); 982 } 983 984 /* 985 * Decrement the use count and release all resources for an mm. 986 */ 987 void mmput(struct mm_struct *mm) 988 { 989 might_sleep(); 990 991 if (atomic_dec_and_test(&mm->mm_users)) 992 __mmput(mm); 993 } 994 EXPORT_SYMBOL_GPL(mmput); 995 996 #ifdef CONFIG_MMU 997 static void mmput_async_fn(struct work_struct *work) 998 { 999 struct mm_struct *mm = container_of(work, struct mm_struct, 1000 async_put_work); 1001 1002 __mmput(mm); 1003 } 1004 1005 void mmput_async(struct mm_struct *mm) 1006 { 1007 if (atomic_dec_and_test(&mm->mm_users)) { 1008 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1009 schedule_work(&mm->async_put_work); 1010 } 1011 } 1012 #endif 1013 1014 /** 1015 * set_mm_exe_file - change a reference to the mm's executable file 1016 * 1017 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1018 * 1019 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1020 * invocations: in mmput() nobody alive left, in execve task is single 1021 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1022 * mm->exe_file, but does so without using set_mm_exe_file() in order 1023 * to do avoid the need for any locks. 1024 */ 1025 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1026 { 1027 struct file *old_exe_file; 1028 1029 /* 1030 * It is safe to dereference the exe_file without RCU as 1031 * this function is only called if nobody else can access 1032 * this mm -- see comment above for justification. 1033 */ 1034 old_exe_file = rcu_dereference_raw(mm->exe_file); 1035 1036 if (new_exe_file) 1037 get_file(new_exe_file); 1038 rcu_assign_pointer(mm->exe_file, new_exe_file); 1039 if (old_exe_file) 1040 fput(old_exe_file); 1041 } 1042 1043 /** 1044 * get_mm_exe_file - acquire a reference to the mm's executable file 1045 * 1046 * Returns %NULL if mm has no associated executable file. 1047 * User must release file via fput(). 1048 */ 1049 struct file *get_mm_exe_file(struct mm_struct *mm) 1050 { 1051 struct file *exe_file; 1052 1053 rcu_read_lock(); 1054 exe_file = rcu_dereference(mm->exe_file); 1055 if (exe_file && !get_file_rcu(exe_file)) 1056 exe_file = NULL; 1057 rcu_read_unlock(); 1058 return exe_file; 1059 } 1060 EXPORT_SYMBOL(get_mm_exe_file); 1061 1062 /** 1063 * get_task_exe_file - acquire a reference to the task's executable file 1064 * 1065 * Returns %NULL if task's mm (if any) has no associated executable file or 1066 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1067 * User must release file via fput(). 1068 */ 1069 struct file *get_task_exe_file(struct task_struct *task) 1070 { 1071 struct file *exe_file = NULL; 1072 struct mm_struct *mm; 1073 1074 task_lock(task); 1075 mm = task->mm; 1076 if (mm) { 1077 if (!(task->flags & PF_KTHREAD)) 1078 exe_file = get_mm_exe_file(mm); 1079 } 1080 task_unlock(task); 1081 return exe_file; 1082 } 1083 EXPORT_SYMBOL(get_task_exe_file); 1084 1085 /** 1086 * get_task_mm - acquire a reference to the task's mm 1087 * 1088 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1089 * this kernel workthread has transiently adopted a user mm with use_mm, 1090 * to do its AIO) is not set and if so returns a reference to it, after 1091 * bumping up the use count. User must release the mm via mmput() 1092 * after use. Typically used by /proc and ptrace. 1093 */ 1094 struct mm_struct *get_task_mm(struct task_struct *task) 1095 { 1096 struct mm_struct *mm; 1097 1098 task_lock(task); 1099 mm = task->mm; 1100 if (mm) { 1101 if (task->flags & PF_KTHREAD) 1102 mm = NULL; 1103 else 1104 mmget(mm); 1105 } 1106 task_unlock(task); 1107 return mm; 1108 } 1109 EXPORT_SYMBOL_GPL(get_task_mm); 1110 1111 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1112 { 1113 struct mm_struct *mm; 1114 int err; 1115 1116 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1117 if (err) 1118 return ERR_PTR(err); 1119 1120 mm = get_task_mm(task); 1121 if (mm && mm != current->mm && 1122 !ptrace_may_access(task, mode)) { 1123 mmput(mm); 1124 mm = ERR_PTR(-EACCES); 1125 } 1126 mutex_unlock(&task->signal->cred_guard_mutex); 1127 1128 return mm; 1129 } 1130 1131 static void complete_vfork_done(struct task_struct *tsk) 1132 { 1133 struct completion *vfork; 1134 1135 task_lock(tsk); 1136 vfork = tsk->vfork_done; 1137 if (likely(vfork)) { 1138 tsk->vfork_done = NULL; 1139 complete(vfork); 1140 } 1141 task_unlock(tsk); 1142 } 1143 1144 static int wait_for_vfork_done(struct task_struct *child, 1145 struct completion *vfork) 1146 { 1147 int killed; 1148 1149 freezer_do_not_count(); 1150 killed = wait_for_completion_killable(vfork); 1151 freezer_count(); 1152 1153 if (killed) { 1154 task_lock(child); 1155 child->vfork_done = NULL; 1156 task_unlock(child); 1157 } 1158 1159 put_task_struct(child); 1160 return killed; 1161 } 1162 1163 /* Please note the differences between mmput and mm_release. 1164 * mmput is called whenever we stop holding onto a mm_struct, 1165 * error success whatever. 1166 * 1167 * mm_release is called after a mm_struct has been removed 1168 * from the current process. 1169 * 1170 * This difference is important for error handling, when we 1171 * only half set up a mm_struct for a new process and need to restore 1172 * the old one. Because we mmput the new mm_struct before 1173 * restoring the old one. . . 1174 * Eric Biederman 10 January 1998 1175 */ 1176 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1177 { 1178 /* Get rid of any futexes when releasing the mm */ 1179 #ifdef CONFIG_FUTEX 1180 if (unlikely(tsk->robust_list)) { 1181 exit_robust_list(tsk); 1182 tsk->robust_list = NULL; 1183 } 1184 #ifdef CONFIG_COMPAT 1185 if (unlikely(tsk->compat_robust_list)) { 1186 compat_exit_robust_list(tsk); 1187 tsk->compat_robust_list = NULL; 1188 } 1189 #endif 1190 if (unlikely(!list_empty(&tsk->pi_state_list))) 1191 exit_pi_state_list(tsk); 1192 #endif 1193 1194 uprobe_free_utask(tsk); 1195 1196 /* Get rid of any cached register state */ 1197 deactivate_mm(tsk, mm); 1198 1199 /* 1200 * Signal userspace if we're not exiting with a core dump 1201 * because we want to leave the value intact for debugging 1202 * purposes. 1203 */ 1204 if (tsk->clear_child_tid) { 1205 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1206 atomic_read(&mm->mm_users) > 1) { 1207 /* 1208 * We don't check the error code - if userspace has 1209 * not set up a proper pointer then tough luck. 1210 */ 1211 put_user(0, tsk->clear_child_tid); 1212 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 1213 1, NULL, NULL, 0); 1214 } 1215 tsk->clear_child_tid = NULL; 1216 } 1217 1218 /* 1219 * All done, finally we can wake up parent and return this mm to him. 1220 * Also kthread_stop() uses this completion for synchronization. 1221 */ 1222 if (tsk->vfork_done) 1223 complete_vfork_done(tsk); 1224 } 1225 1226 /* 1227 * Allocate a new mm structure and copy contents from the 1228 * mm structure of the passed in task structure. 1229 */ 1230 static struct mm_struct *dup_mm(struct task_struct *tsk) 1231 { 1232 struct mm_struct *mm, *oldmm = current->mm; 1233 int err; 1234 1235 mm = allocate_mm(); 1236 if (!mm) 1237 goto fail_nomem; 1238 1239 memcpy(mm, oldmm, sizeof(*mm)); 1240 1241 if (!mm_init(mm, tsk, mm->user_ns)) 1242 goto fail_nomem; 1243 1244 err = dup_mmap(mm, oldmm); 1245 if (err) 1246 goto free_pt; 1247 1248 mm->hiwater_rss = get_mm_rss(mm); 1249 mm->hiwater_vm = mm->total_vm; 1250 1251 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1252 goto free_pt; 1253 1254 return mm; 1255 1256 free_pt: 1257 /* don't put binfmt in mmput, we haven't got module yet */ 1258 mm->binfmt = NULL; 1259 mmput(mm); 1260 1261 fail_nomem: 1262 return NULL; 1263 } 1264 1265 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1266 { 1267 struct mm_struct *mm, *oldmm; 1268 int retval; 1269 1270 tsk->min_flt = tsk->maj_flt = 0; 1271 tsk->nvcsw = tsk->nivcsw = 0; 1272 #ifdef CONFIG_DETECT_HUNG_TASK 1273 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1274 #endif 1275 1276 tsk->mm = NULL; 1277 tsk->active_mm = NULL; 1278 1279 /* 1280 * Are we cloning a kernel thread? 1281 * 1282 * We need to steal a active VM for that.. 1283 */ 1284 oldmm = current->mm; 1285 if (!oldmm) 1286 return 0; 1287 1288 /* initialize the new vmacache entries */ 1289 vmacache_flush(tsk); 1290 1291 if (clone_flags & CLONE_VM) { 1292 mmget(oldmm); 1293 mm = oldmm; 1294 goto good_mm; 1295 } 1296 1297 retval = -ENOMEM; 1298 mm = dup_mm(tsk); 1299 if (!mm) 1300 goto fail_nomem; 1301 1302 good_mm: 1303 tsk->mm = mm; 1304 tsk->active_mm = mm; 1305 return 0; 1306 1307 fail_nomem: 1308 return retval; 1309 } 1310 1311 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1312 { 1313 struct fs_struct *fs = current->fs; 1314 if (clone_flags & CLONE_FS) { 1315 /* tsk->fs is already what we want */ 1316 spin_lock(&fs->lock); 1317 if (fs->in_exec) { 1318 spin_unlock(&fs->lock); 1319 return -EAGAIN; 1320 } 1321 fs->users++; 1322 spin_unlock(&fs->lock); 1323 return 0; 1324 } 1325 tsk->fs = copy_fs_struct(fs); 1326 if (!tsk->fs) 1327 return -ENOMEM; 1328 return 0; 1329 } 1330 1331 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1332 { 1333 struct files_struct *oldf, *newf; 1334 int error = 0; 1335 1336 /* 1337 * A background process may not have any files ... 1338 */ 1339 oldf = current->files; 1340 if (!oldf) 1341 goto out; 1342 1343 if (clone_flags & CLONE_FILES) { 1344 atomic_inc(&oldf->count); 1345 goto out; 1346 } 1347 1348 newf = dup_fd(oldf, &error); 1349 if (!newf) 1350 goto out; 1351 1352 tsk->files = newf; 1353 error = 0; 1354 out: 1355 return error; 1356 } 1357 1358 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1359 { 1360 #ifdef CONFIG_BLOCK 1361 struct io_context *ioc = current->io_context; 1362 struct io_context *new_ioc; 1363 1364 if (!ioc) 1365 return 0; 1366 /* 1367 * Share io context with parent, if CLONE_IO is set 1368 */ 1369 if (clone_flags & CLONE_IO) { 1370 ioc_task_link(ioc); 1371 tsk->io_context = ioc; 1372 } else if (ioprio_valid(ioc->ioprio)) { 1373 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1374 if (unlikely(!new_ioc)) 1375 return -ENOMEM; 1376 1377 new_ioc->ioprio = ioc->ioprio; 1378 put_io_context(new_ioc); 1379 } 1380 #endif 1381 return 0; 1382 } 1383 1384 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1385 { 1386 struct sighand_struct *sig; 1387 1388 if (clone_flags & CLONE_SIGHAND) { 1389 atomic_inc(¤t->sighand->count); 1390 return 0; 1391 } 1392 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1393 rcu_assign_pointer(tsk->sighand, sig); 1394 if (!sig) 1395 return -ENOMEM; 1396 1397 atomic_set(&sig->count, 1); 1398 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1399 return 0; 1400 } 1401 1402 void __cleanup_sighand(struct sighand_struct *sighand) 1403 { 1404 if (atomic_dec_and_test(&sighand->count)) { 1405 signalfd_cleanup(sighand); 1406 /* 1407 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1408 * without an RCU grace period, see __lock_task_sighand(). 1409 */ 1410 kmem_cache_free(sighand_cachep, sighand); 1411 } 1412 } 1413 1414 #ifdef CONFIG_POSIX_TIMERS 1415 /* 1416 * Initialize POSIX timer handling for a thread group. 1417 */ 1418 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1419 { 1420 unsigned long cpu_limit; 1421 1422 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1423 if (cpu_limit != RLIM_INFINITY) { 1424 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1425 sig->cputimer.running = true; 1426 } 1427 1428 /* The timer lists. */ 1429 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1430 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1431 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1432 } 1433 #else 1434 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1435 #endif 1436 1437 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1438 { 1439 struct signal_struct *sig; 1440 1441 if (clone_flags & CLONE_THREAD) 1442 return 0; 1443 1444 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1445 tsk->signal = sig; 1446 if (!sig) 1447 return -ENOMEM; 1448 1449 sig->nr_threads = 1; 1450 atomic_set(&sig->live, 1); 1451 atomic_set(&sig->sigcnt, 1); 1452 1453 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1454 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1455 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1456 1457 init_waitqueue_head(&sig->wait_chldexit); 1458 sig->curr_target = tsk; 1459 init_sigpending(&sig->shared_pending); 1460 seqlock_init(&sig->stats_lock); 1461 prev_cputime_init(&sig->prev_cputime); 1462 1463 #ifdef CONFIG_POSIX_TIMERS 1464 INIT_LIST_HEAD(&sig->posix_timers); 1465 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1466 sig->real_timer.function = it_real_fn; 1467 #endif 1468 1469 task_lock(current->group_leader); 1470 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1471 task_unlock(current->group_leader); 1472 1473 posix_cpu_timers_init_group(sig); 1474 1475 tty_audit_fork(sig); 1476 sched_autogroup_fork(sig); 1477 1478 sig->oom_score_adj = current->signal->oom_score_adj; 1479 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1480 1481 mutex_init(&sig->cred_guard_mutex); 1482 1483 return 0; 1484 } 1485 1486 static void copy_seccomp(struct task_struct *p) 1487 { 1488 #ifdef CONFIG_SECCOMP 1489 /* 1490 * Must be called with sighand->lock held, which is common to 1491 * all threads in the group. Holding cred_guard_mutex is not 1492 * needed because this new task is not yet running and cannot 1493 * be racing exec. 1494 */ 1495 assert_spin_locked(¤t->sighand->siglock); 1496 1497 /* Ref-count the new filter user, and assign it. */ 1498 get_seccomp_filter(current); 1499 p->seccomp = current->seccomp; 1500 1501 /* 1502 * Explicitly enable no_new_privs here in case it got set 1503 * between the task_struct being duplicated and holding the 1504 * sighand lock. The seccomp state and nnp must be in sync. 1505 */ 1506 if (task_no_new_privs(current)) 1507 task_set_no_new_privs(p); 1508 1509 /* 1510 * If the parent gained a seccomp mode after copying thread 1511 * flags and between before we held the sighand lock, we have 1512 * to manually enable the seccomp thread flag here. 1513 */ 1514 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1515 set_tsk_thread_flag(p, TIF_SECCOMP); 1516 #endif 1517 } 1518 1519 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1520 { 1521 current->clear_child_tid = tidptr; 1522 1523 return task_pid_vnr(current); 1524 } 1525 1526 static void rt_mutex_init_task(struct task_struct *p) 1527 { 1528 raw_spin_lock_init(&p->pi_lock); 1529 #ifdef CONFIG_RT_MUTEXES 1530 p->pi_waiters = RB_ROOT_CACHED; 1531 p->pi_top_task = NULL; 1532 p->pi_blocked_on = NULL; 1533 #endif 1534 } 1535 1536 #ifdef CONFIG_POSIX_TIMERS 1537 /* 1538 * Initialize POSIX timer handling for a single task. 1539 */ 1540 static void posix_cpu_timers_init(struct task_struct *tsk) 1541 { 1542 tsk->cputime_expires.prof_exp = 0; 1543 tsk->cputime_expires.virt_exp = 0; 1544 tsk->cputime_expires.sched_exp = 0; 1545 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1546 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1547 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1548 } 1549 #else 1550 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1551 #endif 1552 1553 static inline void 1554 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1555 { 1556 task->pids[type].pid = pid; 1557 } 1558 1559 static inline void rcu_copy_process(struct task_struct *p) 1560 { 1561 #ifdef CONFIG_PREEMPT_RCU 1562 p->rcu_read_lock_nesting = 0; 1563 p->rcu_read_unlock_special.s = 0; 1564 p->rcu_blocked_node = NULL; 1565 INIT_LIST_HEAD(&p->rcu_node_entry); 1566 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1567 #ifdef CONFIG_TASKS_RCU 1568 p->rcu_tasks_holdout = false; 1569 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1570 p->rcu_tasks_idle_cpu = -1; 1571 #endif /* #ifdef CONFIG_TASKS_RCU */ 1572 } 1573 1574 /* 1575 * This creates a new process as a copy of the old one, 1576 * but does not actually start it yet. 1577 * 1578 * It copies the registers, and all the appropriate 1579 * parts of the process environment (as per the clone 1580 * flags). The actual kick-off is left to the caller. 1581 */ 1582 static __latent_entropy struct task_struct *copy_process( 1583 unsigned long clone_flags, 1584 unsigned long stack_start, 1585 unsigned long stack_size, 1586 int __user *child_tidptr, 1587 struct pid *pid, 1588 int trace, 1589 unsigned long tls, 1590 int node) 1591 { 1592 int retval; 1593 struct task_struct *p; 1594 1595 /* 1596 * Don't allow sharing the root directory with processes in a different 1597 * namespace 1598 */ 1599 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1600 return ERR_PTR(-EINVAL); 1601 1602 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1603 return ERR_PTR(-EINVAL); 1604 1605 /* 1606 * Thread groups must share signals as well, and detached threads 1607 * can only be started up within the thread group. 1608 */ 1609 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1610 return ERR_PTR(-EINVAL); 1611 1612 /* 1613 * Shared signal handlers imply shared VM. By way of the above, 1614 * thread groups also imply shared VM. Blocking this case allows 1615 * for various simplifications in other code. 1616 */ 1617 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1618 return ERR_PTR(-EINVAL); 1619 1620 /* 1621 * Siblings of global init remain as zombies on exit since they are 1622 * not reaped by their parent (swapper). To solve this and to avoid 1623 * multi-rooted process trees, prevent global and container-inits 1624 * from creating siblings. 1625 */ 1626 if ((clone_flags & CLONE_PARENT) && 1627 current->signal->flags & SIGNAL_UNKILLABLE) 1628 return ERR_PTR(-EINVAL); 1629 1630 /* 1631 * If the new process will be in a different pid or user namespace 1632 * do not allow it to share a thread group with the forking task. 1633 */ 1634 if (clone_flags & CLONE_THREAD) { 1635 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1636 (task_active_pid_ns(current) != 1637 current->nsproxy->pid_ns_for_children)) 1638 return ERR_PTR(-EINVAL); 1639 } 1640 1641 retval = -ENOMEM; 1642 p = dup_task_struct(current, node); 1643 if (!p) 1644 goto fork_out; 1645 1646 /* 1647 * This _must_ happen before we call free_task(), i.e. before we jump 1648 * to any of the bad_fork_* labels. This is to avoid freeing 1649 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1650 * kernel threads (PF_KTHREAD). 1651 */ 1652 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1653 /* 1654 * Clear TID on mm_release()? 1655 */ 1656 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1657 1658 ftrace_graph_init_task(p); 1659 1660 rt_mutex_init_task(p); 1661 1662 #ifdef CONFIG_PROVE_LOCKING 1663 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1664 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1665 #endif 1666 retval = -EAGAIN; 1667 if (atomic_read(&p->real_cred->user->processes) >= 1668 task_rlimit(p, RLIMIT_NPROC)) { 1669 if (p->real_cred->user != INIT_USER && 1670 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1671 goto bad_fork_free; 1672 } 1673 current->flags &= ~PF_NPROC_EXCEEDED; 1674 1675 retval = copy_creds(p, clone_flags); 1676 if (retval < 0) 1677 goto bad_fork_free; 1678 1679 /* 1680 * If multiple threads are within copy_process(), then this check 1681 * triggers too late. This doesn't hurt, the check is only there 1682 * to stop root fork bombs. 1683 */ 1684 retval = -EAGAIN; 1685 if (nr_threads >= max_threads) 1686 goto bad_fork_cleanup_count; 1687 1688 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1689 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1690 p->flags |= PF_FORKNOEXEC; 1691 INIT_LIST_HEAD(&p->children); 1692 INIT_LIST_HEAD(&p->sibling); 1693 rcu_copy_process(p); 1694 p->vfork_done = NULL; 1695 spin_lock_init(&p->alloc_lock); 1696 1697 init_sigpending(&p->pending); 1698 1699 p->utime = p->stime = p->gtime = 0; 1700 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1701 p->utimescaled = p->stimescaled = 0; 1702 #endif 1703 prev_cputime_init(&p->prev_cputime); 1704 1705 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1706 seqcount_init(&p->vtime.seqcount); 1707 p->vtime.starttime = 0; 1708 p->vtime.state = VTIME_INACTIVE; 1709 #endif 1710 1711 #if defined(SPLIT_RSS_COUNTING) 1712 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1713 #endif 1714 1715 p->default_timer_slack_ns = current->timer_slack_ns; 1716 1717 task_io_accounting_init(&p->ioac); 1718 acct_clear_integrals(p); 1719 1720 posix_cpu_timers_init(p); 1721 1722 p->start_time = ktime_get_ns(); 1723 p->real_start_time = ktime_get_boot_ns(); 1724 p->io_context = NULL; 1725 p->audit_context = NULL; 1726 cgroup_fork(p); 1727 #ifdef CONFIG_NUMA 1728 p->mempolicy = mpol_dup(p->mempolicy); 1729 if (IS_ERR(p->mempolicy)) { 1730 retval = PTR_ERR(p->mempolicy); 1731 p->mempolicy = NULL; 1732 goto bad_fork_cleanup_threadgroup_lock; 1733 } 1734 #endif 1735 #ifdef CONFIG_CPUSETS 1736 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1737 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1738 seqcount_init(&p->mems_allowed_seq); 1739 #endif 1740 #ifdef CONFIG_TRACE_IRQFLAGS 1741 p->irq_events = 0; 1742 p->hardirqs_enabled = 0; 1743 p->hardirq_enable_ip = 0; 1744 p->hardirq_enable_event = 0; 1745 p->hardirq_disable_ip = _THIS_IP_; 1746 p->hardirq_disable_event = 0; 1747 p->softirqs_enabled = 1; 1748 p->softirq_enable_ip = _THIS_IP_; 1749 p->softirq_enable_event = 0; 1750 p->softirq_disable_ip = 0; 1751 p->softirq_disable_event = 0; 1752 p->hardirq_context = 0; 1753 p->softirq_context = 0; 1754 #endif 1755 1756 p->pagefault_disabled = 0; 1757 1758 #ifdef CONFIG_LOCKDEP 1759 p->lockdep_depth = 0; /* no locks held yet */ 1760 p->curr_chain_key = 0; 1761 p->lockdep_recursion = 0; 1762 lockdep_init_task(p); 1763 #endif 1764 1765 #ifdef CONFIG_DEBUG_MUTEXES 1766 p->blocked_on = NULL; /* not blocked yet */ 1767 #endif 1768 #ifdef CONFIG_BCACHE 1769 p->sequential_io = 0; 1770 p->sequential_io_avg = 0; 1771 #endif 1772 1773 /* Perform scheduler related setup. Assign this task to a CPU. */ 1774 retval = sched_fork(clone_flags, p); 1775 if (retval) 1776 goto bad_fork_cleanup_policy; 1777 1778 retval = perf_event_init_task(p); 1779 if (retval) 1780 goto bad_fork_cleanup_policy; 1781 retval = audit_alloc(p); 1782 if (retval) 1783 goto bad_fork_cleanup_perf; 1784 /* copy all the process information */ 1785 shm_init_task(p); 1786 retval = security_task_alloc(p, clone_flags); 1787 if (retval) 1788 goto bad_fork_cleanup_audit; 1789 retval = copy_semundo(clone_flags, p); 1790 if (retval) 1791 goto bad_fork_cleanup_security; 1792 retval = copy_files(clone_flags, p); 1793 if (retval) 1794 goto bad_fork_cleanup_semundo; 1795 retval = copy_fs(clone_flags, p); 1796 if (retval) 1797 goto bad_fork_cleanup_files; 1798 retval = copy_sighand(clone_flags, p); 1799 if (retval) 1800 goto bad_fork_cleanup_fs; 1801 retval = copy_signal(clone_flags, p); 1802 if (retval) 1803 goto bad_fork_cleanup_sighand; 1804 retval = copy_mm(clone_flags, p); 1805 if (retval) 1806 goto bad_fork_cleanup_signal; 1807 retval = copy_namespaces(clone_flags, p); 1808 if (retval) 1809 goto bad_fork_cleanup_mm; 1810 retval = copy_io(clone_flags, p); 1811 if (retval) 1812 goto bad_fork_cleanup_namespaces; 1813 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1814 if (retval) 1815 goto bad_fork_cleanup_io; 1816 1817 if (pid != &init_struct_pid) { 1818 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1819 if (IS_ERR(pid)) { 1820 retval = PTR_ERR(pid); 1821 goto bad_fork_cleanup_thread; 1822 } 1823 } 1824 1825 #ifdef CONFIG_BLOCK 1826 p->plug = NULL; 1827 #endif 1828 #ifdef CONFIG_FUTEX 1829 p->robust_list = NULL; 1830 #ifdef CONFIG_COMPAT 1831 p->compat_robust_list = NULL; 1832 #endif 1833 INIT_LIST_HEAD(&p->pi_state_list); 1834 p->pi_state_cache = NULL; 1835 #endif 1836 /* 1837 * sigaltstack should be cleared when sharing the same VM 1838 */ 1839 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1840 sas_ss_reset(p); 1841 1842 /* 1843 * Syscall tracing and stepping should be turned off in the 1844 * child regardless of CLONE_PTRACE. 1845 */ 1846 user_disable_single_step(p); 1847 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1848 #ifdef TIF_SYSCALL_EMU 1849 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1850 #endif 1851 clear_all_latency_tracing(p); 1852 1853 /* ok, now we should be set up.. */ 1854 p->pid = pid_nr(pid); 1855 if (clone_flags & CLONE_THREAD) { 1856 p->exit_signal = -1; 1857 p->group_leader = current->group_leader; 1858 p->tgid = current->tgid; 1859 } else { 1860 if (clone_flags & CLONE_PARENT) 1861 p->exit_signal = current->group_leader->exit_signal; 1862 else 1863 p->exit_signal = (clone_flags & CSIGNAL); 1864 p->group_leader = p; 1865 p->tgid = p->pid; 1866 } 1867 1868 p->nr_dirtied = 0; 1869 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1870 p->dirty_paused_when = 0; 1871 1872 p->pdeath_signal = 0; 1873 INIT_LIST_HEAD(&p->thread_group); 1874 p->task_works = NULL; 1875 1876 cgroup_threadgroup_change_begin(current); 1877 /* 1878 * Ensure that the cgroup subsystem policies allow the new process to be 1879 * forked. It should be noted the the new process's css_set can be changed 1880 * between here and cgroup_post_fork() if an organisation operation is in 1881 * progress. 1882 */ 1883 retval = cgroup_can_fork(p); 1884 if (retval) 1885 goto bad_fork_free_pid; 1886 1887 /* 1888 * Make it visible to the rest of the system, but dont wake it up yet. 1889 * Need tasklist lock for parent etc handling! 1890 */ 1891 write_lock_irq(&tasklist_lock); 1892 1893 /* CLONE_PARENT re-uses the old parent */ 1894 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1895 p->real_parent = current->real_parent; 1896 p->parent_exec_id = current->parent_exec_id; 1897 } else { 1898 p->real_parent = current; 1899 p->parent_exec_id = current->self_exec_id; 1900 } 1901 1902 klp_copy_process(p); 1903 1904 spin_lock(¤t->sighand->siglock); 1905 1906 /* 1907 * Copy seccomp details explicitly here, in case they were changed 1908 * before holding sighand lock. 1909 */ 1910 copy_seccomp(p); 1911 1912 /* 1913 * Process group and session signals need to be delivered to just the 1914 * parent before the fork or both the parent and the child after the 1915 * fork. Restart if a signal comes in before we add the new process to 1916 * it's process group. 1917 * A fatal signal pending means that current will exit, so the new 1918 * thread can't slip out of an OOM kill (or normal SIGKILL). 1919 */ 1920 recalc_sigpending(); 1921 if (signal_pending(current)) { 1922 retval = -ERESTARTNOINTR; 1923 goto bad_fork_cancel_cgroup; 1924 } 1925 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 1926 retval = -ENOMEM; 1927 goto bad_fork_cancel_cgroup; 1928 } 1929 1930 if (likely(p->pid)) { 1931 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1932 1933 init_task_pid(p, PIDTYPE_PID, pid); 1934 if (thread_group_leader(p)) { 1935 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1936 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1937 1938 if (is_child_reaper(pid)) { 1939 ns_of_pid(pid)->child_reaper = p; 1940 p->signal->flags |= SIGNAL_UNKILLABLE; 1941 } 1942 1943 p->signal->leader_pid = pid; 1944 p->signal->tty = tty_kref_get(current->signal->tty); 1945 /* 1946 * Inherit has_child_subreaper flag under the same 1947 * tasklist_lock with adding child to the process tree 1948 * for propagate_has_child_subreaper optimization. 1949 */ 1950 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1951 p->real_parent->signal->is_child_subreaper; 1952 list_add_tail(&p->sibling, &p->real_parent->children); 1953 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1954 attach_pid(p, PIDTYPE_PGID); 1955 attach_pid(p, PIDTYPE_SID); 1956 __this_cpu_inc(process_counts); 1957 } else { 1958 current->signal->nr_threads++; 1959 atomic_inc(¤t->signal->live); 1960 atomic_inc(¤t->signal->sigcnt); 1961 list_add_tail_rcu(&p->thread_group, 1962 &p->group_leader->thread_group); 1963 list_add_tail_rcu(&p->thread_node, 1964 &p->signal->thread_head); 1965 } 1966 attach_pid(p, PIDTYPE_PID); 1967 nr_threads++; 1968 } 1969 1970 total_forks++; 1971 spin_unlock(¤t->sighand->siglock); 1972 syscall_tracepoint_update(p); 1973 write_unlock_irq(&tasklist_lock); 1974 1975 proc_fork_connector(p); 1976 cgroup_post_fork(p); 1977 cgroup_threadgroup_change_end(current); 1978 perf_event_fork(p); 1979 1980 trace_task_newtask(p, clone_flags); 1981 uprobe_copy_process(p, clone_flags); 1982 1983 return p; 1984 1985 bad_fork_cancel_cgroup: 1986 spin_unlock(¤t->sighand->siglock); 1987 write_unlock_irq(&tasklist_lock); 1988 cgroup_cancel_fork(p); 1989 bad_fork_free_pid: 1990 cgroup_threadgroup_change_end(current); 1991 if (pid != &init_struct_pid) 1992 free_pid(pid); 1993 bad_fork_cleanup_thread: 1994 exit_thread(p); 1995 bad_fork_cleanup_io: 1996 if (p->io_context) 1997 exit_io_context(p); 1998 bad_fork_cleanup_namespaces: 1999 exit_task_namespaces(p); 2000 bad_fork_cleanup_mm: 2001 if (p->mm) 2002 mmput(p->mm); 2003 bad_fork_cleanup_signal: 2004 if (!(clone_flags & CLONE_THREAD)) 2005 free_signal_struct(p->signal); 2006 bad_fork_cleanup_sighand: 2007 __cleanup_sighand(p->sighand); 2008 bad_fork_cleanup_fs: 2009 exit_fs(p); /* blocking */ 2010 bad_fork_cleanup_files: 2011 exit_files(p); /* blocking */ 2012 bad_fork_cleanup_semundo: 2013 exit_sem(p); 2014 bad_fork_cleanup_security: 2015 security_task_free(p); 2016 bad_fork_cleanup_audit: 2017 audit_free(p); 2018 bad_fork_cleanup_perf: 2019 perf_event_free_task(p); 2020 bad_fork_cleanup_policy: 2021 lockdep_free_task(p); 2022 #ifdef CONFIG_NUMA 2023 mpol_put(p->mempolicy); 2024 bad_fork_cleanup_threadgroup_lock: 2025 #endif 2026 delayacct_tsk_free(p); 2027 bad_fork_cleanup_count: 2028 atomic_dec(&p->cred->user->processes); 2029 exit_creds(p); 2030 bad_fork_free: 2031 p->state = TASK_DEAD; 2032 put_task_stack(p); 2033 free_task(p); 2034 fork_out: 2035 return ERR_PTR(retval); 2036 } 2037 2038 static inline void init_idle_pids(struct pid_link *links) 2039 { 2040 enum pid_type type; 2041 2042 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2043 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 2044 links[type].pid = &init_struct_pid; 2045 } 2046 } 2047 2048 struct task_struct *fork_idle(int cpu) 2049 { 2050 struct task_struct *task; 2051 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2052 cpu_to_node(cpu)); 2053 if (!IS_ERR(task)) { 2054 init_idle_pids(task->pids); 2055 init_idle(task, cpu); 2056 } 2057 2058 return task; 2059 } 2060 2061 /* 2062 * Ok, this is the main fork-routine. 2063 * 2064 * It copies the process, and if successful kick-starts 2065 * it and waits for it to finish using the VM if required. 2066 */ 2067 long _do_fork(unsigned long clone_flags, 2068 unsigned long stack_start, 2069 unsigned long stack_size, 2070 int __user *parent_tidptr, 2071 int __user *child_tidptr, 2072 unsigned long tls) 2073 { 2074 struct completion vfork; 2075 struct pid *pid; 2076 struct task_struct *p; 2077 int trace = 0; 2078 long nr; 2079 2080 /* 2081 * Determine whether and which event to report to ptracer. When 2082 * called from kernel_thread or CLONE_UNTRACED is explicitly 2083 * requested, no event is reported; otherwise, report if the event 2084 * for the type of forking is enabled. 2085 */ 2086 if (!(clone_flags & CLONE_UNTRACED)) { 2087 if (clone_flags & CLONE_VFORK) 2088 trace = PTRACE_EVENT_VFORK; 2089 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2090 trace = PTRACE_EVENT_CLONE; 2091 else 2092 trace = PTRACE_EVENT_FORK; 2093 2094 if (likely(!ptrace_event_enabled(current, trace))) 2095 trace = 0; 2096 } 2097 2098 p = copy_process(clone_flags, stack_start, stack_size, 2099 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2100 add_latent_entropy(); 2101 2102 if (IS_ERR(p)) 2103 return PTR_ERR(p); 2104 2105 /* 2106 * Do this prior waking up the new thread - the thread pointer 2107 * might get invalid after that point, if the thread exits quickly. 2108 */ 2109 trace_sched_process_fork(current, p); 2110 2111 pid = get_task_pid(p, PIDTYPE_PID); 2112 nr = pid_vnr(pid); 2113 2114 if (clone_flags & CLONE_PARENT_SETTID) 2115 put_user(nr, parent_tidptr); 2116 2117 if (clone_flags & CLONE_VFORK) { 2118 p->vfork_done = &vfork; 2119 init_completion(&vfork); 2120 get_task_struct(p); 2121 } 2122 2123 wake_up_new_task(p); 2124 2125 /* forking complete and child started to run, tell ptracer */ 2126 if (unlikely(trace)) 2127 ptrace_event_pid(trace, pid); 2128 2129 if (clone_flags & CLONE_VFORK) { 2130 if (!wait_for_vfork_done(p, &vfork)) 2131 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2132 } 2133 2134 put_pid(pid); 2135 return nr; 2136 } 2137 2138 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2139 /* For compatibility with architectures that call do_fork directly rather than 2140 * using the syscall entry points below. */ 2141 long do_fork(unsigned long clone_flags, 2142 unsigned long stack_start, 2143 unsigned long stack_size, 2144 int __user *parent_tidptr, 2145 int __user *child_tidptr) 2146 { 2147 return _do_fork(clone_flags, stack_start, stack_size, 2148 parent_tidptr, child_tidptr, 0); 2149 } 2150 #endif 2151 2152 /* 2153 * Create a kernel thread. 2154 */ 2155 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2156 { 2157 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2158 (unsigned long)arg, NULL, NULL, 0); 2159 } 2160 2161 #ifdef __ARCH_WANT_SYS_FORK 2162 SYSCALL_DEFINE0(fork) 2163 { 2164 #ifdef CONFIG_MMU 2165 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2166 #else 2167 /* can not support in nommu mode */ 2168 return -EINVAL; 2169 #endif 2170 } 2171 #endif 2172 2173 #ifdef __ARCH_WANT_SYS_VFORK 2174 SYSCALL_DEFINE0(vfork) 2175 { 2176 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2177 0, NULL, NULL, 0); 2178 } 2179 #endif 2180 2181 #ifdef __ARCH_WANT_SYS_CLONE 2182 #ifdef CONFIG_CLONE_BACKWARDS 2183 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2184 int __user *, parent_tidptr, 2185 unsigned long, tls, 2186 int __user *, child_tidptr) 2187 #elif defined(CONFIG_CLONE_BACKWARDS2) 2188 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2189 int __user *, parent_tidptr, 2190 int __user *, child_tidptr, 2191 unsigned long, tls) 2192 #elif defined(CONFIG_CLONE_BACKWARDS3) 2193 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2194 int, stack_size, 2195 int __user *, parent_tidptr, 2196 int __user *, child_tidptr, 2197 unsigned long, tls) 2198 #else 2199 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2200 int __user *, parent_tidptr, 2201 int __user *, child_tidptr, 2202 unsigned long, tls) 2203 #endif 2204 { 2205 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2206 } 2207 #endif 2208 2209 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2210 { 2211 struct task_struct *leader, *parent, *child; 2212 int res; 2213 2214 read_lock(&tasklist_lock); 2215 leader = top = top->group_leader; 2216 down: 2217 for_each_thread(leader, parent) { 2218 list_for_each_entry(child, &parent->children, sibling) { 2219 res = visitor(child, data); 2220 if (res) { 2221 if (res < 0) 2222 goto out; 2223 leader = child; 2224 goto down; 2225 } 2226 up: 2227 ; 2228 } 2229 } 2230 2231 if (leader != top) { 2232 child = leader; 2233 parent = child->real_parent; 2234 leader = parent->group_leader; 2235 goto up; 2236 } 2237 out: 2238 read_unlock(&tasklist_lock); 2239 } 2240 2241 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2242 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2243 #endif 2244 2245 static void sighand_ctor(void *data) 2246 { 2247 struct sighand_struct *sighand = data; 2248 2249 spin_lock_init(&sighand->siglock); 2250 init_waitqueue_head(&sighand->signalfd_wqh); 2251 } 2252 2253 void __init proc_caches_init(void) 2254 { 2255 sighand_cachep = kmem_cache_create("sighand_cache", 2256 sizeof(struct sighand_struct), 0, 2257 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2258 SLAB_ACCOUNT, sighand_ctor); 2259 signal_cachep = kmem_cache_create("signal_cache", 2260 sizeof(struct signal_struct), 0, 2261 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2262 NULL); 2263 files_cachep = kmem_cache_create("files_cache", 2264 sizeof(struct files_struct), 0, 2265 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2266 NULL); 2267 fs_cachep = kmem_cache_create("fs_cache", 2268 sizeof(struct fs_struct), 0, 2269 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2270 NULL); 2271 /* 2272 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2273 * whole struct cpumask for the OFFSTACK case. We could change 2274 * this to *only* allocate as much of it as required by the 2275 * maximum number of CPU's we can ever have. The cpumask_allocation 2276 * is at the end of the structure, exactly for that reason. 2277 */ 2278 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2279 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2280 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2281 offsetof(struct mm_struct, saved_auxv), 2282 sizeof_field(struct mm_struct, saved_auxv), 2283 NULL); 2284 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2285 mmap_init(); 2286 nsproxy_cache_init(); 2287 } 2288 2289 /* 2290 * Check constraints on flags passed to the unshare system call. 2291 */ 2292 static int check_unshare_flags(unsigned long unshare_flags) 2293 { 2294 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2295 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2296 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2297 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2298 return -EINVAL; 2299 /* 2300 * Not implemented, but pretend it works if there is nothing 2301 * to unshare. Note that unsharing the address space or the 2302 * signal handlers also need to unshare the signal queues (aka 2303 * CLONE_THREAD). 2304 */ 2305 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2306 if (!thread_group_empty(current)) 2307 return -EINVAL; 2308 } 2309 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2310 if (atomic_read(¤t->sighand->count) > 1) 2311 return -EINVAL; 2312 } 2313 if (unshare_flags & CLONE_VM) { 2314 if (!current_is_single_threaded()) 2315 return -EINVAL; 2316 } 2317 2318 return 0; 2319 } 2320 2321 /* 2322 * Unshare the filesystem structure if it is being shared 2323 */ 2324 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2325 { 2326 struct fs_struct *fs = current->fs; 2327 2328 if (!(unshare_flags & CLONE_FS) || !fs) 2329 return 0; 2330 2331 /* don't need lock here; in the worst case we'll do useless copy */ 2332 if (fs->users == 1) 2333 return 0; 2334 2335 *new_fsp = copy_fs_struct(fs); 2336 if (!*new_fsp) 2337 return -ENOMEM; 2338 2339 return 0; 2340 } 2341 2342 /* 2343 * Unshare file descriptor table if it is being shared 2344 */ 2345 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2346 { 2347 struct files_struct *fd = current->files; 2348 int error = 0; 2349 2350 if ((unshare_flags & CLONE_FILES) && 2351 (fd && atomic_read(&fd->count) > 1)) { 2352 *new_fdp = dup_fd(fd, &error); 2353 if (!*new_fdp) 2354 return error; 2355 } 2356 2357 return 0; 2358 } 2359 2360 /* 2361 * unshare allows a process to 'unshare' part of the process 2362 * context which was originally shared using clone. copy_* 2363 * functions used by do_fork() cannot be used here directly 2364 * because they modify an inactive task_struct that is being 2365 * constructed. Here we are modifying the current, active, 2366 * task_struct. 2367 */ 2368 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2369 { 2370 struct fs_struct *fs, *new_fs = NULL; 2371 struct files_struct *fd, *new_fd = NULL; 2372 struct cred *new_cred = NULL; 2373 struct nsproxy *new_nsproxy = NULL; 2374 int do_sysvsem = 0; 2375 int err; 2376 2377 /* 2378 * If unsharing a user namespace must also unshare the thread group 2379 * and unshare the filesystem root and working directories. 2380 */ 2381 if (unshare_flags & CLONE_NEWUSER) 2382 unshare_flags |= CLONE_THREAD | CLONE_FS; 2383 /* 2384 * If unsharing vm, must also unshare signal handlers. 2385 */ 2386 if (unshare_flags & CLONE_VM) 2387 unshare_flags |= CLONE_SIGHAND; 2388 /* 2389 * If unsharing a signal handlers, must also unshare the signal queues. 2390 */ 2391 if (unshare_flags & CLONE_SIGHAND) 2392 unshare_flags |= CLONE_THREAD; 2393 /* 2394 * If unsharing namespace, must also unshare filesystem information. 2395 */ 2396 if (unshare_flags & CLONE_NEWNS) 2397 unshare_flags |= CLONE_FS; 2398 2399 err = check_unshare_flags(unshare_flags); 2400 if (err) 2401 goto bad_unshare_out; 2402 /* 2403 * CLONE_NEWIPC must also detach from the undolist: after switching 2404 * to a new ipc namespace, the semaphore arrays from the old 2405 * namespace are unreachable. 2406 */ 2407 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2408 do_sysvsem = 1; 2409 err = unshare_fs(unshare_flags, &new_fs); 2410 if (err) 2411 goto bad_unshare_out; 2412 err = unshare_fd(unshare_flags, &new_fd); 2413 if (err) 2414 goto bad_unshare_cleanup_fs; 2415 err = unshare_userns(unshare_flags, &new_cred); 2416 if (err) 2417 goto bad_unshare_cleanup_fd; 2418 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2419 new_cred, new_fs); 2420 if (err) 2421 goto bad_unshare_cleanup_cred; 2422 2423 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2424 if (do_sysvsem) { 2425 /* 2426 * CLONE_SYSVSEM is equivalent to sys_exit(). 2427 */ 2428 exit_sem(current); 2429 } 2430 if (unshare_flags & CLONE_NEWIPC) { 2431 /* Orphan segments in old ns (see sem above). */ 2432 exit_shm(current); 2433 shm_init_task(current); 2434 } 2435 2436 if (new_nsproxy) 2437 switch_task_namespaces(current, new_nsproxy); 2438 2439 task_lock(current); 2440 2441 if (new_fs) { 2442 fs = current->fs; 2443 spin_lock(&fs->lock); 2444 current->fs = new_fs; 2445 if (--fs->users) 2446 new_fs = NULL; 2447 else 2448 new_fs = fs; 2449 spin_unlock(&fs->lock); 2450 } 2451 2452 if (new_fd) { 2453 fd = current->files; 2454 current->files = new_fd; 2455 new_fd = fd; 2456 } 2457 2458 task_unlock(current); 2459 2460 if (new_cred) { 2461 /* Install the new user namespace */ 2462 commit_creds(new_cred); 2463 new_cred = NULL; 2464 } 2465 } 2466 2467 perf_event_namespaces(current); 2468 2469 bad_unshare_cleanup_cred: 2470 if (new_cred) 2471 put_cred(new_cred); 2472 bad_unshare_cleanup_fd: 2473 if (new_fd) 2474 put_files_struct(new_fd); 2475 2476 bad_unshare_cleanup_fs: 2477 if (new_fs) 2478 free_fs_struct(new_fs); 2479 2480 bad_unshare_out: 2481 return err; 2482 } 2483 2484 /* 2485 * Helper to unshare the files of the current task. 2486 * We don't want to expose copy_files internals to 2487 * the exec layer of the kernel. 2488 */ 2489 2490 int unshare_files(struct files_struct **displaced) 2491 { 2492 struct task_struct *task = current; 2493 struct files_struct *copy = NULL; 2494 int error; 2495 2496 error = unshare_fd(CLONE_FILES, ©); 2497 if (error || !copy) { 2498 *displaced = NULL; 2499 return error; 2500 } 2501 *displaced = task->files; 2502 task_lock(task); 2503 task->files = copy; 2504 task_unlock(task); 2505 return 0; 2506 } 2507 2508 int sysctl_max_threads(struct ctl_table *table, int write, 2509 void __user *buffer, size_t *lenp, loff_t *ppos) 2510 { 2511 struct ctl_table t; 2512 int ret; 2513 int threads = max_threads; 2514 int min = MIN_THREADS; 2515 int max = MAX_THREADS; 2516 2517 t = *table; 2518 t.data = &threads; 2519 t.extra1 = &min; 2520 t.extra2 = &max; 2521 2522 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2523 if (ret || !write) 2524 return ret; 2525 2526 set_max_threads(threads); 2527 2528 return 0; 2529 } 2530