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