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 void __mmdrop(struct mm_struct *mm) 596 { 597 BUG_ON(mm == &init_mm); 598 WARN_ON_ONCE(mm == current->mm); 599 WARN_ON_ONCE(mm == current->active_mm); 600 mm_free_pgd(mm); 601 destroy_context(mm); 602 hmm_mm_destroy(mm); 603 mmu_notifier_mm_destroy(mm); 604 check_mm(mm); 605 put_user_ns(mm->user_ns); 606 free_mm(mm); 607 } 608 EXPORT_SYMBOL_GPL(__mmdrop); 609 610 static void mmdrop_async_fn(struct work_struct *work) 611 { 612 struct mm_struct *mm; 613 614 mm = container_of(work, struct mm_struct, async_put_work); 615 __mmdrop(mm); 616 } 617 618 static void mmdrop_async(struct mm_struct *mm) 619 { 620 if (unlikely(atomic_dec_and_test(&mm->mm_count))) { 621 INIT_WORK(&mm->async_put_work, mmdrop_async_fn); 622 schedule_work(&mm->async_put_work); 623 } 624 } 625 626 static inline void free_signal_struct(struct signal_struct *sig) 627 { 628 taskstats_tgid_free(sig); 629 sched_autogroup_exit(sig); 630 /* 631 * __mmdrop is not safe to call from softirq context on x86 due to 632 * pgd_dtor so postpone it to the async context 633 */ 634 if (sig->oom_mm) 635 mmdrop_async(sig->oom_mm); 636 kmem_cache_free(signal_cachep, sig); 637 } 638 639 static inline void put_signal_struct(struct signal_struct *sig) 640 { 641 if (atomic_dec_and_test(&sig->sigcnt)) 642 free_signal_struct(sig); 643 } 644 645 void __put_task_struct(struct task_struct *tsk) 646 { 647 WARN_ON(!tsk->exit_state); 648 WARN_ON(atomic_read(&tsk->usage)); 649 WARN_ON(tsk == current); 650 651 cgroup_free(tsk); 652 task_numa_free(tsk); 653 security_task_free(tsk); 654 exit_creds(tsk); 655 delayacct_tsk_free(tsk); 656 put_signal_struct(tsk->signal); 657 658 if (!profile_handoff_task(tsk)) 659 free_task(tsk); 660 } 661 EXPORT_SYMBOL_GPL(__put_task_struct); 662 663 void __init __weak arch_task_cache_init(void) { } 664 665 /* 666 * set_max_threads 667 */ 668 static void set_max_threads(unsigned int max_threads_suggested) 669 { 670 u64 threads; 671 672 /* 673 * The number of threads shall be limited such that the thread 674 * structures may only consume a small part of the available memory. 675 */ 676 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64) 677 threads = MAX_THREADS; 678 else 679 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE, 680 (u64) THREAD_SIZE * 8UL); 681 682 if (threads > max_threads_suggested) 683 threads = max_threads_suggested; 684 685 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS); 686 } 687 688 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 689 /* Initialized by the architecture: */ 690 int arch_task_struct_size __read_mostly; 691 #endif 692 693 static void task_struct_whitelist(unsigned long *offset, unsigned long *size) 694 { 695 /* Fetch thread_struct whitelist for the architecture. */ 696 arch_thread_struct_whitelist(offset, size); 697 698 /* 699 * Handle zero-sized whitelist or empty thread_struct, otherwise 700 * adjust offset to position of thread_struct in task_struct. 701 */ 702 if (unlikely(*size == 0)) 703 *offset = 0; 704 else 705 *offset += offsetof(struct task_struct, thread); 706 } 707 708 void __init fork_init(void) 709 { 710 int i; 711 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 712 #ifndef ARCH_MIN_TASKALIGN 713 #define ARCH_MIN_TASKALIGN 0 714 #endif 715 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); 716 unsigned long useroffset, usersize; 717 718 /* create a slab on which task_structs can be allocated */ 719 task_struct_whitelist(&useroffset, &usersize); 720 task_struct_cachep = kmem_cache_create_usercopy("task_struct", 721 arch_task_struct_size, align, 722 SLAB_PANIC|SLAB_ACCOUNT, 723 useroffset, usersize, NULL); 724 #endif 725 726 /* do the arch specific task caches init */ 727 arch_task_cache_init(); 728 729 set_max_threads(MAX_THREADS); 730 731 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 732 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 733 init_task.signal->rlim[RLIMIT_SIGPENDING] = 734 init_task.signal->rlim[RLIMIT_NPROC]; 735 736 for (i = 0; i < UCOUNT_COUNTS; i++) { 737 init_user_ns.ucount_max[i] = max_threads/2; 738 } 739 740 #ifdef CONFIG_VMAP_STACK 741 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", 742 NULL, free_vm_stack_cache); 743 #endif 744 745 lockdep_init_task(&init_task); 746 } 747 748 int __weak arch_dup_task_struct(struct task_struct *dst, 749 struct task_struct *src) 750 { 751 *dst = *src; 752 return 0; 753 } 754 755 void set_task_stack_end_magic(struct task_struct *tsk) 756 { 757 unsigned long *stackend; 758 759 stackend = end_of_stack(tsk); 760 *stackend = STACK_END_MAGIC; /* for overflow detection */ 761 } 762 763 static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 764 { 765 struct task_struct *tsk; 766 unsigned long *stack; 767 struct vm_struct *stack_vm_area; 768 int err; 769 770 if (node == NUMA_NO_NODE) 771 node = tsk_fork_get_node(orig); 772 tsk = alloc_task_struct_node(node); 773 if (!tsk) 774 return NULL; 775 776 stack = alloc_thread_stack_node(tsk, node); 777 if (!stack) 778 goto free_tsk; 779 780 stack_vm_area = task_stack_vm_area(tsk); 781 782 err = arch_dup_task_struct(tsk, orig); 783 784 /* 785 * arch_dup_task_struct() clobbers the stack-related fields. Make 786 * sure they're properly initialized before using any stack-related 787 * functions again. 788 */ 789 tsk->stack = stack; 790 #ifdef CONFIG_VMAP_STACK 791 tsk->stack_vm_area = stack_vm_area; 792 #endif 793 #ifdef CONFIG_THREAD_INFO_IN_TASK 794 atomic_set(&tsk->stack_refcount, 1); 795 #endif 796 797 if (err) 798 goto free_stack; 799 800 #ifdef CONFIG_SECCOMP 801 /* 802 * We must handle setting up seccomp filters once we're under 803 * the sighand lock in case orig has changed between now and 804 * then. Until then, filter must be NULL to avoid messing up 805 * the usage counts on the error path calling free_task. 806 */ 807 tsk->seccomp.filter = NULL; 808 #endif 809 810 setup_thread_stack(tsk, orig); 811 clear_user_return_notifier(tsk); 812 clear_tsk_need_resched(tsk); 813 set_task_stack_end_magic(tsk); 814 815 #ifdef CONFIG_CC_STACKPROTECTOR 816 tsk->stack_canary = get_random_canary(); 817 #endif 818 819 /* 820 * One for us, one for whoever does the "release_task()" (usually 821 * parent) 822 */ 823 atomic_set(&tsk->usage, 2); 824 #ifdef CONFIG_BLK_DEV_IO_TRACE 825 tsk->btrace_seq = 0; 826 #endif 827 tsk->splice_pipe = NULL; 828 tsk->task_frag.page = NULL; 829 tsk->wake_q.next = NULL; 830 831 account_kernel_stack(tsk, 1); 832 833 kcov_task_init(tsk); 834 835 #ifdef CONFIG_FAULT_INJECTION 836 tsk->fail_nth = 0; 837 #endif 838 839 return tsk; 840 841 free_stack: 842 free_thread_stack(tsk); 843 free_tsk: 844 free_task_struct(tsk); 845 return NULL; 846 } 847 848 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 849 850 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 851 852 static int __init coredump_filter_setup(char *s) 853 { 854 default_dump_filter = 855 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 856 MMF_DUMP_FILTER_MASK; 857 return 1; 858 } 859 860 __setup("coredump_filter=", coredump_filter_setup); 861 862 #include <linux/init_task.h> 863 864 static void mm_init_aio(struct mm_struct *mm) 865 { 866 #ifdef CONFIG_AIO 867 spin_lock_init(&mm->ioctx_lock); 868 mm->ioctx_table = NULL; 869 #endif 870 } 871 872 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 873 { 874 #ifdef CONFIG_MEMCG 875 mm->owner = p; 876 #endif 877 } 878 879 static void mm_init_uprobes_state(struct mm_struct *mm) 880 { 881 #ifdef CONFIG_UPROBES 882 mm->uprobes_state.xol_area = NULL; 883 #endif 884 } 885 886 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, 887 struct user_namespace *user_ns) 888 { 889 mm->mmap = NULL; 890 mm->mm_rb = RB_ROOT; 891 mm->vmacache_seqnum = 0; 892 atomic_set(&mm->mm_users, 1); 893 atomic_set(&mm->mm_count, 1); 894 init_rwsem(&mm->mmap_sem); 895 INIT_LIST_HEAD(&mm->mmlist); 896 mm->core_state = NULL; 897 mm_pgtables_bytes_init(mm); 898 mm->map_count = 0; 899 mm->locked_vm = 0; 900 mm->pinned_vm = 0; 901 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 902 spin_lock_init(&mm->page_table_lock); 903 mm_init_cpumask(mm); 904 mm_init_aio(mm); 905 mm_init_owner(mm, p); 906 RCU_INIT_POINTER(mm->exe_file, NULL); 907 mmu_notifier_mm_init(mm); 908 hmm_mm_init(mm); 909 init_tlb_flush_pending(mm); 910 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS 911 mm->pmd_huge_pte = NULL; 912 #endif 913 mm_init_uprobes_state(mm); 914 915 if (current->mm) { 916 mm->flags = current->mm->flags & MMF_INIT_MASK; 917 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; 918 } else { 919 mm->flags = default_dump_filter; 920 mm->def_flags = 0; 921 } 922 923 if (mm_alloc_pgd(mm)) 924 goto fail_nopgd; 925 926 if (init_new_context(p, mm)) 927 goto fail_nocontext; 928 929 mm->user_ns = get_user_ns(user_ns); 930 return mm; 931 932 fail_nocontext: 933 mm_free_pgd(mm); 934 fail_nopgd: 935 free_mm(mm); 936 return NULL; 937 } 938 939 /* 940 * Allocate and initialize an mm_struct. 941 */ 942 struct mm_struct *mm_alloc(void) 943 { 944 struct mm_struct *mm; 945 946 mm = allocate_mm(); 947 if (!mm) 948 return NULL; 949 950 memset(mm, 0, sizeof(*mm)); 951 return mm_init(mm, current, current_user_ns()); 952 } 953 954 static inline void __mmput(struct mm_struct *mm) 955 { 956 VM_BUG_ON(atomic_read(&mm->mm_users)); 957 958 uprobe_clear_state(mm); 959 exit_aio(mm); 960 ksm_exit(mm); 961 khugepaged_exit(mm); /* must run before exit_mmap */ 962 exit_mmap(mm); 963 mm_put_huge_zero_page(mm); 964 set_mm_exe_file(mm, NULL); 965 if (!list_empty(&mm->mmlist)) { 966 spin_lock(&mmlist_lock); 967 list_del(&mm->mmlist); 968 spin_unlock(&mmlist_lock); 969 } 970 if (mm->binfmt) 971 module_put(mm->binfmt->module); 972 mmdrop(mm); 973 } 974 975 /* 976 * Decrement the use count and release all resources for an mm. 977 */ 978 void mmput(struct mm_struct *mm) 979 { 980 might_sleep(); 981 982 if (atomic_dec_and_test(&mm->mm_users)) 983 __mmput(mm); 984 } 985 EXPORT_SYMBOL_GPL(mmput); 986 987 #ifdef CONFIG_MMU 988 static void mmput_async_fn(struct work_struct *work) 989 { 990 struct mm_struct *mm = container_of(work, struct mm_struct, 991 async_put_work); 992 993 __mmput(mm); 994 } 995 996 void mmput_async(struct mm_struct *mm) 997 { 998 if (atomic_dec_and_test(&mm->mm_users)) { 999 INIT_WORK(&mm->async_put_work, mmput_async_fn); 1000 schedule_work(&mm->async_put_work); 1001 } 1002 } 1003 #endif 1004 1005 /** 1006 * set_mm_exe_file - change a reference to the mm's executable file 1007 * 1008 * This changes mm's executable file (shown as symlink /proc/[pid]/exe). 1009 * 1010 * Main users are mmput() and sys_execve(). Callers prevent concurrent 1011 * invocations: in mmput() nobody alive left, in execve task is single 1012 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the 1013 * mm->exe_file, but does so without using set_mm_exe_file() in order 1014 * to do avoid the need for any locks. 1015 */ 1016 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 1017 { 1018 struct file *old_exe_file; 1019 1020 /* 1021 * It is safe to dereference the exe_file without RCU as 1022 * this function is only called if nobody else can access 1023 * this mm -- see comment above for justification. 1024 */ 1025 old_exe_file = rcu_dereference_raw(mm->exe_file); 1026 1027 if (new_exe_file) 1028 get_file(new_exe_file); 1029 rcu_assign_pointer(mm->exe_file, new_exe_file); 1030 if (old_exe_file) 1031 fput(old_exe_file); 1032 } 1033 1034 /** 1035 * get_mm_exe_file - acquire a reference to the mm's executable file 1036 * 1037 * Returns %NULL if mm has no associated executable file. 1038 * User must release file via fput(). 1039 */ 1040 struct file *get_mm_exe_file(struct mm_struct *mm) 1041 { 1042 struct file *exe_file; 1043 1044 rcu_read_lock(); 1045 exe_file = rcu_dereference(mm->exe_file); 1046 if (exe_file && !get_file_rcu(exe_file)) 1047 exe_file = NULL; 1048 rcu_read_unlock(); 1049 return exe_file; 1050 } 1051 EXPORT_SYMBOL(get_mm_exe_file); 1052 1053 /** 1054 * get_task_exe_file - acquire a reference to the task's executable file 1055 * 1056 * Returns %NULL if task's mm (if any) has no associated executable file or 1057 * this is a kernel thread with borrowed mm (see the comment above get_task_mm). 1058 * User must release file via fput(). 1059 */ 1060 struct file *get_task_exe_file(struct task_struct *task) 1061 { 1062 struct file *exe_file = NULL; 1063 struct mm_struct *mm; 1064 1065 task_lock(task); 1066 mm = task->mm; 1067 if (mm) { 1068 if (!(task->flags & PF_KTHREAD)) 1069 exe_file = get_mm_exe_file(mm); 1070 } 1071 task_unlock(task); 1072 return exe_file; 1073 } 1074 EXPORT_SYMBOL(get_task_exe_file); 1075 1076 /** 1077 * get_task_mm - acquire a reference to the task's mm 1078 * 1079 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 1080 * this kernel workthread has transiently adopted a user mm with use_mm, 1081 * to do its AIO) is not set and if so returns a reference to it, after 1082 * bumping up the use count. User must release the mm via mmput() 1083 * after use. Typically used by /proc and ptrace. 1084 */ 1085 struct mm_struct *get_task_mm(struct task_struct *task) 1086 { 1087 struct mm_struct *mm; 1088 1089 task_lock(task); 1090 mm = task->mm; 1091 if (mm) { 1092 if (task->flags & PF_KTHREAD) 1093 mm = NULL; 1094 else 1095 mmget(mm); 1096 } 1097 task_unlock(task); 1098 return mm; 1099 } 1100 EXPORT_SYMBOL_GPL(get_task_mm); 1101 1102 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 1103 { 1104 struct mm_struct *mm; 1105 int err; 1106 1107 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 1108 if (err) 1109 return ERR_PTR(err); 1110 1111 mm = get_task_mm(task); 1112 if (mm && mm != current->mm && 1113 !ptrace_may_access(task, mode)) { 1114 mmput(mm); 1115 mm = ERR_PTR(-EACCES); 1116 } 1117 mutex_unlock(&task->signal->cred_guard_mutex); 1118 1119 return mm; 1120 } 1121 1122 static void complete_vfork_done(struct task_struct *tsk) 1123 { 1124 struct completion *vfork; 1125 1126 task_lock(tsk); 1127 vfork = tsk->vfork_done; 1128 if (likely(vfork)) { 1129 tsk->vfork_done = NULL; 1130 complete(vfork); 1131 } 1132 task_unlock(tsk); 1133 } 1134 1135 static int wait_for_vfork_done(struct task_struct *child, 1136 struct completion *vfork) 1137 { 1138 int killed; 1139 1140 freezer_do_not_count(); 1141 killed = wait_for_completion_killable(vfork); 1142 freezer_count(); 1143 1144 if (killed) { 1145 task_lock(child); 1146 child->vfork_done = NULL; 1147 task_unlock(child); 1148 } 1149 1150 put_task_struct(child); 1151 return killed; 1152 } 1153 1154 /* Please note the differences between mmput and mm_release. 1155 * mmput is called whenever we stop holding onto a mm_struct, 1156 * error success whatever. 1157 * 1158 * mm_release is called after a mm_struct has been removed 1159 * from the current process. 1160 * 1161 * This difference is important for error handling, when we 1162 * only half set up a mm_struct for a new process and need to restore 1163 * the old one. Because we mmput the new mm_struct before 1164 * restoring the old one. . . 1165 * Eric Biederman 10 January 1998 1166 */ 1167 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 1168 { 1169 /* Get rid of any futexes when releasing the mm */ 1170 #ifdef CONFIG_FUTEX 1171 if (unlikely(tsk->robust_list)) { 1172 exit_robust_list(tsk); 1173 tsk->robust_list = NULL; 1174 } 1175 #ifdef CONFIG_COMPAT 1176 if (unlikely(tsk->compat_robust_list)) { 1177 compat_exit_robust_list(tsk); 1178 tsk->compat_robust_list = NULL; 1179 } 1180 #endif 1181 if (unlikely(!list_empty(&tsk->pi_state_list))) 1182 exit_pi_state_list(tsk); 1183 #endif 1184 1185 uprobe_free_utask(tsk); 1186 1187 /* Get rid of any cached register state */ 1188 deactivate_mm(tsk, mm); 1189 1190 /* 1191 * Signal userspace if we're not exiting with a core dump 1192 * because we want to leave the value intact for debugging 1193 * purposes. 1194 */ 1195 if (tsk->clear_child_tid) { 1196 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) && 1197 atomic_read(&mm->mm_users) > 1) { 1198 /* 1199 * We don't check the error code - if userspace has 1200 * not set up a proper pointer then tough luck. 1201 */ 1202 put_user(0, tsk->clear_child_tid); 1203 do_futex(tsk->clear_child_tid, FUTEX_WAKE, 1204 1, NULL, NULL, 0, 0); 1205 } 1206 tsk->clear_child_tid = NULL; 1207 } 1208 1209 /* 1210 * All done, finally we can wake up parent and return this mm to him. 1211 * Also kthread_stop() uses this completion for synchronization. 1212 */ 1213 if (tsk->vfork_done) 1214 complete_vfork_done(tsk); 1215 } 1216 1217 /* 1218 * Allocate a new mm structure and copy contents from the 1219 * mm structure of the passed in task structure. 1220 */ 1221 static struct mm_struct *dup_mm(struct task_struct *tsk) 1222 { 1223 struct mm_struct *mm, *oldmm = current->mm; 1224 int err; 1225 1226 mm = allocate_mm(); 1227 if (!mm) 1228 goto fail_nomem; 1229 1230 memcpy(mm, oldmm, sizeof(*mm)); 1231 1232 if (!mm_init(mm, tsk, mm->user_ns)) 1233 goto fail_nomem; 1234 1235 err = dup_mmap(mm, oldmm); 1236 if (err) 1237 goto free_pt; 1238 1239 mm->hiwater_rss = get_mm_rss(mm); 1240 mm->hiwater_vm = mm->total_vm; 1241 1242 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 1243 goto free_pt; 1244 1245 return mm; 1246 1247 free_pt: 1248 /* don't put binfmt in mmput, we haven't got module yet */ 1249 mm->binfmt = NULL; 1250 mmput(mm); 1251 1252 fail_nomem: 1253 return NULL; 1254 } 1255 1256 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 1257 { 1258 struct mm_struct *mm, *oldmm; 1259 int retval; 1260 1261 tsk->min_flt = tsk->maj_flt = 0; 1262 tsk->nvcsw = tsk->nivcsw = 0; 1263 #ifdef CONFIG_DETECT_HUNG_TASK 1264 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 1265 #endif 1266 1267 tsk->mm = NULL; 1268 tsk->active_mm = NULL; 1269 1270 /* 1271 * Are we cloning a kernel thread? 1272 * 1273 * We need to steal a active VM for that.. 1274 */ 1275 oldmm = current->mm; 1276 if (!oldmm) 1277 return 0; 1278 1279 /* initialize the new vmacache entries */ 1280 vmacache_flush(tsk); 1281 1282 if (clone_flags & CLONE_VM) { 1283 mmget(oldmm); 1284 mm = oldmm; 1285 goto good_mm; 1286 } 1287 1288 retval = -ENOMEM; 1289 mm = dup_mm(tsk); 1290 if (!mm) 1291 goto fail_nomem; 1292 1293 good_mm: 1294 tsk->mm = mm; 1295 tsk->active_mm = mm; 1296 return 0; 1297 1298 fail_nomem: 1299 return retval; 1300 } 1301 1302 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 1303 { 1304 struct fs_struct *fs = current->fs; 1305 if (clone_flags & CLONE_FS) { 1306 /* tsk->fs is already what we want */ 1307 spin_lock(&fs->lock); 1308 if (fs->in_exec) { 1309 spin_unlock(&fs->lock); 1310 return -EAGAIN; 1311 } 1312 fs->users++; 1313 spin_unlock(&fs->lock); 1314 return 0; 1315 } 1316 tsk->fs = copy_fs_struct(fs); 1317 if (!tsk->fs) 1318 return -ENOMEM; 1319 return 0; 1320 } 1321 1322 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 1323 { 1324 struct files_struct *oldf, *newf; 1325 int error = 0; 1326 1327 /* 1328 * A background process may not have any files ... 1329 */ 1330 oldf = current->files; 1331 if (!oldf) 1332 goto out; 1333 1334 if (clone_flags & CLONE_FILES) { 1335 atomic_inc(&oldf->count); 1336 goto out; 1337 } 1338 1339 newf = dup_fd(oldf, &error); 1340 if (!newf) 1341 goto out; 1342 1343 tsk->files = newf; 1344 error = 0; 1345 out: 1346 return error; 1347 } 1348 1349 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 1350 { 1351 #ifdef CONFIG_BLOCK 1352 struct io_context *ioc = current->io_context; 1353 struct io_context *new_ioc; 1354 1355 if (!ioc) 1356 return 0; 1357 /* 1358 * Share io context with parent, if CLONE_IO is set 1359 */ 1360 if (clone_flags & CLONE_IO) { 1361 ioc_task_link(ioc); 1362 tsk->io_context = ioc; 1363 } else if (ioprio_valid(ioc->ioprio)) { 1364 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 1365 if (unlikely(!new_ioc)) 1366 return -ENOMEM; 1367 1368 new_ioc->ioprio = ioc->ioprio; 1369 put_io_context(new_ioc); 1370 } 1371 #endif 1372 return 0; 1373 } 1374 1375 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1376 { 1377 struct sighand_struct *sig; 1378 1379 if (clone_flags & CLONE_SIGHAND) { 1380 atomic_inc(¤t->sighand->count); 1381 return 0; 1382 } 1383 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1384 rcu_assign_pointer(tsk->sighand, sig); 1385 if (!sig) 1386 return -ENOMEM; 1387 1388 atomic_set(&sig->count, 1); 1389 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1390 return 0; 1391 } 1392 1393 void __cleanup_sighand(struct sighand_struct *sighand) 1394 { 1395 if (atomic_dec_and_test(&sighand->count)) { 1396 signalfd_cleanup(sighand); 1397 /* 1398 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it 1399 * without an RCU grace period, see __lock_task_sighand(). 1400 */ 1401 kmem_cache_free(sighand_cachep, sighand); 1402 } 1403 } 1404 1405 #ifdef CONFIG_POSIX_TIMERS 1406 /* 1407 * Initialize POSIX timer handling for a thread group. 1408 */ 1409 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1410 { 1411 unsigned long cpu_limit; 1412 1413 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1414 if (cpu_limit != RLIM_INFINITY) { 1415 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC; 1416 sig->cputimer.running = true; 1417 } 1418 1419 /* The timer lists. */ 1420 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1421 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1422 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1423 } 1424 #else 1425 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } 1426 #endif 1427 1428 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1429 { 1430 struct signal_struct *sig; 1431 1432 if (clone_flags & CLONE_THREAD) 1433 return 0; 1434 1435 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1436 tsk->signal = sig; 1437 if (!sig) 1438 return -ENOMEM; 1439 1440 sig->nr_threads = 1; 1441 atomic_set(&sig->live, 1); 1442 atomic_set(&sig->sigcnt, 1); 1443 1444 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ 1445 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); 1446 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head); 1447 1448 init_waitqueue_head(&sig->wait_chldexit); 1449 sig->curr_target = tsk; 1450 init_sigpending(&sig->shared_pending); 1451 seqlock_init(&sig->stats_lock); 1452 prev_cputime_init(&sig->prev_cputime); 1453 1454 #ifdef CONFIG_POSIX_TIMERS 1455 INIT_LIST_HEAD(&sig->posix_timers); 1456 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1457 sig->real_timer.function = it_real_fn; 1458 #endif 1459 1460 task_lock(current->group_leader); 1461 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1462 task_unlock(current->group_leader); 1463 1464 posix_cpu_timers_init_group(sig); 1465 1466 tty_audit_fork(sig); 1467 sched_autogroup_fork(sig); 1468 1469 sig->oom_score_adj = current->signal->oom_score_adj; 1470 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1471 1472 mutex_init(&sig->cred_guard_mutex); 1473 1474 return 0; 1475 } 1476 1477 static void copy_seccomp(struct task_struct *p) 1478 { 1479 #ifdef CONFIG_SECCOMP 1480 /* 1481 * Must be called with sighand->lock held, which is common to 1482 * all threads in the group. Holding cred_guard_mutex is not 1483 * needed because this new task is not yet running and cannot 1484 * be racing exec. 1485 */ 1486 assert_spin_locked(¤t->sighand->siglock); 1487 1488 /* Ref-count the new filter user, and assign it. */ 1489 get_seccomp_filter(current); 1490 p->seccomp = current->seccomp; 1491 1492 /* 1493 * Explicitly enable no_new_privs here in case it got set 1494 * between the task_struct being duplicated and holding the 1495 * sighand lock. The seccomp state and nnp must be in sync. 1496 */ 1497 if (task_no_new_privs(current)) 1498 task_set_no_new_privs(p); 1499 1500 /* 1501 * If the parent gained a seccomp mode after copying thread 1502 * flags and between before we held the sighand lock, we have 1503 * to manually enable the seccomp thread flag here. 1504 */ 1505 if (p->seccomp.mode != SECCOMP_MODE_DISABLED) 1506 set_tsk_thread_flag(p, TIF_SECCOMP); 1507 #endif 1508 } 1509 1510 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1511 { 1512 current->clear_child_tid = tidptr; 1513 1514 return task_pid_vnr(current); 1515 } 1516 1517 static void rt_mutex_init_task(struct task_struct *p) 1518 { 1519 raw_spin_lock_init(&p->pi_lock); 1520 #ifdef CONFIG_RT_MUTEXES 1521 p->pi_waiters = RB_ROOT_CACHED; 1522 p->pi_top_task = NULL; 1523 p->pi_blocked_on = NULL; 1524 #endif 1525 } 1526 1527 #ifdef CONFIG_POSIX_TIMERS 1528 /* 1529 * Initialize POSIX timer handling for a single task. 1530 */ 1531 static void posix_cpu_timers_init(struct task_struct *tsk) 1532 { 1533 tsk->cputime_expires.prof_exp = 0; 1534 tsk->cputime_expires.virt_exp = 0; 1535 tsk->cputime_expires.sched_exp = 0; 1536 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1537 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1538 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1539 } 1540 #else 1541 static inline void posix_cpu_timers_init(struct task_struct *tsk) { } 1542 #endif 1543 1544 static inline void 1545 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) 1546 { 1547 task->pids[type].pid = pid; 1548 } 1549 1550 static inline void rcu_copy_process(struct task_struct *p) 1551 { 1552 #ifdef CONFIG_PREEMPT_RCU 1553 p->rcu_read_lock_nesting = 0; 1554 p->rcu_read_unlock_special.s = 0; 1555 p->rcu_blocked_node = NULL; 1556 INIT_LIST_HEAD(&p->rcu_node_entry); 1557 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1558 #ifdef CONFIG_TASKS_RCU 1559 p->rcu_tasks_holdout = false; 1560 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list); 1561 p->rcu_tasks_idle_cpu = -1; 1562 #endif /* #ifdef CONFIG_TASKS_RCU */ 1563 } 1564 1565 /* 1566 * This creates a new process as a copy of the old one, 1567 * but does not actually start it yet. 1568 * 1569 * It copies the registers, and all the appropriate 1570 * parts of the process environment (as per the clone 1571 * flags). The actual kick-off is left to the caller. 1572 */ 1573 static __latent_entropy struct task_struct *copy_process( 1574 unsigned long clone_flags, 1575 unsigned long stack_start, 1576 unsigned long stack_size, 1577 int __user *child_tidptr, 1578 struct pid *pid, 1579 int trace, 1580 unsigned long tls, 1581 int node) 1582 { 1583 int retval; 1584 struct task_struct *p; 1585 1586 /* 1587 * Don't allow sharing the root directory with processes in a different 1588 * namespace 1589 */ 1590 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1591 return ERR_PTR(-EINVAL); 1592 1593 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS)) 1594 return ERR_PTR(-EINVAL); 1595 1596 /* 1597 * Thread groups must share signals as well, and detached threads 1598 * can only be started up within the thread group. 1599 */ 1600 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1601 return ERR_PTR(-EINVAL); 1602 1603 /* 1604 * Shared signal handlers imply shared VM. By way of the above, 1605 * thread groups also imply shared VM. Blocking this case allows 1606 * for various simplifications in other code. 1607 */ 1608 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1609 return ERR_PTR(-EINVAL); 1610 1611 /* 1612 * Siblings of global init remain as zombies on exit since they are 1613 * not reaped by their parent (swapper). To solve this and to avoid 1614 * multi-rooted process trees, prevent global and container-inits 1615 * from creating siblings. 1616 */ 1617 if ((clone_flags & CLONE_PARENT) && 1618 current->signal->flags & SIGNAL_UNKILLABLE) 1619 return ERR_PTR(-EINVAL); 1620 1621 /* 1622 * If the new process will be in a different pid or user namespace 1623 * do not allow it to share a thread group with the forking task. 1624 */ 1625 if (clone_flags & CLONE_THREAD) { 1626 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) || 1627 (task_active_pid_ns(current) != 1628 current->nsproxy->pid_ns_for_children)) 1629 return ERR_PTR(-EINVAL); 1630 } 1631 1632 retval = -ENOMEM; 1633 p = dup_task_struct(current, node); 1634 if (!p) 1635 goto fork_out; 1636 1637 /* 1638 * This _must_ happen before we call free_task(), i.e. before we jump 1639 * to any of the bad_fork_* labels. This is to avoid freeing 1640 * p->set_child_tid which is (ab)used as a kthread's data pointer for 1641 * kernel threads (PF_KTHREAD). 1642 */ 1643 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1644 /* 1645 * Clear TID on mm_release()? 1646 */ 1647 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1648 1649 ftrace_graph_init_task(p); 1650 1651 rt_mutex_init_task(p); 1652 1653 #ifdef CONFIG_PROVE_LOCKING 1654 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1655 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1656 #endif 1657 retval = -EAGAIN; 1658 if (atomic_read(&p->real_cred->user->processes) >= 1659 task_rlimit(p, RLIMIT_NPROC)) { 1660 if (p->real_cred->user != INIT_USER && 1661 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) 1662 goto bad_fork_free; 1663 } 1664 current->flags &= ~PF_NPROC_EXCEEDED; 1665 1666 retval = copy_creds(p, clone_flags); 1667 if (retval < 0) 1668 goto bad_fork_free; 1669 1670 /* 1671 * If multiple threads are within copy_process(), then this check 1672 * triggers too late. This doesn't hurt, the check is only there 1673 * to stop root fork bombs. 1674 */ 1675 retval = -EAGAIN; 1676 if (nr_threads >= max_threads) 1677 goto bad_fork_cleanup_count; 1678 1679 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1680 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE); 1681 p->flags |= PF_FORKNOEXEC; 1682 INIT_LIST_HEAD(&p->children); 1683 INIT_LIST_HEAD(&p->sibling); 1684 rcu_copy_process(p); 1685 p->vfork_done = NULL; 1686 spin_lock_init(&p->alloc_lock); 1687 1688 init_sigpending(&p->pending); 1689 1690 p->utime = p->stime = p->gtime = 0; 1691 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME 1692 p->utimescaled = p->stimescaled = 0; 1693 #endif 1694 prev_cputime_init(&p->prev_cputime); 1695 1696 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN 1697 seqcount_init(&p->vtime.seqcount); 1698 p->vtime.starttime = 0; 1699 p->vtime.state = VTIME_INACTIVE; 1700 #endif 1701 1702 #if defined(SPLIT_RSS_COUNTING) 1703 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1704 #endif 1705 1706 p->default_timer_slack_ns = current->timer_slack_ns; 1707 1708 task_io_accounting_init(&p->ioac); 1709 acct_clear_integrals(p); 1710 1711 posix_cpu_timers_init(p); 1712 1713 p->start_time = ktime_get_ns(); 1714 p->real_start_time = ktime_get_boot_ns(); 1715 p->io_context = NULL; 1716 p->audit_context = NULL; 1717 cgroup_fork(p); 1718 #ifdef CONFIG_NUMA 1719 p->mempolicy = mpol_dup(p->mempolicy); 1720 if (IS_ERR(p->mempolicy)) { 1721 retval = PTR_ERR(p->mempolicy); 1722 p->mempolicy = NULL; 1723 goto bad_fork_cleanup_threadgroup_lock; 1724 } 1725 #endif 1726 #ifdef CONFIG_CPUSETS 1727 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1728 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1729 seqcount_init(&p->mems_allowed_seq); 1730 #endif 1731 #ifdef CONFIG_TRACE_IRQFLAGS 1732 p->irq_events = 0; 1733 p->hardirqs_enabled = 0; 1734 p->hardirq_enable_ip = 0; 1735 p->hardirq_enable_event = 0; 1736 p->hardirq_disable_ip = _THIS_IP_; 1737 p->hardirq_disable_event = 0; 1738 p->softirqs_enabled = 1; 1739 p->softirq_enable_ip = _THIS_IP_; 1740 p->softirq_enable_event = 0; 1741 p->softirq_disable_ip = 0; 1742 p->softirq_disable_event = 0; 1743 p->hardirq_context = 0; 1744 p->softirq_context = 0; 1745 #endif 1746 1747 p->pagefault_disabled = 0; 1748 1749 #ifdef CONFIG_LOCKDEP 1750 p->lockdep_depth = 0; /* no locks held yet */ 1751 p->curr_chain_key = 0; 1752 p->lockdep_recursion = 0; 1753 lockdep_init_task(p); 1754 #endif 1755 1756 #ifdef CONFIG_DEBUG_MUTEXES 1757 p->blocked_on = NULL; /* not blocked yet */ 1758 #endif 1759 #ifdef CONFIG_BCACHE 1760 p->sequential_io = 0; 1761 p->sequential_io_avg = 0; 1762 #endif 1763 1764 /* Perform scheduler related setup. Assign this task to a CPU. */ 1765 retval = sched_fork(clone_flags, p); 1766 if (retval) 1767 goto bad_fork_cleanup_policy; 1768 1769 retval = perf_event_init_task(p); 1770 if (retval) 1771 goto bad_fork_cleanup_policy; 1772 retval = audit_alloc(p); 1773 if (retval) 1774 goto bad_fork_cleanup_perf; 1775 /* copy all the process information */ 1776 shm_init_task(p); 1777 retval = security_task_alloc(p, clone_flags); 1778 if (retval) 1779 goto bad_fork_cleanup_audit; 1780 retval = copy_semundo(clone_flags, p); 1781 if (retval) 1782 goto bad_fork_cleanup_security; 1783 retval = copy_files(clone_flags, p); 1784 if (retval) 1785 goto bad_fork_cleanup_semundo; 1786 retval = copy_fs(clone_flags, p); 1787 if (retval) 1788 goto bad_fork_cleanup_files; 1789 retval = copy_sighand(clone_flags, p); 1790 if (retval) 1791 goto bad_fork_cleanup_fs; 1792 retval = copy_signal(clone_flags, p); 1793 if (retval) 1794 goto bad_fork_cleanup_sighand; 1795 retval = copy_mm(clone_flags, p); 1796 if (retval) 1797 goto bad_fork_cleanup_signal; 1798 retval = copy_namespaces(clone_flags, p); 1799 if (retval) 1800 goto bad_fork_cleanup_mm; 1801 retval = copy_io(clone_flags, p); 1802 if (retval) 1803 goto bad_fork_cleanup_namespaces; 1804 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls); 1805 if (retval) 1806 goto bad_fork_cleanup_io; 1807 1808 if (pid != &init_struct_pid) { 1809 pid = alloc_pid(p->nsproxy->pid_ns_for_children); 1810 if (IS_ERR(pid)) { 1811 retval = PTR_ERR(pid); 1812 goto bad_fork_cleanup_thread; 1813 } 1814 } 1815 1816 #ifdef CONFIG_BLOCK 1817 p->plug = NULL; 1818 #endif 1819 #ifdef CONFIG_FUTEX 1820 p->robust_list = NULL; 1821 #ifdef CONFIG_COMPAT 1822 p->compat_robust_list = NULL; 1823 #endif 1824 INIT_LIST_HEAD(&p->pi_state_list); 1825 p->pi_state_cache = NULL; 1826 #endif 1827 /* 1828 * sigaltstack should be cleared when sharing the same VM 1829 */ 1830 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1831 sas_ss_reset(p); 1832 1833 /* 1834 * Syscall tracing and stepping should be turned off in the 1835 * child regardless of CLONE_PTRACE. 1836 */ 1837 user_disable_single_step(p); 1838 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1839 #ifdef TIF_SYSCALL_EMU 1840 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1841 #endif 1842 clear_all_latency_tracing(p); 1843 1844 /* ok, now we should be set up.. */ 1845 p->pid = pid_nr(pid); 1846 if (clone_flags & CLONE_THREAD) { 1847 p->exit_signal = -1; 1848 p->group_leader = current->group_leader; 1849 p->tgid = current->tgid; 1850 } else { 1851 if (clone_flags & CLONE_PARENT) 1852 p->exit_signal = current->group_leader->exit_signal; 1853 else 1854 p->exit_signal = (clone_flags & CSIGNAL); 1855 p->group_leader = p; 1856 p->tgid = p->pid; 1857 } 1858 1859 p->nr_dirtied = 0; 1860 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1861 p->dirty_paused_when = 0; 1862 1863 p->pdeath_signal = 0; 1864 INIT_LIST_HEAD(&p->thread_group); 1865 p->task_works = NULL; 1866 1867 cgroup_threadgroup_change_begin(current); 1868 /* 1869 * Ensure that the cgroup subsystem policies allow the new process to be 1870 * forked. It should be noted the the new process's css_set can be changed 1871 * between here and cgroup_post_fork() if an organisation operation is in 1872 * progress. 1873 */ 1874 retval = cgroup_can_fork(p); 1875 if (retval) 1876 goto bad_fork_free_pid; 1877 1878 /* 1879 * Make it visible to the rest of the system, but dont wake it up yet. 1880 * Need tasklist lock for parent etc handling! 1881 */ 1882 write_lock_irq(&tasklist_lock); 1883 1884 /* CLONE_PARENT re-uses the old parent */ 1885 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1886 p->real_parent = current->real_parent; 1887 p->parent_exec_id = current->parent_exec_id; 1888 } else { 1889 p->real_parent = current; 1890 p->parent_exec_id = current->self_exec_id; 1891 } 1892 1893 klp_copy_process(p); 1894 1895 spin_lock(¤t->sighand->siglock); 1896 1897 /* 1898 * Copy seccomp details explicitly here, in case they were changed 1899 * before holding sighand lock. 1900 */ 1901 copy_seccomp(p); 1902 1903 /* 1904 * Process group and session signals need to be delivered to just the 1905 * parent before the fork or both the parent and the child after the 1906 * fork. Restart if a signal comes in before we add the new process to 1907 * it's process group. 1908 * A fatal signal pending means that current will exit, so the new 1909 * thread can't slip out of an OOM kill (or normal SIGKILL). 1910 */ 1911 recalc_sigpending(); 1912 if (signal_pending(current)) { 1913 retval = -ERESTARTNOINTR; 1914 goto bad_fork_cancel_cgroup; 1915 } 1916 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { 1917 retval = -ENOMEM; 1918 goto bad_fork_cancel_cgroup; 1919 } 1920 1921 if (likely(p->pid)) { 1922 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1923 1924 init_task_pid(p, PIDTYPE_PID, pid); 1925 if (thread_group_leader(p)) { 1926 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1927 init_task_pid(p, PIDTYPE_SID, task_session(current)); 1928 1929 if (is_child_reaper(pid)) { 1930 ns_of_pid(pid)->child_reaper = p; 1931 p->signal->flags |= SIGNAL_UNKILLABLE; 1932 } 1933 1934 p->signal->leader_pid = pid; 1935 p->signal->tty = tty_kref_get(current->signal->tty); 1936 /* 1937 * Inherit has_child_subreaper flag under the same 1938 * tasklist_lock with adding child to the process tree 1939 * for propagate_has_child_subreaper optimization. 1940 */ 1941 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper || 1942 p->real_parent->signal->is_child_subreaper; 1943 list_add_tail(&p->sibling, &p->real_parent->children); 1944 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1945 attach_pid(p, PIDTYPE_PGID); 1946 attach_pid(p, PIDTYPE_SID); 1947 __this_cpu_inc(process_counts); 1948 } else { 1949 current->signal->nr_threads++; 1950 atomic_inc(¤t->signal->live); 1951 atomic_inc(¤t->signal->sigcnt); 1952 list_add_tail_rcu(&p->thread_group, 1953 &p->group_leader->thread_group); 1954 list_add_tail_rcu(&p->thread_node, 1955 &p->signal->thread_head); 1956 } 1957 attach_pid(p, PIDTYPE_PID); 1958 nr_threads++; 1959 } 1960 1961 total_forks++; 1962 spin_unlock(¤t->sighand->siglock); 1963 syscall_tracepoint_update(p); 1964 write_unlock_irq(&tasklist_lock); 1965 1966 proc_fork_connector(p); 1967 cgroup_post_fork(p); 1968 cgroup_threadgroup_change_end(current); 1969 perf_event_fork(p); 1970 1971 trace_task_newtask(p, clone_flags); 1972 uprobe_copy_process(p, clone_flags); 1973 1974 return p; 1975 1976 bad_fork_cancel_cgroup: 1977 spin_unlock(¤t->sighand->siglock); 1978 write_unlock_irq(&tasklist_lock); 1979 cgroup_cancel_fork(p); 1980 bad_fork_free_pid: 1981 cgroup_threadgroup_change_end(current); 1982 if (pid != &init_struct_pid) 1983 free_pid(pid); 1984 bad_fork_cleanup_thread: 1985 exit_thread(p); 1986 bad_fork_cleanup_io: 1987 if (p->io_context) 1988 exit_io_context(p); 1989 bad_fork_cleanup_namespaces: 1990 exit_task_namespaces(p); 1991 bad_fork_cleanup_mm: 1992 if (p->mm) 1993 mmput(p->mm); 1994 bad_fork_cleanup_signal: 1995 if (!(clone_flags & CLONE_THREAD)) 1996 free_signal_struct(p->signal); 1997 bad_fork_cleanup_sighand: 1998 __cleanup_sighand(p->sighand); 1999 bad_fork_cleanup_fs: 2000 exit_fs(p); /* blocking */ 2001 bad_fork_cleanup_files: 2002 exit_files(p); /* blocking */ 2003 bad_fork_cleanup_semundo: 2004 exit_sem(p); 2005 bad_fork_cleanup_security: 2006 security_task_free(p); 2007 bad_fork_cleanup_audit: 2008 audit_free(p); 2009 bad_fork_cleanup_perf: 2010 perf_event_free_task(p); 2011 bad_fork_cleanup_policy: 2012 lockdep_free_task(p); 2013 #ifdef CONFIG_NUMA 2014 mpol_put(p->mempolicy); 2015 bad_fork_cleanup_threadgroup_lock: 2016 #endif 2017 delayacct_tsk_free(p); 2018 bad_fork_cleanup_count: 2019 atomic_dec(&p->cred->user->processes); 2020 exit_creds(p); 2021 bad_fork_free: 2022 p->state = TASK_DEAD; 2023 put_task_stack(p); 2024 free_task(p); 2025 fork_out: 2026 return ERR_PTR(retval); 2027 } 2028 2029 static inline void init_idle_pids(struct pid_link *links) 2030 { 2031 enum pid_type type; 2032 2033 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 2034 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 2035 links[type].pid = &init_struct_pid; 2036 } 2037 } 2038 2039 struct task_struct *fork_idle(int cpu) 2040 { 2041 struct task_struct *task; 2042 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, 2043 cpu_to_node(cpu)); 2044 if (!IS_ERR(task)) { 2045 init_idle_pids(task->pids); 2046 init_idle(task, cpu); 2047 } 2048 2049 return task; 2050 } 2051 2052 /* 2053 * Ok, this is the main fork-routine. 2054 * 2055 * It copies the process, and if successful kick-starts 2056 * it and waits for it to finish using the VM if required. 2057 */ 2058 long _do_fork(unsigned long clone_flags, 2059 unsigned long stack_start, 2060 unsigned long stack_size, 2061 int __user *parent_tidptr, 2062 int __user *child_tidptr, 2063 unsigned long tls) 2064 { 2065 struct completion vfork; 2066 struct pid *pid; 2067 struct task_struct *p; 2068 int trace = 0; 2069 long nr; 2070 2071 /* 2072 * Determine whether and which event to report to ptracer. When 2073 * called from kernel_thread or CLONE_UNTRACED is explicitly 2074 * requested, no event is reported; otherwise, report if the event 2075 * for the type of forking is enabled. 2076 */ 2077 if (!(clone_flags & CLONE_UNTRACED)) { 2078 if (clone_flags & CLONE_VFORK) 2079 trace = PTRACE_EVENT_VFORK; 2080 else if ((clone_flags & CSIGNAL) != SIGCHLD) 2081 trace = PTRACE_EVENT_CLONE; 2082 else 2083 trace = PTRACE_EVENT_FORK; 2084 2085 if (likely(!ptrace_event_enabled(current, trace))) 2086 trace = 0; 2087 } 2088 2089 p = copy_process(clone_flags, stack_start, stack_size, 2090 child_tidptr, NULL, trace, tls, NUMA_NO_NODE); 2091 add_latent_entropy(); 2092 2093 if (IS_ERR(p)) 2094 return PTR_ERR(p); 2095 2096 /* 2097 * Do this prior waking up the new thread - the thread pointer 2098 * might get invalid after that point, if the thread exits quickly. 2099 */ 2100 trace_sched_process_fork(current, p); 2101 2102 pid = get_task_pid(p, PIDTYPE_PID); 2103 nr = pid_vnr(pid); 2104 2105 if (clone_flags & CLONE_PARENT_SETTID) 2106 put_user(nr, parent_tidptr); 2107 2108 if (clone_flags & CLONE_VFORK) { 2109 p->vfork_done = &vfork; 2110 init_completion(&vfork); 2111 get_task_struct(p); 2112 } 2113 2114 wake_up_new_task(p); 2115 2116 /* forking complete and child started to run, tell ptracer */ 2117 if (unlikely(trace)) 2118 ptrace_event_pid(trace, pid); 2119 2120 if (clone_flags & CLONE_VFORK) { 2121 if (!wait_for_vfork_done(p, &vfork)) 2122 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid); 2123 } 2124 2125 put_pid(pid); 2126 return nr; 2127 } 2128 2129 #ifndef CONFIG_HAVE_COPY_THREAD_TLS 2130 /* For compatibility with architectures that call do_fork directly rather than 2131 * using the syscall entry points below. */ 2132 long do_fork(unsigned long clone_flags, 2133 unsigned long stack_start, 2134 unsigned long stack_size, 2135 int __user *parent_tidptr, 2136 int __user *child_tidptr) 2137 { 2138 return _do_fork(clone_flags, stack_start, stack_size, 2139 parent_tidptr, child_tidptr, 0); 2140 } 2141 #endif 2142 2143 /* 2144 * Create a kernel thread. 2145 */ 2146 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 2147 { 2148 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn, 2149 (unsigned long)arg, NULL, NULL, 0); 2150 } 2151 2152 #ifdef __ARCH_WANT_SYS_FORK 2153 SYSCALL_DEFINE0(fork) 2154 { 2155 #ifdef CONFIG_MMU 2156 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0); 2157 #else 2158 /* can not support in nommu mode */ 2159 return -EINVAL; 2160 #endif 2161 } 2162 #endif 2163 2164 #ifdef __ARCH_WANT_SYS_VFORK 2165 SYSCALL_DEFINE0(vfork) 2166 { 2167 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 2168 0, NULL, NULL, 0); 2169 } 2170 #endif 2171 2172 #ifdef __ARCH_WANT_SYS_CLONE 2173 #ifdef CONFIG_CLONE_BACKWARDS 2174 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2175 int __user *, parent_tidptr, 2176 unsigned long, tls, 2177 int __user *, child_tidptr) 2178 #elif defined(CONFIG_CLONE_BACKWARDS2) 2179 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, 2180 int __user *, parent_tidptr, 2181 int __user *, child_tidptr, 2182 unsigned long, tls) 2183 #elif defined(CONFIG_CLONE_BACKWARDS3) 2184 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, 2185 int, stack_size, 2186 int __user *, parent_tidptr, 2187 int __user *, child_tidptr, 2188 unsigned long, tls) 2189 #else 2190 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 2191 int __user *, parent_tidptr, 2192 int __user *, child_tidptr, 2193 unsigned long, tls) 2194 #endif 2195 { 2196 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls); 2197 } 2198 #endif 2199 2200 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data) 2201 { 2202 struct task_struct *leader, *parent, *child; 2203 int res; 2204 2205 read_lock(&tasklist_lock); 2206 leader = top = top->group_leader; 2207 down: 2208 for_each_thread(leader, parent) { 2209 list_for_each_entry(child, &parent->children, sibling) { 2210 res = visitor(child, data); 2211 if (res) { 2212 if (res < 0) 2213 goto out; 2214 leader = child; 2215 goto down; 2216 } 2217 up: 2218 ; 2219 } 2220 } 2221 2222 if (leader != top) { 2223 child = leader; 2224 parent = child->real_parent; 2225 leader = parent->group_leader; 2226 goto up; 2227 } 2228 out: 2229 read_unlock(&tasklist_lock); 2230 } 2231 2232 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 2233 #define ARCH_MIN_MMSTRUCT_ALIGN 0 2234 #endif 2235 2236 static void sighand_ctor(void *data) 2237 { 2238 struct sighand_struct *sighand = data; 2239 2240 spin_lock_init(&sighand->siglock); 2241 init_waitqueue_head(&sighand->signalfd_wqh); 2242 } 2243 2244 void __init proc_caches_init(void) 2245 { 2246 sighand_cachep = kmem_cache_create("sighand_cache", 2247 sizeof(struct sighand_struct), 0, 2248 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| 2249 SLAB_ACCOUNT, sighand_ctor); 2250 signal_cachep = kmem_cache_create("signal_cache", 2251 sizeof(struct signal_struct), 0, 2252 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2253 NULL); 2254 files_cachep = kmem_cache_create("files_cache", 2255 sizeof(struct files_struct), 0, 2256 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2257 NULL); 2258 fs_cachep = kmem_cache_create("fs_cache", 2259 sizeof(struct fs_struct), 0, 2260 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2261 NULL); 2262 /* 2263 * FIXME! The "sizeof(struct mm_struct)" currently includes the 2264 * whole struct cpumask for the OFFSTACK case. We could change 2265 * this to *only* allocate as much of it as required by the 2266 * maximum number of CPU's we can ever have. The cpumask_allocation 2267 * is at the end of the structure, exactly for that reason. 2268 */ 2269 mm_cachep = kmem_cache_create_usercopy("mm_struct", 2270 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 2271 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 2272 offsetof(struct mm_struct, saved_auxv), 2273 sizeof_field(struct mm_struct, saved_auxv), 2274 NULL); 2275 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); 2276 mmap_init(); 2277 nsproxy_cache_init(); 2278 } 2279 2280 /* 2281 * Check constraints on flags passed to the unshare system call. 2282 */ 2283 static int check_unshare_flags(unsigned long unshare_flags) 2284 { 2285 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 2286 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 2287 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET| 2288 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP)) 2289 return -EINVAL; 2290 /* 2291 * Not implemented, but pretend it works if there is nothing 2292 * to unshare. Note that unsharing the address space or the 2293 * signal handlers also need to unshare the signal queues (aka 2294 * CLONE_THREAD). 2295 */ 2296 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 2297 if (!thread_group_empty(current)) 2298 return -EINVAL; 2299 } 2300 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) { 2301 if (atomic_read(¤t->sighand->count) > 1) 2302 return -EINVAL; 2303 } 2304 if (unshare_flags & CLONE_VM) { 2305 if (!current_is_single_threaded()) 2306 return -EINVAL; 2307 } 2308 2309 return 0; 2310 } 2311 2312 /* 2313 * Unshare the filesystem structure if it is being shared 2314 */ 2315 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 2316 { 2317 struct fs_struct *fs = current->fs; 2318 2319 if (!(unshare_flags & CLONE_FS) || !fs) 2320 return 0; 2321 2322 /* don't need lock here; in the worst case we'll do useless copy */ 2323 if (fs->users == 1) 2324 return 0; 2325 2326 *new_fsp = copy_fs_struct(fs); 2327 if (!*new_fsp) 2328 return -ENOMEM; 2329 2330 return 0; 2331 } 2332 2333 /* 2334 * Unshare file descriptor table if it is being shared 2335 */ 2336 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 2337 { 2338 struct files_struct *fd = current->files; 2339 int error = 0; 2340 2341 if ((unshare_flags & CLONE_FILES) && 2342 (fd && atomic_read(&fd->count) > 1)) { 2343 *new_fdp = dup_fd(fd, &error); 2344 if (!*new_fdp) 2345 return error; 2346 } 2347 2348 return 0; 2349 } 2350 2351 /* 2352 * unshare allows a process to 'unshare' part of the process 2353 * context which was originally shared using clone. copy_* 2354 * functions used by do_fork() cannot be used here directly 2355 * because they modify an inactive task_struct that is being 2356 * constructed. Here we are modifying the current, active, 2357 * task_struct. 2358 */ 2359 int ksys_unshare(unsigned long unshare_flags) 2360 { 2361 struct fs_struct *fs, *new_fs = NULL; 2362 struct files_struct *fd, *new_fd = NULL; 2363 struct cred *new_cred = NULL; 2364 struct nsproxy *new_nsproxy = NULL; 2365 int do_sysvsem = 0; 2366 int err; 2367 2368 /* 2369 * If unsharing a user namespace must also unshare the thread group 2370 * and unshare the filesystem root and working directories. 2371 */ 2372 if (unshare_flags & CLONE_NEWUSER) 2373 unshare_flags |= CLONE_THREAD | CLONE_FS; 2374 /* 2375 * If unsharing vm, must also unshare signal handlers. 2376 */ 2377 if (unshare_flags & CLONE_VM) 2378 unshare_flags |= CLONE_SIGHAND; 2379 /* 2380 * If unsharing a signal handlers, must also unshare the signal queues. 2381 */ 2382 if (unshare_flags & CLONE_SIGHAND) 2383 unshare_flags |= CLONE_THREAD; 2384 /* 2385 * If unsharing namespace, must also unshare filesystem information. 2386 */ 2387 if (unshare_flags & CLONE_NEWNS) 2388 unshare_flags |= CLONE_FS; 2389 2390 err = check_unshare_flags(unshare_flags); 2391 if (err) 2392 goto bad_unshare_out; 2393 /* 2394 * CLONE_NEWIPC must also detach from the undolist: after switching 2395 * to a new ipc namespace, the semaphore arrays from the old 2396 * namespace are unreachable. 2397 */ 2398 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 2399 do_sysvsem = 1; 2400 err = unshare_fs(unshare_flags, &new_fs); 2401 if (err) 2402 goto bad_unshare_out; 2403 err = unshare_fd(unshare_flags, &new_fd); 2404 if (err) 2405 goto bad_unshare_cleanup_fs; 2406 err = unshare_userns(unshare_flags, &new_cred); 2407 if (err) 2408 goto bad_unshare_cleanup_fd; 2409 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 2410 new_cred, new_fs); 2411 if (err) 2412 goto bad_unshare_cleanup_cred; 2413 2414 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { 2415 if (do_sysvsem) { 2416 /* 2417 * CLONE_SYSVSEM is equivalent to sys_exit(). 2418 */ 2419 exit_sem(current); 2420 } 2421 if (unshare_flags & CLONE_NEWIPC) { 2422 /* Orphan segments in old ns (see sem above). */ 2423 exit_shm(current); 2424 shm_init_task(current); 2425 } 2426 2427 if (new_nsproxy) 2428 switch_task_namespaces(current, new_nsproxy); 2429 2430 task_lock(current); 2431 2432 if (new_fs) { 2433 fs = current->fs; 2434 spin_lock(&fs->lock); 2435 current->fs = new_fs; 2436 if (--fs->users) 2437 new_fs = NULL; 2438 else 2439 new_fs = fs; 2440 spin_unlock(&fs->lock); 2441 } 2442 2443 if (new_fd) { 2444 fd = current->files; 2445 current->files = new_fd; 2446 new_fd = fd; 2447 } 2448 2449 task_unlock(current); 2450 2451 if (new_cred) { 2452 /* Install the new user namespace */ 2453 commit_creds(new_cred); 2454 new_cred = NULL; 2455 } 2456 } 2457 2458 perf_event_namespaces(current); 2459 2460 bad_unshare_cleanup_cred: 2461 if (new_cred) 2462 put_cred(new_cred); 2463 bad_unshare_cleanup_fd: 2464 if (new_fd) 2465 put_files_struct(new_fd); 2466 2467 bad_unshare_cleanup_fs: 2468 if (new_fs) 2469 free_fs_struct(new_fs); 2470 2471 bad_unshare_out: 2472 return err; 2473 } 2474 2475 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 2476 { 2477 return ksys_unshare(unshare_flags); 2478 } 2479 2480 /* 2481 * Helper to unshare the files of the current task. 2482 * We don't want to expose copy_files internals to 2483 * the exec layer of the kernel. 2484 */ 2485 2486 int unshare_files(struct files_struct **displaced) 2487 { 2488 struct task_struct *task = current; 2489 struct files_struct *copy = NULL; 2490 int error; 2491 2492 error = unshare_fd(CLONE_FILES, ©); 2493 if (error || !copy) { 2494 *displaced = NULL; 2495 return error; 2496 } 2497 *displaced = task->files; 2498 task_lock(task); 2499 task->files = copy; 2500 task_unlock(task); 2501 return 0; 2502 } 2503 2504 int sysctl_max_threads(struct ctl_table *table, int write, 2505 void __user *buffer, size_t *lenp, loff_t *ppos) 2506 { 2507 struct ctl_table t; 2508 int ret; 2509 int threads = max_threads; 2510 int min = MIN_THREADS; 2511 int max = MAX_THREADS; 2512 2513 t = *table; 2514 t.data = &threads; 2515 t.extra1 = &min; 2516 t.extra2 = &max; 2517 2518 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 2519 if (ret || !write) 2520 return ret; 2521 2522 set_max_threads(threads); 2523 2524 return 0; 2525 } 2526