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