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/init.h> 16 #include <linux/unistd.h> 17 #include <linux/smp_lock.h> 18 #include <linux/module.h> 19 #include <linux/vmalloc.h> 20 #include <linux/completion.h> 21 #include <linux/mnt_namespace.h> 22 #include <linux/personality.h> 23 #include <linux/mempolicy.h> 24 #include <linux/sem.h> 25 #include <linux/file.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/fs.h> 30 #include <linux/nsproxy.h> 31 #include <linux/capability.h> 32 #include <linux/cpu.h> 33 #include <linux/cpuset.h> 34 #include <linux/security.h> 35 #include <linux/swap.h> 36 #include <linux/syscalls.h> 37 #include <linux/jiffies.h> 38 #include <linux/futex.h> 39 #include <linux/rcupdate.h> 40 #include <linux/ptrace.h> 41 #include <linux/mount.h> 42 #include <linux/audit.h> 43 #include <linux/profile.h> 44 #include <linux/rmap.h> 45 #include <linux/acct.h> 46 #include <linux/tsacct_kern.h> 47 #include <linux/cn_proc.h> 48 #include <linux/delayacct.h> 49 #include <linux/taskstats_kern.h> 50 #include <linux/random.h> 51 52 #include <asm/pgtable.h> 53 #include <asm/pgalloc.h> 54 #include <asm/uaccess.h> 55 #include <asm/mmu_context.h> 56 #include <asm/cacheflush.h> 57 #include <asm/tlbflush.h> 58 59 /* 60 * Protected counters by write_lock_irq(&tasklist_lock) 61 */ 62 unsigned long total_forks; /* Handle normal Linux uptimes. */ 63 int nr_threads; /* The idle threads do not count.. */ 64 65 int max_threads; /* tunable limit on nr_threads */ 66 67 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 68 69 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 70 71 int nr_processes(void) 72 { 73 int cpu; 74 int total = 0; 75 76 for_each_online_cpu(cpu) 77 total += per_cpu(process_counts, cpu); 78 79 return total; 80 } 81 82 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 83 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 84 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 85 static struct kmem_cache *task_struct_cachep; 86 #endif 87 88 /* SLAB cache for signal_struct structures (tsk->signal) */ 89 static struct kmem_cache *signal_cachep; 90 91 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 92 struct kmem_cache *sighand_cachep; 93 94 /* SLAB cache for files_struct structures (tsk->files) */ 95 struct kmem_cache *files_cachep; 96 97 /* SLAB cache for fs_struct structures (tsk->fs) */ 98 struct kmem_cache *fs_cachep; 99 100 /* SLAB cache for vm_area_struct structures */ 101 struct kmem_cache *vm_area_cachep; 102 103 /* SLAB cache for mm_struct structures (tsk->mm) */ 104 static struct kmem_cache *mm_cachep; 105 106 void free_task(struct task_struct *tsk) 107 { 108 free_thread_info(tsk->thread_info); 109 rt_mutex_debug_task_free(tsk); 110 free_task_struct(tsk); 111 } 112 EXPORT_SYMBOL(free_task); 113 114 void __put_task_struct(struct task_struct *tsk) 115 { 116 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 117 WARN_ON(atomic_read(&tsk->usage)); 118 WARN_ON(tsk == current); 119 120 security_task_free(tsk); 121 free_uid(tsk->user); 122 put_group_info(tsk->group_info); 123 delayacct_tsk_free(tsk); 124 125 if (!profile_handoff_task(tsk)) 126 free_task(tsk); 127 } 128 129 void __init fork_init(unsigned long mempages) 130 { 131 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 132 #ifndef ARCH_MIN_TASKALIGN 133 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 134 #endif 135 /* create a slab on which task_structs can be allocated */ 136 task_struct_cachep = 137 kmem_cache_create("task_struct", sizeof(struct task_struct), 138 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 139 #endif 140 141 /* 142 * The default maximum number of threads is set to a safe 143 * value: the thread structures can take up at most half 144 * of memory. 145 */ 146 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 147 148 /* 149 * we need to allow at least 20 threads to boot a system 150 */ 151 if(max_threads < 20) 152 max_threads = 20; 153 154 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 155 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 156 init_task.signal->rlim[RLIMIT_SIGPENDING] = 157 init_task.signal->rlim[RLIMIT_NPROC]; 158 } 159 160 static struct task_struct *dup_task_struct(struct task_struct *orig) 161 { 162 struct task_struct *tsk; 163 struct thread_info *ti; 164 165 prepare_to_copy(orig); 166 167 tsk = alloc_task_struct(); 168 if (!tsk) 169 return NULL; 170 171 ti = alloc_thread_info(tsk); 172 if (!ti) { 173 free_task_struct(tsk); 174 return NULL; 175 } 176 177 *tsk = *orig; 178 tsk->thread_info = ti; 179 setup_thread_stack(tsk, orig); 180 181 #ifdef CONFIG_CC_STACKPROTECTOR 182 tsk->stack_canary = get_random_int(); 183 #endif 184 185 /* One for us, one for whoever does the "release_task()" (usually parent) */ 186 atomic_set(&tsk->usage,2); 187 atomic_set(&tsk->fs_excl, 0); 188 #ifdef CONFIG_BLK_DEV_IO_TRACE 189 tsk->btrace_seq = 0; 190 #endif 191 tsk->splice_pipe = NULL; 192 return tsk; 193 } 194 195 #ifdef CONFIG_MMU 196 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 197 { 198 struct vm_area_struct *mpnt, *tmp, **pprev; 199 struct rb_node **rb_link, *rb_parent; 200 int retval; 201 unsigned long charge; 202 struct mempolicy *pol; 203 204 down_write(&oldmm->mmap_sem); 205 flush_cache_mm(oldmm); 206 /* 207 * Not linked in yet - no deadlock potential: 208 */ 209 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 210 211 mm->locked_vm = 0; 212 mm->mmap = NULL; 213 mm->mmap_cache = NULL; 214 mm->free_area_cache = oldmm->mmap_base; 215 mm->cached_hole_size = ~0UL; 216 mm->map_count = 0; 217 cpus_clear(mm->cpu_vm_mask); 218 mm->mm_rb = RB_ROOT; 219 rb_link = &mm->mm_rb.rb_node; 220 rb_parent = NULL; 221 pprev = &mm->mmap; 222 223 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 224 struct file *file; 225 226 if (mpnt->vm_flags & VM_DONTCOPY) { 227 long pages = vma_pages(mpnt); 228 mm->total_vm -= pages; 229 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 230 -pages); 231 continue; 232 } 233 charge = 0; 234 if (mpnt->vm_flags & VM_ACCOUNT) { 235 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 236 if (security_vm_enough_memory(len)) 237 goto fail_nomem; 238 charge = len; 239 } 240 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 241 if (!tmp) 242 goto fail_nomem; 243 *tmp = *mpnt; 244 pol = mpol_copy(vma_policy(mpnt)); 245 retval = PTR_ERR(pol); 246 if (IS_ERR(pol)) 247 goto fail_nomem_policy; 248 vma_set_policy(tmp, pol); 249 tmp->vm_flags &= ~VM_LOCKED; 250 tmp->vm_mm = mm; 251 tmp->vm_next = NULL; 252 anon_vma_link(tmp); 253 file = tmp->vm_file; 254 if (file) { 255 struct inode *inode = file->f_path.dentry->d_inode; 256 get_file(file); 257 if (tmp->vm_flags & VM_DENYWRITE) 258 atomic_dec(&inode->i_writecount); 259 260 /* insert tmp into the share list, just after mpnt */ 261 spin_lock(&file->f_mapping->i_mmap_lock); 262 tmp->vm_truncate_count = mpnt->vm_truncate_count; 263 flush_dcache_mmap_lock(file->f_mapping); 264 vma_prio_tree_add(tmp, mpnt); 265 flush_dcache_mmap_unlock(file->f_mapping); 266 spin_unlock(&file->f_mapping->i_mmap_lock); 267 } 268 269 /* 270 * Link in the new vma and copy the page table entries. 271 */ 272 *pprev = tmp; 273 pprev = &tmp->vm_next; 274 275 __vma_link_rb(mm, tmp, rb_link, rb_parent); 276 rb_link = &tmp->vm_rb.rb_right; 277 rb_parent = &tmp->vm_rb; 278 279 mm->map_count++; 280 retval = copy_page_range(mm, oldmm, mpnt); 281 282 if (tmp->vm_ops && tmp->vm_ops->open) 283 tmp->vm_ops->open(tmp); 284 285 if (retval) 286 goto out; 287 } 288 retval = 0; 289 out: 290 up_write(&mm->mmap_sem); 291 flush_tlb_mm(oldmm); 292 up_write(&oldmm->mmap_sem); 293 return retval; 294 fail_nomem_policy: 295 kmem_cache_free(vm_area_cachep, tmp); 296 fail_nomem: 297 retval = -ENOMEM; 298 vm_unacct_memory(charge); 299 goto out; 300 } 301 302 static inline int mm_alloc_pgd(struct mm_struct * mm) 303 { 304 mm->pgd = pgd_alloc(mm); 305 if (unlikely(!mm->pgd)) 306 return -ENOMEM; 307 return 0; 308 } 309 310 static inline void mm_free_pgd(struct mm_struct * mm) 311 { 312 pgd_free(mm->pgd); 313 } 314 #else 315 #define dup_mmap(mm, oldmm) (0) 316 #define mm_alloc_pgd(mm) (0) 317 #define mm_free_pgd(mm) 318 #endif /* CONFIG_MMU */ 319 320 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 321 322 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 323 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 324 325 #include <linux/init_task.h> 326 327 static struct mm_struct * mm_init(struct mm_struct * mm) 328 { 329 atomic_set(&mm->mm_users, 1); 330 atomic_set(&mm->mm_count, 1); 331 init_rwsem(&mm->mmap_sem); 332 INIT_LIST_HEAD(&mm->mmlist); 333 mm->core_waiters = 0; 334 mm->nr_ptes = 0; 335 set_mm_counter(mm, file_rss, 0); 336 set_mm_counter(mm, anon_rss, 0); 337 spin_lock_init(&mm->page_table_lock); 338 rwlock_init(&mm->ioctx_list_lock); 339 mm->ioctx_list = NULL; 340 mm->free_area_cache = TASK_UNMAPPED_BASE; 341 mm->cached_hole_size = ~0UL; 342 343 if (likely(!mm_alloc_pgd(mm))) { 344 mm->def_flags = 0; 345 return mm; 346 } 347 free_mm(mm); 348 return NULL; 349 } 350 351 /* 352 * Allocate and initialize an mm_struct. 353 */ 354 struct mm_struct * mm_alloc(void) 355 { 356 struct mm_struct * mm; 357 358 mm = allocate_mm(); 359 if (mm) { 360 memset(mm, 0, sizeof(*mm)); 361 mm = mm_init(mm); 362 } 363 return mm; 364 } 365 366 /* 367 * Called when the last reference to the mm 368 * is dropped: either by a lazy thread or by 369 * mmput. Free the page directory and the mm. 370 */ 371 void fastcall __mmdrop(struct mm_struct *mm) 372 { 373 BUG_ON(mm == &init_mm); 374 mm_free_pgd(mm); 375 destroy_context(mm); 376 free_mm(mm); 377 } 378 379 /* 380 * Decrement the use count and release all resources for an mm. 381 */ 382 void mmput(struct mm_struct *mm) 383 { 384 might_sleep(); 385 386 if (atomic_dec_and_test(&mm->mm_users)) { 387 exit_aio(mm); 388 exit_mmap(mm); 389 if (!list_empty(&mm->mmlist)) { 390 spin_lock(&mmlist_lock); 391 list_del(&mm->mmlist); 392 spin_unlock(&mmlist_lock); 393 } 394 put_swap_token(mm); 395 mmdrop(mm); 396 } 397 } 398 EXPORT_SYMBOL_GPL(mmput); 399 400 /** 401 * get_task_mm - acquire a reference to the task's mm 402 * 403 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 404 * this kernel workthread has transiently adopted a user mm with use_mm, 405 * to do its AIO) is not set and if so returns a reference to it, after 406 * bumping up the use count. User must release the mm via mmput() 407 * after use. Typically used by /proc and ptrace. 408 */ 409 struct mm_struct *get_task_mm(struct task_struct *task) 410 { 411 struct mm_struct *mm; 412 413 task_lock(task); 414 mm = task->mm; 415 if (mm) { 416 if (task->flags & PF_BORROWED_MM) 417 mm = NULL; 418 else 419 atomic_inc(&mm->mm_users); 420 } 421 task_unlock(task); 422 return mm; 423 } 424 EXPORT_SYMBOL_GPL(get_task_mm); 425 426 /* Please note the differences between mmput and mm_release. 427 * mmput is called whenever we stop holding onto a mm_struct, 428 * error success whatever. 429 * 430 * mm_release is called after a mm_struct has been removed 431 * from the current process. 432 * 433 * This difference is important for error handling, when we 434 * only half set up a mm_struct for a new process and need to restore 435 * the old one. Because we mmput the new mm_struct before 436 * restoring the old one. . . 437 * Eric Biederman 10 January 1998 438 */ 439 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 440 { 441 struct completion *vfork_done = tsk->vfork_done; 442 443 /* Get rid of any cached register state */ 444 deactivate_mm(tsk, mm); 445 446 /* notify parent sleeping on vfork() */ 447 if (vfork_done) { 448 tsk->vfork_done = NULL; 449 complete(vfork_done); 450 } 451 452 /* 453 * If we're exiting normally, clear a user-space tid field if 454 * requested. We leave this alone when dying by signal, to leave 455 * the value intact in a core dump, and to save the unnecessary 456 * trouble otherwise. Userland only wants this done for a sys_exit. 457 */ 458 if (tsk->clear_child_tid 459 && !(tsk->flags & PF_SIGNALED) 460 && atomic_read(&mm->mm_users) > 1) { 461 u32 __user * tidptr = tsk->clear_child_tid; 462 tsk->clear_child_tid = NULL; 463 464 /* 465 * We don't check the error code - if userspace has 466 * not set up a proper pointer then tough luck. 467 */ 468 put_user(0, tidptr); 469 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 470 } 471 } 472 473 /* 474 * Allocate a new mm structure and copy contents from the 475 * mm structure of the passed in task structure. 476 */ 477 static struct mm_struct *dup_mm(struct task_struct *tsk) 478 { 479 struct mm_struct *mm, *oldmm = current->mm; 480 int err; 481 482 if (!oldmm) 483 return NULL; 484 485 mm = allocate_mm(); 486 if (!mm) 487 goto fail_nomem; 488 489 memcpy(mm, oldmm, sizeof(*mm)); 490 491 /* Initializing for Swap token stuff */ 492 mm->token_priority = 0; 493 mm->last_interval = 0; 494 495 if (!mm_init(mm)) 496 goto fail_nomem; 497 498 if (init_new_context(tsk, mm)) 499 goto fail_nocontext; 500 501 err = dup_mmap(mm, oldmm); 502 if (err) 503 goto free_pt; 504 505 mm->hiwater_rss = get_mm_rss(mm); 506 mm->hiwater_vm = mm->total_vm; 507 508 return mm; 509 510 free_pt: 511 mmput(mm); 512 513 fail_nomem: 514 return NULL; 515 516 fail_nocontext: 517 /* 518 * If init_new_context() failed, we cannot use mmput() to free the mm 519 * because it calls destroy_context() 520 */ 521 mm_free_pgd(mm); 522 free_mm(mm); 523 return NULL; 524 } 525 526 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 527 { 528 struct mm_struct * mm, *oldmm; 529 int retval; 530 531 tsk->min_flt = tsk->maj_flt = 0; 532 tsk->nvcsw = tsk->nivcsw = 0; 533 534 tsk->mm = NULL; 535 tsk->active_mm = NULL; 536 537 /* 538 * Are we cloning a kernel thread? 539 * 540 * We need to steal a active VM for that.. 541 */ 542 oldmm = current->mm; 543 if (!oldmm) 544 return 0; 545 546 if (clone_flags & CLONE_VM) { 547 atomic_inc(&oldmm->mm_users); 548 mm = oldmm; 549 goto good_mm; 550 } 551 552 retval = -ENOMEM; 553 mm = dup_mm(tsk); 554 if (!mm) 555 goto fail_nomem; 556 557 good_mm: 558 /* Initializing for Swap token stuff */ 559 mm->token_priority = 0; 560 mm->last_interval = 0; 561 562 tsk->mm = mm; 563 tsk->active_mm = mm; 564 return 0; 565 566 fail_nomem: 567 return retval; 568 } 569 570 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 571 { 572 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 573 /* We don't need to lock fs - think why ;-) */ 574 if (fs) { 575 atomic_set(&fs->count, 1); 576 rwlock_init(&fs->lock); 577 fs->umask = old->umask; 578 read_lock(&old->lock); 579 fs->rootmnt = mntget(old->rootmnt); 580 fs->root = dget(old->root); 581 fs->pwdmnt = mntget(old->pwdmnt); 582 fs->pwd = dget(old->pwd); 583 if (old->altroot) { 584 fs->altrootmnt = mntget(old->altrootmnt); 585 fs->altroot = dget(old->altroot); 586 } else { 587 fs->altrootmnt = NULL; 588 fs->altroot = NULL; 589 } 590 read_unlock(&old->lock); 591 } 592 return fs; 593 } 594 595 struct fs_struct *copy_fs_struct(struct fs_struct *old) 596 { 597 return __copy_fs_struct(old); 598 } 599 600 EXPORT_SYMBOL_GPL(copy_fs_struct); 601 602 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 603 { 604 if (clone_flags & CLONE_FS) { 605 atomic_inc(¤t->fs->count); 606 return 0; 607 } 608 tsk->fs = __copy_fs_struct(current->fs); 609 if (!tsk->fs) 610 return -ENOMEM; 611 return 0; 612 } 613 614 static int count_open_files(struct fdtable *fdt) 615 { 616 int size = fdt->max_fdset; 617 int i; 618 619 /* Find the last open fd */ 620 for (i = size/(8*sizeof(long)); i > 0; ) { 621 if (fdt->open_fds->fds_bits[--i]) 622 break; 623 } 624 i = (i+1) * 8 * sizeof(long); 625 return i; 626 } 627 628 static struct files_struct *alloc_files(void) 629 { 630 struct files_struct *newf; 631 struct fdtable *fdt; 632 633 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); 634 if (!newf) 635 goto out; 636 637 atomic_set(&newf->count, 1); 638 639 spin_lock_init(&newf->file_lock); 640 newf->next_fd = 0; 641 fdt = &newf->fdtab; 642 fdt->max_fds = NR_OPEN_DEFAULT; 643 fdt->max_fdset = EMBEDDED_FD_SET_SIZE; 644 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 645 fdt->open_fds = (fd_set *)&newf->open_fds_init; 646 fdt->fd = &newf->fd_array[0]; 647 INIT_RCU_HEAD(&fdt->rcu); 648 fdt->free_files = NULL; 649 fdt->next = NULL; 650 rcu_assign_pointer(newf->fdt, fdt); 651 out: 652 return newf; 653 } 654 655 /* 656 * Allocate a new files structure and copy contents from the 657 * passed in files structure. 658 * errorp will be valid only when the returned files_struct is NULL. 659 */ 660 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 661 { 662 struct files_struct *newf; 663 struct file **old_fds, **new_fds; 664 int open_files, size, i, expand; 665 struct fdtable *old_fdt, *new_fdt; 666 667 *errorp = -ENOMEM; 668 newf = alloc_files(); 669 if (!newf) 670 goto out; 671 672 spin_lock(&oldf->file_lock); 673 old_fdt = files_fdtable(oldf); 674 new_fdt = files_fdtable(newf); 675 size = old_fdt->max_fdset; 676 open_files = count_open_files(old_fdt); 677 expand = 0; 678 679 /* 680 * Check whether we need to allocate a larger fd array or fd set. 681 * Note: we're not a clone task, so the open count won't change. 682 */ 683 if (open_files > new_fdt->max_fdset) { 684 new_fdt->max_fdset = 0; 685 expand = 1; 686 } 687 if (open_files > new_fdt->max_fds) { 688 new_fdt->max_fds = 0; 689 expand = 1; 690 } 691 692 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 693 if (expand) { 694 spin_unlock(&oldf->file_lock); 695 spin_lock(&newf->file_lock); 696 *errorp = expand_files(newf, open_files-1); 697 spin_unlock(&newf->file_lock); 698 if (*errorp < 0) 699 goto out_release; 700 new_fdt = files_fdtable(newf); 701 /* 702 * Reacquire the oldf lock and a pointer to its fd table 703 * who knows it may have a new bigger fd table. We need 704 * the latest pointer. 705 */ 706 spin_lock(&oldf->file_lock); 707 old_fdt = files_fdtable(oldf); 708 } 709 710 old_fds = old_fdt->fd; 711 new_fds = new_fdt->fd; 712 713 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 714 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 715 716 for (i = open_files; i != 0; i--) { 717 struct file *f = *old_fds++; 718 if (f) { 719 get_file(f); 720 } else { 721 /* 722 * The fd may be claimed in the fd bitmap but not yet 723 * instantiated in the files array if a sibling thread 724 * is partway through open(). So make sure that this 725 * fd is available to the new process. 726 */ 727 FD_CLR(open_files - i, new_fdt->open_fds); 728 } 729 rcu_assign_pointer(*new_fds++, f); 730 } 731 spin_unlock(&oldf->file_lock); 732 733 /* compute the remainder to be cleared */ 734 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 735 736 /* This is long word aligned thus could use a optimized version */ 737 memset(new_fds, 0, size); 738 739 if (new_fdt->max_fdset > open_files) { 740 int left = (new_fdt->max_fdset-open_files)/8; 741 int start = open_files / (8 * sizeof(unsigned long)); 742 743 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 744 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 745 } 746 747 out: 748 return newf; 749 750 out_release: 751 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 752 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 753 free_fd_array(new_fdt->fd, new_fdt->max_fds); 754 kmem_cache_free(files_cachep, newf); 755 return NULL; 756 } 757 758 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 759 { 760 struct files_struct *oldf, *newf; 761 int error = 0; 762 763 /* 764 * A background process may not have any files ... 765 */ 766 oldf = current->files; 767 if (!oldf) 768 goto out; 769 770 if (clone_flags & CLONE_FILES) { 771 atomic_inc(&oldf->count); 772 goto out; 773 } 774 775 /* 776 * Note: we may be using current for both targets (See exec.c) 777 * This works because we cache current->files (old) as oldf. Don't 778 * break this. 779 */ 780 tsk->files = NULL; 781 newf = dup_fd(oldf, &error); 782 if (!newf) 783 goto out; 784 785 tsk->files = newf; 786 error = 0; 787 out: 788 return error; 789 } 790 791 /* 792 * Helper to unshare the files of the current task. 793 * We don't want to expose copy_files internals to 794 * the exec layer of the kernel. 795 */ 796 797 int unshare_files(void) 798 { 799 struct files_struct *files = current->files; 800 int rc; 801 802 BUG_ON(!files); 803 804 /* This can race but the race causes us to copy when we don't 805 need to and drop the copy */ 806 if(atomic_read(&files->count) == 1) 807 { 808 atomic_inc(&files->count); 809 return 0; 810 } 811 rc = copy_files(0, current); 812 if(rc) 813 current->files = files; 814 return rc; 815 } 816 817 EXPORT_SYMBOL(unshare_files); 818 819 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 820 { 821 struct sighand_struct *sig; 822 823 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 824 atomic_inc(¤t->sighand->count); 825 return 0; 826 } 827 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 828 rcu_assign_pointer(tsk->sighand, sig); 829 if (!sig) 830 return -ENOMEM; 831 atomic_set(&sig->count, 1); 832 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 833 return 0; 834 } 835 836 void __cleanup_sighand(struct sighand_struct *sighand) 837 { 838 if (atomic_dec_and_test(&sighand->count)) 839 kmem_cache_free(sighand_cachep, sighand); 840 } 841 842 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 843 { 844 struct signal_struct *sig; 845 int ret; 846 847 if (clone_flags & CLONE_THREAD) { 848 atomic_inc(¤t->signal->count); 849 atomic_inc(¤t->signal->live); 850 return 0; 851 } 852 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 853 tsk->signal = sig; 854 if (!sig) 855 return -ENOMEM; 856 857 ret = copy_thread_group_keys(tsk); 858 if (ret < 0) { 859 kmem_cache_free(signal_cachep, sig); 860 return ret; 861 } 862 863 atomic_set(&sig->count, 1); 864 atomic_set(&sig->live, 1); 865 init_waitqueue_head(&sig->wait_chldexit); 866 sig->flags = 0; 867 sig->group_exit_code = 0; 868 sig->group_exit_task = NULL; 869 sig->group_stop_count = 0; 870 sig->curr_target = NULL; 871 init_sigpending(&sig->shared_pending); 872 INIT_LIST_HEAD(&sig->posix_timers); 873 874 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); 875 sig->it_real_incr.tv64 = 0; 876 sig->real_timer.function = it_real_fn; 877 sig->tsk = tsk; 878 879 sig->it_virt_expires = cputime_zero; 880 sig->it_virt_incr = cputime_zero; 881 sig->it_prof_expires = cputime_zero; 882 sig->it_prof_incr = cputime_zero; 883 884 sig->leader = 0; /* session leadership doesn't inherit */ 885 sig->tty_old_pgrp = 0; 886 887 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 888 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 889 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 890 sig->sched_time = 0; 891 INIT_LIST_HEAD(&sig->cpu_timers[0]); 892 INIT_LIST_HEAD(&sig->cpu_timers[1]); 893 INIT_LIST_HEAD(&sig->cpu_timers[2]); 894 taskstats_tgid_init(sig); 895 896 task_lock(current->group_leader); 897 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 898 task_unlock(current->group_leader); 899 900 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 901 /* 902 * New sole thread in the process gets an expiry time 903 * of the whole CPU time limit. 904 */ 905 tsk->it_prof_expires = 906 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 907 } 908 acct_init_pacct(&sig->pacct); 909 910 return 0; 911 } 912 913 void __cleanup_signal(struct signal_struct *sig) 914 { 915 exit_thread_group_keys(sig); 916 kmem_cache_free(signal_cachep, sig); 917 } 918 919 static inline void cleanup_signal(struct task_struct *tsk) 920 { 921 struct signal_struct *sig = tsk->signal; 922 923 atomic_dec(&sig->live); 924 925 if (atomic_dec_and_test(&sig->count)) 926 __cleanup_signal(sig); 927 } 928 929 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 930 { 931 unsigned long new_flags = p->flags; 932 933 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 934 new_flags |= PF_FORKNOEXEC; 935 if (!(clone_flags & CLONE_PTRACE)) 936 p->ptrace = 0; 937 p->flags = new_flags; 938 } 939 940 asmlinkage long sys_set_tid_address(int __user *tidptr) 941 { 942 current->clear_child_tid = tidptr; 943 944 return current->pid; 945 } 946 947 static inline void rt_mutex_init_task(struct task_struct *p) 948 { 949 #ifdef CONFIG_RT_MUTEXES 950 spin_lock_init(&p->pi_lock); 951 plist_head_init(&p->pi_waiters, &p->pi_lock); 952 p->pi_blocked_on = NULL; 953 #endif 954 } 955 956 /* 957 * This creates a new process as a copy of the old one, 958 * but does not actually start it yet. 959 * 960 * It copies the registers, and all the appropriate 961 * parts of the process environment (as per the clone 962 * flags). The actual kick-off is left to the caller. 963 */ 964 static struct task_struct *copy_process(unsigned long clone_flags, 965 unsigned long stack_start, 966 struct pt_regs *regs, 967 unsigned long stack_size, 968 int __user *parent_tidptr, 969 int __user *child_tidptr, 970 int pid) 971 { 972 int retval; 973 struct task_struct *p = NULL; 974 975 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 976 return ERR_PTR(-EINVAL); 977 978 /* 979 * Thread groups must share signals as well, and detached threads 980 * can only be started up within the thread group. 981 */ 982 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 983 return ERR_PTR(-EINVAL); 984 985 /* 986 * Shared signal handlers imply shared VM. By way of the above, 987 * thread groups also imply shared VM. Blocking this case allows 988 * for various simplifications in other code. 989 */ 990 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 991 return ERR_PTR(-EINVAL); 992 993 retval = security_task_create(clone_flags); 994 if (retval) 995 goto fork_out; 996 997 retval = -ENOMEM; 998 p = dup_task_struct(current); 999 if (!p) 1000 goto fork_out; 1001 1002 rt_mutex_init_task(p); 1003 1004 #ifdef CONFIG_TRACE_IRQFLAGS 1005 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1006 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1007 #endif 1008 retval = -EAGAIN; 1009 if (atomic_read(&p->user->processes) >= 1010 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1011 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1012 p->user != &root_user) 1013 goto bad_fork_free; 1014 } 1015 1016 atomic_inc(&p->user->__count); 1017 atomic_inc(&p->user->processes); 1018 get_group_info(p->group_info); 1019 1020 /* 1021 * If multiple threads are within copy_process(), then this check 1022 * triggers too late. This doesn't hurt, the check is only there 1023 * to stop root fork bombs. 1024 */ 1025 if (nr_threads >= max_threads) 1026 goto bad_fork_cleanup_count; 1027 1028 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1029 goto bad_fork_cleanup_count; 1030 1031 if (p->binfmt && !try_module_get(p->binfmt->module)) 1032 goto bad_fork_cleanup_put_domain; 1033 1034 p->did_exec = 0; 1035 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1036 copy_flags(clone_flags, p); 1037 p->pid = pid; 1038 retval = -EFAULT; 1039 if (clone_flags & CLONE_PARENT_SETTID) 1040 if (put_user(p->pid, parent_tidptr)) 1041 goto bad_fork_cleanup_delays_binfmt; 1042 1043 INIT_LIST_HEAD(&p->children); 1044 INIT_LIST_HEAD(&p->sibling); 1045 p->vfork_done = NULL; 1046 spin_lock_init(&p->alloc_lock); 1047 1048 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1049 init_sigpending(&p->pending); 1050 1051 p->utime = cputime_zero; 1052 p->stime = cputime_zero; 1053 p->sched_time = 0; 1054 p->rchar = 0; /* I/O counter: bytes read */ 1055 p->wchar = 0; /* I/O counter: bytes written */ 1056 p->syscr = 0; /* I/O counter: read syscalls */ 1057 p->syscw = 0; /* I/O counter: write syscalls */ 1058 acct_clear_integrals(p); 1059 1060 p->it_virt_expires = cputime_zero; 1061 p->it_prof_expires = cputime_zero; 1062 p->it_sched_expires = 0; 1063 INIT_LIST_HEAD(&p->cpu_timers[0]); 1064 INIT_LIST_HEAD(&p->cpu_timers[1]); 1065 INIT_LIST_HEAD(&p->cpu_timers[2]); 1066 1067 p->lock_depth = -1; /* -1 = no lock */ 1068 do_posix_clock_monotonic_gettime(&p->start_time); 1069 p->security = NULL; 1070 p->io_context = NULL; 1071 p->io_wait = NULL; 1072 p->audit_context = NULL; 1073 cpuset_fork(p); 1074 #ifdef CONFIG_NUMA 1075 p->mempolicy = mpol_copy(p->mempolicy); 1076 if (IS_ERR(p->mempolicy)) { 1077 retval = PTR_ERR(p->mempolicy); 1078 p->mempolicy = NULL; 1079 goto bad_fork_cleanup_cpuset; 1080 } 1081 mpol_fix_fork_child_flag(p); 1082 #endif 1083 #ifdef CONFIG_TRACE_IRQFLAGS 1084 p->irq_events = 0; 1085 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1086 p->hardirqs_enabled = 1; 1087 #else 1088 p->hardirqs_enabled = 0; 1089 #endif 1090 p->hardirq_enable_ip = 0; 1091 p->hardirq_enable_event = 0; 1092 p->hardirq_disable_ip = _THIS_IP_; 1093 p->hardirq_disable_event = 0; 1094 p->softirqs_enabled = 1; 1095 p->softirq_enable_ip = _THIS_IP_; 1096 p->softirq_enable_event = 0; 1097 p->softirq_disable_ip = 0; 1098 p->softirq_disable_event = 0; 1099 p->hardirq_context = 0; 1100 p->softirq_context = 0; 1101 #endif 1102 #ifdef CONFIG_LOCKDEP 1103 p->lockdep_depth = 0; /* no locks held yet */ 1104 p->curr_chain_key = 0; 1105 p->lockdep_recursion = 0; 1106 #endif 1107 1108 #ifdef CONFIG_DEBUG_MUTEXES 1109 p->blocked_on = NULL; /* not blocked yet */ 1110 #endif 1111 1112 p->tgid = p->pid; 1113 if (clone_flags & CLONE_THREAD) 1114 p->tgid = current->tgid; 1115 1116 if ((retval = security_task_alloc(p))) 1117 goto bad_fork_cleanup_policy; 1118 if ((retval = audit_alloc(p))) 1119 goto bad_fork_cleanup_security; 1120 /* copy all the process information */ 1121 if ((retval = copy_semundo(clone_flags, p))) 1122 goto bad_fork_cleanup_audit; 1123 if ((retval = copy_files(clone_flags, p))) 1124 goto bad_fork_cleanup_semundo; 1125 if ((retval = copy_fs(clone_flags, p))) 1126 goto bad_fork_cleanup_files; 1127 if ((retval = copy_sighand(clone_flags, p))) 1128 goto bad_fork_cleanup_fs; 1129 if ((retval = copy_signal(clone_flags, p))) 1130 goto bad_fork_cleanup_sighand; 1131 if ((retval = copy_mm(clone_flags, p))) 1132 goto bad_fork_cleanup_signal; 1133 if ((retval = copy_keys(clone_flags, p))) 1134 goto bad_fork_cleanup_mm; 1135 if ((retval = copy_namespaces(clone_flags, p))) 1136 goto bad_fork_cleanup_keys; 1137 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1138 if (retval) 1139 goto bad_fork_cleanup_namespaces; 1140 1141 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1142 /* 1143 * Clear TID on mm_release()? 1144 */ 1145 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1146 p->robust_list = NULL; 1147 #ifdef CONFIG_COMPAT 1148 p->compat_robust_list = NULL; 1149 #endif 1150 INIT_LIST_HEAD(&p->pi_state_list); 1151 p->pi_state_cache = NULL; 1152 1153 /* 1154 * sigaltstack should be cleared when sharing the same VM 1155 */ 1156 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1157 p->sas_ss_sp = p->sas_ss_size = 0; 1158 1159 /* 1160 * Syscall tracing should be turned off in the child regardless 1161 * of CLONE_PTRACE. 1162 */ 1163 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1164 #ifdef TIF_SYSCALL_EMU 1165 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1166 #endif 1167 1168 /* Our parent execution domain becomes current domain 1169 These must match for thread signalling to apply */ 1170 p->parent_exec_id = p->self_exec_id; 1171 1172 /* ok, now we should be set up.. */ 1173 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1174 p->pdeath_signal = 0; 1175 p->exit_state = 0; 1176 1177 /* 1178 * Ok, make it visible to the rest of the system. 1179 * We dont wake it up yet. 1180 */ 1181 p->group_leader = p; 1182 INIT_LIST_HEAD(&p->thread_group); 1183 INIT_LIST_HEAD(&p->ptrace_children); 1184 INIT_LIST_HEAD(&p->ptrace_list); 1185 1186 /* Perform scheduler related setup. Assign this task to a CPU. */ 1187 sched_fork(p, clone_flags); 1188 1189 /* Need tasklist lock for parent etc handling! */ 1190 write_lock_irq(&tasklist_lock); 1191 1192 /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */ 1193 p->ioprio = current->ioprio; 1194 1195 /* 1196 * The task hasn't been attached yet, so its cpus_allowed mask will 1197 * not be changed, nor will its assigned CPU. 1198 * 1199 * The cpus_allowed mask of the parent may have changed after it was 1200 * copied first time - so re-copy it here, then check the child's CPU 1201 * to ensure it is on a valid CPU (and if not, just force it back to 1202 * parent's CPU). This avoids alot of nasty races. 1203 */ 1204 p->cpus_allowed = current->cpus_allowed; 1205 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1206 !cpu_online(task_cpu(p)))) 1207 set_task_cpu(p, smp_processor_id()); 1208 1209 /* CLONE_PARENT re-uses the old parent */ 1210 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1211 p->real_parent = current->real_parent; 1212 else 1213 p->real_parent = current; 1214 p->parent = p->real_parent; 1215 1216 spin_lock(¤t->sighand->siglock); 1217 1218 /* 1219 * Process group and session signals need to be delivered to just the 1220 * parent before the fork or both the parent and the child after the 1221 * fork. Restart if a signal comes in before we add the new process to 1222 * it's process group. 1223 * A fatal signal pending means that current will exit, so the new 1224 * thread can't slip out of an OOM kill (or normal SIGKILL). 1225 */ 1226 recalc_sigpending(); 1227 if (signal_pending(current)) { 1228 spin_unlock(¤t->sighand->siglock); 1229 write_unlock_irq(&tasklist_lock); 1230 retval = -ERESTARTNOINTR; 1231 goto bad_fork_cleanup_namespaces; 1232 } 1233 1234 if (clone_flags & CLONE_THREAD) { 1235 p->group_leader = current->group_leader; 1236 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1237 1238 if (!cputime_eq(current->signal->it_virt_expires, 1239 cputime_zero) || 1240 !cputime_eq(current->signal->it_prof_expires, 1241 cputime_zero) || 1242 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1243 !list_empty(¤t->signal->cpu_timers[0]) || 1244 !list_empty(¤t->signal->cpu_timers[1]) || 1245 !list_empty(¤t->signal->cpu_timers[2])) { 1246 /* 1247 * Have child wake up on its first tick to check 1248 * for process CPU timers. 1249 */ 1250 p->it_prof_expires = jiffies_to_cputime(1); 1251 } 1252 } 1253 1254 if (likely(p->pid)) { 1255 add_parent(p); 1256 if (unlikely(p->ptrace & PT_PTRACED)) 1257 __ptrace_link(p, current->parent); 1258 1259 if (thread_group_leader(p)) { 1260 p->signal->tty = current->signal->tty; 1261 p->signal->pgrp = process_group(current); 1262 set_signal_session(p->signal, process_session(current)); 1263 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1264 attach_pid(p, PIDTYPE_SID, process_session(p)); 1265 1266 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1267 __get_cpu_var(process_counts)++; 1268 } 1269 attach_pid(p, PIDTYPE_PID, p->pid); 1270 nr_threads++; 1271 } 1272 1273 total_forks++; 1274 spin_unlock(¤t->sighand->siglock); 1275 write_unlock_irq(&tasklist_lock); 1276 proc_fork_connector(p); 1277 return p; 1278 1279 bad_fork_cleanup_namespaces: 1280 exit_task_namespaces(p); 1281 bad_fork_cleanup_keys: 1282 exit_keys(p); 1283 bad_fork_cleanup_mm: 1284 if (p->mm) 1285 mmput(p->mm); 1286 bad_fork_cleanup_signal: 1287 cleanup_signal(p); 1288 bad_fork_cleanup_sighand: 1289 __cleanup_sighand(p->sighand); 1290 bad_fork_cleanup_fs: 1291 exit_fs(p); /* blocking */ 1292 bad_fork_cleanup_files: 1293 exit_files(p); /* blocking */ 1294 bad_fork_cleanup_semundo: 1295 exit_sem(p); 1296 bad_fork_cleanup_audit: 1297 audit_free(p); 1298 bad_fork_cleanup_security: 1299 security_task_free(p); 1300 bad_fork_cleanup_policy: 1301 #ifdef CONFIG_NUMA 1302 mpol_free(p->mempolicy); 1303 bad_fork_cleanup_cpuset: 1304 #endif 1305 cpuset_exit(p); 1306 bad_fork_cleanup_delays_binfmt: 1307 delayacct_tsk_free(p); 1308 if (p->binfmt) 1309 module_put(p->binfmt->module); 1310 bad_fork_cleanup_put_domain: 1311 module_put(task_thread_info(p)->exec_domain->module); 1312 bad_fork_cleanup_count: 1313 put_group_info(p->group_info); 1314 atomic_dec(&p->user->processes); 1315 free_uid(p->user); 1316 bad_fork_free: 1317 free_task(p); 1318 fork_out: 1319 return ERR_PTR(retval); 1320 } 1321 1322 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1323 { 1324 memset(regs, 0, sizeof(struct pt_regs)); 1325 return regs; 1326 } 1327 1328 struct task_struct * __devinit fork_idle(int cpu) 1329 { 1330 struct task_struct *task; 1331 struct pt_regs regs; 1332 1333 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1334 if (!IS_ERR(task)) 1335 init_idle(task, cpu); 1336 1337 return task; 1338 } 1339 1340 static inline int fork_traceflag (unsigned clone_flags) 1341 { 1342 if (clone_flags & CLONE_UNTRACED) 1343 return 0; 1344 else if (clone_flags & CLONE_VFORK) { 1345 if (current->ptrace & PT_TRACE_VFORK) 1346 return PTRACE_EVENT_VFORK; 1347 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1348 if (current->ptrace & PT_TRACE_CLONE) 1349 return PTRACE_EVENT_CLONE; 1350 } else if (current->ptrace & PT_TRACE_FORK) 1351 return PTRACE_EVENT_FORK; 1352 1353 return 0; 1354 } 1355 1356 /* 1357 * Ok, this is the main fork-routine. 1358 * 1359 * It copies the process, and if successful kick-starts 1360 * it and waits for it to finish using the VM if required. 1361 */ 1362 long do_fork(unsigned long clone_flags, 1363 unsigned long stack_start, 1364 struct pt_regs *regs, 1365 unsigned long stack_size, 1366 int __user *parent_tidptr, 1367 int __user *child_tidptr) 1368 { 1369 struct task_struct *p; 1370 int trace = 0; 1371 struct pid *pid = alloc_pid(); 1372 long nr; 1373 1374 if (!pid) 1375 return -EAGAIN; 1376 nr = pid->nr; 1377 if (unlikely(current->ptrace)) { 1378 trace = fork_traceflag (clone_flags); 1379 if (trace) 1380 clone_flags |= CLONE_PTRACE; 1381 } 1382 1383 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr); 1384 /* 1385 * Do this prior waking up the new thread - the thread pointer 1386 * might get invalid after that point, if the thread exits quickly. 1387 */ 1388 if (!IS_ERR(p)) { 1389 struct completion vfork; 1390 1391 if (clone_flags & CLONE_VFORK) { 1392 p->vfork_done = &vfork; 1393 init_completion(&vfork); 1394 } 1395 1396 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1397 /* 1398 * We'll start up with an immediate SIGSTOP. 1399 */ 1400 sigaddset(&p->pending.signal, SIGSTOP); 1401 set_tsk_thread_flag(p, TIF_SIGPENDING); 1402 } 1403 1404 if (!(clone_flags & CLONE_STOPPED)) 1405 wake_up_new_task(p, clone_flags); 1406 else 1407 p->state = TASK_STOPPED; 1408 1409 if (unlikely (trace)) { 1410 current->ptrace_message = nr; 1411 ptrace_notify ((trace << 8) | SIGTRAP); 1412 } 1413 1414 if (clone_flags & CLONE_VFORK) { 1415 wait_for_completion(&vfork); 1416 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1417 current->ptrace_message = nr; 1418 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1419 } 1420 } 1421 } else { 1422 free_pid(pid); 1423 nr = PTR_ERR(p); 1424 } 1425 return nr; 1426 } 1427 1428 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1429 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1430 #endif 1431 1432 static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags) 1433 { 1434 struct sighand_struct *sighand = data; 1435 1436 if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == 1437 SLAB_CTOR_CONSTRUCTOR) 1438 spin_lock_init(&sighand->siglock); 1439 } 1440 1441 void __init proc_caches_init(void) 1442 { 1443 sighand_cachep = kmem_cache_create("sighand_cache", 1444 sizeof(struct sighand_struct), 0, 1445 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1446 sighand_ctor, NULL); 1447 signal_cachep = kmem_cache_create("signal_cache", 1448 sizeof(struct signal_struct), 0, 1449 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1450 files_cachep = kmem_cache_create("files_cache", 1451 sizeof(struct files_struct), 0, 1452 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1453 fs_cachep = kmem_cache_create("fs_cache", 1454 sizeof(struct fs_struct), 0, 1455 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1456 vm_area_cachep = kmem_cache_create("vm_area_struct", 1457 sizeof(struct vm_area_struct), 0, 1458 SLAB_PANIC, NULL, NULL); 1459 mm_cachep = kmem_cache_create("mm_struct", 1460 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1461 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1462 } 1463 1464 1465 /* 1466 * Check constraints on flags passed to the unshare system call and 1467 * force unsharing of additional process context as appropriate. 1468 */ 1469 static inline void check_unshare_flags(unsigned long *flags_ptr) 1470 { 1471 /* 1472 * If unsharing a thread from a thread group, must also 1473 * unshare vm. 1474 */ 1475 if (*flags_ptr & CLONE_THREAD) 1476 *flags_ptr |= CLONE_VM; 1477 1478 /* 1479 * If unsharing vm, must also unshare signal handlers. 1480 */ 1481 if (*flags_ptr & CLONE_VM) 1482 *flags_ptr |= CLONE_SIGHAND; 1483 1484 /* 1485 * If unsharing signal handlers and the task was created 1486 * using CLONE_THREAD, then must unshare the thread 1487 */ 1488 if ((*flags_ptr & CLONE_SIGHAND) && 1489 (atomic_read(¤t->signal->count) > 1)) 1490 *flags_ptr |= CLONE_THREAD; 1491 1492 /* 1493 * If unsharing namespace, must also unshare filesystem information. 1494 */ 1495 if (*flags_ptr & CLONE_NEWNS) 1496 *flags_ptr |= CLONE_FS; 1497 } 1498 1499 /* 1500 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1501 */ 1502 static int unshare_thread(unsigned long unshare_flags) 1503 { 1504 if (unshare_flags & CLONE_THREAD) 1505 return -EINVAL; 1506 1507 return 0; 1508 } 1509 1510 /* 1511 * Unshare the filesystem structure if it is being shared 1512 */ 1513 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1514 { 1515 struct fs_struct *fs = current->fs; 1516 1517 if ((unshare_flags & CLONE_FS) && 1518 (fs && atomic_read(&fs->count) > 1)) { 1519 *new_fsp = __copy_fs_struct(current->fs); 1520 if (!*new_fsp) 1521 return -ENOMEM; 1522 } 1523 1524 return 0; 1525 } 1526 1527 /* 1528 * Unshare the mnt_namespace structure if it is being shared 1529 */ 1530 static int unshare_mnt_namespace(unsigned long unshare_flags, 1531 struct mnt_namespace **new_nsp, struct fs_struct *new_fs) 1532 { 1533 struct mnt_namespace *ns = current->nsproxy->mnt_ns; 1534 1535 if ((unshare_flags & CLONE_NEWNS) && ns) { 1536 if (!capable(CAP_SYS_ADMIN)) 1537 return -EPERM; 1538 1539 *new_nsp = dup_mnt_ns(current, new_fs ? new_fs : current->fs); 1540 if (!*new_nsp) 1541 return -ENOMEM; 1542 } 1543 1544 return 0; 1545 } 1546 1547 /* 1548 * Unsharing of sighand is not supported yet 1549 */ 1550 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1551 { 1552 struct sighand_struct *sigh = current->sighand; 1553 1554 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1555 return -EINVAL; 1556 else 1557 return 0; 1558 } 1559 1560 /* 1561 * Unshare vm if it is being shared 1562 */ 1563 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1564 { 1565 struct mm_struct *mm = current->mm; 1566 1567 if ((unshare_flags & CLONE_VM) && 1568 (mm && atomic_read(&mm->mm_users) > 1)) { 1569 return -EINVAL; 1570 } 1571 1572 return 0; 1573 } 1574 1575 /* 1576 * Unshare file descriptor table if it is being shared 1577 */ 1578 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1579 { 1580 struct files_struct *fd = current->files; 1581 int error = 0; 1582 1583 if ((unshare_flags & CLONE_FILES) && 1584 (fd && atomic_read(&fd->count) > 1)) { 1585 *new_fdp = dup_fd(fd, &error); 1586 if (!*new_fdp) 1587 return error; 1588 } 1589 1590 return 0; 1591 } 1592 1593 /* 1594 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1595 * supported yet 1596 */ 1597 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1598 { 1599 if (unshare_flags & CLONE_SYSVSEM) 1600 return -EINVAL; 1601 1602 return 0; 1603 } 1604 1605 #ifndef CONFIG_IPC_NS 1606 static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns) 1607 { 1608 if (flags & CLONE_NEWIPC) 1609 return -EINVAL; 1610 1611 return 0; 1612 } 1613 #endif 1614 1615 /* 1616 * unshare allows a process to 'unshare' part of the process 1617 * context which was originally shared using clone. copy_* 1618 * functions used by do_fork() cannot be used here directly 1619 * because they modify an inactive task_struct that is being 1620 * constructed. Here we are modifying the current, active, 1621 * task_struct. 1622 */ 1623 asmlinkage long sys_unshare(unsigned long unshare_flags) 1624 { 1625 int err = 0; 1626 struct fs_struct *fs, *new_fs = NULL; 1627 struct mnt_namespace *ns, *new_ns = NULL; 1628 struct sighand_struct *new_sigh = NULL; 1629 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1630 struct files_struct *fd, *new_fd = NULL; 1631 struct sem_undo_list *new_ulist = NULL; 1632 struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL; 1633 struct uts_namespace *uts, *new_uts = NULL; 1634 struct ipc_namespace *ipc, *new_ipc = NULL; 1635 1636 check_unshare_flags(&unshare_flags); 1637 1638 /* Return -EINVAL for all unsupported flags */ 1639 err = -EINVAL; 1640 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1641 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1642 CLONE_NEWUTS|CLONE_NEWIPC)) 1643 goto bad_unshare_out; 1644 1645 if ((err = unshare_thread(unshare_flags))) 1646 goto bad_unshare_out; 1647 if ((err = unshare_fs(unshare_flags, &new_fs))) 1648 goto bad_unshare_cleanup_thread; 1649 if ((err = unshare_mnt_namespace(unshare_flags, &new_ns, new_fs))) 1650 goto bad_unshare_cleanup_fs; 1651 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1652 goto bad_unshare_cleanup_ns; 1653 if ((err = unshare_vm(unshare_flags, &new_mm))) 1654 goto bad_unshare_cleanup_sigh; 1655 if ((err = unshare_fd(unshare_flags, &new_fd))) 1656 goto bad_unshare_cleanup_vm; 1657 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1658 goto bad_unshare_cleanup_fd; 1659 if ((err = unshare_utsname(unshare_flags, &new_uts))) 1660 goto bad_unshare_cleanup_semundo; 1661 if ((err = unshare_ipcs(unshare_flags, &new_ipc))) 1662 goto bad_unshare_cleanup_uts; 1663 1664 if (new_ns || new_uts || new_ipc) { 1665 old_nsproxy = current->nsproxy; 1666 new_nsproxy = dup_namespaces(old_nsproxy); 1667 if (!new_nsproxy) { 1668 err = -ENOMEM; 1669 goto bad_unshare_cleanup_ipc; 1670 } 1671 } 1672 1673 if (new_fs || new_ns || new_mm || new_fd || new_ulist || 1674 new_uts || new_ipc) { 1675 1676 task_lock(current); 1677 1678 if (new_nsproxy) { 1679 current->nsproxy = new_nsproxy; 1680 new_nsproxy = old_nsproxy; 1681 } 1682 1683 if (new_fs) { 1684 fs = current->fs; 1685 current->fs = new_fs; 1686 new_fs = fs; 1687 } 1688 1689 if (new_ns) { 1690 ns = current->nsproxy->mnt_ns; 1691 current->nsproxy->mnt_ns = new_ns; 1692 new_ns = ns; 1693 } 1694 1695 if (new_mm) { 1696 mm = current->mm; 1697 active_mm = current->active_mm; 1698 current->mm = new_mm; 1699 current->active_mm = new_mm; 1700 activate_mm(active_mm, new_mm); 1701 new_mm = mm; 1702 } 1703 1704 if (new_fd) { 1705 fd = current->files; 1706 current->files = new_fd; 1707 new_fd = fd; 1708 } 1709 1710 if (new_uts) { 1711 uts = current->nsproxy->uts_ns; 1712 current->nsproxy->uts_ns = new_uts; 1713 new_uts = uts; 1714 } 1715 1716 if (new_ipc) { 1717 ipc = current->nsproxy->ipc_ns; 1718 current->nsproxy->ipc_ns = new_ipc; 1719 new_ipc = ipc; 1720 } 1721 1722 task_unlock(current); 1723 } 1724 1725 if (new_nsproxy) 1726 put_nsproxy(new_nsproxy); 1727 1728 bad_unshare_cleanup_ipc: 1729 if (new_ipc) 1730 put_ipc_ns(new_ipc); 1731 1732 bad_unshare_cleanup_uts: 1733 if (new_uts) 1734 put_uts_ns(new_uts); 1735 1736 bad_unshare_cleanup_semundo: 1737 bad_unshare_cleanup_fd: 1738 if (new_fd) 1739 put_files_struct(new_fd); 1740 1741 bad_unshare_cleanup_vm: 1742 if (new_mm) 1743 mmput(new_mm); 1744 1745 bad_unshare_cleanup_sigh: 1746 if (new_sigh) 1747 if (atomic_dec_and_test(&new_sigh->count)) 1748 kmem_cache_free(sighand_cachep, new_sigh); 1749 1750 bad_unshare_cleanup_ns: 1751 if (new_ns) 1752 put_mnt_ns(new_ns); 1753 1754 bad_unshare_cleanup_fs: 1755 if (new_fs) 1756 put_fs_struct(new_fs); 1757 1758 bad_unshare_cleanup_thread: 1759 bad_unshare_out: 1760 return err; 1761 } 1762