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