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/config.h> 15 #include <linux/slab.h> 16 #include <linux/init.h> 17 #include <linux/unistd.h> 18 #include <linux/smp_lock.h> 19 #include <linux/module.h> 20 #include <linux/vmalloc.h> 21 #include <linux/completion.h> 22 #include <linux/namespace.h> 23 #include <linux/personality.h> 24 #include <linux/mempolicy.h> 25 #include <linux/sem.h> 26 #include <linux/file.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/fs.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/cn_proc.h> 47 48 #include <asm/pgtable.h> 49 #include <asm/pgalloc.h> 50 #include <asm/uaccess.h> 51 #include <asm/mmu_context.h> 52 #include <asm/cacheflush.h> 53 #include <asm/tlbflush.h> 54 55 /* 56 * Protected counters by write_lock_irq(&tasklist_lock) 57 */ 58 unsigned long total_forks; /* Handle normal Linux uptimes. */ 59 int nr_threads; /* The idle threads do not count.. */ 60 61 int max_threads; /* tunable limit on nr_threads */ 62 63 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 64 65 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 66 67 EXPORT_SYMBOL(tasklist_lock); 68 69 int nr_processes(void) 70 { 71 int cpu; 72 int total = 0; 73 74 for_each_online_cpu(cpu) 75 total += per_cpu(process_counts, cpu); 76 77 return total; 78 } 79 80 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 81 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 82 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 83 static kmem_cache_t *task_struct_cachep; 84 #endif 85 86 /* SLAB cache for signal_struct structures (tsk->signal) */ 87 kmem_cache_t *signal_cachep; 88 89 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 90 kmem_cache_t *sighand_cachep; 91 92 /* SLAB cache for files_struct structures (tsk->files) */ 93 kmem_cache_t *files_cachep; 94 95 /* SLAB cache for fs_struct structures (tsk->fs) */ 96 kmem_cache_t *fs_cachep; 97 98 /* SLAB cache for vm_area_struct structures */ 99 kmem_cache_t *vm_area_cachep; 100 101 /* SLAB cache for mm_struct structures (tsk->mm) */ 102 static kmem_cache_t *mm_cachep; 103 104 void free_task(struct task_struct *tsk) 105 { 106 free_thread_info(tsk->thread_info); 107 free_task_struct(tsk); 108 } 109 EXPORT_SYMBOL(free_task); 110 111 void __put_task_struct_cb(struct rcu_head *rhp) 112 { 113 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 114 115 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 116 WARN_ON(atomic_read(&tsk->usage)); 117 WARN_ON(tsk == current); 118 119 if (unlikely(tsk->audit_context)) 120 audit_free(tsk); 121 security_task_free(tsk); 122 free_uid(tsk->user); 123 put_group_info(tsk->group_info); 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 /* One for us, one for whoever does the "release_task()" (usually parent) */ 182 atomic_set(&tsk->usage,2); 183 atomic_set(&tsk->fs_excl, 0); 184 return tsk; 185 } 186 187 #ifdef CONFIG_MMU 188 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 189 { 190 struct vm_area_struct *mpnt, *tmp, **pprev; 191 struct rb_node **rb_link, *rb_parent; 192 int retval; 193 unsigned long charge; 194 struct mempolicy *pol; 195 196 down_write(&oldmm->mmap_sem); 197 flush_cache_mm(oldmm); 198 down_write(&mm->mmap_sem); 199 200 mm->locked_vm = 0; 201 mm->mmap = NULL; 202 mm->mmap_cache = NULL; 203 mm->free_area_cache = oldmm->mmap_base; 204 mm->cached_hole_size = ~0UL; 205 mm->map_count = 0; 206 cpus_clear(mm->cpu_vm_mask); 207 mm->mm_rb = RB_ROOT; 208 rb_link = &mm->mm_rb.rb_node; 209 rb_parent = NULL; 210 pprev = &mm->mmap; 211 212 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 213 struct file *file; 214 215 if (mpnt->vm_flags & VM_DONTCOPY) { 216 long pages = vma_pages(mpnt); 217 mm->total_vm -= pages; 218 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 219 -pages); 220 continue; 221 } 222 charge = 0; 223 if (mpnt->vm_flags & VM_ACCOUNT) { 224 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 225 if (security_vm_enough_memory(len)) 226 goto fail_nomem; 227 charge = len; 228 } 229 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 230 if (!tmp) 231 goto fail_nomem; 232 *tmp = *mpnt; 233 pol = mpol_copy(vma_policy(mpnt)); 234 retval = PTR_ERR(pol); 235 if (IS_ERR(pol)) 236 goto fail_nomem_policy; 237 vma_set_policy(tmp, pol); 238 tmp->vm_flags &= ~VM_LOCKED; 239 tmp->vm_mm = mm; 240 tmp->vm_next = NULL; 241 anon_vma_link(tmp); 242 file = tmp->vm_file; 243 if (file) { 244 struct inode *inode = file->f_dentry->d_inode; 245 get_file(file); 246 if (tmp->vm_flags & VM_DENYWRITE) 247 atomic_dec(&inode->i_writecount); 248 249 /* insert tmp into the share list, just after mpnt */ 250 spin_lock(&file->f_mapping->i_mmap_lock); 251 tmp->vm_truncate_count = mpnt->vm_truncate_count; 252 flush_dcache_mmap_lock(file->f_mapping); 253 vma_prio_tree_add(tmp, mpnt); 254 flush_dcache_mmap_unlock(file->f_mapping); 255 spin_unlock(&file->f_mapping->i_mmap_lock); 256 } 257 258 /* 259 * Link in the new vma and copy the page table entries. 260 */ 261 *pprev = tmp; 262 pprev = &tmp->vm_next; 263 264 __vma_link_rb(mm, tmp, rb_link, rb_parent); 265 rb_link = &tmp->vm_rb.rb_right; 266 rb_parent = &tmp->vm_rb; 267 268 mm->map_count++; 269 retval = copy_page_range(mm, oldmm, mpnt); 270 271 if (tmp->vm_ops && tmp->vm_ops->open) 272 tmp->vm_ops->open(tmp); 273 274 if (retval) 275 goto out; 276 } 277 retval = 0; 278 out: 279 up_write(&mm->mmap_sem); 280 flush_tlb_mm(oldmm); 281 up_write(&oldmm->mmap_sem); 282 return retval; 283 fail_nomem_policy: 284 kmem_cache_free(vm_area_cachep, tmp); 285 fail_nomem: 286 retval = -ENOMEM; 287 vm_unacct_memory(charge); 288 goto out; 289 } 290 291 static inline int mm_alloc_pgd(struct mm_struct * mm) 292 { 293 mm->pgd = pgd_alloc(mm); 294 if (unlikely(!mm->pgd)) 295 return -ENOMEM; 296 return 0; 297 } 298 299 static inline void mm_free_pgd(struct mm_struct * mm) 300 { 301 pgd_free(mm->pgd); 302 } 303 #else 304 #define dup_mmap(mm, oldmm) (0) 305 #define mm_alloc_pgd(mm) (0) 306 #define mm_free_pgd(mm) 307 #endif /* CONFIG_MMU */ 308 309 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 310 311 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 312 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 313 314 #include <linux/init_task.h> 315 316 static struct mm_struct * mm_init(struct mm_struct * mm) 317 { 318 atomic_set(&mm->mm_users, 1); 319 atomic_set(&mm->mm_count, 1); 320 init_rwsem(&mm->mmap_sem); 321 INIT_LIST_HEAD(&mm->mmlist); 322 mm->core_waiters = 0; 323 mm->nr_ptes = 0; 324 set_mm_counter(mm, file_rss, 0); 325 set_mm_counter(mm, anon_rss, 0); 326 spin_lock_init(&mm->page_table_lock); 327 rwlock_init(&mm->ioctx_list_lock); 328 mm->ioctx_list = NULL; 329 mm->free_area_cache = TASK_UNMAPPED_BASE; 330 mm->cached_hole_size = ~0UL; 331 332 if (likely(!mm_alloc_pgd(mm))) { 333 mm->def_flags = 0; 334 return mm; 335 } 336 free_mm(mm); 337 return NULL; 338 } 339 340 /* 341 * Allocate and initialize an mm_struct. 342 */ 343 struct mm_struct * mm_alloc(void) 344 { 345 struct mm_struct * mm; 346 347 mm = allocate_mm(); 348 if (mm) { 349 memset(mm, 0, sizeof(*mm)); 350 mm = mm_init(mm); 351 } 352 return mm; 353 } 354 355 /* 356 * Called when the last reference to the mm 357 * is dropped: either by a lazy thread or by 358 * mmput. Free the page directory and the mm. 359 */ 360 void fastcall __mmdrop(struct mm_struct *mm) 361 { 362 BUG_ON(mm == &init_mm); 363 mm_free_pgd(mm); 364 destroy_context(mm); 365 free_mm(mm); 366 } 367 368 /* 369 * Decrement the use count and release all resources for an mm. 370 */ 371 void mmput(struct mm_struct *mm) 372 { 373 if (atomic_dec_and_test(&mm->mm_users)) { 374 exit_aio(mm); 375 exit_mmap(mm); 376 if (!list_empty(&mm->mmlist)) { 377 spin_lock(&mmlist_lock); 378 list_del(&mm->mmlist); 379 spin_unlock(&mmlist_lock); 380 } 381 put_swap_token(mm); 382 mmdrop(mm); 383 } 384 } 385 EXPORT_SYMBOL_GPL(mmput); 386 387 /** 388 * get_task_mm - acquire a reference to the task's mm 389 * 390 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 391 * this kernel workthread has transiently adopted a user mm with use_mm, 392 * to do its AIO) is not set and if so returns a reference to it, after 393 * bumping up the use count. User must release the mm via mmput() 394 * after use. Typically used by /proc and ptrace. 395 */ 396 struct mm_struct *get_task_mm(struct task_struct *task) 397 { 398 struct mm_struct *mm; 399 400 task_lock(task); 401 mm = task->mm; 402 if (mm) { 403 if (task->flags & PF_BORROWED_MM) 404 mm = NULL; 405 else 406 atomic_inc(&mm->mm_users); 407 } 408 task_unlock(task); 409 return mm; 410 } 411 EXPORT_SYMBOL_GPL(get_task_mm); 412 413 /* Please note the differences between mmput and mm_release. 414 * mmput is called whenever we stop holding onto a mm_struct, 415 * error success whatever. 416 * 417 * mm_release is called after a mm_struct has been removed 418 * from the current process. 419 * 420 * This difference is important for error handling, when we 421 * only half set up a mm_struct for a new process and need to restore 422 * the old one. Because we mmput the new mm_struct before 423 * restoring the old one. . . 424 * Eric Biederman 10 January 1998 425 */ 426 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 427 { 428 struct completion *vfork_done = tsk->vfork_done; 429 430 /* Get rid of any cached register state */ 431 deactivate_mm(tsk, mm); 432 433 /* notify parent sleeping on vfork() */ 434 if (vfork_done) { 435 tsk->vfork_done = NULL; 436 complete(vfork_done); 437 } 438 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 439 u32 __user * tidptr = tsk->clear_child_tid; 440 tsk->clear_child_tid = NULL; 441 442 /* 443 * We don't check the error code - if userspace has 444 * not set up a proper pointer then tough luck. 445 */ 446 put_user(0, tidptr); 447 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 448 } 449 } 450 451 /* 452 * Allocate a new mm structure and copy contents from the 453 * mm structure of the passed in task structure. 454 */ 455 static struct mm_struct *dup_mm(struct task_struct *tsk) 456 { 457 struct mm_struct *mm, *oldmm = current->mm; 458 int err; 459 460 if (!oldmm) 461 return NULL; 462 463 mm = allocate_mm(); 464 if (!mm) 465 goto fail_nomem; 466 467 memcpy(mm, oldmm, sizeof(*mm)); 468 469 if (!mm_init(mm)) 470 goto fail_nomem; 471 472 if (init_new_context(tsk, mm)) 473 goto fail_nocontext; 474 475 err = dup_mmap(mm, oldmm); 476 if (err) 477 goto free_pt; 478 479 mm->hiwater_rss = get_mm_rss(mm); 480 mm->hiwater_vm = mm->total_vm; 481 482 return mm; 483 484 free_pt: 485 mmput(mm); 486 487 fail_nomem: 488 return NULL; 489 490 fail_nocontext: 491 /* 492 * If init_new_context() failed, we cannot use mmput() to free the mm 493 * because it calls destroy_context() 494 */ 495 mm_free_pgd(mm); 496 free_mm(mm); 497 return NULL; 498 } 499 500 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 501 { 502 struct mm_struct * mm, *oldmm; 503 int retval; 504 505 tsk->min_flt = tsk->maj_flt = 0; 506 tsk->nvcsw = tsk->nivcsw = 0; 507 508 tsk->mm = NULL; 509 tsk->active_mm = NULL; 510 511 /* 512 * Are we cloning a kernel thread? 513 * 514 * We need to steal a active VM for that.. 515 */ 516 oldmm = current->mm; 517 if (!oldmm) 518 return 0; 519 520 if (clone_flags & CLONE_VM) { 521 atomic_inc(&oldmm->mm_users); 522 mm = oldmm; 523 goto good_mm; 524 } 525 526 retval = -ENOMEM; 527 mm = dup_mm(tsk); 528 if (!mm) 529 goto fail_nomem; 530 531 good_mm: 532 tsk->mm = mm; 533 tsk->active_mm = mm; 534 return 0; 535 536 fail_nomem: 537 return retval; 538 } 539 540 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 541 { 542 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 543 /* We don't need to lock fs - think why ;-) */ 544 if (fs) { 545 atomic_set(&fs->count, 1); 546 rwlock_init(&fs->lock); 547 fs->umask = old->umask; 548 read_lock(&old->lock); 549 fs->rootmnt = mntget(old->rootmnt); 550 fs->root = dget(old->root); 551 fs->pwdmnt = mntget(old->pwdmnt); 552 fs->pwd = dget(old->pwd); 553 if (old->altroot) { 554 fs->altrootmnt = mntget(old->altrootmnt); 555 fs->altroot = dget(old->altroot); 556 } else { 557 fs->altrootmnt = NULL; 558 fs->altroot = NULL; 559 } 560 read_unlock(&old->lock); 561 } 562 return fs; 563 } 564 565 struct fs_struct *copy_fs_struct(struct fs_struct *old) 566 { 567 return __copy_fs_struct(old); 568 } 569 570 EXPORT_SYMBOL_GPL(copy_fs_struct); 571 572 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 573 { 574 if (clone_flags & CLONE_FS) { 575 atomic_inc(¤t->fs->count); 576 return 0; 577 } 578 tsk->fs = __copy_fs_struct(current->fs); 579 if (!tsk->fs) 580 return -ENOMEM; 581 return 0; 582 } 583 584 static int count_open_files(struct fdtable *fdt) 585 { 586 int size = fdt->max_fdset; 587 int i; 588 589 /* Find the last open fd */ 590 for (i = size/(8*sizeof(long)); i > 0; ) { 591 if (fdt->open_fds->fds_bits[--i]) 592 break; 593 } 594 i = (i+1) * 8 * sizeof(long); 595 return i; 596 } 597 598 static struct files_struct *alloc_files(void) 599 { 600 struct files_struct *newf; 601 struct fdtable *fdt; 602 603 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 604 if (!newf) 605 goto out; 606 607 atomic_set(&newf->count, 1); 608 609 spin_lock_init(&newf->file_lock); 610 fdt = &newf->fdtab; 611 fdt->next_fd = 0; 612 fdt->max_fds = NR_OPEN_DEFAULT; 613 fdt->max_fdset = __FD_SETSIZE; 614 fdt->close_on_exec = &newf->close_on_exec_init; 615 fdt->open_fds = &newf->open_fds_init; 616 fdt->fd = &newf->fd_array[0]; 617 INIT_RCU_HEAD(&fdt->rcu); 618 fdt->free_files = NULL; 619 fdt->next = NULL; 620 rcu_assign_pointer(newf->fdt, fdt); 621 out: 622 return newf; 623 } 624 625 /* 626 * Allocate a new files structure and copy contents from the 627 * passed in files structure. 628 */ 629 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 630 { 631 struct files_struct *newf; 632 struct file **old_fds, **new_fds; 633 int open_files, size, i, expand; 634 struct fdtable *old_fdt, *new_fdt; 635 636 newf = alloc_files(); 637 if (!newf) 638 goto out; 639 640 spin_lock(&oldf->file_lock); 641 old_fdt = files_fdtable(oldf); 642 new_fdt = files_fdtable(newf); 643 size = old_fdt->max_fdset; 644 open_files = count_open_files(old_fdt); 645 expand = 0; 646 647 /* 648 * Check whether we need to allocate a larger fd array or fd set. 649 * Note: we're not a clone task, so the open count won't change. 650 */ 651 if (open_files > new_fdt->max_fdset) { 652 new_fdt->max_fdset = 0; 653 expand = 1; 654 } 655 if (open_files > new_fdt->max_fds) { 656 new_fdt->max_fds = 0; 657 expand = 1; 658 } 659 660 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 661 if (expand) { 662 spin_unlock(&oldf->file_lock); 663 spin_lock(&newf->file_lock); 664 *errorp = expand_files(newf, open_files-1); 665 spin_unlock(&newf->file_lock); 666 if (*errorp < 0) 667 goto out_release; 668 new_fdt = files_fdtable(newf); 669 /* 670 * Reacquire the oldf lock and a pointer to its fd table 671 * who knows it may have a new bigger fd table. We need 672 * the latest pointer. 673 */ 674 spin_lock(&oldf->file_lock); 675 old_fdt = files_fdtable(oldf); 676 } 677 678 old_fds = old_fdt->fd; 679 new_fds = new_fdt->fd; 680 681 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 682 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 683 684 for (i = open_files; i != 0; i--) { 685 struct file *f = *old_fds++; 686 if (f) { 687 get_file(f); 688 } else { 689 /* 690 * The fd may be claimed in the fd bitmap but not yet 691 * instantiated in the files array if a sibling thread 692 * is partway through open(). So make sure that this 693 * fd is available to the new process. 694 */ 695 FD_CLR(open_files - i, new_fdt->open_fds); 696 } 697 rcu_assign_pointer(*new_fds++, f); 698 } 699 spin_unlock(&oldf->file_lock); 700 701 /* compute the remainder to be cleared */ 702 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 703 704 /* This is long word aligned thus could use a optimized version */ 705 memset(new_fds, 0, size); 706 707 if (new_fdt->max_fdset > open_files) { 708 int left = (new_fdt->max_fdset-open_files)/8; 709 int start = open_files / (8 * sizeof(unsigned long)); 710 711 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 712 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 713 } 714 715 out: 716 return newf; 717 718 out_release: 719 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 720 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 721 free_fd_array(new_fdt->fd, new_fdt->max_fds); 722 kmem_cache_free(files_cachep, newf); 723 goto out; 724 } 725 726 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 727 { 728 struct files_struct *oldf, *newf; 729 int error = 0; 730 731 /* 732 * A background process may not have any files ... 733 */ 734 oldf = current->files; 735 if (!oldf) 736 goto out; 737 738 if (clone_flags & CLONE_FILES) { 739 atomic_inc(&oldf->count); 740 goto out; 741 } 742 743 /* 744 * Note: we may be using current for both targets (See exec.c) 745 * This works because we cache current->files (old) as oldf. Don't 746 * break this. 747 */ 748 tsk->files = NULL; 749 error = -ENOMEM; 750 newf = dup_fd(oldf, &error); 751 if (!newf) 752 goto out; 753 754 tsk->files = newf; 755 error = 0; 756 out: 757 return error; 758 } 759 760 /* 761 * Helper to unshare the files of the current task. 762 * We don't want to expose copy_files internals to 763 * the exec layer of the kernel. 764 */ 765 766 int unshare_files(void) 767 { 768 struct files_struct *files = current->files; 769 int rc; 770 771 if(!files) 772 BUG(); 773 774 /* This can race but the race causes us to copy when we don't 775 need to and drop the copy */ 776 if(atomic_read(&files->count) == 1) 777 { 778 atomic_inc(&files->count); 779 return 0; 780 } 781 rc = copy_files(0, current); 782 if(rc) 783 current->files = files; 784 return rc; 785 } 786 787 EXPORT_SYMBOL(unshare_files); 788 789 void sighand_free_cb(struct rcu_head *rhp) 790 { 791 struct sighand_struct *sp; 792 793 sp = container_of(rhp, struct sighand_struct, rcu); 794 kmem_cache_free(sighand_cachep, sp); 795 } 796 797 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 798 { 799 struct sighand_struct *sig; 800 801 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 802 atomic_inc(¤t->sighand->count); 803 return 0; 804 } 805 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 806 rcu_assign_pointer(tsk->sighand, sig); 807 if (!sig) 808 return -ENOMEM; 809 spin_lock_init(&sig->siglock); 810 atomic_set(&sig->count, 1); 811 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 812 return 0; 813 } 814 815 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 816 { 817 struct signal_struct *sig; 818 int ret; 819 820 if (clone_flags & CLONE_THREAD) { 821 atomic_inc(¤t->signal->count); 822 atomic_inc(¤t->signal->live); 823 return 0; 824 } 825 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 826 tsk->signal = sig; 827 if (!sig) 828 return -ENOMEM; 829 830 ret = copy_thread_group_keys(tsk); 831 if (ret < 0) { 832 kmem_cache_free(signal_cachep, sig); 833 return ret; 834 } 835 836 atomic_set(&sig->count, 1); 837 atomic_set(&sig->live, 1); 838 init_waitqueue_head(&sig->wait_chldexit); 839 sig->flags = 0; 840 sig->group_exit_code = 0; 841 sig->group_exit_task = NULL; 842 sig->group_stop_count = 0; 843 sig->curr_target = NULL; 844 init_sigpending(&sig->shared_pending); 845 INIT_LIST_HEAD(&sig->posix_timers); 846 847 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); 848 sig->it_real_incr.tv64 = 0; 849 sig->real_timer.function = it_real_fn; 850 sig->real_timer.data = tsk; 851 852 sig->it_virt_expires = cputime_zero; 853 sig->it_virt_incr = cputime_zero; 854 sig->it_prof_expires = cputime_zero; 855 sig->it_prof_incr = cputime_zero; 856 857 sig->leader = 0; /* session leadership doesn't inherit */ 858 sig->tty_old_pgrp = 0; 859 860 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 861 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 862 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 863 sig->sched_time = 0; 864 INIT_LIST_HEAD(&sig->cpu_timers[0]); 865 INIT_LIST_HEAD(&sig->cpu_timers[1]); 866 INIT_LIST_HEAD(&sig->cpu_timers[2]); 867 868 task_lock(current->group_leader); 869 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 870 task_unlock(current->group_leader); 871 872 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 873 /* 874 * New sole thread in the process gets an expiry time 875 * of the whole CPU time limit. 876 */ 877 tsk->it_prof_expires = 878 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 879 } 880 881 return 0; 882 } 883 884 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 885 { 886 unsigned long new_flags = p->flags; 887 888 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 889 new_flags |= PF_FORKNOEXEC; 890 if (!(clone_flags & CLONE_PTRACE)) 891 p->ptrace = 0; 892 p->flags = new_flags; 893 } 894 895 asmlinkage long sys_set_tid_address(int __user *tidptr) 896 { 897 current->clear_child_tid = tidptr; 898 899 return current->pid; 900 } 901 902 /* 903 * This creates a new process as a copy of the old one, 904 * but does not actually start it yet. 905 * 906 * It copies the registers, and all the appropriate 907 * parts of the process environment (as per the clone 908 * flags). The actual kick-off is left to the caller. 909 */ 910 static task_t *copy_process(unsigned long clone_flags, 911 unsigned long stack_start, 912 struct pt_regs *regs, 913 unsigned long stack_size, 914 int __user *parent_tidptr, 915 int __user *child_tidptr, 916 int pid) 917 { 918 int retval; 919 struct task_struct *p = NULL; 920 921 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 922 return ERR_PTR(-EINVAL); 923 924 /* 925 * Thread groups must share signals as well, and detached threads 926 * can only be started up within the thread group. 927 */ 928 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 929 return ERR_PTR(-EINVAL); 930 931 /* 932 * Shared signal handlers imply shared VM. By way of the above, 933 * thread groups also imply shared VM. Blocking this case allows 934 * for various simplifications in other code. 935 */ 936 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 937 return ERR_PTR(-EINVAL); 938 939 retval = security_task_create(clone_flags); 940 if (retval) 941 goto fork_out; 942 943 retval = -ENOMEM; 944 p = dup_task_struct(current); 945 if (!p) 946 goto fork_out; 947 948 retval = -EAGAIN; 949 if (atomic_read(&p->user->processes) >= 950 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 951 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 952 p->user != &root_user) 953 goto bad_fork_free; 954 } 955 956 atomic_inc(&p->user->__count); 957 atomic_inc(&p->user->processes); 958 get_group_info(p->group_info); 959 960 /* 961 * If multiple threads are within copy_process(), then this check 962 * triggers too late. This doesn't hurt, the check is only there 963 * to stop root fork bombs. 964 */ 965 if (nr_threads >= max_threads) 966 goto bad_fork_cleanup_count; 967 968 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 969 goto bad_fork_cleanup_count; 970 971 if (p->binfmt && !try_module_get(p->binfmt->module)) 972 goto bad_fork_cleanup_put_domain; 973 974 p->did_exec = 0; 975 copy_flags(clone_flags, p); 976 p->pid = pid; 977 retval = -EFAULT; 978 if (clone_flags & CLONE_PARENT_SETTID) 979 if (put_user(p->pid, parent_tidptr)) 980 goto bad_fork_cleanup; 981 982 p->proc_dentry = NULL; 983 984 INIT_LIST_HEAD(&p->children); 985 INIT_LIST_HEAD(&p->sibling); 986 p->vfork_done = NULL; 987 spin_lock_init(&p->alloc_lock); 988 spin_lock_init(&p->proc_lock); 989 990 clear_tsk_thread_flag(p, TIF_SIGPENDING); 991 init_sigpending(&p->pending); 992 993 p->utime = cputime_zero; 994 p->stime = cputime_zero; 995 p->sched_time = 0; 996 p->rchar = 0; /* I/O counter: bytes read */ 997 p->wchar = 0; /* I/O counter: bytes written */ 998 p->syscr = 0; /* I/O counter: read syscalls */ 999 p->syscw = 0; /* I/O counter: write syscalls */ 1000 acct_clear_integrals(p); 1001 1002 p->it_virt_expires = cputime_zero; 1003 p->it_prof_expires = cputime_zero; 1004 p->it_sched_expires = 0; 1005 INIT_LIST_HEAD(&p->cpu_timers[0]); 1006 INIT_LIST_HEAD(&p->cpu_timers[1]); 1007 INIT_LIST_HEAD(&p->cpu_timers[2]); 1008 1009 p->lock_depth = -1; /* -1 = no lock */ 1010 do_posix_clock_monotonic_gettime(&p->start_time); 1011 p->security = NULL; 1012 p->io_context = NULL; 1013 p->io_wait = NULL; 1014 p->audit_context = NULL; 1015 cpuset_fork(p); 1016 #ifdef CONFIG_NUMA 1017 p->mempolicy = mpol_copy(p->mempolicy); 1018 if (IS_ERR(p->mempolicy)) { 1019 retval = PTR_ERR(p->mempolicy); 1020 p->mempolicy = NULL; 1021 goto bad_fork_cleanup_cpuset; 1022 } 1023 #endif 1024 1025 #ifdef CONFIG_DEBUG_MUTEXES 1026 p->blocked_on = NULL; /* not blocked yet */ 1027 #endif 1028 1029 p->tgid = p->pid; 1030 if (clone_flags & CLONE_THREAD) 1031 p->tgid = current->tgid; 1032 1033 if ((retval = security_task_alloc(p))) 1034 goto bad_fork_cleanup_policy; 1035 if ((retval = audit_alloc(p))) 1036 goto bad_fork_cleanup_security; 1037 /* copy all the process information */ 1038 if ((retval = copy_semundo(clone_flags, p))) 1039 goto bad_fork_cleanup_audit; 1040 if ((retval = copy_files(clone_flags, p))) 1041 goto bad_fork_cleanup_semundo; 1042 if ((retval = copy_fs(clone_flags, p))) 1043 goto bad_fork_cleanup_files; 1044 if ((retval = copy_sighand(clone_flags, p))) 1045 goto bad_fork_cleanup_fs; 1046 if ((retval = copy_signal(clone_flags, p))) 1047 goto bad_fork_cleanup_sighand; 1048 if ((retval = copy_mm(clone_flags, p))) 1049 goto bad_fork_cleanup_signal; 1050 if ((retval = copy_keys(clone_flags, p))) 1051 goto bad_fork_cleanup_mm; 1052 if ((retval = copy_namespace(clone_flags, p))) 1053 goto bad_fork_cleanup_keys; 1054 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1055 if (retval) 1056 goto bad_fork_cleanup_namespace; 1057 1058 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1059 /* 1060 * Clear TID on mm_release()? 1061 */ 1062 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1063 1064 /* 1065 * sigaltstack should be cleared when sharing the same VM 1066 */ 1067 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1068 p->sas_ss_sp = p->sas_ss_size = 0; 1069 1070 /* 1071 * Syscall tracing should be turned off in the child regardless 1072 * of CLONE_PTRACE. 1073 */ 1074 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1075 #ifdef TIF_SYSCALL_EMU 1076 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1077 #endif 1078 1079 /* Our parent execution domain becomes current domain 1080 These must match for thread signalling to apply */ 1081 1082 p->parent_exec_id = p->self_exec_id; 1083 1084 /* ok, now we should be set up.. */ 1085 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1086 p->pdeath_signal = 0; 1087 p->exit_state = 0; 1088 1089 /* 1090 * Ok, make it visible to the rest of the system. 1091 * We dont wake it up yet. 1092 */ 1093 p->group_leader = p; 1094 INIT_LIST_HEAD(&p->ptrace_children); 1095 INIT_LIST_HEAD(&p->ptrace_list); 1096 1097 /* Perform scheduler related setup. Assign this task to a CPU. */ 1098 sched_fork(p, clone_flags); 1099 1100 /* Need tasklist lock for parent etc handling! */ 1101 write_lock_irq(&tasklist_lock); 1102 1103 /* 1104 * The task hasn't been attached yet, so its cpus_allowed mask will 1105 * not be changed, nor will its assigned CPU. 1106 * 1107 * The cpus_allowed mask of the parent may have changed after it was 1108 * copied first time - so re-copy it here, then check the child's CPU 1109 * to ensure it is on a valid CPU (and if not, just force it back to 1110 * parent's CPU). This avoids alot of nasty races. 1111 */ 1112 p->cpus_allowed = current->cpus_allowed; 1113 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1114 !cpu_online(task_cpu(p)))) 1115 set_task_cpu(p, smp_processor_id()); 1116 1117 /* 1118 * Check for pending SIGKILL! The new thread should not be allowed 1119 * to slip out of an OOM kill. (or normal SIGKILL.) 1120 */ 1121 if (sigismember(¤t->pending.signal, SIGKILL)) { 1122 write_unlock_irq(&tasklist_lock); 1123 retval = -EINTR; 1124 goto bad_fork_cleanup_namespace; 1125 } 1126 1127 /* CLONE_PARENT re-uses the old parent */ 1128 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1129 p->real_parent = current->real_parent; 1130 else 1131 p->real_parent = current; 1132 p->parent = p->real_parent; 1133 1134 spin_lock(¤t->sighand->siglock); 1135 if (clone_flags & CLONE_THREAD) { 1136 /* 1137 * Important: if an exit-all has been started then 1138 * do not create this new thread - the whole thread 1139 * group is supposed to exit anyway. 1140 */ 1141 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1142 spin_unlock(¤t->sighand->siglock); 1143 write_unlock_irq(&tasklist_lock); 1144 retval = -EAGAIN; 1145 goto bad_fork_cleanup_namespace; 1146 } 1147 p->group_leader = current->group_leader; 1148 1149 if (current->signal->group_stop_count > 0) { 1150 /* 1151 * There is an all-stop in progress for the group. 1152 * We ourselves will stop as soon as we check signals. 1153 * Make the new thread part of that group stop too. 1154 */ 1155 current->signal->group_stop_count++; 1156 set_tsk_thread_flag(p, TIF_SIGPENDING); 1157 } 1158 1159 if (!cputime_eq(current->signal->it_virt_expires, 1160 cputime_zero) || 1161 !cputime_eq(current->signal->it_prof_expires, 1162 cputime_zero) || 1163 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1164 !list_empty(¤t->signal->cpu_timers[0]) || 1165 !list_empty(¤t->signal->cpu_timers[1]) || 1166 !list_empty(¤t->signal->cpu_timers[2])) { 1167 /* 1168 * Have child wake up on its first tick to check 1169 * for process CPU timers. 1170 */ 1171 p->it_prof_expires = jiffies_to_cputime(1); 1172 } 1173 } 1174 1175 /* 1176 * inherit ioprio 1177 */ 1178 p->ioprio = current->ioprio; 1179 1180 SET_LINKS(p); 1181 if (unlikely(p->ptrace & PT_PTRACED)) 1182 __ptrace_link(p, current->parent); 1183 1184 if (thread_group_leader(p)) { 1185 p->signal->tty = current->signal->tty; 1186 p->signal->pgrp = process_group(current); 1187 p->signal->session = current->signal->session; 1188 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1189 attach_pid(p, PIDTYPE_SID, p->signal->session); 1190 if (p->pid) 1191 __get_cpu_var(process_counts)++; 1192 } 1193 attach_pid(p, PIDTYPE_TGID, p->tgid); 1194 attach_pid(p, PIDTYPE_PID, p->pid); 1195 1196 nr_threads++; 1197 total_forks++; 1198 spin_unlock(¤t->sighand->siglock); 1199 write_unlock_irq(&tasklist_lock); 1200 proc_fork_connector(p); 1201 return p; 1202 1203 bad_fork_cleanup_namespace: 1204 exit_namespace(p); 1205 bad_fork_cleanup_keys: 1206 exit_keys(p); 1207 bad_fork_cleanup_mm: 1208 if (p->mm) 1209 mmput(p->mm); 1210 bad_fork_cleanup_signal: 1211 exit_signal(p); 1212 bad_fork_cleanup_sighand: 1213 exit_sighand(p); 1214 bad_fork_cleanup_fs: 1215 exit_fs(p); /* blocking */ 1216 bad_fork_cleanup_files: 1217 exit_files(p); /* blocking */ 1218 bad_fork_cleanup_semundo: 1219 exit_sem(p); 1220 bad_fork_cleanup_audit: 1221 audit_free(p); 1222 bad_fork_cleanup_security: 1223 security_task_free(p); 1224 bad_fork_cleanup_policy: 1225 #ifdef CONFIG_NUMA 1226 mpol_free(p->mempolicy); 1227 bad_fork_cleanup_cpuset: 1228 #endif 1229 cpuset_exit(p); 1230 bad_fork_cleanup: 1231 if (p->binfmt) 1232 module_put(p->binfmt->module); 1233 bad_fork_cleanup_put_domain: 1234 module_put(task_thread_info(p)->exec_domain->module); 1235 bad_fork_cleanup_count: 1236 put_group_info(p->group_info); 1237 atomic_dec(&p->user->processes); 1238 free_uid(p->user); 1239 bad_fork_free: 1240 free_task(p); 1241 fork_out: 1242 return ERR_PTR(retval); 1243 } 1244 1245 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1246 { 1247 memset(regs, 0, sizeof(struct pt_regs)); 1248 return regs; 1249 } 1250 1251 task_t * __devinit fork_idle(int cpu) 1252 { 1253 task_t *task; 1254 struct pt_regs regs; 1255 1256 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1257 if (!task) 1258 return ERR_PTR(-ENOMEM); 1259 init_idle(task, cpu); 1260 unhash_process(task); 1261 return task; 1262 } 1263 1264 static inline int fork_traceflag (unsigned clone_flags) 1265 { 1266 if (clone_flags & CLONE_UNTRACED) 1267 return 0; 1268 else if (clone_flags & CLONE_VFORK) { 1269 if (current->ptrace & PT_TRACE_VFORK) 1270 return PTRACE_EVENT_VFORK; 1271 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1272 if (current->ptrace & PT_TRACE_CLONE) 1273 return PTRACE_EVENT_CLONE; 1274 } else if (current->ptrace & PT_TRACE_FORK) 1275 return PTRACE_EVENT_FORK; 1276 1277 return 0; 1278 } 1279 1280 /* 1281 * Ok, this is the main fork-routine. 1282 * 1283 * It copies the process, and if successful kick-starts 1284 * it and waits for it to finish using the VM if required. 1285 */ 1286 long do_fork(unsigned long clone_flags, 1287 unsigned long stack_start, 1288 struct pt_regs *regs, 1289 unsigned long stack_size, 1290 int __user *parent_tidptr, 1291 int __user *child_tidptr) 1292 { 1293 struct task_struct *p; 1294 int trace = 0; 1295 long pid = alloc_pidmap(); 1296 1297 if (pid < 0) 1298 return -EAGAIN; 1299 if (unlikely(current->ptrace)) { 1300 trace = fork_traceflag (clone_flags); 1301 if (trace) 1302 clone_flags |= CLONE_PTRACE; 1303 } 1304 1305 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1306 /* 1307 * Do this prior waking up the new thread - the thread pointer 1308 * might get invalid after that point, if the thread exits quickly. 1309 */ 1310 if (!IS_ERR(p)) { 1311 struct completion vfork; 1312 1313 if (clone_flags & CLONE_VFORK) { 1314 p->vfork_done = &vfork; 1315 init_completion(&vfork); 1316 } 1317 1318 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1319 /* 1320 * We'll start up with an immediate SIGSTOP. 1321 */ 1322 sigaddset(&p->pending.signal, SIGSTOP); 1323 set_tsk_thread_flag(p, TIF_SIGPENDING); 1324 } 1325 1326 if (!(clone_flags & CLONE_STOPPED)) 1327 wake_up_new_task(p, clone_flags); 1328 else 1329 p->state = TASK_STOPPED; 1330 1331 if (unlikely (trace)) { 1332 current->ptrace_message = pid; 1333 ptrace_notify ((trace << 8) | SIGTRAP); 1334 } 1335 1336 if (clone_flags & CLONE_VFORK) { 1337 wait_for_completion(&vfork); 1338 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1339 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1340 } 1341 } else { 1342 free_pidmap(pid); 1343 pid = PTR_ERR(p); 1344 } 1345 return pid; 1346 } 1347 1348 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1349 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1350 #endif 1351 1352 void __init proc_caches_init(void) 1353 { 1354 sighand_cachep = kmem_cache_create("sighand_cache", 1355 sizeof(struct sighand_struct), 0, 1356 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1357 signal_cachep = kmem_cache_create("signal_cache", 1358 sizeof(struct signal_struct), 0, 1359 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1360 files_cachep = kmem_cache_create("files_cache", 1361 sizeof(struct files_struct), 0, 1362 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1363 fs_cachep = kmem_cache_create("fs_cache", 1364 sizeof(struct fs_struct), 0, 1365 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1366 vm_area_cachep = kmem_cache_create("vm_area_struct", 1367 sizeof(struct vm_area_struct), 0, 1368 SLAB_PANIC, NULL, NULL); 1369 mm_cachep = kmem_cache_create("mm_struct", 1370 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1371 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1372 } 1373 1374 1375 /* 1376 * Check constraints on flags passed to the unshare system call and 1377 * force unsharing of additional process context as appropriate. 1378 */ 1379 static inline void check_unshare_flags(unsigned long *flags_ptr) 1380 { 1381 /* 1382 * If unsharing a thread from a thread group, must also 1383 * unshare vm. 1384 */ 1385 if (*flags_ptr & CLONE_THREAD) 1386 *flags_ptr |= CLONE_VM; 1387 1388 /* 1389 * If unsharing vm, must also unshare signal handlers. 1390 */ 1391 if (*flags_ptr & CLONE_VM) 1392 *flags_ptr |= CLONE_SIGHAND; 1393 1394 /* 1395 * If unsharing signal handlers and the task was created 1396 * using CLONE_THREAD, then must unshare the thread 1397 */ 1398 if ((*flags_ptr & CLONE_SIGHAND) && 1399 (atomic_read(¤t->signal->count) > 1)) 1400 *flags_ptr |= CLONE_THREAD; 1401 1402 /* 1403 * If unsharing namespace, must also unshare filesystem information. 1404 */ 1405 if (*flags_ptr & CLONE_NEWNS) 1406 *flags_ptr |= CLONE_FS; 1407 } 1408 1409 /* 1410 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1411 */ 1412 static int unshare_thread(unsigned long unshare_flags) 1413 { 1414 if (unshare_flags & CLONE_THREAD) 1415 return -EINVAL; 1416 1417 return 0; 1418 } 1419 1420 /* 1421 * Unshare the filesystem structure if it is being shared 1422 */ 1423 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1424 { 1425 struct fs_struct *fs = current->fs; 1426 1427 if ((unshare_flags & CLONE_FS) && 1428 (fs && atomic_read(&fs->count) > 1)) { 1429 *new_fsp = __copy_fs_struct(current->fs); 1430 if (!*new_fsp) 1431 return -ENOMEM; 1432 } 1433 1434 return 0; 1435 } 1436 1437 /* 1438 * Unshare the namespace structure if it is being shared 1439 */ 1440 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs) 1441 { 1442 struct namespace *ns = current->namespace; 1443 1444 if ((unshare_flags & CLONE_NEWNS) && 1445 (ns && atomic_read(&ns->count) > 1)) { 1446 if (!capable(CAP_SYS_ADMIN)) 1447 return -EPERM; 1448 1449 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs); 1450 if (!*new_nsp) 1451 return -ENOMEM; 1452 } 1453 1454 return 0; 1455 } 1456 1457 /* 1458 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not 1459 * supported yet 1460 */ 1461 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1462 { 1463 struct sighand_struct *sigh = current->sighand; 1464 1465 if ((unshare_flags & CLONE_SIGHAND) && 1466 (sigh && atomic_read(&sigh->count) > 1)) 1467 return -EINVAL; 1468 else 1469 return 0; 1470 } 1471 1472 /* 1473 * Unshare vm if it is being shared 1474 */ 1475 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1476 { 1477 struct mm_struct *mm = current->mm; 1478 1479 if ((unshare_flags & CLONE_VM) && 1480 (mm && atomic_read(&mm->mm_users) > 1)) { 1481 return -EINVAL; 1482 } 1483 1484 return 0; 1485 } 1486 1487 /* 1488 * Unshare file descriptor table if it is being shared 1489 */ 1490 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1491 { 1492 struct files_struct *fd = current->files; 1493 int error = 0; 1494 1495 if ((unshare_flags & CLONE_FILES) && 1496 (fd && atomic_read(&fd->count) > 1)) { 1497 *new_fdp = dup_fd(fd, &error); 1498 if (!*new_fdp) 1499 return error; 1500 } 1501 1502 return 0; 1503 } 1504 1505 /* 1506 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1507 * supported yet 1508 */ 1509 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1510 { 1511 if (unshare_flags & CLONE_SYSVSEM) 1512 return -EINVAL; 1513 1514 return 0; 1515 } 1516 1517 /* 1518 * unshare allows a process to 'unshare' part of the process 1519 * context which was originally shared using clone. copy_* 1520 * functions used by do_fork() cannot be used here directly 1521 * because they modify an inactive task_struct that is being 1522 * constructed. Here we are modifying the current, active, 1523 * task_struct. 1524 */ 1525 asmlinkage long sys_unshare(unsigned long unshare_flags) 1526 { 1527 int err = 0; 1528 struct fs_struct *fs, *new_fs = NULL; 1529 struct namespace *ns, *new_ns = NULL; 1530 struct sighand_struct *sigh, *new_sigh = NULL; 1531 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1532 struct files_struct *fd, *new_fd = NULL; 1533 struct sem_undo_list *new_ulist = NULL; 1534 1535 check_unshare_flags(&unshare_flags); 1536 1537 if ((err = unshare_thread(unshare_flags))) 1538 goto bad_unshare_out; 1539 if ((err = unshare_fs(unshare_flags, &new_fs))) 1540 goto bad_unshare_cleanup_thread; 1541 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs))) 1542 goto bad_unshare_cleanup_fs; 1543 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1544 goto bad_unshare_cleanup_ns; 1545 if ((err = unshare_vm(unshare_flags, &new_mm))) 1546 goto bad_unshare_cleanup_sigh; 1547 if ((err = unshare_fd(unshare_flags, &new_fd))) 1548 goto bad_unshare_cleanup_vm; 1549 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1550 goto bad_unshare_cleanup_fd; 1551 1552 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { 1553 1554 task_lock(current); 1555 1556 if (new_fs) { 1557 fs = current->fs; 1558 current->fs = new_fs; 1559 new_fs = fs; 1560 } 1561 1562 if (new_ns) { 1563 ns = current->namespace; 1564 current->namespace = new_ns; 1565 new_ns = ns; 1566 } 1567 1568 if (new_sigh) { 1569 sigh = current->sighand; 1570 rcu_assign_pointer(current->sighand, new_sigh); 1571 new_sigh = sigh; 1572 } 1573 1574 if (new_mm) { 1575 mm = current->mm; 1576 active_mm = current->active_mm; 1577 current->mm = new_mm; 1578 current->active_mm = new_mm; 1579 activate_mm(active_mm, new_mm); 1580 new_mm = mm; 1581 } 1582 1583 if (new_fd) { 1584 fd = current->files; 1585 current->files = new_fd; 1586 new_fd = fd; 1587 } 1588 1589 task_unlock(current); 1590 } 1591 1592 bad_unshare_cleanup_fd: 1593 if (new_fd) 1594 put_files_struct(new_fd); 1595 1596 bad_unshare_cleanup_vm: 1597 if (new_mm) 1598 mmput(new_mm); 1599 1600 bad_unshare_cleanup_sigh: 1601 if (new_sigh) 1602 if (atomic_dec_and_test(&new_sigh->count)) 1603 kmem_cache_free(sighand_cachep, new_sigh); 1604 1605 bad_unshare_cleanup_ns: 1606 if (new_ns) 1607 put_namespace(new_ns); 1608 1609 bad_unshare_cleanup_fs: 1610 if (new_fs) 1611 put_fs_struct(new_fs); 1612 1613 bad_unshare_cleanup_thread: 1614 bad_unshare_out: 1615 return err; 1616 } 1617