1 /* 2 * linux/fs/namespace.c 3 * 4 * (C) Copyright Al Viro 2000, 2001 5 * Released under GPL v2. 6 * 7 * Based on code from fs/super.c, copyright Linus Torvalds and others. 8 * Heavily rewritten. 9 */ 10 11 #include <linux/config.h> 12 #include <linux/syscalls.h> 13 #include <linux/slab.h> 14 #include <linux/sched.h> 15 #include <linux/smp_lock.h> 16 #include <linux/init.h> 17 #include <linux/quotaops.h> 18 #include <linux/acct.h> 19 #include <linux/capability.h> 20 #include <linux/module.h> 21 #include <linux/seq_file.h> 22 #include <linux/namespace.h> 23 #include <linux/namei.h> 24 #include <linux/security.h> 25 #include <linux/mount.h> 26 #include <asm/uaccess.h> 27 #include <asm/unistd.h> 28 #include "pnode.h" 29 30 extern int __init init_rootfs(void); 31 32 #ifdef CONFIG_SYSFS 33 extern int __init sysfs_init(void); 34 #else 35 static inline int sysfs_init(void) 36 { 37 return 0; 38 } 39 #endif 40 41 /* spinlock for vfsmount related operations, inplace of dcache_lock */ 42 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); 43 44 static int event; 45 46 static struct list_head *mount_hashtable; 47 static int hash_mask __read_mostly, hash_bits __read_mostly; 48 static kmem_cache_t *mnt_cache; 49 static struct rw_semaphore namespace_sem; 50 51 /* /sys/fs */ 52 decl_subsys(fs, NULL, NULL); 53 EXPORT_SYMBOL_GPL(fs_subsys); 54 55 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) 56 { 57 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); 58 tmp += ((unsigned long)dentry / L1_CACHE_BYTES); 59 tmp = tmp + (tmp >> hash_bits); 60 return tmp & hash_mask; 61 } 62 63 struct vfsmount *alloc_vfsmnt(const char *name) 64 { 65 struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL); 66 if (mnt) { 67 memset(mnt, 0, sizeof(struct vfsmount)); 68 atomic_set(&mnt->mnt_count, 1); 69 INIT_LIST_HEAD(&mnt->mnt_hash); 70 INIT_LIST_HEAD(&mnt->mnt_child); 71 INIT_LIST_HEAD(&mnt->mnt_mounts); 72 INIT_LIST_HEAD(&mnt->mnt_list); 73 INIT_LIST_HEAD(&mnt->mnt_expire); 74 INIT_LIST_HEAD(&mnt->mnt_share); 75 INIT_LIST_HEAD(&mnt->mnt_slave_list); 76 INIT_LIST_HEAD(&mnt->mnt_slave); 77 if (name) { 78 int size = strlen(name) + 1; 79 char *newname = kmalloc(size, GFP_KERNEL); 80 if (newname) { 81 memcpy(newname, name, size); 82 mnt->mnt_devname = newname; 83 } 84 } 85 } 86 return mnt; 87 } 88 89 void free_vfsmnt(struct vfsmount *mnt) 90 { 91 kfree(mnt->mnt_devname); 92 kmem_cache_free(mnt_cache, mnt); 93 } 94 95 /* 96 * find the first or last mount at @dentry on vfsmount @mnt depending on 97 * @dir. If @dir is set return the first mount else return the last mount. 98 */ 99 struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, 100 int dir) 101 { 102 struct list_head *head = mount_hashtable + hash(mnt, dentry); 103 struct list_head *tmp = head; 104 struct vfsmount *p, *found = NULL; 105 106 for (;;) { 107 tmp = dir ? tmp->next : tmp->prev; 108 p = NULL; 109 if (tmp == head) 110 break; 111 p = list_entry(tmp, struct vfsmount, mnt_hash); 112 if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { 113 found = p; 114 break; 115 } 116 } 117 return found; 118 } 119 120 /* 121 * lookup_mnt increments the ref count before returning 122 * the vfsmount struct. 123 */ 124 struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) 125 { 126 struct vfsmount *child_mnt; 127 spin_lock(&vfsmount_lock); 128 if ((child_mnt = __lookup_mnt(mnt, dentry, 1))) 129 mntget(child_mnt); 130 spin_unlock(&vfsmount_lock); 131 return child_mnt; 132 } 133 134 static inline int check_mnt(struct vfsmount *mnt) 135 { 136 return mnt->mnt_namespace == current->namespace; 137 } 138 139 static void touch_namespace(struct namespace *ns) 140 { 141 if (ns) { 142 ns->event = ++event; 143 wake_up_interruptible(&ns->poll); 144 } 145 } 146 147 static void __touch_namespace(struct namespace *ns) 148 { 149 if (ns && ns->event != event) { 150 ns->event = event; 151 wake_up_interruptible(&ns->poll); 152 } 153 } 154 155 static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd) 156 { 157 old_nd->dentry = mnt->mnt_mountpoint; 158 old_nd->mnt = mnt->mnt_parent; 159 mnt->mnt_parent = mnt; 160 mnt->mnt_mountpoint = mnt->mnt_root; 161 list_del_init(&mnt->mnt_child); 162 list_del_init(&mnt->mnt_hash); 163 old_nd->dentry->d_mounted--; 164 } 165 166 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, 167 struct vfsmount *child_mnt) 168 { 169 child_mnt->mnt_parent = mntget(mnt); 170 child_mnt->mnt_mountpoint = dget(dentry); 171 dentry->d_mounted++; 172 } 173 174 static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd) 175 { 176 mnt_set_mountpoint(nd->mnt, nd->dentry, mnt); 177 list_add_tail(&mnt->mnt_hash, mount_hashtable + 178 hash(nd->mnt, nd->dentry)); 179 list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts); 180 } 181 182 /* 183 * the caller must hold vfsmount_lock 184 */ 185 static void commit_tree(struct vfsmount *mnt) 186 { 187 struct vfsmount *parent = mnt->mnt_parent; 188 struct vfsmount *m; 189 LIST_HEAD(head); 190 struct namespace *n = parent->mnt_namespace; 191 192 BUG_ON(parent == mnt); 193 194 list_add_tail(&head, &mnt->mnt_list); 195 list_for_each_entry(m, &head, mnt_list) 196 m->mnt_namespace = n; 197 list_splice(&head, n->list.prev); 198 199 list_add_tail(&mnt->mnt_hash, mount_hashtable + 200 hash(parent, mnt->mnt_mountpoint)); 201 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); 202 touch_namespace(n); 203 } 204 205 static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) 206 { 207 struct list_head *next = p->mnt_mounts.next; 208 if (next == &p->mnt_mounts) { 209 while (1) { 210 if (p == root) 211 return NULL; 212 next = p->mnt_child.next; 213 if (next != &p->mnt_parent->mnt_mounts) 214 break; 215 p = p->mnt_parent; 216 } 217 } 218 return list_entry(next, struct vfsmount, mnt_child); 219 } 220 221 static struct vfsmount *skip_mnt_tree(struct vfsmount *p) 222 { 223 struct list_head *prev = p->mnt_mounts.prev; 224 while (prev != &p->mnt_mounts) { 225 p = list_entry(prev, struct vfsmount, mnt_child); 226 prev = p->mnt_mounts.prev; 227 } 228 return p; 229 } 230 231 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, 232 int flag) 233 { 234 struct super_block *sb = old->mnt_sb; 235 struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); 236 237 if (mnt) { 238 mnt->mnt_flags = old->mnt_flags; 239 atomic_inc(&sb->s_active); 240 mnt->mnt_sb = sb; 241 mnt->mnt_root = dget(root); 242 mnt->mnt_mountpoint = mnt->mnt_root; 243 mnt->mnt_parent = mnt; 244 245 if (flag & CL_SLAVE) { 246 list_add(&mnt->mnt_slave, &old->mnt_slave_list); 247 mnt->mnt_master = old; 248 CLEAR_MNT_SHARED(mnt); 249 } else { 250 if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old)) 251 list_add(&mnt->mnt_share, &old->mnt_share); 252 if (IS_MNT_SLAVE(old)) 253 list_add(&mnt->mnt_slave, &old->mnt_slave); 254 mnt->mnt_master = old->mnt_master; 255 } 256 if (flag & CL_MAKE_SHARED) 257 set_mnt_shared(mnt); 258 259 /* stick the duplicate mount on the same expiry list 260 * as the original if that was on one */ 261 if (flag & CL_EXPIRE) { 262 spin_lock(&vfsmount_lock); 263 if (!list_empty(&old->mnt_expire)) 264 list_add(&mnt->mnt_expire, &old->mnt_expire); 265 spin_unlock(&vfsmount_lock); 266 } 267 } 268 return mnt; 269 } 270 271 static inline void __mntput(struct vfsmount *mnt) 272 { 273 struct super_block *sb = mnt->mnt_sb; 274 dput(mnt->mnt_root); 275 free_vfsmnt(mnt); 276 deactivate_super(sb); 277 } 278 279 void mntput_no_expire(struct vfsmount *mnt) 280 { 281 repeat: 282 if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { 283 if (likely(!mnt->mnt_pinned)) { 284 spin_unlock(&vfsmount_lock); 285 __mntput(mnt); 286 return; 287 } 288 atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); 289 mnt->mnt_pinned = 0; 290 spin_unlock(&vfsmount_lock); 291 acct_auto_close_mnt(mnt); 292 security_sb_umount_close(mnt); 293 goto repeat; 294 } 295 } 296 297 EXPORT_SYMBOL(mntput_no_expire); 298 299 void mnt_pin(struct vfsmount *mnt) 300 { 301 spin_lock(&vfsmount_lock); 302 mnt->mnt_pinned++; 303 spin_unlock(&vfsmount_lock); 304 } 305 306 EXPORT_SYMBOL(mnt_pin); 307 308 void mnt_unpin(struct vfsmount *mnt) 309 { 310 spin_lock(&vfsmount_lock); 311 if (mnt->mnt_pinned) { 312 atomic_inc(&mnt->mnt_count); 313 mnt->mnt_pinned--; 314 } 315 spin_unlock(&vfsmount_lock); 316 } 317 318 EXPORT_SYMBOL(mnt_unpin); 319 320 /* iterator */ 321 static void *m_start(struct seq_file *m, loff_t *pos) 322 { 323 struct namespace *n = m->private; 324 struct list_head *p; 325 loff_t l = *pos; 326 327 down_read(&namespace_sem); 328 list_for_each(p, &n->list) 329 if (!l--) 330 return list_entry(p, struct vfsmount, mnt_list); 331 return NULL; 332 } 333 334 static void *m_next(struct seq_file *m, void *v, loff_t *pos) 335 { 336 struct namespace *n = m->private; 337 struct list_head *p = ((struct vfsmount *)v)->mnt_list.next; 338 (*pos)++; 339 return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list); 340 } 341 342 static void m_stop(struct seq_file *m, void *v) 343 { 344 up_read(&namespace_sem); 345 } 346 347 static inline void mangle(struct seq_file *m, const char *s) 348 { 349 seq_escape(m, s, " \t\n\\"); 350 } 351 352 static int show_vfsmnt(struct seq_file *m, void *v) 353 { 354 struct vfsmount *mnt = v; 355 int err = 0; 356 static struct proc_fs_info { 357 int flag; 358 char *str; 359 } fs_info[] = { 360 { MS_SYNCHRONOUS, ",sync" }, 361 { MS_DIRSYNC, ",dirsync" }, 362 { MS_MANDLOCK, ",mand" }, 363 { 0, NULL } 364 }; 365 static struct proc_fs_info mnt_info[] = { 366 { MNT_NOSUID, ",nosuid" }, 367 { MNT_NODEV, ",nodev" }, 368 { MNT_NOEXEC, ",noexec" }, 369 { MNT_NOATIME, ",noatime" }, 370 { MNT_NODIRATIME, ",nodiratime" }, 371 { 0, NULL } 372 }; 373 struct proc_fs_info *fs_infop; 374 375 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); 376 seq_putc(m, ' '); 377 seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); 378 seq_putc(m, ' '); 379 mangle(m, mnt->mnt_sb->s_type->name); 380 seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); 381 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { 382 if (mnt->mnt_sb->s_flags & fs_infop->flag) 383 seq_puts(m, fs_infop->str); 384 } 385 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { 386 if (mnt->mnt_flags & fs_infop->flag) 387 seq_puts(m, fs_infop->str); 388 } 389 if (mnt->mnt_sb->s_op->show_options) 390 err = mnt->mnt_sb->s_op->show_options(m, mnt); 391 seq_puts(m, " 0 0\n"); 392 return err; 393 } 394 395 struct seq_operations mounts_op = { 396 .start = m_start, 397 .next = m_next, 398 .stop = m_stop, 399 .show = show_vfsmnt 400 }; 401 402 /** 403 * may_umount_tree - check if a mount tree is busy 404 * @mnt: root of mount tree 405 * 406 * This is called to check if a tree of mounts has any 407 * open files, pwds, chroots or sub mounts that are 408 * busy. 409 */ 410 int may_umount_tree(struct vfsmount *mnt) 411 { 412 int actual_refs = 0; 413 int minimum_refs = 0; 414 struct vfsmount *p; 415 416 spin_lock(&vfsmount_lock); 417 for (p = mnt; p; p = next_mnt(p, mnt)) { 418 actual_refs += atomic_read(&p->mnt_count); 419 minimum_refs += 2; 420 } 421 spin_unlock(&vfsmount_lock); 422 423 if (actual_refs > minimum_refs) 424 return -EBUSY; 425 426 return 0; 427 } 428 429 EXPORT_SYMBOL(may_umount_tree); 430 431 /** 432 * may_umount - check if a mount point is busy 433 * @mnt: root of mount 434 * 435 * This is called to check if a mount point has any 436 * open files, pwds, chroots or sub mounts. If the 437 * mount has sub mounts this will return busy 438 * regardless of whether the sub mounts are busy. 439 * 440 * Doesn't take quota and stuff into account. IOW, in some cases it will 441 * give false negatives. The main reason why it's here is that we need 442 * a non-destructive way to look for easily umountable filesystems. 443 */ 444 int may_umount(struct vfsmount *mnt) 445 { 446 int ret = 0; 447 spin_lock(&vfsmount_lock); 448 if (propagate_mount_busy(mnt, 2)) 449 ret = -EBUSY; 450 spin_unlock(&vfsmount_lock); 451 return ret; 452 } 453 454 EXPORT_SYMBOL(may_umount); 455 456 void release_mounts(struct list_head *head) 457 { 458 struct vfsmount *mnt; 459 while (!list_empty(head)) { 460 mnt = list_entry(head->next, struct vfsmount, mnt_hash); 461 list_del_init(&mnt->mnt_hash); 462 if (mnt->mnt_parent != mnt) { 463 struct dentry *dentry; 464 struct vfsmount *m; 465 spin_lock(&vfsmount_lock); 466 dentry = mnt->mnt_mountpoint; 467 m = mnt->mnt_parent; 468 mnt->mnt_mountpoint = mnt->mnt_root; 469 mnt->mnt_parent = mnt; 470 spin_unlock(&vfsmount_lock); 471 dput(dentry); 472 mntput(m); 473 } 474 mntput(mnt); 475 } 476 } 477 478 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) 479 { 480 struct vfsmount *p; 481 482 for (p = mnt; p; p = next_mnt(p, mnt)) { 483 list_del(&p->mnt_hash); 484 list_add(&p->mnt_hash, kill); 485 } 486 487 if (propagate) 488 propagate_umount(kill); 489 490 list_for_each_entry(p, kill, mnt_hash) { 491 list_del_init(&p->mnt_expire); 492 list_del_init(&p->mnt_list); 493 __touch_namespace(p->mnt_namespace); 494 p->mnt_namespace = NULL; 495 list_del_init(&p->mnt_child); 496 if (p->mnt_parent != p) 497 p->mnt_mountpoint->d_mounted--; 498 change_mnt_propagation(p, MS_PRIVATE); 499 } 500 } 501 502 static int do_umount(struct vfsmount *mnt, int flags) 503 { 504 struct super_block *sb = mnt->mnt_sb; 505 int retval; 506 LIST_HEAD(umount_list); 507 508 retval = security_sb_umount(mnt, flags); 509 if (retval) 510 return retval; 511 512 /* 513 * Allow userspace to request a mountpoint be expired rather than 514 * unmounting unconditionally. Unmount only happens if: 515 * (1) the mark is already set (the mark is cleared by mntput()) 516 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] 517 */ 518 if (flags & MNT_EXPIRE) { 519 if (mnt == current->fs->rootmnt || 520 flags & (MNT_FORCE | MNT_DETACH)) 521 return -EINVAL; 522 523 if (atomic_read(&mnt->mnt_count) != 2) 524 return -EBUSY; 525 526 if (!xchg(&mnt->mnt_expiry_mark, 1)) 527 return -EAGAIN; 528 } 529 530 /* 531 * If we may have to abort operations to get out of this 532 * mount, and they will themselves hold resources we must 533 * allow the fs to do things. In the Unix tradition of 534 * 'Gee thats tricky lets do it in userspace' the umount_begin 535 * might fail to complete on the first run through as other tasks 536 * must return, and the like. Thats for the mount program to worry 537 * about for the moment. 538 */ 539 540 lock_kernel(); 541 if ((flags & MNT_FORCE) && sb->s_op->umount_begin) 542 sb->s_op->umount_begin(sb); 543 unlock_kernel(); 544 545 /* 546 * No sense to grab the lock for this test, but test itself looks 547 * somewhat bogus. Suggestions for better replacement? 548 * Ho-hum... In principle, we might treat that as umount + switch 549 * to rootfs. GC would eventually take care of the old vfsmount. 550 * Actually it makes sense, especially if rootfs would contain a 551 * /reboot - static binary that would close all descriptors and 552 * call reboot(9). Then init(8) could umount root and exec /reboot. 553 */ 554 if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { 555 /* 556 * Special case for "unmounting" root ... 557 * we just try to remount it readonly. 558 */ 559 down_write(&sb->s_umount); 560 if (!(sb->s_flags & MS_RDONLY)) { 561 lock_kernel(); 562 DQUOT_OFF(sb); 563 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); 564 unlock_kernel(); 565 } 566 up_write(&sb->s_umount); 567 return retval; 568 } 569 570 down_write(&namespace_sem); 571 spin_lock(&vfsmount_lock); 572 event++; 573 574 retval = -EBUSY; 575 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { 576 if (!list_empty(&mnt->mnt_list)) 577 umount_tree(mnt, 1, &umount_list); 578 retval = 0; 579 } 580 spin_unlock(&vfsmount_lock); 581 if (retval) 582 security_sb_umount_busy(mnt); 583 up_write(&namespace_sem); 584 release_mounts(&umount_list); 585 return retval; 586 } 587 588 /* 589 * Now umount can handle mount points as well as block devices. 590 * This is important for filesystems which use unnamed block devices. 591 * 592 * We now support a flag for forced unmount like the other 'big iron' 593 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD 594 */ 595 596 asmlinkage long sys_umount(char __user * name, int flags) 597 { 598 struct nameidata nd; 599 int retval; 600 601 retval = __user_walk(name, LOOKUP_FOLLOW, &nd); 602 if (retval) 603 goto out; 604 retval = -EINVAL; 605 if (nd.dentry != nd.mnt->mnt_root) 606 goto dput_and_out; 607 if (!check_mnt(nd.mnt)) 608 goto dput_and_out; 609 610 retval = -EPERM; 611 if (!capable(CAP_SYS_ADMIN)) 612 goto dput_and_out; 613 614 retval = do_umount(nd.mnt, flags); 615 dput_and_out: 616 path_release_on_umount(&nd); 617 out: 618 return retval; 619 } 620 621 #ifdef __ARCH_WANT_SYS_OLDUMOUNT 622 623 /* 624 * The 2.0 compatible umount. No flags. 625 */ 626 asmlinkage long sys_oldumount(char __user * name) 627 { 628 return sys_umount(name, 0); 629 } 630 631 #endif 632 633 static int mount_is_safe(struct nameidata *nd) 634 { 635 if (capable(CAP_SYS_ADMIN)) 636 return 0; 637 return -EPERM; 638 #ifdef notyet 639 if (S_ISLNK(nd->dentry->d_inode->i_mode)) 640 return -EPERM; 641 if (nd->dentry->d_inode->i_mode & S_ISVTX) { 642 if (current->uid != nd->dentry->d_inode->i_uid) 643 return -EPERM; 644 } 645 if (vfs_permission(nd, MAY_WRITE)) 646 return -EPERM; 647 return 0; 648 #endif 649 } 650 651 static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) 652 { 653 while (1) { 654 if (d == dentry) 655 return 1; 656 if (d == NULL || d == d->d_parent) 657 return 0; 658 d = d->d_parent; 659 } 660 } 661 662 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 663 int flag) 664 { 665 struct vfsmount *res, *p, *q, *r, *s; 666 struct nameidata nd; 667 668 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) 669 return NULL; 670 671 res = q = clone_mnt(mnt, dentry, flag); 672 if (!q) 673 goto Enomem; 674 q->mnt_mountpoint = mnt->mnt_mountpoint; 675 676 p = mnt; 677 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { 678 if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) 679 continue; 680 681 for (s = r; s; s = next_mnt(s, r)) { 682 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { 683 s = skip_mnt_tree(s); 684 continue; 685 } 686 while (p != s->mnt_parent) { 687 p = p->mnt_parent; 688 q = q->mnt_parent; 689 } 690 p = s; 691 nd.mnt = q; 692 nd.dentry = p->mnt_mountpoint; 693 q = clone_mnt(p, p->mnt_root, flag); 694 if (!q) 695 goto Enomem; 696 spin_lock(&vfsmount_lock); 697 list_add_tail(&q->mnt_list, &res->mnt_list); 698 attach_mnt(q, &nd); 699 spin_unlock(&vfsmount_lock); 700 } 701 } 702 return res; 703 Enomem: 704 if (res) { 705 LIST_HEAD(umount_list); 706 spin_lock(&vfsmount_lock); 707 umount_tree(res, 0, &umount_list); 708 spin_unlock(&vfsmount_lock); 709 release_mounts(&umount_list); 710 } 711 return NULL; 712 } 713 714 /* 715 * @source_mnt : mount tree to be attached 716 * @nd : place the mount tree @source_mnt is attached 717 * @parent_nd : if non-null, detach the source_mnt from its parent and 718 * store the parent mount and mountpoint dentry. 719 * (done when source_mnt is moved) 720 * 721 * NOTE: in the table below explains the semantics when a source mount 722 * of a given type is attached to a destination mount of a given type. 723 * --------------------------------------------------------------------------- 724 * | BIND MOUNT OPERATION | 725 * |************************************************************************** 726 * | source-->| shared | private | slave | unbindable | 727 * | dest | | | | | 728 * | | | | | | | 729 * | v | | | | | 730 * |************************************************************************** 731 * | shared | shared (++) | shared (+) | shared(+++)| invalid | 732 * | | | | | | 733 * |non-shared| shared (+) | private | slave (*) | invalid | 734 * *************************************************************************** 735 * A bind operation clones the source mount and mounts the clone on the 736 * destination mount. 737 * 738 * (++) the cloned mount is propagated to all the mounts in the propagation 739 * tree of the destination mount and the cloned mount is added to 740 * the peer group of the source mount. 741 * (+) the cloned mount is created under the destination mount and is marked 742 * as shared. The cloned mount is added to the peer group of the source 743 * mount. 744 * (+++) the mount is propagated to all the mounts in the propagation tree 745 * of the destination mount and the cloned mount is made slave 746 * of the same master as that of the source mount. The cloned mount 747 * is marked as 'shared and slave'. 748 * (*) the cloned mount is made a slave of the same master as that of the 749 * source mount. 750 * 751 * --------------------------------------------------------------------------- 752 * | MOVE MOUNT OPERATION | 753 * |************************************************************************** 754 * | source-->| shared | private | slave | unbindable | 755 * | dest | | | | | 756 * | | | | | | | 757 * | v | | | | | 758 * |************************************************************************** 759 * | shared | shared (+) | shared (+) | shared(+++) | invalid | 760 * | | | | | | 761 * |non-shared| shared (+*) | private | slave (*) | unbindable | 762 * *************************************************************************** 763 * 764 * (+) the mount is moved to the destination. And is then propagated to 765 * all the mounts in the propagation tree of the destination mount. 766 * (+*) the mount is moved to the destination. 767 * (+++) the mount is moved to the destination and is then propagated to 768 * all the mounts belonging to the destination mount's propagation tree. 769 * the mount is marked as 'shared and slave'. 770 * (*) the mount continues to be a slave at the new location. 771 * 772 * if the source mount is a tree, the operations explained above is 773 * applied to each mount in the tree. 774 * Must be called without spinlocks held, since this function can sleep 775 * in allocations. 776 */ 777 static int attach_recursive_mnt(struct vfsmount *source_mnt, 778 struct nameidata *nd, struct nameidata *parent_nd) 779 { 780 LIST_HEAD(tree_list); 781 struct vfsmount *dest_mnt = nd->mnt; 782 struct dentry *dest_dentry = nd->dentry; 783 struct vfsmount *child, *p; 784 785 if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list)) 786 return -EINVAL; 787 788 if (IS_MNT_SHARED(dest_mnt)) { 789 for (p = source_mnt; p; p = next_mnt(p, source_mnt)) 790 set_mnt_shared(p); 791 } 792 793 spin_lock(&vfsmount_lock); 794 if (parent_nd) { 795 detach_mnt(source_mnt, parent_nd); 796 attach_mnt(source_mnt, nd); 797 touch_namespace(current->namespace); 798 } else { 799 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); 800 commit_tree(source_mnt); 801 } 802 803 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { 804 list_del_init(&child->mnt_hash); 805 commit_tree(child); 806 } 807 spin_unlock(&vfsmount_lock); 808 return 0; 809 } 810 811 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) 812 { 813 int err; 814 if (mnt->mnt_sb->s_flags & MS_NOUSER) 815 return -EINVAL; 816 817 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 818 S_ISDIR(mnt->mnt_root->d_inode->i_mode)) 819 return -ENOTDIR; 820 821 err = -ENOENT; 822 mutex_lock(&nd->dentry->d_inode->i_mutex); 823 if (IS_DEADDIR(nd->dentry->d_inode)) 824 goto out_unlock; 825 826 err = security_sb_check_sb(mnt, nd); 827 if (err) 828 goto out_unlock; 829 830 err = -ENOENT; 831 if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) 832 err = attach_recursive_mnt(mnt, nd, NULL); 833 out_unlock: 834 mutex_unlock(&nd->dentry->d_inode->i_mutex); 835 if (!err) 836 security_sb_post_addmount(mnt, nd); 837 return err; 838 } 839 840 /* 841 * recursively change the type of the mountpoint. 842 */ 843 static int do_change_type(struct nameidata *nd, int flag) 844 { 845 struct vfsmount *m, *mnt = nd->mnt; 846 int recurse = flag & MS_REC; 847 int type = flag & ~MS_REC; 848 849 if (nd->dentry != nd->mnt->mnt_root) 850 return -EINVAL; 851 852 down_write(&namespace_sem); 853 spin_lock(&vfsmount_lock); 854 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) 855 change_mnt_propagation(m, type); 856 spin_unlock(&vfsmount_lock); 857 up_write(&namespace_sem); 858 return 0; 859 } 860 861 /* 862 * do loopback mount. 863 */ 864 static int do_loopback(struct nameidata *nd, char *old_name, int recurse) 865 { 866 struct nameidata old_nd; 867 struct vfsmount *mnt = NULL; 868 int err = mount_is_safe(nd); 869 if (err) 870 return err; 871 if (!old_name || !*old_name) 872 return -EINVAL; 873 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 874 if (err) 875 return err; 876 877 down_write(&namespace_sem); 878 err = -EINVAL; 879 if (IS_MNT_UNBINDABLE(old_nd.mnt)) 880 goto out; 881 882 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 883 goto out; 884 885 err = -ENOMEM; 886 if (recurse) 887 mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0); 888 else 889 mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0); 890 891 if (!mnt) 892 goto out; 893 894 err = graft_tree(mnt, nd); 895 if (err) { 896 LIST_HEAD(umount_list); 897 spin_lock(&vfsmount_lock); 898 umount_tree(mnt, 0, &umount_list); 899 spin_unlock(&vfsmount_lock); 900 release_mounts(&umount_list); 901 } 902 903 out: 904 up_write(&namespace_sem); 905 path_release(&old_nd); 906 return err; 907 } 908 909 /* 910 * change filesystem flags. dir should be a physical root of filesystem. 911 * If you've mounted a non-root directory somewhere and want to do remount 912 * on it - tough luck. 913 */ 914 static int do_remount(struct nameidata *nd, int flags, int mnt_flags, 915 void *data) 916 { 917 int err; 918 struct super_block *sb = nd->mnt->mnt_sb; 919 920 if (!capable(CAP_SYS_ADMIN)) 921 return -EPERM; 922 923 if (!check_mnt(nd->mnt)) 924 return -EINVAL; 925 926 if (nd->dentry != nd->mnt->mnt_root) 927 return -EINVAL; 928 929 down_write(&sb->s_umount); 930 err = do_remount_sb(sb, flags, data, 0); 931 if (!err) 932 nd->mnt->mnt_flags = mnt_flags; 933 up_write(&sb->s_umount); 934 if (!err) 935 security_sb_post_remount(nd->mnt, flags, data); 936 return err; 937 } 938 939 static inline int tree_contains_unbindable(struct vfsmount *mnt) 940 { 941 struct vfsmount *p; 942 for (p = mnt; p; p = next_mnt(p, mnt)) { 943 if (IS_MNT_UNBINDABLE(p)) 944 return 1; 945 } 946 return 0; 947 } 948 949 static int do_move_mount(struct nameidata *nd, char *old_name) 950 { 951 struct nameidata old_nd, parent_nd; 952 struct vfsmount *p; 953 int err = 0; 954 if (!capable(CAP_SYS_ADMIN)) 955 return -EPERM; 956 if (!old_name || !*old_name) 957 return -EINVAL; 958 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 959 if (err) 960 return err; 961 962 down_write(&namespace_sem); 963 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 964 ; 965 err = -EINVAL; 966 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 967 goto out; 968 969 err = -ENOENT; 970 mutex_lock(&nd->dentry->d_inode->i_mutex); 971 if (IS_DEADDIR(nd->dentry->d_inode)) 972 goto out1; 973 974 if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) 975 goto out1; 976 977 err = -EINVAL; 978 if (old_nd.dentry != old_nd.mnt->mnt_root) 979 goto out1; 980 981 if (old_nd.mnt == old_nd.mnt->mnt_parent) 982 goto out1; 983 984 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 985 S_ISDIR(old_nd.dentry->d_inode->i_mode)) 986 goto out1; 987 /* 988 * Don't move a mount residing in a shared parent. 989 */ 990 if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent)) 991 goto out1; 992 /* 993 * Don't move a mount tree containing unbindable mounts to a destination 994 * mount which is shared. 995 */ 996 if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt)) 997 goto out1; 998 err = -ELOOP; 999 for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent) 1000 if (p == old_nd.mnt) 1001 goto out1; 1002 1003 if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd))) 1004 goto out1; 1005 1006 spin_lock(&vfsmount_lock); 1007 /* if the mount is moved, it should no longer be expire 1008 * automatically */ 1009 list_del_init(&old_nd.mnt->mnt_expire); 1010 spin_unlock(&vfsmount_lock); 1011 out1: 1012 mutex_unlock(&nd->dentry->d_inode->i_mutex); 1013 out: 1014 up_write(&namespace_sem); 1015 if (!err) 1016 path_release(&parent_nd); 1017 path_release(&old_nd); 1018 return err; 1019 } 1020 1021 /* 1022 * create a new mount for userspace and request it to be added into the 1023 * namespace's tree 1024 */ 1025 static int do_new_mount(struct nameidata *nd, char *type, int flags, 1026 int mnt_flags, char *name, void *data) 1027 { 1028 struct vfsmount *mnt; 1029 1030 if (!type || !memchr(type, 0, PAGE_SIZE)) 1031 return -EINVAL; 1032 1033 /* we need capabilities... */ 1034 if (!capable(CAP_SYS_ADMIN)) 1035 return -EPERM; 1036 1037 mnt = do_kern_mount(type, flags, name, data); 1038 if (IS_ERR(mnt)) 1039 return PTR_ERR(mnt); 1040 1041 return do_add_mount(mnt, nd, mnt_flags, NULL); 1042 } 1043 1044 /* 1045 * add a mount into a namespace's mount tree 1046 * - provide the option of adding the new mount to an expiration list 1047 */ 1048 int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, 1049 int mnt_flags, struct list_head *fslist) 1050 { 1051 int err; 1052 1053 down_write(&namespace_sem); 1054 /* Something was mounted here while we slept */ 1055 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 1056 ; 1057 err = -EINVAL; 1058 if (!check_mnt(nd->mnt)) 1059 goto unlock; 1060 1061 /* Refuse the same filesystem on the same mount point */ 1062 err = -EBUSY; 1063 if (nd->mnt->mnt_sb == newmnt->mnt_sb && 1064 nd->mnt->mnt_root == nd->dentry) 1065 goto unlock; 1066 1067 err = -EINVAL; 1068 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) 1069 goto unlock; 1070 1071 newmnt->mnt_flags = mnt_flags; 1072 if ((err = graft_tree(newmnt, nd))) 1073 goto unlock; 1074 1075 if (fslist) { 1076 /* add to the specified expiration list */ 1077 spin_lock(&vfsmount_lock); 1078 list_add_tail(&newmnt->mnt_expire, fslist); 1079 spin_unlock(&vfsmount_lock); 1080 } 1081 up_write(&namespace_sem); 1082 return 0; 1083 1084 unlock: 1085 up_write(&namespace_sem); 1086 mntput(newmnt); 1087 return err; 1088 } 1089 1090 EXPORT_SYMBOL_GPL(do_add_mount); 1091 1092 static void expire_mount(struct vfsmount *mnt, struct list_head *mounts, 1093 struct list_head *umounts) 1094 { 1095 spin_lock(&vfsmount_lock); 1096 1097 /* 1098 * Check if mount is still attached, if not, let whoever holds it deal 1099 * with the sucker 1100 */ 1101 if (mnt->mnt_parent == mnt) { 1102 spin_unlock(&vfsmount_lock); 1103 return; 1104 } 1105 1106 /* 1107 * Check that it is still dead: the count should now be 2 - as 1108 * contributed by the vfsmount parent and the mntget above 1109 */ 1110 if (!propagate_mount_busy(mnt, 2)) { 1111 /* delete from the namespace */ 1112 touch_namespace(mnt->mnt_namespace); 1113 list_del_init(&mnt->mnt_list); 1114 mnt->mnt_namespace = NULL; 1115 umount_tree(mnt, 1, umounts); 1116 spin_unlock(&vfsmount_lock); 1117 } else { 1118 /* 1119 * Someone brought it back to life whilst we didn't have any 1120 * locks held so return it to the expiration list 1121 */ 1122 list_add_tail(&mnt->mnt_expire, mounts); 1123 spin_unlock(&vfsmount_lock); 1124 } 1125 } 1126 1127 /* 1128 * process a list of expirable mountpoints with the intent of discarding any 1129 * mountpoints that aren't in use and haven't been touched since last we came 1130 * here 1131 */ 1132 void mark_mounts_for_expiry(struct list_head *mounts) 1133 { 1134 struct namespace *namespace; 1135 struct vfsmount *mnt, *next; 1136 LIST_HEAD(graveyard); 1137 1138 if (list_empty(mounts)) 1139 return; 1140 1141 spin_lock(&vfsmount_lock); 1142 1143 /* extract from the expiration list every vfsmount that matches the 1144 * following criteria: 1145 * - only referenced by its parent vfsmount 1146 * - still marked for expiry (marked on the last call here; marks are 1147 * cleared by mntput()) 1148 */ 1149 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { 1150 if (!xchg(&mnt->mnt_expiry_mark, 1) || 1151 atomic_read(&mnt->mnt_count) != 1) 1152 continue; 1153 1154 mntget(mnt); 1155 list_move(&mnt->mnt_expire, &graveyard); 1156 } 1157 1158 /* 1159 * go through the vfsmounts we've just consigned to the graveyard to 1160 * - check that they're still dead 1161 * - delete the vfsmount from the appropriate namespace under lock 1162 * - dispose of the corpse 1163 */ 1164 while (!list_empty(&graveyard)) { 1165 LIST_HEAD(umounts); 1166 mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire); 1167 list_del_init(&mnt->mnt_expire); 1168 1169 /* don't do anything if the namespace is dead - all the 1170 * vfsmounts from it are going away anyway */ 1171 namespace = mnt->mnt_namespace; 1172 if (!namespace || !namespace->root) 1173 continue; 1174 get_namespace(namespace); 1175 1176 spin_unlock(&vfsmount_lock); 1177 down_write(&namespace_sem); 1178 expire_mount(mnt, mounts, &umounts); 1179 up_write(&namespace_sem); 1180 release_mounts(&umounts); 1181 mntput(mnt); 1182 put_namespace(namespace); 1183 spin_lock(&vfsmount_lock); 1184 } 1185 1186 spin_unlock(&vfsmount_lock); 1187 } 1188 1189 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); 1190 1191 /* 1192 * Some copy_from_user() implementations do not return the exact number of 1193 * bytes remaining to copy on a fault. But copy_mount_options() requires that. 1194 * Note that this function differs from copy_from_user() in that it will oops 1195 * on bad values of `to', rather than returning a short copy. 1196 */ 1197 static long exact_copy_from_user(void *to, const void __user * from, 1198 unsigned long n) 1199 { 1200 char *t = to; 1201 const char __user *f = from; 1202 char c; 1203 1204 if (!access_ok(VERIFY_READ, from, n)) 1205 return n; 1206 1207 while (n) { 1208 if (__get_user(c, f)) { 1209 memset(t, 0, n); 1210 break; 1211 } 1212 *t++ = c; 1213 f++; 1214 n--; 1215 } 1216 return n; 1217 } 1218 1219 int copy_mount_options(const void __user * data, unsigned long *where) 1220 { 1221 int i; 1222 unsigned long page; 1223 unsigned long size; 1224 1225 *where = 0; 1226 if (!data) 1227 return 0; 1228 1229 if (!(page = __get_free_page(GFP_KERNEL))) 1230 return -ENOMEM; 1231 1232 /* We only care that *some* data at the address the user 1233 * gave us is valid. Just in case, we'll zero 1234 * the remainder of the page. 1235 */ 1236 /* copy_from_user cannot cross TASK_SIZE ! */ 1237 size = TASK_SIZE - (unsigned long)data; 1238 if (size > PAGE_SIZE) 1239 size = PAGE_SIZE; 1240 1241 i = size - exact_copy_from_user((void *)page, data, size); 1242 if (!i) { 1243 free_page(page); 1244 return -EFAULT; 1245 } 1246 if (i != PAGE_SIZE) 1247 memset((char *)page + i, 0, PAGE_SIZE - i); 1248 *where = page; 1249 return 0; 1250 } 1251 1252 /* 1253 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to 1254 * be given to the mount() call (ie: read-only, no-dev, no-suid etc). 1255 * 1256 * data is a (void *) that can point to any structure up to 1257 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent 1258 * information (or be NULL). 1259 * 1260 * Pre-0.97 versions of mount() didn't have a flags word. 1261 * When the flags word was introduced its top half was required 1262 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. 1263 * Therefore, if this magic number is present, it carries no information 1264 * and must be discarded. 1265 */ 1266 long do_mount(char *dev_name, char *dir_name, char *type_page, 1267 unsigned long flags, void *data_page) 1268 { 1269 struct nameidata nd; 1270 int retval = 0; 1271 int mnt_flags = 0; 1272 1273 /* Discard magic */ 1274 if ((flags & MS_MGC_MSK) == MS_MGC_VAL) 1275 flags &= ~MS_MGC_MSK; 1276 1277 /* Basic sanity checks */ 1278 1279 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) 1280 return -EINVAL; 1281 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) 1282 return -EINVAL; 1283 1284 if (data_page) 1285 ((char *)data_page)[PAGE_SIZE - 1] = 0; 1286 1287 /* Separate the per-mountpoint flags */ 1288 if (flags & MS_NOSUID) 1289 mnt_flags |= MNT_NOSUID; 1290 if (flags & MS_NODEV) 1291 mnt_flags |= MNT_NODEV; 1292 if (flags & MS_NOEXEC) 1293 mnt_flags |= MNT_NOEXEC; 1294 if (flags & MS_NOATIME) 1295 mnt_flags |= MNT_NOATIME; 1296 if (flags & MS_NODIRATIME) 1297 mnt_flags |= MNT_NODIRATIME; 1298 1299 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | 1300 MS_NOATIME | MS_NODIRATIME); 1301 1302 /* ... and get the mountpoint */ 1303 retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); 1304 if (retval) 1305 return retval; 1306 1307 retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); 1308 if (retval) 1309 goto dput_out; 1310 1311 if (flags & MS_REMOUNT) 1312 retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, 1313 data_page); 1314 else if (flags & MS_BIND) 1315 retval = do_loopback(&nd, dev_name, flags & MS_REC); 1316 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 1317 retval = do_change_type(&nd, flags); 1318 else if (flags & MS_MOVE) 1319 retval = do_move_mount(&nd, dev_name); 1320 else 1321 retval = do_new_mount(&nd, type_page, flags, mnt_flags, 1322 dev_name, data_page); 1323 dput_out: 1324 path_release(&nd); 1325 return retval; 1326 } 1327 1328 /* 1329 * Allocate a new namespace structure and populate it with contents 1330 * copied from the namespace of the passed in task structure. 1331 */ 1332 struct namespace *dup_namespace(struct task_struct *tsk, struct fs_struct *fs) 1333 { 1334 struct namespace *namespace = tsk->namespace; 1335 struct namespace *new_ns; 1336 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; 1337 struct vfsmount *p, *q; 1338 1339 new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL); 1340 if (!new_ns) 1341 return NULL; 1342 1343 atomic_set(&new_ns->count, 1); 1344 INIT_LIST_HEAD(&new_ns->list); 1345 init_waitqueue_head(&new_ns->poll); 1346 new_ns->event = 0; 1347 1348 down_write(&namespace_sem); 1349 /* First pass: copy the tree topology */ 1350 new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root, 1351 CL_COPY_ALL | CL_EXPIRE); 1352 if (!new_ns->root) { 1353 up_write(&namespace_sem); 1354 kfree(new_ns); 1355 return NULL; 1356 } 1357 spin_lock(&vfsmount_lock); 1358 list_add_tail(&new_ns->list, &new_ns->root->mnt_list); 1359 spin_unlock(&vfsmount_lock); 1360 1361 /* 1362 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts 1363 * as belonging to new namespace. We have already acquired a private 1364 * fs_struct, so tsk->fs->lock is not needed. 1365 */ 1366 p = namespace->root; 1367 q = new_ns->root; 1368 while (p) { 1369 q->mnt_namespace = new_ns; 1370 if (fs) { 1371 if (p == fs->rootmnt) { 1372 rootmnt = p; 1373 fs->rootmnt = mntget(q); 1374 } 1375 if (p == fs->pwdmnt) { 1376 pwdmnt = p; 1377 fs->pwdmnt = mntget(q); 1378 } 1379 if (p == fs->altrootmnt) { 1380 altrootmnt = p; 1381 fs->altrootmnt = mntget(q); 1382 } 1383 } 1384 p = next_mnt(p, namespace->root); 1385 q = next_mnt(q, new_ns->root); 1386 } 1387 up_write(&namespace_sem); 1388 1389 if (rootmnt) 1390 mntput(rootmnt); 1391 if (pwdmnt) 1392 mntput(pwdmnt); 1393 if (altrootmnt) 1394 mntput(altrootmnt); 1395 1396 return new_ns; 1397 } 1398 1399 int copy_namespace(int flags, struct task_struct *tsk) 1400 { 1401 struct namespace *namespace = tsk->namespace; 1402 struct namespace *new_ns; 1403 int err = 0; 1404 1405 if (!namespace) 1406 return 0; 1407 1408 get_namespace(namespace); 1409 1410 if (!(flags & CLONE_NEWNS)) 1411 return 0; 1412 1413 if (!capable(CAP_SYS_ADMIN)) { 1414 err = -EPERM; 1415 goto out; 1416 } 1417 1418 new_ns = dup_namespace(tsk, tsk->fs); 1419 if (!new_ns) { 1420 err = -ENOMEM; 1421 goto out; 1422 } 1423 1424 tsk->namespace = new_ns; 1425 1426 out: 1427 put_namespace(namespace); 1428 return err; 1429 } 1430 1431 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, 1432 char __user * type, unsigned long flags, 1433 void __user * data) 1434 { 1435 int retval; 1436 unsigned long data_page; 1437 unsigned long type_page; 1438 unsigned long dev_page; 1439 char *dir_page; 1440 1441 retval = copy_mount_options(type, &type_page); 1442 if (retval < 0) 1443 return retval; 1444 1445 dir_page = getname(dir_name); 1446 retval = PTR_ERR(dir_page); 1447 if (IS_ERR(dir_page)) 1448 goto out1; 1449 1450 retval = copy_mount_options(dev_name, &dev_page); 1451 if (retval < 0) 1452 goto out2; 1453 1454 retval = copy_mount_options(data, &data_page); 1455 if (retval < 0) 1456 goto out3; 1457 1458 lock_kernel(); 1459 retval = do_mount((char *)dev_page, dir_page, (char *)type_page, 1460 flags, (void *)data_page); 1461 unlock_kernel(); 1462 free_page(data_page); 1463 1464 out3: 1465 free_page(dev_page); 1466 out2: 1467 putname(dir_page); 1468 out1: 1469 free_page(type_page); 1470 return retval; 1471 } 1472 1473 /* 1474 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. 1475 * It can block. Requires the big lock held. 1476 */ 1477 void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, 1478 struct dentry *dentry) 1479 { 1480 struct dentry *old_root; 1481 struct vfsmount *old_rootmnt; 1482 write_lock(&fs->lock); 1483 old_root = fs->root; 1484 old_rootmnt = fs->rootmnt; 1485 fs->rootmnt = mntget(mnt); 1486 fs->root = dget(dentry); 1487 write_unlock(&fs->lock); 1488 if (old_root) { 1489 dput(old_root); 1490 mntput(old_rootmnt); 1491 } 1492 } 1493 1494 /* 1495 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. 1496 * It can block. Requires the big lock held. 1497 */ 1498 void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, 1499 struct dentry *dentry) 1500 { 1501 struct dentry *old_pwd; 1502 struct vfsmount *old_pwdmnt; 1503 1504 write_lock(&fs->lock); 1505 old_pwd = fs->pwd; 1506 old_pwdmnt = fs->pwdmnt; 1507 fs->pwdmnt = mntget(mnt); 1508 fs->pwd = dget(dentry); 1509 write_unlock(&fs->lock); 1510 1511 if (old_pwd) { 1512 dput(old_pwd); 1513 mntput(old_pwdmnt); 1514 } 1515 } 1516 1517 static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) 1518 { 1519 struct task_struct *g, *p; 1520 struct fs_struct *fs; 1521 1522 read_lock(&tasklist_lock); 1523 do_each_thread(g, p) { 1524 task_lock(p); 1525 fs = p->fs; 1526 if (fs) { 1527 atomic_inc(&fs->count); 1528 task_unlock(p); 1529 if (fs->root == old_nd->dentry 1530 && fs->rootmnt == old_nd->mnt) 1531 set_fs_root(fs, new_nd->mnt, new_nd->dentry); 1532 if (fs->pwd == old_nd->dentry 1533 && fs->pwdmnt == old_nd->mnt) 1534 set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); 1535 put_fs_struct(fs); 1536 } else 1537 task_unlock(p); 1538 } while_each_thread(g, p); 1539 read_unlock(&tasklist_lock); 1540 } 1541 1542 /* 1543 * pivot_root Semantics: 1544 * Moves the root file system of the current process to the directory put_old, 1545 * makes new_root as the new root file system of the current process, and sets 1546 * root/cwd of all processes which had them on the current root to new_root. 1547 * 1548 * Restrictions: 1549 * The new_root and put_old must be directories, and must not be on the 1550 * same file system as the current process root. The put_old must be 1551 * underneath new_root, i.e. adding a non-zero number of /.. to the string 1552 * pointed to by put_old must yield the same directory as new_root. No other 1553 * file system may be mounted on put_old. After all, new_root is a mountpoint. 1554 * 1555 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. 1556 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives 1557 * in this situation. 1558 * 1559 * Notes: 1560 * - we don't move root/cwd if they are not at the root (reason: if something 1561 * cared enough to change them, it's probably wrong to force them elsewhere) 1562 * - it's okay to pick a root that isn't the root of a file system, e.g. 1563 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, 1564 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root 1565 * first. 1566 */ 1567 asmlinkage long sys_pivot_root(const char __user * new_root, 1568 const char __user * put_old) 1569 { 1570 struct vfsmount *tmp; 1571 struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; 1572 int error; 1573 1574 if (!capable(CAP_SYS_ADMIN)) 1575 return -EPERM; 1576 1577 lock_kernel(); 1578 1579 error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, 1580 &new_nd); 1581 if (error) 1582 goto out0; 1583 error = -EINVAL; 1584 if (!check_mnt(new_nd.mnt)) 1585 goto out1; 1586 1587 error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd); 1588 if (error) 1589 goto out1; 1590 1591 error = security_sb_pivotroot(&old_nd, &new_nd); 1592 if (error) { 1593 path_release(&old_nd); 1594 goto out1; 1595 } 1596 1597 read_lock(¤t->fs->lock); 1598 user_nd.mnt = mntget(current->fs->rootmnt); 1599 user_nd.dentry = dget(current->fs->root); 1600 read_unlock(¤t->fs->lock); 1601 down_write(&namespace_sem); 1602 mutex_lock(&old_nd.dentry->d_inode->i_mutex); 1603 error = -EINVAL; 1604 if (IS_MNT_SHARED(old_nd.mnt) || 1605 IS_MNT_SHARED(new_nd.mnt->mnt_parent) || 1606 IS_MNT_SHARED(user_nd.mnt->mnt_parent)) 1607 goto out2; 1608 if (!check_mnt(user_nd.mnt)) 1609 goto out2; 1610 error = -ENOENT; 1611 if (IS_DEADDIR(new_nd.dentry->d_inode)) 1612 goto out2; 1613 if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) 1614 goto out2; 1615 if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) 1616 goto out2; 1617 error = -EBUSY; 1618 if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) 1619 goto out2; /* loop, on the same file system */ 1620 error = -EINVAL; 1621 if (user_nd.mnt->mnt_root != user_nd.dentry) 1622 goto out2; /* not a mountpoint */ 1623 if (user_nd.mnt->mnt_parent == user_nd.mnt) 1624 goto out2; /* not attached */ 1625 if (new_nd.mnt->mnt_root != new_nd.dentry) 1626 goto out2; /* not a mountpoint */ 1627 if (new_nd.mnt->mnt_parent == new_nd.mnt) 1628 goto out2; /* not attached */ 1629 tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ 1630 spin_lock(&vfsmount_lock); 1631 if (tmp != new_nd.mnt) { 1632 for (;;) { 1633 if (tmp->mnt_parent == tmp) 1634 goto out3; /* already mounted on put_old */ 1635 if (tmp->mnt_parent == new_nd.mnt) 1636 break; 1637 tmp = tmp->mnt_parent; 1638 } 1639 if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) 1640 goto out3; 1641 } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) 1642 goto out3; 1643 detach_mnt(new_nd.mnt, &parent_nd); 1644 detach_mnt(user_nd.mnt, &root_parent); 1645 attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ 1646 attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ 1647 touch_namespace(current->namespace); 1648 spin_unlock(&vfsmount_lock); 1649 chroot_fs_refs(&user_nd, &new_nd); 1650 security_sb_post_pivotroot(&user_nd, &new_nd); 1651 error = 0; 1652 path_release(&root_parent); 1653 path_release(&parent_nd); 1654 out2: 1655 mutex_unlock(&old_nd.dentry->d_inode->i_mutex); 1656 up_write(&namespace_sem); 1657 path_release(&user_nd); 1658 path_release(&old_nd); 1659 out1: 1660 path_release(&new_nd); 1661 out0: 1662 unlock_kernel(); 1663 return error; 1664 out3: 1665 spin_unlock(&vfsmount_lock); 1666 goto out2; 1667 } 1668 1669 static void __init init_mount_tree(void) 1670 { 1671 struct vfsmount *mnt; 1672 struct namespace *namespace; 1673 struct task_struct *g, *p; 1674 1675 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); 1676 if (IS_ERR(mnt)) 1677 panic("Can't create rootfs"); 1678 namespace = kmalloc(sizeof(*namespace), GFP_KERNEL); 1679 if (!namespace) 1680 panic("Can't allocate initial namespace"); 1681 atomic_set(&namespace->count, 1); 1682 INIT_LIST_HEAD(&namespace->list); 1683 init_waitqueue_head(&namespace->poll); 1684 namespace->event = 0; 1685 list_add(&mnt->mnt_list, &namespace->list); 1686 namespace->root = mnt; 1687 mnt->mnt_namespace = namespace; 1688 1689 init_task.namespace = namespace; 1690 read_lock(&tasklist_lock); 1691 do_each_thread(g, p) { 1692 get_namespace(namespace); 1693 p->namespace = namespace; 1694 } while_each_thread(g, p); 1695 read_unlock(&tasklist_lock); 1696 1697 set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root); 1698 set_fs_root(current->fs, namespace->root, namespace->root->mnt_root); 1699 } 1700 1701 void __init mnt_init(unsigned long mempages) 1702 { 1703 struct list_head *d; 1704 unsigned int nr_hash; 1705 int i; 1706 1707 init_rwsem(&namespace_sem); 1708 1709 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), 1710 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL); 1711 1712 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); 1713 1714 if (!mount_hashtable) 1715 panic("Failed to allocate mount hash table\n"); 1716 1717 /* 1718 * Find the power-of-two list-heads that can fit into the allocation.. 1719 * We don't guarantee that "sizeof(struct list_head)" is necessarily 1720 * a power-of-two. 1721 */ 1722 nr_hash = PAGE_SIZE / sizeof(struct list_head); 1723 hash_bits = 0; 1724 do { 1725 hash_bits++; 1726 } while ((nr_hash >> hash_bits) != 0); 1727 hash_bits--; 1728 1729 /* 1730 * Re-calculate the actual number of entries and the mask 1731 * from the number of bits we can fit. 1732 */ 1733 nr_hash = 1UL << hash_bits; 1734 hash_mask = nr_hash - 1; 1735 1736 printk("Mount-cache hash table entries: %d\n", nr_hash); 1737 1738 /* And initialize the newly allocated array */ 1739 d = mount_hashtable; 1740 i = nr_hash; 1741 do { 1742 INIT_LIST_HEAD(d); 1743 d++; 1744 i--; 1745 } while (i); 1746 sysfs_init(); 1747 subsystem_register(&fs_subsys); 1748 init_rootfs(); 1749 init_mount_tree(); 1750 } 1751 1752 void __put_namespace(struct namespace *namespace) 1753 { 1754 struct vfsmount *root = namespace->root; 1755 LIST_HEAD(umount_list); 1756 namespace->root = NULL; 1757 spin_unlock(&vfsmount_lock); 1758 down_write(&namespace_sem); 1759 spin_lock(&vfsmount_lock); 1760 umount_tree(root, 0, &umount_list); 1761 spin_unlock(&vfsmount_lock); 1762 up_write(&namespace_sem); 1763 release_mounts(&umount_list); 1764 kfree(namespace); 1765 } 1766