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/syscalls.h> 12 #include <linux/slab.h> 13 #include <linux/sched.h> 14 #include <linux/smp_lock.h> 15 #include <linux/init.h> 16 #include <linux/kernel.h> 17 #include <linux/quotaops.h> 18 #include <linux/acct.h> 19 #include <linux/capability.h> 20 #include <linux/module.h> 21 #include <linux/sysfs.h> 22 #include <linux/seq_file.h> 23 #include <linux/mnt_namespace.h> 24 #include <linux/namei.h> 25 #include <linux/security.h> 26 #include <linux/mount.h> 27 #include <linux/ramfs.h> 28 #include <asm/uaccess.h> 29 #include <asm/unistd.h> 30 #include "pnode.h" 31 32 /* spinlock for vfsmount related operations, inplace of dcache_lock */ 33 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); 34 35 static int event; 36 37 static struct list_head *mount_hashtable __read_mostly; 38 static int hash_mask __read_mostly, hash_bits __read_mostly; 39 static struct kmem_cache *mnt_cache __read_mostly; 40 static struct rw_semaphore namespace_sem; 41 42 /* /sys/fs */ 43 decl_subsys(fs, NULL, NULL); 44 EXPORT_SYMBOL_GPL(fs_subsys); 45 46 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) 47 { 48 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); 49 tmp += ((unsigned long)dentry / L1_CACHE_BYTES); 50 tmp = tmp + (tmp >> hash_bits); 51 return tmp & hash_mask; 52 } 53 54 struct vfsmount *alloc_vfsmnt(const char *name) 55 { 56 struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL); 57 if (mnt) { 58 memset(mnt, 0, sizeof(struct vfsmount)); 59 atomic_set(&mnt->mnt_count, 1); 60 INIT_LIST_HEAD(&mnt->mnt_hash); 61 INIT_LIST_HEAD(&mnt->mnt_child); 62 INIT_LIST_HEAD(&mnt->mnt_mounts); 63 INIT_LIST_HEAD(&mnt->mnt_list); 64 INIT_LIST_HEAD(&mnt->mnt_expire); 65 INIT_LIST_HEAD(&mnt->mnt_share); 66 INIT_LIST_HEAD(&mnt->mnt_slave_list); 67 INIT_LIST_HEAD(&mnt->mnt_slave); 68 if (name) { 69 int size = strlen(name) + 1; 70 char *newname = kmalloc(size, GFP_KERNEL); 71 if (newname) { 72 memcpy(newname, name, size); 73 mnt->mnt_devname = newname; 74 } 75 } 76 } 77 return mnt; 78 } 79 80 int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) 81 { 82 mnt->mnt_sb = sb; 83 mnt->mnt_root = dget(sb->s_root); 84 return 0; 85 } 86 87 EXPORT_SYMBOL(simple_set_mnt); 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_ns == current->nsproxy->mnt_ns; 137 } 138 139 static void touch_mnt_namespace(struct mnt_namespace *ns) 140 { 141 if (ns) { 142 ns->event = ++event; 143 wake_up_interruptible(&ns->poll); 144 } 145 } 146 147 static void __touch_mnt_namespace(struct mnt_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 mnt_namespace *n = parent->mnt_ns; 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_ns = 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_mnt_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 mnt_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 mnt_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 { MNT_RELATIME, ",relatime" }, 372 { 0, NULL } 373 }; 374 struct proc_fs_info *fs_infop; 375 376 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); 377 seq_putc(m, ' '); 378 seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); 379 seq_putc(m, ' '); 380 mangle(m, mnt->mnt_sb->s_type->name); 381 seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); 382 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { 383 if (mnt->mnt_sb->s_flags & fs_infop->flag) 384 seq_puts(m, fs_infop->str); 385 } 386 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { 387 if (mnt->mnt_flags & fs_infop->flag) 388 seq_puts(m, fs_infop->str); 389 } 390 if (mnt->mnt_sb->s_op->show_options) 391 err = mnt->mnt_sb->s_op->show_options(m, mnt); 392 seq_puts(m, " 0 0\n"); 393 return err; 394 } 395 396 struct seq_operations mounts_op = { 397 .start = m_start, 398 .next = m_next, 399 .stop = m_stop, 400 .show = show_vfsmnt 401 }; 402 403 static int show_vfsstat(struct seq_file *m, void *v) 404 { 405 struct vfsmount *mnt = v; 406 int err = 0; 407 408 /* device */ 409 if (mnt->mnt_devname) { 410 seq_puts(m, "device "); 411 mangle(m, mnt->mnt_devname); 412 } else 413 seq_puts(m, "no device"); 414 415 /* mount point */ 416 seq_puts(m, " mounted on "); 417 seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); 418 seq_putc(m, ' '); 419 420 /* file system type */ 421 seq_puts(m, "with fstype "); 422 mangle(m, mnt->mnt_sb->s_type->name); 423 424 /* optional statistics */ 425 if (mnt->mnt_sb->s_op->show_stats) { 426 seq_putc(m, ' '); 427 err = mnt->mnt_sb->s_op->show_stats(m, mnt); 428 } 429 430 seq_putc(m, '\n'); 431 return err; 432 } 433 434 struct seq_operations mountstats_op = { 435 .start = m_start, 436 .next = m_next, 437 .stop = m_stop, 438 .show = show_vfsstat, 439 }; 440 441 /** 442 * may_umount_tree - check if a mount tree is busy 443 * @mnt: root of mount tree 444 * 445 * This is called to check if a tree of mounts has any 446 * open files, pwds, chroots or sub mounts that are 447 * busy. 448 */ 449 int may_umount_tree(struct vfsmount *mnt) 450 { 451 int actual_refs = 0; 452 int minimum_refs = 0; 453 struct vfsmount *p; 454 455 spin_lock(&vfsmount_lock); 456 for (p = mnt; p; p = next_mnt(p, mnt)) { 457 actual_refs += atomic_read(&p->mnt_count); 458 minimum_refs += 2; 459 } 460 spin_unlock(&vfsmount_lock); 461 462 if (actual_refs > minimum_refs) 463 return 0; 464 465 return 1; 466 } 467 468 EXPORT_SYMBOL(may_umount_tree); 469 470 /** 471 * may_umount - check if a mount point is busy 472 * @mnt: root of mount 473 * 474 * This is called to check if a mount point has any 475 * open files, pwds, chroots or sub mounts. If the 476 * mount has sub mounts this will return busy 477 * regardless of whether the sub mounts are busy. 478 * 479 * Doesn't take quota and stuff into account. IOW, in some cases it will 480 * give false negatives. The main reason why it's here is that we need 481 * a non-destructive way to look for easily umountable filesystems. 482 */ 483 int may_umount(struct vfsmount *mnt) 484 { 485 int ret = 1; 486 spin_lock(&vfsmount_lock); 487 if (propagate_mount_busy(mnt, 2)) 488 ret = 0; 489 spin_unlock(&vfsmount_lock); 490 return ret; 491 } 492 493 EXPORT_SYMBOL(may_umount); 494 495 void release_mounts(struct list_head *head) 496 { 497 struct vfsmount *mnt; 498 while (!list_empty(head)) { 499 mnt = list_entry(head->next, struct vfsmount, mnt_hash); 500 list_del_init(&mnt->mnt_hash); 501 if (mnt->mnt_parent != mnt) { 502 struct dentry *dentry; 503 struct vfsmount *m; 504 spin_lock(&vfsmount_lock); 505 dentry = mnt->mnt_mountpoint; 506 m = mnt->mnt_parent; 507 mnt->mnt_mountpoint = mnt->mnt_root; 508 mnt->mnt_parent = mnt; 509 spin_unlock(&vfsmount_lock); 510 dput(dentry); 511 mntput(m); 512 } 513 mntput(mnt); 514 } 515 } 516 517 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) 518 { 519 struct vfsmount *p; 520 521 for (p = mnt; p; p = next_mnt(p, mnt)) 522 list_move(&p->mnt_hash, kill); 523 524 if (propagate) 525 propagate_umount(kill); 526 527 list_for_each_entry(p, kill, mnt_hash) { 528 list_del_init(&p->mnt_expire); 529 list_del_init(&p->mnt_list); 530 __touch_mnt_namespace(p->mnt_ns); 531 p->mnt_ns = NULL; 532 list_del_init(&p->mnt_child); 533 if (p->mnt_parent != p) 534 p->mnt_mountpoint->d_mounted--; 535 change_mnt_propagation(p, MS_PRIVATE); 536 } 537 } 538 539 static int do_umount(struct vfsmount *mnt, int flags) 540 { 541 struct super_block *sb = mnt->mnt_sb; 542 int retval; 543 LIST_HEAD(umount_list); 544 545 retval = security_sb_umount(mnt, flags); 546 if (retval) 547 return retval; 548 549 /* 550 * Allow userspace to request a mountpoint be expired rather than 551 * unmounting unconditionally. Unmount only happens if: 552 * (1) the mark is already set (the mark is cleared by mntput()) 553 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] 554 */ 555 if (flags & MNT_EXPIRE) { 556 if (mnt == current->fs->rootmnt || 557 flags & (MNT_FORCE | MNT_DETACH)) 558 return -EINVAL; 559 560 if (atomic_read(&mnt->mnt_count) != 2) 561 return -EBUSY; 562 563 if (!xchg(&mnt->mnt_expiry_mark, 1)) 564 return -EAGAIN; 565 } 566 567 /* 568 * If we may have to abort operations to get out of this 569 * mount, and they will themselves hold resources we must 570 * allow the fs to do things. In the Unix tradition of 571 * 'Gee thats tricky lets do it in userspace' the umount_begin 572 * might fail to complete on the first run through as other tasks 573 * must return, and the like. Thats for the mount program to worry 574 * about for the moment. 575 */ 576 577 lock_kernel(); 578 if (sb->s_op->umount_begin) 579 sb->s_op->umount_begin(mnt, flags); 580 unlock_kernel(); 581 582 /* 583 * No sense to grab the lock for this test, but test itself looks 584 * somewhat bogus. Suggestions for better replacement? 585 * Ho-hum... In principle, we might treat that as umount + switch 586 * to rootfs. GC would eventually take care of the old vfsmount. 587 * Actually it makes sense, especially if rootfs would contain a 588 * /reboot - static binary that would close all descriptors and 589 * call reboot(9). Then init(8) could umount root and exec /reboot. 590 */ 591 if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { 592 /* 593 * Special case for "unmounting" root ... 594 * we just try to remount it readonly. 595 */ 596 down_write(&sb->s_umount); 597 if (!(sb->s_flags & MS_RDONLY)) { 598 lock_kernel(); 599 DQUOT_OFF(sb); 600 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); 601 unlock_kernel(); 602 } 603 up_write(&sb->s_umount); 604 return retval; 605 } 606 607 down_write(&namespace_sem); 608 spin_lock(&vfsmount_lock); 609 event++; 610 611 retval = -EBUSY; 612 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { 613 if (!list_empty(&mnt->mnt_list)) 614 umount_tree(mnt, 1, &umount_list); 615 retval = 0; 616 } 617 spin_unlock(&vfsmount_lock); 618 if (retval) 619 security_sb_umount_busy(mnt); 620 up_write(&namespace_sem); 621 release_mounts(&umount_list); 622 return retval; 623 } 624 625 /* 626 * Now umount can handle mount points as well as block devices. 627 * This is important for filesystems which use unnamed block devices. 628 * 629 * We now support a flag for forced unmount like the other 'big iron' 630 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD 631 */ 632 633 asmlinkage long sys_umount(char __user * name, int flags) 634 { 635 struct nameidata nd; 636 int retval; 637 638 retval = __user_walk(name, LOOKUP_FOLLOW, &nd); 639 if (retval) 640 goto out; 641 retval = -EINVAL; 642 if (nd.dentry != nd.mnt->mnt_root) 643 goto dput_and_out; 644 if (!check_mnt(nd.mnt)) 645 goto dput_and_out; 646 647 retval = -EPERM; 648 if (!capable(CAP_SYS_ADMIN)) 649 goto dput_and_out; 650 651 retval = do_umount(nd.mnt, flags); 652 dput_and_out: 653 path_release_on_umount(&nd); 654 out: 655 return retval; 656 } 657 658 #ifdef __ARCH_WANT_SYS_OLDUMOUNT 659 660 /* 661 * The 2.0 compatible umount. No flags. 662 */ 663 asmlinkage long sys_oldumount(char __user * name) 664 { 665 return sys_umount(name, 0); 666 } 667 668 #endif 669 670 static int mount_is_safe(struct nameidata *nd) 671 { 672 if (capable(CAP_SYS_ADMIN)) 673 return 0; 674 return -EPERM; 675 #ifdef notyet 676 if (S_ISLNK(nd->dentry->d_inode->i_mode)) 677 return -EPERM; 678 if (nd->dentry->d_inode->i_mode & S_ISVTX) { 679 if (current->uid != nd->dentry->d_inode->i_uid) 680 return -EPERM; 681 } 682 if (vfs_permission(nd, MAY_WRITE)) 683 return -EPERM; 684 return 0; 685 #endif 686 } 687 688 static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) 689 { 690 while (1) { 691 if (d == dentry) 692 return 1; 693 if (d == NULL || d == d->d_parent) 694 return 0; 695 d = d->d_parent; 696 } 697 } 698 699 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 700 int flag) 701 { 702 struct vfsmount *res, *p, *q, *r, *s; 703 struct nameidata nd; 704 705 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) 706 return NULL; 707 708 res = q = clone_mnt(mnt, dentry, flag); 709 if (!q) 710 goto Enomem; 711 q->mnt_mountpoint = mnt->mnt_mountpoint; 712 713 p = mnt; 714 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { 715 if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) 716 continue; 717 718 for (s = r; s; s = next_mnt(s, r)) { 719 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { 720 s = skip_mnt_tree(s); 721 continue; 722 } 723 while (p != s->mnt_parent) { 724 p = p->mnt_parent; 725 q = q->mnt_parent; 726 } 727 p = s; 728 nd.mnt = q; 729 nd.dentry = p->mnt_mountpoint; 730 q = clone_mnt(p, p->mnt_root, flag); 731 if (!q) 732 goto Enomem; 733 spin_lock(&vfsmount_lock); 734 list_add_tail(&q->mnt_list, &res->mnt_list); 735 attach_mnt(q, &nd); 736 spin_unlock(&vfsmount_lock); 737 } 738 } 739 return res; 740 Enomem: 741 if (res) { 742 LIST_HEAD(umount_list); 743 spin_lock(&vfsmount_lock); 744 umount_tree(res, 0, &umount_list); 745 spin_unlock(&vfsmount_lock); 746 release_mounts(&umount_list); 747 } 748 return NULL; 749 } 750 751 /* 752 * @source_mnt : mount tree to be attached 753 * @nd : place the mount tree @source_mnt is attached 754 * @parent_nd : if non-null, detach the source_mnt from its parent and 755 * store the parent mount and mountpoint dentry. 756 * (done when source_mnt is moved) 757 * 758 * NOTE: in the table below explains the semantics when a source mount 759 * of a given type is attached to a destination mount of a given type. 760 * --------------------------------------------------------------------------- 761 * | BIND MOUNT OPERATION | 762 * |************************************************************************** 763 * | source-->| shared | private | slave | unbindable | 764 * | dest | | | | | 765 * | | | | | | | 766 * | v | | | | | 767 * |************************************************************************** 768 * | shared | shared (++) | shared (+) | shared(+++)| invalid | 769 * | | | | | | 770 * |non-shared| shared (+) | private | slave (*) | invalid | 771 * *************************************************************************** 772 * A bind operation clones the source mount and mounts the clone on the 773 * destination mount. 774 * 775 * (++) the cloned mount is propagated to all the mounts in the propagation 776 * tree of the destination mount and the cloned mount is added to 777 * the peer group of the source mount. 778 * (+) the cloned mount is created under the destination mount and is marked 779 * as shared. The cloned mount is added to the peer group of the source 780 * mount. 781 * (+++) the mount is propagated to all the mounts in the propagation tree 782 * of the destination mount and the cloned mount is made slave 783 * of the same master as that of the source mount. The cloned mount 784 * is marked as 'shared and slave'. 785 * (*) the cloned mount is made a slave of the same master as that of the 786 * source mount. 787 * 788 * --------------------------------------------------------------------------- 789 * | MOVE MOUNT OPERATION | 790 * |************************************************************************** 791 * | source-->| shared | private | slave | unbindable | 792 * | dest | | | | | 793 * | | | | | | | 794 * | v | | | | | 795 * |************************************************************************** 796 * | shared | shared (+) | shared (+) | shared(+++) | invalid | 797 * | | | | | | 798 * |non-shared| shared (+*) | private | slave (*) | unbindable | 799 * *************************************************************************** 800 * 801 * (+) the mount is moved to the destination. And is then propagated to 802 * all the mounts in the propagation tree of the destination mount. 803 * (+*) the mount is moved to the destination. 804 * (+++) the mount is moved to the destination and is then propagated to 805 * all the mounts belonging to the destination mount's propagation tree. 806 * the mount is marked as 'shared and slave'. 807 * (*) the mount continues to be a slave at the new location. 808 * 809 * if the source mount is a tree, the operations explained above is 810 * applied to each mount in the tree. 811 * Must be called without spinlocks held, since this function can sleep 812 * in allocations. 813 */ 814 static int attach_recursive_mnt(struct vfsmount *source_mnt, 815 struct nameidata *nd, struct nameidata *parent_nd) 816 { 817 LIST_HEAD(tree_list); 818 struct vfsmount *dest_mnt = nd->mnt; 819 struct dentry *dest_dentry = nd->dentry; 820 struct vfsmount *child, *p; 821 822 if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list)) 823 return -EINVAL; 824 825 if (IS_MNT_SHARED(dest_mnt)) { 826 for (p = source_mnt; p; p = next_mnt(p, source_mnt)) 827 set_mnt_shared(p); 828 } 829 830 spin_lock(&vfsmount_lock); 831 if (parent_nd) { 832 detach_mnt(source_mnt, parent_nd); 833 attach_mnt(source_mnt, nd); 834 touch_mnt_namespace(current->nsproxy->mnt_ns); 835 } else { 836 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); 837 commit_tree(source_mnt); 838 } 839 840 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { 841 list_del_init(&child->mnt_hash); 842 commit_tree(child); 843 } 844 spin_unlock(&vfsmount_lock); 845 return 0; 846 } 847 848 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) 849 { 850 int err; 851 if (mnt->mnt_sb->s_flags & MS_NOUSER) 852 return -EINVAL; 853 854 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 855 S_ISDIR(mnt->mnt_root->d_inode->i_mode)) 856 return -ENOTDIR; 857 858 err = -ENOENT; 859 mutex_lock(&nd->dentry->d_inode->i_mutex); 860 if (IS_DEADDIR(nd->dentry->d_inode)) 861 goto out_unlock; 862 863 err = security_sb_check_sb(mnt, nd); 864 if (err) 865 goto out_unlock; 866 867 err = -ENOENT; 868 if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) 869 err = attach_recursive_mnt(mnt, nd, NULL); 870 out_unlock: 871 mutex_unlock(&nd->dentry->d_inode->i_mutex); 872 if (!err) 873 security_sb_post_addmount(mnt, nd); 874 return err; 875 } 876 877 /* 878 * recursively change the type of the mountpoint. 879 */ 880 static int do_change_type(struct nameidata *nd, int flag) 881 { 882 struct vfsmount *m, *mnt = nd->mnt; 883 int recurse = flag & MS_REC; 884 int type = flag & ~MS_REC; 885 886 if (nd->dentry != nd->mnt->mnt_root) 887 return -EINVAL; 888 889 down_write(&namespace_sem); 890 spin_lock(&vfsmount_lock); 891 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) 892 change_mnt_propagation(m, type); 893 spin_unlock(&vfsmount_lock); 894 up_write(&namespace_sem); 895 return 0; 896 } 897 898 /* 899 * do loopback mount. 900 */ 901 static int do_loopback(struct nameidata *nd, char *old_name, int recurse) 902 { 903 struct nameidata old_nd; 904 struct vfsmount *mnt = NULL; 905 int err = mount_is_safe(nd); 906 if (err) 907 return err; 908 if (!old_name || !*old_name) 909 return -EINVAL; 910 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 911 if (err) 912 return err; 913 914 down_write(&namespace_sem); 915 err = -EINVAL; 916 if (IS_MNT_UNBINDABLE(old_nd.mnt)) 917 goto out; 918 919 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 920 goto out; 921 922 err = -ENOMEM; 923 if (recurse) 924 mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0); 925 else 926 mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0); 927 928 if (!mnt) 929 goto out; 930 931 err = graft_tree(mnt, nd); 932 if (err) { 933 LIST_HEAD(umount_list); 934 spin_lock(&vfsmount_lock); 935 umount_tree(mnt, 0, &umount_list); 936 spin_unlock(&vfsmount_lock); 937 release_mounts(&umount_list); 938 } 939 940 out: 941 up_write(&namespace_sem); 942 path_release(&old_nd); 943 return err; 944 } 945 946 /* 947 * change filesystem flags. dir should be a physical root of filesystem. 948 * If you've mounted a non-root directory somewhere and want to do remount 949 * on it - tough luck. 950 */ 951 static int do_remount(struct nameidata *nd, int flags, int mnt_flags, 952 void *data) 953 { 954 int err; 955 struct super_block *sb = nd->mnt->mnt_sb; 956 957 if (!capable(CAP_SYS_ADMIN)) 958 return -EPERM; 959 960 if (!check_mnt(nd->mnt)) 961 return -EINVAL; 962 963 if (nd->dentry != nd->mnt->mnt_root) 964 return -EINVAL; 965 966 down_write(&sb->s_umount); 967 err = do_remount_sb(sb, flags, data, 0); 968 if (!err) 969 nd->mnt->mnt_flags = mnt_flags; 970 up_write(&sb->s_umount); 971 if (!err) 972 security_sb_post_remount(nd->mnt, flags, data); 973 return err; 974 } 975 976 static inline int tree_contains_unbindable(struct vfsmount *mnt) 977 { 978 struct vfsmount *p; 979 for (p = mnt; p; p = next_mnt(p, mnt)) { 980 if (IS_MNT_UNBINDABLE(p)) 981 return 1; 982 } 983 return 0; 984 } 985 986 static int do_move_mount(struct nameidata *nd, char *old_name) 987 { 988 struct nameidata old_nd, parent_nd; 989 struct vfsmount *p; 990 int err = 0; 991 if (!capable(CAP_SYS_ADMIN)) 992 return -EPERM; 993 if (!old_name || !*old_name) 994 return -EINVAL; 995 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 996 if (err) 997 return err; 998 999 down_write(&namespace_sem); 1000 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 1001 ; 1002 err = -EINVAL; 1003 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 1004 goto out; 1005 1006 err = -ENOENT; 1007 mutex_lock(&nd->dentry->d_inode->i_mutex); 1008 if (IS_DEADDIR(nd->dentry->d_inode)) 1009 goto out1; 1010 1011 if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) 1012 goto out1; 1013 1014 err = -EINVAL; 1015 if (old_nd.dentry != old_nd.mnt->mnt_root) 1016 goto out1; 1017 1018 if (old_nd.mnt == old_nd.mnt->mnt_parent) 1019 goto out1; 1020 1021 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 1022 S_ISDIR(old_nd.dentry->d_inode->i_mode)) 1023 goto out1; 1024 /* 1025 * Don't move a mount residing in a shared parent. 1026 */ 1027 if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent)) 1028 goto out1; 1029 /* 1030 * Don't move a mount tree containing unbindable mounts to a destination 1031 * mount which is shared. 1032 */ 1033 if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt)) 1034 goto out1; 1035 err = -ELOOP; 1036 for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent) 1037 if (p == old_nd.mnt) 1038 goto out1; 1039 1040 if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd))) 1041 goto out1; 1042 1043 spin_lock(&vfsmount_lock); 1044 /* if the mount is moved, it should no longer be expire 1045 * automatically */ 1046 list_del_init(&old_nd.mnt->mnt_expire); 1047 spin_unlock(&vfsmount_lock); 1048 out1: 1049 mutex_unlock(&nd->dentry->d_inode->i_mutex); 1050 out: 1051 up_write(&namespace_sem); 1052 if (!err) 1053 path_release(&parent_nd); 1054 path_release(&old_nd); 1055 return err; 1056 } 1057 1058 /* 1059 * create a new mount for userspace and request it to be added into the 1060 * namespace's tree 1061 */ 1062 static int do_new_mount(struct nameidata *nd, char *type, int flags, 1063 int mnt_flags, char *name, void *data) 1064 { 1065 struct vfsmount *mnt; 1066 1067 if (!type || !memchr(type, 0, PAGE_SIZE)) 1068 return -EINVAL; 1069 1070 /* we need capabilities... */ 1071 if (!capable(CAP_SYS_ADMIN)) 1072 return -EPERM; 1073 1074 mnt = do_kern_mount(type, flags, name, data); 1075 if (IS_ERR(mnt)) 1076 return PTR_ERR(mnt); 1077 1078 return do_add_mount(mnt, nd, mnt_flags, NULL); 1079 } 1080 1081 /* 1082 * add a mount into a namespace's mount tree 1083 * - provide the option of adding the new mount to an expiration list 1084 */ 1085 int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, 1086 int mnt_flags, struct list_head *fslist) 1087 { 1088 int err; 1089 1090 down_write(&namespace_sem); 1091 /* Something was mounted here while we slept */ 1092 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 1093 ; 1094 err = -EINVAL; 1095 if (!check_mnt(nd->mnt)) 1096 goto unlock; 1097 1098 /* Refuse the same filesystem on the same mount point */ 1099 err = -EBUSY; 1100 if (nd->mnt->mnt_sb == newmnt->mnt_sb && 1101 nd->mnt->mnt_root == nd->dentry) 1102 goto unlock; 1103 1104 err = -EINVAL; 1105 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) 1106 goto unlock; 1107 1108 newmnt->mnt_flags = mnt_flags; 1109 if ((err = graft_tree(newmnt, nd))) 1110 goto unlock; 1111 1112 if (fslist) { 1113 /* add to the specified expiration list */ 1114 spin_lock(&vfsmount_lock); 1115 list_add_tail(&newmnt->mnt_expire, fslist); 1116 spin_unlock(&vfsmount_lock); 1117 } 1118 up_write(&namespace_sem); 1119 return 0; 1120 1121 unlock: 1122 up_write(&namespace_sem); 1123 mntput(newmnt); 1124 return err; 1125 } 1126 1127 EXPORT_SYMBOL_GPL(do_add_mount); 1128 1129 static void expire_mount(struct vfsmount *mnt, struct list_head *mounts, 1130 struct list_head *umounts) 1131 { 1132 spin_lock(&vfsmount_lock); 1133 1134 /* 1135 * Check if mount is still attached, if not, let whoever holds it deal 1136 * with the sucker 1137 */ 1138 if (mnt->mnt_parent == mnt) { 1139 spin_unlock(&vfsmount_lock); 1140 return; 1141 } 1142 1143 /* 1144 * Check that it is still dead: the count should now be 2 - as 1145 * contributed by the vfsmount parent and the mntget above 1146 */ 1147 if (!propagate_mount_busy(mnt, 2)) { 1148 /* delete from the namespace */ 1149 touch_mnt_namespace(mnt->mnt_ns); 1150 list_del_init(&mnt->mnt_list); 1151 mnt->mnt_ns = NULL; 1152 umount_tree(mnt, 1, umounts); 1153 spin_unlock(&vfsmount_lock); 1154 } else { 1155 /* 1156 * Someone brought it back to life whilst we didn't have any 1157 * locks held so return it to the expiration list 1158 */ 1159 list_add_tail(&mnt->mnt_expire, mounts); 1160 spin_unlock(&vfsmount_lock); 1161 } 1162 } 1163 1164 /* 1165 * go through the vfsmounts we've just consigned to the graveyard to 1166 * - check that they're still dead 1167 * - delete the vfsmount from the appropriate namespace under lock 1168 * - dispose of the corpse 1169 */ 1170 static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts) 1171 { 1172 struct mnt_namespace *ns; 1173 struct vfsmount *mnt; 1174 1175 while (!list_empty(graveyard)) { 1176 LIST_HEAD(umounts); 1177 mnt = list_entry(graveyard->next, struct vfsmount, mnt_expire); 1178 list_del_init(&mnt->mnt_expire); 1179 1180 /* don't do anything if the namespace is dead - all the 1181 * vfsmounts from it are going away anyway */ 1182 ns = mnt->mnt_ns; 1183 if (!ns || !ns->root) 1184 continue; 1185 get_mnt_ns(ns); 1186 1187 spin_unlock(&vfsmount_lock); 1188 down_write(&namespace_sem); 1189 expire_mount(mnt, mounts, &umounts); 1190 up_write(&namespace_sem); 1191 release_mounts(&umounts); 1192 mntput(mnt); 1193 put_mnt_ns(ns); 1194 spin_lock(&vfsmount_lock); 1195 } 1196 } 1197 1198 /* 1199 * process a list of expirable mountpoints with the intent of discarding any 1200 * mountpoints that aren't in use and haven't been touched since last we came 1201 * here 1202 */ 1203 void mark_mounts_for_expiry(struct list_head *mounts) 1204 { 1205 struct vfsmount *mnt, *next; 1206 LIST_HEAD(graveyard); 1207 1208 if (list_empty(mounts)) 1209 return; 1210 1211 spin_lock(&vfsmount_lock); 1212 1213 /* extract from the expiration list every vfsmount that matches the 1214 * following criteria: 1215 * - only referenced by its parent vfsmount 1216 * - still marked for expiry (marked on the last call here; marks are 1217 * cleared by mntput()) 1218 */ 1219 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { 1220 if (!xchg(&mnt->mnt_expiry_mark, 1) || 1221 atomic_read(&mnt->mnt_count) != 1) 1222 continue; 1223 1224 mntget(mnt); 1225 list_move(&mnt->mnt_expire, &graveyard); 1226 } 1227 1228 expire_mount_list(&graveyard, mounts); 1229 1230 spin_unlock(&vfsmount_lock); 1231 } 1232 1233 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); 1234 1235 /* 1236 * Ripoff of 'select_parent()' 1237 * 1238 * search the list of submounts for a given mountpoint, and move any 1239 * shrinkable submounts to the 'graveyard' list. 1240 */ 1241 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard) 1242 { 1243 struct vfsmount *this_parent = parent; 1244 struct list_head *next; 1245 int found = 0; 1246 1247 repeat: 1248 next = this_parent->mnt_mounts.next; 1249 resume: 1250 while (next != &this_parent->mnt_mounts) { 1251 struct list_head *tmp = next; 1252 struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); 1253 1254 next = tmp->next; 1255 if (!(mnt->mnt_flags & MNT_SHRINKABLE)) 1256 continue; 1257 /* 1258 * Descend a level if the d_mounts list is non-empty. 1259 */ 1260 if (!list_empty(&mnt->mnt_mounts)) { 1261 this_parent = mnt; 1262 goto repeat; 1263 } 1264 1265 if (!propagate_mount_busy(mnt, 1)) { 1266 mntget(mnt); 1267 list_move_tail(&mnt->mnt_expire, graveyard); 1268 found++; 1269 } 1270 } 1271 /* 1272 * All done at this level ... ascend and resume the search 1273 */ 1274 if (this_parent != parent) { 1275 next = this_parent->mnt_child.next; 1276 this_parent = this_parent->mnt_parent; 1277 goto resume; 1278 } 1279 return found; 1280 } 1281 1282 /* 1283 * process a list of expirable mountpoints with the intent of discarding any 1284 * submounts of a specific parent mountpoint 1285 */ 1286 void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts) 1287 { 1288 LIST_HEAD(graveyard); 1289 int found; 1290 1291 spin_lock(&vfsmount_lock); 1292 1293 /* extract submounts of 'mountpoint' from the expiration list */ 1294 while ((found = select_submounts(mountpoint, &graveyard)) != 0) 1295 expire_mount_list(&graveyard, mounts); 1296 1297 spin_unlock(&vfsmount_lock); 1298 } 1299 1300 EXPORT_SYMBOL_GPL(shrink_submounts); 1301 1302 /* 1303 * Some copy_from_user() implementations do not return the exact number of 1304 * bytes remaining to copy on a fault. But copy_mount_options() requires that. 1305 * Note that this function differs from copy_from_user() in that it will oops 1306 * on bad values of `to', rather than returning a short copy. 1307 */ 1308 static long exact_copy_from_user(void *to, const void __user * from, 1309 unsigned long n) 1310 { 1311 char *t = to; 1312 const char __user *f = from; 1313 char c; 1314 1315 if (!access_ok(VERIFY_READ, from, n)) 1316 return n; 1317 1318 while (n) { 1319 if (__get_user(c, f)) { 1320 memset(t, 0, n); 1321 break; 1322 } 1323 *t++ = c; 1324 f++; 1325 n--; 1326 } 1327 return n; 1328 } 1329 1330 int copy_mount_options(const void __user * data, unsigned long *where) 1331 { 1332 int i; 1333 unsigned long page; 1334 unsigned long size; 1335 1336 *where = 0; 1337 if (!data) 1338 return 0; 1339 1340 if (!(page = __get_free_page(GFP_KERNEL))) 1341 return -ENOMEM; 1342 1343 /* We only care that *some* data at the address the user 1344 * gave us is valid. Just in case, we'll zero 1345 * the remainder of the page. 1346 */ 1347 /* copy_from_user cannot cross TASK_SIZE ! */ 1348 size = TASK_SIZE - (unsigned long)data; 1349 if (size > PAGE_SIZE) 1350 size = PAGE_SIZE; 1351 1352 i = size - exact_copy_from_user((void *)page, data, size); 1353 if (!i) { 1354 free_page(page); 1355 return -EFAULT; 1356 } 1357 if (i != PAGE_SIZE) 1358 memset((char *)page + i, 0, PAGE_SIZE - i); 1359 *where = page; 1360 return 0; 1361 } 1362 1363 /* 1364 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to 1365 * be given to the mount() call (ie: read-only, no-dev, no-suid etc). 1366 * 1367 * data is a (void *) that can point to any structure up to 1368 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent 1369 * information (or be NULL). 1370 * 1371 * Pre-0.97 versions of mount() didn't have a flags word. 1372 * When the flags word was introduced its top half was required 1373 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. 1374 * Therefore, if this magic number is present, it carries no information 1375 * and must be discarded. 1376 */ 1377 long do_mount(char *dev_name, char *dir_name, char *type_page, 1378 unsigned long flags, void *data_page) 1379 { 1380 struct nameidata nd; 1381 int retval = 0; 1382 int mnt_flags = 0; 1383 1384 /* Discard magic */ 1385 if ((flags & MS_MGC_MSK) == MS_MGC_VAL) 1386 flags &= ~MS_MGC_MSK; 1387 1388 /* Basic sanity checks */ 1389 1390 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) 1391 return -EINVAL; 1392 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) 1393 return -EINVAL; 1394 1395 if (data_page) 1396 ((char *)data_page)[PAGE_SIZE - 1] = 0; 1397 1398 /* Separate the per-mountpoint flags */ 1399 if (flags & MS_NOSUID) 1400 mnt_flags |= MNT_NOSUID; 1401 if (flags & MS_NODEV) 1402 mnt_flags |= MNT_NODEV; 1403 if (flags & MS_NOEXEC) 1404 mnt_flags |= MNT_NOEXEC; 1405 if (flags & MS_NOATIME) 1406 mnt_flags |= MNT_NOATIME; 1407 if (flags & MS_NODIRATIME) 1408 mnt_flags |= MNT_NODIRATIME; 1409 if (flags & MS_RELATIME) 1410 mnt_flags |= MNT_RELATIME; 1411 1412 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | 1413 MS_NOATIME | MS_NODIRATIME | MS_RELATIME); 1414 1415 /* ... and get the mountpoint */ 1416 retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); 1417 if (retval) 1418 return retval; 1419 1420 retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); 1421 if (retval) 1422 goto dput_out; 1423 1424 if (flags & MS_REMOUNT) 1425 retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, 1426 data_page); 1427 else if (flags & MS_BIND) 1428 retval = do_loopback(&nd, dev_name, flags & MS_REC); 1429 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 1430 retval = do_change_type(&nd, flags); 1431 else if (flags & MS_MOVE) 1432 retval = do_move_mount(&nd, dev_name); 1433 else 1434 retval = do_new_mount(&nd, type_page, flags, mnt_flags, 1435 dev_name, data_page); 1436 dput_out: 1437 path_release(&nd); 1438 return retval; 1439 } 1440 1441 /* 1442 * Allocate a new namespace structure and populate it with contents 1443 * copied from the namespace of the passed in task structure. 1444 */ 1445 struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk, 1446 struct fs_struct *fs) 1447 { 1448 struct mnt_namespace *mnt_ns = tsk->nsproxy->mnt_ns; 1449 struct mnt_namespace *new_ns; 1450 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; 1451 struct vfsmount *p, *q; 1452 1453 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); 1454 if (!new_ns) 1455 return NULL; 1456 1457 atomic_set(&new_ns->count, 1); 1458 INIT_LIST_HEAD(&new_ns->list); 1459 init_waitqueue_head(&new_ns->poll); 1460 new_ns->event = 0; 1461 1462 down_write(&namespace_sem); 1463 /* First pass: copy the tree topology */ 1464 new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, 1465 CL_COPY_ALL | CL_EXPIRE); 1466 if (!new_ns->root) { 1467 up_write(&namespace_sem); 1468 kfree(new_ns); 1469 return NULL; 1470 } 1471 spin_lock(&vfsmount_lock); 1472 list_add_tail(&new_ns->list, &new_ns->root->mnt_list); 1473 spin_unlock(&vfsmount_lock); 1474 1475 /* 1476 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts 1477 * as belonging to new namespace. We have already acquired a private 1478 * fs_struct, so tsk->fs->lock is not needed. 1479 */ 1480 p = mnt_ns->root; 1481 q = new_ns->root; 1482 while (p) { 1483 q->mnt_ns = new_ns; 1484 if (fs) { 1485 if (p == fs->rootmnt) { 1486 rootmnt = p; 1487 fs->rootmnt = mntget(q); 1488 } 1489 if (p == fs->pwdmnt) { 1490 pwdmnt = p; 1491 fs->pwdmnt = mntget(q); 1492 } 1493 if (p == fs->altrootmnt) { 1494 altrootmnt = p; 1495 fs->altrootmnt = mntget(q); 1496 } 1497 } 1498 p = next_mnt(p, mnt_ns->root); 1499 q = next_mnt(q, new_ns->root); 1500 } 1501 up_write(&namespace_sem); 1502 1503 if (rootmnt) 1504 mntput(rootmnt); 1505 if (pwdmnt) 1506 mntput(pwdmnt); 1507 if (altrootmnt) 1508 mntput(altrootmnt); 1509 1510 return new_ns; 1511 } 1512 1513 int copy_mnt_ns(int flags, struct task_struct *tsk) 1514 { 1515 struct mnt_namespace *ns = tsk->nsproxy->mnt_ns; 1516 struct mnt_namespace *new_ns; 1517 int err = 0; 1518 1519 if (!ns) 1520 return 0; 1521 1522 get_mnt_ns(ns); 1523 1524 if (!(flags & CLONE_NEWNS)) 1525 return 0; 1526 1527 if (!capable(CAP_SYS_ADMIN)) { 1528 err = -EPERM; 1529 goto out; 1530 } 1531 1532 new_ns = dup_mnt_ns(tsk, tsk->fs); 1533 if (!new_ns) { 1534 err = -ENOMEM; 1535 goto out; 1536 } 1537 1538 tsk->nsproxy->mnt_ns = new_ns; 1539 1540 out: 1541 put_mnt_ns(ns); 1542 return err; 1543 } 1544 1545 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, 1546 char __user * type, unsigned long flags, 1547 void __user * data) 1548 { 1549 int retval; 1550 unsigned long data_page; 1551 unsigned long type_page; 1552 unsigned long dev_page; 1553 char *dir_page; 1554 1555 retval = copy_mount_options(type, &type_page); 1556 if (retval < 0) 1557 return retval; 1558 1559 dir_page = getname(dir_name); 1560 retval = PTR_ERR(dir_page); 1561 if (IS_ERR(dir_page)) 1562 goto out1; 1563 1564 retval = copy_mount_options(dev_name, &dev_page); 1565 if (retval < 0) 1566 goto out2; 1567 1568 retval = copy_mount_options(data, &data_page); 1569 if (retval < 0) 1570 goto out3; 1571 1572 lock_kernel(); 1573 retval = do_mount((char *)dev_page, dir_page, (char *)type_page, 1574 flags, (void *)data_page); 1575 unlock_kernel(); 1576 free_page(data_page); 1577 1578 out3: 1579 free_page(dev_page); 1580 out2: 1581 putname(dir_page); 1582 out1: 1583 free_page(type_page); 1584 return retval; 1585 } 1586 1587 /* 1588 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. 1589 * It can block. Requires the big lock held. 1590 */ 1591 void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, 1592 struct dentry *dentry) 1593 { 1594 struct dentry *old_root; 1595 struct vfsmount *old_rootmnt; 1596 write_lock(&fs->lock); 1597 old_root = fs->root; 1598 old_rootmnt = fs->rootmnt; 1599 fs->rootmnt = mntget(mnt); 1600 fs->root = dget(dentry); 1601 write_unlock(&fs->lock); 1602 if (old_root) { 1603 dput(old_root); 1604 mntput(old_rootmnt); 1605 } 1606 } 1607 1608 /* 1609 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. 1610 * It can block. Requires the big lock held. 1611 */ 1612 void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, 1613 struct dentry *dentry) 1614 { 1615 struct dentry *old_pwd; 1616 struct vfsmount *old_pwdmnt; 1617 1618 write_lock(&fs->lock); 1619 old_pwd = fs->pwd; 1620 old_pwdmnt = fs->pwdmnt; 1621 fs->pwdmnt = mntget(mnt); 1622 fs->pwd = dget(dentry); 1623 write_unlock(&fs->lock); 1624 1625 if (old_pwd) { 1626 dput(old_pwd); 1627 mntput(old_pwdmnt); 1628 } 1629 } 1630 1631 static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) 1632 { 1633 struct task_struct *g, *p; 1634 struct fs_struct *fs; 1635 1636 read_lock(&tasklist_lock); 1637 do_each_thread(g, p) { 1638 task_lock(p); 1639 fs = p->fs; 1640 if (fs) { 1641 atomic_inc(&fs->count); 1642 task_unlock(p); 1643 if (fs->root == old_nd->dentry 1644 && fs->rootmnt == old_nd->mnt) 1645 set_fs_root(fs, new_nd->mnt, new_nd->dentry); 1646 if (fs->pwd == old_nd->dentry 1647 && fs->pwdmnt == old_nd->mnt) 1648 set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); 1649 put_fs_struct(fs); 1650 } else 1651 task_unlock(p); 1652 } while_each_thread(g, p); 1653 read_unlock(&tasklist_lock); 1654 } 1655 1656 /* 1657 * pivot_root Semantics: 1658 * Moves the root file system of the current process to the directory put_old, 1659 * makes new_root as the new root file system of the current process, and sets 1660 * root/cwd of all processes which had them on the current root to new_root. 1661 * 1662 * Restrictions: 1663 * The new_root and put_old must be directories, and must not be on the 1664 * same file system as the current process root. The put_old must be 1665 * underneath new_root, i.e. adding a non-zero number of /.. to the string 1666 * pointed to by put_old must yield the same directory as new_root. No other 1667 * file system may be mounted on put_old. After all, new_root is a mountpoint. 1668 * 1669 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. 1670 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives 1671 * in this situation. 1672 * 1673 * Notes: 1674 * - we don't move root/cwd if they are not at the root (reason: if something 1675 * cared enough to change them, it's probably wrong to force them elsewhere) 1676 * - it's okay to pick a root that isn't the root of a file system, e.g. 1677 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, 1678 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root 1679 * first. 1680 */ 1681 asmlinkage long sys_pivot_root(const char __user * new_root, 1682 const char __user * put_old) 1683 { 1684 struct vfsmount *tmp; 1685 struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; 1686 int error; 1687 1688 if (!capable(CAP_SYS_ADMIN)) 1689 return -EPERM; 1690 1691 lock_kernel(); 1692 1693 error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, 1694 &new_nd); 1695 if (error) 1696 goto out0; 1697 error = -EINVAL; 1698 if (!check_mnt(new_nd.mnt)) 1699 goto out1; 1700 1701 error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd); 1702 if (error) 1703 goto out1; 1704 1705 error = security_sb_pivotroot(&old_nd, &new_nd); 1706 if (error) { 1707 path_release(&old_nd); 1708 goto out1; 1709 } 1710 1711 read_lock(¤t->fs->lock); 1712 user_nd.mnt = mntget(current->fs->rootmnt); 1713 user_nd.dentry = dget(current->fs->root); 1714 read_unlock(¤t->fs->lock); 1715 down_write(&namespace_sem); 1716 mutex_lock(&old_nd.dentry->d_inode->i_mutex); 1717 error = -EINVAL; 1718 if (IS_MNT_SHARED(old_nd.mnt) || 1719 IS_MNT_SHARED(new_nd.mnt->mnt_parent) || 1720 IS_MNT_SHARED(user_nd.mnt->mnt_parent)) 1721 goto out2; 1722 if (!check_mnt(user_nd.mnt)) 1723 goto out2; 1724 error = -ENOENT; 1725 if (IS_DEADDIR(new_nd.dentry->d_inode)) 1726 goto out2; 1727 if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) 1728 goto out2; 1729 if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) 1730 goto out2; 1731 error = -EBUSY; 1732 if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) 1733 goto out2; /* loop, on the same file system */ 1734 error = -EINVAL; 1735 if (user_nd.mnt->mnt_root != user_nd.dentry) 1736 goto out2; /* not a mountpoint */ 1737 if (user_nd.mnt->mnt_parent == user_nd.mnt) 1738 goto out2; /* not attached */ 1739 if (new_nd.mnt->mnt_root != new_nd.dentry) 1740 goto out2; /* not a mountpoint */ 1741 if (new_nd.mnt->mnt_parent == new_nd.mnt) 1742 goto out2; /* not attached */ 1743 tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ 1744 spin_lock(&vfsmount_lock); 1745 if (tmp != new_nd.mnt) { 1746 for (;;) { 1747 if (tmp->mnt_parent == tmp) 1748 goto out3; /* already mounted on put_old */ 1749 if (tmp->mnt_parent == new_nd.mnt) 1750 break; 1751 tmp = tmp->mnt_parent; 1752 } 1753 if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) 1754 goto out3; 1755 } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) 1756 goto out3; 1757 detach_mnt(new_nd.mnt, &parent_nd); 1758 detach_mnt(user_nd.mnt, &root_parent); 1759 attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ 1760 attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ 1761 touch_mnt_namespace(current->nsproxy->mnt_ns); 1762 spin_unlock(&vfsmount_lock); 1763 chroot_fs_refs(&user_nd, &new_nd); 1764 security_sb_post_pivotroot(&user_nd, &new_nd); 1765 error = 0; 1766 path_release(&root_parent); 1767 path_release(&parent_nd); 1768 out2: 1769 mutex_unlock(&old_nd.dentry->d_inode->i_mutex); 1770 up_write(&namespace_sem); 1771 path_release(&user_nd); 1772 path_release(&old_nd); 1773 out1: 1774 path_release(&new_nd); 1775 out0: 1776 unlock_kernel(); 1777 return error; 1778 out3: 1779 spin_unlock(&vfsmount_lock); 1780 goto out2; 1781 } 1782 1783 static void __init init_mount_tree(void) 1784 { 1785 struct vfsmount *mnt; 1786 struct mnt_namespace *ns; 1787 1788 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); 1789 if (IS_ERR(mnt)) 1790 panic("Can't create rootfs"); 1791 ns = kmalloc(sizeof(*ns), GFP_KERNEL); 1792 if (!ns) 1793 panic("Can't allocate initial namespace"); 1794 atomic_set(&ns->count, 1); 1795 INIT_LIST_HEAD(&ns->list); 1796 init_waitqueue_head(&ns->poll); 1797 ns->event = 0; 1798 list_add(&mnt->mnt_list, &ns->list); 1799 ns->root = mnt; 1800 mnt->mnt_ns = ns; 1801 1802 init_task.nsproxy->mnt_ns = ns; 1803 get_mnt_ns(ns); 1804 1805 set_fs_pwd(current->fs, ns->root, ns->root->mnt_root); 1806 set_fs_root(current->fs, ns->root, ns->root->mnt_root); 1807 } 1808 1809 void __init mnt_init(unsigned long mempages) 1810 { 1811 struct list_head *d; 1812 unsigned int nr_hash; 1813 int i; 1814 int err; 1815 1816 init_rwsem(&namespace_sem); 1817 1818 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), 1819 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL); 1820 1821 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); 1822 1823 if (!mount_hashtable) 1824 panic("Failed to allocate mount hash table\n"); 1825 1826 /* 1827 * Find the power-of-two list-heads that can fit into the allocation.. 1828 * We don't guarantee that "sizeof(struct list_head)" is necessarily 1829 * a power-of-two. 1830 */ 1831 nr_hash = PAGE_SIZE / sizeof(struct list_head); 1832 hash_bits = 0; 1833 do { 1834 hash_bits++; 1835 } while ((nr_hash >> hash_bits) != 0); 1836 hash_bits--; 1837 1838 /* 1839 * Re-calculate the actual number of entries and the mask 1840 * from the number of bits we can fit. 1841 */ 1842 nr_hash = 1UL << hash_bits; 1843 hash_mask = nr_hash - 1; 1844 1845 printk("Mount-cache hash table entries: %d\n", nr_hash); 1846 1847 /* And initialize the newly allocated array */ 1848 d = mount_hashtable; 1849 i = nr_hash; 1850 do { 1851 INIT_LIST_HEAD(d); 1852 d++; 1853 i--; 1854 } while (i); 1855 err = sysfs_init(); 1856 if (err) 1857 printk(KERN_WARNING "%s: sysfs_init error: %d\n", 1858 __FUNCTION__, err); 1859 err = subsystem_register(&fs_subsys); 1860 if (err) 1861 printk(KERN_WARNING "%s: subsystem_register error: %d\n", 1862 __FUNCTION__, err); 1863 init_rootfs(); 1864 init_mount_tree(); 1865 } 1866 1867 void __put_mnt_ns(struct mnt_namespace *ns) 1868 { 1869 struct vfsmount *root = ns->root; 1870 LIST_HEAD(umount_list); 1871 ns->root = NULL; 1872 spin_unlock(&vfsmount_lock); 1873 down_write(&namespace_sem); 1874 spin_lock(&vfsmount_lock); 1875 umount_tree(root, 0, &umount_list); 1876 spin_unlock(&vfsmount_lock); 1877 up_write(&namespace_sem); 1878 release_mounts(&umount_list); 1879 kfree(ns); 1880 } 1881