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 #include "internal.h" 32 33 /* spinlock for vfsmount related operations, inplace of dcache_lock */ 34 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); 35 36 static int event; 37 38 static struct list_head *mount_hashtable __read_mostly; 39 static int hash_mask __read_mostly, hash_bits __read_mostly; 40 static struct kmem_cache *mnt_cache __read_mostly; 41 static struct rw_semaphore namespace_sem; 42 43 /* /sys/fs */ 44 decl_subsys(fs, NULL, NULL); 45 EXPORT_SYMBOL_GPL(fs_subsys); 46 47 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) 48 { 49 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); 50 tmp += ((unsigned long)dentry / L1_CACHE_BYTES); 51 tmp = tmp + (tmp >> hash_bits); 52 return tmp & hash_mask; 53 } 54 55 struct vfsmount *alloc_vfsmnt(const char *name) 56 { 57 struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); 58 if (mnt) { 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; 324 325 down_read(&namespace_sem); 326 return seq_list_start(&n->list, *pos); 327 } 328 329 static void *m_next(struct seq_file *m, void *v, loff_t *pos) 330 { 331 struct mnt_namespace *n = m->private; 332 333 return seq_list_next(v, &n->list, pos); 334 } 335 336 static void m_stop(struct seq_file *m, void *v) 337 { 338 up_read(&namespace_sem); 339 } 340 341 static inline void mangle(struct seq_file *m, const char *s) 342 { 343 seq_escape(m, s, " \t\n\\"); 344 } 345 346 static int show_vfsmnt(struct seq_file *m, void *v) 347 { 348 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); 349 int err = 0; 350 static struct proc_fs_info { 351 int flag; 352 char *str; 353 } fs_info[] = { 354 { MS_SYNCHRONOUS, ",sync" }, 355 { MS_DIRSYNC, ",dirsync" }, 356 { MS_MANDLOCK, ",mand" }, 357 { 0, NULL } 358 }; 359 static struct proc_fs_info mnt_info[] = { 360 { MNT_NOSUID, ",nosuid" }, 361 { MNT_NODEV, ",nodev" }, 362 { MNT_NOEXEC, ",noexec" }, 363 { MNT_NOATIME, ",noatime" }, 364 { MNT_NODIRATIME, ",nodiratime" }, 365 { MNT_RELATIME, ",relatime" }, 366 { 0, NULL } 367 }; 368 struct proc_fs_info *fs_infop; 369 370 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); 371 seq_putc(m, ' '); 372 seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); 373 seq_putc(m, ' '); 374 mangle(m, mnt->mnt_sb->s_type->name); 375 if (mnt->mnt_sb->s_subtype && mnt->mnt_sb->s_subtype[0]) { 376 seq_putc(m, '.'); 377 mangle(m, mnt->mnt_sb->s_subtype); 378 } 379 seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); 380 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { 381 if (mnt->mnt_sb->s_flags & fs_infop->flag) 382 seq_puts(m, fs_infop->str); 383 } 384 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { 385 if (mnt->mnt_flags & fs_infop->flag) 386 seq_puts(m, fs_infop->str); 387 } 388 if (mnt->mnt_sb->s_op->show_options) 389 err = mnt->mnt_sb->s_op->show_options(m, mnt); 390 seq_puts(m, " 0 0\n"); 391 return err; 392 } 393 394 struct seq_operations mounts_op = { 395 .start = m_start, 396 .next = m_next, 397 .stop = m_stop, 398 .show = show_vfsmnt 399 }; 400 401 static int show_vfsstat(struct seq_file *m, void *v) 402 { 403 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); 404 int err = 0; 405 406 /* device */ 407 if (mnt->mnt_devname) { 408 seq_puts(m, "device "); 409 mangle(m, mnt->mnt_devname); 410 } else 411 seq_puts(m, "no device"); 412 413 /* mount point */ 414 seq_puts(m, " mounted on "); 415 seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); 416 seq_putc(m, ' '); 417 418 /* file system type */ 419 seq_puts(m, "with fstype "); 420 mangle(m, mnt->mnt_sb->s_type->name); 421 422 /* optional statistics */ 423 if (mnt->mnt_sb->s_op->show_stats) { 424 seq_putc(m, ' '); 425 err = mnt->mnt_sb->s_op->show_stats(m, mnt); 426 } 427 428 seq_putc(m, '\n'); 429 return err; 430 } 431 432 struct seq_operations mountstats_op = { 433 .start = m_start, 434 .next = m_next, 435 .stop = m_stop, 436 .show = show_vfsstat, 437 }; 438 439 /** 440 * may_umount_tree - check if a mount tree is busy 441 * @mnt: root of mount tree 442 * 443 * This is called to check if a tree of mounts has any 444 * open files, pwds, chroots or sub mounts that are 445 * busy. 446 */ 447 int may_umount_tree(struct vfsmount *mnt) 448 { 449 int actual_refs = 0; 450 int minimum_refs = 0; 451 struct vfsmount *p; 452 453 spin_lock(&vfsmount_lock); 454 for (p = mnt; p; p = next_mnt(p, mnt)) { 455 actual_refs += atomic_read(&p->mnt_count); 456 minimum_refs += 2; 457 } 458 spin_unlock(&vfsmount_lock); 459 460 if (actual_refs > minimum_refs) 461 return 0; 462 463 return 1; 464 } 465 466 EXPORT_SYMBOL(may_umount_tree); 467 468 /** 469 * may_umount - check if a mount point is busy 470 * @mnt: root of mount 471 * 472 * This is called to check if a mount point has any 473 * open files, pwds, chroots or sub mounts. If the 474 * mount has sub mounts this will return busy 475 * regardless of whether the sub mounts are busy. 476 * 477 * Doesn't take quota and stuff into account. IOW, in some cases it will 478 * give false negatives. The main reason why it's here is that we need 479 * a non-destructive way to look for easily umountable filesystems. 480 */ 481 int may_umount(struct vfsmount *mnt) 482 { 483 int ret = 1; 484 spin_lock(&vfsmount_lock); 485 if (propagate_mount_busy(mnt, 2)) 486 ret = 0; 487 spin_unlock(&vfsmount_lock); 488 return ret; 489 } 490 491 EXPORT_SYMBOL(may_umount); 492 493 void release_mounts(struct list_head *head) 494 { 495 struct vfsmount *mnt; 496 while (!list_empty(head)) { 497 mnt = list_first_entry(head, struct vfsmount, mnt_hash); 498 list_del_init(&mnt->mnt_hash); 499 if (mnt->mnt_parent != mnt) { 500 struct dentry *dentry; 501 struct vfsmount *m; 502 spin_lock(&vfsmount_lock); 503 dentry = mnt->mnt_mountpoint; 504 m = mnt->mnt_parent; 505 mnt->mnt_mountpoint = mnt->mnt_root; 506 mnt->mnt_parent = mnt; 507 spin_unlock(&vfsmount_lock); 508 dput(dentry); 509 mntput(m); 510 } 511 mntput(mnt); 512 } 513 } 514 515 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) 516 { 517 struct vfsmount *p; 518 519 for (p = mnt; p; p = next_mnt(p, mnt)) 520 list_move(&p->mnt_hash, kill); 521 522 if (propagate) 523 propagate_umount(kill); 524 525 list_for_each_entry(p, kill, mnt_hash) { 526 list_del_init(&p->mnt_expire); 527 list_del_init(&p->mnt_list); 528 __touch_mnt_namespace(p->mnt_ns); 529 p->mnt_ns = NULL; 530 list_del_init(&p->mnt_child); 531 if (p->mnt_parent != p) 532 p->mnt_mountpoint->d_mounted--; 533 change_mnt_propagation(p, MS_PRIVATE); 534 } 535 } 536 537 static int do_umount(struct vfsmount *mnt, int flags) 538 { 539 struct super_block *sb = mnt->mnt_sb; 540 int retval; 541 LIST_HEAD(umount_list); 542 543 retval = security_sb_umount(mnt, flags); 544 if (retval) 545 return retval; 546 547 /* 548 * Allow userspace to request a mountpoint be expired rather than 549 * unmounting unconditionally. Unmount only happens if: 550 * (1) the mark is already set (the mark is cleared by mntput()) 551 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] 552 */ 553 if (flags & MNT_EXPIRE) { 554 if (mnt == current->fs->rootmnt || 555 flags & (MNT_FORCE | MNT_DETACH)) 556 return -EINVAL; 557 558 if (atomic_read(&mnt->mnt_count) != 2) 559 return -EBUSY; 560 561 if (!xchg(&mnt->mnt_expiry_mark, 1)) 562 return -EAGAIN; 563 } 564 565 /* 566 * If we may have to abort operations to get out of this 567 * mount, and they will themselves hold resources we must 568 * allow the fs to do things. In the Unix tradition of 569 * 'Gee thats tricky lets do it in userspace' the umount_begin 570 * might fail to complete on the first run through as other tasks 571 * must return, and the like. Thats for the mount program to worry 572 * about for the moment. 573 */ 574 575 lock_kernel(); 576 if (sb->s_op->umount_begin) 577 sb->s_op->umount_begin(mnt, flags); 578 unlock_kernel(); 579 580 /* 581 * No sense to grab the lock for this test, but test itself looks 582 * somewhat bogus. Suggestions for better replacement? 583 * Ho-hum... In principle, we might treat that as umount + switch 584 * to rootfs. GC would eventually take care of the old vfsmount. 585 * Actually it makes sense, especially if rootfs would contain a 586 * /reboot - static binary that would close all descriptors and 587 * call reboot(9). Then init(8) could umount root and exec /reboot. 588 */ 589 if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { 590 /* 591 * Special case for "unmounting" root ... 592 * we just try to remount it readonly. 593 */ 594 down_write(&sb->s_umount); 595 if (!(sb->s_flags & MS_RDONLY)) { 596 lock_kernel(); 597 DQUOT_OFF(sb); 598 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); 599 unlock_kernel(); 600 } 601 up_write(&sb->s_umount); 602 return retval; 603 } 604 605 down_write(&namespace_sem); 606 spin_lock(&vfsmount_lock); 607 event++; 608 609 retval = -EBUSY; 610 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { 611 if (!list_empty(&mnt->mnt_list)) 612 umount_tree(mnt, 1, &umount_list); 613 retval = 0; 614 } 615 spin_unlock(&vfsmount_lock); 616 if (retval) 617 security_sb_umount_busy(mnt); 618 up_write(&namespace_sem); 619 release_mounts(&umount_list); 620 return retval; 621 } 622 623 /* 624 * Now umount can handle mount points as well as block devices. 625 * This is important for filesystems which use unnamed block devices. 626 * 627 * We now support a flag for forced unmount like the other 'big iron' 628 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD 629 */ 630 631 asmlinkage long sys_umount(char __user * name, int flags) 632 { 633 struct nameidata nd; 634 int retval; 635 636 retval = __user_walk(name, LOOKUP_FOLLOW, &nd); 637 if (retval) 638 goto out; 639 retval = -EINVAL; 640 if (nd.dentry != nd.mnt->mnt_root) 641 goto dput_and_out; 642 if (!check_mnt(nd.mnt)) 643 goto dput_and_out; 644 645 retval = -EPERM; 646 if (!capable(CAP_SYS_ADMIN)) 647 goto dput_and_out; 648 649 retval = do_umount(nd.mnt, flags); 650 dput_and_out: 651 path_release_on_umount(&nd); 652 out: 653 return retval; 654 } 655 656 #ifdef __ARCH_WANT_SYS_OLDUMOUNT 657 658 /* 659 * The 2.0 compatible umount. No flags. 660 */ 661 asmlinkage long sys_oldumount(char __user * name) 662 { 663 return sys_umount(name, 0); 664 } 665 666 #endif 667 668 static int mount_is_safe(struct nameidata *nd) 669 { 670 if (capable(CAP_SYS_ADMIN)) 671 return 0; 672 return -EPERM; 673 #ifdef notyet 674 if (S_ISLNK(nd->dentry->d_inode->i_mode)) 675 return -EPERM; 676 if (nd->dentry->d_inode->i_mode & S_ISVTX) { 677 if (current->uid != nd->dentry->d_inode->i_uid) 678 return -EPERM; 679 } 680 if (vfs_permission(nd, MAY_WRITE)) 681 return -EPERM; 682 return 0; 683 #endif 684 } 685 686 static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) 687 { 688 while (1) { 689 if (d == dentry) 690 return 1; 691 if (d == NULL || d == d->d_parent) 692 return 0; 693 d = d->d_parent; 694 } 695 } 696 697 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 698 int flag) 699 { 700 struct vfsmount *res, *p, *q, *r, *s; 701 struct nameidata nd; 702 703 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) 704 return NULL; 705 706 res = q = clone_mnt(mnt, dentry, flag); 707 if (!q) 708 goto Enomem; 709 q->mnt_mountpoint = mnt->mnt_mountpoint; 710 711 p = mnt; 712 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { 713 if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) 714 continue; 715 716 for (s = r; s; s = next_mnt(s, r)) { 717 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { 718 s = skip_mnt_tree(s); 719 continue; 720 } 721 while (p != s->mnt_parent) { 722 p = p->mnt_parent; 723 q = q->mnt_parent; 724 } 725 p = s; 726 nd.mnt = q; 727 nd.dentry = p->mnt_mountpoint; 728 q = clone_mnt(p, p->mnt_root, flag); 729 if (!q) 730 goto Enomem; 731 spin_lock(&vfsmount_lock); 732 list_add_tail(&q->mnt_list, &res->mnt_list); 733 attach_mnt(q, &nd); 734 spin_unlock(&vfsmount_lock); 735 } 736 } 737 return res; 738 Enomem: 739 if (res) { 740 LIST_HEAD(umount_list); 741 spin_lock(&vfsmount_lock); 742 umount_tree(res, 0, &umount_list); 743 spin_unlock(&vfsmount_lock); 744 release_mounts(&umount_list); 745 } 746 return NULL; 747 } 748 749 /* 750 * @source_mnt : mount tree to be attached 751 * @nd : place the mount tree @source_mnt is attached 752 * @parent_nd : if non-null, detach the source_mnt from its parent and 753 * store the parent mount and mountpoint dentry. 754 * (done when source_mnt is moved) 755 * 756 * NOTE: in the table below explains the semantics when a source mount 757 * of a given type is attached to a destination mount of a given type. 758 * --------------------------------------------------------------------------- 759 * | BIND MOUNT OPERATION | 760 * |************************************************************************** 761 * | source-->| shared | private | slave | unbindable | 762 * | dest | | | | | 763 * | | | | | | | 764 * | v | | | | | 765 * |************************************************************************** 766 * | shared | shared (++) | shared (+) | shared(+++)| invalid | 767 * | | | | | | 768 * |non-shared| shared (+) | private | slave (*) | invalid | 769 * *************************************************************************** 770 * A bind operation clones the source mount and mounts the clone on the 771 * destination mount. 772 * 773 * (++) the cloned mount is propagated to all the mounts in the propagation 774 * tree of the destination mount and the cloned mount is added to 775 * the peer group of the source mount. 776 * (+) the cloned mount is created under the destination mount and is marked 777 * as shared. The cloned mount is added to the peer group of the source 778 * mount. 779 * (+++) the mount is propagated to all the mounts in the propagation tree 780 * of the destination mount and the cloned mount is made slave 781 * of the same master as that of the source mount. The cloned mount 782 * is marked as 'shared and slave'. 783 * (*) the cloned mount is made a slave of the same master as that of the 784 * source mount. 785 * 786 * --------------------------------------------------------------------------- 787 * | MOVE MOUNT OPERATION | 788 * |************************************************************************** 789 * | source-->| shared | private | slave | unbindable | 790 * | dest | | | | | 791 * | | | | | | | 792 * | v | | | | | 793 * |************************************************************************** 794 * | shared | shared (+) | shared (+) | shared(+++) | invalid | 795 * | | | | | | 796 * |non-shared| shared (+*) | private | slave (*) | unbindable | 797 * *************************************************************************** 798 * 799 * (+) the mount is moved to the destination. And is then propagated to 800 * all the mounts in the propagation tree of the destination mount. 801 * (+*) the mount is moved to the destination. 802 * (+++) the mount is moved to the destination and is then propagated to 803 * all the mounts belonging to the destination mount's propagation tree. 804 * the mount is marked as 'shared and slave'. 805 * (*) the mount continues to be a slave at the new location. 806 * 807 * if the source mount is a tree, the operations explained above is 808 * applied to each mount in the tree. 809 * Must be called without spinlocks held, since this function can sleep 810 * in allocations. 811 */ 812 static int attach_recursive_mnt(struct vfsmount *source_mnt, 813 struct nameidata *nd, struct nameidata *parent_nd) 814 { 815 LIST_HEAD(tree_list); 816 struct vfsmount *dest_mnt = nd->mnt; 817 struct dentry *dest_dentry = nd->dentry; 818 struct vfsmount *child, *p; 819 820 if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list)) 821 return -EINVAL; 822 823 if (IS_MNT_SHARED(dest_mnt)) { 824 for (p = source_mnt; p; p = next_mnt(p, source_mnt)) 825 set_mnt_shared(p); 826 } 827 828 spin_lock(&vfsmount_lock); 829 if (parent_nd) { 830 detach_mnt(source_mnt, parent_nd); 831 attach_mnt(source_mnt, nd); 832 touch_mnt_namespace(current->nsproxy->mnt_ns); 833 } else { 834 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); 835 commit_tree(source_mnt); 836 } 837 838 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { 839 list_del_init(&child->mnt_hash); 840 commit_tree(child); 841 } 842 spin_unlock(&vfsmount_lock); 843 return 0; 844 } 845 846 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) 847 { 848 int err; 849 if (mnt->mnt_sb->s_flags & MS_NOUSER) 850 return -EINVAL; 851 852 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 853 S_ISDIR(mnt->mnt_root->d_inode->i_mode)) 854 return -ENOTDIR; 855 856 err = -ENOENT; 857 mutex_lock(&nd->dentry->d_inode->i_mutex); 858 if (IS_DEADDIR(nd->dentry->d_inode)) 859 goto out_unlock; 860 861 err = security_sb_check_sb(mnt, nd); 862 if (err) 863 goto out_unlock; 864 865 err = -ENOENT; 866 if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) 867 err = attach_recursive_mnt(mnt, nd, NULL); 868 out_unlock: 869 mutex_unlock(&nd->dentry->d_inode->i_mutex); 870 if (!err) 871 security_sb_post_addmount(mnt, nd); 872 return err; 873 } 874 875 /* 876 * recursively change the type of the mountpoint. 877 */ 878 static int do_change_type(struct nameidata *nd, int flag) 879 { 880 struct vfsmount *m, *mnt = nd->mnt; 881 int recurse = flag & MS_REC; 882 int type = flag & ~MS_REC; 883 884 if (!capable(CAP_SYS_ADMIN)) 885 return -EPERM; 886 887 if (nd->dentry != nd->mnt->mnt_root) 888 return -EINVAL; 889 890 down_write(&namespace_sem); 891 spin_lock(&vfsmount_lock); 892 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) 893 change_mnt_propagation(m, type); 894 spin_unlock(&vfsmount_lock); 895 up_write(&namespace_sem); 896 return 0; 897 } 898 899 /* 900 * do loopback mount. 901 */ 902 static int do_loopback(struct nameidata *nd, char *old_name, int recurse) 903 { 904 struct nameidata old_nd; 905 struct vfsmount *mnt = NULL; 906 int err = mount_is_safe(nd); 907 if (err) 908 return err; 909 if (!old_name || !*old_name) 910 return -EINVAL; 911 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 912 if (err) 913 return err; 914 915 down_write(&namespace_sem); 916 err = -EINVAL; 917 if (IS_MNT_UNBINDABLE(old_nd.mnt)) 918 goto out; 919 920 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 921 goto out; 922 923 err = -ENOMEM; 924 if (recurse) 925 mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0); 926 else 927 mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0); 928 929 if (!mnt) 930 goto out; 931 932 err = graft_tree(mnt, nd); 933 if (err) { 934 LIST_HEAD(umount_list); 935 spin_lock(&vfsmount_lock); 936 umount_tree(mnt, 0, &umount_list); 937 spin_unlock(&vfsmount_lock); 938 release_mounts(&umount_list); 939 } 940 941 out: 942 up_write(&namespace_sem); 943 path_release(&old_nd); 944 return err; 945 } 946 947 /* 948 * change filesystem flags. dir should be a physical root of filesystem. 949 * If you've mounted a non-root directory somewhere and want to do remount 950 * on it - tough luck. 951 */ 952 static int do_remount(struct nameidata *nd, int flags, int mnt_flags, 953 void *data) 954 { 955 int err; 956 struct super_block *sb = nd->mnt->mnt_sb; 957 958 if (!capable(CAP_SYS_ADMIN)) 959 return -EPERM; 960 961 if (!check_mnt(nd->mnt)) 962 return -EINVAL; 963 964 if (nd->dentry != nd->mnt->mnt_root) 965 return -EINVAL; 966 967 down_write(&sb->s_umount); 968 err = do_remount_sb(sb, flags, data, 0); 969 if (!err) 970 nd->mnt->mnt_flags = mnt_flags; 971 up_write(&sb->s_umount); 972 if (!err) 973 security_sb_post_remount(nd->mnt, flags, data); 974 return err; 975 } 976 977 static inline int tree_contains_unbindable(struct vfsmount *mnt) 978 { 979 struct vfsmount *p; 980 for (p = mnt; p; p = next_mnt(p, mnt)) { 981 if (IS_MNT_UNBINDABLE(p)) 982 return 1; 983 } 984 return 0; 985 } 986 987 static int do_move_mount(struct nameidata *nd, char *old_name) 988 { 989 struct nameidata old_nd, parent_nd; 990 struct vfsmount *p; 991 int err = 0; 992 if (!capable(CAP_SYS_ADMIN)) 993 return -EPERM; 994 if (!old_name || !*old_name) 995 return -EINVAL; 996 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); 997 if (err) 998 return err; 999 1000 down_write(&namespace_sem); 1001 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 1002 ; 1003 err = -EINVAL; 1004 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) 1005 goto out; 1006 1007 err = -ENOENT; 1008 mutex_lock(&nd->dentry->d_inode->i_mutex); 1009 if (IS_DEADDIR(nd->dentry->d_inode)) 1010 goto out1; 1011 1012 if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) 1013 goto out1; 1014 1015 err = -EINVAL; 1016 if (old_nd.dentry != old_nd.mnt->mnt_root) 1017 goto out1; 1018 1019 if (old_nd.mnt == old_nd.mnt->mnt_parent) 1020 goto out1; 1021 1022 if (S_ISDIR(nd->dentry->d_inode->i_mode) != 1023 S_ISDIR(old_nd.dentry->d_inode->i_mode)) 1024 goto out1; 1025 /* 1026 * Don't move a mount residing in a shared parent. 1027 */ 1028 if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent)) 1029 goto out1; 1030 /* 1031 * Don't move a mount tree containing unbindable mounts to a destination 1032 * mount which is shared. 1033 */ 1034 if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt)) 1035 goto out1; 1036 err = -ELOOP; 1037 for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent) 1038 if (p == old_nd.mnt) 1039 goto out1; 1040 1041 if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd))) 1042 goto out1; 1043 1044 spin_lock(&vfsmount_lock); 1045 /* if the mount is moved, it should no longer be expire 1046 * automatically */ 1047 list_del_init(&old_nd.mnt->mnt_expire); 1048 spin_unlock(&vfsmount_lock); 1049 out1: 1050 mutex_unlock(&nd->dentry->d_inode->i_mutex); 1051 out: 1052 up_write(&namespace_sem); 1053 if (!err) 1054 path_release(&parent_nd); 1055 path_release(&old_nd); 1056 return err; 1057 } 1058 1059 /* 1060 * create a new mount for userspace and request it to be added into the 1061 * namespace's tree 1062 */ 1063 static int do_new_mount(struct nameidata *nd, char *type, int flags, 1064 int mnt_flags, char *name, void *data) 1065 { 1066 struct vfsmount *mnt; 1067 1068 if (!type || !memchr(type, 0, PAGE_SIZE)) 1069 return -EINVAL; 1070 1071 /* we need capabilities... */ 1072 if (!capable(CAP_SYS_ADMIN)) 1073 return -EPERM; 1074 1075 mnt = do_kern_mount(type, flags, name, data); 1076 if (IS_ERR(mnt)) 1077 return PTR_ERR(mnt); 1078 1079 return do_add_mount(mnt, nd, mnt_flags, NULL); 1080 } 1081 1082 /* 1083 * add a mount into a namespace's mount tree 1084 * - provide the option of adding the new mount to an expiration list 1085 */ 1086 int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, 1087 int mnt_flags, struct list_head *fslist) 1088 { 1089 int err; 1090 1091 down_write(&namespace_sem); 1092 /* Something was mounted here while we slept */ 1093 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) 1094 ; 1095 err = -EINVAL; 1096 if (!check_mnt(nd->mnt)) 1097 goto unlock; 1098 1099 /* Refuse the same filesystem on the same mount point */ 1100 err = -EBUSY; 1101 if (nd->mnt->mnt_sb == newmnt->mnt_sb && 1102 nd->mnt->mnt_root == nd->dentry) 1103 goto unlock; 1104 1105 err = -EINVAL; 1106 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) 1107 goto unlock; 1108 1109 newmnt->mnt_flags = mnt_flags; 1110 if ((err = graft_tree(newmnt, nd))) 1111 goto unlock; 1112 1113 if (fslist) { 1114 /* add to the specified expiration list */ 1115 spin_lock(&vfsmount_lock); 1116 list_add_tail(&newmnt->mnt_expire, fslist); 1117 spin_unlock(&vfsmount_lock); 1118 } 1119 up_write(&namespace_sem); 1120 return 0; 1121 1122 unlock: 1123 up_write(&namespace_sem); 1124 mntput(newmnt); 1125 return err; 1126 } 1127 1128 EXPORT_SYMBOL_GPL(do_add_mount); 1129 1130 static void expire_mount(struct vfsmount *mnt, struct list_head *mounts, 1131 struct list_head *umounts) 1132 { 1133 spin_lock(&vfsmount_lock); 1134 1135 /* 1136 * Check if mount is still attached, if not, let whoever holds it deal 1137 * with the sucker 1138 */ 1139 if (mnt->mnt_parent == mnt) { 1140 spin_unlock(&vfsmount_lock); 1141 return; 1142 } 1143 1144 /* 1145 * Check that it is still dead: the count should now be 2 - as 1146 * contributed by the vfsmount parent and the mntget above 1147 */ 1148 if (!propagate_mount_busy(mnt, 2)) { 1149 /* delete from the namespace */ 1150 touch_mnt_namespace(mnt->mnt_ns); 1151 list_del_init(&mnt->mnt_list); 1152 mnt->mnt_ns = NULL; 1153 umount_tree(mnt, 1, umounts); 1154 spin_unlock(&vfsmount_lock); 1155 } else { 1156 /* 1157 * Someone brought it back to life whilst we didn't have any 1158 * locks held so return it to the expiration list 1159 */ 1160 list_add_tail(&mnt->mnt_expire, mounts); 1161 spin_unlock(&vfsmount_lock); 1162 } 1163 } 1164 1165 /* 1166 * go through the vfsmounts we've just consigned to the graveyard to 1167 * - check that they're still dead 1168 * - delete the vfsmount from the appropriate namespace under lock 1169 * - dispose of the corpse 1170 */ 1171 static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts) 1172 { 1173 struct mnt_namespace *ns; 1174 struct vfsmount *mnt; 1175 1176 while (!list_empty(graveyard)) { 1177 LIST_HEAD(umounts); 1178 mnt = list_first_entry(graveyard, struct vfsmount, mnt_expire); 1179 list_del_init(&mnt->mnt_expire); 1180 1181 /* don't do anything if the namespace is dead - all the 1182 * vfsmounts from it are going away anyway */ 1183 ns = mnt->mnt_ns; 1184 if (!ns || !ns->root) 1185 continue; 1186 get_mnt_ns(ns); 1187 1188 spin_unlock(&vfsmount_lock); 1189 down_write(&namespace_sem); 1190 expire_mount(mnt, mounts, &umounts); 1191 up_write(&namespace_sem); 1192 release_mounts(&umounts); 1193 mntput(mnt); 1194 put_mnt_ns(ns); 1195 spin_lock(&vfsmount_lock); 1196 } 1197 } 1198 1199 /* 1200 * process a list of expirable mountpoints with the intent of discarding any 1201 * mountpoints that aren't in use and haven't been touched since last we came 1202 * here 1203 */ 1204 void mark_mounts_for_expiry(struct list_head *mounts) 1205 { 1206 struct vfsmount *mnt, *next; 1207 LIST_HEAD(graveyard); 1208 1209 if (list_empty(mounts)) 1210 return; 1211 1212 spin_lock(&vfsmount_lock); 1213 1214 /* extract from the expiration list every vfsmount that matches the 1215 * following criteria: 1216 * - only referenced by its parent vfsmount 1217 * - still marked for expiry (marked on the last call here; marks are 1218 * cleared by mntput()) 1219 */ 1220 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { 1221 if (!xchg(&mnt->mnt_expiry_mark, 1) || 1222 atomic_read(&mnt->mnt_count) != 1) 1223 continue; 1224 1225 mntget(mnt); 1226 list_move(&mnt->mnt_expire, &graveyard); 1227 } 1228 1229 expire_mount_list(&graveyard, mounts); 1230 1231 spin_unlock(&vfsmount_lock); 1232 } 1233 1234 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); 1235 1236 /* 1237 * Ripoff of 'select_parent()' 1238 * 1239 * search the list of submounts for a given mountpoint, and move any 1240 * shrinkable submounts to the 'graveyard' list. 1241 */ 1242 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard) 1243 { 1244 struct vfsmount *this_parent = parent; 1245 struct list_head *next; 1246 int found = 0; 1247 1248 repeat: 1249 next = this_parent->mnt_mounts.next; 1250 resume: 1251 while (next != &this_parent->mnt_mounts) { 1252 struct list_head *tmp = next; 1253 struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); 1254 1255 next = tmp->next; 1256 if (!(mnt->mnt_flags & MNT_SHRINKABLE)) 1257 continue; 1258 /* 1259 * Descend a level if the d_mounts list is non-empty. 1260 */ 1261 if (!list_empty(&mnt->mnt_mounts)) { 1262 this_parent = mnt; 1263 goto repeat; 1264 } 1265 1266 if (!propagate_mount_busy(mnt, 1)) { 1267 mntget(mnt); 1268 list_move_tail(&mnt->mnt_expire, graveyard); 1269 found++; 1270 } 1271 } 1272 /* 1273 * All done at this level ... ascend and resume the search 1274 */ 1275 if (this_parent != parent) { 1276 next = this_parent->mnt_child.next; 1277 this_parent = this_parent->mnt_parent; 1278 goto resume; 1279 } 1280 return found; 1281 } 1282 1283 /* 1284 * process a list of expirable mountpoints with the intent of discarding any 1285 * submounts of a specific parent mountpoint 1286 */ 1287 void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts) 1288 { 1289 LIST_HEAD(graveyard); 1290 int found; 1291 1292 spin_lock(&vfsmount_lock); 1293 1294 /* extract submounts of 'mountpoint' from the expiration list */ 1295 while ((found = select_submounts(mountpoint, &graveyard)) != 0) 1296 expire_mount_list(&graveyard, mounts); 1297 1298 spin_unlock(&vfsmount_lock); 1299 } 1300 1301 EXPORT_SYMBOL_GPL(shrink_submounts); 1302 1303 /* 1304 * Some copy_from_user() implementations do not return the exact number of 1305 * bytes remaining to copy on a fault. But copy_mount_options() requires that. 1306 * Note that this function differs from copy_from_user() in that it will oops 1307 * on bad values of `to', rather than returning a short copy. 1308 */ 1309 static long exact_copy_from_user(void *to, const void __user * from, 1310 unsigned long n) 1311 { 1312 char *t = to; 1313 const char __user *f = from; 1314 char c; 1315 1316 if (!access_ok(VERIFY_READ, from, n)) 1317 return n; 1318 1319 while (n) { 1320 if (__get_user(c, f)) { 1321 memset(t, 0, n); 1322 break; 1323 } 1324 *t++ = c; 1325 f++; 1326 n--; 1327 } 1328 return n; 1329 } 1330 1331 int copy_mount_options(const void __user * data, unsigned long *where) 1332 { 1333 int i; 1334 unsigned long page; 1335 unsigned long size; 1336 1337 *where = 0; 1338 if (!data) 1339 return 0; 1340 1341 if (!(page = __get_free_page(GFP_KERNEL))) 1342 return -ENOMEM; 1343 1344 /* We only care that *some* data at the address the user 1345 * gave us is valid. Just in case, we'll zero 1346 * the remainder of the page. 1347 */ 1348 /* copy_from_user cannot cross TASK_SIZE ! */ 1349 size = TASK_SIZE - (unsigned long)data; 1350 if (size > PAGE_SIZE) 1351 size = PAGE_SIZE; 1352 1353 i = size - exact_copy_from_user((void *)page, data, size); 1354 if (!i) { 1355 free_page(page); 1356 return -EFAULT; 1357 } 1358 if (i != PAGE_SIZE) 1359 memset((char *)page + i, 0, PAGE_SIZE - i); 1360 *where = page; 1361 return 0; 1362 } 1363 1364 /* 1365 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to 1366 * be given to the mount() call (ie: read-only, no-dev, no-suid etc). 1367 * 1368 * data is a (void *) that can point to any structure up to 1369 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent 1370 * information (or be NULL). 1371 * 1372 * Pre-0.97 versions of mount() didn't have a flags word. 1373 * When the flags word was introduced its top half was required 1374 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. 1375 * Therefore, if this magic number is present, it carries no information 1376 * and must be discarded. 1377 */ 1378 long do_mount(char *dev_name, char *dir_name, char *type_page, 1379 unsigned long flags, void *data_page) 1380 { 1381 struct nameidata nd; 1382 int retval = 0; 1383 int mnt_flags = 0; 1384 1385 /* Discard magic */ 1386 if ((flags & MS_MGC_MSK) == MS_MGC_VAL) 1387 flags &= ~MS_MGC_MSK; 1388 1389 /* Basic sanity checks */ 1390 1391 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) 1392 return -EINVAL; 1393 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) 1394 return -EINVAL; 1395 1396 if (data_page) 1397 ((char *)data_page)[PAGE_SIZE - 1] = 0; 1398 1399 /* Separate the per-mountpoint flags */ 1400 if (flags & MS_NOSUID) 1401 mnt_flags |= MNT_NOSUID; 1402 if (flags & MS_NODEV) 1403 mnt_flags |= MNT_NODEV; 1404 if (flags & MS_NOEXEC) 1405 mnt_flags |= MNT_NOEXEC; 1406 if (flags & MS_NOATIME) 1407 mnt_flags |= MNT_NOATIME; 1408 if (flags & MS_NODIRATIME) 1409 mnt_flags |= MNT_NODIRATIME; 1410 if (flags & MS_RELATIME) 1411 mnt_flags |= MNT_RELATIME; 1412 1413 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | 1414 MS_NOATIME | MS_NODIRATIME | MS_RELATIME); 1415 1416 /* ... and get the mountpoint */ 1417 retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); 1418 if (retval) 1419 return retval; 1420 1421 retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); 1422 if (retval) 1423 goto dput_out; 1424 1425 if (flags & MS_REMOUNT) 1426 retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, 1427 data_page); 1428 else if (flags & MS_BIND) 1429 retval = do_loopback(&nd, dev_name, flags & MS_REC); 1430 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) 1431 retval = do_change_type(&nd, flags); 1432 else if (flags & MS_MOVE) 1433 retval = do_move_mount(&nd, dev_name); 1434 else 1435 retval = do_new_mount(&nd, type_page, flags, mnt_flags, 1436 dev_name, data_page); 1437 dput_out: 1438 path_release(&nd); 1439 return retval; 1440 } 1441 1442 /* 1443 * Allocate a new namespace structure and populate it with contents 1444 * copied from the namespace of the passed in task structure. 1445 */ 1446 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, 1447 struct fs_struct *fs) 1448 { 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 ERR_PTR(-ENOMEM); 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 ERR_PTR(-ENOMEM);; 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 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, 1514 struct fs_struct *new_fs) 1515 { 1516 struct mnt_namespace *new_ns; 1517 1518 BUG_ON(!ns); 1519 get_mnt_ns(ns); 1520 1521 if (!(flags & CLONE_NEWNS)) 1522 return ns; 1523 1524 new_ns = dup_mnt_ns(ns, new_fs); 1525 1526 put_mnt_ns(ns); 1527 return new_ns; 1528 } 1529 1530 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, 1531 char __user * type, unsigned long flags, 1532 void __user * data) 1533 { 1534 int retval; 1535 unsigned long data_page; 1536 unsigned long type_page; 1537 unsigned long dev_page; 1538 char *dir_page; 1539 1540 retval = copy_mount_options(type, &type_page); 1541 if (retval < 0) 1542 return retval; 1543 1544 dir_page = getname(dir_name); 1545 retval = PTR_ERR(dir_page); 1546 if (IS_ERR(dir_page)) 1547 goto out1; 1548 1549 retval = copy_mount_options(dev_name, &dev_page); 1550 if (retval < 0) 1551 goto out2; 1552 1553 retval = copy_mount_options(data, &data_page); 1554 if (retval < 0) 1555 goto out3; 1556 1557 lock_kernel(); 1558 retval = do_mount((char *)dev_page, dir_page, (char *)type_page, 1559 flags, (void *)data_page); 1560 unlock_kernel(); 1561 free_page(data_page); 1562 1563 out3: 1564 free_page(dev_page); 1565 out2: 1566 putname(dir_page); 1567 out1: 1568 free_page(type_page); 1569 return retval; 1570 } 1571 1572 /* 1573 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. 1574 * It can block. Requires the big lock held. 1575 */ 1576 void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, 1577 struct dentry *dentry) 1578 { 1579 struct dentry *old_root; 1580 struct vfsmount *old_rootmnt; 1581 write_lock(&fs->lock); 1582 old_root = fs->root; 1583 old_rootmnt = fs->rootmnt; 1584 fs->rootmnt = mntget(mnt); 1585 fs->root = dget(dentry); 1586 write_unlock(&fs->lock); 1587 if (old_root) { 1588 dput(old_root); 1589 mntput(old_rootmnt); 1590 } 1591 } 1592 1593 /* 1594 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. 1595 * It can block. Requires the big lock held. 1596 */ 1597 void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, 1598 struct dentry *dentry) 1599 { 1600 struct dentry *old_pwd; 1601 struct vfsmount *old_pwdmnt; 1602 1603 write_lock(&fs->lock); 1604 old_pwd = fs->pwd; 1605 old_pwdmnt = fs->pwdmnt; 1606 fs->pwdmnt = mntget(mnt); 1607 fs->pwd = dget(dentry); 1608 write_unlock(&fs->lock); 1609 1610 if (old_pwd) { 1611 dput(old_pwd); 1612 mntput(old_pwdmnt); 1613 } 1614 } 1615 1616 static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) 1617 { 1618 struct task_struct *g, *p; 1619 struct fs_struct *fs; 1620 1621 read_lock(&tasklist_lock); 1622 do_each_thread(g, p) { 1623 task_lock(p); 1624 fs = p->fs; 1625 if (fs) { 1626 atomic_inc(&fs->count); 1627 task_unlock(p); 1628 if (fs->root == old_nd->dentry 1629 && fs->rootmnt == old_nd->mnt) 1630 set_fs_root(fs, new_nd->mnt, new_nd->dentry); 1631 if (fs->pwd == old_nd->dentry 1632 && fs->pwdmnt == old_nd->mnt) 1633 set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); 1634 put_fs_struct(fs); 1635 } else 1636 task_unlock(p); 1637 } while_each_thread(g, p); 1638 read_unlock(&tasklist_lock); 1639 } 1640 1641 /* 1642 * pivot_root Semantics: 1643 * Moves the root file system of the current process to the directory put_old, 1644 * makes new_root as the new root file system of the current process, and sets 1645 * root/cwd of all processes which had them on the current root to new_root. 1646 * 1647 * Restrictions: 1648 * The new_root and put_old must be directories, and must not be on the 1649 * same file system as the current process root. The put_old must be 1650 * underneath new_root, i.e. adding a non-zero number of /.. to the string 1651 * pointed to by put_old must yield the same directory as new_root. No other 1652 * file system may be mounted on put_old. After all, new_root is a mountpoint. 1653 * 1654 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. 1655 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives 1656 * in this situation. 1657 * 1658 * Notes: 1659 * - we don't move root/cwd if they are not at the root (reason: if something 1660 * cared enough to change them, it's probably wrong to force them elsewhere) 1661 * - it's okay to pick a root that isn't the root of a file system, e.g. 1662 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, 1663 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root 1664 * first. 1665 */ 1666 asmlinkage long sys_pivot_root(const char __user * new_root, 1667 const char __user * put_old) 1668 { 1669 struct vfsmount *tmp; 1670 struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; 1671 int error; 1672 1673 if (!capable(CAP_SYS_ADMIN)) 1674 return -EPERM; 1675 1676 lock_kernel(); 1677 1678 error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, 1679 &new_nd); 1680 if (error) 1681 goto out0; 1682 error = -EINVAL; 1683 if (!check_mnt(new_nd.mnt)) 1684 goto out1; 1685 1686 error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd); 1687 if (error) 1688 goto out1; 1689 1690 error = security_sb_pivotroot(&old_nd, &new_nd); 1691 if (error) { 1692 path_release(&old_nd); 1693 goto out1; 1694 } 1695 1696 read_lock(¤t->fs->lock); 1697 user_nd.mnt = mntget(current->fs->rootmnt); 1698 user_nd.dentry = dget(current->fs->root); 1699 read_unlock(¤t->fs->lock); 1700 down_write(&namespace_sem); 1701 mutex_lock(&old_nd.dentry->d_inode->i_mutex); 1702 error = -EINVAL; 1703 if (IS_MNT_SHARED(old_nd.mnt) || 1704 IS_MNT_SHARED(new_nd.mnt->mnt_parent) || 1705 IS_MNT_SHARED(user_nd.mnt->mnt_parent)) 1706 goto out2; 1707 if (!check_mnt(user_nd.mnt)) 1708 goto out2; 1709 error = -ENOENT; 1710 if (IS_DEADDIR(new_nd.dentry->d_inode)) 1711 goto out2; 1712 if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) 1713 goto out2; 1714 if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) 1715 goto out2; 1716 error = -EBUSY; 1717 if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) 1718 goto out2; /* loop, on the same file system */ 1719 error = -EINVAL; 1720 if (user_nd.mnt->mnt_root != user_nd.dentry) 1721 goto out2; /* not a mountpoint */ 1722 if (user_nd.mnt->mnt_parent == user_nd.mnt) 1723 goto out2; /* not attached */ 1724 if (new_nd.mnt->mnt_root != new_nd.dentry) 1725 goto out2; /* not a mountpoint */ 1726 if (new_nd.mnt->mnt_parent == new_nd.mnt) 1727 goto out2; /* not attached */ 1728 tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ 1729 spin_lock(&vfsmount_lock); 1730 if (tmp != new_nd.mnt) { 1731 for (;;) { 1732 if (tmp->mnt_parent == tmp) 1733 goto out3; /* already mounted on put_old */ 1734 if (tmp->mnt_parent == new_nd.mnt) 1735 break; 1736 tmp = tmp->mnt_parent; 1737 } 1738 if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) 1739 goto out3; 1740 } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) 1741 goto out3; 1742 detach_mnt(new_nd.mnt, &parent_nd); 1743 detach_mnt(user_nd.mnt, &root_parent); 1744 attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ 1745 attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ 1746 touch_mnt_namespace(current->nsproxy->mnt_ns); 1747 spin_unlock(&vfsmount_lock); 1748 chroot_fs_refs(&user_nd, &new_nd); 1749 security_sb_post_pivotroot(&user_nd, &new_nd); 1750 error = 0; 1751 path_release(&root_parent); 1752 path_release(&parent_nd); 1753 out2: 1754 mutex_unlock(&old_nd.dentry->d_inode->i_mutex); 1755 up_write(&namespace_sem); 1756 path_release(&user_nd); 1757 path_release(&old_nd); 1758 out1: 1759 path_release(&new_nd); 1760 out0: 1761 unlock_kernel(); 1762 return error; 1763 out3: 1764 spin_unlock(&vfsmount_lock); 1765 goto out2; 1766 } 1767 1768 static void __init init_mount_tree(void) 1769 { 1770 struct vfsmount *mnt; 1771 struct mnt_namespace *ns; 1772 1773 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); 1774 if (IS_ERR(mnt)) 1775 panic("Can't create rootfs"); 1776 ns = kmalloc(sizeof(*ns), GFP_KERNEL); 1777 if (!ns) 1778 panic("Can't allocate initial namespace"); 1779 atomic_set(&ns->count, 1); 1780 INIT_LIST_HEAD(&ns->list); 1781 init_waitqueue_head(&ns->poll); 1782 ns->event = 0; 1783 list_add(&mnt->mnt_list, &ns->list); 1784 ns->root = mnt; 1785 mnt->mnt_ns = ns; 1786 1787 init_task.nsproxy->mnt_ns = ns; 1788 get_mnt_ns(ns); 1789 1790 set_fs_pwd(current->fs, ns->root, ns->root->mnt_root); 1791 set_fs_root(current->fs, ns->root, ns->root->mnt_root); 1792 } 1793 1794 void __init mnt_init(unsigned long mempages) 1795 { 1796 struct list_head *d; 1797 unsigned int nr_hash; 1798 int i; 1799 int err; 1800 1801 init_rwsem(&namespace_sem); 1802 1803 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), 1804 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); 1805 1806 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); 1807 1808 if (!mount_hashtable) 1809 panic("Failed to allocate mount hash table\n"); 1810 1811 /* 1812 * Find the power-of-two list-heads that can fit into the allocation.. 1813 * We don't guarantee that "sizeof(struct list_head)" is necessarily 1814 * a power-of-two. 1815 */ 1816 nr_hash = PAGE_SIZE / sizeof(struct list_head); 1817 hash_bits = 0; 1818 do { 1819 hash_bits++; 1820 } while ((nr_hash >> hash_bits) != 0); 1821 hash_bits--; 1822 1823 /* 1824 * Re-calculate the actual number of entries and the mask 1825 * from the number of bits we can fit. 1826 */ 1827 nr_hash = 1UL << hash_bits; 1828 hash_mask = nr_hash - 1; 1829 1830 printk("Mount-cache hash table entries: %d\n", nr_hash); 1831 1832 /* And initialize the newly allocated array */ 1833 d = mount_hashtable; 1834 i = nr_hash; 1835 do { 1836 INIT_LIST_HEAD(d); 1837 d++; 1838 i--; 1839 } while (i); 1840 err = sysfs_init(); 1841 if (err) 1842 printk(KERN_WARNING "%s: sysfs_init error: %d\n", 1843 __FUNCTION__, err); 1844 err = subsystem_register(&fs_subsys); 1845 if (err) 1846 printk(KERN_WARNING "%s: subsystem_register error: %d\n", 1847 __FUNCTION__, err); 1848 init_rootfs(); 1849 init_mount_tree(); 1850 } 1851 1852 void __put_mnt_ns(struct mnt_namespace *ns) 1853 { 1854 struct vfsmount *root = ns->root; 1855 LIST_HEAD(umount_list); 1856 ns->root = NULL; 1857 spin_unlock(&vfsmount_lock); 1858 down_write(&namespace_sem); 1859 spin_lock(&vfsmount_lock); 1860 umount_tree(root, 0, &umount_list); 1861 spin_unlock(&vfsmount_lock); 1862 up_write(&namespace_sem); 1863 release_mounts(&umount_list); 1864 kfree(ns); 1865 } 1866