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1da177e4 LT |
1 | /* |
2 | * linux/fs/namespace.c | |
3 | * | |
4 | * (C) Copyright Al Viro 2000, 2001 | |
5 | * Released under GPL v2. | |
6 | * | |
7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. | |
8 | * Heavily rewritten. | |
9 | */ | |
10 | ||
11 | #include <linux/config.h> | |
12 | #include <linux/syscalls.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/sched.h> | |
15 | #include <linux/smp_lock.h> | |
16 | #include <linux/init.h> | |
17 | #include <linux/quotaops.h> | |
18 | #include <linux/acct.h> | |
19 | #include <linux/module.h> | |
20 | #include <linux/seq_file.h> | |
21 | #include <linux/namespace.h> | |
22 | #include <linux/namei.h> | |
23 | #include <linux/security.h> | |
24 | #include <linux/mount.h> | |
25 | #include <asm/uaccess.h> | |
26 | #include <asm/unistd.h> | |
27 | ||
28 | extern int __init init_rootfs(void); | |
29 | ||
30 | #ifdef CONFIG_SYSFS | |
31 | extern int __init sysfs_init(void); | |
32 | #else | |
33 | static inline int sysfs_init(void) | |
34 | { | |
35 | return 0; | |
36 | } | |
37 | #endif | |
38 | ||
39 | /* spinlock for vfsmount related operations, inplace of dcache_lock */ | |
40 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); | |
41 | ||
42 | static struct list_head *mount_hashtable; | |
43 | static int hash_mask, hash_bits; | |
44 | static kmem_cache_t *mnt_cache; | |
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_fslink); | |
65 | if (name) { | |
66 | int size = strlen(name)+1; | |
67 | char *newname = kmalloc(size, GFP_KERNEL); | |
68 | if (newname) { | |
69 | memcpy(newname, name, size); | |
70 | mnt->mnt_devname = newname; | |
71 | } | |
72 | } | |
73 | } | |
74 | return mnt; | |
75 | } | |
76 | ||
77 | void free_vfsmnt(struct vfsmount *mnt) | |
78 | { | |
79 | kfree(mnt->mnt_devname); | |
80 | kmem_cache_free(mnt_cache, mnt); | |
81 | } | |
82 | ||
83 | /* | |
84 | * Now, lookup_mnt increments the ref count before returning | |
85 | * the vfsmount struct. | |
86 | */ | |
87 | struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) | |
88 | { | |
89 | struct list_head * head = mount_hashtable + hash(mnt, dentry); | |
90 | struct list_head * tmp = head; | |
91 | struct vfsmount *p, *found = NULL; | |
92 | ||
93 | spin_lock(&vfsmount_lock); | |
94 | for (;;) { | |
95 | tmp = tmp->next; | |
96 | p = NULL; | |
97 | if (tmp == head) | |
98 | break; | |
99 | p = list_entry(tmp, struct vfsmount, mnt_hash); | |
100 | if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { | |
101 | found = mntget(p); | |
102 | break; | |
103 | } | |
104 | } | |
105 | spin_unlock(&vfsmount_lock); | |
106 | return found; | |
107 | } | |
108 | ||
109 | static inline int check_mnt(struct vfsmount *mnt) | |
110 | { | |
111 | return mnt->mnt_namespace == current->namespace; | |
112 | } | |
113 | ||
114 | static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd) | |
115 | { | |
116 | old_nd->dentry = mnt->mnt_mountpoint; | |
117 | old_nd->mnt = mnt->mnt_parent; | |
118 | mnt->mnt_parent = mnt; | |
119 | mnt->mnt_mountpoint = mnt->mnt_root; | |
120 | list_del_init(&mnt->mnt_child); | |
121 | list_del_init(&mnt->mnt_hash); | |
122 | old_nd->dentry->d_mounted--; | |
123 | } | |
124 | ||
125 | static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd) | |
126 | { | |
127 | mnt->mnt_parent = mntget(nd->mnt); | |
128 | mnt->mnt_mountpoint = dget(nd->dentry); | |
129 | list_add(&mnt->mnt_hash, mount_hashtable+hash(nd->mnt, nd->dentry)); | |
130 | list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts); | |
131 | nd->dentry->d_mounted++; | |
132 | } | |
133 | ||
134 | static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) | |
135 | { | |
136 | struct list_head *next = p->mnt_mounts.next; | |
137 | if (next == &p->mnt_mounts) { | |
138 | while (1) { | |
139 | if (p == root) | |
140 | return NULL; | |
141 | next = p->mnt_child.next; | |
142 | if (next != &p->mnt_parent->mnt_mounts) | |
143 | break; | |
144 | p = p->mnt_parent; | |
145 | } | |
146 | } | |
147 | return list_entry(next, struct vfsmount, mnt_child); | |
148 | } | |
149 | ||
150 | static struct vfsmount * | |
151 | clone_mnt(struct vfsmount *old, struct dentry *root) | |
152 | { | |
153 | struct super_block *sb = old->mnt_sb; | |
154 | struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); | |
155 | ||
156 | if (mnt) { | |
157 | mnt->mnt_flags = old->mnt_flags; | |
158 | atomic_inc(&sb->s_active); | |
159 | mnt->mnt_sb = sb; | |
160 | mnt->mnt_root = dget(root); | |
161 | mnt->mnt_mountpoint = mnt->mnt_root; | |
162 | mnt->mnt_parent = mnt; | |
163 | mnt->mnt_namespace = old->mnt_namespace; | |
164 | ||
165 | /* stick the duplicate mount on the same expiry list | |
166 | * as the original if that was on one */ | |
167 | spin_lock(&vfsmount_lock); | |
168 | if (!list_empty(&old->mnt_fslink)) | |
169 | list_add(&mnt->mnt_fslink, &old->mnt_fslink); | |
170 | spin_unlock(&vfsmount_lock); | |
171 | } | |
172 | return mnt; | |
173 | } | |
174 | ||
175 | void __mntput(struct vfsmount *mnt) | |
176 | { | |
177 | struct super_block *sb = mnt->mnt_sb; | |
178 | dput(mnt->mnt_root); | |
179 | free_vfsmnt(mnt); | |
180 | deactivate_super(sb); | |
181 | } | |
182 | ||
183 | EXPORT_SYMBOL(__mntput); | |
184 | ||
185 | /* iterator */ | |
186 | static void *m_start(struct seq_file *m, loff_t *pos) | |
187 | { | |
188 | struct namespace *n = m->private; | |
189 | struct list_head *p; | |
190 | loff_t l = *pos; | |
191 | ||
192 | down_read(&n->sem); | |
193 | list_for_each(p, &n->list) | |
194 | if (!l--) | |
195 | return list_entry(p, struct vfsmount, mnt_list); | |
196 | return NULL; | |
197 | } | |
198 | ||
199 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
200 | { | |
201 | struct namespace *n = m->private; | |
202 | struct list_head *p = ((struct vfsmount *)v)->mnt_list.next; | |
203 | (*pos)++; | |
204 | return p==&n->list ? NULL : list_entry(p, struct vfsmount, mnt_list); | |
205 | } | |
206 | ||
207 | static void m_stop(struct seq_file *m, void *v) | |
208 | { | |
209 | struct namespace *n = m->private; | |
210 | up_read(&n->sem); | |
211 | } | |
212 | ||
213 | static inline void mangle(struct seq_file *m, const char *s) | |
214 | { | |
215 | seq_escape(m, s, " \t\n\\"); | |
216 | } | |
217 | ||
218 | static int show_vfsmnt(struct seq_file *m, void *v) | |
219 | { | |
220 | struct vfsmount *mnt = v; | |
221 | int err = 0; | |
222 | static struct proc_fs_info { | |
223 | int flag; | |
224 | char *str; | |
225 | } fs_info[] = { | |
226 | { MS_SYNCHRONOUS, ",sync" }, | |
227 | { MS_DIRSYNC, ",dirsync" }, | |
228 | { MS_MANDLOCK, ",mand" }, | |
229 | { MS_NOATIME, ",noatime" }, | |
230 | { MS_NODIRATIME, ",nodiratime" }, | |
231 | { 0, NULL } | |
232 | }; | |
233 | static struct proc_fs_info mnt_info[] = { | |
234 | { MNT_NOSUID, ",nosuid" }, | |
235 | { MNT_NODEV, ",nodev" }, | |
236 | { MNT_NOEXEC, ",noexec" }, | |
237 | { 0, NULL } | |
238 | }; | |
239 | struct proc_fs_info *fs_infop; | |
240 | ||
241 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); | |
242 | seq_putc(m, ' '); | |
243 | seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); | |
244 | seq_putc(m, ' '); | |
245 | mangle(m, mnt->mnt_sb->s_type->name); | |
246 | seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); | |
247 | for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { | |
248 | if (mnt->mnt_sb->s_flags & fs_infop->flag) | |
249 | seq_puts(m, fs_infop->str); | |
250 | } | |
251 | for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { | |
252 | if (mnt->mnt_flags & fs_infop->flag) | |
253 | seq_puts(m, fs_infop->str); | |
254 | } | |
255 | if (mnt->mnt_sb->s_op->show_options) | |
256 | err = mnt->mnt_sb->s_op->show_options(m, mnt); | |
257 | seq_puts(m, " 0 0\n"); | |
258 | return err; | |
259 | } | |
260 | ||
261 | struct seq_operations mounts_op = { | |
262 | .start = m_start, | |
263 | .next = m_next, | |
264 | .stop = m_stop, | |
265 | .show = show_vfsmnt | |
266 | }; | |
267 | ||
268 | /** | |
269 | * may_umount_tree - check if a mount tree is busy | |
270 | * @mnt: root of mount tree | |
271 | * | |
272 | * This is called to check if a tree of mounts has any | |
273 | * open files, pwds, chroots or sub mounts that are | |
274 | * busy. | |
275 | */ | |
276 | int may_umount_tree(struct vfsmount *mnt) | |
277 | { | |
278 | struct list_head *next; | |
279 | struct vfsmount *this_parent = mnt; | |
280 | int actual_refs; | |
281 | int minimum_refs; | |
282 | ||
283 | spin_lock(&vfsmount_lock); | |
284 | actual_refs = atomic_read(&mnt->mnt_count); | |
285 | minimum_refs = 2; | |
286 | repeat: | |
287 | next = this_parent->mnt_mounts.next; | |
288 | resume: | |
289 | while (next != &this_parent->mnt_mounts) { | |
290 | struct vfsmount *p = list_entry(next, struct vfsmount, mnt_child); | |
291 | ||
292 | next = next->next; | |
293 | ||
294 | actual_refs += atomic_read(&p->mnt_count); | |
295 | minimum_refs += 2; | |
296 | ||
297 | if (!list_empty(&p->mnt_mounts)) { | |
298 | this_parent = p; | |
299 | goto repeat; | |
300 | } | |
301 | } | |
302 | ||
303 | if (this_parent != mnt) { | |
304 | next = this_parent->mnt_child.next; | |
305 | this_parent = this_parent->mnt_parent; | |
306 | goto resume; | |
307 | } | |
308 | spin_unlock(&vfsmount_lock); | |
309 | ||
310 | if (actual_refs > minimum_refs) | |
311 | return -EBUSY; | |
312 | ||
313 | return 0; | |
314 | } | |
315 | ||
316 | EXPORT_SYMBOL(may_umount_tree); | |
317 | ||
318 | /** | |
319 | * may_umount - check if a mount point is busy | |
320 | * @mnt: root of mount | |
321 | * | |
322 | * This is called to check if a mount point has any | |
323 | * open files, pwds, chroots or sub mounts. If the | |
324 | * mount has sub mounts this will return busy | |
325 | * regardless of whether the sub mounts are busy. | |
326 | * | |
327 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
328 | * give false negatives. The main reason why it's here is that we need | |
329 | * a non-destructive way to look for easily umountable filesystems. | |
330 | */ | |
331 | int may_umount(struct vfsmount *mnt) | |
332 | { | |
333 | if (atomic_read(&mnt->mnt_count) > 2) | |
334 | return -EBUSY; | |
335 | return 0; | |
336 | } | |
337 | ||
338 | EXPORT_SYMBOL(may_umount); | |
339 | ||
340 | void umount_tree(struct vfsmount *mnt) | |
341 | { | |
342 | struct vfsmount *p; | |
343 | LIST_HEAD(kill); | |
344 | ||
345 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
346 | list_del(&p->mnt_list); | |
347 | list_add(&p->mnt_list, &kill); | |
348 | } | |
349 | ||
350 | while (!list_empty(&kill)) { | |
351 | mnt = list_entry(kill.next, struct vfsmount, mnt_list); | |
352 | list_del_init(&mnt->mnt_list); | |
353 | list_del_init(&mnt->mnt_fslink); | |
354 | if (mnt->mnt_parent == mnt) { | |
355 | spin_unlock(&vfsmount_lock); | |
356 | } else { | |
357 | struct nameidata old_nd; | |
358 | detach_mnt(mnt, &old_nd); | |
359 | spin_unlock(&vfsmount_lock); | |
360 | path_release(&old_nd); | |
361 | } | |
362 | mntput(mnt); | |
363 | spin_lock(&vfsmount_lock); | |
364 | } | |
365 | } | |
366 | ||
367 | static int do_umount(struct vfsmount *mnt, int flags) | |
368 | { | |
369 | struct super_block * sb = mnt->mnt_sb; | |
370 | int retval; | |
371 | ||
372 | retval = security_sb_umount(mnt, flags); | |
373 | if (retval) | |
374 | return retval; | |
375 | ||
376 | /* | |
377 | * Allow userspace to request a mountpoint be expired rather than | |
378 | * unmounting unconditionally. Unmount only happens if: | |
379 | * (1) the mark is already set (the mark is cleared by mntput()) | |
380 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
381 | */ | |
382 | if (flags & MNT_EXPIRE) { | |
383 | if (mnt == current->fs->rootmnt || | |
384 | flags & (MNT_FORCE | MNT_DETACH)) | |
385 | return -EINVAL; | |
386 | ||
387 | if (atomic_read(&mnt->mnt_count) != 2) | |
388 | return -EBUSY; | |
389 | ||
390 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
391 | return -EAGAIN; | |
392 | } | |
393 | ||
394 | /* | |
395 | * If we may have to abort operations to get out of this | |
396 | * mount, and they will themselves hold resources we must | |
397 | * allow the fs to do things. In the Unix tradition of | |
398 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
399 | * might fail to complete on the first run through as other tasks | |
400 | * must return, and the like. Thats for the mount program to worry | |
401 | * about for the moment. | |
402 | */ | |
403 | ||
404 | lock_kernel(); | |
405 | if( (flags&MNT_FORCE) && sb->s_op->umount_begin) | |
406 | sb->s_op->umount_begin(sb); | |
407 | unlock_kernel(); | |
408 | ||
409 | /* | |
410 | * No sense to grab the lock for this test, but test itself looks | |
411 | * somewhat bogus. Suggestions for better replacement? | |
412 | * Ho-hum... In principle, we might treat that as umount + switch | |
413 | * to rootfs. GC would eventually take care of the old vfsmount. | |
414 | * Actually it makes sense, especially if rootfs would contain a | |
415 | * /reboot - static binary that would close all descriptors and | |
416 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
417 | */ | |
418 | if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { | |
419 | /* | |
420 | * Special case for "unmounting" root ... | |
421 | * we just try to remount it readonly. | |
422 | */ | |
423 | down_write(&sb->s_umount); | |
424 | if (!(sb->s_flags & MS_RDONLY)) { | |
425 | lock_kernel(); | |
426 | DQUOT_OFF(sb); | |
427 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); | |
428 | unlock_kernel(); | |
429 | } | |
430 | up_write(&sb->s_umount); | |
431 | return retval; | |
432 | } | |
433 | ||
434 | down_write(¤t->namespace->sem); | |
435 | spin_lock(&vfsmount_lock); | |
436 | ||
437 | if (atomic_read(&sb->s_active) == 1) { | |
438 | /* last instance - try to be smart */ | |
439 | spin_unlock(&vfsmount_lock); | |
440 | lock_kernel(); | |
441 | DQUOT_OFF(sb); | |
442 | acct_auto_close(sb); | |
443 | unlock_kernel(); | |
444 | security_sb_umount_close(mnt); | |
445 | spin_lock(&vfsmount_lock); | |
446 | } | |
447 | retval = -EBUSY; | |
448 | if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) { | |
449 | if (!list_empty(&mnt->mnt_list)) | |
450 | umount_tree(mnt); | |
451 | retval = 0; | |
452 | } | |
453 | spin_unlock(&vfsmount_lock); | |
454 | if (retval) | |
455 | security_sb_umount_busy(mnt); | |
456 | up_write(¤t->namespace->sem); | |
457 | return retval; | |
458 | } | |
459 | ||
460 | /* | |
461 | * Now umount can handle mount points as well as block devices. | |
462 | * This is important for filesystems which use unnamed block devices. | |
463 | * | |
464 | * We now support a flag for forced unmount like the other 'big iron' | |
465 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
466 | */ | |
467 | ||
468 | asmlinkage long sys_umount(char __user * name, int flags) | |
469 | { | |
470 | struct nameidata nd; | |
471 | int retval; | |
472 | ||
473 | retval = __user_walk(name, LOOKUP_FOLLOW, &nd); | |
474 | if (retval) | |
475 | goto out; | |
476 | retval = -EINVAL; | |
477 | if (nd.dentry != nd.mnt->mnt_root) | |
478 | goto dput_and_out; | |
479 | if (!check_mnt(nd.mnt)) | |
480 | goto dput_and_out; | |
481 | ||
482 | retval = -EPERM; | |
483 | if (!capable(CAP_SYS_ADMIN)) | |
484 | goto dput_and_out; | |
485 | ||
486 | retval = do_umount(nd.mnt, flags); | |
487 | dput_and_out: | |
488 | path_release_on_umount(&nd); | |
489 | out: | |
490 | return retval; | |
491 | } | |
492 | ||
493 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
494 | ||
495 | /* | |
496 | * The 2.0 compatible umount. No flags. | |
497 | */ | |
498 | ||
499 | asmlinkage long sys_oldumount(char __user * name) | |
500 | { | |
501 | return sys_umount(name,0); | |
502 | } | |
503 | ||
504 | #endif | |
505 | ||
506 | static int mount_is_safe(struct nameidata *nd) | |
507 | { | |
508 | if (capable(CAP_SYS_ADMIN)) | |
509 | return 0; | |
510 | return -EPERM; | |
511 | #ifdef notyet | |
512 | if (S_ISLNK(nd->dentry->d_inode->i_mode)) | |
513 | return -EPERM; | |
514 | if (nd->dentry->d_inode->i_mode & S_ISVTX) { | |
515 | if (current->uid != nd->dentry->d_inode->i_uid) | |
516 | return -EPERM; | |
517 | } | |
518 | if (permission(nd->dentry->d_inode, MAY_WRITE, nd)) | |
519 | return -EPERM; | |
520 | return 0; | |
521 | #endif | |
522 | } | |
523 | ||
524 | static int | |
525 | lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) | |
526 | { | |
527 | while (1) { | |
528 | if (d == dentry) | |
529 | return 1; | |
530 | if (d == NULL || d == d->d_parent) | |
531 | return 0; | |
532 | d = d->d_parent; | |
533 | } | |
534 | } | |
535 | ||
536 | static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry) | |
537 | { | |
538 | struct vfsmount *res, *p, *q, *r, *s; | |
539 | struct list_head *h; | |
540 | struct nameidata nd; | |
541 | ||
542 | res = q = clone_mnt(mnt, dentry); | |
543 | if (!q) | |
544 | goto Enomem; | |
545 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
546 | ||
547 | p = mnt; | |
548 | for (h = mnt->mnt_mounts.next; h != &mnt->mnt_mounts; h = h->next) { | |
549 | r = list_entry(h, struct vfsmount, mnt_child); | |
550 | if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) | |
551 | continue; | |
552 | ||
553 | for (s = r; s; s = next_mnt(s, r)) { | |
554 | while (p != s->mnt_parent) { | |
555 | p = p->mnt_parent; | |
556 | q = q->mnt_parent; | |
557 | } | |
558 | p = s; | |
559 | nd.mnt = q; | |
560 | nd.dentry = p->mnt_mountpoint; | |
561 | q = clone_mnt(p, p->mnt_root); | |
562 | if (!q) | |
563 | goto Enomem; | |
564 | spin_lock(&vfsmount_lock); | |
565 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
566 | attach_mnt(q, &nd); | |
567 | spin_unlock(&vfsmount_lock); | |
568 | } | |
569 | } | |
570 | return res; | |
571 | Enomem: | |
572 | if (res) { | |
573 | spin_lock(&vfsmount_lock); | |
574 | umount_tree(res); | |
575 | spin_unlock(&vfsmount_lock); | |
576 | } | |
577 | return NULL; | |
578 | } | |
579 | ||
580 | static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) | |
581 | { | |
582 | int err; | |
583 | if (mnt->mnt_sb->s_flags & MS_NOUSER) | |
584 | return -EINVAL; | |
585 | ||
586 | if (S_ISDIR(nd->dentry->d_inode->i_mode) != | |
587 | S_ISDIR(mnt->mnt_root->d_inode->i_mode)) | |
588 | return -ENOTDIR; | |
589 | ||
590 | err = -ENOENT; | |
591 | down(&nd->dentry->d_inode->i_sem); | |
592 | if (IS_DEADDIR(nd->dentry->d_inode)) | |
593 | goto out_unlock; | |
594 | ||
595 | err = security_sb_check_sb(mnt, nd); | |
596 | if (err) | |
597 | goto out_unlock; | |
598 | ||
599 | err = -ENOENT; | |
600 | spin_lock(&vfsmount_lock); | |
601 | if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) { | |
602 | struct list_head head; | |
603 | ||
604 | attach_mnt(mnt, nd); | |
605 | list_add_tail(&head, &mnt->mnt_list); | |
606 | list_splice(&head, current->namespace->list.prev); | |
607 | mntget(mnt); | |
608 | err = 0; | |
609 | } | |
610 | spin_unlock(&vfsmount_lock); | |
611 | out_unlock: | |
612 | up(&nd->dentry->d_inode->i_sem); | |
613 | if (!err) | |
614 | security_sb_post_addmount(mnt, nd); | |
615 | return err; | |
616 | } | |
617 | ||
618 | /* | |
619 | * do loopback mount. | |
620 | */ | |
621 | static int do_loopback(struct nameidata *nd, char *old_name, int recurse) | |
622 | { | |
623 | struct nameidata old_nd; | |
624 | struct vfsmount *mnt = NULL; | |
625 | int err = mount_is_safe(nd); | |
626 | if (err) | |
627 | return err; | |
628 | if (!old_name || !*old_name) | |
629 | return -EINVAL; | |
630 | err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); | |
631 | if (err) | |
632 | return err; | |
633 | ||
634 | down_write(¤t->namespace->sem); | |
635 | err = -EINVAL; | |
636 | if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd.mnt))) { | |
637 | err = -ENOMEM; | |
638 | if (recurse) | |
639 | mnt = copy_tree(old_nd.mnt, old_nd.dentry); | |
640 | else | |
641 | mnt = clone_mnt(old_nd.mnt, old_nd.dentry); | |
642 | } | |
643 | ||
644 | if (mnt) { | |
645 | /* stop bind mounts from expiring */ | |
646 | spin_lock(&vfsmount_lock); | |
647 | list_del_init(&mnt->mnt_fslink); | |
648 | spin_unlock(&vfsmount_lock); | |
649 | ||
650 | err = graft_tree(mnt, nd); | |
651 | if (err) { | |
652 | spin_lock(&vfsmount_lock); | |
653 | umount_tree(mnt); | |
654 | spin_unlock(&vfsmount_lock); | |
655 | } else | |
656 | mntput(mnt); | |
657 | } | |
658 | ||
659 | up_write(¤t->namespace->sem); | |
660 | path_release(&old_nd); | |
661 | return err; | |
662 | } | |
663 | ||
664 | /* | |
665 | * change filesystem flags. dir should be a physical root of filesystem. | |
666 | * If you've mounted a non-root directory somewhere and want to do remount | |
667 | * on it - tough luck. | |
668 | */ | |
669 | ||
670 | static int do_remount(struct nameidata *nd, int flags, int mnt_flags, | |
671 | void *data) | |
672 | { | |
673 | int err; | |
674 | struct super_block * sb = nd->mnt->mnt_sb; | |
675 | ||
676 | if (!capable(CAP_SYS_ADMIN)) | |
677 | return -EPERM; | |
678 | ||
679 | if (!check_mnt(nd->mnt)) | |
680 | return -EINVAL; | |
681 | ||
682 | if (nd->dentry != nd->mnt->mnt_root) | |
683 | return -EINVAL; | |
684 | ||
685 | down_write(&sb->s_umount); | |
686 | err = do_remount_sb(sb, flags, data, 0); | |
687 | if (!err) | |
688 | nd->mnt->mnt_flags=mnt_flags; | |
689 | up_write(&sb->s_umount); | |
690 | if (!err) | |
691 | security_sb_post_remount(nd->mnt, flags, data); | |
692 | return err; | |
693 | } | |
694 | ||
695 | static int do_move_mount(struct nameidata *nd, char *old_name) | |
696 | { | |
697 | struct nameidata old_nd, parent_nd; | |
698 | struct vfsmount *p; | |
699 | int err = 0; | |
700 | if (!capable(CAP_SYS_ADMIN)) | |
701 | return -EPERM; | |
702 | if (!old_name || !*old_name) | |
703 | return -EINVAL; | |
704 | err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); | |
705 | if (err) | |
706 | return err; | |
707 | ||
708 | down_write(¤t->namespace->sem); | |
709 | while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) | |
710 | ; | |
711 | err = -EINVAL; | |
712 | if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) | |
713 | goto out; | |
714 | ||
715 | err = -ENOENT; | |
716 | down(&nd->dentry->d_inode->i_sem); | |
717 | if (IS_DEADDIR(nd->dentry->d_inode)) | |
718 | goto out1; | |
719 | ||
720 | spin_lock(&vfsmount_lock); | |
721 | if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) | |
722 | goto out2; | |
723 | ||
724 | err = -EINVAL; | |
725 | if (old_nd.dentry != old_nd.mnt->mnt_root) | |
726 | goto out2; | |
727 | ||
728 | if (old_nd.mnt == old_nd.mnt->mnt_parent) | |
729 | goto out2; | |
730 | ||
731 | if (S_ISDIR(nd->dentry->d_inode->i_mode) != | |
732 | S_ISDIR(old_nd.dentry->d_inode->i_mode)) | |
733 | goto out2; | |
734 | ||
735 | err = -ELOOP; | |
736 | for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent) | |
737 | if (p == old_nd.mnt) | |
738 | goto out2; | |
739 | err = 0; | |
740 | ||
741 | detach_mnt(old_nd.mnt, &parent_nd); | |
742 | attach_mnt(old_nd.mnt, nd); | |
743 | ||
744 | /* if the mount is moved, it should no longer be expire | |
745 | * automatically */ | |
746 | list_del_init(&old_nd.mnt->mnt_fslink); | |
747 | out2: | |
748 | spin_unlock(&vfsmount_lock); | |
749 | out1: | |
750 | up(&nd->dentry->d_inode->i_sem); | |
751 | out: | |
752 | up_write(¤t->namespace->sem); | |
753 | if (!err) | |
754 | path_release(&parent_nd); | |
755 | path_release(&old_nd); | |
756 | return err; | |
757 | } | |
758 | ||
759 | /* | |
760 | * create a new mount for userspace and request it to be added into the | |
761 | * namespace's tree | |
762 | */ | |
763 | static int do_new_mount(struct nameidata *nd, char *type, int flags, | |
764 | int mnt_flags, char *name, void *data) | |
765 | { | |
766 | struct vfsmount *mnt; | |
767 | ||
768 | if (!type || !memchr(type, 0, PAGE_SIZE)) | |
769 | return -EINVAL; | |
770 | ||
771 | /* we need capabilities... */ | |
772 | if (!capable(CAP_SYS_ADMIN)) | |
773 | return -EPERM; | |
774 | ||
775 | mnt = do_kern_mount(type, flags, name, data); | |
776 | if (IS_ERR(mnt)) | |
777 | return PTR_ERR(mnt); | |
778 | ||
779 | return do_add_mount(mnt, nd, mnt_flags, NULL); | |
780 | } | |
781 | ||
782 | /* | |
783 | * add a mount into a namespace's mount tree | |
784 | * - provide the option of adding the new mount to an expiration list | |
785 | */ | |
786 | int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, | |
787 | int mnt_flags, struct list_head *fslist) | |
788 | { | |
789 | int err; | |
790 | ||
791 | down_write(¤t->namespace->sem); | |
792 | /* Something was mounted here while we slept */ | |
793 | while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) | |
794 | ; | |
795 | err = -EINVAL; | |
796 | if (!check_mnt(nd->mnt)) | |
797 | goto unlock; | |
798 | ||
799 | /* Refuse the same filesystem on the same mount point */ | |
800 | err = -EBUSY; | |
801 | if (nd->mnt->mnt_sb == newmnt->mnt_sb && | |
802 | nd->mnt->mnt_root == nd->dentry) | |
803 | goto unlock; | |
804 | ||
805 | err = -EINVAL; | |
806 | if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) | |
807 | goto unlock; | |
808 | ||
809 | newmnt->mnt_flags = mnt_flags; | |
810 | err = graft_tree(newmnt, nd); | |
811 | ||
812 | if (err == 0 && fslist) { | |
813 | /* add to the specified expiration list */ | |
814 | spin_lock(&vfsmount_lock); | |
815 | list_add_tail(&newmnt->mnt_fslink, fslist); | |
816 | spin_unlock(&vfsmount_lock); | |
817 | } | |
818 | ||
819 | unlock: | |
820 | up_write(¤t->namespace->sem); | |
821 | mntput(newmnt); | |
822 | return err; | |
823 | } | |
824 | ||
825 | EXPORT_SYMBOL_GPL(do_add_mount); | |
826 | ||
827 | /* | |
828 | * process a list of expirable mountpoints with the intent of discarding any | |
829 | * mountpoints that aren't in use and haven't been touched since last we came | |
830 | * here | |
831 | */ | |
832 | void mark_mounts_for_expiry(struct list_head *mounts) | |
833 | { | |
834 | struct namespace *namespace; | |
835 | struct vfsmount *mnt, *next; | |
836 | LIST_HEAD(graveyard); | |
837 | ||
838 | if (list_empty(mounts)) | |
839 | return; | |
840 | ||
841 | spin_lock(&vfsmount_lock); | |
842 | ||
843 | /* extract from the expiration list every vfsmount that matches the | |
844 | * following criteria: | |
845 | * - only referenced by its parent vfsmount | |
846 | * - still marked for expiry (marked on the last call here; marks are | |
847 | * cleared by mntput()) | |
848 | */ | |
849 | list_for_each_entry_safe(mnt, next, mounts, mnt_fslink) { | |
850 | if (!xchg(&mnt->mnt_expiry_mark, 1) || | |
851 | atomic_read(&mnt->mnt_count) != 1) | |
852 | continue; | |
853 | ||
854 | mntget(mnt); | |
855 | list_move(&mnt->mnt_fslink, &graveyard); | |
856 | } | |
857 | ||
858 | /* | |
859 | * go through the vfsmounts we've just consigned to the graveyard to | |
860 | * - check that they're still dead | |
861 | * - delete the vfsmount from the appropriate namespace under lock | |
862 | * - dispose of the corpse | |
863 | */ | |
864 | while (!list_empty(&graveyard)) { | |
865 | mnt = list_entry(graveyard.next, struct vfsmount, mnt_fslink); | |
866 | list_del_init(&mnt->mnt_fslink); | |
867 | ||
868 | /* don't do anything if the namespace is dead - all the | |
869 | * vfsmounts from it are going away anyway */ | |
870 | namespace = mnt->mnt_namespace; | |
871 | if (!namespace || atomic_read(&namespace->count) <= 0) | |
872 | continue; | |
873 | get_namespace(namespace); | |
874 | ||
875 | spin_unlock(&vfsmount_lock); | |
876 | down_write(&namespace->sem); | |
877 | spin_lock(&vfsmount_lock); | |
878 | ||
879 | /* check that it is still dead: the count should now be 2 - as | |
880 | * contributed by the vfsmount parent and the mntget above */ | |
881 | if (atomic_read(&mnt->mnt_count) == 2) { | |
882 | struct vfsmount *xdmnt; | |
883 | struct dentry *xdentry; | |
884 | ||
885 | /* delete from the namespace */ | |
886 | list_del_init(&mnt->mnt_list); | |
887 | list_del_init(&mnt->mnt_child); | |
888 | list_del_init(&mnt->mnt_hash); | |
889 | mnt->mnt_mountpoint->d_mounted--; | |
890 | ||
891 | xdentry = mnt->mnt_mountpoint; | |
892 | mnt->mnt_mountpoint = mnt->mnt_root; | |
893 | xdmnt = mnt->mnt_parent; | |
894 | mnt->mnt_parent = mnt; | |
895 | ||
896 | spin_unlock(&vfsmount_lock); | |
897 | ||
898 | mntput(xdmnt); | |
899 | dput(xdentry); | |
900 | ||
901 | /* now lay it to rest if this was the last ref on the | |
902 | * superblock */ | |
903 | if (atomic_read(&mnt->mnt_sb->s_active) == 1) { | |
904 | /* last instance - try to be smart */ | |
905 | lock_kernel(); | |
906 | DQUOT_OFF(mnt->mnt_sb); | |
907 | acct_auto_close(mnt->mnt_sb); | |
908 | unlock_kernel(); | |
909 | } | |
910 | ||
911 | mntput(mnt); | |
912 | } else { | |
913 | /* someone brought it back to life whilst we didn't | |
914 | * have any locks held so return it to the expiration | |
915 | * list */ | |
916 | list_add_tail(&mnt->mnt_fslink, mounts); | |
917 | spin_unlock(&vfsmount_lock); | |
918 | } | |
919 | ||
920 | up_write(&namespace->sem); | |
921 | ||
922 | mntput(mnt); | |
923 | put_namespace(namespace); | |
924 | ||
925 | spin_lock(&vfsmount_lock); | |
926 | } | |
927 | ||
928 | spin_unlock(&vfsmount_lock); | |
929 | } | |
930 | ||
931 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
932 | ||
933 | /* | |
934 | * Some copy_from_user() implementations do not return the exact number of | |
935 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
936 | * Note that this function differs from copy_from_user() in that it will oops | |
937 | * on bad values of `to', rather than returning a short copy. | |
938 | */ | |
939 | static long | |
940 | exact_copy_from_user(void *to, const void __user *from, unsigned long n) | |
941 | { | |
942 | char *t = to; | |
943 | const char __user *f = from; | |
944 | char c; | |
945 | ||
946 | if (!access_ok(VERIFY_READ, from, n)) | |
947 | return n; | |
948 | ||
949 | while (n) { | |
950 | if (__get_user(c, f)) { | |
951 | memset(t, 0, n); | |
952 | break; | |
953 | } | |
954 | *t++ = c; | |
955 | f++; | |
956 | n--; | |
957 | } | |
958 | return n; | |
959 | } | |
960 | ||
961 | int copy_mount_options(const void __user *data, unsigned long *where) | |
962 | { | |
963 | int i; | |
964 | unsigned long page; | |
965 | unsigned long size; | |
966 | ||
967 | *where = 0; | |
968 | if (!data) | |
969 | return 0; | |
970 | ||
971 | if (!(page = __get_free_page(GFP_KERNEL))) | |
972 | return -ENOMEM; | |
973 | ||
974 | /* We only care that *some* data at the address the user | |
975 | * gave us is valid. Just in case, we'll zero | |
976 | * the remainder of the page. | |
977 | */ | |
978 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
979 | size = TASK_SIZE - (unsigned long)data; | |
980 | if (size > PAGE_SIZE) | |
981 | size = PAGE_SIZE; | |
982 | ||
983 | i = size - exact_copy_from_user((void *)page, data, size); | |
984 | if (!i) { | |
985 | free_page(page); | |
986 | return -EFAULT; | |
987 | } | |
988 | if (i != PAGE_SIZE) | |
989 | memset((char *)page + i, 0, PAGE_SIZE - i); | |
990 | *where = page; | |
991 | return 0; | |
992 | } | |
993 | ||
994 | /* | |
995 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
996 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
997 | * | |
998 | * data is a (void *) that can point to any structure up to | |
999 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
1000 | * information (or be NULL). | |
1001 | * | |
1002 | * Pre-0.97 versions of mount() didn't have a flags word. | |
1003 | * When the flags word was introduced its top half was required | |
1004 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
1005 | * Therefore, if this magic number is present, it carries no information | |
1006 | * and must be discarded. | |
1007 | */ | |
1008 | long do_mount(char * dev_name, char * dir_name, char *type_page, | |
1009 | unsigned long flags, void *data_page) | |
1010 | { | |
1011 | struct nameidata nd; | |
1012 | int retval = 0; | |
1013 | int mnt_flags = 0; | |
1014 | ||
1015 | /* Discard magic */ | |
1016 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
1017 | flags &= ~MS_MGC_MSK; | |
1018 | ||
1019 | /* Basic sanity checks */ | |
1020 | ||
1021 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) | |
1022 | return -EINVAL; | |
1023 | if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) | |
1024 | return -EINVAL; | |
1025 | ||
1026 | if (data_page) | |
1027 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
1028 | ||
1029 | /* Separate the per-mountpoint flags */ | |
1030 | if (flags & MS_NOSUID) | |
1031 | mnt_flags |= MNT_NOSUID; | |
1032 | if (flags & MS_NODEV) | |
1033 | mnt_flags |= MNT_NODEV; | |
1034 | if (flags & MS_NOEXEC) | |
1035 | mnt_flags |= MNT_NOEXEC; | |
1036 | flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_ACTIVE); | |
1037 | ||
1038 | /* ... and get the mountpoint */ | |
1039 | retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); | |
1040 | if (retval) | |
1041 | return retval; | |
1042 | ||
1043 | retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); | |
1044 | if (retval) | |
1045 | goto dput_out; | |
1046 | ||
1047 | if (flags & MS_REMOUNT) | |
1048 | retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, | |
1049 | data_page); | |
1050 | else if (flags & MS_BIND) | |
1051 | retval = do_loopback(&nd, dev_name, flags & MS_REC); | |
1052 | else if (flags & MS_MOVE) | |
1053 | retval = do_move_mount(&nd, dev_name); | |
1054 | else | |
1055 | retval = do_new_mount(&nd, type_page, flags, mnt_flags, | |
1056 | dev_name, data_page); | |
1057 | dput_out: | |
1058 | path_release(&nd); | |
1059 | return retval; | |
1060 | } | |
1061 | ||
1062 | int copy_namespace(int flags, struct task_struct *tsk) | |
1063 | { | |
1064 | struct namespace *namespace = tsk->namespace; | |
1065 | struct namespace *new_ns; | |
1066 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; | |
1067 | struct fs_struct *fs = tsk->fs; | |
1068 | struct vfsmount *p, *q; | |
1069 | ||
1070 | if (!namespace) | |
1071 | return 0; | |
1072 | ||
1073 | get_namespace(namespace); | |
1074 | ||
1075 | if (!(flags & CLONE_NEWNS)) | |
1076 | return 0; | |
1077 | ||
1078 | if (!capable(CAP_SYS_ADMIN)) { | |
1079 | put_namespace(namespace); | |
1080 | return -EPERM; | |
1081 | } | |
1082 | ||
1083 | new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL); | |
1084 | if (!new_ns) | |
1085 | goto out; | |
1086 | ||
1087 | atomic_set(&new_ns->count, 1); | |
1088 | init_rwsem(&new_ns->sem); | |
1089 | INIT_LIST_HEAD(&new_ns->list); | |
1090 | ||
1091 | down_write(&tsk->namespace->sem); | |
1092 | /* First pass: copy the tree topology */ | |
1093 | new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root); | |
1094 | if (!new_ns->root) { | |
1095 | up_write(&tsk->namespace->sem); | |
1096 | kfree(new_ns); | |
1097 | goto out; | |
1098 | } | |
1099 | spin_lock(&vfsmount_lock); | |
1100 | list_add_tail(&new_ns->list, &new_ns->root->mnt_list); | |
1101 | spin_unlock(&vfsmount_lock); | |
1102 | ||
1103 | /* | |
1104 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
1105 | * as belonging to new namespace. We have already acquired a private | |
1106 | * fs_struct, so tsk->fs->lock is not needed. | |
1107 | */ | |
1108 | p = namespace->root; | |
1109 | q = new_ns->root; | |
1110 | while (p) { | |
1111 | q->mnt_namespace = new_ns; | |
1112 | if (fs) { | |
1113 | if (p == fs->rootmnt) { | |
1114 | rootmnt = p; | |
1115 | fs->rootmnt = mntget(q); | |
1116 | } | |
1117 | if (p == fs->pwdmnt) { | |
1118 | pwdmnt = p; | |
1119 | fs->pwdmnt = mntget(q); | |
1120 | } | |
1121 | if (p == fs->altrootmnt) { | |
1122 | altrootmnt = p; | |
1123 | fs->altrootmnt = mntget(q); | |
1124 | } | |
1125 | } | |
1126 | p = next_mnt(p, namespace->root); | |
1127 | q = next_mnt(q, new_ns->root); | |
1128 | } | |
1129 | up_write(&tsk->namespace->sem); | |
1130 | ||
1131 | tsk->namespace = new_ns; | |
1132 | ||
1133 | if (rootmnt) | |
1134 | mntput(rootmnt); | |
1135 | if (pwdmnt) | |
1136 | mntput(pwdmnt); | |
1137 | if (altrootmnt) | |
1138 | mntput(altrootmnt); | |
1139 | ||
1140 | put_namespace(namespace); | |
1141 | return 0; | |
1142 | ||
1143 | out: | |
1144 | put_namespace(namespace); | |
1145 | return -ENOMEM; | |
1146 | } | |
1147 | ||
1148 | asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, | |
1149 | char __user * type, unsigned long flags, | |
1150 | void __user * data) | |
1151 | { | |
1152 | int retval; | |
1153 | unsigned long data_page; | |
1154 | unsigned long type_page; | |
1155 | unsigned long dev_page; | |
1156 | char *dir_page; | |
1157 | ||
1158 | retval = copy_mount_options (type, &type_page); | |
1159 | if (retval < 0) | |
1160 | return retval; | |
1161 | ||
1162 | dir_page = getname(dir_name); | |
1163 | retval = PTR_ERR(dir_page); | |
1164 | if (IS_ERR(dir_page)) | |
1165 | goto out1; | |
1166 | ||
1167 | retval = copy_mount_options (dev_name, &dev_page); | |
1168 | if (retval < 0) | |
1169 | goto out2; | |
1170 | ||
1171 | retval = copy_mount_options (data, &data_page); | |
1172 | if (retval < 0) | |
1173 | goto out3; | |
1174 | ||
1175 | lock_kernel(); | |
1176 | retval = do_mount((char*)dev_page, dir_page, (char*)type_page, | |
1177 | flags, (void*)data_page); | |
1178 | unlock_kernel(); | |
1179 | free_page(data_page); | |
1180 | ||
1181 | out3: | |
1182 | free_page(dev_page); | |
1183 | out2: | |
1184 | putname(dir_page); | |
1185 | out1: | |
1186 | free_page(type_page); | |
1187 | return retval; | |
1188 | } | |
1189 | ||
1190 | /* | |
1191 | * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. | |
1192 | * It can block. Requires the big lock held. | |
1193 | */ | |
1194 | void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, | |
1195 | struct dentry *dentry) | |
1196 | { | |
1197 | struct dentry *old_root; | |
1198 | struct vfsmount *old_rootmnt; | |
1199 | write_lock(&fs->lock); | |
1200 | old_root = fs->root; | |
1201 | old_rootmnt = fs->rootmnt; | |
1202 | fs->rootmnt = mntget(mnt); | |
1203 | fs->root = dget(dentry); | |
1204 | write_unlock(&fs->lock); | |
1205 | if (old_root) { | |
1206 | dput(old_root); | |
1207 | mntput(old_rootmnt); | |
1208 | } | |
1209 | } | |
1210 | ||
1211 | /* | |
1212 | * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. | |
1213 | * It can block. Requires the big lock held. | |
1214 | */ | |
1215 | void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, | |
1216 | struct dentry *dentry) | |
1217 | { | |
1218 | struct dentry *old_pwd; | |
1219 | struct vfsmount *old_pwdmnt; | |
1220 | ||
1221 | write_lock(&fs->lock); | |
1222 | old_pwd = fs->pwd; | |
1223 | old_pwdmnt = fs->pwdmnt; | |
1224 | fs->pwdmnt = mntget(mnt); | |
1225 | fs->pwd = dget(dentry); | |
1226 | write_unlock(&fs->lock); | |
1227 | ||
1228 | if (old_pwd) { | |
1229 | dput(old_pwd); | |
1230 | mntput(old_pwdmnt); | |
1231 | } | |
1232 | } | |
1233 | ||
1234 | static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) | |
1235 | { | |
1236 | struct task_struct *g, *p; | |
1237 | struct fs_struct *fs; | |
1238 | ||
1239 | read_lock(&tasklist_lock); | |
1240 | do_each_thread(g, p) { | |
1241 | task_lock(p); | |
1242 | fs = p->fs; | |
1243 | if (fs) { | |
1244 | atomic_inc(&fs->count); | |
1245 | task_unlock(p); | |
1246 | if (fs->root==old_nd->dentry&&fs->rootmnt==old_nd->mnt) | |
1247 | set_fs_root(fs, new_nd->mnt, new_nd->dentry); | |
1248 | if (fs->pwd==old_nd->dentry&&fs->pwdmnt==old_nd->mnt) | |
1249 | set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); | |
1250 | put_fs_struct(fs); | |
1251 | } else | |
1252 | task_unlock(p); | |
1253 | } while_each_thread(g, p); | |
1254 | read_unlock(&tasklist_lock); | |
1255 | } | |
1256 | ||
1257 | /* | |
1258 | * pivot_root Semantics: | |
1259 | * Moves the root file system of the current process to the directory put_old, | |
1260 | * makes new_root as the new root file system of the current process, and sets | |
1261 | * root/cwd of all processes which had them on the current root to new_root. | |
1262 | * | |
1263 | * Restrictions: | |
1264 | * The new_root and put_old must be directories, and must not be on the | |
1265 | * same file system as the current process root. The put_old must be | |
1266 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
1267 | * pointed to by put_old must yield the same directory as new_root. No other | |
1268 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
1269 | * | |
1270 | * Notes: | |
1271 | * - we don't move root/cwd if they are not at the root (reason: if something | |
1272 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
1273 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
1274 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
1275 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
1276 | * first. | |
1277 | */ | |
1278 | ||
1279 | asmlinkage long sys_pivot_root(const char __user *new_root, const char __user *put_old) | |
1280 | { | |
1281 | struct vfsmount *tmp; | |
1282 | struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; | |
1283 | int error; | |
1284 | ||
1285 | if (!capable(CAP_SYS_ADMIN)) | |
1286 | return -EPERM; | |
1287 | ||
1288 | lock_kernel(); | |
1289 | ||
1290 | error = __user_walk(new_root, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &new_nd); | |
1291 | if (error) | |
1292 | goto out0; | |
1293 | error = -EINVAL; | |
1294 | if (!check_mnt(new_nd.mnt)) | |
1295 | goto out1; | |
1296 | ||
1297 | error = __user_walk(put_old, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &old_nd); | |
1298 | if (error) | |
1299 | goto out1; | |
1300 | ||
1301 | error = security_sb_pivotroot(&old_nd, &new_nd); | |
1302 | if (error) { | |
1303 | path_release(&old_nd); | |
1304 | goto out1; | |
1305 | } | |
1306 | ||
1307 | read_lock(¤t->fs->lock); | |
1308 | user_nd.mnt = mntget(current->fs->rootmnt); | |
1309 | user_nd.dentry = dget(current->fs->root); | |
1310 | read_unlock(¤t->fs->lock); | |
1311 | down_write(¤t->namespace->sem); | |
1312 | down(&old_nd.dentry->d_inode->i_sem); | |
1313 | error = -EINVAL; | |
1314 | if (!check_mnt(user_nd.mnt)) | |
1315 | goto out2; | |
1316 | error = -ENOENT; | |
1317 | if (IS_DEADDIR(new_nd.dentry->d_inode)) | |
1318 | goto out2; | |
1319 | if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) | |
1320 | goto out2; | |
1321 | if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) | |
1322 | goto out2; | |
1323 | error = -EBUSY; | |
1324 | if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) | |
1325 | goto out2; /* loop, on the same file system */ | |
1326 | error = -EINVAL; | |
1327 | if (user_nd.mnt->mnt_root != user_nd.dentry) | |
1328 | goto out2; /* not a mountpoint */ | |
1329 | if (new_nd.mnt->mnt_root != new_nd.dentry) | |
1330 | goto out2; /* not a mountpoint */ | |
1331 | tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ | |
1332 | spin_lock(&vfsmount_lock); | |
1333 | if (tmp != new_nd.mnt) { | |
1334 | for (;;) { | |
1335 | if (tmp->mnt_parent == tmp) | |
1336 | goto out3; /* already mounted on put_old */ | |
1337 | if (tmp->mnt_parent == new_nd.mnt) | |
1338 | break; | |
1339 | tmp = tmp->mnt_parent; | |
1340 | } | |
1341 | if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) | |
1342 | goto out3; | |
1343 | } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) | |
1344 | goto out3; | |
1345 | detach_mnt(new_nd.mnt, &parent_nd); | |
1346 | detach_mnt(user_nd.mnt, &root_parent); | |
1347 | attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ | |
1348 | attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ | |
1349 | spin_unlock(&vfsmount_lock); | |
1350 | chroot_fs_refs(&user_nd, &new_nd); | |
1351 | security_sb_post_pivotroot(&user_nd, &new_nd); | |
1352 | error = 0; | |
1353 | path_release(&root_parent); | |
1354 | path_release(&parent_nd); | |
1355 | out2: | |
1356 | up(&old_nd.dentry->d_inode->i_sem); | |
1357 | up_write(¤t->namespace->sem); | |
1358 | path_release(&user_nd); | |
1359 | path_release(&old_nd); | |
1360 | out1: | |
1361 | path_release(&new_nd); | |
1362 | out0: | |
1363 | unlock_kernel(); | |
1364 | return error; | |
1365 | out3: | |
1366 | spin_unlock(&vfsmount_lock); | |
1367 | goto out2; | |
1368 | } | |
1369 | ||
1370 | static void __init init_mount_tree(void) | |
1371 | { | |
1372 | struct vfsmount *mnt; | |
1373 | struct namespace *namespace; | |
1374 | struct task_struct *g, *p; | |
1375 | ||
1376 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); | |
1377 | if (IS_ERR(mnt)) | |
1378 | panic("Can't create rootfs"); | |
1379 | namespace = kmalloc(sizeof(*namespace), GFP_KERNEL); | |
1380 | if (!namespace) | |
1381 | panic("Can't allocate initial namespace"); | |
1382 | atomic_set(&namespace->count, 1); | |
1383 | INIT_LIST_HEAD(&namespace->list); | |
1384 | init_rwsem(&namespace->sem); | |
1385 | list_add(&mnt->mnt_list, &namespace->list); | |
1386 | namespace->root = mnt; | |
1387 | mnt->mnt_namespace = namespace; | |
1388 | ||
1389 | init_task.namespace = namespace; | |
1390 | read_lock(&tasklist_lock); | |
1391 | do_each_thread(g, p) { | |
1392 | get_namespace(namespace); | |
1393 | p->namespace = namespace; | |
1394 | } while_each_thread(g, p); | |
1395 | read_unlock(&tasklist_lock); | |
1396 | ||
1397 | set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root); | |
1398 | set_fs_root(current->fs, namespace->root, namespace->root->mnt_root); | |
1399 | } | |
1400 | ||
1401 | void __init mnt_init(unsigned long mempages) | |
1402 | { | |
1403 | struct list_head *d; | |
1404 | unsigned int nr_hash; | |
1405 | int i; | |
1406 | ||
1407 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), | |
1408 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); | |
1409 | ||
1410 | mount_hashtable = (struct list_head *) | |
1411 | __get_free_page(GFP_ATOMIC); | |
1412 | ||
1413 | if (!mount_hashtable) | |
1414 | panic("Failed to allocate mount hash table\n"); | |
1415 | ||
1416 | /* | |
1417 | * Find the power-of-two list-heads that can fit into the allocation.. | |
1418 | * We don't guarantee that "sizeof(struct list_head)" is necessarily | |
1419 | * a power-of-two. | |
1420 | */ | |
1421 | nr_hash = PAGE_SIZE / sizeof(struct list_head); | |
1422 | hash_bits = 0; | |
1423 | do { | |
1424 | hash_bits++; | |
1425 | } while ((nr_hash >> hash_bits) != 0); | |
1426 | hash_bits--; | |
1427 | ||
1428 | /* | |
1429 | * Re-calculate the actual number of entries and the mask | |
1430 | * from the number of bits we can fit. | |
1431 | */ | |
1432 | nr_hash = 1UL << hash_bits; | |
1433 | hash_mask = nr_hash-1; | |
1434 | ||
1435 | printk("Mount-cache hash table entries: %d\n", nr_hash); | |
1436 | ||
1437 | /* And initialize the newly allocated array */ | |
1438 | d = mount_hashtable; | |
1439 | i = nr_hash; | |
1440 | do { | |
1441 | INIT_LIST_HEAD(d); | |
1442 | d++; | |
1443 | i--; | |
1444 | } while (i); | |
1445 | sysfs_init(); | |
1446 | init_rootfs(); | |
1447 | init_mount_tree(); | |
1448 | } | |
1449 | ||
1450 | void __put_namespace(struct namespace *namespace) | |
1451 | { | |
1452 | struct vfsmount *mnt; | |
1453 | ||
1454 | down_write(&namespace->sem); | |
1455 | spin_lock(&vfsmount_lock); | |
1456 | ||
1457 | list_for_each_entry(mnt, &namespace->list, mnt_list) { | |
1458 | mnt->mnt_namespace = NULL; | |
1459 | } | |
1460 | ||
1461 | umount_tree(namespace->root); | |
1462 | spin_unlock(&vfsmount_lock); | |
1463 | up_write(&namespace->sem); | |
1464 | kfree(namespace); | |
1465 | } |