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Commit | Line | Data |
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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 */ | |
5addc5dd AV |
40 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); |
41 | ||
42 | static int event; | |
1da177e4 LT |
43 | |
44 | static struct list_head *mount_hashtable; | |
6c231b7b | 45 | static int hash_mask __read_mostly, hash_bits __read_mostly; |
1da177e4 LT |
46 | static kmem_cache_t *mnt_cache; |
47 | ||
48 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) | |
49 | { | |
50 | unsigned long tmp = ((unsigned long) mnt / L1_CACHE_BYTES); | |
51 | tmp += ((unsigned long) dentry / L1_CACHE_BYTES); | |
52 | tmp = tmp + (tmp >> hash_bits); | |
53 | return tmp & hash_mask; | |
54 | } | |
55 | ||
56 | struct vfsmount *alloc_vfsmnt(const char *name) | |
57 | { | |
58 | struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL); | |
59 | if (mnt) { | |
60 | memset(mnt, 0, sizeof(struct vfsmount)); | |
61 | atomic_set(&mnt->mnt_count,1); | |
62 | INIT_LIST_HEAD(&mnt->mnt_hash); | |
63 | INIT_LIST_HEAD(&mnt->mnt_child); | |
64 | INIT_LIST_HEAD(&mnt->mnt_mounts); | |
65 | INIT_LIST_HEAD(&mnt->mnt_list); | |
55e700b9 | 66 | INIT_LIST_HEAD(&mnt->mnt_expire); |
1da177e4 LT |
67 | if (name) { |
68 | int size = strlen(name)+1; | |
69 | char *newname = kmalloc(size, GFP_KERNEL); | |
70 | if (newname) { | |
71 | memcpy(newname, name, size); | |
72 | mnt->mnt_devname = newname; | |
73 | } | |
74 | } | |
75 | } | |
76 | return mnt; | |
77 | } | |
78 | ||
79 | void free_vfsmnt(struct vfsmount *mnt) | |
80 | { | |
81 | kfree(mnt->mnt_devname); | |
82 | kmem_cache_free(mnt_cache, mnt); | |
83 | } | |
84 | ||
85 | /* | |
86 | * Now, lookup_mnt increments the ref count before returning | |
87 | * the vfsmount struct. | |
88 | */ | |
89 | struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) | |
90 | { | |
91 | struct list_head * head = mount_hashtable + hash(mnt, dentry); | |
92 | struct list_head * tmp = head; | |
93 | struct vfsmount *p, *found = NULL; | |
94 | ||
95 | spin_lock(&vfsmount_lock); | |
96 | for (;;) { | |
97 | tmp = tmp->next; | |
98 | p = NULL; | |
99 | if (tmp == head) | |
100 | break; | |
101 | p = list_entry(tmp, struct vfsmount, mnt_hash); | |
102 | if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { | |
103 | found = mntget(p); | |
104 | break; | |
105 | } | |
106 | } | |
107 | spin_unlock(&vfsmount_lock); | |
108 | return found; | |
109 | } | |
110 | ||
111 | static inline int check_mnt(struct vfsmount *mnt) | |
112 | { | |
113 | return mnt->mnt_namespace == current->namespace; | |
114 | } | |
115 | ||
5addc5dd AV |
116 | static void touch_namespace(struct namespace *ns) |
117 | { | |
118 | if (ns) { | |
119 | ns->event = ++event; | |
120 | wake_up_interruptible(&ns->poll); | |
121 | } | |
122 | } | |
123 | ||
124 | static void __touch_namespace(struct namespace *ns) | |
125 | { | |
126 | if (ns && ns->event != event) { | |
127 | ns->event = event; | |
128 | wake_up_interruptible(&ns->poll); | |
129 | } | |
130 | } | |
131 | ||
1da177e4 LT |
132 | static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd) |
133 | { | |
134 | old_nd->dentry = mnt->mnt_mountpoint; | |
135 | old_nd->mnt = mnt->mnt_parent; | |
136 | mnt->mnt_parent = mnt; | |
137 | mnt->mnt_mountpoint = mnt->mnt_root; | |
138 | list_del_init(&mnt->mnt_child); | |
139 | list_del_init(&mnt->mnt_hash); | |
140 | old_nd->dentry->d_mounted--; | |
141 | } | |
142 | ||
143 | static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd) | |
144 | { | |
145 | mnt->mnt_parent = mntget(nd->mnt); | |
146 | mnt->mnt_mountpoint = dget(nd->dentry); | |
147 | list_add(&mnt->mnt_hash, mount_hashtable+hash(nd->mnt, nd->dentry)); | |
148 | list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts); | |
149 | nd->dentry->d_mounted++; | |
150 | } | |
151 | ||
152 | static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) | |
153 | { | |
154 | struct list_head *next = p->mnt_mounts.next; | |
155 | if (next == &p->mnt_mounts) { | |
156 | while (1) { | |
157 | if (p == root) | |
158 | return NULL; | |
159 | next = p->mnt_child.next; | |
160 | if (next != &p->mnt_parent->mnt_mounts) | |
161 | break; | |
162 | p = p->mnt_parent; | |
163 | } | |
164 | } | |
165 | return list_entry(next, struct vfsmount, mnt_child); | |
166 | } | |
167 | ||
168 | static struct vfsmount * | |
169 | clone_mnt(struct vfsmount *old, struct dentry *root) | |
170 | { | |
171 | struct super_block *sb = old->mnt_sb; | |
172 | struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); | |
173 | ||
174 | if (mnt) { | |
175 | mnt->mnt_flags = old->mnt_flags; | |
176 | atomic_inc(&sb->s_active); | |
177 | mnt->mnt_sb = sb; | |
178 | mnt->mnt_root = dget(root); | |
179 | mnt->mnt_mountpoint = mnt->mnt_root; | |
180 | mnt->mnt_parent = mnt; | |
68b47139 | 181 | mnt->mnt_namespace = current->namespace; |
1da177e4 LT |
182 | |
183 | /* stick the duplicate mount on the same expiry list | |
184 | * as the original if that was on one */ | |
185 | spin_lock(&vfsmount_lock); | |
55e700b9 MS |
186 | if (!list_empty(&old->mnt_expire)) |
187 | list_add(&mnt->mnt_expire, &old->mnt_expire); | |
1da177e4 LT |
188 | spin_unlock(&vfsmount_lock); |
189 | } | |
190 | return mnt; | |
191 | } | |
192 | ||
7b7b1ace | 193 | static inline void __mntput(struct vfsmount *mnt) |
1da177e4 LT |
194 | { |
195 | struct super_block *sb = mnt->mnt_sb; | |
196 | dput(mnt->mnt_root); | |
197 | free_vfsmnt(mnt); | |
198 | deactivate_super(sb); | |
199 | } | |
200 | ||
7b7b1ace AV |
201 | void mntput_no_expire(struct vfsmount *mnt) |
202 | { | |
203 | repeat: | |
204 | if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { | |
205 | if (likely(!mnt->mnt_pinned)) { | |
206 | spin_unlock(&vfsmount_lock); | |
207 | __mntput(mnt); | |
208 | return; | |
209 | } | |
210 | atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); | |
211 | mnt->mnt_pinned = 0; | |
212 | spin_unlock(&vfsmount_lock); | |
213 | acct_auto_close_mnt(mnt); | |
214 | security_sb_umount_close(mnt); | |
215 | goto repeat; | |
216 | } | |
217 | } | |
218 | ||
219 | EXPORT_SYMBOL(mntput_no_expire); | |
220 | ||
221 | void mnt_pin(struct vfsmount *mnt) | |
222 | { | |
223 | spin_lock(&vfsmount_lock); | |
224 | mnt->mnt_pinned++; | |
225 | spin_unlock(&vfsmount_lock); | |
226 | } | |
227 | ||
228 | EXPORT_SYMBOL(mnt_pin); | |
229 | ||
230 | void mnt_unpin(struct vfsmount *mnt) | |
231 | { | |
232 | spin_lock(&vfsmount_lock); | |
233 | if (mnt->mnt_pinned) { | |
234 | atomic_inc(&mnt->mnt_count); | |
235 | mnt->mnt_pinned--; | |
236 | } | |
237 | spin_unlock(&vfsmount_lock); | |
238 | } | |
239 | ||
240 | EXPORT_SYMBOL(mnt_unpin); | |
1da177e4 LT |
241 | |
242 | /* iterator */ | |
243 | static void *m_start(struct seq_file *m, loff_t *pos) | |
244 | { | |
245 | struct namespace *n = m->private; | |
246 | struct list_head *p; | |
247 | loff_t l = *pos; | |
248 | ||
249 | down_read(&n->sem); | |
250 | list_for_each(p, &n->list) | |
251 | if (!l--) | |
252 | return list_entry(p, struct vfsmount, mnt_list); | |
253 | return NULL; | |
254 | } | |
255 | ||
256 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) | |
257 | { | |
258 | struct namespace *n = m->private; | |
259 | struct list_head *p = ((struct vfsmount *)v)->mnt_list.next; | |
260 | (*pos)++; | |
261 | return p==&n->list ? NULL : list_entry(p, struct vfsmount, mnt_list); | |
262 | } | |
263 | ||
264 | static void m_stop(struct seq_file *m, void *v) | |
265 | { | |
266 | struct namespace *n = m->private; | |
267 | up_read(&n->sem); | |
268 | } | |
269 | ||
270 | static inline void mangle(struct seq_file *m, const char *s) | |
271 | { | |
272 | seq_escape(m, s, " \t\n\\"); | |
273 | } | |
274 | ||
275 | static int show_vfsmnt(struct seq_file *m, void *v) | |
276 | { | |
277 | struct vfsmount *mnt = v; | |
278 | int err = 0; | |
279 | static struct proc_fs_info { | |
280 | int flag; | |
281 | char *str; | |
282 | } fs_info[] = { | |
283 | { MS_SYNCHRONOUS, ",sync" }, | |
284 | { MS_DIRSYNC, ",dirsync" }, | |
285 | { MS_MANDLOCK, ",mand" }, | |
286 | { MS_NOATIME, ",noatime" }, | |
287 | { MS_NODIRATIME, ",nodiratime" }, | |
288 | { 0, NULL } | |
289 | }; | |
290 | static struct proc_fs_info mnt_info[] = { | |
291 | { MNT_NOSUID, ",nosuid" }, | |
292 | { MNT_NODEV, ",nodev" }, | |
293 | { MNT_NOEXEC, ",noexec" }, | |
294 | { 0, NULL } | |
295 | }; | |
296 | struct proc_fs_info *fs_infop; | |
297 | ||
298 | mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); | |
299 | seq_putc(m, ' '); | |
300 | seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); | |
301 | seq_putc(m, ' '); | |
302 | mangle(m, mnt->mnt_sb->s_type->name); | |
303 | seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); | |
304 | for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { | |
305 | if (mnt->mnt_sb->s_flags & fs_infop->flag) | |
306 | seq_puts(m, fs_infop->str); | |
307 | } | |
308 | for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { | |
309 | if (mnt->mnt_flags & fs_infop->flag) | |
310 | seq_puts(m, fs_infop->str); | |
311 | } | |
312 | if (mnt->mnt_sb->s_op->show_options) | |
313 | err = mnt->mnt_sb->s_op->show_options(m, mnt); | |
314 | seq_puts(m, " 0 0\n"); | |
315 | return err; | |
316 | } | |
317 | ||
318 | struct seq_operations mounts_op = { | |
319 | .start = m_start, | |
320 | .next = m_next, | |
321 | .stop = m_stop, | |
322 | .show = show_vfsmnt | |
323 | }; | |
324 | ||
325 | /** | |
326 | * may_umount_tree - check if a mount tree is busy | |
327 | * @mnt: root of mount tree | |
328 | * | |
329 | * This is called to check if a tree of mounts has any | |
330 | * open files, pwds, chroots or sub mounts that are | |
331 | * busy. | |
332 | */ | |
333 | int may_umount_tree(struct vfsmount *mnt) | |
334 | { | |
335 | struct list_head *next; | |
336 | struct vfsmount *this_parent = mnt; | |
337 | int actual_refs; | |
338 | int minimum_refs; | |
339 | ||
340 | spin_lock(&vfsmount_lock); | |
341 | actual_refs = atomic_read(&mnt->mnt_count); | |
342 | minimum_refs = 2; | |
343 | repeat: | |
344 | next = this_parent->mnt_mounts.next; | |
345 | resume: | |
346 | while (next != &this_parent->mnt_mounts) { | |
347 | struct vfsmount *p = list_entry(next, struct vfsmount, mnt_child); | |
348 | ||
349 | next = next->next; | |
350 | ||
351 | actual_refs += atomic_read(&p->mnt_count); | |
352 | minimum_refs += 2; | |
353 | ||
354 | if (!list_empty(&p->mnt_mounts)) { | |
355 | this_parent = p; | |
356 | goto repeat; | |
357 | } | |
358 | } | |
359 | ||
360 | if (this_parent != mnt) { | |
361 | next = this_parent->mnt_child.next; | |
362 | this_parent = this_parent->mnt_parent; | |
363 | goto resume; | |
364 | } | |
365 | spin_unlock(&vfsmount_lock); | |
366 | ||
367 | if (actual_refs > minimum_refs) | |
368 | return -EBUSY; | |
369 | ||
370 | return 0; | |
371 | } | |
372 | ||
373 | EXPORT_SYMBOL(may_umount_tree); | |
374 | ||
375 | /** | |
376 | * may_umount - check if a mount point is busy | |
377 | * @mnt: root of mount | |
378 | * | |
379 | * This is called to check if a mount point has any | |
380 | * open files, pwds, chroots or sub mounts. If the | |
381 | * mount has sub mounts this will return busy | |
382 | * regardless of whether the sub mounts are busy. | |
383 | * | |
384 | * Doesn't take quota and stuff into account. IOW, in some cases it will | |
385 | * give false negatives. The main reason why it's here is that we need | |
386 | * a non-destructive way to look for easily umountable filesystems. | |
387 | */ | |
388 | int may_umount(struct vfsmount *mnt) | |
389 | { | |
390 | if (atomic_read(&mnt->mnt_count) > 2) | |
391 | return -EBUSY; | |
392 | return 0; | |
393 | } | |
394 | ||
395 | EXPORT_SYMBOL(may_umount); | |
396 | ||
52c1da39 | 397 | static void umount_tree(struct vfsmount *mnt) |
1da177e4 LT |
398 | { |
399 | struct vfsmount *p; | |
400 | LIST_HEAD(kill); | |
401 | ||
402 | for (p = mnt; p; p = next_mnt(p, mnt)) { | |
403 | list_del(&p->mnt_list); | |
404 | list_add(&p->mnt_list, &kill); | |
5addc5dd | 405 | __touch_namespace(p->mnt_namespace); |
202322e6 | 406 | p->mnt_namespace = NULL; |
1da177e4 LT |
407 | } |
408 | ||
409 | while (!list_empty(&kill)) { | |
410 | mnt = list_entry(kill.next, struct vfsmount, mnt_list); | |
411 | list_del_init(&mnt->mnt_list); | |
55e700b9 | 412 | list_del_init(&mnt->mnt_expire); |
1da177e4 LT |
413 | if (mnt->mnt_parent == mnt) { |
414 | spin_unlock(&vfsmount_lock); | |
415 | } else { | |
416 | struct nameidata old_nd; | |
417 | detach_mnt(mnt, &old_nd); | |
418 | spin_unlock(&vfsmount_lock); | |
419 | path_release(&old_nd); | |
420 | } | |
421 | mntput(mnt); | |
422 | spin_lock(&vfsmount_lock); | |
423 | } | |
424 | } | |
425 | ||
426 | static int do_umount(struct vfsmount *mnt, int flags) | |
427 | { | |
428 | struct super_block * sb = mnt->mnt_sb; | |
429 | int retval; | |
430 | ||
431 | retval = security_sb_umount(mnt, flags); | |
432 | if (retval) | |
433 | return retval; | |
434 | ||
435 | /* | |
436 | * Allow userspace to request a mountpoint be expired rather than | |
437 | * unmounting unconditionally. Unmount only happens if: | |
438 | * (1) the mark is already set (the mark is cleared by mntput()) | |
439 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] | |
440 | */ | |
441 | if (flags & MNT_EXPIRE) { | |
442 | if (mnt == current->fs->rootmnt || | |
443 | flags & (MNT_FORCE | MNT_DETACH)) | |
444 | return -EINVAL; | |
445 | ||
446 | if (atomic_read(&mnt->mnt_count) != 2) | |
447 | return -EBUSY; | |
448 | ||
449 | if (!xchg(&mnt->mnt_expiry_mark, 1)) | |
450 | return -EAGAIN; | |
451 | } | |
452 | ||
453 | /* | |
454 | * If we may have to abort operations to get out of this | |
455 | * mount, and they will themselves hold resources we must | |
456 | * allow the fs to do things. In the Unix tradition of | |
457 | * 'Gee thats tricky lets do it in userspace' the umount_begin | |
458 | * might fail to complete on the first run through as other tasks | |
459 | * must return, and the like. Thats for the mount program to worry | |
460 | * about for the moment. | |
461 | */ | |
462 | ||
463 | lock_kernel(); | |
464 | if( (flags&MNT_FORCE) && sb->s_op->umount_begin) | |
465 | sb->s_op->umount_begin(sb); | |
466 | unlock_kernel(); | |
467 | ||
468 | /* | |
469 | * No sense to grab the lock for this test, but test itself looks | |
470 | * somewhat bogus. Suggestions for better replacement? | |
471 | * Ho-hum... In principle, we might treat that as umount + switch | |
472 | * to rootfs. GC would eventually take care of the old vfsmount. | |
473 | * Actually it makes sense, especially if rootfs would contain a | |
474 | * /reboot - static binary that would close all descriptors and | |
475 | * call reboot(9). Then init(8) could umount root and exec /reboot. | |
476 | */ | |
477 | if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { | |
478 | /* | |
479 | * Special case for "unmounting" root ... | |
480 | * we just try to remount it readonly. | |
481 | */ | |
482 | down_write(&sb->s_umount); | |
483 | if (!(sb->s_flags & MS_RDONLY)) { | |
484 | lock_kernel(); | |
485 | DQUOT_OFF(sb); | |
486 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); | |
487 | unlock_kernel(); | |
488 | } | |
489 | up_write(&sb->s_umount); | |
490 | return retval; | |
491 | } | |
492 | ||
493 | down_write(¤t->namespace->sem); | |
494 | spin_lock(&vfsmount_lock); | |
5addc5dd | 495 | event++; |
1da177e4 | 496 | |
1da177e4 LT |
497 | retval = -EBUSY; |
498 | if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) { | |
499 | if (!list_empty(&mnt->mnt_list)) | |
500 | umount_tree(mnt); | |
501 | retval = 0; | |
502 | } | |
503 | spin_unlock(&vfsmount_lock); | |
504 | if (retval) | |
505 | security_sb_umount_busy(mnt); | |
506 | up_write(¤t->namespace->sem); | |
507 | return retval; | |
508 | } | |
509 | ||
510 | /* | |
511 | * Now umount can handle mount points as well as block devices. | |
512 | * This is important for filesystems which use unnamed block devices. | |
513 | * | |
514 | * We now support a flag for forced unmount like the other 'big iron' | |
515 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD | |
516 | */ | |
517 | ||
518 | asmlinkage long sys_umount(char __user * name, int flags) | |
519 | { | |
520 | struct nameidata nd; | |
521 | int retval; | |
522 | ||
523 | retval = __user_walk(name, LOOKUP_FOLLOW, &nd); | |
524 | if (retval) | |
525 | goto out; | |
526 | retval = -EINVAL; | |
527 | if (nd.dentry != nd.mnt->mnt_root) | |
528 | goto dput_and_out; | |
529 | if (!check_mnt(nd.mnt)) | |
530 | goto dput_and_out; | |
531 | ||
532 | retval = -EPERM; | |
533 | if (!capable(CAP_SYS_ADMIN)) | |
534 | goto dput_and_out; | |
535 | ||
536 | retval = do_umount(nd.mnt, flags); | |
537 | dput_and_out: | |
538 | path_release_on_umount(&nd); | |
539 | out: | |
540 | return retval; | |
541 | } | |
542 | ||
543 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT | |
544 | ||
545 | /* | |
546 | * The 2.0 compatible umount. No flags. | |
547 | */ | |
548 | ||
549 | asmlinkage long sys_oldumount(char __user * name) | |
550 | { | |
551 | return sys_umount(name,0); | |
552 | } | |
553 | ||
554 | #endif | |
555 | ||
556 | static int mount_is_safe(struct nameidata *nd) | |
557 | { | |
558 | if (capable(CAP_SYS_ADMIN)) | |
559 | return 0; | |
560 | return -EPERM; | |
561 | #ifdef notyet | |
562 | if (S_ISLNK(nd->dentry->d_inode->i_mode)) | |
563 | return -EPERM; | |
564 | if (nd->dentry->d_inode->i_mode & S_ISVTX) { | |
565 | if (current->uid != nd->dentry->d_inode->i_uid) | |
566 | return -EPERM; | |
567 | } | |
568 | if (permission(nd->dentry->d_inode, MAY_WRITE, nd)) | |
569 | return -EPERM; | |
570 | return 0; | |
571 | #endif | |
572 | } | |
573 | ||
574 | static int | |
575 | lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) | |
576 | { | |
577 | while (1) { | |
578 | if (d == dentry) | |
579 | return 1; | |
580 | if (d == NULL || d == d->d_parent) | |
581 | return 0; | |
582 | d = d->d_parent; | |
583 | } | |
584 | } | |
585 | ||
586 | static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry) | |
587 | { | |
588 | struct vfsmount *res, *p, *q, *r, *s; | |
1da177e4 LT |
589 | struct nameidata nd; |
590 | ||
591 | res = q = clone_mnt(mnt, dentry); | |
592 | if (!q) | |
593 | goto Enomem; | |
594 | q->mnt_mountpoint = mnt->mnt_mountpoint; | |
595 | ||
596 | p = mnt; | |
fdadd65f | 597 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
1da177e4 LT |
598 | if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) |
599 | continue; | |
600 | ||
601 | for (s = r; s; s = next_mnt(s, r)) { | |
602 | while (p != s->mnt_parent) { | |
603 | p = p->mnt_parent; | |
604 | q = q->mnt_parent; | |
605 | } | |
606 | p = s; | |
607 | nd.mnt = q; | |
608 | nd.dentry = p->mnt_mountpoint; | |
609 | q = clone_mnt(p, p->mnt_root); | |
610 | if (!q) | |
611 | goto Enomem; | |
612 | spin_lock(&vfsmount_lock); | |
613 | list_add_tail(&q->mnt_list, &res->mnt_list); | |
614 | attach_mnt(q, &nd); | |
615 | spin_unlock(&vfsmount_lock); | |
616 | } | |
617 | } | |
618 | return res; | |
619 | Enomem: | |
620 | if (res) { | |
621 | spin_lock(&vfsmount_lock); | |
622 | umount_tree(res); | |
623 | spin_unlock(&vfsmount_lock); | |
624 | } | |
625 | return NULL; | |
626 | } | |
627 | ||
628 | static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) | |
629 | { | |
630 | int err; | |
631 | if (mnt->mnt_sb->s_flags & MS_NOUSER) | |
632 | return -EINVAL; | |
633 | ||
634 | if (S_ISDIR(nd->dentry->d_inode->i_mode) != | |
635 | S_ISDIR(mnt->mnt_root->d_inode->i_mode)) | |
636 | return -ENOTDIR; | |
637 | ||
638 | err = -ENOENT; | |
639 | down(&nd->dentry->d_inode->i_sem); | |
640 | if (IS_DEADDIR(nd->dentry->d_inode)) | |
641 | goto out_unlock; | |
642 | ||
643 | err = security_sb_check_sb(mnt, nd); | |
644 | if (err) | |
645 | goto out_unlock; | |
646 | ||
647 | err = -ENOENT; | |
648 | spin_lock(&vfsmount_lock); | |
649 | if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) { | |
650 | struct list_head head; | |
651 | ||
652 | attach_mnt(mnt, nd); | |
653 | list_add_tail(&head, &mnt->mnt_list); | |
654 | list_splice(&head, current->namespace->list.prev); | |
655 | mntget(mnt); | |
656 | err = 0; | |
5addc5dd | 657 | touch_namespace(current->namespace); |
1da177e4 LT |
658 | } |
659 | spin_unlock(&vfsmount_lock); | |
660 | out_unlock: | |
661 | up(&nd->dentry->d_inode->i_sem); | |
662 | if (!err) | |
663 | security_sb_post_addmount(mnt, nd); | |
664 | return err; | |
665 | } | |
666 | ||
667 | /* | |
668 | * do loopback mount. | |
669 | */ | |
670 | static int do_loopback(struct nameidata *nd, char *old_name, int recurse) | |
671 | { | |
672 | struct nameidata old_nd; | |
673 | struct vfsmount *mnt = NULL; | |
674 | int err = mount_is_safe(nd); | |
675 | if (err) | |
676 | return err; | |
677 | if (!old_name || !*old_name) | |
678 | return -EINVAL; | |
679 | err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); | |
680 | if (err) | |
681 | return err; | |
682 | ||
683 | down_write(¤t->namespace->sem); | |
684 | err = -EINVAL; | |
ccd48bc7 AV |
685 | if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) |
686 | goto out; | |
1da177e4 | 687 | |
ccd48bc7 AV |
688 | err = -ENOMEM; |
689 | if (recurse) | |
690 | mnt = copy_tree(old_nd.mnt, old_nd.dentry); | |
691 | else | |
692 | mnt = clone_mnt(old_nd.mnt, old_nd.dentry); | |
693 | ||
694 | if (!mnt) | |
695 | goto out; | |
696 | ||
697 | /* stop bind mounts from expiring */ | |
698 | spin_lock(&vfsmount_lock); | |
699 | list_del_init(&mnt->mnt_expire); | |
700 | spin_unlock(&vfsmount_lock); | |
701 | ||
702 | err = graft_tree(mnt, nd); | |
703 | if (err) { | |
1da177e4 | 704 | spin_lock(&vfsmount_lock); |
ccd48bc7 | 705 | umount_tree(mnt); |
1da177e4 | 706 | spin_unlock(&vfsmount_lock); |
ccd48bc7 AV |
707 | } else |
708 | mntput(mnt); | |
1da177e4 | 709 | |
ccd48bc7 | 710 | out: |
1da177e4 LT |
711 | up_write(¤t->namespace->sem); |
712 | path_release(&old_nd); | |
713 | return err; | |
714 | } | |
715 | ||
716 | /* | |
717 | * change filesystem flags. dir should be a physical root of filesystem. | |
718 | * If you've mounted a non-root directory somewhere and want to do remount | |
719 | * on it - tough luck. | |
720 | */ | |
721 | ||
722 | static int do_remount(struct nameidata *nd, int flags, int mnt_flags, | |
723 | void *data) | |
724 | { | |
725 | int err; | |
726 | struct super_block * sb = nd->mnt->mnt_sb; | |
727 | ||
728 | if (!capable(CAP_SYS_ADMIN)) | |
729 | return -EPERM; | |
730 | ||
731 | if (!check_mnt(nd->mnt)) | |
732 | return -EINVAL; | |
733 | ||
734 | if (nd->dentry != nd->mnt->mnt_root) | |
735 | return -EINVAL; | |
736 | ||
737 | down_write(&sb->s_umount); | |
738 | err = do_remount_sb(sb, flags, data, 0); | |
739 | if (!err) | |
740 | nd->mnt->mnt_flags=mnt_flags; | |
741 | up_write(&sb->s_umount); | |
742 | if (!err) | |
743 | security_sb_post_remount(nd->mnt, flags, data); | |
744 | return err; | |
745 | } | |
746 | ||
747 | static int do_move_mount(struct nameidata *nd, char *old_name) | |
748 | { | |
749 | struct nameidata old_nd, parent_nd; | |
750 | struct vfsmount *p; | |
751 | int err = 0; | |
752 | if (!capable(CAP_SYS_ADMIN)) | |
753 | return -EPERM; | |
754 | if (!old_name || !*old_name) | |
755 | return -EINVAL; | |
756 | err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); | |
757 | if (err) | |
758 | return err; | |
759 | ||
760 | down_write(¤t->namespace->sem); | |
761 | while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) | |
762 | ; | |
763 | err = -EINVAL; | |
764 | if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) | |
765 | goto out; | |
766 | ||
767 | err = -ENOENT; | |
768 | down(&nd->dentry->d_inode->i_sem); | |
769 | if (IS_DEADDIR(nd->dentry->d_inode)) | |
770 | goto out1; | |
771 | ||
772 | spin_lock(&vfsmount_lock); | |
773 | if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) | |
774 | goto out2; | |
775 | ||
776 | err = -EINVAL; | |
777 | if (old_nd.dentry != old_nd.mnt->mnt_root) | |
778 | goto out2; | |
779 | ||
780 | if (old_nd.mnt == old_nd.mnt->mnt_parent) | |
781 | goto out2; | |
782 | ||
783 | if (S_ISDIR(nd->dentry->d_inode->i_mode) != | |
784 | S_ISDIR(old_nd.dentry->d_inode->i_mode)) | |
785 | goto out2; | |
786 | ||
787 | err = -ELOOP; | |
788 | for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent) | |
789 | if (p == old_nd.mnt) | |
790 | goto out2; | |
791 | err = 0; | |
792 | ||
793 | detach_mnt(old_nd.mnt, &parent_nd); | |
794 | attach_mnt(old_nd.mnt, nd); | |
5addc5dd | 795 | touch_namespace(current->namespace); |
1da177e4 LT |
796 | |
797 | /* if the mount is moved, it should no longer be expire | |
798 | * automatically */ | |
55e700b9 | 799 | list_del_init(&old_nd.mnt->mnt_expire); |
1da177e4 LT |
800 | out2: |
801 | spin_unlock(&vfsmount_lock); | |
802 | out1: | |
803 | up(&nd->dentry->d_inode->i_sem); | |
804 | out: | |
805 | up_write(¤t->namespace->sem); | |
806 | if (!err) | |
807 | path_release(&parent_nd); | |
808 | path_release(&old_nd); | |
809 | return err; | |
810 | } | |
811 | ||
812 | /* | |
813 | * create a new mount for userspace and request it to be added into the | |
814 | * namespace's tree | |
815 | */ | |
816 | static int do_new_mount(struct nameidata *nd, char *type, int flags, | |
817 | int mnt_flags, char *name, void *data) | |
818 | { | |
819 | struct vfsmount *mnt; | |
820 | ||
821 | if (!type || !memchr(type, 0, PAGE_SIZE)) | |
822 | return -EINVAL; | |
823 | ||
824 | /* we need capabilities... */ | |
825 | if (!capable(CAP_SYS_ADMIN)) | |
826 | return -EPERM; | |
827 | ||
828 | mnt = do_kern_mount(type, flags, name, data); | |
829 | if (IS_ERR(mnt)) | |
830 | return PTR_ERR(mnt); | |
831 | ||
832 | return do_add_mount(mnt, nd, mnt_flags, NULL); | |
833 | } | |
834 | ||
835 | /* | |
836 | * add a mount into a namespace's mount tree | |
837 | * - provide the option of adding the new mount to an expiration list | |
838 | */ | |
839 | int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, | |
840 | int mnt_flags, struct list_head *fslist) | |
841 | { | |
842 | int err; | |
843 | ||
844 | down_write(¤t->namespace->sem); | |
845 | /* Something was mounted here while we slept */ | |
846 | while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) | |
847 | ; | |
848 | err = -EINVAL; | |
849 | if (!check_mnt(nd->mnt)) | |
850 | goto unlock; | |
851 | ||
852 | /* Refuse the same filesystem on the same mount point */ | |
853 | err = -EBUSY; | |
854 | if (nd->mnt->mnt_sb == newmnt->mnt_sb && | |
855 | nd->mnt->mnt_root == nd->dentry) | |
856 | goto unlock; | |
857 | ||
858 | err = -EINVAL; | |
859 | if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) | |
860 | goto unlock; | |
861 | ||
862 | newmnt->mnt_flags = mnt_flags; | |
484e389c | 863 | newmnt->mnt_namespace = current->namespace; |
1da177e4 LT |
864 | err = graft_tree(newmnt, nd); |
865 | ||
866 | if (err == 0 && fslist) { | |
867 | /* add to the specified expiration list */ | |
868 | spin_lock(&vfsmount_lock); | |
55e700b9 | 869 | list_add_tail(&newmnt->mnt_expire, fslist); |
1da177e4 LT |
870 | spin_unlock(&vfsmount_lock); |
871 | } | |
872 | ||
873 | unlock: | |
874 | up_write(¤t->namespace->sem); | |
875 | mntput(newmnt); | |
876 | return err; | |
877 | } | |
878 | ||
879 | EXPORT_SYMBOL_GPL(do_add_mount); | |
880 | ||
24ca2af1 MS |
881 | static void expire_mount(struct vfsmount *mnt, struct list_head *mounts) |
882 | { | |
883 | spin_lock(&vfsmount_lock); | |
884 | ||
ed42c879 MS |
885 | /* |
886 | * Check if mount is still attached, if not, let whoever holds it deal | |
887 | * with the sucker | |
888 | */ | |
889 | if (mnt->mnt_parent == mnt) { | |
890 | spin_unlock(&vfsmount_lock); | |
891 | return; | |
892 | } | |
893 | ||
24ca2af1 MS |
894 | /* |
895 | * Check that it is still dead: the count should now be 2 - as | |
896 | * contributed by the vfsmount parent and the mntget above | |
897 | */ | |
898 | if (atomic_read(&mnt->mnt_count) == 2) { | |
899 | struct nameidata old_nd; | |
900 | ||
901 | /* delete from the namespace */ | |
5addc5dd | 902 | touch_namespace(mnt->mnt_namespace); |
24ca2af1 | 903 | list_del_init(&mnt->mnt_list); |
ac081153 | 904 | mnt->mnt_namespace = NULL; |
24ca2af1 MS |
905 | detach_mnt(mnt, &old_nd); |
906 | spin_unlock(&vfsmount_lock); | |
907 | path_release(&old_nd); | |
24ca2af1 MS |
908 | mntput(mnt); |
909 | } else { | |
910 | /* | |
911 | * Someone brought it back to life whilst we didn't have any | |
912 | * locks held so return it to the expiration list | |
913 | */ | |
55e700b9 | 914 | list_add_tail(&mnt->mnt_expire, mounts); |
24ca2af1 MS |
915 | spin_unlock(&vfsmount_lock); |
916 | } | |
917 | } | |
918 | ||
1da177e4 LT |
919 | /* |
920 | * process a list of expirable mountpoints with the intent of discarding any | |
921 | * mountpoints that aren't in use and haven't been touched since last we came | |
922 | * here | |
923 | */ | |
924 | void mark_mounts_for_expiry(struct list_head *mounts) | |
925 | { | |
926 | struct namespace *namespace; | |
927 | struct vfsmount *mnt, *next; | |
928 | LIST_HEAD(graveyard); | |
929 | ||
930 | if (list_empty(mounts)) | |
931 | return; | |
932 | ||
933 | spin_lock(&vfsmount_lock); | |
934 | ||
935 | /* extract from the expiration list every vfsmount that matches the | |
936 | * following criteria: | |
937 | * - only referenced by its parent vfsmount | |
938 | * - still marked for expiry (marked on the last call here; marks are | |
939 | * cleared by mntput()) | |
940 | */ | |
55e700b9 | 941 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
1da177e4 LT |
942 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
943 | atomic_read(&mnt->mnt_count) != 1) | |
944 | continue; | |
945 | ||
946 | mntget(mnt); | |
55e700b9 | 947 | list_move(&mnt->mnt_expire, &graveyard); |
1da177e4 LT |
948 | } |
949 | ||
950 | /* | |
951 | * go through the vfsmounts we've just consigned to the graveyard to | |
952 | * - check that they're still dead | |
953 | * - delete the vfsmount from the appropriate namespace under lock | |
954 | * - dispose of the corpse | |
955 | */ | |
956 | while (!list_empty(&graveyard)) { | |
55e700b9 MS |
957 | mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire); |
958 | list_del_init(&mnt->mnt_expire); | |
1da177e4 LT |
959 | |
960 | /* don't do anything if the namespace is dead - all the | |
961 | * vfsmounts from it are going away anyway */ | |
962 | namespace = mnt->mnt_namespace; | |
1ce88cf4 | 963 | if (!namespace || !namespace->root) |
1da177e4 LT |
964 | continue; |
965 | get_namespace(namespace); | |
966 | ||
967 | spin_unlock(&vfsmount_lock); | |
968 | down_write(&namespace->sem); | |
24ca2af1 | 969 | expire_mount(mnt, mounts); |
1da177e4 LT |
970 | up_write(&namespace->sem); |
971 | ||
972 | mntput(mnt); | |
973 | put_namespace(namespace); | |
974 | ||
975 | spin_lock(&vfsmount_lock); | |
976 | } | |
977 | ||
978 | spin_unlock(&vfsmount_lock); | |
979 | } | |
980 | ||
981 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); | |
982 | ||
983 | /* | |
984 | * Some copy_from_user() implementations do not return the exact number of | |
985 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. | |
986 | * Note that this function differs from copy_from_user() in that it will oops | |
987 | * on bad values of `to', rather than returning a short copy. | |
988 | */ | |
989 | static long | |
990 | exact_copy_from_user(void *to, const void __user *from, unsigned long n) | |
991 | { | |
992 | char *t = to; | |
993 | const char __user *f = from; | |
994 | char c; | |
995 | ||
996 | if (!access_ok(VERIFY_READ, from, n)) | |
997 | return n; | |
998 | ||
999 | while (n) { | |
1000 | if (__get_user(c, f)) { | |
1001 | memset(t, 0, n); | |
1002 | break; | |
1003 | } | |
1004 | *t++ = c; | |
1005 | f++; | |
1006 | n--; | |
1007 | } | |
1008 | return n; | |
1009 | } | |
1010 | ||
1011 | int copy_mount_options(const void __user *data, unsigned long *where) | |
1012 | { | |
1013 | int i; | |
1014 | unsigned long page; | |
1015 | unsigned long size; | |
1016 | ||
1017 | *where = 0; | |
1018 | if (!data) | |
1019 | return 0; | |
1020 | ||
1021 | if (!(page = __get_free_page(GFP_KERNEL))) | |
1022 | return -ENOMEM; | |
1023 | ||
1024 | /* We only care that *some* data at the address the user | |
1025 | * gave us is valid. Just in case, we'll zero | |
1026 | * the remainder of the page. | |
1027 | */ | |
1028 | /* copy_from_user cannot cross TASK_SIZE ! */ | |
1029 | size = TASK_SIZE - (unsigned long)data; | |
1030 | if (size > PAGE_SIZE) | |
1031 | size = PAGE_SIZE; | |
1032 | ||
1033 | i = size - exact_copy_from_user((void *)page, data, size); | |
1034 | if (!i) { | |
1035 | free_page(page); | |
1036 | return -EFAULT; | |
1037 | } | |
1038 | if (i != PAGE_SIZE) | |
1039 | memset((char *)page + i, 0, PAGE_SIZE - i); | |
1040 | *where = page; | |
1041 | return 0; | |
1042 | } | |
1043 | ||
1044 | /* | |
1045 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to | |
1046 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). | |
1047 | * | |
1048 | * data is a (void *) that can point to any structure up to | |
1049 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent | |
1050 | * information (or be NULL). | |
1051 | * | |
1052 | * Pre-0.97 versions of mount() didn't have a flags word. | |
1053 | * When the flags word was introduced its top half was required | |
1054 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. | |
1055 | * Therefore, if this magic number is present, it carries no information | |
1056 | * and must be discarded. | |
1057 | */ | |
1058 | long do_mount(char * dev_name, char * dir_name, char *type_page, | |
1059 | unsigned long flags, void *data_page) | |
1060 | { | |
1061 | struct nameidata nd; | |
1062 | int retval = 0; | |
1063 | int mnt_flags = 0; | |
1064 | ||
1065 | /* Discard magic */ | |
1066 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) | |
1067 | flags &= ~MS_MGC_MSK; | |
1068 | ||
1069 | /* Basic sanity checks */ | |
1070 | ||
1071 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) | |
1072 | return -EINVAL; | |
1073 | if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) | |
1074 | return -EINVAL; | |
1075 | ||
1076 | if (data_page) | |
1077 | ((char *)data_page)[PAGE_SIZE - 1] = 0; | |
1078 | ||
1079 | /* Separate the per-mountpoint flags */ | |
1080 | if (flags & MS_NOSUID) | |
1081 | mnt_flags |= MNT_NOSUID; | |
1082 | if (flags & MS_NODEV) | |
1083 | mnt_flags |= MNT_NODEV; | |
1084 | if (flags & MS_NOEXEC) | |
1085 | mnt_flags |= MNT_NOEXEC; | |
1086 | flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_ACTIVE); | |
1087 | ||
1088 | /* ... and get the mountpoint */ | |
1089 | retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); | |
1090 | if (retval) | |
1091 | return retval; | |
1092 | ||
1093 | retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); | |
1094 | if (retval) | |
1095 | goto dput_out; | |
1096 | ||
1097 | if (flags & MS_REMOUNT) | |
1098 | retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, | |
1099 | data_page); | |
1100 | else if (flags & MS_BIND) | |
1101 | retval = do_loopback(&nd, dev_name, flags & MS_REC); | |
1102 | else if (flags & MS_MOVE) | |
1103 | retval = do_move_mount(&nd, dev_name); | |
1104 | else | |
1105 | retval = do_new_mount(&nd, type_page, flags, mnt_flags, | |
1106 | dev_name, data_page); | |
1107 | dput_out: | |
1108 | path_release(&nd); | |
1109 | return retval; | |
1110 | } | |
1111 | ||
1112 | int copy_namespace(int flags, struct task_struct *tsk) | |
1113 | { | |
1114 | struct namespace *namespace = tsk->namespace; | |
1115 | struct namespace *new_ns; | |
1116 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; | |
1117 | struct fs_struct *fs = tsk->fs; | |
1118 | struct vfsmount *p, *q; | |
1119 | ||
1120 | if (!namespace) | |
1121 | return 0; | |
1122 | ||
1123 | get_namespace(namespace); | |
1124 | ||
1125 | if (!(flags & CLONE_NEWNS)) | |
1126 | return 0; | |
1127 | ||
1128 | if (!capable(CAP_SYS_ADMIN)) { | |
1129 | put_namespace(namespace); | |
1130 | return -EPERM; | |
1131 | } | |
1132 | ||
1133 | new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL); | |
1134 | if (!new_ns) | |
1135 | goto out; | |
1136 | ||
1137 | atomic_set(&new_ns->count, 1); | |
1138 | init_rwsem(&new_ns->sem); | |
1139 | INIT_LIST_HEAD(&new_ns->list); | |
5addc5dd AV |
1140 | init_waitqueue_head(&new_ns->poll); |
1141 | new_ns->event = 0; | |
1da177e4 LT |
1142 | |
1143 | down_write(&tsk->namespace->sem); | |
1144 | /* First pass: copy the tree topology */ | |
1145 | new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root); | |
1146 | if (!new_ns->root) { | |
1147 | up_write(&tsk->namespace->sem); | |
1148 | kfree(new_ns); | |
1149 | goto out; | |
1150 | } | |
1151 | spin_lock(&vfsmount_lock); | |
1152 | list_add_tail(&new_ns->list, &new_ns->root->mnt_list); | |
1153 | spin_unlock(&vfsmount_lock); | |
1154 | ||
1155 | /* | |
1156 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts | |
1157 | * as belonging to new namespace. We have already acquired a private | |
1158 | * fs_struct, so tsk->fs->lock is not needed. | |
1159 | */ | |
1160 | p = namespace->root; | |
1161 | q = new_ns->root; | |
1162 | while (p) { | |
1163 | q->mnt_namespace = new_ns; | |
1164 | if (fs) { | |
1165 | if (p == fs->rootmnt) { | |
1166 | rootmnt = p; | |
1167 | fs->rootmnt = mntget(q); | |
1168 | } | |
1169 | if (p == fs->pwdmnt) { | |
1170 | pwdmnt = p; | |
1171 | fs->pwdmnt = mntget(q); | |
1172 | } | |
1173 | if (p == fs->altrootmnt) { | |
1174 | altrootmnt = p; | |
1175 | fs->altrootmnt = mntget(q); | |
1176 | } | |
1177 | } | |
1178 | p = next_mnt(p, namespace->root); | |
1179 | q = next_mnt(q, new_ns->root); | |
1180 | } | |
1181 | up_write(&tsk->namespace->sem); | |
1182 | ||
1183 | tsk->namespace = new_ns; | |
1184 | ||
1185 | if (rootmnt) | |
1186 | mntput(rootmnt); | |
1187 | if (pwdmnt) | |
1188 | mntput(pwdmnt); | |
1189 | if (altrootmnt) | |
1190 | mntput(altrootmnt); | |
1191 | ||
1192 | put_namespace(namespace); | |
1193 | return 0; | |
1194 | ||
1195 | out: | |
1196 | put_namespace(namespace); | |
1197 | return -ENOMEM; | |
1198 | } | |
1199 | ||
1200 | asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, | |
1201 | char __user * type, unsigned long flags, | |
1202 | void __user * data) | |
1203 | { | |
1204 | int retval; | |
1205 | unsigned long data_page; | |
1206 | unsigned long type_page; | |
1207 | unsigned long dev_page; | |
1208 | char *dir_page; | |
1209 | ||
1210 | retval = copy_mount_options (type, &type_page); | |
1211 | if (retval < 0) | |
1212 | return retval; | |
1213 | ||
1214 | dir_page = getname(dir_name); | |
1215 | retval = PTR_ERR(dir_page); | |
1216 | if (IS_ERR(dir_page)) | |
1217 | goto out1; | |
1218 | ||
1219 | retval = copy_mount_options (dev_name, &dev_page); | |
1220 | if (retval < 0) | |
1221 | goto out2; | |
1222 | ||
1223 | retval = copy_mount_options (data, &data_page); | |
1224 | if (retval < 0) | |
1225 | goto out3; | |
1226 | ||
1227 | lock_kernel(); | |
1228 | retval = do_mount((char*)dev_page, dir_page, (char*)type_page, | |
1229 | flags, (void*)data_page); | |
1230 | unlock_kernel(); | |
1231 | free_page(data_page); | |
1232 | ||
1233 | out3: | |
1234 | free_page(dev_page); | |
1235 | out2: | |
1236 | putname(dir_page); | |
1237 | out1: | |
1238 | free_page(type_page); | |
1239 | return retval; | |
1240 | } | |
1241 | ||
1242 | /* | |
1243 | * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. | |
1244 | * It can block. Requires the big lock held. | |
1245 | */ | |
1246 | void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, | |
1247 | struct dentry *dentry) | |
1248 | { | |
1249 | struct dentry *old_root; | |
1250 | struct vfsmount *old_rootmnt; | |
1251 | write_lock(&fs->lock); | |
1252 | old_root = fs->root; | |
1253 | old_rootmnt = fs->rootmnt; | |
1254 | fs->rootmnt = mntget(mnt); | |
1255 | fs->root = dget(dentry); | |
1256 | write_unlock(&fs->lock); | |
1257 | if (old_root) { | |
1258 | dput(old_root); | |
1259 | mntput(old_rootmnt); | |
1260 | } | |
1261 | } | |
1262 | ||
1263 | /* | |
1264 | * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. | |
1265 | * It can block. Requires the big lock held. | |
1266 | */ | |
1267 | void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, | |
1268 | struct dentry *dentry) | |
1269 | { | |
1270 | struct dentry *old_pwd; | |
1271 | struct vfsmount *old_pwdmnt; | |
1272 | ||
1273 | write_lock(&fs->lock); | |
1274 | old_pwd = fs->pwd; | |
1275 | old_pwdmnt = fs->pwdmnt; | |
1276 | fs->pwdmnt = mntget(mnt); | |
1277 | fs->pwd = dget(dentry); | |
1278 | write_unlock(&fs->lock); | |
1279 | ||
1280 | if (old_pwd) { | |
1281 | dput(old_pwd); | |
1282 | mntput(old_pwdmnt); | |
1283 | } | |
1284 | } | |
1285 | ||
1286 | static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) | |
1287 | { | |
1288 | struct task_struct *g, *p; | |
1289 | struct fs_struct *fs; | |
1290 | ||
1291 | read_lock(&tasklist_lock); | |
1292 | do_each_thread(g, p) { | |
1293 | task_lock(p); | |
1294 | fs = p->fs; | |
1295 | if (fs) { | |
1296 | atomic_inc(&fs->count); | |
1297 | task_unlock(p); | |
1298 | if (fs->root==old_nd->dentry&&fs->rootmnt==old_nd->mnt) | |
1299 | set_fs_root(fs, new_nd->mnt, new_nd->dentry); | |
1300 | if (fs->pwd==old_nd->dentry&&fs->pwdmnt==old_nd->mnt) | |
1301 | set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); | |
1302 | put_fs_struct(fs); | |
1303 | } else | |
1304 | task_unlock(p); | |
1305 | } while_each_thread(g, p); | |
1306 | read_unlock(&tasklist_lock); | |
1307 | } | |
1308 | ||
1309 | /* | |
1310 | * pivot_root Semantics: | |
1311 | * Moves the root file system of the current process to the directory put_old, | |
1312 | * makes new_root as the new root file system of the current process, and sets | |
1313 | * root/cwd of all processes which had them on the current root to new_root. | |
1314 | * | |
1315 | * Restrictions: | |
1316 | * The new_root and put_old must be directories, and must not be on the | |
1317 | * same file system as the current process root. The put_old must be | |
1318 | * underneath new_root, i.e. adding a non-zero number of /.. to the string | |
1319 | * pointed to by put_old must yield the same directory as new_root. No other | |
1320 | * file system may be mounted on put_old. After all, new_root is a mountpoint. | |
1321 | * | |
1322 | * Notes: | |
1323 | * - we don't move root/cwd if they are not at the root (reason: if something | |
1324 | * cared enough to change them, it's probably wrong to force them elsewhere) | |
1325 | * - it's okay to pick a root that isn't the root of a file system, e.g. | |
1326 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, | |
1327 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root | |
1328 | * first. | |
1329 | */ | |
1330 | ||
1331 | asmlinkage long sys_pivot_root(const char __user *new_root, const char __user *put_old) | |
1332 | { | |
1333 | struct vfsmount *tmp; | |
1334 | struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; | |
1335 | int error; | |
1336 | ||
1337 | if (!capable(CAP_SYS_ADMIN)) | |
1338 | return -EPERM; | |
1339 | ||
1340 | lock_kernel(); | |
1341 | ||
1342 | error = __user_walk(new_root, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &new_nd); | |
1343 | if (error) | |
1344 | goto out0; | |
1345 | error = -EINVAL; | |
1346 | if (!check_mnt(new_nd.mnt)) | |
1347 | goto out1; | |
1348 | ||
1349 | error = __user_walk(put_old, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &old_nd); | |
1350 | if (error) | |
1351 | goto out1; | |
1352 | ||
1353 | error = security_sb_pivotroot(&old_nd, &new_nd); | |
1354 | if (error) { | |
1355 | path_release(&old_nd); | |
1356 | goto out1; | |
1357 | } | |
1358 | ||
1359 | read_lock(¤t->fs->lock); | |
1360 | user_nd.mnt = mntget(current->fs->rootmnt); | |
1361 | user_nd.dentry = dget(current->fs->root); | |
1362 | read_unlock(¤t->fs->lock); | |
1363 | down_write(¤t->namespace->sem); | |
1364 | down(&old_nd.dentry->d_inode->i_sem); | |
1365 | error = -EINVAL; | |
1366 | if (!check_mnt(user_nd.mnt)) | |
1367 | goto out2; | |
1368 | error = -ENOENT; | |
1369 | if (IS_DEADDIR(new_nd.dentry->d_inode)) | |
1370 | goto out2; | |
1371 | if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) | |
1372 | goto out2; | |
1373 | if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) | |
1374 | goto out2; | |
1375 | error = -EBUSY; | |
1376 | if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) | |
1377 | goto out2; /* loop, on the same file system */ | |
1378 | error = -EINVAL; | |
1379 | if (user_nd.mnt->mnt_root != user_nd.dentry) | |
1380 | goto out2; /* not a mountpoint */ | |
0bb6fcc1 MS |
1381 | if (user_nd.mnt->mnt_parent == user_nd.mnt) |
1382 | goto out2; /* not attached */ | |
1da177e4 LT |
1383 | if (new_nd.mnt->mnt_root != new_nd.dentry) |
1384 | goto out2; /* not a mountpoint */ | |
0bb6fcc1 MS |
1385 | if (new_nd.mnt->mnt_parent == new_nd.mnt) |
1386 | goto out2; /* not attached */ | |
1da177e4 LT |
1387 | tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ |
1388 | spin_lock(&vfsmount_lock); | |
1389 | if (tmp != new_nd.mnt) { | |
1390 | for (;;) { | |
1391 | if (tmp->mnt_parent == tmp) | |
1392 | goto out3; /* already mounted on put_old */ | |
1393 | if (tmp->mnt_parent == new_nd.mnt) | |
1394 | break; | |
1395 | tmp = tmp->mnt_parent; | |
1396 | } | |
1397 | if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) | |
1398 | goto out3; | |
1399 | } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) | |
1400 | goto out3; | |
1401 | detach_mnt(new_nd.mnt, &parent_nd); | |
1402 | detach_mnt(user_nd.mnt, &root_parent); | |
1403 | attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ | |
1404 | attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ | |
5addc5dd | 1405 | touch_namespace(current->namespace); |
1da177e4 LT |
1406 | spin_unlock(&vfsmount_lock); |
1407 | chroot_fs_refs(&user_nd, &new_nd); | |
1408 | security_sb_post_pivotroot(&user_nd, &new_nd); | |
1409 | error = 0; | |
1410 | path_release(&root_parent); | |
1411 | path_release(&parent_nd); | |
1412 | out2: | |
1413 | up(&old_nd.dentry->d_inode->i_sem); | |
1414 | up_write(¤t->namespace->sem); | |
1415 | path_release(&user_nd); | |
1416 | path_release(&old_nd); | |
1417 | out1: | |
1418 | path_release(&new_nd); | |
1419 | out0: | |
1420 | unlock_kernel(); | |
1421 | return error; | |
1422 | out3: | |
1423 | spin_unlock(&vfsmount_lock); | |
1424 | goto out2; | |
1425 | } | |
1426 | ||
1427 | static void __init init_mount_tree(void) | |
1428 | { | |
1429 | struct vfsmount *mnt; | |
1430 | struct namespace *namespace; | |
1431 | struct task_struct *g, *p; | |
1432 | ||
1433 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); | |
1434 | if (IS_ERR(mnt)) | |
1435 | panic("Can't create rootfs"); | |
1436 | namespace = kmalloc(sizeof(*namespace), GFP_KERNEL); | |
1437 | if (!namespace) | |
1438 | panic("Can't allocate initial namespace"); | |
1439 | atomic_set(&namespace->count, 1); | |
1440 | INIT_LIST_HEAD(&namespace->list); | |
1441 | init_rwsem(&namespace->sem); | |
5addc5dd AV |
1442 | init_waitqueue_head(&namespace->poll); |
1443 | namespace->event = 0; | |
1da177e4 LT |
1444 | list_add(&mnt->mnt_list, &namespace->list); |
1445 | namespace->root = mnt; | |
1446 | mnt->mnt_namespace = namespace; | |
1447 | ||
1448 | init_task.namespace = namespace; | |
1449 | read_lock(&tasklist_lock); | |
1450 | do_each_thread(g, p) { | |
1451 | get_namespace(namespace); | |
1452 | p->namespace = namespace; | |
1453 | } while_each_thread(g, p); | |
1454 | read_unlock(&tasklist_lock); | |
1455 | ||
1456 | set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root); | |
1457 | set_fs_root(current->fs, namespace->root, namespace->root->mnt_root); | |
1458 | } | |
1459 | ||
1460 | void __init mnt_init(unsigned long mempages) | |
1461 | { | |
1462 | struct list_head *d; | |
1463 | unsigned int nr_hash; | |
1464 | int i; | |
1465 | ||
1466 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), | |
1467 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); | |
1468 | ||
1469 | mount_hashtable = (struct list_head *) | |
1470 | __get_free_page(GFP_ATOMIC); | |
1471 | ||
1472 | if (!mount_hashtable) | |
1473 | panic("Failed to allocate mount hash table\n"); | |
1474 | ||
1475 | /* | |
1476 | * Find the power-of-two list-heads that can fit into the allocation.. | |
1477 | * We don't guarantee that "sizeof(struct list_head)" is necessarily | |
1478 | * a power-of-two. | |
1479 | */ | |
1480 | nr_hash = PAGE_SIZE / sizeof(struct list_head); | |
1481 | hash_bits = 0; | |
1482 | do { | |
1483 | hash_bits++; | |
1484 | } while ((nr_hash >> hash_bits) != 0); | |
1485 | hash_bits--; | |
1486 | ||
1487 | /* | |
1488 | * Re-calculate the actual number of entries and the mask | |
1489 | * from the number of bits we can fit. | |
1490 | */ | |
1491 | nr_hash = 1UL << hash_bits; | |
1492 | hash_mask = nr_hash-1; | |
1493 | ||
1494 | printk("Mount-cache hash table entries: %d\n", nr_hash); | |
1495 | ||
1496 | /* And initialize the newly allocated array */ | |
1497 | d = mount_hashtable; | |
1498 | i = nr_hash; | |
1499 | do { | |
1500 | INIT_LIST_HEAD(d); | |
1501 | d++; | |
1502 | i--; | |
1503 | } while (i); | |
1504 | sysfs_init(); | |
1505 | init_rootfs(); | |
1506 | init_mount_tree(); | |
1507 | } | |
1508 | ||
1509 | void __put_namespace(struct namespace *namespace) | |
1510 | { | |
1ce88cf4 MS |
1511 | struct vfsmount *root = namespace->root; |
1512 | namespace->root = NULL; | |
1513 | spin_unlock(&vfsmount_lock); | |
1da177e4 LT |
1514 | down_write(&namespace->sem); |
1515 | spin_lock(&vfsmount_lock); | |
1ce88cf4 | 1516 | umount_tree(root); |
1da177e4 LT |
1517 | spin_unlock(&vfsmount_lock); |
1518 | up_write(&namespace->sem); | |
1519 | kfree(namespace); | |
1520 | } |