Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/fs/namespace.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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File size: 35677 byte(s)
Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 35677 byte(s)
Tag kernel26-2.6.12-alx-r9
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 | } |