forked from torvalds/linux
-
Notifications
You must be signed in to change notification settings - Fork 0
/
namespace.c
1469 lines (1282 loc) · 34.9 KB
/
namespace.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* linux/fs/namespace.c
*
* (C) Copyright Al Viro 2000, 2001
* Released under GPL v2.
*
* Based on code from fs/super.c, copyright Linus Torvalds and others.
* Heavily rewritten.
*/
#include <linux/config.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/acct.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
extern int __init init_rootfs(void);
#ifdef CONFIG_SYSFS
extern int __init sysfs_init(void);
#else
static inline int sysfs_init(void)
{
return 0;
}
#endif
/* spinlock for vfsmount related operations, inplace of dcache_lock */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
static struct list_head *mount_hashtable;
static int hash_mask, hash_bits;
static kmem_cache_t *mnt_cache;
static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
unsigned long tmp = ((unsigned long) mnt / L1_CACHE_BYTES);
tmp += ((unsigned long) dentry / L1_CACHE_BYTES);
tmp = tmp + (tmp >> hash_bits);
return tmp & hash_mask;
}
struct vfsmount *alloc_vfsmnt(const char *name)
{
struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
if (mnt) {
memset(mnt, 0, sizeof(struct vfsmount));
atomic_set(&mnt->mnt_count,1);
INIT_LIST_HEAD(&mnt->mnt_hash);
INIT_LIST_HEAD(&mnt->mnt_child);
INIT_LIST_HEAD(&mnt->mnt_mounts);
INIT_LIST_HEAD(&mnt->mnt_list);
INIT_LIST_HEAD(&mnt->mnt_expire);
if (name) {
int size = strlen(name)+1;
char *newname = kmalloc(size, GFP_KERNEL);
if (newname) {
memcpy(newname, name, size);
mnt->mnt_devname = newname;
}
}
}
return mnt;
}
void free_vfsmnt(struct vfsmount *mnt)
{
kfree(mnt->mnt_devname);
kmem_cache_free(mnt_cache, mnt);
}
/*
* Now, lookup_mnt increments the ref count before returning
* the vfsmount struct.
*/
struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
{
struct list_head * head = mount_hashtable + hash(mnt, dentry);
struct list_head * tmp = head;
struct vfsmount *p, *found = NULL;
spin_lock(&vfsmount_lock);
for (;;) {
tmp = tmp->next;
p = NULL;
if (tmp == head)
break;
p = list_entry(tmp, struct vfsmount, mnt_hash);
if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
found = mntget(p);
break;
}
}
spin_unlock(&vfsmount_lock);
return found;
}
static inline int check_mnt(struct vfsmount *mnt)
{
return mnt->mnt_namespace == current->namespace;
}
static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
{
old_nd->dentry = mnt->mnt_mountpoint;
old_nd->mnt = mnt->mnt_parent;
mnt->mnt_parent = mnt;
mnt->mnt_mountpoint = mnt->mnt_root;
list_del_init(&mnt->mnt_child);
list_del_init(&mnt->mnt_hash);
old_nd->dentry->d_mounted--;
}
static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
{
mnt->mnt_parent = mntget(nd->mnt);
mnt->mnt_mountpoint = dget(nd->dentry);
list_add(&mnt->mnt_hash, mount_hashtable+hash(nd->mnt, nd->dentry));
list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
nd->dentry->d_mounted++;
}
static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
{
struct list_head *next = p->mnt_mounts.next;
if (next == &p->mnt_mounts) {
while (1) {
if (p == root)
return NULL;
next = p->mnt_child.next;
if (next != &p->mnt_parent->mnt_mounts)
break;
p = p->mnt_parent;
}
}
return list_entry(next, struct vfsmount, mnt_child);
}
static struct vfsmount *
clone_mnt(struct vfsmount *old, struct dentry *root)
{
struct super_block *sb = old->mnt_sb;
struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
if (mnt) {
mnt->mnt_flags = old->mnt_flags;
atomic_inc(&sb->s_active);
mnt->mnt_sb = sb;
mnt->mnt_root = dget(root);
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
mnt->mnt_namespace = old->mnt_namespace;
/* stick the duplicate mount on the same expiry list
* as the original if that was on one */
spin_lock(&vfsmount_lock);
if (!list_empty(&old->mnt_expire))
list_add(&mnt->mnt_expire, &old->mnt_expire);
spin_unlock(&vfsmount_lock);
}
return mnt;
}
void __mntput(struct vfsmount *mnt)
{
struct super_block *sb = mnt->mnt_sb;
dput(mnt->mnt_root);
free_vfsmnt(mnt);
deactivate_super(sb);
}
EXPORT_SYMBOL(__mntput);
/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
struct namespace *n = m->private;
struct list_head *p;
loff_t l = *pos;
down_read(&n->sem);
list_for_each(p, &n->list)
if (!l--)
return list_entry(p, struct vfsmount, mnt_list);
return NULL;
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct namespace *n = m->private;
struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
(*pos)++;
return p==&n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
}
static void m_stop(struct seq_file *m, void *v)
{
struct namespace *n = m->private;
up_read(&n->sem);
}
static inline void mangle(struct seq_file *m, const char *s)
{
seq_escape(m, s, " \t\n\\");
}
static int show_vfsmnt(struct seq_file *m, void *v)
{
struct vfsmount *mnt = v;
int err = 0;
static struct proc_fs_info {
int flag;
char *str;
} fs_info[] = {
{ MS_SYNCHRONOUS, ",sync" },
{ MS_DIRSYNC, ",dirsync" },
{ MS_MANDLOCK, ",mand" },
{ MS_NOATIME, ",noatime" },
{ MS_NODIRATIME, ",nodiratime" },
{ 0, NULL }
};
static struct proc_fs_info mnt_info[] = {
{ MNT_NOSUID, ",nosuid" },
{ MNT_NODEV, ",nodev" },
{ MNT_NOEXEC, ",noexec" },
{ 0, NULL }
};
struct proc_fs_info *fs_infop;
mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
seq_putc(m, ' ');
seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
seq_putc(m, ' ');
mangle(m, mnt->mnt_sb->s_type->name);
seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_sb->s_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
if (mnt->mnt_flags & fs_infop->flag)
seq_puts(m, fs_infop->str);
}
if (mnt->mnt_sb->s_op->show_options)
err = mnt->mnt_sb->s_op->show_options(m, mnt);
seq_puts(m, " 0 0\n");
return err;
}
struct seq_operations mounts_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_vfsmnt
};
/**
* may_umount_tree - check if a mount tree is busy
* @mnt: root of mount tree
*
* This is called to check if a tree of mounts has any
* open files, pwds, chroots or sub mounts that are
* busy.
*/
int may_umount_tree(struct vfsmount *mnt)
{
struct list_head *next;
struct vfsmount *this_parent = mnt;
int actual_refs;
int minimum_refs;
spin_lock(&vfsmount_lock);
actual_refs = atomic_read(&mnt->mnt_count);
minimum_refs = 2;
repeat:
next = this_parent->mnt_mounts.next;
resume:
while (next != &this_parent->mnt_mounts) {
struct vfsmount *p = list_entry(next, struct vfsmount, mnt_child);
next = next->next;
actual_refs += atomic_read(&p->mnt_count);
minimum_refs += 2;
if (!list_empty(&p->mnt_mounts)) {
this_parent = p;
goto repeat;
}
}
if (this_parent != mnt) {
next = this_parent->mnt_child.next;
this_parent = this_parent->mnt_parent;
goto resume;
}
spin_unlock(&vfsmount_lock);
if (actual_refs > minimum_refs)
return -EBUSY;
return 0;
}
EXPORT_SYMBOL(may_umount_tree);
/**
* may_umount - check if a mount point is busy
* @mnt: root of mount
*
* This is called to check if a mount point has any
* open files, pwds, chroots or sub mounts. If the
* mount has sub mounts this will return busy
* regardless of whether the sub mounts are busy.
*
* Doesn't take quota and stuff into account. IOW, in some cases it will
* give false negatives. The main reason why it's here is that we need
* a non-destructive way to look for easily umountable filesystems.
*/
int may_umount(struct vfsmount *mnt)
{
if (atomic_read(&mnt->mnt_count) > 2)
return -EBUSY;
return 0;
}
EXPORT_SYMBOL(may_umount);
static void umount_tree(struct vfsmount *mnt)
{
struct vfsmount *p;
LIST_HEAD(kill);
for (p = mnt; p; p = next_mnt(p, mnt)) {
list_del(&p->mnt_list);
list_add(&p->mnt_list, &kill);
p->mnt_namespace = NULL;
}
while (!list_empty(&kill)) {
mnt = list_entry(kill.next, struct vfsmount, mnt_list);
list_del_init(&mnt->mnt_list);
list_del_init(&mnt->mnt_expire);
if (mnt->mnt_parent == mnt) {
spin_unlock(&vfsmount_lock);
} else {
struct nameidata old_nd;
detach_mnt(mnt, &old_nd);
spin_unlock(&vfsmount_lock);
path_release(&old_nd);
}
mntput(mnt);
spin_lock(&vfsmount_lock);
}
}
static int do_umount(struct vfsmount *mnt, int flags)
{
struct super_block * sb = mnt->mnt_sb;
int retval;
retval = security_sb_umount(mnt, flags);
if (retval)
return retval;
/*
* Allow userspace to request a mountpoint be expired rather than
* unmounting unconditionally. Unmount only happens if:
* (1) the mark is already set (the mark is cleared by mntput())
* (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
*/
if (flags & MNT_EXPIRE) {
if (mnt == current->fs->rootmnt ||
flags & (MNT_FORCE | MNT_DETACH))
return -EINVAL;
if (atomic_read(&mnt->mnt_count) != 2)
return -EBUSY;
if (!xchg(&mnt->mnt_expiry_mark, 1))
return -EAGAIN;
}
/*
* If we may have to abort operations to get out of this
* mount, and they will themselves hold resources we must
* allow the fs to do things. In the Unix tradition of
* 'Gee thats tricky lets do it in userspace' the umount_begin
* might fail to complete on the first run through as other tasks
* must return, and the like. Thats for the mount program to worry
* about for the moment.
*/
lock_kernel();
if( (flags&MNT_FORCE) && sb->s_op->umount_begin)
sb->s_op->umount_begin(sb);
unlock_kernel();
/*
* No sense to grab the lock for this test, but test itself looks
* somewhat bogus. Suggestions for better replacement?
* Ho-hum... In principle, we might treat that as umount + switch
* to rootfs. GC would eventually take care of the old vfsmount.
* Actually it makes sense, especially if rootfs would contain a
* /reboot - static binary that would close all descriptors and
* call reboot(9). Then init(8) could umount root and exec /reboot.
*/
if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) {
/*
* Special case for "unmounting" root ...
* we just try to remount it readonly.
*/
down_write(&sb->s_umount);
if (!(sb->s_flags & MS_RDONLY)) {
lock_kernel();
DQUOT_OFF(sb);
retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
unlock_kernel();
}
up_write(&sb->s_umount);
return retval;
}
down_write(¤t->namespace->sem);
spin_lock(&vfsmount_lock);
if (atomic_read(&sb->s_active) == 1) {
/* last instance - try to be smart */
spin_unlock(&vfsmount_lock);
lock_kernel();
DQUOT_OFF(sb);
acct_auto_close(sb);
unlock_kernel();
security_sb_umount_close(mnt);
spin_lock(&vfsmount_lock);
}
retval = -EBUSY;
if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
if (!list_empty(&mnt->mnt_list))
umount_tree(mnt);
retval = 0;
}
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
up_write(¤t->namespace->sem);
return retval;
}
/*
* Now umount can handle mount points as well as block devices.
* This is important for filesystems which use unnamed block devices.
*
* We now support a flag for forced unmount like the other 'big iron'
* unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
*/
asmlinkage long sys_umount(char __user * name, int flags)
{
struct nameidata nd;
int retval;
retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
if (retval)
goto out;
retval = -EINVAL;
if (nd.dentry != nd.mnt->mnt_root)
goto dput_and_out;
if (!check_mnt(nd.mnt))
goto dput_and_out;
retval = -EPERM;
if (!capable(CAP_SYS_ADMIN))
goto dput_and_out;
retval = do_umount(nd.mnt, flags);
dput_and_out:
path_release_on_umount(&nd);
out:
return retval;
}
#ifdef __ARCH_WANT_SYS_OLDUMOUNT
/*
* The 2.0 compatible umount. No flags.
*/
asmlinkage long sys_oldumount(char __user * name)
{
return sys_umount(name,0);
}
#endif
static int mount_is_safe(struct nameidata *nd)
{
if (capable(CAP_SYS_ADMIN))
return 0;
return -EPERM;
#ifdef notyet
if (S_ISLNK(nd->dentry->d_inode->i_mode))
return -EPERM;
if (nd->dentry->d_inode->i_mode & S_ISVTX) {
if (current->uid != nd->dentry->d_inode->i_uid)
return -EPERM;
}
if (permission(nd->dentry->d_inode, MAY_WRITE, nd))
return -EPERM;
return 0;
#endif
}
static int
lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
{
while (1) {
if (d == dentry)
return 1;
if (d == NULL || d == d->d_parent)
return 0;
d = d->d_parent;
}
}
static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry)
{
struct vfsmount *res, *p, *q, *r, *s;
struct list_head *h;
struct nameidata nd;
res = q = clone_mnt(mnt, dentry);
if (!q)
goto Enomem;
q->mnt_mountpoint = mnt->mnt_mountpoint;
p = mnt;
for (h = mnt->mnt_mounts.next; h != &mnt->mnt_mounts; h = h->next) {
r = list_entry(h, struct vfsmount, mnt_child);
if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
continue;
for (s = r; s; s = next_mnt(s, r)) {
while (p != s->mnt_parent) {
p = p->mnt_parent;
q = q->mnt_parent;
}
p = s;
nd.mnt = q;
nd.dentry = p->mnt_mountpoint;
q = clone_mnt(p, p->mnt_root);
if (!q)
goto Enomem;
spin_lock(&vfsmount_lock);
list_add_tail(&q->mnt_list, &res->mnt_list);
attach_mnt(q, &nd);
spin_unlock(&vfsmount_lock);
}
}
return res;
Enomem:
if (res) {
spin_lock(&vfsmount_lock);
umount_tree(res);
spin_unlock(&vfsmount_lock);
}
return NULL;
}
static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
int err;
if (mnt->mnt_sb->s_flags & MS_NOUSER)
return -EINVAL;
if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
S_ISDIR(mnt->mnt_root->d_inode->i_mode))
return -ENOTDIR;
err = -ENOENT;
down(&nd->dentry->d_inode->i_sem);
if (IS_DEADDIR(nd->dentry->d_inode))
goto out_unlock;
err = security_sb_check_sb(mnt, nd);
if (err)
goto out_unlock;
err = -ENOENT;
spin_lock(&vfsmount_lock);
if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) {
struct list_head head;
attach_mnt(mnt, nd);
list_add_tail(&head, &mnt->mnt_list);
list_splice(&head, current->namespace->list.prev);
mntget(mnt);
err = 0;
}
spin_unlock(&vfsmount_lock);
out_unlock:
up(&nd->dentry->d_inode->i_sem);
if (!err)
security_sb_post_addmount(mnt, nd);
return err;
}
/*
* do loopback mount.
*/
static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
{
struct nameidata old_nd;
struct vfsmount *mnt = NULL;
int err = mount_is_safe(nd);
if (err)
return err;
if (!old_name || !*old_name)
return -EINVAL;
err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
down_write(¤t->namespace->sem);
err = -EINVAL;
if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd.mnt))) {
err = -ENOMEM;
if (recurse)
mnt = copy_tree(old_nd.mnt, old_nd.dentry);
else
mnt = clone_mnt(old_nd.mnt, old_nd.dentry);
}
if (mnt) {
/* stop bind mounts from expiring */
spin_lock(&vfsmount_lock);
list_del_init(&mnt->mnt_expire);
spin_unlock(&vfsmount_lock);
err = graft_tree(mnt, nd);
if (err) {
spin_lock(&vfsmount_lock);
umount_tree(mnt);
spin_unlock(&vfsmount_lock);
} else
mntput(mnt);
}
up_write(¤t->namespace->sem);
path_release(&old_nd);
return err;
}
/*
* change filesystem flags. dir should be a physical root of filesystem.
* If you've mounted a non-root directory somewhere and want to do remount
* on it - tough luck.
*/
static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
void *data)
{
int err;
struct super_block * sb = nd->mnt->mnt_sb;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!check_mnt(nd->mnt))
return -EINVAL;
if (nd->dentry != nd->mnt->mnt_root)
return -EINVAL;
down_write(&sb->s_umount);
err = do_remount_sb(sb, flags, data, 0);
if (!err)
nd->mnt->mnt_flags=mnt_flags;
up_write(&sb->s_umount);
if (!err)
security_sb_post_remount(nd->mnt, flags, data);
return err;
}
static int do_move_mount(struct nameidata *nd, char *old_name)
{
struct nameidata old_nd, parent_nd;
struct vfsmount *p;
int err = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!old_name || !*old_name)
return -EINVAL;
err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
down_write(¤t->namespace->sem);
while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
goto out;
err = -ENOENT;
down(&nd->dentry->d_inode->i_sem);
if (IS_DEADDIR(nd->dentry->d_inode))
goto out1;
spin_lock(&vfsmount_lock);
if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
goto out2;
err = -EINVAL;
if (old_nd.dentry != old_nd.mnt->mnt_root)
goto out2;
if (old_nd.mnt == old_nd.mnt->mnt_parent)
goto out2;
if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
S_ISDIR(old_nd.dentry->d_inode->i_mode))
goto out2;
err = -ELOOP;
for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent)
if (p == old_nd.mnt)
goto out2;
err = 0;
detach_mnt(old_nd.mnt, &parent_nd);
attach_mnt(old_nd.mnt, nd);
/* if the mount is moved, it should no longer be expire
* automatically */
list_del_init(&old_nd.mnt->mnt_expire);
out2:
spin_unlock(&vfsmount_lock);
out1:
up(&nd->dentry->d_inode->i_sem);
out:
up_write(¤t->namespace->sem);
if (!err)
path_release(&parent_nd);
path_release(&old_nd);
return err;
}
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
*/
static int do_new_mount(struct nameidata *nd, char *type, int flags,
int mnt_flags, char *name, void *data)
{
struct vfsmount *mnt;
if (!type || !memchr(type, 0, PAGE_SIZE))
return -EINVAL;
/* we need capabilities... */
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
mnt = do_kern_mount(type, flags, name, data);
if (IS_ERR(mnt))
return PTR_ERR(mnt);
return do_add_mount(mnt, nd, mnt_flags, NULL);
}
/*
* add a mount into a namespace's mount tree
* - provide the option of adding the new mount to an expiration list
*/
int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
int mnt_flags, struct list_head *fslist)
{
int err;
down_write(¤t->namespace->sem);
/* Something was mounted here while we slept */
while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
if (!check_mnt(nd->mnt))
goto unlock;
/* Refuse the same filesystem on the same mount point */
err = -EBUSY;
if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
nd->mnt->mnt_root == nd->dentry)
goto unlock;
err = -EINVAL;
if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
goto unlock;
newmnt->mnt_flags = mnt_flags;
newmnt->mnt_namespace = current->namespace;
err = graft_tree(newmnt, nd);
if (err == 0 && fslist) {
/* add to the specified expiration list */
spin_lock(&vfsmount_lock);
list_add_tail(&newmnt->mnt_expire, fslist);
spin_unlock(&vfsmount_lock);
}
unlock:
up_write(¤t->namespace->sem);
mntput(newmnt);
return err;
}
EXPORT_SYMBOL_GPL(do_add_mount);
static void expire_mount(struct vfsmount *mnt, struct list_head *mounts)
{
spin_lock(&vfsmount_lock);
/*
* Check if mount is still attached, if not, let whoever holds it deal
* with the sucker
*/
if (mnt->mnt_parent == mnt) {
spin_unlock(&vfsmount_lock);
return;
}
/*
* Check that it is still dead: the count should now be 2 - as
* contributed by the vfsmount parent and the mntget above
*/
if (atomic_read(&mnt->mnt_count) == 2) {
struct nameidata old_nd;
/* delete from the namespace */
list_del_init(&mnt->mnt_list);
mnt->mnt_namespace = NULL;
detach_mnt(mnt, &old_nd);
spin_unlock(&vfsmount_lock);
path_release(&old_nd);
/*
* Now lay it to rest if this was the last ref on the superblock
*/
if (atomic_read(&mnt->mnt_sb->s_active) == 1) {
/* last instance - try to be smart */
lock_kernel();
DQUOT_OFF(mnt->mnt_sb);
acct_auto_close(mnt->mnt_sb);
unlock_kernel();
}
mntput(mnt);
} else {
/*
* Someone brought it back to life whilst we didn't have any
* locks held so return it to the expiration list
*/
list_add_tail(&mnt->mnt_expire, mounts);
spin_unlock(&vfsmount_lock);
}
}
/*
* process a list of expirable mountpoints with the intent of discarding any
* mountpoints that aren't in use and haven't been touched since last we came
* here
*/
void mark_mounts_for_expiry(struct list_head *mounts)
{
struct namespace *namespace;
struct vfsmount *mnt, *next;
LIST_HEAD(graveyard);
if (list_empty(mounts))
return;
spin_lock(&vfsmount_lock);
/* extract from the expiration list every vfsmount that matches the
* following criteria:
* - only referenced by its parent vfsmount
* - still marked for expiry (marked on the last call here; marks are
* cleared by mntput())
*/
list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
if (!xchg(&mnt->mnt_expiry_mark, 1) ||
atomic_read(&mnt->mnt_count) != 1)
continue;
mntget(mnt);
list_move(&mnt->mnt_expire, &graveyard);
}
/*
* go through the vfsmounts we've just consigned to the graveyard to
* - check that they're still dead
* - delete the vfsmount from the appropriate namespace under lock
* - dispose of the corpse
*/
while (!list_empty(&graveyard)) {
mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
list_del_init(&mnt->mnt_expire);
/* don't do anything if the namespace is dead - all the
* vfsmounts from it are going away anyway */
namespace = mnt->mnt_namespace;
if (!namespace || !namespace->root)
continue;
get_namespace(namespace);
spin_unlock(&vfsmount_lock);
down_write(&namespace->sem);
expire_mount(mnt, mounts);
up_write(&namespace->sem);
mntput(mnt);
put_namespace(namespace);
spin_lock(&vfsmount_lock);
}
spin_unlock(&vfsmount_lock);
}
EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
/*
* Some copy_from_user() implementations do not return the exact number of
* bytes remaining to copy on a fault. But copy_mount_options() requires that.
* Note that this function differs from copy_from_user() in that it will oops
* on bad values of `to', rather than returning a short copy.
*/
static long
exact_copy_from_user(void *to, const void __user *from, unsigned long n)
{
char *t = to;
const char __user *f = from;
char c;
if (!access_ok(VERIFY_READ, from, n))
return n;
while (n) {
if (__get_user(c, f)) {
memset(t, 0, n);
break;
}
*t++ = c;
f++;
n--;
}
return n;
}
int copy_mount_options(const void __user *data, unsigned long *where)
{
int i;
unsigned long page;
unsigned long size;
*where = 0;
if (!data)
return 0;
if (!(page = __get_free_page(GFP_KERNEL)))
return -ENOMEM;
/* We only care that *some* data at the address the user
* gave us is valid. Just in case, we'll zero
* the remainder of the page.
*/
/* copy_from_user cannot cross TASK_SIZE ! */
size = TASK_SIZE - (unsigned long)data;
if (size > PAGE_SIZE)
size = PAGE_SIZE;
i = size - exact_copy_from_user((void *)page, data, size);
if (!i) {
free_page(page);
return -EFAULT;
}
if (i != PAGE_SIZE)
memset((char *)page + i, 0, PAGE_SIZE - i);
*where = page;
return 0;
}