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git.proxmox.com Git - mirror_ubuntu-focal-kernel.git/blob - fs/overlayfs/namei.c
2 * Copyright (C) 2011 Novell Inc.
3 * Copyright (C) 2016 Red Hat, Inc.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
11 #include <linux/namei.h>
12 #include <linux/xattr.h>
13 #include <linux/ratelimit.h>
14 #include "overlayfs.h"
15 #include "ovl_entry.h"
17 struct ovl_lookup_data
{
26 static int ovl_check_redirect(struct dentry
*dentry
, struct ovl_lookup_data
*d
,
27 size_t prelen
, const char *post
)
30 char *s
, *next
, *buf
= NULL
;
32 res
= vfs_getxattr(dentry
, OVL_XATTR_REDIRECT
, NULL
, 0);
34 if (res
== -ENODATA
|| res
== -EOPNOTSUPP
)
38 buf
= kzalloc(prelen
+ res
+ strlen(post
) + 1, GFP_TEMPORARY
);
45 res
= vfs_getxattr(dentry
, OVL_XATTR_REDIRECT
, buf
, res
);
51 for (s
= buf
; *s
++ == '/'; s
= next
) {
52 next
= strchrnul(s
, '/');
57 if (strchr(buf
, '/') != NULL
)
60 memmove(buf
+ prelen
, buf
, res
);
61 memcpy(buf
, d
->name
.name
, prelen
);
67 d
->name
.name
= d
->redirect
;
68 d
->name
.len
= strlen(d
->redirect
);
76 pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res
);
79 pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf
);
83 static bool ovl_is_opaquedir(struct dentry
*dentry
)
88 if (!d_is_dir(dentry
))
91 res
= vfs_getxattr(dentry
, OVL_XATTR_OPAQUE
, &val
, 1);
92 if (res
== 1 && val
== 'y')
98 static int ovl_lookup_single(struct dentry
*base
, struct ovl_lookup_data
*d
,
99 const char *name
, unsigned int namelen
,
100 size_t prelen
, const char *post
,
106 this = lookup_one_len_unlocked(name
, base
, namelen
);
110 if (err
== -ENOENT
|| err
== -ENAMETOOLONG
)
117 if (ovl_dentry_weird(this)) {
118 /* Don't support traversing automounts and other weirdness */
122 if (ovl_is_whiteout(this)) {
123 d
->stop
= d
->opaque
= true;
126 if (!d_can_lookup(this)) {
133 if (!d
->last
&& ovl_is_opaquedir(this)) {
134 d
->stop
= d
->opaque
= true;
137 err
= ovl_check_redirect(this, d
, prelen
, post
);
154 static int ovl_lookup_layer(struct dentry
*base
, struct ovl_lookup_data
*d
,
157 /* Counting down from the end, since the prefix can change */
158 size_t rem
= d
->name
.len
- 1;
159 struct dentry
*dentry
= NULL
;
162 if (d
->name
.name
[0] != '/')
163 return ovl_lookup_single(base
, d
, d
->name
.name
, d
->name
.len
,
166 while (!IS_ERR_OR_NULL(base
) && d_can_lookup(base
)) {
167 const char *s
= d
->name
.name
+ d
->name
.len
- rem
;
168 const char *next
= strchrnul(s
, '/');
169 size_t thislen
= next
- s
;
172 /* Verify we did not go off the rails */
173 if (WARN_ON(s
[-1] != '/'))
176 err
= ovl_lookup_single(base
, d
, s
, thislen
,
177 d
->name
.len
- rem
, next
, &base
);
187 if (WARN_ON(rem
>= d
->name
.len
))
195 * Returns next layer in stack starting from top.
196 * Returns -1 if this is the last layer.
198 int ovl_path_next(int idx
, struct dentry
*dentry
, struct path
*path
)
200 struct ovl_entry
*oe
= dentry
->d_fsdata
;
204 ovl_path_upper(dentry
, path
);
206 return oe
->numlower
? 1 : -1;
209 BUG_ON(idx
> oe
->numlower
);
210 *path
= oe
->lowerstack
[idx
- 1];
212 return (idx
< oe
->numlower
) ? idx
+ 1 : -1;
215 struct dentry
*ovl_lookup(struct inode
*dir
, struct dentry
*dentry
,
218 struct ovl_entry
*oe
;
219 const struct cred
*old_cred
;
220 struct ovl_fs
*ofs
= dentry
->d_sb
->s_fs_info
;
221 struct ovl_entry
*poe
= dentry
->d_parent
->d_fsdata
;
222 struct path
*stack
= NULL
;
223 struct dentry
*upperdir
, *upperdentry
= NULL
;
224 unsigned int ctr
= 0;
225 struct inode
*inode
= NULL
;
226 bool upperopaque
= false;
227 char *upperredirect
= NULL
;
231 struct ovl_lookup_data d
= {
232 .name
= dentry
->d_name
,
236 .last
= !poe
->numlower
,
240 if (dentry
->d_name
.len
> ofs
->namelen
)
241 return ERR_PTR(-ENAMETOOLONG
);
243 old_cred
= ovl_override_creds(dentry
->d_sb
);
244 upperdir
= ovl_upperdentry_dereference(poe
);
246 err
= ovl_lookup_layer(upperdir
, &d
, &upperdentry
);
250 if (upperdentry
&& unlikely(ovl_dentry_remote(upperdentry
))) {
257 upperredirect
= kstrdup(d
.redirect
, GFP_KERNEL
);
260 if (d
.redirect
[0] == '/')
261 poe
= dentry
->d_sb
->s_root
->d_fsdata
;
263 upperopaque
= d
.opaque
;
266 if (!d
.stop
&& poe
->numlower
) {
268 stack
= kcalloc(ofs
->numlower
, sizeof(struct path
),
274 for (i
= 0; !d
.stop
&& i
< poe
->numlower
; i
++) {
275 struct path lowerpath
= poe
->lowerstack
[i
];
277 d
.last
= i
== poe
->numlower
- 1;
278 err
= ovl_lookup_layer(lowerpath
.dentry
, &d
, &this);
285 stack
[ctr
].dentry
= this;
286 stack
[ctr
].mnt
= lowerpath
.mnt
;
293 d
.redirect
[0] == '/' &&
294 poe
!= dentry
->d_sb
->s_root
->d_fsdata
) {
295 poe
= dentry
->d_sb
->s_root
->d_fsdata
;
297 /* Find the current layer on the root dentry */
298 for (i
= 0; i
< poe
->numlower
; i
++)
299 if (poe
->lowerstack
[i
].mnt
== lowerpath
.mnt
)
301 if (WARN_ON(i
== poe
->numlower
))
306 oe
= ovl_alloc_entry(ctr
);
311 if (upperdentry
|| ctr
) {
312 struct dentry
*realdentry
;
313 struct inode
*realinode
;
315 realdentry
= upperdentry
? upperdentry
: stack
[0].dentry
;
316 realinode
= d_inode(realdentry
);
319 if (upperdentry
&& !d_is_dir(upperdentry
)) {
320 inode
= ovl_get_inode(dentry
->d_sb
, realinode
);
322 inode
= ovl_new_inode(dentry
->d_sb
, realinode
->i_mode
,
325 ovl_inode_init(inode
, realinode
, !!upperdentry
);
329 ovl_copyattr(realdentry
->d_inode
, inode
);
332 revert_creds(old_cred
);
333 oe
->opaque
= upperopaque
;
334 oe
->redirect
= upperredirect
;
335 oe
->__upperdentry
= upperdentry
;
336 memcpy(oe
->lowerstack
, stack
, sizeof(struct path
) * ctr
);
339 dentry
->d_fsdata
= oe
;
340 d_add(dentry
, inode
);
347 for (i
= 0; i
< ctr
; i
++)
348 dput(stack
[i
].dentry
);
352 kfree(upperredirect
);
355 revert_creds(old_cred
);
359 bool ovl_lower_positive(struct dentry
*dentry
)
361 struct ovl_entry
*oe
= dentry
->d_fsdata
;
362 struct ovl_entry
*poe
= dentry
->d_parent
->d_fsdata
;
363 const struct qstr
*name
= &dentry
->d_name
;
365 bool positive
= false;
369 * If dentry is negative, then lower is positive iff this is a
372 if (!dentry
->d_inode
)
375 /* Negative upper -> positive lower */
376 if (!oe
->__upperdentry
)
379 /* Positive upper -> have to look up lower to see whether it exists */
380 for (i
= 0; !done
&& !positive
&& i
< poe
->numlower
; i
++) {
382 struct dentry
*lowerdir
= poe
->lowerstack
[i
].dentry
;
384 this = lookup_one_len_unlocked(name
->name
, lowerdir
,
387 switch (PTR_ERR(this)) {
394 * Assume something is there, we just couldn't
402 positive
= !ovl_is_whiteout(this);