a) ovl_need_xattr_filter() is wrong, we can have multiple lower layers
overlaid, all of which (except the lowest one) honouring the
"trusted.overlay.opaque" xattr. So need to filter everything except the
bottom and the pure-upper layer.
b) we no longer can assume that inode is attached to dentry in
get/setxattr.
This patch unconditionally filters private xattrs to fix both of the above.
Performance impact for get/removexattrs is likely in the noise.
For listxattrs it might be measurable in pathological cases, but I very
much hope nobody cares. If they do, we'll fix it then.
Reported-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Fixes: b96809173e94 ("security_d_instantiate(): move to the point prior to attaching dentry to inode")
---
fs/overlayfs/inode.c | 26 ++++++--------------------
1 file changed, 6 insertions(+), 20 deletions(-)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -238,41 +238,27 @@ int ovl_setxattr(struct dentry *dentry,
return err;
}
-static bool ovl_need_xattr_filter(struct dentry *dentry,
- enum ovl_path_type type)
-{
- if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
- return S_ISDIR(dentry->d_inode->i_mode);
- else
- return false;
-}
-
ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
const char *name, void *value, size_t size)
{
- struct path realpath;
- enum ovl_path_type type = ovl_path_real(dentry, &realpath);
+ struct dentry *realdentry = ovl_dentry_real(dentry);
- if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
+ if (ovl_is_private_xattr(name))
return -ENODATA;
- return vfs_getxattr(realpath.dentry, name, value, size);
+ return vfs_getxattr(realdentry, name, value, size);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
- struct path realpath;
- enum ovl_path_type type = ovl_path_real(dentry, &realpath);
+ struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
int off;
- res = vfs_listxattr(realpath.dentry, list, size);
+ res = vfs_listxattr(realdentry, list, size);
if (res <= 0 || size == 0)
return res;
- if (!ovl_need_xattr_filter(dentry, type))
- return res;
-
/* filter out private xattrs */
for (off = 0; off < res;) {
char *s = list + off;
@@ -302,7 +288,7 @@ int ovl_removexattr(struct dentry *dentr
goto out;
err = -ENODATA;
- if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
+ if (ovl_is_private_xattr(name))
goto out_drop_write;
if (!OVL_TYPE_UPPER(type)) {
--
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