On Thu, Jun 02, 2016 at 10:13:33AM +0200, Miklos Szeredi wrote:
> 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 <vgo...@redhat.com>
> Signed-off-by: Miklos Szeredi <mszer...@redhat.com>
> Fixes: b96809173e94 ("security_d_instantiate(): move to the point prior to
> attaching dentry to inode")
Hi Miklos,
This patch fixes the issue for me. Thanks.
Reviewed-by: Vivek Goyal <vgo...@redhat.com>
Vivek
> ---
> 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)) {
