Re: [PATCH v2 1/3] virtiofs: forbid newlines in tags

On Thu, Feb 08, 2024 at 02:32:09PM -0500, Stefan Hajnoczi wrote:
> Newlines in virtiofs tags are awkward for users and potential vectors
> for string injection attacks.
> 
> Signed-off-by: Stefan Hajnoczi <[email protected]>
> ---
>  fs/fuse/virtio_fs.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 5f1be1da92ce..de9a38efdf1e 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -323,6 +323,16 @@ static int virtio_fs_read_tag(struct virtio_device *vdev, struct virtio_fs *fs)
>  		return -ENOMEM;
>  	memcpy(fs->tag, tag_buf, len);
>  	fs->tag[len] = '\0';
> +
> +	/* While the VIRTIO specification allows any character, newlines are
> +	 * awkward on mount(8) command-lines and cause problems in the sysfs
> +	 * "tag" attr and uevent TAG= properties. Forbid them.
> +	 */
> +	if (strchr(fs->tag, '\n')) {
> +		dev_err(&vdev->dev, "refusing virtiofs tag with newline character\n");

Please don't let userspace spam mthe kernel log if they are the ones
that are setting the tags.  Just make this a debug message instead.

thanks,

greg k-h