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

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Feb 09, 2024 at 10:33:20AM +0000, Greg KH wrote:
> 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 <stefanha@redhat.com>
> > ---
> >  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.

This check is performed while probing the device. Userspace is not
involved but I'll change it to dev_dbg() anyway.

Stefan

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