[Virtio-fs] [PATCH 3/3] virtiofsd: Don't allow empty filenames

[Connor Kuehl]

On 3/12/21 8:10 AM, Greg Kurz wrote:
> POSIX.1-2017 clearly stipulates that empty filenames aren't
> allowed ([1] and [2]). Since virtiofsd is supposed to mirror
> the host file system hierarchy and the host can be assumed to
> be linux, we don't really expect clients to pass requests with
> an empty path in it. If they do so anyway, this would eventually
> cause an error when trying to create/lookup the actual inode
> on the underlying POSIX filesystem. But this could still confuse
> some code that wouldn't be ready to cope with this.
> 
> Filter out empty names coming from the client at the top level,
> so that the rest doesn't have to care about it. This is done
> everywhere we already call is_safe_path_component(), but
> in a separate helper since the usual error for empty path
> names is ENOENT instead of EINVAL.
> 
> [1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_170
> [2] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
> 
> Signed-off-by: Greg Kurz <groug at kaod.org>

Reviewed-by: Connor Kuehl <ckuehl at redhat.com>