x25: possible skb leak on bad facilities

[Andy Whitcroft]

Looking at the changes introduced in the commit below, we seem to
introduce an skb leak when a packet with bad facilities are present:

    commit a6331d6f9a4298173b413cf99a40cc86a9d92c37
    Author: andrew hendry <andrew.hendry@xxxxxxxxx>
    Date:   Wed Nov 3 12:54:53 2010 +0000

        memory corruption in X.25 facilities parsing

If I am understanding things correctly then we trigger a -1 return to
the main packet dispatch loop, this being non-zero implies that we have
requeued the skb and it should not be freed.  As it was not requeued,
I believe the skb is no longer referenced and then is leaked.

Perhaps someone better aquainted with this code could review my analysis
in the patch leader below.  If accurate I believe we need the patch below
to resolve this.  If it is not then I suspect a comment is required on
the -1 return.

Thoughts?

-apw