There is an identical report in the netfilter bugzilla, also crashes
(on x86_64) in ipt_do_table with Xen. I haven't heard anything of
similar crashes without Xen, so I doubt that the bug is in the
netfilter code.
https://bugzilla.netfilter.org/bugzilla/show_bug.cgi?id=478
Yep... too coincidental. I'd say it has _something_ to do with Xen. I've been doing different things on my side to try to reduce the severity of the problem, but I'd really like to hear what the Xen guys have to say about this now..