On Fri, Jun 29, 2012 at 02:29:37PM +0200, Hans Schillstrom wrote:

quoted

Hello,

There is a "hard to find" problem in ctnetlink_conntrack_event() when calling
netlink_has_listeners() net->nfnl is NULL.

The rcu stuff seems to be right at a first look but who knows...

The line below fix the problem, but that is not the root cause.

 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 {
-       return netlink_has_listeners(net->nfnl, group);
+       return net->nfnl ? netlink_has_listeners(net->nfnl, group) : 0 ;
 }

Yes it is a 3.0.26 kernel but this patch is applied
netfilter: nf_conntrack: make event callback registration per-netns

I think this patch above is missing some rcu_access_pointer usage.

Please, see patch attached.

Thanks it looks like it's the missing patch.

/Hans