On Thu, 2017-03-09 at 20:31 -0700, Subash Abhinov Kasiviswanathan wrote:
> Certain system process significant unconnected UDP workload.
> It would be preferrable to disable UDP early demux for those systems
> and enable it for TCP only.
> +void tcp_v4_early_demux_configure(int enable)
> +{
> + if (enable)
> + tcp_protocol.early_demux = tcp_v4_early_demux;
> + else
> + tcp_protocol.early_demux = NULL;
> +}
> +
> +void udp_v4_early_demux_configure(int enable)
> +{
> + if (enable)
> + udp_protocol.early_demux = udp_v4_early_demux;
> + else
> + udp_protocol.early_demux = NULL;
> +}
> +
Well, then you need to make sure ipprot->early_demux is read once in the
callers, like ip_rcv_finish(), otherwise compiler could read it twice
and we could deref a NULL pointer.
ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot && ipprot->early_demux) {
ipprot->early_demux(skb); // crash
