Re: [PATCH v2] gre: Avoid kernel panic by clearing IPCB before dst_link_failure called

From: Bernie Harris <redacted>
Date: Tue, 16 Feb 2016 14:10:16 +1300

skb->cb may contain data from previous layers (in the observed case the
qdisc layer). In the observed scenario, the data was misinterpreted as
ip header options, which later caused the ihl to be set to an invalid
value (<5). This resulted in an infinite loop in the mips implementation
of ip_fast_csum.

This patch clears IPCB before dst_link_failure is called from the functions
ip_tunnel_xmit and ip6gre_xmit2, similar to what commit 11c21a30 does for
an ipv4 case.

Signed-off-by: Bernie Harris <redacted>

Again, I want to see this implemented in a way which causes things to be
treated consistently across all tunneling types.

Which means fixing the exact problem, IPCB(skb)->opt needing initilization.

Thanks.