Description of problem:
The upstream commit d5aa407f59f5b83d2c50ec88f5bf56d40f1f8978 ("tunnels: fix
netns vs proto registration ordering") was not backported correctly, and results in a NULL pointer dereference in ip6_tunnel.c.

https://bugs.gentoo.org/show_bug.cgi?id=380609
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=633738

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 7fb3e02..53e0d51 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1466,7 +1466,7 @@ static int __init ip6_tunnel_init(void)
 {
        int  err;
 
-       err = register_pernet_device(&ip6_tnl_net_ops);
+       err = register_pernet_gen_device(&ip6_tnl_net_id, &ip6_tnl_net_ops);
        if (err < 0)
                goto out_pernet;

The upstream commit d5aa407 that has this regression was previously backported in 6.1.z via RHSA-2011:0928.