There was several problems:
- skb_dst(skb) can be NULL when the packet comes from a gretap tunnel;
- skb_dst(skb)->ops may point to md_dst_ops, which doesn't set ->mtu
handler, thus calling dst_mtu() leads to a panic.
I also wonder if ->cow_metrics may be called if skb_dst(skb)->ops points
to ovs_dst_ops.
Don't try to do anything in one of those cases.
Fixes: 962924fa2b7a ("ip_gre: Refactor collect metatdata mode tunnel xmit to
ip_md_tunnel_xmit")
CC: wenxu <we...@ucloud.cn>
Signed-off-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
---
net/ipv4/ip_tunnel.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 2756fb725bf0..e2e0e4601c0f 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -508,6 +508,12 @@ static int tnl_update_pmtu(struct net_device *dev, struct
sk_buff *skb,
int pkt_size;
int mtu;
+ if (!skb_dst(skb) ||
+ !skb_dst(skb)->ops->mtu ||
+ (dst_metrics_read_only(skb_dst(skb)) &&
+ !skb_dst(skb)->ops->cow_metrics))
+ return 0;
+
tunnel_hlen = md ? tunnel_hlen : tunnel->hlen;
pkt_size = skb->len - tunnel_hlen - dev->hard_header_len;
--
2.21.0
