Subject: [PATCH 05/16] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

From: Eli Cooper <[email-masked]>
Date: Tue, 1 Nov 2016 23:45:12 +0800

[ Upstream commit 23f4ffedb7d751c7e298732ba91ca75d224bc1a6 ]

skb->cb may contain data from previous layers. In the observed scenario,
the garbage data were misinterpreted as IP6CB(skb)->frag_max_size, so
that small packets sent through the tunnel are mistakenly fragmented.

This patch unconditionally clears the control buffer in ip6tunnel_xmit(),
which affects ip6_tunnel, ip6_udp_tunnel and ip6_gre. Currently none of
these tunnels set IP6CB(skb)->flags, otherwise it needs to be done earlier.

Cc: [email-masked]
Signed-off-by: Eli Cooper <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/net/ip6_tunnel.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h
index ff788b6..9c2c044 100644
--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -86,6 +86,7 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
 	struct net_device_stats *stats = &dev->stats;
 	int pkt_len, err;
 
+	memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
 	pkt_len = skb->len - skb_inner_network_offset(skb);
 	err = ip6_local_out(dev_net(skb_dst(skb)->dev), sk, skb);
 
-- 
2.7.4