Subject: [PATCH 02/30] ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation

From: Yohei Kanemaru <[email-masked]>
Date: Tue, 29 Jan 2019 15:52:34 +0900

[ Upstream commit ef489749aae508e6f17886775c075f12ff919fb1 ]

skb->cb may contain data from previous layers (in an observed case
IPv4 with L3 Master Device). In the observed scenario, the data in
IPCB(skb)->frags was misinterpreted as IP6CB(skb)->frag_max_size,
eventually caused an unexpected IPv6 fragmentation in ip6_fragment()
through ip6_finish_output().

This patch clears IP6CB(skb), which potentially contains garbage data,
on the SRH ip4ip6 encapsulation.

Fixes: 32d99d0b6702 ("ipv6: sr: add support for ip4ip6 encapsulation")
Signed-off-by: Yohei Kanemaru <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv6/seg6_iptunnel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 8181ee7e1e27..ee5403cbe655 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -146,6 +146,8 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 	} else {
 		ip6_flow_hdr(hdr, 0, flowlabel);
 		hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
+
+		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 	}
 
 	hdr->nexthdr = NEXTHDR_ROUTING;
-- 
2.20.1