[PATCH 4.20 02/80] ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation

Greg Kroah-Hartman
2019-02-04T10:50:39Z

From: Yohei Kanemaru <yohei.kanemaru@gmail.com>

[ 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 <yohei.kanemaru@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/seg6_iptunnel.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -146,6 +146,8 @@ int seg6_do_srh_encap(struct sk_buff *sk
} 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;