[PATCH 3.12 100/127] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

From: Jiri Slaby
Date: Fri Nov 25 2016 - 03:47:03 EST

From: Eli Cooper <elicooper@xxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


[ 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: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eli Cooper <elicooper@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
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 6d1549c4893c..e6f0917d1ab5 100644
--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -75,6 +75,7 @@ static inline void ip6tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
struct net_device_stats *stats = &dev->stats;
int pkt_len, err;

+ memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
pkt_len = skb->len;
err = ip6_local_out(skb);