ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

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@vger.kernel.org
Signed-off-by: Eli Cooper <elicooper@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h
index 20ed969..1b1cf33 100644 (file)
--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -146,6 +146,7 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
 {
        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);
        if (unlikely(net_xmit_eval(err)))