linux-kernel - [PATCH 4.8 05/49] ip6_tunnel: Clear IP6CB in ip6tunnel

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Date:   Sat, 19 Nov 2016 10:22:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eli Cooper <elicooper@....com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.8 05/49] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

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

------------------

From: Eli Cooper <elicooper@....com>

[ 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@...r.kernel.org
Signed-off-by: Eli Cooper <elicooper@....com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/net/ip6_tunnel.h |    1 +
 1 file changed, 1 insertion(+)

--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -145,6 +145,7 @@ static inline void ip6tunnel_xmit(struct
 {
 	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)))