linux-kernel - [PATCH 3.12 100/127] ip6_tunnel: Clear IP6CB in ip6tunnel

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Date:   Fri, 25 Nov 2016 09:30:13 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Eli Cooper <elicooper@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 100/127] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

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

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@...r.kernel.org
Signed-off-by: Eli Cooper <elicooper@....com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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);

-- 
2.10.2