linux-kernel - [PATCH 3.13.y-ckt 07/96] ipv4: fix a potential use after free in ip_tunnel

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Message-Id: <1418671616-25482-8-git-send-email-kamal@canonical.com>
Date:	Mon, 15 Dec 2014 11:25:27 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Pravin B Shelar <pshelar@...ira.com>,
	Li RongQing <roy.qing.li@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 07/96] ipv4: fix a potential use after free in ip_tunnel_core.c

3.13.11-ckt13 -stable review patch.  If anyone has any objections, please let me know.

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

From: Li RongQing <roy.qing.li@...il.com>

[ Upstream commit 1245dfc8cadb258386fcd27df38215a0eccb1f17 ]

pskb_may_pull() maybe change skb->data and make eth pointer oboslete,
so set eth after pskb_may_pull()

Fixes:3d7b46cd("ip_tunnel: push generic protocol handling to ip_tunnel module")
Cc: Pravin B Shelar <pshelar@...ira.com>
Signed-off-by: Li RongQing <roy.qing.li@...il.com>
Acked-by: Pravin B Shelar <pshelar@...ira.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 net/ipv4/ip_tunnel_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 67bd005..e67e4be 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -91,11 +91,12 @@ int iptunnel_pull_header(struct sk_buff *skb, int hdr_len, __be16 inner_proto)
 	skb_pull_rcsum(skb, hdr_len);
 
 	if (inner_proto == htons(ETH_P_TEB)) {
-		struct ethhdr *eh = (struct ethhdr *)skb->data;
+		struct ethhdr *eh;
 
 		if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
 			return -ENOMEM;
 
+		eh = (struct ethhdr *)skb->data;
 		if (likely(ntohs(eh->h_proto) >= ETH_P_802_3_MIN))
 			skb->protocol = eh->h_proto;
 		else
-- 
1.9.1

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