netdev - [PATCH] ipv4: fix a potential use after free in fou.c

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Message-Id: <1413536027-15700-1-git-send-email-roy.qing.li@gmail.com>
Date:	Fri, 17 Oct 2014 16:53:47 +0800
From:	roy.qing.li@...il.com
To:	netdev@...r.kernel.org
Cc:	therbert@...gle.com
Subject: [PATCH] ipv4: fix a potential use after free in fou.c

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

pskb_may_pull() maybe change skb->data and make uh pointer oboslete,
so reload uh and guehdr

Fixes: 37dd0247 ("gue: Receive side for Generic UDP Encapsulation")
Cc: Tom Herbert <therbert@...gle.com>
Signed-off-by: Li RongQing <roy.qing.li@...il.com>
---
 net/ipv4/fou.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index efa70ad..32e7892 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -87,6 +87,9 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
 	if (!pskb_may_pull(skb, len))
 		goto drop;
 
+	uh = udp_hdr(skb);
+	guehdr = (struct guehdr *)&uh[1];
+
 	if (guehdr->version != 0)
 		goto drop;
 
-- 
1.7.10.4

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