netdev - [PATCH] openvswitch: fix a use after free

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Message-Id: <1413450075-5044-1-git-send-email-roy.qing.li@gmail.com>
Date:	Thu, 16 Oct 2014 17:01:15 +0800
From:	roy.qing.li@...il.com
To:	netdev@...r.kernel.org
Subject: [PATCH] openvswitch: fix a use after free

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

pskb_may_pull() called by arphdr_ok can change skb->data, so put the arp
setting after arphdr_ok to avoid the use the freed memory

Signed-off-by: Li RongQing <roy.qing.li@...il.com>
---
 net/openvswitch/flow.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 62db02b..b13ba5e 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -557,10 +557,11 @@ static int key_extract(struct sk_buff *skb, struct sw_flow_key *key)
 	} else if (key->eth.type == htons(ETH_P_ARP) ||
 		   key->eth.type == htons(ETH_P_RARP)) {
 		struct arp_eth_header *arp;
+		bool arp_t = arphdr_ok(skb);
 
 		arp = (struct arp_eth_header *)skb_network_header(skb);
 
-		if (arphdr_ok(skb) &&
+		if (arp_t &&
 		    arp->ar_hrd == htons(ARPHRD_ETHER) &&
 		    arp->ar_pro == htons(ETH_P_IP) &&
 		    arp->ar_hln == ETH_ALEN &&
-- 
1.7.10.4

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