netdev - [PATCH] vxlan: fix a use after free in vxlan_encap

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Message-Id: <1413420581-12989-1-git-send-email-roy.qing.li@gmail.com>
Date:	Thu, 16 Oct 2014 08:49:41 +0800
From:	roy.qing.li@...il.com
To:	netdev@...r.kernel.org
Subject: [PATCH] vxlan: fix a use after free in vxlan_encap_bypass

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

when netif_rx() is done, the netif_rx handled skb maybe be freed,
and should not be used.

Signed-off-by: Li RongQing <roy.qing.li@...il.com>
---
 drivers/net/vxlan.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 6f83be7..f677cd0 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1668,6 +1668,8 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
 	struct pcpu_sw_netstats *tx_stats, *rx_stats;
 	union vxlan_addr loopback;
 	union vxlan_addr *remote_ip = &dst_vxlan->default_dst.remote_ip;
+	struct net_device *dev = skb->dev;
+	int len = skb->len;
 
 	tx_stats = this_cpu_ptr(src_vxlan->dev->tstats);
 	rx_stats = this_cpu_ptr(dst_vxlan->dev->tstats);
@@ -1691,16 +1693,16 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
 
 	u64_stats_update_begin(&tx_stats->syncp);
 	tx_stats->tx_packets++;
-	tx_stats->tx_bytes += skb->len;
+	tx_stats->tx_bytes += len;
 	u64_stats_update_end(&tx_stats->syncp);
 
 	if (netif_rx(skb) == NET_RX_SUCCESS) {
 		u64_stats_update_begin(&rx_stats->syncp);
 		rx_stats->rx_packets++;
-		rx_stats->rx_bytes += skb->len;
+		rx_stats->rx_bytes += len;
 		u64_stats_update_end(&rx_stats->syncp);
 	} else {
-		skb->dev->stats.rx_dropped++;
+		dev->stats.rx_dropped++;
 	}
 }
 
-- 
1.7.10.4

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