netdev - [PATCH net-next] veth: fix NULL dereference in veth

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Message-ID: <1360390249.6696.22.camel@edumazet-glaptop>
Date:	Fri, 08 Feb 2013 22:10:49 -0800
From:	Eric Dumazet <erdnetdev@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] veth: fix NULL dereference in veth_dellink()

From: Eric Dumazet <edumazet@...gle.com>

commit d0e2c55e7c940 (veth: avoid a NULL deref in veth_stats_one)
added another NULL deref in veth_dellink().

# ip link add name veth1 type veth peer name veth0
# rmmod veth

We crash because veth_dellink() is called twice, so we must
take care of NULL peer.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 drivers/net/veth.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index e1da42a..07a4af0 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -426,12 +426,13 @@ static void veth_dellink(struct net_device *dev, struct list_head *head)
 	 * not being freed before one RCU grace period.
 	 */
 	RCU_INIT_POINTER(priv->peer, NULL);
-
-	priv = netdev_priv(peer);
-	RCU_INIT_POINTER(priv->peer, NULL);
-
 	unregister_netdevice_queue(dev, head);
-	unregister_netdevice_queue(peer, head);
+
+	if (peer) {
+		priv = netdev_priv(peer);
+		RCU_INIT_POINTER(priv->peer, NULL);
+		unregister_netdevice_queue(peer, head);
+	}
 }
 
 static const struct nla_policy veth_policy[VETH_INFO_MAX + 1] = {


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