[PATCH] veth: Cleanly handle a missing peer_tb argument on creation.

[ebiederm@xmission.com (Eric W. Biederman)]

I was getting strange kernel crashes when attempting to
create veth devices when I did not specify a peer argument
to /bin/ip.

So this patch defaults peer_tb to all zeros and doesn't attempt to
reuse the netlink attributes for the primary link to create the
secondary link and now I can't reproduce the failures.

Given that some of the most interesting netlink attributes to specify
like a mac address or a network device name seem are generally
the wrong thing to do this seems like the right approach.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 drivers/net/veth.c |   16 +++++++---------
 1 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 9e6a746..d49bd2c 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -313,7 +313,7 @@ static int veth_newlink(struct net_device *dev,
 	struct net_device *peer;
 	struct veth_priv *priv;
 	char ifname[IFNAMSIZ];
-	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp;
+	struct nlattr *peer_tb[IFLA_MAX + 1];
 
 	/*
 	 * create and register peer first
@@ -322,6 +322,7 @@ static int veth_newlink(struct net_device *dev,
 	 * skip it since no info from it is useful yet
 	 */
 
+	memset(peer_tb, 0, sizeof(peer_tb));
 	if (data != NULL && data[VETH_INFO_PEER] != NULL) {
 		struct nlattr *nla_peer;
 
@@ -336,21 +337,18 @@ static int veth_newlink(struct net_device *dev,
 		err = veth_validate(peer_tb, NULL);
 		if (err < 0)
 			return err;
+	}
 
-		tbp = peer_tb;
-	} else
-		tbp = tb;
-
-	if (tbp[IFLA_IFNAME])
-		nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
+	if (peer_tb[IFLA_IFNAME])
+		nla_strlcpy(ifname, peer_tb[IFLA_IFNAME], IFNAMSIZ);
 	else
 		snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
 
-	peer = rtnl_create_link(dev->nd_net, ifname, &veth_link_ops, tbp);
+	peer = rtnl_create_link(dev->nd_net, ifname, &veth_link_ops, peer_tb);
 	if (IS_ERR(peer))
 		return PTR_ERR(peer);
 
-	if (tbp[IFLA_ADDRESS] == NULL)
+	if (peer_tb[IFLA_ADDRESS] == NULL)
 		random_ether_addr(peer->dev_addr);
 
 	err = register_netdevice(peer);
-- 
1.5.3.rc6.17.g1911