[PATCH] bridge: dont send notification when skb->len == 0 in rtnl_bridge_notify

[roopa@cumulusnetworks.com]

From: Roopa Prabhu <roopa@cumulusnetworks.com>

Reported in: https://bugzilla.kernel.org/show_bug.cgi?id=92081

This patch avoids calling rtnl_notify if the device ndo_bridge_getlink
handler does not return any bytes in the skb.

Alternately, the skb->len check can be moved inside rtnl_notify.

For the bridge vlan case described in 92081, there is also a fix needed
in bridge driver to generate a proper notification. Will fix that in
subsequent patch.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
---
 net/core/rtnetlink.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 07447d1..e9d0f86 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2934,7 +2934,7 @@ static int rtnl_bridge_notify(struct net_device *dev)
 	}
 
 	err = dev->netdev_ops->ndo_bridge_getlink(skb, 0, 0, dev, 0);
-	if (err < 0)
+	if (err < 0 || !skb->len)
 		goto errout;
 
 	rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL, GFP_ATOMIC);
@@ -2942,7 +2942,8 @@ static int rtnl_bridge_notify(struct net_device *dev)
 errout:
 	WARN_ON(err == -EMSGSIZE);
 	kfree_skb(skb);
-	rtnl_set_sk_err(net, RTNLGRP_LINK, err);
+	if (err)
+		rtnl_set_sk_err(net, RTNLGRP_LINK, err);
 	return err;
 }
 
-- 
1.7.10.4