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

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.

v2: rebase patch on net tree

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 9cf6fe9ddc0c..446cbaf81185 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2895,12 +2895,16 @@ static int rtnl_bridge_notify(struct net_device *dev, u16 flags)
                         goto errout;
         }
 
+        if (!skb->len)
+                goto errout;
+
         rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL, GFP_ATOMIC);
         return 0;
 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;
 }