Further, there's an additional issue that I saw in testing:
ipoib_mcast_send may get called when priv->broadcast is NULL (e.g. if
the device was downed and then upped internally because of a port
event).
If this happends and the send-only join request gets completed before
priv->broadcast is set, we get an oops.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
         */
        spin_lock(&priv->lock);
 
-       if (!test_bit(IPOIB_MCAST_STARTED, &priv->flags)) {
+       if (!test_bit(IPOIB_MCAST_STARTED, &priv->flags) || !priv->broadcast) {
                ++priv->stats.tx_dropped;
                dev_kfree_skb_any(skb);
                goto unlock;