cfg80211: reject invalid IBSS BSSIDs in wext compat code

Don't allow using a multicast address as the BSSID, that
isn't a valid configuration.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/ibss.c

@@ -481,6 +481,9 @@ int cfg80211_ibss_wext_siwap(struct net_device *dev,
 	if (is_zero_ether_addr(bssid) || is_broadcast_ether_addr(bssid))
 		bssid = NULL;
 
+	if (bssid && !is_valid_ether_addr(bssid))
+		return -EINVAL;
+
 	/* both automatic */
 	if (!bssid && !wdev->wext.ibss.bssid)
 		return 0;