cfg80211: fix NULL dereference in IBSS SIOCGIWAP

This patch avoids memcpy from wdev->wext.ibss.bssid if it is NULL.
This could happen if we SIOCGIWAP before SIOCSIWAP.
Signed-off-by: NZhu Yi <yi.zhu@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/wireless/ibss.c

@@ -487,8 +487,11 @@ int cfg80211_ibss_wext_giwap(struct net_device *dev,
 	wdev_lock(wdev);
 	if (wdev->current_bss)
 		memcpy(ap_addr->sa_data, wdev->current_bss->pub.bssid, ETH_ALEN);
-	else
+	else if (wdev->wext.ibss.bssid)
 		memcpy(ap_addr->sa_data, wdev->wext.ibss.bssid, ETH_ALEN);
+	else
+		memset(ap_addr->sa_data, 0, ETH_ALEN);
+
 	wdev_unlock(wdev);
 
 	return 0;