hostapd: Avoid crashing on station mode disassoc event

Some driver wrappers may end up indicating a disassociation or
deauthentication event without the address of the station, e.g.,
based on a previous non-AP mode event. Avoid crashing hostapd
by verifying that the require address parameter is available in
the event before processing it.

src/ap/drv_callbacks.c

@@ -195,6 +195,19 @@ void hostapd_notif_disassoc(struct hostapd_data *hapd, const u8 *addr)
 {
 	struct sta_info *sta;
 
+	if (addr == NULL) {
+		/*
+		 * This could potentially happen with unexpected event from the
+		 * driver wrapper. This was seen at least in one case where the
+		 * driver ended up reporting a station mode event while hostapd
+		 * was running, so better make sure we stop processing such an
+		 * event here.
+		 */
+		wpa_printf(MSG_DEBUG, "hostapd_notif_disassoc: Skip event "
+			   "with no address");
+		return -1;
+	}
+
 	hostapd_logger(hapd, addr, HOSTAPD_MODULE_IEEE80211,
 		       HOSTAPD_LEVEL_INFO, "disassociated");