Check SSID length first

Check the lengths of the two SSIDs first before using 'memcmp'.
Otherwise, unexpected results might occur.
(In C99 standard : "The 'memcmp' function compares the first n
characters of the object pointed to by s1 to the first n
characters of the object pointed to by s2.")

Author: jychen0611

vwifi.c

@@ -2086,7 +2086,8 @@ static int vwifi_join_ibss(struct wiphy *wiphy,
         memcpy(vif->bssid, ndev->dev_addr, ETH_ALEN);
         struct vwifi_vif *ibss_vif = NULL;
         list_for_each_entry (ibss_vif, &vwifi->ibss_list, ibss_list) {
-            if (!memcmp(ibss_vif->ssid, vif->ssid, vif->ssid_len) &&
+            if (ibss_vif->ssid_len == vif->ssid_len &&
+                !memcmp(ibss_vif->ssid, vif->ssid, vif->ssid_len) &&
                 ibss_vif->ibss_chandef.center_freq1 ==
                     vif->ibss_chandef.center_freq1) {
                 memcpy(vif->bssid, ibss_vif->bssid, ETH_ALEN);