Staging: rtl8723bs: rtw_wlan_util: Add size check of SSID IE

Add size check of SSID information element in incoming 802.11
frames, to prevent memcpy() of IE in array bssid->Ssid.Ssid, with
size more than 32 bytes.
Signed-off-by: Denis Straghkov <d.straghkov@ispras.ru>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200421212525.24962-1-d.straghkov@ispras.ruSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/core/rtw_wlan_util.c

@@ -1271,13 +1271,13 @@ int rtw_check_bcn_info(struct adapter *Adapter, u8 *pframe, u32 packet_len)
 	unsigned char *pbuf;
 	u32 wpa_ielen = 0;
 	u8 *pbssid = GetAddr3Ptr(pframe);
-	u32 hidden_ssid = 0;
 	struct HT_info_element *pht_info = NULL;
 	struct rtw_ieee80211_ht_cap *pht_cap = NULL;
 	u32 bcn_channel;
 	unsigned short	ht_cap_info;
 	unsigned char ht_info_infos_0;
 	struct mlme_priv *pmlmepriv = &Adapter->mlmepriv;
+	int ssid_len;
 
 	if (is_client_associated_to_ap(Adapter) == false)
 		return true;
@@ -1370,21 +1370,15 @@ int rtw_check_bcn_info(struct adapter *Adapter, u8 *pframe, u32 packet_len)
 	}
 
 	/* checking SSID */
+	ssid_len = 0;
 	p = rtw_get_ie(bssid->IEs + _FIXED_IE_LENGTH_, _SSID_IE_, &len, bssid->IELength - _FIXED_IE_LENGTH_);
-	if (!p) {
-		DBG_871X("%s marc: cannot find SSID for survey event\n", __func__);
-		hidden_ssid = true;
-	} else {
-		hidden_ssid = false;
-	}
-
-	if ((NULL != p) && (false == hidden_ssid && (*(p + 1)))) {
-		memcpy(bssid->Ssid.Ssid, (p + 2), *(p + 1));
-		bssid->Ssid.SsidLength = *(p + 1);
-	} else {
-		bssid->Ssid.SsidLength = 0;
-		bssid->Ssid.Ssid[0] = '\0';
+	if (p) {
+		ssid_len = *(p + 1);
+		if (ssid_len > NDIS_802_11_LENGTH_SSID)
+			ssid_len = 0;
 	}
+	memcpy(bssid->Ssid.Ssid, (p + 2), ssid_len);
+	bssid->Ssid.SsidLength = ssid_len;
 
 	RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("%s bssid.Ssid.Ssid:%s bssid.Ssid.SsidLength:%d "
 				"cur_network->network.Ssid.Ssid:%s len:%d\n", __func__, bssid->Ssid.Ssid,