GAS: Clean up Query Response length validation

Previous version was correct, but apparently too complex for some static
analyzers. (CID 68119)

Signed-off-by: Jouni Malinen <j@w1.fi>

wpa_supplicant/gas_query.c

@@ -442,6 +442,7 @@ int gas_query_rx(struct gas_query *gas, const u8 *da, const u8 *sa,
 	u16 comeback_delay, resp_len;
 	const u8 *pos, *adv_proto;
 	int prot, pmf;
+	unsigned int left;
 
 	if (gas == NULL || len < 4)
 		return -1;
@@ -543,17 +544,17 @@ int gas_query_rx(struct gas_query *gas, const u8 *da, const u8 *sa,
 	resp_len = WPA_GET_LE16(pos);
 	pos += 2;
 
-	if (pos + resp_len > data + len) {
+	left = data + len - pos;
+	if (resp_len > left) {
 		wpa_printf(MSG_DEBUG, "GAS: Truncated Query Response in "
 			   "response from " MACSTR, MAC2STR(sa));
 		return 0;
 	}
 
-	if (pos + resp_len < data + len) {
+	if (resp_len < left) {
 		wpa_printf(MSG_DEBUG, "GAS: Ignore %u octets of extra data "
 			   "after Query Response from " MACSTR,
-			   (unsigned int) (data + len - pos - resp_len),
-			   MAC2STR(sa));
+			   left - resp_len, MAC2STR(sa));
 	}
 
 	if (action == WLAN_PA_GAS_COMEBACK_RESP)