AST-2016-003 udptl.c: Fix uninitialized values.

Sending UDPTL packets to Asterisk with the right amount of missing
sequence numbers and enough redundant 0-length IFP packets, can make
Asterisk crash.

ASTERISK-25603 #close
Reported by: Walter Doekes

ASTERISK-25742 #close
Reported by: Torrey Searle

Change-Id: I97df8375041be986f3f266ac1946a538023a5255

main/udptl.c

@@ -305,16 +305,15 @@ static int decode_open_type(uint8_t *buf, unsigned int limit, unsigned int *len,
 	if (decode_length(buf, limit, len, &octet_cnt) != 0)
 		return -1;
 
-	if (octet_cnt > 0) {
-		/* Make sure the buffer contains at least the number of bits requested */
-		if ((*len + octet_cnt) > limit)
-			return -1;
-
-		*p_num_octets = octet_cnt;
-		*p_object = &buf[*len];
-		*len += octet_cnt;
+	/* Make sure the buffer contains at least the number of bits requested */
+	if ((*len + octet_cnt) > limit) {
+		return -1;
 	}
 
+	*p_num_octets = octet_cnt;
+	*p_object = &buf[*len];
+	*len += octet_cnt;
+
 	return 0;
 }
 /*- End of function --------------------------------------------------------*/