iu_helpers: check length before accessing buf

in ranap_transp_layer_addr_decode() we access the buffer buf before
checking the length field. This can lead to a segfault when the buffer
has a length of 0.

Change-Id: I983f6e5e4cee47b3f5719829e1310b8e2e33ffaf

src/iu_helpers.c

@@ -113,7 +113,7 @@ int ranap_transp_layer_addr_decode(char *addr, unsigned int addr_len,
 	buf = trasp_layer_addr->buf;
 	len = trasp_layer_addr->size;
 
-	if (buf[0] == 0x35 && len >= 7)
+	if (len >= 7 && buf[0] == 0x35)
 		rc = inet_ntop(AF_INET, buf + 3, addr, addr_len);
 	else if (len > 3)
 		rc = inet_ntop(AF_INET, buf, addr, addr_len);