farsync: fix info leak in ioctl

[ Upstream commit 96b34040 ]

The fst_get_iface() code fails to initialize the two padding bytes of
struct sync_serial_settings after the ->loopback member. Add an explicit
memset(0) before filling the structure to avoid the info leak.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/wan/farsync.c

@@ -1972,6 +1972,7 @@ fst_get_iface(struct fst_card_info *card, struct fst_port_info *port,
 	}
 
 	i = port->index;
+	memset(&sync, 0, sizeof(sync));
 	sync.clock_rate = FST_RDL(card, portConfig[i].lineSpeed);
 	/* Lucky card and linux use same encoding here */
 	sync.clock_type = FST_RDB(card, portConfig[i].internalClock) ==