virtio_console: initialize vtermno value for ports

BugLink: https://bugs.launchpad.net/bugs/1832661

[ Upstream commit 4b0a2c5f ]

For regular serial ports we do not initialize value of vtermno
variable. A garbage value is assigned for non console ports.
The value can be observed as a random integer with [1].

[1] vim /sys/kernel/debug/virtio-ports/vport*p*

This patch initialize the value of vtermno for console serial
ports to '1' and regular serial ports are initiaized to '0'.

Reported-by: siliu@redhat.com
Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/char/virtio_console.c

@@ -76,7 +76,7 @@ struct ports_driver_data {
 	/* All the console devices handled by this driver */
 	struct list_head consoles;
 };
-static struct ports_driver_data pdrvdata;
+static struct ports_driver_data pdrvdata = { .next_vtermno = 1};
 
 static DEFINE_SPINLOCK(pdrvdata_lock);
 static DECLARE_COMPLETION(early_console_added);
@@ -1419,6 +1419,7 @@ static int add_port(struct ports_device *portdev, u32 id)
 	port->async_queue = NULL;
 
 	port->cons.ws.ws_row = port->cons.ws.ws_col = 0;
+	port->cons.vtermno = 0;
 
 	port->host_connected = port->guest_connected = false;
 	port->stats = (struct port_stats) { 0 };