virtio: console: Fix crash when hot-unplugging a port and read is blocked

When removing a port we don't check if a program was blocked for read.
This leads to a crash when SIGTERM is sent to the program after
hot-unplugging the port.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/virtio_console.c

@@ -1099,6 +1099,13 @@ static int remove_port(struct port *port)
 {
 	struct port_buffer *buf;
 
+	if (port->guest_connected) {
+		port->guest_connected = false;
+		port->host_connected = false;
+		wake_up_interruptible(&port->waitqueue);
+		send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
+	}
+
 	spin_lock_irq(&port->portdev->ports_lock);
 	list_del(&port->list);
 	spin_unlock_irq(&port->portdev->ports_lock);
@@ -1120,9 +1127,6 @@ static int remove_port(struct port *port)
 		hvc_remove(port->cons.hvc);
 #endif
 	}
-	if (port->guest_connected)
-		send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
-
 	sysfs_remove_group(&port->dev->kobj, &port_attribute_group);
 	device_destroy(pdrvdata.class, port->dev->devt);
 	cdev_del(&port->cdev);