virtio: console: Ensure only one process can have a port open at a time
Add a guest_connected field that ensures only one process
can have a port open at a time.
This also ensures we don't have a race when we later add support for
dropping buffers when closing the char dev and buffer caching is turned
off for the particular port.
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index ece1546..5e3503a 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -175,6 +175,9 @@
/* Is the host device open */
bool host_connected;
+
+ /* We should allow only one process to open a port */
+ bool guest_connected;
};
/* This is the very early arch-specified put chars function. */
@@ -528,6 +531,8 @@
/* Notify host of port being closed */
send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
+ port->guest_connected = false;
+
return 0;
}
@@ -546,6 +551,16 @@
if (is_console_port(port))
return -ENXIO;
+ /* Allow only one process to open a particular port at a time */
+ spin_lock_irq(&port->inbuf_lock);
+ if (port->guest_connected) {
+ spin_unlock_irq(&port->inbuf_lock);
+ return -EMFILE;
+ }
+
+ port->guest_connected = true;
+ spin_unlock_irq(&port->inbuf_lock);
+
/* Notify host of port being opened */
send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
@@ -709,6 +724,7 @@
pdrvdata.next_vtermno++;
list_add_tail(&port->cons.list, &pdrvdata.consoles);
spin_unlock_irq(&pdrvdata_lock);
+ port->guest_connected = true;
/* Notify host of port being opened */
send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
@@ -856,7 +872,7 @@
port->inbuf = NULL;
port->cons.hvc = NULL;
- port->host_connected = false;
+ port->host_connected = port->guest_connected = false;
port->in_vq = portdev->in_vqs[port->id];
port->out_vq = portdev->out_vqs[port->id];
