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Commit 3c7969cc authored by Amit Shah's avatar Amit Shah Committed by Rusty Russell
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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: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 2030fa49

drivers/char/virtio_console.c

+17 −1
Original line number Diff line number Diff line
@@ -175,6 +175,9 @@ struct port { 


	/* 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 @@ static int port_fops_release(struct inode *inode, struct file *filp) 
	/* 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 @@ static int port_fops_open(struct inode *inode, struct file *filp) 
	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 @@ int init_port_console(struct port *port) 
	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 @@ static int add_port(struct ports_device *portdev, u32 id) 
	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];