[PATCH 11/15] virtio_console: Ensure only one process can have a port open at a time

[Amit Shah <amit.shah@xxxxxxxxxx>]

Add a guest_connected field that ensures only one process
can have a port open at a time.

Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
---
 drivers/char/virtio_console.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c3498ec..8c9bac8 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -138,6 +138,9 @@ struct virtio_console_port {
 
 	/* Is the host device open */
 	bool host_connected;
+
+	/* We should allow only one process to open a port */
+	bool guest_connected;
 };
 
 struct virtio_console_struct virtconsole;
@@ -455,6 +458,10 @@ static int virtconsole_release(struct inode *inode, struct file *filp)
 	send_buf(filp->private_data, (char *)&cpkt, sizeof(cpkt),
 		 VIRTIO_CONSOLE_ID_CONTROL, false);
 
+	spin_lock(&port->readbuf_list_lock);
+	port->guest_connected = false;
+	spin_unlock(&port->readbuf_list_lock);
+
 	return 0;
 }
 
@@ -474,6 +481,15 @@ static int virtconsole_open(struct inode *inode, struct file *filp)
 	if (port->hvc)
 		return -ENXIO;
 
+	/* Allow only one process to open a particular port at a time */
+	spin_lock(&port->readbuf_list_lock);
+	if (port->guest_connected) {
+		spin_unlock(&port->readbuf_list_lock);
+		return -EMFILE;
+	}
+	port->guest_connected = true;
+	spin_unlock(&port->readbuf_list_lock);
+
 	/* Notify host of port being opened */
 	cpkt.event = VIRTIO_CONSOLE_PORT_OPEN;
 	cpkt.value = 1;
@@ -639,6 +655,7 @@ int init_port_console(struct virtio_console_port *port)
 		port->hvc = NULL;
 	} else {
 		port->vtermno = port->vcon->hvc_vtermno++;
+		port->guest_connected = true;
 	}
 	return ret;
 }
-- 
1.6.2.5

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