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@xxxxxxxxxx>
---
drivers/char/virtio_console.c | 15 +++++++++++++++
1 files changed, 15 insertions(+), 0 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 66875d6..3a305f8 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -168,6 +168,9 @@ 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. */
@@ -471,6 +474,8 @@ 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;
}
@@ -489,6 +494,15 @@ 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->readbuf_list_lock);
+ if (port->guest_connected) {
+ spin_unlock_irq(&port->readbuf_list_lock);
+ return -EMFILE;
+ }
+ port->guest_connected = true;
+ spin_unlock_irq(&port->readbuf_list_lock);
+
/* Notify host of port being opened */
send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
@@ -656,6 +670,7 @@ 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;
return 0;
}
--
1.6.2.5
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