There's a window between find_port_by_devt() returning a port and us taking a kref on the port, where the port could get unplugged. Fix it by taking the reference in find_port_by_devt() itself.
Problem reported and analyzed by Mateusz Guzik. CC: <[email protected]> Reported-by: Mateusz Guzik <[email protected]> Signed-off-by: Amit Shah <[email protected]> --- drivers/char/virtio_console.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 1b456fe..291f437 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -272,9 +272,12 @@ static struct port *find_port_by_devt_in_portdev(struct ports_device *portdev, unsigned long flags; spin_lock_irqsave(&portdev->ports_lock, flags); - list_for_each_entry(port, &portdev->ports, list) - if (port->cdev->dev == dev) + list_for_each_entry(port, &portdev->ports, list) { + if (port->cdev->dev == dev) { + kref_get(&port->kref); goto out; + } + } port = NULL; out: spin_unlock_irqrestore(&portdev->ports_lock, flags); @@ -1019,14 +1022,10 @@ static int port_fops_open(struct inode *inode, struct file *filp) struct port *port; int ret; + /* We get the port with a kref here */ port = find_port_by_devt(cdev->dev); filp->private_data = port; - /* Prevent against a port getting hot-unplugged at the same time */ - spin_lock_irq(&port->portdev->ports_lock); - kref_get(&port->kref); - spin_unlock_irq(&port->portdev->ports_lock); - /* * Don't allow opening of console port devices -- that's done * via /dev/hvc -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
