Re: [PATCH 4.4 059/268] xen-netfront: Fix race between device setup and open

[Ben Hutchings]

On Mon, 2018-05-28 at 12:00 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.ÂÂIf anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> 
> [ Upstream commit f599c64fdf7d9c108e8717fb04bc41c680120da4 ]
[...]
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
[...]
> @@ -1839,6 +1824,7 @@ static int talk_to_netback(struct xenbus
> Â		goto out;

This "goto out" is outside the locked section...

> Â	}
> Â
> +	rtnl_lock();
> Â	if (info->queues)
> Â		xennet_destroy_queues(info);
> Â
> @@ -1849,6 +1835,7 @@ static int talk_to_netback(struct xenbus
> Â		info->queues = NULL;
> Â		goto out;
> Â	}
> +	rtnl_unlock();
> Â
> Â	/* Create shared ring, alloc event channel -- for each queue */
> Â	for (i = 0; i < num_queues; ++i) {
> @@ -1945,8 +1932,10 @@ abort_transaction_no_dev_fatal:
> Â	xenbus_transaction_end(xbt, 1);
> Â destroy_ring:
> Â	xennet_disconnect_backend(info);
> +	rtnl_lock();
> Â	xennet_destroy_queues(info);
> Â out:
> +	rtnl_unlock();

...so this will be an unmatched unlock.

You need to add another label below the rtnl_unlock().

Ben.

> Â	device_unregister(&dev->dev);
> Â	return err;
> Â}
[...]

-- 
Ben Hutchings, Software Developer                Â        Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom