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SubjectRe: [PATCH 4.4 059/268] xen-netfront: Fix race between device setup and open
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On Mon, 2018-05-28 at 12:00 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Ross Lagerwall <ross.lagerwall@citrix.com>
>
> [ 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
>   goto out;

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

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

...so this will be an unmatched unlock.

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

Ben.

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

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

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