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

[Ross Lagerwall]

On 06/11/2018 03:29 PM, Ben Hutchings wrote:
> 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	}
> >   
> > +	rtnl_lock();
> >  Â	if (info->queues)
> >  Â		xennet_destroy_queues(info);
> >   
> > @@ -1849,6 +1835,7 @@ static int talk_to_netback(struct xenbus
> >  Â		info->queues = NULL;
> >  Â		goto out;
> >  Â	}
> > +	rtnl_unlock();
> >   
> >  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().

Thanks for spotting this. I've sent patches to the list to fix this and 
another issue with the original patch.

Regards,
--
Ross Lagerwall