Re: [Xen-devel] [PATCH net-next V2] xen-netfront: avoid leaking resources when setup_netfront fails

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, May 20, 2013 at 12:05:12PM +0100, Wei Liu wrote:
> We should correctly free related resources (grant ref, memory page, evtchn)
> when setup_netfront fails.

Looks ok to me.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> ---
>  drivers/net/xen-netfront.c |   33 +++++++++++++++++++++------------
>  1 file changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 1db10141..5770e3b 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -1532,40 +1532,49 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  	FRONT_RING_INIT(&info->tx, txs, PAGE_SIZE);
>  
>  	err = xenbus_grant_ring(dev, virt_to_mfn(txs));
> -	if (err < 0) {
> -		free_page((unsigned long)txs);
> -		goto fail;
> -	}
> +	if (err < 0)
> +		goto grant_tx_ring_fail;
>  
>  	info->tx_ring_ref = err;
>  	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
>  	if (!rxs) {
>  		err = -ENOMEM;
>  		xenbus_dev_fatal(dev, err, "allocating rx ring page");
> -		goto fail;
> +		goto alloc_rx_ring_fail;
>  	}
>  	SHARED_RING_INIT(rxs);
>  	FRONT_RING_INIT(&info->rx, rxs, PAGE_SIZE);
>  
>  	err = xenbus_grant_ring(dev, virt_to_mfn(rxs));
> -	if (err < 0) {
> -		free_page((unsigned long)rxs);
> -		goto fail;
> -	}
> +	if (err < 0)
> +		goto grant_rx_ring_fail;
>  	info->rx_ring_ref = err;
>  
>  	err = xenbus_alloc_evtchn(dev, &info->evtchn);
>  	if (err)
> -		goto fail;
> +		goto alloc_evtchn_fail;
>  
>  	err = bind_evtchn_to_irqhandler(info->evtchn, xennet_interrupt,
>  					0, netdev->name, netdev);
>  	if (err < 0)
> -		goto fail;
> +		goto bind_fail;
>  	netdev->irq = err;
>  	return 0;
>  
> - fail:
> +	/* If we fail to setup netfront, it is safe to just revoke access to
> +	 * granted pages because backend is not accessing it at this point.
> +	 */
> +bind_fail:
> +	xenbus_free_evtchn(dev, info->evtchn);
> +alloc_evtchn_fail:
> +	gnttab_end_foreign_access_ref(info->rx_ring_ref, 0);
> +grant_rx_ring_fail:
> +	free_page((unsigned long)rxs);
> +alloc_rx_ring_fail:
> +	gnttab_end_foreign_access_ref(info->tx_ring_ref, 0);
> +grant_tx_ring_fail:
> +	free_page((unsigned long)txs);
> +fail:
>  	return err;
>  }
>  
> -- 
> 1.7.10.4
> 
> 
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