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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

We should correctly free related resources (grant ref, memory page, evtchn)
when setup_netfront fails.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 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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