[PATCH net] ibmveth: Disable tx queue while changing mtu

[Thomas Falcon <tlfalcon@linux.vnet.ibm.com>]

If the device is running while the MTU is changed, ibmveth
is closed and the bounce buffer is freed. If a transmission
is sent before ibmveth can be reopened, ibmveth_start_xmit
tries to copy to the null bounce buffer, leading to a kernel
oops. The proposed solution disables the tx queue until
ibmveth is restarted.

Reported-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index ebe6071..9a74e4c 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -1362,6 +1362,7 @@ static int ibmveth_change_mtu(struct net_device *dev, int new_mtu)
 	/* Deactivate all the buffer pools so that the next loop can activate
 	   only the buffer pools necessary to hold the new MTU */
 	if (netif_running(adapter->netdev)) {
+		netif_tx_disable(dev);
 		need_restart = 1;
 		adapter->pool_config = 1;
 		ibmveth_close(adapter->netdev);
@@ -1378,14 +1379,18 @@ static int ibmveth_change_mtu(struct net_device *dev, int new_mtu)
 						ibmveth_get_desired_dma
 						(viodev));
 			if (need_restart) {
-				return ibmveth_open(adapter->netdev);
+				rc = ibmveth_open(adapter->netdev);
+				netif_wake_queue(dev);
+				return rc;
 			}
 			return 0;
 		}
 	}
 
-	if (need_restart && (rc = ibmveth_open(adapter->netdev)))
+	if (need_restart && (rc = ibmveth_open(adapter->netdev))) {
+		netif_wake_queue(dev);
 		return rc;
+	}
 
 	return -EINVAL;
 }
-- 
2.4.11