virtio-net: fix race between ndo_open() and virtio_device_ready()

Bugzilla: http://bugzilla.redhat.com/2153210

commit 50c0ada
Author: Jason Wang <jasowang@redhat.com>
Date:   Fri Jun 17 15:29:49 2022 +0800

    virtio-net: fix race between ndo_open() and virtio_device_ready()

    We currently call virtio_device_ready() after netdev
    registration. Since ndo_open() can be called immediately
    after register_netdev, this means there exists a race between
    ndo_open() and virtio_device_ready(): the driver may start to use the
    device before DRIVER_OK which violates the spec.

    Fix this by switching to use register_netdevice() and protect the
    virtio_device_ready() with rtnl_lock() to make sure ndo_open() can
    only be called after virtio_device_ready().

    Fixes: 4baf1e3 ("virtio_net: enable VQs early")
    Signed-off-by: Jason Wang <jasowang@redhat.com>
    Message-Id: <20220617072949.30734-1-jasowang@redhat.com>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Conflict in the context because of missing commit:

    c7114b1 ("drivers/net/virtio_net: Added basic RSS support.")

Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Author: vivier

drivers/net/virtio_net.c

@@ -3269,14 +3269,20 @@ static int virtnet_probe(struct virtio_device *vdev)
 		}
 	}
 
-	err = register_netdev(dev);
+	/* serialize netdev register + virtio_device_ready() with ndo_open() */
+	rtnl_lock();
+
+	err = register_netdevice(dev);
 	if (err) {
 		pr_debug("virtio_net: registering device failed\n");
+		rtnl_unlock();
 		goto free_failover;
 	}
 
 	virtio_device_ready(vdev);
 
+	rtnl_unlock();
+
 	err = virtnet_cpu_notif_add(vi);
 	if (err) {
 		pr_debug("virtio_net: registering cpu notifier failed\n");