On Mon, Jun 27, 2022 at 3:44 PM Michael S. Tsirkin [off-list ref] wrote:

On Mon, Jun 27, 2022 at 02:36:56PM +0800, Jason Wang wrote:

quoted

We used to call virtio_device_ready() after netdev registration.

s/used to call/currently call/

quoted

This
cause

s/This cause/Since ndo_open can be called immediately
after register_netdev, this means there exists/

quoted

a race between ndo_open() and virtio_device_ready(): if
ndo_open() is called before virtio_device_ready(), the driver may
start to use the device before DRIVER_OK which violates the spec.

Fixing

s/Fixing/Fix/

quoted

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: 4baf1e33d0842 ("virtio_net: enable VQs early")

it's an unusual use of Fixes - the patch in question does not
introduce the problem, it just does not fix it completely.

Yes, but I couldn't find a better commit.

But OK I guess.

quoted

Signed-off-by: Jason Wang <jasowang@redhat.com>

With commit log changes:

Will post a new version with the above fixed.

Thanks

Acked-by: Michael S. Tsirkin <mst@redhat.com>

quoted

---
 drivers/net/virtio_net.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index db05b5e930be..8a5810bcb839 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -3655,14 +3655,20 @@ static int virtnet_probe(struct virtio_device *vdev)
      if (vi->has_rss || vi->has_rss_hash_report)
              virtnet_init_default_rss(vi);

-     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");
--

2.25.1