netdev - [PATCH] virtio-net: fix race between ndo_open() and virtio_device

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Date:   Fri, 17 Jun 2022 15:29:49 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com, davem@...emloft.net,
        kuba@...nel.org
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] virtio-net: fix race between ndo_open() and virtio_device_ready()

We used to call virtio_device_ready() after netdev registration. This
cause 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 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")
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 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