netdev - [PATCH 2/3] caif_virtio: fix the race between virtio_device_ready() and ndo

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Message-Id: <20220620051115.3142-3-jasowang@redhat.com>
Date:   Mon, 20 Jun 2022 13:11:14 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        mst@...hat.com, jasowang@...hat.com
Cc:     davem@...emloft.net, kuba@...nel.org, erwan.yvin@...ricsson.com
Subject: [PATCH 2/3] caif_virtio: fix the race between virtio_device_ready() and ndo_open()

We used to depend on the virtio_device_ready() that is called after
probe() by virtio_dev_probe() 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 (e.g TX) 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: 0d2e1a2926b18 ("caif_virtio: Introduce caif over virtio")
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/net/caif/caif_virtio.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/caif/caif_virtio.c b/drivers/net/caif/caif_virtio.c
index c677ded81133..66375bea2fcd 100644
--- a/drivers/net/caif/caif_virtio.c
+++ b/drivers/net/caif/caif_virtio.c
@@ -719,13 +719,21 @@ static int cfv_probe(struct virtio_device *vdev)
 	/* Carrier is off until netdevice is opened */
 	netif_carrier_off(netdev);
 
+	/* serialize netdev register + virtio_device_ready() with ndo_open() */
+	rtnl_lock();
+
 	/* register Netdev */
-	err = register_netdev(netdev);
+	err = register_netdevice(netdev);
 	if (err) {
+		rtnl_unlock();
 		dev_err(&vdev->dev, "Unable to register netdev (%d)\n", err);
 		goto err;
 	}
 
+	virtio_device_ready(vdev);
+
+	rtnl_unlock();
+
 	debugfs_init(cfv);
 
 	return 0;
-- 
2.25.1