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Subject[PATCH 3/3] caif_virtio: fix the race between reset and netdev unregister
Date
We use to do the following steps during .remove():

static void cfv_remove(struct virtio_device *vdev)
{
struct cfv_info *cfv = vdev->priv;

rtnl_lock();
dev_close(cfv->ndev);
rtnl_unlock();

tasklet_kill(&cfv->tx_release_tasklet);
debugfs_remove_recursive(cfv->debugfs);

vringh_kiov_cleanup(&cfv->ctx.riov);
virtio_reset_device(vdev);
vdev->vringh_config->del_vrhs(cfv->vdev);
cfv->vr_rx = NULL;
vdev->config->del_vqs(cfv->vdev);
unregister_netdev(cfv->ndev);
}

This is racy since device could be re-opened after dev_close() but
before unregister_netdevice():

1) RX vringh is cleaned before resetting the device, rx callbacks that
is called after the vringh_kiov_cleanup() will result a UAF
2) Network stack can still try to use TX virtqueue even if it has been
deleted after dev_vqs()

Fixing this by unregistering the network device first to make sure not
device access from both TX and RX side.

Fixes: 0d2e1a2926b18 ("caif_virtio: Introduce caif over virtio")
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/caif/caif_virtio.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/caif/caif_virtio.c b/drivers/net/caif/caif_virtio.c
index 66375bea2fcd..a29f9b2df5b1 100644
--- a/drivers/net/caif/caif_virtio.c
+++ b/drivers/net/caif/caif_virtio.c
@@ -752,9 +752,8 @@ static void cfv_remove(struct virtio_device *vdev)
{
struct cfv_info *cfv = vdev->priv;

- rtnl_lock();
- dev_close(cfv->ndev);
- rtnl_unlock();
+ /* Make sure NAPI/TX won't try to access the device */
+ unregister_netdev(cfv->ndev);

tasklet_kill(&cfv->tx_release_tasklet);
debugfs_remove_recursive(cfv->debugfs);
@@ -764,7 +763,6 @@ static void cfv_remove(struct virtio_device *vdev)
vdev->vringh_config->del_vrhs(cfv->vdev);
cfv->vr_rx = NULL;
vdev->config->del_vqs(cfv->vdev);
- unregister_netdev(cfv->ndev);
}

static struct virtio_device_id id_table[] = {
--
2.25.1
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