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Tsirkin" To: Jason Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, erwan.yvin@stericsson.com Subject: Re: [PATCH 3/3] caif_virtio: fix the race between reset and netdev unregister Message-ID: <20220620050446-mutt-send-email-mst@kernel.org> References: <20220620051115.3142-1-jasowang@redhat.com> <20220620051115.3142-4-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220620051115.3142-4-jasowang@redhat.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jun 20, 2022 at 01:11:15PM +0800, Jason Wang wrote: > We use to do the following steps during .remove(): We currently do > 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 > --- > 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); > } This gives me pause, callbacks can now trigger after device has been unregistered. Are we sure this is safe? Won't it be safer to just keep the rtnl_lock around the whole process? > static struct virtio_device_id id_table[] = { > -- > 2.25.1