[PATCH 3/4] vsock/virtio: fix flush of works during the .remove()

[Stefano Garzarella]

We flush all pending works before to call vdev->config->reset(vdev),
but other works can be queued before the vdev->config->del_vqs(vdev),
so we add another flush after it, to avoid use after free.

Suggested-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
---
 net/vmw_vsock/virtio_transport.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index e694df10ab61..ad093ce96693 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -660,6 +660,15 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
        return ret;
 }
 
+static void virtio_vsock_flush_works(struct virtio_vsock *vsock)
+{
+       flush_work(&vsock->loopback_work);
+       flush_work(&vsock->rx_work);
+       flush_work(&vsock->tx_work);
+       flush_work(&vsock->event_work);
+       flush_work(&vsock->send_pkt_work);
+}
+
 static void virtio_vsock_remove(struct virtio_device *vdev)
 {
        struct virtio_vsock *vsock = vdev->priv;
@@ -668,12 +677,6 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
        mutex_lock(&the_virtio_vsock_mutex);
        the_virtio_vsock = NULL;
 
-       flush_work(&vsock->loopback_work);
-       flush_work(&vsock->rx_work);
-       flush_work(&vsock->tx_work);
-       flush_work(&vsock->event_work);
-       flush_work(&vsock->send_pkt_work);
-
        /* Reset all connected sockets when the device disappear */
        vsock_for_each_connected_socket(virtio_vsock_reset_sock);
 
@@ -690,6 +693,9 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
        vsock->event_run = false;
        mutex_unlock(&vsock->event_lock);
 
+       /* Flush all pending works */
+       virtio_vsock_flush_works(vsock);
+
        /* Flush all device writes and interrupts, device will not use any
         * more buffers.
         */
@@ -726,6 +732,11 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
        /* Delete virtqueues and flush outstanding callbacks if any */
        vdev->config->del_vqs(vdev);
 
+       /* Other works can be queued before 'config->del_vqs()', so we flush
+        * all works before to free the vsock object to avoid use after free.
+        */
+       virtio_vsock_flush_works(vsock);
+
        kfree(vsock);
        mutex_unlock(&the_virtio_vsock_mutex);
 }
-- 
2.20.1