From: Maxime Coquelin <maxime.coquelin@redhat.com>

This patch fixes a crash that happens when vhost-user iommu
support is enabled and vhost-user socket is closed.

When it happens, if an IOTLB invalidation notification is sent
by the IOMMU, vhost_ops's NULL pointer is dereferenced.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/vhost-backend.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 4e31de1..cb055e8 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -309,7 +309,10 @@ int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
         return -EINVAL;
     }
 
-    return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
+    if (dev->vhost_ops && dev->vhost_ops->vhost_send_device_iotlb_msg)
+        return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
+
+    return -ENODEV;
 }
 
 int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
@@ -321,7 +324,10 @@ int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
     imsg.size = len;
     imsg.type = VHOST_IOTLB_INVALIDATE;
 
-    return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
+    if (dev->vhost_ops && dev->vhost_ops->vhost_send_device_iotlb_msg)
+        return dev->vhost_ops->vhost_send_device_iotlb_msg(dev, &imsg);
+
+    return -ENODEV;
 }
 
 int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
-- 
MST