[PATCH v11 17/23] vfio: Move vfio_device_group_unregister() to be the first operation in unregister

[Yi Liu <yi.l.liu@intel.com>]

This can avoid endless vfio_device refcount increasement by userspace,
which would keep blocking the vfio_unregister_group_dev().

Tested-by: Yanting Jiang <yanting.jiang@intel.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/vfio/vfio_main.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 89720b73fa30..541bfd9ce004 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -333,6 +333,12 @@ void vfio_unregister_group_dev(struct vfio_device *device)
 	bool interrupted = false;
 	long rc;
 
+	/*
+	 * Prevent new device opened by userspace via the
+	 * VFIO_GROUP_GET_DEVICE_FD in the group path.
+	 */
+	vfio_device_group_unregister(device);
+
 	vfio_device_put_registration(device);
 	rc = try_wait_for_completion(&device->comp);
 	while (rc <= 0) {
@@ -356,8 +362,6 @@ void vfio_unregister_group_dev(struct vfio_device *device)
 		}
 	}
 
-	vfio_device_group_unregister(device);
-
 	/* Balances device_add in register path */
 	device_del(&device->device);
 
-- 
2.34.1