[PATCH v10 17/22] vfio: Move vfio_device_group_unregister() to be the first operation in unregister

Yi Liu
2023-04-26T15:04:56Z

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

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 c0459872d79a..c3263cb2ea75 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -322,6 +322,12 @@ 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) {
@@ -345,8 +351,6 @@ 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