Linux Virtualization - Nov 2014 - [PATCH v7 22/46] virtio_blk: fix race at module removal

If a device appears while module is being removed,
driver will get a callback after we've given up
on the major number.

In theory this means this major number can get reused
by something else, resulting in a conflict.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 drivers/block/virtio_blk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 055f3df..1f8b111 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -884,8 +884,8 @@ out_destroy_workqueue:
 
 static void __exit fini(void)
 {
-	unregister_blkdev(major, "virtblk");
 	unregister_virtio_driver(&virtio_blk);
+	unregister_blkdev(major, "virtblk");
 	destroy_workqueue(virtblk_wq);
 }
 module_init(init);
-- 
MST

On Sun, 30 Nov 2014 17:11:06 +0200
"Michael S. Tsirkin" <mst at redhat.com> wrote:
> If a device appears while module is being removed,
> driver will get a callback after we've given up
> on the major number.
> 
> In theory this means this major number can get reused
> by something else, resulting in a conflict.
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
>  drivers/block/virtio_blk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com>