Re: [PATCH] virtio_blk: fix race at module removal

[Rusty Russell]

Ming Lei tom.leim...@gmail.com writes:
 On Fri, Oct 24, 2014 at 12:12 AM, Michael S. Tsirkin m...@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.

 Yes, there is a tiny race window.

Applied.

Thanks,
Rusty.
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[PATCH] virtio_blk: fix race at module removal

[Michael S. Tsirkin]

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.

To fix, cleanup in reverse order of initialization.

Signed-off-by: Michael S. Tsirkin m...@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 56aadbc..adfba9f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -883,8 +883,8 @@ 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
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Re: [PATCH] virtio_blk: fix race at module removal

[Ming Lei]

On Fri, Oct 24, 2014 at 12:12 AM, Michael S. Tsirkin m...@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.

Yes, there is a tiny race window.


 To fix, cleanup in reverse order of initialization.

Reviewed-by: Ming Lei ming@canonical.com

 Signed-off-by: Michael S. Tsirkin m...@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 56aadbc..adfba9f 100644
 --- a/drivers/block/virtio_blk.c
 +++ b/drivers/block/virtio_blk.c
 @@ -883,8 +883,8 @@ 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);

Thanks,
-- 
Ming Lei
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