Re: [PATCH] cxl/region: Fix a race bug in delete_region_store

[Ira Weiny]

Sungwoo Kim wrote:
> A race exists when two concurrent sysfs writes to delete_region specify
> the same region name. Both calls succeed in cxl_find_region_by_name()
> (which only does device_find_child_by_name and takes a reference), and
> both then proceed to call devm_release_action(). The first call atomically
> removes and releases the devres entry successfully. The second call finds
> no matching entry, causing devres_release() to return -ENOENT, which trips
> the WARN_ON.
> 
> Fix this by replacing devm_release_action() with devm_remove_action_nowarn()
> followed by a manual call to unregister_region(). devm_remove_action_nowarn()
> removes the devres tracking entry and returns an error code.
> 

[snip]

> 
> Fixes: 779dd20cfb56 ("cxl/region: Add region creation support")
> Signed-off-by: Sungwoo Kim <iam@xxxxxxxxxxxx>

Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>

[snip]