[PATCH] cxl/region: Fix potential double free of region device in delete_region_store

[Ma Ke]

cxl_find_region_by_name() uses device_find_child_by_name() to locate a
region device by name. This function implicitly increments the
device's reference count before returning the pointer by calling
device_find_child(). However, in delete_region_store(), after calling
devm_release_action() which synchronously executes
unregister_region(), an additional explicit put_device() is invoked.
The unregister_region() callback already contains a put_device() call
to decrement the reference count. This results in two consecutive
decrements of the same device's reference count. First decrement
occurs in unregister_region() via its put_device() call. Second
decrement occurs in delete_region_store() via the explicit
put_device(). We should remove the additional put_device().

As comment of device_find_child() says, 'NOTE: you will need to drop
the reference with put_device() after use'.

Found by code review.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 779dd20cfb56 ("cxl/region: Add region creation support")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
 drivers/cxl/core/region.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 6e5e1460068d..eacf726cf463 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -2672,7 +2672,6 @@ static ssize_t delete_region_store(struct device *dev,
 		return PTR_ERR(cxlr);
 
 	devm_release_action(port->uport_dev, unregister_region, cxlr);
-	put_device(&cxlr->dev);
 
 	return len;
 }
-- 
2.25.1