linux-kernel - [PATCH] cxl/region: Fix potential double free of region device in delete_region

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Message-Id: <20250718022940.3387882-1-make24@iscas.ac.cn>
Date: Fri, 18 Jul 2025 10:29:40 +0800
From: Ma Ke <make24@...as.ac.cn>
To: dave@...olabs.net,
	jonathan.cameron@...wei.com,
	dave.jiang@...el.com,
	alison.schofield@...el.com,
	vishal.l.verma@...el.com,
	ira.weiny@...el.com,
	dan.j.williams@...el.com,
	rrichter@....com,
	ming.li@...omail.com,
	bwidawsk@...nel.org
Cc: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	Ma Ke <make24@...as.ac.cn>,
	stable@...r.kernel.org
Subject: [PATCH] cxl/region: Fix potential double free of region device in delete_region_store

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@...r.kernel.org
Fixes: 779dd20cfb56 ("cxl/region: Add region creation support")
Signed-off-by: Ma Ke <make24@...as.ac.cn>
---
 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