netdev - [PATCH 5.10] net: mdio: fix unbalanced fwnode reference count in mdio_device

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Message-Id: <20260116-backport_cb37617687f2_20260115100804-v1-1-9796615d93ab@est.tech>
Date: Fri, 16 Jan 2026 11:14:45 +0100
From: David Nyström <david.nystrom@....tech>
To: stable@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Sasha Levin <sashal@...nel.org>, 
 David Nyström <david.nystrom@....tech>, 
 netdev@...r.kernel.org, Zeng Heng <zengheng4@...wei.com>, 
 Paolo Abeni <pabeni@...hat.com>, Yang Yingliang <yangyingliang@...wei.com>, 
 "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Subject: [PATCH 5.10] net: mdio: fix unbalanced fwnode reference count in
 mdio_device_release()

[ Upstream commit cb37617687f2bfa5b675df7779f869147c9002bd ]

There is warning report about of_node refcount leak
while probing mdio device:

OF: ERROR: memory leak, expected refcount 1 instead of 2,
of_node_get()/of_node_put() unbalanced - destroy cset entry:
attach overlay node /spi/soc@...dio@...700c0/ethernet@4

In of_mdiobus_register_device(), we increase fwnode refcount
by fwnode_handle_get() before associating the of_node with
mdio device, but it has never been decreased in normal path.
Since that, in mdio_device_release(), it needs to call
fwnode_handle_put() in addition instead of calling kfree()
directly.

After above, just calling mdio_device_free() in the error handle
path of of_mdiobus_register_device() is enough to keep the
refcount balanced.

(cherry picked from commit cb37617687f2bfa5b675df7779f869147c9002bd)

Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
Signed-off-by: Zeng Heng <zengheng4@...wei.com>
Reviewed-by: Yang Yingliang <yangyingliang@...wei.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Link: https://lore.kernel.org/r/20221203073441.3885317-1-zengheng4@huawei.com
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: David Nyström <david.nystrom@....tech>
---
This series backports 1 commit(s) to the 5.10 stable tree.
---
 drivers/net/mdio/of_mdio.c    | 3 ++-
 drivers/net/phy/mdio_device.c | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index b254127cea50..355c3ee21cd7 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -168,8 +168,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
 	/* All data is now stored in the mdiodev struct; register it. */
 	rc = mdio_device_register(mdiodev);
 	if (rc) {
+		device_set_node(&mdiodev->dev, NULL);
+		fwnode_handle_put(fwnode);
 		mdio_device_free(mdiodev);
-		of_node_put(child);
 		return rc;
 	}
 
diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
index 797c41f5590e..f72d18ee2792 100644
--- a/drivers/net/phy/mdio_device.c
+++ b/drivers/net/phy/mdio_device.c
@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/unistd.h>
+#include <linux/property.h>
 
 void mdio_device_free(struct mdio_device *mdiodev)
 {
@@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
 
 static void mdio_device_release(struct device *dev)
 {
+	fwnode_handle_put(dev->fwnode);
 	kfree(to_mdio_device(dev));
 }
 

---
base-commit: f964b940099f9982d723d4c77988d4b0dda9c165
change-id: 20260115-backport_cb37617687f2_20260115100804-bb6cefe39d44

Best regards,
--  
David Nyström <david.nystrom@....tech>