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

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Date:   Thu, 1 Dec 2022 17:22:02 +0800
From:   Zeng Heng <zengheng4@...wei.com>
To:     <f.fainelli@...il.com>, <pabeni@...hat.com>, <andrew@...n.ch>,
        <kuba@...nel.org>, <linux@...linux.org.uk>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <hkallweit1@...il.com>
CC:     <netdev@...r.kernel.org>, <liwei391@...wei.com>,
        <zengheng4@...wei.com>
Subject: [PATCH] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

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 after that.
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.

Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
Signed-off-by: Zeng Heng <zengheng4@...wei.com>
---
 drivers/net/mdio/of_mdio.c    | 1 -
 drivers/net/phy/mdio_device.c | 2 ++
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index 796e9c7857d0..296317a6b333 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -69,7 +69,6 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
 	rc = mdio_device_register(mdiodev);
 	if (rc) {
 		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 250742ffdfd9..044828d081d2 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));
 }
 
-- 
2.25.1