netdev - [PATCH v4] net: mdiobus: fix an OF node reference leak

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Message-Id: <20241218035106.1436405-1-joe@pf.is.s.u-tokyo.ac.jp>
Date: Wed, 18 Dec 2024 12:51:06 +0900
From: Joe Hattori <joe@...is.s.u-tokyo.ac.jp>
To: andrew@...n.ch,
	hkallweit1@...il.com,
	linux@...linux.org.uk,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com
Cc: netdev@...r.kernel.org,
	Joe Hattori <joe@...is.s.u-tokyo.ac.jp>
Subject: [PATCH v4] net: mdiobus: fix an OF node reference leak

fwnode_find_mii_timestamper() calls of_parse_phandle_with_fixed_args()
but does not decrement the refcount of the obtained OF node. Add an
of_node_put() call before returning from the function.

This bug was detected by an experimental static analysis tool that I am
developing.

Fixes: bc1bee3b87ee ("net: mdiobus: Introduce fwnode_mdiobus_register_phy()")
Signed-off-by: Joe Hattori <joe@...is.s.u-tokyo.ac.jp>
---
Changes in v4:
- Reorder the variables.
- Add and use put_node label for cleanup.

Changes in v3:
- Call of_node_put() when arg.args_count != 1 holds.

Changes in v2:
- Call of_node_put() after calling register_mii_timestamper() to avoid
  UAF.
---
 drivers/net/mdio/fwnode_mdio.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
index b156493d7084..aea0f0357568 100644
--- a/drivers/net/mdio/fwnode_mdio.c
+++ b/drivers/net/mdio/fwnode_mdio.c
@@ -40,6 +40,7 @@ fwnode_find_pse_control(struct fwnode_handle *fwnode)
 static struct mii_timestamper *
 fwnode_find_mii_timestamper(struct fwnode_handle *fwnode)
 {
+	struct mii_timestamper *mii_ts;
 	struct of_phandle_args arg;
 	int err;
 
@@ -53,10 +54,16 @@ fwnode_find_mii_timestamper(struct fwnode_handle *fwnode)
 	else if (err)
 		return ERR_PTR(err);
 
-	if (arg.args_count != 1)
-		return ERR_PTR(-EINVAL);
+	if (arg.args_count != 1) {
+		mii_ts = ERR_PTR(-EINVAL);
+		goto put_node;
+	}
+
+	mii_ts = register_mii_timestamper(arg.np, arg.args[0]);
 
-	return register_mii_timestamper(arg.np, arg.args[0]);
+put_node:
+	of_node_put(arg.np);
+	return mii_ts;
 }
 
 int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
-- 
2.34.1