netdev - [PATCH v3] net: mdiobus: fix an OF node reference leak

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Message-Id: <20241216014055.324461-1-joe@pf.is.s.u-tokyo.ac.jp>
Date: Mon, 16 Dec 2024 10:40:55 +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 v3] 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 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 | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
index b156493d7084..b18a1934018e 100644
--- a/drivers/net/mdio/fwnode_mdio.c
+++ b/drivers/net/mdio/fwnode_mdio.c
@@ -41,6 +41,7 @@ static struct mii_timestamper *
 fwnode_find_mii_timestamper(struct fwnode_handle *fwnode)
 {
 	struct of_phandle_args arg;
+	struct mii_timestamper *mii_ts;
 	int err;
 
 	if (is_acpi_node(fwnode))
@@ -53,10 +54,14 @@ fwnode_find_mii_timestamper(struct fwnode_handle *fwnode)
 	else if (err)
 		return ERR_PTR(err);
 
-	if (arg.args_count != 1)
+	if (arg.args_count != 1) {
+		of_node_put(arg.np);
 		return ERR_PTR(-EINVAL);
+	}
 
-	return register_mii_timestamper(arg.np, arg.args[0]);
+	mii_ts = register_mii_timestamper(arg.np, arg.args[0]);
+	of_node_put(arg.np);
+	return mii_ts;
 }
 
 int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
-- 
2.34.1