netdev - [PATCH net v2 3/3] dpaa2-switch: Fix device reference count leak in MAC endpoint handling

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Message-Id: <20250717022309.3339976-3-make24@iscas.ac.cn>
Date: Thu, 17 Jul 2025 10:23:09 +0800
From: Ma Ke <make24@...as.ac.cn>
To: ioana.ciornei@....com,
	davem@...emloft.net,
	andrew+netdev@...n.ch,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	Ma Ke <make24@...as.ac.cn>,
	stable@...r.kernel.org
Subject: [PATCH net v2 3/3] dpaa2-switch: Fix device reference count leak in MAC endpoint handling

The fsl_mc_get_endpoint() function uses device_find_child() for
localization, which implicitly calls get_device() to increment the
device's reference count before returning the pointer. However, the
caller dpaa2_switch_port_connect_mac() fails to properly release this 
reference in multiple scenarios. We should call put_device() to 
decrement reference count properly.

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: 84cba72956fd ("dpaa2-switch: integrate the MAC endpoint support")
Signed-off-by: Ma Ke <make24@...as.ac.cn>
---
 .../net/ethernet/freescale/dpaa2/dpaa2-switch.c   | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
index 147a93bf9fa9..4643a3380618 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
@@ -1448,12 +1448,19 @@ static int dpaa2_switch_port_connect_mac(struct ethsw_port_priv *port_priv)
 	if (PTR_ERR(dpmac_dev) == -EPROBE_DEFER)
 		return PTR_ERR(dpmac_dev);
 
-	if (IS_ERR(dpmac_dev) || dpmac_dev->dev.type != &fsl_mc_bus_dpmac_type)
+	if (IS_ERR(dpmac_dev))
 		return 0;
 
+	if (dpmac_dev->dev.type != &fsl_mc_bus_dpmac_type) {
+		err = 0;
+		goto out_put_device;
+	}
+
 	mac = kzalloc(sizeof(*mac), GFP_KERNEL);
-	if (!mac)
-		return -ENOMEM;
+	if (!mac) {
+		err = -ENOMEM;
+		goto out_put_device;
+	}
 
 	mac->mc_dev = dpmac_dev;
 	mac->mc_io = port_priv->ethsw_data->mc_io;
@@ -1483,6 +1490,8 @@ static int dpaa2_switch_port_connect_mac(struct ethsw_port_priv *port_priv)
 	dpaa2_mac_close(mac);
 err_free_mac:
 	kfree(mac);
+out_put_device:
+	put_device(&dpmac_dev->dev);
 	return err;
 }
 
-- 
2.25.1