linux-kernel - [PATCH] net: arc_emac: Fix use after free in arc_mdio

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Date:   Thu,  3 Mar 2022 09:30:22 +0800
From:   Jianglei Nie <niejianglei2021@....com>
To:     davem@...emloft.net, kuba@...nel.org, caihuoqing@...du.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jianglei Nie <niejianglei2021@....com>
Subject: [PATCH] net: arc_emac: Fix use after free in arc_mdio_probe()

If bus->state is equal to MDIOBUS_ALLOCATED, mdiobus_free(bus) will free
the "bus". But bus->name is still used in the next line, which will lead
to a use after free.

We can fix it by assigning dev_err_probe() to dev_err before the bus is
freed to avoid the uaf.

Signed-off-by: Jianglei Nie <niejianglei2021@....com>
---
 drivers/net/ethernet/arc/emac_mdio.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/arc/emac_mdio.c b/drivers/net/ethernet/arc/emac_mdio.c
index 9acf589b1178..795a25c5848a 100644
--- a/drivers/net/ethernet/arc/emac_mdio.c
+++ b/drivers/net/ethernet/arc/emac_mdio.c
@@ -165,9 +165,10 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
 
 	error = of_mdiobus_register(bus, priv->dev->of_node);
 	if (error) {
-		mdiobus_free(bus);
-		return dev_err_probe(priv->dev, error,
+		int dev_err = dev_err_probe(priv->dev, error,
 				     "cannot register MDIO bus %s\n", bus->name);
+		mdiobus_free(bus);
+		return dev_err;
 	}
 
 	return 0;
-- 
2.25.1