linux-kernel - [PATCH v2 1/2] Revert "net: mdiobus: Fix memory leak in __mdiobus

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Date:   Tue, 28 Sep 2021 23:39:15 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, kuba@...nel.org, buytenh@...vell.com,
        afleming@...escale.com, dan.carpenter@...cle.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        Yanfei Xu <yanfei.xu@...driver.com>
Subject: [PATCH v2 1/2] Revert "net: mdiobus: Fix memory leak in __mdiobus_register"

This reverts commit ab609f25d19858513919369ff3d9a63c02cd9e2e.

This patch is correct in the sense that we _should_ call device_put() in
case of device_register() failure, but the problem in this code is more
vast.

We need to set bus->state to UNMDIOBUS_REGISTERED before calling
device_register() to correctly release the device in mdiobus_free().
This patch prevents us from doing it, since in case of device_register()
failure put_device() will be called 2 times and it will cause UAF or
something else.

Also, Reported-by: tag in revered commit was wrong, since syzbot
reported different leak in same function.

Link: https://lore.kernel.org/netdev/20210928092657.GI2048@kadam/
Cc: Yanfei Xu <yanfei.xu@...driver.com>
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---

Changes in v2:
	Added this revert

---
 drivers/net/phy/mdio_bus.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 6f4b4e5df639..53f034fc2ef7 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -537,7 +537,6 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 	err = device_register(&bus->dev);
 	if (err) {
 		pr_err("mii_bus %s failed to register\n", bus->id);
-		put_device(&bus->dev);
 		return -EINVAL;
 	}

-- 
2.33.0