linux-kernel - [PATCH 5.14 015/125] Revert "net: mdiobus: Fix memory leak in __mdiobus

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Date:   Mon,  1 Nov 2021 10:16:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yanfei Xu <yanfei.xu@...driver.com>,
        Pavel Skripkin <paskripkin@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 5.14 015/125] Revert "net: mdiobus: Fix memory leak in __mdiobus_register"

From: Pavel Skripkin <paskripkin@...il.com>

commit 10eff1f5788b6ffac212c254e2f3666219576889 upstream.

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/
Acked-by: Yanfei Xu <yanfei.xu@...driver.com>
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Link: https://lore.kernel.org/r/f12fb1faa4eccf0f355788225335eb4309ff2599.1633024062.git.paskripkin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/phy/mdio_bus.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -548,7 +548,6 @@ int __mdiobus_register(struct mii_bus *b
 	err = device_register(&bus->dev);
 	if (err) {
 		pr_err("mii_bus %s failed to register\n", bus->id);
-		put_device(&bus->dev);
 		return -EINVAL;
 	}