netdev - [PATCH] net: mdiobus: fix device unregistering in mdiobus

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Message-Id: <20200826095141.5156-1-s.hauer@pengutronix.de>
Date:   Wed, 26 Aug 2020 11:51:41 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>, kernel@...gutronix.de,
        Sascha Hauer <s.hauer@...gutronix.de>
Subject: [PATCH] net: mdiobus: fix device unregistering in mdiobus_register

__mdiobus_register() can fail between calling device_register() and
setting bus->state to MDIOBUS_REGISTERED. When this happens the caller
will call mdiobus_free() which then frees the mdio bus structure. This
is not allowed as the embedded struct device is already registered, thus
must be freed dropping the reference count using put_device(). To
accomplish this set bus->state to MDIOBUS_UNREGISTERED after having
registered the device. With this mdiobus_free() correctly calls
put_device() instead of freeing the mdio bus structure directly.

Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
---
 drivers/net/phy/mdio_bus.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 0af20faad69d..85cbaab4a591 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -540,6 +540,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 		return -EINVAL;
 	}

+	bus->state = MDIOBUS_UNREGISTERED;
+
 	mutex_init(&bus->mdio_lock);
 	mutex_init(&bus->shared_lock);

-- 
2.28.0