netdev - [PATCH] phy: mdio: fix memory leak

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Date:   Mon, 27 Sep 2021 14:20:17 +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
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+398e7dc692ddbbb4cfec@...kaller.appspotmail.com
Subject: [PATCH] phy: mdio: fix memory leak

Syzbot reported memory leak in MDIO bus interface, the problem was in
wrong state logic.

MDIOBUS_ALLOCATED indicates 2 states:
	1. Bus is only allocated
	2. Bus allocated and __mdiobus_register() fails, but
	   device_register() was called

In case of device_register() has been called we should call put_device()
to correctly free the memory allocated for this device, but mdiobus_free()
was just calling kfree(dev) in case of MDIOBUS_ALLOCATED state

To avoid this behaviour we can add new intermediate state, which means,
that we have called device_regiter(), but failed on any of the next steps.
Clean up process for this state is the same as for MDIOBUS_UNREGISTERED,
but MDIOBUS_UNREGISTERED name does not fit to the logic described above.

Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
Reported-and-tested-by: syzbot+398e7dc692ddbbb4cfec@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---
 drivers/net/phy/mdio_bus.c | 4 +++-
 include/linux/phy.h        | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 53f034fc2ef7..ed764638b449 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_DEV_REGISTERED;
+
 	mutex_init(&bus->mdio_lock);
 	mutex_init(&bus->shared_lock);
 
@@ -647,7 +649,7 @@ void mdiobus_free(struct mii_bus *bus)
 		return;
 	}
 
-	BUG_ON(bus->state != MDIOBUS_UNREGISTERED);
+	BUG_ON(bus->state != MDIOBUS_UNREGISTERED && bus->state != MDIOBUS_DEV_REGISTERED);
 	bus->state = MDIOBUS_RELEASED;
 
 	put_device(&bus->dev);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 736e1d1a47c4..41d2ccdacd5e 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -343,6 +343,7 @@ struct mii_bus {
 		MDIOBUS_REGISTERED,
 		MDIOBUS_UNREGISTERED,
 		MDIOBUS_RELEASED,
+		MDIOBUS_DEV_REGISTERED,
 	} state;
 
 	/** @dev: Kernel device representation */
-- 
2.33.0