netdev - Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in mdio_device

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Message-ID: <dc48342f-7a01-13e3-18c3-7c7a9f1ec41b@huawei.com>
Date:   Tue, 6 Dec 2022 19:49:37 +0800
From:   Zeng Heng <zengheng4@...wei.com>
To:     Paolo Abeni <pabeni@...hat.com>, <hkallweit1@...il.com>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <davem@...emloft.net>,
        <andrew@...n.ch>, <f.fainelli@...il.com>, <linux@...linux.org.uk>,
        Yang Yingliang <yangyingliang@...wei.com>
CC:     <liwei391@...wei.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] net: mdio: fix unbalanced fwnode reference count in
 mdio_device_release()


On 2022/12/6 19:34, Paolo Abeni wrote:
> Hello,
> On Sat, 2022-12-03 at 15:34 +0800, Zeng Heng wrote:
>> There is warning report about of_node refcount leak
>> while probing mdio device:
>>
>> OF: ERROR: memory leak, expected refcount 1 instead of 2,
>> of_node_get()/of_node_put() unbalanced - destroy cset entry:
>> attach overlay node /spi/soc@...dio@...700c0/ethernet@4
>>
>> In of_mdiobus_register_device(), we increase fwnode refcount
>> by fwnode_handle_get() before associating the of_node with
>> mdio device, but it has never been decreased in normal path.
>> Since that, in mdio_device_release(), it needs to call
>> fwnode_handle_put() in addition instead of calling kfree()
>> directly.
>>
>> After above, just calling mdio_device_free() in the error handle
>> path of of_mdiobus_register_device() is enough to keep the
>> refcount balanced.
>>
>> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
>> Signed-off-by: Zeng Heng <zengheng4@...wei.com>
>> Reviewed-by: Yang Yingliang <yangyingliang@...wei.com>
>> ---
>>   changes in v2:
>>    - Add operation about setting device node as NULL-pointer.
>>      There is no practical changes.
>>    - Add reviewed-by tag.
>> ---
>>   drivers/net/mdio/of_mdio.c    | 3 ++-
>>   drivers/net/phy/mdio_device.c | 2 ++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
>> index 796e9c7857d0..510822d6d0d9 100644
>> --- a/drivers/net/mdio/of_mdio.c
>> +++ b/drivers/net/mdio/of_mdio.c
>> @@ -68,8 +68,9 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
>>   	/* All data is now stored in the mdiodev struct; register it. */
>>   	rc = mdio_device_register(mdiodev);
>>   	if (rc) {
>> +		device_set_node(&mdiodev->dev, NULL);
>> +		fwnode_handle_put(fwnode);
>>   		mdio_device_free(mdiodev);
>> -		of_node_put(child);
>>   		return rc;
>>   	}
>>   
>> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
>> index 250742ffdfd9..044828d081d2 100644
>> --- a/drivers/net/phy/mdio_device.c
>> +++ b/drivers/net/phy/mdio_device.c
>> @@ -21,6 +21,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/string.h>
>>   #include <linux/unistd.h>
>> +#include <linux/property.h>
>>   
>>   void mdio_device_free(struct mdio_device *mdiodev)
>>   {
>> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>>   
>>   static void mdio_device_release(struct device *dev)
>>   {
>> +	fwnode_handle_put(dev->fwnode);
>>   	kfree(to_mdio_device(dev));
>>   }
>>
> The patch LGTM, but I'll wait a bit more just in case Andrew want to
> comment on it.
>
> Cheers,
>
> Paolo
+CC Yang Yingliang <yangyingliang@...wei.com>