netdev - Re: [PATCH net 1/3] net/mlx5e: Harden uplink netdev access against device unbind

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Message-ID: <dbabdfb6-e6cc-40a4-97ee-fcfd29371e8e@intel.com>
Date: Fri, 12 Sep 2025 13:07:51 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Jianbo Liu <jianbol@...dia.com>
CC: Tariq Toukan <tariqt@...dia.com>, Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Saeed Mahameed <saeedm@...dia.com>, "Leon
 Romanovsky" <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Gal Pressman <gal@...dia.com>, Jakub Kicinski
	<kuba@...nel.org>
Subject: Re: [PATCH net 1/3] net/mlx5e: Harden uplink netdev access against
 device unbind

On 9/11/25 09:09, Jianbo Liu wrote:
> 
> 
> On 9/11/2025 8:45 AM, Jakub Kicinski wrote:
>> On Wed, 10 Sep 2025 11:23:09 +0800 Jianbo Liu wrote:
>>> On 9/10/2025 9:23 AM, Jakub Kicinski wrote:
>>>> On Mon, 8 Sep 2025 13:07:04 +0300 Tariq Toukan wrote:
>>>>> +    struct net_device *netdev = mlx5_uplink_netdev_get(dev);
>>>>> +    struct mlx5e_priv *priv;
>>>>> +    int err;
>>>>> +
>>>>> +    if (!netdev)
>>>>> +        return 0;
>>>>
>>>> Please don't call in variable init functions which require cleanup
>>>> or error checking.
>>>
>>> But in this function, a NULL return from mlx5_uplink_netdev_get is a
>>> valid condition where it should simply return 0. No cleanup or error
>>> check is needed.
>>
>> You have to check if it succeeded, and if so, you need to clean up
>> later. Do no hide meaningful code in variable init.
> 
> My focus was on the NULL case, but I see now that the real issue is 
> ensuring the corresponding cleanup (_put) happens on the successful 
> path. Hiding the _get call in the initializer makes that less clear.
> 
> I will refactor the code to follow the correct pattern, like this:
> 
> struct net_device *netdev;
> 
> netdev = mlx5_uplink_netdev_get(dev);
> if (!netdev)
>      return 0;
> 
> Thank you for the explanation.
> 

that would be much better, and make it obvious that there is
matched get() and put() calls

would be also great to minify stacktrace
https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages