linux-kernel - Re: [PATCH net-next v3] net: phy: Fix suspicious rcu

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Message-ID: <8686406e-6124-483e-af87-cc40e4d760b1@tuxon.dev>
Date: Tue, 21 Jan 2025 12:29:46 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Kory Maincent <kory.maincent@...tlin.com>,
 Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
 thomas.petazzoni@...tlin.com, Andrew Lunn <andrew@...n.ch>,
 Heiner Kallweit <hkallweit1@...il.com>, Russell King
 <linux@...linux.org.uk>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next v3] net: phy: Fix suspicious rcu_dereference
 usage

Hi, Kory,

On 21.01.2025 11:38, Kory Maincent wrote:
> On Mon, 20 Jan 2025 11:12:28 -0800
> Jakub Kicinski <kuba@...nel.org> wrote:
> 
>> On Mon, 20 Jan 2025 15:19:25 +0100 Kory Maincent wrote:
>>> The path reported to not having RTNL lock acquired is the suspend path of
>>> the ravb MAC driver. Without this fix we got this warning:  
>>
>> I maintain that ravb is buggy, plenty of drivers take rtnl_lock 
>> from the .suspend callback. We need _some_ write protection here,
>> the patch as is only silences a legitimate warning.
> 
> Indeed if the suspend path is buggy we should fix it. Still there is lots of
> ethernet drivers calling phy_disconnect without rtnl (IIUC) if probe return an
> error or in the remove path. What should we do about it?
> 
> About ravb suspend, I don't have the board, Claudiu could you try this instead
> of the current fix:
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
> b/drivers/net/ethernet/renesas/ravb_main.c index bc395294a32d..c9a0d2d6f371
> 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -3215,15 +3215,22 @@ static int ravb_suspend(struct device *dev)
>         if (!netif_running(ndev))
>                 goto reset_assert;
>  
> +       rtnl_lock();
>         netif_device_detach(ndev);
>  
> -       if (priv->wol_enabled)
> -               return ravb_wol_setup(ndev);
> +       if (priv->wol_enabled) {
> +               ret = ravb_wol_setup(ndev);
> +               rtnl_unlock();
> +               return ret;
> +       }
>  
>         ret = ravb_close(ndev);
> -       if (ret)
> +       if (ret) {
> +               rtnl_unlock();
>                 return ret;
> +       }
>  
> +       rtnl_unlock();
>         ret = pm_runtime_force_suspend(&priv->pdev->dev);
>         if (ret)
>                 return ret;

The warning is gone with this, as well.

Thank you,
Claudiu


> 
> Regards,