linux-kernel - Re: [PATCH net 1/2] net: ravb: Fix missing rtnl lock in suspend path

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Message-ID: <20250123150814.6c46ec9a@kmaincent-XPS-13-7390>
Date: Thu, 23 Jan 2025 15:08:14 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: Paul Barker <paul.barker.ct@...renesas.com>, Niklas Söderlund <niklas.soderlund@...natech.se>, Andrew Lunn
 <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Mikhail Ulyanov
 <mikhail.ulyanov@...entembedded.com>, Sergei Shtylyov
 <sergei.shtylyov@...entembedded.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, Niklas Söderlund
 <niklas.soderlund+renesas@...natech.se>, Claudiu Beznea
 <claudiu.beznea.uj@...renesas.com>, netdev@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ravb: Fix missing rtnl lock in suspend
 path

On Thu, 23 Jan 2025 13:33:30 +0200
Claudiu Beznea <claudiu.beznea@...on.dev> wrote:

> Hi, Kory,
> 
> On 22.01.2025 18:19, Kory Maincent wrote:
> > Fix the suspend path by ensuring the rtnl lock is held where required.
> > Calls to ravb_open, ravb_close and wol operations must be performed under
> > the rtnl lock to prevent conflicts with ongoing ndo operations.

> 
> I've test it. Looks good.
> 
> Thank you for your patch. However, I think this could be simplified. The
> locking scheme looks complicated to me. E.g., this one works too:
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
> b/drivers/net/ethernet/renesas/ravb_main.c
> index bc395294a32d..cfe4f0f364f3 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -3217,10 +3217,16 @@ static int ravb_suspend(struct device *dev)
> 
>         netif_device_detach(ndev);
> 
> -       if (priv->wol_enabled)
> -               return ravb_wol_setup(ndev);
> +       if (priv->wol_enabled) {
> +               rtnl_lock();
> +               ret = ravb_wol_setup(ndev);
> +               rtnl_unlock();
> +               return ret;
> +       }

What happen if wol_enabled flag changes it state between the rtnl_lock and the
if condition? We will be in the wrong path.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com