netdev - Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference during phylink_pcs_poll

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Message-ID: <8ddb55c3-a960-7e61-75d1-88733fa9b116@engleder-embedded.com>
Date:   Wed, 29 Jun 2022 22:14:34 +0200
From:   Gerhard Engleder <gerhard@...leder-embedded.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next] net: phylink: fix NULL pl->pcs dereference
 during phylink_pcs_poll_start


On 29.06.22 21:42, Russell King (Oracle) wrote:
> On Wed, Jun 29, 2022 at 10:33:58PM +0300, Vladimir Oltean wrote:
>> The current link mode of the phylink instance may not require an
>> attached PCS. However, phylink_major_config() unconditionally
>> dereferences this potentially NULL pointer when restarting the link poll
>> timer, which will panic the kernel.
>>
>> Fix the problem by checking whether a PCS exists in phylink_pcs_poll_start(),
>> otherwise do nothing. The code prior to the blamed patch also only
>> looked at pcs->poll within an "if (pcs)" block.
>>
>> Fixes: bfac8c490d60 ("net: phylink: disable PCS polling over major configuration")
>> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Thanks.
>
> Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
>
Fixes the problem on my side.

Tested-by: Gerhard Engleder <gerhard@...leder-embedded.com>