linux-kernel - Re: [PATCH] net: phy: Fix potential null pointer access

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Message-ID: <2508da6b-a099-4271-a1d0-04cfe5d39daf@weidmueller.com>
Date:   Mon, 20 Nov 2023 13:38:06 +0100
From:   Lukas Funke <lukas.funke-oss@...dmueller.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lukas Funke <lukas.funke@...dmueller.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: Fix potential null pointer access

Hi Russel,

On 20.11.2023 10:51, Russell King (Oracle) wrote:
> On Mon, Nov 20, 2023 at 10:32:54AM +0100, Lukas Funke wrote:
>> From: Lukas Funke <lukas.funke@...dmueller.com>
>>
>> When there is no driver associated with the phydev, there will be a
>> nullptr access. The commit checks if the phydev driver is set before
>> access.
> 
> What's the call path that we encounter a NULL drv pointer?


The patch is a bit older and the path is reconstructed from my memory:

macb_phylink_connect -> phylink_of_phy_connect -> of_phy_connect -> 
phy_connect_direct -> phy_request_interrupt

It happend when we used the Xilinx gmii2rgmii phy driver. We did a 
missconfiguration in the dt and bumped into the nullpointer exception. 
Since other functions like phy_aneg_done() also check for driver 
existence I thought it would be a good addition.

> 
> Thanks.
>