netdev - Re: [PATCH net 6/7] net: dsa: mt7530: fix kernel bug in mdiobus

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Date:   Mon, 7 Feb 2022 18:49:05 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Oleksij Rempel <linux@...pel-privat.de>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Rafael Richter <rafael.richter@....de>,
        Daniel Klauer <daniel.klauer@....de>
Subject: Re: [PATCH net 6/7] net: dsa: mt7530: fix kernel bug in
 mdiobus_free() when unbinding



On 2/7/2022 8:15 AM, Vladimir Oltean wrote:
> Nobody in this driver calls mdiobus_unregister(), which is necessary if
> mdiobus_register() completes successfully. So if the devres callbacks
> that free the mdiobus get invoked (this is the case when unbinding the
> driver), mdiobus_free() will BUG if the mdiobus is still registered,
> which it is.
> 
> My speculation is that this is due to the fact that prior to commit
> ac3a68d56651 ("net: phy: don't abuse devres in devm_mdiobus_register()")
> from June 2020, _devm_mdiobus_free() used to call mdiobus_unregister().
> But at the time that the mt7530 support was introduced in May 2021, the
> API was already changed. It's therefore likely that the blamed patch was
> developed on an older tree, and incorrectly adapted to net-next. This
> makes the Fixes: tag correct.
> 
> Fix the problem by using the devres variant of mdiobus_register.
> 
> Fixes: ba751e28d442 ("net: dsa: mt7530: add interrupt support")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian