linux-kernel - Re: [RFC PATCH] spi: fix use-after-free of the add

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Date:   Thu, 11 Nov 2021 06:19:23 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Vladimir Oltean <olteanv@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [RFC PATCH] spi: fix use-after-free of the add_lock mutex

On Wed, Nov 10, 2021 at 05:08:36PM +0100, Michael Walle wrote:
> Commit 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on
> SPI buses") introduced a per-controller mutex. But mutex_unlock() of
> said lock is called after the controller is already freed:
> 
>   spi_unregister_controller(ctlr)
>    -> put_device(&ctlr->dev)
>     -> spi_controller_release(dev)
>   mutex_unlock(&ctrl->add_lock)
> 
> Move the put_device() after the mutex_unlock().
> 
> Fixes: 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses")
> Signed-off-by: Michael Walle <michael@...le.cc>

Reviewed-by: Lukas Wunner <lukas@...ner.de>
Cc: stable@...r.kernel.org # v5.15