linux-kernel - Re: [PATCH v2 2/2] ASoC: mediatek: mt8195: fix use-after-free in driver remove path

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Message-ID: <a66c9e7c-3a8b-f32a-7ac2-5717024599a4@baylibre.com>
Date:   Mon, 5 Jun 2023 15:27:43 +0200
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     Trevor Wu <trevor.wu@...iatek.com>, broonie@...nel.org,
        lgirdwood@...il.com, tiwai@...e.com, perex@...ex.cz,
        matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com
Cc:     dianders@...omium.org, alsa-devel@...a-project.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ASoC: mediatek: mt8195: fix use-after-free in
 driver remove path

On 01/06/2023 05:33, Trevor Wu wrote:
> During mt8195_afe_init_clock(), mt8195_audsys_clk_register() was called
> followed by several other devm functions. At mt8195_afe_deinit_clock()
> located at mt8195_afe_pcm_dev_remove(), mt8195_audsys_clk_unregister()
> was called.
> 
> However, there was an issue with the order in which these functions were
> called. Specifically, the remove callback of platform_driver was called
> before devres released the resource, resulting in a use-after-free issue
> during remove time.
> 
> At probe time, the order of calls was:
> 1. mt8195_audsys_clk_register
> 2. afe_priv->clk = devm_kcalloc
> 3. afe_priv->clk[i] = devm_clk_get
> 
> At remove time, the order of calls was:
> 1. mt8195_audsys_clk_unregister
> 3. free afe_priv->clk[i]
> 2. free afe_priv->clk
> 
> To resolve the problem, we can utilize devm_add_action_or_reset() in
> mt8195_audsys_clk_register() so that the remove order can be changed to
> 3->2->1.

Reviewed-by: Alexandre Mergnat <amergnat@...libre.com>

-- 
Regards,
Alexandre