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

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Message-ID: <b7864c7d-172e-9903-278c-63df45f6a0ff@collabora.com>
Date:   Thu, 1 Jun 2023 12:02:42 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Trevor Wu <trevor.wu@...iatek.com>, broonie@...nel.org,
        lgirdwood@...il.com, tiwai@...e.com, perex@...ex.cz,
        matthias.bgg@...il.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

Il 01/06/23 05:33, Trevor Wu ha scritto:
> 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.
> 
> Fixes: 6746cc858259 ("ASoC: mediatek: mt8195: add platform driver")
> Signed-off-by: Trevor Wu <trevor.wu@...iatek.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>