linux-kernel - Re: [PATCH] ASoC: samsung: i2s: Null pointer dereference on samsung_i2s

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Date:   Thu, 10 Aug 2017 18:23:48 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     Anton Vasilyev <vasilyev@...ras.ru>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>,
        Sangbeom Kim <sbkim73@...sung.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] ASoC: samsung: i2s: Null pointer dereference on
 samsung_i2s_remove

On 08/10/2017 05:56 PM, Anton Vasilyev wrote:
> If (quirks & QUIRK_SEC_DAI == 0) then samsung_i2s_probe() doesn't allocate
> sec_dai and pri_dai->sec_dai remains Null, but samsung_i2s_remove()
> permorms pri_dai->sec_dai dereference in any case.

s/permorms/performs

> The patch adds sec_dai check on Null before derefence at
> samsung_i2s_remove().
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Anton Vasilyev <vasilyev@...ras.ru>
> ---
>   sound/soc/samsung/i2s.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/samsung/i2s.c b/sound/soc/samsung/i2s.c
> index af3ba4d..6beeea8 100644
> --- a/sound/soc/samsung/i2s.c
> +++ b/sound/soc/samsung/i2s.c
> @@ -1382,7 +1382,8 @@ static int samsung_i2s_remove(struct platform_device *pdev)
>   	sec_dai = pri_dai->sec_dai;
>   
>   	pri_dai->sec_dai = NULL;
> -	sec_dai->pri_dai = NULL;

Thanks for the patch.  AFAICS above 4 lines could be removed altogether
since pri_dai and sec_dai is being allocated with devm_kzalloc().
So initializing in remove() is meaningless as afterwards the data will
not be used any more.  The memory will be just freed by the devres code.

> +	if (sec_dai)
> +		sec_dai->pri_dai = NULL;

-- 
Regards,
Sylwester