linux-kernel - Re: [PATCH] ASoC: wcd934x: Fix a incorrect use of kstrndup

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Date:   Tue, 14 Dec 2021 18:35:45 +0100
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Banajit Goswami <bgoswami@...eaurora.org>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH] ASoC: wcd934x: Fix a incorrect use of kstrndup

On 12/14/21 4:25 PM, Miaoqian Lin wrote:
> In wcd934x_codec_enable_dec(), widget_name is allocated by kstrndup().
> However, according to doc: "Note: Use kmemdup_nul() instead if the size
> is known exactly." So we should use kmemdup_nul() here instead of
> kstrndup(). It's similar to CVE-2019-12454.
>
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>   sound/soc/codecs/wcd934x.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/codecs/wcd934x.c b/sound/soc/codecs/wcd934x.c
> index e63c6b723d76..c6677cfbce59 100644
> --- a/sound/soc/codecs/wcd934x.c
> +++ b/sound/soc/codecs/wcd934x.c
> @@ -5005,7 +5005,7 @@ static int wcd934x_codec_enable_dec(struct snd_soc_dapm_widget *w,
>   	char *dec;
>   	u8 hpf_coff_freq;
>   
> -	widget_name = kstrndup(w->name, 15, GFP_KERNEL);
> +	widget_name = kmemdup_nul(w->name, 15, GFP_KERNEL);
I'm wondering if it isn't better to re-structure the code to not 
allocate any memory.

something like

ret = sscan(w->name, "ADC MUX%d", &decimator);
if (ret != 1)
     ...