linux-kernel - Re: [PATCH] soc: meson: fix a missing check on list iterator

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Date:   Sun, 27 Mar 2022 13:03:14 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Xiaomeng Tong <xiam0nd.tong@...il.com>, lgirdwood@...il.com,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        narmstrong@...libre.com, khilman@...libre.com
Cc:     martin.blumenstingl@...glemail.com, alsa-devel@...a-project.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] soc: meson: fix a missing check on list iterator


On Sun 27 Mar 2022 at 16:18, Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:

> The bug is here:
> 	*dai_name = dai->driver->name;
>
> For for_each_component_dais(), just like list_for_each_entry,
> the list iterator 'runtime' will point to a bogus position
> containing HEAD if the list is empty or no element is found.
> This case must be checked before any use of the iterator,
> otherwise it will lead to a invalid memory access.
>
> To fix the bug, just move the assignment into loop and return
> 0 when element is found, otherwise return -EINVAL;

Except we already checked that the id is valid and know an element will
be be found once we enter the loop. No bug here and this patch does not
seem necessary to me.

>
> Cc: stable@...r.kernel.org
> Fixes: 6ae9ca9ce986b ("ASoC: meson: aiu: add i2s and spdif support")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
> ---
>  sound/soc/meson/aiu.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/sound/soc/meson/aiu.c b/sound/soc/meson/aiu.c
> index d299a70db7e5..b52915c6f53b 100644
> --- a/sound/soc/meson/aiu.c
> +++ b/sound/soc/meson/aiu.c
> @@ -61,14 +61,14 @@ int aiu_of_xlate_dai_name(struct snd_soc_component *component,
>  		return -EINVAL;
>  
>  	for_each_component_dais(component, dai) {
> -		if (id == 0)
> -			break;
> +		if (id == 0) {
> +			*dai_name = dai->driver->name;
> +			return 0;
> +		}
>  		id--;
>  	}
>  
> -	*dai_name = dai->driver->name;
> -
> -	return 0;
> +	return -EINVAL;
>  }
>  
>  static int aiu_cpu_of_xlate_dai_name(struct snd_soc_component *component,