Re: [PATCH 5/6] ASoC: samsung: tm2_wm5110: check of_parse return value

[Krzysztof Kozlowski <krzk@kernel.org>]

On Fri, Feb 19, 2021 at 05:09:17PM -0600, Pierre-Louis Bossart wrote:
> cppcheck warning:
> 
> sound/soc/samsung/tm2_wm5110.c:605:6: style: Variable 'ret' is
> reassigned a value before the old one has been
> used. [redundantAssignment]
>  ret = devm_snd_soc_register_component(dev, &tm2_component,
>      ^
> sound/soc/samsung/tm2_wm5110.c:554:7: note: ret is assigned
>   ret = of_parse_phandle_with_args(dev->of_node, "i2s-controller",
>       ^
> sound/soc/samsung/tm2_wm5110.c:605:6: note: ret is overwritten
>  ret = devm_snd_soc_register_component(dev, &tm2_component,
>      ^
> 
> it seems wise to first test the return value before checking if the
> returned argument is not null?

Actually this is real bug. The args is a stack variable, so it could
have junk (uninitialized) therefore args.np could have a non-NULL and
random value even though property was missing. Later could trigger
invalid pointer dereference.

  Fixes: 8d1513cef51a ("ASoC: samsung: Add support for HDMI audio on TM2 board")
  Cc: <stable@vger.kernel.org>

> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> ---
>  sound/soc/samsung/tm2_wm5110.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/soc/samsung/tm2_wm5110.c b/sound/soc/samsung/tm2_wm5110.c
> index 9300fef9bf26..da6204248f82 100644
> --- a/sound/soc/samsung/tm2_wm5110.c
> +++ b/sound/soc/samsung/tm2_wm5110.c
> @@ -553,7 +553,7 @@ static int tm2_probe(struct platform_device *pdev)
>  
>  		ret = of_parse_phandle_with_args(dev->of_node, "i2s-controller",
>  						 cells_name, i, &args);
> -		if (!args.np) {
> +		if (ret || !args.np) {

Only "if (ret)" because args.np won't be initialized on errors.

Best regards,
Krzysztof