Re: [PATCH] cpufreq: mediatek: guard error paths to avoid kernel panic

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 23/03/23 12:04, Daniel Golle ha scritto:
> Guard pointer access in error path of mtk_cpu_dvfs_info_init() to
> make sure info->proc_reg and info->sram_reg are valid pointers before
> accessing them, which would result in kernel panic e.g. in case of
> them being set to -EPROBE_DEFER.
> 
> Fixes: 4b9ceb757bbb ("cpufreq: mediatek: Enable clocks and regulators")
> Reported-by: Sam Shih <sam.shih@mediatek.com>
> Suggested-by: Sam Shih <sam.shih@mediatek.com>
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> ---
>   drivers/cpufreq/mediatek-cpufreq.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
> index 4466d0c91a6a..980a31ddd0f2 100644
> --- a/drivers/cpufreq/mediatek-cpufreq.c
> +++ b/drivers/cpufreq/mediatek-cpufreq.c
> @@ -579,10 +579,12 @@ static int mtk_cpu_dvfs_info_init(struct mtk_cpu_dvfs_info *info, int cpu)
>   	dev_pm_opp_of_cpumask_remove_table(&info->cpus);
>   
>   out_free_resources:
> -	if (regulator_is_enabled(info->proc_reg))
> -		regulator_disable(info->proc_reg);
> -	if (info->sram_reg && regulator_is_enabled(info->sram_reg))
> -		regulator_disable(info->sram_reg);
> +	if (!IS_ERR(info->proc_reg))
> +		if (regulator_is_enabled(info->proc_reg))
> +			regulator_disable(info->proc_reg);
> +	if (!IS_ERR(info->sram_reg))

For both, actually, if you suspect that (xxxx)_reg may be NULL, then you should
use IS_ERR_OR_NULL() instead...

> +		if (info->sram_reg && regulator_is_enabled(info->sram_reg))

...otherwise, here it's useless to check if it's not NULL?

Regards,
Angelo