Re: [PATCH] PM / devfreq: mediatek: Fix possible dereference of null pointer

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

Il 17/06/22 15:33, matthias.bgg@kernel.org ha scritto:
> From: Matthias Brugger <matthias.bgg@gmail.com>
> 
> We dereference the driver data before checking of it's valid.
> This patch fixes this, by accessing the PLL data struct after cheching
> the pointer
> 

Hello Matthias,

honestly, I don't think that this commit is right: mtk_ccifreq_target() is the
devfreq_dev_profile's .target() callback!

Checking mtk_ccifreq_probe(), we are setting drvdata long before adding the
devfreq device so, actually, it's impossible for dev_get_drvdata(dev) to return
NULL, or whatever invalid pointer.

This means that the right thing to do in mtk_ccifreq_target() is to simply remove
the `drv` NULL check, as this can never happen! :-)

Cheers,
Angelo

> Fixes: 07dc787be231 ("Add linux-next specific files for 20220617")
> Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
> ---
>   drivers/devfreq/mtk-cci-devfreq.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/devfreq/mtk-cci-devfreq.c b/drivers/devfreq/mtk-cci-devfreq.c
> index 71abb3fbd042..77522f16c878 100644
> --- a/drivers/devfreq/mtk-cci-devfreq.c
> +++ b/drivers/devfreq/mtk-cci-devfreq.c
> @@ -127,7 +127,7 @@ static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
>   			      u32 flags)
>   {
>   	struct mtk_ccifreq_drv *drv = dev_get_drvdata(dev);
> -	struct clk *cci_pll = clk_get_parent(drv->cci_clk);
> +	struct clk *cci_pll;
>   	struct dev_pm_opp *opp;
>   	unsigned long opp_rate;
>   	int voltage, pre_voltage, inter_voltage, target_voltage, ret;
> @@ -138,6 +138,7 @@ static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
>   	if (drv->pre_freq == *freq)
>   		return 0;
>   
> +	cci_pll = clk_get_parent(drv->cci_clk);
>   	inter_voltage = drv->inter_voltage;
>   
>   	opp_rate = *freq;
>