linux-kernel - Re: [PATCH v1 4/4] thermal: tegra: fix coverity defect

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Message-ID: <20181108123709.GC1340@ulmo>
Date:   Thu, 8 Nov 2018 13:37:09 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Wei Ni <wni@...dia.com>
Cc:     daniel.lezcano@...aro.org, linux-tegra@...r.kernel.org,
        rui.zhang@...el.com, edubezval@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/4] thermal: tegra: fix coverity defect

On Mon, Nov 05, 2018 at 05:32:34PM +0800, Wei Ni wrote:
> Fix dereference dev before null check.
> 
> Signed-off-by: Wei Ni <wni@...dia.com>
> ---
>  drivers/thermal/tegra/soctherm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/tegra/soctherm.c b/drivers/thermal/tegra/soctherm.c
> index 3042837364e8..96527df91f2a 100644
> --- a/drivers/thermal/tegra/soctherm.c
> +++ b/drivers/thermal/tegra/soctherm.c
> @@ -397,7 +397,7 @@ static int throttrip_program(struct device *dev,
>  			     struct soctherm_throt_cfg *stc,
>  			     int trip_temp)
>  {
> -	struct tegra_soctherm *ts = dev_get_drvdata(dev);
> +	struct tegra_soctherm *ts;
>  	int temp, cpu_throt, gpu_throt;
>  	unsigned int throt;
>  	u32 r, reg_off;
> @@ -405,6 +405,8 @@ static int throttrip_program(struct device *dev,
>  	if (!sg || !stc || !stc->init)
>  		return -EINVAL;
>  
> +	ts = dev_get_drvdata(dev);

I think coverity is wrong. How is dev ever going to be NULL in this
case? We allocate all of these struct tegra_thermctl_zone structures in
tegra_soctherm_probe() and assign zone->dev = &pdev->dev, which can
never be NULL.

And even if it could, the code would've crashed earlier in
tegra_soctherm_probe() already.

Furthermore, I fail to see how your patch would fix the defect. None of
the checks in the conditional above actually check the dev value.

Thierry

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