linux-kernel - Re: [PATCH 2/2] drm/amd/powerplay: vega20: fix uninitialized variable use

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Date:   Mon, 8 Jul 2019 12:03:09 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Rex Zhu <rex.zhu@....com>, Evan Quan <evan.quan@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Chengming Gui <Jack.Gui@....com>,
        Kevin Wang <kevin1.wang@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Huang Rui <ray.huang@....com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>, Likun Gao <Likun.Gao@....com>,
        Hawking Zhang <Hawking.Zhang@....com>
Subject: Re: [PATCH 2/2] drm/amd/powerplay: vega20: fix uninitialized variable use

On Mon, Jul 8, 2019 at 10:08 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> If smu_get_current_rpm() fails, we can't use the output,
> as that may be uninitialized:
>
> drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3023:8: error: variable 'current_rpm' is used uninitialized whenever '?:' condition is false [-Werror,-Wsometimes-uninitialized]
>         ret = smu_get_current_rpm(smu, &current_rpm);
>               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:735:3: note: expanded from macro 'smu_get_current_rpm'
>         ((smu)->funcs->get_current_rpm ? (smu)->funcs->get_current_rpm((smu), (speed)) : 0)
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3024:12: note: uninitialized use occurs here
>         percent = current_rpm * 100 / pptable->FanMaximumRpm;
>                   ^~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3023:8: note: remove the '?:' if its condition is always true
>         ret = smu_get_current_rpm(smu, &current_rpm);
>               ^
> drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:735:3: note: expanded from macro 'smu_get_current_rpm'
>         ((smu)->funcs->get_current_rpm ? (smu)->funcs->get_current_rpm((smu), (speed)) : 0)
>          ^
> drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:3020:22: note: initialize the variable 'current_rpm' to silence this warning
>         uint32_t current_rpm;
>
> Propagate the error code in that case.
>
> Fixes: ee0db82027ee ("drm/amd/powerplay: move PPTable_t uses into asic level")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied.  thanks!

Alex

> ---
>  drivers/gpu/drm/amd/powerplay/vega20_ppt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/vega20_ppt.c b/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
> index 9ce3f1c8ae0f..20d477f8dc84 100644
> --- a/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
> +++ b/drivers/gpu/drm/amd/powerplay/vega20_ppt.c
> @@ -3021,10 +3021,13 @@ static int vega20_get_fan_speed_percent(struct smu_context *smu,
>         PPTable_t *pptable = smu->smu_table.driver_pptable;
>
>         ret = smu_get_current_rpm(smu, &current_rpm);
> +       if (ret)
> +               return ret;
> +
>         percent = current_rpm * 100 / pptable->FanMaximumRpm;
>         *speed = percent > 100 ? 100 : percent;
>
> -       return ret;
> +       return 0;
>  }
>
>  static int vega20_get_gpu_power(struct smu_context *smu, uint32_t *value)
> --
> 2.20.0
>
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> dri-devel@...ts.freedesktop.org
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