linux-kernel - Re: [PATCH] drm/amd/display: Fix unsigned variable compared to less than zero

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Date:   Mon, 11 Nov 2019 12:46:32 -0500
From:   Mikita Lipski <mlipski@....com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....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>,
        Mikita Lipski <mikita.lipski@....com>,
        Lyude Paul <lyude@...hat.com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Fix unsigned variable compared to less
 than zero


Thanks for catching it!

Reviewed-by: Mikita Lipski <mikita.lipski@....com>


On 11.11.2019 12:25, Gustavo A. R. Silva wrote:
> Currenly, the error check below on variable*vcpi_slots*  is always
> false because it is a uint64_t type variable, hence, the values
> this variable can hold are never less than zero:
> 
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:
> 4870         if (dm_new_connector_state->vcpi_slots < 0) {
> 4871                 DRM_DEBUG_ATOMIC("failed finding vcpi slots: %d\n", (int)dm_new_connector_stat     e->vcpi_slots);
> 4872                 return dm_new_connector_state->vcpi_slots;
> 4873         }
> 
> Fix this by making*vcpi_slots*  of int type
> 
> Addresses-Coverity: 1487838 ("Unsigned compared against 0")
> Fixes: b4c578f08378 ("drm/amd/display: Add MST atomic routines")
> Signed-off-by: Gustavo A. R. Silva<gustavo@...eddedor.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> index 6db07e9e33ab..a8fc90a927d6 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> @@ -403,7 +403,7 @@ struct dm_connector_state {
>   	bool underscan_enable;
>   	bool freesync_capable;
>   	uint8_t abm_level;
> -	uint64_t vcpi_slots;
> +	int vcpi_slots;
>   	uint64_t pbn;
>   };
>   
> -- 2.23.0

-- 
Thanks,
Mikita Lipski
Software Engineer, AMD
mikita.lipski@....com