linux-kernel - Re: [PATCH] drm/amd/display: Fix potential NULL pointer dereferences in amdgpu_dm_atomic_commit

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Date:   Tue, 28 Nov 2017 09:33:22 -0500
From:   Andrey Grodzovsky <Andrey.Grodzovsky@....com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Fix potential NULL pointer dereferences
 in amdgpu_dm_atomic_commit_tail

Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@....com>

Thanks,

Andrey

On 11/27/2017 09:57 AM, Gustavo A. R. Silva wrote:
> dm_new_crtc_state->stream and disconnected_acrtc are being dereferenced
> before they are null checked, hence there is a potential null pointer
> dereference.
>
> Fix this by null checking such pointers before they are dereferenced.
>
> Addresses-Coverity-ID: 1423745 ("Dereference before null check")
> Addresses-Coverity-ID: 1423833 ("Dereference before null check")
> Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_types and amdgpu_dm")
> Fixes: 54d765752467 ("drm/amd/display: Unify amdgpu_dm state variable namings.")
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 889ed24..3bdd137 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4190,6 +4190,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
>   
>   		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
>   
> +		if (!dm_new_crtc_state->stream)
> +			continue;
> +
>   		update_stream_scaling_settings(&dm_new_con_state->base.crtc->mode,
>   				dm_new_con_state, (struct dc_stream_state *)dm_new_crtc_state->stream);
>   
> @@ -4197,9 +4200,6 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
>   		WARN_ON(!status);
>   		WARN_ON(!status->plane_count);
>   
> -		if (!dm_new_crtc_state->stream)
> -			continue;
> -
>   		/*TODO How it works with MPO ?*/
>   		if (!dc_commit_planes_to_stream(
>   				dm->dc,
> @@ -4332,9 +4332,11 @@ void dm_restore_drm_connector_state(struct drm_device *dev,
>   		return;
>   
>   	disconnected_acrtc = to_amdgpu_crtc(connector->encoder->crtc);
> -	acrtc_state = to_dm_crtc_state(disconnected_acrtc->base.state);
> +	if (!disconnected_acrtc)
> +		return;
>   
> -	if (!disconnected_acrtc || !acrtc_state->stream)
> +	acrtc_state = to_dm_crtc_state(disconnected_acrtc->base.state);
> +	if (!acrtc_state->stream)
>   		return;
>   
>   	/*