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Subject: Re: [PATCH] drm/amd/display: Fix potential NULL pointer dereferences
 in amdgpu_dm_atomic_commit_tail
To:     "Gustavo A. R. Silva" <garsilva@embeddedor.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        David Airlie <airlied@linux.ie>
Cc:     dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
References: <20171127145700.GA18395@embeddedor.com>
From:   Harry Wentland <harry.wentland@amd.com>
Message-ID: <3ff97f37-946a-a795-e57c-6d835e93be21@amd.com>
Date:   Mon, 27 Nov 2017 14:23:12 -0500
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On 2017-11-27 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@embeddedor.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;

This part is already in https://lists.freedesktop.org/archives/amd-gfx/2017-November/016389.html on its way to be merged.

The rest of the patch is
Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

>  
>  	/*
> 

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