linux-kernel - Re: [PATCH] drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm

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Date: Fri, 9 Feb 2024 13:11:06 -0500
From: Alex Deucher <alexdeucher@...il.com>
To: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
Cc: Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>, 
	Alex Deucher <alexander.deucher@....com>, Christian König <christian.koenig@....com>, 
	Rodrigo Siqueira <Rodrigo.Siqueira@....com>, "Pan, Xinhui" <Xinhui.Pan@....com>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	lvc-project@...uxtesting.org
Subject: Re: [PATCH] drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()

Applied.  Thanks!

Alex

On Tue, Feb 6, 2024 at 11:51 AM Nikita Zhandarovich
<n.zhandarovich@...tech.ru> wrote:
>
> Since 'adev->dm.dc' in amdgpu_dm_fini() might turn out to be NULL
> before the call to dc_enable_dmub_notifications(), check
> beforehand to ensure there will not be a possible NULL-ptr-deref
> there.
>
> Also, since commit 1e88eb1b2c25 ("drm/amd/display: Drop
> CONFIG_DRM_AMD_DC_HDCP") there are two separate checks for NULL in
> 'adev->dm.dc' before dc_deinit_callbacks() and dc_dmub_srv_destroy().
> Clean up by combining them all under one 'if'.
>
> Found by Linux Verification Center (linuxtesting.org) with static
> analysis tool SVACE.
>
> Fixes: 81927e2808be ("drm/amd/display: Support for DMUB AUX")
> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c    | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 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 d292f290cd6e..46ac3e6f42bb 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -1938,17 +1938,15 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
>                 adev->dm.hdcp_workqueue = NULL;
>         }
>
> -       if (adev->dm.dc)
> +       if (adev->dm.dc) {
>                 dc_deinit_callbacks(adev->dm.dc);
> -
> -       if (adev->dm.dc)
>                 dc_dmub_srv_destroy(&adev->dm.dc->ctx->dmub_srv);
> -
> -       if (dc_enable_dmub_notifications(adev->dm.dc)) {
> -               kfree(adev->dm.dmub_notify);
> -               adev->dm.dmub_notify = NULL;
> -               destroy_workqueue(adev->dm.delayed_hpd_wq);
> -               adev->dm.delayed_hpd_wq = NULL;
> +               if (dc_enable_dmub_notifications(adev->dm.dc)) {
> +                       kfree(adev->dm.dmub_notify);
> +                       adev->dm.dmub_notify = NULL;
> +                       destroy_workqueue(adev->dm.delayed_hpd_wq);
> +                       adev->dm.delayed_hpd_wq = NULL;
> +               }
>         }
>
>         if (adev->dm.dmub_bo)
> --
> 2.25.1
>