linux-kernel - Re: [PATCH v2] drm/amd/display: fix dereference before NULL check

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Message-ID: <CADnq5_N9b_Wm2GrLfL9Ug4rXN4Wqqv6kM+KxGf+kguoj6Wfytw@mail.gmail.com>
Date:   Mon, 27 Dec 2021 12:57:19 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     José Expósito <jose.exposito89@...il.com>
Cc:     "Wentland, Harry" <harry.wentland@....com>,
        Charlene Liu <charlene.liu@....com>,
        "Leo (Sunpeng) Li" <sunpeng.li@....com>,
        xinhui pan <Xinhui.Pan@....com>,
        "Siqueira, Rodrigo" <Rodrigo.Siqueira@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Dave Airlie <airlied@...ux.ie>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        "Deucher, Alexander" <alexander.deucher@....com>,
        Christian Koenig <christian.koenig@....com>
Subject: Re: [PATCH v2] drm/amd/display: fix dereference before NULL check

Applied.  Thanks!

Alex

On Sun, Dec 26, 2021 at 6:16 AM José Expósito <jose.exposito89@...il.com> wrote:
>
> The "plane_state" pointer was access before checking if it was NULL.
>
> Avoid a possible NULL pointer dereference by accessing the plane
> address after the check.
>
> Addresses-Coverity-ID: 1493892 ("Dereference before null check")
> Fixes: 3f68c01be9a22 ("drm/amd/display: add cyan_skillfish display support")
> Signed-off-by: José Expósito <jose.exposito89@...il.com>
> Reviewed-by: Harry Wentland <harry.wentland@....com>
>
> ---
>
> v2:
>
>  - Fix coverity report ID
>
>  - Add Reviewed-by tag (thanks to Harry Wentland)
> ---
>  drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> index cfd09b3f705e..fe22530242d2 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> @@ -134,11 +134,12 @@ void dcn201_update_plane_addr(const struct dc *dc, struct pipe_ctx *pipe_ctx)
>         PHYSICAL_ADDRESS_LOC addr;
>         struct dc_plane_state *plane_state = pipe_ctx->plane_state;
>         struct dce_hwseq *hws = dc->hwseq;
> -       struct dc_plane_address uma = plane_state->address;
> +       struct dc_plane_address uma;
>
>         if (plane_state == NULL)
>                 return;
>
> +       uma = plane_state->address;
>         addr_patched = patch_address_for_sbs_tb_stereo(pipe_ctx, &addr);
>
>         plane_address_in_gpu_space_to_uma(hws, &uma);
> --
> 2.25.1
>