linux-kernel - Re: [PATCH -next] drm/amd/display: check top_pipe_to

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Date:   Wed, 17 Nov 2021 16:40:31 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Yang Li <yang.lee@...ux.alibaba.com>
Cc:     Daniel Vetter <daniel@...ll.ch>, Dave Airlie <airlied@...ux.ie>,
        llvm@...ts.linux.dev,
        "Siqueira, Rodrigo" <Rodrigo.Siqueira@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        "Leo (Sunpeng) Li" <sunpeng.li@....com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Christian Koenig <christian.koenig@....com>
Subject: Re: [PATCH -next] drm/amd/display: check top_pipe_to_program pointer

Applied.  Thanks!

On Mon, Nov 15, 2021 at 3:10 AM Yang Li <yang.lee@...ux.alibaba.com> wrote:
>
> Clang static analysis reports this error
>
> drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:2870:7: warning:
> Dereference of null pointer [clang-analyzer-core.NullDereference]
>                 if
> (top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
>                     ^
>
> top_pipe_to_program being NULL is caught as an error
> But then it is used to report the error.
>
> So add a check before using it.
>
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
> index 39ad385..34382d0 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
> @@ -2867,7 +2867,8 @@ static void commit_planes_for_stream(struct dc *dc,
>  #endif
>
>         if ((update_type != UPDATE_TYPE_FAST) && stream->update_flags.bits.dsc_changed)
> -               if (top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
> +               if (top_pipe_to_program &&
> +                       top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
>                         if (should_use_dmub_lock(stream->link)) {
>                                 union dmub_hw_lock_flags hw_locks = { 0 };
>                                 struct dmub_hw_lock_inst_flags inst_flags = { 0 };
> --
> 1.8.3.1
>