Re: [PATCH 1/2] drm/amd/display: Fix null check for pipe_ctx->plane_state in dcn20_program_pipe

["Chung, ChiaHsuan (Tom)" <chiahsuan.chung@amd.com>]

Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>

On 11/5/2024 10:01 PM, Zicheng Qu wrote:
> This commit addresses a null pointer dereference issue in
> dcn20_program_pipe(). Previously, commit 8e4ed3cf1642 ("drm/amd/display:
> Add null check for pipe_ctx->plane_state in dcn20_program_pipe")
> partially fixed the null pointer dereference issue. However, in
> dcn20_update_dchubp_dpp(), the variable pipe_ctx is passed in, and
> plane_state is accessed again through pipe_ctx. Multiple if statements
> directly call attributes of plane_state, leading to potential null
> pointer dereference issues. This patch adds necessary null checks to
> ensure stability.
>
> Fixes: 8e4ed3cf1642 ("drm/amd/display: Add null check for pipe_ctx->plane_state in dcn20_program_pipe")
> Signed-off-by: Zicheng Qu <quzicheng@huawei.com>
> ---
>   drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
> index a80c08582932..36d12db8d022 100644
> --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
> +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
> @@ -1923,9 +1923,9 @@ static void dcn20_program_pipe(
>   				dc->res_pool->hubbub, pipe_ctx->plane_res.hubp->inst, pipe_ctx->hubp_regs.det_size);
>   	}
>   
> -	if (pipe_ctx->update_flags.raw ||
> -	    (pipe_ctx->plane_state && pipe_ctx->plane_state->update_flags.raw) ||
> -	    pipe_ctx->stream->update_flags.raw)
> +	if (pipe_ctx->plane_state && (pipe_ctx->update_flags.raw ||
> +	    pipe_ctx->plane_state->update_flags.raw ||
> +	    pipe_ctx->stream->update_flags.raw))
>   		dcn20_update_dchubp_dpp(dc, pipe_ctx, context);
>   
>   	if (pipe_ctx->plane_state && (pipe_ctx->update_flags.bits.enable ||