[PATCH 2/2] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

[Chung, ChiaHsuan (Tom)]

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

On 7/22/2024 9:46 AM, Srinivasan Shanmugam wrote:
> This commit addresses a potential null pointer dereference issue in the
> `dcn32_acquire_idle_pipe_for_head_pipe_in_layer` function. The issue
> could occur when `head_pipe` is null.
>
> The fix adds a check to ensure `head_pipe` is not null before asserting
> it. If `head_pipe` is null, the function returns NULL to prevent a
> potential null pointer dereference.
>
> Reported by smatch:
> drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn32/dcn32_resource.c:2690 dcn32_acquire_idle_pipe_for_head_pipe_in_layer() error: we previously assumed 'head_pipe' could be null (see line 2681)
>
> Cc: Tom Chung <chiahsuan.chung at amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
> Cc: Roman Li <roman.li at amd.com>
> Cc: Alex Hung <alex.hung at amd.com>
> Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Cc: Hamza Mahfooz <hamza.mahfooz at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
>   .../gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c    | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> index 6eaf3cfebcb7..a124ad9bd108 100644
> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
> @@ -2678,8 +2678,10 @@ static struct pipe_ctx *dcn32_acquire_idle_pipe_for_head_pipe_in_layer(
>   	struct resource_context *old_ctx = &stream->ctx->dc->current_state->res_ctx;
>   	int head_index;
>   
> -	if (!head_pipe)
> +	if (!head_pipe) {
>   		ASSERT(0);
> +		return NULL;
> +	}
>   
>   	/*
>   	 * Modified from dcn20_acquire_idle_pipe_for_layer