Re: [PATCH] drm/amd/display: fix array-bounds errors in dc_stream_remove_writeback()

[Hamza Mahfooz]

On 12/25/22 10:10, wenyang.linux@xxxxxxxxxxx wrote:
> From: Wen Yang <wenyang.linux@xxxxxxxxxxx>
>
> The following errors occurred when using gcc 7.5.0-3ubuntu1~18.04:
> drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c: In function ‘dc_stream_remove_writeback’:
> drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:543:55: warning: array subscript is above array bounds [-Warray-bounds]
>       stream->writeback_info[j] = stream->writeback_info[i];
>                                   ~~~~~~~~~~~~~~~~~~~~~~^~~
> Add a check to make sure that num_wb_info won't overflowing the writeback_info buffer.
>
> Fixes: 6fbefb84a98e ("drm/amd/display: Add DC core changes for DCN2")
>
> Signed-off-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
> Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
> Cc: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: Harry Wentland <harry.wentland@xxxxxxx>
> Cc: Leo Li <sunpeng.li@xxxxxxx>
> Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx

Applied, thanks!

> ---
>   drivers/gpu/drm/amd/display/dc/core/dc_stream.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
> index 20e534f73513..9825c30f2ca0 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
> @@ -481,6 +481,7 @@ bool dc_stream_add_writeback(struct dc *dc,
>   	}
>   
>   	if (!isDrc) {
> +		ASSERT(stream->num_wb_info + 1 <= MAX_DWB_PIPES);
>   		stream->writeback_info[stream->num_wb_info++] = *wb_info;
>   	}
>   
> @@ -526,6 +527,11 @@ bool dc_stream_remove_writeback(struct dc *dc,
>   		return false;
>   	}
>   
> +	if (stream->num_wb_info > MAX_DWB_PIPES) {
> +		dm_error("DC: num_wb_info is invalid!\n");
> +		return false;
> +	}
> +
>   //	stream->writeback_info[dwb_pipe_inst].wb_enabled = false;
>   	for (i = 0; i < stream->num_wb_info; i++) {
>   		/*dynamic update*/
> @@ -540,7 +546,8 @@ bool dc_stream_remove_writeback(struct dc *dc,
>   		if (stream->writeback_info[i].wb_enabled) {
>   			if (j < i)
>   				/* trim the array */
> -				stream->writeback_info[j] = stream->writeback_info[i];
> +				memcpy(&stream->writeback_info[j], &stream->writeback_info[i],
> +						sizeof(struct dc_writeback_info));
>   			j++;
>   		}
>   	}

--
Hamza