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

[Felix Kuehling]

I'm still seeing a warning even with this fix:

/home/fkuehlin/compute/kernel/drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c: In function ?dc_stream_remove_writeback?:
/home/fkuehlin/compute/kernel/drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:527:55: warning: array subscript 1 is above array bounds of ?struct dc_writeback_info[1]? [-Warray-bounds]
   527 |     stream->writeback_info[j] = stream->writeback_info[i];
       |                                 ~~~~~~~~~~~~~~~~~~~~~~^~~

Regards,
   Felix


Am 2022-09-27 um 16:35 schrieb Pillai, Aurabindo:
>
> [AMD Official Use Only - General]
>
>
> [AMD Official Use Only - General]
>
>
> Reviewed-by: Aurabindo Pillai <aurabindo.pillai at amd.com>
>
> --
>
> Regards,
> Jay
> ------------------------------------------------------------------------
> *From:* Mahfooz, Hamza <Hamza.Mahfooz at amd.com>
> *Sent:* Tuesday, September 27, 2022 3:12 PM
> *To:* linux-kernel at vger.kernel.org <linux-kernel at vger.kernel.org>
> *Cc:* Mahfooz, Hamza <Hamza.Mahfooz at amd.com>; Wentland, Harry 
> <Harry.Wentland at amd.com>; Li, Sun peng (Leo) <Sunpeng.Li at amd.com>; 
> Siqueira, Rodrigo <Rodrigo.Siqueira at amd.com>; Deucher, Alexander 
> <Alexander.Deucher at amd.com>; Koenig, Christian 
> <Christian.Koenig at amd.com>; Pan, Xinhui <Xinhui.Pan at amd.com>; David 
> Airlie <airlied at linux.ie>; Daniel Vetter <daniel at ffwll.ch>; Lee, Alvin 
> <Alvin.Lee2 at amd.com>; Hung, Alex <Alex.Hung at amd.com>; Kotarac, Pavle 
> <Pavle.Kotarac at amd.com>; Wang, Chao-kai (Stylon) 
> <Stylon.Wang at amd.com>; Pillai, Aurabindo <Aurabindo.Pillai at amd.com>; 
> Ma, Leo <Hanghong.Ma at amd.com>; Wu, Hersen <hersenxs.wu at amd.com>; Po-Yu 
> Hsieh Paul <Paul.Hsieh at amd.com>; Jimmy Kizito <Jimmy.Kizito at amd.com>; 
> amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; 
> dri-devel at lists.freedesktop.org <dri-devel at lists.freedesktop.org>
> *Subject:* [PATCH] drm/amd/display: fix array-bounds error in 
> dc_stream_remove_writeback()
> Address the following error:
> 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:527:55: 
> error: array subscript [0, 0] is outside array bounds of ‘struct 
> dc_writeback_info[1]’ [-Werror=array-bounds]
>   527 | stream->writeback_info[j] = stream->writeback_info[i];
>       | ~~~~~~~~~~~~~~~~~~~~~~^~~
> In file included from 
> ./drivers/gpu/drm/amd/amdgpu/../display/dc/dc.h:1269,
>                  from 
> ./drivers/gpu/drm/amd/amdgpu/../display/dc/inc/core_types.h:29,
>                  from 
> ./drivers/gpu/drm/amd/amdgpu/../display/dc/basics/dc_common.h:29,
>                  from 
> drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_stream.c:27:
> ./drivers/gpu/drm/amd/amdgpu/../display/dc/dc_stream.h:241:34: note: 
> while referencing ‘writeback_info’
>   241 |         struct dc_writeback_info writeback_info[MAX_DWB_PIPES];
>       |
>
> Currently, we aren't checking to see if j remains within
> writeback_info[]'s bounds. So, add a check to make sure that we aren't
> overflowing the buffer.
>
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz at amd.com>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_stream.c | 2 +-
>  1 file changed, 1 insertion(+), 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 3ca1592ce7ac..ae13887756bf 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
> @@ -520,7 +520,7 @@ bool dc_stream_remove_writeback(struct dc *dc,
>          }
>
>          /* remove writeback info for disabled writeback pipes from 
> stream */
> -       for (i = 0, j = 0; i < stream->num_wb_info; i++) {
> +       for (i = 0, j = 0; i < stream->num_wb_info && j < 
> MAX_DWB_PIPES; i++) {
>                  if (stream->writeback_info[i].wb_enabled) {
>                          if (i != j)
>                                  /* trim the array */
> -- 
> 2.37.2
>