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

[Felix Kuehling]

Am 2022-09-29 um 11:41 schrieb Hamza Mahfooz:
>
>
> On 2022-09-29 11:36, Felix Kuehling wrote:
>> 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];
>>        | ~~~~~~~~~~~~~~~~~~~~~~^~~
>>
>
> What version of GCC are you using? I don't see it on GCC 12.2 with 
> this patch applied.

gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0

Regards,
   Felix


>
>> 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
>>>
>