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

[Pillai, Aurabindo]

[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

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