linux-kernel - [PATCH] drm/amd/display: fix array-bounds error in dc_stream_remove

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Date:   Tue, 27 Sep 2022 15:12:00 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     <linux-kernel@...r.kernel.org>
CC:     Hamza Mahfooz <hamza.mahfooz@....com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "Lee, Alvin" <Alvin.Lee2@....com>, Alex Hung <alex.hung@....com>,
        Pavle Kotarac <Pavle.Kotarac@....com>,
        Stylon Wang <stylon.wang@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        "Leo (Hanghong) Ma" <hanghong.ma@....com>,
        Hersen Wu <hersenwu@....com>,
        "Paul Hsieh" <paul.hsieh@....com>,
        Jimmy Kizito <Jimmy.Kizito@....com>,
        <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.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@....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