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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Hamza Mahfooz <hamza.mahfooz@amd.com>,
        Aurabindo Pillai <aurabindo.pillai@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>, harry.wentland@amd.com,
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        paul.hsieh@amd.com, Jimmy.Kizito@amd.com,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: [PATCH AUTOSEL 5.4 14/14] drm/amd/display: fix array-bounds error in dc_stream_remove_writeback()
Date:   Sun,  9 Oct 2022 19:57:10 -0400
Message-Id: <20221009235710.1231937-14-sashal@kernel.org>
In-Reply-To: <20221009235710.1231937-1-sashal@kernel.org>
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From: Hamza Mahfooz <hamza.mahfooz@amd.com>

[ Upstream commit 5d8c3e836fc224dfe633e41f7f2856753b39a905 ]

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.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 bb09243758fe..95d36cb79e28 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
@@ -458,7 +458,7 @@ 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 */
-- 
2.35.1