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

From: Hamza Mahfooz
Date: Wed Jan 04 2023 - 17:22:53 EST


On 12/25/22 10:10, wenyang.linux@xxxxxxxxxxx wrote:
From: Wen Yang <wenyang.linux@xxxxxxxxxxx>

The following errors occurred when using gcc 7.5.0-3ubuntu1~18.04:
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:543:55: warning: array subscript is above array bounds [-Warray-bounds]
     stream->writeback_info[j] = stream->writeback_info[i];
                                 ~~~~~~~~~~~~~~~~~~~~~~^~~
Add a check to make sure that num_wb_info won't overflowing the writeback_info buffer.

Fixes: 6fbefb84a98e ("drm/amd/display: Add DC core changes for DCN2")

Signed-off-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Cc: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Harry Wentland <harry.wentland@xxxxxxx>
Cc: Leo Li <sunpeng.li@xxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Applied, thanks!

---
drivers/gpu/drm/amd/display/dc/core/dc_stream.c | 9 ++++++++-
1 file changed, 8 insertions(+), 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 20e534f73513..9825c30f2ca0 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
@@ -481,6 +481,7 @@ bool dc_stream_add_writeback(struct dc *dc,
}
if (!isDrc) {
+ ASSERT(stream->num_wb_info + 1 <= MAX_DWB_PIPES);
stream->writeback_info[stream->num_wb_info++] = *wb_info;
}
@@ -526,6 +527,11 @@ bool dc_stream_remove_writeback(struct dc *dc,
return false;
}
+ if (stream->num_wb_info > MAX_DWB_PIPES) {
+ dm_error("DC: num_wb_info is invalid!\n");
+ return false;
+ }
+
// stream->writeback_info[dwb_pipe_inst].wb_enabled = false;
for (i = 0; i < stream->num_wb_info; i++) {
/*dynamic update*/
@@ -540,7 +546,8 @@ bool dc_stream_remove_writeback(struct dc *dc,
if (stream->writeback_info[i].wb_enabled) {
if (j < i)
/* trim the array */
- stream->writeback_info[j] = stream->writeback_info[i];
+ memcpy(&stream->writeback_info[j], &stream->writeback_info[i],
+ sizeof(struct dc_writeback_info));
j++;
}
}

--
Hamza