From faf4d8e07f5b67bece91723ad3e8b3f88a3dbf23 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Sun, 9 Oct 2022 23:05:12 -0700 Subject: [PATCH] drm/amd/display: fix array-bounds error in dc_stream_remove_writeback() [take 2] Commit 5d8c3e836fc2 ("drm/amd/display: fix array-bounds error in dc_stream_remove_writeback()") tried to fix an array bounds error seen with gcc 12.0. Unfortunately, that results in another array bounds error, seen with older versions of gcc. Building csky:allmodconfig ... failed -------------- Error log: 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:527:83: error: array subscript 1 is above 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]; We could check both i and j for overflow to fix the problem. That would, however, be not make much sense since it is known and provable that j <= i. Also, the check introduced with commit 5d8c3e836fc2 does not really add value since it checks if j < MAX_DWB_PIPES. Since it is known that j <= i, it would make more sense to check if i < MAX_DWB_PIPES. Unfortunately, that does not help to solve the problem observed here: gcc still complains. To solve the problem, replace the subsequent check for 'i != j' with 'j < i'. This is identical to the original check since we know that j <= i, and it makes all versions of gcc happy. Drop the check introduced with commit 5d8c3e836fc2 since it is not really useful and does not solve the problem. Cc: Aurabindo Pillai Cc: Hamza Mahfooz Fixes: 5d8c3e836fc2 ("drm/amd/display: fix array-bounds error in dc_stream_remove_writeback()") Signed-off-by: Guenter Roeck Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/display/dc/core/dc_stream.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) 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 9998f58c14b9..38d71b5c1f2d 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c @@ -524,9 +524,9 @@ 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 && j < MAX_DWB_PIPES; i++) { + for (i = 0, j = 0; i < stream->num_wb_info; i++) { if (stream->writeback_info[i].wb_enabled) { - if (i != j) + if (j < i) /* trim the array */ stream->writeback_info[j] = stream->writeback_info[i]; j++; -- 2.34.1