[PATCH AUTOSEL 6.2 13/13] drm/amd/display: fix shift-out-of-bounds in CalculateVMAndRowBytes

Sasha Levin
2023-03-14T12:45:52Z

From: Alex Hung <alex.hung@amd.com>

[ Upstream commit 031f196d1b1b6d5dfcb0533b431e3ab1750e6189 ]

[WHY]
When PTEBufferSizeInRequests is zero, UBSAN reports the following
warning because dml_log2 returns an unexpected negative value:

shift exponent 4294966273 is too large for 32-bit type 'int'

[HOW]

In the case PTEBufferSizeInRequests is zero, skip the dml_log2() and
assign the result directly.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c b/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
index 379729b028474..c3d75e56410cc 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn30/display_mode_vba_30.c
@@ -1802,7 +1802,10 @@ static unsigned int CalculateVMAndRowBytes(
}

if (SurfaceTiling == dm_sw_linear) {
- *dpte_row_height = dml_min(128, 1 << (unsigned int) dml_floor(dml_log2(PTEBufferSizeInRequests * *PixelPTEReqWidth / Pitch), 1));
+ if (PTEBufferSizeInRequests == 0)
+ *dpte_row_height = 1;
+ else
+ *dpte_row_height = dml_min(128, 1 << (unsigned int) dml_floor(dml_log2(PTEBufferSizeInRequests * *PixelPTEReqWidth / Pitch), 1));
*dpte_row_width_ub = (dml_ceil(((double) SwathWidth - 1) / *PixelPTEReqWidth, 1) + 1) * *PixelPTEReqWidth;
*PixelPTEBytesPerRow = *dpte_row_width_ub / *PixelPTEReqWidth * *PTERequestSize;
} else if (ScanDirection != dm_vert) {
--
2.39.2