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

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Message-Id: <20230314124305.470657-13-sashal@kernel.org>
Date:   Tue, 14 Mar 2023 08:43:05 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alex Hung <alex.hung@....com>, Jun Lei <Jun.Lei@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, christian.koenig@....com,
        airlied@...ux.ie, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.2 13/13] drm/amd/display: fix shift-out-of-bounds in CalculateVMAndRowBytes

From: Alex Hung <alex.hung@....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@....com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@....com>
Signed-off-by: Alex Hung <alex.hung@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.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