linux-kernel - [PATCH AUTOSEL 6.10 01/24] drm/mediatek: Set sensible cursor width/height values to fix crash

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Message-ID: <20240823140121.1974012-1-sashal@kernel.org>
Date: Fri, 23 Aug 2024 10:00:23 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Fei Shao <fshao@...omium.org>,
	Daniel Stone <daniels@...labora.com>,
	CK Hu <ck.hu@...iatek.com>,
	Chun-Kuang Hu <chunkuang.hu@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	p.zabel@...gutronix.de,
	airlied@...il.com,
	daniel@...ll.ch,
	matthias.bgg@...il.com,
	dri-devel@...ts.freedesktop.org,
	linux-mediatek@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.10 01/24] drm/mediatek: Set sensible cursor width/height values to fix crash

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

[ Upstream commit 042b8711a0beafb2c3b888bebe3c300ab4c817fa ]

Hardware-speaking, there is no feature-reduced cursor specific
plane, so this driver reserves the last all Overlay plane as a
Cursor plane, but sets the maximum cursor width/height to the
maximum value that the full overlay plane can use.

While this could be ok, it raises issues with common userspace
using libdrm (especially Mutter, but other compositors too) which
will crash upon performing allocations and/or using said cursor
plane.

Reduce the maximum width/height for the cursor to 512x512 pixels,
value taken from IGT's maximum cursor size test, which succeeds.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Reviewed-by: Fei Shao <fshao@...omium.org>
Tested-by: Fei Shao <fshao@...omium.org>
Reviewed-by: Daniel Stone <daniels@...labora.com>
Reviewed-by: CK Hu <ck.hu@...iatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240718082410.204459-1-angelogioacchino.delregno@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 56f409ad7f390..ab2bace792e46 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -539,8 +539,8 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	}
 
 	/* IGT will check if the cursor size is configured */
-	drm->mode_config.cursor_width = drm->mode_config.max_width;
-	drm->mode_config.cursor_height = drm->mode_config.max_height;
+	drm->mode_config.cursor_width = 512;
+	drm->mode_config.cursor_height = 512;
 
 	/* Use OVL device for all DMA memory allocations */
 	crtc = drm_crtc_from_index(drm, 0);
-- 
2.43.0