[PATCH] video: fbdev: kyro: Validate overlay viewport coordinates
From: Danila Chernetsov <hidden>
Date: 2026-07-24 00:44:39
Also in:
dri-devel, lkml
Subsystem:
framebuffer layer, the rest · Maintainers:
Helge Deller, Linus Torvalds
The overlay viewport end coordinates are computed from the viewport
origin and dimensions using 32-bit unsigned arithmetic. Large input
values can cause these calculations to wrap around before the resulting
coordinates are passed to SetOverlayViewPort().
SetOverlayViewPort() packs the viewport coordinates into 16-bit
register fields. The X coordinates are additionally adjusted by +2
and +1 before being written. Validate the coordinate calculations
for 32-bit wraparound and ensure that the adjusted coordinates fit
within their 16-bit register fields before calling
SetOverlayViewPort().
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Danila Chernetsov <redacted>
---
drivers/video/fbdev/kyro/fbdev.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/kyro/fbdev.c b/drivers/video/fbdev/kyro/fbdev.c
index d756b3603fa6..133c91716c49 100644
--- a/drivers/video/fbdev/kyro/fbdev.c
+++ b/drivers/video/fbdev/kyro/fbdev.c@@ -369,6 +369,9 @@ static int kyro_dev_overlay_create(u32 ulWidth, static int kyro_dev_overlay_viewport_set(u32 x, u32 y, u32 ulWidth, u32 ulHeight) { + u32 right; + u32 bottom; + if (deviceInfo.ulOverlayOffset == 0) /* probably haven't called CreateOverlay yet */ return -EINVAL;
@@ -378,11 +381,30 @@ static int kyro_dev_overlay_viewport_set(u32 x, u32 y, u32 ulWidth, u32 ulHeight (x < 2 && ulWidth + 2 == 0)) return -EINVAL; + /* + * SetOverlayViewPort() adjusts X coordinates by +2 (left) and +1 + * (right) before packing them into 16-bit register fields. + */ + if (x > U16_MAX - 2 || y > U16_MAX) + return -EINVAL; + + right = x + ulWidth; + bottom = y + ulHeight; + + if (right < x || bottom < y) + return -EINVAL; + + right--; + bottom--; + + if (right > U16_MAX - 1 || bottom > U16_MAX) + return -EINVAL; + /* Stop Ramdac Output */ DisableRamdacOutput(deviceInfo.pSTGReg); SetOverlayViewPort(deviceInfo.pSTGReg, - x, y, x + ulWidth - 1, y + ulHeight - 1); + x, y, right, bottom); EnableOverlayPlane(deviceInfo.pSTGReg); /* Start Ramdac Output */
--
2.25.1