From 7b5c7bc55e13e7f5ac7b1eaf5c6d690389ea5ee3 Mon Sep 17 00:00:00 2001 From: Danila Chernetsov Date: Fri, 24 Jul 2026 00:42:45 +0000 Subject: [PATCH] fbdev: kyro: Validate overlay viewport coordinates 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 Signed-off-by: Helge Deller --- 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..c23738988822 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 */