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From 7e142cb2a848acb6af986fa91d254d4c23963b24 Mon Sep 17 00:00:00 2001
From: luporl <luporl@FreeBSD.org>
Date: Wed, 9 Dec 2020 11:11:15 -0300
Subject: [PATCH] xserver: fix RGB mask handling
On FreeBSD 13.0-CURRENT for PowerPC64 big-endian (BE), X was
crashing in some cases. For instance, when twm was started
and the background was clicked to open its menu, X crashed
with a segmentation fault, trying to dereference a null pointer
at CreatePicture().
There were 2 issues with xorg-server handling of RGB masks that
caused the pointer above to be null and thus the crash:
- wrong use of ffs() to get the RGB offsets from the masks
- overflow when shifting a 16-bit integer
This change fixes both issues. They happen when the system is BE
but has a video adapter using a little-endian (LE) ARGB32
framebuffer. In order to display the correct colors, this setup
requires a BE RGBA32 color format to be used by X, by setting
the RGB masks appropriately, that didn't work properly because of
the issues above.
---
hw/xfree86/common/xf86Helper.c | 6 +++---
render/picture.c | 12 ++++++------
2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/hw/xfree86/common/xf86Helper.c b/hw/xfree86/common/xf86Helper.c
index 31aa068e0e..16ab309e27 100644
--- a/hw/xfree86/common/xf86Helper.c
+++ b/hw/xfree86/common/xf86Helper.c
@@ -729,9 +729,9 @@ xf86SetWeight(ScrnInfoPtr scrp, rgb weight, rgb mask)
scrp->mask.red = mask.red;
scrp->mask.green = mask.green;
scrp->mask.blue = mask.blue;
- scrp->offset.red = ffs(mask.red);
- scrp->offset.green = ffs(mask.green);
- scrp->offset.blue = ffs(mask.blue);
+ scrp->offset.red = ffs(mask.red) - 1;
+ scrp->offset.green = ffs(mask.green) - 1;
+ scrp->offset.blue = ffs(mask.blue) - 1;
}
return TRUE;
}
diff --git a/render/picture.c b/render/picture.c
index 876316dc1c..afa0d258fa 100644
--- a/render/picture.c
+++ b/render/picture.c
@@ -523,12 +523,12 @@ PictureMatchVisual(ScreenPtr pScreen, int depth, VisualPtr pVisual)
return format;
}
else {
- if (format->direct.redMask << format->direct.red ==
- pVisual->redMask &&
- format->direct.greenMask << format->direct.green ==
- pVisual->greenMask &&
- format->direct.blueMask << format->direct.blue ==
- pVisual->blueMask) {
+ if ((unsigned long)format->direct.redMask <<
+ format->direct.red == pVisual->redMask &&
+ (unsigned long)format->direct.greenMask <<
+ format->direct.green == pVisual->greenMask &&
+ (unsigned long)format->direct.blueMask <<
+ format->direct.blue == pVisual->blueMask) {
return format;
}
}
--
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