From 7777d325a3d049cc233c004cba288ed5d10539c2 Mon Sep 17 00:00:00 2001
From: Eric Anholt <anholt@freebsd.org>
Date: Tue, 30 Aug 2005 03:05:21 +0000
Subject: [PATCH] Apply an xserver patch from cworth: Avoid buffer ovverrun
 when a     trapezoid's right edge is on a pixel boundary.

---
 fb/fbedgeimp.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fb/fbedgeimp.h b/fb/fbedgeimp.h
index 136a15e36..877393516 100644
--- a/fb/fbedgeimp.h
+++ b/fb/fbedgeimp.h
@@ -108,7 +108,12 @@ rasterizeEdges (FbBits		*buf,
 			AddAlpha (N_X_FRAC(N_BITS));
 			StepAlpha;
 		    }
-		    AddAlpha (rxs);
+		    /* Do not add in a 0 alpha here. This check is necessary
+		     * to avoid a buffer overrun when rx is exactly on a pixel
+		     * boundary.
+		     */
+		    if (rxs != 0)
+			AddAlpha (rxs);
 		}
 	    }
 #endif