From 04b927ab7f9322fd388d24f2aee9b92eb3c336e2 Mon Sep 17 00:00:00 2001
From: emufan4568 <geoster3d@gmail.com>
Date: Wed, 7 Sep 2022 23:44:36 +0300
Subject: [PATCH] morton_swizzle: Avoid buffer underflow

* Check the y coordinate before decrementing linear_buffer
---
 src/video_core/rasterizer_cache/morton_swizzle.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/video_core/rasterizer_cache/morton_swizzle.h b/src/video_core/rasterizer_cache/morton_swizzle.h
index 73c31b216..7e9200743 100644
--- a/src/video_core/rasterizer_cache/morton_swizzle.h
+++ b/src/video_core/rasterizer_cache/morton_swizzle.h
@@ -90,7 +90,11 @@ static void MortonCopy(u32 stride, u32 height, u8* linear_buffer, PAddr base, PA
         x = (x + 8) % stride;
         linear_buffer += 8 * aligned_bytes_per_pixel;
         if (!x) {
-            y += 8;
+            y  = (y + 8) % height;
+            if (!y) {
+                return;
+            }
+
             linear_buffer -= stride * 9 * aligned_bytes_per_pixel;
         }
     };