From 866cbdca4b907a1a8588ef4749e63d4d6761050b Mon Sep 17 00:00:00 2001
From: Albert Liu <45282415+ggrtk@users.noreply.github.com>
Date: Sat, 12 Dec 2020 00:02:24 -0800
Subject: [PATCH] GPU: Prevent potential overflow in CRTC visible area
 calculation

---
 src/core/gpu.cpp | 16 ++++++++++++++++
 src/core/gpu.h   |  1 +
 2 files changed, 17 insertions(+)

diff --git a/src/core/gpu.cpp b/src/core/gpu.cpp
index 0a1f3c99a..00f5e8e52 100644
--- a/src/core/gpu.cpp
+++ b/src/core/gpu.cpp
@@ -568,6 +568,14 @@ void GPU::UpdateCRTCDisplayParameters()
         cs.vertical_visible_end = vertical_display_end;
         break;
     }
+    cs.horizontal_visible_start =
+      std::clamp<u16>(cs.horizontal_visible_start, PAL_HORIZONTAL_ACTIVE_START, PAL_HORIZONTAL_ACTIVE_END);
+    cs.horizontal_visible_end =
+      std::clamp<u16>(cs.horizontal_visible_end, cs.horizontal_visible_start, PAL_HORIZONTAL_ACTIVE_END);
+    cs.vertical_visible_start =
+      std::clamp<u16>(cs.vertical_visible_start, PAL_VERTICAL_ACTIVE_START, PAL_VERTICAL_ACTIVE_END);
+    cs.vertical_visible_end =
+      std::clamp<u16>(cs.vertical_visible_end, cs.vertical_visible_start, PAL_VERTICAL_ACTIVE_END);
   }
   else
   {
@@ -597,6 +605,14 @@ void GPU::UpdateCRTCDisplayParameters()
         cs.vertical_visible_end = vertical_display_end;
         break;
     }
+    cs.horizontal_visible_start =
+      std::clamp<u16>(cs.horizontal_visible_start, NTSC_HORIZONTAL_ACTIVE_START, NTSC_HORIZONTAL_ACTIVE_END);
+    cs.horizontal_visible_end =
+      std::clamp<u16>(cs.horizontal_visible_end, cs.horizontal_visible_start, NTSC_HORIZONTAL_ACTIVE_END);
+    cs.vertical_visible_start =
+      std::clamp<u16>(cs.vertical_visible_start, NTSC_VERTICAL_ACTIVE_START, NTSC_VERTICAL_ACTIVE_END);
+    cs.vertical_visible_end =
+      std::clamp<u16>(cs.vertical_visible_end, cs.vertical_visible_start, NTSC_VERTICAL_ACTIVE_END);
   }
 
   // If force-progressive is enabled, we only double the height in 480i mode. This way non-interleaved 480i framebuffers
diff --git a/src/core/gpu.h b/src/core/gpu.h
index 1b6ba782b..47242a74f 100644
--- a/src/core/gpu.h
+++ b/src/core/gpu.h
@@ -497,6 +497,7 @@ protected:
     u16 display_vram_width;
     u16 display_vram_height;
 
+    // Visible range of the screen, in GPU ticks/lines. Clamped to lie within the active video region.
     u16 horizontal_visible_start;
     u16 horizontal_visible_end;
     u16 vertical_visible_start;