From d386930fa2d12d874c7631ab0786dfde00df1606 Mon Sep 17 00:00:00 2001
From: Adam Gashlin <agashlin@gmail.com>
Date: Sun, 23 Jan 2022 18:14:10 -0800
Subject: [PATCH] Avoid length overflow when fetch starts beyond ROM

---
 pi/controller.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pi/controller.c b/pi/controller.c
index 5ef279c..1ce9662 100644
--- a/pi/controller.c
+++ b/pi/controller.c
@@ -90,7 +90,9 @@ static int pi_dma_read(struct pi_controller *pi) {
 
 static void pi_rom_fetch(struct pi_controller *pi, uint32_t source, int32_t length, uint8_t *dest) {
   int l = length;
-  if (source + length > pi->rom_size)
+  if (source >= pi->rom_size)
+    l = 0;
+  else if (source + length > pi->rom_size)
     l = pi->rom_size - source;
   memcpy(dest, pi->rom + source, l);