From c2ad0fc11fb5e4aed540c487324c7b37cc2237b7 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Thu, 14 Aug 2025 12:15:23 +1000
Subject: [PATCH] Fix out of bounds in mmap WriteTo

---
 storage/file-io-mmap.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/storage/file-io-mmap.go b/storage/file-io-mmap.go
index ed181f3c..422c1c0a 100644
--- a/storage/file-io-mmap.go
+++ b/storage/file-io-mmap.go
@@ -186,7 +186,11 @@ type mmapFileHandle struct {
 }
 
 func (me *mmapFileHandle) WriteTo(w io.Writer) (n int64, err error) {
-	n1, err := w.Write(me.shared.f.m[me.pos:])
+	b := me.shared.f.m
+	if me.pos >= int64(len(b)) {
+		return
+	}
+	n1, err := w.Write(b[me.pos:])
 	n = int64(n1)
 	me.pos += n
 	return
-- 
2.51.0