From 2b7b8c6ef5de6788619d2a365a03d79d7875d919 Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Thu, 12 Dec 2019 12:28:21 +0100
Subject: [PATCH] eth/tracers: handle invalid mem access better

---
 eth/tracers/tracer.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/eth/tracers/tracer.go b/eth/tracers/tracer.go
index 63d38ed32d..a90cdbe5c4 100644
--- a/eth/tracers/tracer.go
+++ b/eth/tracers/tracer.go
@@ -93,6 +93,13 @@ type memoryWrapper struct {
 
 // slice returns the requested range of memory as a byte slice.
 func (mw *memoryWrapper) slice(begin, end int64) []byte {
+	if end == begin {
+		return nil
+	}
+	if end < begin || begin < 0 {
+		log.Warn("Tracer accessed memory incorrectly", "offset", begin, "size", end-begin)
+		return nil
+	}
 	if mw.memory.Len() < int(end) {
 		// TODO(karalabe): We can't js-throw from Go inside duktape inside Go. The Go
 		// runtime goes belly up https://github.com/golang/go/issues/15639.