From ebb9591c4d860e85fe1a015e6c9d7e85b7500b9a Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Fri, 20 Nov 2020 08:53:10 +0100
Subject: [PATCH] crypto/bn256: fix bn256Mul fuzzer to not hang on large input
 (#21872)

* crypto/bn256: fix bn256Mul fuzzer to not hang on large input

* Update crypto/bn256/bn256_fuzz.go

Co-authored-by: ligi <ligi@ligi.de>

Co-authored-by: ligi <ligi@ligi.de>
---
 crypto/bn256/bn256_fuzz.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/crypto/bn256/bn256_fuzz.go b/crypto/bn256/bn256_fuzz.go
index 585d509bf..b34043487 100644
--- a/crypto/bn256/bn256_fuzz.go
+++ b/crypto/bn256/bn256_fuzz.go
@@ -80,6 +80,12 @@ func FuzzMul(data []byte) int {
 	if remaining == 0 {
 		return 0
 	}
+	if remaining > 128 {
+		// The evm only ever uses 32 byte integers, we need to cap this otherwise
+		// we run into slow exec. A 236Kb byte integer cause oss-fuzz to report it as slow.
+		// 128 bytes should be fine though
+		return 0
+	}
 	buf := make([]byte, remaining)
 	input.Read(buf)