From b595727f2fe42dcd2e85a733fd2f2c321920b0d2 Mon Sep 17 00:00:00 2001
From: Tobias Scharnowski <tobias.scharnowski@rub.de>
Date: Fri, 10 Jun 2022 18:38:37 +0200
Subject: [PATCH] Fix Byte Decrement Havoc Mutation

While looking at the source code of the havoc mutations I realized that there seems to be a typo / copy+paste error with the SUBBYTE_ mutation. It is currently incrementing, instead of decrementing the value.

Alternative Fix: Change the documentation to "/* Decrease byte by minus 1. */" to make it work as documented :-P
---
 src/afl-fuzz-one.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/afl-fuzz-one.c b/src/afl-fuzz-one.c
index 19f41ebe..ef80524f 100644
--- a/src/afl-fuzz-one.c
+++ b/src/afl-fuzz-one.c
@@ -2585,7 +2585,7 @@ havoc_stage:
           snprintf(afl->m_tmp, sizeof(afl->m_tmp), " SUBBYTE_");
           strcat(afl->mutation, afl->m_tmp);
 #endif
-          out_buf[rand_below(afl, temp_len)]++;
+          out_buf[rand_below(afl, temp_len)]--;
           break;
 
         }