diff options
| -rw-r--r-- | include/afl-fuzz.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/afl-fuzz.h b/include/afl-fuzz.h index 24e8ca9b..5c391049 100644 --- a/include/afl-fuzz.h +++ b/include/afl-fuzz.h @@ -1027,7 +1027,12 @@ static inline u32 rand_below(afl_state_t *afl, u32 limit) { } - return rand_next(afl) % limit; + /* Modulo is biased - we don't want our fuzzing to be biased so let's do it right. */ + u64 unbiased_rnd; + do { + unbiased_rnd = rand_next(afl); + } while (unbiased_rnd >= (UINT64_MAX - (UINT64_MAX % limit))); + return unbiased_rnd % limit; } |