Allow the custom mutator to generate larger trimmed data
MODIFY
src/afl-fuzz-mutators.c
src/afl-fuzz-mutators.c
@@ -282,10 +282,24 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf,
} else if (unlikely(retlen > orig_len)) {
- FATAL(
+ /* Do not exit the fuzzer, even if the trimmed data returned by the custom
+ mutator is larger than the original data. For some use cases, like the
+ grammar mutator, the definition of "size" may have different meanings.
+ For example, the trimming function in a grammar mutator aims at
+ reducing the objects in a grammar structure, but does not guarantee to
+ generate a smaller binary buffer.
+
+ Thus, we allow the custom mutator to generate the trimmed data that is
+ larger than the original data. */
+
+ if (afl->not_on_tty && afl->debug) {
+
+ WARNF(
"Trimmed data returned by custom mutator is larger than original "
"data");
+ }
+
} else if (unlikely(retlen == 0)) {
/* Do not run the empty test case on the target. To keep the custom

Allow the custom mutator to generate larger trimmed data (#463)