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-rw-r--r--src/afl-fuzz-mutators.c11
-rw-r--r--src/afl-fuzz-run.c2
2 files changed, 12 insertions, 1 deletions
diff --git a/src/afl-fuzz-mutators.c b/src/afl-fuzz-mutators.c
index 9fc77ffe..f6b36843 100644
--- a/src/afl-fuzz-mutators.c
+++ b/src/afl-fuzz-mutators.c
@@ -286,6 +286,15 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf,
           "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
+         trimming function running, we simply treat the empty test case as an
+         unsuccessful trimming and skip it, instead of aborting the trimming. */
+
+      ++afl->trim_execs;
+      goto unsuccessful_trimming;
+
     }
 
     write_to_testcase(afl, retbuf, retlen);
@@ -325,6 +334,8 @@ u8 trim_case_custom(afl_state_t *afl, struct queue_entry *q, u8 *in_buf,
 
     } else {
 
+unsuccessful_trimming:
+
       /* Tell the custom mutator that the trimming was unsuccessful */
       afl->stage_cur = mutator->afl_custom_post_trim(mutator->data, 0);
       if (unlikely(afl->stage_cur < 0)) {
diff --git a/src/afl-fuzz-run.c b/src/afl-fuzz-run.c
index f1da9c65..2a1664e2 100644
--- a/src/afl-fuzz-run.c
+++ b/src/afl-fuzz-run.c
@@ -109,7 +109,7 @@ void write_to_testcase(afl_state_t *afl, void *mem, u32 len) {
 
     });
 
-    if (unlikely(!new_buf && (new_size < 0))) {
+    if (unlikely(!new_buf && (new_size <= 0))) {
 
       FATAL("Custom_post_process failed (ret: %lu)", (long unsigned)new_size);