[PATCH] D60538: [libFuzzer] Skip too long inputs in the data flow scripts.

[Max Moroz via Phabricator via llvm-commits]

Dor1s created this revision.
Dor1s added a reviewer: kcc.
Herald added subscribers: Sanitizers, delcypher.
Herald added projects: LLVM, Sanitizers.

Otherwise, the scripts might be wasting too much time trying to
collect and process traces from the long inputs. For more context, see
https://github.com/google/oss-fuzz/issues/1632#issuecomment-481761789

I suspect that the problem might be in the `if ret and r[1] - r[0] >= 2`
condition. When the second part is false, we might want to break out of the
loop and skip the input at all, but am not 100% sure.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D60538

Files:
  lib/fuzzer/scripts/collect_data_flow.py


Index: lib/fuzzer/scripts/collect_data_flow.py
===================================================================
--- lib/fuzzer/scripts/collect_data_flow.py
+++ lib/fuzzer/scripts/collect_data_flow.py
@@ -63,13 +63,26 @@
     r = q.pop()
     print("******* Trying:  ", r)
     tmpfile = os.path.join(tmpdir, str(r[0]) + "-" + str(r[1]))
-    ret = subprocess.call([exe, str(r[0]), str(r[1]), inp, tmpfile])
+
+    proc = subprocess.Popen([exe, str(r[0]), str(r[1]), inp, tmpfile],
+                            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    output, err = proc.communicate()
+    if b'FATAL: DataFlowSanitizer: out of labels' in err:
+      print('The input is too long, skipping.')
+      break
+
+    ret = proc.returncode
     if ret and r[1] - r[0] >= 2:
       q.append([r[0], (r[1] + r[0]) / 2])
       q.append([(r[1] + r[0]) / 2, r[1]])
     else:
       outputs.append(tmpfile)
       print("******* Success: ", r)
+
+  if len(outputs) == 0:
+    print('No traces to merge. Exiting.')
+    sys.exit(1)
+
   f = sys.stdout
   if len(argv) >= 4:
     f = open(argv[3], "w")


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