[libFuzzer] Unpoison parameters before calling user callback.

Summary:
Fixes an MSan false positive when compiling with
-fsanitize=memory,fuzzer.

See https://github.com/google/oss-fuzz/issues/2369 for more details.

Reviewers: kcc

Reviewed By: kcc

Subscribers: llvm-commits, metzman, eugenis

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61753

llvm-svn: 360390
diff --git a/compiler-rt/lib/fuzzer/FuzzerLoop.cpp b/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
index d1ad3e3..cb3d821 100644
--- a/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerLoop.cpp
@@ -542,6 +542,8 @@
   memcpy(DataCopy, Data, Size);
   if (EF->__msan_unpoison)
     EF->__msan_unpoison(DataCopy, Size);
+  if (EF->__msan_unpoison_param)
+    EF->__msan_unpoison_param(2);
   if (CurrentUnitData && CurrentUnitData != Data)
     memcpy(CurrentUnitData, Data, Size);
   CurrentUnitSize = Size;
@@ -702,7 +704,7 @@
       break;  // We will mutate this input more in the next rounds.
     }
     if (Options.ReduceDepth && !FoundUniqFeatures)
-        break;
+      break;
   }
 }