1 files changed, 2 insertions, 1 deletions
diff --git a/llvm/lib/Fuzzer/FuzzerLoop.cpp b/llvm/lib/Fuzzer/FuzzerLoop.cpp
index f09ac058a8d..afdc9fa8540 100644
--- a/llvm/lib/Fuzzer/FuzzerLoop.cpp
+++ b/llvm/lib/Fuzzer/FuzzerLoop.cpp
@@ -503,8 +503,9 @@ void Fuzzer::MutateAndTestOne() {
 
   auto &U = ChooseUnitToMutate();
   MutateInPlaceHere.resize(Options.MaxLen);
-  memcpy(MutateInPlaceHere.data(), U.data(), U.size());
   size_t Size = U.size();
+  assert(Size <= Options.MaxLen && "Oversized Unit");
+  memcpy(MutateInPlaceHere.data(), U.data(), Size);
 
   for (int i = 0; i < Options.MutateDepth; i++) {
     size_t NewSize = 0;