[libFuzzer] make sure the input data is not overwritten in the fuzz target (if it is -- report an error)

llvm-svn: 302494

3 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Fuzzer/test/CMakeLists.txt b/llvm/lib/Fuzzer/test/CMakeLists.txt
index cd049d3f03d..b39938a705f 100644
--- a/llvm/lib/Fuzzer/test/CMakeLists.txt
+++ b/llvm/lib/Fuzzer/test/CMakeLists.txt
@@ -104,6 +104,7 @@ set(Tests
   OneHugeAllocTest
   OutOfMemoryTest
   OutOfMemorySingleLargeMallocTest
+  OverwriteInputTest
   RepeatedMemcmp
   RepeatedBytesTest
   SimpleCmpTest
diff --git a/llvm/lib/Fuzzer/test/OverwriteInputTest.cpp b/llvm/lib/Fuzzer/test/OverwriteInputTest.cpp
new file mode 100644
index 00000000000..e688682346a
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/OverwriteInputTest.cpp
@@ -0,0 +1,13 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// Simple test for a fuzzer. Make sure we abort if Data is overwritten.
+#include <cstdint>
+#include <iostream>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  if (Size)
+    *const_cast<uint8_t*>(Data) = 1;
+  return 0;
+}
+
diff --git a/llvm/lib/Fuzzer/test/overwrite-input.test b/llvm/lib/Fuzzer/test/overwrite-input.test
new file mode 100644
index 00000000000..81c27909e8d
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/overwrite-input.test
@@ -0,0 +1,2 @@
+RUN: not LLVMFuzzer-OverwriteInputTest 2>&1 | FileCheck %s
+CHECK: ERROR: libFuzzer: fuzz target overwrites it's const input