1 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2 // See https://llvm.org/LICENSE.txt for license information.
3 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4 
5 // Triggers the bug described here:
6 // https://github.com/google/oss-fuzz/issues/2369#issuecomment-490240627
7 //
8 // In a nutshell, MSan's parameter shadow does not get unpoisoned before calls
9 // to LLVMFuzzerTestOneInput.  This test case causes the parameter shadow to be
10 // poisoned by the call to foo(), which will trigger an MSan false positive on
11 // the Size == 0 check if the parameter shadow is still poisoned.
12 #include <cstdint>
13 #include <cstdio>
14 #include <cstdlib>
15 #include <cstring>
16 
17 volatile int zero = 0;
18 __attribute__((noinline)) int foo(int arg1, int arg2) { return zero; }
19 
20 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
21   if (Size == 0)
22     return 0;
23 
24   // Pass uninitialized values to foo().  Since foo doesn't do anything with
25   // them, MSan should not report an error here.
26   int a, b;
27   return foo(a, b);
28 }
29