[PATCH] D60008: Use binary write mode in WriteToFile function to avoid appended \r characters on Windows

[tuktuk via llvm-commits]

Hello,

I am happy to provide a simple example but I do not know the code base 
enough to turn it into a test.

With the following fuzz target:

// fuzz_target.cc
#include <cstdint>

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
   if (Data[0] == '\n') {
     __builtin_trap();
   }
   return 0;
}

The produced crash is not reproducible:

>"C:\Program Files\LLVM\bin\clang++.exe" -fsanitize=address,fuzzer 
fuzz_target.cc -o fuzzer.exe

>fuzzer.exe
SUMMARY: libFuzzer: deadly signal
Test unit written to ./crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc
Base64: Cg==

>fuzzer.exe crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc
Running: crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc
Executed crash-adc83b19e793491b1c6ea0fd8b46cd9f32e592fc in 2 ms
***
*** NOTE: fuzzing was not performed, you have only
***       executed the target code on a fixed set of inputs.
***

Indeed the contents of the produced file is "\r\n", not "\n".

The expected result is the one obtained with the following fuzz target:

// fuzz_target.cc
#include <cstdint>

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
   if (Data[0] == 'a') {
     __builtin_trap();
   }
   return 0;
}

The produced crash is reproducible as expected:

>"C:\Program Files\LLVM\bin\clang++.exe" -fsanitize=address,fuzzer 
fuzz_target.cc -o fuzzer.exe

>fuzzer.exe
SUMMARY: libFuzzer: deadly signal
Test unit written to ./crash-86f7e437faa5a7fce15d1ddcb9eaeaea377667b8
Base64: YQ==

 >fuzzer.exe crash-86f7e437faa5a7fce15d1ddcb9eaeaea377667b8
fuzzer: Running 1 inputs 1 time(s) each.
Running: crash-86f7e437faa5a7fce15d1ddcb9eaeaea377667b8
==12580== ERROR: libFuzzer: deadly signal

Le 29/03/2019 à 20:49, Vitaly Buka via Phabricator a écrit :
> vitalybuka added a comment.
> 
> Oh, can you add a test so it fail without the patch on Windows?
> 
> 
> Repository:
>    rCRT Compiler Runtime
> 
> CHANGES SINCE LAST ACTION
>    https://reviews.llvm.org/D60008/new/
> 
> https://reviews.llvm.org/D60008
> 
> 
>