[PATCH] fuzz: avoid double-fetches by default

[PATCH] fuzz: avoid double-fetches by default

[Alexander Bulekov]

The generic fuzzer can find double-fetch bugs. However:
* We currently have no good way of producing qemu-system reproducers for
  double-fetch bugs. Even if we can get developers to run the binary-blob
  reproducers with the qemu-fuzz builds, we currently don't have a minimizer for
  these reproducers, so they are usually not easy to follow.
* Often times the fuzzer will provide a reproducer containing a
  double-fetch for a bug that can be reproduced without double-fetching.

Until we find a way to build nice double-fetch reproducers that
developers are willing to look at, lets tell OSS-Fuzz to avoid
double-fetches.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
 tests/qtest/fuzz/generic_fuzz.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index 262a963d2e..07ad690683 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -916,6 +916,7 @@ static GString *generic_fuzz_predefined_config_cmdline(FuzzTarget *t)
     g_assert(t->opaque);
 
     config = t->opaque;
+    setenv("QEMU_AVOID_DOUBLE_FETCH", "1", 1);
     setenv("QEMU_FUZZ_ARGS", config->args, 1);
     setenv("QEMU_FUZZ_OBJECTS", config->objects, 1);
     return generic_fuzz_cmdline(t);
-- 
2.28.0

Re: [PATCH] fuzz: avoid double-fetches by default

[Darren Kenny]

On Wednesday, 2020-12-02 at 11:42:14 -05, Alexander Bulekov wrote:
> The generic fuzzer can find double-fetch bugs. However:
> * We currently have no good way of producing qemu-system reproducers for
>   double-fetch bugs. Even if we can get developers to run the binary-blob
>   reproducers with the qemu-fuzz builds, we currently don't have a minimizer for
>   these reproducers, so they are usually not easy to follow.
> * Often times the fuzzer will provide a reproducer containing a
>   double-fetch for a bug that can be reproduced without double-fetching.
>
> Until we find a way to build nice double-fetch reproducers that
> developers are willing to look at, lets tell OSS-Fuzz to avoid
> double-fetches.
>
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>

> ---
>  tests/qtest/fuzz/generic_fuzz.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
> index 262a963d2e..07ad690683 100644
> --- a/tests/qtest/fuzz/generic_fuzz.c
> +++ b/tests/qtest/fuzz/generic_fuzz.c
> @@ -916,6 +916,7 @@ static GString *generic_fuzz_predefined_config_cmdline(FuzzTarget *t)
>      g_assert(t->opaque);
>  
>      config = t->opaque;
> +    setenv("QEMU_AVOID_DOUBLE_FETCH", "1", 1);
>      setenv("QEMU_FUZZ_ARGS", config->args, 1);
>      setenv("QEMU_FUZZ_OBJECTS", config->objects, 1);
>      return generic_fuzz_cmdline(t);
> -- 
> 2.28.0