On Thu, Sep 21, 2023 at 03:58:01PM -0500, Eric Blake wrote:
When fuzzing, it is more desirable to always provoke the server into sending a response, rather than sometimes accidentally skipping a wire call because a client-side strictness test failed.
[Our fuzzer could probably be made even more powerful by changing the fuzzer input file to be a series of records, where each record is the API to call and then the server's response; right now, the sequence of APIs called is hard-coded, which is not as powerful at testing potential cross-command coupling. But that's a project for another day.]
Intrigued by how this would work exactly. The current file is just a stream of bytes from the "server" (the output from libnbd is discarded). Would the input file be of the form: ( [ request + args ] [ stream of bytes from server ] )* where [ request + args ] would be a simple serialized representation of a synchronous nbd_* API call? I think that would work ... Rich.
Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Richard W.M. Jones <rjones@redhat.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> --- fuzzing/libnbd-fuzz-wrapper.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fuzzing/libnbd-fuzz-wrapper.c b/fuzzing/libnbd-fuzz-wrapper.c index cbd55380..fcd1d04c 100644 --- a/fuzzing/libnbd-fuzz-wrapper.c +++ b/fuzzing/libnbd-fuzz-wrapper.c @@ -193,8 +193,11 @@ client (int sock) }
/* Note we ignore errors in these calls because we are only - * interested in whether the process crashes. + * interested in whether the process crashes. Likewise, we don't + * want to accidentally avoid sending traffic to the server merely + * because client side strictness sees a problem. */ + nbd_set_strict_mode (nbd, 0);
/* Enable a metadata context, for block status below. */ nbd_add_meta_context (nbd, LIBNBD_CONTEXT_BASE_ALLOCATION); -- 2.41.0
-- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top