Re: [PATCH passt 4/5] XXX build: Add extra syscalls needed by AFL instrumentation

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 17 Nov 2022 12:26:13 +0000
"Richard W.M. Jones" <rjones@redhat.com> wrote:

> This is a hack.  Ideally there'd be a way to build a "non-production"
> build of passt which would turn off all the encapsulation features.
> They are not relevant for fuzzing and simply add overhead.

I'm not sure how quantitatively relevant this is, but I was thinking
about cases where sandboxing or "security" features cause issues (not
necessarily security-relevant ones) that would be discovered by
fuzzing.

Partially fitting example:
  https://archives.passt.top/passt-dev/20221115012400.2240327-1-sbrivio@redhat.com/

there, perror() in glibc results in a dup() call, with seccomp
terminating the proceess, in a way that was totally unexpected to me.

Should fuzzing trigger a case like this one, without a seccomp filter
loaded, we won't notice.

Now, the guest affecting its own availability isn't security relevant,
and that's the worst that can happen, but still it would be something
to fix.

Considering this, I'm actually more inclined to polish your hack (into
an 'afl' Makefile target or similar).

-- 
Stefano