linux-kernel - Re: [PATCH v2 0/3] kcov: collect coverage from usb and vhost

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Date:   Thu, 24 Oct 2019 14:47:31 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     USB list <linux-usb@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Windsor <dwindsor@...il.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>
Subject: Re: [PATCH v2 0/3] kcov: collect coverage from usb and vhost

On Thu, Oct 24, 2019 at 12:04 AM Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Wed, 23 Oct 2019 17:24:28 +0200 Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> > This patchset extends kcov to allow collecting coverage from the USB
> > subsystem and vhost workers. See the first patch description for details
> > about the kcov extension. The other two patches apply this kcov extension
> > to USB and vhost.
> >
> > These patches have been used to enable coverage-guided USB fuzzing with
> > syzkaller for the last few years
>
> I find it surprising that this material is so focused on USB.  Is
> there something unique about USB that gave rise to this situation, or

USB fuzzing is the thing that I've been working on that requires this
functionality. But the idea is to make the interface generic enough to
make it useful for other subsystems as well as long as the annotations
are added.

> is it expected that the new kcov feature will be used elsewhere in the
> kernel?
>
> If the latter, which are the expected subsystems?

Currently we encountered two cases where this is useful: USB and vhost
workers. Most probably there are more subsystems that will benefit
from this kcov extension to get better fuzzing coverage. I don't have
a list of them, but the provided interface should be easy to use when
more of such cases are encountered.