linux-kernel - Re: [PATCH v1 0/3] kcov: collect coverage from usb soft interrupts

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Date:   Thu, 27 Feb 2020 16:44:42 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>
Subject: Re: [PATCH v1 0/3] kcov: collect coverage from usb soft interrupts

On Thu, Feb 27, 2020 at 2:41 AM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 26 Feb 2020 19:48:06 +0100 Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> > This patchset extends kcov to allow collecting coverage from soft
> > interrupts and then uses the new functionality to collect coverage from
> > USB code.
> >
> > This has allowed to find at least one new HID bug [1], which was recently
> > fixed by Alan [2].
>
> I might have asked this before, but I don't see this obvious question
> addressed in the changelogs so maybe I didn't...

You've asked this for the previous patchset about collecting coverage
from background threads :)

> Will this only ever be useful for USB?  Or is it anticipated that other
> subsystems will use this?  If the latter, which ones?

Any subsystem that uses softirqs (e.g. timers) can make use of this.
Looking at the recent syzbot reports, an obvious candidate is the
networking subsystem [1, 2, 3 and many more]. I'll add this info into
the cover letter in the next version.

Thanks!

[1] https://syzkaller.appspot.com/bug?extid=522ab502c69badc66ab7
[2] https://syzkaller.appspot.com/bug?extid=57f89d05946c53dbbb31
[3] https://syzkaller.appspot.com/bug?extid=df358e65d9c1b9d3f5f4