netdev - Re: [PATCH net-next v2] net: WireGuard secure network tunnel

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Date:   Thu, 19 Dec 2019 11:07:43 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH net-next v2] net: WireGuard secure network tunnel

On Thu, Dec 19, 2019 at 10:35 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> > Is this precise enough for race
> > condition bugs?
>
> It's finding lots of race conditions provoked bugs (I would say it's
> the most common cause of kernel bugs).

I meant -- are the reproducers it makes precise enough to retrigger
network-level race conditions?

> Well, you are missing that wireguard is not the only subsystem
> syzkaller tests (in fact, it does not test it at all) and there are
> 3000 other subsystems :)

Oooo! Everything is tested at the same time. I understand now; that
makes a lot more sense.

I'll look into splitting out the option, as you've asked. Note,
though, that there are currently only three spots that have the "extra
checks" at the moment, and one of them can be optimized out by the
compiler with aggressive enough inlining added everywhere. The other
two will result in an immediately corrupted stack frame that should be
caught immediately by other things. So for now, I think you can get
away with turning the debug option off, and you won't be missing much
from the "extra checks", at least until we add more.

That's exciting about syzcaller having at it with WireGuard. Is there
some place where I can "see" it fuzzing WireGuard, or do I just wait
for the bug reports to come rolling in?

Jason