netdev - Re: UBSAN: object-size-mismatch in wg

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Message-ID: <CAH8yC8na1pNcGPBrfuBwyNbfC4JjOOo_xHODAkbjs1j-1h0+2A@mail.gmail.com>
Date:   Thu, 7 Jan 2021 14:06:42 -0500
From:   Jeffrey Walton <noloader@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        WireGuard mailing list <wireguard@...ts.zx2c4.com>
Subject: Re: UBSAN: object-size-mismatch in wg_xmit

On Thu, Jan 7, 2021 at 2:03 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> On Thu, Jan 7, 2021 at 1:22 PM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> >
> > On Mon, Dec 21, 2020 at 12:23 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
> > >
> > > ...
> >
> > These UBSAN checks were just enabled recently.
> > It's indeed super easy to trigger: 133083 VMs were crashed on this already:
> > https://syzkaller.appspot.com/bug?extid=8f90d005ab2d22342b6d
> > So it's one of the top crashers by now.
>
> Ahh, makes sense. So it is easily reproducible after all.
>
> You're still of the opinion that it's a false positive, right? I
> shouldn't spend more cycles on this?

You might consider making a test build with -fno-lto in case LTO is
mucking things up.

Google Posts Patches So The Linux Kernel Can Be LTO-Optimized By
Clang, https://www.phoronix.com/scan.php?page=news_item&px=Linux-Kernel-Clang-LTO-Patches

Jeff