UBSAN: object-size-mismatch in wg_xmit

[Nathan Chancellor]

On Fri, Jan 08, 2021 at 10:33:19AM +0100, Dmitry Vyukov wrote:
> On Thu, Jan 7, 2021 at 8:06 PM Jeffrey Walton <noloader at gmail.com> wrote:
> >
> > On Thu, Jan 7, 2021 at 2:03 PM Jason A. Donenfeld <Jason at zx2c4.com> wrote:
> > >
> > > On Thu, Jan 7, 2021 at 1:22 PM Dmitry Vyukov <dvyukov at google.com> wrote:
> > > >
> > > > On Mon, Dec 21, 2020 at 12:23 PM Jason A. Donenfeld <Jason at zx2c4.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
> 
> Hi Jeff,
> 
> Are these patches upstream now?
> syzbot doesn't enable LTO intentionally, nor I see CONFIG_LTO in the
> provided config.

Those patches are not upstream yet and LTO will have to be explicitly
enabled via config.

Cheers,
Nathan