linux-kernel - Re: riscv+KASAN does not boot

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Date:   Tue, 16 Feb 2021 18:35:36 +0100
From:   Tobias Klauser <tklauser@...tanz.ch>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Alex Ghiti <alex@...ti.fr>, Albert Ou <aou@...s.berkeley.edu>,
        Bjorn Topel <bjorn.topel@...il.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, nylon7@...estech.com,
        syzkaller <syzkaller@...glegroups.com>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: riscv+KASAN does not boot

On 2021-02-16 at 12:17:30 +0100, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Fri, Jan 29, 2021 at 9:11 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> > > I was fixing KASAN support for my sv48 patchset so I took a look at your
> > > issue: I built a kernel on top of the branch riscv/fixes using
> > > https://github.com/google/syzkaller/blob/269d24e857a757d09a898086a2fa6fa5d827c3e1/dashboard/config/linux/upstream-riscv64-kasan.config
> > > and Buildroot 2020.11. I have the warnings regarding the use of
> > > __virt_to_phys on wrong addresses (but that's normal since this function
> > > is used in virt_addr_valid) but not the segfaults you describe.
> >
> > Hi Alex,
> >
> > Let me try to rebuild buildroot image. Maybe there was something wrong
> > with my build, though, I did 'make clean' before doing. But at the
> > same time it worked back in June...
> >
> > Re WARNINGs, they indicate kernel bugs. I am working on setting up a
> > syzbot instance on riscv. If there a WARNING during boot then the
> > kernel will be marked as broken. No further testing will happen.
> > Is it a mis-use of WARN_ON? If so, could anybody please remove it or
> > replace it with pr_err.
> 
> 
> Hi,
> 
> I've localized one issue with riscv/KASAN:
> KASAN breaks VDSO and that's I think the root cause of weird faults I
> saw earlier. The following patch fixes it.
> Could somebody please upstream this fix? I don't know how to add/run
> tests for this.

Thanks. I've tested the fix locally using vDSO selftests and sent the
fix upstream [1]

[1] https://lore.kernel.org/linux-riscv/20210216173305.2500-1-tklauser@distanz.ch/T/#u