linux-kernel - Re: BUG: KASAN: stack-out-of-bounds in unwind_next

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Date:   Wed, 3 Feb 2021 16:52:42 -0800
From:   Ivan Babrou <ivan@...udflare.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        kernel-team <kernel-team@...udflare.com>,
        Ignat Korchagin <ignat@...udflare.com>,
        Hailong liu <liu.hailong6@....com.cn>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Julien Thierry <jthierry@...hat.com>,
        Jiri Slaby <jirislaby@...nel.org>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel <linux-kernel@...r.kernel.org>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Robert Richter <rric@...nel.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        bpf@...r.kernel.org, Alexey Kardashevskiy <aik@...abs.ru>
Subject: Re: BUG: KASAN: stack-out-of-bounds in unwind_next_frame+0x1df5/0x2650

On Wed, Feb 3, 2021 at 4:17 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Wed, Feb 03, 2021 at 03:30:35PM -0800, Ivan Babrou wrote:
> > > > > Can you recreate with this patch, and add "unwind_debug" to the cmdline?
> > > > > It will spit out a bunch of stack data.
> > > >
> > > > Here's the three I'm building:
> > > >
> > > > * https://github.com/bobrik/linux/tree/ivan/static-call-5.9
> > > >
> > > > It contains:
> > > >
> > > > * v5.9 tag as the base
> > > > * static_call-2020-10-12 tag
> > > > * dm-crypt patches to reproduce the issue with KASAN
> > > > * x86/unwind: Add 'unwind_debug' cmdline option
> > > > * tracepoint: Fix race between tracing and removing tracepoint
> > > >
> > > > The very same issue can be reproduced on 5.10.11 with no patches,
> > > > but I'm going with 5.9, since it boils down to static call changes.
> > > >
> > > > Here's the decoded stack from the kernel with unwind debug enabled:
> > > >
> > > > * https://gist.github.com/bobrik/ed052ac0ae44c880f3170299ad4af56b
> > > >
> > > > See my first email for the exact commands that trigger this.
> > >
> > > Thanks.  Do you happen to have the original dmesg, before running it
> > > through the post-processing script?
> >
> > Yes, here it is:
> >
> > * https://gist.github.com/bobrik/8c13e6a02555fb21cadabb74cdd6f9ab
>
> It appears the unwinder is getting lost in crypto code.  No idea what
> this has to do with static calls though.  Or maybe you're seeing
> multiple issues.
>
> Does this fix it?

It does for the dm-crypt case! But so does the following commit in
5.11 (and 5.10.12):

* https://github.com/torvalds/linux/commit/ce8f86ee94?w=1

The reason I stuck to dm-crypt reproduction is that it reproduces reliably.

We also have the following stack that doesn't touch any crypto:

* https://gist.github.com/bobrik/40e2559add2f0b26ae39da30dc451f1e

I cannot reproduce this one, and it took 2 days of uptime for it to
happen. Is there anything I can do to help diagnose it?

My goal is to enable multishot KASAN in our pre-production
environment, but currently it sometimes starves TX queues on the NIC
due to multiple reports in a row in an interrupt about
unwind_next_frame, which disables network interface, which is not
something we can tolerate.