linux-kernel - Re: [next] arm: Internal error: Oops: 5 PC is at __read_once_word

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Message-ID: <CAMj1kXHTdk1Abm7ShoZzrW6EpM9eyFMPSdaa58Ziie4ZMecCnQ@mail.gmail.com>
Date:   Wed, 9 Mar 2022 11:46:33 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [next] arm: Internal error: Oops: 5 PC is at __read_once_word_nocheck

On Wed, 9 Mar 2022 at 11:37, Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Wed, Mar 09, 2022 at 03:18:12PM +0530, Naresh Kamboju wrote:
> > While boting linux next-20220308 on BeagleBoard-X15 and qemu arm the following
> > kernel crash reported which is CONFIG_KASAN enabled build [1] & [2].
>
> The unwinder is currently broken in linux-next. Please try reverting
> 532319b9c418 ("ARM: unwind: disregard unwind info before stack frame is
> set up")
>

Yeah.

This is the same spot Corentin hit before, where the double
dereference of vsp is not guarded by anything like
get_kernel_nofault(). We should probably fix that, but that doesn't
address the underlying issue, of course.

I'm a bit puzzled, though, that this appears now, and didn't before.

Naresh, I take it you did not see this occurring on earlier linux-nexts?

I'll try to reproduce this, and see if I can make sense of it. In the
mean time, please do the revert Russell suggested, and if that doesn't
help, maybe try a bisect?