linux-kernel - Re: [syzbot] kernel panic: corrupted stack end in openat

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Date:   Tue, 16 Mar 2021 10:51:14 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     syzbot <syzbot+0b06ef9b44d00d600183@...kaller.appspotmail.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] kernel panic: corrupted stack end in openat

On Tue, Mar 16, 2021 at 10:24 AM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> On Tue, Mar 16, 2021 at 08:59:17AM +0100, Dmitry Vyukov wrote:
> > On Tue, Mar 16, 2021 at 8:18 AM syzbot
> > <syzbot+0b06ef9b44d00d600183@...kaller.appspotmail.com> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    1e28eed1 Linux 5.12-rc3
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=167535e6d00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e0cee1f53de33ca3
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=0b06ef9b44d00d600183
> > > userspace arch: arm
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+0b06ef9b44d00d600183@...kaller.appspotmail.com
> >
> > +arm32 maintainer
> > I think this is a real stack overflow on arm32, the stack is indeed deep.
>
> There's no way to know for sure because there's no indication of the
> stack pointer in this, so we don't know how much space remains.
> Therefore we don't know whether this is something in the dumped
> path, or an interrupt causing it.

Agree, to know for sure we would need support for VMAP_STACK.
But do we really need to know it? If it's an interrupt on top, it does
not make any difference?