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

[Dmitry Vyukov]

On Tue, Mar 16, 2021 at 10:24 AM Russell King - ARM Linux admin
<linux@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > +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?