Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <00000000000069802205bda22b7f@google.com> <CACT4Y+Yaq-zDh5FAzHt4g-5jXrXC3rSLw6CM=kjcfR6oxJ1+CA@mail.gmail.com>
 <20210316092420.GN1463@shell.armlinux.org.uk>
In-Reply-To: <20210316092420.GN1463@shell.armlinux.org.uk>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 16 Mar 2021 10:51:14 +0100
Message-ID: <CACT4Y+ZhQCU6g28jD5gVxu=2h-Zd+uE6Ski2-sYmd_HrjLioyg@mail.gmail.com>
Subject: Re: [syzbot] kernel panic: corrupted stack end in openat
To:     Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc:     syzbot <syzbot+0b06ef9b44d00d600183@syzkaller.appspotmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Linus Walleij <linus.walleij@linaro.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, Mar 16, 2021 at 10:24 AM Russell King - ARM Linux admin
<linux@armlinux.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@syzkaller.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@syzkaller.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?