linux-kernel - Re: BUG: stack guard page was hit in unwind_next

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Date:   Mon, 4 May 2020 18:06:13 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     syzbot <syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        shile.zhang@...ux.alibaba.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org>
Subject: Re: BUG: stack guard page was hit in unwind_next_frame

On Mon, May 4, 2020 at 12:08 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Sat, May 02, 2020 at 11:36:11PM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    8999dc89 net/x25: Fix null-ptr-deref in x25_disconnect
> > git tree:       net
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16004440100000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=b7a70e992f2f9b68
> > dashboard link: https://syzkaller.appspot.com/bug?extid=e73ceacfd8560cc8a3ca
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com
>
> Infinite loop in network code.

It is not a loop, it is an unbound recursion where netdev events
trigger between bond master and slave back and forth.

Let me see how this can be fixed properly.

Thanks!