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From:   Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date:   Thu, 3 Jan 2019 15:15:06 -0600
Message-ID: <CA+FuTScFwA3F44MvbaWrOYJ2EYgdKAmoMzEGjOLcz3ZPVQLLDA@mail.gmail.com>
Subject: Re: kernel panic: stack is corrupted in udp4_lib_lookup2
To:     Stefano Brivio <sbrivio@redhat.com>
Cc:     Eric Dumazet <eric.dumazet@gmail.com>,
        syzbot <syzbot+4ad25edc7a33e4ab91e0@syzkaller.appspotmail.com>,
        David Miller <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        syzkaller-bugs@googlegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
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On Thu, Jan 3, 2019 at 2:07 PM Stefano Brivio <sbrivio@redhat.com> wrote:
>
> On Thu, 3 Jan 2019 12:01:29 -0800
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> > On 01/03/2019 05:07 AM, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit:    195303136f19 Merge tag 'kconfig-v4.21-2' of git://git.kern..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=12245d8f400000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=5e7dc790609552d7
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=4ad25edc7a33e4ab91e0
> > > compiler:       gcc (GCC) 8.0.1 20180413 (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+4ad25edc7a33e4ab91e0@syzkaller.appspotmail.com
> > >
> > > protocol 88fb is buggy, dev hsr_slave_1
> > > protocol 88fb is buggy, dev hsr_slave_0
> > > protocol 88fb is buggy, dev hsr_slave_1
> > > FAT-fs (loop0): invalid media value (0x00)
> > > FAT-fs (loop0): Can't find a valid FAT filesystem
> > > Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: udp4_lib_lookup2+0x7ea/0x7f0 net/ipv4/udp.c:455
> > > CPU: 1 PID: 17960 Comm: syz-executor2 Not tainted 4.20.0+ #176
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > Call Trace:
> > > Kernel Offset: disabled
> > > Rebooting in 86400 seconds..
> > >
> > >
> > > ---
> > > This bug is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@googlegroups.com.
> > >
> > > syzbot will keep track of this bug report. See:
> > > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.
> >
> > Maybe commit 11789039da536fea96c98a40c2b441decf2e7323
> > Author: Stefano Brivio <sbrivio@redhat.com>
> > Date:   Tue Dec 18 00:13:17 2018 +0100
> >
> >     fou: Prevent unbounded recursion in GUE error handler
> >
> > Forgot to deal with IPv6 ?
>
> Damn, yes. :( Thanks both for pointing that out, patch coming.
>
> Still, I can't be sure this is the same issue.

syzbot generated stack traces with

[  183.517380]  udpv6_err+0x46/0x60
[  183.520739]  ? __udp6_lib_err+0x1890/0x1890
[  183.525054]  gue6_err_proto_handler+0x199/0x280

so it is quite likely