Subject: Re: kernel panic: stack is corrupted in udp4_lib_lookup2

From: Stefano Brivio <[email-masked]>
Date: Thu, 3 Jan 2019 21:07:43 +0100

On Thu, 3 Jan 2019 12:01:29 -0800
Eric Dumazet <[email-masked]> 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: [email-masked]
> > 
> > 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 [email-masked].
> > 
> > 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 <[email-masked]>
> 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.

-- 
Stefano