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Message-ID: <20190103210015.56917c3b@redhat.com>
Date: Thu, 3 Jan 2019 21:00:15 +0100
From: Stefano Brivio <sbrivio@...hat.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: syzbot <syzbot+4ad25edc7a33e4ab91e0@...kaller.appspotmail.com>,
David Miller <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
linux-kernel <linux-kernel@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>,
syzkaller-bugs@...glegroups.com,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: kernel panic: stack is corrupted in udp4_lib_lookup2
Hi Willem,
On Thu, 3 Jan 2019 13:41:43 -0600
Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
> On Thu, Jan 3, 2019 at 1:39 PM Willem de Bruijn
> <willemdebruijn.kernel@...il.com> wrote:
> >
> > On Thu, Jan 3, 2019 at 7:07 AM syzbot
> > <syzbot+4ad25edc7a33e4ab91e0@...kaller.appspotmail.com> 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@...kaller.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:
> >
> > This sounds similar to the stack corruption fixed recently in commit
> > e7cc082455cb ("udp: Support for error handlers of tunnels ...").
> >
> > That fix is for ipv4 gue_err(). ipv6 gue6_err() probably needs the same.
>
> Correction. The fix is 11789039da ("fou: prevent unbounded recursion
> in GUE error handler")
Yes, I looked into this, the fix for that issue is on the tree tested by
syzbot, and I think this is unrelated, also because KASan should say
something before we hit that.
By the way, do you happen to know if I objects from kernels tested by
syzbot are stored anywhere? It would be helpful to know for sure what's
at udp4_lib_lookup2+0x7ea.
--
Stefano
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