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Date:   Sun, 12 Apr 2020 10:32:01 +0200
From:   Florian Westphal <fw@strlen.de>
To:     syzbot <syzbot+ffec3741d41140477097@syzkaller.appspotmail.com>
Cc:     davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org,
        mathew.j.martineau@linux.intel.com, matthieu.baerts@tessares.net,
        mptcp@lists.01.org, netdev@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: WARNING: bad unlock balance in mptcp_listen
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syzbot <syzbot+ffec3741d41140477097@syzkaller.appspotmail.com> wrote:
> syzbot found the following crash on:
> 
> HEAD commit:    5b8b9d0c Merge branch 'akpm' (patches from Andrew)
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1712bdb3e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=23c5a352e32a1944
> dashboard link: https://syzkaller.appspot.com/bug?extid=ffec3741d41140477097
> 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+ffec3741d41140477097@syzkaller.appspotmail.com
> 
> =====================================
> WARNING: bad unlock balance detected!
> 5.6.0-syzkaller #0 Not tainted
> -------------------------------------
> syz-executor.0/25417 is trying to release lock (sk_lock-AF_INET6) at:
> [<ffffffff87c65063>] mptcp_listen+0x1c3/0x2e0 net/mptcp/protocol.c:1783
> but there are no more locks to release!

#syz dup: WARNING: bad unlock balance in mptcp_poll