netdev - Re: WARNING: refcount bug in l2cap_chan

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Date:   Tue, 25 Feb 2020 07:29:20 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        syzbot <syzbot+198362c76088d1515529@...kaller.appspotmail.com>,
        "David S. Miller" <davem@...emloft.net>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING: refcount bug in l2cap_chan_put

Hi Luiz,

>> (Resent in plain text; sorry for double send)
>> 
>> I took a brief look at this error and uncovered that 6lowpan uses zero
>> locks when using l2cap (should be using the channel lock).
>> 
>> It seems like it would be better just to convert its direct use of
>> l2cap channel into using an l2cap socket.
> 
> I recall having some thought on that, I think having a socket like
> RFCOMM does would be better but I don't remember why I haven't
> follow-up on that, well we wanted to discontinue the bt specific
> 6lowpan on the kernel side though.

because sockets have their own locking issues for Bluetooth. We actually want to get rid of the internal socket usage.

Regards

Marcel