netdev - Re: unregister_netdevice: waiting for DEV to become free (2)

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Date:   Wed, 16 Oct 2019 12:34:45 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        syzbot <syzbot+30209ea299c09d8785c9@...kaller.appspotmail.com>,
        ddstreet@...e.org, Dmitry Vyukov <dvyukov@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        bpf <bpf@...r.kernel.org>
Subject: Re: unregister_netdevice: waiting for DEV to become free (2)

Alexei Starovoitov <alexei.starovoitov@...il.com> writes:

> On Fri, Oct 11, 2019 at 3:15 AM Tetsuo Handa
> <penguin-kernel@...ove.sakura.ne.jp> wrote:
>>
>> Hello.
>>
>> I noticed that syzbot is reporting that refcount incremented by bpf(BPF_MAP_UPDATE_ELEM)
>> syscall is not decremented when unregister_netdevice() is called. Is this a BPF bug?
>
> Jesper, Toke,
> please take a look.

Yeah, that unregister notification handler definitely looks broken for
hashmaps; I'll send a patch :)

-Toke