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From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu, 8 Dec 2016 16:32:10 -0800
Message-ID: <CAM_iQpXxF_N+3VYRqjd4jySBbySPsZAAVVkNCBEXqc8gHJ6ZMQ@mail.gmail.com>
Subject: Re: net: deadlock on genl_mutex
To: Dmitry Vyukov <dvyukov@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>,
        Eric Dumazet <edumazet@google.com>, David Miller <davem@davemloft.net>,
        Matti Vaittinen <matti.vaittinen@nokia.com>,
        Tycho Andersen <tycho.andersen@canonical.com>,
        Florian Westphal <fw@strlen.de>,
        stephen hemminger <stephen@networkplumber.org>,
        Tom Herbert <tom@herbertland.com>, netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Richard Guy Briggs <rgb@redhat.com>, netdev-owner@vger.kernel.org
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On Thu, Dec 8, 2016 at 9:16 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> Chain exists of:
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(genl_mutex);
>                                lock(nlk->cb_mutex);
>                                lock(genl_mutex);
>   lock(rtnl_mutex);
>
>  *** DEADLOCK ***

This one looks legitimate, because nlk->cb_mutex could be rtnl_mutex.
Let me think about it.