netdev - Re: net: possible deadlock in skb_queue

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Message-ID: <CAM_iQpX9gBPOqGo_hwhNmFrUE=R1CdfJvUfkJ+HSK67ybk9LEg@mail.gmail.com>
Date:   Mon, 20 Feb 2017 14:51:39 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Patrick McHardy <kaber@...sh.net>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: possible deadlock in skb_queue_tail

On Mon, Feb 20, 2017 at 5:29 AM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> other info that might help us debug this:
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&(&pcpu->lock)->rlock);
>                                lock(&(&list->lock)->rlock#3);
>                                lock(&(&pcpu->lock)->rlock);
>   lock(&(&list->lock)->rlock#3);
>

They are different types of sockets and different lists of skb's,
one is netlink socket the other is udp socket, so I don't think
we could have a deadlock in this scenario, we probably need to
explicitly mark them as different lockdep classes.