netdev - Re: net: suspicious RCU usage in nf

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Message-ID: <1485877498.6360.115.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 31 Jan 2017 07:44:58 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Eric Dumazet <edumazet@...gle.com>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        netfilter-devel@...r.kernel.org,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: suspicious RCU usage in nf_hook

On Mon, 2017-01-30 at 22:19 -0800, Cong Wang wrote:

> 
> The context is process context (TX path before hitting qdisc), and
> BH is not disabled, so in_interrupt() doesn't catch it. Hmm, this
> makes me thinking maybe we really need to disable BH in this
> case for nf_hook()? But it is called in RX path too, and BH is
> already disabled there.

ipt_do_table() and similar netfilter entry points disable BH.

Maybe it is done too late.