From: Shakeel Butt <shakeelb@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Florian Westphal <fw@strlen.de>,
Pablo Neira Ayuso <pablo@netfilter.org>,
Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
Roopa Prabhu <roopa@cumulusnetworks.com>,
Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
bridge@lists.linux-foundation.org,
LKML <linux-kernel@vger.kernel.org>,
syzbot+7713f3aa67be76b1552c@syzkaller.appspotmail.com
Subject: Re: [PATCH] netfilter: account ebt_table_info to kmemcg
Date: Sat, 29 Dec 2018 11:34:29 -0800 [thread overview]
Message-ID: <CALvZod7v-CC1XipLAerFj1Zp_M=qXZq6MzDL4pubJMTRCsMFNw@mail.gmail.com> (raw)
In-Reply-To: <20181229100615.GB16738@dhcp22.suse.cz>
On Sat, Dec 29, 2018 at 2:06 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Sat 29-12-18 10:52:15, Florian Westphal wrote:
> > Michal Hocko <mhocko@kernel.org> wrote:
> > > On Fri 28-12-18 17:55:24, Shakeel Butt wrote:
> > > > The [ip,ip6,arp]_tables use x_tables_info internally and the underlying
> > > > memory is already accounted to kmemcg. Do the same for ebtables. The
> > > > syzbot, by using setsockopt(EBT_SO_SET_ENTRIES), was able to OOM the
> > > > whole system from a restricted memcg, a potential DoS.
> > >
> > > What is the lifetime of these objects? Are they bound to any process?
> >
> > No, they are not.
> > They are free'd only when userspace requests it or the netns is
> > destroyed.
>
> Then this is problematic, because the oom killer is not able to
> guarantee the hard limit and so the excessive memory consumption cannot
> be really contained. As a result the memcg will be basically useless
> until somebody tears down the charged objects by other means. The memcg
> oom killer will surely kill all the existing tasks in the cgroup and
> this could somehow reduce the problem. Maybe this is sufficient for
> some usecases but that should be properly analyzed and described in the
> changelog.
>
Can you explain why you think the memcg hard limit will not be
enforced? From what I understand, the memcg oom-killer will kill the
allocating processes as you have mentioned. We do force charging for
very limited conditions but here the memcg oom-killer will take care
of
Anyways, the kernel is already charging the memory for
[ip,ip6,arp]_tables and this patch adds the charging for ebtables.
Without this patch, as Kirill has described and shown by syzbot, a low
priority memcg can force system OOM.
Shakeel
next prev parent reply other threads:[~2018-12-29 19:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-29 1:55 [PATCH] netfilter: account ebt_table_info to kmemcg Shakeel Butt
2018-12-29 7:33 ` Michal Hocko
2018-12-29 9:52 ` Florian Westphal
2018-12-29 10:06 ` Michal Hocko
2018-12-29 19:34 ` Shakeel Butt [this message]
2018-12-30 7:45 ` Michal Hocko
2018-12-30 8:00 ` Michal Hocko
2018-12-31 3:59 ` Shakeel Butt
2018-12-31 10:11 ` Michal Hocko
2019-01-03 20:52 ` Shakeel Butt
2019-01-04 13:21 ` Michal Hocko
2018-12-31 4:00 ` Shakeel Butt
2018-12-29 9:52 ` Kirill Tkhai
2018-12-29 19:39 ` Shakeel Butt
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