linux-kernel - Re: [PATCH v2] netfilter: account ebt_table

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Date:   Fri, 11 Jan 2019 00:57:46 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Florian Westphal <fw@...len.de>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        syzbot+7713f3aa67be76b1552c@...kaller.appspotmail.com,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v2] netfilter: account ebt_table_info to kmemcg

On Wed, Jan 02, 2019 at 07:14:31PM -0800, 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.
> 
> By accounting the ebt_table_info, the memory used for ebt_table_info can
> be contained within the memcg of the allocating process. However the
> lifetime of ebt_table_info is independent of the allocating process and
> is tied to the network namespace. So, the oom-killer will not be able to
> relieve the memory pressure due to ebt_table_info memory. The memory for
> ebt_table_info is allocated through vmalloc. Currently vmalloc does not
> handle the oom-killed allocating process correctly and one large
> allocation can bypass memcg limit enforcement. So, with this patch,
> at least the small allocations will be contained. For large allocations,
> we need to fix vmalloc.

OK, patch is applied, thanks.