linux-kernel - Re: [PATCH] netfilter/x_tables: do not fail xt_alloc_table

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Message-ID: <20180816164110.g2dedcm7nh75zjms@salvia>
Date:   Thu, 16 Aug 2018 18:41:10 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Florian Westphal <fw@...len.de>, Vlastimil Babka <vbabka@...e.cz>,
        Georgi Nikolov <gnikolov@...soft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] netfilter/x_tables: do not fail xt_alloc_table_info too
 easilly

On Tue, Aug 07, 2018 at 09:54:00PM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> eacd86ca3b03 ("net/netfilter/x_tables.c: use kvmalloc()
> in xt_alloc_table_info()") has unintentionally fortified
> xt_alloc_table_info allocation when __GFP_RETRY has been dropped from
> the vmalloc fallback. Later on there was a syzbot report that this
> can lead to OOM killer invocations when tables are too large and
> 0537250fdc6c ("netfilter: x_tables: make allocation less aggressive")
> has been merged to restore the original behavior. Georgi Nikolov however
> noticed that he is not able to install his iptables anymore so this can
> be seen as a regression.
> 
> The primary argument for 0537250fdc6c was that this allocation path
> shouldn't really trigger the OOM killer and kill innocent tasks. On the
> other hand the interface requires root and as such should allow what the
> admin asks for. Root inside a namespaces makes this more complicated
> because those might be not trusted in general. If they are not then such
> namespaces should be restricted anyway. Therefore drop the __GFP_NORETRY
> and replace it by __GFP_ACCOUNT to enfore memcg constrains on it.

Applied, thanks.