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	id 1u1jUG-0003Sy-Dd; Mon, 07 Apr 2025 12:13:52 +0200
Date: Mon, 7 Apr 2025 12:13:52 +0200
From: Florian Westphal <fw@strlen.de>
To: lvxiafei <xiafei_xupt@163.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Simon Horman <horms@kernel.org>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	lvxiafei <lvxiafei@sensetime.com>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org,
	coreteam@netfilter.org
Subject: Re: [PATCH] netfilter: netns nf_conntrack: per-netns
 net.netfilter.nf_conntrack_max sysctl
Message-ID: <20250407101352.GA10818@breakpoint.cc>
References: <20250407095052.49526-1-xiafei_xupt@163.com>
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User-Agent: Mutt/1.10.1 (2018-07-13)

lvxiafei <xiafei_xupt@163.com> wrote:
> The modification of nf_conntrack_max in one netns
> should not affect the value in another one.

nf_conntrack_max can only be changed in init_net.

Given the check isn't removed:
   /* Don't allow non-init_net ns to alter global sysctls */
   if (!net_eq(&init_net, net)) {
       table[NF_SYSCTL_CT_MAX].mode = 0444;

... this patch seems untested?

But, removing this check would allow any netns to consume
arbitrary amount of kernel memory.

How do you prevent this?