linux-kernel - Re: [PATCH net-next v3 2/2] ipvs: allow some sysctls in non-init user namespaces

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Message-ID: <8e70d6d3-6852-7b84-81b3-5d1a798f224f@ssi.bg>
Date: Fri, 3 May 2024 16:06:24 +0300 (EEST)
From: Julian Anastasov <ja@....bg>
To: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
cc: horms@...ge.net.au, netdev@...r.kernel.org, lvs-devel@...r.kernel.org,
        netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stéphane Graber <stgraber@...raber.org>,
        Christian Brauner <brauner@...nel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>
Subject: Re: [PATCH net-next v3 2/2] ipvs: allow some sysctls in non-init
 user namespaces


	Hello,

On Thu, 18 Apr 2024, Alexander Mikhalitsyn wrote:

> Let's make all IPVS sysctls writtable even when
> network namespace is owned by non-initial user namespace.
> 
> Let's make a few sysctls to be read-only for non-privileged users:
> - sync_qlen_max
> - sync_sock_size
> - run_estimation
> - est_cpulist
> - est_nice
> 
> I'm trying to be conservative with this to prevent
> introducing any security issues in there. Maybe,
> we can allow more sysctls to be writable, but let's
> do this on-demand and when we see real use-case.
> 
> This patch is motivated by user request in the LXC
> project [1]. Having this can help with running some
> Kubernetes [2] or Docker Swarm [3] workloads inside the system
> containers.
> 
> Link: https://github.com/lxc/lxc/issues/4278 [1]
> Link: https://github.com/kubernetes/kubernetes/blob/b722d017a34b300a2284b890448e5a605f21d01e/pkg/proxy/ipvs/proxier.go#L103 [2]
> Link: https://github.com/moby/libnetwork/blob/3797618f9a38372e8107d8c06f6ae199e1133ae8/osl/namespace_linux.go#L682 [3]
> 
> Cc: Stéphane Graber <stgraber@...raber.org>
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: Julian Anastasov <ja@....bg>
> Cc: Simon Horman <horms@...ge.net.au>
> Cc: Pablo Neira Ayuso <pablo@...filter.org>
> Cc: Jozsef Kadlecsik <kadlec@...filter.org>
> Cc: Florian Westphal <fw@...len.de>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 32be24f0d4e4..c3ba71aa2654 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c

..

> @@ -4284,12 +4285,6 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
>  		tbl = kmemdup(vs_vars, sizeof(vs_vars), GFP_KERNEL);
>  		if (tbl == NULL)
>  			return -ENOMEM;
> -
> -		/* Don't export sysctls to unprivileged users */
> -		if (net->user_ns != &init_user_ns) {
> -			tbl[0].procname = NULL;
> -			ctl_table_size = 0;
> -		}
>  	} else
>  		tbl = vs_vars;
>  	/* Initialize sysctl defaults */

	Sorry but you have to send v4 because above if-block was
changed with net-next commit 635470eb0aa7 from today...

Regards

--
Julian Anastasov <ja@....bg>