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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@xxxxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Julian Anastasov <ja@xxxxxx>
> Cc: Simon Horman <horms@xxxxxxxxxxxx>
> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>
> Cc: Florian Westphal <fw@xxxxxxxxx>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
Looks good to me, thanks!
Acked-by: Julian Anastasov <ja@xxxxxx>
> ---
> 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
> @@ -4270,6 +4270,7 @@ static int __net_init
> ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
> struct ctl_table *tbl;
> int idx, ret;
> size_t ctl_table_size = ARRAY_SIZE(vs_vars);
> + bool unpriv = net->user_ns != &init_user_ns;
>
> atomic_set(&ipvs->dropentry, 0);
> spin_lock_init(&ipvs->dropentry_lock);
> @@ -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 */
> @@ -4315,10 +4310,17 @@ static int __net_init
> ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
> ipvs->sysctl_sync_ports = 1;
> tbl[idx++].data = &ipvs->sysctl_sync_ports;
> tbl[idx++].data = &ipvs->sysctl_sync_persist_mode;
> +
> ipvs->sysctl_sync_qlen_max = nr_free_buffer_pages() / 32;
> + if (unpriv)
> + tbl[idx].mode = 0444;
> tbl[idx++].data = &ipvs->sysctl_sync_qlen_max;
> +
> ipvs->sysctl_sync_sock_size = 0;
> + if (unpriv)
> + tbl[idx].mode = 0444;
> tbl[idx++].data = &ipvs->sysctl_sync_sock_size;
> +
> tbl[idx++].data = &ipvs->sysctl_cache_bypass;
> tbl[idx++].data = &ipvs->sysctl_expire_nodest_conn;
> tbl[idx++].data = &ipvs->sysctl_sloppy_tcp;
> @@ -4341,15 +4343,22 @@ static int __net_init
> ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
> tbl[idx++].data = &ipvs->sysctl_conn_reuse_mode;
> tbl[idx++].data = &ipvs->sysctl_schedule_icmp;
> tbl[idx++].data = &ipvs->sysctl_ignore_tunneled;
> +
> ipvs->sysctl_run_estimation = 1;
> + if (unpriv)
> + tbl[idx].mode = 0444;
> tbl[idx].extra2 = ipvs;
> tbl[idx++].data = &ipvs->sysctl_run_estimation;
>
> ipvs->est_cpulist_valid = 0;
> + if (unpriv)
> + tbl[idx].mode = 0444;
> tbl[idx].extra2 = ipvs;
> tbl[idx++].data = &ipvs->sysctl_est_cpulist;
>
> ipvs->sysctl_est_nice = IPVS_EST_NICE;
> + if (unpriv)
> + tbl[idx].mode = 0444;
> tbl[idx].extra2 = ipvs;
> tbl[idx++].data = &ipvs->sysctl_est_nice;
>
> --
> 2.34.1
>
>
Regards
--
Julian Anastasov <ja@xxxxxx>
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