ipvs: allow some sysctls in non-init user namespaces
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:b722d017a3/pkg/proxy/ipvs/proxier.go (L103)
[2] Link:3797618f9a/osl/namespace_linux.go (L682)
[3] Cc: Julian Anastasov <ja@ssi.bg> Cc: Simon Horman <horms@verge.net.au> Cc: Pablo Neira Ayuso <pablo@netfilter.org> Cc: Jozsef Kadlecsik <kadlec@netfilter.org> Cc: Florian Westphal <fw@strlen.de> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com> Acked-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -4269,6 +4269,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
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struct ctl_table *tbl;
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int idx, ret;
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size_t ctl_table_size = ARRAY_SIZE(vs_vars);
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bool unpriv = net->user_ns != &init_user_ns;
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atomic_set(&ipvs->dropentry, 0);
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spin_lock_init(&ipvs->dropentry_lock);
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@ -4283,10 +4284,6 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
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tbl = kmemdup(vs_vars, sizeof(vs_vars), GFP_KERNEL);
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if (tbl == NULL)
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return -ENOMEM;
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/* Don't export sysctls to unprivileged users */
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if (net->user_ns != &init_user_ns)
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ctl_table_size = 0;
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} else
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tbl = vs_vars;
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/* Initialize sysctl defaults */
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@ -4312,10 +4309,17 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
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ipvs->sysctl_sync_ports = 1;
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tbl[idx++].data = &ipvs->sysctl_sync_ports;
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tbl[idx++].data = &ipvs->sysctl_sync_persist_mode;
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ipvs->sysctl_sync_qlen_max = nr_free_buffer_pages() / 32;
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if (unpriv)
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tbl[idx].mode = 0444;
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tbl[idx++].data = &ipvs->sysctl_sync_qlen_max;
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ipvs->sysctl_sync_sock_size = 0;
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if (unpriv)
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tbl[idx].mode = 0444;
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tbl[idx++].data = &ipvs->sysctl_sync_sock_size;
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tbl[idx++].data = &ipvs->sysctl_cache_bypass;
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tbl[idx++].data = &ipvs->sysctl_expire_nodest_conn;
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tbl[idx++].data = &ipvs->sysctl_sloppy_tcp;
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@ -4338,15 +4342,22 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
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tbl[idx++].data = &ipvs->sysctl_conn_reuse_mode;
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tbl[idx++].data = &ipvs->sysctl_schedule_icmp;
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tbl[idx++].data = &ipvs->sysctl_ignore_tunneled;
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ipvs->sysctl_run_estimation = 1;
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if (unpriv)
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tbl[idx].mode = 0444;
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tbl[idx].extra2 = ipvs;
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tbl[idx++].data = &ipvs->sysctl_run_estimation;
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ipvs->est_cpulist_valid = 0;
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if (unpriv)
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tbl[idx].mode = 0444;
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tbl[idx].extra2 = ipvs;
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tbl[idx++].data = &ipvs->sysctl_est_cpulist;
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ipvs->sysctl_est_nice = IPVS_EST_NICE;
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if (unpriv)
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tbl[idx].mode = 0444;
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tbl[idx].extra2 = ipvs;
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tbl[idx++].data = &ipvs->sysctl_est_nice;
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