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> --- 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
