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Message-Id: <20240418145743.248109-2-aleksandr.mikhalitsyn@canonical.com>
Date: Thu, 18 Apr 2024 16:57:43 +0200
From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: horms@...ge.net.au
Cc: netdev@...r.kernel.org,
lvs-devel@...r.kernel.org,
netfilter-devel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>,
Stéphane Graber <stgraber@...raber.org>,
Christian Brauner <brauner@...nel.org>,
Julian Anastasov <ja@....bg>,
Pablo Neira Ayuso <pablo@...filter.org>,
Jozsef Kadlecsik <kadlec@...filter.org>,
Florian Westphal <fw@...len.de>
Subject: [PATCH net-next v3 2/2] 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: 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
@@ -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
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