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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>
This commit is contained in:
Alexander Mikhalitsyn 2024-05-06 16:14:44 +02:00 committed by David S. Miller
parent 643bb5dbae
commit 2b696a2a10
1 changed files with 15 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
net/netfilter/ipvs/ip_vs_ctl.c
View File

@ -4269,6 +4269,7 @@ 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);
@ -4283,10 +4284,6 @@ 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)
ctl_table_size = 0;
} else
tbl = vs_vars;
/* Initialize sysctl defaults */
@ -4312,10 +4309,17 @@ 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;
@ -4338,15 +4342,22 @@ 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;