[NET] sysctl: make the sys.net.core sysctls per-namespace

Making them per-namespace is required for the following
two reasons:

 First, some ctl values have a per-namespace meaning.
 Second, making them writable from the sub-namespace
 is an isolation hole.

So I introduce the pernet operations to create these
tables. For init_net I use the existing statically
declared tables, for sub-namespace they are duplicated
and the write bits are removed from the mode.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 45 insertions, 5 deletions

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index e322713e590a..57a7eadb8551 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -151,18 +151,58 @@ static struct ctl_table net_core_table[] = {
         { .ctl_name = 0 }
 };
 
-static __initdata struct ctl_path net_core_path[] = {
+static __net_initdata struct ctl_path net_core_path[] = {
         { .procname = "net", .ctl_name = CTL_NET, },
         { .procname = "core", .ctl_name = NET_CORE, },
         { },
 };
 
-static __init int sysctl_core_init(void)
+static __net_init int sysctl_core_net_init(struct net *net)
 {
-        struct ctl_table_header *hdr;
+        struct ctl_table *tbl, *tmp;
+
+        tbl = net_core_table;
+        if (net != &init_net) {
+                tbl = kmemdup(tbl, sizeof(net_core_table), GFP_KERNEL);
+                if (tbl == NULL)
+                        goto err_dup;
+
+                for (tmp = tbl; tmp->procname; tmp++)
+                        tmp->mode &= ~0222;
+        }
+
+        net->sysctl_core_hdr = register_net_sysctl_table(net,
+                        net_core_path, tbl);
+        if (net->sysctl_core_hdr == NULL)
+                goto err_reg;
 
-        hdr = register_sysctl_paths(net_core_path, net_core_table);
-        return hdr == NULL ? -ENOMEM : 0;
+        return 0;
+
+err_reg:
+        if (tbl != net_core_table)
+                kfree(tbl);
+err_dup:
+        return -ENOMEM;
+}
+
+static __net_exit void sysctl_core_net_exit(struct net *net)
+{
+        struct ctl_table *tbl;
+
+        tbl = net->sysctl_core_hdr->ctl_table_arg;
+        unregister_net_sysctl_table(net->sysctl_core_hdr);
+        BUG_ON(tbl == net_core_table);
+        kfree(tbl);
+}
+
+static __net_initdata struct pernet_operations sysctl_core_ops = {
+        .init = sysctl_core_net_init,
+        .exit = sysctl_core_net_exit,
+};
+
+static __init int sysctl_core_init(void)
+{
+        return register_pernet_subsys(&sysctl_core_ops);
 }
 
 __initcall(sysctl_core_init);