net sysctl: Register an empty /proc/sys/net

Implementation limitations of the sysctl core won't let /proc/sys/net
reside in a network namespace.  /proc/sys/net at least must be registered
as a normal sysctl.  So register /proc/sys/net early as an empty directory
to guarantee we don't violate this constraint and hit bugs in the sysctl
implementation.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index 3865c4f76b82..2b2986dd04ae 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -88,9 +88,18 @@ static struct pernet_operations sysctl_pernet_ops = {
         .exit = sysctl_net_exit,
 };
 
+static struct ctl_table_header *net_header;
 static __init int net_sysctl_init(void)
 {
-        int ret;
+        static struct ctl_table empty[1];
+        int ret = -ENOMEM;
+        /* Avoid limitations in the sysctl implementation by
+         * registering "/proc/sys/net" as an empty directory not in a
+         * network namespace.
+         */
+        net_header = register_sysctl("net", empty);
+        if (!net_header)
+                goto out;
         ret = register_pernet_subsys(&sysctl_pernet_ops);
         if (ret)
                 goto out;