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>

diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index 3865c4f76b821105da75e696469279e5adb0ea2c..2b2986dd04ae7d109848ee52f3a06b6270c78d10 100644 (file)
--- 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;