net: Don't export sysctls to unprivileged users

In preparation for supporting the creation of network namespaces
by unprivileged users, modify all of the per net sysctl exports
and refuse to allow them to unprivileged users.

This makes it safe for unprivileged users in general to access
per net sysctls, and allows sysctls to be exported to unprivileged
users on an individual basis as they are deemed safe.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/unix/sysctl_net_unix.c b/net/unix/sysctl_net_unix.c
index b34b5b9792f0..8800604c93f4 100644
--- a/net/unix/sysctl_net_unix.c
+++ b/net/unix/sysctl_net_unix.c
@@ -34,6 +34,10 @@ int __net_init unix_sysctl_register(struct net *net)
         if (table == NULL)
                 goto err_alloc;
 
+        /* Don't export sysctls to unprivileged users */
+        if (net->user_ns != &init_user_ns)
+                table[0].procname = NULL;
+
         table[0].data = &net->unx.sysctl_max_dgram_qlen;
         net->unx.ctl = register_net_sysctl(net, "net/unix", table);
         if (net->unx.ctl == NULL)