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>

4 files changed, 19 insertions, 0 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index f6db227c1fd9..6e06e924ed99 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1815,6 +1815,10 @@ static int __devinet_sysctl_register(struct net *net, char *dev_name,
                 t->devinet_vars[i].extra2 = net;
         }
 
+        /* Don't export sysctls to unprivileged users */
+        if (net->user_ns != &init_user_ns)
+                t->devinet_vars[0].procname = NULL;
+
         snprintf(path, sizeof(path), "net/ipv4/conf/%s", dev_name);
 
         t->sysctl_header = register_net_sysctl(net, path, t->devinet_vars);
@@ -1900,6 +1904,10 @@ static __net_init int devinet_init_net(struct net *net)
                 tbl[0].data = &all->data[IPV4_DEVCONF_FORWARDING - 1];
                 tbl[0].extra1 = all;
                 tbl[0].extra2 = net;
+
+                /* Don't export sysctls to unprivileged users */
+                if (net->user_ns != &init_user_ns)
+                        tbl[0].procname = NULL;
 #endif
         }
 
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 448e68546827..1cf6a768cd53 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -802,6 +802,10 @@ static int __net_init ip4_frags_ns_ctl_register(struct net *net)
                 table[0].data = &net->ipv4.frags.high_thresh;
                 table[1].data = &net->ipv4.frags.low_thresh;
                 table[2].data = &net->ipv4.frags.timeout;
+
+                /* Don't export sysctls to unprivileged users */
+                if (net->user_ns != &init_user_ns)
+                        table[0].procname = NULL;
         }
 
         hdr = register_net_sysctl(net, "net/ipv4", table);
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a8c651216fa6..5b58788db863 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2493,6 +2493,10 @@ static __net_init int sysctl_route_net_init(struct net *net)
                 tbl = kmemdup(tbl, sizeof(ipv4_route_flush_table), GFP_KERNEL);
                 if (tbl == NULL)
                         goto err_dup;
+
+                /* Don't export sysctls to unprivileged users */
+                if (net->user_ns != &init_user_ns)
+                        tbl[0].procname = NULL;
         }
         tbl[0].extra1 = net;
 
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 63d4eccc674d..d84400b65049 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -883,6 +883,9 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
                 table[6].data =
                         &net->ipv4.sysctl_ping_group_range;
 
+                /* Don't export sysctls to unprivileged users */
+                if (net->user_ns != &init_user_ns)
+                        table[0].procname = NULL;
         }
 
         /*