net: Enable a userns root rtnl calls that are safe for unprivilged users

- Only allow moving network devices to network namespaces you have
  CAP_NET_ADMIN privileges over.

- Enable creating/deleting/modifying interfaces
- Enable adding/deleting addresses
- Enable adding/setting/deleting neighbour entries
- Enable adding/removing routes
- Enable adding/removing fib rules
- Enable setting the forwarding state
- Enable adding/removing ipv6 address labels
- Enable setting bridge parameter

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

1 files changed, 4 insertions, 9 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a40c10b96f4..575a6ee8994 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1316,6 +1316,10 @@ static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
                         err = PTR_ERR(net);
                         goto errout;
                 }
+                if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) {
+                        err = -EPERM;
+                        goto errout;
+                }
                 err = dev_change_net_namespace(dev, net, ifname);
                 put_net(net);
                 if (err)
@@ -1547,9 +1551,6 @@ static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         struct nlattr *tb[IFLA_MAX+1];
         char ifname[IFNAMSIZ];
 
-        if (!capable(CAP_NET_ADMIN))
-                return -EPERM;
-
         err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFLA_MAX, ifla_policy);
         if (err < 0)
                 goto errout;
@@ -1593,9 +1594,6 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         int err;
         LIST_HEAD(list_kill);
 
-        if (!capable(CAP_NET_ADMIN))
-                return -EPERM;
-
         err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFLA_MAX, ifla_policy);
         if (err < 0)
                 return err;
@@ -1726,9 +1724,6 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
         struct nlattr *linkinfo[IFLA_INFO_MAX+1];
         int err;
 
-        if (!capable(CAP_NET_ADMIN))
-                return -EPERM;
-
 #ifdef CONFIG_MODULES
 replay:
 #endif