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>

3 files changed, 4 insertions, 24 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index bf5b5b8af56..58a4ba27dfe 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -275,9 +275,6 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 	struct nlattr *tb[FRA_MAX+1];
 	int err = -EINVAL, unresolved = 0;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh)))
 		goto errout;
 
@@ -427,9 +424,6 @@ static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 	struct nlattr *tb[FRA_MAX+1];
 	int err = -EINVAL;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh)))
 		goto errout;
 
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 7adcdaf91c4..f1c0c2e9cad 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1620,9 +1620,6 @@ static int neigh_delete(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct net_device *dev = NULL;
 	int err = -EINVAL;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	ASSERT_RTNL();
 	if (nlmsg_len(nlh) < sizeof(*ndm))
 		goto out;
@@ -1687,9 +1684,6 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct net_device *dev = NULL;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	ASSERT_RTNL();
 	err = nlmsg_parse(nlh, sizeof(*ndm), tb, NDA_MAX, NULL);
 	if (err < 0)
@@ -1968,9 +1962,6 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct nlattr *tb[NDTA_MAX+1];
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = nlmsg_parse(nlh, sizeof(*ndtmsg), tb, NDTA_MAX,
 			  nl_neightbl_policy);
 	if (err < 0)
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