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>

net/bridge/br_netlink.c

@@ -240,9 +240,6 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh)
 	struct nlattr *tb[IFLA_BRPORT_MAX];
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	ifm = nlmsg_data(nlh);
 
 	protinfo = nlmsg_find_attr(nlh, sizeof(*ifm), IFLA_PROTINFO);

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;
 

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)

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

net/ipv4/devinet.c

@@ -539,9 +539,6 @@ static int inet_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg
 
 	ASSERT_RTNL();
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_ipv4_policy);
 	if (err < 0)
 		goto errout;
@@ -649,9 +646,6 @@ static int inet_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg
 
 	ASSERT_RTNL();
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	ifa = rtm_to_ifaddr(net, nlh);
 	if (IS_ERR(ifa))
 		return PTR_ERR(ifa);

net/ipv4/fib_frontend.c

@@ -613,9 +613,6 @@ static int inet_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh, void *ar
 	struct fib_table *tb;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = rtm_to_fib_config(net, skb, nlh, &cfg);
 	if (err < 0)
 		goto errout;
@@ -638,9 +635,6 @@ static int inet_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh, void *ar
 	struct fib_table *tb;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = rtm_to_fib_config(net, skb, nlh, &cfg);
 	if (err < 0)
 		goto errout;

net/ipv6/addrconf.c

@@ -3514,9 +3514,6 @@ inet6_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct in6_addr *pfx;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_ipv6_policy);
 	if (err < 0)
 		return err;
@@ -3587,9 +3584,6 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	u8 ifa_flags;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_ipv6_policy);
 	if (err < 0)
 		return err;

net/ipv6/addrlabel.c

@@ -425,9 +425,6 @@ static int ip6addrlbl_newdel(struct sk_buff *skb, struct nlmsghdr *nlh,
 	u32 label;
 	int err = 0;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = nlmsg_parse(nlh, sizeof(*ifal), tb, IFAL_MAX, ifal_policy);
 	if (err < 0)
 		return err;

net/ipv6/route.c

@@ -2446,9 +2446,6 @@ static int inet6_rtm_delroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *a
 	struct fib6_config cfg;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = rtm_to_fib6_config(skb, nlh, &cfg);
 	if (err < 0)
 		return err;
@@ -2464,9 +2461,6 @@ static int inet6_rtm_newroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *a
 	struct fib6_config cfg;
 	int err;
 
-	if (!capable(CAP_NET_ADMIN))
-		return -EPERM;
-
 	err = rtm_to_fib6_config(skb, nlh, &cfg);
 	if (err < 0)
 		return err;