net: Make CAP_NET_BIND_SERVICE per user namespace

Allow privileged users in any user namespace to bind to
privileged sockets in network namespaces they control.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 4b29f6b..b043c60 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -283,7 +283,7 @@
 		return -EINVAL;
 
 	snum = ntohs(addr->sin6_port);
-	if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
+	if (snum && snum < PROT_SOCK && !ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
 		return -EACCES;
 
 	lock_sock(sk);