rtnetlink: enable IFLA_IF_NETNSID for RTM_NEWLINK

- Backwards Compatibility:
  If userspace wants to determine whether RTM_NEWLINK supports the
  IFLA_IF_NETNSID property they should first send an RTM_GETLINK request
  with IFLA_IF_NETNSID on lo. If either EACCESS is returned or the reply
  does not include IFLA_IF_NETNSID userspace should assume that
  IFLA_IF_NETNSID is not supported on this kernel.
  If the reply does contain an IFLA_IF_NETNSID property userspace
  can send an RTM_NEWLINK with a IFLA_IF_NETNSID property. If they receive
  EOPNOTSUPP then the kernel does not support the IFLA_IF_NETNSID property
  with RTM_NEWLINK. Userpace should then fallback to other means.

- Security:
  Callers must have CAP_NET_ADMIN in the owning user namespace of the
  target network namespace.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 061e27cb6c121249c18d763c0856305e8f32c435..204297dffd2aecc7d5616f839dc4f34c9359f7da 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2952,14 +2952,10 @@ replay:
                        name_assign_type = NET_NAME_ENUM;
                }
 
-               dest_net = rtnl_link_get_net(net, tb);
+               dest_net = rtnl_link_get_net_capable(skb, net, tb, CAP_NET_ADMIN);
                if (IS_ERR(dest_net))
                        return PTR_ERR(dest_net);
 
-               err = -EPERM;
-               if (!netlink_ns_capable(skb, dest_net->user_ns, CAP_NET_ADMIN))
-                       goto out;
-
                if (tb[IFLA_LINK_NETNSID]) {
                        int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);