userns: Print out socket uids in a user namespace aware fashion.

Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

net/key/af_key.c

@@ -3661,7 +3661,7 @@ static int pfkey_seq_show(struct seq_file *f, void *v)
 			       atomic_read(&s->sk_refcnt),
 			       sk_rmem_alloc_get(s),
 			       sk_wmem_alloc_get(s),
-			       sock_i_uid(s),
+			       from_kuid_munged(seq_user_ns(f), sock_i_uid(s)),
 			       sock_i_ino(s)
 			       );
 	return 0;