nfsd: Modify nfsd4_cb_sec to use kuids and kgids

Change uid and gid in struct nfsd4_cb_sec to be of type kuid_t and
kgid_t.

In nfsd4_decode_cb_sec when reading uids and gids off the wire convert
them to kuids and kgids, and if they don't convert to valid kuids or
valid kuids ignore RPC_AUTH_UNIX and don't fill in any of the fields.

Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index d1c229f..1a8c739 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -152,8 +152,8 @@
 
 struct nfsd4_cb_sec {
 	u32	flavor; /* (u32)(-1) used to mean "no valid flavor" */
-	u32	uid;
-	u32	gid;
+	kuid_t	uid;
+	kgid_t	gid;
 };
 
 struct nfsd4_create_session {