nfsd: don't assume copy notify when preprocessing the stateid

Move the stateid handling to nfsd4_copy_notify.
If nfs4_preprocess_stateid_op did not produce an output stateid, error out.

Copy notify specifically does not permit the use of special stateids,
so enforce that outside generic stateid pre-processing.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Olga Kornievskaia <aglo@umich.edu>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1942,7 +1942,7 @@ nfsd4_copy_notify(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	struct nfsd4_copy_notify *cn = &u->copy_notify;
 	__be32 status;
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
-	struct nfs4_stid *stid;
+	struct nfs4_stid *stid = NULL;
 	struct nfs4_cpntf_state *cps;
 	struct nfs4_client *clp = cstate->clp;
 
@@ -1951,6 +1951,8 @@ nfsd4_copy_notify(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 					&stid);
 	if (status)
 		return status;
+	if (!stid)
+		return nfserr_bad_stateid;
 
 	cn->cpn_lease_time.tv_sec = nn->nfsd4_lease;
 	cn->cpn_lease_time.tv_nsec = 0;

fs/nfsd/nfs4state.c

@@ -7022,11 +7022,7 @@ nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
 		*nfp = NULL;
 
 	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid)) {
-		if (cstid)
-			status = nfserr_bad_stateid;
-		else
-			status = check_special_stateids(net, fhp, stateid,
-									flags);
+		status = check_special_stateids(net, fhp, stateid, flags);
 		goto done;
 	}