nfsd: only fill out return pointer on success in nfsd4_lookup_stateid

In the case of a revoked delegation, we still fill out the pointer even
when returning an error, which is bad form. Only overwrite the pointer
on success.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -6266,6 +6266,7 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
 		     struct nfs4_stid **s, struct nfsd_net *nn)
 {
 	__be32 status;
+	struct nfs4_stid *stid;
 	bool return_revoked = false;
 
 	/*
@@ -6288,15 +6289,16 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
 	}
 	if (status)
 		return status;
-	*s = find_stateid_by_type(cstate->clp, stateid, typemask);
-	if (!*s)
+	stid = find_stateid_by_type(cstate->clp, stateid, typemask);
+	if (!stid)
 		return nfserr_bad_stateid;
-	if (((*s)->sc_type == NFS4_REVOKED_DELEG_STID) && !return_revoked) {
-		nfs4_put_stid(*s);
+	if ((stid->sc_type == NFS4_REVOKED_DELEG_STID) && !return_revoked) {
+		nfs4_put_stid(stid);
 		if (cstate->minorversion)
 			return nfserr_deleg_revoked;
 		return nfserr_bad_stateid;
 	}
+	*s = stid;
 	return nfs_ok;
 }