fs/cifs: correctly to anonymous authentication for the NTLM(v2) authentication

Only server which map unknown users to guest will allow
access using a non-null NTLMv2_Response.

For Samba it's the "map to guest = bad user" option.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913Signed-off-by: Stefan Metzmacher <metze@samba.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/sess.c

@@ -895,6 +895,7 @@ sess_auth_ntlmv2(struct sess_data *sess_data)
 	/* LM2 password would be here if we supported it */
 	pSMB->req_no_secext.CaseInsensitivePasswordLength = 0;
 
+	if (ses->user_name != NULL) {
 		/* calculate nlmv2 response and session key */
 		rc = setup_ntlmv2_rsp(ses, sess_data->nls_cp);
 		if (rc) {
@@ -911,6 +912,9 @@ sess_auth_ntlmv2(struct sess_data *sess_data)
 		 */
 		pSMB->req_no_secext.CaseSensitivePasswordLength =
 			cpu_to_le16(ses->auth_key.len - CIFS_SESS_KEY_SIZE);
+	} else {
+		pSMB->req_no_secext.CaseSensitivePasswordLength = 0;
+	}
 
 	if (ses->capabilities & CAP_UNICODE) {
 		if (sess_data->iov[0].iov_len % 2) {