[CIFS] Fix oops when negotiating lanman and no password specified

Pointed out by Guenter Kukkukk
Signed-of-by: Steve French <sfrench@us.ibm.com>
(cherry picked from bbf33d512da608c7221fec42b56b9ef89c25a5ee commit)

fs/cifs/cifsencrypt.c

@@ -277,7 +277,8 @@ void calc_lanman_hash(struct cifsSesInfo * ses, char * lnm_session_key)
 		return;
 
 	memset(password_with_pad, 0, CIFS_ENCPWD_SIZE);
-	strncpy(password_with_pad, ses->password, CIFS_ENCPWD_SIZE);
+	if(ses->password)
+		strncpy(password_with_pad, ses->password, CIFS_ENCPWD_SIZE);
 
 	if((ses->server->secMode & SECMODE_PW_ENCRYPT) == 0)
 		if(extended_security & CIFSSEC_MAY_PLNTXT) {