conf-parser: reject utf8-invalid lines

src/shared/conf-parser.c

@@ -211,6 +211,9 @@ static int parse_line(
                 return config_parse(unit, fn, NULL, sections, lookup, table, flags, userdata);
         }
 
+        if (!utf8_is_valid(l))
+                return log_syntax_invalid_utf8(unit, LOG_WARNING, filename, line, l);
+
         if (*l == '[') {
                 size_t k;
                 char *n;