MDEV-19349 mysql_install_db: segfault at tmp_file_prefix check

mysql-test/t/bootstrap.test

@@ -66,4 +66,13 @@ SELECT 'bug' as '' FROM INFORMATION_SCHEMA.ENGINES WHERE engine='innodb'
 --error 1
 --exec $MYSQLD_BOOTSTRAP_CMD --myisam_recover_options=NONE
 
+#
+# MDEV-19349 mysql_install_db: segfault at tmp_file_prefix check
+#
+--write_file $MYSQLTEST_VARDIR/tmp/1
+use test;
+EOF
+--exec $MYSQLD_BOOTSTRAP_CMD < $MYSQLTEST_VARDIR/tmp/1 >> $MYSQLTEST_VARDIR/tmp/bootstrap.log 2>&1
+--remove_file $MYSQLTEST_VARDIR/tmp/1
+
 --echo End of 5.5 tests

sql/sql_base.cc

@@ -9301,13 +9301,7 @@ my_bool mysql_rm_tmp_tables(void)
     {
       file=dirp->dir_entry+idx;
 
-      /* skiping . and .. */
-      if (file->name[0] == '.' && (!file->name[1] ||
-                                   (file->name[1] == '.' &&  !file->name[2])))
-        continue;
-
-      if (!memcmp(file->name, tmp_file_prefix,
-                  tmp_file_prefix_length))
+      if (!strncmp(file->name, tmp_file_prefix, tmp_file_prefix_length))
       {
         char *ext= fn_ext(file->name);
         uint ext_len= strlen(ext);