From 04c5cdffeb419f7679d8c300a4dccb56c23958fa Mon Sep 17 00:00:00 2001
From: Varun Gupta <varun.gupta@mariadb.com>
Date: Tue, 9 Jun 2020 10:23:47 +0530
Subject: [PATCH] MDEV-22836: Server crashes in err_conv / ErrBuff::set_str

The issue here is charset for Sort_param::tmp_buffer is cleared when bzero is done for Sort_param.
Make sure to set the charset explicitly in the constructor for tmp_buffer.
---
 mysql-test/main/order_by.result | 10 ++++++++++
 mysql-test/main/order_by.test   | 11 +++++++++++
 sql/sql_sort.h                  |  5 +++++
 3 files changed, 26 insertions(+)

diff --git a/mysql-test/main/order_by.result b/mysql-test/main/order_by.result
index cc10ab6f1a1..c750b5ca10c 100644
--- a/mysql-test/main/order_by.result
+++ b/mysql-test/main/order_by.result
@@ -3955,4 +3955,14 @@ ORDER BY surname_first ASC LIMIT 1 OFFSET 1;
 name	surname_first
 Charles Dickens	Dickens, Charles
 DROP TABLE t1;
+#
+# MDEV-22836: Server crashes in err_conv / ErrBuff::set_str
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (0),(1);
+SELECT * FROM t1 ORDER BY CONVERT(AES_ENCRYPT(1,a), CHAR(4));
+a
+1
+0
+DROP TABLE t1;
 # End of 10.5 tests
diff --git a/mysql-test/main/order_by.test b/mysql-test/main/order_by.test
index 41a2403cff5..c78add674ba 100644
--- a/mysql-test/main/order_by.test
+++ b/mysql-test/main/order_by.test
@@ -2454,4 +2454,15 @@ ORDER BY surname_first ASC LIMIT 1 OFFSET 1;
 
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-22836: Server crashes in err_conv / ErrBuff::set_str
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (0),(1);
+--disable_warnings
+SELECT * FROM t1 ORDER BY CONVERT(AES_ENCRYPT(1,a), CHAR(4));
+--enable_warnings
+DROP TABLE t1;
+
 --echo # End of 10.5 tests
diff --git a/sql/sql_sort.h b/sql/sql_sort.h
index cff54f18bde..40f0c5ede5f 100644
--- a/sql/sql_sort.h
+++ b/sql/sql_sort.h
@@ -545,6 +545,11 @@ public:
   {
     memset(reinterpret_cast<void*>(this), 0, sizeof(*this));
     tmp_buffer.set_thread_specific();
+    /*
+      Fix memset() clearing the charset.
+      TODO: The constructor should be eventually rewritten not to use memset().
+    */
+    tmp_buffer.set_charset(&my_charset_bin);
   }
   void init_for_filesort(uint sortlen, TABLE *table,
                          ha_rows maxrows, bool sort_positions);