From 732d1ec3aef8000885d7faa908a2c448e1b21d17 Mon Sep 17 00:00:00 2001
From: Aleksey Midenkov <midenok@gmail.com>
Date: Thu, 27 Jul 2023 19:43:45 +0300
Subject: [PATCH] MDEV-29873 MSAN uninitialized value errors in bcmp / 	  
 prep_alter_part_table upon re-partitioning by system time

memcmp() tries to compare beyond the last member of interval because
sizeof(Vers_part_info::interval) is 80. It is sizeof of variable,
sizeof of type is 76.

Now we compare interval_t struct C++ way.
---
 mysql-test/suite/versioning/r/partition.result | 7 +++++++
 mysql-test/suite/versioning/t/partition.test   | 9 +++++++++
 sql/partition_info.h                           | 7 ++++++-
 sql/sql_partition.cc                           | 5 +----
 4 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/mysql-test/suite/versioning/r/partition.result b/mysql-test/suite/versioning/r/partition.result
index 58497db555b35..fd2804cbf3888 100644
--- a/mysql-test/suite/versioning/r/partition.result
+++ b/mysql-test/suite/versioning/r/partition.result
@@ -3406,4 +3406,11 @@ f()
 drop procedure p;
 drop function f;
 drop table t;
+#
+# MDEV-29873 MSAN uninitialized value errors in bcmp /
+#            prep_alter_part_table upon re-partitioning by system time
+#
+create table t (a int) with system versioning partition by system_time interval 5 week;
+alter table t partition by system_time interval 10 week;
+drop table t;
 set global innodb_stats_persistent= @save_persistent;
diff --git a/mysql-test/suite/versioning/t/partition.test b/mysql-test/suite/versioning/t/partition.test
index d15be0959ec24..3013353d23f35 100644
--- a/mysql-test/suite/versioning/t/partition.test
+++ b/mysql-test/suite/versioning/t/partition.test
@@ -2624,6 +2624,15 @@ drop procedure p;
 drop function f;
 drop table t;
 
+--echo #
+--echo # MDEV-29873 MSAN uninitialized value errors in bcmp /
+--echo #            prep_alter_part_table upon re-partitioning by system time
+--echo #
+create table t (a int) with system versioning partition by system_time interval 5 week;
+alter table t partition by system_time interval 10 week;
+# cleanup
+drop table t;
+
 --disable_prepare_warnings
 set global innodb_stats_persistent= @save_persistent;
 --source suite/versioning/common_finish.inc
diff --git a/sql/partition_info.h b/sql/partition_info.h
index 833a231e6ce3c..3a8c3a3752435 100644
--- a/sql/partition_info.h
+++ b/sql/partition_info.h
@@ -78,11 +78,16 @@ struct Vers_part_info : public Sql_alloc
     }
     return false;
   }
-  struct {
+  struct interval_t {
     my_time_t start;
     INTERVAL step;
     enum interval_type type;
     bool is_set() const { return type < INTERVAL_LAST; }
+    bool operator==(const interval_t &rhs) const
+    {
+      /* TODO: equivalent intervals like 1 hour and 60 mins should be considered equal */
+      return start == rhs.start && type == rhs.type && !memcmp(&step, &rhs.step, sizeof(INTERVAL));
+    }
   } interval;
   ulonglong limit;
   bool auto_hist;
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index ba9a370a06890..8c0efb7d3d0b2 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -6035,10 +6035,7 @@ the generated partition syntax in a correct manner.
       {
         if (part_info->vers_info->interval.is_set() && (
             !tab_part_info->vers_info->interval.is_set() ||
-            /* TODO: equivalent intervals like 1 hour and 60 mins should be considered equal */
-            memcmp(&part_info->vers_info->interval,
-                   &tab_part_info->vers_info->interval,
-                   sizeof(Vers_part_info::interval))))
+            part_info->vers_info->interval == tab_part_info->vers_info->interval))
         {
           /* If interval is changed we can not do fast alter */
           tab_part_info= tab_part_info->get_clone(thd);