MDEV-24865 : Server crashes when truncate mysql user table

For truncate we try to find out possible foreign key tables
using open_tables. However, table_list was not cleaned up
properly and there was no error handling. Fixed by cleaning
table_list and adding proper error handling.

mysql-test/suite/galera/r/galera_truncate.result

@@ -32,6 +32,17 @@ SELECT AUTO_INCREMENT = 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME IN ('t
 AUTO_INCREMENT = 1
 1
 1
+connection node_1;
+TRUNCATE TABLE mysql.user;
+ERROR 42S02: Table 'mysql.user' doesn't exist
+TRUNCATE TABLE performance_schema.threads;
+ERROR HY000: Invalid performance_schema usage
+TRUNCATE TABLE information_schema.tables;
+ERROR 42000: Access denied for user 'root'@'localhost' to database 'information_schema'
+TRUNCATE TABLE mysql.innodb_index_stats;
+TRUNCATE TABLE foo.bar;
+ERROR 42S02: Table 'foo.bar' doesn't exist
+TRUNCATE TABLE t1;
 DROP TABLE t1;
 DROP TABLE t2;
 DROP TABLE t3;

mysql-test/suite/galera/t/galera_truncate.test

@@ -3,8 +3,7 @@
 #
 
 --source include/galera_cluster.inc
---source include/have_innodb.inc
-
+--source include/have_perfschema.inc
 #
 # Simple case
 #
@@ -54,6 +53,23 @@ TRUNCATE TABLE t4;
 --connection node_2
 SELECT AUTO_INCREMENT = 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME IN ('t3', 't4');
 
+
+#
+# MDEV-24865 : Server crashes when truncate mysql user table
+#
+--connection node_1
+
+--error ER_NO_SUCH_TABLE
+TRUNCATE TABLE mysql.user;
+--error ER_WRONG_PERFSCHEMA_USAGE
+TRUNCATE TABLE performance_schema.threads;
+--error ER_DBACCESS_DENIED_ERROR
+TRUNCATE TABLE information_schema.tables;
+TRUNCATE TABLE mysql.innodb_index_stats;
+--error ER_NO_SUCH_TABLE
+TRUNCATE TABLE foo.bar;
+TRUNCATE TABLE t1;
+
 DROP TABLE t1;
 DROP TABLE t2;
 DROP TABLE t3;

sql/sql_truncate.cc

@@ -416,20 +416,23 @@ bool Sql_cmd_truncate_table::truncate_table(THD *thd, TABLE_LIST *table_ref)
     bool hton_can_recreate;
 
 #ifdef WITH_WSREP
-    if (WSREP(thd))
+    if (WSREP(thd) && wsrep_thd_is_local(thd))
     {
       wsrep::key_array keys;
-      wsrep_append_fk_parent_table(thd, table_ref, &keys);
-      if (keys.empty())
+      /* Do not start TOI if table is not found */
+      if (!wsrep_append_fk_parent_table(thd, table_ref, &keys))
       {
-        WSREP_TO_ISOLATION_BEGIN_IF(table_ref->db.str, table_ref->table_name.str, NULL)
+        if (keys.empty())
         {
-          DBUG_RETURN(TRUE);
-        }
-      } else {
-        WSREP_TO_ISOLATION_BEGIN_FK_TABLES(NULL, NULL, table_ref, &keys)
-        {
-          DBUG_RETURN(TRUE);
+          WSREP_TO_ISOLATION_BEGIN_IF(table_ref->db.str, table_ref->table_name.str, NULL)
+          {
+            DBUG_RETURN(TRUE);
+          }
+        } else {
+          WSREP_TO_ISOLATION_BEGIN_FK_TABLES(NULL, NULL, table_ref, &keys)
+          {
+            DBUG_RETURN(TRUE);
+          }
         }
       }
     }

sql/wsrep_mysqld.cc

@@ -1184,10 +1184,17 @@ void wsrep_keys_free(wsrep_key_arr_t* key_arr)
     key_arr->keys_len= 0;
 }
 
-void
+/*!
+ * @param thd    thread
+ * @param tables list of tables
+ * @param keys   prepared keys
+
+ * @return true if parent table append was successfull, otherwise false.
+*/
+bool
 wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* tables, wsrep::key_array* keys)
 {
-  if (!WSREP(thd) || !WSREP_CLIENT(thd)) return;
+    bool fail= false;
     TABLE_LIST *table;
 
     thd->release_transactional_locks();
@@ -1198,6 +1205,8 @@ wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* tables, wsrep::key_array* key
          open_tables(thd, &tables, &counter, MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL))
     {
       WSREP_DEBUG("unable to open table for FK checks for %s", thd->query());
+      fail= true;
+      goto exit;
     }
 
     for (table= tables; table; table= table->next_local)
@@ -1219,14 +1228,18 @@ wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* tables, wsrep::key_array* key
       }
     }
 
+exit:
     /* close the table and release MDL locks */
     close_thread_tables(thd);
     thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
     for (table= tables; table; table= table->next_local)
     {
       table->table= NULL;
+      table->next_global= NULL;
       table->mdl_request.ticket= NULL;
     }
+
+    return fail;
 }
 
 /*!
@@ -1965,7 +1978,7 @@ static int wsrep_TOI_begin(THD *thd, const char *db, const char *table,
 {
   DBUG_ASSERT(thd->variables.wsrep_OSU_method == WSREP_OSU_TOI);
 
-  WSREP_DEBUG("TOI Begin");
+  WSREP_DEBUG("TOI Begin for %s", WSREP_QUERY(thd));
   if (wsrep_can_run_in_toi(thd, db, table, table_list) == false)
   {
     WSREP_DEBUG("No TOI for %s", WSREP_QUERY(thd));
@@ -2055,22 +2068,20 @@ static void wsrep_TOI_end(THD *thd) {
   wsrep_to_isolation--;
   wsrep::client_state& client_state(thd->wsrep_cs());
   DBUG_ASSERT(wsrep_thd_is_local_toi(thd));
-  WSREP_DEBUG("TO END: %lld: %s", client_state.toi_meta().seqno().get(),
-              WSREP_QUERY(thd));
 
-  if (wsrep_thd_is_local_toi(thd))
+  wsrep_set_SE_checkpoint(client_state.toi_meta().gtid());
+
+  int ret= client_state.leave_toi_local(wsrep::mutable_buffer());
+
+  if (!ret)
   {
-    wsrep_set_SE_checkpoint(client_state.toi_meta().gtid());
-    int ret= client_state.leave_toi_local(wsrep::mutable_buffer());
-    if (!ret)
-    {
-      WSREP_DEBUG("TO END: %lld", client_state.toi_meta().seqno().get());
-    }
-    else
-    {
-      WSREP_WARN("TO isolation end failed for: %d, schema: %s, sql: %s",
-                 ret, (thd->db.str ? thd->db.str : "(null)"), WSREP_QUERY(thd));
-    }
+    WSREP_DEBUG("TO END: %lld: %s",
+                client_state.toi_meta().seqno().get(), WSREP_QUERY(thd));
+  }
+  else
+  {
+    WSREP_WARN("TO isolation end failed for: %d, sql: %s",
+                ret, WSREP_QUERY(thd));
   }
 }
 

sql/wsrep_mysqld.h

@@ -212,7 +212,7 @@ wsrep_sync_wait_upto (THD* thd, wsrep_gtid_t* upto, int timeout);
 extern void wsrep_last_committed_id (wsrep_gtid_t* gtid);
 extern int  wsrep_check_opts();
 extern void wsrep_prepend_PATH (const char* path);
-void wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* table, wsrep::key_array* keys);
+extern bool wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* table, wsrep::key_array* keys);
 
 /* Other global variables */
 extern wsrep_seqno_t wsrep_locked_seqno;