BUG#12611785 - AUDIT INTERFACE STRICT-ALIASING WARNINGS

The types mysql_event_general/mysql_event_connection are
being cast to the incompatible type mysql_event. The way
mysql_event and the other types are designed are prone to
strict aliasing violations and can break things depending
on how compilers optimizes this code.

This patch fixes audit interface, so it confirms to strict-
aliasing rules. It introduces incompatible changes to audit
interface:
- mysql_event type has been removed;
- event_class has been removed from mysql_event_generic and
  mysql_event_connection types;
- st_mysql_audit::event_notify() second argument is event_class;
- st_mysql_audit::event_notify() third argument is event of type
  (const void *).

"Writing Audit Plugins" section of manual should be updated:
http://dev.mysql.com/doc/refman/5.5/en/writing-audit-plugins.html

include/mysql/plugin_audit.h:
  event_class has been moved out of mysql_event types.
include/mysql/plugin_audit.h.pp:
  event_class has been moved out of mysql_event types.
plugin/audit_null/audit_null.c:
  event_class has been moved out of mysql_event types.
sql/sql_audit.cc:
  event_class has been moved out of mysql_event types.

1 files changed, 21 insertions, 11 deletions

diff --git a/sql/sql_audit.cc b/sql/sql_audit.cc
index 74e9e603ebe..ba2c72b7266 100644
--- a/sql/sql_audit.cc
+++ b/sql/sql_audit.cc
@@ -21,11 +21,18 @@ extern int finalize_audit_plugin(st_plugin_int *plugin);
 
 #ifndef EMBEDDED_LIBRARY
 
+struct st_mysql_event_generic
+{
+  unsigned int event_class;
+  const void *event;
+};
+
 unsigned long mysql_global_audit_mask[MYSQL_AUDIT_CLASS_MASK_SIZE];
 
 static mysql_mutex_t LOCK_audit_mask;
 
-static void event_class_dispatch(THD *thd, const struct mysql_event *event);
+static void event_class_dispatch(THD *thd, unsigned int event_class,
+                                 const void *event);
 
 
 static inline
@@ -64,7 +71,6 @@ typedef void (*audit_handler_t)(THD *thd, uint event_subtype, va_list ap);
 static void general_class_handler(THD *thd, uint event_subtype, va_list ap)
 {
   mysql_event_general event;
-  event.event_class= MYSQL_AUDIT_GENERAL_CLASS;
   event.event_subclass= event_subtype;
   event.general_error_code= va_arg(ap, int);
   event.general_thread_id= thd ? thd->thread_id : 0;
@@ -77,14 +83,13 @@ static void general_class_handler(THD *thd, uint event_subtype, va_list ap)
   event.general_query_length= va_arg(ap, unsigned int);
   event.general_charset= va_arg(ap, struct charset_info_st *);
   event.general_rows= (unsigned long long) va_arg(ap, ha_rows);
-  event_class_dispatch(thd, (const mysql_event*) &event);
+  event_class_dispatch(thd, MYSQL_AUDIT_GENERAL_CLASS, &event);
 }
 
 
 static void connection_class_handler(THD *thd, uint event_subclass, va_list ap)
 {
   mysql_event_connection event;
-  event.event_class= MYSQL_AUDIT_CONNECTION_CLASS;
   event.event_subclass= event_subclass;
   event.status= va_arg(ap, int);
   event.thread_id= va_arg(ap, unsigned long);
@@ -102,7 +107,7 @@ static void connection_class_handler(THD *thd, uint event_subclass, va_list ap)
   event.ip_length= va_arg(ap, unsigned int);
   event.database= va_arg(ap, const char *);
   event.database_length= va_arg(ap, unsigned int);
-  event_class_dispatch(thd, (const mysql_event *) &event);
+  event_class_dispatch(thd, MYSQL_AUDIT_CONNECTION_CLASS, &event);
 }
 
 
@@ -433,18 +438,19 @@ int finalize_audit_plugin(st_plugin_int *plugin)
 
 static my_bool plugins_dispatch(THD *thd, plugin_ref plugin, void *arg)
 {
-  const struct mysql_event *event= (const struct mysql_event *) arg;
+  const struct st_mysql_event_generic *event_generic=
+    (const struct st_mysql_event_generic *) arg;
   unsigned long event_class_mask[MYSQL_AUDIT_CLASS_MASK_SIZE];
   st_mysql_audit *data= plugin_data(plugin, struct st_mysql_audit *);
 
-  set_audit_mask(event_class_mask, event->event_class);
+  set_audit_mask(event_class_mask, event_generic->event_class);
 
   /* Check to see if the plugin is interested in this event */
   if (check_audit_mask(data->class_mask, event_class_mask))
     return 0;
 
   /* Actually notify the plugin */
-  data->event_notify(thd, event);
+  data->event_notify(thd, event_generic->event_class, event_generic->event);
 
   return 0;
 }
@@ -457,15 +463,19 @@ static my_bool plugins_dispatch(THD *thd, plugin_ref plugin, void *arg)
   @param[in] event
 */
 
-static void event_class_dispatch(THD *thd, const struct mysql_event *event)
+static void event_class_dispatch(THD *thd, unsigned int event_class,
+                                 const void *event)
 {
+  struct st_mysql_event_generic event_generic;
+  event_generic.event_class= event_class;
+  event_generic.event= event;
   /*
     Check if we are doing a slow global dispatch. This event occurs when
     thd == NULL as it is not associated with any particular thread.
   */
   if (unlikely(!thd))
   {
-    plugin_foreach(thd, plugins_dispatch, MYSQL_AUDIT_PLUGIN, (void*) event);
+    plugin_foreach(thd, plugins_dispatch, MYSQL_AUDIT_PLUGIN, &event_generic);
   }
   else
   {
@@ -476,7 +486,7 @@ static void event_class_dispatch(THD *thd, const struct mysql_event *event)
     plugins_last= plugins + thd->audit_class_plugins.elements;
 
     for (; plugins < plugins_last; plugins++)
-      plugins_dispatch(thd, *plugins, (void*) event);
+      plugins_dispatch(thd, *plugins, &event_generic);
   }
 }