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MDEV-363 - Server crashes in intern_plugin_lock on concurrent installing

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semisync plugin and setting rpl_semi_sync_master_enabled

There was race condition between INSTALL PLUGIN and SET. It was caused by a
gap in INSTALL PLUGIN when plugin variables were registered but not fully
initialized. Accessing such variables concurrently may reference uninitialized
memory, specifically sys_var_pluginvar::plugin.

Fixed by initializing sys_var_pluginvar::plugin early, before variable is
registered.
This commit is contained in:
Sergey Vojtovich 2015-06-09 13:50:43 +04:00
parent 49a3392441
commit 3a50a8c9be
1 changed files with 6 additions and 20 deletions
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26
sql/sql_plugin.cc
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@ -271,13 +271,15 @@ public:
{ TRASH(ptr_arg, size); }
sys_var_pluginvar(sys_var_chain *chain, const char *name_arg,
struct st_mysql_sys_var *plugin_var_arg)
struct st_mysql_sys_var *plugin_var_arg,
struct st_plugin_int *plugin_arg)
:sys_var(chain, name_arg, plugin_var_arg->comment,
(plugin_var_arg->flags & PLUGIN_VAR_THDLOCAL ? SESSION : GLOBAL) |
(plugin_var_arg->flags & PLUGIN_VAR_READONLY ? READONLY : 0),
0, -1, NO_ARG, pluginvar_show_type(plugin_var_arg), 0, 0,
VARIABLE_NOT_IN_BINLOG, NULL, NULL, NULL),
plugin_var(plugin_var_arg), orig_pluginvar_name(plugin_var_arg->name)
plugin(plugin_arg), plugin_var(plugin_var_arg),
orig_pluginvar_name(plugin_var_arg->name)
{ plugin_var->name= name_arg; }
sys_var_pluginvar *cast_pluginvar() { return this; }
bool check_update_type(Item_result type);
@ -1407,22 +1409,6 @@ static int plugin_initialize(MEM_ROOT *tmp_root, struct st_plugin_int *plugin,
#endif /* FIX_LATER */
}
/*
set the plugin attribute of plugin's sys vars so they are pointing
to the active plugin
*/
if (plugin->system_vars)
{
sys_var_pluginvar *var= plugin->system_vars->cast_pluginvar();
for (;;)
{
var->plugin= plugin;
if (!var->next)
break;
var= var->next->cast_pluginvar();
}
}
ret= 0;
err:
@ -3925,7 +3911,7 @@ static int test_plugin_options(MEM_ROOT *tmp_root, struct st_plugin_int *tmp,
if (o->flags & PLUGIN_VAR_NOSYSVAR)
continue;
if ((var= find_bookmark(plugin_name.str, o->name, o->flags)))
v= new (mem_root) sys_var_pluginvar(&chain, var->key + 1, o);
v= new (mem_root) sys_var_pluginvar(&chain, var->key + 1, o, tmp);
else
{
len= plugin_name.length + strlen(o->name) + 2;
@ -3933,7 +3919,7 @@ static int test_plugin_options(MEM_ROOT *tmp_root, struct st_plugin_int *tmp,
strxmov(varname, plugin_name.str, "-", o->name, NullS);
my_casedn_str(&my_charset_latin1, varname);
convert_dash_to_underscore(varname, len-1);
v= new (mem_root) sys_var_pluginvar(&chain, varname, o);
v= new (mem_root) sys_var_pluginvar(&chain, varname, o, tmp);
}
DBUG_ASSERT(v); /* check that an object was actually constructed */
} /* end for */