Fixed ##72433: Use After Free Vulnerability in PHP's GC algorithm and…

… unserialize

Zend/tests/gc_024.phpt

@@ -13,5 +13,5 @@ var_dump(gc_collect_cycles());
 echo "ok\n";
 ?>
 --EXPECT--
-int(1)
+int(2)
 ok

ext/spl/spl_array.c

@@ -831,6 +831,16 @@ static HashTable* spl_array_get_debug_info(zval *obj, int *is_temp TSRMLS_DC) /*
 }
 /* }}} */
 
+static HashTable *spl_array_get_gc(zval *object, zval ***gc_data, int *gc_data_count TSRMLS_DC) /* {{{ */
+{
+	spl_array_object *intern = (spl_array_object*)zend_object_store_get_object(object TSRMLS_CC);
+
+	*gc_data = &intern->array;
+	*gc_data_count = 1;
+	return zend_std_get_properties(object);
+}
+/* }}} */
+
 static zval *spl_array_read_property(zval *object, zval *member, int type, const zend_literal *key TSRMLS_DC) /* {{{ */
 {
 	spl_array_object *intern = (spl_array_object*)zend_object_store_get_object(object TSRMLS_CC);
@@ -1961,6 +1971,7 @@ PHP_MINIT_FUNCTION(spl_array)
 
 	spl_handler_ArrayObject.get_properties = spl_array_get_properties;
 	spl_handler_ArrayObject.get_debug_info = spl_array_get_debug_info;
+	spl_handler_ArrayObject.get_gc = spl_array_get_gc;
 	spl_handler_ArrayObject.read_property = spl_array_read_property;
 	spl_handler_ArrayObject.write_property = spl_array_write_property;
 	spl_handler_ArrayObject.get_property_ptr_ptr = spl_array_get_property_ptr_ptr;

ext/standard/tests/strings/bug72433.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Bug #72433: Use After Free Vulnerability in PHP's GC algorithm and unserialize
+--FILE--
+<?php
+// Fill any potential freed spaces until now.
+$filler = array();
+for($i = 0; $i < 100; $i++)
+	$filler[] = "";
+// Create our payload and unserialize it.
+$serialized_payload = 'a:3:{i:0;r:1;i:1;r:1;i:2;C:11:"ArrayObject":19:{x:i:0;r:1;;m:a:0:{}}}';
+$free_me = unserialize($serialized_payload);
+// We need to increment the reference counter of our ArrayObject s.t. all reference counters of our unserialized array become 0.
+$inc_ref_by_one = $free_me[2];
+// The call to gc_collect_cycles will free '$free_me'.
+gc_collect_cycles();
+// We now have multiple freed spaces. Fill all of them.
+$fill_freed_space_1 = "filler_zval_1";
+$fill_freed_space_2 = "filler_zval_2";
+var_dump($free_me);
+?>
+--EXPECTF--
+array(3) {
+  [0]=>
+  *RECURSION*
+  [1]=>
+  *RECURSION*
+  [2]=>
+  object(ArrayObject)#%d (1) {
+    ["storage":"ArrayObject":private]=>
+    *RECURSION*
+  }
+}