Fixed bug #78379 (Cast to object confuses GC, causes crash)

NEWS

@@ -4,6 +4,7 @@ PHP                                                                        NEWS
 
 - Core:
   . Fixed bug #78363 (Buffer overflow in zendparse). (Nikita)
+  . Fixed bug #78379 (Cast to object confuses GC, causes crash). (Dmitry)
 
 - Curl:
   . Fixed bug #77946 (Bad cURL resources returned by curl_multi_info_read()).

Zend/tests/bug78379.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Bug #78379 (Cast to object confuses GC, causes crash)
+--INI--
+opcache.enable=0
+--FILE--
+<?php
+class C {
+	public function __construct() {
+		$this->p = (object)["x" => [1]];
+	}
+}
+class E {
+}
+$e = new E;
+$e->f = new E;
+$e->f->e = $e;
+$e->a = new C;
+$e = null;
+gc_collect_cycles();
+var_dump(new C);
+?>
+--EXPECTF--
+object(C)#%d (1) {
+  ["p"]=>
+  object(stdClass)#%d (1) {
+    ["x"]=>
+    array(1) {
+      [0]=>
+      int(1)
+    }
+  }
+}

Zend/zend_object_handlers.c

@@ -138,6 +138,11 @@ ZEND_API HashTable *zend_std_get_gc(zval *object, zval **table, int *n) /* {{{ *
 		if (zobj->properties) {
 			*table = NULL;
 			*n = 0;
+			if (UNEXPECTED(GC_REFCOUNT(zobj->properties) > 1)
+			 && EXPECTED(!(GC_FLAGS(zobj->properties) & IS_ARRAY_IMMUTABLE))) {
+				GC_REFCOUNT(zobj->properties)--;
+				zobj->properties = zend_array_dup(zobj->properties);
+			}
 			return zobj->properties;
 		} else {
 			*table = zobj->properties_table;