Fix use-after-free during lazy object initialization (#16004)

Zend/tests/lazy_objects/gh15999_001.phpt

@@ -0,0 +1,112 @@
+--TEST--
+Lazy Objects: GH-15999 001: Object is released during initialization
+--FILE--
+<?php
+
+class C {
+    public $s;
+    public function __destruct() {
+        var_dump(__METHOD__);
+    }
+}
+
+print "# Ghost:\n";
+
+$r = new ReflectionClass(C::class);
+
+$o = $r->newLazyGhost(function ($obj) {
+    global $o;
+    $o = null;
+});
+$p = new stdClass;
+
+try {
+    $o->s = $p;
+} catch (Error $e) {
+    printf("%s: %s\n", $e::class, $e->getMessage());
+}
+
+print "# Proxy:\n";
+
+$o = $r->newLazyProxy(function ($obj) {
+    global $o;
+    $o = null;
+    return new C();
+});
+$p = new stdClass;
+
+try {
+    $o->s = $p;
+} catch (Error $e) {
+    printf("%s: %s\n", $e::class, $e->getMessage());
+}
+
+print "# GC cycle:\n";
+
+$o = $r->newLazyGhost(function ($obj) {
+    global $o;
+    $o->s = $o;
+    $o = null;
+    gc_collect_cycles();
+});
+$p = new stdClass;
+
+$o->s = $p;
+gc_collect_cycles();
+
+print "# Nested error (ghost):\n";
+
+$r = new ReflectionClass(C::class);
+
+$o = $r->newLazyGhost(function ($obj) {
+    global $o;
+    $o = null;
+    return new stdClass;
+});
+$p = new stdClass;
+
+try {
+    $o->s = $p;
+} catch (Error $e) {
+    do {
+        printf("%s: %s\n", $e::class, $e->getMessage());
+    } while ($e = $e->getPrevious());
+}
+
+print "# Nested error (proxy):\n";
+
+$r = new ReflectionClass(C::class);
+
+$o = $r->newLazyProxy(function ($obj) {
+    global $o;
+    $o = null;
+    return new stdClass;
+});
+$p = new stdClass;
+
+try {
+    $o->s = $p;
+} catch (Error $e) {
+    do {
+        printf("%s: %s\n", $e::class, $e->getMessage());
+    } while ($e = $e->getPrevious());
+}
+
+?>
+==DONE==
+--EXPECT--
+# Ghost:
+string(13) "C::__destruct"
+Error: Lazy object was released during initialization
+# Proxy:
+string(13) "C::__destruct"
+Error: Lazy object was released during initialization
+# GC cycle:
+string(13) "C::__destruct"
+# Nested error (ghost):
+Error: Lazy object was released during initialization
+TypeError: Lazy object initializer must return NULL or no value
+# Nested error (proxy):
+Error: Lazy object was released during initialization
+TypeError: The real instance class stdClass is not compatible with the proxy class C. The proxy must be a instance of the same class as the real instance, or a sub-class with no additional properties, and no overrides of the __destructor or __clone methods.
+==DONE==

Zend/tests/lazy_objects/gh15999_002.phpt

@@ -0,0 +1,55 @@
+--TEST--
+Lazy Objects: GH-15999 002: Assigned value is changed during lazy object initialization
+--FILE--
+<?php
+
+class C {
+    public $s;
+    public function __destruct() {
+        var_dump(__METHOD__);
+    }
+}
+
+print "# Ghost:\n";
+
+$r = new ReflectionClass(C::class);
+
+$o = $r->newLazyGhost(function ($obj) {
+    global $p;
+    $p = null;
+});
+
+$p = new stdClass;
+var_dump($o->s = $p);
+var_dump($o->s);
+
+print "# Proxy:\n";
+
+$r = new ReflectionClass(C::class);
+
+$o = $r->newLazyProxy(function ($obj) {
+    global $p;
+    $p = null;
+    return new C();
+});
+
+$p = new stdClass;
+var_dump($o->s = $p);
+var_dump($o->s);
+
+?>
+==DONE==
+--EXPECTF--
+# Ghost:
+object(stdClass)#%d (0) {
+}
+object(stdClass)#%d (0) {
+}
+# Proxy:
+string(13) "C::__destruct"
+object(stdClass)#%d (0) {
+}
+object(stdClass)#%d (0) {
+}
+==DONE==
+string(13) "C::__destruct"

Zend/zend_lazy_objects.c

@@ -429,6 +429,9 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 	ZEND_ASSERT(zend_object_is_lazy_proxy(obj));
 	ZEND_ASSERT(!zend_lazy_object_initialized(obj));
 
+	/* Prevent object from being released during initialization */
+	GC_ADDREF(obj);
+
 	zend_lazy_object_info *info = zend_lazy_object_get_info(obj);
 
 	/* prevent reentrant initialization */
@@ -440,6 +443,7 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 	zval zobj;
 	HashTable *named_params = NULL;
 	zend_fcall_info_cache *initializer = &info->u.initializer.fcc;
+	zend_object *instance = NULL;
 
 	ZVAL_OBJ(&zobj, obj);
 
@@ -447,7 +451,7 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 
 	if (UNEXPECTED(EG(exception))) {
 		OBJ_EXTRA_FLAGS(obj) |= IS_OBJ_LAZY_UNINITIALIZED|IS_OBJ_LAZY_PROXY;
-		return NULL;
+		goto exit;
 	}
 
 	if (UNEXPECTED(Z_TYPE(retval) != IS_OBJECT)) {
@@ -456,8 +460,7 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 				ZSTR_VAL(obj->ce->name),
 				zend_zval_value_name(&retval));
 		zval_ptr_dtor(&retval);
-		return NULL;
-
+		goto exit;
 	}
 
 	if (UNEXPECTED(Z_TYPE(retval) != IS_OBJECT || !zend_lazy_object_compatible(Z_OBJ(retval), obj))) {
@@ -466,14 +469,14 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 				zend_zval_value_name(&retval),
 				ZSTR_VAL(obj->ce->name));
 		zval_ptr_dtor(&retval);
-		return NULL;
+		goto exit;
 	}
 
 	if (UNEXPECTED(Z_OBJ(retval) == obj || zend_object_is_lazy(Z_OBJ(retval)))) {
 		OBJ_EXTRA_FLAGS(obj) |= IS_OBJ_LAZY_UNINITIALIZED|IS_OBJ_LAZY_PROXY;
 		zend_throw_error(NULL, "Lazy proxy factory must return a non-lazy object");
 		zval_ptr_dtor(&retval);
-		return NULL;
+		goto exit;
 	}
 
 	zend_fcc_dtor(&info->u.initializer.fcc);
@@ -495,7 +498,18 @@ static zend_object *zend_lazy_object_init_proxy(zend_object *obj)
 		}
 	}
 
-	return Z_OBJ(retval);
+	instance = Z_OBJ(retval);
+
+exit:
+	if (UNEXPECTED(GC_DELREF(obj) == 0)) {
+		zend_throw_error(NULL, "Lazy object was released during initialization");
+		zend_objects_store_del(obj);
+		instance = NULL;
+	} else {
+		gc_check_possible_root((zend_refcounted*) obj);
+	}
+
+	return instance;
 }
 
 /* Initialize a lazy object. */
@@ -529,6 +543,9 @@ ZEND_API zend_object *zend_lazy_object_init(zend_object *obj)
 		return zend_lazy_object_init_proxy(obj);
 	}
 
+	/* Prevent object from being released during initialization */
+	GC_ADDREF(obj);
+
 	zend_fcall_info_cache *initializer = zend_lazy_object_get_initializer_fcc(obj);
 
 	/* Prevent reentrant initialization */
@@ -562,6 +579,7 @@ ZEND_API zend_object *zend_lazy_object_init(zend_object *obj)
 	int argc = 1;
 	zval zobj;
 	HashTable *named_params = NULL;
+	zend_object *instance = NULL;
 
 	ZVAL_OBJ(&zobj, obj);
 
@@ -569,14 +587,14 @@ ZEND_API zend_object *zend_lazy_object_init(zend_object *obj)
 
 	if (EG(exception)) {
 		zend_lazy_object_revert_init(obj, properties_table_snapshot, properties_snapshot);
-		return NULL;
+		goto exit;
 	}
 
 	if (Z_TYPE(retval) != IS_NULL) {
 		zend_lazy_object_revert_init(obj, properties_table_snapshot, properties_snapshot);
 		zval_ptr_dtor(&retval);
 		zend_type_error("Lazy object initializer must return NULL or no value");
-		return NULL;
+		goto exit;
 	}
 
 	if (properties_table_snapshot) {
@@ -598,7 +616,18 @@ ZEND_API zend_object *zend_lazy_object_init(zend_object *obj)
 	 * zend_lazy_object_has_stale_info() check */
 	zend_lazy_object_del_info(obj);
 
-	return obj;
+	instance = obj;
+
+exit:
+	if (UNEXPECTED(GC_DELREF(obj) == 0)) {
+		zend_throw_error(NULL, "Lazy object was released during initialization");
+		zend_objects_store_del(obj);
+		instance = NULL;
+	} else {
+		gc_check_possible_root((zend_refcounted*) obj);
+	}
+
+	return instance;
 }
 
 /* Mark an object as non-lazy (after all properties were initialized) */

Zend/zend_object_handlers.c

@@ -1183,13 +1183,21 @@ write_std_property:
 exit:
 	return variable_ptr;
 
-lazy_init:
+lazy_init:;
+	/* backup value as it may change during initialization */
+	zval backup;
+	ZVAL_COPY(&backup, value);
+
 	zobj = zend_lazy_object_init(zobj);
 	if (UNEXPECTED(!zobj)) {
 		variable_ptr = &EG(error_zval);
+		zval_ptr_dtor(&backup);
 		goto exit;
 	}
-	return zend_std_write_property(zobj, name, value, cache_slot);
+
+	variable_ptr = zend_std_write_property(zobj, name, &backup, cache_slot);
+	zval_ptr_dtor(&backup);
+	return variable_ptr;
 }
 /* }}} */