standard: Fail unserialization when the C format is used for classes that are not Serializable

ext/standard/tests/serialize/serialization_objects_009.phpt

@@ -8,17 +8,16 @@ eval('class C {}');
 $b = unserialize($ser);
 
 var_dump($a, $b);
-
 echo "Done";
 ?>
 --EXPECTF--
-Warning: Class __PHP_Incomplete_Class has no unserializer in %sserialization_objects_009.php on line %d
+Warning: Class __PHP_Incomplete_Class has no unserializer in %s on line %d
+
+Warning: unserialize(): Error at offset 11 of 18 bytes in %s on line %d
+
+Warning: Class C has no unserializer in %s on line %d
 
-Warning: Class C has no unserializer in %sserialization_objects_009.php on line %d
-object(__PHP_Incomplete_Class)#%d (1) {
-  ["__PHP_Incomplete_Class_Name"]=>
-  string(1) "C"
-}
-object(C)#%d (0) {
-}
+Warning: unserialize(): Error at offset 11 of 18 bytes in %s on line %d
+bool(false)
+bool(false)
 Done

ext/standard/var_unserializer.re

@@ -770,7 +770,7 @@ static inline int object_custom(UNSERIALIZE_PARAMETER, zend_class_entry *ce)
 
 	if (ce->unserialize == NULL) {
 		zend_error(E_WARNING, "Class %s has no unserializer", ZSTR_VAL(ce->name));
-		object_init_ex(rval, ce);
+		return 0;
 	} else if (ce->unserialize(rval, ce, (const unsigned char*)*p, datalen, (zend_unserialize_data *)var_hash) != SUCCESS) {
 		return 0;
 	}

ext/uri/tests/gh22046.phpt

@@ -0,0 +1,19 @@
+--TEST--
+GH-22046: The unserialize function can lead to segfault when internal classes are serialized back with the unsupported C format
+--FILE--
+<?php
+
+$payload = 'C:14:"Uri\WhatWg\Url":0:{}';
+unserialize($payload);
+
+$payload = 'C:15:"Uri\Rfc3986\Uri":0:{}';
+unserialize($payload);
+?>
+--EXPECTF--
+Warning: Class Uri\WhatWg\Url has no unserializer in %s on line %d
+
+Warning: unserialize(): Error at offset 25 of 26 bytes in %s on line %d
+
+Warning: Class Uri\Rfc3986\Uri has no unserializer in %s on line %d
+
+Warning: unserialize(): Error at offset 26 of 27 bytes in %s on line %d