Fix assign-op/inc/dec on untyped hooked property backing value

Fixes OSS-Fuzz #478009707
Closes phpGH-21124

Author: iluuu1994

NEWS

@@ -8,6 +8,8 @@ PHP                                                                        NEWS
     by setRawValueWithoutLazyInitialization() and newLazyGhost()). (Arnaud)
   . Fixed bug GH-20504 (Assertion failure in zend_get_property_guard when
     accessing properties on Reflection LazyProxy via isset()). (Arnaud)
+  . Fixed OSS-Fuzz #478009707 (Borked assign-op/inc/dec on untyped hooked
+    property backing value). (ilutov)
 
 - Curl:
   . Fixed bug GH-21023 (CURLOPT_XFERINFOFUNCTION crash with a null callback).

Zend/tests/oss-fuzz-478009707.phpt

@@ -0,0 +1,23 @@
+--TEST--
+OSS-Fuzz #478009707: Assign-op/inc/dec on untyped hooked property backing value
+--FILE--
+<?php
+
+class C {
+    public $prop {
+        set {
+            $this->prop = $value;
+            $this->prop += 1;
+            $this->prop++;
+            ++$this->prop;
+        }
+    }
+}
+
+$c = new C(1);
+$c->prop = 1;
+var_dump($c->prop);
+
+?>
+--EXPECT--
+int(4)

Zend/zend_vm_def.h

@@ -1070,7 +1070,7 @@ ZEND_VM_C_LABEL(assign_op_object):
 					}
 
 					prop_info = (zend_property_info*)CACHED_PTR_EX(cache_slot + 2);
-					if (prop_info) {
+					if (prop_info && ZEND_TYPE_IS_SET(prop_info->type)) {
 						/* special case for typed properties */
 						zend_binary_assign_op_typed_prop(prop_info, zptr, value OPLINE_CC EXECUTE_DATA_CC);
 					} else {
@@ -1326,7 +1326,8 @@ ZEND_VM_C_LABEL(pre_incdec_object):
 				}
 			} else {
 				prop_info = (zend_property_info *) CACHED_PTR_EX(cache_slot + 2);
-				zend_pre_incdec_property_zval(zptr, prop_info OPLINE_CC EXECUTE_DATA_CC);
+				zend_pre_incdec_property_zval(zptr,
+					prop_info && ZEND_TYPE_IS_SET(prop_info->type) ? prop_info : NULL OPLINE_CC EXECUTE_DATA_CC);
 			}
 		} else {
 			zend_pre_incdec_overloaded_property(zobj, name, cache_slot OPLINE_CC EXECUTE_DATA_CC);
@@ -1394,7 +1395,8 @@ ZEND_VM_C_LABEL(post_incdec_object):
 				ZVAL_NULL(EX_VAR(opline->result.var));
 			} else {
 				prop_info = (zend_property_info*)CACHED_PTR_EX(cache_slot + 2);
-				zend_post_incdec_property_zval(zptr, prop_info OPLINE_CC EXECUTE_DATA_CC);
+				zend_post_incdec_property_zval(zptr,
+					prop_info && ZEND_TYPE_IS_SET(prop_info->type) ? prop_info : NULL OPLINE_CC EXECUTE_DATA_CC);
 			}
 		} else {
 			zend_post_incdec_overloaded_property(zobj, name, cache_slot OPLINE_CC EXECUTE_DATA_CC);