From 6f452ac46f17b89f8a9f661ffc8fadc663ae124e Mon Sep 17 00:00:00 2001
From: Coleen Phillimore <coleenp@openjdk.org>
Date: Mon, 3 Nov 2025 12:37:00 +0000
Subject: [PATCH] 8364360: Defining hidden class with no room in constant pool
 crashes the VM

Reviewed-by: matsaave, liach, dholmes
---
 .../share/classfile/classFileParser.cpp       |  1 +
 .../runtime/ClassFile/HiddenClassesTest.java  | 63 +++++++++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 test/hotspot/jtreg/runtime/ClassFile/HiddenClassesTest.java

diff --git a/src/hotspot/share/classfile/classFileParser.cpp b/src/hotspot/share/classfile/classFileParser.cpp
index 87f2da91288..eb8a2a389b9 100644
--- a/src/hotspot/share/classfile/classFileParser.cpp
+++ b/src/hotspot/share/classfile/classFileParser.cpp
@@ -5523,6 +5523,7 @@ void ClassFileParser::parse_stream(const ClassFileStream* const stream,
 
   _orig_cp_size = cp_size;
   if (is_hidden()) { // Add a slot for hidden class name.
+    guarantee_property((u4)cp_size < 0xffff, "Overflow in constant pool size for hidden class %s", CHECK);
     cp_size++;
   }
 
diff --git a/test/hotspot/jtreg/runtime/ClassFile/HiddenClassesTest.java b/test/hotspot/jtreg/runtime/ClassFile/HiddenClassesTest.java
new file mode 100644
index 00000000000..0c67ce829ae
--- /dev/null
+++ b/test/hotspot/jtreg/runtime/ClassFile/HiddenClassesTest.java
@@ -0,0 +1,63 @@
+/*
+* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+*
+* This code is free software; you can redistribute it and/or modify it
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+* or visit www.oracle.com if you need additional information or have any
+* questions.
+*/
+
+/*
+ * @test
+ * @summary Test that parsing a hidden class with max constant pool entries
+ *          doesn't crash the VM when adding an entry for the hidden class name.
+ *          Instead throws ClassFormatError.
+ * @bug 8364360
+ * @modules java.base/jdk.internal.access
+ *          java.base/jdk.internal.reflect
+ * @library /testlibrary/asm
+ * @run main HiddenClassesTest
+ */
+
+import java.lang.invoke.MethodHandles;
+
+import org.objectweb.asm.ClassWriter;
+import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
+import static org.objectweb.asm.Opcodes.V17;
+
+public class HiddenClassesTest {
+
+    public static void main(String[] args) throws Exception {
+        var cw = new ClassWriter(0);
+        cw.visit(V17, ACC_PUBLIC, "Hidden", null, "java/lang/Object", null);
+        // This magic number causes a constant pool index overflow with this asm generated class.
+        int i = 0;
+        while (i < 65535-1) {
+            i = cw.newUTF8(Integer.toString(i));
+        }
+        try {
+            MethodHandles.lookup().defineHiddenClass(cw.toByteArray(), false);
+            throw new RuntimeException("Test Failed: ClassFormatError expected.");
+        } catch (ClassFormatError cfe) {
+            String message = cfe.getMessage();
+            if (message == null || !message.contains("Overflow in constant pool size for hidden class")) {
+                throw new RuntimeException("Test Failed: wrong ClassFormatError " + message);
+            }
+            System.out.println("ClassFormatError thrown as expected. Message: " + cfe.getMessage());
+        }
+    }
+}