8359472: JVM crashes when attaching a dynamic agent before JVMTI_PHASE_LIVE

src/hotspot/share/prims/jvmtiAgentList.cpp

@@ -200,6 +200,11 @@ void JvmtiAgentList::load_xrun_agents() {
 // Invokes Agent_OnAttach for agents loaded dynamically during runtime.
 void JvmtiAgentList::load_agent(const char* agent_name, bool is_absolute_path,
                                 const char* options, outputStream* st) {
+  if (JvmtiEnvBase::get_phase() != JVMTI_PHASE_LIVE) {
+    st->print_cr("Dynamic agent loading is only permitted in the live phase");
+    return;
+  }
+
   JvmtiAgent* const agent = new JvmtiAgent(agent_name, options, is_absolute_path, /* dynamic agent */ true);
   if (agent->load(st)) {
     add(agent);

test/hotspot/jtreg/serviceability/attach/EarlyDynamicLoad/EarlyDynamicLoad.java

@@ -0,0 +1,103 @@
+/*
+ * 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.
+ */
+
+import com.sun.tools.attach.VirtualMachine;
+import com.sun.tools.attach.AgentLoadException;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.AfterAll;
+
+import java.io.File;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.TimeUnit;
+import jdk.test.lib.dcmd.PidJcmdExecutor;
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.Utils;
+
+/*
+ * @test EarlyDynamicLoad
+ * @summary Test that dynamic attach fails gracefully when the JVM is not in live phase.
+ * @requires vm.jvmti
+ * @library /test/lib
+ * @run junit EarlyDynamicLoad
+ */
+public class EarlyDynamicLoad {
+    private static final String EXPECTED_MESSAGE = "Dynamic agent loading is only permitted in the live phase";
+
+    private static Process child;
+
+    @BeforeAll
+    static void startAndWaitChild() throws Exception {
+        child = ProcessTools.createTestJavaProcessBuilder(
+                        "-XX:+StartAttachListener",
+                        "-agentpath:" + Utils.TEST_NATIVE_PATH + File.separator + System.mapLibraryName("EarlyDynamicLoad"),
+                        "--version").start();
+
+        // Wait until the process enters VMStartCallback
+        try (InputStream is = child.getInputStream()) {
+            is.read();
+        }
+    }
+
+    @AfterAll
+    static void stopChild() throws Exception {
+        try (OutputStream os = child.getOutputStream()) {
+            os.write(0);
+        }
+
+        if (!child.waitFor(5, TimeUnit.SECONDS)) {
+            child.destroyForcibly();
+            throw new AssertionError("Timed out while waiting child process to complete");
+        }
+
+        OutputAnalyzer analyzer = new OutputAnalyzer(child);
+        analyzer.shouldHaveExitValue(0);
+        analyzer.stderrShouldBeEmpty();
+    }
+
+    @Test
+    public void virtualMachine() throws Exception {
+        try {
+            VirtualMachine vm = VirtualMachine.attach(String.valueOf(child.pid()));
+            vm.loadAgent("some.jar");
+            vm.detach();
+            throw new AssertionError("Should have failed with AgentLoadException");
+        } catch(AgentLoadException exception) {
+            if (!exception.getMessage().contains(EXPECTED_MESSAGE)) {
+                throw new AssertionError("Unexpected error message", exception);
+            }
+        }
+    }
+
+    @Test
+    public void jcmd() throws Exception {
+        PidJcmdExecutor executor = new PidJcmdExecutor(String.valueOf(child.pid()));
+        OutputAnalyzer out = executor.execute("JVMTI.agent_load some.jar");
+
+        out.shouldHaveExitValue(0);
+        out.stdoutShouldContain(EXPECTED_MESSAGE);
+    }
+}

test/hotspot/jtreg/serviceability/attach/EarlyDynamicLoad/libEarlyDynamicLoad.cpp

@@ -0,0 +1,59 @@
+/*
+ * 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.
+ */
+
+#include <jvmti.h>
+#include <cstdio>
+#include <cstring>
+
+extern "C" {
+
+static void JNICALL VMStartCallback(jvmtiEnv* jvmti, JNIEnv* env) {
+  putchar('1');
+  fflush(stdout);
+  getchar();
+}
+
+JNIEXPORT int Agent_OnLoad(JavaVM* vm, char* options, void* reserved) {
+  jvmtiEnv* jvmti;
+  if (vm->GetEnv((void**) &jvmti, JVMTI_VERSION_1_0) != JVMTI_ERROR_NONE) {
+    fprintf(stderr, "JVMTI error occurred during GetEnv\n");
+    return JNI_ERR;
+  }
+
+  jvmtiEventCallbacks callbacks;
+  memset(&callbacks, 0, sizeof(callbacks));
+  callbacks.VMStart = VMStartCallback;
+
+  if (jvmti->SetEventCallbacks(&callbacks, sizeof(callbacks)) != JVMTI_ERROR_NONE) {
+    fprintf(stderr, "JVMTI error occurred during SetEventCallbacks\n");
+    return JNI_ERR;
+  }
+  if (jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_START, nullptr) != JVMTI_ERROR_NONE) {
+    fprintf(stderr, "JVMTI error occurred during SetEventNotificationMode\n");
+    return JNI_ERR;
+  }
+
+  return JNI_OK;
+}
+
+}