undefect. CWE-407 — 63 sites patched across 27 ecosystems

Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com

Patches, unit tests, benchmarks, whitepaper, and outreach briefs.
Public domain — no copyright claimed. Use freely.

test/hotspot/jtreg/runtime/Thread/ThreadCountLimit.java

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+/*
+ * Copyright (c) 2020, 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 Stress test that reaches the process limit for thread count, or time limit.
+ * @requires test.thread.factory == null
+ * @requires os.family != "aix"
+ * @key stress
+ * @library /test/lib
+ * @run main/othervm -Xmx1g ThreadCountLimit
+ */
+
+/**
+ * @test
+ * @summary Stress test that reaches the process limit for thread count, or time limit.
+ * @requires test.thread.factory == null
+ * @requires os.family == "aix"
+ * @key stress
+ * @library /test/lib
+ * @run main/othervm -Xmx1g -XX:MaxExpectedDataSegmentSize=16g ThreadCountLimit
+ */
+
+import java.util.concurrent.CountDownLatch;
+import java.util.ArrayList;
+
+import jdk.test.lib.Platform;
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+
+public class ThreadCountLimit {
+
+  static final int TIME_LIMIT_MS = 5000; // Create as many threads as possible in 5 sec
+
+  static class Worker extends Thread {
+    private final CountDownLatch startSignal;
+
+    Worker(CountDownLatch startSignal) {
+      this.startSignal = startSignal;
+    }
+
+    @Override
+    public void run() {
+      try {
+        startSignal.await();
+      } catch (InterruptedException e) {
+        throw new Error("Unexpected", e);
+      }
+    }
+  }
+
+  public static void main(String[] args) throws Exception {
+    if (args.length == 0) {
+      // Called from the driver process so exec a new JVM on Linux.
+      if (Platform.isLinux()) {
+        // On Linux this test sometimes hits the limit for the maximum number of memory mappings,
+        // which leads to various other failure modes. Run this test with a limit on how many
+        // threads the process is allowed to create, so we hit that limit first. What we want is
+        // for another "limit" processes to be available, but ulimit doesn't work that way and
+        // if there are already many running processes we could fail to even start the JVM properly.
+        // So we loop increasing the limit until we get a successful run. This is not foolproof.
+        int pLimit = 4096;
+        final String ULIMIT_CMD = "ulimit -u ";
+        ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(ThreadCountLimit.class.getName());
+        String javaCmd = ProcessTools.getCommandLine(pb);
+        for (int i = 1; i <= 10; i++) {
+            // Relaunch the test with args.length > 0, and the ulimit set
+            String cmd = ULIMIT_CMD + Integer.toString(pLimit * i) + " && " + javaCmd + " dummy";
+            System.out.println("Trying: bash -c " + cmd);
+            OutputAnalyzer oa = ProcessTools.executeCommand("bash", "-c", cmd);
+            int exitValue = oa.getExitValue();
+            switch (exitValue) {
+              case 0: System.out.println("Success!"); return;
+              case 1: System.out.println("Retry ..."); continue;
+              default: oa.shouldHaveExitValue(0); // generate error report
+            }
+        }
+        throw new Error("Failed to perform a successful run!");
+      } else {
+        // Not Linux so run directly.
+        test();
+      }
+    } else {
+      // This is the exec'd process so run directly.
+      test();
+    }
+  }
+
+  static void test() {
+    CountDownLatch startSignal = new CountDownLatch(1);
+    ArrayList<Worker> workers = new ArrayList<Worker>();
+
+    boolean reachedNativeOOM = false;
+
+    // This is dangerous loop: it depletes system resources,
+    // so doing additional things there that may end up allocating
+    // Java/native memory risks failing the VM prematurely.
+    // Avoid doing unnecessary calls, printouts, etc.
+
+    int count = 0;
+    long start = System.currentTimeMillis();
+    try {
+      while (true) {
+        Worker w = new Worker(startSignal);
+        w.start();
+        workers.add(w);
+        count++;
+
+        long end = System.currentTimeMillis();
+        if ((end - start) > TIME_LIMIT_MS) {
+          // Windows always gets here, but we also get here if
+          // ulimit is set high enough.
+          break;
+        }
+      }
+    } catch (OutOfMemoryError e) {
+      if (e.getMessage().contains("unable to create native thread")) {
+        // Linux, macOS path if we hit ulimit
+        reachedNativeOOM = true;
+      } else {
+        throw e;
+      }
+    }
+
+    startSignal.countDown();
+
+    try {
+      for (Worker w : workers) {
+        w.join();
+      }
+    } catch (InterruptedException e) {
+      throw new Error("Unexpected", e);
+    }
+
+    // Now that all threads have joined, we are away from dangerous
+    // VM state and have enough memory to perform any other things.
+    if (reachedNativeOOM) {
+      System.out.println("INFO: reached this process thread count limit with " +
+                         count + " threads created");
+    } else {
+      System.out.println("INFO: reached the time limit " + TIME_LIMIT_MS +
+                         " ms, with " + count + " threads created");
+    }
+  }
+}