diff --git a/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java b/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
index 2d09c795743d1d6b9bd22c39a33d5a77099d0d42..0024f2fb5bfee18f5988de6dcc7a5273945ec5e4 100644
--- a/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
+++ b/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2010, 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
@@ -77,6 +77,8 @@ public class ClassReader implements Completer {
     protected static final Context.Key<ClassReader> classReaderKey =
         new Context.Key<ClassReader>();
 
+    public static final int INITIAL_BUFFER_SIZE = 0x0fff0;
+
     Annotate annotate;
 
     /** Switch: verbose output.
@@ -185,7 +187,7 @@ public class ClassReader implements Completer {
 
     /** The buffer containing the currently read class file.
      */
-    byte[] buf = new byte[0x0fff0];
+    byte[] buf = new byte[INITIAL_BUFFER_SIZE];
 
     /** The current input pointer.
      */
@@ -2419,8 +2421,14 @@ public class ClassReader implements Completer {
                 }
             }
         }
+        /*
+         * ensureCapacity will increase the buffer as needed, taking note that
+         * the new buffer will always be greater than the needed and never
+         * exactly equal to the needed size or bp. If equal then the read (above)
+         * will infinitely loop as buf.length - bp == 0.
+         */
         private static byte[] ensureCapacity(byte[] buf, int needed) {
-            if (buf.length < needed) {
+            if (buf.length <= needed) {
                 byte[] old = buf;
                 buf = new byte[Integer.highestOneBit(needed) << 1];
                 System.arraycopy(old, 0, buf, 0, old.length);
diff --git a/test/tools/javac/6567415/T6567415.java b/test/tools/javac/6567415/T6567415.java
new file mode 100644
index 0000000000000000000000000000000000000000..683197e6e84f0e62c901bd8481c2c95c04509811
--- /dev/null
+++ b/test/tools/javac/6567415/T6567415.java
@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 2010, 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
+ * @bug 6567415
+ * @summary Test to ensure javac does not go into an infinite loop, while
+ *               reading a classfile of a specific length.
+ * @compile -XDignore.symbol.file T6567415.java
+ * @run main T6567415
+ * @author ksrini
+ */
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+
+/*
+ * this test compiles Bar.java into a classfile and enlarges the file to the
+ * magic file length, then use this mutated file on the classpath to compile
+ * Foo.java which references Bar.java and Ka-boom. QED.
+ */
+public class T6567415 {
+    final static String TEST_FILE_NAME = "Bar";
+    final static String TEST_JAVA = TEST_FILE_NAME + ".java";
+    final static String TEST_CLASS = TEST_FILE_NAME + ".class";
+
+    final static String TEST2_FILE_NAME = "Foo";
+    final static String TEST2_JAVA = TEST2_FILE_NAME + ".java";
+
+    /*
+     * the following is the initial buffer length set in ClassReader.java
+     * thus this value needs to change if ClassReader buf length changes.
+     */
+
+    final static int BAD_FILE_LENGTH =
+            com.sun.tools.javac.jvm.ClassReader.INITIAL_BUFFER_SIZE;
+
+    static void createClassFile() throws IOException {
+        FileOutputStream fos = null;
+        try {
+            fos = new FileOutputStream(TEST_JAVA);
+            PrintStream ps = new PrintStream(fos);
+            ps.println("public class " + TEST_FILE_NAME + " {}");
+        } finally {
+            fos.close();
+        }
+        String cmds[] = {TEST_JAVA};
+        com.sun.tools.javac.Main.compile(cmds);
+    }
+
+    static void enlargeClassFile() throws IOException {
+        File f = new File(TEST_CLASS);
+        if (!f.exists()) {
+            System.out.println("file not found: " + TEST_CLASS);
+            System.exit(1);
+        }
+        File tfile = new File(f.getAbsolutePath() + ".tmp");
+        f.renameTo(tfile);
+
+        RandomAccessFile raf = null;
+        FileChannel wfc = null;
+
+        FileInputStream fis = null;
+        FileChannel rfc = null;
+
+        try {
+            raf =  new RandomAccessFile(f, "rw");
+            wfc = raf.getChannel();
+
+            fis = new FileInputStream(tfile);
+            rfc = fis.getChannel();
+
+            ByteBuffer bb = MappedByteBuffer.allocate(BAD_FILE_LENGTH);
+            rfc.read(bb);
+            bb.rewind();
+            wfc.write(bb);
+            wfc.truncate(BAD_FILE_LENGTH);
+        } finally {
+            wfc.close();
+            raf.close();
+            rfc.close();
+            fis.close();
+        }
+        System.out.println("file length = " + f.length());
+    }
+
+    static void createJavaFile() throws IOException {
+        FileOutputStream fos = null;
+        try {
+            fos = new FileOutputStream(TEST2_JAVA);
+            PrintStream ps = new PrintStream(fos);
+            ps.println("public class " + TEST2_FILE_NAME +
+                    " {" + TEST_FILE_NAME + " b = new " +
+                    TEST_FILE_NAME  + " ();}");
+        } finally {
+            fos.close();
+        }
+    }
+
+    public static void main(String... args) throws Exception {
+        createClassFile();
+        enlargeClassFile();
+        createJavaFile();
+        Thread t = new Thread () {
+            @Override
+            public void run() {
+                String cmds[] = {"-verbose", "-cp", ".", TEST2_JAVA};
+                int ret = com.sun.tools.javac.Main.compile(cmds);
+                System.out.println("test compilation returns: " + ret);
+            }
+        };
+        t.start();
+        t.join(1000*10);
+        System.out.println(t.getState());
+        if (t.isAlive()) {
+            throw new RuntimeException("Error: compilation is looping");
+        }
+    }
+}