8014477: (str) Race condition in String.contentEquals when comparing with StringBuffer
Reviewed-by: alanb, mduigou, dholmes
--- a/jdk/src/share/classes/java/lang/String.java Sat May 18 18:55:56 2013 -0700
+++ b/jdk/src/share/classes/java/lang/String.java Fri May 17 14:41:39 2013 +0200
@@ -1010,13 +1010,14 @@
private boolean nonSyncContentEquals(AbstractStringBuilder sb) {
char v1[] = value;
char v2[] = sb.getValue();
- int i = 0;
- int n = value.length;
- while (n-- != 0) {
+ int n = v1.length;
+ if (n != sb.length()) {
+ return false;
+ }
+ for (int i = 0; i < n; i++) {
if (v1[i] != v2[i]) {
return false;
}
- i++;
}
return true;
}
@@ -1038,8 +1039,6 @@
* @since 1.5
*/
public boolean contentEquals(CharSequence cs) {
- if (value.length != cs.length())
- return false;
// Argument is a StringBuffer, StringBuilder
if (cs instanceof AbstractStringBuilder) {
if (cs instanceof StringBuffer) {
@@ -1055,12 +1054,14 @@
return true;
// Argument is a generic CharSequence
char v1[] = value;
- int i = 0;
- int n = value.length;
- while (n-- != 0) {
- if (v1[i] != cs.charAt(i))
+ int n = v1.length;
+ if (n != cs.length()) {
+ return false;
+ }
+ for (int i = 0; i < n; i++) {
+ if (v1[i] != cs.charAt(i)) {
return false;
- i++;
+ }
}
return true;
}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/lang/String/StringContentEqualsBug.java Fri May 17 14:41:39 2013 +0200
@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2013, 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 8014477
+ * @summary test String.contentEquals(StringBuffer)
+ */
+public class StringContentEqualsBug {
+
+ static abstract class Task extends Thread {
+ volatile StringBuffer sb;
+ volatile Exception exception;
+
+ Task(StringBuffer sb) {
+ this.sb = sb;
+ }
+
+ @Override
+ public void run() {
+ try {
+ StringBuffer sb;
+ while ((sb = this.sb) != null) {
+ doWith(sb);
+ }
+ }
+ catch (Exception e) {
+ exception = e;
+ }
+ }
+
+ protected abstract void doWith(StringBuffer sb);
+ }
+
+ static class Tester extends Task {
+ Tester(StringBuffer sb) {
+ super(sb);
+ }
+
+ @Override
+ protected void doWith(StringBuffer sb) {
+ "AA".contentEquals(sb);
+ }
+ }
+
+ static class Disturber extends Task {
+ Disturber(StringBuffer sb) {
+ super(sb);
+ }
+
+ @Override
+ protected void doWith(StringBuffer sb) {
+ sb.setLength(0);
+ sb.trimToSize();
+ sb.append("AA");
+ }
+ }
+
+
+ public static void main(String[] args) throws Exception {
+ StringBuffer sb = new StringBuffer();
+ Task[] tasks = new Task[3];
+ (tasks[0] = new Tester(sb)).start();
+ for (int i = 1; i < tasks.length; i++) {
+ (tasks[i] = new Disturber(sb)).start();
+ }
+
+ try
+ {
+ // wait at most 5 seconds for any of the threads to throw exception
+ for (int i = 0; i < 20; i++) {
+ for (Task task : tasks) {
+ if (task.exception != null) {
+ throw task.exception;
+ }
+ }
+ Thread.sleep(250L);
+ }
+ }
+ finally {
+ for (Task task : tasks) {
+ task.sb = null;
+ task.join();
+ }
+ }
+ }
+}