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 normally. {mc} what does this mean? ~DS -> as long as the specification is followed. {mc}  Programmers often try to forcefully terminate threads when they believe that the task is accomplished, the request has been canceled or the program or JVM needs to quickly shut down. 

A few thread APIs were introduced to facilitate thread suspension, resumption and termination but were later deprecated because of inherent design weaknesses. The {{Thread.stop()}} method is one example. It causes the thread to immediately throw a {{ThreadDeath}} exception, which usually stops the thread. 

Invoking {{Thread.stop()}} results in the release of all the locks a thread has acquired which may corrupt the state of the object. The thread could catch the {{ThreadDeath}} exception and use a {{finally}} block in an attempt to repair the inconsistent object, however, this requires careful inspection of all the synchronized methods and blocks because a {{ThreadDeath}} exception can be thrown 

at any point during the 

thread's execution. Furthermore, code must be protected from {{ThreadDeath}} exceptions that may result when executing the {{catch}} or {{finally}} blocks \[[Sun 99|AA. Java References#Sun 99]\]

.

More information about 

deprecated methods is available in [MET15-J. Do not use deprecated or obsolete methods]. Also, refer to [EXC09-J. Prevent inadvertent calls to System.exit() or forced shutdown] for information on preventing data corruption when the JVM is abruptly shut down

.

     
h2. Noncompliant Code Example (Deprecated {{Thread.stop()}})

This noncompliant code example shows a thread that fills a vector with pseudorandom numbers. The thread is forcefully stopped after a given amount of time.

{code

:bgColor

=#FFcccc

}
public final class Container implements Runnable {
  private final Vector<Integer> vector = new Vector<Integer>(1000);

  public Vector<Integer> getVector() {
    return vector;
  }
  
  public synchronized void run() {
    Random number = new Random(123L);
    int i = vector.capacity();
    while (i > 0) {
      vector.add(number.nextInt(100));
      i--;
    }    
  }

  public static void main(String[] args) throws InterruptedException {
    Thread thread = new Thread(new Container());
    thread.start();
    Thread.sleep(5000);
    thread.stop();
  }
}
{code}

Because the class {{Vector}} is thread-safe, operations performed by multiple threads on its shared instance are expected to leave it in a consistent state. For instance, the {{Vector.size()}} method always returns the correct number of elements in the vector

 even in the face of concurrent changes to the vector.  This is because the vector instance uses its own intrinsic lock to prevent other threads from accessing it while its state is temporarily inconsistent. 

However, the {{Thread.stop()}} method causes the thread to stop what it is doing and throw a {{ThreadDeath}} exception. All acquired locks are subsequently released \[[API 06|AA. Java References#API 06]\]. If the thread is in the process of adding a new integer to the vector when it is stopped, the vector may become accessible while it is in an inconsistent state. For example, {{Vector.size()}} may return two even though the vector contains three elements (as the element count is incremented after adding the element).


h2.

 Compliant Solution ({{volatile}} flag)

This compliant solution uses a {{volatile}} flag to stop the thread. An accessor method {{shutdown()}} is used to set the flag to {{true}}. The thread's {{run()}} method polls the {{done}} flag, and terminates when it becomes {{true}}.

{code

:bgColor

=#ccccff

}
public final class Container implements Runnable {
  private final Vector<Integer> vector = new Vector<Integer>(1000);
  private volatile boolean done = false;
  
  public Vector<Integer> getVector() {
    return vector;
  }
  
  public void shutdown() {
    done = true;
  }

  public synchronized void run() {
    Random number = new Random(123L);
    int i = vector.capacity();
    while (!done && i > 0) {
      vector.add(number.nextInt(100));
      i--;
    }
  }

  public static void main(String[] args) throws InterruptedException {
    Container container = new Container();
    Thread thread = new Thread(container);
    thread.start();
    Thread.sleep(5000);
    container.shutdown();
  }
}

{code} 


h2. Compliant Solution (Interruptible)

This compliant solution stops the thread using the {{Thread.interrupt()}} method.

Upon receiving the interruption, the interrupted status of the thread is cleared and an {{InterruptedException}} is thrown. No guarantees are provided by the JVM on when the interruption will be detected by blocking methods such as {{Thread.sleep()}} and {{Object.wait()}}.  A thread may use interruption for performing tasks other than cancellation and shutdown. Consequently, a thread should not be interrupted unless its [interruption policy|BB. Definitions#interruption policy] is known in advance. Failure to follow this advice can result in failed interruption requests {mc} I don't think this is true ~DS -> the corruption of mutable shared state.

 {mc}


h2. Compliant Solution ({{RuntimePermission stopThread}})

Remove the default permission {{java.lang.RuntimePermission}} {{stopThread}} from the security policy file to deny the {{Thread.stop()}} invoking code, the required privileges

. 


h2. Risk Assessment

Forcing a thread to stop can result in inconsistent object state. Critical resources may also leak if clean-up operations are not carried out as required.

|| Rule || Severity || Likelihood || Remediation Cost || Priority || Level ||
| CON13- J | low | probable | medium | {color:green}{*}P4{*}{color} | {color:green}{*}L3{*}{color} |



h3. Automated Detection

TODO



h3. Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the [CERT website|https://www.kb.cert.org/vulnotes/bymetric?searchview&query=FIELD+KEYWORDS+contains+CON35-J].

h2. References

\[[API 06|AA. Java References#API 06]\] Class Thread, method {{stop}}, interface ExecutorService
\[[Sun 99|AA. Java References#Sun 99]\] 
\[[Darwin 04|AA. Java References#Darwin 04]\] 24.3 Stopping a Thread
\[[JDK7 08|AA. Java References#JDK7 08]\] Concurrency Utilities, More information: Java Thread Primitive Deprecation 
\[[JPL 06|AA. Java References#JPL 06]\] 14.12.1. Don't stop and 23.3.3. Shutdown Strategies
\[[JavaThreads 04|AA. Java References#JavaThreads 04]\] 2.4 Two Approaches to Stopping a Thread
\[[Goetz 06|AA. Java References#Goetz 06]\] Chapter 7: Cancellation and shutdown

----
[!The CERT Sun Microsystems Secure Coding Standard for Java^button_arrow_left.png!|CON12-J. Avoid deadlock by requesting and releasing locks in the same

 order]      [!The CERT Sun Microsystems Secure Coding Standard for Java^button_arrow_up.png!|11. Concurrency (CON)]      [!The CERT Sun Microsystems Secure Coding Standard for Java^button_arrow_right.png!|CON15-J. Ensure actively held locks are released on exceptional conditions]