Race condition within a thread

Overview
If two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined.

Consequences

 * Integrity: The main problem is that - if a lock is overcome - data could be altered in a bad state.

Exposure period

 * Design: Use a language which provides facilities to easily use threads safely.

Platform

 * Languages: Any language with threads


 * Operating platforms: All

Required resources
Any

Severity
High

Likelihood of exploit
Medium

Discussion

 * Design: Use locking functionality. This is the recommended solution. Implement some form of locking mechanism around code which alters or reads persistent data in a multi-threaded environment.


 * Design: Create resource-locking sanity checks. If no inherent locking mechanisms exist, use flags and signals to enforce your own blocking scheme when resources are being used by other threads of execution.

Examples
In C/C++:

int foo = 0; int storenum(int num) {       static int counter = 0; counter++; if (num > foo) foo = num; return foo; }

In Java:

public classRace { static int foo = 0;

public static void main { new Threader.start; foo = 1; }

public static class Threader extends Thread { public void run { System.out.println(foo); } } }

Related problems
Not available.