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- A memory leak
- An infinite loop
- The program requires more memory than is present by default in the heap
- Incorrect implementation of common data structures (hash tables, vectors, etc.)
- Unbound deserialization
- Upon writing a large number of objects to an
ObjectOutputStream
Noncompliant Code Example (1)
This example places no upper bound on the memory space required due to which the program can easily exhaust the heap.
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| Code Block | ||
|---|---|---|
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public class ShowHeapError {
Vector<String> names = new Vector<String>();
String newName=null;
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(input);
public void addNames(){
do{
//Adding unknown number of records to a list
//the user can enter as much data as he wants and exhaust the heap
System.out.print(" To quit, enter \"quit\"\nEnter record: ");
try {
newName = reader.readLine();
if(!newName.equalsIgnoreCase("quit")){
//names are continued to be added without bothering about the size on the heap
names.addElement(newName);
}
} catch (IOException e) {
}
System.out.println(newName);
}while (!newName.equalsIgnoreCase("quit"));
}
public static void main(String[] args) {
ShowHeapError demo = new ShowHeapError();
demo.addNames();
}
}
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Compliant Solution (1)
If the objects or data structures are large enough to potentially cause heap exhaustion, the programmer must consider using databases instead, to ensure that records are written to the disk in a timely fashion. Hence, this structure will never outgrow the heap.
In the above example, the user can reuse a single long variable to store the input and write that value into a simple database containing a table User with a field userID along with any other required fields. This will prevent the heap from getting exhausted.
Noncompliant Code Example (2)
| Wiki Markup |
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In this example, the program needs more memory on the heap than is available by default. In a server-class machine running either VM (client or server) with a parallel garbage collector, the default initial and maximum heap sizes are as follows for J2SE 6.0 \[[Sun 06|AA. Java References#Sun 06]\]: |
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| Code Block | ||
|---|---|---|
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public class ShowHeapError {
/*Assuming the heap size as 512mB (calculated as 1/4th of 2 GB RAM = 512mB)
* Considering long values being entered (64 bits each, the max number of elements
* would be 5122mB/64bits = 67108864)
*/
Vector<Long> names = new Vector<Long>(67108865);
long newID=0L;
int count = 67108865;
int i = 0;
InputStreamReader input = new InputStreamReader(System.in);
Scanner reader = new Scanner(input);
public void addNames(){
do{
/* Adding unknown number of records to a list
* the user can enter more number of IDs than what the heap can support and
* exhaust the heap. Assume that the record ID is a 64 bit long value
*/
System.out.print(" To quit, enter -1\nEnter recordID: ");
newID = reader.nextLong();
//names are continued to be added without bothering about the size on the heap
names.addElement(newID);
System.out.println(newID);
i++;
}while (i<count || newID!=-1);
}
public static void main(String[] args) {
ShowHeapError demo = new ShowHeapError();
demo.addNames();
}
}
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Compliant Solution (2)
| Wiki Markup |
|---|
The {{OutOfMemoryError}} can be avoided by making sure that there are no infinite loops, memory leaks or unnecessary object retention. If memory requirements are known ahead of time, the heap size in Java can be tailored using the following runtime parameters \[[Java 06|AA. Java References#Java 06]\]: |
...
This setting can be done either in the Java Control Panel or on the command line. It cannot be adjusted through the application itself.
Noncompliant Code Example (2)
| Wiki Markup |
|---|
According to \[[API 06|AA. Java References#API 06]\], Class {{ObjectInputStream}} documentation: |
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| Code Block | ||
|---|---|---|
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FileOutputStream fos = new FileOutputStream("data.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(new Date());
// ...
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Compliant Solution (3)
If heap related issues arise, it is recommended that ObjectOutputStream.reset method be called so that references to previously written objects may be garbage collected.
| Code Block | ||
|---|---|---|
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FileOutputStream fos = new FileOutputStream("data.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(new Date());
oos.reset(); // Reset the Object-Handle table to its initial state
// ...
|
Risk Assessment
It is difficult to identify code that can lead to a heap exhaustion since static analysis tools are currently unable to pinpoint violations. The heap size may also differ in different machines.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
FIO07 FIO03-J | low | probable | medium | P4 | L3 |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website
Other Languages
This rule appears in the C Secure Coding Standard as MEM11-C. Do not assume infinite heap space.
This rule appears in the C++ Secure Coding Standard as MEM12-CPP. Do not assume infinite heap space.
References
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\[[Sun 06|AA. Java References#Sun 06]\] [Garbage Collection Ergonomics|http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html ], "Default values for the Initial and Maximum heap size" \[[Java 06|AA. Java References#Java 06]\] [java - the Java application launcher|http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html ], "Syntax for increasing the heap size" \[[Sun 03|AA. Java References#Sun 03]\] Chapter 5: Tuning the Java Runtime System, [Tuning the Java Heap|http://docs.sun.com/source/817-2180-10/pt_chap5.html#wp57027] \[[API 06|AA. Java References#API 06]\] Class ObjectInputStream and ObjectOutputStream \[[SDN 08|AA. Java References#SDN 08]\] [Serialization FAQ|http://java.sun.com/javase/technologies/core/basic/serializationFAQ.jsp] \[[MITRE 09|AA. Java References#MITRE 09]\] [CWE ID 400|http://cwe.mitre.org/data/definitions/400.html] "Uncontrolled Resource Consumption (aka 'Resource Exhaustion')" |
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