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Also note that on the Windows platform, attempts to delete open files fail silently. See FIO34-J. Do not create temporary files in shared directories for more information.
Noncompliant Code Example
The problem of resource pool exhaustion is aggravated in the case of database connections. Traditionally, database servers allow a fixed number of connections, depending on configuration and licensing. Failing to release database connections can result in rapid exhaustion of available connections. This noncompliant code example does not close the connection if an error occurs while executing the statement or while processing the results.
| Code Block | ||
|---|---|---|
| ||
public void getResults(String sqlQuery) {
try {
Connection conn = getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sqlQuery);
processResults(rs);
stmt.close();
} catch (SQLException e) { /* forward to handler */ }
}
|
Noncompliant Code Example
While being slightly better than the previous noncompliant code example, this code is also noncompliant. Both rs and stmt might be null and the clean-up code in the finally block may result in a NullPointerException.
| Code Block | ||
|---|---|---|
| ||
Statement stmt = null;
ResultSet rs = null
Connection conn = getConnection(0;
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(sqlQuery);
processResults(rs);
} catch(SQLException e) {
// forward to handler
} finally {
rs.close();
stmt.close();
}
|
Noncompliant Code Example
Again, while being still better, this code snippet is still noncompliant. This is because rs.close() might itself result in a SQLException, and so stmt.close() will never be called.
| Code Block | ||
|---|---|---|
| ||
Statement stmt = null;
ResultSet rs = null;
Connection conn = getConnection();
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(sqlQuery);
processResults(rs);
} catch(SQLException e) {
// forward to handler
} finally {
if(rs != null) {
rs.close();
}
if(stmt != null) {
stmt.close();
}
}
|
Compliant Solution
This compliant solution ensures that resources are released as required.
| Code Block | ||
|---|---|---|
| ||
Statement stmt = null;
ResultSet rs = null;
Connection conn = getConnection();
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(sqlQuery);
processResults(rs);
} catch(SQLException e) {
// forward to handler
} finally {
try {
if(rs != null) {
rs.close();
}
} finally {
try {
if(stmt != null) {
stmt.close();
}
}
finally {
conn.close();
}
}
}
|
Noncompliant Code Example
This noncompliant code example opens a file, uses it, but does not explicitly close the handle.
| Code Block | ||
|---|---|---|
| ||
public int processFile(String fileName) throws IOException, FileNotFoundException {
FileInputStream stream = new FileInputStream(fileName);
BufferedReader bufRead = new BufferedReader(new InputStreamReader(stream));
String line;
while((line = bufRead.readLine()) != null) {
sendLine(line);
}
return 1;
}
|
Compliant Solution
This compliant solution releases all acquired resources, regardless of any exceptions that might occur. Even though bufRead might result in an exception, if a FileInputStream object is instantiated, it will be closed as required.
| Code Block | ||
|---|---|---|
| ||
FileInputStream stream = null;
BufferedReader bufRead = null;
String line;
try {
stream = new FileInputStream(fileName);
bufRead = new BufferedReader(new InputStreamReader(stream));
while((line = bufRead.readLine()) != null) {
sendLine(line);
}
} catch (IOException e) {
// forward to handler
} finally {
if(stream != null) {
stream.close();
}
}
|
Risk Assessment
Acquiring non-memory system resources and not releasing them explicitly may result in resource exhaustion.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
FIO32- 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 FIO42-C. Ensure files are properly closed when they are no longer needed.
This rule appears in the C++ Secure Coding Standard as FIO42-CPP. Ensure files are properly closed when they are no longer needed.
References
| Wiki Markup |
|---|
\[[API 06|AA. Java References#API 06]\] [Class Object| http://java.sun.com/javase/6/docs/api/java/lang/Object.html] \[[Goetz 06b|AA. Java References#Goetz 06b]\] \[[MITRE 09|AA. Java References#MITRE 09]\] [CWE ID 405|http://cwe.mitre.org/data/definitions/405.html] "Asymmetric Resource Consumption (Amplification)", [CWE ID 404|http://cwe.mitre.org/data/definitions/404.html] "Improper Resource Shutdown or Release", [CWE ID 459 |http://cwe.mitre.org/data/definitions/459.html] "Incomplete Cleanup" |
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