github / github/codeql

False Negative: CloseSql.ql misses leaked JDBC resources once the allocation site is split across helper calls or `getResultSet()`.

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Description

Version
codeql 2.24.3

## Checker
- Checker id: `Likely Bugs/Resource Leaks/CloseSql.ql`
- Checker description: This checker detects SQL resource objects (Connection, Statement, ResultSet) that are initialized locally and not guaranteed to be closed on method exit.

## Description of the false negative
These cases still leak JDBC resources. One is the simplest possible leaked `Connection`. The other two leak `ResultSet` instances that come from a `Statement` parameter and are never closed before the method returns.

What changes between the samples is only how the resource is obtained: directly, through a helper method, or through `Statement.getResultSet()` after `execute(...)`.

## Affected test cases
### `PosCase1.java`
The method opens a `Connection` and exits without closing it. This should be a baseline match for the rule.

### `PosCase6_Var3.java`
The `ResultSet` comes back from a helper, but it still originates from the passed-in `Statement` and still leaks.

### `PosCase6_Var4.java`
The `ResultSet` is retrieved through `stmt.getResultSet()` after `execute(...)`. That is still a live SQL resource that needs to be closed.

## Reproduction code
### `PosCase1.java`
```java
// Scenario 1: A java.sql.Connection is locally initialized, not assigned, not passed to a local constructor, has no parent, and is not closed.
package scensct.core.pos;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class PosCase1 {
public void test() throws SQLException {
// Locally initialized Connection, assigned to a variable but not closed.
Connection conn = DriverManager.getConnection("jdbc:example:db");
// No close() call before method exit.
}
}
```

### `PosCase6_Var3.java`
```java
// Scenario 6: A java.sql.ResultSet is locally initialized as a child of a non-locally-initialized Statement parameter, used directly, and not closed.
package scensct.var.pos;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class PosCase6_Var3 {
public void test(Statement stmt) throws SQLException {
ResultSet rs = fetchResult(stmt);
// rs not closed
}

private ResultSet fetchResult(Statement s) throws SQLException {
return s.executeQuery("SELECT 1");
}
}
```

### `PosCase6_Var4.java`
```java
// Scenario 6: A java.sql.ResultSet is locally initialized as a child of a non-locally-initialized Statement parameter, used directly, and not closed.
package scensct.var.pos;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class PosCase6_Var4 {
public void test(Statement stmt) throws SQLException {
boolean hasResults = stmt.execute("SELECT 1");
if (hasResults) {
ResultSet rs = stmt.getResultSet();
// rs not closed
}
}
}
```

## Cause analysis
`Likely Bugs/Resource Leaks/CloseSql.ql` appears to be tied too closely to one acquisition shape. It handles some direct JDBC constructions, but coverage gets weaker once the returned resource is produced through a helper or through a second-stage API like `getResultSet()`.

That leaves a real blind spot. In production JDBC code, `ResultSet` objects are often obtained indirectly rather than from a single inline `executeQuery(...)` call. The leak is still the same: the method owns a SQL resource and does not close it.

Contributor guide

Open the contributing guide

Research direction

Start with Likely Bugs/Resource Leaks/CloseSql.ql and compare its acquisition handling with the affected PosCase1.java, PosCase6_Var3.java, and PosCase6_Var4.java examples. Verify the checker reports the leaked Connection and both indirectly obtained ResultSet instances, while preserving existing coverage.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
devtools, security
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
50/100

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