[DBCP-476] AbandonedTrace.getTrace() contains race condition

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.3.0
• Assignee: Pascal Schumacher
• Reporter: Richard Cordova
• Created: 26/Apr/17 05:51
• Updated: 07/May/18 18:46
• Resolved: 07/May/18 18:46

Description

The clean up code in AbandonedTrace is subject to the reference being cleared in between the condition being checked and the referent being added to the result.

            while (iter.hasNext()) {
                WeakReference<AbandonedTrace> ref = iter.next();
                if (ref.get() == null) {
                    // Clean-up since we are here anyway
                    iter.remove();
                } else {
                    result.add(ref.get());
                }
            }

This can surface as a NullPointerException, e.g.

Caused by: java.lang.NullPointerException
	at org.apache.tomcat.dbcp.dbcp2.DelegatingStatement.close(DelegatingStatement.java:149)