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https://issues.apache.org/jira/browse/WW-3576?focusedWorklogId=1048041&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-1048041
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ASF GitHub Bot logged work on WW-3576:
--------------------------------------
Author: ASF GitHub Bot
Created on: 17/Oct/26 15:29
Start Date: 17/Oct/26 15:29
Worklog Time Spent: 10m
Work Description: lukaszlenart commented on PR #1577:
URL: https://github.com/apache/struts/pull/1577#issuecomment-6235779480
Closing in favour of a redesigned fix. The NPE race is confirmed on current
main, but this approach changes the lock from the session id to the map
instance (dropping cross-request serialization) and swallows
IllegalStateException, which changes behaviour beyond the fix. A new PR for
WW-3576 will follow with a deterministic reproduction test.
Issue Time Tracking
-------------------
Worklog Id: (was: 1048041)
Time Spent: 1h (was: 50m)
> SessionMap is not thread-safe
> -----------------------------
>
> Key: WW-3576
> URL: https://issues.apache.org/jira/browse/WW-3576
> Project: Struts 2
> Issue Type: Bug
> Components: Other
> Affects Versions: 2.2.1
> Reporter: Sylvain Veyrié
> Assignee: Lukasz Lenart
> Priority: Major
> Fix For: 7.5.0
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> Searching for a bug after some stress test (Exception on "getAttribute":
> already invalidated session), I reviewed SessionMap.java.
> Following WW-239, SessionMap has been made thread-safe.
> All methods are like this :
> public void doSomething() {
> if (session == null) {
> return;
> }
>
> synchronized (session) {
> session.doSometing();
> }
> }
> For example:
> public void invalidate() {
> if (session == null) {
> return;
> }
>
> synchronized (session) {
> session.invalidate();
> session = null;
> entries = null;
> }
> }
> IMHO this is not thread-safe. With the example of invalidate(), if there is a
> context switch just before the synchronized, the nullity is no more checked.
> If another invalidate() is called at least a NPE can be thrown. There are
> probably other side-effects like my exception problem.
> As now Struts 2 only supports Java 5+, there is two ways to fix it :
> * use a double-check-locking (DCL) and set session "volatile" (easy way)
> * use java.util.concurrent instead of synchronized keyword
> If you agree and choose one of those fixes, I can provide a patch.
> For the moment, I don't know if my bug is resolved if we directly use javax
> session, without this wrapper.
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