From 7212e02a9b4eb02759f7b2195187a6e6db6bfb33 Mon Sep 17 00:00:00 2001
From: Johannes Dahlström <johannesd@vaadin.com>
Date: Mon, 5 Aug 2013 15:47:16 +0300
Subject: Fix race in VaadinService.lockSession() (#12282)

The session might be invalidated before lockSession() acquires the lock.
Check if the session is still valid after locking and ensure
SessionExpiredException is thrown if not.

Change-Id: Iad716332a65b7c198427fce5198f6808140c140c
---
 server/src/com/vaadin/server/VaadinService.java | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/server/src/com/vaadin/server/VaadinService.java b/server/src/com/vaadin/server/VaadinService.java
index 17bce7ad15..c9a5f0974a 100644
--- a/server/src/com/vaadin/server/VaadinService.java
+++ b/server/src/com/vaadin/server/VaadinService.java
@@ -564,6 +564,9 @@ public abstract class VaadinService implements Serializable {
      * 
      * @param wrappedSession
      *            The session to lock
+     * 
+     * @throws IllegalStateException
+     *             if the session is invalidated before it can be locked
      */
     protected void lockSession(WrappedSession wrappedSession) {
         Lock lock = getSessionLock(wrappedSession);
@@ -584,6 +587,17 @@ public abstract class VaadinService implements Serializable {
             }
         }
         lock.lock();
+
+        try {
+            // Someone might have invalidated the session between fetching the
+            // lock and acquiring it. Guard for this by calling a method that's
+            // specified to throw IllegalStateException if invalidated
+            // (#12282)
+            wrappedSession.getAttribute(getLockAttributeName());
+        } catch (IllegalStateException e) {
+            lock.unlock();
+            throw e;
+        }
     }
 
     /**
@@ -607,7 +621,12 @@ public abstract class VaadinService implements Serializable {
         WrappedSession wrappedSession = getWrappedSession(request,
                 requestCanCreateSession);
 
-        lockSession(wrappedSession);
+        try {
+            lockSession(wrappedSession);
+        } catch (IllegalStateException e) {
+            throw new SessionExpiredException();
+        }
+
         try {
             return doFindOrCreateVaadinSession(request, requestCanCreateSession);
         } finally {
-- 
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