https://bz.apache.org/bugzilla/show_bug.cgi?id=66325
Bug ID: 66325
Summary: NestedState concurrency issue
Product: Tomcat 8
Version: 8.5.69
Hardware: Other
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: EL
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ----
We faced a jsp exception because the nestedState object is not properly
synchronized. Even though the line triggering the exception is commented with
"Should never happen", it happened to us making the page break.
The lines involved are:
<c:set var="aName">
<c:out value="${someVariable.stream().filter(i -> i.getEvent() ==
'a-value').map(e -> e.getAsJson()).findFirst().orElse('')}" />
</c:set>
The error is:
SEVERE: Servlet.service() for servlet [bestsecret] in context with path []
threw exception [An exception occurred processing [/...] at line ...
...
java.lang.IllegalStateException: Nested state may only be set once
at
org.apache.el.parser.AstLambdaExpression.setNestedState(AstLambdaExpression.java:123)
at
org.apache.el.parser.AstLambdaExpression.getNestedState(AstLambdaExpression.java:114)
at
org.apache.el.parser.AstLambdaExpression.getValue(AstLambdaExpression.java:43)
at
org.apache.el.parser.AstMethodParameters.getParameters(AstMethodParameters.java:33)
at org.apache.el.parser.AstValue.getValue(AstValue.java:157)
at
org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:189)
Lines with the issue:
https://github.com/apache/tomcat/blob/main/java/org/apache/el/parser/AstLambdaExpression.java#L112-L124
The issue IMO is that between the check at line 113 and the check at line 121,
the nestedState is set, so the execution enters in the if triggering the
unexpected exception, breaking the whole JSP page. The blocks should be
synchronized on the object or any other measure taken.
Please fix it as you consider the better.
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