Kenny MacLeod created LOG4J2-1893:
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Summary: JdkMapAdapterStringMap#toMap can return an immutable map
Key: LOG4J2-1893
URL: https://issues.apache.org/jira/browse/LOG4J2-1893
Project: Log4j 2
Issue Type: Bug
Components: Core
Affects Versions: 2.8.2
Reporter: Kenny MacLeod
Priority: Minor
The Javadoc for {{ReadOnlyStringMap#toMap}} states that
bq. Returns a non-null mutable Map<String, String> containing a snapshot of
this data structure
In the case of {{JdkMapAdapterStringMap}}, the {{toMap}} method just returns
whatever map was passed in to its constructor, so there's no guarantee of its
mutability. In fact, {{ThreadContextDataInjector#injectContextData}} creates a
{{JdkMapAdapterStringMap}} explicitly with an immutable map.
The obvious fix is for {{JdkMapAdapterStringMap}} to clone the map before
returning it from {{toMap}}, which not only guarantees the method constract is
fulfilled, but also protects the internals of {{JdkMapAdapterStringMap}} from
inadvertent modification by whoever calls {{toMap}}.
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