[Backport 2.x] Fix a race condition in Derived Field parsing from search request

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Remote Store] Rate limiter for remote store low priority uploads ([#14374](https://github.com/opensearch-project/OpenSearch/pull/14374/))
 - Apply the date histogram rewrite optimization to range aggregation ([#13865](https://github.com/opensearch-project/OpenSearch/pull/13865))
 - [Writable Warm] Add composite directory implementation and integrate it with FileCache ([12782](https://github.com/opensearch-project/OpenSearch/pull/12782))
+- Fix race condition while parsing derived fields from search definition ([14445](https://github.com/opensearch-project/OpenSearch/pull/14445))
 
 ### Dependencies
 - Update to Apache Lucene 9.11.0 ([#14042](https://github.com/opensearch-project/OpenSearch/pull/14042))

server/src/main/java/org/opensearch/index/mapper/DefaultDerivedFieldResolver.java

@@ -15,6 +15,8 @@
 import org.opensearch.script.Script;
 
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -189,9 +191,10 @@ private void initDerivedFieldTypes(Map<String, Object> derivedFieldsObject, List
 
     private Map<String, DerivedFieldType> getAllDerivedFieldTypeFromObject(Map<String, Object> derivedFieldObject) {
         Map<String, DerivedFieldType> derivedFieldTypes = new HashMap<>();
+        // deep copy of derivedFieldObject is required as DocumentMapperParser modifies the map
         DocumentMapper documentMapper = queryShardContext.getMapperService()
             .documentMapperParser()
-            .parse(DerivedFieldMapper.CONTENT_TYPE, derivedFieldObject);
+            .parse(DerivedFieldMapper.CONTENT_TYPE, (Map) deepCopy(derivedFieldObject));
         if (documentMapper != null && documentMapper.mappers() != null) {
             for (Mapper mapper : documentMapper.mappers()) {
                 if (mapper instanceof DerivedFieldMapper) {
@@ -226,4 +229,27 @@ private DerivedFieldType resolveUsingMappings(String name) {
         }
         return null;
     }
+
+    private static Object deepCopy(Object value) {
+        if (value instanceof Map) {
+            Map<?, ?> mapValue = (Map<?, ?>) value;
+            Map<Object, Object> copy = new HashMap<>(mapValue.size());
+            for (Map.Entry<?, ?> entry : mapValue.entrySet()) {
+                copy.put(entry.getKey(), deepCopy(entry.getValue()));
+            }
+            return copy;
+        } else if (value instanceof List) {
+            List<?> listValue = (List<?>) value;
+            List<Object> copy = new ArrayList<>(listValue.size());
+            for (Object itemValue : listValue) {
+                copy.add(deepCopy(itemValue));
+            }
+            return copy;
+        } else if (value instanceof byte[]) {
+            byte[] bytes = (byte[]) value;
+            return Arrays.copyOf(bytes, bytes.length);
+        } else {
+            return value;
+        }
+    }
 }