Fix painless casting bug causing opensearch to crash (#8315) (#8607)

* Created a failing test to reproduce painless bug Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> * Removed unused import Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> * Throw exception when trying to cast def to void Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> * Removed update context change Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> * Created a different test Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> --------- Signed-off-by: Shivansh Arora <shivansh.arora@protonmail.com> (cherry picked from commit a39f60f)
opensearch-project · Jul 11, 2023 · bab8cca · bab8cca
1 parent 7c12f80
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -102,6 +102,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Refactor] OpenSearchException streamables to a registry ([#7646](https://github.com/opensearch-project/OpenSearch/pull/7646))
 - [Refactor] Serverless common classes to libraries ([#8065](https://github.com/opensearch-project/OpenSearch/pull/8065))
 - [Refactor] StreamIO and OpenSearchException foundation to core library ([#8035](https://github.com/opensearch-project/OpenSearch/pull/8035))
+- Fix painless casting bug, which crashes the OpenSearch process ([#8315](https://github.com/opensearch-project/OpenSearch/pull/8315))
 
 ### Deprecated
 

diff --git a/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java b/modules/lang-painless/src/main/java/org/opensearch/painless/AnalyzerCaster.java
@@ -412,7 +412,7 @@ public static PainlessCast getLegalCast(Location location, Class<?> actual, Clas
             }
         }
 
-        if (actual == def.class
+        if ((actual == def.class && expected != void.class)
             || (actual != void.class && expected == def.class)
             || expected.isAssignableFrom(actual)
             || (actual.isAssignableFrom(expected) && explicit)) {

diff --git a/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java b/modules/lang-painless/src/test/java/org/opensearch/painless/FactoryTests.java
@@ -360,6 +360,14 @@ public void testVoidReturn() {
         assertEquals(iae.getMessage(), "not a statement: result not used from addition operation [+]");
     }
 
+    public void testDefToVoidReturnThrowsException() {
+        ClassCastException exception = expectScriptThrows(
+            ClassCastException.class,
+            () -> getEngine().compile("def_return_in_void", "def x=1;return x;", VoidReturnTestScript.CONTEXT, Collections.emptyMap())
+        );
+        assertEquals(exception.getMessage(), "Cannot cast from [def] to [void].");
+    }
+
     public abstract static class FactoryTestConverterScript {
         private final Map<String, Object> params;