Fix ByteBuffer Thread-Safety in WebSocket Binary Message Handling

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketSession.java

@@ -205,7 +205,7 @@ protected void sendTextMessage(TextMessage message) throws IOException {
 
 	@Override
 	protected void sendBinaryMessage(BinaryMessage message) throws IOException {
-		useSession((session, callback) -> session.sendBinary(message.getPayload(), callback));
+		useSession((session, callback) -> session.sendBinary(message.getPayload().asReadOnlyBuffer(), callback));
 	}
 
 	@Override

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/StandardWebSocketSession.java

@@ -208,7 +208,7 @@ protected void sendTextMessage(TextMessage message) throws IOException {
 
 	@Override
 	protected void sendBinaryMessage(BinaryMessage message) throws IOException {
-		getNativeSession().getBasicRemote().sendBinary(message.getPayload(), message.isLast());
+		getNativeSession().getBasicRemote().sendBinary(message.getPayload().asReadOnlyBuffer(), message.isLast());
 	}
 
 	@Override

spring-websocket/src/test/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketSessionTests.java

@@ -16,17 +16,23 @@
 
 package org.springframework.web.socket.adapter.jetty;
 
+import java.nio.ByteBuffer;
 import java.util.Map;
+import java.util.function.BiConsumer;
 
+import org.eclipse.jetty.websocket.api.Callback;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.UpgradeRequest;
 import org.eclipse.jetty.websocket.api.UpgradeResponse;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.testfixture.security.TestPrincipal;
+import org.springframework.web.socket.BinaryMessage;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -117,4 +123,48 @@ void getAcceptedProtocol() {
 		verifyNoMoreInteractions(nativeSession);
 	}
 
+	@Test
+	void binaryMessageWithSharedBufferSendsToMultipleSessions() throws Exception {
+		byte[] data = {1, 2, 3, 4, 5};
+		ByteBuffer sharedBuffer = ByteBuffer.wrap(data);
+		BinaryMessage message = new BinaryMessage(sharedBuffer);
+
+		ByteBuffer[] captured = new ByteBuffer[2];
+		JettyWebSocketSession session1 = createMockSession((buffer, idx) -> captured[0] = buffer);
+		JettyWebSocketSession session2 = createMockSession((buffer, idx) -> captured[1] = buffer);
+
+		session1.sendMessage(message);
+		session2.sendMessage(message);
+
+		assertThat(captured[0].array()).isEqualTo(data);
+		assertThat(captured[1].array()).isEqualTo(data);
+
+		assertThat(sharedBuffer.position()).isEqualTo(0);
+	}
+
+	private JettyWebSocketSession createMockSession(BiConsumer<ByteBuffer, Integer> captureFunction) {
+		Session mockSession = mock(Session.class);
+
+		given(mockSession.getUpgradeRequest()).willReturn(request);
+		given(mockSession.getUpgradeResponse()).willReturn(response);
+		given(mockSession.isOpen()).willReturn(true);
+		given(request.getUserPrincipal()).willReturn(null);
+		given(response.getAcceptedSubProtocol()).willReturn(null);
+
+		doAnswer(invocation -> {
+			ByteBuffer buffer = invocation.getArgument(0);
+			Callback callback = invocation.getArgument(1);
+			ByteBuffer copy = ByteBuffer.allocate(buffer.remaining());
+			copy.put(buffer);
+			copy.flip();
+			captureFunction.accept(copy, 0);
+			callback.succeed();
+			return null;
+		}).when(mockSession).sendBinary(any(ByteBuffer.class), any(Callback.class));
+
+		JettyWebSocketSession session = new JettyWebSocketSession(attributes);
+		session.initializeNativeSession(mockSession);
+		return session;
+	}
+
 }

spring-websocket/src/test/java/org/springframework/web/socket/adapter/standard/StandardWebSocketSessionTests.java

@@ -16,17 +16,24 @@
 
 package org.springframework.web.socket.adapter.standard;
 
+import java.nio.ByteBuffer;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.function.BiConsumer;
 
+import jakarta.websocket.RemoteEndpoint.Basic;
 import jakarta.websocket.Session;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.testfixture.security.TestPrincipal;
 import org.springframework.http.HttpHeaders;
+import org.springframework.web.socket.BinaryMessage;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -106,4 +113,44 @@ void addAttributesWithNullKeyOrValue() {
 				.hasSize(1).containsEntry("foo", "bar");
 	}
 
+	@Test
+	void binaryMessageWithSharedBufferSendsToMultipleSessions() throws Exception {
+		byte[] data = {1, 2, 3, 4, 5};
+		ByteBuffer sharedBuffer = ByteBuffer.wrap(data);
+		BinaryMessage message = new BinaryMessage(sharedBuffer);
+
+		ByteBuffer[] captured = new ByteBuffer[2];
+		StandardWebSocketSession session1 = createMockSession((buffer, idx) -> captured[0] = buffer);
+		StandardWebSocketSession session2 = createMockSession((buffer, idx) -> captured[1] = buffer);
+
+		session1.sendMessage(message);
+		session2.sendMessage(message);
+
+		assertThat(captured[0].array()).isEqualTo(data);
+		assertThat(captured[1].array()).isEqualTo(data);
+
+		assertThat(sharedBuffer.position()).isEqualTo(0);
+	}
+
+	private StandardWebSocketSession createMockSession(BiConsumer<ByteBuffer, Integer> captureFunction) throws Exception {
+		Session nativeSession = mock(Session.class);
+		Basic basicRemote = mock(Basic.class);
+
+		given(nativeSession.getBasicRemote()).willReturn(basicRemote);
+		given(nativeSession.isOpen()).willReturn(true);
+
+		doAnswer(invocation -> {
+			ByteBuffer buffer = invocation.getArgument(0);
+			ByteBuffer copy = ByteBuffer.allocate(buffer.remaining());
+			copy.put(buffer);
+			copy.flip();
+			captureFunction.accept(copy, 0);
+			return null;
+		}).when(basicRemote).sendBinary(any(ByteBuffer.class), anyBoolean());
+
+		StandardWebSocketSession session = new StandardWebSocketSession(this.headers, this.attributes, null, null);
+		session.initializeNativeSession(nativeSession);
+		return session;
+	}
+
 }