[UNDERTOW-2344] Take into account that close could run concurrently with a read operation

servlet/src/main/java/io/undertow/servlet/spec/ServletInputStreamImpl.java

@@ -194,18 +194,19 @@ public int read(final byte[] b, final int off, final int len) throws IOException
         return copied;
     }
 
-    private void readIntoBuffer() throws IOException {
+    private PooledByteBuffer readIntoBuffer() throws IOException {
         if (pooled == null && !anyAreSet(state, FLAG_FINISHED)) {
-            pooled = bufferPool.allocate();
-
+            final PooledByteBuffer buffer = pooled = bufferPool.allocate();
             int res = Channels.readBlocking(channel, pooled.getBuffer());
             pooled.getBuffer().flip();
             if (res == -1) {
                 setFlags(FLAG_FINISHED);
                 pooled.close();
                 pooled = null;
             }
+            return buffer;
         }
+        return null;
     }
 
     private void readIntoBufferNonBlocking() throws IOException {
@@ -263,7 +264,12 @@ public void close() throws IOException {
         setFlags(FLAG_CLOSED);
         try {
             while (allAreClear(state, FLAG_FINISHED)) {
-                readIntoBuffer();
+                // read is always supposed to run from the same thread, but
+                // close is a different story... specially in tests
+                PooledByteBuffer buffer = readIntoBuffer();
+                if (buffer != null) {
+                    buffer.close();
+                }
                 if (pooled != null) {
                     pooled.close();
                     pooled = null;