fix: a possible closer leak in SelectObjectHandler (#16598)

cmd/object-handlers.go

@@ -242,7 +242,7 @@ func (api objectAPIHandlers) SelectObjectContentHandler(w http.ResponseWriter, r
 		},
 		actualSize,
 	)
-
+	defer objectRSC.Close()
 	s3Select, err := s3select.NewS3Select(r.Body)
 	if err != nil {
 		if serr, ok := err.(s3select.SelectError); ok {
@@ -3124,7 +3124,7 @@ func (api objectAPIHandlers) PostRestoreObjectHandler(w http.ResponseWriter, r *
 				},
 				actualSize,
 			)
-
+			defer objectRSC.Close()
 			if err = rreq.SelectParameters.Open(objectRSC); err != nil {
 				if serr, ok := err.(s3select.SelectError); ok {
 					encodedErrorResponse := encodeResponse(APIErrorResponse{

internal/s3select/select.go

@@ -698,6 +698,11 @@ type ObjectReadSeekCloser struct {
 	size   int64 // actual object size regardless of compression/encryption
 	offset int64
 	reader io.ReadCloser
+
+	// reader can be closed idempotently multiple times
+	closerOnce sync.Once
+	// Error storing reader.Close()
+	closerErr error
 }
 
 // NewObjectReadSeekCloser creates a new ObjectReadSeekCloser.
@@ -749,12 +754,11 @@ func (rsc *ObjectReadSeekCloser) Read(p []byte) (n int, err error) {
 // object for reading and a subsequent Close call is required to ensure
 // resources are freed.
 func (rsc *ObjectReadSeekCloser) Close() error {
-	if rsc.reader != nil {
+	rsc.closerOnce.Do(func() {
-		err := rsc.reader.Close()
+		if rsc.reader != nil {
-		if err == nil {
+			rsc.closerErr = rsc.reader.Close()
 			rsc.reader = nil
 		}
-		return err
+	})
-	}
+	return rsc.closerErr
-	return nil
 }