[bugfix] Close ReadClosers properly in the media package (#434)

* defer lock reader

* close readers when finished with them

* close the reader in the teereader when finished

2 files changed, 23 insertions, 3 deletions

diff --git a/internal/processing/media/getfile.go b/internal/processing/media/getfile.go
index 1faa8702f..c74951e38 100644
--- a/internal/processing/media/getfile.go
+++ b/internal/processing/media/getfile.go
@@ -180,9 +180,15 @@ func (p *processor) getAttachmentContent(ctx context.Context, requestingAccount
 				return nil, 0, err
 			}
 
-			// everything read from the readCloser by the media manager will be written into the bufferedWriter
-			teeReader := io.TeeReader(readCloser, bufferedWriter)
-			return teeReader, fileSize, nil
+			// Make a TeeReader so that everything read from the readCloser by the media manager will be written into the bufferedWriter.
+			// We wrap this in a teeReadCloser which implements io.ReadCloser, so that whoever uses the teeReader can close the readCloser
+			// when they're done with it.
+			trc := teeReadCloser{
+				teeReader: io.TeeReader(readCloser, bufferedWriter),
+				close:     readCloser.Close,
+			}
+
+			return trc, fileSize, nil
 		}
 
 		// close the pipewriter after data has been piped into it, so the reader on the other side doesn't block;
diff --git a/internal/processing/media/util.go b/internal/processing/media/util.go
index 37dc87979..9739e70b7 100644
--- a/internal/processing/media/util.go
+++ b/internal/processing/media/util.go
@@ -20,6 +20,7 @@ package media
 
 import (
 	"fmt"
+	"io"
 	"strconv"
 	"strings"
 )
@@ -61,3 +62,16 @@ func parseFocus(focus string) (focusx, focusy float32, err error) {
 	focusy = float32(fy)
 	return
 }
+
+type teeReadCloser struct {
+	teeReader io.Reader
+	close     func() error
+}
+
+func (t teeReadCloser) Read(p []byte) (n int, err error) {
+	return t.teeReader.Read(p)
+}
+
+func (t teeReadCloser) Close() error {
+	return t.close()
+}