rlp: fix encReader returning nil buffers to the pool

The bug can cause crashes if Read is called after EOF has been returned.
No code performs such calls right now, but hitting the bug gets more
likely as rlp.EncodeToReader gets used in more places.

1 files changed, 23 insertions, 0 deletions

diff --git a/rlp/encode_test.go b/rlp/encode_test.go
index 60bd95692..b550d4303 100644
--- a/rlp/encode_test.go
+++ b/rlp/encode_test.go
@@ -23,6 +23,7 @@ import (
 	"io"
 	"io/ioutil"
 	"math/big"
+	"sync"
 	"testing"
 )
 
@@ -306,3 +307,25 @@ func TestEncodeToReaderPiecewise(t *testing.T) {
 		return output, nil
 	})
 }
+
+// This is a regression test verifying that encReader
+// returns its encbuf to the pool only once.
+func TestEncodeToReaderReturnToPool(t *testing.T) {
+	buf := make([]byte, 50)
+	wg := new(sync.WaitGroup)
+	for i := 0; i < 5; i++ {
+		wg.Add(1)
+		go func() {
+			for i := 0; i < 1000; i++ {
+				_, r, _ := EncodeToReader("foo")
+				ioutil.ReadAll(r)
+				r.Read(buf)
+				r.Read(buf)
+				r.Read(buf)
+				r.Read(buf)
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+}