Fix data race in WAL

tsdb/engine/tsm1/wal.go

@@ -901,7 +901,14 @@ func (w *DeleteWALEntry) MarshalBinary() ([]byte, error) {
 
 // UnmarshalBinary deserializes the byte slice into w.
 func (w *DeleteWALEntry) UnmarshalBinary(b []byte) error {
-	w.Keys = bytes.Split(b, []byte("\n"))
+	if len(b) == 0 {
+		return nil
+	}
+
+	// b originates from a pool. Copy what needs to be retained.
+	buf := make([]byte, len(b))
+	copy(buf, b)
+	w.Keys = bytes.Split(buf, []byte("\n"))
 	return nil
 }
 
@@ -977,7 +984,11 @@ func (w *DeleteRangeWALEntry) UnmarshalBinary(b []byte) error {
 		if i+sz > len(b) {
 			return ErrWALCorrupt
 		}
-		w.Keys = append(w.Keys, b[i:i+sz])
+
+		// b originates from a pool. Copy what needs to be retained.
+		buf := make([]byte, sz)
+		copy(buf, b[i:i+sz])
+		w.Keys = append(w.Keys, buf)
 		i += sz
 	}
 	return nil

tsdb/engine/tsm1/wal_test.go

@@ -4,9 +4,11 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"reflect"
 	"testing"
 
 	"github.com/golang/snappy"
+	"github.com/influxdata/influxdb/pkg/slices"
 	"github.com/influxdata/influxdb/tsdb/engine/tsm1"
 )
 
@@ -685,6 +687,51 @@ func TestWriteWALSegment_UnmarshalBinary_WriteWALCorrupt(t *testing.T) {
 	}
 }
 
+func TestDeleteWALEntry_UnmarshalBinary(t *testing.T) {
+	examples := []struct {
+		In  []string
+		Out [][]byte
+	}{
+		{
+			In:  []string{""},
+			Out: nil,
+		},
+		{
+			In:  []string{"foo"},
+			Out: [][]byte{[]byte("foo")},
+		},
+		{
+			In:  []string{"foo", "bar"},
+			Out: [][]byte{[]byte("foo"), []byte("bar")},
+		},
+		{
+			In:  []string{"foo", "bar", "z", "abc"},
+			Out: [][]byte{[]byte("foo"), []byte("bar"), []byte("z"), []byte("abc")},
+		},
+		{
+			In:  []string{"foo", "bar", "z", "a"},
+			Out: [][]byte{[]byte("foo"), []byte("bar"), []byte("z"), []byte("a")},
+		},
+	}
+
+	for i, example := range examples {
+		w := &tsm1.DeleteWALEntry{Keys: slices.StringsToBytes(example.In...)}
+		b, err := w.MarshalBinary()
+		if err != nil {
+			t.Fatalf("[example %d] unexpected error, got %v", i, err)
+		}
+
+		out := &tsm1.DeleteWALEntry{}
+		if err := out.UnmarshalBinary(b); err != nil {
+			t.Fatalf("[example %d] %v", i, err)
+		}
+
+		if !reflect.DeepEqual(example.Out, out.Keys) {
+			t.Errorf("[example %d] got %v, expected %v", i, out.Keys, example.Out)
+		}
+	}
+}
+
 func TestWriteWALSegment_UnmarshalBinary_DeleteWALCorrupt(t *testing.T) {
 	w := &tsm1.DeleteWALEntry{
 		Keys: [][]byte{[]byte("foo"), []byte("bar")},