add fix and test for non-regular files

Author: mauri870

src/archive/tar/writer.go

@@ -5,6 +5,7 @@
 package tar
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
@@ -419,6 +420,10 @@ func (tw *Writer) AddFS(fsys fs.FS) error {
 		if err != nil {
 			return err
 		}
+		// TODO(#49580): Handle symlinks when fs.ReadLinkFS is available.
+		if !info.Mode().IsRegular() {
+			return errors.New("tar: cannot add non-regular file")
+		}
 		h, err := FileInfoHeader(info, "")
 		if err != nil {
 			return err

src/archive/tar/writer_test.go

@@ -9,6 +9,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"io"
+	"io/fs"
 	"os"
 	"path"
 	"reflect"
@@ -1335,7 +1336,7 @@ func TestFileWriter(t *testing.T) {
 	}
 }
 
-func TestWriterAddFs(t *testing.T) {
+func TestWriterAddFS(t *testing.T) {
 	fsys := fstest.MapFS{
 		"file.go":              {Data: []byte("hello")},
 		"subfolder/another.go": {Data: []byte("world")},
@@ -1358,8 +1359,7 @@ func TestWriterAddFs(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		data := make([]byte, hdr.Size)
-		_, err = io.ReadFull(tr, data)
+		data, err := io.ReadAll(tr)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1375,3 +1375,15 @@ func TestWriterAddFs(t *testing.T) {
 		}
 	}
 }
+
+func TestWriterAddFSNonRegularFiles(t *testing.T) {
+	fsys := fstest.MapFS{
+		"device":  {Data: []byte("hello"), Mode: 0755 | fs.ModeDevice},
+		"symlink": {Data: []byte("world"), Mode: 0755 | fs.ModeSymlink},
+	}
+	var buf bytes.Buffer
+	tw := NewWriter(&buf)
+	if err := tw.AddFS(fsys); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}