From 60f78f517dccff9fd7df71ba945465ca72e6d7e9 Mon Sep 17 00:00:00 2001
From: "Y.Horie" <u5.horie@gmail.com>
Date: Sun, 7 Jun 2026 13:36:59 +0900
Subject: [PATCH] fix(fs): remove temporary file when compression fails (#2264)

compressFileNolock created a ".tmp" file but left it on disk when the
compression copy, os.Chtimes, or os.Rename step failed, leaking partial
files that accumulate over time. Remove the temporary file in each error
path.

Fixes #2239

Signed-off-by: Y.Horie <u5.horie@gmail.com>
---
 fs.go      |  3 +++
 fs_test.go | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/fs.go b/fs.go
index 1273f72..ba532a9 100644
--- a/fs.go
+++ b/fs.go
@@ -1740,13 +1740,16 @@ func (h *fsHandler) compressFileNolock(
 	_ = zf.Close()
 	_ = f.Close()
 	if err != nil {
+		_ = os.Remove(tmpFilePath)
 		return nil, fmt.Errorf("error when compressing file %q to %q: %w", filePath, tmpFilePath, err)
 	}
 	if err = os.Chtimes(tmpFilePath, time.Now(), fileInfo.ModTime()); err != nil {
+		_ = os.Remove(tmpFilePath)
 		return nil, fmt.Errorf("cannot change modification time to %v for tmp file %q: %v",
 			fileInfo.ModTime(), tmpFilePath, err)
 	}
 	if err = os.Rename(tmpFilePath, compressedFilePath); err != nil {
+		_ = os.Remove(tmpFilePath)
 		return nil, fmt.Errorf("cannot move compressed file from %q to %q: %w", tmpFilePath, compressedFilePath, err)
 	}
 	return h.newCompressedFSFile(compressedFilePath, fileEncoding)
diff --git a/fs_test.go b/fs_test.go
index cc283ad..6e872e5 100644
--- a/fs_test.go
+++ b/fs_test.go
@@ -3,8 +3,10 @@ package fasthttp
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
+	iofs "io/fs"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -882,6 +884,42 @@ func runFSCompressSingleThread(t *testing.T, fs *FS) {
 	testFSCompress(t, h, "/README.md")
 }
 
+// errReadFile is an fs.File whose Read always fails, used to force the
+// compression step in compressFileNolock to return an error.
+type errReadFile struct {
+	fi iofs.FileInfo
+}
+
+func (f *errReadFile) Stat() (iofs.FileInfo, error) { return f.fi, nil }
+func (f *errReadFile) Read([]byte) (int, error)     { return 0, errors.New("forced read error") }
+func (f *errReadFile) Close() error                 { return nil }
+
+func TestFSCompressTmpFileRemovedOnError(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	// Use this test file as the source for a valid fs.FileInfo.
+	fi, err := os.Stat("fs_test.go")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	h := &fsHandler{}
+	compressedFilePath := filepath.Join(dir, "out.gz")
+	tmpFilePath := compressedFilePath + ".tmp"
+
+	_, err = h.compressFileNolock(
+		&errReadFile{fi: fi}, fi, "fs_test.go", compressedFilePath, "gzip")
+	if err == nil {
+		t.Fatalf("expecting error when compression fails")
+	}
+
+	if _, err := os.Stat(tmpFilePath); !os.IsNotExist(err) {
+		t.Fatalf("temporary file %q must be removed on compression error, stat err: %v", tmpFilePath, err)
+	}
+}
+
 func testFSCompress(t *testing.T, h RequestHandler, filePath string) {
 	t.Helper()