fsnotify can crash on windows if raw.FileNameLength exceeds syscall.MAX_PATH #318
Description
Before reporting an issue, please ensure you are using the latest release of fsnotify.
Yeah
Which operating system (GOOS) and version are you using?
Windows: go 1.12, windows 10
Please describe the issue that occurred.
panic: runtime error: slice bounds out of range
goroutine 765 [running, locked to thread]:
filesync_daemon/fsnotify.(*Watcher).readEvents(0xc000c78f40)
/home/builder/go/src/filesync_daemon/fsnotify/windows.go:456 +0xfb1
created by filesync_daemon/fsnotify.NewWatcher
/home/builder/go/src/filesync_daemon/fsnotify/windows.go:46 +0x21c
On windows, when we try to extract the event path name from the OS, we create a buf with length as syscall.MAX_PATH (https://github.com/fsnotify/fsnotify/blob/master/windows.go#L454).
However, it is possible to create a file name whose length exceeds this.
So, can we instead of using a fixed syscall.MAX_PATH buf, we create a buf that is the size of the path name based on the raw.FileNameLength like the following?
size := int(raw.FileNameLength / 2)
var buf []uint16
sh := (*reflect.SliceHeader)(unsafe.Pointer(&buf))
sh.Data = uintptr(unsafe.Pointer(&raw.FileName))
sh.Len = size
sh.Cap = size
name := syscall.UTF16ToString(buf)
Code to create a long path dir exceeding syscall.MAX_PATH:
// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build windows
package main
import (
"crypto/rand"
"encoding/hex"
fmt "fmt"
"os"
"path/filepath"
)
func RandString(bytes int) string {
buf := make([]byte, bytes)
_, err := rand.Read(buf)
if err != nil {
return ""
}
return hex.EncodeToString(buf[:])[:len(buf)]
}
func main() {
longPath := ""
for i := 0; i < 10; i++ {
longPath = filepath.Join(longPath, RandString(26))
}
parentDir := "C:/Users/hangk/Downloads/temp"
fmt.Println(longPath)
err := os.MkdirAll(filepath.Join(parentDir, longPath), 0700)
fmt.Println(err)
}
Now if we enable recursive watch on windows here: https://github.com/fsnotify/fsnotify/blob/master/windows.go#L350 by changing flag false to true, fsnotify will crash.