Firebase cloud function for file upload

I have this cloud function that I wrote to upload file to google cloud storage:

const gcs = require('@google-cloud/storage')({keyFilename:'2fe4e3d2bfdc.json'});

var filePath = file.path + "/" + file.name;

    return bucket.upload(filePath, {
        destination: file.name
    }).catch(reason => {
            console.error(reason);
    });

I used formidable to parse the uploaded file and I tried to log the properties of the uploaded file and it seems fine; it is uploaded to a temp dir '/tmp/upload_2866bbe4fdcc5beb30c06ae6c3f6b1aa/ but when I try to upload the file to the gcs am getting this error:

{ Error: EACCES: permission denied, stat '/tmp/upload_2866bbe4fdcc5beb30c06ae6c3f6b1aa/thumb_ttttttt.jpg'
    at Error (native)
  errno: -13,
  code: 'EACCES',
  syscall: 'stat',
  path: '/tmp/upload_2866bbe4fdcc5beb30c06ae6c3f6b1aa/thumb_ttttttt.jpg' }

I am using this html form to upload the file:

<!DOCTYPE html>
<html>
<body>

<form action="https://us-central1-appname.cloudfunctions.net/uploadFile" method="post" enctype="multipart/form-data">
    Select image to upload:
    <input type="file" name="fileToUpload" id="fileToUpload">
    <input type="submit" value="Upload Image" name="submit">
</form>

</body>
</html>