Re: [PATCH v4 2/2] cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

> @@ -1415,8 +1415,15 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
>          */
>         lock_two_nondirectories(target_inode, src_inode);
>
> -       if (len == 0)
> -               len = src_inode->i_size - off;
> +       if (len == 0) {
> +               loff_t src_size = i_size_read(src_inode);
> +
> +               if (off > src_size) {
> +                       rc = -EINVAL;
> +                       goto unlock;
> +               }
> +               len = src_size - off;
I have checked __generic_remap_file_range_prep(). Shouldn't this treat
off == src_size && len == 0 as a successful no-op ?

                    if (!len) {
                         rc = 0;
                         goto unlock;
                   }