[PATCH] proc: Track /proc/$pid/attr/ opener mm_struct

[Linus Torvalds]

On Mon, Jun 14, 2021 at 9:45 AM Kees Cook <keescook at chromium.org> wrote:
>
>         /* A task may only write when it was the opener. */
> -       if (file->private_data != current->mm)
> +       if (!file->private_data || file->private_data != current->mm)

I don't think this is necessary.

If file->private_data is NULL, then the old test for private_data !=
current->mm will still work just fine.

Because if you can fool kernel threads to do the write for you, you
have bigger security issues than that test.

               Linus