Re: [PATCH AUTOSEL 4.19 2/3] efi: efivars: prevent double registration

[Ard Biesheuvel]

On Wed, 1 Mar 2023 at 17:30, Sasha Levin <sashal@xxxxxxxxxx> wrote:
>
> From: Johan Hovold <johan+linaro@xxxxxxxxxx>
>
> [ Upstream commit 0217a40d7ba6e71d7f3422fbe89b436e8ee7ece7 ]
>
> Add the missing sanity check to efivars_register() so that it is no
> longer possible to override an already registered set of efivar ops
> (without first deregistering them).
>
> This can help debug initialisation ordering issues where drivers have so
> far unknowingly been relying on overriding the generic ops.
>
> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

NAK this is not a bugfix.

> ---
>  drivers/firmware/efi/vars.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index e619ced030d52..462e88b9d2ba4 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -1195,19 +1195,28 @@ int efivars_register(struct efivars *efivars,
>                      const struct efivar_operations *ops,
>                      struct kobject *kobject)
>  {
> +       int rv;
> +
>         if (down_interruptible(&efivars_lock))
>                 return -EINTR;
>
> +       if (__efivars) {
> +               pr_warn("efivars already registered\n");
> +               rv = -EBUSY;
> +               goto out;
> +       }
> +
>         efivars->ops = ops;
>         efivars->kobject = kobject;
>
>         __efivars = efivars;
>
>         pr_info("Registered efivars operations\n");
> -
> +       rv = 0;
> +out:
>         up(&efivars_lock);
>
> -       return 0;
> +       return rv;
>  }
>  EXPORT_SYMBOL_GPL(efivars_register);
>
> --
> 2.39.2
>