Re: [PATCH v3 1/8] efi: efivars: don't crash in efivar_set_variable{,_locked} in r/o case

[Ard Biesheuvel]

On Tue, 24 Jun 2025 at 12:14, Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxxxxxxxx> wrote:
>
> If efivar implementation doesn't provide write support, then calling
> efivar_set_variable() (e.g. when PM8xxx RTC driver tries to update the
> RTC offset) will crash the system. Prevent that by checking that
> set_variable callback is actually provided and fail with an
> EFI_WRITE_PROTECTED if it is not.
>
> Fixes: 472831d4c4b2 ("efi: vars: Add thin wrapper around EFI get/set variable interface")
> Reported-by: Johan Hovold <johan@xxxxxxxxxx>
> Closes: https://lore.kernel.org/r/aFlps9iUcD42vN4w@xxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
> ---
>  drivers/firmware/efi/vars.c | 2 ++
>  1 file changed, 2 insertions(+)
>

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

Feel free to merge this along with the rest of the series.

> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index 3700e98697676d8e6f04f061f447391503f9abba..11c5f785c09364f61642d82416822cb2e1a027fd 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -227,6 +227,8 @@ efi_status_t efivar_set_variable_locked(efi_char16_t *name, efi_guid_t *vendor,
>         setvar = __efivars->ops->set_variable_nonblocking;
>         if (!setvar || !nonblocking)
>                  setvar = __efivars->ops->set_variable;
> +       if (!setvar)
> +               return EFI_WRITE_PROTECTED;
>
>         return setvar(name, vendor, attr, data_size, data);
>  }
>
> --
> 2.39.5
>
>