linux-kernel - Re: [PATCH v3 1/8] efi: efivars: don't crash in efivar_set_variable{,

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Message-ID: <CAMj1kXGi55_bRD_Q4n6hKO6-fCUHrWfpKD29Rc+r+gv1odHm9w@mail.gmail.com>
Date: Tue, 8 Jul 2025 13:18:52 +1000
From: Ard Biesheuvel <ardb@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Maximilian Luz <luzmaximilian@...il.com>, 
	Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Johan Hovold <johan@...nel.org>, Steev Klimaszewski <steev@...i.org>, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-efi@...r.kernel.org
Subject: Re: [PATCH v3 1/8] efi: efivars: don't crash in efivar_set_variable{,_locked}
 in r/o case

On Tue, 24 Jun 2025 at 12:14, Dmitry Baryshkov
<dmitry.baryshkov@....qualcomm.com> 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@...nel.org>
> Closes: https://lore.kernel.org/r/aFlps9iUcD42vN4w@hovoldconsulting.com
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> ---
>  drivers/firmware/efi/vars.c | 2 ++
>  1 file changed, 2 insertions(+)
>

Acked-by: Ard Biesheuvel <ardb@...nel.org>

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
>
>