linux-kernel - Re: [PATCH] kexec: move KEXEC_SIG

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Date:   Thu, 10 Feb 2022 09:33:13 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Michal Suchanek <msuchanek@...e.de>
Cc:     kexec@...ts.infradead.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Nicholas Piggin <npiggin@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Colin Ian King <colin.king@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kexec: move KEXEC_SIG_FORCE from arch/x86 to arch

On Thu, Feb 10, 2022 at 02:16:48PM +0100, Michal Suchanek wrote:
> There is nothing x86-specific about KEXEC_SIG_FORCE
> 
> Signed-off-by: Michal Suchanek <msuchanek@...e.de>
> ---
>  arch/Kconfig     | 7 +++++++
>  arch/x86/Kconfig | 7 -------
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 678a80713b21..dc2446f01ac1 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -24,6 +24,13 @@ config KEXEC_ELF
>  config HAVE_IMA_KEXEC
>  	bool
>  
> +config KEXEC_SIG_FORCE
> +	bool "Require a valid signature in kexec_file_load() syscall"
> +	depends on KEXEC_SIG
> +	help
> +	  This option makes kernel signature verification mandatory for
> +	  the kexec_file_load() syscall.
> +
>  config SET_FS
>  	bool
>  
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 9f5bd41bf660..3ea648dad6b6 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2032,13 +2032,6 @@ config KEXEC_SIG
>  	  verification for the corresponding kernel image type being
>  	  loaded in order for this to work.
>  
> -config KEXEC_SIG_FORCE
> -	bool "Require a valid signature in kexec_file_load() syscall"
> -	depends on KEXEC_SIG
> -	help
> -	  This option makes kernel signature verification mandatory for
> -	  the kexec_file_load() syscall.
> -

This means it is no longer folded under KEXEC_SIG in menuconfig,
which makes it harder to find. I would prefer seeing KEXEC_SIG (and
KEXEC_SIG_FORCE) moved out of the per-arch Kconfig files into a common
location, and then arch Kconfig can add something like:

	select ARCH_SUPPORTS_KEXEC

>  config KEXEC_BZIMAGE_VERIFY_SIG
>  	bool "Enable bzImage signature verification support"
>  	depends on KEXEC_SIG
> -- 
> 2.31.1
> 

-- 
Kees Cook