linux-kernel - Re: [PATCH] x86/boot: Fix regression--secure boot info loss from bootparam sanitizing

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Date:   Sun, 1 Sep 2019 11:36:08 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     John S Gruber <JohnSGruber@...il.com>, <john.hubbard@...il.com>,
        <bp@...en8.de>, <hpa@...or.com>, <linux-kernel@...r.kernel.org>,
        <mingo@...hat.com>, <tglx@...utronix.de>, <x86@...nel.org>,
        <gregkh@...uxfoundation.org>
CC:     <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/boot: Fix regression--secure boot info loss from
 bootparam sanitizing

On 9/1/19 8:38 AM, John S Gruber wrote:
> From: "John S. Gruber" <JohnSGruber@...il.com>
> 
> commit a90118c445cc ("x86/boot: Save fields explicitly, zero out everything
> else") now zeros the secure boot information passed by the boot loader or
> by the kernel's efi handover mechanism.
> 
> Include boot-params.secure_boot in the preserve field list.
> 
> Signed-off-by: John S. Gruber <JohnSGruber@...il.com>
> ---
> 
> I noted a change in my computers between running signed 5.3-rc4 and 5.3-rc6
> with signed kernels using the efi handoff protocol with grub. The kernel
> log message "Secure boot enabled" becomes "Secure boot could not be
> determined". The efi_main function in arch/x86/boot/compressed/eboot.c sets
> this field early but it is subsequently zeroed by the above referenced commit
> in the file arch/x86/include/asm/bootparam_utils.h
> 
> Applies to 5.3-rc6.
> 

Hi,

The fix itself looks good, so you can add:

     Reviewed-by: John Hubbard <jhubbard@...dia.com>

...but note that the commit description should get a few tweaks:

1. Your description above is actually well-suited for the commit log,
so please add that in. Especially the symptoms are desirable to have
on record.

2. This should Cc: stable@...r.kernel.org, because the whole thing
made it into -stable and those kernels need this fix.

3. Also need a Fixes tag:

Fixes: commit a90118c445cc ("x86/boot: Save fields explicitly, zero out everything else")

thanks,
-- 
John Hubbard
NVIDIA

>   arch/x86/include/asm/bootparam_utils.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/include/asm/bootparam_utils.h
> b/arch/x86/include/asm/bootparam_utils.h
> index 9e5f3c7..981fe92 100644
> --- a/arch/x86/include/asm/bootparam_utils.h
> +++ b/arch/x86/include/asm/bootparam_utils.h
> @@ -70,6 +70,7 @@ static void sanitize_boot_params(struct boot_params
> *boot_params)
>   			BOOT_PARAM_PRESERVE(eddbuf_entries),
>   			BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
>   			BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
> +			BOOT_PARAM_PRESERVE(secure_boot),
>   			BOOT_PARAM_PRESERVE(hdr),
>   			BOOT_PARAM_PRESERVE(e820_table),
>   			BOOT_PARAM_PRESERVE(eddbuf),
>