linux-kernel - Re: [PATCH 17/17] x86/boot: Drop CRC-32 checksum and the build tool that generates it

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Message-ID: <46832047-567e-5699-fbec-8c3e991cfe0a@zytor.com>
Date:   Sat, 19 Aug 2023 18:03:31 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Evgeniy Baskov <baskov@...ras.ru>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Jones <pjones@...hat.com>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Marvin Häuser <mhaeuser@...teo.de>
Subject: Re: [PATCH 17/17] x86/boot: Drop CRC-32 checksum and the build tool
 that generates it



On 8/18/23 06:44, Ard Biesheuvel wrote:
> The only remaining task carried out by the boot/tools/build.c build tool
> is generating the CRC-32 checksum of the bzImage. This feature was added
> in commit
> 
>    7d6e737c8d2698b6 ("x86: add a crc32 checksum to the kernel image.")
> 
> without any motivation (or any commit log text, for that matter). This
> checksum is not verified by any known bootloader, and given that
> 
> a) the checksum of the entire bzImage is reported by most tools (zlib,
>     rhash) as 0xffffffff and not 0x0 as documented,
> b) the checksum is corrupted when the image is signed for secure boot,
>     which means that no distro ships x86 images with valid CRCs,
> 
> it seems quite unlikely that this checksum is being used, so let's just
> drop it, along with the tool that generates it.
> 

This one I have concerns with.

	-hpa