linux-kernel - Re: [PATCH v8 1/1] use crc32 instead of md5 for hibernation e820 integrity check

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Date:   Thu, 15 Apr 2021 13:09:23 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Chris von Recklinghausen <crecklin@...hat.com>
Cc:     ardb@...nel.org, simo@...hat.com, rafael@...nel.org,
        decui@...rosoft.com, linux-pm@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 1/1] use crc32 instead of md5 for hibernation e820
 integrity check

On Thu, Apr 15, 2021 at 03:46:46PM -0400, Chris von Recklinghausen wrote:
> Hibernation fails on a system in fips mode because md5 is used for the e820
> integrity check and is not available. Use crc32 instead.
> 
> This patch changes the integrity check algorithm from md5 to crc32.

The second paragraph is redundant with the first.

>  /**
> - * get_e820_md5 - calculate md5 according to given e820 table
> + * compute_e820_crc32 - calculate md5 according to given e820 table
>   *
>   * @table: the e820 table to be calculated
> - * @buf: the md5 result to be stored to
>   */

This comment still mentions MD5.

Also, this isn't a well-formed kerneldoc comment, since it doesn't document the
return value.

Also, this function is calculating the checksum *of* the table, not calculating
a checksum "according to" it (whatever that means).

Something like this would be good, I think:

/**
 * compute_e820_crc32 - compute the CRC-32 of the given e820 table
 *
 * @table: the e820 table to be checksummed
 *
 * Return: the resulting checksum
 */

Also, please try 'git grep -i md5 arch/x86/kernel/'.  There is still another
reference to MD5 that should be updated, in arch/x86/kernel/e820.c.

- Eric