linux-kernel - Re: [PATCH] kexec: Do not verify the signature without the lockdown or mandatory signature

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Date:   Wed, 27 May 2020 11:15:49 +0800
From:   lijiang <lijiang@...hat.com>
To:     Jiri Bohac <jbohac@...e.cz>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        ebiederm@...ssion.com, jmorris@...ei.org, mjg59@...gle.com,
        dyoung@...hat.com, bhe@...hat.com
Subject: Re: [PATCH] kexec: Do not verify the signature without the lockdown
 or mandatory signature

在 2020年05月26日 21:59, Jiri Bohac 写道:
> On Mon, May 25, 2020 at 01:23:51PM +0800, Lianbo Jiang wrote:
>> So, here, let's simplify the logic to improve code readability. If the
>> KEXEC_SIG_FORCE enabled or kexec lockdown enabled, signature verification
>> is mandated. Otherwise, we lift the bar for any kernel image.
> 
> I agree completely; in fact that was my intention when
> introducing the code, but I got overruled about the return codes:
> https://lore.kernel.org/lkml/20180119125425.l72meyyc2qtrriwe@dwarf.suse.cz/
> 
> I like this simplification very much, except this part:
> 
>> +	if (ret) {
>> +		pr_debug("kernel signature verification failed (%d).\n", ret);
> 
> ...
> 
>> -		pr_notice("kernel signature verification failed (%d).\n", ret);
> 
> I think the log level should stay at most PR_NOTICE when the
> verification failure results in rejecting the kernel. Perhaps
> even lower.
> 

Thank you for the comment, Jiri Bohac.

I like the idea of staying at most PR_NOTICE, but the pr_notice() will output
some messages that kernel could want to ignore, such as the case you mentioned
below.

> In case verification is not enforced and the failure is
> ignored, KERN_DEBUG seems reasonable.
> 

Yes, good understanding. It seems that the pr_debug() is still a good option here?
Any other thoughts?

Thanks.
Lianbo


> Regards,
>