linux-kernel - Re: [PATCH] lockdown: kexec_file: prevent unsigned kernel image when KEXEC

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Date:   Fri, 30 Dec 2022 15:00:28 +0800
From:   Coiby Xu <coxu@...hat.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     kexec@...ts.infradead.org, Matthew Garrett <mjg59@...f.ucam.org>,
        Jiri Bohac <jbohac@...e.cz>,
        David Howells <dhowells@...hat.com>,
        linux-integrity@...r.kernel.org,
        Eric Biederman <ebiederm@...ssion.com>,
        James Morris <jmorris@...ei.org>,
        Matthew Garrett <mjg59@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lockdown: kexec_file: prevent unsigned kernel image when
 KEXEC_SIG not enabled

On Mon, Nov 28, 2022 at 12:16:08PM -0500, Mimi Zohar wrote:
>On Tue, 2022-11-22 at 10:36 +0800, Coiby Xu wrote:
>> Hi Mimi,
>>
>> On Mon, Nov 21, 2022 at 01:23:57PM -0500, Mimi Zohar wrote:
>> >Hi Coiby,
>> >
>> >On Mon, 2022-11-21 at 15:29 +0800, Coiby Xu wrote:
>> >> A kernel builder may not enable KEXEC_SIG and some architectures like
>> >> ppc64 simply don't have KEXEC_SIG. In these cases, unless both
>> >> IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
>> >> unsigned kernel image from being kexec'ed via the kexec_file_load
>> >> syscall whereas it could prevent one via the kexec_load syscall. Mandate
>> >> signature verification for those cases.
>> >>
>> >> Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
>> >> Cc: Matthew Garrett <mjg59@...f.ucam.org>
>> >> Cc: Jiri Bohac <jbohac@...e.cz>
>> >> Cc: David Howells <dhowells@...hat.com>
>> >> Cc: kexec@...ts.infradead.org
>> >> Cc: linux-integrity@...r.kernel.org
>> >> Signed-off-by: Coiby Xu <coxu@...hat.com>
>> >
>> >Other than correcting the function name to mandate_signature_verificati
>> >on(),
>>
>> Applied to v2, thanks for correcting me! Btw, I realize I overwrote the
>> return code of kexec_image_verify_sig with
>> mandate_signature_verification's. v2 has fixed this issue as well.
>>
>> >
>> >Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
>>
>> And thanks for the review!
>
>You're welcome.
>
>Without either IMA_ARCH or KEXEC_SIG enabled, the kexec selftest
>test_kexec_file_load.sh properly failed with "kexec_file_load failed
>[PASS]", but from the informational messages output, it isn't clear why
>it failed.  This should be corrected.

Thanks for the suggestion! I've added some tests in v3 and now the
message is "# kexec_file_load failed (missing IMA sig) [PASS]".

>
>-- 
>thanks,
>
>Mimi
>

-- 
Best regards,
Coiby