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

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Message-ID: <2204915d319ff9acf80f68ccba8600aaeb5578d7.camel@linux.ibm.com>
Date:   Mon, 28 Nov 2022 12:16:08 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Coiby Xu <coxu@...hat.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 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,

Mimi