linux-kernel - Re: [PATCH v3 1/2] lockdown: kexec_file: prevent unsigned kernel image when KEXEC

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Date:   Tue, 03 Jan 2023 09:42:26 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Coiby Xu <coxu@...hat.com>, kexec@...ts.infradead.org
Cc:     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>,
        Matthew Garrett <mjg59@...gle.com>,
        James Morris <jmorris@...ei.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] lockdown: kexec_file: prevent unsigned kernel
 image when KEXEC_SIG not enabled

Hi Coiby,

On Fri, 2022-12-30 at 14:58 +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.

The phrase "unless both IMA_ARCH_POLICY and secure boot also enabled"
doesn't reflect the code.  IMA could contain a custom policy rule which
requires the kexec kernel image signature verification as well.  Refer
to the comment now in mandate_signature_verification().

thanks,

Mimi