linux-kernel - Re: [PATCH 5.15 0/6] arm64: kexec_file: use more system keyrings to verify kernel image signature + dependencies

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Date:   Sat, 24 Sep 2022 16:44:03 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        keyrings@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Will Deacon <will@...nel.org>, Sasha Levin <sashal@...nel.org>,
        "open list:S390" <linux-s390@...r.kernel.org>,
        Coiby Xu <coxu@...hat.com>, Baoquan He <bhe@...hat.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        Philipp Rudo <prudo@...hat.com>,
        " open list:KEXEC" <kexec@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James Morse <james.morse@....com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 5.15 0/6] arm64: kexec_file: use more system keyrings to
 verify kernel image signature + dependencies

On Fri, Sep 23, 2022 at 09:16:50PM +0200, Michal Suchánek wrote:
> Hello,
> 
> On Fri, Sep 23, 2022 at 03:03:36PM -0400, Mimi Zohar wrote:
> > On Fri, 2022-09-23 at 19:10 +0200, Michal Suchanek wrote:
> > > Hello,
> > > 
> > > this is backport of commit 0d519cadf751
> > > ("arm64: kexec_file: use more system keyrings to verify kernel image signature")
> > > to table 5.15 tree including the preparatory patches.
> > > 
> > > Some patches needed minor adjustment for context.
> > 
> > In general when backporting this patch set, there should be a
> > dependency on backporting these commits as well.  In this instance for
> > linux-5.15.y, they've already been backported.
> > 
> > 543ce63b664e ("lockdown: Fix kexec lockdown bypass with ima policy")

AFAICT this is everywhere relevant, likely because it's considered a CVE
fix.

> > af16df54b89d ("ima: force signature verification when CONFIG_KEXEC_SIG is configured")

This is missing in 5.4, and 5.4 is missing this prerequisite:
fd7af71be542 ("kexec: do not verify the signature without the lockdown or mandatory signature")

> 
> Thanks for bringing these up. It might be in general useful to backport
> these fixes as well.
> 
> However, this patchset does one very specific thing: it lifts the x86
> kexec_file signature verification to arch-independent and uses it on
> arm64 to unify all features (and any existing warts) between EFI
> architectures.
> 
> So unless I am missing something the fixes you pointed out are
> completely independent of this.
> 
> Thanks
> 
> Michal