linux-kernel - Re: [RFC Patch 0/7] kernel: Introduce multikernel architecture support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAM_iQpWRZ-vihMEa=k-j9EYN9itUeZLhZ14AoCvZ9mturFxAyw@mail.gmail.com>
Date: Wed, 24 Sep 2025 11:28:04 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Stefan Hajnoczi <stefanha@...hat.com>
Cc: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org, 
	pasha.tatashin@...een.com, Cong Wang <cwang@...tikernel.io>, 
	Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>, 
	Alexander Graf <graf@...zon.com>, Mike Rapoport <rppt@...nel.org>, Changyuan Lyu <changyuanl@...gle.com>, 
	kexec@...ts.infradead.org, linux-mm@...ck.org, multikernel@...ts.linux.dev
Subject: Re: [RFC Patch 0/7] kernel: Introduce multikernel architecture support

On Wed, Sep 24, 2025 at 5:51 AM Stefan Hajnoczi <stefanha@...hat.com> wrote:
>
> On Wed, Sep 24, 2025 at 01:38:31PM +0200, David Hildenbrand wrote:
> > > >
> > > > Two more points:
> > > >
> > > > 1) Security lockdown. Security lockdown transforms multikernel from
> > > > "0-day means total compromise" to "0-day means single workload
> > > > compromise with rapid recovery." This is still a significant improvement
> > > > over containers where a single kernel 0-day compromises everything
> > > > simultaneously.
> > >
> > > I don't follow. My understanding is that multikernel currently does not
> > > prevent spawned kernels from affecting each other, so a kernel 0-day in
> > > multikernel still compromises everything?
> >
> > I would assume that if there is no enforced isolation by the hardware (e.g.,
> > virtualization, including partitioning hypervisors like jailhouse, pkvm etc)
> > nothing would stop a kernel A to access memory assigned to kernel B.
> >
> > And of course, memory is just one of the resources that would not be
> > properly isolated.
> >
> > Not sure if encrypting memory per kernel would really allow to not let other
> > kernels still damage such kernels.
> >
> > Also, what stops a kernel to just reboot the whole machine? Happy to learn
> > how that will be handled such that there is proper isolation.
>
> The reason I've been asking about the fault isolation and security
> statements in the cover letter is because it's unclear:
> 1. What is implemented today in multikernel.
> 2. What is on the roadmap for multikernel.
> 3. What is out of scope for multikernel.
>
> Cong: Can you clarify this? If the answer is that fault isolation and
> security are out of scope, then this discussion can be skipped.

It is my pleasure. The email is too narrow, therefore I wrote a
complete document for you:
https://docs.google.com/document/d/1yneO6O6C_z0Lh3A2QyT8XsH7ZrQ7-naGQT-rpdjWa_g/edit?usp=sharing

I hope it answers all of the above questions and provides a clear
big picture. If not, please let me know.

(If you need edit permission for the above document, please just
request, I will approve.)

Regards,
Cong Wang