linux-kernel - Re: [PATCH v1 0/8] x86_64 SandBox Mode arch hooks

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Date: Wed, 14 Feb 2024 10:42:57 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Petr Tesařík <petr@...arici.cz>
Cc: Petr Tesarik <petrtesarik@...weicloud.com>,
 Jonathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
 "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
 Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Xin Li <xin3.li@...el.com>, Arnd Bergmann <arnd@...db.de>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Kees Cook <keescook@...omium.org>,
 "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
 Pengfei Xu <pengfei.xu@...el.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Ze Gao <zegao2021@...il.com>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Kai Huang <kai.huang@...el.com>, David Woodhouse <dwmw@...zon.co.uk>,
 Brian Gerst <brgerst@...il.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Joerg Roedel <jroedel@...e.de>, "Mike Rapoport (IBM)" <rppt@...nel.org>,
 Tina Zhang <tina.zhang@...el.com>, Jacob Pan
 <jacob.jun.pan@...ux.intel.com>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 Roberto Sassu <roberto.sassu@...weicloud.com>,
 Petr Tesarik <petr.tesarik1@...wei-partners.com>
Subject: Re: [PATCH v1 0/8] x86_64 SandBox Mode arch hooks

On 2/14/24 10:22, Petr Tesařík wrote:
> Anyway, in the long term I would like to work on gradual decomposition
> of the kernel into a core part and many self-contained components.
> Sandbox mode is a useful tool to enforce isolation.

I'd want to see at least a few examples of how this decomposition would
work and how much of a burden it is on each site that deployed it.

But I'm skeptical that this could ever work.  Ring-0 execution really is
special and it's _increasingly_ so.  Think of LASS or SMAP or SMEP.
We're even seeing hardware designers add hardware security defenses to
ring-0 that are not applied to ring-3.

In other words, ring-3 isn't just a deprivileged ring-0, it's more
exposed to attacks.

> I'd rather fail fast than maintain hundreds of patches in an
> out-of-tree branch before submitting (and failing anyway).

I don't see any remotely feasible path forward for this approach.