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Date: Wed, 14 Feb 2024 10:42:57 -0800
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Subject: Re: [PATCH v1 0/8] x86_64 SandBox Mode arch hooks
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To: =?UTF-8?B?UGV0ciBUZXNhxZnDrWs=?= <petr@tesarici.cz>
Cc: Petr Tesarik <petrtesarik@huaweicloud.com>,
 Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>,
 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
 Dave Hansen <dave.hansen@linux.intel.com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
 "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
 Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
 Xin Li <xin3.li@intel.com>, Arnd Bergmann <arnd@arndb.de>,
 Andrew Morton <akpm@linux-foundation.org>,
 Rick Edgecombe <rick.p.edgecombe@intel.com>,
 Kees Cook <keescook@chromium.org>,
 "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
 Pengfei Xu <pengfei.xu@intel.com>, Josh Poimboeuf <jpoimboe@kernel.org>,
 Ze Gao <zegao2021@gmail.com>,
 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
 Kai Huang <kai.huang@intel.com>, David Woodhouse <dwmw@amazon.co.uk>,
 Brian Gerst <brgerst@gmail.com>, Jason Gunthorpe <jgg@ziepe.ca>,
 Joerg Roedel <jroedel@suse.de>, "Mike Rapoport (IBM)" <rppt@kernel.org>,
 Tina Zhang <tina.zhang@intel.com>, Jacob Pan
 <jacob.jun.pan@linux.intel.com>,
 "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
 open list <linux-kernel@vger.kernel.org>,
 Roberto Sassu <roberto.sassu@huaweicloud.com>,
 Petr Tesarik <petr.tesarik1@huawei-partners.com>
References: <20240214113516.2307-1-petrtesarik@huaweicloud.com>
 <c424618c-d6c6-430a-8975-8851a617204e@intel.com>
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From: Dave Hansen <dave.hansen@intel.com>
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In-Reply-To: <20240214192214.78734652@meshulam.tesarici.cz>
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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.