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

From: Dave Hansen <dave.hansen@intel.com>
To: "Petr Tesařík" <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>
Subject: Re: [PATCH v1 0/8] x86_64 SandBox Mode arch hooks
Date: Wed, 14 Feb 2024 10:42:57 -0800	[thread overview]
Message-ID: <a762aaba-feb7-46ab-9e13-cea3a097311e@intel.com> (raw)
In-Reply-To: <20240214192214.78734652@meshulam.tesarici.cz>

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.