Re: [PATCH v8 0/4] Introduce mseal

From: "Theo de Raadt" <deraadt@openbsd.org>
To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
	Jeff Xu <jeffxu@chromium.org>, Jeff Xu <jeffxu@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	akpm@linux-foundation.org, keescook@chromium.org,
	jannh@google.com, sroettger@google.com, willy@infradead.org,
	gregkh@linuxfoundation.org, torvalds@linux-foundation.org,
	usama.anjum@collabora.com, rdunlap@infradead.org,
	jorgelo@chromium.org, groeck@chromium.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-mm@kvack.org, pedro.falcato@gmail.com,
	dave.hansen@intel.com, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v8 0/4] Introduce mseal
Date: Fri, 02 Feb 2024 12:32:16 -0700	[thread overview]
Message-ID: <85714.1706902336@cvs.openbsd.org> (raw)
In-Reply-To: <20240202192137.6lupguvhtdt72rbr@revolver>

> What I'm more concerned about is what happens if you call mseal() on a
> range and it can mseal a portion.  Like, what happens to the first vma
> in your test_seal_unmapped_middle case?  I see it returns an error, but
> is the first VMA mseal()'ed? (no it's not, but test that)

That is correct, Liam.

Unix system calls must be atomic.

They either return an error, and that is a promise they made no changes.

Or they do the work required, and then return success.

In OpenBSD, all mimmutable() aspects were carefully studied to gaurantee
this behaviour.

I am not an expert in the Linux kernel to make the assessment; someone
who is qualified must make that assessment.  Fuzzing with tests is a good
way to judge it simpler.