linux-hardening - Re: [PATCH v8 0/4] Introduce mseal

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Date: Fri, 02 Feb 2024 12:32:16 -0700
From: "Theo de Raadt" <deraadt@...nbsd.org>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
    Jeff Xu <jeffxu@...omium.org>, Jeff Xu <jeffxu@...gle.com>,
    Jonathan Corbet <corbet@....net>, akpm@...ux-foundation.org,
    keescook@...omium.org, jannh@...gle.com, sroettger@...gle.com,
    willy@...radead.org, gregkh@...uxfoundation.org,
    torvalds@...ux-foundation.org, usama.anjum@...labora.com,
    rdunlap@...radead.org, jorgelo@...omium.org, groeck@...omium.org,
    linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
    linux-mm@...ck.org, pedro.falcato@...il.com, dave.hansen@...el.com,
    linux-hardening@...r.kernel.org
Subject: Re: [PATCH v8 0/4] Introduce mseal

> 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.