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From: "Theo de Raadt" <deraadt@openbsd.org>
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Subject: Re: [PATCH v8 0/4] Introduce mseal
In-reply-to: <20240202192137.6lupguvhtdt72rbr@revolver>
References: <20240131175027.3287009-1-jeffxu@chromium.org> <20240131193411.opisg5yoyxkwoyil@revolver> <CABi2SkXOX4SRMs0y8FYccoj+XrEiPCJk2seqT+sgO7Na7NWwLg@mail.gmail.com> <20240201204512.ht3e33yj77kkxi4q@revolver> <CALmYWFupdK_wc6jaamjbrZf-PzHwJ_4=b69yCtAik_7uu3hZug@mail.gmail.com> <20240202151345.kj4nhb5uog4aknsp@revolver> <CABi2SkUSWLHM5KD=eK9bJrt3bBsEaB3gEpvJgr0LSTAE2G00Tg@mail.gmail.com> <20240202192137.6lupguvhtdt72rbr@revolver>
Comments: In-reply-to "Liam R. Howlett" <Liam.Howlett@Oracle.com>
   message dated "Fri, 02 Feb 2024 14:21:37 -0500."
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Content-ID: <98845.1706902336.1@cvs.openbsd.org>
Date: Fri, 02 Feb 2024 12:32:16 -0700
Message-ID: <85714.1706902336@cvs.openbsd.org>

> 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.