linux-kernel - Re: [PATCH v5 23/23] integrity: Switch from rbtree to LSM-managed blob for integrity_iint

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Date:   Fri, 1 Dec 2023 10:54:54 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     "Dr. Greg" <greg@...ellic.com>,
        Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     Paul Moore <paul@...l-moore.com>, viro@...iv.linux.org.uk,
        brauner@...nel.org, chuck.lever@...cle.com, jlayton@...nel.org,
        neilb@...e.de, kolga@...app.com, Dai.Ngo@...cle.com,
        tom@...pey.com, jmorris@...ei.org, serge@...lyn.com,
        zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
        dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        mic@...ikod.net, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        selinux@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v5 23/23] integrity: Switch from rbtree to LSM-managed
 blob for integrity_iint_cache

On 11/30/2023 5:05 PM, Dr. Greg wrote:
> A suggestion has been made in this thread that there needs to be broad
> thinking on this issue, and by extension, other tough problems.  On
> that note, we would be interested in any thoughts regarding the notion
> of a long term solution for this issue being the migration of EVM to a
> BPF based implementation?
>
> There appears to be consensus that the BPF LSM will always go last, a
> BPF implementation would seem to address the EVM ordering issue.
>
> In a larger context, there have been suggestions in other LSM threads
> that BPF is the future for doing LSM's.  Coincident with that has come
> some disagreement about whether or not BPF embodies sufficient
> functionality for this role.
>
> The EVM codebase is reasonably modest with a very limited footprint of
> hooks that it handles.  A BPF implementation on this scale would seem
> to go a long ways in placing BPF sufficiency concerns to rest.
>
> Thoughts/issues?

Converting EVM to BPF looks like a 5 to 10 year process. Creating a
EVM design description to work from, building all the support functions
required, then getting sufficient reviews and testing isn't going to be
a walk in the park. That leaves out the issue of distribution of the
EVM-BPF programs. Consider how the rush to convert kernel internals to
Rust is progressing. EVM isn't huge, but it isn't trivial, either. Tetsuo
had a good hard look at converting TOMOYO to BPF, and concluded that it
wasn't practical. TOMOYO is considerably less complicated than EVM.