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Date:   Wed, 19 Oct 2022 11:33:38 -0700
From:   Kees Cook <>
To:     Mickaël Salaün <>
Cc:     Mimi Zohar <>, Paul Moore <>,
        James Morris <>,
        "Serge E. Hallyn" <>,
        Dmitry Kasatkin <>,,, KP Singh <>,
        Casey Schaufler <>,
        John Johansen <>,,
Subject: Re: [PATCH 1/9] integrity: Prepare for having "ima" and "evm"
 available in "integrity" LSM

On Mon, Oct 17, 2022 at 11:26:44AM +0200, Mickaël Salaün wrote:
> On 14/10/2022 19:59, Kees Cook wrote:
> > On Fri, Oct 14, 2022 at 04:40:01PM +0200, Mickaël Salaün wrote:
> > > This is not backward compatible
> > 
> > Why? Nothing will be running LSM hooks until init finishes, at which
> > point the integrity inode cache will be allocated. And ima and evm don't
> > start up until lateinit.
> > 
> > > , but can easily be fixed thanks to
> > > DEFINE_LSM().order
> > 
> > That forces the LSM to be enabled, which may not be desired?
> This is not backward compatible because currently IMA is enabled
> independently of the "lsm=" cmdline, which means that for all installed
> systems using IMA and also with a custom "lsm=" cmdline, updating the kernel
> with this patch will (silently) disable IMA. Using ".order =
> LSM_ORDER_FIRST," should keep this behavior.

This isn't true. If "integrity" is removed from the lsm= line today, IMA
will immediately panic:

        if (!iint_cache)
                panic("%s: lsm=integrity required.\n", __func__);

and before v5.12 (where the panic was added), it would immediately NULL
deref. (And it took 3 years to even notice.)

Kees Cook

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