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From:   Paul Moore <paul@paul-moore.com>
Date:   Tue, 26 Apr 2022 14:15:23 -0400
Message-ID: <CAHC9VhS0ht0wWtruDjVvOsy_1LOCswF0kjmd9u8XZXm00jHvOw@mail.gmail.com>
Subject: Re: [PATCH v35 26/29] Audit: Add record for multiple task security contexts
To:     John Johansen <john.johansen@canonical.com>
Cc:     Casey Schaufler <casey@schaufler-ca.com>,
        casey.schaufler@intel.com, jmorris@namei.org,
        linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
        linux-audit@redhat.com, keescook@chromium.org,
        penguin-kernel@i-love.sakura.ne.jp, stephen.smalley.work@gmail.com,
        linux-kernel@vger.kernel.org
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On Mon, Apr 25, 2022 at 9:08 PM John Johansen
<john.johansen@canonical.com> wrote:
> On 4/18/22 07:59, Casey Schaufler wrote:
> > Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
> > An example of the MAC_TASK_CONTEXTS (1420) record is:
> >
> >     type=MAC_TASK_CONTEXTS[1420]
> >     msg=audit(1600880931.832:113)
> >     subj_apparmor=unconfined
> >     subj_smack=_
> >
> > When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
> > the "subj=" field in other records in the event will be "subj=?".
> > An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
> > multiple security modules that may make access decisions based
> > on a subject security context.
> >
> > Functions are created to manage the skb list in the audit_buffer.
> >
> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>
> Besides moving the aux fns, and the whining below
> Reviewed-by: John Johansen <john.johansen@canonical.com>

...

> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 4d44c05053b0..8ed2d717c217 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -2185,16 +2238,44 @@ int audit_log_task_context(struct audit_buffer *ab)
> >       if (!lsmblob_is_set(&blob))
> >               return 0;
> >
> > -     error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
> > +     if (!lsm_multiple_contexts()) {
> > +             error = security_secid_to_secctx(&blob, &context,
> > +                                              LSMBLOB_FIRST);
> > +             if (error) {
> > +                     if (error != -EINVAL)
> > +                             goto error_path;
> > +                     return 0;
> > +             }
> >
> > -     if (error) {
> > -             if (error != -EINVAL)
> > +             audit_log_format(ab, " subj=%s", context.context);
> > +             security_release_secctx(&context);
> > +     } else {
> > +             /* Multiple LSMs provide contexts. Include an aux record. */
> > +             audit_log_format(ab, " subj=?");
>
> just me whining, you sure we can't just drop subj= here

Have I recently given you my "the audit code is crap" speech? ;)

I more or less answered this with my comments on the earlier patch,
but we need to keep this around for compatibility.  It will get better
in the future.

-- 
paul-moore.com