[PATCH v28 22/25] Audit: Add record for multiple process LSM attributes

[Casey Schaufler]

On 8/20/2021 12:06 PM, Paul Moore wrote:
> On Thu, Aug 19, 2021 at 6:41 PM Casey Schaufler <casey at schaufler-ca.com> wrote:
>> On 8/18/2021 5:56 PM, Casey Schaufler wrote:
>>> On 8/18/2021 5:47 PM, Paul Moore wrote:
>>>> ...
>>>> I just spent a few minutes tracing the code paths up from audit
>>>> through netlink and then through the socket layer and I'm not seeing
>>>> anything obvious where the path differs from any other syscall;
>>>> current->audit_context *should* be valid just like any other syscall.
>>>> However, I do have to ask, are you only seeing these audit records
>>>> with a current->audit_context equal to NULL during early boot?
>>> Nope. Sorry.
>> It looks as if all of the NULL audit_context cases are for either
>> auditd or systemd. Given what the events are, this isn't especially
>> surprising.
> I think we may be back to the "early boot" theory.
>
> Unless you explicitly enable audit on the kernel cmdline, e.g.
> "audit=1", processes started before userspace enables audit will not
> have a properly allocated audit_context; see the "if
> (likely(!audit_ever_enabled))" check at the top of audit_alloc() for
> the reason why.
>
> I could be wrong here, but I suspect if you add "audit=1" to your
> kernel command line those remaining cases of NULL audit_contexts will
> resolve themselves.  If not, we still have work to do ... well, I mean
> we still have (different) work to do even if this solves the mystery,
> it's just that we can now explain what you are seeing :)

Yup, adding "audit=1" to the command line appears to have gotten
systemd an audit context. It looks like user space enabling audit
doesn't assign an audit context to the existing systemd process.