linux-kernel - Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy

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Message-ID: <CAGXu5jLTEa7sPxOnrWj8SNi-crEPQpTBXtdqdfppOE_vf9GriQ@mail.gmail.com>
Date:   Wed, 14 Feb 2018 22:16:52 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Paris <eparis@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        Steve Grubb <sgrubb@...hat.com>
Subject: Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled
 and audit_dummy_context

On Wed, Feb 14, 2018 at 6:33 PM, Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2018-02-14 09:51, Kees Cook wrote:
>> On Wed, Feb 14, 2018 at 8:18 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
>> > Audit link denied events emit disjointed records when audit is disabled.
>> > No records should be emitted when audit is disabled.
>> >
>> > See: https://github.com/linux-audit/audit-kernel/issues/21
>> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
>> > ---
>> >  kernel/audit.c | 3 +++
>> >  1 file changed, 3 insertions(+)
>> >
>> > diff --git a/kernel/audit.c b/kernel/audit.c
>> > index 227db99..4c3fd24 100644
>> > --- a/kernel/audit.c
>> > +++ b/kernel/audit.c
>> > @@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
>> >         struct audit_buffer *ab;
>> >         struct audit_names *name;
>> >
>> > +       if (!audit_enabled || audit_dummy_context())
>> > +               return;
>> > +
>> >         name = kzalloc(sizeof(*name), GFP_NOFS);
>> >         if (!name)
>> >                 return;
>>
>> Doesn't this means errors here would be silent if audit isn't enabled?
>> I don't that; sysadmins should see this notification regardless of the
>> audit state...
>
> This is a user error and not a system error, so I would think if system
> auditing is disabled, they don't care about this kind of error.

It could indicate an attack attempt...

-Kees

>
> Steve?
>
>> -Kees
>
> - RGB
>
> --
> Richard Guy Briggs <rgb@...hat.com>
> Sr. S/W Engineer, Kernel Security, Base Operating Systems
> Remote, Ottawa, Red Hat Canada
> IRC: rgb, SunRaycer
> Voice: +1.647.777.2635, Internal: (81) 32635



-- 
Kees Cook
Pixel Security