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

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Message-ID: <CAHC9VhRiS9rb44m7dTDWU_p4Bo=SM_kSF9bvJw39Wee20zei6w@mail.gmail.com>
Date:   Thu, 15 Feb 2018 17:51:34 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Richard Guy Briggs <rgb@...hat.com>,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Paris <eparis@...hat.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 Thu, Feb 15, 2018 at 1:16 AM, Kees Cook <keescook@...omium.org> wrote:
> 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...

We get beat up by several folks when we emit audit records with audit
disabled, and they have a very valid point.

I'm not arguing that the information isn't useful, I'm arguing that if
you are interested in the sort of information that audit provides you
should enable audit.  :)

-- 
paul moore
www.paul-moore.com