linux-kernel - Re: [PATCH ghak90 V8 14/16] audit: check contid depth and add limit config param

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Date:   Wed, 22 Jan 2020 16:29:22 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        sgrubb@...hat.com, omosnace@...hat.com, dhowells@...hat.com,
        simo@...hat.com, Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com, Dan Walsh <dwalsh@...hat.com>,
        mpatel@...hat.com
Subject: Re: [PATCH ghak90 V8 14/16] audit: check contid depth and add limit
 config param

On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs <rgb@...hat.com> wrote:
>
> Clamp the depth of audit container identifier nesting to limit the
> netlink and disk bandwidth used and to prevent losing information from
> record text size overflow in the contid field.
>
> Add a configuration parameter AUDIT_STATUS_CONTID_DEPTH_LIMIT (0x80) to
> set the audit container identifier depth limit.  This can be used to
> prevent overflow of the contid field in CONTAINER_OP and CONTAINER_ID
> messages, losing information, and to limit bandwidth used by these
> messages.
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  include/uapi/linux/audit.h |  2 ++
>  kernel/audit.c             | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/audit.h             |  2 ++
>  3 files changed, 50 insertions(+)

Since setting an audit container ID, and hence acting as an
orchestrator and creating a new nested level of audit container IDs,
is a privileged operation I think we can equate this to the infamous
"shooting oneself in the foot" problem.  Let's leave this limitation
out of the patchset for now, if it becomes a problem in the future we
can consider restricting the nesting depth.

--
paul moore
www.paul-moore.com