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From:   Paul Moore <paul@paul-moore.com>
Date:   Wed, 18 Apr 2018 20:11:30 -0400
Message-ID: <CAHC9VhTSfpXDGg7LeUjh3SvN_GVvAP2f89MHmYKskdzGkR8u6Q@mail.gmail.com>
Subject: Re: [RFC PATCH ghak32 V2 02/13] audit: check children and threading
 before allowing containerid
To:     Richard Guy Briggs <rgb@redhat.com>
Cc:     cgroups@vger.kernel.org, containers@lists.linux-foundation.org,
        linux-api@vger.kernel.org,
        Linux-Audit Mailing List <linux-audit@redhat.com>,
        linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        netdev@vger.kernel.org, ebiederm@xmission.com, luto@kernel.org,
        jlayton@redhat.com, carlos@redhat.com, dhowells@redhat.com,
        viro@zeniv.linux.org.uk, simo@redhat.com,
        Eric Paris <eparis@parisplace.org>, serge@hallyn.com
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On Fri, Mar 16, 2018 at 5:00 AM, Richard Guy Briggs <rgb@redhat.com> wrote:
> Check if a task has existing children or co-threads and refuse to set
> the container ID if either are present.  Failure to check this could
> permit games where a child scratches its parent's back to work around
> inheritance and double-setting policy.
>
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  kernel/auditsc.c | 4 ++++
>  1 file changed, 4 insertions(+)

I would just include this in patch 1/2 as I can't think of world where
we wouldn't this check.

> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 29c8482..a6b0a52 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2087,6 +2087,10 @@ static int audit_set_containerid_perm(struct task_struct *task, u64 containerid)
>         /* if we don't have caps, reject */
>         if (!capable(CAP_AUDIT_CONTROL))
>                 return -EPERM;
> +       /* if task has children or is not single-threaded, deny */
> +       if (!list_empty(&task->children) ||
> +           !(thread_group_leader(task) && thread_group_empty(task)))
> +               return -EPERM;
>         /* if containerid is unset, allow */
>         if (!audit_containerid_set(task))
>                 return 0;
> --
> 1.8.3.1

-- 
paul moore
www.paul-moore.com