Received: by 2002:a25:8b91:0:0:0:0:0 with SMTP id j17csp1101433ybl; Thu, 23 Jan 2020 13:37:17 -0800 (PST) X-Google-Smtp-Source: APXvYqw6/zKnljwZLkFi4+09dXg4bNF78GzQxW/hirnziQ/kgaGgb1FtcwcH7DXxy38w3zOt2VHz X-Received: by 2002:a05:6830:1515:: with SMTP id k21mr301481otp.177.1579815437527; Thu, 23 Jan 2020 13:37:17 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1579815437; cv=none; d=google.com; s=arc-20160816; b=KYAAN1IwgqcErytd01XZj/3HJDKlmU5td744FKwXIL/UEdnE3W4v5IiS+krcZAjQj1 kMdIY5neTQIw5JmpcT3x9PQqCIkP6XA81lCNkkQIoSNZKCHjT7+Xwktp/2e7G8WadYzg wmOz9VtuIJtCYq+LJys0q5G7nR6NTPAJMWOHXFTbQNalOdq7/ramBvvzFnUZcj8YRYl6 xfPICNrfm7xN7d9VjwV61uWlvcphDVJ/Q6majNYcCESwdgWw/nUu4HGnaQFFXeHQJCzt fb2QCiWw6NrTLy3trDgb/kItbNMrBIX4+GZTMuRSP13e3ABNC2DuueBB5DIUJswelSUO zpJw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:dkim-signature; bh=hMyXK37D1SY1vwV+WlcNr41eq9aZRtXuphVComfAQVQ=; b=k5QfFsCARUslScdL0DykCzzA9uIyi/LRRt988YRKrDijg1AKQcG2evqdsBrP6hed0R gu/fxAzzDiGBBr7wbaZRXEUSKqcR3hD4g9qL/QLQndNLZQf2R5ien3upPKi3elXKSMXh jH82b9IyB6KrWyhB3uC9pHQQHfFZW4jwltFE8h2lHjq131AH4sqi6zrKHo7ks9Infdzm B2nsBqUddZZQ7S4oK0y0YXm4HEw28NGi/hgdbqHBBugSCN2fVV69D+4NHMr3y7V/Bs4H mw4jD+MDJctm2E13qK4NzYZz4hvLvc6IcKSmNtZIGiiPPnVd1S2gFVEaQ1X6TByrxNk9 3JJw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@paul-moore-com.20150623.gappssmtp.com header.s=20150623 header.b=JGf6hitG; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id i11si1831723otc.105.2020.01.23.13.37.05; Thu, 23 Jan 2020 13:37:17 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@paul-moore-com.20150623.gappssmtp.com header.s=20150623 header.b=JGf6hitG; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729049AbgAWVgK (ORCPT + 99 others); Thu, 23 Jan 2020 16:36:10 -0500 Received: from mail-lj1-f193.google.com ([209.85.208.193]:42380 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726191AbgAWVgJ (ORCPT ); Thu, 23 Jan 2020 16:36:09 -0500 Received: by mail-lj1-f193.google.com with SMTP id y4so5396387ljj.9 for ; Thu, 23 Jan 2020 13:36:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=hMyXK37D1SY1vwV+WlcNr41eq9aZRtXuphVComfAQVQ=; b=JGf6hitGz+m+ANGWCtXXNmlHWR+dQ/BZUfRkAld6SD6nyEJJWkhHMwDQZL8Tg3rEI6 E5wDExHPHU3tOhZaD3uMzylwgNwR/Wf9C3XHKUpDzVGdRtuGWPx6tbstejnrgJrQeN+g Dmso35KzWIS2UCBggmhhuHBvnfIpWhxJWW0gyGW2SsOAh/Ff5Bltiu0u80w/D/v+iq7e wnzu7aJ0+yCcORXR2HzC8GaXEygtzUvCvvQD4T5mdqKgxlH9t+1HZeBY5CJ65wYPgaLh LteK7V9iBlHEF5ip9MJqmX9Yg28imNv8LPKe1tmJV6DDUXayP+pLl8zZYp33fO+aOwDN QytQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hMyXK37D1SY1vwV+WlcNr41eq9aZRtXuphVComfAQVQ=; b=c7135O3gVZyPTXDJtoCMOg78X2+lwv4yqFFBq/9PIfFSnWYjkbEiESX8XHoaJ/rl/Y BZmY9AS/AbnGOtmrKKZKvJKuIzkBcfdgKy5ll4+76mHluHHxcyx2MJsKztwfxsi6EaJN 0Ed0izx2Pbr4egN+dXc8wsj2aF+7/taEPUt9P02cRZ13aN6rQ5MdG7edGU0kso05FFFN TIQr4E6SniwTPuCZOs4XJAjNKw2MoWgczC7ExFN8MRD7oLawqHx4XcEXeutdT81iuEPS rYBfDFiWYg4NSt73oiVA2PtYCOWu8ipiA+tzWUBLU+/mShrQq0e09B5lakaXiNFPHgYx xahg== X-Gm-Message-State: APjAAAVrpdfOqTRtIQ4ZJxCCg4ppIuPbUBzASE5YTuyokIJPYab7RPkm RVkHD5BCHkdphod7au/S/+OT9aW4CJCg464dveiS X-Received: by 2002:a2e:b52b:: with SMTP id z11mr236562ljm.155.1579815366587; Thu, 23 Jan 2020 13:36:06 -0800 (PST) MIME-Version: 1.0 References: <7d7933d742fdf4a94c84b791906a450b16f2e81f.1577736799.git.rgb@redhat.com> <20200123162918.b3jbed7tbvr2sf2p@madcap2.tricolour.ca> <20200123200412.j2aucdp3cvk57prw@madcap2.tricolour.ca> In-Reply-To: <20200123200412.j2aucdp3cvk57prw@madcap2.tricolour.ca> From: Paul Moore Date: Thu, 23 Jan 2020 16:35:55 -0500 Message-ID: Subject: Re: [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon To: Richard Guy Briggs Cc: nhorman@tuxdriver.com, linux-api@vger.kernel.org, containers@lists.linux-foundation.org, LKML , dhowells@redhat.com, Linux-Audit Mailing List , netfilter-devel@vger.kernel.org, ebiederm@xmission.com, simo@redhat.com, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, Eric Paris , mpatel@redhat.com, Serge Hallyn Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 23, 2020 at 3:04 PM Richard Guy Briggs wrote: > On 2020-01-23 12:09, Paul Moore wrote: > > On Thu, Jan 23, 2020 at 11:29 AM Richard Guy Briggs wrote: > > > On 2020-01-22 16:28, Paul Moore wrote: > > > > On Tue, Dec 31, 2019 at 2:50 PM Richard Guy Briggs wrote: > > > > > > > > > > Add audit container identifier support to the action of signalling the > > > > > audit daemon. > > > > > > > > > > Since this would need to add an element to the audit_sig_info struct, > > > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new > > > > > audit_sig_info2 struct. Corresponding support is required in the > > > > > userspace code to reflect the new record request and reply type. > > > > > An older userspace won't break since it won't know to request this > > > > > record type. > > > > > > > > > > Signed-off-by: Richard Guy Briggs > > > > > --- > > > > > include/linux/audit.h | 7 +++++++ > > > > > include/uapi/linux/audit.h | 1 + > > > > > kernel/audit.c | 35 +++++++++++++++++++++++++++++++++++ > > > > > kernel/audit.h | 1 + > > > > > security/selinux/nlmsgtab.c | 1 + > > > > > 5 files changed, 45 insertions(+) > > > > > > > > ... > > > > > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > > index 0871c3e5d6df..51159c94041c 100644 > > > > > --- a/kernel/audit.c > > > > > +++ b/kernel/audit.c > > > > > @@ -126,6 +126,14 @@ struct auditd_connection { > > > > > kuid_t audit_sig_uid = INVALID_UID; > > > > > pid_t audit_sig_pid = -1; > > > > > u32 audit_sig_sid = 0; > > > > > +/* Since the signal information is stored in the record buffer at the > > > > > + * time of the signal, but not retrieved until later, there is a chance > > > > > + * that the last process in the container could terminate before the > > > > > + * signal record is delivered. In this circumstance, there is a chance > > > > > + * the orchestrator could reuse the audit container identifier, causing > > > > > + * an overlap of audit records that refer to the same audit container > > > > > + * identifier, but a different container instance. */ > > > > > +u64 audit_sig_cid = AUDIT_CID_UNSET; > > > > > > > > I believe we could prevent the case mentioned above by taking an > > > > additional reference to the audit container ID object when the signal > > > > information is collected, dropping it only after the signal > > > > information is collected by userspace or another process signals the > > > > audit daemon. Yes, it would block that audit container ID from being > > > > reused immediately, but since we are talking about one number out of > > > > 2^64 that seems like a reasonable tradeoff. > > > > > > I had thought that through and should have been more explicit about that > > > situation when I documented it. We could do that, but then the syscall > > > records would be connected with the call from auditd on shutdown to > > > request that signal information, rather than the exit of that last > > > process that was using that container. This strikes me as misleading. > > > Is that really what we want? > > > > ??? > > > > I think one of us is not understanding the other; maybe it's me, maybe > > it's you, maybe it's both of us. > > > > Anyway, here is what I was trying to convey with my original comment > > ... When we record the audit container ID in audit_signal_info() we > > take an extra reference to the audit container ID object so that it > > will not disappear (and get reused) until after we respond with an > > AUDIT_SIGNAL_INFO2. In audit_receive_msg() when we do the > > AUDIT_SIGNAL_INFO2 processing we drop the extra reference we took in > > audit_signal_info(). Unless I'm missing some other change you made, > > this *shouldn't* affect the syscall records, all it does is preserve > > the audit container ID object in the kernel's ACID store so it doesn't > > get reused. > > This is exactly what I had understood. I hadn't considered the extra > details below in detail due to my original syscall concern, but they > make sense. > > The syscall I refer to is the one connected with the drop of the > audit container identifier by the last process that was in that > container in patch 5/16. The production of this record is contingent on > the last ref in a contobj being dropped. So if it is due to that ref > being maintained by audit_signal_info() until the AUDIT_SIGNAL_INFO2 > record it fetched, then it will appear that the fetch action closed the > container rather than the last process in the container to exit. > > Does this make sense? More so than your original reply, at least to me anyway. It makes sense that the audit container ID wouldn't be marked as "dead" since it would still be very much alive and available for use by the orchestrator, the question is if that is desirable or not. I think the answer to this comes down the preserving the correctness of the audit log. If the audit container ID reported by AUDIT_SIGNAL_INFO2 has been reused then I think there is a legitimate concern that the audit log is not correct, and could be misleading. If we solve that by grabbing an extra reference, then there could also be some confusion as userspace considers a container to be "dead" while the audit container ID still exists in the kernel, and the kernel generated audit container ID death record will not be generated until much later (and possibly be associated with a different event, but that could be solved by unassociating the container death record). Of the two approaches, I think the latter is safer in that it preserves the correctness of the audit log, even though it could result in a delay of the container death record. Neither way is perfect, so if you have any other ideas I'm all ears. > > (We do need to do some extra housekeeping in audit_signal_info() to > > deal with the case where nobody asks for AUDIT_SIGNAL_INFO2 - > > basically if audit_sig_cid is not NULL we should drop a reference > > before assigning it a new object pointer, and of course we would need > > to set audit_sig_cid to NULL in audit_receive_msg() after sending it > > up to userspace and dropping the extra ref.) -- paul moore www.paul-moore.com