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[209.132.180.67]) by mx.google.com with ESMTP id q21si4412787ooq.38.2020.03.28.20.17.59; Sat, 28 Mar 2020 20:18:16 -0700 (PDT) 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=hUOW7wlG; 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 S1727336AbgC2DRa (ORCPT + 99 others); Sat, 28 Mar 2020 23:17:30 -0400 Received: from mail-ed1-f65.google.com ([209.85.208.65]:42664 "EHLO mail-ed1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726899AbgC2DR3 (ORCPT ); Sat, 28 Mar 2020 23:17:29 -0400 Received: by mail-ed1-f65.google.com with SMTP id cw6so15978557edb.9 for ; Sat, 28 Mar 2020 20:17:27 -0700 (PDT) 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=73jM7UJ1SiInp3qgWBqwVopBoGUW8da3yGoLPO2s510=; b=hUOW7wlGLFSvtHFZFzYEk7uCZM0H4qRyVG1Nq3cJ6E529xu/itB2Sw5XZwbQ+u0atq IyUnfYEn/D0SlrwCk47/eOrsUScgL3N5AGSU1dSkADlcDK/uKgu0oxbrZ7a+4AuMZ3/i u+eRvLFW/3YH6/NomvPTj4lTDuRjf4b8+lzYhV5sdgOcQV5z633Ayp/5ldFb0ouvIGof /UFc5isFg/YJtxKJ3Lma2Q7GC1+Cogl7V2tEkB04nQPioaCwIH+ECkq5ZE4XVZ6Ih5Vv wIA1iofcg4YPsZ2gIQ5fdRfyxTKX/BpU+PLevB4xhg1RS674R3j7mNprN6l2A7i+2HnX C7lg== 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=73jM7UJ1SiInp3qgWBqwVopBoGUW8da3yGoLPO2s510=; b=Kqwms59gyHvrBg0Xg2HlTwHZH+cXuENTdfrv8gE4YT/iDMEnj9ttyDzVQAOdxCUL/x QrKKsazhMa74pq2pw3ofsWHVmSItooP7eARZVATf2jgbnbhMU6jqBDpChJZdLXZ5jT7Z Fz9i2TQGkC19q8eynyL0SHFJwNI/ohzr4vnAAHc3IcfR1YkEDp62QjNX7qlurm5w2OCw 6GMsFGsyIHyADcJXqXRcRC7T6vS//xdLvC/nA7VQc7qoBmHXjV9ZN7wd4OgbavJbEjSE 8yYLOn2OpCig9VeS4vwjz97y35QnYlOT6SLI7Cjxs1QKsxyM572ZbgeFOepI0BUh3sEw 2ryA== X-Gm-Message-State: ANhLgQ0nHd++IzebXkQgaCE6QQy+S6fLfUUma0erB2FDy/Ema7HfpIIK Q6zHuPVMC80XsLelJ2Sb2EuIkrcQ0PYQrYiZNS87 X-Received: by 2002:aa7:d2cb:: with SMTP id k11mr6032886edr.128.1585451846873; Sat, 28 Mar 2020 20:17:26 -0700 (PDT) MIME-Version: 1.0 References: <3142237.YMNxv0uec1@x2> <20200312202733.7kli64zsnqc4mrd2@madcap2.tricolour.ca> <20200313192306.wxey3wn2h4htpccm@madcap2.tricolour.ca> <20200318214154.ycxy5dl4pxno6fvi@madcap2.tricolour.ca> <20200319214759.qgxt2sfkmd6srdol@madcap2.tricolour.ca> <20200325122903.obkpyog7fjabzrpf@madcap2.tricolour.ca> In-Reply-To: <20200325122903.obkpyog7fjabzrpf@madcap2.tricolour.ca> From: Paul Moore Date: Sat, 28 Mar 2020 23:17:15 -0400 Message-ID: Subject: Re: [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon To: Richard Guy Briggs Cc: Steve Grubb , linux-audit@redhat.com, nhorman@tuxdriver.com, linux-api@vger.kernel.org, containers@lists.linux-foundation.org, LKML , dhowells@redhat.com, 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 Wed, Mar 25, 2020 at 8:29 AM Richard Guy Briggs wrote: > On 2020-03-20 17:56, Paul Moore wrote: > > On Thu, Mar 19, 2020 at 5:48 PM Richard Guy Briggs wrote: > > > On 2020-03-18 17:47, Paul Moore wrote: > > > > On Wed, Mar 18, 2020 at 5:42 PM Richard Guy Briggs wrote: > > > > > On 2020-03-18 17:01, Paul Moore wrote: > > > > > > On Fri, Mar 13, 2020 at 3:23 PM Richard Guy Briggs wrote: > > > > > > > On 2020-03-13 12:42, Paul Moore wrote: > > > > > > > > > > > > ... > > > > > > > > > > > > > > The thread has had a lot of starts/stops, so I may be repeating a > > > > > > > > previous suggestion, but one idea would be to still emit a "death > > > > > > > > record" when the final task in the audit container ID does die, but > > > > > > > > block the particular audit container ID from reuse until it the > > > > > > > > SIGNAL2 info has been reported. This gives us the timely ACID death > > > > > > > > notification while still preventing confusion and ambiguity caused by > > > > > > > > potentially reusing the ACID before the SIGNAL2 record has been sent; > > > > > > > > there is a small nit about the ACID being present in the SIGNAL2 > > > > > > > > *after* its death, but I think that can be easily explained and > > > > > > > > understood by admins. > > > > > > > > > > > > > > Thinking quickly about possible technical solutions to this, maybe it > > > > > > > makes sense to have two counters on a contobj so that we know when the > > > > > > > last process in that container exits and can issue the death > > > > > > > certificate, but we still block reuse of it until all further references > > > > > > > to it have been resolved. This will likely also make it possible to > > > > > > > report the full contid chain in SIGNAL2 records. This will eliminate > > > > > > > some of the issues we are discussing with regards to passing a contobj > > > > > > > vs a contid to the audit_log_contid function, but won't eliminate them > > > > > > > all because there are still some contids that won't have an object > > > > > > > associated with them to make it impossible to look them up in the > > > > > > > contobj lists. > > > > > > > > > > > > I'm not sure you need a full second counter, I imagine a simple flag > > > > > > would be okay. I think you just something to indicate that this ACID > > > > > > object is marked as "dead" but it still being held for sanity reasons > > > > > > and should not be reused. > > > > > > > > > > Ok, I see your point. This refcount can be changed to a flag easily > > > > > enough without change to the api if we can be sure that more than one > > > > > signal can't be delivered to the audit daemon *and* collected by sig2. > > > > > I'll have a more careful look at the audit daemon code to see if I can > > > > > determine this. > > > > > > > > Maybe I'm not understanding your concern, but this isn't really > > > > different than any of the other things we track for the auditd signal > > > > sender, right? If we are worried about multiple signals being sent > > > > then it applies to everything, not just the audit container ID. > > > > > > Yes, you are right. In all other cases the information is simply > > > overwritten. In the case of the audit container identifier any > > > previous value is put before a new one is referenced, so only the last > > > signal is kept. So, we only need a flag. Does a flag implemented with > > > a rcu-protected refcount sound reasonable to you? > > > > Well, if I recall correctly you still need to fix the locking in this > > patchset so until we see what that looks like it is hard to say for > > certain. Just make sure that the flag is somehow protected from > > races; it is probably a lot like the "valid" flags you sometimes see > > with RCU protected lists. > > This is like looking for a needle in a haystack. Can you point me to > some code that does "valid" flags with RCU protected lists. Sigh. Come on Richard, you've been playing in the kernel for some time now. I can't think of one off the top of my head as I write this, but there are several resources that deal with RCU protected lists in the kernel, Google is your friend and Documentation/RCU is your friend. Spending time to learn how RCU works and how to use it properly is not time wasted. It's a tricky thing to get right (I have to refresh my memory on some of the more subtle details each time I write/review RCU code), but it's very cool when done correctly. -- paul moore www.paul-moore.com