From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC79DC433DF for ; Mon, 8 Jun 2020 18:04:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C502F208B8 for ; Mon, 8 Jun 2020 18:04:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D9fTI1IW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730175AbgFHSEC (ORCPT ); Mon, 8 Jun 2020 14:04:02 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:53053 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729843AbgFHSEB (ORCPT ); Mon, 8 Jun 2020 14:04:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591639439; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=uw5NjJ0WopWX8Tckd6/nHTcQhEVOsQbonk1220jJm6A=; b=D9fTI1IW3bvq2obozeWrpvNTqCyeK7j7sa1GVbd3Vl4DH0ZkXpG1d9SEM18UrJotlvSisA 4W6Yjblw3JzQOaEVZSPMx4F3JI7tl6NLgbeKu9HGydcpwW7ucnyoEeAg2xw3djxfsrBdhp CFEE0kZnlETzWYzAGQX38wCmqzSuf+k= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-170-mA0IjPaLOdWDFywZFnhrIg-1; Mon, 08 Jun 2020 14:03:52 -0400 X-MC-Unique: mA0IjPaLOdWDFywZFnhrIg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6FAD91005510; Mon, 8 Jun 2020 18:03:49 +0000 (UTC) Received: from madcap2.tricolour.ca (unknown [10.10.110.54]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9756760BF3; Mon, 8 Jun 2020 18:03:33 +0000 (UTC) Date: Mon, 8 Jun 2020 14:03:30 -0400 From: Richard Guy Briggs To: Paul Moore Cc: "Eric W. Biederman" , nhorman@tuxdriver.com, linux-api@vger.kernel.org, containers@lists.linux-foundation.org, LKML , dhowells@redhat.com, linux-audit@redhat.com, netfilter-devel@vger.kernel.org, simo@redhat.com, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, Eric Paris , mpatel@redhat.com, Serge Hallyn Subject: Re: [PATCH ghak90 V8 07/16] audit: add contid support for signalling the audit daemon Message-ID: <20200608180330.z23hohfa2nclhxf5@madcap2.tricolour.ca> References: <20200330134705.jlrkoiqpgjh3rvoh@madcap2.tricolour.ca> <20200330162156.mzh2tsnovngudlx2@madcap2.tricolour.ca> <20200330174937.xalrsiev7q3yxsx2@madcap2.tricolour.ca> <871ronf9x2.fsf@x220.int.ebiederm.org> <871rol7nw3.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-04-22 13:24, Paul Moore wrote: > On Fri, Apr 17, 2020 at 6:26 PM Eric W. Biederman wrote: > > Paul Moore writes: > > > On Thu, Apr 16, 2020 at 4:36 PM Eric W. Biederman wrote: > > >> Paul Moore writes: > > >> > On Mon, Mar 30, 2020 at 1:49 PM Richard Guy Briggs wrote: > > >> >> On 2020-03-30 13:34, Paul Moore wrote: > > >> >> > On Mon, Mar 30, 2020 at 12:22 PM Richard Guy Briggs wrote: > > >> >> > > On 2020-03-30 10:26, Paul Moore wrote: > > >> >> > > > On Mon, Mar 30, 2020 at 9:47 AM Richard Guy Briggs wrote: > > >> >> > > > > On 2020-03-28 23:11, Paul Moore wrote: > > >> >> > > > > > On Tue, Mar 24, 2020 at 5:02 PM Richard Guy Briggs wrote: > > >> >> > > > > > > On 2020-03-23 20:16, Paul Moore wrote: > > >> >> > > > > > > > On Thu, Mar 19, 2020 at 6:03 PM Richard Guy Briggs wrote: > > >> >> > > > > > > > > On 2020-03-18 18:06, Paul Moore wrote: > > >> > > > >> > ... > > >> > > > >> >> > > Well, every time a record gets generated, *any* record gets generated, > > >> >> > > we'll need to check for which audit daemons this record is in scope and > > >> >> > > generate a different one for each depending on the content and whether > > >> >> > > or not the content is influenced by the scope. > > >> >> > > > >> >> > That's the problem right there - we don't want to have to generate a > > >> >> > unique record for *each* auditd on *every* record. That is a recipe > > >> >> > for disaster. > > >> >> > > > >> >> > Solving this for all of the known audit records is not something we > > >> >> > need to worry about in depth at the moment (although giving it some > > >> >> > casual thought is not a bad thing), but solving this for the audit > > >> >> > container ID information *is* something we need to worry about right > > >> >> > now. > > >> >> > > >> >> If you think that a different nested contid value string per daemon is > > >> >> not acceptable, then we are back to issuing a record that has only *one* > > >> >> contid listed without any nesting information. This brings us back to > > >> >> the original problem of keeping *all* audit log history since the boot > > >> >> of the machine to be able to track the nesting of any particular contid. > > >> > > > >> > I'm not ruling anything out, except for the "let's just completely > > >> > regenerate every record for each auditd instance". > > >> > > >> Paul I am a bit confused about what you are referring to when you say > > >> regenerate every record. > > >> > > >> Are you saying that you don't want to repeat the sequence: > > >> audit_log_start(...); > > >> audit_log_format(...); > > >> audit_log_end(...); > > >> for every nested audit daemon? > > > > > > If it can be avoided yes. Audit performance is already not-awesome, > > > this would make it even worse. > > > > As far as I can see not repeating sequences like that is fundamental > > for making this work at all. Just because only the audit subsystem > > should know about one or multiple audit daemons. Nothing else should > > care. > > Yes, exactly, this has been mentioned in the past. Both the > performance hit and the code complication in the caller are things we > must avoid. > > > >> Or are you saying that you would like to literraly want to send the same > > >> skb to each of the nested audit daemons? > > > > > > Ideally we would reuse the generated audit messages as much as > > > possible. Less work is better. That's really my main concern here, > > > let's make sure we aren't going to totally tank performance when we > > > have a bunch of nested audit daemons. > > > > So I think there are two parts of this answer. Assuming we are talking > > about nesting audit daemons in containers we will have different > > rulesets and I expect most of the events for a nested audit daemon won't > > be of interest to the outer audit daemon. > > Yes, this is another thing that Richard and I have discussed in the > past. We will basically need to create per-daemon queues, rules, > tracking state, etc.; that is easy enough. What will be slightly more > tricky is the part where we apply the filters to the individual > records and decide if that record is valid/desired for a given daemon. > I think it can be done without too much pain, and any changes to the > callers, but it will require a bit of work to make sure it is done > well and that records are needlessly duplicated in the kernel. > > > Beyond that it should be very straight forward to keep a pointer and > > leave the buffer as a scatter gather list until audit_log_end > > and translate pids, and rewrite ACIDs attributes in audit_log_end > > when we build the final packet. Either through collaboration with > > audit_log_format or a special audit_log command that carefully sets > > up the handful of things that need that information. > > In order to maximize record re-use I think we will want to hold off on > assembling the final packet until it is sent to the daemons in the > kauditd thread. We'll also likely need to create special > audit_log_XXX functions to capture fields which we know will need > translation, e.g. ACID information. (the reason for the new > audit_log_XXX functions would be to mark the new sg element and ensure > the buffer is handled correctly) > > Regardless of the details, I think the scatter gather approach is the > key here - that seems like the best design idea I've seen thus far. > It enables us to replace portions of the record as needed ... and > possibly use the existing skb cow stuff ... it has been a while, but > does the skb cow functions handle scatter gather skbs or do they need > to be linear? How does the selection of this data management technique affect our choice of field format? Does this lock the field value to a fixed length? Does the use of scatter/gather techniques or structures allow the use of different lengths of data for each destination (auditd)? I could see different target audit daemons triggering or switching to a different chunk of data and length. This does raise a concern related to the previous sig_info2 discussion that the struct contobj that exists at the time of audit_log_exit called could have been reaped by the time the buffer is pulled from the queue for transmission to auditd, but we could hold a reference to it as is done for sig_info2. Looking through the kernel scatter/gather possibilities, I see struct iovec which is used by the readv/writev/preadv/pwritev syscalls, but I'm understanding that this is a kernel implementation that will be not visible to user space. So would the struct scatterlist be the right choice? > paul moore - RGB -- Richard Guy Briggs Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635