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Tue, 17 Dec 2019 19:56:46 +0000 (UTC) Received: from madcap2.tricolour.ca (ovpn-112-28.phx2.redhat.com [10.3.112.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7331C5C548; Tue, 17 Dec 2019 19:56:34 +0000 (UTC) Date: Tue, 17 Dec 2019 14:56:31 -0500 From: Richard Guy Briggs To: Steve Grubb Cc: Paul Moore , Neil Horman , containers@lists.linux-foundation.org, linux-api@vger.kernel.org, Linux-Audit Mailing List , linux-fsdevel@vger.kernel.org, LKML , netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, omosnace@redhat.com, dhowells@redhat.com, simo@redhat.com, Eric Paris , Serge Hallyn , ebiederm@xmission.com, Dan Walsh , mpatel@redhat.com Subject: Re: [PATCH ghak90 V7 06/21] audit: contid limit of 32k imposed to avoid DoS Message-ID: <20191217195631.3obqll4nf5poe7cz@madcap2.tricolour.ca> References: <20191217184541.tagssqt4zujbanf6@madcap2.tricolour.ca> <2318345.msVmMTmnKu@x2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2318345.msVmMTmnKu@x2> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On 2019-12-17 14:25, Steve Grubb wrote: > On Tuesday, December 17, 2019 1:45:41 PM EST Richard Guy Briggs wrote: > > On 2019-11-08 12:49, Paul Moore wrote: > > > On Thu, Oct 24, 2019 at 5:23 PM Richard Guy Briggs > wrote: > > > > On 2019-10-10 20:38, Paul Moore wrote: > > > > > On Fri, Sep 27, 2019 at 8:52 AM Neil Horman > wrote: > > > > > > On Wed, Sep 18, 2019 at 09:22:23PM -0400, Richard Guy Briggs wrote: > > > > > > > Set an arbitrary limit on the number of audit container > > > > > > > identifiers to > > > > > > > limit abuse. > > > > > > > > > > > > > > Signed-off-by: Richard Guy Briggs > > > > > > > --- > > > > > > > kernel/audit.c | 8 ++++++++ > > > > > > > kernel/audit.h | 4 ++++ > > > > > > > 2 files changed, 12 insertions(+) > > > > > > > > > > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > > > > index 53d13d638c63..329916534dd2 100644 > > > > > > > --- a/kernel/audit.c > > > > > > > +++ b/kernel/audit.c > > > > > > > > > > ... > > > > > > > > > > > > @@ -2465,6 +2472,7 @@ int audit_set_contid(struct task_struct > > > > > > > *task, u64 contid) newcont->owner = current; > > > > > > > refcount_set(&newcont->refcount, 1); > > > > > > > list_add_rcu(&newcont->list, &audit_contid_hash[h]); > > > > > > > + audit_contid_count++; > > > > > > > } else { > > > > > > > rc = -ENOMEM; > > > > > > > goto conterror; > > > > > > > diff --git a/kernel/audit.h b/kernel/audit.h > > > > > > > index 162de8366b32..543f1334ba47 100644 > > > > > > > --- a/kernel/audit.h > > > > > > > +++ b/kernel/audit.h > > > > > > > @@ -219,6 +219,10 @@ static inline int audit_hash_contid(u64 > > > > > > > contid) > > > > > > > return (contid & (AUDIT_CONTID_BUCKETS-1)); > > > > > > > } > > > > > > > > > > > > > > +extern int audit_contid_count; > > > > > > > + > > > > > > > +#define AUDIT_CONTID_COUNT 1 << 16 > > > > > > > + > > > > > > > > > > > > Just to ask the question, since it wasn't clear in the changelog, > > > > > > what > > > > > > abuse are you avoiding here? Ostensibly you should be able to > > > > > > create as > > > > > > many container ids as you have space for, and the simple creation > > > > > > of > > > > > > container ids doesn't seem like the resource strain I would be > > > > > > concerned > > > > > > about here, given that an orchestrator can still create as many > > > > > > containers as the system will otherwise allow, which will consume > > > > > > significantly more ram/disk/etc. > > > > > > > > > > I've got a similar question. Up to this point in the patchset, there > > > > > is a potential issue of hash bucket chain lengths and traversing them > > > > > with a spinlock held, but it seems like we shouldn't be putting an > > > > > arbitrary limit on audit container IDs unless we have a good reason > > > > > for it. If for some reason we do want to enforce a limit, it should > > > > > probably be a tunable value like a sysctl, or similar. > > > > > > > > Can you separate and clarify the concerns here? > > > > > > "Why are you doing this?" is about as simple as I can pose the question. > > > > It was more of a concern for total system resources, primarily memory, > > but this is self-limiting and an arbitrary concern. > > > > The other limit of depth of nesting has different concerns that arise > > depending on how reporting is done. > > Well, there is a limit on the audit record size. So, whatever is being sent > in the record plus the size of the timestamp deducted from > MAX_AUDIT_MESSAGE_LENGTH (8970) is the limit. That can be divided by however > many ID's fit in that space and you have the real limit. This will be addressed in the v8 patch set. > -Steve - 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