From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH] sctp: Do not trigger BUG_ON when deleting assoc without primary path Date: Thu, 17 Oct 2013 20:52:58 +0200 Message-ID: <5260320A.7040109@redhat.com> References: <1382031042-27339-1-git-send-email-vyasevich@gmail.com> <526025F2.2040304@redhat.com> <52602BA3.5020405@redhat.com> <52602E0C.6000300@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-sctp@vger.kernel.org, Mark Thomas , Neil Horman To: Vlad Yasevich Return-path: Received: from mx1.redhat.com ([209.132.183.28]:29347 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758227Ab3JQSxT (ORCPT ); Thu, 17 Oct 2013 14:53:19 -0400 In-Reply-To: <52602E0C.6000300@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On 10/17/2013 08:35 PM, Vlad Yasevich wrote: > On 10/17/2013 02:25 PM, Daniel Borkmann wrote: >> On 10/17/2013 08:01 PM, Daniel Borkmann wrote: >>> On 10/17/2013 07:30 PM, Vlad Yasevich wrote: >>>> It is possible to enter sctp_cmd_delete_tcb() without having a >>>> primary path. The situations this most often happens in is >>>> when duplication cookie processing is triggered. In this >>>> case, we are deleting a temporarily created association that >>>> is not fully populated. Additially, at the time we >>>> are deleting the offending association, it is really too >>>> late to issue a BUG! >>>> >>>> This was introduced by: >>>> commit f9e42b853523cda0732022c2e0473c183f7aec65 >>>> net: sctp: sideeffect: throw BUG if primary_path is NULL >>> >>> Sure, lets remove it, but then we could still get a WARN() [sure, >>> better than BUG], if the user at the very same time checks procfs >>> through sctp_seq_dump_local_addrs(), see discussion we had here [1]: >>> >>> It may trigger the crash later if the user performs some action on the >>> association that touches the primary. That's the reason why I was >>> proposing the checks below. >>> >>> With the checks in command interpreter, we are only left with the >>> possibility that primary_path changes to NULL during the association >>> lifetime, which code audit doesn't support right now. If that ever >>> changes we would at least have a bit more information to go on. >>> >>> [1] http://patchwork.ozlabs.org/patch/251099/ >> >> Meaning, all I'm saying is that with f9e42b853 we wanted to find exactly >> such a case we have right now, that is, that an assoc could enter the >> hashtable w/o primary path, no? > > But it didn't enter a hash table in this case. SCTP_CMD_NEW_ASOC > was never issued. The sequence was: > SCTP_CMD_SET_ASOC > SCTP_CMD_DELETE_TCB > > Such association would never be found through /proc since it was never > hashed. Such association would never be found the user since it > is only really alive while the packet is processed. By all rights > it should be marked as 'temp', but it isn't due to cookie processing. > > May be we should update cookie processing function to allow it > to create temp associations if so desired. Yes, I think that might be the better way to move on. > -vlad