From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: netfilter: nf_conntrack: there maybe a bug in __nf_conntrack_confirm, when it race against get_next_corpse Date: Thu, 6 Nov 2014 14:00:13 +0100 Message-ID: <20141106140013.5110dd6e@redhat.com> References: <012601cff7d1$7ce2d620$76a88260$@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: , , "Pablo Neira Ayuso" , "Patrick McHardy" , , , "Changli Gao" , "Andrey Vagin" , brouer@redhat.com, "netfilter-devel@vger.kernel.org" , "netdev@vger.kernel.org" To: "billbonaparte" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:45152 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751021AbaKFNAr (ORCPT ); Thu, 6 Nov 2014 08:00:47 -0500 In-Reply-To: <012601cff7d1$7ce2d620$76a88260$@gmail.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Tue, 4 Nov 2014 09:48:32 +0800 "billbonaparte" wrote: > (sorry to send this e-mail again, last mail is rejected by server due to > non-acceptable content) There is several issues with your submission. I'll take care of resubmitting a patch in your name (so you will get credit in the git log). If you care to know, issues are: 1. you are not sending to the appropriate mailing lists, 2. patch is as an attachment (should be inlined), 3. the patch have style and white-space issues. > Florian Westphal [mailto:fw@strlen.de] wrote: > >Correct. This is broken since the central spin lock removal, since > >nf_conntrack_lock no longer protects both get_next_corpse and > >conntrack_confirm. > > > >Please send a patch, moving dying check after removal of conntrack from > >the percpu list, > > Since unconfirmed conntrack is stored in unconfirmed-list which is per-cpu > list and protected by per-cpu spin-lock, we can remove it from > uncomfirmed-list and insert it into ct-hash-table separately. that is to > say, we can remove it from uncomfirmed-list without holding corresponding > hash-lock, then check if it is dying. > if it is dying, we add it to the dying-list, then quit > __nf_conntrack_confirm. we do this to follow the rules that the conntrack > must alternatively at unconfirmed-list or dying-list when it is abort to be > destroyed. In the resubmit. I'll take a slightly more conservative approach, by keeping the DYING check under the hash-lock, as it is currently. I guess we could do it without holding the hash-lock, but I want to keep the fix as simple as possible. > >> 2. operation on ct->status should be atomic, because it race aginst > >> get_next_corpse. [...] > if there is a race at operating ct->status, there will be in alternative > case: > 1) IPS_DYING bit which set in get_next_corpse override other bits (e.g. > IPS_SRC_NAT_DONE_BIT), or > 2) other bits (e.g. IPS_SRC_NAT_DONE_BIT) which set in nf_nat_setup_info > override IPS_DYING bit. Notice the set_bit() is atomic, so we don't have these issues (of bits getting overridden). -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer