From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.sys4.de (mail.sys4.de [194.126.158.139]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail09.linbit.com (LINBIT Mail Daemon) with ESMTPS id B840F101AC7E for ; Tue, 23 Sep 2014 19:08:26 +0200 (CEST) Received: from localhost (ip2505fba1.dynamic.kabel-deutschland.de [37.5.251.161]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.sys4.de (Postfix) with ESMTPSA id 3j2TVx5HlmzJC for ; Tue, 23 Sep 2014 19:08:25 +0200 (CEST) Date: Tue, 23 Sep 2014 19:08:24 +0200 From: Marc Schiffbauer To: drbd-dev@lists.linbit.com Message-ID: <20140923170824.GA32597@schiffbauer.net> References: <20140919094909.GA21578@schiffbauer.net> <20140919144805.GS13125@soda.linbit> <20140919151653.GH21578@schiffbauer.net> <20140923110348.GA19076@soda.linbit> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20140923110348.GA19076@soda.linbit> Subject: Re: [Drbd-dev] drbd 8.4.3: refcounter overflow on re-sync List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , * Lars Ellenberg schrieb am 23.09.14 um 13:03 Uhr: >On Fri, Sep 19, 2014 at 05:16:53PM +0200, Marc Schiffbauer wrote: >> * Lars Ellenberg schrieb am 19.09.14 um 16:48 Uhr: >> >On Fri, Sep 19, 2014 at 11:49:09AM +0200, Marc Schiffbauer wrote: >> >>Hi, >> >> >> > >> >If you resolve that to a code line, >> >I may be able to figure out what PAX is talking about. >> > >> >But from this stack trace alone, I have absolutely no idea what PAX >> >is trying to say, which refcount could possibly be meant there, >> >let alone why it could possibly overflow or. >> > >> >Ah, ok. Looking at [1], "PaX Team" says: >> >.--- >> >| after having looked at the drbd code a bit i think this could be a >> >| real bug in drbd but only upstream can tell for sure so you'll have to >> >| contact them. you can show them the following that i figured out so far: >> >| >> >| the refcount overflow was detected in >> >| drivers/block/drbd/drbd_bitmap.c:bm_page_io_async at the >> >| >> >| atomic_add(len >> 9, &mdev->rs_sect_ev) >> > >> >Well, yes, why would it not overflow. >> >It is *not* a refcount. >> >It is an atomic counter. >> >It is meant to overflow. >> >> Ok, then I can report this back and it should be fixed in PaX as a >> false postive. Thanks for clarifying this. > >I still don't get why PAX is even sending a signal there. >How could sending a signal possibly help against an overflowing counter? PAX is a patchset for the linux kernel that hardens the kernel in several ways. The REFCOUNT feature will detect and prevent overflowing of refcounters. This is a good introduction of what it does: http://wiki.gentoo.org/wiki/Hardened/PaX_Quickstart -Marc -- [*] sys4 AG http://sys4.de, +49 (89) 30 90 46 64 Franziskanerstraße 15, 81669 München Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263 Vorstand: Patrick Ben Koetter, Marc Schiffbauer Aufsichtsratsvorsitzender: Florian Kirstein