Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754928Ab1FCNAu (ORCPT ); Fri, 3 Jun 2011 09:00:50 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:62238 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754730Ab1FCNAs convert rfc822-to-8bit (ORCPT ); Fri, 3 Jun 2011 09:00:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=syJes1cDxCePcstvyv3pOFLemF3nqoZYcPalHtcemb0++p3AsnZWuuyA2XN3UaKScK rtCa9iGKL25O0uSuZ9K3xDo+oLWXimAka97aPsCM4VMtk5wRh6znG1Zk8C+PgRzCWJay 5iaRmLrjuB6vcU3R0BU+wVrSAp5vTwYYyrxBc= MIME-Version: 1.0 In-Reply-To: <4DE8D50F.1090406@redhat.com> References: <1306925044-2828-1-git-send-email-imammedo@redhat.com> <20110601123913.GC4266@tiehlicka.suse.cz> <4DE6399C.8070802@redhat.com> <20110601134149.GD4266@tiehlicka.suse.cz> <4DE64F0C.3050203@redhat.com> <20110601152039.GG4266@tiehlicka.suse.cz> <4DE66BEB.7040502@redhat.com> <4DE8D50F.1090406@redhat.com> Date: Fri, 3 Jun 2011 22:00:47 +0900 Message-ID: Subject: Re: [PATCH] memcg: do not expose uninitialized mem_cgroup_per_node to world From: Hiroyuki Kamezawa To: Igor Mammedov Cc: Michal Hocko , linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, balbir@linux.vnet.ibm.com, akpm@linux-foundation.org, linux-mm@kvack.org, Paul Menage , Li Zefan , containers@lists.linux-foundation.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2118 Lines: 57 2011/6/3 Igor Mammedov : > On 06/02/2011 01:10 AM, Hiroyuki Kamezawa wrote: >>> >>> pc = list_entry(list->prev, struct page_cgroup, lru); >> >> Hmm, I disagree your patch is a fix for mainline. At least, a cgroup >> before completion of >> create() is not populated to userland and you never be able to rmdir() >> it because you can't >> find it. >> >> >> ?>26: ? e8 7d 12 30 00 ? ? ? ? ?call ? 0x3012a8 >> ?>2b:* ?8b 73 08 ? ? ? ? ? ? ? ?mov ? ?0x8(%ebx),%esi<-- trapping >> instruction >> ?>2e: ? 8b 7c 24 24 ? ? ? ? ? ? mov ? ?0x24(%esp),%edi >> ?>32: ? 8b 07 ? ? ? ? ? ? ? ? ? mov ? ?(%edi),%eax >> >> Hm, what is the call 0x3012a8 ? >> > ? ? ? ? ? ? ? ?pc = list_entry(list->prev, struct page_cgroup, lru); > ? ? ? ? ? ? ? ?if (busy == pc) { > ? ? ? ? ? ? ? ? ? ? ? ?list_move(&pc->lru, list); > ? ? ? ? ? ? ? ? ? ? ? ?busy = 0; > ? ? ? ? ? ? ? ? ? ? ? ?spin_unlock_irqrestore(&zone->lru_lock, flags); > ? ? ? ? ? ? ? ? ? ? ? ?continue; > ? ? ? ? ? ? ? ?} > ? ? ? ? ? ? ? ?spin_unlock_irqrestore(&zone->lru_lock, flags); <---- is > ?call 0x3012a8 > ? ? ? ? ? ? ? ?ret = mem_cgroup_move_parent(pc, mem, GFP_KERNEL); > > and ?mov 0x8(%ebx),%esi > is dereferencing of 'pc' in inlined mem_cgroup_move_parent > Ah, thank you for input..then panicd at accessing pc->page and "pc" was 0xfffffff4. it means list->prev was NULL. > I've looked at vmcore once more and indeed there isn't any parallel task > that touches cgroups code path. > Will investigate if it is xen to blame for incorrect data in place. > > Thanks very much for your opinion. What curious to me is that the fact "list->prev" is NULL. I can see why you doubt the initialization code ....the list pointer never contains NULL once it's used.... it smells like memory corruption or some to me. If you have vmcore, what the problematic mem_cgroup_per_zone(node) contains ? Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/