Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751122Ab1FJECu (ORCPT ); Fri, 10 Jun 2011 00:02:50 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:33789 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750769Ab1FJECs (ORCPT ); Fri, 10 Jun 2011 00:02:48 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Fri, 10 Jun 2011 12:55:51 +0900 From: KAMEZAWA Hiroyuki To: KAMEZAWA Hiroyuki Cc: Hugh Dickins , Ying Han , Dave Jones , Linux Kernel , "linux-mm@kvack.org" Subject: Re: 3.0rc2 oops in mem_cgroup_from_task Message-Id: <20110610125551.385ea7ed.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20110610121949.622e4629.kamezawa.hiroyu@jp.fujitsu.com> References: <20110609212956.GA2319@redhat.com> <20110610091355.2ce38798.kamezawa.hiroyu@jp.fujitsu.com> <20110610113311.409bb423.kamezawa.hiroyu@jp.fujitsu.com> <20110610121949.622e4629.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.1.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1921 Lines: 61 On Fri, 10 Jun 2011 12:19:49 +0900 KAMEZAWA Hiroyuki wrote: > On Fri, 10 Jun 2011 11:33:11 +0900 > KAMEZAWA Hiroyuki wrote: > > > On Thu, 9 Jun 2011 18:30:49 -0700 (PDT) > > Hugh Dickins wrote: > > > > 781cc621 : > > > 781cc621: 55 push %ebp > > > 781cc622: 31 c0 xor %eax,%eax > > > 781cc624: 89 e5 mov %esp,%ebp > > > 781cc626: 8b 55 08 mov 0x8(%ebp),%edx > > > 781cc629: 85 d2 test %edx,%edx > > > 781cc62b: 74 09 je 781cc636 > > > 781cc62d: 8b 82 fc 08 00 00 mov 0x8fc(%edx),%eax > > > 781cc633: 8b 40 1c mov 0x1c(%eax),%eax <========== > > > 781cc636: c9 leave > > > 781cc637: c3 ret > > > > > > > then, access to task->cgroups->subsys[?] causes access to 6b6b6b87... > > > > Then, task->cgroups or task->cgroups->subsys contains bad pointer. > > Considering khugepaged, it grabs mm_struct and memcg make an access to > > (mm->owner)->cgroups->subsys. > > > > Then, from memcg's point of view, we need to doubt mm->owner is valid or not > > for this kind of tasks. > > > > Dave's log shows 6b6b6b6b6b..., too. > > I guess it as "POISON_FREE" of slab object. Then, task->cgroups may used after free. > Ah, sorry. 0x1c(%eax) == 6b6b6b87 means %eax was 0x6b6b6b6b. The %eax was the contents of [task->cgroups]....hmm, then, task itself is freed pointer (and poisoned). So, it seems a problem of accessing mm->owner.. 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/