From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755467AbdLTPOk (ORCPT ); Wed, 20 Dec 2017 10:14:40 -0500 Received: from mail-qt0-f181.google.com ([209.85.216.181]:33290 "EHLO mail-qt0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755149AbdLTPOi (ORCPT ); Wed, 20 Dec 2017 10:14:38 -0500 X-Google-Smtp-Source: ACJfBosgXnRGG5a2LVM5vGf7nQtanGOD2jqWeDGek+z6uCaFNFdsyocI0fIVT7+LqgPKW42kufJFBQ== Date: Wed, 20 Dec 2017 07:14:35 -0800 From: Tejun Heo To: vcaputo@pengaru.com Cc: Bronek Kozicki , linux-kernel@vger.kernel.org Subject: Re: PROBLEM: NULL pointer dereference in kernel 4.14.6 Message-ID: <20171220151435.GB3413940@devbig577.frc2.facebook.com> References: <1513512885.3653140.1207725096.395A9CCC@webmail.messagingengine.com> <08995310-d853-ee77-ed1f-26cc336a4a30@incorrekt.com> <20171217232448.yfaxxew2ijaay7iu@shells.gnugeneration.com> <20171219134239.GN3919388@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171219134239.GN3919388@devbig577.frc2.facebook.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 19, 2017 at 05:42:39AM -0800, Tejun Heo wrote: > On Sun, Dec 17, 2017 at 03:24:48PM -0800, vcaputo@pengaru.com wrote: > > On Sun, Dec 17, 2017 at 05:49:44PM +0000, Bronek Kozicki wrote: > > > I just upgraded to 4.14.7 and tried to reproduce this error, this time under strace. As you can see this happens when systemctl tries to read a specific entry under /sys/fs . In case this matters, the entry is for a small virtual machine running under qemu/kvm and managed by libvirt. > > > > > > open("/sys/fs/cgroup/unified/machine.slice", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5 > > > fstat(5, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0 > > > getdents(5, /* 12 entries */, 32768) = 464 > > > openat(AT_FDCWD, "/sys/fs/cgroup/unified/machine.slice/machine-qemu\\x2d1\\x2dkartuzy\\x2dspice.scope/cgroup.procs", O_RDONLY|O_CLOEXEC) = 8 > > > fstat(8, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0 > > > read(8, ) = ? > > > +++ killed by SIGKILL +++ > > > [1] 12078 killed strace -- systemctl status > > > > > > > > > > This recently came through lkml, may be related: > > https://marc.info/?l=linux-kernel&m=151320108922415&w=2 > > It looks like it could be the same problem. Working on the fix now. > Will let you know when I have something. Fix posted. http://lkml.kernel.org/r/20171220151331.GA3413940@devbig577.frc2.facebook.com Thanks. -- tejun