linux-kernel - Re: [PATCHSET] mempool, percpu, blkcg: fix percpu stat allocation and remove stats

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120227142529.GA27677@redhat.com>
Date:	Mon, 27 Feb 2012 09:25:29 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, hughd@...gle.com, avi@...hat.com, nate@...nel.net,
	cl@...ux-foundation.org, linux-kernel@...r.kernel.org,
	dpshah@...gle.com, ctalbott@...gle.com, rni@...gle.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCHSET] mempool, percpu, blkcg: fix percpu stat allocation
 and remove stats_lock

On Sun, Feb 26, 2012 at 07:21:13AM +0900, Tejun Heo wrote:
> On Sun, Feb 26, 2012 at 06:46:41AM +0900, Tejun Heo wrote:
> > Hello,
> > 
> > On Fri, Feb 24, 2012 at 10:44:32PM -0500, Vivek Goyal wrote:
> > > Booting with blkcg-stacking branch and changing io scheduler from cfq to
> > > deadline oopsed.
> > > 
> > > login: [   67.382768] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
> > > [   67.383037] CPU 1 
> > > [   67.383037] Modules linked in: floppy [last unloaded: scsi_wait_scan]
> > > [   67.383037] 
> > > [   67.383037] Pid: 4763, comm: bash Not tainted 3.3.0-rc3-tejun-misc+ #6 Hewlett-Packard HP xw6600 Workstation/0A9Ch
> > > [   67.383037] RIP: 0010:[<ffffffff81311793>]  [<ffffffff81311793>] cfq_put_queue+0xb3/0x1d0
> > 
> > Hmmm... weird.  Looking into it.  I'm away from office for a week and
> > will probably be slow.
> 
> It won't reproduce here.  Can you please explain how to trigger it?
> Can you please also run addr2line on the oops address?

I have BLK_CGROUP enabled. CFQ is deafult scheduler. I boot the system and
just change the scheduler to deadline on sda and crash happens. It is
consistently reproducible on my machine.

add2line points to, blk-cgroup.h

blkg_put() {
	WARN_ON_ONCE(blkg->refcnt <= 0);
}

I put more printk and we are putting down async queues when crash happens.

cfq_put_async_queues().

So looks like a group might have already been freed. May be it is a group
refcount issue. I see 6b6b6b... pattern in RBX. Sounds like a use after
free thing.

Thanks
Vivek
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/