linux-kernel - Re: [PATCH] slub: Fix sysfs circular locking dependency

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: <alpine.DEB.2.00.1101061107500.8655@router.home>
Date:	Thu, 6 Jan 2011 12:10:59 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>
cc:	Pekka Enberg <penberg@...nel.org>,
	Bart Van Assche <bvanassche@....org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] slub: Fix sysfs circular locking dependency

On Thu, 6 Jan 2011, David Rientjes wrote:

> > Thanks for testing. David, does Christoph's patch look OK to you?
> >
>
> I think it certainly fixes the problem at hand, but I think we also need
> to do lock_memory_hotplug() for memory hotplug in
> slab_mem_going_online_callback() to make show_slab_objects() consistent
> when being printed during concurrent node hot-add since it sets bits in
> N_NORMAL_MEMORY.  The MEM_OFFLINE callback is already handled at a higher
> level by taking the lock in the hotplug layer, but we need to protect the
> MEM_GOING_ONLINE and MEM_CANCEL_ONLINE callbacks if slub_lock is no longer
> used to protect node arrays (which was admittedly always convenient since
> it's typically associated with an iteration through slab_caches).

Hmm, I would have expected the callbacks all to be done under hotplug
locking.

The MEM_GOING_ONLINE callback is not that critical since a node that is
coming online presumably has only a minimal set of objects necessary for
potential future allocations.

slab_mem_going_online_callback() etc already take the slub_lock since they
have to iterate over the list of slab caches in existence. We could take
the hotplug lock there as well.

Kame-san: Can you enlighten us on hotplug locking? And also check this
patch?


--
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/