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: <20120305174509.GR22536@google.com>
Date:	Mon, 5 Mar 2012 09:45:09 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
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

Hello,

On Mon, Feb 27, 2012 at 09:40:45AM -0500, Vivek Goyal wrote:
> So we call following.
> 
> elevator_switch()
>   blkg_destroy_all()
>     update_root_blkg();
> 
> Here update_root_blkg() will free up the blkg->pd for cfq. 
> 
> And later we call.
> 
> elevator_exit()
>   cfq_exit_queue()
>     cfq_put_async_queues()
>       cfq_put_queue()
>         blkg_put(cfqg_to_blkg(cfqg)); <------ trying to reach blkg through
> already freed policy data.
> 
> So we should not free up root group policy data till old elevator has
> exited.

Yeah, this analysis seems correct.  For some reason, I still can't
reproduce it even with slab debugging turned on.  I modified the free
path to fill *pd with pattern w/o actually freeing it and now can see
similar crashes.  Will post fix soon.

Thanks a lot.

-- 
tejun
--
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/