linux-kernel - Re: netfilter: Hung task

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Message-ID: <alpine.DEB.2.00.1203191501140.23632@router.home>
Date:	Mon, 19 Mar 2012 15:03:14 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Sasha Levin <levinsasha928@...il.com>
cc:	Pablo Neira Ayuso <pablo@...filter.org>, kaber@...sh.net,
	davem@...emloft.net, Dave Jones <davej@...hat.com>,
	netfilter-devel@...r.kernel.org,
	"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: netfilter: Hung task

On Mon, 19 Mar 2012, Sasha Levin wrote:

> lockdep listed all the held locks there.

None of the locks listed are slub locks.

> I've mentioned that it looks very similar to
> https://lkml.org/lkml/2012/1/14/45 where the userspace helper tried to
> read from the sysfs files, but got into a deadlock since the kernel
> side held them before it called the usermode helper.

Ah yes. In that case slub held a semaphore. Code was changed since then to
no longer hold a semaphore when calling into sysfs.

The uevent handler can execute arbitrary user space code. Do you have to
hold locks while calling kmem_cache_destroy?


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