linux-kernel - Re: [PATCH] iommu/vt-d: fix race between free_irte() and get

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Message-ID: <20140723144917.GA26986@psuche.datadirectnet.com>
Date:	Wed, 23 Jul 2014 08:49:17 -0600
From:	Greg Edwards <gedwards@....com>
To:	Joerg Roedel <joro@...tes.org>
CC:	David Woodhouse <dwmw2@...radead.org>,
	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/vt-d: fix race between free_irte() and get_irte()

On Wed, Jul 23, 2014 at 04:40:24PM +0200, Joerg Roedel wrote:
> On Tue, Jul 22, 2014 at 08:27:19AM -0600, Greg Edwards wrote:
>> get_irte() can race with free_irte() and dereference a NULL iommu
>> pointer.
>
> Have you seen any real occurance of this race? Get_irte is called in the
> set_affinity path, how can that race with the irq being freed?

Yes, that's how we hit it.  A process was setting the CPU affinity while
QEMU was releasing the IRQ.  We have a CI stress test that turned this
up.

Greg
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