linux-kernel - Re: [patch] x86: pci: Prevent mmconfig memory corruption

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Date:	Thu, 25 Feb 2010 08:31:26 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>
Subject: Re: [patch] x86: pci: Prevent mmconfig memory corruption

On Thu, 25 Feb 2010 16:42:11 +0100 (CET)
Thomas Gleixner <tglx@...utronix.de> wrote:

> commit ff097ddd4 (x86/PCI: MMCONFIG: manage pci_mmcfg_region as a
> list, not a table) introduced a nasty memory corruption when
> pci_mmcfg_list is empty.
> 
> pci_mmcfg_check_end_bus_number() dereferences pci_mmcfg_list.prev even
> when the list is empty. The following write hits some variable near to
> pci_mmcfg_list.
> 
> Further down a similar problem exists, where cfg->list.next is
> dereferenced unconditionally and a comparison with some variable near
> to pci_mmcfg_list happens.
> 
> Add a check for the last element into the for_each_entry() loop and
> remove all the other crappy logic which is just a leftover of the old
> array based code which was replaced by the list conversion.
> 
> Reported-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Bjorn Helgaas <bjorn.helgaas@...com>
> Cc: Yinghai Lu <yinghai@...nel.org>
> Cc: Jesse Barnes <jbarnes@...tuousgeek.org>
> Cc: stable@...nel.org
> ---

Applied to my linux-next branch, thanks.  I'll be part of my pull
request to Linus tomorrow.

-- 
Jesse Barnes, Intel Open Source Technology Center
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