linux-kernel - Re: [PATCH] Intel-IOMMU Alignment Issue in dma_pte_clear

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Message-Id: <1239054502.22733.102.camel@macbook.infradead.org>
Date:	Mon, 06 Apr 2009 14:48:22 -0700
From:	David Woodhouse <dwmw2@...radead.org>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, "Zhao, Yu" <yu.zhao@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	iommu <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH] Intel-IOMMU Alignment Issue in dma_pte_clear_range()

On Mon, 2009-04-06 at 11:21 -0700, Fenghua Yu wrote:
> This issue was pointed out by Linus.
> 
> In dma_pte_clear_range() in intel-iommu.c
> 
> start = PAGE_ALIGN(start);
> end &= PAGE_MASK;
> npages = (end - start) / VTD_PAGE_SIZE;
> 
> In partial page case, start could be bigger than end and npages will be
> negative.
> 
> Currently the issue doesn't show up as a real bug in testing because start and
> end have been aligned to page boundary already by all callers. So the issue has
> been hiden. But it is dangerous programming practice.
> 
> The following patch fixes the issue. It's applied on iommu-2.6.git tree.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>

Applied to git://git.infradead.org/iommu-2.6.git; thanks.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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