Messages in this thread | | | Date | Mon, 1 Dec 2014 17:27:40 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH] iommu/vt-d: Fix an off-by-one bug in __domain_mapping() |
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On Wed, Nov 26, 2014 at 09:42:10AM +0800, Jiang Liu wrote: > There's an off-by-one bug in function __domain_mapping(), which may > trigger the BUG_ON(nr_pages < lvl_pages) when > (nr_pages + 1) & superpage_mask == 0
What is the superpage_mask?
> The issue was introduced by commit 9051aa0268dc "intel-iommu: Combine > domain_pfn_mapping() and domain_sg_mapping()", which sets sg_res to > "nr_pages + 1" to avoid some of the 'sg_res==0' code paths. > > It's safe to remove extra "+1" because sg_res is only used to calculate > page size now.
From your description and the (hard to read) code in __domain_mapping I don't really understand the issue yet. Can you please elaborate on this issue can be triggered?
Is the BUG_ON the only issue and, if yes, can that be fixed by just changing the BUG_ON condition?
> This issue was introduced in v2.6.31, but intel-iommu.c has > been moved into drivers/iommu in v3.1. So what's the preferred way > to deal with stable kernels between v2.6.31 and v3.1?
Just remove the kernel version marker from the stable tag. The stable kernel maintainers for kernels >3.1 will ask you to backport the patch or just backport it by themselfes.
Joerg
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