From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
To: Jiang Liu <jiang.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] iommu/vt-d: Fix an off-by-one bug in __domain_mapping()
Date: Mon, 1 Dec 2014 17:27:40 +0100 [thread overview]
Message-ID: <20141201162740.GK3762@8bytes.org> (raw)
In-Reply-To: <1416966130-866-1-git-send-email-jiang.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
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
next prev parent reply other threads:[~2014-12-01 16:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-26 1:42 [PATCH] iommu/vt-d: Fix an off-by-one bug in __domain_mapping() Jiang Liu
[not found] ` <1416966130-866-1-git-send-email-jiang.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2014-12-01 16:27 ` Joerg Roedel [this message]
[not found] ` <20141201162740.GK3762-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2014-12-02 0:06 ` Jiang Liu
2014-12-02 10:34 ` David Woodhouse
[not found] ` <1417516475.5525.57.camel-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2014-12-02 12:04 ` Joerg Roedel
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