From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] x86: mm: Check if PUD is large when validating a kernel address
Date: Mon, 11 Feb 2013 14:41:20 -0500 [thread overview]
Message-ID: <51194960.5080909@redhat.com> (raw)
In-Reply-To: <20130211145236.GX21389@suse.de>
On 02/11/2013 09:52 AM, Mel Gorman wrote:
> A user reported the following oops when a backup process read
> /proc/kcore.
>
> BUG: unable to handle kernel paging request at ffffbb00ff33b000
> Investigation determined that the bug triggered when reading system RAM
> at the 4G mark. On this system, that was the first address using 1G pages
> for the virt->phys direct mapping so the PUD is pointing to a physical
> address, not a PMD page. The problem is that the page table walker in
> kern_addr_valid() is not checking pud_large() and treats the physical
> address as if it was a PMD. If it happens to look like pmd_none then it'll
> silently fail, probably returning zeros instead of real data. If the data
> happens to look like a present PMD though, it will be walked resulting in
> the oops above. This patch adds the necessary pud_large() check.
>
> Unfortunately the problem was not readily reproducible and now they are
> running the backup program without accessing /proc/kcore so the patch has
> not been validated but I think it makes sense. If reviewers agree then it
> should also be included in -stable back as far as 3.0-stable.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.coM>
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next prev parent reply other threads:[~2013-02-11 19:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-11 14:52 [PATCH] x86: mm: Check if PUD is large when validating a kernel address Mel Gorman
2013-02-11 19:41 ` Rik van Riel [this message]
2013-02-12 6:40 ` Johannes Weiner
2013-02-12 17:43 ` Michal Hocko
2013-02-13 11:02 ` [PATCH] x86: mm: Check if PUD is large when validating a kernel address v2 Mel Gorman
2013-02-13 11:10 ` Ingo Molnar
2013-02-13 11:14 ` Mel Gorman
2013-03-01 6:43 ` Simon Jeons
2013-03-01 9:15 ` Chen Gong
2013-03-01 9:21 ` Simon Jeons
2013-03-01 9:35 ` Chen Gong
2013-03-01 9:39 ` Simon Jeons
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