linux-kernel - Re: [PATCH] drivers: memory: check for missing sections in test_pages_in_a

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Date:	Fri, 11 Dec 2015 16:52:54 -0600
From:	andrew banman <abanman@....com>
To:	Andrew Banman <abanman@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Russ Anderson <rja@....com>, Alex Thorlton <athorlton@....com>,
	Yinghai Lu <yinghai@...nel.org>, Greg KH <greg@...ah.com>,
	Seth Jennings <sjennings@...iantweb.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: memory: check for missing sections in
	test_pages_in_a_zone

On Fri, Dec 11, 2015 at 04:21:03PM -0600, Andrew Banman wrote:
> test_pages_in_a_zone does not account for the possibility of missing
> sections in the given pfn range. pfn_valid_within always returns 1 when
> CONFIG_HOLES_IN_ZONE is not set, allowing invalid pfns from missing
> sections to pass the test, leading to a kernel oops.
> 
> Wrap an additional pfn loop with PAGES_PER_SECTION granularity to check
> for missing sections before proceeding into the zone-check code.
> 
> This also prevents a crash from offlining memory devices with missing
> sections. Despite this, it may be a good idea to keep the related patch
> '[PATCH 3/3] drivers: memory: prohibit offlining of memory blocks
> with missing sections' because missing sections in a memory block may lead
> to other problems not covered by the scope of this fix.
> 
> ---

Oops, the signed-off-by got absorbed the email headers. I'll resend. The patch
applies cleanly to the current mainline and to the 4.3.2 and 4.2.7 stable
branches. I'll edit the patch description to reflect that as well.

- Andrew
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