linux-kernel - Re: [PATCH 2/4] mm: migrate: Close race between migration completion and mprotect

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Date:	Thu, 02 Oct 2014 11:48:56 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>, Dave Jones <davej@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Michel Lespinasse <walken@...gle.com>,
	Kirill A Shutemov <kirill.shutemov@...ux.intel.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] mm: migrate: Close race between migration completion
 and mprotect

On 10/02/2014 09:29 AM, Mel Gorman wrote:
> A migration entry is marked as write if pte_write was true at the time the
> entry was created. The VMA protections are not double checked when migration
> entries are being removed as mprotect marks write-migration-entries as
> read. It means that potentially we take a spurious fault to mark PTEs write
> again but it's straight-forward. However, there is a race between write
> migrations being marked read and migrations finishing. This potentially
> allows a PTE to be write that should have been read. Close this race by
> double checking the VMA permissions when migration completes.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Acked-by: Rik van Riel <riel@...hat.com>

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