linux-kernel - Re: [PATCH] mm/numa/thp: fix assumptions of migrate_misplaced_transhuge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Thu, 5 May 2016 10:53:56 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	jglisse@...hat.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH] mm/numa/thp: fix assumptions of
 migrate_misplaced_transhuge_page()

On Tue, May 03, 2016 at 02:33:51PM +0200, jglisse@...hat.com wrote:
> From: Jérôme Glisse <jglisse@...hat.com>
> 
> Fix assumptions in migrate_misplaced_transhuge_page() which is only
> call by do_huge_pmd_numa_page() itself only call by __handle_mm_fault()
> for pmd with PROT_NONE. This means that if the pmd stays the same
> then there can be no concurrent get_user_pages / get_user_pages_fast
> (GUP/GUP_fast). More over because migrate_misplaced_transhuge_page()
> abort if page is mapped more than once then there can be no GUP from
> a different process. Finaly, holding the pmd lock assure us that no
> other part of the kernel can take an extra reference on the page.
> 
> In the end this means that the failure code path should never be
> taken unless something is horribly wrong, so convert it to BUG_ON().
> 
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs