linux-kernel - Re: [PATCH 1/2] mm,migration: Prevent rmap_walk_[anon|ksm] seeing the wrong VMA information

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

Message-ID: <4BE2C6E8.2030609@redhat.com>
Date:	Thu, 06 May 2010 09:40:56 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 1/2] mm,migration: Prevent rmap_walk_[anon|ksm] seeing
 the wrong VMA information

On 05/05/2010 01:34 PM, Linus Torvalds wrote:

>   - you always lock the _deepest_ anon_vma you can find.

The emphasis should be on "always" :)

> That means just a single lock. And the "deepest" anon_vma is well-defined
> for all anon_vma's, because each same_anon_vma chain is always rooted in
> the original anon_vma that caused it.

It should work, but only if we always take the deepest
anon_vma lock.

Not just in the migration code, but also in mmap, munmap,
mprotect (for split_vma), expand_stack, etc...

Otherwise we will still not provide exclusion of migrate
vs. those events.

I'm guessing that means changing both anon_vma_lock and
page_lock_anon_vma to always take the deepest anon_vma
lock - not introducing a new function that is only called
by the migration code.

-- 
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/