linux-kernel - Re: [PATCH 1/4] mm/rmap: per anon

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20131101092942.GD27063@gmail.com>
Date:	Fri, 1 Nov 2013 10:29:42 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Yuanhan Liu <yuanhan.liu@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/4] mm/rmap: per anon_vma lock


* Michel Lespinasse <walken@...gle.com> wrote:

> On Fri, Nov 1, 2013 at 1:43 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>
> > AFAICT this isn't correct at all. We used to protect the vma 
> > interval tree with the root lock, now we don't. All we've got 
> > left is the mmap_sem, but anon_vma chains can cross 
> > address-spaces and thus we're up some creek without no paddle.
> 
> Yes, that was my first thought as well (though I wanted to double 
> check at first).
> 
> I also want to point out that lately we've seen several changes 
> sent out that relax locking with no accompanying explanation of 
> why the relaxed locking would be safe. Please don't do that - 
> having a lot of performance data is worthless if you can't explain 
> why the new locking is safe. And I'm not asking to prove a 
> negative ('lack of any possible races') there, but at least in 
> this case one could dig out why the root anon vma locking was 
> introduced and if they think that this reason doesn't apply 
> anymore, explain why...

By the looks of it it seems to be an unintentional bug, not an 
intended feature.

Thanks,

	Ingo
--
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/