linux-kernel - Re: Revert "aio: fix aio request leak when events are reaped by user space"

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Message-ID: <20140824181140.GD4376@kvack.org>
Date:	Sun, 24 Aug 2014 14:11:40 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dan Aloni <dan@...nelim.com>,
	"security@...nel.org" <security@...nel.org>, linux-aio@...ck.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mateusz Guzik <mguzik@...hat.com>,
	Petr Matousek <pmatouse@...hat.com>,
	Kent Overstreet <kmo@...erainc.com>,
	Jeff Moyer <jmoyer@...hat.com>, stable <stable@...r.kernel.org>
Subject: Re: Revert "aio: fix aio request leak when events are reaped by user space"

On Fri, Aug 22, 2014 at 02:43:56PM -0700, Linus Torvalds wrote:
> Ugh.
> 
> Ben, at this point my gut feel is that we should just revert the
> original "fix", and you should take a much deeper look at this all.
> The original "fix" was more broken then the leak it purported to fix,
> and now the patch to fix your fix has gone through two iterations and
> *still* Dan is finding bugs in it.  I'm getting the feeling that this
> code needs more thinking than you are actually putting into it.

That's why I had't sent it out as an official [PATCH] just yet.  I think 
things worked out okay since the untested patch I sent out pointed Dan in 
the right direction and he was able to put some effort into it while I 
didn't have to immediate time to do so.  I just put in a few hours to 
polish off the final details on this fix now, and it should be coming your 
way as soon as I get an ack back from Dan.  Hopefully Kent can review it 
as well, since I had to modify the approach to try to retain the advantages 
of his batched reqs_available handling and avoid bouncing the cacheline 
ctx->completion_lock is on during io_submit().  Cheers,

		-ben

>                 Linus

-- 
"Thought is the essence of where you are now."
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