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

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Message-ID: <20140819165404.GD13858@kvack.org>
Date:	Tue, 19 Aug 2014 12:54:04 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Dan Aloni <dan@...nelim.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	security@...nel.org, linux-aio@...ck.org,
	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@...r.kernel.org
Subject: Re: Revert "aio: fix aio request leak when events are reaped by user space"

On Tue, Aug 19, 2014 at 07:37:33PM +0300, Dan Aloni wrote:
> Some testing I've done today indicates that the original commit broke
> AIO with regard to users that overflow the maximum number of request
> per IO context (where -EAGAIN is returned).
> 
> In fact, it did worse - the attached C program can easily overrun the
> ring buffer that is responsible for managing the completed requests,
> and caused notification about their completion never to be returned.

Argh, that would be a problem.

...
> This reverts commit b34e0e1319b31202eb142dcd9688cf7145a30bf6.

Reverting isn't okay, as that reintroduces another regression.  We need 
to come up with a fix for this issue that doesn't reintroduce the other 
regression for events reaped in user space.  Let me have a look and see 
what I can come up with...

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