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

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Date:	Fri, 22 Aug 2014 19:15:02 +0300
From:	Dan Aloni <dan@...nelim.com>
To:	Benjamin LaHaise <bcrl@...ck.org>
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 Fri, Aug 22, 2014 at 12:01:11PM -0400, Benjamin LaHaise wrote:
> On Tue, Aug 19, 2014 at 08:46:51PM -0400, Benjamin LaHaise wrote:
> > You can trigger the behaviour with fio by using userspace event reaping.  
> > Adding a test case for that behaviour to libaio would be a good idea.
> 
> > I thought about how to fix this, and it isn't actually that hard.  Move 
> > the put_reqs_available() call back into event consumption, and then add 
> > code in the submit path to call put_reqs_available() if the system runs 
> > out of events by noticing that there is free space in the event ring.  
> > Something along the lines below should do it (please note, this is 
> > completely untested!).  I'll test and polish this off tomorrow, as it's 
> > getting a bit late here.
> 
> Dan, does this patch work for you?  It seems to pass your test program 
> when I run it in a vm...

Sorry, I was waiting for a new patch from your direction, I should
have replied earlier. What bothered me about the patch you sent is that
completed_events is added as a new field but nothing assigns to it, so I 
wonder how it can be effective.

-- 
Dan Aloni
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