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From: David Laight <David.Laight@ACULAB.COM>
To: 'Pavel Begunkov' <asml.silence@gmail.com>,
	Jens Axboe <axboe@kernel.dk>,
	"io-uring@vger.kernel.org" <io-uring@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] io_uring: fix iovec leaks
Date: Tue, 11 Feb 2020 11:16:40 +0000
Message-ID: <0d61cafdb0b040ac8bb3542b6022d0fc@AcuMS.aculab.com> (raw)
In-Reply-To: <045f6c04-a6d8-146c-75f3-2c0d65e482d6@gmail.com>

From: Pavel Begunkov
> Sent: 11 February 2020 11:05
> On 2/11/2020 1:07 PM, David Laight wrote:
> > From: Pavel Begunkov
> >> Sent: 07 February 2020 19:05
> >> Allocated iovec is freed only in io_{read,write,send,recv)(), and just
> >> leaves it if an error occured. There are plenty of such cases:
> >> - cancellation of non-head requests
> >> - fail grabbing files in __io_queue_sqe()
> >> - set REQ_F_NOWAIT and returning in __io_queue_sqe()
> >> - etc.
> >>
> >> Add REQ_F_NEED_CLEANUP, which will force such requests with custom
> >> allocated resourses go through cleanup handlers on put.
> >
> > This looks horribly fragile.
> 
> Well, not as horrible as it may appear -- set the flag, whenever you
> want the corresponding destructor to be called, and clear it when is not
> needed anymore.
> 
> I'd love to have something better, maybe even something more intrusive
> for-next, but that shouldn't hurt the hot path. Any ideas?

Given all the 'cud chewing' that happens in code paths
like the one that read iov from userspace just adding:

	if (unlikely(foo->ptr))
		kfree(foo->ptr);

before 'foo' goes out of scope (or is reused) is probably
not measurable.

	David

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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 19:04 Pavel Begunkov
2020-02-07 19:09 ` Pavel Begunkov
2020-02-07 20:40   ` Jens Axboe
2020-02-11 10:07 ` David Laight
2020-02-11 11:05   ` Pavel Begunkov
2020-02-11 11:16     ` David Laight [this message]
2020-02-11 11:43       ` Pavel Begunkov

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