linux-kernel - Re: [PATCH v2 3/3] pppoatm: protect against freeing of vcc

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Message-ID: <1354206269.21562.189.camel@shinybook.infradead.org>
Date:	Thu, 29 Nov 2012 16:24:29 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	chas williams - CONTRACTOR <chas@....nrl.navy.mil>
Cc:	Krzysztof Mazur <krzysiek@...lesie.net>,
	David Laight <David.Laight@...LAB.COM>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	nathan@...verse.com.au
Subject: Re: [PATCH v2 3/3] pppoatm: protect against freeing of vcc

On Thu, 2012-11-29 at 10:59 -0500, chas williams - CONTRACTOR wrote:
> the part that bothers me (and i dont have the programmer's guide for
> the solos hardware) is that you are watching for the PKT_PCLOSE to be
> sent to the card.  shouldnt you be watching for the PKT_PCLOSE to be
> returned from the card (assuming it does such a thing) so that you can
> be assured that the tx/rx for this vpi/vci pair has been "stopped"?

Define "stopped".

For the RX case... the other end may *always* take it upon itself to
send us a packet marked with arbitrary VCI/VPI, right? There's no
connection setup for it "on the wire", in the case of PVC?

So bearing that in mind: from the moment ATM_VF_READY gets cleared, as
far as the ATM core is concerned, we will no longer receive packets on
the given VCC. If we receive any, we'll just complain about receiving
packets for an unknown VCI/VPI.

For the TX case ... yes, we need to be sure we aren't continuing to send
packets after our close() routine completes. We *used* to, but the
resulting ->pop() calls were causing problems, and that's why we're
looking at this code path closer. The currently proposed patches (except
one suggestion from Krzyztof that we both shouted down) would fix that.

-- 
dwmw2

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