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

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Date:	Tue, 27 Nov 2012 18:02:29 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Krzysztof Mazur <krzysiek@...lesie.net>
Cc:	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 Tue, 2012-11-27 at 18:39 +0100, Krzysztof Mazur wrote:
> Yes, I missed that one - it's even worse, I introduced that bug 
> in "[PATCH 1/7] atm: detach protocol before closing vcc". Before that
> patch that scenario shouldn't happen because vcc was closed before
> calling pppoatm_send(vcc, NULL) - the driver should provide appropriate
> synchronization.
> 
> I think that we should just drop that patch. With later changes it's not
> necessary - the pppoatm_send() can be safely called while closing vcc.

I'm not running with that patch. This bug exists for br2684 even before
it, and I think also for pppoatm.

In solos-pci at least, the ops->close() function doesn't flush all
pending skbs for this vcc before returning. So can be a tasklet
somewhere which has loaded the address of the vcc->pop function from one
of them, and is going to call it in some unspecified amount of time.

Should we make the device's ->close function wait for all TX and RX skbs
for this vcc to complete? 

-- 
dwmw2

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