netdev - Re: [PATCH v2] net: af_packet: don't call tpacket_destruct

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Message-ID: <20100922105901.GB16028@redhat.com>
Date:	Wed, 22 Sep 2010 12:59:01 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	David Miller <davem@...emloft.net>, eric.dumazet@...il.com,
	socketcan@...tkopp.net, netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: af_packet: don't call tpacket_destruct_skb()
 until the skb is sent out

On Wed, Sep 22, 2010 at 05:35:07PM +0800, Changli Gao wrote:
> On Wed, Sep 15, 2010 at 1:23 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > Hmm, and there's another issue I think I see here:
> > destructor_arg now points to a socket.
> > What happens if the skb gets queued on an interface for a very long time
> > (as can be the case with e.g. tap), and meanwhile
> > you try to kill the task that owns the socket, which
> > will try to destroy the socket?
> >
> > Original code handles this by relevant devices orphaning an skb
> > if it's queued indefinitely.
> >
> 
> I don't think the skb_orphan() there is used to destroy the socket in
> time, but notify the socket that skbs are sent out and it can send new
> skbs.

Well, the result is that we drop a socket reference from the skb,
so it becomes possible to free the socket.

> -- 
> Regards,
> Changli Gao(xiaosuo@...il.com)
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