netdev - Re: Question about an assignment in handle

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Message-ID: <20100525124636.GA13161@gondor.apana.org.au>
Date:	Tue, 25 May 2010 22:46:36 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	jamal <hadi@...erus.ca>
Cc:	Jiri Pirko <jpirko@...hat.com>, netdev@...r.kernel.org,
	davem@...emloft.net, kaber@...sh.net
Subject: Re: Question about an assignment in handle_ing()

On Tue, May 25, 2010 at 08:20:38AM -0400, jamal wrote:
> On Tue, 2010-05-25 at 22:12 +1000, Herbert Xu wrote:
> 
> > It is guaranteed, it is illegal to hold onto the skb contents
> > without the reference that comes from cloning an skb.
> 
> As i recall this was an issue. And the example i described earlier
> would have tcpdump show edited contents coming out of eth0.

That's not very surprising as you're not checking whether the
skb is cloned in act_pedit.c:

	if (!(skb->tc_verd & TC_OK2MUNGE)) {
		/* should we set skb->cloned? */
		if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
			return p->tcf_action;
		}
	}

This code needs to be changed to something like

	if (skb_cloned(skb)) {
		if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
			return p->tcf_action;
		}
	}

BTW, this error handling also looks a bit suss.  Shouldn't it
drop the packet instead of continuing as if we have successfully
modified it?

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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