netdev - RE: [PATCH 1/1 V3] bridge: fix br_multicast_ipv6

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Date:	Mon, 03 Jan 2011 11:41:59 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	"Winkler, Tomas" <tomas.winkler@...el.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Stephen Hemminger <shemminger@...tta.com>
Subject: RE: [PATCH 1/1 V3] bridge: fix br_multicast_ipv6_rcv for paged skbs

On Mon, 2011-01-03 at 12:17 +0200, Winkler, Tomas wrote:

> > > > > -		struct mld_msg *mld = (struct mld_msg *)icmp6h;
> > > > > +		struct mld_msg *mld;
> > > > > +		if (!pskb_may_pull(skb2, sizeof(*mld))) {
> > > > > +			err = -EINVAL;
> > > > > +			goto out;
> > > > > +		}
> > > > > +		mld = (struct mld_msg *)icmp6h;
> > > >
> > > > This (and the second instance) is incorrect afaict -- the pointer
> > > > "icmp6h" should be reloaded after the pskb_may_pull(), no?
> > >
> > > mld_msg is bigger than icmp6h by sizeof(in6_addr) so we have to try pull
> > again a bigger chunk.
> > 
> > Right, I know, the pskb_may_pull() is needed, but I believe you need to
> > re-calculate icmp6h here.
> 
> You are right, it can be moved to new memory buffer.
> 
> Probably something like that will do it:
> 
> if (!pskb_may_pull(skb2, sizeof(*mld))) {
> 	err = -EINVAL;
> 	goto out;
> }
> mld = (struct mld_msg *)skb_transport_header(skb2) 

Yeah, that'll do, although I see more callers of icmp6_hdr() here
instead even for mld stuff (which is an inline though doing just this)

johannes

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