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

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Message-ID: <1294049058.4165.3.camel@jlt3.sipsolutions.net>
Date:	Mon, 03 Jan 2011 11:04:18 +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 11:43 +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.

> > Also, the "out_nopush" thing is pointless since the push is completely
> > unnecessary as "skb2 != skb" is always true.
> 
> You are right if skb_clone doesn't return the same pointer then yes.
> Shame, but I'm not a sbk expert. I'm diving into it now.

I'm pretty sure it's guaranteed to return a new pointer.

johannes

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