Re: [B.A.T.M.A.N.] [PATCH 2/3] batman-adv: Receive fragmented packets and merge

[Marek Lindner <lindner_marek@yahoo.de>]

On Wednesday, April 24, 2013 03:30:04 Antonio Quartulli wrote:
> On Wed, Apr 24, 2013 at 03:17:26AM +0800, Marek Lindner wrote:
> > On Sunday, April 21, 2013 00:17:33 Martin Hundebøll wrote:
> > > +	/* Make room for the rest of the fragments. */
> > > +	if (pskb_expand_head(skb_out, 0, size - skb->len, GFP_ATOMIC) < 0) {
> > > +		kfree_skb(skb_out);
> > > +		goto free;
> > > +	}
> > 
> > If pskb_expand_head() really fails this function will lead to a crash
> > because skb_out points to undefined memory.
> 
> I'm not sure about this. pskb_expand_head() can only fail in the early
> phase and in that case it seems to return the original skb as it was.

I guess I did not make myself sufficiently clear: If pskb_expand_head() fails 
the skb is free'd with "kfree_skb(skb_out);" followed by a jump to "free" 
where the recently free'd buffer is returned ...


> > Btw, is pskb_expand_head() enough to handle all cases ? Did you try this
> > with a large (4000 bytes or more) packet ?
> 
> I don't personally see any problem with this. But maybe I am overlooking
> something..however, proper testing will make everybody happy :P

Agreed. I wasn't sure there is a problem but wanted to know whether it was 
tested.

Cheers,
Marek