Re: [PATCH] Bluetooth: 6lowpan: Memory leak as the skb is not freed

[Alexander Aring <alex.aring@gmail.com>]

On Wed, Oct 01, 2014 at 09:08:52AM +0200, Alexander Aring wrote:
> Hi Jukka,
> 
> On Wed, Oct 01, 2014 at 10:00:53AM +0300, Jukka Rissanen wrote:
> > The earlier multicast commit 36b3dd250dde ("Bluetooth: 6lowpan:
> > Ensure header compression does not corrupt IPv6 header") lost one
> > skb free which then caused memory leak.
> > 
> > Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
> > ---
> >  net/bluetooth/6lowpan.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
> > index f0432ae..bcbee3d 100644
> > --- a/net/bluetooth/6lowpan.c
> > +++ b/net/bluetooth/6lowpan.c
> > @@ -625,6 +625,8 @@ static netdev_tx_t bt_xmit(struct sk_buff *skb, struct net_device *netdev)
> >  		send_mcast_pkt(skb, netdev);
> >  	}
> >  
> > +	kfree_skb(skb);
> > +
> 
> not dropping afterwards? Then this should be consume_skb or
> dev_kfree_skb.
> 
> Also I detected we can't make:
> 
> 	skb = skb_unshare(skb, GFP_ATOMIC);
> 	if (!skb)
> 		return NET_XMIT_DROP;
> 
> We need something like:
> 
> 	tmpskb = skb_unshare(skb, GFP_ATOMIC);
> 	if (!tmpskb) {
> 		kfree_skb(skb);
> 		return NET_XMIT_DROP;
> 	}
> 	skb = tmpskb;
> 

I mean it depends, I don't see that skb_unshare free the skb when
allocation failed and then we lost the reference to the skb which
should be unshared.

- Alex