Messages in this thread | | | Date | Mon, 18 Jan 2016 10:44:57 +0100 | From | Daniel Borkmann <> | Subject | Re: [PATCH] af_packet: Raw socket destruction warning fix |
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On 01/18/2016 07:37 AM, Maninder Singh wrote: > Receieve queue is not purged when socket dectruction is called > results in kernel warning because of non zero sk_rmem_alloc. > > WARNING: at net/packet/af_packet.c:1142 packet_sock_destruct > > Backtrace: > WARN_ON(atomic_read(&sk->sk_rmem_alloc) > packet_sock_destruct > __sk_free > sock_wfree > skb_release_head_state > skb_release_all > __kfree_skb > net_tx_action > __do_softirq > run_ksoftirqd > > Signed-off-by: Vaneet Narang <v.narang@samsung.com> > Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Thanks for the fix. While it fixes the WARN_ON(), I believe some more investigation is needed here on why it is happening:
We call first into packet_release(), which removes the socket hook from the kernel (unregister_prot_hook()), later calls synchronize_net() to make sure no more skbs will come in. The receive queue is purged right after the synchronize_net() already.
packet_sock_destruct() will be called afterwards, when there are no more refs on the socket anymore and no af_packet skbs in tx waiting for completion. Only then, in sk_destruct(), we'll call into packet_sock_destruct().
So, eventually double purging the sk_receive_queue seems not the right thing to do at first look, and w/o any deeper analysis in the commit description.
Could you look a bit further into the issue? Do you have a reproducer to trigger it?
Thanks, Daniel
> --- > net/packet/af_packet.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 81b4b81..bcb37ba 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -1310,6 +1310,7 @@ static bool packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb) > > static void packet_sock_destruct(struct sock *sk) > { > + skb_queue_purge(&sk->sk_receive_queue); > skb_queue_purge(&sk->sk_error_queue); > > WARN_ON(atomic_read(&sk->sk_rmem_alloc)); >
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