Re: [PATCH 1/1] af_packet: Raw socket destruction warning fix

On Wed, 2016-02-10 at 17:35 +0530, Maninder Singh wrote:

This Patch fixes below warning:-
WARNING: at net/packet/af_packet.c:xxx packet_sock_destruct

There is following race between packet_rcv and packet_close
which keeps unfree packet in receive queue.

CPU 1					CPU2
packet_rcv

					packet_close                       
skb_set_owner_r(skb, sk);

					skb_queue_purge(&sk->sk_receive_queue);

spin_lock(&sk->sk_receive_queue.lock);
__skb_queue_tail(&sk->sk_receive_queue, skb);
spin_unlock(&sk->sk_receive_queue.lock);

This absolutely can not happen.

CPU 1 holds rcu read lock, so cpu 2 can not possibly call
skb_queue_purge()

(cpu 1 is blocked in synchronize_net(), waiting that all cpus are no
longer in packet_rcv())

This patch does not address the root cause of your problem, and only
slightly changes probability for the bug to trigger.