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Commit 7234e030 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'netdev_unregister_races' 



Julian Anastasov says:

====================
net: fixes for device unregistration

Test script from Eric W. Biederman can catch a problem
where packets from backlog are processed long after the last
synchronize_net call. This can be reproduced after few tests
if commit 381c759d ("ipv4: Avoid crashing in ip_error")
is reverted for the test. Incoming packets do not hold
reference to device but even if they do, subsystems do not
expect packets to fly during and after the NETDEV_UNREGISTER
event.

The first fix has the cost of netif_running check in fast path.
The second fix calls rcu_read_lock while local IRQ is disabled,
I hope this is not against the rules.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents a7d35f9d 2c17d27c

net/core/dev.c

+20 −18
Original line number Diff line number Diff line
@@ -3448,6 +3448,8 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, 
	local_irq_save(flags);



	rps_lock(sd);

	if (!netif_running(skb->dev))

		goto drop;

	qlen = skb_queue_len(&sd->input_pkt_queue);

	if (qlen <= netdev_max_backlog && !skb_flow_limit(skb, qlen)) {

		if (qlen) {
@@ -3469,6 +3471,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, 
		goto enqueue;

	}



drop:

	sd->dropped++;

	rps_unlock(sd);
@@ -3771,8 +3774,6 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 


	pt_prev = NULL;



	rcu_read_lock();



another_round:

	skb->skb_iif = skb->dev->ifindex;
@@ -3782,7 +3783,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 
	    skb->protocol == cpu_to_be16(ETH_P_8021AD)) {

		skb = skb_vlan_untag(skb);

		if (unlikely(!skb))

			goto unlock;

			goto out;

	}



#ifdef CONFIG_NET_CLS_ACT
@@ -3812,10 +3813,10 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 
	if (static_key_false(&ingress_needed)) {

		skb = handle_ing(skb, &pt_prev, &ret, orig_dev);

		if (!skb)

			goto unlock;

			goto out;



		if (nf_ingress(skb, &pt_prev, &ret, orig_dev) < 0)

			goto unlock;

			goto out;

	}

#endif

#ifdef CONFIG_NET_CLS_ACT
@@ -3833,7 +3834,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 
		if (vlan_do_receive(&skb))

			goto another_round;

		else if (unlikely(!skb))

			goto unlock;

			goto out;

	}



	rx_handler = rcu_dereference(skb->dev->rx_handler);
@@ -3845,7 +3846,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 
		switch (rx_handler(&skb)) {

		case RX_HANDLER_CONSUMED:

			ret = NET_RX_SUCCESS;

			goto unlock;

			goto out;

		case RX_HANDLER_ANOTHER:

			goto another_round;

		case RX_HANDLER_EXACT:
@@ -3899,8 +3900,7 @@ static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) 
		ret = NET_RX_DROP;

	}



unlock:

	rcu_read_unlock();

out:

	return ret;

}
@@ -3931,29 +3931,30 @@ static int __netif_receive_skb(struct sk_buff *skb) 


static int netif_receive_skb_internal(struct sk_buff *skb)

{

	int ret;



	net_timestamp_check(netdev_tstamp_prequeue, skb);



	if (skb_defer_rx_timestamp(skb))

		return NET_RX_SUCCESS;



	rcu_read_lock();



#ifdef CONFIG_RPS

	if (static_key_false(&rps_needed)) {

		struct rps_dev_flow voidflow, *rflow = &voidflow;

		int cpu, ret;



		rcu_read_lock();



		cpu = get_rps_cpu(skb->dev, skb, &rflow);

		int cpu = get_rps_cpu(skb->dev, skb, &rflow);



		if (cpu >= 0) {

			ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);

			rcu_read_unlock();

			return ret;

		}

		rcu_read_unlock();

	}

#endif

	return __netif_receive_skb(skb);

	ret = __netif_receive_skb(skb);

	rcu_read_unlock();

	return ret;

}



/**
@@ -4498,8 +4499,10 @@ static int process_backlog(struct napi_struct *napi, int quota) 
		struct sk_buff *skb;



		while ((skb = __skb_dequeue(&sd->process_queue))) {

			rcu_read_lock();

			local_irq_enable();

			__netif_receive_skb(skb);

			rcu_read_unlock();

			local_irq_disable();

			input_queue_head_incr(sd);

			if (++work >= quota) {
@@ -6135,6 +6138,7 @@ static void rollback_registered_many(struct list_head *head) 
		unlist_netdevice(dev);



		dev->reg_state = NETREG_UNREGISTERING;

		on_each_cpu(flush_backlog, dev, 1);

	}



	synchronize_net();
@@ -6770,8 +6774,6 @@ void netdev_run_todo(void) 


		dev->reg_state = NETREG_UNREGISTERED;



		on_each_cpu(flush_backlog, dev, 1);



		netdev_wait_allrefs(dev);



		/* paranoia */