Commit 2c17d27c authored by Julian Anastasov's avatar Julian Anastasov Committed by David S. Miller
Browse files

net: call rcu_read_lock early in process_backlog 



Incoming packet should be either in backlog queue or
in RCU read-side section. Otherwise, the final sequence of
flush_backlog() and synchronize_net() may miss packets
that can run without device reference:

CPU 1                  CPU 2
                       skb->dev: no reference
                       process_backlog:__skb_dequeue
                       process_backlog:local_irq_enable

on_each_cpu for
flush_backlog =>       IPI(hardirq): flush_backlog
                       - packet not found in backlog

                       CPU delayed ...
synchronize_net
- no ongoing RCU
read-side sections

netdev_run_todo,
rcu_barrier: no
ongoing callbacks
                       __netif_receive_skb_core:rcu_read_lock
                       - too late
free dev
                       process packet for freed dev

Fixes: 6e583ce5 ("net: eliminate refcounting in backlog queue")
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: default avatarJulian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e9e4dd32

net/core/dev.c

+16 −16
Original line number Diff line number Diff line
@@ -3774,8 +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;
@@ -3785,7 +3783,7 @@ another_round: 
	    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
@@ -3815,10 +3813,10 @@ skip_taps: 
	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
@@ -3836,7 +3834,7 @@ ncls: 
		if (vlan_do_receive(&skb))

			goto another_round;

		else if (unlikely(!skb))

			goto unlock;

			goto out;

	}



	rx_handler = rcu_dereference(skb->dev->rx_handler);
@@ -3848,7 +3846,7 @@ ncls: 
		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:
@@ -3902,8 +3900,7 @@ drop: 
		ret = NET_RX_DROP;

	}



unlock:

	rcu_read_unlock();

out:

	return ret;

}
@@ -3934,29 +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;

}



/**
@@ -4501,8 +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) {

CRA Git | Maintained and supported by SUSTech CRA and CCSE