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Patch "net: call rcu_read_lock early in process_backlog" has been added to the 3.14-stable tree

PATCH [email protected] 1 participant 1 message Sep 26, 2015

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This is a note to let you know that I've just added the patch titled

net: call rcu_read_lock early in process_backlog

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-call-rcu_read_lock-early-in-process_backlog.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Sat Sep 26 11:19:08 PDT 2015

From: Julian Anastasov <[email protected]>
Date: Thu, 9 Jul 2015 09:59:10 +0300
Subject: net: call rcu_read_lock early in process_backlog

From: Julian Anastasov <[email protected]>

[ Upstream commit 2c17d27c36dcce2b6bf689f41a46b9e909877c21 ]

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 6e583ce5242f ("net: eliminate refcounting in backlog queue")
Cc Eric W. Biederman <[email protected]>
Cc Stephen Hemminger <[email protected]>
Signed-off-by Julian Anastasov <[email protected]>
Signed-off-by David S. Miller <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 net/core/dev.c |   29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)
net/core/dev.c +14 -15
@@ -3554,8 +3554,6 @@ static int __netif_receive_skb_core(stru
 
 	pt_prev = NULL;
 
-	rcu_read_lock();
-
 another_round:
 	skb->skb_iif = skb->dev->ifindex;
 

@@ -3565,7 +3563,7 @@ 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

@@ -3590,7 +3588,7 @@ skip_taps:
 #ifdef CONFIG_NET_CLS_ACT
 	skb = handle_ing(skb, &pt_prev, &ret, orig_dev);
 	if (!skb)
-		goto unlock;
+		goto out;
 ncls:
 #endif
 

@@ -3605,7 +3603,7 @@ 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);

@@ -3617,7 +3615,7 @@ 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:

@@ -3669,8 +3667,6 @@ drop:
 		ret = NET_RX_DROP;
 	}
 
-unlock:
-	rcu_read_unlock();
 out:
 	return ret;
 }

@@ -3702,29 +3698,30 @@ static int __netif_receive_skb(struct sk
 
 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;
 }
 
 /**

@@ -4185,8 +4182,10 @@ static int process_backlog(struct napi_s
 		unsigned int qlen;
 
 		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) {

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/net-call-rcu_read_lock-early-in-process_backlog.patch queue-3.14/net-do-not-process-device-backlog-during-unregistration.patch