From e9e4dd3267d0c5234c5c0f47440456b10875dec9 Mon Sep 17 00:00:00 2001 From: Julian Anastasov Date: Thu, 9 Jul 2015 09:59:09 +0300 Subject: net: do not process device backlog during unregistration commit 381c759d9916 ("ipv4: Avoid crashing in ip_error") fixes a problem where processed packet comes from device with destroyed inetdev (dev->ip_ptr). This is not expected because inetdev_destroy is called in NETDEV_UNREGISTER phase and packets should not be processed after dev_close_many() and synchronize_net(). Above fix is still required because inetdev_destroy can be called for other reasons. But it shows the real problem: backlog can keep packets for long time and they do not hold reference to device. Such packets are then delivered to upper levels at the same time when device is unregistered. Calling flush_backlog after NETDEV_UNREGISTER_FINAL still accounts all packets from backlog but before that some packets continue to be delivered to upper levels long after the synchronize_net call which is supposed to wait the last ones. Also, as Eric pointed out, processed packets, mostly from other devices, can continue to add new packets to backlog. Fix the problem by moving flush_backlog early, after the device driver is stopped and before the synchronize_net() call. Then use netif_running check to make sure we do not add more packets to backlog. We have to do it in enqueue_to_backlog context when the local IRQ is disabled. As result, after the flush_backlog and synchronize_net sequence all packets should be accounted. Thanks to Eric W. Biederman for the test script and his valuable feedback! Reported-by: Vittorio Gambaletta Fixes: 6e583ce5242f ("net: eliminate refcounting in backlog queue") Cc: Eric W. Biederman Cc: Stephen Hemminger Signed-off-by: Julian Anastasov Signed-off-by: David S. Miller --- net/core/dev.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 1e57efda055b..6dd126a69aa0 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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 @@ enqueue: goto enqueue; } +drop: sd->dropped++; rps_unlock(sd); @@ -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 */ -- cgit v1.2.3 From 2c17d27c36dcce2b6bf689f41a46b9e909877c21 Mon Sep 17 00:00:00 2001 From: Julian Anastasov Date: Thu, 9 Jul 2015 09:59:10 +0300 Subject: 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: 6e583ce5242f ("net: eliminate refcounting in backlog queue") Cc: Eric W. Biederman Cc: Stephen Hemminger Signed-off-by: Julian Anastasov Signed-off-by: David S. Miller --- net/core/dev.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 6dd126a69aa0..a8e4dd430285 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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) { -- cgit v1.2.3