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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: 6e583ce524 ("net: eliminate refcounting in backlog queue")
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Julian Anastasov 2015-07-09 09:59:10 +03:00 committed by David S. Miller
parent e9e4dd3267
commit 2c17d27c36
1 changed files with 16 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
net/core/dev.c
View File

@ -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) {