3.2.71-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Julian Anastasov <ja@xxxxxx>
commit 2c17d27c36dcce2b6bf689f41a46b9e909877c21 upstream.
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 <ebiederm@xxxxxxxxxxxx>
Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- No need to rename the label in __netif_receive_skb()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3261,8 +3261,6 @@ static int __netif_receive_skb(struct sk
pt_prev = NULL;
- rcu_read_lock();
-
another_round:
__this_cpu_inc(softnet_data.processed);
@@ -3357,7 +3355,6 @@ ncls:
}
out:
- rcu_read_unlock();
return ret;
}
@@ -3378,34 +3375,31 @@ out:
*/
int netif_receive_skb(struct sk_buff *skb)
{
+ int ret;
+
if (netdev_tstamp_prequeue)
net_timestamp_check(skb);
if (skb_defer_rx_timestamp(skb))
return NET_RX_SUCCESS;
+ rcu_read_lock();
+
#ifdef CONFIG_RPS
{
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();
- } else {
- rcu_read_unlock();
- ret = __netif_receive_skb(skb);
+ return ret;
}
-
- return ret;
}
-#else
- return __netif_receive_skb(skb);
#endif
+ ret = __netif_receive_skb(skb);
+ rcu_read_unlock();
+ return ret;
}
EXPORT_SYMBOL(netif_receive_skb);
@@ -3796,8 +3790,10 @@ 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) {
--
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