net: disable preemption before call smp_processor_id()

[ Upstream commit cece1945bffcf1a823cdfa36669beae118419351 ]

Although netif_rx() isn't expected to be called in process context with
preemption enabled, it'd better handle this case. And this is why get_cpu()
is used in the non-RPS #ifdef branch. If tree RCU is selected,
rcu_read_lock() won't disable preemption, so preempt_disable() should be
called explictly.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/core/dev.c b/net/core/dev.c
index c4e89ef60160c68b7d6b7ea27bb3e61bac49a013..95cc48618043394ff01011685b43780b27cb1831 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2504,6 +2504,7 @@ int netif_rx(struct sk_buff *skb)
                struct rps_dev_flow voidflow, *rflow = &voidflow;
                int cpu;
 
+               preempt_disable();
                rcu_read_lock();
 
                cpu = get_rps_cpu(skb->dev, skb, &rflow);
@@ -2513,6 +2514,7 @@ int netif_rx(struct sk_buff *skb)
                ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
 
                rcu_read_unlock();
+               preempt_enable();
        }
 #else
        {