netpoll: take rcu_read_lock_bh() in netpoll_rx()

In __netpoll_rx(), it dereferences ->npinfo without rcu_dereference_bh(),
this patch fixes it by using the 'npinfo' passed from netpoll_rx()
where it is already dereferenced with rcu_dereference_bh().

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 3 insertions, 4 deletions

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 907812efb4d9..5d881c388273 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -52,7 +52,7 @@ void netpoll_set_trap(int trap);
 void __netpoll_cleanup(struct netpoll *np);
 void __netpoll_free_rcu(struct netpoll *np);
 void netpoll_cleanup(struct netpoll *np);
-int __netpoll_rx(struct sk_buff *skb);
+int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo);
 void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
                              struct net_device *dev);
 static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
@@ -77,7 +77,7 @@ static inline bool netpoll_rx(struct sk_buff *skb)
 
         spin_lock(&npinfo->rx_lock);
         /* check rx_flags again with the lock held */
-        if (npinfo->rx_flags && __netpoll_rx(skb))
+        if (npinfo->rx_flags && __netpoll_rx(skb, npinfo))
                 ret = true;
         spin_unlock(&npinfo->rx_lock);
 
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index dc17f1db1479..d055bb01328b 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -543,13 +543,12 @@ static void arp_reply(struct sk_buff *skb)
         spin_unlock_irqrestore(&npinfo->rx_lock, flags);
 }
 
-int __netpoll_rx(struct sk_buff *skb)
+int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
 {
         int proto, len, ulen;
         int hits = 0;
         const struct iphdr *iph;
         struct udphdr *uh;
-        struct netpoll_info *npinfo = skb->dev->npinfo;
         struct netpoll *np, *tmp;
 
         if (list_empty(&npinfo->rx_np))