netpoll: take rcu_read_lock_bh() in netpoll_send_skb_on_dev()

This patch fixes several problems in the call path of
netpoll_send_skb_on_dev():

1. Disable IRQ's before calling netpoll_send_skb_on_dev().

2. All the callees of netpoll_send_skb_on_dev() should use
   rcu_dereference_bh() to dereference ->npinfo.

3. Rename arp_reply() to netpoll_arp_reply(), the former is too generic.

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, 20 insertions, 14 deletions

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 2d178baa49df..61aee86cf21d 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -57,7 +57,10 @@ 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)
 {
+        unsigned long flags;
+        local_irq_save(flags);
         netpoll_send_skb_on_dev(np, skb, np->dev);
+        local_irq_restore(flags);
 }
 
 
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index d055bb01328b..174346ac15a0 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -54,7 +54,7 @@ static atomic_t trapped;
          MAX_UDP_CHUNK)
 
 static void zap_completion_queue(void);
-static void arp_reply(struct sk_buff *skb);
+static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo);
 
 static unsigned int carrier_timeout = 4;
 module_param(carrier_timeout, uint, 0644);
@@ -170,7 +170,8 @@ static void poll_napi(struct net_device *dev)
         list_for_each_entry(napi, &dev->napi_list, dev_list) {
                 if (napi->poll_owner != smp_processor_id() &&
                     spin_trylock(&napi->poll_lock)) {
-                        budget = poll_one_napi(dev->npinfo, napi, budget);
+                        budget = poll_one_napi(rcu_dereference_bh(dev->npinfo),
+                                               napi, budget);
                         spin_unlock(&napi->poll_lock);
 
                         if (!budget)
@@ -185,13 +186,14 @@ static void service_arp_queue(struct netpoll_info *npi)
                 struct sk_buff *skb;
 
                 while ((skb = skb_dequeue(&npi->arp_tx)))
-                        arp_reply(skb);
+                        netpoll_arp_reply(skb, npi);
         }
 }
 
 static void netpoll_poll_dev(struct net_device *dev)
 {
         const struct net_device_ops *ops;
+        struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo);
 
         if (!dev || !netif_running(dev))
                 return;
@@ -206,17 +208,18 @@ static void netpoll_poll_dev(struct net_device *dev)
         poll_napi(dev);
 
         if (dev->flags & IFF_SLAVE) {
-                if (dev->npinfo) {
+                if (ni) {
                         struct net_device *bond_dev = dev->master;
                         struct sk_buff *skb;
-                        while ((skb = skb_dequeue(&dev->npinfo->arp_tx))) {
+                        struct netpoll_info *bond_ni = rcu_dereference_bh(bond_dev->npinfo);
+                        while ((skb = skb_dequeue(&ni->arp_tx))) {
                                 skb->dev = bond_dev;
-                                skb_queue_tail(&bond_dev->npinfo->arp_tx, skb);
+                                skb_queue_tail(&bond_ni->arp_tx, skb);
                         }
                 }
         }
 
-        service_arp_queue(dev->npinfo);
+        service_arp_queue(ni);
 
         zap_completion_queue();
 }
@@ -302,6 +305,7 @@ static int netpoll_owner_active(struct net_device *dev)
         return 0;
 }
 
+/* call with IRQ disabled */
 void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
                              struct net_device *dev)
 {
@@ -309,8 +313,11 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
         unsigned long tries;
         const struct net_device_ops *ops = dev->netdev_ops;
         /* It is up to the caller to keep npinfo alive. */
-        struct netpoll_info *npinfo = np->dev->npinfo;
+        struct netpoll_info *npinfo;
+
+        WARN_ON_ONCE(!irqs_disabled());
 
+        npinfo = rcu_dereference_bh(np->dev->npinfo);
         if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {
                 __kfree_skb(skb);
                 return;
@@ -319,11 +326,9 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
         /* don't get messages out of order, and no recursion */
         if (skb_queue_len(&npinfo->txq) == 0 && !netpoll_owner_active(dev)) {
                 struct netdev_queue *txq;
-                unsigned long flags;
 
                 txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
 
-                local_irq_save(flags);
                 /* try until next clock tick */
                 for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
                      tries > 0; --tries) {
@@ -347,10 +352,9 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
                 }
 
                 WARN_ONCE(!irqs_disabled(),
-                        "netpoll_send_skb(): %s enabled interrupts in poll (%pF)\n",
+                        "netpoll_send_skb_on_dev(): %s enabled interrupts in poll (%pF)\n",
                         dev->name, ops->ndo_start_xmit);
 
-                local_irq_restore(flags);
         }
 
         if (status != NETDEV_TX_OK) {
@@ -423,9 +427,8 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 }
 EXPORT_SYMBOL(netpoll_send_udp);
 
-static void arp_reply(struct sk_buff *skb)
+static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo)
 {
-        struct netpoll_info *npinfo = skb->dev->npinfo;
         struct arphdr *arp;
         unsigned char *arp_ptr;
         int size, type = ARPOP_REPLY, ptype = ETH_P_ARP;