net: neigh: don't call kfree_skb() under spin_lock_irqsave()

It is not allowed to call kfree_skb() from hardware interrupt
context or with interrupts being disabled. So add all skb to
a tmp list, then free them after spin_unlock_irqrestore() at
once.

Fixes: 66ba215cb513 ("neigh: fix possible DoS due to net iface start/stop loop")
Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 5b669eb..78cc8fb 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -309,14 +309,17 @@ static int neigh_del_timer(struct neighbour *n)
 
 static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
 {
+       struct sk_buff_head tmp;
        unsigned long flags;
        struct sk_buff *skb;
 
+       skb_queue_head_init(&tmp);
        spin_lock_irqsave(&list->lock, flags);
        skb = skb_peek(list);
        while (skb != NULL) {
                struct sk_buff *skb_next = skb_peek_next(skb, list);
                struct net_device *dev = skb->dev;
+
                if (net == NULL || net_eq(dev_net(dev), net)) {
                        struct in_device *in_dev;
 
@@ -326,13 +329,16 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net)
                                in_dev->arp_parms->qlen--;
                        rcu_read_unlock();
                        __skb_unlink(skb, list);
-
-                       dev_put(dev);
-                       kfree_skb(skb);
+                       __skb_queue_tail(&tmp, skb);
                }
                skb = skb_next;
        }
        spin_unlock_irqrestore(&list->lock, flags);
+
+       while ((skb = __skb_dequeue(&tmp))) {
+               dev_put(skb->dev);
+               kfree_skb(skb);
+       }
 }
 
 static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,