[PATCH 4.19 56/56] net: neigh: dont call kfree_skb() under spin_lock_irqsave()

[Greg Kroah-Hartman]

From: Yang Yingliang <yangyingliang@xxxxxxxxxx>

commit d5485d9dd24e1d04e5509916515260186eb1455c upstream.

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@xxxxxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Reviewed-by: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/neighbour.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -226,21 +226,27 @@ static int neigh_del_timer(struct neighb
 
 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);
 		if (net == NULL || net_eq(dev_net(skb->dev), net)) {
 			__skb_unlink(skb, list);
-			dev_put(skb->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)