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

stable inclusion
from stable-v5.10.141
commit bdc786d737ec0eac92131d76372cd7f29c1e02e6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I685FC

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bdc786d737ec0eac92131d76372cd7f29c1e02e6

--------------------------------

commit d5485d9d 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: 66ba215c ("neigh: fix possible DoS due to net iface start/stop loop")
Suggested-by: NDenis V. Lunev <den@openvz.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NNikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/core/neighbour.c

@@ -282,21 +282,27 @@ 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);
 		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,