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

stable inclusion
from stable-v4.19.257
commit 509e1b324aad95019ff14b8eb88fdfa500d9a489
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5UQH4


CVE: NA

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

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>