netfilter: clear skb->next in NF_HOOK_LIST()

stable inclusion
from linux-4.19.161
commit 5460d62d661c0fc53bfe83493821b1dc3dc969f4

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

NF_HOOK_LIST() uses list_del() to remove skb from the linked list,
however, it is not sufficient as skb->next still points to other
skb. We should just call skb_list_del_init() to clear skb->next,
like the rest places which using skb list.

This has been fixed in upstream by commit ca58fbe0
("netfilter: add and use nf_hook_slow_list()").

Fixes: 9f17dbf0 ("netfilter: fix use-after-free in NF_HOOK_LIST")
Reported-by: liuzx@knownsec.com
Tested-by: liuzx@knownsec.com
Cc: Florian Westphal <fw@strlen.de>
Cc: Edward Cree <ecree@solarflare.com>
Cc: stable@vger.kernel.org # between 4.19 and 5.4
Signed-off-by: NCong Wang <cong.wang@bytedance.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/netfilter.h

@@ -300,7 +300,7 @@ NF_HOOK_LIST(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk,
 
 	INIT_LIST_HEAD(&sublist);
 	list_for_each_entry_safe(skb, next, head, list) {
-		list_del(&skb->list);
+		skb_list_del_init(skb);
 		if (nf_hook(pf, hook, net, sk, skb, in, out, okfn) == 1)
 			list_add_tail(&skb->list, &sublist);
 	}