netdev - [Patch stable] netfilter: clear skb->next in NF_HOOK

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Date:   Fri, 20 Nov 2020 19:43:17 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <cong.wang@...edance.com>, liuzx@...wnsec.com,
        Florian Westphal <fw@...len.de>,
        Edward Cree <ecree@...arflare.com>, stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [Patch stable] netfilter: clear skb->next in NF_HOOK_LIST()

From: Cong Wang <cong.wang@...edance.com>

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 ca58fbe06c54
("netfilter: add and use nf_hook_slow_list()").

Fixes: 9f17dbf04ddf ("netfilter: fix use-after-free in NF_HOOK_LIST")
Reported-by: liuzx@...wnsec.com
Tested-by: liuzx@...wnsec.com
Cc: Florian Westphal <fw@...len.de>
Cc: Edward Cree <ecree@...arflare.com>
Cc: stable@...r.kernel.org # between 4.19 and 5.4
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
---
 include/linux/netfilter.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 77ebb61faf48..4c0e6539effd 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -316,7 +316,7 @@ 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);
 	}
-- 
2.25.1