From: Cong Wang cong.wang@bytedance.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@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 Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Cong Wang cong.wang@bytedance.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); }