[PATCH 4.19 02/57] netfilter: clear skb->next in NF_HOOK_LIST()

[Greg Kroah-Hartman]

From: Cong Wang <cong.w...@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: li...@knownsec.com
Tested-by: li...@knownsec.com
Cc: Florian Westphal <f...@strlen.de>
Cc: Edward Cree <ec...@solarflare.com>
Cc: sta...@vger.kernel.org # between 4.19 and 5.4
Signed-off-by: Cong Wang <cong.w...@bytedance.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 include/linux/netfilter.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -300,7 +300,7 @@ NF_HOOK_LIST(uint8_t pf, unsigned int ho
 
        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);
        }