net/sched: cls_fw: No longer copy tcf_result on update to avoid use-after-free

stable inclusion
from stable-v5.10.190
commit a8d478200b104ff356f51e1f63499fe46ba8c9b8
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7SAP1
CVE: CVE-2023-4128

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8d478200b104ff356f51e1f63499fe46ba8c9b8

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

[ Upstream commit 76e42ae831991c828cffa8c37736ebfb831ad5ec ]

When fw_change() is called on an existing filter, the whole
tcf_result struct is always copied into the new instance of the filter.

This causes a problem when updating a filter bound to a class,
as tcf_unbind_filter() is always called on the old instance in the
success path, decreasing filter_cnt of the still referenced class
and allowing it to be deleted, leading to a use-after-free.

Fix this by no longer copying the tcf_result struct from the old filter.

Fixes: e35a8ee5 ("net: sched: fw use RCU")
Reported-by: Nvalis <sec@valis.email>
Reported-by: NBing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: Nvalis <sec@valis.email>
Signed-off-by: NJamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: NVictor Nogueira <victor@mojatatu.com>
Reviewed-by: NPedro Tammela <pctammela@mojatatu.com>
Reviewed-by: NM A Ramdhan <ramdhan@starlabs.sg>
Link: https://lore.kernel.org/r/20230729123202.72406-3-jhs@mojatatu.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NLiu Jian <liujian56@huawei.com>

net/sched/cls_fw.c

@@ -266,7 +266,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
 			return -ENOBUFS;
 
 		fnew->id = f->id;
-		fnew->res = f->res;
 		fnew->ifindex = f->ifindex;
 		fnew->tp = f->tp;