net/sched: cls_u32: No longer copy tcf_result on update to avoid use-after-free

stable inclusion
from stable-v5.10.190
commit b4256c99a7116c9514224847e8aaee2ecf110a0a
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=b4256c99a7116c9514224847e8aaee2ecf110a0a

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

[ Upstream commit 3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81 ]

When u32_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: de5df632 ("net: sched: cls_u32 changes to knode must appear atomic to readers")
Reported-by: Nvalis <sec@valis.email>
Reported-by: NM A Ramdhan <ramdhan@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/20230729123202.72406-2-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>
(cherry picked from commit 3b77be79)

net/sched/cls_u32.c

@@ -812,7 +812,6 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp,
 
 	new->ifindex = n->ifindex;
 	new->fshift = n->fshift;
-	new->res = n->res;
 	new->flags = n->flags;
 	RCU_INIT_POINTER(new->ht_down, ht);