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

stable inclusion
from stable-v4.19.291
commit ad8f36f96696a7f1d191da66637c415959bab6d8
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=ad8f36f96696a7f1d191da66637c415959bab6d8



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

[ Upstream commit b80b829e ]

When route4_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: 1109c005 ("net: sched: RCU cls_route")
Reported-by: valis <sec@valis.email>
Reported-by: Bing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: valis <sec@valis.email>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: M A Ramdhan <ramdhan@starlabs.sg>
Link: https://lore.kernel.org/r/20230729123202.72406-4-jhs@mojatatu.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Liu Jian <liujian56@huawei.com>