From: valis sec@valis.email

Commit 76e42ae831991c828cffa8c37736ebfb831ad5ec upstream.

[ Fixed small conflict as 'fnew->ifindex' assignment is not protected by CONFIG_NET_CLS_IND on upstream since a51486266c3 ]

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: e35a8ee5993b ("net: sched: fw use RCU") 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/20230729123202.72406-3-jhs@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Luiz Capitulino luizcap@amazon.com --- net/sched/cls_fw.c | 1 - 1 file changed, 1 deletion(-)

Valis, Greg,

I noticed that 4.14 is missing this fix while we backported all three fixes from this series to all stable kernels:

https://lore.kernel.org/all/20230729123202.72406-1-jhs@mojatatu.com

Is there a reason to have skipped 4.14 for this fix? It seems we need it.

This is only compiled-tested though, would be good to have a confirmation from Valis that the issue is present on 4.14 before applying.

- Luiz

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c index e63f9c2e37e5..7b04b315b2bd 100644 --- a/net/sched/cls_fw.c +++ b/net/sched/cls_fw.c @@ -281,7 +281,6 @@ static int fw_change(struct net *net, struct sk_buff *in_skb, return -ENOBUFS;

fnew->id = f->id; - fnew->res = f->res; #ifdef CONFIG_NET_CLS_IND fnew->ifindex = f->ifindex; #endif /* CONFIG_NET_CLS_IND */