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

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 <[email protected]>
Reported-by: Bing-Jhong Billy Jheng <[email protected]>
Signed-off-by: valis <[email protected]>
Signed-off-by: Jamal Hadi Salim <[email protected]>
Reviewed-by: Victor Nogueira <[email protected]>
Reviewed-by: Pedro Tammela <[email protected]>
Reviewed-by: M A Ramdhan <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

1 files changed, 0 insertions, 1 deletions

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index 8641f8059317..c49d6af0e048 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -267,7 +267,6 @@ 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;