net_sched: fix a use-after-free in tc_ctl_tfilter()

When tcf_destroy() returns true, tp could be already destroyed,
we should not use tp->next after that.

For long term, we probably should move tp list to list_head.

Fixes: 1e052be69d04 ("net_sched: destroy proto tp when all filters are gone")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 4 deletions

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 8b0470e418dc..b6ef9a04de06 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -308,12 +308,11 @@ replay:
                 case RTM_DELTFILTER:
                         err = tp->ops->delete(tp, fh);
                         if (err == 0) {
-                                tfilter_notify(net, skb, n, tp, fh, RTM_DELTFILTER);
-                                if (tcf_destroy(tp, false)) {
-                                        struct tcf_proto *next = rtnl_dereference(tp->next);
+                                struct tcf_proto *next = rtnl_dereference(tp->next);
 
+                                tfilter_notify(net, skb, n, tp, fh, RTM_DELTFILTER);
+                                if (tcf_destroy(tp, false))
                                         RCU_INIT_POINTER(*back, next);
-                                }
                         }
                         goto errout;
                 case RTM_GETTFILTER: