[Patch net] net_sched: fix a use-after-free in tc_ctl_tfilter()

[Patch net] net_sched: fix a use-after-free in tc_ctl_tfilter()

[Cong Wang]

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>
---
 net/sched/cls_api.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 8b0470e..b6ef9a0 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -308,12 +308,11 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n)
 		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:
-- 
1.8.3.1

Re: [Patch net] net_sched: fix a use-after-free in tc_ctl_tfilter()

[Jamal Hadi Salim]

On 05/05/15 18:22, Cong Wang wrote:
> 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>


cheers,
jamal

Re: [Patch net] net_sched: fix a use-after-free in tc_ctl_tfilter()

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue,  5 May 2015 15:22:02 -0700

> 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>

Applied, thank you.