2023-05-24 01:30:11

by Peilin Ye

Subject: [PATCH v5 net 4/6] net/sched: Prohibit regrafting ingress or clsact Qdiscs

From: Peilin Ye <[email protected]>

Currently, after creating an ingress (or clsact) Qdisc and grafting it
under TC_H_INGRESS (TC_H_CLSACT), it is possible to graft it again under
e.g. a TBF Qdisc:

$ ip link add ifb0 type ifb
$ tc qdisc add dev ifb0 handle 1: root tbf rate 20kbit buffer 1600 limit 3000
$ tc qdisc add dev ifb0 clsact
$ tc qdisc link dev ifb0 handle ffff: parent 1:1
$ tc qdisc show dev ifb0
qdisc tbf 1: root refcnt 2 rate 20Kbit burst 1600b lat 560.0ms
qdisc clsact ffff: parent ffff:fff1 refcnt 2
^^^^^^^^

clsact's refcount has increased: it is now grafted under both
TC_H_CLSACT and 1:1.

ingress and clsact Qdiscs should only be used under TC_H_INGRESS
(TC_H_CLSACT). Prohibit regrafting them.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: 1f211a1b929c ("net, sched: add clsact qdisc")
Reviewed-by: Jamal Hadi Salim <[email protected]>
Acked-by: Jamal Hadi Salim <[email protected]>
Signed-off-by: Peilin Ye <[email protected]>
---
change in v3, v4:
- add in-body From: tag

net/sched/sch_api.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 383195955b7d..49b9c1bbfdd9 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1596,6 +1596,11 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
NL_SET_ERR_MSG(extack, "Invalid qdisc name");
return -EINVAL;
}
+ if (q->flags & TCQ_F_INGRESS) {
+ NL_SET_ERR_MSG(extack,
+ "Cannot regraft ingress or clsact Qdiscs");
+ return -EINVAL;
+ }
if (q == p ||
(p && check_loop(q, p, 0))) {
NL_SET_ERR_MSG(extack, "Qdisc parent/child loop detected");
--
2.20.1

2023-05-24 16:12:08

by Pedro Tammela

Subject: Re: [PATCH v5 net 4/6] net/sched: Prohibit regrafting ingress or clsact Qdiscs

On 23/05/2023 22:19, Peilin Ye wrote:
> From: Peilin Ye <[email protected]>
>
> Currently, after creating an ingress (or clsact) Qdisc and grafting it
> under TC_H_INGRESS (TC_H_CLSACT), it is possible to graft it again under
> e.g. a TBF Qdisc:
>
> $ ip link add ifb0 type ifb
> $ tc qdisc add dev ifb0 handle 1: root tbf rate 20kbit buffer 1600 limit 3000
> $ tc qdisc add dev ifb0 clsact
> $ tc qdisc link dev ifb0 handle ffff: parent 1:1
> $ tc qdisc show dev ifb0
> qdisc tbf 1: root refcnt 2 rate 20Kbit burst 1600b lat 560.0ms
> qdisc clsact ffff: parent ffff:fff1 refcnt 2
> ^^^^^^^^
>
> clsact's refcount has increased: it is now grafted under both
> TC_H_CLSACT and 1:1.
>
> ingress and clsact Qdiscs should only be used under TC_H_INGRESS
> (TC_H_CLSACT). Prohibit regrafting them.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Fixes: 1f211a1b929c ("net, sched: add clsact qdisc")
> Reviewed-by: Jamal Hadi Salim <[email protected]>
> Acked-by: Jamal Hadi Salim <[email protected]>
> Signed-off-by: Peilin Ye <[email protected]>

Tested-by: Pedro Tammela <[email protected]>

> ---
> change in v3, v4:
> - add in-body From: tag
>
> net/sched/sch_api.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 383195955b7d..49b9c1bbfdd9 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -1596,6 +1596,11 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
> NL_SET_ERR_MSG(extack, "Invalid qdisc name");
> return -EINVAL;
> }
> + if (q->flags & TCQ_F_INGRESS) {
> + NL_SET_ERR_MSG(extack,
> + "Cannot regraft ingress or clsact Qdiscs");
> + return -EINVAL;
> + }
> if (q == p ||
> (p && check_loop(q, p, 0))) {
> NL_SET_ERR_MSG(extack, "Qdisc parent/child loop detected");