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

Pedro Tammela
2023-05-24T15:41:22Z

On 23/05/2023 22:19, Peilin Ye wrote:
> From: Peilin Ye <peilin.ye@bytedance.com>
>
> 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 <jhs@mojatatu.com>
> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>

Tested-by: Pedro Tammela <pctammela@mojatatu.com>

> ---
> 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");