Re: [PATCH net v3 6/7] net/sched: act_gate: reject empty schedule list

[Victor Nogueira]

On 21/01/2026 16:44, Victor Nogueira wrote:
> On 21/01/2026 10:20, Paul Moses wrote:
> > Reject empty schedules (num_entries == 0) so next_entry is always 
> > valid and
> > RCU readers/timer logic never walk an empty list. taprio enforces the 
> > same
> > constraint on schedules (sch_taprio.c, commit 09dbdf28f9f9fa).
> >
> > Fixes: a51c328df310 ("net: qos: introduce a gate control flow action")
> > Signed-off-by: Paul Moses <p@xxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> >   net/sched/act_gate.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
> > index 48ff378bb051a..e4134b9a4a314 100644
> > --- a/net/sched/act_gate.c
> > +++ b/net/sched/act_gate.c
> > @@ -509,6 +509,12 @@ static int tcf_gate_init(struct net *net, struct 
> > nlattr *nla,
> >           cycletime_ext = nla_get_u64(tb[TCA_GATE_CYCLE_TIME_EXT]);
> >       p->tcfg_cycletime_ext = cycletime_ext;
> > +    if (p->num_entries == 0) {
> > +        NL_SET_ERR_MSG(extack, "The entry list is empty");
> > +        err = -EINVAL;
> > +        goto release_mem;
> > +    }
>
> It would be simpler to check this in parse_gate_list.
> That way you could return -EINVAL there directly
> in case 0 entries were passed.

On second thought, I believe it would be better
to check whether parse_gate_list's return is 0
and the op is a create. Something like:

err = parse_gate_list(tb[TCA_GATE_ENTRY_LIST], p, extack);
...
if (!err && ret == ACT_P_CREATED) {
    NL_SET_ERR_MSG(extack, "The entry list is empty");
    err = -EINVAL;
    goto release_mem;
}

so that you don't need to add new arguments to
parse_gate_list.

cheers,
Victor