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Message-ID: <20231019124202.fldo2cc5s6w4hrxz@skbuf>
Date: Thu, 19 Oct 2023 15:42:02 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Gerhard Engleder <gerhard@...leder-embedded.com>,
Lai Peter Jun Ann <jun.ann.lai@...el.com>,
Vinicius Costa Gomes <vinicius.gomes@...el.com>,
Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/1] taprio: Add boundary check for
sched-entry values
On Thu, Oct 19, 2023 at 12:35:30PM +0200, Paolo Abeni wrote:
> On Wed, 2023-10-18 at 19:56 +0200, Gerhard Engleder wrote:
> > On 18.10.23 05:28, Lai Peter Jun Ann wrote:
> > > Adds boundary checks for the gatemask provided against the number of
> > > traffic class defined for each sched-entry.
> > >
> > > Without this check, the user would not know that the gatemask provided is
> > > invalid and the driver has already truncated the gatemask provided to
> > > match the number of traffic class defined.
> > >
> > > Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com>
> > > Signed-off-by: Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>
> > > Signed-off-by: Lai Peter Jun Ann <jun.ann.lai@...el.com>
> > > ---
> > > net/sched/sch_taprio.c | 8 ++++++++
> > > 1 file changed, 8 insertions(+)
> > >
> > > diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> > > index 1cb5e41..44b9e21 100644
> > > --- a/net/sched/sch_taprio.c
> > > +++ b/net/sched/sch_taprio.c
> > > @@ -102,6 +102,7 @@ struct taprio_sched {
> > > u32 max_sdu[TC_MAX_QUEUE]; /* save info from the user */
> > > u32 fp[TC_QOPT_MAX_QUEUE]; /* only for dump and offloading */
> > > u32 txtime_delay;
> > > + u8 num_tc;
To the patch: I would oppose introducing an "u8 num_tc" to struct
taprio_sched for one purpose only. It is a duplication of
netdev->num_tc, the only problem is that it hasn't yet been set, which
can be solved with a bit of code reorganization.
> > > };
> > >
> > > struct __tc_taprio_qopt_offload {
> > > @@ -1063,6 +1064,11 @@ static int fill_sched_entry(struct taprio_sched *q, struct nlattr **tb,
> > > return -EINVAL;
> > > }
> > >
> > > + if (entry->gate_mask >= q->num_tc) {
> >
> > As far as I know within gate_mask every bit represents a traffic class.
> > So for 3 traffic classes at gate_mask of 0x7 is valid but this check
> > fails with 0x7 >= 3.
>
> Additionally whatever check we put in place previously just ignored by
> the existing code, could break the existing user-space: we can't accept
> such change.
I agree, and I would oppose erroring out.
I used to have this patch which simply masks off the excess bits,
calling netdev_warn() - which can be transformed into a warning netlink
extack - instead.
https://patchwork.kernel.org/project/netdevbpf/patch/20230130173145.475943-15-vladimir.oltean@nxp.com/
I didn't have a strong motivation for the patch, and I dropped it.
If Lai Peter Jun Ann can come with the motivation, we can go with that
approach.
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