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Message-ID: <CAM0EoM=4DOj3Np3a_uYxKp2fD2pUPkaF_QiZjuD57c00pjncuA@mail.gmail.com>
Date: Fri, 7 Apr 2023 12:09:07 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
Vinicius Costa Gomes <vinicius.gomes@...el.com>,
Kurt Kanzenbach <kurt@...utronix.de>,
Gerhard Engleder <gerhard@...leder-embedded.com>,
Amritha Nambiar <amritha.nambiar@...el.com>,
Ferenc Fejes <ferenc.fejes@...csson.com>,
Xiaoliang Yang <xiaoliang.yang_1@....com>,
Roger Quadros <rogerq@...nel.org>,
Pranavi Somisetty <pranavi.somisetty@....com>,
Harini Katakam <harini.katakam@....com>,
Giuseppe Cavallaro <peppe.cavallaro@...com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>,
Oleksij Rempel <linux@...pel-privat.de>,
Jacob Keller <jacob.e.keller@...el.com>,
linux-kernel@...r.kernel.org,
Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH v4 net-next 5/9] net/sched: pass netlink extack to mqprio
and taprio offload
On Mon, Apr 3, 2023 at 6:35 AM Vladimir Oltean <vladimir.oltean@....com> wrote:
>
> With the multiplexed ndo_setup_tc() model which lacks a first-class
> struct netlink_ext_ack * argument, the only way to pass the netlink
> extended ACK message down to the device driver is to embed it within the
> offload structure.
>
> Do this for struct tc_mqprio_qopt_offload and struct tc_taprio_qopt_offload.
>
> Since struct tc_taprio_qopt_offload also contains a tc_mqprio_qopt_offload
> structure, and since device drivers might effectively reuse their mqprio
> implementation for the mqprio portion of taprio, we make taprio set the
> extack in both offload structures to point at the same netlink extack
> message.
>
> In fact, the taprio handling is a bit more tricky, for 2 reasons.
>
> First is because the offload structure has a longer lifetime than the
> extack structure. The driver is supposed to populate the extack
> synchronously from ndo_setup_tc() and leave it alone afterwards.
> To not have any use-after-free surprises, we zero out the extack pointer
> when we leave taprio_enable_offload().
>
> The second reason is because taprio does overwrite the extack message on
> ndo_setup_tc() error. We need to switch to the weak form of setting an
> extack message, which preserves a potential message set by the driver.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> Reviewed-by: Simon Horman <simon.horman@...igine.com>
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
cheers,
jamal
> ---
> v3->v4: none
> v2->v3: patch is new
>
> include/net/pkt_sched.h | 2 ++
> net/sched/sch_mqprio.c | 5 ++++-
> net/sched/sch_taprio.c | 12 ++++++++++--
> 3 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
> index bb0bd69fb655..b43ed4733455 100644
> --- a/include/net/pkt_sched.h
> +++ b/include/net/pkt_sched.h
> @@ -166,6 +166,7 @@ struct tc_mqprio_caps {
> struct tc_mqprio_qopt_offload {
> /* struct tc_mqprio_qopt must always be the first element */
> struct tc_mqprio_qopt qopt;
> + struct netlink_ext_ack *extack;
> u16 mode;
> u16 shaper;
> u32 flags;
> @@ -193,6 +194,7 @@ struct tc_taprio_sched_entry {
>
> struct tc_taprio_qopt_offload {
> struct tc_mqprio_qopt_offload mqprio;
> + struct netlink_ext_ack *extack;
> u8 enable;
> ktime_t base_time;
> u64 cycle_time;
> diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
> index 9ee5a9a9b9e9..5287ff60b3f9 100644
> --- a/net/sched/sch_mqprio.c
> +++ b/net/sched/sch_mqprio.c
> @@ -33,9 +33,12 @@ static int mqprio_enable_offload(struct Qdisc *sch,
> const struct tc_mqprio_qopt *qopt,
> struct netlink_ext_ack *extack)
> {
> - struct tc_mqprio_qopt_offload mqprio = {.qopt = *qopt};
> struct mqprio_sched *priv = qdisc_priv(sch);
> struct net_device *dev = qdisc_dev(sch);
> + struct tc_mqprio_qopt_offload mqprio = {
> + .qopt = *qopt,
> + .extack = extack,
> + };
> int err, i;
>
> switch (priv->mode) {
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 1f469861eae3..cbad43019172 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -1520,7 +1520,9 @@ static int taprio_enable_offload(struct net_device *dev,
> return -ENOMEM;
> }
> offload->enable = 1;
> + offload->extack = extack;
> mqprio_qopt_reconstruct(dev, &offload->mqprio.qopt);
> + offload->mqprio.extack = extack;
> taprio_sched_to_offload(dev, sched, offload, &caps);
>
> for (tc = 0; tc < TC_MAX_QUEUE; tc++)
> @@ -1528,14 +1530,20 @@ static int taprio_enable_offload(struct net_device *dev,
>
> err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, offload);
> if (err < 0) {
> - NL_SET_ERR_MSG(extack,
> - "Device failed to setup taprio offload");
> + NL_SET_ERR_MSG_WEAK(extack,
> + "Device failed to setup taprio offload");
> goto done;
> }
>
> q->offloaded = true;
>
> done:
> + /* The offload structure may linger around via a reference taken by the
> + * device driver, so clear up the netlink extack pointer so that the
> + * driver isn't tempted to dereference data which stopped being valid
> + */
> + offload->extack = NULL;
> + offload->mqprio.extack = NULL;
> taprio_offload_free(offload);
>
> return err;
> --
> 2.34.1
>
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