[PATCH 6.9 338/374] net/sched: taprio: make q->picos_per_byte available to fill_sched_entry()

Greg Kroah-Hartman
2024-06-06T14:11:14Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

[ Upstream commit e634134180885574d1fe7aa162777ba41e7fcd5b ]

In commit b5b73b26b3ca ("taprio: Fix allowing too small intervals"), a
comparison of user input against length_to_duration(q, ETH_ZLEN) was
introduced, to avoid RCU stalls due to frequent hrtimers.

The implementation of length_to_duration() depends on q->picos_per_byte
being set for the link speed. The blamed commit in the Fixes: tag has
moved this too late, so the checks introduced above are ineffective.
The q->picos_per_byte is zero at parse_taprio_schedule() ->
parse_sched_list() -> parse_sched_entry() -> fill_sched_entry() time.

Move the taprio_set_picos_per_byte() call as one of the first things in
taprio_change(), before the bulk of the netlink attribute parsing is
done. That's because it is needed there.

Add a selftest to make sure the issue doesn't get reintroduced.

Fixes: 09dbdf28f9f9 ("net/sched: taprio: fix calculation of maximum gate durations")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240527153955.553333-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_taprio.c | 4 +++-
.../tc-testing/tc-tests/qdiscs/taprio.json | 22 +++++++++++++++++++
2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index a0d54b422186f..631140c1f6e5f 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1851,6 +1851,9 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
}
q->flags = taprio_flags;

+ /* Needed for length_to_duration() during netlink attribute parsing */
+ taprio_set_picos_per_byte(dev, q);
+
err = taprio_parse_mqprio_opt(dev, mqprio, extack, q->flags);
if (err < 0)
return err;
@@ -1910,7 +1913,6 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
if (err < 0)
goto free_sched;

- taprio_set_picos_per_byte(dev, q);
taprio_update_queue_max_sdu(q, new_admin, stab);

if (FULL_OFFLOAD_IS_ENABLED(q->flags))
diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/taprio.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/taprio.json
index 12da0a939e3e5..8f12f00a4f572 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/taprio.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/taprio.json
@@ -132,6 +132,28 @@
"echo \"1\" > /sys/bus/netdevsim/del_device"
]
},
+ {
+ "id": "6f62",
+ "name": "Add taprio Qdisc with too short interval",
+ "category": [
+ "qdisc",
+ "taprio"
+ ],
+ "plugins": {
+ "requires": "nsPlugin"
+ },
+ "setup": [
+ "echo \"1 1 8\" > /sys/bus/netdevsim/new_device"
+ ],
+ "cmdUnderTest": "$TC qdisc add dev $ETH root handle 1: taprio num_tc 2 queues 1@0 1@1 sched-entry S 01 300 sched-entry S 02 1700 clockid CLOCK_TAI",
+ "expExitCode": "2",
+ "verifyCmd": "$TC qdisc show dev $ETH",
+ "matchPattern": "qdisc taprio 1: root refcnt",
+ "matchCount": "0",
+ "teardown": [
+ "echo \"1\" > /sys/bus/netdevsim/del_device"
+ ]
+ },
{
"id": "3e1e",
"name": "Add taprio Qdisc with an invalid cycle-time",
--
2.43.0