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| author | Peilin Ye <peilin.ye@bytedance.com> | 2022-06-17 02:43:36 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2022-06-18 06:29:38 +0300 |
| commit | a2b1a5d40bd12b44322c2ccd40bb0ec1699708b6 (patch) | |
| tree | bfd9c9898cad65244668a9e520e334317b3dae30 /net/sched | |
| parent | a3bb7b63813f674fb62bac321cdd897cc62de094 (diff) | |
| download | linux-a2b1a5d40bd12b44322c2ccd40bb0ec1699708b6.tar.xz | |
net/sched: sch_netem: Fix arithmetic in netem_dump() for 32-bit platforms
As reported by Yuming, currently tc always show a latency of UINT_MAX
for netem Qdisc's on 32-bit platforms:
$ tc qdisc add dev dummy0 root netem latency 100ms
$ tc qdisc show dev dummy0
qdisc netem 8001: root refcnt 2 limit 1000 delay 275s 275s
^^^^^^^^^^^^^^^^
Let us take a closer look at netem_dump():
qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency,
UINT_MAX);
qopt.latency is __u32, psched_tdiff_t is signed long,
(psched_tdiff_t)(UINT_MAX) is negative for 32-bit platforms, so
qopt.latency is always UINT_MAX.
Fix it by using psched_time_t (u64) instead.
Note: confusingly, users have two ways to specify 'latency':
1. normally, via '__u32 latency' in struct tc_netem_qopt;
2. via the TCA_NETEM_LATENCY64 attribute, which is s64.
For the second case, theoretically 'latency' could be negative. This
patch ignores that corner case, since it is broken (i.e. assigning a
negative s64 to __u32) anyways, and should be handled separately.
Thanks Ted Lin for the analysis [1] .
[1] https://github.com/raspberrypi/linux/issues/3512
Reported-by: Yuming Chen <chenyuming.junnan@bytedance.com>
Fixes: 112f9cb65643 ("netem: convert to qdisc_watchdog_schedule_ns")
Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Link: https://lore.kernel.org/r/20220616234336.2443-1-yepeilin.cs@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_netem.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index ed4ccef5d6a8..5449ed114e40 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -1146,9 +1146,9 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb) struct tc_netem_rate rate; struct tc_netem_slot slot; - qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency), + qopt.latency = min_t(psched_time_t, PSCHED_NS2TICKS(q->latency), UINT_MAX); - qopt.jitter = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->jitter), + qopt.jitter = min_t(psched_time_t, PSCHED_NS2TICKS(q->jitter), UINT_MAX); qopt.limit = q->limit; qopt.loss = q->loss; |