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authorPeilin Ye <peilin.ye@bytedance.com>2022-06-17 02:43:36 +0300
committerJakub Kicinski <kuba@kernel.org>2022-06-18 06:29:38 +0300
commita2b1a5d40bd12b44322c2ccd40bb0ec1699708b6 (patch)
treebfd9c9898cad65244668a9e520e334317b3dae30 /net/sched
parenta3bb7b63813f674fb62bac321cdd897cc62de094 (diff)
downloadlinux-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.c4
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;