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| author | Jamal Hadi Salim <jhs@mojatatu.com> | 2026-09-01 17:39:25 -0400 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-09-05 13:47:30 -0700 |
| commit | eb56a495f59baf6cad5ed80e3ffb9078098b1346 (patch) | |
| tree | aa7293245bce13a09f7a72e0b4aef9a78e625a51 /net | |
| parent | fb9f88a33c516ea5c0bcd9a22ca288b246b34567 (diff) | |
| download | linux-next-eb56a495f59baf6cad5ed80e3ffb9078098b1346.tar.gz linux-next-eb56a495f59baf6cad5ed80e3ffb9078098b1346.zip | |
net/sched: hhf: clamp quantum in change and init paths
hhf_change() accepts any quantum from userspace, including 1. With a
crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes
the deficit-refill loop spin ~2^31 times under the qdisc lock
(a soft lockup / denial of service).
Add max(256U, ...) in hhf_change() matching fq_codel_change(). Clamp
hhf_init() to [256, 1<<20] matching the siblings, and remove the old
fallback that only set quantum=256 on overflow.
Conditions to recreate the bug:
CONFIG_NET_SCH_HHF=y. Requires CAP_NET_ADMIN (namespace-local via
unshare -Urn suffices).
tc qdisc add dev dummy0 root hhf
tc qdisc change dev dummy0 root hhf quantum 1 stab data 32768 size_log 15 cell_log 0
Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Reported-by: Vega <vega@nebusec.ai>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/QDISC-0CFC.v3.20260901204856@mojatatu.com.5
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_hhf.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c index 96acab6a8da0..fc72f825fbd9 100644 --- a/net/sched/sch_hhf.c +++ b/net/sched/sch_hhf.c @@ -551,7 +551,7 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt, return err; if (tb[TCA_HHF_QUANTUM]) - new_quantum = nla_get_u32(tb[TCA_HHF_QUANTUM]); + new_quantum = max(256U, nla_get_u32(tb[TCA_HHF_QUANTUM])); if (tb[TCA_HHF_NON_HH_WEIGHT]) new_hhf_non_hh_weight = nla_get_u32(tb[TCA_HHF_NON_HH_WEIGHT]); @@ -613,7 +613,7 @@ static int hhf_init(struct Qdisc *sch, struct nlattr *opt, int i; sch->limit = 1000; - q->quantum = psched_mtu(qdisc_dev(sch)); + q->quantum = clamp_t(u32, psched_mtu(qdisc_dev(sch)), 256, 1 << 20); get_random_bytes(&q->perturbation, sizeof(q->perturbation)); INIT_LIST_HEAD(&q->new_buckets); INIT_LIST_HEAD(&q->old_buckets); @@ -624,10 +624,6 @@ static int hhf_init(struct Qdisc *sch, struct nlattr *opt, q->hhf_evict_timeout = HZ; /* 1 sec */ q->hhf_non_hh_weight = 2; - if ((int)q->quantum <= 0 || - (u64)q->quantum * q->hhf_non_hh_weight > INT_MAX) - q->quantum = 256; - if (opt) { int err = hhf_change(sch, opt, extack); |