6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jamal Hadi Salim <jhs@mojatatu.com>
[ Upstream commit 2164b512b97bb053e8ce4d6e95576f11bed6a005 ]
hhf_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) with no overflow
check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting
MTU 2147483634) makes weight * quantum overflow the signed deficit in
hhf_dequeue(), spinning forever.
Clamp q->quantum before hhf_change() so both the opt and !opt paths see
a sane quantum. Without this, bare "tc qdisc add ... hhf" succeeds with
a clamped quantum but "tc qdisc add ... hhf limit 1000" (any option
present) fails with -EINVAL because hhf_change() re-validates the
unclamped default (sch_hhf.c:559). 256 matches fq_codel's floor and is
a sane minimum for a DRR quantum.
Conditions to recreate the bug: a device whose MTU (plus
hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy
device with max_mtu == 0 accepting MTU 2147483634). Requires
CAP_NET_ADMIN in a user namespace.
Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Reported-by: <redacted>
Tested-by: Victor Nogueira <redacted>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20260822195509.112717-6-jhs@mojatatu.com (local)
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_hhf.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
index aca4795c4101f..f9eab403ac161 100644
--- a/net/sched/sch_hhf.c
+++ b/net/sched/sch_hhf.c
@@ -617,6 +617,10 @@ 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);
--
2.53.0