diff options
| author | Jamal Hadi Salim <jhs@mojatatu.com> | 2026-08-22 15:55:07 -0400 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-08-25 13:09:32 +0200 |
| commit | c86cd7ed0b0e44779a3d1683f03e4353baf4bdc9 (patch) | |
| tree | bb56074adcd9080d3d4d8e28a68cdf34d971f41b | |
| parent | 6439461f1618ae176c048673ad28bdb6c68efbfc (diff) | |
net/sched: fq_pie: clamp default quantum to avoid signed overflow
fq_pie_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) without
clamping. A device with a huge MTU (e.g. dummy with max_mtu == 0
accepting MTU 2147483634) makes psched_mtu() return 0x80000000, which
overflows the signed flow->deficit to INT_MIN in fq_pie_qdisc_dequeue(),
causing an infinite loop and soft lockup. Emulate fq_pie_policy which
is already bounded to [1, 1 << 20]; clamp the default to [256, 1 << 20].
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: ec97ecf1ebe4 ("net: sched: add Flow Queue PIE packet scheduler")
Reported-by: vega@nebusec.ai
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20260822195509.112717-5-jhs@mojatatu.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | net/sched/sch_fq_pie.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c index 069e1facd413..b27d95418707 100644 --- a/net/sched/sch_fq_pie.c +++ b/net/sched/sch_fq_pie.c @@ -427,7 +427,8 @@ static int fq_pie_init(struct Qdisc *sch, struct nlattr *opt, pie_params_init(&q->p_params); sch->limit = 10 * 1024; q->p_params.limit = sch->limit; - q->quantum = psched_mtu(qdisc_dev(sch)); + q->quantum = clamp_t(u32, psched_mtu(qdisc_dev(sch)), + 256, 1 << 20); q->sch = sch; q->ecn_prob = 10; q->flows_cnt = 1024; |