In the Linux kernel, the following vulnerability has been resolved:

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