CVE-2026-98011

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