CVE-2026-98011net/sched: hhf: clamp quantum in change and init paths

Official description

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

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a328698d046098e6f55b3b1460cac6bab577be58
• https://git.kernel.org/stable/c/c364ad3ab3c8a6bce469a5cbf02881ab1324c5da
• https://git.kernel.org/stable/c/2c6dd9fc86d446a03728c43f3b96d9ae29aa058f
• https://git.kernel.org/stable/c/6570f326a6a96bedf3d1d1dab6acc9f8c29104ec
• https://git.kernel.org/stable/c/1113b674307ffddd402524bd1fd9d7d5629b705b
• https://git.kernel.org/stable/c/2e77947bbf6c166e76c038663832d0914418f761
• https://git.kernel.org/stable/c/0898c6f9fa9ce2632ae88bd0f34a878ccc6335af
• https://git.kernel.org/stable/c/eb56a495f59baf6cad5ed80e3ffb9078098b1346