CVE-2026-90074

Summary

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

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < 1f43e4dbc93b7d02761a024d5f895df823c07b72affected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < f7942b2693bc24c7d609a03d06f97bee3b0bd96aaffected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < 6f1be05faecef4c0f9a008200209f66ef2e133f7affected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < 435da3734a8e63d3067016accc977ed1d10aaaa0affected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < 44dad8fe99b58a7fe2961e9eec6a5f07ace5b51faffected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < 044fa2498bbc2900f0c48a6ef2fdd5b2bdfc3795affected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < bf97fd2163ad1191ef8daa3d4df8372aee19e396affected
LinuxLinuxec97ecf1ebe485a17cd8395a5f35e6b80b57665a < c86cd7ed0b0e44779a3d1683f03e4353baf4bdc9affected
LinuxLinux5.6affected
LinuxLinux0 < 5.6unaffected
LinuxLinux5.10.270 <= 5.10.*unaffected
LinuxLinux5.15.221 <= 5.15.*unaffected
LinuxLinux6.1.188 <= 6.1.*unaffected
LinuxLinux6.6.157 <= 6.6.*unaffected
LinuxLinux6.12.110 <= 6.12.*unaffected
LinuxLinux6.18.52 <= 6.18.*unaffected
LinuxLinux7.2.6 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References