CVE-2026-90074

net/sched: fq_pie: clamp default quantum to avoid signed overflow

State: Published
Severity: Not scored
Published: Sep 17, 2026
Updated: Oct 19, 2026
Reserved: Sep 11, 2026

Description

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.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 1f43e4dbc93b7d02761a024d5f895df823c07b72Affected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before f7942b2693bc24c7d609a03d06f97bee3b0bd96aAffected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 6f1be05faecef4c0f9a008200209f66ef2e133f7Affected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 435da3734a8e63d3067016accc977ed1d10aaaa0Affected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 44dad8fe99b58a7fe2961e9eec6a5f07ace5b51fAffected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 044fa2498bbc2900f0c48a6ef2fdd5b2bdfc3795Affected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before bf97fd2163ad1191ef8daa3d4df8372aee19e396Affected ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before c86cd7ed0b0e44779a3d1683f03e4353baf4bdc9Affected
LinuxLinux	5.6Affected before 5.6Not affected 5.10.270 through 5.10.Not affected 5.15.221 through 5.15.Not affected 6.1.188 through 6.1.Not affected 6.6.157 through 6.6.Not affected 6.12.110 through 6.12.Not affected 6.18.52 through 6.18.Not affected 7.2.6 through 7.2.*Not affected 7.3 and laterNot affected

Product

Versions

LinuxLinux

ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 1f43e4dbc93b7d02761a024d5f895df823c07b72Affected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before f7942b2693bc24c7d609a03d06f97bee3b0bd96aAffected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 6f1be05faecef4c0f9a008200209f66ef2e133f7Affected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 435da3734a8e63d3067016accc977ed1d10aaaa0Affected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 44dad8fe99b58a7fe2961e9eec6a5f07ace5b51fAffected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before 044fa2498bbc2900f0c48a6ef2fdd5b2bdfc3795Affected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before bf97fd2163ad1191ef8daa3d4df8372aee19e396Affected
ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to before c86cd7ed0b0e44779a3d1683f03e4353baf4bdc9Affected

LinuxLinux

5.6Affected
before 5.6Not affected
5.10.270 through 5.10.*Not affected
5.15.221 through 5.15.*Not affected
6.1.188 through 6.1.*Not affected
6.6.157 through 6.6.*Not affected
6.12.110 through 6.12.*Not affected
6.18.52 through 6.18.*Not affected
7.2.6 through 7.2.*Not affected
7.3 and laterNot affected

References

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