CVE-2024-53057: net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-11-19 · updated 2026-10-15
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT In qdisc_tree_reduce_backlog, Qdiscs with major handle ffff: are assumed to be either root or ingress. This assumption is bogus since it's valid to create egress qdiscs with major handle ffff: Budimir Markovic found that for qdiscs like DRR that maintain an active class list, it will cause a UAF with a dangling class pointer. In 066a3b5b2346, the concern was to avoid iterating over the ingress qdisc since its parent is itself. The proper fix is to stop when parent TC_H_ROOT is reached because the only way to retrieve ingress is when a hierarchy which does not contain a ffff: major handle call into qdisc_lookup with TC_H_MAJ(TC_H_ROOT). In the scenario where major ffff: is an egress qdisc in any of the tree levels, the updates will also propagate to TC_H_ROOT, which then the iteration must stop. net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Affected products

Linux kernel: from 2.6.25 before 4.19.323; from 4.20 before 5.4.285; from 5.5 before 5.10.229; from 5.11 before 5.15.171; from 5.16 before 6.1.116; from 6.2 before 6.6.60 — fixed in 4.19.323, 5.10.229, 5.15.171, 5.4.285, 6.1.116, 6.11.7

How to fix

Upgrade to a fixed version: Linux kernel 4.19.323, 5.10.229, 5.15.171, 5.4.285. Check the vendor advisory for mitigations.

References

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