CVE-2024-35985: sched/eevdf: Prevent vlag from going out of bounds in reweight_eevdf()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-20 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: sched/eevdf: Prevent vlag from going out of bounds in reweight_eevdf() It was possible to have pick_eevdf() return NULL, which then causes a NULL-deref. This turned out to be due to entity_eligible() returning falsely negative because of a s64 multiplcation overflow. Specifically, reweight_eevdf() computes the vlag without considering the limit placed upon vlag as update_entity_lag() does, and then the scaling multiplication (remember that weight is 20bit fixed point) can overflow. This then leads to the new vruntime being weird which then causes the above entity_eligible() to go side-ways and claim nothing is eligible. Thus limit the range of vlag accordingly. All this was quite rare, but fatal when it does happen.

Affected products

Linux kernel: from 6.6.4 before 6.6.30; from 6.7 before 6.8.9; 6.9-rc1, 6.9-rc2, 6.9-rc3, 6.9-rc4, 6.9-rc5 — fixed in 6.6.30, 6.8.9

How to fix

Upgrade to a fixed version: Linux kernel 6.6.30, 6.8.9. Check the vendor advisory for mitigations.

References

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