CVE-2024-35985

Summary

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 Software

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

• https://git.kernel.org/stable/c/470d347b14b0ecffa9b39cf8f644fa2351db3efb
• https://git.kernel.org/stable/c/06f27e6d7bf0abf54488259ef36bbf0e1fccb35c
• https://git.kernel.org/stable/c/1560d1f6eb6b398bddd80c16676776c0325fe5fe

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

References

• https://git.kernel.org/stable/c/470d347b14b0ecffa9b39cf8f644fa2351db3efb
• https://git.kernel.org/stable/c/06f27e6d7bf0abf54488259ef36bbf0e1fccb35c
• https://git.kernel.org/stable/c/1560d1f6eb6b398bddd80c16676776c0325fe5fe

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