Linux Kernel Forced Idle Warning in Core Scheduling Mechanism

CVE-2026-68421

What is CVE-2026-68421?

In the Linux kernel, a vulnerability exists that impacts core scheduling mechanics, specifically when a runnable task transitions to a forced idle state. This occurs in the function 'put_prev_task_scx()', which previously raised a warning under certain conditions. With the introduction of core scheduling, there's a risk that the task management is not properly balanced when the task shifts to a lower scheduling class without appropriate flags. The recent fix now conditions this warning based on matching CPU cookies, thereby preventing false alerts and ensuring that the core scheduling process functions correctly and efficiently.

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