Linux Kernel Preemption Control Vulnerability in BPF Scheduler

A vulnerability in the Linux kernel's BPF scheduler can lead to a system hang. This issue occurs in the 'sched_ext' component, specifically in versions through 6.12. The problem arises when a task is preempted after claiming an exit but before initiating the necessary helper work. If the BPF scheduler fails to return the task to execution, the system can become unresponsive. The vulnerability has been addressed by disabling preemption during critical operations, ensuring that the helper work is always executed as needed.

Impact

The vulnerability can cause the system to become unresponsive, as tasks stop being dispatched and the system 'wedges'.

Reproduction

To reproduce this vulnerability, a task must be preempted after it has claimed an exit in the BPF scheduler but before it has kicked off the required helper work. This can create a scenario where the task is not scheduled back for execution, leading to a system hang.

Remediation

Users can upgrade to the patched version of the Linux kernel available in the Linux kernel stable tree.