Linux Kernel Preempt-RT Invalid Context Sleep Vulnerability on Ampere Altra

A vulnerability in the Linux kernel's handling of the ARM SDEI firmware interface can lead to improper sleep management during CPU hotplug operations. This issue occurs in preempt-RT versions of the kernel when running on Ampere Altra processors. The problem arises because the SDEI hotplug callback is executed in a context that does not allow sleeping, which can disrupt normal processing and potentially lead to performance issues.

Impact

This vulnerability can cause a kernel panic by attempting to sleep in an invalid context, disrupting the CPU hotplug process.

Reproduction

To reproduce this vulnerability, run a preempt-RT (version 6.2-rc3-rt1) kernel on an Ampere Altra processor. During the CPU hotplug process, the SDEI hotplug callback will be triggered in a context that does not allow sleeping, leading to a 'sleeping function called from invalid context' error.

Remediation

The vulnerability has been addressed in the Linux kernel. Users should upgrade to the latest version where this issue has been fixed.