CVE-2026-64373

In the Linux kernel, the following vulnerability has been resolved:

cpufreq: Fix hotplug-suspend race during reboot

During system reboot, cpufreq_suspend() is called via the kernel_restart() -> device_shutdown() path. Unlike the normal system suspend path, the reboot path does not call freeze_processes(), so userspace processes and kernel threads remain active.

This allows CPU hotplug operations to run concurrently with cpufreq_suspend(). The original code has no synchronization with CPU hotplug, leading to a race condition where governor_data can be freed by the hotplug path while cpufreq_suspend() is still accessing it, resulting in a null pointer dereference:

Unable to handle kernel NULL pointer dereference Call Trace: do_kernel_fault+0x28/0x3c cpufreq_suspend+0xdc/0x160 device_shutdown+0x18/0x200 kernel_restart+0x40/0x80 arm64_sys_reboot+0x1b0/0x200

Fix this by adding cpus_read_lock()/cpus_read_unlock() to cpufreq_suspend() to block CPU hotplug operations while suspend is in progress.

[ rjw: Changelog edits ]

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/6d5dd354c37abaf4d60400c55c71f23ba2b33639
• https://git.kernel.org/stable/c/6e175c00c62dca3d91b987015808b5d52e8db2b4
• https://git.kernel.org/stable/c/73255d702c7560185fd5951aadcf7eb057c2f453
• https://git.kernel.org/stable/c/9103078c7b3091a2fbb52af176f95982ee7dd7f8
• https://git.kernel.org/stable/c/a0106b41f9a724868d390b8b3b4ea5ca0e04ea53
• https://git.kernel.org/stable/c/a0ef2fc89d28ca62923376c4b8ffaa57136a36be
• https://git.kernel.org/stable/c/a9029dd55696c651ee46912afa2a166fa456bb3e
• https://git.kernel.org/stable/c/cd4524ff6567fa4458a5bec4b017105e671d393e