CVE-2023-52493

What it actually does

Race condition in the Linux kernel MHI host bus driver where parse_xfer_event holds a channel read lock across a client callback, allowing the callback to queue buffers and acquire the write lock, resulting in lock ordering violation and potential soft lockup.

Why it matters to the business

Systems using affected Linux kernels on MHI-enabled hardware may experience kernel hangs or soft lockups, leading to service disruption on servers, embedded devices, or networking equipment until reboot or manual intervention.

How an attack unfolds

An attacker with local access or the ability to trigger MHI channel events induces the race by causing parse_xfer_event to invoke a client callback that attempts to queue buffers while the read lock remains held, violating lock ordering and producing a soft lockup.

How to fix it

Upgrade the Linux kernel to a fixed version such as 6.1.7-1 on Debian 12/13 or apply commit 20a6dea2d1c68d4e03c6bb50bc12e72e226b5c0e from the stable tree; rebuild and reboot with the patched kernel.

How to confirm the fix worked

Verify the running kernel version or commit hash includes the fix; attempt to reproduce MHI channel activity and confirm absence of soft lockup warnings in dmesg; review source for the read-lock drop before the callback.

Typical attack path

1. Obtain local execution or hardware event injection capability on an MHI-equipped system
2. Trigger MHI transfer events that invoke parse_xfer_event
3. Cause the client callback to attempt buffer queueing while the channel read lock is still acquired
4. Induce repeated lock acquisition attempts resulting in soft lockup detection

How to detect it

Search kernel logs (dmesg, syslog) for soft lockup or watchdog messages referencing mhi, parse_xfer_event, or channel locks; examine crash dumps or stack traces showing nested lock attempts during buffer queueing.

• soft lockup.*mhi
• parse_xfer_event
• chan lock.*queueing buffers

What your security team should do

• Prioritize kernel upgrades on all MHI-using systems within the next patching cycle
• Monitor kernel logs for soft lockup messages involving mhi or parse_xfer_event
• Test patched kernels in staging environments before broad deployment
• Restrict untrusted local access on systems exposing MHI interfaces until patched