CVE-2024-40967

What it actually does

The vulnerability is a missing timeout in the i.MX serial driver that can cause an indefinite wait for the USR2_TXDC transmitter-empty flag, resulting in a deadlock due to a race condition.

Why it matters to the business

Systems running affected Linux kernel versions on i.MX hardware risk hangs or loss of availability during serial operations, potentially disrupting embedded devices, industrial equipment, or any workloads relying on continuous kernel operation; widespread kernel usage increases exposure across many environments.

How an attack unfolds

An attacker with the ability to influence serial port activity triggers conditions where the transmitter never signals empty; the driver then blocks forever waiting for the flag, deadlocking the affected code path and impacting system stability.

How to fix it

Upgrade the Linux kernel to the fixed commit 7f2b9ab6d0b26f16cd38dd9fd91d51899635f7c7 or any later stable release that includes the one-second timeout for USR2_TXDC.

How to confirm the fix worked

Confirm the timeout logic and 1-second bound are present in the imx serial driver source; exercise serial transmit paths under load and verify the driver no longer blocks indefinitely.

Typical attack path

1. Gain local execution or serial-port control on a system using the imx driver
2. Manipulate transmitter state so USR2_TXDC never asserts
3. Force the driver into the unbounded wait loop
4. Cause kernel deadlock or unresponsiveness

How to detect it

Inspect kernel logs and dmesg output for repeated waits or stalls referencing the imx serial transmitter; correlate with process or thread activity that performs serial writes on affected hardware.

What your security team should do

• Apply the kernel update containing commit 7f2b9ab6d0b26f16cd38dd9fd91d51899635f7c7 as soon as possible
• Prioritize patching on any i.MX-based devices or servers handling serial traffic
• Review kernel logs for serial-related stalls after upgrade to confirm resolution