CVE-2024-46691

What it actually does

Calling ucsi_unregister from atomic context (due to spinlock-protected pmic_glink client list accessed from IRQ) violates sleep requirements and risks deadlock or corruption; added NULL check in pmic_glink_send prevents dereference after remote processor loss but surfaces as kernel log error.

Why it matters to the business

Kernel instability or crashes on Linux systems using Qualcomm PMIC GLINK with UCSI USB Type-C hardware can interrupt operations and require reboots; widespread kernel dependency increases patch urgency across servers and devices.

How an attack unfolds

Local attacker triggers UCSI registration or power events that invoke glink callbacks from IRQ context, forcing unregister into atomic section; if the communication link is already gone this leads to attempted NULL dereference (mitigated by check) or other undefined behavior causing denial of service.

How to fix it

Apply the kernel commit 095b0001aefddcd9361097c971b7debc84e72714 (or equivalent stable backports); update github.com/sylabs/singularity to version 3.6.3 where applicable.

How to confirm the fix worked

Confirm running kernel contains commit 095b0001aefddcd9361097c971b7debc84e72714; reproduce UCSI events and verify absence of 'failed to send UCSI write request: -5' messages and no atomic-context warnings or crashes.

Typical attack path

1. Obtain local user access on affected Linux system
2. Generate USB Type-C or power-management events that exercise pmic_glink_ucsi paths
3. Force unregister while in atomic context to trigger crash or instability

How to detect it

Search kernel logs for pmic_glink_ucsi entries containing 'failed to send UCSI write request' or unregister-related atomic context warnings; correlate with system crashes or USB Type-C device events.

What your security team should do

• Patch kernels on all systems with Qualcomm PMIC GLINK hardware immediately
• Add kernel log monitoring for pmic_glink_ucsi and UCSI errors
• Validate USB Type-C functionality after updates in test environments