CVE-2021-46941

What it actually does

Missing GCTL.CoreSoftReset and DCTL.CSftRst steps during DRD mode switches in the dwc3 driver allow the USB controller to enter an unrecoverable state, resulting in a system lockup that affects availability.

Why it matters to the business

Affected Linux systems using DWC3-based USB controllers can experience sudden unresponsiveness requiring physical reboot, causing operational downtime on servers, embedded devices, and workstations with high ecosystem prevalence.

How an attack unfolds

A local attacker triggers a host-to-device or device-to-host transition on a DRD controller; because the driver omits the required core soft reset and subsequent host/device reset, the controller locks up as reported on HiKey960 and similar platforms.

How to fix it

Update the Linux kernel to a version containing the core soft reset logic before setting PrtCapDir and the conditional DCTL.CSftRst on host-to-device transitions; apply the fix referenced in the 2021 commit that resolves the lockup.

How to confirm the fix worked

Inspect dwc3 core mode-switch code for GCTL.CoreSoftReset followed by clock synchronization wait and the device-specific reset; reproduce mode transitions on DWC3 hardware and confirm no lockup occurs.

Typical attack path

1. Gain local access with unprivileged account
2. Invoke USB mode switch through driver interfaces or user-space tools
3. Omit or bypass the missing reset sequence
4. Induce controller lockup and system hang

How to detect it

Review dmesg and kernel logs for dwc3 or USB controller lockup messages around mode-switch events; examine system uptime and crash dumps for unexplained hangs on DWC3 platforms.

What your security team should do

• Apply kernel updates containing the dwc3 mode-switch reset fix on all affected systems
• Limit local user access on devices with DWC3 USB controllers
• Monitor kernel logs for USB controller stalls during mode changes
• Test mode-switch behavior in staging environments before broad deployment