CVE-2025-21746

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

Input: synaptics - fix crash when enabling pass-through port

When enabling a pass-through port an interrupt might come before psmouse driver binds to the pass-through port. However synaptics sub-driver tries to access psmouse instance presumably associated with the pass-through port to figure out if only 1 byte of response or entire protocol packet needs to be forwarded to the pass-through port and may crash if psmouse instance has not been attached to the port yet.

Fix the crash by introducing open() and close() methods for the port and check if the port is open before trying to access psmouse instance. Because psmouse calls serio_open() only after attaching psmouse instance to serio port instance this prevents the potential crash.

This vulnerability is rated as having a Moderate severity for Red Hat Enterprise Linux because exploitation requires local access or physical presence to interact with Synaptics touchpad hardware, and the resulting impact is confined to a denial of service (system crash) without direct compromise of data confidentiality or integrity. The race condition occurs during pass-through port initialization in the Synaptics PS/2 mouse sub-driver when an interrupt arrives before device binding completes. Enterprise server deployments typically do not utilize this input hardware or run headless, substantially limiting real-world exposure to workstations and laptops with affected pointing devices.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.