CVE-2025-21695

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

platform/x86: dell-uart-backlight: fix serdev race

The delluartblserdevprobe() function calls devmserdevdeviceopen() before setting the client ops via serdevdevicesetclientops(). This ordering can trigger a NULL pointer dereference in the serdev controller's receivebuf handler, as it assumes serdev->ops is valid when SERPORT_ACTIVE is set.

This is similar to the issue fixed in commit 5e700b384ec1 ("platform/chrome: crosecuart: properly fix race condition") where devmserdevdevice_open() was called before fully initializing the device.

Fix the race by ensuring client ops are set before enabling the port via devmserdevdevice_open().

Note, serdevdevicesetbaudrate() and serdevdevicesetflowcontrol() calls should be after the devmserdevdeviceopen() call.