CVE-2026-89741: Undefined Security Weakness

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

Revert "media: v4l2-dev: fix error handling in __video_register_device()"

This reverts commit 2a934fdb01db6458288fc9386d3d8ceba6dd551a.

The intentions of that patch were good, but it doesn't work.

The idea is that if device_register fails, you have to do a put_device to let the ref counter release resources.

However, the V4L2 API says that if video_register_device() fails, then you have to call video_device_release(), which kfree()s the video_device struct.

But the put_device() will already have freed the struct, so you end up in a double-free scenario.

There is not really a good way of fixing this without breaking video_register_device() into two parts, one that initializes everything, and one that does the actual device_register, and then converting all V4L2 drivers to this new model.

That is a massive job, and it is very unlikely that device_register will fail.

So rather than ending up in a double-free scenario, just revert this patch, and in that case we'll have a small memory leak. Which is a lot more robust.