CVE-2026-31576: Use After Free

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

media: hackrf: fix to not free memory after the device is registered in hackrf_probe()

In hackrf driver, the following race condition occurs: ``` CPU0 CPU1 hackrf_probe() kzalloc(); // alloc hackrf_dev .... v4l2_device_register(); .... fd = sys_open("/path/to/dev"); // open hackrf fd .... v4l2_device_unregister(); .... kfree(); // free hackrf_dev .... sys_ioctl(fd, ...); v4l2_ioctl(); video_is_registered() // UAF!! .... sys_close(fd); v4l2_release() // UAF!! hackrf_video_release() kfree(); // DFB!! ```

When a V4L2 or video device is unregistered, the device node is removed so new open() calls are blocked.

However, file descriptors that are already open-and any in-flight I/O-do not terminate immediately; they remain valid until the last reference is dropped and the driver's release() is invoked.

Therefore, freeing device memory on the error path after hackrf_probe() has registered dev it will lead to a race to use-after-free vuln, since those already-open handles haven't been released yet.

And since release() free memory too, race to use-after-free and double-free vuln occur.

To prevent this, if device is registered from probe(), it should be modified to free memory only through release() rather than calling kfree() directly.