CVE-2026-31576: media: hackrf: fix to not free memory after the device is registered in hackrf_probe()

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

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

In hackrf driver, the following race condition occurs: CPU0 CPU1 hackrfprobe() kzalloc(); // alloc hackrfdev .... v4l2deviceregister(); .... fd = sysopen("/path/to/dev"); // open hackrf fd .... v4l2deviceunregister(); .... kfree(); // free hackrfdev .... sysioctl(fd, ...); v4l2ioctl(); videoisregistered() // UAF!! .... sysclose(fd); v4l2release() // UAF!! hackrfvideorelease() 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 hackrfprobe() 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.