NuytsTech Security

CVE-2026-31576

by ·

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.

More information : https://git.kernel.org/stable/c/07e9e674b6146b1f6fc41b1f54b8968bf2802824

Tags: