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.

Cc: stable@vger.kernel.org Reported-by: syzbot+6ffd76b5405c006a46b7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6ffd76b5405c006a46b7 Reported-by: syzbot+f1b20958f93d2d250727@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f1b20958f93d2d250727 Fixes: 8bc4a9ed8504 ("[media] hackrf: add support for transmitter") Signed-off-by: Jeongjun Park aha310510@gmail.com --- v3: Fix potential memory leak bug - Link to v2: https://lore.kernel.org/all/20250904054232.3848637-1-aha310510@gmail.com/ v2: Fix incorrect patch description style and CC stable mailing list - Link to v1: https://lore.kernel.org/all/20250822142729.1156816-1-aha310510@gmail.com/ --- drivers/media/usb/hackrf/hackrf.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/media/usb/hackrf/hackrf.c b/drivers/media/usb/hackrf/hackrf.c index 0b50de8775a3..c3c4247194d1 100644 --- a/drivers/media/usb/hackrf/hackrf.c +++ b/drivers/media/usb/hackrf/hackrf.c @@ -1485,7 +1485,7 @@ static int hackrf_probe(struct usb_interface *intf, if (ret) { dev_err(dev->dev, "Failed to register as video device (%d)\n", ret); - goto err_v4l2_device_unregister; + goto err_v4l2_device_put; } dev_info(dev->dev, "Registered as %s\n", video_device_node_name(&dev->rx_vdev)); @@ -1513,8 +1513,9 @@ static int hackrf_probe(struct usb_interface *intf, return 0; err_video_unregister_device_rx: video_unregister_device(&dev->rx_vdev); -err_v4l2_device_unregister: - v4l2_device_unregister(&dev->v4l2_dev); +err_v4l2_device_put: + v4l2_device_put(&dev->v4l2_dev); + return ret; err_v4l2_ctrl_handler_free_tx: v4l2_ctrl_handler_free(&dev->tx_ctrl_handler); err_v4l2_ctrl_handler_free_rx: --