[PATCH v3] media: hackrf: fix to not free memory after the device is registered in hackrf_probe()

[Jeongjun Park <aha310510@gmail.com>]

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:
--