[PATCH 6.18 195/198] media: hackrf: fix to not free memory after the device is registered in hackrf_probe()

Greg Kroah-Hartman
2026-04-20T16:05:34Z

From: Jeongjun Park <aha310510@gmail.com>

commit 3b7da2b4d0fe014eff181ed37e3bf832eb8ed258 upstream.

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>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/usb/hackrf/hackrf.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/media/usb/hackrf/hackrf.c
+++ b/drivers/media/usb/hackrf/hackrf.c
@@ -1485,7 +1485,7 @@ static int hackrf_probe(struct usb_inter
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_inter
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: