On Tue, Dec 17, 2024 at 11:53:52AM +0800, Ma Ke wrote:

When device_add(&udev->dev) failed, calling put_device() to explicitly release udev->dev. Otherwise, it could cause double free problem.

If you're worried that the same object might be freed more than once (double free), how can calling put_device() help? Won't that cause udev->dev to be freed a third time?

Found by code review.

In your code review, did you check to see whether the routine which calls usb_new_device() will do the put_device() when an error occurs?

Cc: stable@vger.kernel.org Fixes: 9f8b17e643fe ("USB: make usbdevices export their device nodes instead of using a separate class") Signed-off-by: Ma Ke make_ruc2021@163.com

---

drivers/usb/core/hub.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 4b93c0bd1d4b..05b778d2ad63 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2651,6 +2651,7 @@ int usb_new_device(struct usb_device *udev) err = device_add(&udev->dev); if (err) { dev_err(&udev->dev, "can't device_add, error %d\n", err);

• put_device(&udev->dev);
  

  goto fail; }

@@ -2683,6 +2684,9 @@ int usb_new_device(struct usb_device *udev) pm_runtime_put_sync_autosuspend(&udev->dev); return err; +out_del_dev:

• device_del(&udev->dev);
• put_device(&udev->dev);

You added a new statement label but you did not add any jumps to that label. As a result, these two lines will never be executed.

Alan Stern

fail: usb_set_device_state(udev, USB_STATE_NOTATTACHED); pm_runtime_disable(&udev->dev); -- 2.25.1