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@xxxxxxxxxxxxxxx
> Fixes: 9f8b17e643fe ("USB: make usbdevices export their device nodes instead of using a separate class")
> Signed-off-by: Ma Ke <make_ruc2021@xxxxxxx>
> ---
> 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
>
