On Tue, Jul 21, 2020 at 11:15:58PM +0300, Evgeny Novikov wrote:
> Driver does not release memory for device on error handling paths in
> net2280_probe() when gadget_release() is not registered yet.
>
> The patch fixes the bug like in other similar drivers.
>
> Found by Linux Driver Verification project (linuxtesting.org).
>
> Signed-off-by: Evgeny Novikov <novikov@xxxxxxxxx>
> ---
> drivers/usb/gadget/udc/net2280.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/udc/net2280.c b/drivers/usb/gadget/udc/net2280.c
> index 5eff85eeaa5a..d5fe071b2db2 100644
> --- a/drivers/usb/gadget/udc/net2280.c
> +++ b/drivers/usb/gadget/udc/net2280.c
> @@ -3781,8 +3781,10 @@ static int net2280_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> return 0;
>
> done:
> - if (dev)
> + if (dev) {
> net2280_remove(pdev);
> + kfree(dev);
> + }
> return retval;
> }
This patch seems to be the tip of an iceberg. Following through its
implications led to a couple of discoveries.
usb_del_gadget_udc() calls device_unregister(&gadget->dev). Once this
call returns, gadget has to be regarded as a stale pointer. But the
very next line of code does:
memset(&gadget->dev, 0x00, sizeof(gadget->dev));
for no apparent reason. I'm amazed this hasn't caused problems already.
Is there any justification for keeping this memset? It's hard to
imagine that it does any good.
Similarly, net2280_remove() calls usb_del_gadget_udc(&dev->gadget) at
its start, and so dev must be a stale pointer for the entire remainder
of the routine. But it gets used repeatedly. Surely we ought to have
a device_get() and device_put() in there.
Alan Stern
