From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CBAFC433E2 for ; Wed, 22 Jul 2020 14:17:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 40C0620729 for ; Wed, 22 Jul 2020 14:17:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732432AbgGVORm (ORCPT ); Wed, 22 Jul 2020 10:17:42 -0400 Received: from netrider.rowland.org ([192.131.102.5]:54667 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726003AbgGVORm (ORCPT ); Wed, 22 Jul 2020 10:17:42 -0400 Received: (qmail 1312491 invoked by uid 1000); 22 Jul 2020 10:17:41 -0400 Date: Wed, 22 Jul 2020 10:17:41 -0400 From: Alan Stern To: Evgeny Novikov Cc: Felipe Balbi , Greg Kroah-Hartman , Benjamin Herrenschmidt , Kees Cook , Arnd Bergmann , Corentin Labbe , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org Subject: Re: [PATCH] usb: gadget: net2280: fix memory leak on probe error handling paths Message-ID: <20200722141741.GA1310843@rowland.harvard.edu> References: <20200721201558.20069-1-novikov@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200721201558.20069-1-novikov@ispras.ru> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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