From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751663AbdJDIIe (ORCPT ); Wed, 4 Oct 2017 04:08:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:54305 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751120AbdJDII3 (ORCPT ); Wed, 4 Oct 2017 04:08:29 -0400 Date: Wed, 04 Oct 2017 10:08:24 +0200 Message-ID: From: Takashi Iwai To: Greg Kroah-Hartman Cc: Alan Stern , Andrey Konovalov , alsa-devel@alsa-project.org, Arvind Yadav , Jaroslav Kysela , Takashi Sakamoto , LKML , Dmitry Vyukov , Kostya Serebryany , syzkaller , linux-usb@vger.kernel.org Subject: Re: usb/sound/bcd2000: warning in bcd2000_init_device In-Reply-To: <20171004075236.GA23771@kroah.com> References: <20171003174221.GA13006@kroah.com> <20171004075236.GA23771@kroah.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 04 Oct 2017 09:52:36 +0200, Greg Kroah-Hartman wrote: > > On Wed, Oct 04, 2017 at 08:10:59AM +0200, Takashi Iwai wrote: > > On Tue, 03 Oct 2017 19:42:21 +0200, > > Greg Kroah-Hartman wrote: > > > > > > On Tue, Oct 03, 2017 at 12:50:08PM -0400, Alan Stern wrote: > > > > On Tue, 3 Oct 2017, Takashi Iwai wrote: > > > > > > > > > > It's a dev_WARN because it indicates a potentially serious error in the > > > > > > driver: The driver has submitted an interrupt URB to a bulk endpoint. > > > > > > That may not sound bad, but the same check gets triggered if a driver > > > > > > submits a bulk URB to an isochronous endpoint, or any other invalid > > > > > > combination. > > > > > > > > > > > > Most likely the explanation here is that the driver doesn't bother to > > > > > > check the endpoint type because it expects the endpoint will always be > > > > > > interrupt. But that is not a safe strategy. USB devices and their > > > > > > firmware should not be trusted unnecessarily. > > > > > > > > > > > > The best fix is, like you said, to add a sanity check in the caller. > > > > > > > > > > OK, but then do we have some handy helper for the check? > > > > > As other bug reports by syzkaller suggest, there are a few other > > > > > drivers that do the same, submitting a urb with naive assumption of > > > > > the fixed EP for specific devices. In the end we'll need to put the > > > > > very same checks there in multiple places. > > > > > > > > Perhaps we could add a helper routine that would take a list of > > > > expected endpoint types and check that the actual endpoints match the > > > > types. But of course, all the drivers you're talking about would have > > > > to add a call to this helper routine. > > > > > > We have almost this type of function, usb_find_common_endpoints(), > > > what's wrong with using that? Johan has already swept the tree and > > > added a lot of these checks, odds are no one looked at the sound/ > > > subdir... > > > > Well, what I had in my mind is just a snippet from usb_submit_urb(), > > something like: > > > > bool usb_sanity_check_urb_pipe(struct urb *urb) > > { > > struct usb_host_endpoint *ep; > > int xfertype; > > static const int pipetypes[4] = { > > PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT > > }; > > > > ep = usb_pipe_endpoint(urb->dev, urb->pipe); > > xfertype = usb_endpoint_type(&ep->desc); > > return usb_pipetype(urb->pipe) != pipetypes[xfertype]; > > } > > > > And calling this before usb_submit_urb() in each place that assigns > > the fixed EP as device-specific quirks. > > Does it make sense? > > Yes, kind of, but checking the endpoint type/direction is what you are > expecting it to be as you "know" what the type should be for each > driver as it is unique. Yes, it can be simplified, but if we want a common helper function, this style would have an advantage that it can be used generically for all drivers. > Anyway, a "real" patch might make more sense to me. I can cook up a patch if you find it a good idea to add such a common function to usb core side. OTOH, if each driver should open-code this in each place, I can work on that, too. Which would you prefer? thanks, Takashi