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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 66884C433DF for ; Tue, 14 Jul 2020 19:47:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A15E22BEF for ; Tue, 14 Jul 2020 19:47:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729597AbgGNTrz (ORCPT ); Tue, 14 Jul 2020 15:47:55 -0400 Received: from netrider.rowland.org ([192.131.102.5]:56107 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726634AbgGNTry (ORCPT ); Tue, 14 Jul 2020 15:47:54 -0400 Received: (qmail 1035129 invoked by uid 1000); 14 Jul 2020 15:47:53 -0400 Date: Tue, 14 Jul 2020 15:47:53 -0400 From: Alan Stern To: syzbot Cc: andreyknvl@google.com, fweisbec@gmail.com, Jarod Wilson , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, mingo@kernel.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de Subject: Re: INFO: rcu detected stall in dummy_timer (3) Message-ID: <20200714194753.GA1033470@rowland.harvard.edu> References: <000000000000e7493205aa694785@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <000000000000e7493205aa694785@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Jul 14, 2020 at 09:27:18AM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 25051b55 udc: lpc32xx: make symbol 'lpc32xx_usbddata' static > git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing > console output: https://syzkaller.appspot.com/x/log.txt?x=12e0ba00900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=999be4eb2478ffa5 > dashboard link: https://syzkaller.appspot.com/bug?extid=4d3749e9612c2cfab956 > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127354e7100000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10ba8500900000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+4d3749e9612c2cfab956@syzkaller.appspotmail.com > > mceusb 5-1:0.0: Error: urb status = -71 > mceusb 3-1:0.0: Error: urb status = -71 > mceusb 4-1:0.0: Error: urb status = -71 > mceusb 6-1:0.0: Error: urb status = -71 > mceusb 5-1:0.0: Error: urb status = -71 > rcu: INFO: rcu_sched self-detected stall on CPU This looks like an error in mceusb_dev_recv() in drivers/media/rc/mceusb.c. In the case of a -EPROTO error (indeed, any error code it doesn't recognize), the routine immediately resubmits the URB. Instead it should do the same thing as in the other error cases: return without resubmitting. (Incidentally, the calls to usb_unlink_urb() in that routine are useless and look very strange. The URB is already unlinked, since mceusb_dev_recv() is the completion handler.) Alan Stern