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=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C0393C32751 for ; Wed, 7 Aug 2019 14:07:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A196321E6C for ; Wed, 7 Aug 2019 14:07:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387670AbfHGOHR (ORCPT ); Wed, 7 Aug 2019 10:07:17 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:42468 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1729968AbfHGOHR (ORCPT ); Wed, 7 Aug 2019 10:07:17 -0400 Received: (qmail 2698 invoked by uid 2102); 7 Aug 2019 10:07:16 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 7 Aug 2019 10:07:16 -0400 Date: Wed, 7 Aug 2019 10:07:16 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: syzbot , , , , , , , Subject: Re: possible deadlock in open_rio In-Reply-To: <1565185044.15973.0.camel@suse.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, 7 Aug 2019, Oliver Neukum wrote: > Am Dienstag, den 06.08.2019, 15:13 -0400 schrieb Alan Stern: > > On Thu, 1 Aug 2019, syzbot wrote: > > > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: 7f7867ff usb-fuzzer: main usb gadget fuzzer driver > > > git tree: https://github.com/google/kasan.git usb-fuzzer > > > console output: https://syzkaller.appspot.com/x/log.txt?x=136b6aec600000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=792eb47789f57810 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=7bbcbe9c9ff0cd49592a > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+7bbcbe9c9ff0cd49592a@syzkaller.appspotmail.com > > > > > > ====================================================== > > > WARNING: possible circular locking dependency detected > > > 5.3.0-rc2+ #23 Not tainted > > > ------------------------------------------------------ > > > > Andrey: > > > > This should be completely reproducible, since it's a simple ABBA > > locking violation. Maybe just introducing a time delay (to avoid races > > and give the open() call time to run) between the gadget creation and > > gadget removal would be enough to do it. > > Hi, > > technically yes. However in practical terms the straight revert I sent > out yesterday should fix it. I didn't see the revert, and it doesn't appear to have reached the mailing list archive. Can you post it again? Alan Stern PS: syzbot reported a similar lock inversion problem (involving two mutexes rather than just one) in drivers/usb/misc/iowarrior.c. Probably the two drivers need similar fixes.