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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36FEFECAAD3 for ; Wed, 14 Sep 2022 14:03:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229977AbiINOD0 (ORCPT ); Wed, 14 Sep 2022 10:03:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbiINOCt (ORCPT ); Wed, 14 Sep 2022 10:02:49 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0AD407A539; Wed, 14 Sep 2022 07:02:03 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 86AD261D8F; Wed, 14 Sep 2022 14:02:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75F73C4347C; Wed, 14 Sep 2022 14:02:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663164121; bh=NCcTwwKCAlQIABfOl9WvMf92ki9ZXJbGa5QXGi7eAl0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=V0LhkLbO2f6F3xXrHc9/jVO4fcaYmxCR62Ja689Fi3VSJOxzM4Bp+Mcmejl1filee XTeFYZrz4E5LbxZGSzxz2S7OIx2ernyNrVc6BNxHlrb7+kSR2vJ40gQ1/Zus8MEwcN +L5358vSEtKN5IOQxwcDrUeAL2TgNpzKOEdneQ5k= Date: Wed, 14 Sep 2022 16:02:25 +0200 From: Greg KH To: Rondreis Cc: balbi@kernel.org, john@metanate.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: possible deadlock in f_midi_transmit Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 14, 2022 at 08:49:49PM +0800, Rondreis wrote: > Hello, > > When fuzzing the Linux kernel driver v6.0-rc4, the following crash was > triggered. > > HEAD commit: 7e18e42e4b280c85b76967a9106a13ca61c16179 > git tree: upstream > > kernel config: https://pastebin.com/raw/xtrgsXP3 > C reproducer: https://pastebin.com/raw/C1xYEf7Q > console output: https://pastebin.com/raw/3RLhvQHE > > Basically, in the c reproducer, we use the gadget module to emulate > attaching a USB device(vendor id: 0x403, product id: 0xff3d, with the > midi function) and executing some simple sequence of system calls. > To reproduce this crash, we utilize a third-party library to emulate > the attaching process: https://github.com/linux-usb-gadgets/libusbgx. > Just clone this repository, install it, and compile the c > reproducer with ``` gcc crash.c -lusbgx -lconfig -o crash ``` will do > the trick. > > I would appreciate it if you have any idea how to solve this bug. > > The crash report is as follows: > > > ============================================ > WARNING: possible recursive locking detected > 6.0.0-rc4+ #20 Not tainted > -------------------------------------------- > kworker/0:1H/9 is trying to acquire lock: > ffff888057ed9228 (&midi->transmit_lock){....}-{2:2}, at: > f_midi_transmit+0x18c/0x1460 drivers/usb/gadget/function/f_midi.c:683 > > but task is already holding lock: > ffff888057ed9228 (&midi->transmit_lock){....}-{2:2}, at: > f_midi_transmit+0x18c/0x1460 drivers/usb/gadget/function/f_midi.c:683 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&midi->transmit_lock); > lock(&midi->transmit_lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation That's a lockdep warning, is this really deadlocking? If so, I'd recommend asking the midi developers... thanks, greg k-h