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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 7B7C9C3A5A2 for ; Tue, 3 Sep 2019 18:18:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51FED22CF8 for ; Tue, 3 Sep 2019 18:18:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567534737; bh=UbR9zr74CHqTiq2rkGIGMBcWCy/78myqSwovEjuKNO4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=pIF83g1v50BN2SOTHOvX4Iaw27prslBS+XwHQ4YEInyDH4oHh2li56GN0ejyLrbfN H85NJJxPA8156AaH8Cl2EK9ij4xTpTyThGkmDQHmeOFlZVx4Wf01G67i7I/c5qCEAv dUwkb44s9pHMkVvwdKeiAdrzXUhnr4Z9JR3Fbup8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729653AbfICSS4 (ORCPT ); Tue, 3 Sep 2019 14:18:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:43890 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727667AbfICSS4 (ORCPT ); Tue, 3 Sep 2019 14:18:56 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E3CEC21897; Tue, 3 Sep 2019 18:18:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567534735; bh=UbR9zr74CHqTiq2rkGIGMBcWCy/78myqSwovEjuKNO4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M0MTmNKEQl06GbOF0O3rQOAQSly+IlMo88UaN9x60qebKZlcuSBwbd/kAJDSIP3ji qGIZiyRAbhRxz6dzFClHz+ieP/Pwcei6RR28+lb5nHwChfFzQo177gs7OGZBU95vHd sLmz+/hEfmiAnRf+KiVIliaWQiJGiOdR1usvaip0= Date: Tue, 3 Sep 2019 20:18:53 +0200 From: Greg KH To: Alan Stern Cc: Andrey Konovalov , Oliver Neukum , syzkaller-bugs , USB list Subject: Re: [PATCH] USB: rio500: Fix lockdep violation Message-ID: <20190903181853.GA3612@kroah.com> References: <20190815124821.GA25619@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Aug 15, 2019 at 10:47:45AM -0400, Alan Stern wrote: > On Thu, 15 Aug 2019, Greg KH wrote: > > > On Thu, Aug 08, 2019 at 02:23:00PM -0400, Alan Stern wrote: > > > On Thu, 8 Aug 2019, Greg KH wrote: > > > > > > > On Thu, Aug 08, 2019 at 01:34:08PM -0400, Alan Stern wrote: > > > > > The syzbot fuzzer found a lockdep violation in the rio500 driver: > > > > > > > > > > ====================================================== > > > > > WARNING: possible circular locking dependency detected > > > > > 5.3.0-rc2+ #23 Not tainted > > > > > ------------------------------------------------------ > > > > > syz-executor.2/20386 is trying to acquire lock: > > > > > 00000000772249c6 (rio500_mutex){+.+.}, at: open_rio+0x16/0xc0 > > > > > drivers/usb/misc/rio500.c:64 > > > > > > > > > > but task is already holding lock: > > > > > 00000000d3e8f4b9 (minor_rwsem){++++}, at: usb_open+0x23/0x270 > > > > > drivers/usb/core/file.c:39 > > > > > > > > > > which lock already depends on the new lock. > > > > > > > > > > The problem is that the driver's open_rio() routine is called while > > > > > the usbcore's minor_rwsem is locked for reading, and it acquires the > > > > > rio500_mutex; whereas conversely, probe_rio() and disconnect_rio() > > > > > first acquire the rio500_mutex and then call usb_register_dev() or > > > > > usb_deregister_dev(), which lock minor_rwsem for writing. > > > > > > > > > > The correct ordering of acquisition should be: minor_rwsem first, then > > > > > rio500_mutex (since the locking in open_rio() cannot be changed). > > > > > Thus, the probe and disconnect routines should avoid holding > > > > > rio500_mutex while doing their registration and deregistration. > > > > > > > > > > This patch adjusts the code in those two routines to do just that. It > > > > > also relies on the fact that the probe and disconnect routines are > > > > > protected by the device mutex, so the initial test of rio->present > > > > > needs no extra locking. > > > > > > > > > > Reported-by: syzbot+7bbcbe9c9ff0cd49592a@syzkaller.appspotmail.com > > > > > Signed-off-by: Alan Stern > > > > > Fixes: d710734b0677 ("USB: rio500: simplify locking") > > > > > CC: Oliver Neukum > > > > > CC: > > > > > > > > > > --- > > > > > > > > > > This patch is different from the one I posted earlier. I realized that > > > > > we don't want to register the device's char file until after the > > > > > buffers have been allocated. > > > > > > > > Should I revert Oliver's patch? > > > > > > Sorry, I should have explained more clearly: This goes on top of > > > Oliver's patch. In fact, Oliver's patch is the one listed in the > > > Fixes: tag. > > > > > > You do not need to apply Oliver's reversion. Assuming he agrees that > > > this patch is correct, of course. > > > > Ok, I applied the revert, and that's in 5.3-rc4. So of course this does > > not apply :) > > > > Shoudl I revert the revert and then apply this? I will if I can get an > > ack from Oliver... > > Either that or else Oliver and I can squash the two patches into one. I've now merged both, thanks. greg k-h