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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 715A4C4CECF for ; Mon, 23 Sep 2019 15:22:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 512A121841 for ; Mon, 23 Sep 2019 15:22:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731747AbfIWPWM (ORCPT ); Mon, 23 Sep 2019 11:22:12 -0400 Received: from mga07.intel.com ([134.134.136.100]:52530 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbfIWPWM (ORCPT ); Mon, 23 Sep 2019 11:22:12 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Sep 2019 08:22:11 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,540,1559545200"; d="scan'208";a="203143434" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by fmsmga001.fm.intel.com with SMTP; 23 Sep 2019 08:22:07 -0700 Received: by stinkbox (sSMTP sendmail emulation); Mon, 23 Sep 2019 18:22:06 +0300 Date: Mon, 23 Sep 2019 18:22:06 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Tony Camuso Cc: Jani Nikula , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, airlied@linux.ie, dkwon@redhat.com, Joe Donahue , John Feeney Subject: Re: [PATCH] drm: assure aux_dev is nonzero before using it Message-ID: <20190923152206.GN1208@intel.com> References: <20190523110905.22445-1-tcamuso@redhat.com> <87v9y0mept.fsf@intel.com> <5111581c-9d73-530d-d3ff-4f6950bf3f8c@redhat.com> <20190710135617.GE5942@intel.com> <374b7e4e-40a2-f3c0-ae14-c533bd42243f@redhat.com> <20190712170657.GL5942@intel.com> <841db615-a353-2174-6fd6-a3302f352b08@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <841db615-a353-2174-6fd6-a3302f352b08@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 23, 2019 at 11:03:35AM -0400, Tony Camuso wrote: > On 7/12/19 1:06 PM, Ville Syrjälä wrote: > > On Fri, Jul 12, 2019 at 12:07:46PM -0400, Tony Camuso wrote: > >> On 7/10/19 9:56 AM, Ville Syrjälä wrote: > >>> On Wed, Jul 10, 2019 at 09:47:11AM -0400, Tony Camuso wrote: > >>>> On 5/24/19 4:36 AM, Jani Nikula wrote: > >>>>> On Thu, 23 May 2019, tcamuso wrote: > >>>>>> From Daniel Kwon > >>>>>> > >>>>>> The system was crashed due to invalid memory access while trying to access > >>>>>> auxiliary device. > >>>>>> > >>>>>> crash> bt > >>>>>> PID: 9863 TASK: ffff89d1bdf11040 CPU: 1 COMMAND: "ipmitool" > >>>>>> #0 [ffff89cedd7f3868] machine_kexec at ffffffffb0663674 > >>>>>> #1 [ffff89cedd7f38c8] __crash_kexec at ffffffffb071cf62 > >>>>>> #2 [ffff89cedd7f3998] crash_kexec at ffffffffb071d050 > >>>>>> #3 [ffff89cedd7f39b0] oops_end at ffffffffb0d6d758 > >>>>>> #4 [ffff89cedd7f39d8] no_context at ffffffffb0d5bcde > >>>>>> #5 [ffff89cedd7f3a28] __bad_area_nosemaphore at ffffffffb0d5bd75 > >>>>>> #6 [ffff89cedd7f3a78] bad_area at ffffffffb0d5c085 > >>>>>> #7 [ffff89cedd7f3aa0] __do_page_fault at ffffffffb0d7080c > >>>>>> #8 [ffff89cedd7f3b10] do_page_fault at ffffffffb0d70905 > >>>>>> #9 [ffff89cedd7f3b40] page_fault at ffffffffb0d6c758 > >>>>>> [exception RIP: drm_dp_aux_dev_get_by_minor+0x3d] > >>>>>> RIP: ffffffffc0a589bd RSP: ffff89cedd7f3bf0 RFLAGS: 00010246 > >>>>>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff89cedd7f3fd8 > >>>>>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffc0a613e0 > >>>>>> RBP: ffff89cedd7f3bf8 R8: ffff89f1bcbabbd0 R9: 0000000000000000 > >>>>>> R10: ffff89f1be7a1cc0 R11: 0000000000000000 R12: 0000000000000000 > >>>>>> R13: ffff89f1b32a2830 R14: ffff89d18fadfa00 R15: 0000000000000000 > >>>>>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 > >>>>>> RIP: 00002b45f0d80d30 RSP: 00007ffc416066a0 RFLAGS: 00010246 > >>>>>> RAX: 0000000000000002 RBX: 000056062e212d80 RCX: 00007ffc41606810 > >>>>>> RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007ffc41606ec0 > >>>>>> RBP: 0000000000000000 R8: 000056062dfed229 R9: 00002b45f0cdf14d > >>>>>> R10: 0000000000000002 R11: 0000000000000246 R12: 00007ffc41606ec0 > >>>>>> R13: 00007ffc41606ed0 R14: 00007ffc41606ee0 R15: 0000000000000000 > >>>>>> ORIG_RAX: 0000000000000002 CS: 0033 SS: 002b > >>>>>> > >>>>>> ---------------------------------------------------------------------------- > >>>>>> > >>>>>> It was trying to open '/dev/ipmi0', but as no entry in aux_dir, it returned > >>>>>> NULL from 'idr_find()'. This drm_dp_aux_dev_get_by_minor() should have done a > >>>>>> check on this, but had failed to do it. > >>>>> > >>>>> I think the better question is, *why* does the idr_find() return NULL? I > >>>>> don't think it should, under any circumstances. I fear adding the check > >>>>> here papers over some other problem, taking us further away from the > >>>>> root cause. > >>>>> > >>>>> Also, can you reproduce this on a recent upstream kernel? The aux device > >>>>> nodes were introduced in kernel v4.6. Whatever you reproduced on v3.10 > >>>>> is pretty much irrelevant for upstream. > >>>>> > >>>>> > >>>>> BR, > >>>>> Jani. > >>>> > >>>> I have not been able to reproduce this problem. > >>> > >>> mknod /dev/foo c 255 > >>> cat /dev/foo > >>> > >>> should do it. > >> > >> How do I determine ? > > > > ls,file,stat. Take your pick. > > > > Problem here is I can't ls,file,stat /dev/foo until after it's created, > but I need to know the drm_dp_aux major number befroe I can use mknod. > > What am I missing here? udev/whatever should create a bunch of these for you so you can check from them. If not, then dig around in /sys/class/drm_dp_aux_dev. -- Ville Syrjälä Intel