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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 3487CC072B5 for ; Fri, 24 May 2019 11:58:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 104F620851 for ; Fri, 24 May 2019 11:58:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391393AbfEXL6e (ORCPT ); Fri, 24 May 2019 07:58:34 -0400 Received: from mga02.intel.com ([134.134.136.20]:14156 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390961AbfEXL6d (ORCPT ); Fri, 24 May 2019 07:58:33 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 May 2019 04:58:33 -0700 X-ExtLoop1: 1 Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by orsmga006.jf.intel.com with SMTP; 24 May 2019 04:58:30 -0700 Received: by stinkbox (sSMTP sendmail emulation); Fri, 24 May 2019 14:58:29 +0300 Date: Fri, 24 May 2019 14:58:29 +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 Subject: Re: [PATCH] drm: assure aux_dev is nonzero before using it Message-ID: <20190524115829.GC5942@intel.com> References: <20190523110905.22445-1-tcamuso@redhat.com> <87v9y0mept.fsf@intel.com> <04ae1fb0-02ab-88e9-94b3-e36f48cc65d5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <04ae1fb0-02ab-88e9-94b3-e36f48cc65d5@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 Fri, May 24, 2019 at 06:48:32AM -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. > > That's a very good question. > > > 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. > > I will look into this deeper, using the upstream kernel. Should be trivial to reproduce with mknod. I wonder if we should stick a test like that into igt actually. Not sure how happy people would be if igt creates new device nodes... -- Ville Syrjälä Intel