From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753133AbdBUNJz (ORCPT ); Tue, 21 Feb 2017 08:09:55 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:53468 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752752AbdBUNDy (ORCPT ); Tue, 21 Feb 2017 08:03:54 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Airlie , Chris Wilson , Nathan D Ciobanu , Dhinakaran Pandiyan , Sean Paul , Pierre-Louis Bossart , Jani Nikula Subject: [PATCH 4.9 11/22] drm/dp/mst: fix kernel oops when turning off secondary monitor Date: Tue, 21 Feb 2017 14:03:25 +0100 Message-Id: <20170221130219.352979369@linuxfoundation.org> X-Mailer: git-send-email 2.11.1 In-Reply-To: <20170221130218.888428471@linuxfoundation.org> References: <20170221130218.888428471@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pierre-Louis Bossart commit bb08c04dc867b5f392caec635c097d5d5fcd8c9f upstream. 100% reproducible issue found on SKL SkullCanyon NUC with two external DP daisy-chained monitors in DP/MST mode. When turning off or changing the input of the second monitor the machine stops with a kernel oops. This issue happened with 4.8.8 as well as drm/drm-intel-nightly. This issue is traced to an inconsistent control flow in drm_dp_update_payload_part1(): the 'port' pointer is set to NULL at the same time as 'req_payload.num_slots' is set to zero, but the pointer is dereferenced even when req_payload.num_slot is zero. The problematic dereference was introduced in commit dfda0df34 ("drm/mst: rework payload table allocation to conform better") and may impact all versions since v3.18 The fix suggested by Chris Wilson removes the kernel oops and was found to work well after 10mn of monkey-testing with the second monitor power and input buttons Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98990 Fixes: dfda0df34264 ("drm/mst: rework payload table allocation to conform better.") Cc: Dave Airlie Cc: Chris Wilson Cc: Nathan D Ciobanu Cc: Dhinakaran Pandiyan Cc: Sean Paul Tested-by: Nathan D Ciobanu Reviewed-by: Dhinakaran Pandiyan Signed-off-by: Pierre-Louis Bossart Signed-off-by: Jani Nikula Link: http://patchwork.freedesktop.org/patch/msgid/1487076561-2169-1-git-send-email-jani.nikula@intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_dp_mst_topology.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1817,7 +1817,7 @@ int drm_dp_update_payload_part1(struct d mgr->payloads[i].vcpi = req_payload.vcpi; } else if (mgr->payloads[i].num_slots) { mgr->payloads[i].num_slots = 0; - drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]); + drm_dp_destroy_payload_step1(mgr, port, mgr->payloads[i].vcpi, &mgr->payloads[i]); req_payload.payload_state = mgr->payloads[i].payload_state; mgr->payloads[i].start_slot = 0; }