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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 8876AC2BB55 for ; Thu, 16 Apr 2020 15:32:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 64C2021927 for ; Thu, 16 Apr 2020 15:32:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587051148; bh=K9lFfffFugUy+h1cvQ1mHkNgiJTJE5NKNzyDaEc4UG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VZuRgieRxeGACAB3bnp0L4+PB7LU3UnpUrJvdhffgXERO5lRdhOMDda6QaSgchid7 fHpmMN1Dt9cmTZKxm03Q6BCSo83PH/piUjZ1XhJXBZD1SBMQxaGPoCdw+/YSo7HTkr kjEeFnX50wm/ix2+vW0GeRkM2usVZOY9VHGcZN7g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2410471AbgDPPc1 (ORCPT ); Thu, 16 Apr 2020 11:32:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:55196 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726599AbgDPNmP (ORCPT ); Thu, 16 Apr 2020 09:42:15 -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 98C70218AC; Thu, 16 Apr 2020 13:42:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587044535; bh=K9lFfffFugUy+h1cvQ1mHkNgiJTJE5NKNzyDaEc4UG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dA4w+rqnC65WTS1y2oKSQrtsSzklK2uOH8wU635zj6nsXGnXU3NP2tSx1cyR2e6g7 xXB+rIJwU794/4oB6Ym2YNdM1qX9+0cuFRzF+4pcHEvIzHj8EyObBhzgsx7J8RIz1C 4FR1sbOmr2IYpv7DSRRMLw4DVfb3o6dE6JEjyTF4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Paul , Wayne Lin , =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Lyude Paul , Sasha Levin Subject: [PATCH 5.5 248/257] drm/dp_mst: Fix clearing payload state on topology disable Date: Thu, 16 Apr 2020 15:24:59 +0200 Message-Id: <20200416131356.646429535@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200416131325.891903893@linuxfoundation.org> References: <20200416131325.891903893@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lyude Paul [ Upstream commit 8732fe46b20c951493bfc4dba0ad08efdf41de81 ] The issues caused by: commit 64e62bdf04ab ("drm/dp_mst: Remove VCPI while disabling topology mgr") Prompted me to take a closer look at how we clear the payload state in general when disabling the topology, and it turns out there's actually two subtle issues here. The first is that we're not grabbing &mgr.payload_lock when clearing the payloads in drm_dp_mst_topology_mgr_set_mst(). Seeing as the canonical lock order is &mgr.payload_lock -> &mgr.lock (because we always want &mgr.lock to be the inner-most lock so topology validation always works), this makes perfect sense. It also means that -technically- there could be racing between someone calling drm_dp_mst_topology_mgr_set_mst() to disable the topology, along with a modeset occurring that's modifying the payload state at the same time. The second is the more obvious issue that Wayne Lin discovered, that we're not clearing proposed_payloads when disabling the topology. I actually can't see any obvious places where the racing caused by the first issue would break something, and it could be that some of our higher-level locks already prevent this by happenstance, but better safe then sorry. So, let's make it so that drm_dp_mst_topology_mgr_set_mst() first grabs &mgr.payload_lock followed by &mgr.lock so that we never race when modifying the payload state. Then, we also clear proposed_payloads to fix the original issue of enabling a new topology with a dirty payload state. This doesn't clear any of the drm_dp_vcpi structures, but those are getting destroyed along with the ports anyway. Changes since v1: * Use sizeof(mgr->payloads[0])/sizeof(mgr->proposed_vcpis[0]) instead - vsyrjala Cc: Sean Paul Cc: Wayne Lin Cc: Ville Syrjälä Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Lyude Paul Reviewed-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20200122194321.14953-1-lyude@redhat.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index c4b692dff5956..c9dd41175853e 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3439,6 +3439,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms int ret = 0; struct drm_dp_mst_branch *mstb = NULL; + mutex_lock(&mgr->payload_lock); mutex_lock(&mgr->lock); if (mst_state == mgr->mst_state) goto out_unlock; @@ -3497,7 +3498,10 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms /* this can fail if the device is gone */ drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0); ret = 0; - memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload)); + memset(mgr->payloads, 0, + mgr->max_payloads * sizeof(mgr->payloads[0])); + memset(mgr->proposed_vcpis, 0, + mgr->max_payloads * sizeof(mgr->proposed_vcpis[0])); mgr->payload_mask = 0; set_bit(0, &mgr->payload_mask); mgr->vcpi_mask = 0; @@ -3505,6 +3509,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms out_unlock: mutex_unlock(&mgr->lock); + mutex_unlock(&mgr->payload_lock); if (mstb) drm_dp_mst_topology_put_mstb(mstb); return ret; -- 2.20.1