From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8040D13C838 for ; Fri, 26 Apr 2024 09:25:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714123512; cv=none; b=c8KrZDGqeTl9kqeZYhqy2iGO2tWWqDqw7c2AHX9OllQV0vBn5XujmtVVh5IMWorRhqxg0vLwFHeamQFUJM+HihjOPBvVRSvNr+j2TLeneIbhBioqtQCMVNNVCe2dOjlylNnhpFysdJNJlWve4VJd5K+IQQ479EDnsduDT6bnnZA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714123512; c=relaxed/simple; bh=4sk3SkM9lTZY2JBkhhraAd6ifVIO1oEjvKtMkIamMGs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EsM84CG4IwhLaoDXX2te+s/VqAFULm0LddokO1bPIr0xtcDsaqF7FnfGQqKBtTGHBhilFZVUyrRfGc+nDnjN4DTkYdYT0xmS9yQzC51Kfete7Us6dQF/pe/l6yygirWnt67Mv0fDCr1BuQ2SqgDLzQ7Mwb4g9EWNTGuf8Crj+3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=HQTUOZDY; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="HQTUOZDY" Received: from pendragon.ideasonboard.com (117.145-247-81.adsl-dyn.isp.belgacom.be [81.247.145.117]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 114E466B; Fri, 26 Apr 2024 11:24:15 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1714123455; bh=4sk3SkM9lTZY2JBkhhraAd6ifVIO1oEjvKtMkIamMGs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HQTUOZDYmjmdlbB0bcbZ2NEqb+R83Hd10+hCsRKTTuc2aXnYepiQVDrzkOdEXdpbe d2lnDfNujb83VAOOpY4k7/HArtBk6L/7WL5hbogkzkdBm72Uem8gGBt7ditsbS1n7Y GED8BGTR2J/2mgslVwPguHMUvptabgDXo0R3XAsM= Date: Fri, 26 Apr 2024 12:25:00 +0300 From: Laurent Pinchart To: Tomi Valkeinen Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Michal Simek , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Vishal Sagar , Anatoliy Klymenko Subject: Re: [PATCH] drm: xlnx: zynqmp_dpsub: Fix missing drm_bridge_add() call Message-ID: <20240426092500.GA4524@pendragon.ideasonboard.com> References: <20240312-xilinx-dp-lock-fix-v1-1-1698f9f03bac@ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240312-xilinx-dp-lock-fix-v1-1-1698f9f03bac@ideasonboard.com> Hi Tomi, Thank you for the patch. On Tue, Mar 12, 2024 at 10:51:15AM +0200, Tomi Valkeinen wrote: > The driver creates a bridge, but never calls drm_bridge_add() when > non-live input is used. This leaves the bridge's hpd_mutex > uninitialized, leading to: > > WARNING: CPU: 0 PID: 9 at kernel/locking/mutex.c:582 __mutex_lock+0x708/0x840 > > Add the bridge add & remove calls so that the bridge gets managed > correctly. > > Signed-off-by: Tomi Valkeinen > Fixes: 561671612394 ("drm: xlnx: zynqmp_dpsub: Add support for live video input") > --- > drivers/gpu/drm/xlnx/zynqmp_dp.c | 4 ++++ > drivers/gpu/drm/xlnx/zynqmp_dpsub.c | 4 ---- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c > index a0606fab0e22..9f750740dfb8 100644 > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c > @@ -1761,6 +1761,8 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub) > > dpsub->dp = dp; > > + drm_bridge_add(dpsub->bridge); > + This means that the bridge will be exposed to users before zynqmp_disp_probe() is called, opening the door to a potential use-before-init. The risk is mostly theoretical at this point I believe, but it's still not a direction I'd like to that. Could you call drm_bridge_add() in zynqmp_dpsub_probe(), between zynqmp_disp_probe() and zynqmp_dpsub_drm_init() ? > dev_dbg(dp->dev, "ZynqMP DisplayPort Tx probed with %u lanes\n", > dp->num_lanes); > > @@ -1789,4 +1791,6 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub) > > zynqmp_dp_phy_exit(dp); > zynqmp_dp_reset(dp, true); > + > + drm_bridge_remove(dpsub->bridge); > } > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dpsub.c b/drivers/gpu/drm/xlnx/zynqmp_dpsub.c > index 88eb33acd5f0..3933c4f1a44f 100644 > --- a/drivers/gpu/drm/xlnx/zynqmp_dpsub.c > +++ b/drivers/gpu/drm/xlnx/zynqmp_dpsub.c > @@ -260,8 +260,6 @@ static int zynqmp_dpsub_probe(struct platform_device *pdev) > ret = zynqmp_dpsub_drm_init(dpsub); > if (ret) > goto err_disp; > - } else { > - drm_bridge_add(dpsub->bridge); > } > > dev_info(&pdev->dev, "ZynqMP DisplayPort Subsystem driver probed"); > @@ -288,8 +286,6 @@ static void zynqmp_dpsub_remove(struct platform_device *pdev) > > if (dpsub->drm) > zynqmp_dpsub_drm_cleanup(dpsub); > - else > - drm_bridge_remove(dpsub->bridge); > > zynqmp_disp_remove(dpsub); > zynqmp_dp_remove(dpsub); > > --- > base-commit: e8f897f4afef0031fe618a8e94127a0934896aba > change-id: 20240312-xilinx-dp-lock-fix-cf68f43a7bab -- Regards, Laurent Pinchart