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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 44B5BC0218B for ; Thu, 23 Jan 2025 16:20:43 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B6DA710E876; Thu, 23 Jan 2025 16:20:42 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="vYvPSUAw"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id BE2EC10E876 for ; Thu, 23 Jan 2025 16:20:40 +0000 (UTC) Received: from [192.168.88.20] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 3299E1189; Thu, 23 Jan 2025 17:19:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1737649175; bh=b++psFFn/rY5Dao2k1BfJsVMxThYoR4AEpwAfFmUKZQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vYvPSUAwKqOtyxNprbgLVvN5XhjOlsH4vEOQeXu/BTpMIglH7FMmKQbC5+YkVG1L6 u1GG9JChRLIkz/vbDUoFLXabZkNtdMjJQpWDw+FUkSL+acOXDi0bM2F9zIacIbB9jx iVMmmJpiKynxDpPiaCOPiyjEVeDv1WtdybcHRf0M= Message-ID: Date: Thu, 23 Jan 2025 18:20:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference To: Jayesh Choudhary , dri-devel@lists.freedesktop.org, sjakhade@cadence.com, jsarha@ti.com, mripard@kernel.org, Laurent.pinchart@ideasonboard.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org Cc: amishin@t-argos.ru, jani.nikula@intel.com, tzimmermann@suse.de, maarten.lankhorst@linux.intel.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, linux-kernel@vger.kernel.org, devarsht@ti.com References: <20250116111636.157641-1-j-choudhary@ti.com> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On 16/01/2025 13:16, Jayesh Choudhary wrote: > For the cases we have DRM_BRIDGE_ATTACH_NO_CONNECTOR flag set, Any idea if any other platform than K3 is using this driver? tidss supports DRM_BRIDGE_ATTACH_NO_CONNECTOR, so if K3 is the only user, we could drop the legacy !DRM_BRIDGE_ATTACH_NO_CONNECTOR case. Which would remove quite a bit of code, I think, and make the driver a bit more easy to understand (although I think it could use a major cleanup...). > the connector structure is not initialised in the bridge. That's done > by encoder. So in case of some failure in cdns_mhdp_atomic_enable, > when we schedule work for modeset_retry_work, we will use the mutex > of connector which will result in NULL pointer dereference. > Handle it by adding condition for the connector. Otherwise, since > the modeset_retry_work tries to set the connector status as bad, > set the mhdp->plugged as false which would give the connector > status as disconnected in detect hook. I'm not quite sure if this whole system makes sense (no one else is doing it), but I think you can find the connector from the current state. Then setting the property could be done for DRM_BRIDGE_ATTACH_NO_CONNECTOR case too. Tomi > Fixes: fb43aa0acdfd ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge") > Signed-off-by: Jayesh Choudhary > --- > > NOTE: Found this issue in one particular board where edid read failed. > Issue log: > > Adding conditional fixes the null pointer issue but there is still > flooding of these logs (128 times): > "cdns-mhdp8546 a000000.bridge: Failed to read DPCD addr 0" > > Sending RFC as I am still not sure about how to handle this flooding. > Is it okay to decrease the log level for DPCD read and DPCD write in > the cdns_mhdp_transfer to debug? > > .../drm/bridge/cadence/cdns-mhdp8546-core.c | 24 ++++++++++--------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c > index d081850e3c03..6a121a2700d2 100644 > --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c > +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c > @@ -2363,18 +2363,20 @@ static void cdns_mhdp_modeset_retry_fn(struct work_struct *work) > > mhdp = container_of(work, typeof(*mhdp), modeset_retry_work); > > - conn = &mhdp->connector; > - > - /* Grab the locks before changing connector property */ > - mutex_lock(&conn->dev->mode_config.mutex); > - > - /* > - * Set connector link status to BAD and send a Uevent to notify > - * userspace to do a modeset. > - */ > - drm_connector_set_link_status_property(conn, DRM_MODE_LINK_STATUS_BAD); > - mutex_unlock(&conn->dev->mode_config.mutex); > + if (mhdp->connector.dev) { > + conn = &mhdp->connector; > + /* Grab the locks before changing connector property */ > + mutex_lock(&conn->dev->mode_config.mutex); > > + /* > + * Set connector link status to BAD and send a Uevent to notify > + * userspace to do a modeset. > + */ > + drm_connector_set_link_status_property(conn, DRM_MODE_LINK_STATUS_BAD); > + mutex_unlock(&conn->dev->mode_config.mutex); > + } else { > + mhdp->plugged = false; > + } > /* Send Hotplug uevent so userspace can reprobe */ > drm_kms_helper_hotplug_event(mhdp->bridge.dev); > }