From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCHv5 4/6] drm/omap: fix incorrect union usage Date: Fri, 23 Nov 2018 09:33:10 -0800 Message-ID: <20181123173310.GI53235@atomide.com> References: <20181121160916.22017-1-sebastian.reichel@collabora.com> <20181121160916.22017-5-sebastian.reichel@collabora.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181121160916.22017-5-sebastian.reichel@collabora.com> Sender: linux-kernel-owner@vger.kernel.org To: Sebastian Reichel Cc: Sebastian Reichel , Tomi Valkeinen , Pavel Machek , Laurent Pinchart , "H. Nikolaus Schaller" , dri-devel@lists.freedesktop.org, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@collabora.com List-Id: linux-omap@vger.kernel.org * Sebastian Reichel [181121 16:09]: > The DSI encoder sets dssdev->ops->dsi.set_config, which is stored at the > same offset as dssdev->ops->hdmi.set_hdmi_mode. The code in omap_encoder > only checks if dssdev->ops->hdmi.set_hdmi_mode is NULL. Due to the way > union works, it won't be NULL if dsi.set_config is set. This means > dsi_set_config will be called with config=hdmi_mode=false=NULL parameter > resulting in a NULL dereference. Also the dereference happens while > console is locked, so kernel hangs without any debug output without > "fb.lockless_register_fb=1" parameter. > > This restructures the code, so that the HDMI mode is only configured > for HDMI output types. The new function also has a safe-guard directly > before accessing the union, that can be optimized away by the compiler > when the function is inlined and HDMI type has already been checked. > > Fixes: 83910ad3f51fb ("drm/omap: Move most omap_dss_driver operations to omap_dss_device_ops") > Signed-off-by: Sebastian Reichel Works for me: Tested-by: Tony Lindgren