tegra: fix kernel NULL pointer dereference

Closing Qt application caused video mode to change, which in turn
triggered NULL pointer deference bug in tegra kernel.

Task-number: QTBUG-60417
Change-Id: I0dffc3cd6773637742a1e54f6c495fdde0fbd895
Reviewed-by: Kari Oikarinen <kari.oikarinen@qt.io>

2 files changed, 76 insertions, 0 deletions

diff --git a/meta-tegra-extras/recipes/linux/linux-tegra/0001-fbcon-Compare-variable-screen-info-instead-of-modes-.patch b/meta-tegra-extras/recipes/linux/linux-tegra/0001-fbcon-Compare-variable-screen-info-instead-of-modes-.patch
new file mode 100644
index 00000000..c700e0e4
--- /dev/null
+++ b/meta-tegra-extras/recipes/linux/linux-tegra/0001-fbcon-Compare-variable-screen-info-instead-of-modes-.patch
@@ -0,0 +1,43 @@
+From 727c2a7dd80589e99b6061f362cf5f1f4d5a84d7 Mon Sep 17 00:00:00 2001
+From: Samuli Piippo <samuli.piippo@qt.io>
+Date: Mon, 8 May 2017 08:47:27 +0300
+Subject: [PATCH] fbcon: Compare variable screen info instead of modes (FIX)
+
+Previous commit changed behavior, so that when trying to match a mode to a
+variable screen info structure, the mode was first converted to a variable
+screen structure rather than the variable screen info structure to a mode.
+
+However, when new mode was being added to the modelist, matching was still
+being done using mode structure. This could cause situation, where existing
+mode would match when comparing with mode structure, but not when compared
+using variable screen info structure. This would eventually result in a
+NULL pointer dereference in fbcon_switch.
+
+Fix the issue by using the variable screen info structure also when adding
+new mode to the modelist.
+---
+ drivers/video/modedb.c | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
+index 12dadab..e5093cf 100644
+--- a/drivers/video/modedb.c
++++ b/drivers/video/modedb.c
+@@ -2190,13 +2190,14 @@ int fb_add_videomode(const struct fb_videomode *mode, struct list_head *head)
+ {
+ 	struct list_head *pos;
+ 	struct fb_modelist *modelist;
+-	struct fb_videomode *m;
++	struct fb_var_screeninfo v1, v2;
+ 	int found = 0;
+ 
++	fb_videomode_to_var(&v1, mode);
+ 	list_for_each(pos, head) {
+ 		modelist = list_entry(pos, struct fb_modelist, list);
+-		m = &modelist->mode;
+-		if (fb_mode_is_equal(m, mode)) {
++		fb_videomode_to_var(&v2, &modelist->mode);
++		if (fb_var_is_equal(&v1, &v2)) {
+ 			found = 1;
+ 			break;
+ 		}
diff --git a/meta-tegra-extras/recipes/linux/linux-tegra_%.bbappend b/meta-tegra-extras/recipes/linux/linux-tegra_%.bbappend
new file mode 100644
index 00000000..db152a32
--- /dev/null
+++ b/meta-tegra-extras/recipes/linux/linux-tegra_%.bbappend
@@ -0,0 +1,33 @@
+############################################################################
+##
+## Copyright (C) 2017 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the Boot to Qt meta layer.
+##
+## $QT_BEGIN_LICENSE:GPL$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 3 or (at your option) any later version
+## approved by the KDE Free Qt Foundation. The licenses are as published by
+## the Free Software Foundation and appearing in the file LICENSE.GPL3
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+############################################################################
+
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+SRC_URI += "\
+    file://0001-fbcon-Compare-variable-screen-info-instead-of-modes-.patch \
+    "