From: =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>
Date: Mon, 14 Aug 2017 23:53:45 +0200
Subject: drm/tegra: Fix NULL deref in debugfs/iova
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Git-commit: 68d890a3cca5a96a5443972922c84df89f6301e6
Patch-mainline: v4.14-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

When IOMMU is off, ->mm_lock is not initialized and ->mm is NULL.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/tegra/drm.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -1035,9 +1035,11 @@ static int tegra_debugfs_iova(struct seq
 	struct tegra_drm *tegra = drm->dev_private;
 	struct drm_printer p = drm_seq_file_printer(s);
 
-	mutex_lock(&tegra->mm_lock);
-	drm_mm_print(&tegra->mm, &p);
-	mutex_unlock(&tegra->mm_lock);
+	if (tegra->domain) {
+		mutex_lock(&tegra->mm_lock);
+		drm_mm_print(&tegra->mm, &p);
+		mutex_unlock(&tegra->mm_lock);
+	}
 
 	return 0;
 }