linux-kernel - [PATCH] drm/mm: avoid possible null pointer dereference

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Message-Id: <1463602639-4861-1-git-send-email-xypron.glpk@gmx.de>
Date:	Wed, 18 May 2016 22:17:19 +0200
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	David Airlie <airlied@...ux.ie>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH] drm/mm: avoid possible null pointer dereference

Do not dereference node before the check if node is NULL.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
 drivers/gpu/drm/drm_mm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 04de6fd..cb39f45 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -179,12 +179,14 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
 int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
 {
 	struct drm_mm_node *hole;
-	u64 end = node->start + node->size;
+	u64 end;
 	u64 hole_start;
 	u64 hole_end;
 
 	BUG_ON(node == NULL);
 
+	end = node->start + node->size;
+
 	/* Find the relevant hole to add our node to */
 	drm_mm_for_each_hole(hole, mm, hole_start, hole_end) {
 		if (hole_start > node->start || hole_end < end)
-- 
2.1.4