[PATCH] drm/mm: prevent a potential null-pointer dereference

[Jing Xiangfeng]

The macro 'DECLARE_NEXT_HOLE_ADDR' may hit a potential null-pointer
dereference. So use 'entry' after checking it.

Fixes: 5fad79fd66ff ("drm/mm: cleanup and improve next_hole_*_addr()")
Signed-off-by: Jing Xiangfeng <jingxiangfeng at huawei.com>
---
 drivers/gpu/drm/drm_mm.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index a4a04d246135..6fcf70f71962 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -392,11 +392,14 @@ first_hole(struct drm_mm *mm,
 #define DECLARE_NEXT_HOLE_ADDR(name, first, last)			\
 static struct drm_mm_node *name(struct drm_mm_node *entry, u64 size)	\
 {									\
-	struct rb_node *parent, *node = &entry->rb_hole_addr;		\
+	struct rb_node *parent, *node;					\
 									\
-	if (!entry || RB_EMPTY_NODE(node))				\
+	if (!entry)							\
 		return NULL;						\
 									\
+	node = &entry->rb_hole_addr;					\
+	if (RB_EMPTY_NODE(node))					\
+		return NULL;						\
 	if (usable_hole_addr(node->first, size)) {			\
 		node = node->first;					\
 		while (usable_hole_addr(node->last, size))		\
-- 
2.17.1