[PATCH 1/9] maple_tree: Fix allocation when min is equal to max in mas_empty_area/_area_rev()

[Peng Zhang <zhangpeng.00@bytedance.com>]

Make the allocation valid when min is equal to max in mas_empty_area()
and mas_empty_area_rev(). As Liam R. Howlett said, VMA doesn't make this
allocation, so now this bug won't trigger.

Also add some checks for invalid parameters.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
---
 lib/maple_tree.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 110a36479dced..72099b4b32169 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5289,7 +5289,10 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
 	unsigned long *pivots;
 	enum maple_type mt;
 
-	if (min >= max)
+	if (unlikely(min > max))
+		return -EINVAL;
+
+	if (unlikely(size == 0) || unlikely(max - min < size - 1))
 		return -EINVAL;
 
 	if (mas_is_start(mas))
@@ -5344,7 +5347,10 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 {
 	struct maple_enode *last = mas->node;
 
-	if (min >= max)
+	if (unlikely(min > max))
+		return -EINVAL;
+
+	if (unlikely(size == 0) || unlikely(max - min < size - 1))
 		return -EINVAL;
 
 	if (mas_is_start(mas)) {
@@ -5380,7 +5386,7 @@ int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
 		return -EBUSY;
 
 	/* Trim the upper limit to the max. */
-	if (max <= mas->last)
+	if (max < mas->last)
 		mas->last = max;
 
 	mas->index = mas->last - size + 1;
-- 
2.20.1