mm/damon/sysfs-schemes: use kmalloc_array() and size_add()

It's safer to use kmalloc_array() and size_add() because it can prevent
possible overflow problem.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Su Hui <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Su Hui

mm/damon/sysfs-schemes.c

@@ -465,7 +465,8 @@ static ssize_t memcg_path_store(struct kobject *kobj,
 {
 	struct damon_sysfs_scheme_filter *filter = container_of(kobj,
 			struct damon_sysfs_scheme_filter, kobj);
-	char *path = kmalloc(sizeof(*path) * (count + 1), GFP_KERNEL);
+	char *path = kmalloc_array(size_add(count, 1), sizeof(*path),
+				   GFP_KERNEL);
 
 	if (!path)
 		return -ENOMEM;
@@ -2064,7 +2065,7 @@ static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
 	if (!memcg_path)
 		return -EINVAL;
 
-	path = kmalloc(sizeof(*path) * PATH_MAX, GFP_KERNEL);
+	path = kmalloc_array(PATH_MAX, sizeof(*path), GFP_KERNEL);
 	if (!path)
 		return -ENOMEM;