mnt_idmapping: Use kmemdup_array instead of kmemdup for multiple allocation

Let the kememdup_array() take care about multiplication and possible
overflows.

v2:Add a new modification for reverse array.
Signed-off-by: Yu Jiaoliang <yujiaoliang@vivo.com>
Link: https://lore.kernel.org/r/20240823015542.3006262-1-yujiaoliang@vivo.comReviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/mnt_idmapping.c

@@ -228,15 +228,15 @@ static int copy_mnt_idmap(struct uid_gid_map *map_from,
 		return 0;
 	}
 
-	forward = kmemdup(map_from->forward,
-			  nr_extents * sizeof(struct uid_gid_extent),
-			  GFP_KERNEL_ACCOUNT);
+	forward = kmemdup_array(map_from->forward, nr_extents,
+				sizeof(struct uid_gid_extent),
+				GFP_KERNEL_ACCOUNT);
 	if (!forward)
 		return -ENOMEM;
 
-	reverse = kmemdup(map_from->reverse,
-			  nr_extents * sizeof(struct uid_gid_extent),
-			  GFP_KERNEL_ACCOUNT);
+	reverse = kmemdup_array(map_from->reverse, nr_extents,
+				sizeof(struct uid_gid_extent),
+				GFP_KERNEL_ACCOUNT);
 	if (!reverse) {
 		kfree(forward);
 		return -ENOMEM;