diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 1facd0153399..f35e076ee47d 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4755,8 +4755,7 @@ static int handle_reshape_read_error(struct mddev *mddev,
 	int idx = 0;
 	struct page **pages;
 
-	r10b = kmalloc(sizeof(*r10b) +
-	       sizeof(struct r10dev) * conf->copies, GFP_NOIO);
+	r10b = kmalloc(struct_size(r10b, devs, conf->copies), GFP_NOIO);
 	if (!r10b) {
 		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
 		return -ENOMEM;