Avoid manual sizeof math by using the proper helper.

Also use struct_size for the buffer size.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/greybus/svc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/greybus/svc.c b/drivers/greybus/svc.c
index 1b854f53f21e..490577731a19 100644
--- a/drivers/greybus/svc.c
+++ b/drivers/greybus/svc.c
@@ -775,10 +775,9 @@ static void gb_svc_pwrmon_debugfs_init(struct gb_svc *svc)
 	if (!rail_count || rail_count > GB_SVC_PWRMON_MAX_RAIL_COUNT)
 		goto err_pwrmon_debugfs;
 
-	bufsize = sizeof(*rail_names) +
-		GB_SVC_PWRMON_RAIL_NAME_BUFSIZE * rail_count;
+	bufsize = struct_size(rail_names, name, rail_count);
 
-	rail_names = kzalloc(bufsize, GFP_KERNEL);
+	rail_names = kzalloc_flex(*rail_names, name, rail_count);
 	if (!rail_names)
 		goto err_pwrmon_debugfs;
 
-- 
2.53.0