[PATCH][next] staging: unisys: visorinput: Use struct_size() helper in kzalloc()

["Gustavo A. R. Silva" <gustavoars@kernel.org>]

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
drivers/staging/unisys/visorinput/visorinput.c:409:27: warning: using sizeof on a flexible structure

Link: https://github.com/KSPP/linux/issues/174
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/staging/unisys/visorinput/visorinput.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/unisys/visorinput/visorinput.c b/drivers/staging/unisys/visorinput/visorinput.c
index 426deab22d62..dffa71ac3cc5 100644
--- a/drivers/staging/unisys/visorinput/visorinput.c
+++ b/drivers/staging/unisys/visorinput/visorinput.c
@@ -406,7 +406,8 @@ static struct visorinput_devdata *devdata_create(struct visor_device *dev,
 	if (dtype == visorinput_keyboard)
 		/* allocate room for devdata->keycode_table, filled in below */
 		extra_bytes = KEYCODE_TABLE_BYTES * 2;
-	devdata = kzalloc(sizeof(*devdata) + extra_bytes, GFP_KERNEL);
+	devdata = kzalloc(struct_size(devdata, keycode_table, extra_bytes),
+			  GFP_KERNEL);
 	if (!devdata)
 		return NULL;
 	mutex_init(&devdata->lock_visor_dev);
-- 
2.27.0