staging: unisys: visorinput: Use struct_size() helper in kzalloc()

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>
Link: https://lore.kernel.org/r/20220125223443.GA76937@embeddedor
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/unisys/visorinput/visorinput.c b/drivers/staging/unisys/visorinput/visorinput.c
index 426deab..dffa71a 100644 (file)
--- 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);