tty: Use the preferred form for passing the size of a structure type

Use the preferred form for passing the size of a structure type. The
alternative form where the structure type is spelled out hurts
readability and introduces an opportunity for a bug when the object
type is changed but the corresponding object identifier to which the
sizeof operator is applied is not.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/b04dd8cdd67bd6ffde3fd12940aeef35fdb824a6.1595543280.git.gustavoars@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -1405,7 +1405,7 @@ void tty_save_termios(struct tty_struct *tty)
 	/* Stash the termios data */
 	tp = tty->driver->termios[idx];
 	if (tp == NULL) {
-		tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
+		tp = kmalloc(sizeof(*tp), GFP_KERNEL);
 		if (tp == NULL)
 			return;
 		tty->driver->termios[idx] = tp;
@@ -2489,7 +2489,7 @@ static int tty_tiocsserial(struct tty_struct *tty, struct serial_struct __user *
 	struct serial_struct v;
 	int flags;
 
-	if (copy_from_user(&v, ss, sizeof(struct serial_struct)))
+	if (copy_from_user(&v, ss, sizeof(*ss)))
 		return -EFAULT;
 
 	flags = v.flags & ASYNC_DEPRECATED;
@@ -2507,11 +2507,11 @@ static int tty_tiocgserial(struct tty_struct *tty, struct serial_struct __user *
 	struct serial_struct v;
 	int err;
 
-	memset(&v, 0, sizeof(struct serial_struct));
+	memset(&v, 0, sizeof(v));
 	if (!tty->ops->get_serial)
 		return -ENOTTY;
 	err = tty->ops->get_serial(tty, &v);
-	if (!err && copy_to_user(ss, &v, sizeof(struct serial_struct)))
+	if (!err && copy_to_user(ss, &v, sizeof(v)))
 		err = -EFAULT;
 	return err;
 }
@@ -2705,7 +2705,7 @@ static int compat_tty_tiocsserial(struct tty_struct *tty,
 	struct serial_struct v;
 	int flags;
 
-	if (copy_from_user(&v32, ss, sizeof(struct serial_struct32)))
+	if (copy_from_user(&v32, ss, sizeof(*ss)))
 		return -EFAULT;
 
 	memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
@@ -2743,7 +2743,7 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
 			0xfffffff : ptr_to_compat(v.iomem_base);
 		v32.iomem_reg_shift = v.iomem_reg_shift;
 		v32.port_high = v.port_high;
-		if (copy_to_user(ss, &v32, sizeof(struct serial_struct32)))
+		if (copy_to_user(ss, &v32, sizeof(v32)))
 			err = -EFAULT;
 	}
 	return err;
@@ -3215,7 +3215,7 @@ struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
 	if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
 		return ERR_PTR(-EINVAL);
 
-	driver = kzalloc(sizeof(struct tty_driver), GFP_KERNEL);
+	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
 	if (!driver)
 		return ERR_PTR(-ENOMEM);