can: raw: fix getsockopt() for new CAN_RAW_XL_VCID_OPTS

The code for the CAN_RAW_XL_VCID_OPTS getsockopt() was incompletely adopted
from the CAN_RAW_FILTER getsockopt().

Add the missing put_user() and return statements.

Flagged by Smatch.

Fixes: c83c22ec ("can: canxl: add virtual CAN network identifier support")
Reported-by: Simon Horman <horms@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://lore.kernel.org/all/20240219200021.12113-1-socketcan@hartkopp.netSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/raw.c

@@ -835,7 +835,9 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 			if (copy_to_user(optval, &ro->raw_vcid_opts, len))
 				err = -EFAULT;
 		}
-		break;
+		if (!err)
+			err = put_user(len, optlen);
+		return err;
 
 	case CAN_RAW_JOIN_FILTERS:
 		if (len > sizeof(int))