ASoC: SOF: ipc4-topology: Use size_add() in call to struct_size()

If, for any reason, the open-coded arithmetic causes a wraparound,
the protection that `struct_size()` adds against potential integer
overflows is defeated. Fix this by hardening call to `struct_size()`
with `size_add()`.

Fixes: f9efae95 ("ASoC: SOF: ipc4-topology: Add support for base config extension")
Signed-off-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/ZQSr15AYJpDpipg6@workSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-topology.c

@@ -895,7 +895,8 @@ static int sof_ipc4_widget_setup_comp_process(struct snd_sof_widget *swidget)
 	if (process->init_config == SOF_IPC4_MODULE_INIT_CONFIG_TYPE_BASE_CFG_WITH_EXT) {
 		struct sof_ipc4_base_module_cfg_ext *base_cfg_ext;
 		u32 ext_size = struct_size(base_cfg_ext, pin_formats,
-						swidget->num_input_pins + swidget->num_output_pins);
+					   size_add(swidget->num_input_pins,
+						    swidget->num_output_pins));
 
 		base_cfg_ext = kzalloc(ext_size, GFP_KERNEL);
 		if (!base_cfg_ext) {