firmware: arm_scmi: Improve checks in the info_get operations

SCMI protocols abstract and expose a number of protocol specific
resources like clocks, sensors and so on. Information about such
specific domain resources are generally exposed via an `info_get`
protocol operation.

Improve the sanity check on these operations where needed.

Link: https://lore.kernel.org/r/20220817172731.1185305-3-cristian.marussi@arm.com
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/clock.c

@@ -450,9 +450,13 @@ static int scmi_clock_count_get(const struct scmi_protocol_handle *ph)
 static const struct scmi_clock_info *
 scmi_clock_info_get(const struct scmi_protocol_handle *ph, u32 clk_id)
 {
+	struct scmi_clock_info *clk;
 	struct clock_info *ci = ph->get_priv(ph);
-	struct scmi_clock_info *clk = ci->clk + clk_id;
 
+	if (clk_id >= ci->num_clocks)
+		return NULL;
+
+	clk = ci->clk + clk_id;
 	if (!clk->name[0])
 		return NULL;
 

drivers/firmware/arm_scmi/sensors.c

@@ -948,6 +948,9 @@ scmi_sensor_info_get(const struct scmi_protocol_handle *ph, u32 sensor_id)
 {
 	struct sensors_info *si = ph->get_priv(ph);
 
+	if (sensor_id >= si->num_sensors)
+		return NULL;
+
 	return si->sensors + sensor_id;
 }
 

include/linux/scmi_protocol.h

@@ -84,7 +84,7 @@ struct scmi_protocol_handle;
 struct scmi_clk_proto_ops {
 	int (*count_get)(const struct scmi_protocol_handle *ph);
 
-	const struct scmi_clock_info *(*info_get)
+	const struct scmi_clock_info __must_check *(*info_get)
 		(const struct scmi_protocol_handle *ph, u32 clk_id);
 	int (*rate_get)(const struct scmi_protocol_handle *ph, u32 clk_id,
 			u64 *rate);
@@ -466,7 +466,7 @@ enum scmi_sensor_class {
  */
 struct scmi_sensor_proto_ops {
 	int (*count_get)(const struct scmi_protocol_handle *ph);
-	const struct scmi_sensor_info *(*info_get)
+	const struct scmi_sensor_info __must_check *(*info_get)
 		(const struct scmi_protocol_handle *ph, u32 sensor_id);
 	int (*trip_point_config)(const struct scmi_protocol_handle *ph,
 				 u32 sensor_id, u8 trip_id, u64 trip_value);