firmware: arm_scmi: Rework clock domain info lookups

Accessing clock domains descriptors by the index from the SCMI drivers
can potentially lead to out-of-bound violations if the SCMI drivers
misbehaves.

Use a common helper to check the consistency of such accesses.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240110120916.2482603-1-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/clock.c

@@ -167,6 +167,15 @@ static enum scmi_clock_protocol_cmd evt_2_cmd[] = {
 	CLOCK_RATE_CHANGE_REQUESTED_NOTIFY,
 };
 
+static inline struct scmi_clock_info *
+scmi_clock_domain_lookup(struct clock_info *ci, u32 clk_id)
+{
+	if (clk_id >= ci->num_clocks)
+		return ERR_PTR(-EINVAL);
+
+	return ci->clk + clk_id;
+}
+
 static int
 scmi_clock_protocol_attributes_get(const struct scmi_protocol_handle *ph,
 				   struct clock_info *ci)
@@ -580,10 +589,9 @@ scmi_clock_set_parent(const struct scmi_protocol_handle *ph, u32 clk_id,
 	struct clock_info *ci = ph->get_priv(ph);
 	struct scmi_clock_info *clk;
 
-	if (clk_id >= ci->num_clocks)
-		return -EINVAL;
-
-	clk = ci->clk + clk_id;
+	clk = scmi_clock_domain_lookup(ci, clk_id);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
 
 	if (parent_id >= clk->num_parents)
 		return -EINVAL;
@@ -800,10 +808,10 @@ 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);
 
-	if (clk_id >= ci->num_clocks)
+	clk = scmi_clock_domain_lookup(ci, clk_id);
+	if (IS_ERR(clk))
 		return NULL;
 
-	clk = ci->clk + clk_id;
 	if (!clk->name[0])
 		return NULL;