[v2 PATCH] powernv-cpuidle: Validate DT property array size

[Gautham R. Shenoy]

From: "Gautham R. Shenoy" <ego@xxxxxxxxxxxxxxxxxx>

The various properties associated with powernv idle states such as
names, flags, residency-ns, latencies-ns, psscr, psscr-mask are
exposed in the device-tree as property arrays such the pointwise
entries in each of these arrays correspond to the properties of the
same idle state.

This patch validates that the lengths of the property arrays are the
same. If there is a mismatch, the patch will ensure that we bail out
and not expose the platform idle states via cpuidle.

Signed-off-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
---
v1: https://lkml.org/lkml/2017/2/23/349
Changes from v1: Print the full property array name in warning message.

 drivers/cpuidle/cpuidle-powernv.c | 64 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 61 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 3705930..a06df51 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -197,11 +197,25 @@ static inline void add_powernv_state(int index, const char *name,
 	stop_psscr_table[index].mask = psscr_mask;
 }
 
+/*
+ * Returns 0 if prop1_len == prop2_len. Else returns -1
+ */
+static inline int validate_dt_prop_sizes(const char *prop1, int prop1_len,
+					 const char *prop2, int prop2_len)
+{
+	if (prop1_len == prop2_len)
+		return 0;
+
+	pr_warn("cpuidle-powernv: array sizes don't match for %s and %s\n",
+		prop1, prop2);
+	return -1;
+}
+
 static int powernv_add_idle_states(void)
 {
 	struct device_node *power_mgt;
 	int nr_idle_states = 1; /* Snooze */
-	int dt_idle_states;
+	int dt_idle_states, count;
 	u32 latency_ns[CPUIDLE_STATE_MAX];
 	u32 residency_ns[CPUIDLE_STATE_MAX];
 	u32 flags[CPUIDLE_STATE_MAX];
@@ -226,6 +240,21 @@ static int powernv_add_idle_states(void)
 		goto out;
 	}
 
+	count = of_property_count_u32_elems(power_mgt,
+					    "ibm,cpu-idle-state-latencies-ns");
+
+	if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags", dt_idle_states,
+				   "ibm,cpu-idle-state-latencies-ns",
+				   count) != 0)
+		goto out;
+
+	count = of_property_count_strings(power_mgt,
+					  "ibm,cpu-idle-state-names");
+	if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags", dt_idle_states,
+				   "ibm,cpu-idle-state-names",
+				   count) != 0)
+		goto out;
+
 	/*
 	 * Since snooze is used as first idle state, max idle states allowed is
 	 * CPUIDLE_STATE_MAX -1
@@ -260,6 +289,22 @@ static int powernv_add_idle_states(void)
 	has_stop_states = (flags[0] &
 			   (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP));
 	if (has_stop_states) {
+		count = of_property_count_u64_elems(power_mgt,
+						    "ibm,cpu-idle-state-psscr");
+		if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
+					   dt_idle_states,
+					   "ibm,cpu-idle-state-psscr",
+					   count) != 0)
+			goto out;
+
+		count = of_property_count_u64_elems(power_mgt,
+						    "ibm,cpu-idle-state-psscr-mask");
+		if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
+					   dt_idle_states,
+					   "ibm,cpu-idle-state-psscr-mask",
+					   count) != 0)
+			goto out;
+
 		if (of_property_read_u64_array(power_mgt,
 		    "ibm,cpu-idle-state-psscr", psscr_val, dt_idle_states)) {
 			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-psscr in DT\n");
@@ -274,8 +319,21 @@ static int powernv_add_idle_states(void)
 		}
 	}
 
-	rc = of_property_read_u32_array(power_mgt,
-		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
+	count = of_property_count_u32_elems(power_mgt,
+					    "ibm,cpu-idle-state-residency-ns");
+
+	if (count < 0) {
+		rc = count;
+	} else if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
+					  dt_idle_states,
+					  "ibm,cpu-idle-state-residency-ns",
+					  count) != 0) {
+		goto out;
+	} else {
+		rc = of_property_read_u32_array(power_mgt,
+						"ibm,cpu-idle-state-residency-ns",
+						residency_ns, dt_idle_states);
+	}
 
 	for (i = 0; i < dt_idle_states; i++) {
 		unsigned int exit_latency, target_residency;
-- 
1.9.4