[PATCH 1/3] hwmon: (occ) Fix division by zero in occ_show_power_1()

[Pradhan, Sanman]

From: Sanman Pradhan <psanman@xxxxxxxxxxx>

In occ_show_power_1() case 1, the accumulator is divided by
update_tag without checking for zero. If no samples have been
collected yet (e.g. during early boot when the sensor block is
included but hasn't been updated), update_tag is zero, causing
a kernel divide-by-zero crash.

The 2019 fix in commit 211186cae14d ("hwmon: (occ) Fix division by
zero issue") only addressed occ_get_powr_avg() used by
occ_show_power_2() and occ_show_power_a0(). This separate code
path in occ_show_power_1() was missed.

Fix this by reusing the existing occ_get_powr_avg() helper, which
already handles the zero-sample case and uses mul_u64_u32_div()
to multiply before dividing for better precision. Move the helper
above occ_show_power_1() so it is visible at the call site.

Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sanman Pradhan <psanman@xxxxxxxxxxx>
---
 drivers/hwmon/occ/common.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 89928d38831b..f02f815dc960 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -420,6 +420,12 @@ static ssize_t occ_show_freq_2(struct device *dev,
 	return sysfs_emit(buf, "%u\n", val);
 }
 
+static u64 occ_get_powr_avg(u64 accum, u32 samples)
+{
+	return (samples == 0) ? 0 :
+		mul_u64_u32_div(accum, 1000000UL, samples);
+}
+
 static ssize_t occ_show_power_1(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
@@ -441,9 +447,9 @@ static ssize_t occ_show_power_1(struct device *dev,
 		val = get_unaligned_be16(&power->sensor_id);
 		break;
 	case 1:
-		val = get_unaligned_be32(&power->accumulator) /
-			get_unaligned_be32(&power->update_tag);
-		val *= 1000000ULL;
+		val = occ_get_powr_avg(
+			get_unaligned_be32(&power->accumulator),
+			get_unaligned_be32(&power->update_tag));
 		break;
 	case 2:
 		val = (u64)get_unaligned_be32(&power->update_tag) *
@@ -459,12 +465,6 @@ static ssize_t occ_show_power_1(struct device *dev,
 	return sysfs_emit(buf, "%llu\n", val);
 }
 
-static u64 occ_get_powr_avg(u64 accum, u32 samples)
-{
-	return (samples == 0) ? 0 :
-		mul_u64_u32_div(accum, 1000000UL, samples);
-}
-
 static ssize_t occ_show_power_2(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
-- 
2.34.1