hwmon: (occ) Fix division by zero in occ_show_power_1()

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@vger.kernel.org
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
Link: https://lore.kernel.org/r/20260326224510.294619-2-sanman.pradhan@hpe.com
[groeck: Fix alignment problems reported by checkpatch]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 89928d38831b612e911adfc9e87e5a75da4e552a..ec7dbb94de0b7f7e6307d89d52f2d6f3fd76b5ce 100644 (file)
--- 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 +447,8 @@ 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 +464,6 @@ 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)
 {