[PATCH 6.1 207/312] hwmon: (occ) Fix division by zero in occ_show_power_1()

Greg Kroah-Hartman
2026-04-08T18:15:44Z

From: Sanman Pradhan <psanman@juniper.net>

commit 39e2a5bf970402a8530a319cf06122e216ba57b8 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/hwmon/occ/common.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -420,6 +420,12 @@ static ssize_t occ_show_freq_2(struct de
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 d
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 d
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)
{