Commit 39e2a5bf authored by Sanman Pradhan's avatar Sanman Pradhan Committed by Guenter Roeck
Browse files

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 211186ca ("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: c10e753d ("hwmon (occ): Add sensor types and versions")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSanman 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: default avatarGuenter Roeck <linux@roeck-us.net>
parent ca34ee6d

drivers/hwmon/occ/common.c

+8 −9
Original line number Diff line number Diff line
@@ -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)

{