[PATCH 2/2] hwmon: (ltc2992) Fix u32 overflow in power read path
From: Pradhan, Sanman
Date: Thu Apr 16 2026 - 18:01:56 EST
From: Sanman Pradhan <psanman@xxxxxxxxxxx>
ltc2992_get_power() computes the divisor for mul_u64_u32_div() as
r_sense_uohm * 1000. This multiplication overflows u32 when
r_sense_uohm exceeds about 4.29 ohms (4294967 micro-ohms), producing
a truncated divisor and an incorrect power reading.
Cancel the factor of 1000 from both the numerator
(VADC_UV_LSB * IADC_NANOV_LSB = 312500000) and the divisor
(r_sense_uohm * 1000), giving (VADC_UV_LSB / 1000) * IADC_NANOV_LSB
= 312500 as the numerator and plain r_sense_uohm as the divisor.
The cancellation is exact because LTC2992_VADC_UV_LSB (25000) is
divisible by 1000.
This is the read-path counterpart of the write-path fix applied in
the preceding patch.
Fixes: b0bd407e94b03 ("hwmon: (ltc2992) Add support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sanman Pradhan <psanman@xxxxxxxxxxx>
---
drivers/hwmon/ltc2992.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/ltc2992.c b/drivers/hwmon/ltc2992.c
index 1069736196763..2617c4538af91 100644
--- a/drivers/hwmon/ltc2992.c
+++ b/drivers/hwmon/ltc2992.c
@@ -637,8 +637,10 @@ static int ltc2992_get_power(struct ltc2992_state *st, u32 reg, u32 channel, lon
if (reg_val < 0)
return reg_val;
- *val = mul_u64_u32_div(reg_val, LTC2992_VADC_UV_LSB * LTC2992_IADC_NANOV_LSB,
- st->r_sense_uohm[channel] * 1000);
+ *val = mul_u64_u32_div(reg_val,
+ LTC2992_VADC_UV_LSB / 1000 *
+ LTC2992_IADC_NANOV_LSB,
+ st->r_sense_uohm[channel]);
return 0;
}
--
2.34.1