6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Lechner <dlechner@xxxxxxxxxxxx>
[ Upstream commit e9b24deb84863c5a77dda5be57b6cb5bf4127b85 ]
Fix use of DIV_ROUND_CLOSEST where a possibly negative value is divided
by an unsigned type by casting the unsigned type to the signed type of
the same size (st->r_sense_uohm[channel] has type of u32).
The docs on the DIV_ROUND_CLOSEST macro explain that dividing a negative
value by an unsigned type is undefined behavior. The actual behavior is
that it converts both values to unsigned before doing the division, for
example:
int ret = DIV_ROUND_CLOSEST(-100, 3U);
results in ret == 1431655732 instead of -33.
Fixes: 2b9ea4262ae9 ("hwmon: Add driver for ltc2991")
Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250115-hwmon-ltc2991-fix-div-round-closest-v1-1-b4929667e457@xxxxxxxxxxxx
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/hwmon/ltc2991.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/hwmon/ltc2991.c b/drivers/hwmon/ltc2991.c
index 7ca139e4b6aff..6d5d4cb846daf 100644
--- a/drivers/hwmon/ltc2991.c
+++ b/drivers/hwmon/ltc2991.c
@@ -125,7 +125,7 @@ static int ltc2991_get_curr(struct ltc2991_state *st, u32 reg, int channel,
/* Vx-Vy, 19.075uV/LSB */
*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 19075,
- st->r_sense_uohm[channel]);
+ (s32)st->r_sense_uohm[channel]);
return 0;
}
--
2.39.5
