6.12-stable review patch. If anyone has any objections, please let me know.
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From: David Lechner dlechner@baylibre.com
[ 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@baylibre.com Link: https://lore.kernel.org/r/20250115-hwmon-ltc2991-fix-div-round-closest-v1-1-... Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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; }