diff options
| author | Uwe Kleine-König <u.kleine-koenig@pengutronix.de> | 2020-12-15 10:20:30 +0100 |
|---|---|---|
| committer | Guenter Roeck <linux@roeck-us.net> | 2020-12-30 08:21:04 -0800 |
| commit | 1eda52334e6d13eb1a85f713ce06dd39342b5020 (patch) | |
| tree | 0fa3f0d27a960dc576165a63797b564731333737 | |
| parent | e042f151ec7474b88b8c1edaaddd1ff7415d7117 (diff) | |
hwmon: (pwm-fan) Ensure that calculation doesn't discard big period values
With MAX_PWM being defined to 255 the code
unsigned long period;
...
period = ctx->pwm->args.period;
state.duty_cycle = DIV_ROUND_UP(pwm * (period - 1), MAX_PWM);
calculates a too small value for duty_cycle if the configured period is
big (either by discarding the 64 bit value ctx->pwm->args.period or by
overflowing the multiplication). As this results in a too slow fan and
so maybe an overheating machine better be safe than sorry and error out
in .probe.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201215092031.152243-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
| -rw-r--r-- | drivers/hwmon/pwm-fan.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c index 777439f48c14..111a91dc6b79 100644 --- a/drivers/hwmon/pwm-fan.c +++ b/drivers/hwmon/pwm-fan.c @@ -334,8 +334,18 @@ static int pwm_fan_probe(struct platform_device *pdev) ctx->pwm_value = MAX_PWM; - /* Set duty cycle to maximum allowed and enable PWM output */ pwm_init_state(ctx->pwm, &state); + /* + * __set_pwm assumes that MAX_PWM * (period - 1) fits into an unsigned + * long. Check this here to prevent the fan running at a too low + * frequency. + */ + if (state.period > ULONG_MAX / MAX_PWM + 1) { + dev_err(dev, "Configured period too big\n"); + return -EINVAL; + } + + /* Set duty cycle to maximum allowed and enable PWM output */ state.duty_cycle = ctx->pwm->args.period - 1; state.enabled = true; |