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authorUwe Kleine-König <u.kleine-koenig@pengutronix.de>2020-12-15 10:20:30 +0100
committerGuenter Roeck <linux@roeck-us.net>2020-12-30 08:21:04 -0800
commit1eda52334e6d13eb1a85f713ce06dd39342b5020 (patch)
tree0fa3f0d27a960dc576165a63797b564731333737
parente042f151ec7474b88b8c1edaaddd1ff7415d7117 (diff)
downloadlinux-stericsson-1eda52334e6d13eb1a85f713ce06dd39342b5020.tar.gz
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.c12
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;