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hwmon: (lm90) Add lock protection to lm90_alert

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Sashiko reports:

lm90_alert() executes in the smbus alert context and calls
lm90_update_confreg() to disable the hardware alert line, without
acquiring hwmon_lock.

Concurrently, sysfs write operations (such as lm90_write_convrate) hold
the hwmon_lock, temporarily modify data->config, and then restore it.

If an alert interrupt occurs concurrently with a sysfs write, the sysfs
path will overwrite the alert handler's modifications to data->config
and the hardware register.

This unintentionally re-enables the hardware alert line while the alarm is
still active, causing an interrupt storm.

Add the missing lock to lm90_alert() to solve the problem.

Fixes: 7a1d220ccb ("hwmon: (lm90) Introduce function to update configuration register")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Guenter Roeck 2026-05-14 14:41:00 -07:00
parent b09a456010
commit 873e919e31
1 changed files with 2 additions and 0 deletions
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2
drivers/hwmon/lm90.c
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@ -2946,6 +2946,7 @@ static void lm90_alert(struct i2c_client *client, enum i2c_alert_protocol type,
*/
struct lm90_data *data = i2c_get_clientdata(client);
hwmon_lock(data->hwmon_dev);
if (!data->shutdown && (data->flags & LM90_HAVE_BROKEN_ALERT) &&
(data->current_alarms & data->alert_alarms)) {
if (!(data->config & 0x80)) {
@ -2955,6 +2956,7 @@ static void lm90_alert(struct i2c_client *client, enum i2c_alert_protocol type,
schedule_delayed_work(&data->alert_work,
max_t(int, HZ, msecs_to_jiffies(data->update_interval)));
}
hwmon_unlock(data->hwmon_dev);
} else {
dev_dbg(&client->dev, "Everything OK\n");
}