hwmon: (lm90) Add lock protection to lm90_alert

Overview

In the Linux kernel, the following vulnerability has been resolved:

hwmon: (lm90) Add lock protection to lm90_alert

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.

Affected

• Linux >= 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f < 02b88fa993582b4fe228b4143b330b0bb9f28353
• Linux >= 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f < 165ef777ec6f634a5e4b8d9b0dadca8ef91fa90e
• Linux >= 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f < bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
• Linux >= 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f < b0b66aae8a94c3663d47e4000b0e81b89ce32186
• Linux >= 7a1d220ccb0cc2b808eb176fb05bf55a38179f3f < 873e919e3101063a7a75989510ccfc125a4391cf
• Linux 5.3

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.