Linux Kernel PMBus Regulator Race: Unprotected Voltage Access
CVE-2026-31486 Published on April 22, 2026
hwmon: (pmbus/core) Protect regulator operations with mutex
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (pmbus/core) Protect regulator operations with mutex
The regulator operations pmbus_regulator_get_voltage(),
pmbus_regulator_set_voltage(), and pmbus_regulator_list_voltage()
access PMBus registers and shared data but were not protected by
the update_lock mutex. This could lead to race conditions.
However, adding mutex protection directly to these functions causes
a deadlock because pmbus_regulator_notify() (which calls
regulator_notifier_call_chain()) is often called with the mutex
already held (e.g., from pmbus_fault_handler()). If a regulator
callback then calls one of the now-protected voltage functions,
it will attempt to acquire the same mutex.
Rework pmbus_regulator_notify() to utilize a worker function to
send notifications outside of the mutex protection. Events are
stored as atomics in a per-page bitmask and processed by the worker.
Initialize the worker and its associated data during regulator
registration, and ensure it is cancelled on device removal using
devm_add_action_or_reset().
While at it, remove the unnecessary include of linux/of.h.
Products Associated with CVE-2026-31486
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Affected Versions
Linux:- Version ddbb4db4ced1ba784fcd3500179a7291b6c5d7b7 and below 4e9d723d9f198b86f6882a84c501ba1f39e8d055 is affected.
- Version ddbb4db4ced1ba784fcd3500179a7291b6c5d7b7 and below 2c77ae315f3ce9d2c8e1609be74c9358c1fe4e07 is affected.
- Version ddbb4db4ced1ba784fcd3500179a7291b6c5d7b7 and below 754bd2b4a084b90b5e7b630e1f423061a9b9b761 is affected.
- Version 3.19 is affected.
- Before 3.19 is unaffected.
- Version 6.18.21, <= 6.18.* is unaffected.
- Version 6.19.11, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.