AZL-97338

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

hwmon: (pmbus) Fix type confusion in notification logic

Sashiko reports:

At the start of the loop in pmbusnotify(), the code unconditionally casts every attribute to a struct sensordevice_attribute:

drivers/hwmon/pmbus/pmbuscore.c:pmbusnotify() { for (i = 0; i < data->numattributes; i++) { struct deviceattribute *da = todevattr(data->group.attrs[i]); struct sensordeviceattribute *attr = tosensordev_attr(da); int index = attr->index; ... }

However, data->group.attrs can contain other types like struct pmbussamplesreg or struct pmbussensor, which only embed a base struct deviceattribute.

If da is a struct pmbussamplesreg, devattr is the last member. Casting it to struct sensordevice_attribute and reading the index field appears to access memory past the end of the allocation, which might trigger a slab-out-of-bounds read.

Additionally, if da is a struct pmbus_sensor, casting it causes the index field to overlap with the page, phase, and reg fields. Could this produce a garbage mask on little-endian systems that spuriously matches the target reg, page, and flags during an alert?

Fix the problem by using struct sensordeviceattr in struct pmbussensor and struct pmbuslabel. Since those attributes never trigger a notification, set the value of attr->index to -1 for them. Use this value to distinguish from boolean attributes which can trigger a notification and use the index field to encode mask, page, and register values.