Affected: Linux

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

dpll: fix NULL deref in dpll_device_ops() during teardown race

When the last owner of a dpll device unregisters while a foreign driver still holds a pin on it via dpll_pin_on_pin_register(), the dpll object stays alive with an empty registration list. A pin notification queued before the unregister (e.g. ice reacting to zl3073x_i2c removal) then walks pin->dpll_refs into dpll_device_ops(), which trips the WARN_ON and dereferences the missing registration. dpll_lock cannot help because the notification work was queued before the unregistering driver took the lock.

Treat the empty registration list as a legitimate transient state. Make dpll_priv() and dpll_device_ops() return NULL in that case and make every pin netlink path that resolves a device from a pin skip such dplls. dpll_cmd_pin_get_one() picks a ref with a live registration and returns -ENODEV when there is none, the pin dumpit skips such a pin instead of aborting the dump, dpll_msg_add_pin_dplls() and the frequency, esync, reference sync and phase adjust set paths skip dead refs, and dpll_pin_parent_device_set() validates the parent with dpll_device_get_by_id(). dpll_pin_register() is the last caller that dereferenced the device ops without a check, so move its frequency monitor validation under dpll_lock and tolerate a missing registration there as well.

The empty registration list is equivalent to a cleared DPLL_REGISTERED mark, both transitio…