In the Linux kernel, the following vulnerability has been resolved:
mailbox: mtk-cmdq: Move devm_mbox_controller_register() after devm_pm_runtime_enable()
When mtk-cmdq unbinds, a WARN_ON message with condition
pm_runtime_get_sync() < 0 occurs.
According to the call tracei below:
cmdq_mbox_shutdown
mbox_free_channel
mbox_controller_unregister
__devm_mbox_controller_unregister
…
The root cause can be deduced to be calling pm_runtime_get_sync() after
calling pm_runtime_disable() as observed below:
To fix this problem, cmdq_probe() needs to move
devm_mbox_controller_register() after devm_pm_runtime_enable() to make
devm_pm_runtime_disable() be called after
devm_mbox_controller_unregister().