Linux: net: airoha: npu: cancel wdt_work after releasing the WDT IRQ

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

net: airoha: npu: cancel wdt_work after releasing the WDT IRQ

airoha_npu_remove() calls cancel_work_sync() on each core's wdt_work, but the watchdog IRQ that queues it is requested with devm_request_irq() and is freed only after .remove() returns. airoha_npu_wdt_handler() can therefore schedule_work() again once the cancel has returned. struct airoha_npu, which contains the work, is devm_kzalloc()'d and is freed in that same unwind, so the late work dereferences freed memory.

Register the work with devm_work_autocancel() before devm_request_irq() and drop .remove(). Devres runs in reverse order, so the IRQ is freed before cancel_work_sync(), including when probe fails. A cancel left in .remove() cannot get that order. Initializing the work first also stops a pending watchdog interrupt from queuing an uninitialized work item. Probe currently calls INIT_WORK() only after devm_request_irq().

This issue was identified during our ongoing static-analysis research while reviewing kernel code.